Document:

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                                                                     EXHIBIT 4.1

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                        TRI-UNION DEVELOPMENT CORPORATION
                                    AS ISSUER

                                       AND

                           TRIBO PETROLEUM CORPORATION
                               AS PARENT GUARANTOR

                              SERIES A AND SERIES B

                       12.5% SENIOR SECURED NOTES DUE 2006

                                   ----------

                                    INDENTURE

                            DATED AS OF JUNE 18, 2001

                                   ----------

                                   ----------

                       FIRSTAR BANK, NATIONAL ASSOCIATION

                                     TRUSTEE

                                   ----------

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                             CROSS-REFERENCE TABLE*
<Table>
<Caption>

Trust Indenture
   Act Section                                                             Indenture Section
----------------                                                           -----------------
<S>                                                                        <C>
310(a)(1).................................................................          7.10
   (a)(2).................................................................          7.10
   (a)(3).................................................................           N/A
   (a)(4).................................................................           N/A
   (a)(5).................................................................          7.10
   (b)....................................................................          7.10
   (c)....................................................................           N/A
311(a)....................................................................          7.11
   (b)....................................................................          7.11
   (c)....................................................................           N/A
312(a)....................................................................          2.05
   (b)....................................................................         11.03
   (c)....................................................................         11.03
313(a)....................................................................          7.06
   (b)(1).................................................................          7.06
   (b)(2).................................................................    7.06, 7.07
   (c)....................................................................   7.06, 11.02
   (d)....................................................................          7.06
314(a)....................................................................   4.03, 11.02
   (b)....................................................................           N/A
   (c)(1).................................................................         11.04
   (c)(2).................................................................         11.04
   (c)(3).................................................................           N/A
   (d)....................................................................           N/A
   (e)....................................................................         11.05
   (f)....................................................................           N/A
315(a)....................................................................          7.01
   (b)....................................................................   7.05, 11.02
   (c) ...................................................................          7.01
   (d)....................................................................          7.01
   (e)....................................................................          6.11
316(a)(last sentence).....................................................          2.09
   (a)(1)(A)..............................................................          6.05
   (a)(1)(B)..............................................................          6.04
   (a)(2).................................................................           N/A
   (b)....................................................................          6.07
   (c)....................................................................          2.12
317(a)(1).................................................................          6.08
   (a)(2).................................................................          6.09
   (b)....................................................................          2.04
318(a)....................................................................         11.01
   (b)....................................................................           N/A
</Table>

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<Table>

<S>                                                                                <C>
   (c)....................................................................         11.01
</Table>

----------

N/A means not applicable.

*This Cross-Reference Table is not part of the Indenture.

<PAGE>   4

                                TABLE OF CONTENTS

<Table>
<Caption>

                                                                                                       Page
                                                                                                       ----
<S>              <C>                                                                                   <C>
ARTICLE 1        DEFINITIONS AND INCORPORATION BY REFERENCE...............................................1
         SECTION 1.01.  DEFINITIONS.......................................................................1
         SECTION 1.02.  OTHER DEFINITIONS................................................................29
         SECTION 1.03.  INCORPORATION BY REFERENCE OF TRUST INDENTURE ACT................................29
         SECTION 1.04.  RULES OF CONSTRUCTION............................................................29
ARTICLE 2        THE NOTES ..............................................................................30
         SECTION 2.01.  FORM AND DATING..................................................................30
         SECTION 2.02.  EXECUTION AND AUTHENTICATION.....................................................31
         SECTION 2.03.  REGISTRAR AND PAYING AGENT.......................................................32
         SECTION 2.04.  PAYING AGENT TO HOLD MONEY IN TRUST..............................................33
         SECTION 2.05.  HOLDER LISTS.....................................................................33
         SECTION 2.06.  TRANSFER AND EXCHANGE............................................................33
         SECTION 2.07.  REPLACEMENT NOTES................................................................39
         SECTION 2.08.  OUTSTANDING NOTES................................................................40
         SECTION 2.09.  TREASURY NOTES...................................................................40
         SECTION 2.10.  TEMPORARY NOTES..................................................................40
         SECTION 2.11.  CANCELLATION.....................................................................41
         SECTION 2.12.  DEFAULT INTEREST.................................................................41
ARTICLE 3        REDEMPTION AND REPURCHASE...............................................................41
         SECTION 3.01.  NOTICES TO TRUSTEE...............................................................41
         SECTION 3.02.  SELECTION OF NOTES TO BE REDEEMED................................................41
         SECTION 3.03.  NOTICE OF REDEMPTION.............................................................42
         SECTION 3.04.  EFFECT OF NOTICE OF REDEMPTION...................................................43
         SECTION 3.05.  DEPOSIT OF REDEMPTION PRICE......................................................43
         SECTION 3.06.  NOTES REDEEMED IN PART...........................................................43
         SECTION 3.07.  OPTIONAL REDEMPTION..............................................................43
         SECTION 3.08.  MANDATORY REDEMPTION.............................................................44
         SECTION 3.09.  OFFER TO PURCHASE BY APPLICATION OF EXCESS PROCEEDS..............................44
ARTICLE 4        COVENANTS ..............................................................................46
         SECTION 4.01.  PAYMENT OF NOTES.................................................................46
         SECTION 4.02.  MAINTENANCE OF OFFICE OR AGENCY..................................................47
         SECTION 4.03.  REPORTS..........................................................................47
         SECTION 4.04.  COMPLIANCE CERTIFICATE...........................................................48
         SECTION 4.05.  TAXES............................................................................49
         SECTION 4.06.  STAY, EXTENSION AND USURY LAWS...................................................49
         SECTION 4.07.  RESTRICTED PAYMENTS..............................................................49
         SECTION 4.08.  DIVIDEND AND OTHER PAYMENT RESTRICTIONS AFFECTING SUBSIDIARIES...................51
         SECTION 4.09.  INCURRENCE OF INDEBTEDNESS.......................................................52
         SECTION 4.10.  ASSET SALES......................................................................54
         SECTION 4.11.  TRANSACTIONS WITH AFFILIATES.....................................................55
         SECTION 4.12.  LIENS............................................................................56
         SECTION 4.13.  ADDITIONAL SUBSIDIARY GUARANTEES.................................................56
</Table>

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<Table>

<S>                     <C>                                                                             <C>
         SECTION 4.14.  CORPORATE EXISTENCE..............................................................56
         SECTION 4.15.  OFFER TO PURCHASE UPON CHANGE OF CONTROL.........................................56
         SECTION 4.16.  ISSUANCES AND SALES OF CAPITAL STOCK OF RESTRICTED SUBSIDIARIES..................58
         SECTION 4.17.  SYNTHETIC LEASE TRANSACTIONS.....................................................58
         SECTION 4.18.  CALCULATION OF ORIGINAL ISSUE DISCOUNT...........................................58
         SECTION 4.19.  EXCESS CASH FLOW OFFER...........................................................58
         SECTION 4.20.  EXPLORATION COSTS................................................................60
         SECTION 4.21.  CONDUCT OF BUSINESS..............................................................60
         SECTION 4.22.  LIMITATION ON IMPAIRMENT OF LIEN.................................................60
         SECTION 4.23.  LIEN ON ADDITIONAL COLLATERAL....................................................61
         SECTION 4.24.  RESERVE REPORTS..................................................................62
         SECTION 4.25.  HEDGING OBLIGATIONS..............................................................63
         SECTION 4.26.  THE COMPANY AS A WHOLLY OWNED SUBSIDIARY.........................................64
         SECTION 4.27.  INDEPENDENT BOARD OF THE PARENT GUARANTOR........................................64
ARTICLE 5        SUCCESSORS .............................................................................65
         SECTION 5.01.  MERGER, CONSOLIDATION OR SALE OF ASSETS..........................................65
         SECTION 5.02.  SUCCESSOR CORPORATION SUBSTITUTED................................................66
ARTICLE 6        DEFAULTS AND REMEDIES...................................................................67
         SECTION 6.01.  EVENTS OF DEFAULT................................................................67
         SECTION 6.02.  ACCELERATION.....................................................................69
         SECTION 6.03.  OTHER REMEDIES...................................................................69
         SECTION 6.04.  WAIVER OF PAST DEFAULTS..........................................................70
         SECTION 6.05.  CONTROL BY MAJORITY..............................................................70
         SECTION 6.06.  LIMITATION ON SUITS..............................................................70
         SECTION 6.07.  RIGHTS OF HOLDERS OF NOTES TO RECEIVE PAYMENT....................................71
         SECTION 6.08.  COLLECTION SUIT BY TRUSTEE.......................................................71
         SECTION 6.09.  TRUSTEE MAY FILE PROOFS OF CLAIM.................................................71
         SECTION 6.10.  PRIORITIES.......................................................................72
         SECTION 6.11.  UNDERTAKING FOR COSTS............................................................72
ARTICLE 7        TRUSTEE ................................................................................72
         SECTION 7.01.  DUTIES OF TRUSTEE................................................................72
         SECTION 7.02.  RIGHTS OF TRUSTEE................................................................73
         SECTION 7.03.  INDIVIDUAL RIGHTS OF TRUSTEE.....................................................74
         SECTION 7.04.  TRUSTEE'S DISCLAIMER.............................................................74
         SECTION 7.05.  NOTICE OF DEFAULTS...............................................................75
         SECTION 7.06.  REPORTS BY TRUSTEE TO HOLDERS OF THE NOTES.......................................75
         SECTION 7.07.  COMPENSATION AND INDEMNITY.......................................................75
         SECTION 7.08.  REPLACEMENT OF TRUSTEE...........................................................76
         SECTION 7.09.  SUCCESSOR TRUSTEE BY MERGER, ETC. ...............................................77
         SECTION 7.10.  ELIGIBILITY; DISQUALIFICATION....................................................77
         SECTION 7.11.  PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY................................77
ARTICLE 8        LEGAL DEFEASANCE AND COVENANT DEFEASANCE; SATISFACTION AND DISCHARGE OF NOTES...........78
         SECTION 8.01.  DISCHARGE OF LIABILITY ON SECURITIES; DEFEASANCE.................................78
         SECTION 8.02.  CONDITIONS TO DEFEASANCE.........................................................79
         SECTION 8.03.  APPLICATION OF TRUST MONEY E.....................................................80
</Table>

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<Table>

<S>                     <C>                                                                             <C>
         SECTION 8.04.  REPAYMENT TO COMPANY.............................................................80
         SECTION 8.05   INDEMNITY FOR GOVERNMENT OBLIGATIONS.............................................80
         SECTION 8.06.  REINSTATEMENT....................................................................80
ARTICLE 9        AMENDMENT, SUPPLEMENT AND WAIVER........................................................81
         SECTION 9.01.  WITHOUT CONSENT OF HOLDERS OF NOTES..............................................81
         SECTION 9.02.  WITH CONSENT OF HOLDERS OF NOTES.................................................81
         SECTION 9.03.  COMPLIANCE WITH TRUST INDENTURE ACT..............................................83
         SECTION 9.04.  REVOCATION AND EFFECT OF CONSENTS................................................83
         SECTION 9.05.  NOTATION ON OR EXCHANGE OF NOTES.................................................83
         SECTION 9.06.  TRUSTEE TO SIGN AMENDMENTS, ETC. ................................................83
ARTICLE 10       GUARANTEES OF NOTES.....................................................................84
         SECTION 10.01. PARENT GUARANTEE AND SUBSIDIARY GUARANTEES.......................................84
ARTICLE 11       MISCELLANEOUS...........................................................................84
         SECTION 11.01. TRUST INDENTURE ACT CONTROLS.....................................................84
         SECTION 11.02. NOTICES..........................................................................84
         SECTION 11.03. COMMUNICATION BY HOLDERS OF NOTES WITH OTHER HOLDERS OF NOTES....................85
         SECTION 11.04. CERTIFICATE AND OPINION AS TO CONDITIONS PRECEDENT...............................85
         SECTION 11.05. STATEMENTS REQUIRED IN CERTIFICATE OR OPINION....................................85
         SECTION 11.06. RULES BY TRUSTEE AND AGENTS......................................................86
         SECTION 11.07. NO PERSONAL LIABILITY OF DIRECTORS, OFFICERS, EMPLOYEES AND SHAREHOLDERS.........86
         SECTION 11.08. GOVERNING LAW....................................................................86
         SECTION 11.09. NO ADVERSE INTERPRETATION OF OTHER AGREEMENTS....................................86
         SECTION 11.10. SUCCESSORS.......................................................................86
         SECTION 11.11. SEVERABILITY.....................................................................87
         SECTION 11.12. COUNTERPART ORIGINALS............................................................87
         SECTION 11.13. TABLE OF CONTENTS, HEADINGS, ETC. ...............................................87
         SECTION 11.14. CONSENT TO JURISDICTION..........................................................87
         SECTION 11.15  INTERCREDITOR AGREEMENT..........................................................88
ARTICLE 12       SECURITY ...............................................................................88
         SECTION 12.01  GRANT OF SECURITY INTEREST.......................................................88
         SECTION 12.02  EXECUTION OF INTERCREDITOR AGREEMENT.............................................88
</Table>

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                         EXHIBITS, ANNEXES AND SCHEDULES

<Table>

<S>            <C>                                                                                      <C>
EXHIBIT A-1    Form of Note..............................................................................A-1-1
EXHIBIT A-2    Form of Regulation S Temporary Global Note................................................A-2-1
EXHIBIT B-1    Certificate of Transferor from 144A Global Note to Regulation S Global Note...............B-1-1
EXHIBIT B-2    Certificate of Transferor from Regulation S Global Note to 144A Global Note...............B-2-1
EXHIBIT B-3    Certificate of Transferor of Definitive Notes.............................................B-3-1
EXHIBIT C      Certificate of Institutional Accredited Investor............................................C-1
EXHIBIT D      Guaranty Agreement..........................................................................D-1

ANNEX A        Registration Rights Agreement...........................................................ANNEX-1
</Table>

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         This Indenture, dated as of June 18, 2001, is among Tri-Union
Development Corporation, a Texas corporation (the "Company"), the Parent
Guarantor (as hereinafter defined), and Firstar Bank, National Association, a
national banking association, as trustee (the "Trustee").

                                    RECITAL:

         The Company, the Parent Guarantor and the Trustee agree as follows for
the benefit of each other and for the equal and ratable benefit of the Holders
of the 12.5% Series A Senior Secured Notes due 2006 (the "Series A Notes") and
the 12.5% Series B Senior Secured Notes due 2006 (the "Series B Notes" and,
together with the Series A Notes, the "Notes"), without preference of one series
of Notes over the other:

                                    ARTICLE 1

                          DEFINITIONS AND INCORPORATION
                                  BY REFERENCE

SECTION 1.01.     DEFINITIONS.

         "144A Global Note" means a permanent global senior secured note that
contains the paragraph referred to in footnote 1 and the additional schedule
referred to in footnote 3 to the form of the Note attached hereto as Exhibit
A-1, and that is deposited with the Note Custodian and registered in the name of
the Depository or its nominee, representing Notes originally issued or
transferred in reliance on Rule 144A.

         "Accreted Value" means $945.00 per Note initially, increasing by $27.50
for each quarter following the Closing Date, not to exceed $1,000.00 at any
time.

         "Acquired Indebtedness" means Indebtedness of the Parent Guarantor or
any of the Restricted Subsidiaries of the type described under clause (b)(6) of
Section 4.09 hereof.

         "Additional Assets" means (i) any property or assets (other than cash
or cash equivalents, Indebtedness and Capital Stock) used or useful in the Oil
and Gas Business; or (ii) the Capital Stock of a Person that becomes a
Restricted Subsidiary as a result of the acquisition of such Capital Stock by
the Parent Guarantor or a Restricted Subsidiary; provided, however, that any
such Restricted Subsidiary described in clause (ii) above is primarily engaged
in the Oil and Gas Business.

         "Adjusted Consolidated Net Tangible Assets" means (without
duplication), as of the date of determination,

                  (a) the sum of:

                           (i) discounted future net revenues from proved oil
                  and gas reserves of the Parent Guarantor and any Restricted
                  Subsidiaries calculated in accordance with SEC guidelines
                  before any state or federal income taxes, as estimated in a
                  reserve report prepared as of the end of the Parent
                  Guarantor's most recently completed fiscal year,

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                  which reserve report is prepared or reviewed by independent
                  petroleum engineers, as increased by, as of the date of
                  determination, the discounted future net revenues of (A)
                  estimated proved oil and gas reserves of the Parent Guarantor
                  and any Restricted Subsidiaries attributable to any material
                  acquisition consummated since the date of such year-end
                  reserve report, and (B) estimated proved oil and gas reserves
                  of the Parent Guarantor and any Restricted Subsidiaries
                  attributable to material extensions, discoveries and other
                  additions and upward determinations of estimates of proved oil
                  and gas reserves due to exploration, development or
                  exploitation, production or other activities conducted or
                  otherwise occurring since the date of such year-end reserve
                  report which would, in the case of determinations made
                  pursuant to clauses (A) and (B), in accordance with standard
                  industry practice, result in such additions or revisions, in
                  each case calculated in accordance with SEC guidelines
                  (utilizing the prices utilized in such year-end reserve
                  report), and decreased by, as of the date of determination,
                  the discounted future net revenues of (C) estimated proved oil
                  and gas reserves of the Parent Guarantor and any Restricted
                  Subsidiaries produced or disposed of since the date of such
                  year-end reserve report and (D) reductions in the estimated
                  proved oil and gas reserves of the Parent Guarantor and any
                  Restricted Subsidiaries since the date of such year-end
                  reserve report attributable to material downward
                  determinations of estimates of proved oil and gas reserves due
                  to exploration, development or exploitation, production or
                  other activities conducted or otherwise occurring since the
                  date of such year-end reserve report which would, in the case
                  of determinations made pursuant to clauses (C) and (D), in
                  accordance with standard industry practice, result in such
                  determinations, in each case calculated in accordance with SEC
                  guidelines (utilizing the prices utilized in such year-end
                  reserve report); provided that, in the case of each of the
                  determinations made pursuant to clauses (A) through (D), such
                  increases and decreases shall be as estimated by the Parent
                  Guarantor's engineers unless, if as a result of such
                  acquisitions, dispositions, discoveries, extensions or
                  revisions, there is a Material Change, then such increases and
                  decreases in the discounted future net revenue shall be
                  confirmed in writing by an independent petroleum engineer;

                           (ii) the capitalized costs that are attributable to
                  oil and gas properties of the Parent Guarantor and any
                  Restricted Subsidiaries to which no proved oil and gas
                  reserves are attributed, based on the Parent Guarantor's and
                  the Restricted Subsidiaries' books and records as of a date no
                  earlier than the date of the Parent Guarantor's latest annual
                  or quarterly financial statements;

                           (iii) the Net Working Capital on a date no earlier
                  than the date of the Parent Guarantor's latest annual or
                  quarterly financial statements; and

                           (iv) the greater of (I) the net book value on a date
                  no earlier than the date of the Parent Guarantor's latest
                  annual or quarterly financial statements and (II) the
                  appraised value, as estimated by independent appraisers, of
                  other tangible assets of the Parent Guarantor and any
                  Restricted Subsidiaries as of a date no earlier than the date
                  of the Parent Guarantor's latest audited financial statements
                  (provided that the

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<PAGE>   10

                  Parent Guarantor shall not be required to obtain such an
                  appraisal of such assets if no such appraisal has been
                  performed); minus

                  (b)      the sum of:

                           (i) minority interests;

                           (ii) any gas balancing liabilities of the Parent
                  Guarantor and any Restricted Subsidiaries reflected in the
                  Parent Guarantor's latest audited financial statements;

                           (iii) the discounted future net revenue, calculated
                  in accordance with SEC guidelines (utilizing the same prices
                  utilized in the Parent Guarantor's year-end reserve report),
                  attributable to reserves subject to participation interests,
                  overriding royalty interests or other interests of third
                  parties, pursuant to participation, partnership, vendor
                  financing or other agreements then in effect, or which
                  otherwise are required to be delivered to third parties;

                           (iv) the discounted future net revenues, calculated
                  in accordance with SEC guidelines (utilizing the same prices
                  utilized in the Parent Guarantor's year-end reserve report),
                  attributable to reserves that are required to be delivered to
                  third parties to fully satisfy the obligations of the Parent
                  Guarantor and any Restricted Subsidiaries with respect to
                  Volumetric Production Payments on the schedules specified with
                  respect thereto; and

                           (v) the discounted future net revenues, calculated in
                  accordance with SEC guidelines, attributable to reserves
                  subject to Dollar-Denominated Production Payments that, based
                  on the estimates of production included in determining the
                  discounted future net revenues specified in the immediately
                  preceding clause (a)(i) (utilizing the same prices utilized in
                  the Parent Guarantor's year-end reserve report), would be
                  necessary to satisfy fully the obligations of the Parent
                  Guarantor and any Restricted Subsidiaries with respect to
                  Dollar-Denominated Production Payments on the schedules
                  specified with respect thereto.

         "Affiliate" of any specified Person means any other Person, directly or
indirectly, controlling or controlled by or under direct or indirect common
control with such specified Person, and if such Person is an individual, any
family member of such Person within four degrees of consanguinity and spouses of
such Persons. For the purposes of this definition, "control" when used with
respect to any Person means the power to direct the management and policies of
such Person, directly or indirectly, whether through the ownership of voting
securities, by contract or otherwise; and the terms "controlling" and
"controlled" have meanings correlative to the preceding. For purposes of the
provisions of Sections 4.07, 4.10 and 4.11 hereof only, "Affiliate" shall also
mean any beneficial owner of Capital Stock representing 10% or more of the total
voting power of the Voting Stock (on a fully diluted basis) of a Person or of
rights or warrants to purchase such Capital Stock (whether or not currently
exercisable) and any Person who would be an Affiliate of any such beneficial
owner pursuant to the first sentence hereof.

                                       3
<PAGE>   11

         "Affiliate Transaction" has the meaning given such term in Section 4.11
hereof.

         "Agent" means any Registrar or Paying Agent.

         "Applicable Procedures" means, with respect to any transfer or exchange
of beneficial interests in a Global Note, the rules and procedures of the
Depository, Euroclear or Clearstream that apply to such transfer or exchange.

         "Approved Hedge Agreement" means (A) any Oil and Gas Hedging Contract
with Bank of America, N.A., (B) any Oil and Gas Hedging Contract with any other
Approved Hedge Counterparty (i) which designates in the confirmation or other
transaction statement pursuant to which such Oil and Gas Hedging Contract is
evidenced that it is an "Approved Hedge Agreement" for purposes of the
Intercreditor Agreement, this Indenture and the Security Documents and (ii) a
copy of which has been delivered to the Collateral Agent and the Trustee, in
case of either (A) or (B) until (a) the Approved Hedge Counterparty ceases to be
an Approved Hedge Counterparty under the Intercreditor Agreement or (b) the
Approved Hedge Counterparty specifies in writing to the Collateral Agent, the
Trustee and the Company that such contract ceased to be an Approved Hedge
Agreement, and (C) any Oil and Gas Hedging Contract that is a price floor,
option for a price floor or other similar arrangement for which, upon entering
into such contract, neither the Parent Guarantor nor any Restricted Subsidiary
will have any liability other than the payment of an initial premium price.

         "Approved Hedge Counterparties" means (A) Bank of America, N.A., unless
it has ceased to be an Approved Hedge Counterparty, (B) any other Person that
(i) executes an Oil and Gas Hedging Contract with the Company or a Restricted
Subsidiary, (ii) has, or receives credit support in the form of an unconditional
guarantee of payment from a parent who has a long-term unsecured senior debt
rating of at least BBB- by Standard & Poor's Rating Service or Baa3 by Moody's
Investors Service, Inc., (iii) is designated as such by the Company in writing
to the Trustee and the Collateral Agent and (iv) if no Hedge Liquidity Provider
is then (or thereafter) providing letters of credit as collateral for the
Hedging Obligations owed to such Person or such Person has not otherwise ceased
to be an Approved Hedge Counterparty, executes and delivers to the Collateral
Agent and the Trustee a supplement to the Intercreditor Agreement, and (C) for
purposes of the provisions of Section 4.25 hereof and the definition of "Hedged
Revenues" only, the Persons in clauses (A) and (B) above and any Person who
meets the requirement set forth in subclause (B)(ii) above and who enters into
any Oil and Gas Hedging Contract with the Company or a Restricted Subsidiary
that is a price floor, option for a price floor or other similar arrangement for
which, upon entering into such contract, neither the Company nor any Restricted
Subsidiary will have any liability other than the payment of an initial premium
price.

         "Asset Disposition" means any sale, lease, transfer or other
disposition (or series of related sales, leases, transfers or dispositions) by
the Parent Guarantor or any Restricted Subsidiary, including any disposition by
means of a merger, consolidation or similar transaction (each referred to for
the purposes of this definition as a "disposition"), of (i) any shares of
Capital Stock of a Restricted Subsidiary (other than directors' qualifying
shares or shares required by applicable law to be held by a Person other than
the Parent Guarantor or a Restricted Subsidiary), (ii) all or substantially all
the assets of any division or line of business of the Parent Guarantor or any
Restricted Subsidiary or (iii) any other assets of the Parent Guarantor or any
Restricted Subsidiary

                                       4
<PAGE>   12

outside of the ordinary course of business of the Parent Guarantor or such
Restricted Subsidiary. Notwithstanding the preceding, none of the following
shall be deemed to be an Asset Disposition: (1) a disposition by a Restricted
Subsidiary to the Parent Guarantor or by the Parent Guarantor or a Restricted
Subsidiary to a Wholly Owned Subsidiary, (2) the sale or transfer (whether or
not in the ordinary course of business) of oil and gas properties; provided,
however, that at the time of such sale or transfer such properties do not have
associated with them any proved reserves, (3) the abandonment, farm-out, lease
or sublease of developed or undeveloped oil and gas properties in the ordinary
course of business, (4) the trade or exchange by the Parent Guarantor or any
Restricted Subsidiary of any oil and gas property owned or held by the Parent
Guarantor or such Restricted Subsidiary for any oil and gas property owned or
held by another Person, provided that if any property so contains proved
reserves, then the property received therefor contains a reasonably equivalent
value of proved reserves, (5) the trade or exchange by the Parent Guarantor or
any Restricted Subsidiary of any oil and gas property owned or held by the
Parent Guarantor or such Restricted Subsidiary for any Investment in equity
interests of a Person engaged in the Oil and Gas Business, provided that if any
property so traded or exchanged contains proved reserves, then (A) the Parent
Guarantor's or such Restricted Subsidiary's pro rata Investment in such Person
shall represent a reasonably equivalent value of proved reserves and (B) such
Person is or becomes by virtue of such Investment a Restricted Subsidiary, or
(6) the sale or transfer of hydrocarbons or other mineral products or surplus or
obsolete equipment all in the ordinary course of business.

         "Attributable Debt" in respect of a Synthetic Lease means, as at the
time of determination, the present value (discounted at the interest rate
implicit in the Synthetic Lease, compounded annually) of the total obligations
of the lessee for rental payments during the remaining term of the lease
included in such Synthetic Lease (including any period for which such lease has
been extended).

         "Average Life" means, as of the date of determination, with respect to
any Indebtedness or Preferred Stock, the quotient obtained by dividing (i) the
sum of the products of numbers of years from the date of determination to the
dates of each successive scheduled principal payment of such Indebtedness or
redemption or similar payment with respect to such Preferred Stock multiplied by
the amount of such payment by (ii) the sum of all such payments.

         "Bankruptcy Law" means Title 11, United States Code, or any similar
federal or state law for the relief of debtors.

         "Board of Directors" means with respect to any Person, the board of
directors of such Person or any committee thereof duly authorized to act on
behalf of such board of directors.

         "Board Resolution" means a copy of a resolution certified by the
Secretary or an Assistant Secretary of a Person to have been duly adopted by the
Board of Directors of such Person and to be in full force and effect on the date
of such certification.

         "Business Day" means each day which is not a Legal Holiday.

         "Capital Expenditures" means the amount of any expenditures in respect
of fixed or capital assets.

                                       5
<PAGE>   13

         "Capital Lease Obligations" means an obligation that is required to be
classified and accounted for as a capital lease for financial reporting purposes
in accordance with GAAP, and the amount of Indebtedness represented by such
obligation shall be the capitalized amount of such obligation determined in
accordance with GAAP; and the Stated Maturity thereof shall be the date of the
last payment of rent or any other amount due under such lease prior to the first
date upon which such lease may be terminated by the lessee without payment of a
penalty.

         "Capital Stock" of any Person means any and all shares, interests,
rights to purchase, warrants, options, participations or other equivalents of or
interests in (however designated) equity of such Person, including any Preferred
Stock, but excluding any debt securities convertible into such equity and any
warrants or options granted to directors, officers or employees of such Person
in the ordinary course of business and the issuance of equity upon the exercise
thereof.

         "Change of Control" means the occurrence of any of the following
events:

                  (a) any "person" (as such term is used in Sections 13(d) and
         14(d) of the Exchange Act), other than one or more Permitted Holders,
         is or becomes the beneficial owner (as defined in Rules l3d-3 and l3d-5
         under the Exchange Act, except that for purposes of this clause (a)
         such person shall be deemed to have "beneficial ownership" of all
         shares that such person has the right to acquire, whether such right is
         exercisable immediately or only after the passage of time), directly or
         indirectly, of more than 35% of the total voting power of the Voting
         Stock of the Parent Guarantor; provided, however, that the Permitted
         Holders beneficially own (as defined in Rules 13d-3 and l3d-5 under the
         Exchange Act), directly or indirectly, in the aggregate a lesser
         percentage of the total voting power of the Voting Stock of the Parent
         Guarantor than such other person and do not have the right or ability
         by voting power, contract or otherwise to elect or designate for
         election a majority of its Board of Directors (for the purposes of this
         clause (a), such other person shall be deemed to beneficially own any
         Voting Stock of a specified corporation held by a parent corporation,
         if such other person is the beneficial owner (as defined in this clause
         (a)), directly, or indirectly, of more than 35% of the voting power of
         the Voting Stock of such parent corporation and the Permitted Holders
         beneficially own (as defined in this proviso), directly or indirectly,
         in the aggregate a lesser percentage of the voting power of the Voting
         Stock of such parent corporation and do not have the right or ability
         by voting power, contract or otherwise to elect or designate for
         election a majority of the Board of Directors of such parent
         corporation);

                  (b) during any period of two consecutive years from and after
         the Closing Date, individuals who at the beginning of such period
         constituted the Board of Directors of the Parent Guarantor (together
         with any new directors whose election by such Board of Directors or
         whose nomination for election by the shareholders of the Parent
         Guarantor was approved by a vote of a majority of the directors of the
         Parent Guarantor then still in office who were either directors at the
         beginning of such period or whose election or nomination for election
         was previously so approved) cease for any reason to constitute a
         majority of the Board of Directors of the Parent Guarantor then in
         office other than as a result of the election of directors by the
         holders of the Class B Common Stock of the Parent Guarantor; or

                                       6
<PAGE>   14

                  (c) the merger or consolidation of the Parent Guarantor with
         or into another Person or the merger of another Person with or into the
         Parent Guarantor, or the sale of all or substantially all the assets of
         the Parent Guarantor to another Person (other than a Person that is
         controlled by the Permitted Holders), and, in the case of any such
         merger or consolidation, the securities of the Parent Guarantor that
         are outstanding immediately prior to such transaction and which
         represent 100% of the aggregate voting power of the Voting Stock of the
         Parent Guarantor are changed into or exchanged for cash, securities or
         property, unless pursuant to such transaction such securities are
         changed into or exchanged for, in addition to any other consideration,
         securities of the surviving corporation that represent immediately
         after such transaction, at least a majority of the aggregate voting
         power of the Voting Stock of the surviving corporation.

         "Clearstream" means Clearstream Banking, societe anonyme.

         "Closing Date" means the date on which this Indenture is executed.

         "Code" means the Internal Revenue Code of 1986, as amended.

         "Collateral" means, collectively, all of the property and assets
(including, without limitation, Trust Moneys) that are from time to time subject
to, or purported to be subject to, the Lien of this Indenture or any of the
Security Documents.

         "Collateral Account" has the meaning given such term in Section 3.03 of
the Intercreditor Agreement.

         "Collateral Agent" means Wells Fargo Bank Minnesota, National
Association, until a successor replaces it in accordance with the terms of the
Intercreditor Agreement and thereafter means the successor serving thereunder.

         "Company" means the party named as such in the first paragraph of this
Indenture until a successor replaces it in accordance with the applicable
provisions of this Indenture and thereafter means such successor.

         "Consolidated Coverage Ratio" as of any date of determination means the
ratio of (i) the aggregate amount of EBITDA for the period of the most recent
four consecutive fiscal quarters for which financial statements are available
prior to the date of such determination to (ii) Consolidated Interest Expense
for such four fiscal quarters; provided, however, that (1) if the Parent
Guarantor or any Restricted Subsidiary has Incurred any Indebtedness since the
beginning of such period that remains outstanding or if the transaction giving
rise to the need to calculate the Consolidated Coverage Ratio is an Incurrence
of Indebtedness, or both, EBITDA and Consolidated Interest Expense for such
period shall be calculated after giving effect on a pro forma basis to such
Indebtedness as if such Indebtedness had been Incurred on the first day of such
period and the discharge of any other Indebtedness repaid, repurchased, defeased
or otherwise discharged with the proceeds of such new Indebtedness as if such
discharge had occurred on the first day of such period, (2) if the Parent
Guarantor or any Restricted Subsidiary has repaid, repurchased, defeased or
otherwise discharged any Indebtedness since the beginning of such period or if
any Indebtedness is

                                       7
<PAGE>   15

to be repaid, repurchased, defeased or otherwise discharged on the date of the
transaction giving rise to the need to calculate the Consolidated Coverage
Ratio, EBITDA and Consolidated Interest Expense for such period shall be
calculated on a pro forma basis as if such discharge had occurred on the first
day of such period and as if the Parent Guarantor or such Restricted Subsidiary
has not earned the interest income actually earned during such period in respect
of cash or Temporary Cash Investments used to repay, repurchase, defease or
otherwise discharge such Indebtedness, (3) if since the beginning of such period
the Parent Guarantor or any Restricted Subsidiary shall have made any Asset
Disposition (other than an Asset Disposition involving assets having a fair
market value of less than the greater of one percent (1%) of Adjusted
Consolidated Net Tangible Assets as of the end of the Parent Guarantor's then
most recently completed fiscal year and $2,000,000), then EBITDA for such period
shall be reduced by an amount equal to EBITDA (if positive) or increased by an
amount equal to EBITDA (if negative), in each case, directly attributable
thereto for such period and Consolidated Interest Expense for such period shall
be reduced by an amount equal to the Consolidated Interest Expense directly
attributable to any Indebtedness of the Parent Guarantor or any Restricted
Subsidiary repaid, repurchased, defeased or otherwise discharged with respect to
the Parent Guarantor and the continuing Restricted Subsidiaries in connection
with such Asset Disposition for such period (or, if the Capital Stock of any
Restricted Subsidiary is sold, the Consolidated Interest Expense for such period
directly attributable to the Indebtedness of such Restricted Subsidiary to the
extent the Parent Guarantor and the continuing Restricted Subsidiaries are no
longer liable for such Indebtedness after such sale), (4) if since the beginning
of such period the Parent Guarantor or any Restricted Subsidiary (by merger or
otherwise) shall have made an Investment in any Restricted Subsidiary (or any
Person which becomes a Restricted Subsidiary) or an acquisition (including by
way of lease) of assets, including any acquisition of assets occurring in
connection with a transaction requiring a calculation to be made hereunder,
EBITDA and Consolidated Interest Expense for such period shall be calculated
after giving pro forma effect thereto (including the Incurrence of any
Indebtedness) as if such Investment or acquisition occurred on the first day of
such period and (5) if since the beginning of such period any Person (that
subsequently became a Restricted Subsidiary or was merged with or into the
Parent Guarantor or any Restricted Subsidiary since the beginning of such
period) shall have made any Asset Disposition, any Investment or acquisition of
assets that would have required an adjustment pursuant to clause (3) or (4)
above if made by the Parent Guarantor or a Restricted Subsidiary during such
period, EBITDA and Consolidated Interest Expense for such period shall be
calculated after giving pro forma effect thereto as if such Asset Disposition,
Investment or acquisition occurred on the first day of such period. For purposes
of this definition, whenever pro forma effect is to be given to an acquisition
or disposition of assets, the amount of income or earnings relating thereto and
the amount of Consolidated Interest Expense associated with any Indebtedness
Incurred or repaid in connection therewith, the pro forma calculations shall be
determined in good faith by a responsible financial or accounting officer of the
Parent Guarantor. If any Indebtedness bears a floating rate of interest and is
being given pro forma effect, the interest of such Indebtedness shall be
calculated as if the rate in effect on the date of determination had been the
applicable rate for the entire period (taking into account any Interest Rate
Agreement applicable to such Indebtedness if such Interest Rate Agreement has a
remaining term in excess of 12 months).

         "Consolidated Interest Expense" means, for any period, the total
interest expense of the Parent Guarantor and the Restricted Subsidiaries for
such period, determined on a consolidated basis

                                       8
<PAGE>   16

in accordance with GAAP, plus, to the extent not included in such total interest
expense, without duplication, (i) interest expense attributable to capital
leases and imputed interest with respect to Attributable Debt, (ii) capitalized
interest, (iii) non-cash interest expenses, (iv) commissions, discounts and
other fees and charges owed with respect to letters of credit and bankers'
acceptance financing, (v) net costs (including amortization of fees and upfront
payments) associated with interest rate caps and other interest rate and
currency options that, at the time entered into, resulted in the Parent
Guarantor and the Restricted Subsidiaries being net payees as to future payouts
under such caps or options, and interest rate and currency swaps and forwards
for which the Parent Guarantor or the Restricted Subsidiaries has paid a
premium, (vi) Preferred Stock dividends in respect of all Preferred Stock held
by Persons other than the Parent Guarantor or a Wholly Owned Subsidiary, to the
extent that, by the terms of the Preferred Stock, failure to pay such dividends
would result in a bankruptcy of the issuer thereof and (vii) interest accruing
on any Indebtedness of any other Person to the extent such Indebtedness is
Guaranteed by the Parent Guarantor or any Restricted Subsidiary or secured by a
Lien on assets of the Parent Guarantor or any Restricted Subsidiary to the
extent such Indebtedness constitutes Indebtedness of the Parent Guarantor or any
Restricted Subsidiary (whether or not such Guarantee or Lien is called upon);
provided, however, "Consolidated Interest Expense" shall not include any (x)
amortization of costs relating to debt issuances (including the amortization of
debt discount) other than the amortization of debt discount related to the
issuance of securities with an original issue price of not more than 90% of the
principal thereof, (y) amortization of debt discount to the extent it relates to
revaluations of financial instruments recognized in connection with the
consolidation, and (z) noncash interest expense Incurred in connection with
interest rate caps and other interest rate and currency options that, at the
time entered into, resulted in the Parent Guarantor and the Restricted
Subsidiaries being either neutral or net payors as to future payouts under such
caps or options.

         "Consolidated Net Income" means, for any period, the net income of the
Parent Guarantor and the consolidated Subsidiaries; provided, however, that
there shall not be included in such Consolidated Net Income any of the following
(without duplication): (i) any net income of any Person (other than the Parent
Guarantor) if such Person is not a Restricted Subsidiary, except that (A)
subject to the exclusion contained in clause (iv) below, the Parent Guarantor's
equity in the net income of any such Person for such period shall be included in
such Consolidated Net Income up to the aggregate amount of cash actually
distributed by such Person during such period to the Parent Guarantor or a
Restricted Subsidiary as a dividend or other distribution (subject, in the case
of a dividend or other distribution paid to a Restricted Subsidiary, to the
limitations contained in clause (iii) below) and (B) the Parent Guarantor's
equity in a net loss of any such Person for such period shall be included in
determining such Consolidated Net Income; (ii) any net income (or loss) of any
Restricted Subsidiary acquired by the Parent Guarantor or a consolidated
Subsidiary in a pooling of interests transaction for any period prior to the
date of such acquisition; (iii) any net income of any Restricted Subsidiary if
such Restricted Subsidiary is subject to restrictions, directly or indirectly,
on the payment of dividends or the making of distributions by such Restricted
Subsidiary, directly or indirectly, to the Parent Guarantor, except that (A)
subject to the exclusion contained in clause (iv) below, the Parent Guarantor's
equity in the net income of any such Restricted Subsidiary for such period shall
be included in such Consolidated Net Income up to the aggregate amount of cash
actually distributed by such Restricted Subsidiary during such period to the
Parent Guarantor or another Restricted Subsidiary as a dividend or other
distribution (subject, in the case of a dividend

                                       9
<PAGE>   17

or other distribution paid to another Restricted Subsidiary, to the limitation
contained in this clause) and (B) the Parent Guarantor's equity in a net loss of
any such Restricted Subsidiary for such period shall be included in determining
such Consolidated Net Income; (iv) any gain or loss realized upon the sale or
other disposition of any assets of the Parent Guarantor or its consolidated
Restricted Subsidiaries (including pursuant to any sale-and-leaseback
arrangement) which is not sold or otherwise disposed of in the ordinary course
of business and any gain or loss realized upon the sale or other disposition of
any Capital Stock of any Person; (v) extraordinary gains or losses; and (vi) the
cumulative effect of a change in accounting principles.

         "Consolidated Net Worth" means, with respect to any Person, the total
of the amounts shown on the balance sheet of the Person and its Restricted
Subsidiaries, determined on a consolidated basis in accordance with GAAP, as of
the end of the most recent fiscal quarter of the Person for which financial
statements are available, as (i) the par or stated value of all outstanding
Capital Stock of the Person plus (ii) paid-in capital or capital surplus
relating to such Capital Stock plus (iii) any retained earnings or earned
surplus less (A) any accumulated deficit and (B) any amounts attributable to
Disqualified Stock.

         "Corporate Trust Office of the Trustee" shall be at the address of the
Trustee specified in Section 11.02 hereof or such other address as to which the
Trustee may give notice to the Company.

         "Custodian" means any receiver, trustee, assignee, liquidator,
sequestrator or similar official under any Bankruptcy Law. "Default" means any
event that is, or after notice or passage of time or both would be, an Event of
Default.

         "Definitive Notes" means Notes that are in the form of Exhibit A-1
attached hereto (but without including the text referred to in footnotes 1 and 3
thereto).

         "Depository" means, with respect to the Notes issuable or issued in
whole or in part in global form, the Person specified in Section 2.03 hereof as
the Depository with respect to the Notes, until a successor shall have been
appointed and becomes such pursuant to the applicable provision of this
Indenture, and, thereafter, "Depository" shall mean or include such successor.

         "Disqualified Stock" means, with respect to any Person, any Capital
Stock to the extent that by its terms (or by the terms of any security into
which it is convertible or for which it is exchangeable) or upon the happening
of any event, it (i) matures or is mandatorily redeemable pursuant to a sinking
fund obligation or otherwise, (ii) is convertible or exchangeable for
Indebtedness or Disqualified Stock or (iii) is redeemable, in whole or in part,
at the option of the holder thereof, in each case described in this clause (iii)
and in the immediately preceding clauses (i) and (ii), on or prior to the Stated
Maturity of the Notes; provided, however, that any Capital Stock that would not
constitute Disqualified Stock but for provisions thereof giving holders thereof
the right to require such Person to repurchase or redeem such stock upon the
occurrence of an "Asset Disposition" or "change of control" occurring prior to
the Stated Maturity of the Notes shall not constitute Disqualified Stock if the
"Asset Disposition" or "change of control" provisions applicable

                                       10
<PAGE>   18

to such Capital Stock are not more favorable to the holders of such Capital
Stock than the provisions of Sections 4.10 and 4.15 hereof.

         "$," "dollars" and "U.S. dollars" denote the lawful currency of the
United States of America.

         "Dollar-Denominated Production Payments" means production payment
obligations recorded as liabilities in accordance with GAAP, together with all
undertakings and obligations in connection therewith.

         "EBITDA" for any period means the sum of Consolidated Net Income for
such period, Consolidated Interest Expense for such period, and each of the
following (without duplication) to the extent deducted in calculating such
Consolidated Net Income for such period: (a) provision for taxes based on income
or profits, (b) depletion and depreciation expense, (c) amortization expense,
(d) exploration costs, (e) reorganization costs and (f) all other non-cash
charges (excluding any such non-cash charge to the extent that it represents an
accrual of or reserve for cash charges in any future period or amortization of a
prepaid cash expense that was paid in a prior period except such amounts as the
Parent Guarantor determines in good faith are nonrecurring), and less, to the
extent included in calculating such Consolidated Net Income and in excess of any
costs or expenses attributable thereto and deducted in calculating such
Consolidated Net Income, the sum of (x) the amount of deferred revenues that are
amortized during such period and are attributable to reserves that are subject
to Volumetric Production Payments and (y) amounts recorded in accordance with
GAAP as repayments of principal, premium, if any, and interest pursuant to
Dollar-Denominated Production Payments. Notwithstanding the preceding, the
provision for taxes based on the income or profits of, and the depreciation and
amortization and other non-cash charges of, a Restricted Subsidiary shall be
added to Consolidated Net Income to compute EBITDA only to the extent (and in
the same proportion) that the net income of such Subsidiary was included in
calculating Consolidated Net Income and only if a corresponding amount would be
permitted at the date of determination to be dividended to the Parent Guarantor
by such Subsidiary without prior approval (that has not been obtained) pursuant
to the terms of its charter and all agreements, instruments, judgments, decrees,
orders, statutes, rules and governmental regulations applicable to such
Subsidiary or its stockholders. Solely for the purpose of calculating EBITDA for
determining Excess Cash Flow, EBITDA shall be reduced by estimated cash income
tax expense for any quarter or increased for any cash income tax credits for any
quarter to the extent not already reflected in such calculation of EBITDA.

         "Equity Offering" means a primary public offering of shares of Capital
Stock of the Parent Guarantor.

         "Euroclear" means Euroclear Bank N.V./S.A or its successor as operator
of the Euroclear system.

         "Event of Default" has the meaning given such term in Section 6.01
hereof.

         "Excess Cash Flow" means, for any fiscal quarter, EBITDA for the Parent
Guarantor and the Restricted Subsidiaries for such quarter, minus each of the
following: (i) interest expense of the Parent Guarantor and the Restricted
Subsidiaries determined in accordance with GAAP and (ii) all

                                       11
<PAGE>   19

Capital Expenditures made during such quarter by the Parent Guarantor and the
Restricted Subsidiaries.

         "Excess Proceeds" has the meaning given such term in Section 4.10
hereof.

         "Excess Proceeds Offer" has the meaning given such term in Section 4.10
hereof.

         "Excess Proceeds Payment" has the meaning given such term in Section
4.10 hereof.

         "Exchange Act" means the Securities Exchange Act of 1934, as amended.

         "Exchange Offer" means the offer that may be made by the Company
pursuant to a Registration Rights Agreement to issue Series B Notes in exchange
for Series A Notes.

         "GAAP" means generally accepted accounting principles in the United
States as in effect from time to time, including those set forth in (i) the
opinions and pronouncements of the Accounting Principles Board of the American
Institute of Certified Public Accountants, (ii) statements and pronouncements of
the Financial Accounting Standards Board, (iii) such other statements by such
other entity as approved by a significant segment of the accounting profession,
and (iv) the rules and regulations of the SEC governing the inclusion of
financial statements (including pro forma financial statements) in periodic
reports required to be filed pursuant to Section 13 of the Exchange Act,
including opinions and pronouncements in staff accounting bulletins and similar
written statements from the accounting staff of the SEC.

         "Global Note" means, individually and collectively, the Unrestricted
Global Note, the IAI Global Note, the Regulation S Global Note and the 144A
Global Note.

         "Guarantee" means, without duplication, any obligation, contingent or
otherwise, of any Person directly or indirectly guaranteeing any Indebtedness of
any other Person and any obligation, direct or indirect, contingent or
otherwise, of such Person (i) to purchase or pay (or advance or supply funds for
the purchase or payment of) such Indebtedness of such other Person (whether
arising by virtue of partnership arrangements, or by agreements to keep-well, to
purchase assets, goods, securities or services, to take-or-pay or to maintain
financial statement conditions or otherwise) or (ii) entered into for the
purpose of assuring in any other manner the obligee of such Indebtedness of the
payment thereof or to protect such obligee against loss in respect thereof (in
whole or in part); provided, however, that the term "Guarantee" shall not
include endorsements for collection or deposit in the ordinary course of
business. The term "Guarantee" used as a verb has a corresponding meaning.

         "Guarantors" means the Parent Guarantor and each of the Subsidiary
Guarantors.

         "Guaranty Agreement" means the Guaranty Agreement, dated as of the
Closing Date, by the Parent Guarantor and the Subsidiary Guarantors party
thereto, in favor of the Trustee, the Approved Hedge Counterparties party to the
Intercreditor Agreement, the Hedge Liquidity Providers party to the
Intercreditor Agreement and each Holder, as the same may be amended,
supplemented or modified from time to time in accordance with the terms thereof
and of the Intercreditor Agreement, a copy of which is attached hereto as
Exhibit D.

                                       12
<PAGE>   20

         "Hedge Liquidity Agreements" has the meaning set forth in clause (b)(8)
of Section 4.09 hereof.

         "Hedge Liquidity Providers" means the financial institutions party to
Hedge Liquidity Agreements.

         "Hedge Period" means, as of the first Business Day of any month, the
period commencing on the date of determination pro forma to be entered into and
ending on the date which is two years after such date of determination.

         "Hedged Revenue Ratio" means for the Parent Guarantor and the
Restricted Subsidiaries, the ratio, calculated on a consolidated basis as of the
first Business Day of each month for the then current Hedge Period, of (i)
Hedged Revenues for such period to (ii) Projected Consolidated Interest Expense
for such period.

         "Hedged Revenues" means, for the Parent Guarantor and the Restricted
Subsidiaries, the amount, calculated on a consolidated basis as of the first
Business Day of each month for the then current Hedge Period, equal to (A) for
all Oil and Gas Hedging Contracts with an Approved Hedge Counterparty which are
price swaps or fixed price purchase and sales contracts, the sum of the products
attained by multiplying the notional or physical volume of crude oil or natural
gas for each month during such Hedge Period hedged therein and the fixed price
for such month, plus (B) for all Oil and Gas Hedging Contracts with an Approved
Hedge Counterparty which are price collars or price floors, the sum of the
products attained by multiplying the notional volume of crude oil or natural gas
for each month during such Hedge Period hedged therein and the fixed price floor
for such month, minus (C) both (i) the sum of each premium for any Oil and Gas
Hedging Contract for which a premium has been paid during such Hedge Period by
the Parent Guarantor or any Restricted Subsidiary and (ii) all amounts due under
any Oil and Gas Hedging Contract for which the counterparty thereunder is either
in default or in respect of which a termination event has occurred and is
continuing.

         "Hedging Obligations" of any Person means the obligations of such
Person pursuant to any Oil and Gas Hedging Contract or Interest Rate Agreement.

         "Holder" means a Person in whose name a Note is registered on the
Registrar's book.

         "IAI Global Note" means a permanent global senior note that contains
the paragraph referred to in footnote 1 and the additional schedule referred to
in footnote 3 to the form of the Note attached hereto as Exhibit A-1, and that
is deposited with the Note Custodian and registered in the name of the
Depository or its nominee, representing Notes originally issued or transferred
to Institutional Accredited Investors.

         "Immediate Family" means a Person's spouse, parents, children,
siblings, mother-in-law, father-in-law, brother-in-law, sister-in-law,
son-in-law, daughter-in-law and anyone who resides in such Person's home (other
than a domestic servant).

         "Incur" means issue, assume, Guarantee, incur or otherwise become
liable for, provided, however, that any Indebtedness, Capital Stock or Lien of a
Person existing at the time such Person

                                       13
<PAGE>   21

becomes a Subsidiary (whether by merger, consolidation, acquisition or
otherwise) shall be deemed to be Incurred by such Subsidiary at the time it
becomes a Subsidiary. The term "Incurrence" when used as a noun shall have a
correlative meaning. The accretion of principal of a non-interest bearing or
other discount security shall not be deemed the Incurrence of Indebtedness.

         "Indebtedness" means, with respect to any Person on any date of
determination (without duplication), (i) the principal of and premium (if any)
in respect of (A) indebtedness of such Person for money borrowed and (B)
indebtedness evidenced by notes, debentures, bonds or other similar instruments
for the payment of which such Person is responsible or liable; (ii) all Capital
Lease Obligations of such Person and all Attributable Debt of such Person; (iii)
all obligations of such Person issued or assumed as the deferred purchase price
of property (which purchase price is due more than six months after the date of
taking delivery of title to such property), including all obligations of such
Person for the deferred purchase price of property under any title retention
agreement (but excluding trade accounts payable arising in the ordinary course
of business); (iv) all obligations of such Person for the reimbursement of any
obligor on any letter of credit, banker's acceptance or similar credit
transaction (other than obligations with respect to letters of credit securing
obligations (other than obligations described in (i) through (iii) above)
entered into in the ordinary course of business of such Person to the extent
such letters of credit are not drawn upon or, if and to the extent drawn upon,
such drawing is reimbursed no later than the tenth Business Day following
receipt by such Person of a demand for reimbursement following payment on the
letter of credit); (v) the amount of all obligations of such Person with respect
to the redemption, repayment or other repurchase of any Disqualified Stock or,
with respect to any Subsidiary of such Person the liquidation preference with
respect to, any Preferred Stock (but excluding, in each case, any accrued
dividends); (vi) all obligations of such Person relating to any Production
Payment or in respect of production imbalances (but excluding production
imbalances arising in the ordinary course of business); (vii) all obligations of
the type referred to in clauses (i) through (vi) of other Persons and all
dividends of other Persons for the payment of which, in either case, such Person
is responsible or liable, directly or indirectly, as obligor, guarantor or
otherwise, including by means of any Guarantee (including, with respect to any
Production Payment, any warranties or Guarantees of production or payment by
such Person with respect to such Production Payment but excluding other
contractual obligations of such Person with respect to such Production Payment);
(viii) all obligations of the type referred to in clauses (i) through (vii) of
other Persons secured by any Lien on any property or asset of such
first-mentioned Person (whether or not such obligation is assumed by such
first-mentioned Person), the amount of such obligation being deemed to be the
lesser of the value of such property or assets or the amount of the obligation
so secured and (ix) to the extent not otherwise included in this definition,
Hedging Obligations of such Person.

         The "amount" or "principal amount" of Indebtedness at any time of
determination as used herein represented by: (1) any Capital Lease Obligation
shall be the amount determined in accordance with the definition thereof, (2)
all other unconditional obligations shall be the amount of the liability thereof
determined in accordance with GAAP, and (3) all other contingent obligations
shall be the maximum liability at such date of such Person.

         It is understood that none of the following shall constitute
Indebtedness: (i) indebtedness arising from agreements providing for
indemnification or adjustment of purchase price or from Guarantees securing any
obligations of the Parent Guarantor or any of its Subsidiaries pursuant to

                                       14
<PAGE>   22

such agreements, incurred or assumed in connection with the disposition of any
business, assets or Subsidiary of the Parent Guarantor, other than Guarantees or
similar credit support by the Parent Guarantor or any of its Subsidiaries of
Indebtedness incurred by any Person acquiring all or any portion of such
business, assets or Subsidiary for the purpose of financing such acquisition;
(ii) any trade payables and other accrued current liabilities incurred in the
ordinary course of business (including as the deferred purchase price of
property), (iii) obligations arising from Guarantees to suppliers, lessors,
licensees, contractors, franchisees or customers incurred in the ordinary course
of business; (iv) obligations (other than express Guarantees of indebtedness for
borrowed money) in respect of Indebtedness of other Persons arising in
connection with (A) the sale or discount of accounts receivable, (B) trade
acceptances and (C) endorsements of instruments for deposit in the ordinary
course of business, (v) obligations in respect of performance bonds provided by
the Parent Guarantor or its Subsidiaries in the ordinary course of business and
refinancings thereof; (vi) obligations arising from the honoring by a bank or
other financial institution of a check, draft or similar instrument drawn
against insufficient funds in the ordinary course of business, provided,
however, that such obligation is extinguished within two Business Days of its
incurrence; and (vii) obligations in respect of any obligations under workers'
compensation laws and similar legislation.

         "Indenture" means this Indenture, as amended or supplemented from time
to time.

         "Independent Director" means a director who has no relationship to the
Parent Guarantor or a Restricted Subsidiary or other Affiliate that could
reasonably be expected to interfere with the exercise of his or her independence
from management and the company on whose board the director sits. In addition,
the following persons may not serve as Independent Directors: (i) Persons
employed by the Parent Guarantor or any of the Restricted Subsidiaries or other
Affiliates of the foregoing during the current year or any of the three past
years; (ii) Persons who during the current year are or any of the past three
years were partners, controlling shareholders or executive officers of an
organization that has a business relationship or who have direct business
relationships with the Parent Guarantor or any of the Restricted Subsidiaries or
other Affiliates of the foregoing; (iii) a Person who is employed as an
executive officer of another entity where any of the Parent Guarantor's or a
Restricted Subsidiaries' or other Affiliates' executive officers serve on that
entity's compensation committee; and (iv) Persons who are Immediate Family of an
individual who is, or has been, during the current year or any of the past three
years, employed by the Parent Guarantor or any Restricted Subsidiary or other
Affiliate as an executive officer of such.

         "Indirect Participant" means a Person who holds an interest through a
Participant.

         "Initial Purchaser" means Jefferies & Company, Inc.

         "Institutional Accredited Investor" means an "accredited investor" as
defined in Rule 501(a)(1), (2), (3) or (7) under the Securities Act other than a
QIB.

         "Intercreditor Agreement" means the Intercreditor and Collateral Agency
Agreement among the Parent Guarantor, the Company and the Subsidiary Guarantors
party thereto, the Approved Hedge Counterparties or Hedge Liquidity Providers
party thereto, the Collateral Agent and the Trustee, dated as of the Closing
Date, as the same may be amended, supplemented or modified from time to time in
accordance with the terms thereof.

                                       15
<PAGE>   23

         "Interest Rate Agreement" means any interest rate swap agreement,
interest rate cap agreement or other financial agreement or arrangement designed
to protect a Person and its Subsidiaries against fluctuations in interest rates.

         "Investment" in any Person means any direct or indirect advance, loan
(other than advances to customers or joint interest partners or drilling
partnerships sponsored by the Parent Guarantor or any Restricted Subsidiary in
the ordinary course of business that are recorded as accounts receivable on the
balance sheet of the lender) or other extensions of credit (including by way of
Guarantee or similar arrangement) or capital contribution to (by means of any
transfer of cash or other property to others or any payment for property or
services for the account or use of others), or any purchase, short sale or
acquisition of Capital Stock, Indebtedness or other similar instruments issued
by such Person. For purposes of the definition of "Unrestricted Subsidiary," the
definition of "Restricted Payment" and the provisions of Section 4.07 hereof,
(i) "Investment" shall include the portion (proportionate to the Parent
Guarantor's equity interest in such Subsidiary) of the fair market value of the
net assets of any Subsidiary of the Parent Guarantor at the time that such
Subsidiary is designated an Unrestricted Subsidiary; provided, however, that
upon a redesignation of such Subsidiary as a Restricted Subsidiary, the Parent
Guarantor shall be deemed to continue to have a permanent "Investment" in an
Unrestricted Subsidiary equal to an amount (if positive) equal to (x) the Parent
Guarantor's "Investment" in such Subsidiary at the time of such redesignation
less (y) the portion (proportionate to the Parent Guarantor's equity interest in
such Subsidiary) of the fair market value of the net assets of such Subsidiary
at the time of such redesignation; and (ii) any property transferred to or from
an Unrestricted Subsidiary shall be valued at its fair market value at the time
of such transfer, in each case as determined in good faith by the Board of
Directors of the Parent Guarantor.

         "Issue Date" means the first date on which the Series A Notes are
issued hereunder.

         "Issue Price" of any Note means, in connection with the original
issuance of such Note, the initial issue price as set forth on the face of the
Note.

         "Legal Holiday" means a Saturday, a Sunday or a day on which banking
institutions in New York, New York, or at a place of payment with respect to the
Notes are authorized by law, regulation or executive order to remain closed. If
a payment date is a Legal Holiday at a place of payment, payment may be made at
that place on the next succeeding day that is not a Legal Holiday, and no
interest shall accrue for the intervening period.

         "Lien" means any mortgage, pledge, security interest, encumbrance, lien
or charge of any kind (including any conditional sale or other title retention
agreement or lease in the nature thereof).

         "Liquidated Damages" means all additional interest then owing pursuant
to a Registration Rights Agreement.

         "Major Asset Sale" has the meaning given such term in Section 4.10
hereof.

         "Major Asset Sale Offer" has the meaning given such term in Section
4.10 hereof.

         "Make-Up Period" has the meaning ascribed such term in clause (iii) of
Section 4.25 hereof.

                                       16
<PAGE>   24

         "Material Change" means an increase or decrease (excluding changes that
result solely from changes in prices) of more than 10% during a fiscal quarter
in the discounted future net revenues from proved oil and gas reserves of the
Parent Guarantor and the Restricted Subsidiaries, calculated in accordance with
clause (a) (i) of the definition of Adjusted Consolidated Net Tangible Assets;
provided, however, that the following will be excluded from the calculation of
Material Change: (i) any acquisitions during the fiscal quarter of oil and gas
reserves that have been estimated by independent petroleum engineers and with
respect to which a report or reports of such engineers exist and (ii) any
disposition of properties existing at the beginning of such fiscal quarter that
have been disposed of in compliance with the provisions described in Section
4.10 hereof.

         "MMBtu" means one million British thermal units.

         "Moody's" means Moody's Investors Service, Inc. or any successor to the
rating agency business thereof.

         "Mortgage" means mortgage, deed of trust, assignment of production,
security agreement, fixture filing and financing statement granted by the
Company or the Parent Guarantor or any Subsidiary Guarantor to the Collateral
Agent for the benefit of the Approved Hedge Counterparties or Hedge Liquidity
Providers, as applicable, Trustee and the Holders and pursuant to which one or
more Liens on Oil and Gas Assets or interests therein are created, as the same
may be amended, supplemented or modified from time to time in accordance with
the terms thereof and of the Intercreditor Agreement.

         "Net Available Cash" from an Asset Disposition means cash payments
received therefrom (including any cash payments received by way of deferred
payment of principal pursuant to a note or installment receivable or otherwise,
but only as and when received, but excluding any other consideration received in
the form of assumption by the acquiring Person of Indebtedness or other
obligations relating to such properties or assets or received in any other
noncash form) in each case net of (i) all legal, title and recording tax
expenses, commissions and other fees (including financial and other advisory
fees) and expenses incurred, and all federal, state, provincial, foreign and
local taxes required to be accrued as a liability under GAAP, as a consequence
of such Asset Disposition, (ii) all payments made on any Indebtedness (including
termination payments made on Approved Hedge Agreements on account of settlement
amounts, unpaid amounts, interest and other amounts due thereunder, but
excluding Subordinated Obligations) which is secured by a senior Lien on any
assets subject to such Asset Disposition, in accordance with the terms of any
Lien upon or other security agreement of any kind with respect to such assets,
or which must by its terms, or in order to obtain a necessary consent to such
Asset Disposition, or by applicable law, be repaid out of the proceeds from such
Asset Disposition, (iii) all distributions and other payments required to be
made to minority interest holders in Subsidiaries or joint ventures as a result
of such Asset Disposition and (iv) the deduction of appropriate amounts provided
by the seller as a reserve, in accordance with GAAP, against any liabilities
associated with the property or other assets disposed in such Asset Disposition
and retained by the Parent Guarantor or any Restricted Subsidiary after such
Asset Disposition.

         "Net Cash Proceeds" means, with respect to any Equity Offering, the
cash proceeds of such issuance or sale net of attorneys' fees, accountants'
fees, underwriters' or placement agents' fees,

                                       17
<PAGE>   25

discounts or commissions and brokerage, consultant and other fees actually
incurred in connection with such issuance or sale and net of taxes paid or
payable as a result thereof.

         "Net Working Capital" means (a) all current assets of the Parent
Guarantor and its Restricted Subsidiaries minus (b) all current liabilities of
the Parent Guarantor and its Restricted Subsidiaries, except current liabilities
included in Indebtedness, determined in accordance with GAAP.

         "Non-Recourse Indebtedness" with respect to any Person means
Indebtedness of such Person for which (i) the sole legal recourse for collection
of principal, premium, if any, and interest on such Indebtedness is against the
specific property identified in the instruments evidencing or securing such
Indebtedness and such property was acquired with the proceeds of such
Indebtedness or such Indebtedness was incurred within 90 days after the
acquisition of such property and (ii) no other assets of such Person may be
realized upon in collection of principal or interest on such Indebtedness;
provided, however, that any such Indebtedness shall not cease to be
"Non-Recourse Indebtedness" solely as a result of the instrument governing such
Indebtedness containing terms pursuant to which such Indebtedness becomes
recourse upon (a) fraud or misrepresentation by the Person in connection with
such Indebtedness, (b) such Person failing to pay taxes or other charges that
result in the creation of Liens on any portion of the specific property securing
such Indebtedness or failing to maintain any insurance on such property required
under the instruments securing such Indebtedness, (c) the conversion of any of
the collateral for such Indebtedness, (d) such Person failing to maintain any of
the collateral for such Indebtedness in the condition required under the
instruments securing the Indebtedness, (e) any income generated by the specific
property securing such Indebtedness being applied in a manner not otherwise
allowed in the instruments securing such Indebtedness, (f) the violation of any
applicable law or ordinance governing hazardous materials or substances or
otherwise affecting the environmental condition of the specific property
securing the Indebtedness or (g) the rights of the holder of such Indebtedness
to the specific property becoming impaired, suspended or reduced by any act,
omission or misrepresentation of such Person; provided, further, however, that
upon the occurrence of any of the foregoing clauses (a) through (g) above, any
such Indebtedness which shall have ceased to be "Non-Recourse Indebtedness"
shall be deemed to have been Indebtedness incurred by such Person at such time.

         "Notes" has the meaning attributed thereto in the Recital of this
Indenture.

         "Note Custodian" means the Trustee, as custodian with respect to the
Notes in global form, or any successor entity thereto.

         "Obligations" means all obligations for principal, premium, interest,
penalties, fees, indemnifications, reimbursements, damages and other liabilities
payable under this Indenture and other documentation governing the Notes.

         "Officer" means, with respect to any Person, the Chairman of the Board,
the Chief Executive Officer, the President, the Chief Operating Officer, the
Chief Financial Officer, the Chief Administrative Officer, the Treasurer, any
Assistant Treasurer, the Controller, the Secretary or any Vice-President of such
Person.

                                       18
<PAGE>   26

         "Officers' Certificate" means a certificate signed on behalf of a
Person, other than a natural person, by two Officers of such Person, one of whom
must be the principal executive officer, the principal financial officer, the
treasurer or the principal accounting officer of such Person, that meets the
requirements of Section 11.05 hereof.

         "Oil and Gas Assets" means, in respect of any Person, all proved oil
and gas reserves and natural gas processing facilities of such Person.

         "Oil and Gas Business" means the business of the exploration for, and
exploitation, development, acquisition, production, processing (but not
refining), marketing, storage and transportation of, hydrocarbons, and other
related energy and natural resource businesses.

         "Oil and Gas Hedging Contract" means any oil and gas purchase or
hedging agreement, and other agreement or arrangement, in each case, that is
designed to provide protection against oil and gas price fluctuations.

         "Opinion of Counsel" means an opinion from legal counsel who is
reasonably acceptable to the Trustee, that meets the requirements of Section
11.05 hereof, as applicable. Unless otherwise provided in this Indenture, the
counsel may be an employee of or counsel to the Company, any Subsidiary of the
Company or the Trustee.

         "Original Issue Discount" of any Note means the difference between the
Issue Price and the Principal Amount at Maturity of the Note as set forth on the
face of the Note, which shall accrue as set forth in the form of Note.

         "Original Notes" has the meaning set forth in Section 2.02 hereof.

         "Parent Guarantee" means the joint and several guarantees issued by the
Parent Guarantor pursuant to the Guaranty Agreement.

         "Parent Guarantor" means (a) Tribo Petroleum Corporation, a Texas
corporation, and (b) any permitted successors and assigns of Tribo Petroleum
Corporation under Article 5 hereof.

         "Participant" means with respect to DTC, Euroclear or Clearstream, a
Person who has an account with DTC, Euroclear or Clearstream, respectively (and
with respect to DTC shall include Euroclear and Clearstream).

         "Payment Restrictions" has the meaning given such term in Section 4.08
hereof.

         "Permitted Business Investment" means any Investment or expenditure
made in the ordinary course of, and of a nature that is or shall have become
customary in, the Oil and Gas Business as a means of actively exploiting,
exploring for, acquiring, developing, producing, processing, gathering,
marketing or transporting oil and gas through agreements, transactions,
interests or arrangements which permit one to share risks or costs, comply with
regulatory requirements regarding local ownership or satisfy other objectives
customarily achieved through the conduct of Oil and Gas Business jointly with
third parties, including (i) ownership interests in oil and gas properties,
processing facilities, gathering systems or ancillary real property interests
and (ii) Investments in the

                                       19
<PAGE>   27

form of or pursuant to operating agreements, processing agreements, farm-in
agreements, farm-out agreements, development agreements, area of mutual interest
agreements, unitization agreements, pooling agreements, joint bidding
agreements, service contracts, joint venture agreements, partnership agreements
(whether general or limited), subscription agreements, stock purchase agreements
and other similar agreements with third parties.

         "Permitted Holders" means (i) Richard Bowman, (ii) any Affiliates of
Richard Bowman or the Parent Guarantor, (iii) Richard Bowman's heirs, estate and
any trust or family limited partnership (or similar estate planning vehicle) in
which Mr. Bowman and/or his Immediate Family members own, directly or
indirectly, at least a majority of the outstanding beneficial interests, and
(iv) Jefferies & Company, Inc. and its Affiliates.

         "Permitted Investment" means an Investment by the Parent Guarantor or
any Restricted Subsidiary in (i) a Restricted Subsidiary or a Person that will,
upon the making of such Investment, become a Restricted Subsidiary; provided,
however, that the primary business of such Restricted Subsidiary is an Oil and
Gas Business; (ii) another Person if as a result of such Investment such other
Person is merged or consolidated with or into, or transfers or conveys all or
substantially all its assets to, the Parent Guarantor or a Restricted
Subsidiary; provided, however, that such Person's primary business is an Oil and
Gas Business; (iii) Temporary Cash Investments; (iv) receivables owing to the
Parent Guarantor or any Restricted Subsidiary if created or acquired in the
ordinary course of business and payable or dischargeable in accordance with
customary trade terms; provided, however, that such trade terms may include such
concessionary trade terms as the Parent Guarantor or any such Restricted
Subsidiary deems reasonable under the circumstances; (v) payroll, travel and
similar advances to cover matters that are expected at the time of such advances
ultimately to be treated as expenses for accounting purposes and that are made
in the ordinary course of business; (vi) loans or advances to employees made in
the ordinary course of business; (vii) stock, obligations or securities received
in settlement of debts created in the ordinary course of business and owing to
the Parent Guarantor or any Restricted Subsidiary or in satisfaction of
judgments; (viii) any Person to the extent such Investment represents the
non-cash portion of the consideration received for an Asset Disposition as
permitted pursuant to the provisions of Section 4.10 hereof and (ix) Permitted
Business Investments.

         "Permitted Joint Venture" means any Person engaged in the Oil and Gas
Business in which the Parent Guarantor or a Restricted Subsidiary makes a
Permitted Business Investment and which cannot, by the terms of such Person's
constituent documents, Incur or Guarantee Indebtedness.

         "Permitted Liens" means, with respect to any Person:

                  (a) pledges or deposits by such Person under workers'
         compensation laws, unemployment insurance laws or similar legislation,
         or good faith deposits in connection with bids, tenders, contracts
         (other than for the payment of Indebtedness) or leases to which such
         Person is a party, or deposits to secure public, statutory or
         regulatory obligations of such Person or deposits of cash or United
         States government bonds to secure surety or appeal bonds to which such
         Person is a party, or deposits as security for contested taxes or
         import duties or for the payment of rent, in each case Incurred in the
         ordinary course of business;

                                       20
<PAGE>   28

                  (b) Liens imposed by law, such as carriers', warehousemen's
         and mechanics' Liens, in each case for sums not yet due or being
         contested in good faith by appropriate proceedings;

                  (c) Liens for property taxes not yet subject to penalties for
         non-payment or which are being contested in good faith and by
         appropriate proceedings;

                  (d) minor survey exceptions, minor encumbrances, easements or
         reservations of, or rights of others for, licenses, rights of way,
         sewers, electric lines, telegraph and telephone lines and other similar
         purposes, or zoning or other restrictions as to the use of real
         property or Liens incidental to the conduct of the business of such
         Person or to the ownership of its properties which were not Incurred in
         connection with Indebtedness and which do not in the aggregate
         materially impair their use in the operation of the business of such
         Person;

                  (e) Liens securing Indebtedness Incurred under clause (b) (6)
         of Section 4.09 hereof; provided, however, that the Lien may not extend
         to any other property owned by such Person or any of its Subsidiaries
         at the time the Lien is Incurred, and the Indebtedness secured by the
         Lien may not be Incurred more than 365 days after the later of the
         acquisition, completion of construction, repair, improvement, addition
         or commencement of full operation of the property subject to the Lien;

                  (f) Liens existing on the Closing Date;

                  (g) Liens securing Indebtedness or other obligations of a
         Subsidiary of such Person owing to such Person or a wholly owned
         Subsidiary of such Person (or, in the case of the Parent Guarantor, a
         Wholly Owned Subsidiary);

                  (h) Liens securing Hedging Obligations pursuant to any
         Interest Rate Agreement so long as such Hedging Obligations relate to
         Indebtedness that is, and is permitted to be Incurred under this
         Indenture, secured by a Lien on the same property (other than
         Collateral) securing such Hedging Obligations;

                  (i) Liens securing Hedging Obligations under the Approved
         Hedge Agreements required to be maintained by the Parent Guarantor and
         the Company under the provisions of Section 4.25 hereof or securing
         obligations to Hedge Liquidity Providers under Hedge Liquidity
         Agreements;

                  (j) Liens on accounts receivable, related general intangibles
         and related proceeds of the Parent Guarantor and its Restricted
         Subsidiaries to secure up to $20,000,000 of Indebtedness under the
         Working Capital Revolver;

                  (k) Liens arising in the ordinary course of business in favor
         of the United States, any state thereof, any foreign country or any
         department, agency, instrumentality or political subdivision of any
         such jurisdiction, to secure partial, progress, advance or other
         payments pursuant to any contract or statute;

                  (l) Liens on pipeline or pipeline facilities which arise out
         of operation of law;

                                       21
<PAGE>   29

                  (m) Liens reserved in oil and gas mineral leases for bonus or
         rental payments and for compliance with the terms of such leases;

                  (n) Liens arising under partnership agreements, oil and gas
         leases, farm-out agreements, division orders, contracts for the sale,
         purchase, exchange, transportation or processing (but not the refining)
         of oil, gas or other hydrocarbons, unitization and pooling declarations
         and agreements, development agreements, operating agreements, area of
         mutual interest agreements and other similar agreements which are
         customary in the Oil and Gas Business;

                  (o) Liens arising out of judgments or awards against such
         Person with respect to which such Person shall then be proceeding with
         an appeal or other proceedings for review; and

                  (p) Liens arising pursuant to this Indenture or any Security
         Document or otherwise securing the Obligations, the Parent Guarantee or
         the Subsidiary Guarantees.

         "Person" means any individual, corporation, partnership, limited
liability company, joint venture, association, joint-stock company, trust,
unincorporated organization, government or any agency or political subdivision
thereof or any other entity.

         "Plan" means the Company's First Amended Plan of Reorganization dated
May 9, 2001, pursuant to Chapter 11 of the United States Bankruptcy Code.

         "Preferred Stock," as applied to the Capital Stock of any Person, means
Capital Stock of any class or classes (however designated) which is preferred as
to the payment of dividends or as to the distribution of assets upon any
voluntary or involuntary liquidation or dissolution of such Person over shares
of Capital Stock of any other class of such Person.

         "principal" of a Note means the stated principal of the Note plus the
premium, if any, payable on the Note which is due or overdue or is to become due
at the relevant time.

         "Principal Amount at Maturity" of a Note means the Principal Amount at
Maturity as set forth on the face of the Note.

         "Production Payments" means, collectively, Dollar-Denominated
Production Payments and Volumetric Production Payments.

         "Projected Consolidated Interest Expense" means, for the Parent
Guarantor and the Restricted Subsidiaries, the amount, calculated on a
consolidated basis as of the first Business Day of each month for the then
current Hedge Period, equal to the pro forma Consolidated Interest Expense of
the Parent Guarantor and the Restricted Subsidiaries for such Hedge Period,
calculated based upon the following assumptions: (i) all obligations giving rise
to any amount characterized as interest in the definition of Consolidated
Interest Expense will be outstanding for the entire balance of such Hedge
Period, except that all scheduled amortization of such obligations will be paid
when due; (ii) if any such obligation bears interest at a floating rate,
interest expense shall be calculated as if the rate in effect on the date of
determination will be in effect for the entire Hedge Period

                                       22
<PAGE>   30

(taking into account any Interest Rate Agreements in respect of such
obligations); and (iii) balances of Indebtedness used to calculate interest
expense shall be increased or decreased, as the case may be, to the extent that
asset acquisitions or dispositions result in additions to or reductions in
interest expense of the Parent Guarantor and the Restricted Subsidiaries.

         "Projected Proved Developed Producing Production" means, as of any date
of determination, for the Parent Guarantor and the Restricted Subsidiaries, the
volumes of hydrocarbons (either crude oil or natural gas or crude oil and
natural gas, on an Mcfe basis, as applicable) that are projected to be produced
from such Persons' proved developed producing oil and natural gas properties
during the then current Hedge Period, in each case as reflected as of the most
recently delivered Reserve Report and after giving effect to any acquisition,
sale, exchange or other disposition of any such Person's Oil and Gas Assets.

         "PV-10 Value" means with respect to any Oil and Gas Assets of the
Parent Guarantor and the Restricted Subsidiaries the aggregate net present value
of such Oil and Gas Assets calculated before income taxes and discounted at 10
percent in accordance with SEC guidelines (including using pricing provisions
based on the most recent year-end prices), as reported in the most recently
prepared or audited report of the Parent Guarantor's independent petroleum
engineers.

         "QIB" means a "qualified institutional buyer" as defined in Rule 144A
under the Securities Act.

         "Refinance" means, in respect of any Indebtedness, to refinance,
extend, renew, refund, repay, prepay, redeem, defease or retire, or to issue
other Indebtedness in exchange or replacement for, such Indebtedness (including
an Incurrence pursuant to clause (iii) of Section 5.01(a), clause (ii) of
Section 5.01(b) or clause (ii) of Section 5.01(c) hereof. "Refinanced" and
"Refinancing" shall have correlative meanings.

         "Refinancing Indebtedness" means Indebtedness that Refinances any
Indebtedness of the Parent Guarantor or any Restricted Subsidiary existing on
the Closing Date or Incurred in compliance with this Indenture, including
Indebtedness that Refinances Refinancing Indebtedness and Indebtedness that is
deemed to be Incurred at the time of a merger or consolidation pursuant to
clause (iii) of Section 5.01(a), clause (ii) of Section 5.01(b) or clause (ii)
of Section 5.01(c) hereof; provided, however, that (i) such Refinancing
Indebtedness has a Stated Maturity no earlier than the Stated Maturity of the
Indebtedness being Refinanced, (ii) such Refinancing Indebtedness has an Average
Life at the time such Refinancing Indebtedness is Incurred that is equal to or
greater than the Average Life of the Indebtedness being Refinanced and (iii)
such Refinancing Indebtedness has an aggregate principal amount (or if Incurred
with original issue discount, an aggregate issue price) that is equal to or less
than the aggregate principal amount (or if Incurred with original issue
discount, the aggregate accreted value) then outstanding or committed (plus fees
and expenses, including any premium and defeasance costs) under the Indebtedness
being Refinanced; provided further, however, that Refinancing Indebtedness shall
not include (x) Indebtedness of a Subsidiary (other than a Subsidiary Guarantor)
that Refinances Indebtedness of the Parent Guarantor or another Subsidiary or
(y) Indebtedness of the Parent Guarantor or a Restricted Subsidiary that
Refinances Indebtedness of an Unrestricted Subsidiary.

                                       23
<PAGE>   31

         "Registration Rights Agreement" means (a) the Registration Rights
Agreement, dated as of the Issue Date, by and among the Company, the Guarantors
and the Initial Purchaser relating to the Original Notes, a copy of which is
attached hereto as Annex A, and (b) any similar agreement that the Company may
enter into in relation to any other Series A Notes, in each case as such
agreement may be amended, modified or supplemented from time to time.

         "Regulation S" means Regulation S under the Securities Act.

         "Regulation S Global Note" means a Regulation S Permanent Global Note
or a Regulation S Temporary Global Note, as appropriate.

         "Regulation S Permanent Global Note" means a permanent global senior
secured note that contains the paragraph referred to in footnote 1 and the
additional schedule referred to in footnote 3 to the form of the Note attached
hereto as Exhibit A-1, and that is deposited with the Note Custodian and
registered in the name of the Depository or its nominee, representing Notes
transferred in reliance on Regulation S.

         "Regulation S Temporary Global Note" means a single temporary global
senior secured note in the form of the Note attached hereto as Exhibit A-2 that
is deposited with the Note Custodian and registered in the name of the
Depository or its nominee, representing Notes transferred in reliance on
Regulation S.

         "Replacement Assets" has the meaning given such term in Section 4.10
hereof.

         "Reserve Report" means the most recently delivered annual report of one
or more independent petroleum engineers of recognized national standing
delivered by the Parent Guarantor pursuant to Section 4.24 hereof.

         "Responsible Officer," when used with respect to the Trustee, means any
officer within the Corporate Trust Department of the Trustee (or any successor
department of the Trustee) or any other officer of the Trustee customarily
performing functions similar to those performed by any of the above designated
officers and also means, with respect to a particular corporate trust matter,
any other officer to whom such matter is referred because of his knowledge of
and familiarity with the particular subject.

         "Restricted Beneficial Interest" means any beneficial interest of a
Participant or Indirect Participant in a Restricted Global Note.

         "Restricted Definitive Notes" means the Definitive Notes that are
required to bear the legend set forth in Section 2.06(f) hereof.

         "Restricted Global Notes" means the 144A Global Note, the IAI Global
Note and the Regulation S Global Note, each of which is required to bear the
legend set forth in Section 2.06(f) hereof.

         "Restricted Payment" with respect to any Person means (i) the
declaration or payment of any dividends or any other distributions of any sort
in respect of its Capital Stock (including any payment

                                       24
<PAGE>   32

in connection with any merger or consolidation involving such Person) or similar
payment to the direct or indirect holders of its Capital Stock (other than (x)
dividends or distributions payable solely in its Capital Stock (other than
Disqualified Stock), (y) dividends or distributions payable solely to the Parent
Guarantor or a Restricted Subsidiary, and (z) pro rata dividends or other
distributions made by a Subsidiary that is not a Wholly Owned Subsidiary to
minority stockholders (or owners of an equivalent interest in the case of a
Subsidiary that is an entity other than a corporation)), (ii) the purchase,
redemption or other acquisition or retirement for value of any Capital Stock of
the Parent Guarantor held by any Person or of any Capital Stock of a Restricted
Subsidiary held by any Affiliate of the Parent Guarantor (other than a
Restricted Subsidiary), including the exercise of any option to exchange any
Capital Stock (other than into Capital Stock of the Parent Guarantor that is not
Disqualified Stock), (iii) the purchase, repurchase, redemption, defeasance or
other acquisition or retirement for value, prior to scheduled maturity,
scheduled repayment or scheduled sinking fund payment of any Subordinated
Obligations, or (iv) the making of any Investment in any Person (other than a
Permitted Investment).

         "Restricted Subsidiary" means any Subsidiary of the Parent Guarantor
that is not an Unrestricted Subsidiary.

         "Rule 144A" means Rule 144A promulgated under the Securities Act.

         "S&P" means Standard & Poor's Ratings Services, a division of The
McGraw-Hill Companies, Inc., or any successor to the rating agency business
thereof.

         "SEC" means the Securities and Exchange Commission.

         "Securities Act" means the Securities Act of 1933, as amended.

         "Security Documents" means, collectively, the Intercreditor Agreement,
the Mortgages, and all security agreements, mortgages, deeds of trust,
collateral assignments or other instruments evidencing or creating any Lien in
favor of the Collateral Agent in all or any portion of the Collateral, in each
case as amended, supplemented or modified from time to time in accordance with
their terms and the terms of this Indenture.

         "Series A Notes" has the meaning attributed thereto in the Recital of
this Indenture.

         "Series B Notes" has the meaning attributed thereto in the Recital of
this Indenture.

         "Stated Maturity" means, with respect to any security, the date
specified in such security as the fixed date on which the final payment of
principal of such security is due and payable, including pursuant to any
mandatory redemption provision (but excluding any provision providing for the
repurchase of such security at the option of the holder thereof upon the
happening of any contingency unless such contingency has occurred).

         "Subordinated Obligations" means any Indebtedness or Preferred Stock of
the Company, the Parent Guarantor or any Subsidiary Guarantor (whether
outstanding on the Closing Date or thereafter Incurred) which is subordinate or
junior in right of payment to the Notes, the Parent Guarantee or any Subsidiary
Guarantee pursuant to a written agreement to that effect.

                                       25
<PAGE>   33

         "Subsidiary" means, with respect to any Person, any corporation,
association, partnership or other business entity of which more than 50% of the
total voting power of shares of Capital Stock or other interests (including
partnership interests) entitled (without regard to the occurrence of any
contingency) to vote in the election of directors, managers or trustees thereof
is at the time owned or controlled, directly or indirectly, by (i) such Person,
(ii) such Person and one or more Subsidiaries of such Person or (iii) one or
more Subsidiaries of such Person. Unless otherwise indicated, references to
Subsidiaries in this Indenture refer to Subsidiaries of the Parent Guarantor.

         "Subsidiary Guarantees" means the joint and several guarantees issued
by all of the Subsidiary Guarantors pursuant to the Guaranty Agreement.

         "Subsidiary Guarantor" means (a) Tri-Union Operating Company, a
Delaware corporation, (b) any other Restricted Subsidiary of the Parent
Guarantor (other than the Company) that executes an Assumption Agreement in the
form of Annex 1 to the Guaranty Agreement and (c) the respective successors and
assigns of such Restricted Subsidiaries, in each case until such time as any
such Restricted Subsidiary shall be released and relieved of its obligations
pursuant to the Guaranty Agreement.

         "Successor Company" has the meaning given such term in Section 5.01
hereof.

         "Synthetic Leases" means in respect of any Person, all leases which
shall have been, or should have been, in accordance with GAAP, treated as
operating leases on the financial statements of the Person liable (whether
contingently or otherwise) for the payment of rent thereunder and which were
properly treated as indebtedness for borrowed money for purposes of United
States federal income taxes, if the lessee in respect thereof is obligated to
either purchase for an amount in excess of, or pay upon early termination an
amount in excess of, 80% of the residual value of the property subject to such
operating lease upon expiration or early termination of such lease.

         "Tack-On Senior Secured Notes" means additional Notes not to exceed
$20,000,000 in aggregate principal amount issued by the Company after the
Closing Date in accordance with clause (a) of Section 4.09 hereof.

         "Temporary Cash Investments" means any of the following: (i) any
investment in direct obligations of the United States or any agency thereof or
obligations guaranteed by the United States or any agency thereof having
maturities not more than 180 days from the date of acquisition, (ii) investments
in time deposit accounts, certificates of deposit and money market deposits
maturing within 180 days of the date of acquisition thereof issued by a bank or
trust company which is organized under the laws of the United States, any state
thereof or any foreign country recognized by the United States, and which bank
or trust company has capital, surplus and undivided profits aggregating in
excess of $50,000,000 (or the foreign currency equivalent thereof) and has
outstanding debt which is rated "A" (or such similar equivalent rating) or
higher by at least one nationally recognized statistical rating organization (as
used in the Securities Act and the Exchange Act and the rules promulgated
thereunder) or any money-market fund sponsored by a registered broker dealer or
mutual fund distributor, (iii) repurchase obligations with a term of not more
than 30 days for underlying securities of the types described in clause (i)
above entered into with a bank meeting the qualifications described in clause
(ii) above, (iv) investments in commercial paper,

                                       26
<PAGE>   34

maturing not more than 180 days after the date of acquisition, issued by a
Person (other than an Affiliate of the Company) organized and in existence under
the laws of the United States or any foreign country recognized by the United
States with a rating at the time as of which any investment therein is made of
"P-2" (or higher) according to Moody's Investors Service, Inc. or "A-2" (or
higher) according to Standard & Poor's Ratings Services, and (v) investments in
securities with maturities of six months or less from the date of acquisition
issued or fully guaranteed by any state, commonwealth or territory of the United
States, or by any political subdivision or taxing authority thereof, and rated
at least "A" by Standard & Poor's Ratings Services or "A" by Moody's Investors
Service, Inc.

         "TIA" means the Trust Indenture Act of 1939 (15 U.S.C. Sections
77aaa-77bbbb) as in effect on the date on which this Indenture is qualified
under the TIA.

         "Transfer Restricted Securities" means securities that bear or are
required to bear the legend set forth in Section 2.06(f) hereof.

         "Trust Moneys" means all cash or Temporary Cash Investments received by
the Trustee:

                  (1) upon the release of Collateral from the Lien of this
         Indenture and the Security Documents, including investment earnings
         thereon;

                  (2) pursuant to the provisions of any Mortgage;

                  (3) as proceeds of any Asset Disposition or other sale or
         other disposition of all or any part of the Collateral by or on behalf
         of the Trustee or any collection, recovery, receipt, appropriation or
         other realization of or from all or any part of the Collateral pursuant
         to this Indenture or any of the Security Documents or otherwise; or

                  (4) for application under this Indenture as provided for in
         this Indenture or the Security Documents, or whose disposition is not
         elsewhere specifically provided for in this Indenture or in the
         Security Documents; provided, however, that Trust Moneys shall not
         include any property deposited with the Trustee pursuant to any Change
         of Control offer, Excess Proceeds Offer or redemption or defeasance of
         any Notes.

         "Trustee" means the party named as such in the first paragraph of this
Indenture until a successor replaces it in accordance with the applicable
provisions of this Indenture and thereafter means the successor serving
hereunder.

         "United States Government Obligations" means direct obligations (or
certificates representing an ownership interest in such obligations) of the
United States (including any agency or instrumentality thereof) for the payment
of which the full faith and credit of the United States is pledged and which are
not callable at the issuer's option.

         "Unrestricted Global Notes" means one or more Global Notes that do not
and are not required to bear the legend set forth in Section 2.06(f) hereof.

                                       27
<PAGE>   35

         "Unrestricted Subsidiary" means (i) any Subsidiary of the Parent
Guarantor (other than the Company) that at the time of determination shall be
designated an Unrestricted Subsidiary by the Board of Directors of the Parent
Guarantor in the manner provided below and (ii) any Subsidiary of an
Unrestricted Subsidiary. The Board of Directors of the Parent Guarantor may
designate any Subsidiary of the Parent Guarantor (including any newly acquired
or newly formed Subsidiary) to be an Unrestricted Subsidiary unless such
Subsidiary or any of its Subsidiaries owns any Capital Stock or Indebtedness of,
or holds any Lien on any property of, the Parent Guarantor or any other
Subsidiary of the Parent Guarantor that is not a Subsidiary of the Subsidiary to
be so designated; provided, however, that the Company may not be designated as
an Unrestricted Subsidiary. The Board of Directors of the Parent Guarantor may
designate any Unrestricted Subsidiary to be a Restricted Subsidiary; provided,
however, that immediately after giving effect to such designation (x) the Parent
Guarantor could Incur $1.00 of additional Indebtedness under paragraph (a) of
Section 4.09 hereof and (y) no Default (including no Default under Section 4.07
hereof) shall have occurred and be continuing or would result from such action.
For the avoidance of doubt, on the date any Restricted Subsidiary is
redesignated to be an Unrestricted Subsidiary, such redesignation shall be
deemed to be an Investment in an Unrestricted Subsidiary in an amount equal to
the fair market value of the assets of that Unrestricted Subsidiary. Any such
designation by the Board of Directors of the Parent Guarantor shall be evidenced
by the Company to the Trustee by promptly filing with the Trustee a copy of the
Board Resolution giving effect to such designation and an Officers' Certificate
certifying that such designation complied with the preceding provisions.

         "Volumetric Production Payments" means production payment obligations
recorded as deferred revenue in accordance with GAAP, together with all
undertakings and obligations in connection therewith.

         "Voting Stock" of a Person means all classes of Capital Stock of such
Person then outstanding and normally entitled (without regard to the occurrence
of any contingency) to vote in the election of directors, managers or trustees
thereof.

         "Wholly Owned Subsidiary" means a Restricted Subsidiary all the Capital
Stock of which (other than directors' qualifying shares and shares held by other
Persons to the extent such shares are required by applicable law to be held by a
Person other than the Parent Guarantor or a Restricted Subsidiary) is owned by
the Parent Guarantor or one or more Wholly Owned Subsidiaries.

         "Working Capital Revolver" means with respect to the Parent Guarantor
or any Restricted Subsidiary, one or more debt facilities or commercial paper
facilities with banks or other institutional lenders providing for revolving
working capital loans.

                                       28
<PAGE>   36

SECTION 1.02.     OTHER DEFINITIONS.

<Table>
<Caption>

                                                                    Defined in
         Term                                                          Section
         ----                                                       ------------
<S>                                                                  <C>
         "Affiliate Transaction"....................................    4.11
         "Change of Control Offer"..................................    4.15
         "Change of Control Payment"................................    4.15
         "Change of Control Payment Date"...........................    4.15
         "Covenant Defeasance"......................................    8.01
         "DTC"......................................................    2.03
         "Event of Default".........................................    6.01
         "Excess Cash Flow Offer"...................................    4.19
         "Excess Cash Flow Offer Period"............................    4.19
         "Excess Cash Flow Payment Date"............................    4.19
         "Excess Proceeds"..........................................    4.10
         "Excess Proceeds Offer"....................................    4.10
         "Excess Proceeds Payment"..................................    4.10
         "Hedge Liquidity Agreements"...............................    4.09
         "Legal Defeasance".........................................    8.01
         "Major Asset Sale".........................................    4.10
         "Major Asset Sale Offer"...................................    4.10
         "Make-Up Period"...........................................    4.25
         "Offer Amount".............................................    3.09
         "Offer Period".............................................    3.09
         "Original Notes"...........................................    2.02
         "Paying Agent".............................................    2.03
         "Payment Default"..........................................    6.01
         "Payment Restrictions".....................................    4.08
         "Purchase Date"............................................    3.09
         "Registrar"................................................    2.03
         "Replacement Assets".......................................    4.10
         "Successor Company"........................................    5.01
</Table>

SECTION 1.03.     INCORPORATION BY REFERENCE OF TRUST INDENTURE ACT.

         Whenever this Indenture refers to a provision of the TIA, the provision
is incorporated by reference in and made a part of this Indenture. Any terms
incorporated in this Indenture that are defined by the TIA, defined by TIA
reference to another statute or defined by SEC rule under the TIA have the
meanings so assigned to them.

SECTION 1.04.     RULES OF CONSTRUCTION.

         Unless the context otherwise requires:

                  (1) a term has the meaning assigned to it;

                  (2) an accounting term not otherwise defined has the meaning
         assigned to it in accordance with GAAP;

                  (3) "or" is not exclusive;

                  (4) words in the singular include the plural, and in the
         plural include the singular;

                  (5) provisions apply to successive events and transactions;

                                       29
<PAGE>   37

                  (6) the term "merger" includes a compulsory share exchange, a
         conversion of a corporation into another business entity and any other
         transaction having effects substantially similar to a merger under the
         Business Corporation Act of the State of Texas; and

                  (7) references to sections of or rules under the Securities
         Act or the Exchange Act shall be deemed to include substitute,
         replacement or successor sections or rules adopted by the SEC from time
         to time.

                                    ARTICLE 2

                                    THE NOTES

SECTION 2.01.     FORM AND DATING.

         The Notes shall be issued only in registered form. The Notes and the
Trustee's certificate of authentication shall be substantially in the form of
Exhibit A-1 or A-2 hereto. The Notes may have notations, legends or endorsements
required by law, stock exchange rule or usage. Each Note shall be dated the date
of its authentication. The Notes shall be issued in denominations of $1,000 and
integral multiples thereof.

         The Series A Notes and the Series B Notes shall be considered
collectively to be a single class for all purposes of this Indenture, including,
without limitation, waivers, amendments, redemptions and offers to purchase.

         The terms and provisions contained in the Notes shall constitute, and
are hereby expressly made, a part of this Indenture and the Company, the Parent
Guarantor and the Trustee, by their execution and delivery of this Indenture,
expressly agree to such terms and provisions and to be bound thereby.
Notwithstanding the foregoing, to the extent any provision of any Note conflicts
with the express provisions of this Indenture, the provisions of this Indenture
shall govern and be controlling.

         (a) Global Notes. Series A Notes offered and sold to QIBs in reliance
on Rule 144A shall be issued initially in the form of one or more 144A Global
Notes, which shall be deposited on behalf of the purchasers of the Series A
Notes represented thereby with the Note Custodian and registered in the name of
the Depository or a nominee of the Depository, duly executed by the Company and
authenticated by the Trustee as hereinafter provided.

         Series A Notes offered and sold to Institutional Accredited Investors
shall be issued initially in the form of one or more IAI Global Notes, which
shall be deposited on behalf of the purchasers of the Series A Notes represented
thereby with the Note Custodian and registered in the name of the Depository or
a nominee of the Depository, duly executed by the Company and authenticated by
the Trustee as hereinafter provided.

         Any Series A Notes transferred during the 40-day restricted period (as
defined in Regulation S) offered and sold in reliance on Regulation S shall be
issued initially in the form of the Regulation S Temporary Global Note, which
shall be deposited on behalf of the purchasers of the

                                       30
<PAGE>   38

Series A Notes represented thereby with the Note Custodian and registered in the
name of the Depository or the nominee of the Depository for the accounts of
designated agents holding on behalf of Euroclear or Clearstream, duly executed
by the Company and authenticated by the Trustee as hereinafter provided. The
"40-day restricted period" shall be terminated upon the receipt by the Trustee
of (i) a written certificate from the Depository, together with copies of
certificates from Euroclear and Clearstream certifying that they have received
certification of non-United States beneficial ownership of 100% of the aggregate
principal amount of the Regulation S Temporary Global Note (except to the extent
of any beneficial owners thereof who acquired an interest therein pursuant to
another exemption from registration under the Securities Act and who will take
delivery of a beneficial ownership interest in a 144A Global Note or an IAI
Global Note, all as contemplated by Section 2.06(a)(ii) or (iii) hereof), and
(ii) an Officers' Certificate from the Company. Following the termination of the
40-day restricted period, beneficial interests in the Regulation S Temporary
Global Note shall be exchanged for beneficial interests in one or more
Regulation S Permanent Global Notes pursuant to the Applicable Procedures.
Simultaneously with the authentication of Regulation S Permanent Global Notes,
the Trustee shall cancel the Regulation S Temporary Global Note.

         Each Global Note shall represent such of the outstanding Notes as shall
be specified therein and each shall provide that it shall represent the
aggregate amount of outstanding Notes from time to time endorsed thereon and
that the aggregate amount of outstanding Notes represented thereby may from time
to time be reduced or increased, as appropriate, to reflect exchanges,
installment payments, redemptions, repurchases and transfers of interests. Any
endorsement of a Global Note to reflect the amount of any increase or decrease
in the amount of outstanding Notes represented thereby shall be made by the
Trustee or the Note Custodian, at the direction of the Trustee, in accordance
with instructions given by the Holder thereof as required by Section 2.06
hereof.

         (b) Book-Entry Provisions. Participants shall have no rights either
under this Indenture with respect to any Global Note held on their behalf by the
Depository or by the Note Custodian as custodian for the Depository or under
such Global Note, and the Depository (or its nominee, if the Depository is not
the Holder) may be treated by the Company, the Trustee and any Agent of the
Company or the Trustee as the absolute owner of such Global Note for all
purposes whatsoever. Notwithstanding the foregoing, nothing herein shall prevent
the Company, the Trustee or any Agent of the Company or the Trustee from giving
effect to any written certification, proxy or other authorization furnished by
the Depository or impair, as between the Depository and its Participants, the
operation of customary practices of such Depository governing the exercise of
the rights of an owner of a beneficial interest in any Global Note.

SECTION 2.02.     EXECUTION AND AUTHENTICATION.

         One Officer shall sign the Notes for the Company by manual or facsimile
signature. If the Company has a corporate seal, it may be reproduced on the
Notes and, if so, it may be in facsimile form.

         If an Officer whose signature is on a Note no longer holds that office
at the time a Note is authenticated, the Note shall nevertheless be valid.

                                       31
<PAGE>   39

         A Note shall not be valid until authenticated by the manual signature
of an authorized signatory of the Trustee. Such signature shall be conclusive
evidence that the Note has been authenticated under this Indenture. The form of
Trustee's certificate of authentication to be borne by the Notes shall be
substantially as set forth in Exhibit A-1 or A-2 hereto.

         Each Note shall be dated the date of its authentication.

         The Trustee shall authenticate (i) the Series A Notes for original
issue on the Issue Date in the aggregate principal amount of $130,000,000 (the
"Original Notes"), (ii) additional Series A Notes for original issue from time
to time after the Issue Date in such principal amounts not to exceed $20,000,000
in the aggregate as may be set forth in a written order of the Company described
in this sentence and (iii) the Series B Notes for original issue from time to
time for issue only in exchange for a like principal amount of Series A Notes,
in each case upon a written order of the Company signed by one Officer, which
written order shall specify (a) the amount of Notes to be authenticated and the
date of original issue thereof, (b) whether the Notes are Series A Notes or
Series B Notes, and (c) the amount of Notes to be issued in global form or
definitive form. The aggregate principal amount of Notes outstanding at any time
may not exceed $130,000,000 plus such additional principal amounts as may be
issued and authenticated pursuant to clause (ii) of this paragraph, except as
provided in Section 2.07 hereof.

         The Trustee may appoint an authenticating agent acceptable to the
Company to authenticate Notes. An authenticating agent may authenticate Notes
whenever the Trustee may do so. Each reference in this Indenture to
authentication by the Trustee includes authentication by such agent. An
authenticating agent has the same rights as an Agent to deal with the Company,
any Guarantor or an Affiliate of the Company.

SECTION 2.03.     REGISTRAR AND PAYING AGENT.

         The Company shall maintain an office or agency in the continental
United States where Notes may be presented for registration of transfer or for
exchange ("Registrar"). The Company shall also maintain an office or agency in
the continental United States where Notes may be presented for payment ("Paying
Agent"), which shall initially be the agency of the Trustee located in the
Borough of Manhattan, New York, New York. The Registrar shall keep a register of
the Notes and of their transfer and exchange. The Company may appoint one or
more co-registrars and one or more additional paying agents. The term
"Registrar" includes any co-registrar and the term "Paying Agent" includes any
additional paying agent. The Company may change any Paying Agent or Registrar
without notice to any Holder. The Company shall notify the Trustee in writing of
the name and address of any Agent not named in this Indenture. If the Company
fails to appoint or maintain another entity as Registrar or Paying Agent, the
Trustee shall act as such. The Company shall enter into an appropriate agency
agreement with any Agent not a party to this Indenture, and such agreement shall
incorporate the TIA's provisions of this Indenture that relate to such Agent.
The Company or any of its Subsidiaries may act as Paying Agent or Registrar.

         The Company initially appoints The Depository Trust Company ("DTC") to
act as Depository with respect to the Global Notes.

                                       32
<PAGE>   40

         The Company initially appoints the Trustee to act as Registrar at its
Corporate Trust Office, to act as Paying Agent at its agency in the Borough of
Manhattan in New York, New York, and to act as Note Custodian with respect to
the Global Notes.

SECTION 2.04.     PAYING AGENT TO HOLD MONEY IN TRUST.

         The Company shall require each Paying Agent other than the Trustee to
agree in writing that the Paying Agent will hold in trust for the benefit of
Holders or the Trustee all money held by the Paying Agent for the payment of
principal of or premium, interest or Liquidated Damages, if any, on the Notes,
and will notify the Trustee of any default by the Company in making any such
payment. While any such default continues, the Trustee may require a Paying
Agent to pay all money held by it to the Trustee. The Company at any time may
require a Paying Agent to pay all money held by it to the Trustee. Upon payment
over to the Trustee, the Paying Agent (if other than the Company or a
Subsidiary) shall have no further liability for the money. If the Company or a
Subsidiary acts as Paying Agent, it shall segregate and hold in a separate trust
fund for the benefit of the Holders all money held by it as Paying Agent. Upon
the occurrence and during the continuance of any Event of Default described in
clause (h) or (i) of Section 6.01 hereof, the Trustee shall serve as Paying
Agent for the Notes.

SECTION 2.05.     HOLDER LISTS.

         The Trustee shall preserve in as current a form as is reasonably
practicable the most recent list available to it of the names and addresses of
all Holders and shall otherwise comply with TIA Section 312(a). If the Trustee
is not the Registrar, the Company shall furnish to the Trustee at least seven
Business Days before each interest payment date and at such other times as the
Trustee may request in writing, a list in such form and as of such date as the
Trustee may reasonably require of the names and addresses of the Holders of
Notes and the Company shall otherwise comply with TIA Section 312(a).

SECTION 2.06.     TRANSFER AND EXCHANGE.

         (a) Transfer and Exchange of Global Notes. The transfer and exchange of
Global Notes or beneficial interests therein shall be effected through the
Depository, in accordance with this Indenture and the Applicable Procedures.
Transfers of beneficial interests in the Restricted Global Notes shall be
permitted as follows:

                  (i) Restricted Global Note to Regulation S Global Note. If an
         owner of a beneficial interest in a Restricted Global Note wishes to
         transfer its beneficial interest in such Global Note to a Person who is
         required or permitted to take delivery thereof in the form of an
         interest in a Regulation S Global Note, such owner shall, subject to
         the Applicable Procedures, exchange or cause the exchange of such
         interest for an equivalent beneficial interest in a Regulation S Global
         Note as provided in this Section 2.06(a)(i). Upon receipt by the
         Trustee of (A) instructions given in accordance with the Applicable
         Procedures directing the Trustee, as Registrar and Note Custodian, to
         credit a beneficial interest in the Regulation S Global Note in an
         amount equal to the beneficial interest in the Restricted Global Note
         to be transferred and (B) a certificate substantially in the form of
         Exhibit B-1 hereto given by the owner of such beneficial interest
         stating that the transfer of such interest

                                       33
<PAGE>   41

         has been made in compliance with the transfer restrictions applicable
         to the Restricted Global Notes and pursuant to and in accordance with
         Rule 903 or Rule 904 of Regulation S, then the Trustee, as Registrar
         and Note Custodian, shall reduce the aggregate principal amount of such
         Restricted Global Note and increase the aggregate principal amount of
         the applicable Regulation S Global Note by the principal amount of the
         beneficial interest in the Restricted Global Note to be transferred.

                  (ii) Restricted Global Note to 144A Global Note. If an owner
         of a beneficial interest in a Restricted Global Note wishes to transfer
         its beneficial interest in such Restricted Global Note to a Person who
         is required or permitted to take delivery thereof in the form of an
         interest in a 144A Global Note, such owner shall, subject to the
         Applicable Procedures, exchange or cause the exchange of such interest
         for an equivalent beneficial interest in a 144A Global Note as provided
         in this Section 2.06(a)(ii). Upon receipt by the Trustee of (A)
         instructions given in accordance with the Applicable Procedures
         directing the Trustee, as Registrar and Note Custodian, to credit a
         beneficial interest in the 144A Global Note equal to the beneficial
         interest in the Restricted Global Note to be transferred and (B) a
         certificate substantially in the form of Exhibit B-2 attached hereto
         given by the owner of such beneficial interest stating that the Person
         transferring such interest in a Restricted Global Note reasonably
         believes that the Person acquiring such interest in a 144A Global Note
         is a QIB and is obtaining such beneficial interest in a transaction
         meeting the requirements of Rule 144A, then the Trustee, as Registrar
         and Note Custodian, shall reduce the aggregate principal amount of such
         Restricted Global Note and increase the aggregate principal amount of
         the applicable 144A Global Note by the principal amount of the
         beneficial interest in the Restricted Global Note to be transferred.

                  (iii) Restricted Global Note to IAI Global Note. If an owner
         of a beneficial interest in a Restricted Global Note wishes to transfer
         its beneficial interest in such Restricted Global Note to a Person who
         is required to take delivery thereof in the form of an interest in an
         IAI Global Note, such owner shall, subject to the Applicable
         Procedures, exchange or cause the exchange of such interest for an
         equivalent beneficial interest in an IAI Global Note as provided in
         this Section 2.06(a)(iii). Upon receipt by the Trustee of (A)
         instructions given in accordance with the Applicable Procedures
         directing the Trustee, as Registrar and Note Custodian, to credit a
         beneficial interest in the IAI Global Note equal to the beneficial
         interest in the Restricted Global Note to be transferred and (B) a
         certificate substantially in the form of Exhibit B-2 hereto from the
         transferor and a certificate substantially in the form of Exhibit C
         hereto from the transferee, then the Trustee, as Registrar and Note
         Custodian, shall reduce the aggregate principal amount of such
         Restricted Global Note and increase the aggregate principal amount of
         the applicable IAI Global Note by the principal amount of the
         beneficial interest in the Restricted Global Note to be transferred.

                  (iv) Restricted Global Note to Unrestricted Global Note. If an
         owner of a beneficial interest in a Restricted Global Note wishes to
         transfer its beneficial interest in such Restricted Global Note to a
         Person who is required or permitted to take delivery thereof in the
         form of an interest in an Unrestricted Global Note, such owner shall,
         subject to the Applicable Procedures, exchange or cause the exchange of
         such interest for an equivalent beneficial interest in an Unrestricted
         Global Note as provided in this Section 2.06(a)(iv).

                                       34
<PAGE>   42

         Upon receipt by the Trustee of (A) instructions given in accordance
         with the Applicable Procedures directing the Trustee, as Registrar and
         Note Custodian, to credit a beneficial interest in an Unrestricted
         Global Note equal to the beneficial interest in the Restricted Global
         Note to be transferred and (B) a certificate substantially in the form
         of Exhibit B-3 attached hereto given by the owner of such beneficial
         interest stating (1) if the transfer is pursuant to Rule 144, that the
         transfer complies with the requirements of Rule 144, (2) the transfer
         is pursuant to an effective registration statement under the Securities
         Act, or (3) the transfer is to the Company or any of its Subsidiaries,
         then the Trustee, as Registrar and Note Custodian, shall reduce the
         aggregate principal amount of such Restricted Global Note and increase
         the aggregate principal amount of the applicable Unrestricted Global
         Note by the principal amount of the beneficial interest in the
         Restricted Global Note to be transferred.

         (b) Transfer and Exchange of Definitive Notes. If issued, Definitive
Notes may not be exchanged or transferred for beneficial interests in a Global
Note, except upon consummation of an Exchange Offer as contemplated by Section
2.06(f)(iv) hereof. When Definitive Notes are presented by a Holder to the
Registrar with a request to register the transfer of the Definitive Notes or to
exchange such Definitive Notes for an equal principal amount of Definitive Notes
of other authorized denominations, the Registrar shall register the transfer or
make the exchange as requested only if the Definitive Notes are presented or
surrendered for registration of transfer or exchange, are endorsed or
accompanied by a written instrument of transfer in form satisfactory to the
Registrar duly executed by such Holder or by its attorney, duly authorized in
writing, and the Registrar receives the following (all of which may be submitted
by facsimile):

                  (i) in the case of Definitive Notes that are Transfer
         Restricted Securities, such request shall be accompanied by the
         following additional information and documents, as applicable:

                           (A) if such Transfer Restricted Security is being
                  delivered to the Registrar by a Holder for registration in the
                  name of such Holder, without transfer, or such Transfer
                  Restricted Security is being transferred (1) to the Company or
                  any of its Subsidiaries, (2) in a transaction permitted by
                  Rule 144 under the Securities Act or (3) pursuant to an
                  effective registration statement under the Securities Act, a
                  certification to that effect from such Holder (substantially
                  in the form of Exhibit B-3 hereto);

                           (B) if such Transfer Restricted Security is being
                  transferred to a Person the transferor reasonably believes is
                  a QIB in accordance with Rule 144A under the Securities Act or
                  pursuant to an exemption from registration in accordance with
                  Rule 144 under the Securities Act, a certification to that
                  effect from such Holder (in substantially the form of Exhibit
                  B-3 hereto);

                           (C) if such Transfer Restricted Security is being
                  transferred to a Non-U.S. Person in an offshore transaction in
                  accordance with Rule 903 or 904 under Regulation S of the
                  Securities Act, a certification to that effect from such
                  Holder (substantially in the form of Exhibit B-3 hereto but
                  containing the certification called for by clauses (1) through
                  (4) of Exhibit B-1 hereto); or

                                       35
<PAGE>   43

                           (D) if such Transfer Restricted Security is being
                  transferred to an Institutional Accredited Investor in
                  reliance on an exemption from the registration requirements of
                  the Securities Act other than those listed in subparagraph (B)
                  or (C) above, a certification to that effect from such Holder
                  (substantially in the form of Exhibit B-3 hereto), and a
                  certification substantially in the form of Exhibit C hereto
                  from the transferee.

         (c) [Intentionally omitted.]

         (d) Restrictions on Transfer and Exchange of Global Notes.
Notwithstanding any other provision of this Indenture, a Global Note may not be
transferred as a whole except by the Depository to a nominee of the Depository
or by a nominee of the Depository to the Depository or another nominee of the
Depository or by the Depository or any such nominee to a successor Depository or
a nominee of such successor Depository.

         (e) Authentication of Definitive Notes in Absence of Depository or at
Company's Election. If at any time (i) the Depository for the Notes notifies the
Company that the Depository is unwilling or unable to continue as Depository for
the Global Notes or has ceased to be a clearing agency registered under the
Exchange Act and in either case a successor Depository for the Global Notes is
not appointed by the Company within 90 days after delivery of such notice or
(ii) the Company, at its option, notifies the Trustee in writing that it elects
to cause the issuance of Definitive Notes, then the Company shall execute, and
the Trustee shall, upon receipt of an authentication order in accordance with
Section 2.02 hereof, authenticate and deliver Definitive Notes in an aggregate
principal amount equal to the principal amount of the Global Notes in exchange
for such Global Notes. Definitive Notes issued in exchange for beneficial
interests in the Global Notes pursuant to this Section 2.06(e) shall be
registered in such names and in such authorized denominations as the Depository,
pursuant to instructions from its direct or Indirect Participants or otherwise,
shall instruct the Trustee. The Trustee shall deliver such Definitive Notes to
the Persons in whose names such Notes are so registered.

         (f) Legends.

                  (i) Except as permitted by the following paragraphs (ii) and
         (iv), each Note certificate evidencing a Global Note or a Definitive
         Note (and all Notes issued in exchange therefor or substitution
         thereof) shall bear a legend in substantially the following form, until
         the expiration of the applicable holding period with respect to the
         Notes set forth in Rule 144(k) promulgated under the Securities Act:

                  "THE SECURITY (OR ITS PREDECESSORS) EVIDENCED HEREBY HAS NOT
                  BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED
                  (THE "SECURITIES ACT") OR ANY STATE SECURITIES LAWS AND WAS
                  ORIGINALLY ISSUED IN A TRANSACTION EXEMPT FROM REGISTRATION
                  UNDER SECTION 5 OF THE SECURITIES ACT. THE SECURITY EVIDENCED
                  HEREBY MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED IN
                  THE ABSENCE OF SUCH REGISTRATION OR AN APPLICABLE

                                       36
<PAGE>   44

                  EXEMPTION THEREFROM. EACH PURCHASER OF THE SECURITY EVIDENCED
                  HEREBY IS HEREBY NOTIFIED THAT THE SELLER MAY BE RELYING ON
                  THE EXEMPTION FROM THE PROVISIONS OF SECTION 5 OF THE
                  SECURITIES ACT PROVIDED BY RULE 144A THEREUNDER. THE HOLDER OF
                  THE SECURITY EVIDENCED HEREBY AGREES FOR THE BENEFIT OF THE
                  COMPANY THAT PRIOR TO THE DATE WHICH IS TWO YEARS (OR SUCH
                  SHORTER PERIOD THAT MAY HEREAFTER BE PROVIDED UNDER RULE
                  144(K) AS PERMITTING RESALES BY NON-AFFILIATES OF RESTRICTED
                  SECURITIES WITHOUT REGISTRATION), AFTER THE LATER OF THE DATE
                  OF ORIGINAL ISSUE AND THE LAST DATE ON WHICH THE COMPANY OR
                  ANY OF ITS AFFILIATES WERE THE OWNER OF THE SECURITY EVIDENCED
                  HEREBY (OR ANY PREDECESSOR THEREOF) (A) SUCH SECURITY MAY BE
                  RESOLD, PLEDGED OR OTHERWISE TRANSFERRED, ONLY (1) TO THE
                  COMPANY, (2) FOR SO LONG AS THE SECURITIES ARE ELIGIBLE FOR
                  RESALE PURSUANT TO RULE 144A, TO A PERSON WHO THE SELLER
                  REASONABLY BELIEVES IS AN INSTITUTIONAL INVESTOR THAT IS A
                  QUALIFIED INSTITUTIONAL BUYER IN A TRANSACTION MEETING THE
                  REQUIREMENTS OF RULE 144A, (3) TO AN INSTITUTIONAL "ACCREDITED
                  INVESTOR" WITHIN THE MEANING OF RULE 501(a)(1), (2), (3) OR
                  (7) UNDER THE SECURITIES ACT THAT IS PURCHASING FOR ITS OWN
                  ACCOUNT OR FOR THE ACCOUNT OF SUCH AN INSTITUTIONAL
                  "ACCREDITED INVESTOR" FOR INVESTMENT PURPOSES AND NOT WITH A
                  VIEW TO, OR FOR OFFER OR SALE IN CONNECTION WITH, ANY
                  DISTRIBUTION VIOLATION OF THE SECURITIES ACT (AND BASED UPON
                  AN OPINION OF COUNSEL IF THE COMPANY SO REQUESTS), (4) IN A
                  TRANSACTION MEETING THE REQUIREMENTS OF RULE 144 UNDER THE
                  SECURITIES ACT (IF AVAILABLE), (5) OUTSIDE THE UNITED STATES
                  IN AN OFFSHORE TRANSACTION MEETING THE REQUIREMENTS OF
                  REGULATION S UNDER THE SECURITIES ACT, (6) IN ACCORDANCE WITH
                  ANOTHER EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE
                  SECURITIES ACT (AND BASED UPON AN OPINION OF COUNSEL IF THE
                  COMPANY SO REQUESTS), OR (7) PURSUANT TO AN EFFECTIVE
                  REGISTRATION STATEMENT AND, IN EACH CASE, IN ACCORDANCE WITH
                  ANY APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED
                  STATES OR ANY OTHER APPLICABLE JURISDICTION AND (B) THE HOLDER
                  WILL, AND EACH SUBSEQUENT HOLDER IS REQUIRED TO, NOTIFY ANY
                  PURCHASER FROM IT OF THE SECURITY EVIDENCED HEREBY OF THE
                  RESALE RESTRICTIONS SET FORTH IN (A) ABOVE."

                                       37
<PAGE>   45

                  (ii) Upon any sale or transfer of a Transfer Restricted
         Security (including any Transfer Restricted Security represented by a
         Global Note) pursuant to Rule 144 under the Securities Act or pursuant
         to an effective registration statement under the Securities Act:

                           (A) in the case of any Transfer Restricted Security
                  that is a Definitive Note, the Registrar shall permit the
                  Holder thereof to exchange such Transfer Restricted Security
                  for a Definitive Note that does not bear the legend set forth
                  in (i) above and rescind any restriction on the transfer of
                  such Transfer Restricted Security upon certification from the
                  transferring holder substantially in the form of Exhibit B-3
                  hereto; and

                           (B) in the case of any beneficial interest in a
                  Restricted Global Note, such interest shall be sold or
                  transferred in compliance with the provisions of Section
                  2.06(a)(iv) hereof and the Global Note thereafter representing
                  such interest shall not be sold or transferred in compliance
                  with the provisions of Section 2.06(a)(iv) hereof and the
                  Global Note thereafter representing such interest shall not be
                  required to bear the legend set forth in (i) above.

         (g) Cancellation or Adjustment of Global Notes. At such time as all
beneficial interests in Global Notes have been exchanged for Definitive Notes,
redeemed, repurchased or cancelled, all Global Notes shall be returned to or
retained and cancelled by the Trustee in accordance with Section 2.11 hereof. At
any time prior to such cancellation, if any beneficial interest in a Global Note
is exchanged for Definitive Notes or a beneficial interest in another Global
Note, repaid, redeemed, repurchased or cancelled, the principal amount of Notes
represented by such Global Note shall be reduced accordingly and an endorsement
shall be made on such Global Note by the Trustee, as Registrar and Note
Custodian, to reflect such reduction; and if the beneficial interest is being
exchanged or transferred to a Person who will take delivery thereof in the form
of a beneficial interest in another Global Note, such other Global Note shall be
increased accordingly and an endorsement shall be made on such Global Note by
the Trustee, as Registrar and Note Custodian, to reflect such increase.

         (h) General Provisions Relating to Transfers and Exchanges.

                  (i) To permit registrations of transfers and exchanges,
         subject to this Section 2.06, the Company shall execute and, upon the
         written order of the Company signed by an Officer of the Company, the
         Trustee shall authenticate Definitive Notes and Global Notes at the
         Registrar's request.

                  (ii) No service charge shall be made to a Holder for any
         registration of transfer or exchange, but the Company may require
         payment of a sum sufficient to cover any transfer tax or similar
         governmental charge payable in connection therewith (other than any
         such transfer taxes or similar governmental charge payable upon
         exchange or transfer pursuant to Sections 3.07, 4.10, 4.15 and 9.05
         hereof).

                  (iii) Notwithstanding any other provision of this Section
         2.06, prior to 40 days after the later of the commencement of the
         offering of any Series A Notes and the date of

                                       38
<PAGE>   46

         original issuance of such Notes, beneficial interests in a Regulation S
         Global Note may be held only through Euroclear or Clearstream (as
         Indirect Participants in DTC), unless transferred to a Person that
         takes delivery through a 144A Global Note or an IAI Global Note in
         accordance with Section 2.06(a)(ii) or (iii) hereof.

                  (iv) All Definitive Notes and Global Notes issued upon any
         registration of transfer or exchange of Definitive Notes or Global
         Notes shall be the valid obligations of the Company, evidencing the
         same debt, and entitled to the same benefits under this Indenture, as
         the Definitive Notes or Global Notes surrendered upon such registration
         of transfer or exchange.

                  (v) The Company and the Registrar shall not be required:

                           (A) to issue, to register the transfer of or to
                  exchange Notes during a period beginning at the opening of
                  business 15 days before the day of any selection of Notes for
                  redemption under Section 3.02 hereof and ending at the close
                  of business on the day of selection;

                           (B) to register the transfer of or to exchange any
                  Note so selected for redemption in whole or in part, except
                  the unredeemed portion of any Note being redeemed in part; or

                           (C) to register the transfer of a Note other than in
                  amounts of $1,000 or multiple integrals thereof.

                  (vi) Prior to due presentment for the registration of a
         transfer of any Note, the Trustee, any Agent and the Company may deem
         and treat the Person in whose name any Note is registered as the
         absolute owner of such Note for the purpose of receiving payment of
         principal of, premium, if any, interest and Liquidated Damages, if any,
         on such Notes, and neither the Trustee, any Agent nor the Company shall
         be affected by notice to the contrary.

                  (vii) The Trustee shall authenticate Definitive Notes and
         Global Notes in accordance with the provisions of Sections 2.02 and
         2.06(h)(i) hereof.

SECTION 2.07.     REPLACEMENT NOTES.

         If any mutilated Note is surrendered to the Trustee or the Company, or
the Trustee receives evidence to its satisfaction of the destruction, loss or
theft of any Note, the Company shall issue and the Trustee, upon the written
order of the Company signed by one Officer of the Company, shall authenticate a
replacement Note if the Trustee's requirements are met. If required by the
Trustee and the Company, an indemnity bond must be supplied by the Holder that
is sufficient in the judgment of the Trustee and the Company to protect the
Company, the Trustee, any Agent and any authenticating agent from any loss that
any of them may suffer if a Note is replaced. The Company may charge for its
expenses in replacing a Note. If, after the delivery of such replacement Note, a
bona fide purchaser of the original Note in lieu of which such replacement Note
was issued presents for payment or registration such original Note, the Trustee
shall be entitled to recover such replacement Note from the Person to whom it
was delivered or any Person taking therefrom, except

                                       39
<PAGE>   47

a bona fide purchaser, and shall be entitled to recover upon the security or
indemnity provided therefor to the extent of any loss, damage, cost or expense
incurred by the Company, the Trustee, any Agent and any authenticating agent in
connection therewith.

         Subject to the provisions of the final sentence of the preceding
paragraph of this Section 2.07, every replacement Note is an additional
obligation of the Company and shall be entitled to all of the benefits of this
Indenture equally and proportionately with all other Notes duly issued
hereunder.

SECTION 2.08.     OUTSTANDING NOTES.

         The Notes outstanding at any time are all the Notes authenticated by
the Trustee except for those cancelled by it, those delivered to it for
cancellation, those reductions in the interests in a Global Note effected by the
Trustee in accordance with the provisions hereof, and those described in this
Section as not outstanding. Except as set forth in Section 2.09 hereof, a Note
does not cease to be outstanding because the Company, the Parent Guarantor, any
Subsidiary of the Parent Guarantor or an Affiliate of the Parent Guarantor holds
the Note.

         If a Note is replaced pursuant to Section 2.07 hereof, it ceases to be
outstanding unless the Trustee receives proof satisfactory to it that the
replaced Note is held by a bona fide purchaser.

         If the entire principal of and premium, interest and Liquidated
Damages, if any, on any Note are considered paid under Section 4.01 hereof, it
ceases to be outstanding and interest and Liquidated Damages, if any, on it
cease to accrue as of the date of such payment.

SECTION 2.09.     TREASURY NOTES.

         In determining whether the Holders of the required principal amount of
Notes have concurred in any direction, waiver or consent, Notes owned by the
Company, the Parent Guarantor, a Subsidiary of the Parent Guarantor or an
Affiliate of the Parent Guarantor , shall be considered as though not
outstanding, except that for the purposes of determining whether the Trustee
shall be protected in relying on any such direction, waiver or consent, only
Notes that a Trustee knows are so owned shall be so disregarded. Notwithstanding
the foregoing, Notes that the Company, the Parent Guarantor, a Subsidiary of the
Parent Guarantor or an Affiliate of the Parent Guarantor offers to purchase or
acquires pursuant to an offer, exchange offer, tender offer or otherwise shall
not be deemed to be owned by the Company, the Parent Guarantor, a Subsidiary of
the Parent Guarantor or an Affiliate of the Parent Guarantor until legal title
to such Notes passes to the Company, such Subsidiary or such Affiliate as the
case may be.

SECTION 2.10.     TEMPORARY NOTES.

         Until definitive Notes are ready for delivery, the Company may prepare
and the Trustee shall authenticate temporary Notes upon a written order of the
Company signed by one Officer of the Company. Temporary Notes shall be
substantially in the form of definitive Notes but may have variations that the
Company considers appropriate for temporary Notes and as shall be reasonably
acceptable to the Trustee. Without unreasonable delay, the Company shall prepare
and the Trustee

                                       40
<PAGE>   48

shall authenticate definitive Notes in exchange for temporary Notes. Until such
exchange, Holders of temporary Notes shall be entitled to all of the benefits of
this Indenture.

SECTION 2.11.     CANCELLATION.

         The Company at any time may deliver Notes to the Trustee for
cancellation. The Registrar and Paying Agent shall forward to the Trustee any
Notes surrendered to them for registration of transfer, exchange or payment. The
Trustee and no one else shall cancel all Notes surrendered for registration of
transfer, exchange, payment, replacement or cancellation and, at the request of
the Company, shall destroy cancelled Notes (subject to the record retention
requirement of the Exchange Act). Certification of the destruction of all
cancelled Notes shall be delivered to the Company upon its written request. The
Company may not issue new Notes to replace Notes that it has paid or that have
been delivered to the Trustee for cancellation, other than as contemplated by
the Exchange Offer.

SECTION 2.12.     DEFAULT INTEREST.

         If the Company defaults in a payment of interest on the Notes, it shall
pay the default interest in any lawful manner plus, to the extent lawful,
interest payable on the default interest, to the Persons who are Holders on a
subsequent special record date, in each case at the rate provided in the Notes
and in Section 4.01 hereof. The Company shall notify the Trustee in writing of
the amount of default interest proposed to be paid on each Note and the date of
the proposed payment. The Company shall fix or cause to be fixed each such
special record date and payment date, provided, however, that no such special
record date shall be less than 10 days prior to the related payment date for
such default interest. At least 15 days before the special record date, the
Company (or, upon the written request of the Company, the Trustee in the name
and at the expense of the Company) shall mail or cause to be mailed to Holders a
notice that states the special record date, the related payment date and the
amount of such interest to be paid.

                                    ARTICLE 3

                            REDEMPTION AND REPURCHASE

SECTION 3.01.     NOTICES TO TRUSTEE.

         If the Company elects to redeem Notes pursuant to the optional
redemption provisions of Section 3.07 hereof, it shall furnish to the Trustee,
at least 30 days but not more than 60 days before a redemption date, an
Officers' Certificate setting forth (i) the clause of this Indenture pursuant to
which the redemption shall occur, (ii) the redemption date, (iii) the principal
amount of Notes to be redeemed and (iv) the redemption price.

SECTION 3.02.     SELECTION OF NOTES TO BE REDEEMED

         If less than all of the Notes are to be redeemed at any time, the
Trustee shall select the Notes to be redeemed among the Holders of the Notes on
a pro rata basis, by lot or in accordance with any other method the Trustee in
its sole discretion considers fair and appropriate. In the event of partial
redemption by lot, the particular Notes to be redeemed shall be selected, unless
otherwise provided

                                       41
<PAGE>   49

herein, not less than 30 days nor more than 60 days prior to the redemption date
by the Trustee from the outstanding Notes not previously called for redemption.

         The Trustee shall promptly notify the Company in writing of the Notes
selected for redemption and, in the case of any Note selected for partial
redemption, the principal amount thereof to be redeemed. Notes and portions of
Notes selected shall be in amounts of $1,000 or whole multiples of $1,000.
Provisions of this Indenture that apply to Notes called for redemption also
apply to portions of Notes called for redemption.

         The provisions of the two preceding paragraphs of this Section 3.02
shall not apply with respect to any redemption affecting only a Global Note,
whether such Global Note is to be redeemed in whole or in part. In case of any
such redemption in part, the unredeemed portion of the principal amount of the
Global Note shall be in an authorized denomination.

SECTION 3.03.     NOTICE OF REDEMPTION.

         At least 30 days but not more than 60 days before a redemption date,
the Company shall mail or cause to be mailed, by first class mail, a notice of
redemption to each Holder whose Notes are to be redeemed at its registered
address.

         The notice shall identify the Notes to be redeemed and shall state:

                  (a) the redemption date;

                  (b) the redemption price;

                  (c) if any Note is being redeemed in part, the portion of the
         principal amount of such Note to be redeemed and that, after the
         redemption date upon surrender of such Note, a new Note or Notes in a
         principal amount equal to the unredeemed portion shall be issued upon
         cancellation of the original Note;

                  (d) the name and address of the Paying Agent;

                  (e) that Notes called for redemption must be surrendered to
         the Paying Agent to collect the redemption price;

                  (f) that, unless the Company defaults in making such
         redemption payment, interest and Liquidated Damages, if any, on Notes
         called for redemption cease to accrue on and after the redemption date;

                  (g) the clause of this Indenture pursuant to which the Notes
         called for redemption are being redeemed; and

                  (h) that no representation is made as to the correctness or
         accuracy of the CUSIP number, if any, listed in such notice or printed
         on the Notes.

                                       42
<PAGE>   50

         If any of the Notes to be redeemed is in the form of a Global Note,
then the Company shall modify such notice to the extent necessary to accord with
the procedures of the Depository applicable to redemption.

         At the Company's request, the Trustee shall give the notice of
redemption in the Company's name and at its expense; provided, however, that the
Company shall have delivered to the Trustee, at least 60 days (unless the
Company and the Trustee agree to a shorter period) prior to the redemption date,
an Officers' Certificate requesting that the Trustee give such notice and
setting forth the information to be stated in such notice as provided in the
preceding paragraph.

SECTION 3.04.     EFFECT OF NOTICE OF REDEMPTION.

         Once notice of redemption is mailed in accordance with Section 3.03
hereof, Notes called for redemption become irrevocably due and payable on the
redemption date at the redemption price. A notice of redemption may not be
conditional.

SECTION 3.05.     DEPOSIT OF REDEMPTION PRICE.

         No later than 10:00 a.m., New York City time, on the redemption date,
the Company shall deposit with the Paying Agent (or, if the Company is acting as
its own Paying Agent, segregate and hold in trust as provided in Section 2.04
hereof) money sufficient to pay the redemption price of and accrued interest and
Liquidated Damages, if any, on all Notes to be redeemed on that date. The Paying
Agent shall promptly return to the Company any money deposited with the Paying
Agent by the Company in excess of the amounts necessary to pay the redemption
price of and accrued interest and Liquidated Damages, if any, on all Notes to be
redeemed.

         If the Company complies with the provisions of the preceding paragraph,
on and after the redemption date, interest and Liquidated Damages, if any, shall
cease to accrue on the Notes or the portions of Notes called for redemption. If
a Note is redeemed on or after an interest record date but on or prior to the
related interest payment date, then any accrued and unpaid interest and
Liquidated Damages, if any, shall be paid to the Person in whose name such Note
was registered at the close of business on such record date. If any Note called
for redemption shall not be so paid upon surrender for redemption because of the
failure of the Company to comply with the preceding paragraph, interest shall be
paid on the unpaid principal, from the redemption date until such principal is
paid, and to the extent lawful on any interest and Liquidated Damages, if any,
not paid on such unpaid principal, in each case at the rate provided in the
Notes and in Section 4.01 hereof.

SECTION 3.06.     NOTES REDEEMED IN PART.

         Upon surrender of a Note that is redeemed in part, the Company shall
issue and the Trustee shall authenticate for the Holder at the expense of the
Company a new Note equal in principal amount to the unredeemed portion of the
Note surrendered.

SECTION 3.07.     OPTIONAL REDEMPTION.

         (a) At any time on or after June 1, 2004, the Company shall have the
option to redeem the Notes, in whole or in part, at (i) a redemption price of
104% (expressed as a percentage of

                                       43
<PAGE>   51

principal amount) plus accrued and unpaid interest and Liquidated Damages, if
any, thereon, to the applicable redemption date, if redeemed during the period
beginning on June 1, 2004 and ending on May 31, 2005 and (ii) a redemption price
of 100% (expressed as a percentage of principal amount) plus accrued and unpaid
interest and Liquidated Damages, if any, thereon, to the applicable redemption
date, if redeemed on or after June 1, 2005.

         (b) Further, at any time and from time to time prior to June 1, 2003,
the Company may redeem in the aggregate up to 30% of the then outstanding
aggregate principal amount of the Notes with the Net Cash Proceeds of one or
more Equity Offerings at a redemption price of 112.5% (expressed as a percentage
of principal amount) plus accrued and unpaid interest thereon and Liquidated
Damages, if any, thereon, to the applicable redemption date (subject to the
right of Holders of record on the relevant record date to receive interest due
on the relevant interest payment date); provided, however, that the redemption
occurs within 60 days after the consummation of such Equity Offering and at
least 70% of the then outstanding aggregate principal amount of the Notes must
remain outstanding after each such redemption.

         (c) Any redemption pursuant to this Section 3.07 shall be made pursuant
to the provisions of Section 3.01 through Section 3.06 hereof.

SECTION 3.08.     MANDATORY REDEMPTION.

         Except as set forth in Sections 4.10, 4.15 and 4.19 hereof, and except
as set forth in the form of Note attached hereto as Exhibit A-1, the Company
shall not be required to purchase or to make mandatory redemption or sinking
fund payments with respect to the Notes.

SECTION 3.09.     OFFER TO PURCHASE BY APPLICATION OF EXCESS PROCEEDS.

         In the event that, pursuant to Section 4.10 hereof, the Company shall
be required to commence an Excess Proceeds Offer or a Major Asset Sale Offer,
the Company shall follow the procedures specified below.

         The Excess Proceeds Offer or the Major Asset Sale Offer, as the case
may be, shall remain open for a period of 20 Business Days following its
commencement and no longer, except to the extent that a longer period is
required by applicable law (the "Offer Period"). No later than five Business
Days after the termination of the Offer Period (the "Purchase Date"), the
Company shall purchase the principal amount of Notes required to be purchased
pursuant to Section 4.10 hereof (the "Offer Amount") or, if less than the Offer
Amount has been tendered, all Notes validly tendered in response to the Excess
Proceeds Offer. Payment for any Notes so purchased shall be made in the same
manner as principal payments are made at Stated Maturity. The Parent Guarantor
shall not and shall not permit any Restricted Subsidiary to enter into or suffer
to exist any agreement that would place any restriction of any kind (other than
pursuant to law or regulation) on the ability of the Company to make an Excess
Proceeds Offer. Further, the Company shall comply with the requirements of Rule
14e-1 under the Exchange Act and any other securities laws and regulations
thereunder to the extent such laws and regulations are applicable in connection
with the purchase of Notes as a result of an Excess Proceeds Offer. To the
extent that the provisions of any securities laws or regulations conflict with
the provisions relating to an Excess Proceeds Offer, the Company

                                       44
<PAGE>   52

shall comply with the applicable securities laws and regulations and shall not
be deemed to have breached its obligations described above by virtue thereof.

         If the Purchase Date is on or after an interest record date and on or
before the related interest payment date, any accrued and unpaid interest and
Liquidated Damages, if any, shall be paid to the Person in whose name a Note is
registered at the close of business on such record date, and no additional
interest or Liquidated Damages, if any, shall be payable to Holders who tender
Notes pursuant to the Excess Proceeds Offer or the Major Asset Sale Offer, as
the case may be.

         Upon the commencement of an Excess Proceeds Offer or the Major Asset
Sale Offer, as the case may be, the Company shall send, not less than 30 days
nor more than 60 days before the Purchase Date, by first class mail, a notice to
each of the Holders, with a copy to the Trustee. The notice shall contain all
instructions and materials necessary to enable such Holders to tender Notes
pursuant to the Excess Proceeds Offer or the Major Asset Sale Offer, as the case
may be. The Excess Proceeds Offer or the Major Asset Sale Offer, as the case may
be shall be made to all Holders. The notice, which shall govern the terms of the
Excess Proceeds Offer or the Major Asset Sale Offer, as the case may be, shall
state:

                  (a) that the Excess Proceeds Offer or the Major Asset Sale
         Offer, as the case may be is being made pursuant to this Section 3.09
         and Section 4.10 hereof and the length of time the Excess Proceeds
         Offer or the Major Asset Sale Offer, as the case may be, shall remain
         open;

                  (b) the Offer Amount, the purchase price and the Purchase
         Date;

                  (c) that Holders may elect to tender their Notes in whole or
         in integral multiples of $1,000 principal amount in exchange for cash
         and that any Note not tendered or accepted for payment shall continue
         to accrue interest and Liquidated Damages, if any;

                  (d) that, unless the Company defaults in making such payment,
         any Note accepted for payment pursuant to the Excess Proceeds Offer or
         the Major Asset Sale Offer, as the case may be, shall cease to accrue
         interest and Liquidated Damages, if any, after the Purchase Date;

                  (e) that Holders electing to have a Note purchased pursuant to
         an Excess Proceeds Offer or the Major Asset Sale Offer, as the case may
         be, may only elect to have all of such Note purchased and may not elect
         to have only a portion of such Note purchased;

                  (f) that Holders electing to have a Note purchased pursuant to
         any Excess Proceeds Offer or the Major Asset Sale Offer, as the case
         may be, shall be required to surrender the Note, with the form entitled
         "Option of Holder to Elect Purchase" on the reverse of the Note
         completed, to the Company or a Paying Agent at the address specified in
         the notice at least three days before the Purchase Date;

                  (g) that Holders shall be entitled to withdraw their election
         if the Company or the Paying Agent, as the case may be, receives, not
         later than the expiration of the Offer Period, a telegram, facsimile
         transmission or letter setting forth the name of the Holder, the
         principal

                                       45
<PAGE>   53

         amount of the Note the Holder delivered for purchase and a statement
         that such Holder is withdrawing his election to have such Note
         purchased;

                  (h) that, if the aggregate principal amount of Notes
         surrendered by Holders exceeds the Offer Amount, the Trustee shall
         select the Notes to be purchased on a pro rata basis (with such
         adjustments as may be deemed appropriate by the Trustee so that only
         Notes in denominations of $1,000, or integral multiples thereof, shall
         be purchased); and

                  (i) that Holders whose Notes were purchased only in part shall
         be issued new Notes equal in principal amount to the unpurchased
         portion of the Notes surrendered (or transferred by book-entry
         transfer).

         If any of the Notes subject to an Excess Proceeds Offer or the Major
Asset Sale Offer, as the case may be, is in the form of a Global Note, then the
Company shall modify such notice to the extent necessary to accord with the
procedures of the Depository applicable to repurchases.

         On or before the Purchase Date, the Company shall, to the extent
lawful, accept for payment, on a pro rata basis to the extent necessary, the
Offer Amount of Notes or portions thereof tendered pursuant to the Excess
Proceeds Offer or the Major Asset Sale Offer, as the case may be, or if less
than the Offer Amount has been tendered, all Notes tendered, and shall deliver
to the Trustee an Officers' Certificate stating that such Notes or portions
thereof were accepted for payment by the Company in accordance with the terms of
this Section 3.09. The Company or the Paying Agent, as the case may be, shall
promptly (but in any case not later than five days after the Purchase Date) mail
or deliver to each tendering Holder an amount equal to the purchase price of the
Notes tendered by such Holder and accepted by the Company for purchase, and the
Company shall promptly issue a new Note, and the Trustee shall authenticate and
mail or deliver such new Note to such Holder, in a principal amount equal to any
unpurchased portion of the Note surrendered. Any Note not so accepted shall be
promptly mailed or delivered by the Company to the Holder thereof. The Company
shall publicly announce the results of the Excess Proceeds Offer or the Major
Asset Sale Offer, as the case may be on the Purchase Date.

         Other than as specifically provided in this Section 3.09, any purchase
pursuant to this Section 3.09 shall be made pursuant to the provisions of
Section 3.01 through Section 3.06 hereof.

                                    ARTICLE 4

                                    COVENANTS

SECTION 4.01.     PAYMENT OF NOTES.

         The Company shall pay or cause to be paid the principal of and premium,
interest and Liquidated Damages, if any, on the Notes on the dates and in the
manner provided in the Notes. Principal, premium, interest and Liquidated
Damages, if any, shall be considered paid on the date due if a Paying Agent, if
other than the Company or a Subsidiary thereof, holds as of 10:00 a.m., New York
City time, on the due date money deposited by the Company in immediately
available

                                       46
<PAGE>   54

funds and designated for and sufficient to pay all principal, premium, interest
and Liquidated Damages, if any, then due.

         The Company shall pay interest (including post-petition interest in any
proceeding under any Bankruptcy Law) on overdue principal and premium, if any,
at the rate equal to the interest rate on the Notes to the extent lawful; it
shall pay interest (including post-petition interest in any proceeding under any
Bankruptcy Law) on overdue installments of interest and Liquidated Damages, if
any (without regard to any applicable grace period), at the same rate to the
extent lawful.

SECTION 4.02.     MAINTENANCE OF OFFICE OR AGENCY.

         The Company shall maintain an office or agency in the continental
United States as required under Section 2.03 where Notes may be presented or
surrendered for payment, where Notes may be surrendered for registration of
transfer or for exchange and where notices and demands to or upon the Company in
respect of the Notes and this Indenture may be served. If at any time the
Company shall fail to maintain any such required office or agency or shall fail
to furnish the Trustee with the address thereof, such presentations, surrenders,
notices and demands may be made or served at the Corporate Trust Office of the
Trustee.

         The Company may also from time to time designate one or more other
offices or agencies where the Notes may be presented or surrendered for any or
all such purposes and may from time to time rescind such designations. Further,
if at any time there shall be no such office or agency in the continental United
States where the Notes may be presented or surrendered for payment, the Company
shall forthwith designate and maintain such an office or agency in the
continental United States, in order that the Notes shall at all times be payable
in the continental United States. The Company shall give prompt written notice
to the Trustee of any such designation or rescission and of any change in the
location of any such other office or agency.

         The Company hereby designates the Corporate Trust Office of the Trustee
as one such office or agency of the Company in accordance with Section 2.03.

SECTION 4.03.     REPORTS.

         (a) Notwithstanding that neither the Parent Guarantor nor the Company
may not at any time be subject to the reporting requirements of Section 13 or 15
of the Exchange Act, the Parent Guarantor shall provide the Trustee and the
Holders (i) all quarterly and annual financial information that would be
required to be contained in a filing by the Parent Guarantor with the SEC on
Forms 10-Q and 10-K if the Parent Guarantor were required to file such form,
including a "Management's Discussion and Analysis of Financial Condition and
Results of Operations" that describes the financial condition and results of
operations of the Parent Guarantor and its Subsidiaries, determined on a
consolidated basis in accordance with GAAP, (showing in reasonable detail,
either on the face of the financial statements or in the footnotes thereto and
in "Management's Discussion and Analysis of Financial Condition and Results of
Operations," the financial conditions and results of operations of the Parent
Guarantor and the Restricted Subsidiaries separate from the financial condition
and results of operations of the Unrestricted Subsidiaries) and, with respect to
the annual information only, a report thereon by the Parent Guarantor's
certified independent accountants, and (ii) all current

                                       47
<PAGE>   55

reports that would be required to be filed with the SEC on Form 8-K if the
Parent Guarantor were required to file such reports, in each case within 15 days
after the time periods specified for such filings in the SEC's rules and
regulations; provided, however, that after the date that the Exchange Offer
Registration Statement or the Shelf Registration Statement, as the case may be,
is due to be filed, and notwithstanding that the Parent Guarantor may not be
subject to the reporting requirements of Section 13 or 15 of the Exchange Act,
the Parent Guarantor will file with the SEC, to the extent permitted, and
provide the Trustee and the Holders with such annual and quarterly reports and
such information, documents and other reports specified in Sections 13 and 15(d)
of the Exchange Act.

         (b) For so long as any Notes remain outstanding, the Company and the
Guarantors shall furnish to the Holders of the Notes and prospective purchasers
of the Notes, upon their request, the information, if any, required to be
delivered pursuant to Rule 144A(d)(4) under the Securities Act.

SECTION 4.04.     COMPLIANCE CERTIFICATE.

         (a) The Company and the Parent Guarantor shall deliver to the Trustee,
within 120 days after the end of each fiscal year, an Officers' Certificate
stating that a review of the activities of the Parent Guarantor and the
Restricted Subsidiaries during the preceding fiscal year has been made under the
supervision of the signing Officers with a view to determining whether the
Parent Guarantor and the Restricted Subsidiaries have kept, observed, performed
and fulfilled their obligations under this Indenture and the Security Documents,
and further stating, as to each such Officer signing such certificate, that to
the best of his or her knowledge the Parent Guarantor and the Restricted
Subsidiaries have kept, observed, performed and fulfilled each and every
covenant contained in this Indenture and is not in default in the performance or
observance of any of the terms, provisions and conditions of this Indenture or
any Security Document (or, if a Default or Event of Default shall have occurred,
describing all such Defaults or Events of Default of which he or she may have
knowledge and what action the Parent Guarantor or any Restricted Subsidiary, as
applicable, is taking or proposes to take with respect thereto) and that to the
best of his or her knowledge no event has occurred and remains in existence by
reason of which payments on account of the principal of or interest, if any, on
the Notes is prohibited or if such event has occurred, a description of the
event and what action the Parent Guarantor or any Restricted Subsidiary, as
applicable, is taking or proposes to take with respect thereto.

         (b) So long as not contrary to the then current recommendations of the
American Institute of Certified Public Accountants, the year-end financial
statements delivered pursuant to Section 4.03(a) above shall be accompanied by a
written statement of the Company's independent public accountants (who shall be
a firm of established national reputation) that in making the examination
necessary for certification of such financial statements, nothing has come to
their attention that would lead them to believe that the Company has violated
any provisions of Article 4 or Article 5 hereof or, if any such violation has
occurred, specifying the nature and period of existence thereof, it being
understood that such accountants shall not be liable directly or indirectly to
any Person for any failure to obtain knowledge of any such violation.

         (c) The Company and the Parent Guarantor shall, so long as any of the
Notes are outstanding, deliver to the Trustee, within 30 days after any Officer
becoming aware of any Default or Event of Default, an Officers' Certificate
specifying such Default or Event of Default, their status

                                       48
<PAGE>   56

and what action the Company or the Parent Guarantor, as applicable, is taking or
proposes to take with respect thereto.

SECTION 4.05.     TAXES.

         The Parent Guarantor shall pay, and shall cause each of the Restricted
Subsidiaries to pay, prior to delinquency, all material taxes, assessments, and
governmental levies except such as are contested in good faith and by
appropriate proceedings or where the failure to effect such payment is not
adverse in any material respect to the Holders of the Notes.

SECTION 4.06.     STAY, EXTENSION AND USURY LAWS.

         The Parent Guarantor covenants (to the extent that it may lawfully do
so) that it shall not, and shall not permit any of the Restricted Subsidiaries
to, at any time insist upon, plead, or in any manner whatsoever claim or take
the benefit or advantage of, any stay, extension or usury law wherever enacted,
now or at any time hereafter in force, that may affect the covenants or the
performance of this Indenture; and the Parent Guarantor (to the extent that it
may lawfully do so) hereby expressly waives all benefit or advantage of any such
law, and covenants that it shall not, and shall not permit any of the Restricted
Subsidiaries to, by resort to any such law, hinder, delay or impede the
execution of any power herein granted to the Trustee, but shall suffer and
permit the execution of every such power as though no such law has been enacted.

SECTION 4.07.     RESTRICTED PAYMENTS.

         (a) The Parent Guarantor shall not, and shall not permit any
Restricted Subsidiary to, directly or indirectly, make a Restricted Payment
unless, at the time of such Restricted Payment:

                  (1) no Default or Event of Default shall have occurred and be
         continuing or would occur as a consequence thereof;

                  (2) immediately after giving effect thereto on a pro forma
         basis, the Parent Guarantor could incur at least $1.00 of additional
         Indebtedness under clause (a) of Section 4.09 hereof; and

                  (3) such Restricted Payment, together with the aggregate
         amount of all other Restricted Payments made by the Parent Guarantor
         and its Restricted Subsidiaries after the Closing Date is less than the
         sum of the following:

                           (A) 25% of the Consolidated Net Income of the Parent
                  Guarantor for the period (taken as one accounting period) from
                  January 1, 2002 to the end of the Parent Guarantor's most
                  recently ended fiscal quarter for which internal financial
                  statements are available at the time of such Restricted
                  Payment (or, if such Consolidated Net Income for such period
                  is a deficit, less 100% of such deficit), plus

                           (B) 100% of the aggregate net cash proceeds received
                  by the Parent Guarantor since the Closing Date from the issue
                  or sale of Capital Stock of the Parent Guarantor (other than
                  Disqualified Stock) or of Disqualified Stock or debt
                  securities

                                       49
<PAGE>   57

                  of the Parent Guarantor that have been converted into, or
                  exchanged for, such Capital Stock (other than any such Capital
                  Stock, Disqualified Stock or convertible debt securities sold
                  to a Restricted Subsidiary of the Parent Guarantor and other
                  than Disqualified Stock or convertible debt securities that
                  have been converted into, or exchanged for, Disqualified
                  Stock), plus

                           (C) to the extent that any Permitted Investment that
                  was made after the Closing Date is sold for cash or otherwise
                  liquidated or repaid for cash, the lesser of (1) the cash
                  return of capital with respect to such Permitted Investment
                  (less the cost of disposition, if any) and (2) the initial
                  amount of such Permitted Investment, plus

                           (D) in the event that any Unrestricted Subsidiary is
                  redesignated as a Restricted Subsidiary, the lesser of (1) an
                  amount equal to the fair market value of the Investments in
                  such Subsidiary previously made by the Parent Guarantor and
                  its Restricted Subsidiaries as of the date of such
                  redesignation and (2) the amount of such Investments, plus

                           (E) $1,000,000.

         (b) The provisions of the preceding paragraph (a) shall not prohibit:

                  (1) the payment of any dividend within 60 days after the date
         of declaration of such dividend if the dividend would have been
         permitted on the date of declaration;

                  (2) if no Default or Event of Default shall have occurred and
         be continuing, the acquisition of any shares of Capital Stock (other
         than Disqualified Stock) of the Parent Guarantor or any Restricted
         Subsidiary, either (A) solely in exchange for shares of Capital Stock
         of the Parent Guarantor (other than Disqualified Stock) or (B) through
         the application of net cash proceeds of a substantially concurrent sale
         for cash (other than to a Restricted Subsidiary) of shares of Capital
         Stock (other than Disqualified Stock) of the Parent Guarantor;

                  (3) if no Default or Event of Default shall have occurred and
         be continuing, the acquisition or retirement for value of any
         Subordinated Obligations (other than Disqualified Stock) of the Parent
         Guarantor, the Company or a Subsidiary Guarantor either (A) solely in
         exchange for shares of Capital Stock (other than Disqualified Stock) of
         the Parent Guarantor, (B) through the application of net cash proceeds
         of a substantially concurrent sale for cash (other than to a Restricted
         Subsidiary) of shares of Capital Stock (other than Disqualified Stock)
         of the Parent Guarantor or (C) through Refinancing Indebtedness that
         also constitutes Subordinated Obligations; or

                  (4) net advances to Richard Bowman and his Affiliates
         (excluding the Parent Guarantor and the Restricted Subsidiaries),
         provided that any net advances in excess of $150,000 shall not be
         outstanding for more than 30 consecutive days.

                                       50
<PAGE>   58

SECTION 4.08.    DIVIDEND AND OTHER PAYMENT RESTRICTIONS AFFECTING SUBSIDIARIES.

         The Parent Guarantor will not, and will not cause or permit any of the
Restricted Subsidiaries to, directly or indirectly, create or otherwise cause or
permit to exist or become effective any encumbrance or restriction on the
ability of any Restricted Subsidiary to:

                  (1) pay dividends or make any other distributions on or in
         respect of its Capital Stock;

                  (2) make loans or advances, or pay any Indebtedness or other
         obligation owed, to the Parent Guarantor or any Restricted Subsidiary;

                  (3) Guarantee the Notes, the Approved Hedge Agreements or any
         Hedge Liquidity Agreement (if applicable);

                  (4) transfer any of its property or assets to the Parent
         Guarantor or any other Restricted Subsidiary; or

                  (5) grant Liens on its property or assets to secure the
         Obligations, the Approved Hedge Agreements or any Hedge Liquidity
         Agreement (if applicable) (each such encumbrance or restriction, a
         "Payment Restriction").

         The preceding will not apply, however, to encumbrances or restrictions
existing under or by reason of the following (which are excluded from the term
"Payment Restriction"):

                  (1) applicable law;

                  (2) this Indenture or any Security Document;

                  (3) customary non-assignment provisions of any contract or any
         lease governing a leasehold interest of the Parent Guarantor or any
         Restricted Subsidiary;

                  (4) any instrument governing Acquired Indebtedness, provided
         that such restriction is limited only to the properties or assets the
         subject of such Capital Lease, mortgage or purchase money financing;

                  (5) agreements existing on the Closing Date to the extent and
         in the manner such agreements were in effect on the Closing Date;

                  (6) customary restrictions with respect to a Restricted
         Subsidiary pursuant to an agreement that has been entered into for the
         sale or disposition of Capital Stock or assets of such Restricted
         Subsidiary to be consummated in accordance with the terms of this
         Indenture solely in respect of the assets or Capital Stock to be sold
         or disposed of;

                  (7) any instrument governing a Permitted Lien, to the extent
         and only to the extent such instrument restricts the transfer or other
         disposition of assets subject to such Permitted Lien;

                                       51
<PAGE>   59

                  (8) an agreement governing Refinancing Indebtedness incurred
         to Refinance the Indebtedness issued, assumed or incurred pursuant to
         an agreement referred to in clause (2), (4) or (5) above; provided,
         however, that the provisions relating to such encumbrance or
         restriction contained in any such Refinancing Indebtedness are no less
         favorable to the Holders in any material respect as determined by the
         Board of Directors of the Parent Guarantor in its reasonable and good
         faith judgment than the provisions relating to such encumbrance or
         restriction contained in the applicable agreement referred to in such
         clause (2), (4) or (5); and

                  (9) any instrument governing a Working Capital Revolver, to
         the extent and only to the extent such instrument restricts the
         transfer or other disposition of accounts receivable, related general
         intangibles and related proceeds of the Parent Guarantor and the
         Restricted Subsidiaries securing such Working Capital Revolver.

SECTION 4.09.     INCURRENCE OF INDEBTEDNESS.

         (a) The Parent Guarantor shall not, and shall not permit any Restricted
Subsidiary to, Incur, directly or indirectly, any Indebtedness; provided,
however, that the Parent Guarantor or a Restricted Subsidiary may Incur
Indebtedness if, on the date of such Incurrence and after giving effect thereto,
both (1) the Consolidated Coverage Ratio equals or exceeds 2.5 to 1.0 and (2)
Adjusted Consolidated Net Tangible Assets equals or exceeds 150% of the
aggregate consolidated Indebtedness of the Parent Guarantor and the Restricted
Subsidiaries.

         (b) Notwithstanding the preceding paragraph (a), the Parent Guarantor
and any Restricted Subsidiary may Incur the following Indebtedness:

                  (1) Indebtedness Incurred pursuant to any Working Capital
         Revolver, so long as the aggregate principal amount of all Indebtedness
         outstanding under all Working Capital Revolvers does not at any one
         time exceed $20,000,000;

                  (2) Indebtedness owed to and held by the Parent Guarantor or a
         Wholly Owned Subsidiary; provided, however, that any subsequent
         issuance or transfer of any Capital Stock which results in any such
         Wholly Owned Subsidiary ceasing to be a Wholly Owned Subsidiary or any
         subsequent transfer of such Indebtedness (other than to the Parent
         Guarantor or another Wholly Owned Subsidiary) shall be deemed, in each
         case, to constitute the Incurrence of such Indebtedness by the issuer
         thereof;

                  (3) the Notes (other than the Tack-On Senior Secured Notes),
         this Indenture, the Security Documents, the Parent Guarantee and the
         Subsidiary Guarantees;

                  (4) Indebtedness outstanding on the Closing Date, to the
         extent not discharged in the Company's bankruptcy case;

                  (5) Refinancing Indebtedness in respect of Indebtedness
         Incurred pursuant to paragraph (a) or pursuant to clause (3) or (4)
         above or clause (6) below;

                                       52
<PAGE>   60

                  (6) Indebtedness of the Parent Guarantor or a Restricted
         Subsidiary represented by Capital Lease Obligations, mortgage
         financings or purchase money obligations, in each case Incurred for the
         purpose of financing all or any part of the purchase price or cost of
         construction or improvement of property used in the Oil and Gas
         Business and in each case Incurred no later than 365 days after the
         date of such acquisition or the date of completion of such construction
         or improvement; provided, however, that the principal amount of all
         such Indebtedness at any one time outstanding shall not exceed
         $5,000,000;

                  (7) Indebtedness consisting of Interest Rate Agreements
         directly related to Indebtedness permitted to be Incurred by the Parent
         Guarantor and the Restricted Subsidiaries pursuant to this Section
         4.09;

                  (8) Indebtedness under Oil and Gas Hedging Contracts entered
         into in the ordinary course of business for the purpose of limiting
         risks that arise in the ordinary course of business of the Parent
         Guarantor and the Restricted Subsidiaries or required to be entered
         into by the Parent Guarantor and the Restricted Subsidiaries under the
         provisions of Section 4.25 hereof and under certain revolving credit or
         loan agreements or letters of credit reimbursement agreements ("Hedge
         Liquidity Agreements") to permit the Parent Guarantor or any of the
         Restricted Subsidiaries to provide letters of credit as margin in lieu
         of the collateral to secure excess market exposure and settlement and
         related amounts due on early termination under the Approved Hedge
         Agreement and Security Documents;

                  (9) Non-Recourse Indebtedness;

                  (10) the Guarantee by the Parent Guarantor or any of the
         Restricted Subsidiaries of Indebtedness that was permitted to be
         incurred by another clause of this Section 4.09; and

                  (11) Indebtedness in an aggregate principal amount which,
         together with the principal amount of all other Indebtedness of the
         Parent Guarantor and the Restricted Subsidiaries outstanding on the
         date of such Incurrence (other than Indebtedness permitted by clauses
         (1) through (10) above or paragraph (a)) does not exceed $5,000,000.

         (c) Notwithstanding the preceding, the Parent Guarantor and the
Restricted Subsidiaries shall not Incur any Indebtedness pursuant to the
preceding paragraph (b) if the proceeds thereof are used, directly or
indirectly, to Refinance any Subordinated Obligations unless such Indebtedness
shall be subordinated to the Notes to at least the same extent as such
Subordinated Obligations.

         (d) For purposes of determining compliance with the preceding clauses,
(i) in the event that an item of Indebtedness meets the criteria of more than
one of the types of Indebtedness described above, the Parent Guarantor, in its
sole discretion, will classify such item of Indebtedness and only be required to
include the amount and type of such Indebtedness in one of the above clauses and
(ii) an item of Indebtedness may be divided and classified in more than one of
the types of Indebtedness described above.

                                       53
<PAGE>   61

SECTION 4.10.     ASSET SALES.

         (a) The Parent Guarantor will not, and will not cause or permit any of
the Restricted Subsidiaries to, consummate an Asset Disposition unless:

                  (1) the Parent Guarantor or the relevant Restricted
         Subsidiary, as the case may be, receives consideration at the time of
         such Asset Disposition at least equal to the fair market value of the
         assets sold or otherwise disposed of (as determined in good faith by
         the Board of Directors of the Parent Guarantor); and

                  (2) at least 70% of the consideration received by the Parent
         Guarantor or such Restricted Subsidiary, as the case may be, from such
         Asset Disposition shall be in the form of cash or Temporary Cash
         Investments and is received at the time of such disposition.

         Within 270 days after an Asset Disposition, the Parent Guarantor or
such Restricted Subsidiary shall apply or cause to be applied the Net Available
Cash of such Asset Disposition as follows and in accordance with the procedures
set forth in Section 3.09 hereof:

         The Company shall make an offer to purchase (the "Excess Proceeds
Offer") from the Holders, on a pro rata basis, an aggregate stated principal
amount of Notes equal to the Excess Proceeds (rounded down to the nearest
multiple of $1,000) at a purchase price equal to the Accreted Value of the
Notes, together with accrued interest (if any) to the date of purchase (the
"Excess Proceeds Payment"); provided that the Company will not be required to
apply the Net Available Cash from any Asset Disposition pursuant to this clause
if, and only to the extent that such Net Available Cash is applied to, within
270 days of such Asset Disposition, (i) an Investment or Investments in
Additional Assets, (ii) an Investment or Investments in properties or assets
that replace the properties or assets that were the subject of such Asset
Disposition (the "Replacement Assets"), and the assets constituting such
Additional Assets or Replacement Assets and any non-cash consideration received
are made subject to the Lien of this Indenture and the Security Documents in
accordance with Section 4.23 hereof or (iii) to the extent such Net Available
Cash is received from an Asset Disposition not involving the sale, transfer or
disposition of Collateral, to repay any Indebtedness secured by the assets
involved in such Asset Disposition together with a concomitant permanent
reduction in the amount of such Indebtedness so repaid; provided, however, that
such use of Net Available Cash shall not exceed $7,000,000 in any one year. For
purposes of this paragraph, "Excess Proceeds" means any Net Available Cash from
Asset Dispositions remaining after investments in any Additional Assets or
Replacement Assets as provided for in the preceding sentence.

         The Company may defer the Excess Proceeds Offer until there are
aggregate unutilized Excess Proceeds equal to or in excess of $5,000,000
resulting from one or more Asset Dispositions (at which time the entire
unutilized Excess Proceeds, and not just the amounts in excess of $5,000,000,
shall be applied as required pursuant to the preceding paragraph).

         Notwithstanding the foregoing, in the event that the Parent Guarantor
or any of the Restricted Subsidiaries consummates or causes to be consummated a
single or a series of related Asset Dispositions representing more than 20% of
the consolidated proved reserves of the Parent

                                       54
<PAGE>   62

Guarantor and the Restricted Subsidiaries (a "Major Asset Sale"), the Company
shall make an offer to purchase (the "Major Asset Sale Offer") from the Holders
on a pro rata basis an aggregate stated principal amount of Notes equal to 50%
of the gross proceeds from such Major Asset Sale at a purchase price equal to
100% of the stated principal amount of such Notes, together with accrued
interest (if any) to the date of purchase. Any Net Available Cash remaining
following the completion of the Major Asset Sale Offer shall be applied to,
within 270 days of the date of completion of the Major Asset Sale Offer, an
Investment or Investments in Additional Assets or Replacement Assets.

         (b) In the event of the transfer of substantially all (but not all) the
property and assets of the Parent Guarantor or the Company as an entirety to a
Person in a transaction not constituting a Change of Control that is permitted
by Section 5.01 hereof, the Successor Company shall be deemed to have sold the
properties and assets of the Parent Guarantor or the Company, as applicable, not
so transferred for purposes of this clause, and shall comply with the provisions
of this clause with respect to such deemed sale as if it were an Asset
Disposition and the Successor Company shall be deemed to have received Net
Available Cash in an amount equal to the fair market value (as determined in
good faith by the Board of Directors of the Parent Guarantor) of the properties
and assets not so transferred or sold.

         (c) All Net Available Cash in excess of $1,000,000 in any fiscal year
from any Asset Disposition involving Collateral shall constitute Trust Moneys
and shall be delivered by the Parent Guarantor or the Company, as applicable, to
the Collateral Agent and shall be deposited in the Collateral Account in
accordance with the Intercreditor Agreement. Net Available Cash so deposited may
be withdrawn from the Collateral Account for application by the Parent Guarantor
or the Company in accordance with this clause or otherwise pursuant to this
Indenture as described in the Intercreditor Agreement.

SECTION 4.11.     TRANSACTIONS WITH AFFILIATES.

         (a) The Parent Guarantor shall not, and shall not permit any Restricted
Subsidiary to, enter into or permit to exist any transaction (including the
purchase, sale, lease or exchange of any stock, property, employee compensation
arrangements or the rendering of any service) with any Affiliate of the Parent
Guarantor (an "Affiliate Transaction") unless the terms thereof (1) are no less
favorable to the Parent Guarantor or such Restricted Subsidiary than those that
could be obtained at the time of such transaction in arm's-length dealings with
a Person who is not such an Affiliate, (2) if such Affiliate Transaction
involves an amount between $500,000 and $3,000,000, are certified in an
Officers' Certificate to the effect that such Affiliate Transaction complies
with this clause, and have been approved by a majority of the members of the
Board of Directors of the Parent Guarantor having no personal stake in such
Affiliate Transaction or (3) if such Affiliate Transaction involves an amount in
excess of $3,000,000, are certified in an Officers' Certificate to the effect
that such Affiliate Transaction complies with this clause, has been approved by
a majority of the members of the Board of Directors of the Parent Guarantor
having no personal stake in such Affiliate Transaction and has been determined
by a nationally recognized investment banking firm to be fair, from a financial
standpoint, to the Parent Guarantor or the Restricted Subsidiary, as the case
may be. In addition, the net balance of advances made by the Parent Guarantor
and the Restricted Subsidiaries to Richard Bowman and his Affiliates shall not
exceed $150,000 for more than 30 consecutive days.

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<PAGE>   63

         (b) The provisions of the preceding paragraph (a) shall not prohibit
(i) reasonable fees and compensation paid to and indemnity provided on behalf
of, officers, directors, employees or consultants of the Parent Guarantor or any
Restricted Subsidiary as determined in good faith by the Board of Directors of
the Parent Guarantor; (ii) transactions exclusively between or among the
Restricted Subsidiaries; provided, however, that such transactions are not
otherwise prohibited by this Indenture; and (iii) Restricted Payments permitted
by this Indenture.

SECTION 4.12.     LIENS.

         The Parent Guarantor shall not, and shall not cause or permit any of
the Restricted Subsidiaries to, directly or indirectly, create, incur, assume or
permit or suffer to exist or remain in effect any Liens other than Permitted
Liens.

SECTION 4.13.     ADDITIONAL SUBSIDIARY GUARANTEES.

         From and after the Closing Date, the Parent Guarantor shall cause each
of its Subsidiaries which is or becomes a Restricted Subsidiary to execute an
Assumption Agreement in the form of Annex 1 to the Guaranty Agreement.

SECTION 4.14.     CORPORATE EXISTENCE.

         Subject to Article 5 hereof, the Parent Guarantor shall do or cause to
be done all things necessary to preserve and keep in full force and effect its
corporate existence, and, subject to the provisions of the Guaranty Agreement,
the corporate, partnership or other existence of each of the Restricted
Subsidiaries, in accordance with the respective organizational documents (as the
same may be amended from time to time) of the Parent Guarantor or any such
Restricted Subsidiary; provided, however, that the Parent Guarantor shall not be
required to preserve the existence of any of its Restricted Subsidiaries (other
than the Company), if the Parent Guarantor shall determine that the preservation
thereof is no longer desirable in the conduct of the business of the Parent
Guarantor and the Restricted Subsidiaries, taken as a whole.

SECTION 4.15.     OFFER TO PURCHASE UPON CHANGE OF CONTROL.

         (a) Upon the occurrence of a Change of Control, the Company shall make
an offer (a "Change of Control Offer") to purchase all or any portion (equal to
$1,000 or an integral multiple thereof) of each Holder's Notes, at a purchase
price in cash equal to 101% of the aggregate principal amount thereof, plus
accrued and unpaid interest and Liquidated Damages, if any, thereon to the date
of purchase (the "Change of Control Payment"). Within 30 days following a Change
of Control, the Company shall give notice to each Holder and the Trustee
stating: (1) that the Change of Control Offer is being made pursuant to this
Section 4.15 and that all Notes validly tendered and not withdrawn will be
accepted for payment; (2) the purchase price and the purchase date, which shall
be no earlier than 30 days but no later than 60 days from the date such notice
is given (the "Change of Control Payment Date"); (3) that any Note not tendered
will continue to accrue interest and Liquidated Damages, if any; (4) that,
unless the Company defaults in the payment of the Change of Control Payment, all
Notes accepted for payment pursuant to the Change of Control Offer shall cease
to accrue interest and Liquidated Damages, if any, after the Change of Control
Payment Date; (5)

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<PAGE>   64

that Holders electing to have any Notes purchased pursuant to a Change of
Control Offer will be required to surrender the Notes, properly endorsed for
transfer, together with the form entitled "Option of Holder to Elect Purchase"
on the reverse of the Notes completed and such customary documents as the
Company may reasonably request, to the Paying Agent at the address specified in
the notice prior to the close of business on the third Business Day preceding
the Change of Control Payment Date; (6) that Holders will be entitled to
withdraw their election if the Paying Agent receives, not later than the close
of business on the second Business Day preceding the Change of Control Payment
Date, a telegram, facsimile transmission or letter setting forth the name of the
Holder, the principal amount of Notes delivered for purchase, and a statement
that such Holder is withdrawing his election to have the Notes purchased; and
(7) that Holders whose Notes are being purchased only in part will be issued new
Notes equal in principal amount to the unpurchased portion of the Notes
surrendered, which unpurchased portion must be equal to $1,000 in principal
amount or an integral multiple thereof. If any of the Notes subject to a Change
of Control Offer is in the form of a Global Note, then the Company shall modify
such notice to the extent necessary to comply with the procedures of the
Depository applicable to repurchases. Further, the Company shall comply with the
requirements of Rule 14e-1 under the Exchange Act and any other securities laws
and regulations thereunder to the extent such laws and regulations are
applicable in connection with the purchase of Notes as a result of a Change of
Control. To the extent that the provisions of any securities laws or regulations
conflict with the provisions relating to the Change of Control Offer, the
Company shall comply with the applicable securities laws and regulations and
shall not be deemed to have breached its obligations described above by virtue
thereof.

         (b) On or before 10:00 a.m. New York time on the Change of Control
Payment Date, the Company shall, to the extent lawful, (a) accept for payment
all Notes or portions thereof properly tendered pursuant to the Change of
Control Offer, (b) deposit with the Paying Agent an amount equal to the Change
of Control Payment in respect of all Notes or portions thereof so tendered and
(c) deliver or cause to be delivered to the Trustee the Notes so accepted
together with an Officers' Certificate stating the aggregate principal amount of
Notes or portions thereof being purchased by the Company. The Paying Agent shall
promptly deliver to each Holder of Notes so tendered the Change of Control
Payment for such Notes, and the Trustee shall promptly authenticate and mail (or
cause to be transferred by book entry) to each Holder a new Note equal in
principal amount to any unpurchased portion of the Notes surrendered, if any;
provided, however, that each such new Note will be in a principal amount of
$1,000 or an integral multiple thereof. The Company shall publicly announce the
results of the Change of Control Offer on or as soon as practicable after the
Change of Control Payment Date.

         (c) The foregoing provisions of this Section 4.15 that require the
Company to make a Change of Control Offer following a Change of Control shall be
applicable regardless of whether any other provisions of this Indenture are
applicable. The Company shall not be required to make a Change of Control Offer
following a Change of Control if a third party makes the Change of Control Offer
in the manner, at the time and otherwise in compliance with the requirements set
forth in this Indenture applicable to a Change of Control Offer made by the
Company and purchases all Notes validly tendered and not withdrawn under such
Change of Control Offer.

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<PAGE>   65

SECTION 4.16.   ISSUANCES AND SALES OF CAPITAL STOCK OF RESTRICTED SUBSIDIARIES.

         The Parent Guarantor shall not sell or otherwise dispose of any shares
of Capital Stock of a Restricted Subsidiary, and shall not permit any Restricted
Subsidiary, directly or indirectly, to issue or sell or otherwise dispose of any
shares of its Capital Stock except (i) to the Parent Guarantor or a Wholly Owned
Subsidiary, (ii) if all shares of Capital Stock of such Restricted Subsidiary
(other than the Company) are sold or otherwise disposed of or (iii) to the
extent such shares represent directors' qualifying shares or shares required by
applicable law to be held by a Person other than the Parent Guarantor or a
Restricted Subsidiary; provided that in the case of clause (ii), the Parent
Guarantor complies with the provisions of Section 4.10 hereof and provided
further, the Parent Guarantor shall not sell or otherwise dispose of any Capital
Stock of the Company. If the Parent Guarantor or a Restricted Subsidiary shall
dispose of all of the Capital Stock of any Subsidiary Guarantor, such Subsidiary
Guarantor shall be released from the obligations under its Subsidiary Guarantee.

SECTION 4.17.   SYNTHETIC LEASE TRANSACTIONS.

         The Parent Guarantor shall not, and shall not permit any Restricted
Subsidiary to, enter into any Synthetic Lease Transaction with respect to any
property unless (i) the Parent Guarantor or such Restricted Subsidiary would be
entitled to Incur Indebtedness in an amount equal to the Attributable Debt with
respect to such Synthetic Lease pursuant to the provisions of Section 4.09
hereof (ii) the net cash proceeds received by the Parent Guarantor or any
Restricted Subsidiary in connection with such Synthetic Lease are at least equal
to the fair value (as determined by the Board of Directors of the Parent
Guarantor) of such property and (iii) the Parent Guarantor or such Restricted
Subsidiary shall apply or cause to be applied the proceeds of such transaction
in compliance with the provisions of Section 4.10 hereof.

SECTION 4.18.   CALCULATION OF ORIGINAL ISSUE DISCOUNT.

         The Company shall file with the Trustee promptly at the end of each
calendar year (i) a written notice specifying the amount of Original Issue
Discount (including daily rates and accrual periods) accrued on the outstanding
Notes as of the end of such year and (ii) such other specific information
relating to such Original Issue Discount as may then be relevant under the Code.

SECTION 4.19.   EXCESS CASH FLOW OFFER.

         On the 45th day following the end of each fiscal quarter, commencing
with the quarter ended June 30, 2004, the Parent Guarantor shall calculate its
Excess Cash Flow for the most recently ended fiscal quarter, certify to the
Trustee in writing the calculations to compute such Excess Cash Flow, and if the
Parent Guarantor has Excess Cash Flow of at least $1,000,000, the Company will
make an offer (an "Excess Cash Flow Offer") to purchase Notes at 100% of the
aggregate principal amount thereof, plus accrued interest, if any, to the date
of purchase; provided that the amount required to be paid by the Company to
repurchase such Notes shall be limited to an amount equal to 50% of such Excess
Cash Flow. The Company must commence its Excess Cash Flow Offer not later than
the date on which the certificate computing the Excess Cash Flow is delivered to
the Trustee. If the aggregate purchase price for the Notes (exclusive of
interest) tendered pursuant to such Excess Cash

                                       58
<PAGE>   66

Flow Offer is less than the Excess Cash Flow, then the Parent Guarantor and the
Restricted Subsidiaries may use the remaining Excess Cash Flow for general
corporate purposes not prohibited by the terms of this Indenture.

         Each Excess Cash Flow Offer shall remain open for a period of 20
Business Days, unless a longer period is required by law (the "Excess Cash Flow
Offer Period"). Promptly after the termination of the Excess Cash Flow Period
(the "Excess Cash Flow Payment Date"), the Company shall purchase and mail or
deliver payment for the Notes or portions thereof tendered pro rata or by such
other method as may be required by law.

         If an Excess Cash Flow Offer is required by the terms of this
Indenture, the Company shall commence such offer by mailing to the Trustee and
each Holder, at such Holder's last registered address, a notice, which shall
govern the terms of the Excess Cash Flow Offer and shall state:

                  (1) that the Excess Cash Flow Offer is being made pursuant to
         this covenant "Excess Cash Flow Offer," the principal amount of Notes
         which shall be accepted for payment and that all Notes validly tendered
         for which the Holders thereof have requested prepayment shall be
         accepted for payment on a pro rata basis (or by such other method as
         may be required by law).

                  (2) the purchase price and the date of purchase;

                  (3) that any Notes not tendered or accepted for payment
         pursuant to the Excess Cash Flow Offer shall continue to accrue
         interest;

                  (4) that, unless the Company defaults in the payment of the
         purchase price with respect to any Notes tendered, Notes accepted for
         payment pursuant to the Excess Cash Flow Offer shall cease to accrue
         interest after the Excess Cash Flow Payment Date;

                  (5) that Holders electing to have Notes purchased pursuant to
         an Excess Cash Flow Offer shall be required to surrender their Notes,
         with the form entitled "Option of Holder to Elect Purchase" on the
         reverse of the Note completed, to the Company prior to the close of
         business on the third Business Day immediately preceding the Excess
         Cash Flow Payment Date;

                  (6) that Holders shall be entitled to withdraw their election
         if the Company receives, not later than the close of business on the
         second Business Day preceding the Excess Cash Flow Payment Date, a
         telegram, facsimile transmission or letter setting forth the name of
         the Holder, the principal amount of Notes the Holder delivered for
         purchase and a statement that such Holder is withdrawing his election
         to have such Notes purchased;

                  (7) that if the aggregate purchase price for the Notes
         (exclusive of interest) tendered pursuant to the Excess Cash Flow Offer
         is less than the Excess Cash Flow, the Parent Guarantor and its
         Restricted Subsidiaries may use the remaining Excess Cash Flow for
         general corporate purposes not prohibited by the terms of this
         Indenture;

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<PAGE>   67

                  (8) that Holders whose Notes are purchased only in part shall
         be issued Notes representing the unpurchased portion of the Notes
         surrendered, provided that each Note purchased and each new Note issued
         shall be in principal amount of $1,000 or whole multiples thereof; and

                  (9) the instructions that Holders must follow in order to
         tender their Notes.

         On or before the Excess Cash Flow Payment Date, the Company shall (i)
accept for payment, on a pro rata basis to the extent necessary (unless some
other method is required by law), the Notes or portions thereof tendered
pursuant to the Excess Cash Flow Offer, (ii) deposit with the Payment Agent
money sufficient to pay the purchase price of all Notes or portions thereof so
accepted and (iii) deliver to the Trustee the Notes so accepted, together with
an Officers' Certificate stating that the Notes or portions thereof tendered to
the Company are accepted for payment. The Paying Agent shall promptly mail to
each Holder of Notes so accepted payment in an amount equal to the purchase
price of such Notes, including accrued and unpaid interest, and the Company
shall issue new Notes, and the Trustee shall promptly authenticate and mail such
new Notes to such Holders, in a principal amount equal to the unpurchased
portion of the Note surrendered.

         The Company shall make a public announcement of the results of the
Excess Cash Flow Offer as soon as practicable after the Excess Cash Flow Payment
Date. For the purposes of this covenant, the Trustee shall act as the Paying
Agent.

         Each Excess Cash Flow Offer shall be conducted in compliance with all
applicable laws, including without limitation, Regulation 14E of the Exchange
Act and the rules thereunder and all other applicable federal and state
securities laws. To the extent that the provisions of any securities laws or
regulations conflict with the provisions of this Section 4.19, the Company shall
comply with the applicable securities laws and regulations and shall not be
deemed to have breached its obligations under this Section 4.19 by virtue
thereof.

SECTION 4.20.     EXPLORATION COSTS.

         The Parent Guarantor and the Restricted Subsidiaries shall not incur
exploration costs (as reported in the supplemental oil and natural gas
information in the Parent Guarantor's annual financial statements in accordance
with GAAP) in excess of $10,000,000 in any fiscal year.

SECTION 4.21.     CONDUCT OF BUSINESS.

         The Parent Guarantor shall not, and shall not permit any of the
Restricted Subsidiaries to, engage in the conduct of any business other than the
Oil and Gas Business.

SECTION 4.22.     LIMITATION ON IMPAIRMENT OF LIEN.

         Neither the Parent Guarantor, the Company nor any of their Affiliates
will take or omit to take any action which action or omission would have the
result of adversely affecting or impairing the Lien in favor of the Collateral
Agent, on behalf of itself, the Approved Hedge Counterparties or Hedge Liquidity
Providers (as applicable), the Trustee and the Holders or the priority thereof,
with respect to the Collateral, and neither the Parent Guarantor, the Company
nor any of their Affiliates

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<PAGE>   68

shall grant to any Person, or suffer any Person (other than the Parent Guarantor
and the Restricted Subsidiaries) to have (other than to the Collateral Agent on
behalf of the Approved Hedge Counterparties or Hedge Liquidity Providers (as
applicable), the Trustee and the Holders) any interest whatsoever in the
Collateral other than Permitted Liens. Neither the Parent Guarantor nor any of
the Restricted Subsidiaries will enter into any agreement or instrument that by
its terms requires the proceeds received from any sale of Collateral to be
applied to repay, redeem, defease or otherwise acquire or retire any
Indebtedness, other than pursuant to this Indenture and the Security Documents.

SECTION 4.23.     LIEN ON ADDITIONAL COLLATERAL.

         (a) If, after the Closing Date, the Parent Guarantor or any of the
Restricted Subsidiaries shall (i) acquire any (x) Oil and Gas Assets or (y)
other assets as non-cash consideration for any Asset Disposition or (ii) engage
in successful drilling and exploration activities resulting in the creation of
new proved oil and gas reserves having a PV-10 Value in excess of $500,000, then
the Parent Guarantor shall, and shall cause each of the Restricted Subsidiaries
to, execute and file in the appropriate filing offices additional Security
Documents granting to the Collateral Agent for the benefit of the Approved Hedge
Counterparties or Hedge Liquidity Providers (as applicable), the Trustee and the
Holders a first Lien, subject only to Permitted Liens (or in the case of
property securing Acquired Indebtedness, to the extent not prohibited by the
terms of the instruments creating such Acquired Indebtedness, a junior Lien), as
is necessary or appropriate to ensure that the Lien of this Indenture and the
Security Documents covers substantially all of such new assets.

         (b) Without limitation of clause (a), on the date any Oil and Gas
Assets or interests in a Permitted Joint Venture shall be acquired in exchange
for or replacement of any Collateral, the Parent Guarantor shall, and shall
cause each of the Restricted Subsidiaries to, execute and file in the
appropriate filing offices additional Security Documents granting to the
Collateral Agent, for the benefit of the Approved Hedge Counterparties or Hedge
Liquidity Providers (as applicable), the Trustee and the Holders, a first Lien,
subject only to Permitted Liens (or in the case of property securing Acquired
Indebtedness, to the extent not prohibited by the terms of the instruments
creating such Acquired Indebtedness, a junior Lien), on such portion of such
assets as is necessary to ensure that the Lien of this Indenture and the
Security Documents covers substantially all of such assets received in exchange
or trade or on such interests in such Permitted Joint Venture.

         (c) In connection with any Security Documents executed and filed under
clause (a) or (b), the Parent Guarantor shall, and shall cause each Restricted
Subsidiary to, comply with the terms of the TIA to the extent applicable.

         (d) On March l5th of each year that the Notes are outstanding,
beginning with March 15, 2002, the Parent Guarantor and the Company shall review
the Oil and Gas Assets of the Parent Guarantor and the Restricted Subsidiaries
as of the preceding January 1st to ascertain whether substantially all of such
Oil and Gas Assets as of such January 1st are then subject to the Lien of this
Indenture and the Security Documents, provided that to the extent any such Oil
and Gas Assets secure Acquired Indebtedness, the discounted future net revenues
attributable to such Oil and Gas Assets may be excluded to the extent the
instruments securing such Acquired Indebtedness prohibit the Incurrence of a
Lien on such assets. If substantially all of such assets are not then subject to
the

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<PAGE>   69

Lien of this Indenture and the Security Documents, then the Parent Guarantor
shall, and shall cause the Restricted Subsidiaries to, execute and file in the
appropriate filing offices additional Security Documents granting to the
Collateral Agent for the benefit of the Approved Hedge Counterparties or Hedge
Liquidity Providers (as applicable), the Trustee and the Holders a first Lien,
subject only to Permitted Liens (or in the case of property securing Acquired
Indebtedness, to the extent not prohibited by the terms of instruments creating
such Acquired Indebtedness, a junior Lien), as is necessary or appropriate to
encumber substantially all such assets.

SECTION 4.24.     RESERVE REPORTS.

         (a) Not later than March 15 of each year, commencing March 15, 2002,
the Parent Guarantor shall furnish to the Trustee a Reserve Report that (i)
evaluates the Oil and Gas Assets of the Parent Guarantor and the Restricted
Subsidiaries as of the immediately preceding January 1st, and (ii) sets forth
the projected production from proved producing properties for each month during
the period commencing on such March 15 and ending 36 months after such date, for
both crude oil and natural gas production, individually, and in the aggregate on
an Mcfe basis. In addition, not later than 30 days following any acquisition or
exchange (or series of such transactions) of any Oil and Gas Assets having
aggregate volumes of proved developed producing reserves in excess of 20% of the
aggregate proved producing reserves set forth in the most recently delivered
Reserve Report, the Parent Guarantor shall furnish to the Trustee a supplemental
Reserve Report pertaining to the Oil and Gas Assets acquired in such exchange.
Each such Reserve Report of each year shall be prepared by certified independent
petroleum engineers or other independent petroleum consultant(s) of recognized
national standing.

         (b) With the delivery of each March 15 Reserve Report, the Parent
Guarantor shall provide to the Trustee, an Officers' Certificate certifying
that, in all material respects: (i) the information contained in the Reserve
Report and any other information delivered in connection therewith is true and
correct, (ii) the Parent Guarantor and/or a Restricted Subsidiary owns good and
defensible title to the Oil and Gas Assets evaluated in such Reserve Report and
such properties are free of all Liens except for Permitted Liens, (iii) except
as set forth on an exhibit to the certificate, on a net basis there are no gas
imbalances, take or pay or other prepayments with respect to the Oil and Gas
Assets evaluated in such Reserve Report which would require the Parent Guarantor
or a Restricted Subsidiary to deliver hydrocarbons produced from such Oil and
Gas Assets at some future time without then or thereafter receiving full payment
therefor, (iv) none of the Oil and Gas Assets have been sold since the date of
the last Reserve Report except as set forth on an exhibit to the certificate,
which certificate shall list all of its Oil and Gas Assets sold, (v) attached to
the certificate is a list of the Oil and Gas Assets added to and deleted from
the immediately prior Reserve Report and a list of all Persons disbursing
proceeds to the Parent Guarantor or a Restricted Subsidiary from the Oil and Gas
Assets, (vi) except as set forth on a schedule attached to the certificate all
of the Oil and Gas Assets evaluated by such Reserve Report are subject to the
Lien created by the Security Documents and showing calculations to demonstrate
compliance with clause (d) of Section 4.23 hereof and (vii) any change in
working interest or net revenue interest in its Oil and Gas Assets occurring and
the reason for such change.

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SECTION 4.25.     HEDGING OBLIGATIONS.

         The Company and/or a Restricted Subsidiary will enter into and maintain
Oil and Gas Hedging Contracts with an Approved Hedge Counterparty pursuant to
which the Company and/or a Restricted Subsidiary will receive a fixed price
payment or a minimum floor price so that at all times from the first day of the
month following the month in which the Closing Date occurs (subject to the
availability of hedge contracts) to July 1, 2006, the Parent Guarantor and/or a
Restricted Subsidiary will have a Hedged Revenue Ratio of not less than 3.0 to
1.0 as of the first Business Day of each month for the then current Hedge
Period; provided that:

                  (i) in no event shall the Company and/or a Restricted
         Subsidiary enter into Oil and Gas Hedging Contracts that, when in
         effect, hedge aggregate volumes in excess of 80% of (A) the Projected
         Proved Developed Producing Production of each of crude oil and natural
         gas and (B) the Projected Proved Developed Producing Production of both
         crude oil and natural gas, in each case, from the Oil and Gas Assets of
         the Company and/or the Restricted Subsidiaries for the then current
         Hedge Period and each month in the then current Hedge Period, except
         that the Company and/or a Restricted Subsidiary may enter into Oil and
         Gas Hedging Contracts which are price floor contracts, options for a
         price floor or other similar arrangements (and for which neither the
         Company nor any Restricted Subsidiary has any liability other than the
         payment of an initial premium price) which, with all Oil and Gas
         Hedging Contracts then in effect, result in the aggregate volumes
         exceeding 80% (but in no event in excess of 100%) of the Projected
         Proved Developed Producing Production of each of oil and natural gas of
         the Company and the Restricted Subsidiaries;

                  (ii) any Oil and Gas Hedging Contract executed pursuant to
         this Section 4.25 may be terminated (for any reason) without violation
         of this Section 4.25 if either (A) termination is required pursuant to
         clause (iv) below or (B) a replacement Oil and Gas Hedging Contract
         with an Approved Hedge Counterparty is entered into such that, after
         giving effect to such termination and the execution and delivery of
         such replacement Oil and Gas Hedging Contract, the Hedged Revenue Ratio
         is not less than 3.0 to 1.0, subject to clause (i) of this Section
         4.25;

                  (iii) if, as of any date of determination, NYMEX prices
         available for natural gas (Henry Hub) and crude oil (West Texas
         Intermediate) are less than $2.75 per MMBtu of natural gas (Henry Hub)
         or $18.00 per barrel of crude oil (West Texas Intermediate) for the one
         or more months during the then current Hedge Period (such period during
         which such prices are not available being the "Make-Up Period"), then
         the Hedged Revenue Ratio shall not be tested during such Make-Up
         Period, and as soon thereafter as available hedge prices for such
         Make-Up Period or any month during such Make-Up Period exceed the
         relevant minimum levels, then the Company and/or a Restricted
         Subsidiary shall be required to have a Hedged Revenue Ratio for the
         then current Hedge Period of not less than 3.0 to 1.0, subject to
         clause (i) of this Section 4.25; and

                  (iv) in the event of any sale, exchange or other disposition
         of Oil and Gas Assets by the Company and/or any Restricted Subsidiary,
         the Company and/or a Restricted Subsidiary shall calculate its Hedged
         Revenue Ratio on a pro forma basis (to exclude the Oil

                                       63
<PAGE>   71

         and Gas Asset disposed of utilizing the Projected Proved Developed
         Producing Production for such asset reflected in the most recently
         delivered Reserve Report) as of the first day of the month during which
         such sale, exchange or other disposition occurred for the Hedge Period
         commencing on such date and shall either (A) be in compliance with this
         Section 4.25 as of such day for the entirety of such Hedge Period or
         (B) terminate one or more Oil and Gas Hedging Contracts such that after
         giving effect to such termination, it would be in compliance with this
         Section 4.25.

         Notwithstanding anything herein to the contrary, the Company and/or a
Restricted Subsidiary will enter into Oil and Gas Hedging Contracts for ordinary
business purposes, to hedge their and the Restricted Subsidiaries' actual
exposure to fluctuations in commodity prices and not for speculative purposes.

         For the avoidance of doubt, it is the intention of the parties that if
(a) as of the first Business Day of each month for the then current Hedge Period
the Hedged Revenue Ratio is less than 3.0 to 1.0, and (b) a Reserve Report is
delivered which indicates an increase in the Projected Proved Producing
Production for any month or months in the then current Hedge Period or in the
aggregate Projected Proved Producing Production, then the Company and/or a
Restricted Subsidiary shall be obligated to enter into and maintain incremental
Oil and Gas Hedging Contracts with an Approved Hedge Counterparty to hedge
incremental volumes such that it has either met the minimum Hedge Revenue Ratio
of 3.0 to 1.0 or hedged the maximum amount of revenue for each month in the then
current Hedge Period possible without violating the volume caps established in
clause (i) of this Section 4.25.

SECTION 4.26.     THE COMPANY AS A WHOLLY OWNED SUBSIDIARY.

         Except as otherwise permitted by this Indenture, the Parent Guarantor
will ensure that the Company remains a Wholly Owned Subsidiary so long as any of
the Notes remains outstanding.

SECTION 4.27.     INDEPENDENT BOARD OF THE PARENT GUARANTOR.

         Within 45 days of the Closing Date, the Board of Directors of the
Parent Guarantor shall consist of at least three directors, at least 60% of whom
shall be Independent Directors, and such composition of the Board of Directors
shall be maintained so long as any of the Notes remain outstanding. Until such
time as a Board of Directors meeting the requirements of this Section 4.27 shall
have been appointed, the Parent Guarantor and the Restricted Subsidiaries shall
not engage in any activities requiring the approval of the Board of Directors of
the Parent Guarantor under the terms of this Indenture, except for the
transactions disclosed in the Company's Offering Memorandum dated June 13, 2001
with respect to, among other things, the sale of the Notes. Jefferies & Company,
Inc. shall have the right to require that the Parent Guarantor cause to be
appointed to its Board of Directors a person designated by Jefferies & Company,
Inc. for so long as any of the Notes remain outstanding.

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                                    ARTICLE 5

                                   SUCCESSORS

SECTION 5.01.     MERGER, CONSOLIDATION OR SALE OF ASSETS.

         (a) The Company shall not consolidate with or merge with or into, or
convey, transfer or lease, in one transaction or a series of transactions, all
or substantially all its assets to, any Person, unless (i) the Company or the
Parent Guarantor shall be the resulting, surviving or transferee corporation
(the "Successor Company"), (ii) the Successor Company (if not the Company) shall
expressly assume by a supplemental indenture, in a form acceptable to the
Trustee, all the obligations of the Company under this Indenture, the Notes and
the Security Documents; (iii) immediately after giving effect to such
transaction on a pro forma basis (and, treating any Indebtedness which becomes
an obligation of the Successor Company as a result of such transaction as having
been issued by such Person at the time of such transaction), no Default shall
have occurred and be continuing; (iv) immediately after giving effect to such
transaction, the Successor Company would be able to Incur an additional $1.00 of
Indebtedness pursuant to paragraph (a) of Section 4.09 hereof; (v) immediately
after giving effect to such transaction, the Successor Company shall have
Consolidated Net Worth in an amount that is not less than the Consolidated Net
Worth of the Parent Guarantor immediately prior to such transaction; and (vi)
the Company delivers to the Trustee an Officers' Certificate and an Opinion of
Counsel, each stating that such consolidation, merger or transfer and such
supplemental indenture, if any, complies with this Indenture. The Successor
Company shall be the successor to the Company and shall succeed to, and be
substituted for, and may exercise every right and power of, the Company under
this Indenture.

         (b) The Parent Guarantor shall not consolidate with or merge with or
into, or convey, transfer or lease, in one transaction or a series of
transactions, all or substantially all its assets to any Person unless: (i) the
Successor Company (if not the Parent Guarantor) shall expressly assume by a
supplemental indenture, in a form acceptable to the Trustee, all the obligations
of such Guarantor, if any, under this Indenture, the Guaranty Agreement and the
Security Documents; (ii) immediately after giving effect to such transaction or
transactions on a pro forma basis (and, treating any Indebtedness which becomes
an obligation of the Successor Company as a result of such transaction as having
been issued by such Person at the time of such transaction), no Default shall
have occurred and be continuing; (iii) immediately after giving effect to such
transaction, the Successor Company would be able to Incur an additional $1.00 of
Indebtedness pursuant to paragraph (a) of Section 4.09 hereof; (iv) immediately
after giving effect to such transaction, the Successor Company shall have
Consolidated Net Worth in an amount that is not less than the Consolidated Net
Worth of the Parent Guarantor immediately prior to such transaction; and (v) the
Company delivers to the Trustee an Officers' Certificate and an Opinion of
Counsel, each stating that such consolidation, merger or transfer and such
supplemental indenture, if any, complies with this Indenture.

         (c) No Subsidiary Guarantor shall consolidate with or merge with or
into (whether or not such Subsidiary Guarantor is the surviving Person), or
convey, transfer or lease, in one transaction or a series of transactions, all
or substantially all its assets to any Person (other than the Parent Guarantor,
the Company or another Subsidiary Guarantor), unless: (i) the Successor Company
(if other than such Subsidiary Guarantor) assumes all the obligations of such
Subsidiary Guarantor

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under this Indenture, the Guaranty Agreement and the Security Documents,
pursuant to an Assumption Agreement in substantially the form of Annex 1 to the
Guaranty Agreement; (ii) immediately after giving effect to such transaction on
a pro forma basis (and, treating any Indebtedness which becomes an obligation of
the Successor Company as a result of such transaction as having been issued by
such Person at the time of such transaction), no Default shall have occurred and
be continuing; (iii) such Subsidiary Guarantor, or the Successor Company, would
have a Consolidated Net Worth (immediately after giving effect to such
transaction) equal to or greater than the Consolidated Net Worth of such
Subsidiary Guarantor immediately preceding the transaction; and (iv) the Parent
Guarantor, immediately after giving pro forma effect to such transaction, would
be able to incur at least $1.00 of additional Indebtedness pursuant to paragraph
(a) of Section 4.09 hereof.

SECTION 5.02.     SUCCESSOR CORPORATION SUBSTITUTED.

         (a) Upon any consolidation or merger, or any sale, assignment,
transfer, lease, conveyance or other disposition of all or substantially all of
the assets of the Company in accordance with Section 5.01 hereof, the Successor
Company shall succeed to, and be substituted for (so that from and after the
date of such consolidation, merger, sale, assignment, transfer, lease,
conveyance or other disposition, the provisions of this Indenture referring to
the "Company" shall refer instead to the Successor Company and not to the
Company), and may exercise every right and power of the Company under this
Indenture with the same effect as if such Successor Company had been named as
the Company herein; provided, however, that the predecessor Company shall not be
relieved from its obligations under this Indenture or the Notes in the case of
any such lease.

         (b) Upon any consolidation or merger, or any sale, assignment,
transfer, lease, conveyance or other disposition of all or substantially all of
the assets of the Parent Guarantor in accordance with Section 5.01 hereof, the
Successor Company formed by such consolidation or into or with which the Parent
Guarantor is merged or to which such sale, assignment, transfer, lease,
conveyance or other disposition is made shall succeed to, and be substituted for
(so that from and after the date of such consolidation, merger, sale,
assignment, transfer, lease, conveyance or other disposition, the provisions of
this Indenture referring to the "Parent Guarantor" shall refer instead to the
Successor Company and not to the Parent Guarantor), and may exercise every right
and power of the Parent Guarantor under this Indenture with the same effect as
if such Successor Company had been named as the Parent Guarantor herein;
provided, however, that the predecessor Parent Guarantor shall not be relieved
from its obligations under this Indenture or the Notes in the case of any such
lease.

         (c) Upon any consolidation or merger, or any sale, assignment,
transfer, lease, conveyance or other disposition of all or substantially all of
the assets of a Subsidiary Guarantor in accordance with Section 5.01 hereof, the
Successor Company formed by such consolidation, or into or with which the
Subsidiary Guarantor is merged or to which such sale, assignment, transfer,
lease, conveyance or other disposition is made shall succeed to, and be
substituted for (so that from and after the date of such consolidation, merger,
sale, assignment, transfer, lease, conveyance or other disposition, the
provisions of this Indenture referring to the "Subsidiary Guarantor" shall refer
instead to the Successor Company and not to the Subsidiary Guarantor), and may
exercise every right and power of the Subsidiary Guarantor under this Indenture
with the same effect as if such Successor

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Company had been named as the Subsidiary Guarantor herein; provided, however,
that the predecessor Subsidiary Guarantor shall not be relieved from its
obligations under this Indenture or the Notes in the case of any such lease.

                                    ARTICLE 6

                              DEFAULTS AND REMEDIES

SECTION 6.01.     EVENTS OF DEFAULT.

         An "Event of Default" occurs if:

                  (a) the Company defaults in the payment when due of interest
         on, or Liquidated Damages, if any, with respect to, the Notes, and such
         default continues for a period of 30 days;

                  (b) the Company defaults in the payment of principal of or
         premium, if any, on any Note at its Stated Maturity, upon optional
         redemption, upon required repurchase, upon declaration or otherwise
         when due;

                  (c) the Company, the Parent Guarantor or any Subsidiary
         Guarantor fails to comply with any of the provisions of Section 5.01
         hereof;

                  (d) the Parent Guarantor or any Restricted Subsidiary fails to
         comply, after notice from the Trustee or the Holders of at least 25% in
         principal amount of the Notes then outstanding, with any of the
         applicable provisions under Sections 4.03, 4.07, 4.08, 4.09, 4.10
         (other than a failure to purchase Notes), 4.11, 4.12, 4.13, 4.15, 4.16,
         4.17, 4.18, 4.19, 4.20, 4.21, 4.22, 4.23, 4.24, 4.25, 4.26 or 4.27
         hereof and such default continues for a period of 30 days;

                  (e) the Company, the Parent Guarantor or any Subsidiary
         Guarantor fails to comply with any other agreement in this Indenture,
         the Notes or any Security Document for 60 days after the Company
         receives written notice of such failure from the Trustee or the Holders
         of at least 25% in principal amount of the Notes then outstanding;

                  (f) a default occurs under any mortgage, indenture or
         instrument under which there may be issued or by which there may be
         secured or evidenced any Indebtedness for money borrowed by the Parent
         Guarantor or any Restricted Subsidiary (or the payment of which is
         guaranteed by the Parent Guarantor or any Restricted Subsidiary),
         whether such Indebtedness or guarantee now exists, or is created after
         the date of this Indenture, which default (i) is caused by a failure to
         pay principal of or premium or interest on such Indebtedness prior to
         the expiration of any grace period provided in such Indebtedness,
         including any extension thereof (a "Payment Default") or (ii) results
         in the acceleration of such Indebtedness prior to its express maturity
         and, in each case, the principal amount of any such Indebtedness,
         together with the principal amount of any other such Indebtedness under
         which there has been a Payment Default or the maturity of which has
         been so accelerated,

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         aggregates in excess of $5,000,000; and provided, further, that if such
         default is cured or waived or any such acceleration rescinded, or such
         Indebtedness is repaid, within a period of 10 days from the
         continuation of such default beyond the applicable grace period or the
         occurrence of such acceleration, as the case may be, an Event of
         Default and any consequential acceleration of the Notes shall be
         automatically rescinded, so long as such rescission does not conflict
         with any judgment or decree;

                  (g) a judgment or decree for the payment of money in excess of
         $5,000,000 is rendered against the Parent Guarantor or any Restricted
         Subsidiary and such judgment decree is not paid or discharged for a
         period (during which execution shall not be effectively stayed,
         discharged or waived within 10 days after notice from the Trustee or
         the Holders of at least 25% in principal amount of the Notes then
         outstanding) of 60 days;

                  (h) the Guaranty Agreement or any Security Document ceases to
         be in full force and effect (other than in accordance with the terms of
         such Guaranty Agreement or Security Document) or the Parent Guarantor,
         the Company or a Subsidiary Guarantor denies or disaffirms its
         obligations under any Security Document to which it is a party or the
         Guaranty Agreement, as applicable, if such default continues for a
         period of 10 days after notice from the Trustee or any Holder to the
         Company; or

                  (i) the Parent Guarantor or any Restricted Subsidiary pursuant
         to or within the meaning of Bankruptcy Law:

                           (i) commences a voluntary case,

                           (ii) consents to the entry of an order for relief
                  against it in an involuntary case,

                           (iii) consents to the appointment of a Custodian of
                  it or for all or substantially all of its property,

                           (iv) makes a general assignment for the benefit of
                  its creditors, or

                           (v) generally is not paying its debts as they become
                  due;

                  (j) a court of competent jurisdiction enters an order or
         decree under any Bankruptcy Law that:

                           (i) is for relief against the Parent Guarantor or any
                  Restricted Subsidiary in an involuntary case;

                           (ii) appoints a Custodian of the Parent Guarantor or
                  any Restricted Subsidiary or for all or substantially all of
                  the property of the Parent Guarantor or any Restricted
                  Subsidiary; or

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                           (iii) orders the liquidation of the Parent Guarantor
                  or any Restricted Subsidiary;

         and the order or decree remains unstayed and in effect for 60
         consecutive days;

                  (k) a material breach of the representations or warranties
         contained in any Security Document or in this Indenture or a material
         misstatement in any certification provided pursuant to any Security
         Document or this Indenture after notice from the Trustee or the Holders
         of at least 25% in principal amount of the Notes then outstanding
         occurs and such breach continues unremedied for a period of 30 days.

SECTION 6.02.     ACCELERATION.

         If any Event of Default occurs and is continuing, the Trustee may, by
notice to the Company, or the Holders of at least 25% in principal amount of the
then outstanding Notes may, by notice to the Company and the Trustee, and the
Trustee shall, upon the request of such Holders, declare all the Notes to be due
and payable immediately at 100% of the principal amount thereof. Upon any such
declaration, the Notes shall become due and payable immediately at 100% of the
principal amount thereof. Notwithstanding the foregoing, if an Event of Default
specified in clause (i) or (j) of Section 6.01 hereof occurs with respect to the
Parent Guarantor or any Restricted Subsidiary, all outstanding Notes shall be
due and payable immediately at 100% of the principal amount thereof without
further action or notice. The Holders of a majority in principal amount of the
then outstanding Notes by written notice to the Trustee may on behalf of all of
the Holders rescind an acceleration and its consequences if the rescission would
not conflict with any judgment or decree and if all existing Events of Default
(except nonpayment of principal, interest, premium or Liquidated Damages, if
any, that have become due solely because of such acceleration) have been cured
or waived.

         If an Event of Default occurs by reason of any willful action (or
inaction) taken (or not taken) by or on behalf of the Company with the intention
of avoiding payment of the premium that the Company would have had to pay if the
Company then had elected to redeem the Notes pursuant to Section 3.07(a) hereof,
then, upon acceleration of the Notes, an equivalent premium shall also become
and be immediately due and payable, to the extent permitted by law, anything in
this Indenture or in the Notes to the contrary notwithstanding.

SECTION 6.03.     OTHER REMEDIES.

         If an Event of Default occurs and is continuing, the Trustee may pursue
any available remedy to collect the payment of principal of and premium,
interest and Liquidated Damages, if any, on the Notes or to enforce the
performance of any provision of the Notes, this Indenture or the Guaranty
Agreement.

         The Trustee may maintain a proceeding even if it does not possess any
of the Notes or does not produce any of them in the proceeding. A delay or
omission by the Trustee or any Holder of a Note in exercising any right or
remedy accruing upon an Event of Default shall not impair the right

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or remedy or constitute a waiver of or acquiescence in the Event of Default. All
remedies are cumulative to the extent permitted by law.

SECTION 6.04.     WAIVER OF PAST DEFAULTS.

         Holders of a majority in principal amount of the then outstanding Notes
by notice to the Trustee may on behalf of the Holders of all of the Notes waive
any existing Default or Event of Default and its consequences hereunder, except
a continuing Default or Event of Default in the payment of the principal of or
premium, interest or Liquidated Damages, if any, on the Notes (including in
connection with an offer to purchase). Upon any such waiver, such Default shall
cease to exist, and any Event of Default arising therefrom shall be deemed to
have been cured for every purpose of this Indenture; but no such waiver shall
extend to any subsequent or other Default or impair any right consequent
thereon.

SECTION 6.05.     CONTROL BY MAJORITY.

         Holders of a majority in principal amount of the then outstanding Notes
may direct the time, method and place of conducting any proceeding for
exercising any remedy available to the Trustee or exercising any trust or power
conferred on it. However, the Trustee may refuse to follow any direction that
conflicts with law or this Indenture or that the Trustee determines may be
unduly prejudicial to the rights of other Holders of Notes or that may involve
the Trustee in personal liability.

SECTION 6.06.     LIMITATION ON SUITS.

         A Holder of a Note may pursue a remedy with respect to this Indenture,
the Notes or the Guaranty Agreement only if:

                  (a) the Holder of a Note gives to the Trustee written notice
         of a continuing Event of Default;

                  (b) the Holders of at least 25% in principal amount of the
         then outstanding Notes make a written request to the Trustee to pursue
         the remedy;

                  (c) such Holder of a Note or Holders of Notes offer and, if
         requested, provide to the Trustee reasonable security or indemnity
         satisfactory to the Trustee against any loss, liability or expense;

                  (d) the Trustee does not comply with the request within 60
         days after receipt of the request and the offer and, if requested, the
         provision of indemnity; and

                  (e) during such 60-day period the Holders of a majority in
         principal amount of the then outstanding Notes do not give the Trustee
         a direction inconsistent with the request.

No Holder may enforce any right or remedy provided in any Security Document
(other than the Guaranty Agreement). Such rights and remedies will be enforced
by the Collateral Agent subject to the terms of the Intercreditor Agreement. A
Holder of a Note may not use this Indenture to

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prejudice the rights of another Holder of a Note or to obtain a preference or
priority over another Holder of a Note.

SECTION 6.07.     RIGHTS OF HOLDERS OF NOTES TO RECEIVE PAYMENT.

         Notwithstanding any other provision of this Indenture, the right of any
Holder of a Note to receive payment of principal of and premium, interest and
Liquidated Damages, if any, on the Note, on or after the respective due dates
expressed in the Note (including in connection with an offer to purchase), or to
bring suit for the enforcement of any such payment on or after such respective
dates, shall not be impaired or affected without the consent of such Holder.

SECTION 6.08.     COLLECTION SUIT BY TRUSTEE.

         If an Event of Default specified in Section 6.01(a) or (b) occurs and
is continuing, the Trustee is authorized to recover judgment in its own name and
as trustee of an express trust against the Company, the Parent Guarantor or any
Subsidiary Guarantor for the whole amount of principal of, premium, interest and
Liquidated Damages, if any, remaining unpaid on the Notes and interest on
overdue principal and, to the extent lawful, interest and Liquidated Damages, if
any, and such further amount as shall be sufficient to cover the costs and
expenses of collection, including the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel.

SECTION 6.09.     TRUSTEE MAY FILE PROOFS OF CLAIM.

         The Trustee is authorized to file such proofs of claim and other papers
or documents as may be necessary or advisable in order to have the claims of the
Trustee (including any claim for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel) and the
Holders of the Notes allowed in any judicial proceedings relative to the Company
(or any other obligor upon the Notes), its creditors or its property and shall
be entitled and empowered to collect, receive and distribute any money or other
property payable or deliverable on any such claims and any custodian in any such
judicial proceeding is hereby authorized by each Holder to make such payments to
the Trustee, and in the event that the Trustee shall consent to the making of
such payments directly to the Holders, to pay to the Trustee any amount due to
it for the reasonable compensation, expenses, disbursements and advances of the
Trustee, its agents and counsel, and any other amounts due the Trustee under
Section 7.07 hereof. To the extent that the payment of any such compensation,
expenses, disbursements and advances of the Trustee, its agents and counsel, and
any other amounts due the Trustee under Section 7.07 hereof out of the estate in
any such proceeding, shall be denied for any reason, payment of the same shall
be secured by a Lien on, and shall be paid out of, any and all distributions,
dividends, money, securities and other properties that the Holders may be
entitled to receive in such proceeding whether in liquidation or under any plan
of reorganization or arrangement or otherwise. Nothing herein contained shall be
deemed to authorize the Trustee to authorize or consent to or accept or adopt on
behalf of any Holder any plan of reorganization, arrangement, adjustment or
composition affecting the Notes or the rights of any Holder, or to authorize the
Trustee to vote in respect of the claim of any Holder in any such proceeding.

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SECTION 6.10.     PRIORITIES.

         If the Trustee collects any money pursuant to this Article or receives
any moneys under the Intercreditor Agreement, it shall pay out the money in the
following order:

                  First: to the Trustee, its agents and attorneys for amounts
         due under Section 7.07 hereof, including payment of all compensation,
         expense and liabilities incurred, and all advances made, by the Trustee
         and the Trustee's reasonable costs and expenses of collection;

                  Second: to Holders of Notes for amounts due and unpaid on the
         Notes for principal, premium, interest and Liquidated Damages, if any,
         ratably, without preference or priority of any kind, according to the
         amounts due and payable on the Notes for principal, premium, interest
         and Liquidated Damages, if any, respectively; and

                  Third: to the Company or to such party as a court of competent
         jurisdiction shall direct.

         The Trustee may fix a record date and payment date for any payment to
Holders of Notes pursuant to this Section 6.10.

SECTION 6.11.     UNDERTAKING FOR COSTS.

         In any suit for the enforcement of any right or remedy under this
Indenture or in any suit against the Trustee for any action taken or omitted by
it as a Trustee, a court in its discretion may require the filing by any party
litigant in the suit of an undertaking to pay the costs of the suit, and the
court in its discretion may assess reasonable costs, including reasonable
attorneys' fees, against any party litigant in the suit, having due regard to
the merits and good faith of the claims or defenses made by the party litigant.
This Section does not apply to a suit by the Trustee, a suit by a Holder of a
Note pursuant to Section 6.07 hereof, or a suit by Holders of more than 10% in
principal amount of the then outstanding Notes.

                                    ARTICLE 7

                                     TRUSTEE

SECTION 7.01.     DUTIES OF TRUSTEE.

         (a) If an Event of Default has occurred and is continuing, the Trustee
shall exercise such of the rights and powers vested in it by this Indenture, and
use the same degree of care and skill in its exercise, as a prudent man would
exercise or use under the circumstances in the conduct of his own affairs.

         (b) Except during the continuance of an Event of Default:

                  (i) the duties of the Trustee shall be determined solely by
         the express provisions of this Indenture and the Trustee need perform
         only those duties that are specifically set forth

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         in this Indenture and no others, and no implied covenants or
         obligations shall be read into this Indenture against the Trustee; and

                  (ii) in the absence of bad faith on its part, the Trustee may
         conclusively rely, as to the truth of the statements and the
         correctness of the opinions expressed therein, upon certificates or
         opinions furnished to the Trustee and conforming to the requirements of
         this Indenture. However, the Trustee shall examine the certificates and
         opinions to determine whether or not they conform to the requirements
         of this Indenture.

         (c) The Trustee may not be relieved from liabilities for its own
negligent action, its own negligent failure to act, or its own willful
misconduct, except that:

                  (i) this paragraph does not limit the effect of paragraph (b)
         of this Section 7.01;

                  (ii) the Trustee shall not be liable for any error of judgment
         made in good faith by a Responsible Officer, unless it is proved that
         the Trustee was negligent in ascertaining the pertinent facts; and

                  (iii) the Trustee shall not be liable with respect to any
         action it takes or omits to take in good faith in accordance with a
         direction received by it pursuant to Section 6.05 hereof.

         (d) Whether or not therein expressly so provided, every provision of
this Indenture that in any way relates to the Trustee is subject to paragraphs
(a), (b) and (c) of this Section 7.01.

         (e) No provision of this Indenture shall require the Trustee to expend
or risk its own funds or incur any liability. The Trustee shall be under no
obligation to exercise any of its rights and powers under this Indenture at the
request of any Holders, unless such Holder shall have offered to the Trustee
security and indemnity satisfactory to it against any loss, liability or
expense.

         (f) The Trustee shall not be liable for interest on any money received
by it except as the Trustee may agree in writing with the Company. Money held in
trust by the Trustee need not be segregated from other funds except to the
extent required by law.

SECTION 7.02.     RIGHTS OF TRUSTEE.

         (a) The Trustee may conclusively rely upon any document believed by it
to be genuine and to have been signed or presented by the proper Person. The
Trustee need not investigate any fact or matter stated in the document.

         (b) Before the Trustee acts or refrains from acting, it may require an
Officers' Certificate or an Opinion of Counsel or both. The Trustee shall not be
liable for any action it takes or omits to take in good faith in reliance on
such Officers' Certificate or Opinion of Counsel. The Trustee may consult with
counsel and the written advice of such counsel or any Opinion of Counsel shall
be full and complete authorization and protection from liability in respect of
any action taken, suffered or omitted by it hereunder in good faith and in
reliance thereon.

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         (c) The Trustee may act through its attorneys and agents and shall not
be responsible for the misconduct or negligence of any agent appointed with due
care.

         (d) The Trustee shall not be liable for any action it takes or omits to
take in good faith that it believes to be authorized or within the rights or
powers conferred upon it by this Indenture.

         (e) Unless otherwise specifically provided in this Indenture, any
demand, request, direction or notice from the Company shall be sufficient if
signed by an Officer of the Company.

         (f) The Trustee shall be under no obligation to exercise any of the
rights or powers vested in it by this Indenture at the request or direction of
any of the Holders unless such Holders shall have offered to the Trustee
reasonable security or indemnity against the costs, expenses and liabilities
that might be incurred by it in compliance with such request or direction.

         (g) The Trustee shall have no duty to inquire as to the performance of
the Company's or the Parent Guarantor's covenants in Article 4 hereof. In
addition, the Trustee shall not be deemed to have knowledge of any Default or
Event of Default except: (1) any Event of Default occurring pursuant to Section
6.01(a) or 6.01(b) hereof; or (2) any Default or Event of Default of which is
Responsible Officer shall have received written notification or obtained actual
knowledge.

         (h) The Trustee is not required to give any bond or surety with respect
to the performance of its duties or the exercise of its powers under this
Indenture.

         (i) In the event the Trustee receives inconsistent or conflicting
requests and indemnity from two or more groups of Holders of Notes, each
representing less than a majority in aggregate principal amount of the Notes
then outstanding, pursuant to the provisions of this Indenture, the Trustee, in
its sole discretion, may determine what action, if any, shall be taken.

         (j) The permissive right of the Trustee to take the actions permitted
by this Indenture shall not be construed as an obligation or duty to do so.

         (k) Except for information provided by the Trustee concerning the
Trustee, the Trustee shall have no responsibility for any information in any
offering memorandum or other disclosure material distributed with respect to the
Notes, and the Trustee shall have no responsibility for compliance with any
state or federal securities laws in connection with the Notes.

SECTION 7.03.     INDIVIDUAL RIGHTS OF TRUSTEE.

         The Trustee in its individual or any other capacity may become the
owner or pledgee of Notes and may otherwise deal with the Company, any Guarantor
or any Affiliate of the Company or the Parent Guarantor with the same rights it
would have if it were not Trustee. Any Agent may do the same with like rights
and duties. The Trustee is also subject to Sections 7.10 and 7.11 hereof.

SECTION 7.04.     TRUSTEE'S DISCLAIMER.

         The Trustee shall not be responsible for and makes no representation as
to the validity or adequacy of this Indenture or the Notes, it shall not be
accountable for the Company's use of the

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proceeds from the Notes or any money paid to the Company or upon the Company's
direction under any provision of this Indenture, it shall not be responsible for
the use or application of any money received by any Paying Agent other than the
Trustee, and it shall not be responsible for any statement or recital herein or
any statement in the Notes or any other document in connection with the sale of
the Notes or pursuant to this Indenture other than its certificate of
authentication.

SECTION 7.05.     NOTICE OF DEFAULTS.

         If a Default or Event of Default occurs and is continuing and if it is
known to the Trustee, the Trustee shall mail to Holders of Notes a notice of the
Default or Event of Default within 90 days after it occurs. Except in the case
of a Default or Event of Default in payment of principal of or premium, if any,
or interest on any Note, the Trustee may withhold the notice if and so long as a
committee of its Responsible Officers in good faith determines that withholding
the notice is not opposed to the interests of the Holders of the Notes.

SECTION 7.06.     REPORTS BY TRUSTEE TO HOLDERS OF THE NOTES.

         Within 60 days after each May 15 beginning with the May 15 following
the date of this Indenture, and for so long as Notes remain outstanding, the
Trustee shall mail to the Holders of the Notes a brief report dated as of such
reporting date that complies with TIA Section 313(a) (but if no event described
in TIA Section 313(a) has occurred within the twelve months preceding the
reporting date, no report need be transmitted). The Trustee also shall comply
with TIA Section 313(b)(2) and Section 313(b)(1). The Trustee shall also
transmit by mail all reports as required by TIA Section 313(c).

         Commencing at the time this Indenture is qualified under the TIA, a
copy of each report at the time of its mailing to the Holders of Notes shall be
mailed to the Company and filed with the SEC and each stock exchange on which
the Notes are listed in accordance with TIA Section 313(d). The Company shall
promptly notify the Trustee when the Notes are listed on any stock exchange.

SECTION 7.07.     COMPENSATION AND INDEMNITY.

         The Company shall pay to the Trustee from time to time reasonable
compensation for its acceptance of this Indenture and services hereunder. The
Trustee's compensation shall not be limited by any law on compensation of a
trustee of an express trust. The Company shall reimburse the Trustee promptly
upon request for all reasonable disbursements, advances and expenses incurred or
made by it in addition to the compensation for its services. Such expenses shall
include the reasonable compensation, disbursements and expenses of the Trustee's
agents and counsel.

         The Company and the Guarantors shall indemnify the Trustee against any
and all losses, liabilities or expenses incurred by it arising out of or in
connection with the acceptance or administration of its duties under this
Indenture, including the costs and expenses of enforcing this Indenture against
the Company (including this Section 7.07) and defending itself against any claim
(whether asserted by the Company, any Guarantor or any Holder or any other
person) or liability in connection with the exercise or performance of any of
its powers or duties hereunder, except to the extent any such loss, liability or
expense may be attributable to its negligence, bad faith or willful misconduct.
The Trustee shall notify the Company promptly of any claim for which it may seek

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<PAGE>   83

indemnity. Failure by the Trustee to so notify the Company shall not relieve the
Company or the Guarantors of their obligations hereunder. The Company shall
defend the claim and the Trustee shall cooperate in the defense. The Trustee may
have separate counsel and the Company shall pay the reasonable fees and expenses
of such counsel. The Company need not pay for any settlement made without its
consent, which consent shall not be unreasonably withheld.

         The obligations of the Company and the Guarantors under this Section
7.07 shall survive the satisfaction and discharge of this Indenture.

         To secure the Company's payment obligations in this Section 7.07, the
Trustee shall have a Lien prior to the Notes on all money or property held or
collected by the Trustee, except that held in trust to pay principal and
interest on particular Notes. Such Lien shall survive the satisfaction and
discharge of this Indenture.

         When the Trustee incurs expenses or renders services after an Event of
Default specified in Section 6.01(i) or (j ) hereof occurs, the expenses and the
compensation for the services (including the fees and expenses of its agents and
counsel) are intended to constitute expenses of administration under any
applicable bankruptcy law.

         The Trustee shall comply with the provisions of TIA Section 313(b)(2)
to the extent applicable.

SECTION 7.08.     REPLACEMENT OF TRUSTEE.

         A resignation or removal of the Trustee and appointment of a successor
Trustee shall become effective only upon the successor Trustee's acceptance of
appointment as provided in this Section.

         The Trustee may resign in writing at any time and be discharged from
the trust hereby created by so notifying the Company. The Holders of Notes of a
majority in principal amount of the then outstanding Notes may remove the
Trustee by so notifying the Trustee and the Company in writing. The Company may
remove the Trustee if:

                  (a) the Trustee fails to comply with Section 7.10 hereof;

                  (b) the Trustee is adjudged a bankrupt or an insolvent or an
         order for relief is entered with respect to the Trustee under any
         applicable bankruptcy law;

                  (c) a Custodian or public officer takes charge of the Trustee
         or its property; or

                  (d) the Trustee becomes incapable of acting.

         If the Trustee resigns or is removed or if a vacancy exists in the
office of Trustee for any reason, the Company shall promptly appoint a successor
Trustee. Within one year after the successor Trustee takes office, the Holders
of a majority in principal amount of the then outstanding Notes may appoint a
successor Trustee to replace the successor Trustee appointed by the Company.

         If a successor Trustee does not take office within 60 days after the
retiring Trustee resigns or is removed, the retiring Trustee, the Company, or
the Holders of Notes of at least 10% in principal

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<PAGE>   84

amount of the then outstanding Notes may petition any court of competent
jurisdiction for the appointment of a successor Trustee.

         If the Trustee, after written request by any Holder of a Note who has
been a Holder of a Note for at least six months, fails to comply with Section
7.10 hereof, such Holder of a Note may petition any court of competent
jurisdiction for the removal of the Trustee and the appointment of a successor
Trustee.

         A successor Trustee shall deliver a written acceptance of its
appointment to the retiring Trustee and to the Company. Thereupon, the
resignation or removal of the retiring Trustee shall become effective, and the
successor Trustee shall have all the rights, powers and duties of the Trustee
under this Indenture. The successor Trustee shall mail a notice of its
succession to Holders of the Notes. The retiring Trustee shall promptly transfer
all property held by it as Trustee to the successor Trustee, provided that all
sums owing to the Trustee hereunder have been paid and subject to the Lien
provided for in Section 7.07 hereof. Notwithstanding replacement of the Trustee
pursuant to this Section 7.08, the Company's obligations under Section 7.07
hereof shall continue for the benefit of the retiring Trustee.

SECTION 7.09.     SUCCESSOR TRUSTEE BY MERGER, ETC.

         If the Trustee consolidates, merges or converts into, or transfers all
or substantially all of its corporate trust business to, another corporation,
the successor corporation without any further act shall be the successor
Trustee. As soon as practicable, the successor Trustee shall mail a notice of
its succession to the Company and the Holders of the Notes. Any such successor
must nevertheless be eligible and qualified under the provisions of Section 7.10
hereof.

SECTION 7.10.     ELIGIBILITY; DISQUALIFICATION.

         There shall at all times be a Trustee hereunder that is a corporation
organized and doing business under the laws of the United States of America or
of any state thereof that is authorized under such laws to exercise corporate
trustee power, that is subject to supervision or examination by federal or state
authorities and that has a combined capital and surplus of at least $100,000,000
as set forth in its most recent published annual report of condition.

         This Indenture shall always have a Trustee who satisfies the
requirements of TIA Section 310(a)(1), (2) and (5). The Trustee is subject to
TIA Section 310(b); provided, however, that there shall be excluded from the
operation of TIA Section 310(b)(1) any indenture or indentures under which other
securities, or certificates of interest or participation in other securities, of
the Company are outstanding, if the requirements for such exclusion set forth in
TIA Section 310(b)(1) are met.

SECTION 7.11.     PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY.

         The Trustee is subject to TIA Section 311(a), excluding any creditor
relationship listed in TIA Section 311(b). A Trustee who has resigned or been
removed shall be subject to TIA Section 311(a) to the extent indicated therein.

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<PAGE>   85

                                    ARTICLE 8

                    LEGAL DEFEASANCE AND COVENANT DEFEASANCE;
                       SATISFACTION AND DISCHARGE OF NOTES

SECTION 8.01.     DISCHARGE OF LIABILITY ON SECURITIES; DEFEASANCE.

         (a) When (i) the Company delivers to the Trustee all outstanding Notes
(other than Notes replaced pursuant to Section 2.07) for cancellation or (ii)
all outstanding Notes have become due and payable, whether at maturity or as a
result of the mailing of a notice of redemption pursuant to Article 3 hereof and
the Company irrevocably deposits with the Trustee funds sufficient to pay at
maturity or upon redemption all outstanding Notes, including interest and any
Liquidated Damages thereon to maturity or such redemption date (other than Notes
replaced pursuant to Section 2.07), and if in either case the Company pays all
other sums payable hereunder by the Company, then this Indenture shall, subject
to Section 8.01(c), cease to be of further effect. The Trustee shall acknowledge
satisfaction and discharge of this Indenture on demand of the Company
accompanied by an Officers' Certificate and an Opinion of Counsel and at the
cost and expense of the Company.

         (b) Subject to Sections 8.01(c) and 8.02, (i) the Company at any time
may terminate all its obligations under the Notes and this Indenture and all of
the obligations of the Parent Guarantor and the Subsidiary Guarantors under the
Guaranty Agreement and this Indenture ("Legal Defeasance") or (ii) the Company
and the Parent Guarantor may terminate (a) their obligations contained in
Article 4 hereof (other than those in Sections 4.01, 4.02, 4.05, 4.06 and 4.14);
(b) the operation of Sections 6.01(f), 6.01(i) and (j) (with respect to
Restricted Subsidiaries only) and 6.01(g) hereof and (c) the limitations
contained in clauses (iv) and (v) of Section 5.01(a) hereof and clauses (iii)
and (iv) of Section 5.01(b) hereof ("Covenant Defeasance"). The Company may
exercise its Legal Defeasance option notwithstanding its prior exercise of its
Covenant Defeasance option.

         If the Company exercises its Legal Defeasance option, payment of the
Notes may not be accelerated because of an Event of Default with respect
thereto. If the Parent Guarantor and the Company exercise their Covenant
Defeasance option, payment of the Notes may not be accelerated because of an
Event of Default specified in Section 6.01(d), 6.01(e), 6.01(f), 6.01(g),
6.01(i) (but only with respect to Restricted Subsidiaries), 6.01(j) (but only
with respect to Restricted Subsidiaries) or because of the failure to comply
with Section 5.01(a)(iv) and (v) and 5.01(b)(iii) and (iv). If the Company
exercises its Legal Defeasance option or its Covenant Defeasance option, the
Parent Guarantor and each Subsidiary Guarantor, if any, will be released from
all its obligations with respect to its Guarantee, and the Lien of the Security
Documents will also be released.

         Upon satisfaction of the conditions set forth herein and upon request
of the Company, the Trustee shall acknowledge in writing the discharge of those
obligations that the Company terminates.

         (c) Notwithstanding clauses (a) and (b) above, the Company's
obligations in Sections 2.03, 2.04, 2.05, 2.06, 2.07, 2.10, 2.12, 7.07, 7.08 and
this Article 8 shall survive until the Notes have been paid in full. Thereafter
the Company's obligations in Sections 7.07, 8.04 and 8.05 shall survive.

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<PAGE>   86

SECTION 8.02.     CONDITIONS TO DEFEASANCE.

         The Company may exercise its Legal Defeasance option or its Covenant
Defeasance option only if:

                  (1) the Company irrevocably deposits in trust with the Trustee
         money or United States Government Obligations for the payment of
         principal and interest and Liquidated Damages, if any, on the Notes to
         maturity or redemption, as the case may be;

                  (2) the Company delivers to the Trustee a certificate from a
         nationally recognized firm of independent accountants expressing their
         opinion that the payments of principal of and interest and Liquidated
         Damages, if any, when due and without reinvestment on the deposited
         United States Government Obligations plus any deposited money without
         investment will provide cash at such times and in such amounts as will
         be sufficient to pay principal and interest and Liquidated Damages, if
         any, when due on all the Notes to maturity or redemption, as the case
         may be;

                  (3) 123 days pass after the deposit is made and during the
         123-day period no Default specified in Section 6.01(i) or (j) with
         respect to the Company occurs which is continuing at the end of the
         period;

                  (4) the deposit does not constitute a default under any other
         agreement binding on the Company, the Parent Guarantor or any
         Subsidiary Guarantor;

                  (5) the Company delivers to the Trustee an Opinion of Counsel
         to the effect that the trust resulting from the deposit does not
         constitute, or is qualified as, a regulated investment company under
         the Investment Company Act of 1940;

                  (6) in the case of the Legal Defeasance option, the Company
         shall have delivered to the Trustee an Opinion of Counsel stating that
         (i) the Company has received from, or there has been published by, the
         Internal Revenue Service a ruling, or (ii) since the date of this
         Indenture there has been a change in the applicable Federal income tax
         law, in either case to the effect that, and based thereon such Opinion
         of Counsel shall confirm that, the Holders will not recognize income,
         gain or loss for Federal income tax purposes as a result of such
         defeasance and will be subject to Federal income tax on the same
         amounts, in the same manner and at the same times as would have been
         the case if such defeasance had not occurred;

                  (7) in the case of the Covenant Defeasance option, the Company
         shall have delivered to the Trustee an Opinion of Counsel to the effect
         that the Holders will not recognize income, gain or loss for Federal
         income tax purposes as a result of such Covenant Defeasance and will be
         subject to Federal income tax on the same amounts, in the same manner
         and at the same times as would have been the case if such Covenant
         Defeasance had not occurred; and

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<PAGE>   87

                  (8) the Company delivers to the Trustee an Officers'
         Certificate and an Opinion of Counsel, each stating that all conditions
         precedent to the defeasance and discharge of the Notes as contemplated
         by this Article 8 have been complied with.

         Before or after a deposit, the Company may make arrangements
satisfactory to the Trustee for the redemption of Notes at a future date in
accordance with Article 3.

SECTION 8.03.     APPLICATION OF TRUST MONEY.

         The Trustee shall hold in trust money or United States Government
Obligations deposited with it pursuant to this Article 8. It shall apply the
deposited money and the money from United States Government Obligations through
the Paying Agent and in accordance with this Indenture to the payment of
principal of and interest and Liquidated Damages, if any, on the Notes.

SECTION 8.04.     REPAYMENT TO COMPANY.

         The Trustee and the Paying Agent shall promptly turn over to the
Company upon request any excess money or securities held by them at any time.

         Subject to any applicable abandoned property law, the Trustee and the
Paying Agent shall pay to the Company upon request any money held by them for
the payment of principal or interest and Liquidated Damages, if any, that
remains unclaimed for two years, and, thereafter, Holders entitled to the money
must look to the Company for payment as general creditors.

SECTION 8.05.     INDEMNITY FOR GOVERNMENT OBLIGATIONS.

         The Company and the Parent Guarantor jointly and severally shall pay
and shall indemnify the Trustee against any tax, fee or other charge imposed on
or assessed against deposited United States Government Obligations or the
principal and interest received on such United States Government Obligations.

SECTION 8.06.     REINSTATEMENT.

         If the Trustee or Paying Agent is unable to apply any money or United
States Government Obligations in accordance with this Article 8 by reason of any
legal proceeding or by reason of any order or judgment of any court or
governmental authority enjoining, restraining or other prohibiting such
application, then the Company's obligations under this Indenture and the Notes
and any Security Documents shall be revived and reinstated as though no deposit
had occurred pursuant to this Article 8 until such time as the Trustee or Paying
Agent is permitted to apply all such money or United States Government
Obligations in accordance with this Article 8; provided, however, that, if the
Company has made any payment of interest on or Liquidated Damages, if any, or
principal of any Notes because of the reinstatement of its obligations, the
Company shall be subrogated to the rights of the Holders of such Notes to
receive such payment from the money or United States Government Obligations held
by the Trustee or Paying Agent.

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<PAGE>   88

                                    ARTICLE 9

                        AMENDMENT, SUPPLEMENT AND WAIVER

SECTION 9.01.     WITHOUT CONSENT OF HOLDERS OF NOTES.

         Notwithstanding Section 9.02 of this Indenture, the Company, the Parent
Guarantor and the Trustee may amend or supplement this Indenture or the Notes
without the consent of any Holder of a Note:

                  (a) to cure any ambiguity, omission, defect or inconsistency;

                  (b) to provide for uncertificated Notes in addition to or in
         place of certificated Notes;

                  (c) to provide for the assumption of the Company's obligations
         to the Holders of the Notes pursuant to Article 5 hereof;

                  (d) to make any change that would provide any additional
         rights or benefits to the Holders of the Notes or that does not
         materially adversely affect the legal rights hereunder of any Holder of
         the Note; or

                  (e) to comply with requirements of the SEC in order to effect
         or maintain the qualification of this Indenture under the TIA.

         Upon the request of the Company accompanied by a resolution of the
Board of Directors of the Parent Guarantor authorizing the execution of any such
amended or supplemental indenture, and upon receipt by the Trustee of the
documents described in Section 7.02 hereof, the Trustee shall join with the
Company and the Parent Guarantor in the execution of any amended or supplemental
indenture authorized or permitted by the terms of this Indenture and to make any
further appropriate agreements and stipulations that may be therein contained,
but the Trustee shall not be obligated to enter into such amended or
supplemental Indenture that affects its own rights, duties or immunities under
this Indenture or otherwise.

SECTION 9.02.     WITH CONSENT OF HOLDERS OF NOTES.

         Except as provided below in this Section 9.02, the Company, the Parent
Guarantor and the Trustee may amend or supplement this Indenture and the Notes
may be amended or supplemented with the consent of the Holders of at least a
majority in principal amount of the Notes then outstanding (including, without
limitation, consents obtained in connection with a purchase of, or tender offer
or exchange offer for the Notes), and, subject to Sections 6.04 and 6.07 hereof,
any existing Default or Event of Default or compliance with any provision of
this Indenture or the Notes may be waived with the consent of the Holders of a
majority in principal amount of the then outstanding Notes (including, without
limitation, consents obtained in connection with a tender offer or exchange
offer for the Notes).

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<PAGE>   89

         Upon the request of the Company accompanied by a resolution of the
Board of Directors of the Parent Guarantor authorizing the execution of any such
amended or supplemental indenture, and upon the filing with the Trustee of
evidence satisfactory to the Trustee of the consent of the Holders of Notes as
aforesaid, and upon receipt by the Trustee of the documents described in Section
9.06 hereof, the Trustee shall join with the Company and the Parent Guarantor in
the execution of such amended or supplemental indenture unless such amended or
supplemental indenture affects the Trustee's own rights, duties or immunities
under this Indenture or otherwise, in which case the Trustee may in its
discretion, but shall not be obligated to, enter into such amended or
supplemental indenture.

         It shall not be necessary for the consent of the Holders of Notes under
this Section 9.02 to approve the particular form of any proposed amendment,
supplement or waiver, but it shall be sufficient if such consent approves the
substance thereof.

         After an amendment, supplement or waiver under this Section becomes
effective, the Company shall mail to the Holders of Notes affected thereby a
notice briefly describing the amendment, supplement or waiver. Any failure of
the Company to mail such notice, or any defect therein, shall not, however, in
any way impair or affect the validity of any such amended or supplemental
Indenture or waiver. Subject to Sections 6.04 and 6.07 hereof, the Holders of a
majority in principal amount of the Notes then outstanding may waive compliance
in a particular instance by the Company with any provision of this Indenture or
the Notes. However, without the consent of each Holder affected, an amendment,
supplement or waiver may not (with respect to any Notes held by a non-consenting
Holder):

                  (a) reduce the principal amount of Notes whose Holders must
         consent to an amendment, supplement or waiver;

                  (b) reduce the rate of or extend the time for payment of
         interest on any Note;

                  (c) reduce the principal of or extend the Stated Maturity of
         any Note or alter any of the provisions with respect to the redemption
         or purchase of the Notes by the Company (except as provided in Sections
         3.09, 4.10, 4.15 and 4.19 hereof);

                  (d) waive a Default or Event of Default in the payment of
         principal of or premium, interest or Liquidated Damages, if any, on the
         Notes (except a rescission of acceleration of the Notes by the Holders
         of at least a majority in principal amount of the Notes and a waiver of
         the payment default that resulted from such acceleration);

                  (e) make any Note payable in money other than that stated in
         the Notes;

                  (f) make any change in the provisions of this Indenture
         relating to waivers of past Defaults or Events of Default or the rights
         of Holders of Notes to receive payments of principal of or premium,
         interest or Liquidated Damages, if any, on the Notes (except as
         permitted in clause (g) below);

                  (g) waive a redemption or repurchase payment with respect to
         any Note (other than a payment required by Sections 4.10, 4.15 and 4.19
         hereof);

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<PAGE>   90

                  (h) make any change in the ranking of the Notes relative to
         other Indebtedness of the Company in a manner adverse to the Holders of
         Notes;

                  (i) make any change in the foregoing amendment provisions
         which require each Holder's consent or in the waiver provisions; or

                  (j) release any Collateral from the Liens created pursuant to
         the Indenture and the Security Documents or release the Parent
         Guarantor or any Subsidiary Guarantor from any of its obligations under
         the Indenture or the Guaranty Agreement, as the case may be, in any
         case otherwise than in accordance with the terms of this Indenture, the
         Guaranty Agreement and the Security Documents.

SECTION 9.03.     COMPLIANCE WITH TRUST INDENTURE ACT.

         Every amendment or supplement to this Indenture or the Notes shall be
set forth in an amended or supplemental Indenture that complies with the TIA as
then in effect.

SECTION 9.04.     REVOCATION AND EFFECT OF CONSENTS.

         Until an amendment, supplement or waiver becomes effective, a consent
to it by a Holder of a Note is a continuing consent by the Holder of a Note and
every subsequent Holder of a Note or portion of a Note that evidences the same
debt as the consenting Holder's Note, even if notation of the consent is not
made on any Note. However, any such Holder of a Note or subsequent Holder of a
Note may revoke the consent as to its Note if the Trustee receives written
notice of revocation before the date the waiver, supplement or amendment becomes
effective. An amendment, supplement or waiver becomes effective in accordance
with its terms and thereafter binds every Holder.

SECTION 9.05.     NOTATION ON OR EXCHANGE OF NOTES.

         The Trustee may place an appropriate notation about an amendment,
supplement or waiver on any Note thereafter authenticated. The Company in
exchange for all Notes may issue and the Trustee shall authenticate new Notes
that reflect the amendment, supplement or waiver.

         Failure to make the appropriate notation or issue a new Note shall not
affect the validity and effect of such amendment, supplement or waiver.

SECTION 9.06.     TRUSTEE TO SIGN AMENDMENTS, ETC.

         The Trustee shall sign any amended or supplemental indenture authorized
pursuant to this Article 9 if the amendment or supplement does not adversely
affect the rights, duties, liabilities or immunities of the Trustee. The Company
may not sign an amendment or supplemental indenture until the Board of Directors
of the Parent Guarantor approves it. In executing any amended or supplemental
indenture, the Trustee shall be entitled to receive and (subject to Section
7.01) shall be fully protected in relying upon, an Officers' Certificate and an
Opinion of Counsel stating that the execution of such amended or supplemental
indenture is authorized or permitted by this Indenture.

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<PAGE>   91

                                   ARTICLE 10

                               GUARANTEES OF NOTES

SECTION 10.01.      PARENT GUARANTEE AND SUBSIDIARY GUARANTEES.

         Payment of the principal of and interest on the Notes is guaranteed by
the Guarantors as set forth in the Guaranty Agreement.

                                   ARTICLE 11

                                  MISCELLANEOUS

SECTION 11.01.      TRUST INDENTURE ACT CONTROLS.

         If any provision of this Indenture limits, qualifies or conflicts with
the duties imposed by TIA Section 318(c), the imposed duties shall control.

SECTION 11.02.      NOTICES.

         Any notice or communication by the Company, the Parent Guarantor or the
Trustee to the others is duly given if in writing (in the English language) and
delivered in person or mailed by first class mail (registered or certified,
return receipt requested), telecopier or overnight air courier guaranteeing next
day delivery, to the others' address:

         If to the Company or the Parent Guarantor:

                           Tri-Union Development Corporation
                           530 Lovett Boulevard
                           Houston, Texas 77006
                           Attention:  Chief Financial Officer
                           Telephone:       (713) 533-4000
                           Telecopy No.:    (713) 627-2769

         If to the Trustee:

                           Firstar Bank, National Association
                           101 East 5th Street
                           St. Paul, Minnesota  55101
                           Telephone:       (651) 229-2600
                           Telecopy No.:    (651) 229-6415

         The Company, the Parent Guarantor or the Trustee, by notice to the
others may designate additional or different addresses for subsequent notices or
communications.

         Any notice or communication to a Holder shall be mailed by first class
mail, certified or registered, return receipt requested, or delivered by
overnight air courier guaranteeing next day

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<PAGE>   92

delivery, in each case to its address shown on the register kept by the
Registrar. Any notice or communication shall also be so mailed to any Person
described in TIA Section 313(c), to the extent required by the TIA. Failure to
provide a notice or communication to a Holder or any defect in it shall not
affect its sufficiency with respect to other Holders.

         All notices and communications shall be deemed to have been duly given:
at the time delivered by hand, if personally delivered; five Business Days after
being deposited in the mail, postage prepaid, if mailed; when receipt
acknowledged, if telecopied; and the next Business Day after timely delivery to
the courier, if sent by overnight air courier guaranteeing next day delivery.
Notwithstanding the foregoing, notices to the Trustee shall be effective only
upon receipt.

         If a notice or communication is given in the manner provided above
within the time prescribed, it is duly given, whether or not the addressee
receives it.

         If the Company gives a notice or communication to Holders, it shall
give a copy at the same time to the Trustee and each Agent.

         In case by reason of the suspension of regular mail service, or by
reason of any other cause, it shall be impossible to mail any notice required by
this Indenture, then such method of notification as shall be made with the
approval of the Trustee shall constitute a sufficient mailing of such notice.

SECTION 11.03.    COMMUNICATION BY HOLDERS OF NOTES WITH OTHER HOLDERS OF NOTES.

         Holders may communicate pursuant to TIA Section 312(b) with other
Holders with respect to their rights under this Indenture or the Notes. The
Company, the Trustee, the Registrar and anyone else shall have the protection of
TIA Section 312(c).

SECTION 11.04.      CERTIFICATE AND OPINION AS TO CONDITIONS PRECEDENT.

         Upon any request or application by the Company to the Trustee to take
any action under this Indenture, the Company shall furnish to the Trustee:

                  (a) an Officers' Certificate in form and substance reasonably
         satisfactory to the Trustee (which shall include the statements set
         forth in Section 11.05 hereof) stating that, in the opinion of the
         signers, all conditions precedent and covenants, if any, provided for
         in this Indenture relating to the proposed action have been satisfied;
         and

                  (b) an Opinion of Counsel in form and substance reasonably
         satisfactory to the Trustee (which shall include the statements set
         forth in Section 11.05 hereof) stating that, in the opinion of such
         counsel, all such conditions precedent and covenants have been
         satisfied.

SECTION 11.05.      STATEMENTS REQUIRED IN CERTIFICATE OR OPINION.

         Each certificate or opinion with respect to compliance with a condition
or covenant provided for in this Indenture (other than a certificate provided
pursuant to TIA Section 314(a)(4)) shall comply with the provisions of TIA
Section 314(e) and shall include:

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<PAGE>   93

                  (a) a statement that the Person making such certificate or
         opinion has read such covenant or condition;

                  (b) a brief statement as to the nature and scope of the
         examination or investigation upon which the statements or opinions
         contained in such certificate or opinion are based;

                  (c) a statement that, in the opinion of such Person, he or she
         has made such examination or investigation as is necessary to enable
         him or her to express an informed opinion as to whether or not such
         covenant or condition has been satisfied; and

                  (d) a statement as to whether or not, in the opinion of such
         Person, such condition or covenant has been satisfied.

SECTION 11.06.      RULES BY TRUSTEE AND AGENTS.

         The Trustee may make reasonable rules for action by or at a meeting of
Holders. The Registrar or Paying Agent may make reasonable rules and set
reasonable requirements for its functions.

SECTION 11.07.      NO PERSONAL LIABILITY OF DIRECTORS, OFFICERS, EMPLOYEES
                    AND SHAREHOLDERS.

         No past, present or future director, officer, employee, incorporator,
member, partner or shareholder or other owner of Capital Stock of the Company or
any Guarantor, as such, shall have any liability for any obligations of the
Company or any Guarantor under the Notes, the Parent Guarantee, the Subsidiary
Guarantees, this Indenture or for any claim based on, in respect of, or by
reason of, such obligations or their creation. Each Holder by accepting a Note
waives and releases all such liability. The waiver and release are part of the
consideration for issuance of the Notes.

SECTION 11.08.      GOVERNING LAW.

         THE LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE
AND ENFORCE THIS INDENTURE AND THE NOTES.

SECTION 11.09.      NO ADVERSE INTERPRETATION OF OTHER AGREEMENTS.

         This Indenture may not be used to interpret any other indenture, loan
or debt agreement of the Parent Guarantor or the Restricted Subsidiaries or of
any other Person. Any such indenture, loan or debt agreement may not be used to
interpret this Indenture.

SECTION 11.10.      SUCCESSORS.

         All agreements of the Company and the Guarantors in this Indenture and
the Notes shall bind their successors. All agreements of the Trustee in this
Indenture shall bind its successors.

                                       86
<PAGE>   94

SECTION 11.11.      SEVERABILITY.

         In case any provision in this Indenture or in the Notes shall be
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby.

SECTION 11.12.      COUNTERPART ORIGINALS.

         The parties may sign any number of copies of this Indenture. Each
signed copy shall be an original, but all of them together represent the same
agreement.

SECTION 11.13.      TABLE OF CONTENTS, HEADINGS, ETC.

         The Table of Contents, Cross-Reference Table and Headings of the
Articles and Sections of this Indenture have been inserted for convenience of
reference only, are not to be considered a part of this Indenture and shall in
no way modify or restrict any of the terms or provisions hereof.

SECTION 11.14.      CONSENT TO JURISDICTION.

         (a) Each of the Company and the Parent Guarantor irrevocably submits to
the non-exclusive jurisdiction of any New York state or U.S. federal court
located in the Borough of Manhattan in the City and State of New York over any
suit, action or proceeding arising out of or relating to this Indenture, a
Registration Rights Agreement or any Guarantee or Note. Each of the Company and
the Parent Guarantor irrevocably waives, to the fullest extent permitted by law,
any objection which it may have to the laying of the venue of any such suit,
action or proceeding brought in such a court and any claim that any such suit,
action or proceeding brought in such a court has been brought in any
inconvenient forum.

         (b) Each of the Company and the Parent Guarantor hereby irrevocably
consents to the service of process of any of the aforementioned courts in any
such action or proceeding by the mailing of copies thereof by registered or
certified mail, postage prepaid, to such Company or Parent Guarantor at its
respective address, such service to become effective thirty (30) days after such
mailing.

         (c) Nothing herein shall affect the right of the Trustee or any Holder
to serve process in any other manner permitted by law or to commence legal
proceedings or otherwise proceed against the Company or the Parent Guarantor in
any other jurisdiction.

         (d) Each of the Company and the Parent Guarantor hereby (i) irrevocably
and unconditionally waives, to the fullest extent permitted by law, trial by
jury in any legal action or proceeding relating to this Indenture and for any
counterclaim therein; (ii) irrevocably waives, to the maximum extent not
prohibited by law, any right it may have to claim or recover in any such
litigation any special, exemplary, punitive or consequential damages, or damages
other than, or in addition to, actual damages; (iii) certifies that no party
hereto nor any representative or agent of counsel for any party hereto has
represented, expressly or otherwise, or implied that such party would not, in
the event of litigation, seek to enforce the foregoing waivers, and (iv)
acknowledges that it

                                       87
<PAGE>   95

has been induced to enter into this Indenture and the transactions contemplated
hereby and thereby by, among other things, the waivers and certifications
contained in this Section 11.14.

SECTION 11.15       INTERCREDITOR AGREEMENT.

         This Indenture is subject to the limitations, terms and conditions set
forth in the Intercreditor Agreement. Each Holder of a Note, by its acceptance
thereof, is deemed to have authorized and instructed the Trustee to enter into
the Intercreditor Agreement on its behalf.

                                   ARTICLE 12

                                    SECURITY

SECTION 12.01       GRANT OF SECURITY INTEREST.

         In order to secure the due and punctual payment of the principal of,
premium, if any, and interest on the Notes when and as the same shall be due and
payable, whether on the date installments of interest are due to be paid, at
maturity, by acceleration, purchase, repurchase, redemption or otherwise, and
interest on the overdue principal of, premium, if any, and interest (to the
extent permitted by law), if any, on the Notes and the performance of all other
Obligations of the Company to the Holders or the Trustee under this Indenture
and the Notes, the Company, the Parent Guarantor and the Subsidiary Guarantors
hereby covenant to execute and deliver the Security Documents concurrently with
this Indenture. The Security Documents shall grant to the Collateral Agent a
security interest in the Collateral and when filed shall be deemed hereby
incorporated by reference herein to the same extent and as fully as if set forth
in their entirety at this place, and reference is made hereby to each Security
Document for a more complete description of the terms and provisions thereof.
Each Holder, by accepting a Note, agrees to all of the terms and provisions of
the Security Documents and the Trustee agrees to all of the terms and provisions
of the Security Documents signed by it.

SECTION 12.02       EXECUTION OF INTERCREDITOR AGREEMENT.

         Concurrently with the execution and delivery of this Indenture, the
Company, the Parent Guarantor, the Subsidiary Guarantors, any Approved Hedge
Counterparties or Hedge Liquidity Providers party thereto, the Collateral Agent
and the Trustee will execute and deliver the Intercreditor Agreement.

                         [Signatures on following page]

                                       88
<PAGE>   96

                                            SIGNATURES

                                            TRI-UNION DEVELOPMENT CORPORATION,
                                            as the Company

                                            By:
                                               ---------------------------------
                                            Name:
                                                 -------------------------------
                                            Title:

                                            TRIBO PETROLEUM CORPORATION,
                                            as Parent Guarantor

                                            ---------------------------------
                                            By:
                                               ---------------------------------
                                            Name:
                                                 -------------------------------
                                            Title:

                                            FIRSTAR BANK, NATIONAL ASSOCIATION,
                                            as Trustee

                                            By:
                                               ---------------------------------

                                       89<PAGE>   1
                                                                     EXHIBIT 4.2

                           TRIBO PETROLEUM CORPORATION
                        TRI-UNION DEVELOPMENT CORPORATION
                           TRI-UNION OPERATING COMPANY

                                  130,000 UNITS
                                  CONSISTING OF

         $1,000 PRINCIPAL AMOUNT OF 12.5% SENIOR SECURED NOTES DUE 2006
                      OF TRI-UNION DEVELOPMENT CORPORATION

                                      WITH

                        ONE SHARE OF CLASS A Common Stock
                         OF TRIBO PETROLEUM CORPORATION

                               PURCHASE AGREEMENT

                                                                   June 13, 2001

JEFFERIES & COMPANY INC.
909 Fannin, Suite 3100
Houston, TX 77010

Ladies and Gentlemen:

         Tri-Union Development Corporation, a Texas corporation (the "Company"
or the "Issuer"), Tri-Union Operating Company, a Delaware corporation and a
wholly owned subsidiary of the Company (the "Subsidiary"), and Tribo Petroleum
Corporation, a Texas corporation and the parent corporation of the Issuer
("Tribo", and together with the Subsidiary, the "Guarantors"), hereby confirm
their agreement with you (the "Initial Purchaser") as set forth below.

         1. The Securities. Subject to the terms and conditions herein
contained, the Issuer and Tribo propose to issue and sell to the Initial
Purchaser an aggregate of 130,000 units (each a "Unit" and collectively, the
"Units"), each Unit consisting of $1,000 principal amount of 12.5% Series A
Senior Secured Notes due 2006 of the Issuer (the "Notes") and one share of
Tribo's Class A Common Stock, par value $.01 per share, of Tribo (the "Class A
Common Stock"). The Notes will initially be guaranteed (the "Guarantees") on a
senior secured basis by the Guarantors pursuant to a Guaranty Agreement, dated
as of the Closing Date, among the Company, the Guarantors and the other parties
thereto (the "Guaranty Agreement"). The Notes are to be issued under an
indenture (the "Indenture") to be dated as of June 18, 2001 by and among the
Issuer, Tribo and Firstar Bank, National Association (the "Trustee").
Additionally, the Initial Purchaser shall receive an aggregate of 65,000 shares
of Class B Common Stock, par value $.01 per share, of Tribo (the "Class B Common
Stock," and together with the Class A Common Stock, the

<PAGE>   2

"Common Stock"). The Notes, the Units, the Guarantees and the Common Stock are
collectively referred to herein as the "Securities." Pursuant to the Mortgage,
Deed of Trust, Assignment of Production, Security Agreement and Financing
Statement, dated as of the Closing Date, given by each of the Issuer and the
Subsidiary (the "Mortgages"), the Issuer and the Subsidiary will grant and
pledge to Wells Fargo Bank Minnesota, National Association, as collateral agent
(the "Collateral Agent"), for the equal and ratable benefit of the holders of
the Notes (the "Noteholders") and certain other parties described therein, a
security interest in substantially all of the crude oil and natural gas
properties of the Company and the Subsidiary. The Mortgages, together with (i)
the Guaranty Agreement, (ii) the Pledge and Collateral Account Agreement, dated
as of the Closing Date, among the Company, the Collateral Agent and the other
parties thereto (the "Pledge Agreement"), and (iii) the Intercreditor and
Collateral Agency Agreement, dated as of the Closing Date, among the Company,
the Guarantors, the Trustee, the Collateral Agent and the other parties thereto,
are sometimes referred to herein collectively as the "Security Documents."

         The Securities will be offered and sold to the Initial Purchaser
without being registered under the Securities Act of 1933, as amended (the
"Act"), in reliance on exemptions therefrom. The Notes will be issued pursuant
to the Issuer's First Amended Plan of Reorganization (the "Plan") and an order
(the "Confirmation Order") entered by The United States Bankruptcy Court for the
Southern District of Texas, Houston Division (the "Bankruptcy Court") in In re
Tri-Union Development Corporation (Case No. 00-32498-H4-11) (the "Bankruptcy
Case"), on May 23, 2001 (the "Confirmation Date") in accordance with 11 U.S.C.
Section 1129.

         In connection with the sale of the Securities, the Issuer and the
Guarantors have prepared a final offering memorandum dated June 13, 2001 (the
"Final Memorandum" or "Memorandum"), setting forth or including, among other
things, a description of the terms of the Securities, the terms of the offering
of the Securities and a description of the business and assets of the Issuer and
the Guarantors and any material developments relating to the Issuer and the
Guarantors occurring after the date of the most recent historical financial
statements included therein.

         The Initial Purchaser and its direct and indirect transferees of the
Units (and the related Guarantees) will be entitled to the benefits of a
registration rights agreement to be dated as of the Closing Date (as defined in
Section 3 below) (the "Notes Registration Rights Agreement"), pursuant to which
the Issuer and the Guarantors will agree, among other things, to file with the
Securities and Exchange Commission (the "Commission"), under the circumstances
set forth therein, (i) a registration statement under the Act (the "Exchange
Offer Registration Statement"), relating to Series B Senior Secured Notes due
2006 of the Issuer (the "Exchange Notes") to be offered in exchange (the
"Exchange Offer") for the Notes, and (ii) as and to the extent required by the
Notes Registration Rights Agreement, a shelf registration statement pursuant to
Rule 415 under the Act (the "Notes Shelf Registration Statement"), relating to
the resale by certain holders of the Notes. The Initial Purchaser and its direct
and indirect transferees will also be entitled to the benefits of an additional
registration rights agreement, dated as of the Closing Date (the "Equity
Registration Rights Agreement"), pursuant to which the Noteholders and the
Initial Purchaser will be entitled to, among other things, the registration
under the Act of their shares of Common Stock pursuant to a registration
statement to be filed by Tribo (the "Equity Registration Statement," and,
together with the Exchange Offer Registration Statement and the Notes Shelf

                                       2
<PAGE>   3

Registration Statement, the "Registration Statements") and to use their best
efforts to cause such Registration Statements to be declared effective. This
Purchase Agreement (this "Agreement"), the Securities, the Indenture, the Notes
Registration Rights Agreement, the Equity Registration Rights Agreement, and the
Security Documents are hereinafter referred to collectively as the "Operative
Documents."

         2. Representations and Warranties. The Issuer and the Guarantors,
jointly and severally, represent and warrant to the Initial Purchaser that:

                  (a) Neither the Final Memorandum nor any amendment or
         supplement thereto as of the date thereof and at all times subsequent
         thereto up to the Closing Date contained or contains any untrue
         statement of a material fact or omitted or omits to state a material
         fact necessary to make the statements therein, in the light of the
         circumstances under which they were made, not misleading, except that
         the representations and warranties set forth in this Section 2(a) do
         not apply to statements or omissions made in reliance upon and in
         conformity with information relating to the Initial Purchaser furnished
         to the Issuer or the Guarantors in writing by the Initial Purchaser
         expressly for use in the Final Memorandum or any amendment or
         supplement thereto.

                  (b) Tribo has the authorized, issued and outstanding
         capitalization as set forth in the Final Memorandum; all of the
         outstanding shares of capital stock of the Issuer and of each of the
         Guarantors have been, and as of the Closing Date will be, duly
         authorized and validly issued, are fully paid and nonassessable and
         were not issued in violation of any preemptive or similar rights; all
         of the outstanding shares of capital stock of the Subsidiary are and,
         as of the Closing Date, will be, owned by the Company free and clear of
         all liens, encumbrances, equities and claims or restrictions on
         transferability (other than those imposed by the Act and the securities
         or "Blue Sky" laws of certain jurisdictions) or voting; all of the
         outstanding shares of capital stock of the Company are and, as of the
         Closing Date, will be, owned by Tribo free and clear of all liens,
         encumbrances, equities and claims or restrictions on transferability
         (other than those imposed by the Act and the securities or "Blue Sky"
         laws of certain jurisdictions) or voting; except as set forth in the
         Final Memorandum, there are no outstanding (i) options, warrants or
         other rights to purchase, (ii) agreements or other obligations of the
         Issuer or the Guarantor to issue or (iii) other rights to convert any
         obligation into, or exchange any securities for, shares of capital
         stock of or ownership interests in the Issuer or the Guarantors. Except
         as disclosed in the Final Memorandum, neither the Issuer nor any of the
         Guarantors owns, directly or indirectly, any shares of capital stock or
         any other equity or long-term debt securities or have any equity
         interest in any firm, partnership, joint venture or other entity.

                  (c) The Issuer and each of the Guarantors is duly
         incorporated, validly existing and in good standing under the laws of
         its respective jurisdiction of incorporation and has all requisite
         corporate power and authority to own its properties and conduct its
         business as now conducted and as described in the Final Memorandum; the
         Issuer and each of the Guarantors is duly qualified to do business as a
         foreign corporation in good standing in all other jurisdictions where
         the ownership or leasing of its properties or the conduct of its
         business requires such qualification, except where the failure to be so

                                       3
<PAGE>   4

         qualified would not, individually or in the aggregate, have a material
         adverse effect on the general affairs, management, business, assets,
         condition (financial or otherwise) or results of operations of the
         Issuer and the Guarantors considered as a whole (any such event, a
         "Material Adverse Effect").

                  (d) The Issuer and each of the Guarantors has all requisite
         corporate power and authority to execute, deliver and perform its
         respective obligations under this Agreement and the other Operative
         Documents to which it is a party and to consummate the transactions
         contemplated hereby and thereby, including, without limitation, the
         power and authority to issue, sell and deliver the Securities as
         contemplated by this Agreement.

                  (e) This Agreement has been duly and validly authorized,
         executed and delivered by the Issuer and each of the Guarantors.

                  (f) The Indenture and each other Operative Document to which
         the Issuer or any of the Guarantors is a party has been duly and
         validly authorized by the Issuer and the Guarantors (to the extent a
         party thereto) and, when duly executed and delivered (assuming the due
         authorization, execution and delivery thereof by each other party
         thereto), will be the valid and legally binding agreement of the Issuer
         and the Guarantors, enforceable against each of them in accordance with
         its terms, except as such enforceability may be limited by bankruptcy,
         insolvency, reorganization, moratorium and other similar laws now or
         hereinafter in effect relating to or affecting creditors' rights
         generally and to general principles of equity (regardless of whether
         such enforceability is considered in a proceeding in equity or at law).
         The Indenture meets the requirements for qualification under the Trust
         Indenture Act of 1939, as amended (the "TIA").

                  (g) The Notes have been duly and validly authorized for
         issuance and sale to the Initial Purchaser by the Issuer pursuant to
         this Agreement and, when issued and authenticated in accordance with
         the terms of the Indenture and delivered against payment therefor in
         accordance with the terms hereof, will be the legally valid and binding
         obligations of the Issuer, enforceable against it in accordance with
         their terms and entitled to the benefits of the Indenture, except as
         such enforceability may be limited by bankruptcy, insolvency,
         reorganization, moratorium and other similar laws now or hereinafter in
         effect relating to or affecting creditors' rights generally and to
         general principles of equity (regardless of whether such enforceability
         is considered in a proceeding in equity or at law).

                  (h) The Exchange Notes have been duly and validly authorized
         for issuance by the Issuer and, when issued and authenticated in
         accordance with the terms of the Indenture, the Notes Registration
         Rights Agreement and the Exchange Offer, will be the legally valid and
         binding obligations of the Issuer, enforceable against it in accordance
         with their terms and entitled to the benefits of the Indenture, except
         as such enforceability may be limited by bankruptcy, insolvency,
         reorganization, moratorium and other similar laws now or hereinafter in
         effect relating to or affecting creditors' rights generally and to
         general principles of equity (regardless of whether such enforceability
         is considered in a proceeding in equity or at law).

                                       4
<PAGE>   5

                  (i) Each of the Notes Registration Rights Agreement and the
         Equity Registration Rights Agreement have been duly authorized by the
         Issuer, the Subsidiary and Tribo, as applicable, and, when duly
         executed and delivered by the Issuer, the Subsidiary and Tribo, as
         applicable (assuming the due execution and delivery thereof by the
         Initial Purchaser), will be the legally valid and binding obligation of
         the Issuer, the Subsidiary and Tribo, as applicable, enforceable
         against each of them in accordance with its terms, except as such
         enforceability may be limited by bankruptcy, insolvency,
         reorganization, moratorium and other similar laws now or hereinafter in
         effect relating to or affecting creditors' rights generally and to
         general principles of equity (regardless of whether such enforceability
         is considered in a proceeding in equity or at law) and, as to rights of
         indemnification and contribution, by principles of public policy or
         U.S. federal or state securities laws relating thereto.

                  (j) The shares of Class A Common Stock and Class B Common
         Stock to be issued to the Noteholders and the Initial Purchaser,
         respectively, have been duly and validly authorized for issuance by
         Tribo and, when issued, will be duly authorized, validly issued, fully
         paid and non-assessable and will not be subject to any preemptive or
         similar rights.

                  (k) After giving effect to the Plan and the Confirmation
         Order, no consent, waiver, approval, authorization or order of or
         filing, registration, qualification, license or permit of or with any
         court or governmental agency or body, or third party is required for
         (i) the issuance and sale by the Issuer of the Notes to the Initial
         Purchaser or the consummation by the Issuer of each of the other
         transactions contemplated hereby or by any of the other Operative
         Documents, (ii) the issuance and sale by the Guarantors of the
         Guarantees or the consummation by the Guarantors of the other
         transactions contemplated hereby or by any of the Operative Documents,
         or (iii) the issuance and sale by Tribo of the Common Stock, except, in
         each case, such as have been or, prior to the Closing Date, will be
         obtained, and other than such as may be required under state securities
         or "Blue Sky" laws in connection with the purchase and resale of the
         Securities by the Initial Purchaser and the receipt by the Issuer and
         the Guarantors of an order from the Commission declaring the Exchange
         Offer Registration Statement, the Shelf Registration Statement and/or
         the Equity Registration Statement effective. Neither the Issuer nor any
         of the Guarantors is (i) in violation of its charter or bylaws, (ii)
         after giving effect to the Plan and the Confirmation Order, in breach
         or violation of any statute, judgment, decree, order, rule or
         regulation applicable to any of them or any of their respective
         properties or assets, except for any such breach or violation which
         would not, individually or in the aggregate, have a Material Adverse
         Effect, or (iii) after giving effect to the Plan and the Confirmation
         Order, in breach of or default under (nor has any event occurred which,
         with notice or passage of time or both, would constitute a default
         under) or in violation of any of the terms or provisions of any
         indenture, mortgage, deed of trust, loan agreement, note, lease,
         license, permit, certificate, contract or other agreement or instrument
         to which any of them is a party or to which any of them or their
         respective properties or assets is subject (collectively, "Contracts"),
         except for any such breach, default, violation or event which would
         not, individually or in the aggregate, have a Material Adverse Effect.

                                       5
<PAGE>   6

                  (l) As of the Closing Date, the execution, delivery and
         performance by the Issuer and the Guarantors of this Agreement and each
         of the other Operative Documents (to the extent a party thereto) and
         the consummation of the transactions contemplated hereby and thereby
         (including, without limitation, the issuance and sale of the Securities
         to the Initial Purchaser and the issuance of the Exchange Notes in the
         Exchange Offer), do not and will not violate, conflict with or
         constitute or result in a breach of or a default under (or constitute
         an event which with notice or passage of time or both would constitute
         a default under) or cause an acceleration of any obligation under, or
         (except for the transactions contemplated hereby and thereby) result in
         the imposition or creation of (or the obligation to create or impose)
         any lien, security interest or encumbrance on any properties or assets
         of either the Issuer or any Guarantor with respect to (i) the terms or
         provisions of any Contract, except for any such conflict, breach,
         violation, default or event which would not, individually or in the
         aggregate, have a Material Adverse Effect, (ii) the charter or bylaws
         (or similar organizational document) of the Issuer or any of the
         Guarantors, or (iii) (assuming compliance with all applicable state
         securities or "Blue Sky" laws and assuming the accuracy of the
         representations and warranties of the Initial Purchaser in Section 8
         hereof) any statute, judgment, decree, order, rule or regulation
         applicable to the Issuer or any of the Guarantors or any of their
         respective properties or assets.

                  (m) Each of BDO Seidman, LLP and Hidalgo, Banfill, Zlotnik &
         Kermali, P.C., who are reporting on the audited financial statements of
         the Issuer included in the Final Memorandum, are, with respect to the
         Issuer and each of the Guarantors, independent public accountants
         within the meaning of the Act and the rules and regulations promulgated
         thereunder. The audited financial statements of Tribo and related notes
         thereto included in the Final Memorandum present fairly in all material
         respects the consolidated financial position of the Issuer and the
         Guarantors, as of the dates indicated and the consolidated results of
         their operations and cash flow for the periods specified, and are in
         accordance in all material respects with the applicable requirements of
         Regulation S-X promulgated under the Securities Exchange Act of 1934,
         as amended (the "Exchange Act"), as though such audited financial
         statements were being presented in a registration statement on Form S-1
         under the Act. The summary and selected financial and statistical data
         included in the Final Memorandum present fairly in all material
         respects the information shown therein and have been prepared and
         compiled on a basis consistent with the audited financial statements
         included therein.

                  (n) The pro forma financial statements (including the notes
         thereto) and the other pro forma financial information included in the
         Final Memorandum (i) comply as to form in all material respects with
         the applicable requirements of Regulation S-X promulgated under the
         Exchange Act, (ii) have been prepared in all material respects in
         accordance with the Commission's rules and guidelines with respect to
         pro forma financial statements, and (iii) have been properly computed
         on the bases described therein; in each case as though such pro forma
         financial statements were being presented in a registration statement
         on Form S-1 under the Act, the assumptions used in the preparation of
         the pro forma financial data and other pro forma financial information
         included in the Final Memorandum are reasonable and the adjustments
         used therein are appropriate to give effect to the transactions or
         circumstances referred to therein.

                                       6
<PAGE>   7

                  (o) The historical information underlying the estimates of the
         reserves of the Company and the Guarantors supplied by the Company and
         the Guarantors to Huddleston & Co., Inc. and DeGolyer and MacNaughton,
         independent petroleum and geological engineering firms (the "Petroleum
         Engineers"), for the purposes of preparing the reserve reports of the
         Company referenced in the Final Memorandum (the "Reserve Reports"),
         including, without limitation, production volumes, sales prices for
         production, contractual pricing provisions under oil or gas sales or
         marketing contracts or under hedging arrangements, costs of operations
         and development, and working interest and net revenue information
         relating to the Company's and the Guarantors' ownership interests in
         properties, was true and correct in all material respects on the date
         of such Reserve Reports; the estimates of future capital expenditures
         and other future exploration and development costs supplied to the
         Petroleum Engineers were prepared in good faith and with a reasonable
         basis; the information provided to the Petroleum Engineers for purposes
         of preparing the Reserve Reports was prepared in accordance with
         customary industry practices; to the best of the Company's knowledge,
         the Petroleum Engineers were, as of the date of the Reserve Reports
         prepared by them, and are, as of the date hereof, independent petroleum
         and geological engineers with respect to the Company; and other than
         normal production of reserves and intervening spot market product price
         fluctuations, and except as disclosed in the Final Memorandum, neither
         the Company nor any of the Guarantors is aware of any facts or
         circumstances that have the potential to have a Material Adverse Effect
         on the reserves in the aggregate, or the aggregate present value of
         future net cash flows therefrom, as described in the Final Memorandum
         and as reflected in the Reserve Reports.

                  (p) Except as described in the Final Memorandum, as of the
         date hereof, (i) except for royalties held in suspense by the Issuer in
         the ordinary course of business, all royalties, rentals, deposits and
         other amounts due on the oil and gas properties of the Company and the
         Guarantors have been properly and timely paid, and no proceeds from the
         sale or production attributable to the oil and gas properties of the
         Company and the Guarantors are currently being held in suspense by any
         purchaser thereof, except where such amounts due could not, singly or
         in the aggregate, have a Material Adverse Effect on the Company or the
         Guarantors, and (ii) there are no claims under take-or-pay contracts
         pursuant to which natural gas purchasers have any make-up rights
         affecting the interests of the Company or the Guarantors in their
         respective oil and gas properties, except where such claims could not,
         singly or in the aggregate, have a Material Adverse Effect on the
         Company or the Guarantors.

                  (q) The Bankruptcy Court has entered the Confirmation Order in
         the Bankruptcy Case, confirming the Plan on the Confirmation Date in
         accordance with 11 U.S.C. Section 1129. The Confirmation Order is a
         Final Order (as defined in the Plan) and the Plan is not subject and,
         as of the Closing Date, will not be subject to a stay or injunction
         issued by any court of competent jurisdiction. Neither the Plan nor the
         Confirmation Order have been modified, amended or revoked, and the Plan
         and Confirmation Order are in full force and effect.

                  (r) No order has been entered in the Bankruptcy Case
         converting such Bankruptcy Case to a case under Chapter 7 of the United
         States Bankruptcy Code,

                                       7
<PAGE>   8

         appointing a trustee or examiner in the Bankruptcy Case pursuant to 11
         U.S.C. Section 1104, dismissing the Bankruptcy Case or granting relief
         from the automatic stay of 11 U.S.C. Section 362 to allow any person or
         entity to enforce any lien or security interest in any portion of the
         Issuer's assets or properties.

                  (s) Except as disclosed in the Final Memorandum, there is not
         pending or, to the knowledge of the Issuer or the Guarantors,
         threatened any action, suit, proceeding, inquiry or investigation to
         which the Issuer or any of the Guarantors is a party, or to which the
         property or assets of the Issuer or any of the Guarantors is subject,
         before or brought by any court, arbitrator or governmental agency or
         body which, if determined adversely to the Issuer or any of the
         Guarantors, would, individually or in the aggregate, have a Material
         Adverse Effect or which seeks to restrain, enjoin, prevent the
         consummation of or otherwise challenge the issuance or sale of the
         Securities to be sold hereunder or the consummation of the other
         transactions described in the Final Memorandum.

                  (t) Each of the Issuer and the Guarantors possesses all
         licenses, permits, certificates, consents, orders, approvals and other
         authorizations from, and has made all declarations and filings with,
         all federal, state, local and other governmental authorities, all
         self-regulatory organizations and all courts and other tribunals,
         presently required or necessary to own or lease, as the case may be,
         and to operate its respective properties and to carry on its respective
         businesses as now or proposed to be conducted as set forth in the Final
         Memorandum ("Permits"), except where the failure to obtain such Permits
         would not, individually or in the aggregate, have a Material Adverse
         Effect; each of the Issuer and the Guarantors has fulfilled and
         performed all of its obligations with respect to such Permits and no
         event has occurred which allows, or after notice or lapse of time would
         allow, revocation or termination thereof or results in any other
         material impairment of the rights of the holder of any such Permit,
         except where the failure to perform such obligations or the occurrence
         of such event would not have a Material Adverse Effect; and neither the
         Issuer nor any of the Guarantors has received any notice of any
         proceeding relating to revocation or modification of any such Permit,
         except as described in the Final Memorandum and except where such
         revocation or modification would not, individually or in the aggregate,
         have a Material Adverse Effect.

                  (u) Since the respective dates as of which information is
         given in the Final Memorandum, except as described therein and except
         for the transactions contemplated in the Operative Documents, (i)
         neither the Issuer nor any of the Guarantors has incurred any
         liabilities or obligations (whether liquidated, unliquidated, fixed,
         contingent, matured, unmatured, disputed, undisputed, legal, equitable,
         secured or unsecured), or entered into or agreed to enter into any
         transactions or contracts (whether written or oral) not in the ordinary
         course of business, (ii) the Issuer and each Guarantor has timely paid
         all liabilities or obligations incurred in the ordinary course of its
         business consistent with past practices, (iii) neither the Issuer nor
         any of the Guarantors has purchased any of its outstanding capital
         stock, nor declared, paid or otherwise made any dividend or
         distribution of any kind on its capital stock and (iv) there has not
         been any change in the capital stock or long-term indebtedness of the
         Issuer or any of the Guarantors.

                                       8
<PAGE>   9

                  (v) Each of the Issuer and the Guarantors has filed all
         necessary federal, state and foreign income and franchise tax returns,
         except where the failure to so file such returns would not,
         individually or in the aggregate, have a Material Adverse Effect, and
         has paid all taxes shown as due thereon except as to taxes any of the
         Issuer or Guarantors is contesting in good faith; and other than tax
         deficiencies which the Issuer or Guarantors is contesting in good faith
         and for which such Issuer or such Guarantors has provided adequate
         reserves in accordance with generally accepted accounting principles,
         there is no tax deficiency that has been asserted against the Issuer or
         the Guarantors that would have, individually or in the aggregate, a
         Material Adverse Effect.

                  (w) The statistical and market-related data included in the
         Final Memorandum are based on or derived from sources which the Issuer
         believes to be reliable and accurate.

                  (x) Neither the Issuer nor any of the Guarantors or any agent
         acting on their behalf has taken or will take any action that might
         cause this Agreement or the sale of the Securities to violate
         Regulation T, U or X of the Board of Governors of the Federal Reserve
         System, in each case as in effect, or as the same may hereafter be in
         effect, on the Closing Date.

                  (y) As of the Closing Date, each of the Issuer and the
         Guarantors has good and defensible title to all real property and good
         title to all personal property described in the Final Memorandum as
         being owned by it and good and defensible title to a leasehold estate
         in the real and personal property described in the Final Memorandum as
         being leased by it free and clear of all liens, security interests,
         charges, encumbrances or restrictions, except (i) as described in the
         Final Memorandum, or (ii) Permitted Liens (as defined in the Indenture)
         to the extent the failure to have such title or the existence of such
         liens, security interests, charges, encumbrances or restrictions would
         not, individually or in the aggregate, have a Material Adverse Effect.
         As of the Closing Date, all Contracts to which the Issuer or any
         Guarantor is a party or by which any of them is bound are valid and
         enforceable against the Issuer and each Guarantor, as the case may be,
         and, to the knowledge of the Issuer and each Guarantor, are valid and
         enforceable against the other party or parties thereto and are in full
         force and effect, except as such enforceability may be limited by
         bankruptcy, insolvency, reorganization, moratorium and other similar
         laws now or hereinafter in effect relating to or affecting creditors'
         rights generally, by general equitable principles (regardless of
         whether such enforceability is considered in a proceeding in equity or
         at law) or the discretion of the court before which any proceeding
         therefor may be brought.

                  (z) The Issuer and the Guarantors own or possess adequate
         licenses or other rights to use all patents, trademarks, service marks,
         trade names, copyrights and know-how necessary to conduct the
         businesses now or proposed to be operated by them as described in the
         Final Memorandum, and neither the Issuer nor any of the Guarantors has
         received any notice of infringement of or conflict with (or knows of
         any such infringement of or conflict with) asserted rights of others
         with respect to any patents, trademarks, service marks, trade names,
         copyrights or know-how which, if such assertion of infringement or
         conflict were sustained, would have a Material Adverse Effect.

                                       9
<PAGE>   10

                  (aa) There are no legal or governmental proceedings involving
         or affecting the Issuer or any of the Guarantors or any of their
         respective properties or assets which would be required to be described
         in a prospectus pursuant to the Act that are not so described in the
         Final Memorandum, nor are there any material contracts or other
         documents which would be required to be described in a prospectus
         pursuant to the Act that are not so described in the Final Memorandum.

                  (bb) Except as disclosed in the Final Memorandum or as would
         not, individually or in the aggregate, have the potential to have a
         Material Adverse Effect (i) each of the Issuer and the Guarantors is in
         compliance with and not subject to any pending or, to the knowledge of
         the Issuer or any of the Guarantors, threatened liability under
         applicable Environmental Laws (as defined below), (ii) each of the
         Issuer and the Guarantors has made all filings and provided all notices
         required under any applicable Environmental Law, and has, and is in
         compliance with, all Permits required under any applicable
         Environmental Laws for the current operations and each of them is in
         full force and effect, (iii) there is no civil, criminal or
         administrative action, suit, demand, claim, hearing, notice of
         violation, investigation, proceeding, notice or demand letter or
         request for information pending or, to the knowledge of the Issuer and
         the Guarantors, threatened against the Issuer or the Guarantors under
         any Environmental Law, (iv) no lien, charge, encumbrance or restriction
         has been recorded under any Environmental Law with respect to any
         assets, facility or property owned, operated, leased or controlled by
         the Issuer or any of the Guarantors, (v) neither the Issuer nor any of
         the Guarantors has received notice that it has been identified as a
         potentially responsible party under the Comprehensive Environmental
         Response, Compensation and Liability Act of 1980, as amended
         ("CERCLA"), or any comparable state law, (vi) no property or facility
         of any of the Issuer or the Guarantors is (A) listed or, to the
         knowledge of the Issuer and the Guarantors proposed for listing on the
         National Priorities List under CERCLA or (B) listed in the
         Comprehensive Environmental Response, Compensation, Liability
         Information System List promulgated pursuant to CERCLA, or on any
         comparable list maintained by any United States federal, state,
         municipal, local, territorial or other governmental subdivision,
         department, commission, board, bureau, agency, regulatory authority,
         instrumentality or judicial or administrative body (each a
         "Governmental Authority"), and (vii) notwithstanding anything in this
         Section 2(bb) to the contrary, no facts or circumstances exist and no
         event or condition is occurring or, to any of Issuer's or Guarantors'
         knowledge, has occurred, with respect to Issuer or the Guarantors and
         relating to any Environmental Law, any release of any hazardous, toxic,
         dangerous, or petroleum hydrocarbon material, substance, or waste, any
         chemical, any solid waste, or any other pollutant or contaminant, or
         any of Issuer's or Guarantors' compliance with all current or
         reasonably foreseeable future requirements of Environmental Law, that
         individually or in the aggregate has the potential to have a Material
         Adverse Effect.

                  For purposes of this Agreement, "Environmental Laws" means the
         common law and all applicable federal, state and local laws,
         regulations, rules, ordinances, codes, orders, decrees, judgments,
         injunctions or any other legally enforceable requirement issued,
         promulgated, approved or entered thereunder, relating to pollution or
         protection of public or employee health and safety or the environment,
         including, without limitation, laws relating to (i) emissions,
         discharges, releases or threatened releases of hazardous

                                       10
<PAGE>   11

         materials into the environment (including, without limitation, ambient
         air, surface water, ground water, land surface or subsurface strata),
         (ii) the manufacture, processing, distribution, use, generation,
         treatment, storage, disposal, transport, arrangement for disposal or
         transport or handling of hazardous, toxic, dangerous, or petroleum
         hydrocarbon material, substance, or waste, any chemical, any solid
         waste, or any other pollutant or contaminant, and (iii) underground and
         above ground storage tanks and related piping, and emissions,
         discharges, releases or threatened releases therefrom.

                  (cc) There is no strike, labor dispute, slowdown or work
         stoppage with the employees of any of the Issuer or the Guarantors
         which is pending or, to the knowledge of the Issuer, threatened.

                  (dd) Each of the Issuer and the Guarantors carries insurance,
         including self-insurance, in such amounts and covering such risks as in
         its reasonable determination is adequate for the conduct of its
         business and the value of its properties.

                  (ee) Neither the Issuer nor any of the Guarantors has incurred
         any liability for any prohibited transaction or funding deficiency or
         any complete or partial withdrawal liability with respect to any
         pension, profit sharing or other plan which is subject to the Employee
         Retirement Income Security Act of 1974, as amended ("ERISA"), to which
         the Issuer or the Guarantors makes or ever has made a contribution and
         in which any employee of the Issuer or the Guarantors is or has ever
         been a participant, which in the aggregate could have a Material
         Adverse Effect. With respect to such plans, each of the Issuer and the
         Guarantors is in compliance in all respects with all applicable
         provisions of ERISA, except where the failure to so comply would not,
         individually or in the aggregate, have a Material Adverse Effect.

                  (ff) Each of the Issuer and the Guarantors (i) makes and keeps
         accurate books and records and (ii) maintains internal accounting
         controls which provide reasonable assurance that (A) transactions are
         executed in accordance with management's authorization, (B)
         transactions are recorded as necessary to permit preparation of its
         financial statements and to maintain accountability for its assets, (C)
         access to its assets is permitted only in accordance with management's
         authorization and (D) the reported accountability for its assets is
         compared with existing assets at reasonable intervals.

                  (gg) As of the Closing, after giving effect to the
         transactions contemplated hereby, neither the Issuer nor any of the
         Guarantors will be an "investment company" or "promoter" or "principal
         underwriter" for an "investment company," as such terms are defined in
         the Investment Company Act of 1940, as amended, and the rules and
         regulations thereunder.

                  (hh) The Units, the Notes, the Guarantees, the Class A Common
         Stock, the Class B Common Stock, the Indenture, and the Notes
         Registration Rights Agreement, the Equity Registration Rights Agreement
         and the Security Documents conform in all material respects to the
         descriptions thereof contained in the Final Memorandum.

                                       11
<PAGE>   12

                  (ii) The Final Memorandum, as of its date, contains all the
         information specified in, and meeting the requirements of, Rule
         144A(d)(4) under the Act.

                  (jj) No holder of securities of the Issuer or any Guarantor
         will be entitled to have such securities registered under the
         registration statements required to be filed by the Issuer or any
         Guarantor pursuant to either of the Registration Rights Agreement or
         the Equity Registration Rights Agreement, other than as expressly
         permitted thereby.

                  (kk) Credit Lyonnais, New York Branch, as agent for certain
         lenders ("Credit Lyonnais") party to that certain Amended and Restated
         Credit Agreement (as heretofore modified and amended, the "Credit
         Agreement") by and among the Issuer, Credit Lyonnais and said lenders,
         dated as of March 31, 1998, has delivered a letter (the "Payoff
         Letter") acknowledging, among other things, the payment in full on the
         Closing Date by the Issuer of the Obligations (as defined in the Credit
         Agreement) and the unconditional release by Credit Lyonnais of all
         Lender Liens (as defined in the Credit Agreement) under the Credit
         Agreement and all related Collateral Documents (as defined in the
         Credit Agreement). With respect to each of the claims and liabilities
         described on Exhibit A hereto (collectively, the "Lien Claims"), fully
         executed releases of such claims and liabilities and any and all liens
         and security interests securing the same, suitable for filing with the
         appropriate Governmental Authorities and otherwise satisfactory in form
         and substance to counsel for the Initial Purchaser, have been delivered
         to the Lien Agent. Upon receipt from the Issuer by the Lien Agent of
         the full amount of the Lien Claims, the Lien Agent is unconditionally
         obligated to release and deliver such releases for filing with the
         appropriate Governmental Authorities.

                  (ll) The total aggregate amount of the Issuer's and
         Guarantors' liability on the date hereof with respect to the disputed
         claims and liabilities is described on Exhibit B attached hereto
         (collectively, the "Disputed Claims"). To the best of the Issuer's and
         the Guarantors' knowledge, there are no facts or circumstances which
         (with the passage of time or the giving of notice or both) could give
         rise to any additional claims or liabilities against the Issuer or the
         Guarantors in connection with the Disputed Claims or increase the total
         aggregate amount of the Disputed Claims.

                  (mm) Immediately after the consummation of the transactions
         contemplated by this Agreement and the Indenture, (i) the fair value
         and present fair saleable value of the assets of each of the Issuer and
         the Guarantors will exceed the sum of its stated liabilities and
         identified contingent liabilities; neither the Issuer nor any of the
         Guarantors (each on a consolidated basis) is, nor will the Issuer or
         the Guarantors (each on a consolidated basis) be, after giving effect
         to the execution, delivery and performance of this Agreement and each
         of the other Operative Documents, and the consummation of the
         transactions contemplated hereby and thereby, (A) left with
         unreasonably small capital with which to carry on its business as it is
         proposed to be conducted, (B) unable to pay its debts (contingent or
         otherwise) as they mature or (C) otherwise insolvent, and (ii) the
         Issuer and each of the Guarantors will, upon the issuance of the Notes
         and the grant of the Mortgages, Guarantees and liens and security
         interests in connection therewith, receive a reasonably equivalent
         value or fair consideration for such indebtedness and the grant of
         security therefor, so that, in any event, the issuance of the Notes and
         the grant of security

                                       12
<PAGE>   13

         therefor will not constitute a fraudulent transfer or conveyance under
         any applicable federal or state law providing protection for creditors
         from and against a fraudulent transfer or conveyance.

                  (nn) Neither the Issuer nor any of the Guarantors or any of
         their respective Affiliates (as defined in Rule 501(b) of Regulation D
         under the Act) has directly, or through any agent, (i) sold, offered
         for sale, solicited offers to buy or otherwise negotiated in respect
         of, any "security" (as defined in the Act) which is or could be
         integrated with the sale of the Securities in a manner that would
         require the registration under the Act of the Securities or (ii)
         engaged in any form of general solicitation or general advertising (as
         those terms are used in Regulation D under the Act) in connection with
         the offering of the Securities or in any manner involving a public
         offering within the meaning of Section 4(2) of the Act.

                  (oo) When the Securities are delivered pursuant to this
         Agreement, none of the Securities will be of the same class (within the
         meaning of Rule 144A under the Act) as any other securities of the
         Issuer or any Guarantor that are listed on a national securities
         exchange registered under Section 6 of the Exchange Act or that are
         quoted in a United States automated inter-dealer quotation system.

                  (pp) Subsequent to the respective dates as of which
         information is given in the Final Memorandum and up to the Closing
         Date, except as set forth in the Final Memorandum, there has not been,
         individually or in the aggregate, any material adverse change, or any
         development which may reasonably be expected to involve a material
         adverse change, in the assets, properties, business, results of
         operations, condition (financial or otherwise), affairs or prospects of
         the Issuer and the Guarantors taken as a whole (including, without
         limitation, any material downward revision in the Issuer's estimated
         proved reserves) other than any such effect caused solely by decreases
         in crude oil, natural gas liquids and natural gas prices (any such
         event, a "Material Adverse Change").

                  (qq) Assuming that the representations and warranties of the
         Initial Purchaser contained in Section 8 are true and correct, it is
         not necessary in connection with the offer, sale and delivery of the
         Securities to the Initial Purchaser or the reoffer and resale by the
         Initial Purchaser in the manner contemplated by this Agreement to
         register the Securities under the Act or to qualify the Indenture in
         respect of the Notes under the TIA.

                  (rr) The form of the Security Documents, including the
         financing statements for the Mortgages (the "Financing Statements") and
         the form of acknowledgments thereto, comply with the laws of the
         jurisdiction where the property and interests covered by such documents
         are located, including all applicable recording, filing and
         registration laws and regulations, and are adequate and legally
         sufficient for the purposes intended to be accomplished thereby.

                  (ss) The descriptions of those portions of the Mortgaged
         Property (as defined in the Mortgages) or collateral which are
         described in the Mortgages are legally sufficient descriptions for the
         purpose of creating and maintaining the liens and security interests

                                       13
<PAGE>   14

         purported to be created by the Mortgages and for the purposes of all
         applicable recording, filing and registration laws in the jurisdiction
         where the property and interests covered by such documents are located.

                  (tt) Upon the recordings and filings as provided in the
         following paragraph, the Mortgages are effective to create in favor of
         the Trustee for the benefit of the Noteholders, as security for the
         payment of the Indebtedness (as defined in the Mortgages), a valid
         mortgage or deed of trust lien on all of the Issuer's and the
         Guarantors' right, title and interest in and to the portion of the
         Mortgaged Property constituting real property described in the
         Mortgages as being mortgaged thereby and a perfected security interest
         in all of the Issuer's and the Guarantors' right, title and interest in
         and to the portion of the Mortgaged Property constituting property,
         other than real property, in which a security interest can be created,
         and perfected by the filings contemplated by the following paragraph,
         under Article 9 of the Uniform Commercial Code as in effect in the
         States of Texas, Louisiana and California.

                  (uu) Fully executed counterparts of the Mortgages should be
         filed for record in each county or parish in the States of Texas,
         Louisiana and California where any portion of the Mortgaged Property is
         located (or, in the case of properties located on the Outer Continental
         Shelf, in the adjacent county or parish). Fully executed counterparts
         of the Financing Statements should be filed for record with the
         Secretary of State of the States of Texas and California and with the
         Parish Clerk of the Parish of East Baton Rouge, Louisiana. Other than
         the foregoing, no authorization, consent, approval, license or
         exemption of, or filing or registration with, any Governmental
         Authority of the States of Texas, Louisiana or California is necessary
         for either the due execution and delivery by the Issuer and the
         Guarantors of the Mortgages or the Financing Statements or with the
         holding and enforcement by the Trustee of the Mortgages secured
         thereby, except for such authorizations, consents, approvals, licenses
         or exemptions of, or filings or registrations with any Governmental
         Authority that are required to be obtained or maintained, as the case
         may be, by the Trustee in order for the Trustee to be or remain
         qualified to act in the capacity of trustee.

                  (vv) For so long as the Notes are outstanding and not matured,
         after the recordings and filings specified in the previous paragraph
         have occurred, no instruments need be recorded, registered or filed or
         re-recorded, re-registered or re-filed in any public office in the
         States of Texas, Louisiana or California in connection with the
         execution and delivery of the Mortgages or the Financing Statements in
         order to maintain the perfection and priority of the liens and security
         interests created thereby after the date of recordation, other than (i)
         that in the case of proceeds constituting a portion of the Mortgaged
         Property, continuation of perfection of the Trustee's security interest
         therein is limited to the extent set forth in the Uniform Commercial
         Code as in effect in the States of Texas, Louisiana and California,
         (ii) that in the case of property which becomes Mortgaged Property
         after the date hereof, 11 U.S.C. Section 552 limits the extent to which
         property acquired by a debtor after the commencement of a case under
         the United States Bankruptcy Code may be subject to a security interest
         arising from a security agreement entered into by the debtor before the
         commencement of such case, and (iii) continuation

                                       14
<PAGE>   15

         statements as required by the Uniform Commercial Code as in effect in
         the States of Texas, Louisiana and California.

                  (ww) No state or local recording tax, stamp tax or other
         similar fee, tax or governmental charge (other than statutory filing
         and recording fees to be paid upon the filing of the Mortgages or the
         Financing Statements) is required to be paid in connection with the
         filing and recording of the Mortgages or the Financing Statements.

                  (xx) The execution, delivery and performance of by the Issuer
         and each of the Guarantors of its obligations under the Mortgages will
         not result in a violation of any laws, rules and regulations of the
         States of Texas, Louisiana or California which are normally applicable
         to transactions of the type provided for in the Security Documents.

                  (yy) A state court of competent jurisdiction or a federal
         court sitting in the State of Texas, Louisiana or California of
         competent jurisdiction and applying conflicts of laws principles of
         such states, as applicable, if properly presented with a choice of law
         issue, should honor the choice of New York law to govern the Indenture
         and the other Security Documents that state such documents shall be
         governed by the laws of the State of New York, except to the extent the
         laws of other jurisdictions may be mandatorily applicable to certain
         matters under the Security Documents.

                  (zz) The representations and warranties of the Issuer and the
         Guarantors, as applicable, contained in Article IV of each of the
         Mortgages are true and correct and are hereby incorporated herein
         mutatis mutandis as representations and warranties of the Issuer and
         the Guarantors, respectively.

                  (aaa) The Company and the Subsidiary have negotiated
         definitive oil and gas production hedging agreements (the "Approved
         Hedging Agreements") with the Approved Hedge Counterparties (as defined
         in the Final Memorandum) party thereto as described under the heading
         "Description of Notes--Certain Covenants--Hedging Obligations" in the
         Final Memorandum.

         Any certificate signed by any officer of the Issuer or any Guarantor
and delivered to the Initial Purchaser or to counsel for the Initial Purchaser
shall be deemed a joint and several representation and warranty by the Issuer
and the Guarantors to the Initial Purchaser as to the matters covered thereby.

         3. Purchase, Sale and Delivery of the Securities. On the basis of the
representations, warranties, agreements and covenants herein contained and
subject to the terms and conditions set forth herein, the Issuer agrees to issue
and sell to the Initial Purchaser, and the Initial Purchaser agrees to purchase,
130,000 Units (and the related Guarantees) at a purchase price of $907.50 per
Unit, as described below. As additional consideration for services rendered by
the Initial Purchaser in connection with the transactions contemplated by this
Purchase Agreement, Tribo agrees to issue to the Initial Purchaser an aggregate
of 65,000 shares of Class B Common Stock. At the closing, (i) one or more
certificates representing the Units (comprised of a global Note and a global
certificate representing the Class A Common Stock) in definitive global form,
registered in the name of Cede & Co., as nominee of The Depository Trust Company
("DTC")

                                       15
<PAGE>   16

(the "Global Certificates"), (ii) one or more certificates representing the
Units (comprised of a certificated Note and a physical certificate representing
the Class A Common Stock) in certificated form and registered in the name of
such Persons as the Initial Purchaser shall designate prior to the Closing Date,
and (iii) a global certificate representing the Class B Common Stock, registered
in the name of Cede & Co., a nominee of DTC, shall be issued and delivered by
the Issuer and Tribo, as applicable, to the Initial Purchaser, against payment
by or on behalf of the Initial Purchaser of the purchase price therefore by wire
transfer (same-day funds) to such account or accounts as the Issuer and Tribo
shall specify prior to the Closing Date (or by such means as the parties hereto
shall agree prior to the Closing Date). Closing of the issuance, purchase, sale
and delivery of the Securities (the "Closing") shall take place at the offices
of Vinson & Elkins L.L.P., 2300 First City Tower, 1001 Fannin Street, Houston,
Texas 77002 at 8:00 a.m., central daylight time, on June 18, 2001, or such other
date, time or location as may be mutually acceptable, such time and date of
delivery against payment being referred to herein as the "Closing Date."

         4. Offering by the Initial Purchaser. The Initial Purchaser proposes to
make an offering of the Units at the price and upon the terms set forth in the
Final Memorandum, as soon as practicable after this Agreement is entered into
and as in the judgment of the Initial Purchaser is advisable.

         5. Covenants of the Issuer and the Guarantors. The Issuer and the
Guarantors, jointly and severally, covenant and agree with the Initial Purchaser
that:

                  (a) The Issuer and the Guarantors will not amend or supplement
         the Final Memorandum or any amendment or supplement thereto of which
         the Initial Purchaser shall not previously have been advised and
         furnished a copy for a reasonable period of time prior to the proposed
         amendment or supplement and as to which the Initial Purchaser shall not
         have given its consent, which consent shall not unreasonably be
         withheld. The Issuer and the Guarantors will promptly, upon the
         reasonable request of the Initial Purchaser or counsel for the Initial
         Purchaser, make any amendments or supplements to the Final Memorandum
         that may be necessary or advisable in connection with the resale of the
         Securities by the Initial Purchaser.

                  (b) The Issuer and the Guarantors will cooperate with the
         Initial Purchaser in arranging for the qualification of the Securities
         for offering and sale under the securities or "Blue Sky" laws of such
         jurisdictions as the Initial Purchaser may designate and will continue
         such qualifications in effect for as long as may be necessary to
         complete the resale of the Securities; provided, however, that in
         connection therewith, neither the Issuer nor the Guarantors shall be
         required to qualify as a foreign corporation or to execute a general
         consent to service of process in any jurisdiction or subject itself to
         taxation in excess of a nominal dollar amount in any such jurisdiction
         where it is not then so subject.

                  (c) If, at any time prior to the initial resale by the Initial
         Purchaser of the Units (and the related Guarantees) or the Exchange
         Notes, any event occurs or information becomes known as a result of
         which the Final Memorandum as then amended or supplemented would
         include any untrue statement of a material fact, or omit to state a

                                       16
<PAGE>   17

         material fact necessary to make the statements therein, in the light of
         the circumstances under which they were made, not misleading, or if for
         any other reason it is necessary at any time to amend or supplement the
         Final Memorandum to comply with applicable law, the Issuer will
         promptly notify the Initial Purchaser thereof and will prepare, at the
         expense of the Issuer, an amendment or supplement to the Final
         Memorandum that corrects such statement or omission or effects such
         compliance.

                  (d) The Issuer will, without charge, provide to the Initial
         Purchaser and to counsel for the Initial Purchaser as many copies of
         the Final Memorandum or any amendment or supplement thereto as the
         Initial Purchaser may reasonably request.

                  (e) The Issuer will apply the net proceeds from the sale of
         the Securities as set forth under "Use of Proceeds" in the Final
         Memorandum.

                  (f) For so long as any of the Securities (other than the
         Common Stock) remain outstanding, the Issuer and the Guarantors will
         furnish to the Initial Purchaser copies of all reports and other
         communications (financial or otherwise) furnished by the Issuer and the
         Guarantors to the Trustee or to the holders of the Securities and, as
         soon as available, copies of any reports or financial statements
         furnished to or filed by the Issuer or Tribo with the Commission or any
         national securities exchange on which any class of securities of the
         Issuer or Tribo may be listed.

                  (g) Prior to the Closing Date, Tribo will furnish to the
         Initial Purchaser, as soon as they have been prepared, if at all, a
         copy of any available unaudited consolidated interim financial
         statements of Tribo for any period subsequent to the period covered by
         the most recent financial statements of the Company appearing in the
         Final Memorandum.

                  (h) Neither the Issuer nor any of its Affiliates will sell,
         offer for sale or solicit offers to buy or otherwise negotiate in
         respect of any "security" (as defined in the Act) which could be
         integrated with the sale of the Securities in a manner which would
         require the registration under the Act of the Securities.

                  (i) The Issuer will not, and will not permit any of the
         Guarantors to, solicit any offer to buy or offer to sell the Securities
         by means of any form of general solicitation or general advertising (as
         those terms are used in Regulation D under the Act) or in any manner
         involving a public offering within the meaning of Section 4(2) of the
         Act.

                  (j) For so long as any of the Securities remain outstanding,
         the Company will make available at its expense, upon request, to any
         holder of such Securities and any prospective purchaser thereof, the
         information specified in Rule 144A(d)(4) under the Act, unless the
         Company is then subject to Section 13 or 15(d) of the Exchange Act.

                  (k) The Issuer will use its best efforts to (i) permit the
         Securities to be designated for trading in the Private Offerings,
         Resales and Trading through Automated Linkages market (the "PORTAL
         Market") of the NASD and (ii) permit the Securities to be eligible for
         clearance and settlement through DTC.

                                       17
<PAGE>   18

                  (l) The Issuer and each Guarantor will comply with their
         respective obligations under the Plan, the Confirmation Order and any
         Plan Documents (as defined in the Plan).

                  (m) Prior to the Closing Date, the Issuer and the Guarantors
         shall not modify or amend the Plan or the Confirmation Order without
         the written consent of the Initial Purchaser which consent shall not be
         unreasonably withheld.

                  (n) Concurrently with the Closing, the Company and the
         Subsidiary shall execute and deliver the Approved Hedging Agreements
         and shall execute one or more hedging transactions with the Approved
         Hedge Counterparties under the Approved Hedging Agreements.

                  (o) The Company will cure promptly any defects in the creation
         and issuance of the Securities and the execution and delivery of the
         Security Documents and any amendments thereto. At its expense, the
         Company will promptly execute and deliver to the Collateral Agent upon
         request all such other documents, agreements and instruments to comply
         with or accomplish the covenants and agreements of the Company in the
         Security Documents and any amendments thereto or to further evidence
         and more fully describe the collateral intended as security for the
         Notes, or to correct any omissions in the Security Documents and any
         amendments thereto, or to state more fully the security obligations set
         out herein or in any of the Security Documents or any amendments
         thereto, or to perfect, protect, preserve and maintain any liens
         created pursuant to any of the Security Documents or any amendments
         thereto and the first priority status of such liens (subject only to
         Permitted Liens (as defined in the Indenture)), or to make any
         recordings, to file any notices or obtain any consents, all as may be
         necessary or appropriate in connection therewith. The Company and the
         Guarantors will warrant and defend the first priority status of the
         liens created by the Security Documents and any amendments thereto,
         subject only to Permitted Liens.

                  (p) If delivery of the local counsel opinions required by
         Section 7(a)(ii) is waived by the Initial Purchaser on the Closing
         Date, then the Issuer shall deliver such local counsel opinions on or
         before the fifth business day following the Closing Date.

                  (q) To the extent waived by the Initial Purchaser on the
         Closing Date, the Issuer shall deliver the opinions of local counsel
         required by Section 7(a)(ii) of the Agreement on or before the fourth
         business day following the Closing Date.

                  (r) Each of the Company and the Guarantors shall use their
         best efforts to do and perform all things required or necessary to be
         done and performed under this Agreement by them prior to the Closing
         Date and to satisfy all conditions precedent to the delivery of the
         Securities.

         6. Fees and Expenses. The Issuer and the Guarantors agree, jointly and
severally, to pay all costs and expenses incident to the performance of their
respective obligations under this Agreement, whether or not the transactions
contemplated herein are consummated or this Agreement is terminated pursuant to
Section 11 hereof, including all costs and expenses incident

                                       18
<PAGE>   19

to (i) the printing, word processing or other production of documents with
respect to the transactions contemplated hereby, including any costs of printing
the Final Memorandum and any amendment or supplement thereto, and any "Blue Sky"
memoranda, (ii) all arrangements relating to the delivery to the Initial
Purchaser of copies of the foregoing documents, (iii) the fees and disbursements
of the counsel, the accountants and any other experts or advisors retained by
the Issuer, (iv) preparation (including printing), issuance and delivery to the
Initial Purchaser of the Securities, (v) the qualification of the Securities
under state securities and "Blue Sky" laws, including filing fees and reasonable
fees and disbursements of counsel for the Initial Purchaser relating thereto,
(vi) expenses in connection with any meetings with prospective investors in the
Securities, (vii) fees and expenses of the Trustee including reasonable fees and
expenses of its counsel, (viii) all expenses and listing fees incurred in
connection with the application for quotation of the Securities on the PORTAL
Market, (ix) any fees charged by investment rating agencies for the rating of
the Securities and (x) all reasonable fees, disbursements and out-of-pocket
expenses incurred by the Initial Purchaser in connection with the transactions
contemplated hereby (including fees and expenses of Vinson & Elkins L.L.P., as
counsel to the Initial Purchaser). If the sale of the Securities provided for
herein is not consummated because any condition to the obligations of the
Initial Purchaser set forth in Section 7 hereof is not satisfied, because this
Agreement is terminated or because of any failure, refusal or inability on the
part of the Issuer and the Guarantors to perform all obligations and satisfy all
conditions on their part to be performed or satisfied hereunder (other than
solely by reason of a default by the Initial Purchaser of its obligations
hereunder after all conditions hereunder have been satisfied in accordance
herewith), the Issuer and the Guarantors agree, jointly and severally, to
promptly reimburse the Initial Purchaser upon demand for all out-of-pocket
expenses that shall have been incurred by the Initial Purchaser in connection
with the proposed purchase and sale of the Securities. Additionally, the Issuer
and the Guarantors shall pay to the Initial Purchaser, on the Closing Date, a
financial advisory fee in the amount of $4,000,000 for financial advisory
services rendered by the Initial Purchaser to the Issuer and the Guarantors in
connection with the transactions contemplated by this Agreement.

         7. Conditions of the Initial Purchaser's Obligations. The obligation of
the Initial Purchaser to purchase and pay for the Securities shall, in its sole
discretion, be subject to the satisfaction or waiver of each of the following
conditions on or prior to the Closing Date:

                  (a) On the Closing Date, the Initial Purchaser shall have
         received the opinions, dated as of the Closing Date and addressed to
         the Initial Purchaser, of (i) Thompson & Knight LLP, counsel for the
         Issuer and the Guarantors, and (ii) local counsel for the Issuer and
         the Guarantors in the States of Louisiana and California, each in form
         and substance reasonably satisfactory to counsel for the Initial
         Purchaser, and each subject to customary assumptions and
         qualifications.

                  (b) On the Closing Date, the Initial Purchaser shall have
         received the opinion, in form and substance satisfactory to the Initial
         Purchaser, dated as of the Closing Date and addressed to the Initial
         Purchaser, of Vinson & Elkins L.L.P., counsel for the Initial
         Purchaser, with respect to certain legal matters relating to this
         Agreement and such other related matters as the Initial Purchaser may
         reasonably require.

                                       19
<PAGE>   20

                  (c) The Initial Purchaser shall have received from each of BDO
         Seidman, LLP and Hidalgo, Banfill, Zlotnik & Kermali, P.C. a comfort
         letter or letters dated the date hereof and dated as of the Closing
         Date, in form and substance satisfactory to the Initial Purchaser and
         its counsel.

                  (d) The representations and warranties of the Issuer and the
         Guarantors contained in this Agreement shall be true and correct in all
         material respects on and as of the date hereof and on and as of the
         Closing Date as if made on and as of the Closing Date (except for the
         representations and warranties that were true and correct as of a
         certain specified date, which shall continue to be true and correct as
         of such date); the statements of the Issuer's and the Guarantors'
         officers made pursuant to any certificate delivered in accordance with
         the provisions hereof shall be true and correct in all material
         respects on and as of the date made and on and as of the Closing Date;
         the Issuer and the Guarantors shall have performed all covenants and
         agreements and satisfied all conditions on their part to be performed
         or satisfied hereunder at or prior to the Closing Date; and, except as
         described in the Final Memorandum (exclusive of any amendment or
         supplement thereto after the date hereof), subsequent to the date of
         the most recent financial statements in such Final Memorandum, there
         shall have been no event or development, and no information shall have
         become known, that, individually or in the aggregate, has or would be
         reasonably likely to have a Material Adverse Effect.

                  (e) The sale of the Securities hereunder shall not be enjoined
         or stayed (temporarily or permanently) on the Closing Date.

                  (f) Subsequent to the date of the most recent financial
         statements in the Final Memorandum (exclusive of any amendment or
         supplement thereto after the date hereof), neither the Issuer nor any
         of the Guarantors shall have sustained any loss or interference with
         respect to its business or properties from fire, flood, hurricane,
         accident or other calamity, whether or not covered by insurance, or
         from any strike, labor dispute, slow down or work stoppage or from any
         legal or governmental proceeding, order or decree, which loss or
         interference, individually or in the aggregate, has or would be
         reasonably likely to have a Material Adverse Effect.

                  (g) The Initial Purchaser shall have received a certificate,
         dated the Closing Date, of the Company and each of the Guarantors,
         signed on behalf of the Company and each of the Guarantors by their
         respective Chairmen of the Board, Presidents or any Senior Vice
         Presidents and Chief Financial Officers, to the effect that:

                           (i) The representations and warranties of the Issuer
                  and the Guarantors, as applicable, contained in the Purchase
                  Agreement are true and correct on and as of the date hereof
                  and on and as of the Closing Date (except for the
                  representations and warranties that were true and correct as
                  of a certain specified date, which shall continue to be true
                  and correct as of such date), and the Issuer and the
                  Guarantors, as applicable, have performed all covenants and
                  agreements and satisfied all conditions on their part to be
                  performed or satisfied hereunder at or prior to the Closing
                  Date;

                                       20
<PAGE>   21

                           (ii) At the Closing Date, since the date hereof or
                  since the date of the most recent financial statements in the
                  Final Memorandum (exclusive of any amendment or supplement
                  thereto after the date hereof), no event or development has
                  occurred, and no information has become known to the Issuer or
                  the Guarantors, as applicable, that, individually or in the
                  aggregate, has or would be reasonably likely to have a
                  Material Adverse Effect (including, without limitation, any
                  material downward revision in the Issuer's or the Guarantors'
                  estimated proved reserves) other than any such effect caused
                  solely by decreases in the prices of crude oil, natural gas
                  liquids and natural gas; and

                           (iii) The sale of the Securities hereunder has not
                  been enjoined or stayed (temporarily or permanently).

                  (h) On the Closing Date, the Initial Purchaser shall have
         received each of the Notes Registration Rights Agreement and the Equity
         Registration Rights Agreement executed by the Issuer and each of the
         Guarantors.

                  (i) On or before the Closing Date, the Initial Purchaser and
         counsel for the Initial Purchaser shall have received from the Issuer
         and the Guarantors executed Security Documents.

                  (j) On or before the Closing Date, the Initial Purchaser shall
         have received from the Issuer and the Guarantors evidence of the
         unconditional release of the liens and security interests granted in
         favor of Credit Lyonnais on any property of Richard Bowman ("Bowman"),
         the Issuer and the Guarantors and the Issuer shall have, concurrently
         with the Closing, paid to Credit Lyonnais all amounts set forth in the
         Payoff Letter.

                  (k) On or before the Closing Date, the Initial Purchaser shall
         have received from the Issuer and the Guarantors evidence of the
         unconditional release of the liens and security interests granted on
         any property of Bowman, the Issuer and the Guarantors in favor of each
         of the creditors under Classes 2 and 3 of the Plan.

                  (l) On or before the Closing Date, the Initial Purchaser shall
         have received from the Issuer and the Guarantors evidence of the
         execution of the agreed order of dismissal with prejudice and mutual
         releases of the Lawsuits (as defined in the Confirmation Order) by the
         Lawsuit Parties (as defined in the Confirmation Order) as required by
         the Confirmation Order.

                  (m) Concurrently with the Closing, the Issuer shall have
         transferred to the Lien Agent an amount equal to the Initial Escrow
         Funding (as defined in the Plan).

                  (n) Concurrently with the Closing, the Issuer shall have
         transferred to the Disbursing Agent an amount equal to the Class 5
         Funding (as defined in the Plan).

                  (o) Concurrently with the Closing, the Issuer shall have
         certified to the Initial Purchaser that it has executed one or more
         hedging transactions with the Approved Hedge Counterparties under the
         Approved Hedging Agreements.

                                       21
<PAGE>   22

                  (p) On the Closing Date, the Initial Purchaser shall have
         received letters, dated as of the Closing Date and addressed to the
         Initial Purchaser, of Huddleston & Co., Inc. and DeGolyer and
         MacNaughton, independent petroleum engineers for the Company, in form
         and substance reasonably satisfactory to the Initial Purchaser.

                  (q) The Confirmation Order shall be a Final Order and
         consummation of the Plan shall not be enjoined or stayed (temporarily
         or permanently) on the Closing Date.

                  (r) On or before the Closing Date, the Initial Purchaser and
         counsel for the Initial Purchaser shall have received certified copies
         of the Plan, the Confirmation Order and the docket of the Bankruptcy
         Court after June 4, 2001 showing that the Confirmation Order is a Final
         Order.

                  (s) On or before the Closing Date, the Issuer shall have
         received executed withdrawal of claim forms from Bowman and Tribo
         whereby each of them withdrawal all of their respective claims filed in
         the Bankruptcy Case.

                  (t) On or before the Closing Date, the Issuer shall have (i)
         consummated the Receipt, Release and Settlement Agreement (as amended,
         the "MMS Settlement Agreement") between the Issuer and the United
         States of America, by and through the Department of the Interior,
         Minerals Management Service (the "MMS"), as approved by the Bankruptcy
         Court in the Confirmation Order, (ii) replaced Frontier (as defined in
         the MMS Settlement Agreement) with a surety approved by the United
         States Treasury, (iii) caused such replacement surety to issue new
         bonds as required by the terms of the MMS Settlement Agreement, (iv)
         entered into an indemnity agreement in favor of such replacement
         surety, (v) paid all amounts due and owing on the Closing Date under
         the MMS Settlement Agreement, and (vi) received executed withdrawal of
         claim forms from the MMS withdrawing all claims filed in the Bankruptcy
         Case.

                  (u) On or before the Closing Date, the Issuer shall have
         executed a disbursing services agreement with each of the Lien Agent
         and the Disbursing Agent.

                  (v) On or before the Closing Date, the Issuer shall have filed
         objections with the Bankruptcy Court to all Disputed Claims as required
         by the Plan.

                  (w) On or before the Closing Date, the Initial Purchaser and
         counsel for the Initial Purchaser shall have received such further
         documents, opinions, certificates, letters and schedules or instruments
         relating to the business, corporate, legal and financial affairs of the
         Issuer and the Guarantors as they shall have heretofore reasonably
         requested from the Issuer.

         All such documents, opinions, certificates, letters, schedules or
instruments delivered pursuant to this Agreement will comply with the provisions
hereof only if they are reasonably satisfactory in all material respects to the
Initial Purchaser and counsel for the Initial Purchaser. The Issuer shall
furnish or cause to be furnished to the Initial Purchaser such conformed copies
of such documents, opinions, certificates, letters, schedules and instruments in
such quantities as the Initial Purchaser shall reasonably request. If the
Initial Purchaser waives the satisfaction of any of the foregoing conditions on
or prior to the Closing Date, the Company shall use its best

                                       22
<PAGE>   23

efforts to cause such conditions to be satisfied within five business days
following the Closing Date.

         8. Offering of Units; Restrictions on Transfer. The Initial Purchaser
has advised the Issuer that it proposes to offer the Units (and the related
Guarantees) for sale upon the terms and conditions set forth in this Agreement
and in the Final Memorandum. The Initial Purchaser hereby represents and
warrants to, and agrees with, the Issuer and the Guarantors that the Initial
Purchaser (i) is purchasing the Units (and the related Guarantees) pursuant to a
private sale exempt from registration under the Act, (ii) has not solicited and
will not solicit offers for, or offer or sell, the Units (and the related
Guarantees) by means of any form of general solicitation or general advertising
or in any manner involving a public offering within the meaning of Section 4(2)
of the Act, and (iii) will solicit offers for the Units (and the related
Guarantees) only from, and will offer, sell or deliver the Units (and the
related Guarantees) as part of their initial offering only to, (A) persons whom
the Initial Purchaser reasonably believes to be qualified institutional buyers
as defined in Rule 144A promulgated under the Act ("QIBs"), or if any such
person is buying for one or more institutional accounts for which such person is
acting as fiduciary or agent, only when such person has represented to the
Initial Purchaser that each such account is a QIB, to whom notice has been given
that such sale or delivery is being made in reliance on Rule 144A, in each case,
in transactions under Rule 144A or (B) to a limited number of accredited
investors as defined in Rule 501(a)(1), (2), (3) or (7) promulgated under the
Act that make the representations to and agreements with the Company specified
in Annex A to the Final Memorandum in private sales exempt from registration
under the Act. The Initial Purchaser will deliver to each purchaser of the Units
(and the related Guarantees) in connection with its original distribution of the
Units (and the related Guarantees), a copy of the Final Memorandum, as amended
and supplemented at the date of such delivery.

         9. Indemnification and Contribution.

                  (a) The Issuer and the Guarantors agree, jointly and
severally, to indemnify and hold harmless the Initial Purchaser, its affiliates
and each person, if any, who controls the Initial Purchaser within the meaning
of Section 15 of the Act or Section 20 of the Exchange Act, against any losses,
claims, damages or liabilities to which the Initial Purchaser or such
controlling person may become subject under the Act, the Exchange Act or
otherwise, insofar as any such losses, claims, damages or liabilities (or
actions in respect thereof) arise out of or are based upon:

                           (i) any untrue statement or alleged untrue statement
                  of any material fact contained in the Final Memorandum or any
                  amendment or supplement thereto or any application or other
                  document, or any amendment or supplement thereto, executed by
                  the Issuer or based upon written information furnished by or
                  on behalf of the Issuer filed in any jurisdiction in order to
                  qualify the Securities under the securities or "Blue Sky" laws
                  thereof or filed with any securities association or securities
                  exchange (each an "Application"); or

                           (ii) the omission or alleged omission to state, in
                  the Final Memorandum or any amendment or supplement thereto or
                  any Application, a material fact required to be stated therein
                  or necessary to make the statements

                                       23
<PAGE>   24

                  therein, in the light of the circumstances under which they
                  were made, not misleading,

and will reimburse, as incurred, the Initial Purchaser, each such affiliate and
each such controlling person for any reasonable legal or other reasonable
expenses incurred by the Initial Purchaser, such affiliate or such controlling
person in connection with investigating, defending against or appearing as a
third-party witness in connection with any such loss, claim, damage, liability
or action; provided, however, that the Issuer and the Guarantors will not be
liable in any such case to the extent that any such loss, claim, damage, or
liability arises out of or is based upon any untrue statement or alleged untrue
statement or omission or alleged omission made in the Final Memorandum or any
amendment or supplement thereto or any Application in reliance upon and in
conformity with written information concerning the Initial Purchaser furnished
to the Issuer by the Initial Purchaser specifically for use therein. This
indemnity agreement will be in addition to any liability that the Issuer and the
Guarantors may otherwise have to the indemnified parties. The Issuer and the
Guarantors shall not be liable under this Section 9 for any settlement of any
claim or action effected without their prior written consent, which shall not be
unreasonably withheld.

                  The Initial Purchaser shall not, without the prior written
consent of the Issuer, effect any settlement or compromise of any pending or
threatened proceeding in respect of which the Issuer is or could have been a
party, or indemnity could have been sought hereunder by the Issuer, unless such
settlement (A) included an unconditional written release of the Issuer, in form
and substance reasonably satisfactory to the Issuer, from all liability on
claims that are the subject matter of such proceeding and (B) does not include
any statement as to an admission of fault, culpability or failure to act by or
on behalf of the Issuer.

                  (b) The Initial Purchaser agrees to indemnify and hold
harmless the Issuer and the Guarantors, their respective directors and their
respective officers and each person, if any, who controls the Issuer or the
Guarantors within the meaning of Section 15 of the Act or Section 20 of the
Exchange Act against any losses, claims, damages or liabilities to which the
Issuer or any of the Guarantors or any such director, officer or controlling
person may become subject under the Act, the Exchange Act or otherwise, insofar
as such losses, claims, damages or liabilities (or actions in respect thereof)
arise out of or are based upon (i) any untrue statement or alleged untrue
statement of any material fact contained in the Final Memorandum or any
amendment or supplement thereto or any Application, or (ii) the omission or the
alleged omission to state therein a material fact required to be stated in the
Final Memorandum or any amendment or supplement thereto or any Application, or
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading, in each case to the extent, but only
to the extent, that such untrue statement or alleged untrue statement or
omission or alleged omission was made in reliance upon and in conformity with
written information concerning the Initial Purchaser, furnished to the Issuer by
the Initial Purchaser specifically for use therein; and subject to the
limitation set forth immediately preceding this clause, will reimburse, as
incurred, any reasonable legal or other expenses incurred by the Issuer or any
of the Guarantors or any such director, officer or controlling person in
connection with investigating or defending against or appearing as a third party
witness in connection with any such loss, claim, damage, liability or action in
respect thereof. This indemnity agreement will be in addition to any liability
that the Initial Purchaser may otherwise have to the indemnified

                                       24
<PAGE>   25

parties. The Initial Purchaser shall not be liable under this Section 9 for any
settlement of any claim or action effected without its consent, which shall not
be unreasonably withheld.

                  The Issuer shall not, without the prior written consent of the
Initial Purchaser, effect any settlement or compromise of any pending or
threatened proceeding in respect of which the Initial Purchaser is or could have
been a party, or indemnity could have been sought hereunder by the Initial
Purchaser, unless such settlement (A) includes an unconditional written release
of the Initial Purchaser, in form and substance reasonably satisfactory to the
Initial Purchaser, from all liability on claims that are the subject matter of
such proceeding and (B) does not include any statement as to an admission of
fault, culpability or failure to act by or on behalf of the Initial Purchaser.

                  (c) Promptly after receipt by an indemnified party under this
Section 9 of notice of the commencement of any action for which such indemnified
party is entitled to indemnification under this Section 9, such indemnified
party will, if a claim in respect thereof is to be made against the indemnifying
party under this Section 9, notify the indemnifying party of the commencement
thereof in writing; but the omission to so notify the indemnifying party (i)
will not relieve the indemnifying party from any liability under paragraph (a)
or (b) above unless and to the extent such failure results in the forfeiture by
the indemnifying party of substantial rights and defenses and (ii) will not, in
any event, relieve the indemnifying party from any obligations to any
indemnified party other than the indemnification obligation provided in
paragraphs (a) and (b) above. In case any such action is brought against any
indemnified party, and it notifies the indemnifying party of the commencement
thereof, the indemnifying party will be entitled to participate therein and, to
the extent that it may wish, jointly with any other indemnifying party similarly
notified, to assume the defense thereof, with counsel reasonably satisfactory to
such indemnified party; provided, however, that if (i) the use of counsel chosen
by the indemnifying party to represent the indemnified party would present such
counsel with a conflict of interest, (ii) the defendants in any such action
include both the indemnified party and the indemnifying party and the
indemnified party shall have been advised by counsel that there may be one or
more legal defenses available to it and/or other indemnified parties that are
different from or additional to those available to the indemnifying party, or
(iii) the indemnifying party shall not have employed counsel reasonably
satisfactory to the indemnified party to represent the indemnified party within
a reasonable time after receipt by the indemnifying party of notice of the
institution of such action, then, in each such case, the indemnifying party
shall not have the right to direct the defense of such action on behalf of such
indemnified party or parties and such indemnified party or parties shall have
the right to select separate counsel to defend such action on behalf of such
indemnified party or parties. After notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof and approval
by such indemnified party of counsel appointed to defend such action, the
indemnifying party will not be liable to such indemnified party under this
Section 9 for any legal or other expenses, other than reasonable costs of
investigation, subsequently incurred by such indemnified party in connection
with the defense thereof, unless (i) the indemnified party shall have employed
separate counsel in accordance with the proviso to the immediately preceding
sentence (it being understood, however, that in connection with such action the
indemnifying party shall not be liable for the expenses of more than one
separate counsel (in addition to local counsel) in any one action or separate
but substantially similar actions in the same jurisdiction arising out of the
same general allegations or circumstances, designated by the Initial Purchaser

                                       25
<PAGE>   26

in the case of paragraph (a) of this Section 9 or the Issuer in the case of
paragraph (b) of this Section 9, representing the indemnified parties under such
paragraph (a) or paragraph (b), as the case may be, who are parties to such
action or actions) or (ii) the indemnifying party has authorized in writing the
employment of counsel for the indemnified party at the expense of the
indemnifying party. After such notice from the indemnifying party to such
indemnified party, the indemnifying party will not be liable for the costs and
expenses of any settlement of such action effected by such indemnified party
without the prior written consent of the indemnifying party (which consent shall
not be unreasonably withheld), unless such indemnified party waived in writing
its rights under this Section 9, in which case the indemnified party may effect
such a settlement without such consent.

                  (d) In circumstances in which the indemnity agreement provided
for in the preceding paragraphs of this Section 9 is unavailable to, or
insufficient to hold harmless, an indemnified party in respect of any losses,
claims, damages or liabilities (or actions in respect thereof), each
indemnifying party, in order to provide for just and equitable contribution,
shall contribute to the amount paid or payable by such indemnified party as a
result of such losses, claims, damages or liabilities (or actions in respect
thereof) in such proportion as is appropriate to reflect (i) the relative
benefits received by the indemnifying party or parties on the one hand and the
indemnified party on the other from the offering of the Securities or (ii) if
the allocation provided by the foregoing clause (i) is not permitted by
applicable law, not only such relative benefits but also the relative fault of
the indemnifying party or parties on the one hand and the indemnified party on
the other in connection with the statements or omissions or alleged statements
or omissions that resulted in such losses, claims, damages or liabilities (or
actions in respect thereof). The relative benefits received by the Issuer on the
one hand and the Initial Purchaser on the other shall be deemed to be in the
same proportion as the total proceeds from the offering (before deducting
expenses) received by the Issuer bear to the total discounts and commissions
received by the Initial Purchaser. The relative fault of the parties shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to state
a material fact relates to information supplied by the Issuer on the one hand,
or the Initial Purchaser on the other, the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such statement or
omission or alleged statement or omission, and any other equitable
considerations appropriate in the circumstances. The Issuer and the Initial
Purchaser agree that it would not be equitable if the amount of such
contribution were determined by pro rata or per capita allocation or by any
other method of allocation that does not take into account the equitable
considerations referred to in the first sentence of this paragraph (d).
Notwithstanding any other provision of this paragraph (d), the Initial Purchaser
shall not be obligated to make contributions hereunder that in the aggregate
exceed the total discounts, commissions and other compensation received by the
Initial Purchaser under this Agreement, less the aggregate amount of any damages
that the Initial Purchaser has otherwise been required to pay by reason of the
untrue or alleged untrue statements or the omissions or alleged omissions to
state a material fact, and no person guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. For purposes of this paragraph (d), each affiliate of the
Initial Purchaser, and each person, if any, who controls the Initial Purchaser
within the meaning of Section 15 of the Act or Section 20 of the Exchange Act,
shall have the same rights to contribution as the Initial Purchaser, and each
director of the Issuer, each officer of the Issuer and each person, if any, who

                                       26
<PAGE>   27

controls the Issuer within the meaning of Section 15 of the Act or Section 20 of
the Exchange Act, shall have the same rights to contribution as the Issuer.

         10. Survival Clause. The respective representations, warranties,
agreements, covenants, indemnities and other statements of the Issuer and the
Guarantors, their respective officers and the Initial Purchaser set forth in
this Agreement or made by or on behalf of them pursuant to this Agreement shall
remain in full force and effect, regardless of (i) any investigation made by or
on behalf of the Issuer and the Guarantors, any of their respective officers or
directors, the Initial Purchaser or any controlling person referred to in
Section 9 hereof and (ii) delivery of and payment for the Securities. The
respective agreements, covenants, indemnities and other statements set forth in
Sections 6, 9 and 15 hereof shall remain in full force and effect, regardless of
any termination or cancellation of this Agreement.

         11. Termination.

                  (a) This Agreement may be terminated in the sole discretion of
the Initial Purchaser by notice to the Issuer given prior to the Closing Date in
the event that the Issuer or any Guarantor shall have failed, refused or been
unable to perform all obligations and satisfy all conditions on its part to be
performed or satisfied hereunder at or prior thereto or, if at or prior to the
Closing Date:

                           (i) the Issuer or any of the Guarantors shall have
                  sustained any loss or interference with respect to its
                  businesses or properties from fire, flood, hurricane, accident
                  or other calamity, whether or not covered by insurance, or
                  from any strike, labor dispute, slow down or work stoppage or
                  any legal or governmental proceeding, which loss or
                  interference, in the sole judgment of the Initial Purchaser,
                  has had or has a Material Adverse Effect, or there shall have
                  been, in the sole judgment of the Initial Purchaser, any event
                  or development that, individually or in the aggregate, has or
                  could be reasonably likely to have a Material Adverse Effect
                  (including without limitation a change in control of any of
                  the Issuer or the Guarantors), except in each case as
                  described in the Final Memorandum (exclusive of any amendment
                  or supplement thereto);

                           (ii) trading in securities generally on the New York
                  Stock Exchange, American Stock Exchange or the NASDAQ National
                  Market shall have been suspended or minimum or maximum prices
                  shall have been established on any such exchange or market;

                           (iii) a banking moratorium shall have been declared
                  by New York or United States authorities;

                           (iv) there shall have been (A) an outbreak or
                  escalation of hostilities between the United States and any
                  foreign power, or (B) an outbreak or escalation of any other
                  insurrection or armed conflict involving the United States or
                  any other national or international calamity or emergency, or
                  (C) any material change in the financial markets of the United
                  States which, in the case of (A), (B) or (C) above and in the
                  sole judgment of the Initial Purchaser, makes it impracticable
                  or

                                       27
<PAGE>   28

                  inadvisable to proceed with the offering or the delivery of
                  the Securities as contemplated by the Final Memorandum;

                           (v) the Notes fail to receive a rating or, if the
                  Notes have received such rating, are thereafter downgraded
                  such that the Notes are rated below "B-3" by Moody's Investors
                  Service, Inc. or "B-" by Standard & Poor's Ratings Services;

                           (vi) an order is entered in the Bankruptcy Case
                  converting the Bankruptcy Case to a case under Chapter 7 of
                  the United States Bankruptcy Code, appointing a trustee or
                  examiner in the Bankruptcy Case pursuant to 11 U.S.C. Section
                  1104, dismissing the Bankruptcy Case or granting relief from
                  the automatic stay of Section 362 to allow any person or
                  entity to enforce any lien or security interest in any portion
                  of the Issuer's assets or properties; or

                           (vii) the Confirmation Order shall have been revoked
                  or vacated.

                  (b) Termination of this Agreement pursuant to this Section 11
shall be without liability of any party to any other party except as provided in
Section 10 hereof.

         12. Information Supplied by the Initial Purchaser. The statements set
forth in the last paragraph on the front cover page, the paragraph regarding
stabilization on page i, the first and third sentences of the third paragraph,
the fourth and sixth paragraphs, the fifth and sixth sentences of the seventh
paragraph and the eighth paragraph under the heading "Plan of Distribution" in
the Final Memorandum (to the extent such statements relate to the Initial
Purchaser) constitute the only information furnished by the Initial Purchaser to
the Issuer for the purposes of Sections 2(a) and 9 hereof and the Initial
Purchaser confirms that such statements are correct as of the date hereof and as
of the Closing Date.

         13. Notices. All communications hereunder shall be in writing and, if
sent to the Initial Purchaser, shall be mailed or delivered to Jefferies &
Company, Inc., 909 Fannin, Suite 3100, Houston, Texas 77010, Attention: Todd A.
Dittmann, with a copy to Vinson & Elkins L.L.P., 1001 Fannin, Suite 2300,
Houston, Texas 77002-6760, Attention: T. Mark Kelly; if sent to the Issuer or
the Guarantors, if any, shall be mailed or delivered to the Issuer at 530 Lovett
Boulevard, Houston, Texas 77006-4021, Attention: R. Kelly Plato, with a copy to
Thompson & Knight, LLP, 1200 Smith Street, Suite 1600, Houston, Texas 77002,
Attention: Barry Davis.

         All such notices and communications shall be deemed to have been duly
given: when delivered by hand, if personally delivered; five business days after
being deposited in the mail, postage prepaid, if mailed; and one business day
after being timely delivered to a next-day air courier.

         14. Successors. This Agreement shall inure to the benefit of and be
binding upon the Initial Purchaser, the Issuer and the Guarantors and their
respective successors and legal representatives, and nothing expressed or
mentioned in this Agreement is intended or shall be construed to give any other
person any legal or equitable right, remedy or claim under or in respect of this
Agreement, or any provisions herein contained; this Agreement and all conditions
and provisions hereof being intended to be and being for the sole and exclusive
benefit of such persons and for the benefit of no other person except that (i)
the indemnities of the Issuer and the

                                       28

<PAGE>   29

Guarantors contained in Section 9 of this Agreement shall also be for the
benefit of any person or persons who control the Initial Purchaser within the
meaning of Section 15 of the Act or Section 20 of the Exchange Act and (ii) the
indemnities of the Initial Purchaser contained in Section 9 of this Agreement
shall also be for the benefit of the directors of the Issuer and the Guarantors,
if any, their respective officers and any person or persons who control the
Issuer within the meaning of Section 15 of the Act or Section 20 of the Exchange
Act. No purchaser of Securities from the Initial Purchaser will be deemed a
successor because of such purchase.

         15. APPLICABLE LAW. THE VALIDITY AND INTERPRETATION OF THIS AGREEMENT,
AND THE TERMS AND CONDITIONS SET FORTH HEREIN SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO CONTRACTS
MADE AND TO BE PERFORMED WHOLLY THEREIN, WITHOUT GIVING EFFECT TO ANY PROVISIONS
THEREOF RELATING TO CONFLICTS OF LAW.

         16. Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

                                       29
<PAGE>   30

         If the foregoing correctly sets forth our understanding, please
indicate your acceptance thereof in the space provided below for that purpose,
whereupon this letter, which has been executed on June 13, 2001, shall
constitute a binding agreement between the Issuer, the Guarantors and the
Initial Purchaser.

                                             Very truly yours,

                                             TRI-UNION DEVELOPMENT CORPORATION

                                             ---------------------------------
                                             Richard Bowman, President

                                             TRI-UNION OPERATING COMPANY

                                             ---------------------------------
                                             Richard Bowman, President

                                             TRIBO PETROLEUM CORPORATION

                                             ---------------------------------
                                             Richard Bowman, President

The foregoing Agreement is hereby
confirmed and accepted on June 13, 2001.

JEFFERIES & COMPANY INC.

By:
   -------------------------------------
Name:
Title:

                                       30

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