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                                                                   EXHIBIT 4.(p)



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                                   MAPCO INC.

                                      and

                 THE FIRST NATIONAL BANK OF CHICAGO, as Trustee



                      ---------------------------------  


                          SUPPLEMENTAL INDENTURE NO. 2

                              Dated March 5, 1997


                      ---------------------------------




                                   Series of
                           7.70% Debentures due 2027
                                  $100,000,000


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                                   MAPCO INC.

                          SUPPLEMENTAL INDENTURE NO. 2

                                  $100,000,000
                           7.70% Debentures due 2027


                 SUPPLEMENTAL INDENTURE NO. 2, dated as of March 5, 1997,
between MAPCO INC., a Delaware corporation (the "Company"), and THE FIRST
NATIONAL BANK OF CHICAGO, a national banking association, as trustee (the
"Trustee").


                                    Recitals


                 The Company has heretofore executed and delivered to the
Trustee a Senior Indenture, dated as of February 25, 1997 (the "Indenture"),
providing for the issuance from time to time of a series of the Company's
Securities.

                 Section 3.1 of the Indenture provides for various matters with
respect to any series of Securities issued under the Indenture to be
established in an indenture supplemental to the Indenture.

                 Section 8.1(7) of the Indenture provides for the Company and
the Trustee to enter into an indenture supplemental to the Indenture to
establish the form or terms of Securities of any series as permitted by
Sections 2.1 and 3.1 of the Indenture.

                 For and in consideration of the premises and the issuance of
the series of Securities provided for herein, it is mutually covenanted and
agreed as follows for the equal and ratable benefit of the Holders of the
Securities of such series:






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                                   ARTICLE 1

                       Relation to Indenture; Definitions

                 Section 1.1.  This Supplemental Indenture No. 2 constitutes an
integral part of the Indenture.

                 Section 1.2.  For all purposes of this Supplemental Indenture
No. 2:

                 (1)  Capitalized terms used herein without definition shall
         have the meanings specified in the Indenture;

                 (2)  all references herein to Articles and Sections, unless
         otherwise specified, refer to the corresponding Articles and Sections
         of this Supplemental Indenture No. 2; and

                 (3)  the terms "herein", "hereof", "hereunder" and other words
         of similar import refer to this Supplemental Indenture No. 2.


                                   ARTICLE 2

                            The Series of Debentures

                 Section 2.1.  Title of the Securities.  There shall be a series
of Securities designated as the "7.70% Debentures due 2027" (the "Debentures").

                 Section 2.2.  Limitation on Aggregate Principal Amount; Date of
Debentures.  The aggregate principal amount of the Debentures shall not exceed
$100,000,000.  Each Debenture shall be dated the date of its authentication.

                 Section 2.3.  Principal Payment Date.  The principal of the
Debentures shall be payable in a single installment on March 1, 2027.





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                 Section 2.4.  Interest and Interest Rates.  Interest on the
Debentures shall be payable semi-annually on March 1 and September 1 of each
year beginning on September 1, 1997 (each, an "Interest Payment Date");
provided, however, that if an Interest Payment Date would otherwise be a day
that is not a Business Day, such Interest Payment Date shall be the succeeding
Business Day.  The interest so payable on any Note which is punctually paid or
duly provided for on any Interest Payment Date shall be paid to the Person in
whose name such Note is registered at the close of business on the February 15
or August 15, respectively (whether or not a Business Day), preceding such
Interest Payment Date (each, a "Regular Record Date").

                 The interest payable on each Interest Payment Date shall be
the amount of interest accrued for the period from and including March 5, 1997
or from and including the most recent Interest Payment Date to which interest
has been paid or duly provided for, as the case may be, to, but excluding, such
Interest Payment Date.  Interest shall be computed on the basis of a 360-day
year consisting of twelve 30-day months.

                 The interest rate borne by the Debentures will be 7.70% per
annum until paid in full.

                 Section 2.5.  Place of Payment.  The Place of Payment where the
Debentures may be presented or surrendered for payment, where the principal of
and interest and any other payments due on the Debentures are payable, where
the Debentures may be surrendered for registration of transfer or exchange and
where notices and demands to and upon the Company in respect of the Debentures
and the Indenture may be served shall be in the Borough of Manhattan, The City
of New York, and the office or agency maintained by the Company for such
purpose shall initially be the Corporate Trust Office of the Trustee.

                 Section 2.6.  Redemption.  The Debentures shall not be subject
to redemption at the option of the Company at





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any time prior to their Stated Maturity, and the Company shall have no
obligation to redeem or purchase the Debentures pursuant to any sinking fund or
analogous provisions or upon the happening of any specified event or at the
option of any Holder of the Debentures.

                 Section 2.7.  Denomination.  The Debentures shall be issued in
denominations of $1,000 and integral multiples thereof.

                 Section 2.8.  Currency.  Principal and interest on the
Debentures shall be payable in Dollars.

                 Section 2.9.  Registered Securities.  The Debentures shall be
issued as Registered Securities, without coupons.

                 Section 2.10.  Debentures to be Issued in Global Form; Exchange
for Certificated Debentures.  The Debentures will be initially represented by
one or more Debentures in global form (the "Global Debentures").  The Company
hereby designates The Depository Trust Company as the initial Depositary for
the Global Debentures.  The Global Debentures will be deposited with the
Trustee, as custodian for the Depositary.  Unless and until they are exchanged
in whole or in part for Debentures in certificated form, the Global Debentures
may not be transferred except as a whole by the Depositary to a nominee of the
Depositary or by a nominee of the Depositary to the Depositary or another
nominee of the Depositary or by the Depositary or any such nominee to a
successor Depositary for the Debentures or a nominee of such successor
Depositary.  The Depositary may surrender a Global Debenture in exchange in
whole or in part for Debentures in certificated form on such terms as are
acceptable to the Company and the Depositary.

                 The Company may at any time in its sole discretion determine
that all or any portion of the Debentures shall no longer be represented by a
Debenture or Debentures in global form.  In such event the Company shall
execute, and





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the Trustee, upon receipt of a Company Order for the authentication and
delivery of certificated Debentures of like tenor, shall authenticate and
deliver Debentures of like tenor in certificated form, in authorized
denominations and in an aggregate principal amount equal to the applicable
principal amount of the Global Debenture or Global Debentures, in exchange for
such Global Debenture or Global Debentures (or the applicable portion thereof).

                 Section 2.11.  Form of Debentures.  The Debentures shall be
substantially in the form attached as Exhibit A hereto.

                 Section 2.12.  Defeasance and Covenant Defeasance.  The
provisions of Sections 4.4 and 4.5 of the Indenture shall apply to the
Debentures.

                 Section 2.13.  Registrar and Paying Agent.  The Trustee shall
initially serve as Registrar and Paying Agent.


                                   ARTICLE 3

                            Miscellaneous Provisions

                 Section 3.1.  The Indenture, as supplemented and amended by
this Supplemental Indenture No. 2, is in all respects hereby adopted, ratified
and confirmed.

                 Section 3.2.  This Supplemental Indenture No. 2 may be executed
in any number of counterparts, each of which when so executed shall be deemed
an original; and all such counterparts shall together constitute but one and
the same instrument.

                 SECTION 3.3.  THIS SUPPLEMENTAL INDENTURE NO. 2 AND EACH
DEBENTURE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF NEW YORK.





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                 IN WITNESS WHEREOF, the parties hereto have caused this
Supplemental Indenture No. 2 to be duly executed, as of the day and year first
written above.

                                           By /s/ PHILIP W. BAXTER
                                             ----------------------------------
                                             Name:  Philip W. Baxter
                                             Title: Executive Vice President
                                                    Officer and Chief Financial 

[Corporate Seal]

ATTEST:


By  /s/ JAMES N. CUNDIFF
  ---------------------------------
  Name:  James N. Cundiff
  Title: Assistant Secretary

                                           THE FIRST NATIONAL BANK OF
                                             CHICAGO, Trustee


                                           By /s/ JOHN R. PRENDIVILLE
                                             ----------------------------------
                                             Name:  John R. Prendiville
                                             Title: Vice President

[Seal]

ATTEST:


By  /s/ JEFFREY L. KINNEY
  ---------------------------------
  Name:  Jeffrey L. Kinney
  Title: Assistant Vice President





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                                                                       EXHIBIT A





                          [FORM OF FACE OF DEBENTURE]

                 THIS DEBENTURE IS IN GLOBAL FORM WITHIN THE MEANING OF THE
         INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A
         DEPOSITARY OR A NOMINEE OF A DEPOSITARY.  UNLESS AND UNTIL IT IS
         EXCHANGED IN WHOLE OR IN PART FOR DEBENTURES IN CERTIFICATED FORM,
         THIS DEBENTURE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE
         DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE
         DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR
         BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A
         NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

                                   MAPCO INC.

                           7.70% Debentures due 2027


                                                           CUSIP No. 565097 AF 9

No. 1
                                                                    $100,000,000


                 MAPCO Inc., a corporation duly organized and existing under
the laws of the State of Delaware (herein called the "Company", which term
includes any successor corporation under the Indenture referred to herein), for
value received, hereby promises to pay to Cede & Co., or registered assigns,
the principal sum of one hundred million Dollars (U.S. $100,000,000) on March
1, 2027, and to pay on March 1 and September 1 of each year beginning on
September 1, 1997 (each, an "Interest Payment Date"; provided, however, that if
an Interest Payment Date would otherwise be a day that is not a Business Day,
such Interest Payment Date shall be the succeeding Business Day) the amount of
interest accrued thereon for the period from and including March 5, 1997 or
from and including the most recent Interest Payment Date to which interest has
been paid or duly provided for,





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as the case may be, to, but excluding, such Interest Payment Date, at the rate
of 7.70% per annum.  The rate of interest on any overdue principal and, to the
extent permitted by applicable law, overdue interest shall be the rate of
interest in effect on this Debenture from time to time.  Interest shall be
computed on the basis of a 360-day year consisting of twelve 30-day months.
The interest so payable on any Interest Payment Date which is punctually paid
or duly provided for on such Interest Payment Date will, as provided in the
Indenture referred to on the reverse hereof, be paid to the Person in whose
name this Debenture is registered at the close of business on the Regular
Record Date for such interest, which shall be the February 15 or August 15,
respectively (whether or not a Business Day), preceding such Interest Payment
Date.  Interest payable on this Debenture which is not punctually paid or duly
provided for on any Interest Payment Date therefor shall forthwith cease to be
payable to the Person in whose name this Debenture is registered at the close
of business on the Regular Record Date preceding such Interest Payment Date,
and such defaulted interest shall instead be payable to the Person in whose
name this Debenture is registered on the special record date or other specified
date determined in accordance with the Indenture referred to on the reverse
hereof.

                 Payment of the principal of and interest on this Debenture
will be made at the office or agency of the Company maintained for that purpose
in the Borough of Manhattan, The City of New York (which shall initially be an
office or agency of the Trustee), in such coin or currency of the United States
of America as at the time of payment is legal tender for payment of public and
private debts; provided, however, that at the option of the Company, interest
on the Debentures may be paid (i) by check mailed to the address of the Person
entitled thereto as such address shall appear in the register of Holders of the
Debentures or (ii) at the expense of the Company, by wire transfer to an
account maintained by the Person entitled thereto as specified in the register
of Holders of the Debentures.





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                 Reference is hereby made to the further provisions of this
Debenture set forth on the reverse hereof, which further provisions shall for
all purposes have the same effect as if set forth at this place.

                 Unless the certificate of authentication hereon has been
executed by the Trustee referred to on the reverse hereof by manual signature,
this Debenture shall not be entitled to any benefit under the Indenture
referred to on the reverse hereof or be valid or obligatory for any purpose.

                 IN WITNESS WHEREOF, MAPCO Inc. has caused this instrument to
be duly executed under its corporate seal.

Dated:

[Corporate Seal]                       MAPCO INC.



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


               [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

          This is one of the Securities of a series described in the
within-mentioned Indenture.


                                       THE FIRST NATIONAL BANK OF
                                         CHICAGO, as Trustee



                                       By:                           
                                          -------------------------------------
                                          Authorized Signatory





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                         [FORM OF REVERSE OF DEBENTURE]


                 This Debenture is one of a duly authorized issue of securities
of the Company (herein called the "Securities"), issued and to be issued in one
or more series under an Indenture, dated as of February 25, 1997 (herein called
the "Indenture"), between the Company and The First National Bank of Chicago
(herein called the "Trustee", which term includes any successor trustee under
the Indenture), to which Indenture and all indentures supplemental thereto
reference is hereby made for a statement of the respective rights, limitations
of rights, duties and immunities thereunder of the Company, the Trustee and the
Holders of the Securities and of the terms upon which the Securities are, and
are to be, authenticated and delivered.  This Debenture is one of the series
designated on the face hereof (collectively, the "Debentures"), limited to
$100,000,000 in aggregate principal amount, and is issued pursuant to
Supplemental Indenture No. 2, dated March 5, 1997, between the Company and the
Trustee, relating to the Debentures.

                 The Debentures shall not be subject to redemption at the
option of the Company at any time and the Company shall have no obligation to
redeem or purchase the Debentures pursuant to any sinking fund or upon the
happening of any specified event or at the option of any Holder of the
Debentures.

                 The Indenture contains provisions for defeasance and covenant
defeasance at any time of the indebtedness on this Debenture upon compliance by
the Company with certain conditions set forth therein, which provisions apply
to this Debenture.

                 If an Event of Default with respect to the Debentures shall
occur and be continuing, the principal of the Debentures may be declared due
and payable in the manner and with the effect provided in the Indenture.





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                 The Indenture permits, with certain exceptions as therein
provided, the amendment thereof and the modification of the rights and
obligations of the Company and the rights of the Holders of the Securities of
each series to be affected under the Indenture at any time by the Company and
the Trustee with the consent of the Holders of not less than a majority in
aggregate principal amount of the Securities at the time Outstanding of all
series adversely affected (voting as one class).  The Indenture also contains
provisions permitting the Holders of specified percentages in principal amount
of the Securities of each series at the time Outstanding, on behalf of the
Holders of all Securities of such series, to waive past Defaults or Events of
Default under the Indenture and their consequences.  Any such consent or waiver
by the Holder of this Debenture shall be conclusive and binding upon such
Holder and upon all future Holders of this Debenture and of any Debenture
issued upon the registration of transfer hereof or in exchange herefor or in
lieu hereof, whether or not notation of such consent or waiver is made upon
this Debenture.

                 No reference herein to the Indenture and no provision of this
Debenture or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of, and
interest on, this Debenture at the times, place and rate, and in the coin or
currency, herein prescribed.

                 As provided in the Indenture and subject to certain
limitations as therein set forth, the transfer of this Debenture is registrable
on the Register, upon surrender of this Debenture for registration of transfer
at the office or agency of the Company to be maintained for that purpose in The
City of New York, duly endorsed by, or accompanied by a written instrument of
transfer in form satisfactory to the Company, the Trustee and the Registrar
duly executed by, the Holder hereof or his attorney duly authorized in writing,
and thereupon one or more new Debentures, of like tenor, of authorized
denominations and for the same aggregate principal amount, will be issued to
the designated transferee or transferees.





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                 The Debentures are issuable only in registered form in
denominations of $1,000 and any integral multiple thereof.  As provided in the
Indenture and subject to certain limitations therein set forth, the Debentures
are exchangeable for Debentures having a like aggregate principal amount, of
like tenor and having a different authorized denomination, as requested by the
Holder surrendering the same.

                 No service charge shall be made for any such registration of
transfer or exchange, but the Company may require payment of a sum sufficient
to cover any tax or other governmental charge that may be imposed in connection
therewith.

                 Prior to due presentment of this Debenture for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Debenture is registered as the owner
hereof for the purpose of receiving payment of principal of and (subject to
Section 3.7 of the Indenture) interest on this Debenture and for all other
purposes whatsoever, whether or not this Debenture shall be overdue, and
neither the Company, the Trustee nor any agent of the Company or the Trustee
shall be affected by notice to the contrary.

                 Capitalized terms used in this Debenture without definition
shall have the meanings specified in the Indenture.





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