Document:

<PAGE>
                                                                   Exhibit 4.4.3
------------------------------------------------------------------------------

                         CHESAPEAKE ENERGY CORPORATION

                                      and

                    the Subsidiary Guarantors named herein

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

                         8.375% SENIOR NOTES DUE 2008
                   ----------------------------------------

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

                         THIRD SUPPLEMENTAL INDENTURE

                           DATED AS OF July 8, 2002

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

                             THE BANK OF NEW YORK

                                  as Trustee

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

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

<PAGE>

      THIS THIRD SUPPLEMENTAL INDENTURE, dated as of July 8, 2002, is among
Chesapeake Energy Corporation, an Oklahoma corporation (the "Company"), each of
the parties identified under the caption "Subsidiary Guarantors" on the
signature page hereto (the "Subsidiary Guarantors") and The Bank of New York, as
Trustee.

                                   RECITALS

      WHEREAS, the Company, the Subsidiary Guarantors a party thereto and the
Trustee entered into an Indenture, dated as of November 5, 2001 (the
"Indenture"), pursuant to which the Company has originally issued $250,000,000
in principal amount of 8.375% Senior Notes due 2008 (the "Notes"); and

      WHEREAS, Section 9.01(3) of the Indenture provides that the Company, the
Subsidiary Guarantors and the Trustee may amend or supplement the Indenture
without notice to or consent of any Holder to reflect the addition of any
Subsidiary Guarantor, as provided for in the Indenture; and

      WHEREAS, the Board of Directors of the Company has designated Chesapeake
Alpha Corp., Chesapeake Beta Corp., Chesapeake Delta Corp. and Chesapeake Sigma,
L.P. as Restricted Subsidiaries of the Company and desires to add such entities
as Subsidiary Guarantors under the Indenture; and

      WHEREAS, all acts and things prescribed by the Indenture, by law and by
the charter and the bylaws (or comparable constituent documents) of the Company,
of the Subsidiary Guarantors and of the Trustee necessary to make this Third
Supplemental Indenture a valid instrument legally binding on the Company, the
Subsidiary Guarantors and the Trustee, in accordance with its terms, have been
duly done and performed;

      NOW, THEREFORE, to comply with the provisions of the Indenture and in
consideration of the above premises, the Company, the Subsidiary Guarantors and
the Trustee covenant and agree for the equal and proportionate benefit of the
respective Holders of the Notes as follows:

                                   ARTICLE 1

      Section 1.01. This Third Supplemental Indenture is supplemental to the
Indenture and does and shall be deemed to form a part of, and shall be construed
in connection with and as part of, the Indenture for any and all purposes.

      Section 1.02. This Third Supplemental Indenture shall become effective
immediately upon its execution and delivery by each of the Company, the
Subsidiary Guarantors and the Trustee.

                                   ARTICLE 2

      From this date, in accordance with Section 10.03 and by executing this
Third Supplemental Indenture, Chesapeake Alpha Corp., an Oklahoma corporation,
Chesapeake Beta Corp., an Oklahoma corporation, Chesapeake Delta Corp. an
Oklahoma corporation, and Chesapeake Sigma, L.P., an

                                      -2-
<PAGE>

Oklahoma limited partnership, are subject to the provisions of the Indenture as
Subsidiary Guarantors to the extent provided for in Article Ten thereunder.

                                   ARTICLE 3

      Section 3.01. Except as specifically modified herein, the Indenture and
the Notes are in all respects ratified and confirmed (mutatis mutandis) and
shall remain in full force and effect in accordance with their terms with all
capitalized terms used herein without definition having the same respective
meanings ascribed to them as in the Indenture.

      Section 3.02. Except as otherwise expressly provided herein, no duties,
responsibilities or liabilities are assumed, or shall be construed to be
assumed, by the Trustee by reason of this Third Supplemental Indenture. This
Third Supplemental Indenture is executed and accepted by the Trustee subject to
all the terms and conditions set forth in the Indenture with the same force and
effect as if those terms and conditions were repeated at length herein and made
applicable to the Trustee with respect hereto.

      Section 3.03. The Company hereby notifies the Trustee that Chesapeake
Alpha Corp., Chesapeake Beta Corp., Chesapeake Delta Corp. and Chesapeake Sigma,
L.P. have each been designated by the Board of Directors of the Company as a
Restricted Subsidiary (as that term is defined in the Indenture).

      Section 3.04. THE LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO
CONSTRUE AND ENFORCE THIS THIRD SUPPLEMENTAL INDENTURE.

      Section 3.05. The parties may sign any number of copies of this Third
Supplemental Indenture. Each signed copy shall be an original, but all of such
executed copies together shall represent the same agreement.

                         [NEXT PAGE IS SIGNATURE PAGE]

                                      -3-
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have caused this Third Supplemental
Indenture to be duly executed, all as of the date first written above.

                                     COMPANY:

                                     CHESAPEAKE ENERGY CORPORATION

                                     By /s/ Aubrey K. McClendon
                                       ----------------------------------------
                                     Name: Aubrey K. McClendon
                                           ------------------------------------
                                     Title:Chief Executive Officer
                                           ------------------------------------

                                     SUBSIDIARY GUARANTORS:

                                     CARMEN ACQUISITION CORP.
                                     CHESAPEAKE ACQUISITION CORPORATION
                                     CHESAPEAKE ENERGY LOUISIANA
                                     CORPORATION
                                     CHESAPEAKE MOUNTAIN FRONT CORP.
                                     CHESAPEAKE OPERATING, INC.
                                     CHESAPEAKE ROYALTY COMPANY
                                     GOTHIC ENERGY CORPORATION
                                     GOTHIC PRODUCTION CORPORATION
                                     NOMAC DRILLING CORPORATION
                                     SAP ACQUISITION CORP.
                                     THE AMES COMPANY, INC.
                                     CHESAPEAKE KNAN ACQUISITION
                                     CORPORATION
                                     CHESAPEAKE FOCUS CORP.
                                     CHESAPEAKE ALPHA CORP.
                                     CHESAPEAKE BETA CORP.
                                     CHESAPEAKE DELTA CORP.

                                     By /s/ Aubrey K. McClendon
                                       ----------------------------------------
                                     Name: Aubrey K. McClendon
                                           ------------------------------------
                                     Title:Chief Executive Officer
                                           ------------------------------------

                                      -4-
<PAGE>

                                     CHESAPEAKE EXPLORATION LIMITED
                                     PARTNERSHIP
                                     CHESAPEAKE LOUISIANA, L.P.
                                     CHESAPEAKE PANHANDLE LIMITED
                                     PARTNERSHIP
                                     CHESAPEAKE-STAGHORN ACQUISITION L.P.
                                     CHESAPEAKE SIGMA, L.P.

                                     By:   Chesapeake Operating, Inc. as general
                                           partner of each representative entity

                                     By /s/ Aubrey K. McClendon
                                       ----------------------------------
                                     Name: Aubrey K. McClendon
                                           ------------------------------
                                     Title:Chief Executive Officer
                                           ------------------------------

                                     TRUSTEE:

                                     THE BANK OF NEW YORK, as Trustee

                                     By /s/ Louis P. Young
                                       --------------------------------------
                                     Name: Louis P. Young
                                          -----------------------------------
                                     Title: Vice President
                                           ----------------------------------

                                      -5-<PAGE>
                                                                   Exhibit 4.6.2

                         UNION BANK OF CALIFORNIA, N.A.
                               4200 LINCOLN PLAZA
                                 500 NORTH AKARD
                               DALLAS, TEXAS 75201

                                 August 2, 2002

Chesapeake Energy Corporation
Chesapeake Exploration Limited Partnership
6100 North Western Avenue
Oklahoma City, Oklahoma 73118

Re:   Second Amended and Restated Credit Agreement dated as of June 11, 2001 (as
      amended, supplemented or restated, the "Credit Agreement"), by and among
      Chesapeake Exploration Limited Partnership, an Oklahoma limited
      partnership ("Borrower"), Chesapeake Energy Corporation, an Oklahoma
      corporation ("Company"), Bear Stearns Corporate Lending Inc., as
      syndication agent ("Syndication Agent"), Union Bank of California, N.A.,
      as administrative agent and collateral agent ("Administrative Agent"), and
      the several banks and other financial institutions or entities from time
      to time parties thereto ("Lenders")

Ladies and Gentlemen:

      Reference is hereby made to the Credit Agreement. Terms which are defined
in the Credit Agreement and not otherwise defined herein are used herein with
the meanings given them in the Credit Agreement.

      Borrower and Company have informed Administrative Agent and Lenders that
Company intends to issue new Senior Notes (in one or more series) in the
aggregate face amount of up to $375,000,000, providing (i) for an interest rate
at the then prevailing market rate of interest, but not more than 9-1/4%, (ii)
for a maturity date of not sooner than ten years from the date of issuance, and
(iii) for covenants, mandatory prepayments, defaults, and events of default no
more restrictive than Company's 8-1/8% Notes (the "New Notes").

      Borrower and Company have requested that Administrative Agent and Lenders
consent to the issuance of the New Notes. Accordingly, subject to the terms and
provisions hereof, Administrative Agent and Lenders hereby (i) consent to the
issuance of the New Notes, (ii) waive any violations of Section 7.2 of the
Credit Agreement resulting therefrom, and (iii) agree that such New Notes shall
be permitted in addition to the Indebtedness otherwise permitted pursuant to
Section 7.2 of the Credit Agreement; provided that (1) at the time of the
issuance of
<PAGE>
the New Notes, no Default or Event of Default has occurred that is continuing,
(2) the issuance of the New Notes shall be approved by the Board of Directors of
Company, (3) the issuance of the New Notes shall be consummated on or before
September 30, 2002, (4) to the extent that the aggregate face amount of the New
Notes exceeds $250,000,000, the issuance of such New Notes in excess of
$250,000,000 shall be used to exchange and/or redeem the 7-7/8% Notes, and (5)
except as otherwise provided herein, nothing in this Letter Agreement shall
allow any Person to incur any other new Indebtedness not allowed pursuant to
Section 7.2 of the Credit Agreement.

      Borrower will pay to Administrative Agent, for the account of each Lender
signatory to this Letter Agreement on or before 5:00 p.m., Dallas, Texas time on
the date hereof, a consent fee of $50,000 that shall be distributed to such
Lenders on a pro rata basis according to the Revolving Percentages of such
Lenders. Such fee shall be due and payable at such time as Majority Lenders are
signatory to this Letter Agreement.

      The Credit Agreement is hereby ratified and confirmed in all respects.
Except as expressly set forth above, the execution, delivery and effectiveness
of this Letter Agreement shall not operate as a waiver of any right, power or
remedy of Administrative Agent or Lenders under the Credit Agreement, the Notes,
or any other Loan Document, nor constitute a waiver of any provision of the
Credit Agreement, the Notes, or any other Loan Document.

      By its execution below, each Guarantor hereby (i) consents to the
provisions of this Letter Agreement and the transactions contemplated herein,
(ii) ratifies and confirms the Guarantee Agreement dated as of June 11, 2001
made by it for the benefit of Administrative Agent and Lenders and the other
Loan Documents executed pursuant to the Credit Agreement, (iii) agrees that all
of its respective obligations and covenants thereunder shall remain unimpaired
by the execution and delivery of this Letter Agreement and the other documents
and instruments executed in connection herewith, and (iv) agrees that the
Guarantee Agreement and such other Loan Documents shall remain in full force and
effect.

      This Letter Agreement is a "Loan Document" as defined and described in the
Credit Agreement and all of the terms and provisions of the Credit Agreement
relating to Loan Documents shall apply hereto. This Letter Agreement may be
executed in multiple counterparts, all of which shall constitute one Letter
Agreement. This Letter Agreement may be validly executed by facsimile or other
electronic transmission.

           [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK.]
<PAGE>
      Please execute a copy of this Letter Agreement in the space provided below
to evidence your agreement to and acknowledgment of the foregoing.

                                    Very truly yours,

                                    UNION BANK OF CALIFORNIA, N.A.
                                    Administrative Agent, Collateral Agent
                                    and Lender

                                    By:  /s/ RANDALL OSTERBERG
                                         ----------------------------------
                                         Name: Randall Osterberg
                                         Title: Senior Vice President

                                    By:  /s/ JOHN CLARK
                                         ------------------------------------
                                         Name: John Clark
                                         Title: Vice President

ACKNOWLEDGED AND AGREED
to as of the date first written above:

BORROWER:
--------

CHESAPEAKE EXPLORATION LIMITED PARTNERSHIP

By:   Chesapeake Operating, Inc., its general partner

By:    /s/ MARTHA A. BURGER
      -----------------------------------
      Name: Martha A. Burger
      Title: Treasurer & Sr. Vice President Human Resources
<PAGE>
GUARANTORS:

CHESAPEAKE ENERGY CORPORATION

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer & Sr. Vice President Human Resources

THE AMES COMPANY, INC.

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

CHESAPEAKE ACQUISITION CORPORATION

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

CHESAPEAKE ENERGY LOUISIANA CORPORATION

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

CHESAPEAKE OPERATING, INC.

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer & Sr. Vice President Human Resources
<PAGE>
CHESAPEAKE PANHANDLE LIMITED PARTNERSHIP

By:   CHESAPEAKE OPERATING, INC., its General Partner

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer & Sr. Vice President Human Resources

CHESAPEAKE ROYALTY COMPANY

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

CHESAPEAKE-STAGHORN ACQUISITION L .P.

By:   CHESAPEAKE OPERATING, INC., its General Partner

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer & Sr. Vice President Human Resources

CHESAPEAKE LOUISIANA, L.P.

By:   CHESAPEAKE OPERATING, INC., its General Partner

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer & Sr. Vice President Human Resources

GOTHIC ENERGY CORPORATION

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer
<PAGE>
GOTHIC PRODUCTION CORPORATION

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

NOMAC DRILLING CORPORATION

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

CARMEN ACQUSITION CORP.

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

SAP ACQUISITION CORP.

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer

CHESAPEAKE MOUNTAIN FRONT CORP.

By:    /s/ MARTHA A. BURGER
      ---------------------------------
      Name: Martha A. Burger
      Title: Treasurer
<PAGE>
                                    LENDERS:

                                    BANK OF OKLAHOMA, N.A.

                                    By:    /s/ JOHN N. HUFF
                                          ------------------------------------
                                          Name: John N. Huff
                                          Title: Vice President

                                    BANK OF SCOTLAND

                                    By:    /s/ JOSEPH FRATUS
                                          ------------------------------------
                                          Name: Joseph Fratus
                                          Title: First Vice President

                                    BEAR STEARNS CORPORATE LENDING INC.

                                    By:    /s/ VICTOR BULZACCHELLI
                                          ------------------------------------
                                          Name: Victor Bulzacchelli
                                          Title: Authorized Agent

                                    BNP PARIBAS

                                    By:    /s/ BETSY JOCHER
                                          ------------------------------------
                                          Name: Betsy Jocher
                                          Title: Vice President

                                    By:    /s/ GABE ELLISOR
                                          ------------------------------------
                                          Name: Gabe Ellisor
                                          Title: Vice President

                                    COMERICA BANK - TEXAS

                                    By:    /s/ PETER L. SEFZIK
                                          ------------------------------------
                                          Name: Peter L. Sefzik
                                          Title: Assistant Vice President

                                    COMPASS BANK

                                    By:    /s/ KATHLEEN J. BOWEN
                                          ------------------------------------
                                          Name: Kathleen J. Bowen
                                          Title: Vice President
<PAGE>
                                    CREDIT AGRICOLE INDOSUEZ

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

                                    NATEXIS BANQUES POPULAIRES

                                    By:    /s/ DONOVAN C. BROUSSARD
                                          ------------------------------------
                                          Name: Donovan C. Broussard
                                          Title: Vice President

                                    By:    /s/ DANIEL PAYER
                                          ------------------------------------
                                          Name: Daniel Payer
                                          Title: Vice President

                                    PNC BANK, NATIONAL ASSOCIATION

                                    By:    /s/ DOUG CLARK
                                          ------------------------------------
                                          Name: Doug Clark
                                          Title: Vice President

                                    RZB FINANCE LLC

                                    By:    /s/ FRANK J. YAUTZ
                                          ------------------------------------
                                          Name: Frank J. Yautz
                                          Title: First Vice President

                                    By:    /s/ JOHN A. VALISKA
                                          ------------------------------------
                                          Name: John A. Valiska
                                          Title: Group Vice President

                                    SUMITOMO MITSUI BANKING
                                    CORPORATION

                                    By:    /s/ DAVID A. BUCK
                                          ------------------------------------
                                          Name: David A. Buck
                                          Title: Senior Vice President
<PAGE>
                                    TORONTO DOMINION (TEXAS), INC.

                                    By:    /s/ DEBBIE A. GREENE
                                          ------------------------------------
                                          Name: Debbie A. Greene
                                          Title: Vice President

                                    WASHINGTON MUTUAL BANK, FA

                                    By:    /s/ MARK ISENSEE
                                          ------------------------------------
                                          Name: Mark Isensee
                                          Title: Vice President

                                    CREDIT LYONNAIS NEW YORK BRANCH

                                    By:    /s/ BERNARD WEYMULLER
                                          ------------------------------------
                                          Name: Bernard Weymuller
                                          Title: Senior Vice President

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