EXHIBIT 4.2.3

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                          CHESAPEAKE ENERGY CORPORATION

                                       and

                     the Subsidiary Guarantors named herein

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

                          8 1/2% SENIOR NOTES DUE 2012

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

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                         ELEVENTH SUPPLEMENTAL INDENTURE


                            DATED AS OF July 8, 2002

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


                              THE BANK OF NEW YORK

                             as successor Trustee to

                     United States Trust Company of New York

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



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      THIS ELEVENTH 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
successor to United States Trust Company 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 March 15, 1997, as supplemented
prior to the date hereof (the "Indenture"), pursuant to which the Company has
originally issued $150,000,000 in principal amount of 8 1/2% Senior Notes due
2012 (the "Notes"); and

      WHEREAS, Section 9.1(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 Eleventh
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 Eleventh 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 Eleventh Supplemental Indenture shall become effective
immediately upon its execution and delivery by each of the Company, the
Subsidiary Guarantors and the Trustee.


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                                    ARTICLE 2

      From this date, in accordance with Section 10.3 and by executing this
Eleventh 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 Oklahoma limited
partnership, are subject to the provisions of the Indenture as Subsidiary
Guarantors to the extent provided for in Article X 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 Eleventh Supplemental Indenture. This
Eleventh 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 ELEVENTH SUPPLEMENTAL INDENTURE.

      Section 3.05. The parties may sign any number of copies of this Eleventh
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]




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      IN WITNESS WHEREOF, the parties hereto have caused this Eleventh
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
                                            ------------------------------------



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                                    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 successor to United
                                    States Trust Company of New York, as Trustee

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


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