Document:

<PAGE>
                                                                   EXHIBIT 4.2.3

================================================================================

                          CHESAPEAKE ENERGY CORPORATION

                                       and

                     the Subsidiary Guarantors named herein

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

                          8 1/2% SENIOR NOTES DUE 2012
                    ----------------------------------------

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

                          EIGHTH SUPPLEMENTAL INDENTURE

                           DATED AS OF October 1, 2001

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

                              THE BANK OF NEW YORK

                             as successor Trustee to

                     United States Trust Company of New York

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

================================================================================

<PAGE>

         THIS EIGHTH SUPPLEMENTAL INDENTURE, dated as of October 1, 2001, 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 release of any
Subsidiary Guarantor, as provided for in the Indenture; and

         WHEREAS, the Company has taken all actions required to effect the
release, pursuant to Section 10.4 of the Indenture, of Chesapeake Canada
Corporation, an Alberta, Canada corporation ("Chesapeake Canada"), as a
Subsidiary Guarantor; 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 Eighth
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 Eighth 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 Eighth Supplemental Indenture shall become effective
immediately upon its execution and delivery by each of the Company, the
Subsidiary Guarantors and the Trustee.

                                    ARTICLE 2

         Chesapeake Canada shall for all purposes be released as a Subsidiary
Guarantor from all of its Guarantee and related obligations in the Indenture,
pursuant to Section 10.4 of the Indenture. The notation on the Securities
relating to the Guarantee shall be deemed to exclude the name of Chesapeake
Canada and the signature of an Officer of Chesapeake Canada on its behalf.

<PAGE>

                                    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 Eighth Supplemental Indenture. This
Eighth 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 LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED
TO CONSTRUE AND ENFORCE THIS EIGHTH SUPPLEMENTAL INDENTURE.

         Section 3.04. The parties may sign any number of copies of this Eighth
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]

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Eighth
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:

                                   THE AMES COMPANY, INC.
                                   CHESAPEAKE ACQUISITION CORPORATION
                                   CHESAPEAKE ROYALTY COMPANY
                                   NOMAC DRILLING CORPORATION
                                   CHESAPEAKE ENERGY LOUISIANA
                                   CORPORATION
                                   CHESAPEAKE OPERATING, INC.
                                   CHESAPEAKE MOUNTAIN FRONT CORP.
                                   GOTHIC ENERGY CORPORATION
                                   GOTHIC PRODUCTION CORPORATION

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

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

<PAGE>

                                     ARKOMA PITTSBURG HOLDING
                                     CORPORATION

                                     By     /s/ HENRY J. HOOD
                                       ----------------------------------------
                                     Name:    Henry J. Hood
                                          -------------------------------------
                                     Title:   President
                                           ------------------------------------

                                     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:   Authorized Signer
                                           ------------------------------------<PAGE>

                                                                   EXHIBIT 4.3.1
================================================================================

                          CHESAPEAKE ENERGY CORPORATION

                                       and

                           the Guarantors named herein

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

                           8 1/8% SENIOR NOTES DUE 2011

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

                                   ----------

                          SECOND SUPPLEMENTAL INDENTURE

                         DATED AS OF September 12, 2001

                                   ----------

                                BANK OF NEW YORK

                                     Trustee

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

================================================================================

<PAGE>

         THIS SECOND SUPPLEMENTAL INDENTURE, dated as of September 12, 2001, is
among Chesapeake Energy Corporation, an Oklahoma corporation (the "Company"),
each of the parties identified under the caption "Guarantors" on the signature
page hereto (the "Guarantors") and Bank of New York, 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 April 6, 2001, as supplemented by
that certain Supplemental Indenture dated May 14, 2001 (the "Indenture"),
pursuant to which the Company has originally issued $800,000,000 in principal
amount of 8 1/8% Senior Notes due 2011 (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
in order to execute and deliver a guarantee to comply with Section 10.03 thereof
without the consent of the Holders of the Notes; 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 Guarantors and of the Trustee necessary to make this Second Supplemental
Indenture a valid instrument legally binding on the Company, the 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 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 Second 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 Second Supplemental Indenture shall become effective
immediately upon its execution and delivery by each of the Company, the
Guarantors and the Trustee.

                                    ARTICLE 2

         From this date, in accordance with Section 10.03 and by executing this
Second Supplemental Indenture, each of Chesapeake Mountain Front Corp., an
Oklahoma corporation, and Chesapeake- Staghorn Acquisition L.P., an Oklahoma
limited partnership, are subject to the provisions of the Indenture as
Subsidiary Guarantors to the extent provided for in Article 10 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

<PAGE>

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 Second Supplemental Indenture. This
Second 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 each of
Chesapeake Mountain Front Corp. and Chesapeake-Staghorn Acquisition L.P. have
been designated by the Board of Directors of the Company as Restricted
Subsidiaries pursuant to Section 10.03 (a) of the Indenture.

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

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

<PAGE>

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

                                   GUARANTORS:

                                   THE AMES COMPANY, INC.
                                   CHESAPEAKE ACQUISITION CORPORATION
                                   CHESAPEAKE ROYALTY COMPANY
                                   NOMAC DRILLING CORPORATION
                                   CHESAPEAKE ENERGY LOUISIANA
                                   CORPORATION
                                   CHESAPEAKE CANADA CORPORATION
                                   CHESAPEAKE OPERATING, INC.
                                   CHESAPEAKE MOUNTAIN FRONT CORP.
                                   GOTHIC ENERGY CORPORATION
                                   GOTHIC PRODUCTION CORPORATION

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

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

<PAGE>

                                   ARKOMA PITTSBURG HOLDING
                                   CORPORATION

                                   By    /s/ HENRY J. HOOD
                                     ------------------------------------------
                                   Name:    Henry J. Hood
                                        ---------------------------------------
                                   Title:   President
                                         --------------------------------------

                                   TRUSTEE:

                                   BANK OF NEW YORK, successor to United States
                                   Trust Company of New York, as Trustee

                                   By    /s/ LOUIS P. YOUNG
                                     ------------------------------------------
                                   Name:     Louis P. Young
                                        ---------------------------------------
                                   Title:    Authorized Signer
                                         --------------------------------------

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