UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED):

September 20, 2005  (September 2, 2005)

TGC INDUSTRIES, INC.

(Exact name of registrant as specified in its charter)

1304 Summit Ave., Ste 2

Plano, TX  75074

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code:  (972) 881-1099

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

o            Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o            Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o            Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o            Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Section 1 – Registrant’s Business and Operations

Item 1.01  Entry into a Material Definitive Agreement.

Amendment to Promissory Note

On September 16, 2005, TGC Industries, Inc. (“TGC” or the “Company”) entered into an amendment (the “Amendment”) to its promissory note with Sovereign Bank, N.A., dated April 26, 2005.  The Amendment allows TGC to borrow, repay and re-borrow from time to time until September 16, 2005, up to $3,500,000.  TGC’s obligations under the Amendment are secured by a security interest in the Company’s accounts receivable.  Interest on the outstanding amount under the Amendment is payable monthly at a rate of prime plus 1.0%.  The Company also amended the related business loan agreement to reflect the increase in the amount available under the Amendment and the new maturity date.  The business loan agreement provides for non-financial and financial covenants, including a minimum debt to worth ratio of 1 to 1.50 and a minimum liquidity of $500,000.  A copy of the Amendment and the related business loan agreement are being filed as Exhibits 10.1 and 10.2 to this Current Report on Form 8-K.

Promissory Notes

On September 2, 2005, TGC entered into a promissory note (the “September 2^nd Note”) with General Electric Capital Corporation (“GECC”) to finance the purchase of a vibration vehicle.  The September 2^nd Note is for the principal sum of $286,235, which will be repaid in thirty-six monthly principal payments of $8,870.86 with the final payment equal to the total outstanding unpaid principal.  In addition to the principal payments, accrued interest will also be payable on all payment dates. Interest on the unpaid principal balance will accrue at a rate of 7.25% per annum.  The September 2^nd Note also provides for a pre-payment penalty equal to 3% of the original principal amount in the first year and 1% of the original principal amount in the second and third years of the September 2^nd Note.  The first monthly payment is due and payable on October 2, 2005.  On September 9, 2005, the September 2^nd Note was amended to change the amount of the first thirty-five monthly principal payments from $8,870.86 to $7,950.97.  A copy of the September 2^nd Note and the related amendment are being filed as Exhibit 10.3 and 10.4 to this Current Report on Form 8-K.

On September 12, 2005, TGC entered into a promissory note (the “September 12^th Note”) with GECC to finance the purchase of a second vibration vehicle.  The September 12^th Note is for the principal sum of $286,235, which will be repaid in thirty-six monthly principal payments of $8,906.59 with the final payment equal to the total outstanding unpaid principal.  In addition to the principal payments, accrued interest will also be payable on all payment dates. Interest on the unpaid principal balance will accrue at a rate of 7.25% per annum.  The September 12^th Note also provides for a pre-payment penalty equal to 3% of the original principal amount in the first year and 1% of the original principal amount in the second and third years of the September 12^th  Note.  The first monthly payment is due and payable on November 2, 2005.  On September 9, 2005, and becoming effective on September 12, 2005, the September 12^th Note was amended to change the amount of the first thirty-five monthly principal payments from $8,906.59 to $7,950.97.  The September 12^th Note was also amended on September 12, 2005, to change the date of the initial periodic payment from November 2, 2005 to October 12, 2005.  A copy of the September 12^th Note and the related amendments are being filed as Exhibit 10.5, 10.6 and 10.7 to this Current Report on Form 8-K.

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Item 2.03  Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of the Registrant.

See Item 1.01 “Entry into a Material Definitive Agreement – Amendment to Promissory Note” and “Entry into a Material Definitive Agreement – Promissory Notes.”

Section 9 – Financial Statements and Exhibits

Item 9.01  Financial Statements and Exhibits.

(c)           Exhibits.

10.1         Promissory Note by and among TGC Industries, Inc. and Sovereign Bank, N.A., dated September 16, 2005.

10.2         Business Loan Agreement by and among TGC Industries, Inc. and Sovereign Bank, N.A., dated September 16, 2005.

10.3         Promissory Note by and among TGC Industries, Inc. and General Electric Capital Corporation, dated September 2, 2005.

10.4         Amendment, dated September 9, 2005, to the Promissory Note by and among TGC Industries, Inc. and General Electric Capital Corporation, dated September 2, 2005.

10.5         Promissory Note by and among TGC Industries, Inc. and General Electric Capital Corporation, dated September 12, 2005.

10.6         Amendment, dated September 9, 2005 and effective September 12, 2005, to the Promissory Note by and among TGC Industries, Inc. and General Electric Capital Corporation, dated September 12, 2005.

10.7         Amendment, dated September 12, 2005, to the Promissory Note by and among TGC Industries, Inc. and General Electric Capital Corporation, dated September 12, 2005.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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EXHIBIT INDEX

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Exhibit 10.1

CORPORATE RESOLUTION TO BORROW / GRANT COLLATERAL

References in the shaded area are for Lender’s use only and do not limit the applicability
of this document to any particular loan or item.
Any item above containing “* * *” has been omitted due to text length limitations.

I, THE UNDERSIGNED, DO HEREBY CERTIFY THAT:

THE CORPORATION’S EXISTENCE.  The complete and correct name of the Corporation is TGC Industries, Inc. (“Corporation”). The Corporation is a corporation for profit which is, and at all times shall be, duly organized, validly existing, and in good standing under and by virtue of the laws of the State of Texas. The Corporation is duly authorized to transact business in all other states in which the Corporation is doing business, having obtained all necessary filings, governmental licenses and approvals for each state in which the Corporation is doing business. Specifically, the Corporation is, and at all times shall be, duly qualified as a foreign corporation in all states in which the failure to so qualify would have a material adverse effect on its business or financial condition. The Corporation has the full power and authority to own its properties and to transact the business in which it is presently engaged or presently proposes to engage. The Corporation maintains an office at 1304 Summit Avenue, Ste. 2, Plano, TX 75074. Unless the Corporation has designated otherwise in writing, the principal office is the office at which the Corporation keeps its books and records. The Corporation will notify Lender prior to any change in the location of The Corporation’s state of organization or any change in The Corporation’s name. The Corporation shall do all things necessary to preserve and to keep in full force and effect its existence, rights and privileges, and shall comply with all regulations, rules, ordinances, statutes, orders and decrees of any governmental or quasi-governmental authority or court applicable to the Corporation and The Corporation’s business activities.

RESOLUTIONS ADOPTED.  At a meeting of the Directors of the Corporation, or if the Corporation is a close corporation having no Board of Directors then at a meeting of the Corporation’s shareholders, duly called and held on                               , at which a quorum was present and voting, or by other duly authorized action in lieu of a meeting, the resolutions set forth in this Resolution were adopted.

OFFICER.  The following named person is an officer of TGC Industries, Inc.:

ACTIONS AUTHORIZED.  The authorized person listed above may enter into any agreements of any nature with Lender, and those agreements will bind the Corporation. Specifically, but without limitation, the authorized person is authorized, empowered, and directed to do the following for and on behalf of the Corporation:

Borrow Money.  To borrow, as a cosigner or otherwise, from time to time from Lender, on such terms as may be agreed upon between the Corporation and Lender, such sum or sums of money as in his or her judgment should be borrowed, without limitation.

Execute Notes.  To execute and deliver to Lender the promissory note or notes, or other evidence of the Corporation’s credit accommodations, on Lender’s forms, at such rates of interest and on such terms as may be agreed upon, evidencing the sums of money so borrowed or any of the Corporation’s indebtedness to Lender, and also to execute and deliver to Lender one or more renewals, extensions, modifications, refinancings, consolidations, or substitutions for one or more of the notes, any portion of the notes, or any other evidence of credit accommodations.

Grant Security.  To mortgage, pledge, transfer, endorse, hypothecate, or otherwise encumber and deliver to Lender any property now or hereafter belonging to the Corporation or in which the Corporation now or hereafter may have an interest, including without limitation all of the Corporation’s real property and all of the Corporation’s personal property (tangible or intangible), as security for the payment of any loans or credit accommodations so obtained, any promissory notes so executed (including any amendments to or modifications, renewals, and extensions of such promissory notes), or any other or further indebtedness of the Corporation to Lender at any time owing, however the same may be evidenced. Such property may be mortgaged, pledged, transferred, endorsed, hypothecated or encumbered at the time such loans are obtained or such indebtedness is incurred, or at any other time or times, and may be either in addition to or in lieu of any property theretofore mortgaged, pledged, transferred, endorsed, hypothecated or encumbered.

Execute Security Documents.  To execute and deliver to Lender the forms of mortgage, deed of trust, pledge agreement, hypothecation agreement, and other security agreements and financing statements which Lender may require and which shall evidence the terms and conditions under and pursuant to which such liens and encumbrances, or any of them, are given; and also to execute and deliver to Lender any other written instruments, any chattel paper, or any other collateral, of any kind or nature, which Lender may deem necessary or proper in connection with or pertaining to the giving of the liens and encumbrances.

Negotiate Items.  To draw, endorse, and discount with Lender all drafts, trade acceptances, promissory notes, or other evidences of indebtedness payable to or belonging to the Corporation or in which the Corporation may have an interest, and either to receive cash for the same or to cause such proceeds to be credited to the Corporation’s account with Lender, or to cause such other disposition of the proceeds derived therefrom as he or she may deem advisable.

Further Acts.  In the case of lines of credit, to designate additional or alternate individuals as being authorized to request advances under such lines, and in all cases, to do and perform such other acts and things, to pay any and all fees and costs, and to execute and deliver such other documents and agreements as the officer may in his or her discretion deem reasonably necessary or proper in order to carry into effect the provisions of this Resolution.

ASSUMED BUSINESS NAMES.  The Corporation has filed or recorded all documents or filings required by law relating to all assumed business names used by the Corporation. Excluding the name of the Corporation, the following is a complete list of all assumed business names under which the Corporation does business: None.

NOTICES TO LENDER.  The Corporation will promptly notify Lender in writing at Lender’s address shown above (or such other addresses as Lender may designate from time to time) prior to any (A) change in the Corporation’s name; (B) change in the Corporation’s assumed business name(s); (C) change in the management of the Corporation; (D) change in the authorized signer(s); (E) change in the Corporation’s principal office address; (F) change in the Corporation’s state of organization; (G) conversion of the Corporation to a new or different type of business entity; or (H) change in any other aspect of the Corporation that directly or indirectly relates to any agreements between the Corporation and Lender. No change in the Corporation’s name or state of organization will take effect until after Lender has received notice.

CERTIFICATION CONCERNING OFFICERS AND RESOLUTIONS.  The officer named above is duly elected, appointed, or employed by or for the Corporation, as the case may be, and occupies the position set opposite his or her respective name. This Resolution now stands of record on the books of the Corporation, is in full force and effect, and has not been modified or revoked in any manner whatsoever.

NO CORPORATE SEAL.  The Corporation has no corporate seal, and therefore, no seal is affixed to this Resolution.

CONTINUING VALIDITY.  Any and all acts authorized pursuant to this Resolution and performed prior to the passage of this Resolution are hereby ratified and approved. This Resolution shall be continuing, shall remain in full force and effect and Lender may rely on it until written notice of its revocation shall have been delivered to Lender and receipt acknowledged by Lender in writing at Lender’s address shown above (or such addresses as Lender may designate from time to time). Any such notice shall not affect any of the Corporation’s agreements or commitments in effect at the time notice is given.

IN TESTIMONY WHEREOF, I have hereunto set my hand and attest that the signature set opposite the name listed above is his or her genuine signature.

I have read all the provisions of this Resolution, and I personally and on behalf of the Corporation certify that all statements and representations made in this Resolution are true and correct. This Corporate Resolution to Borrow / Grant Collateral is dated                                      .

NOTE: If the officer signing this Resolution is designated by the foregoing document as one of the officers authorized to act on the Corporation’s behalf, it is advisable to have this Resolution signed by at least one non-authorized officer of the Corporation.

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PROMISSORY NOTE

References in the shaded area are for Lender’s use only and do not limit the applicability
of this document to any particular loan or item.

Any item above containing “* * *” has been omitted due to text length limitations.

PROMISE TO PAY.  TGC Industries, Inc. (“Borrower”) promises to pay to Sovereign Bank, N.A. (“Lender”), or order, in lawful money of the United States of America, the principal amount of Three Million Five Hundred Thousand & 00/100 Dollars ($3,500,000.00) or so much as may be outstanding, together with interest on the unpaid outstanding principal balance of each advance. Interest shall be calculated from the date of each advance until repayment of each advance or maturity, whichever occurs first.

CHOICE OF USURY CEILING AND INTEREST RATE.  The interest rate on this Note has been implemented under the “Quarterly Ceiling” as referred to in Section 303.006 of the Texas Finance Code. The terms, including the rate, or index, formula, or provision of law used to compute the rate on the Note, will be subject to revision as to current and future balances, from time to time by notice from Lender in compliance with Section 303.103 of the Texas Finance Code.

PAYMENT.  Borrower will pay this loan in one payment of all outstanding principal plus all accrued unpaid interest on September 16, 2006. In addition, Borrower will pay regular monthly payments of all accrued unpaid interest due as of each payment date, beginning October 16, 2005, with all subsequent interest payments to be due on the same day of each month after that. Unless otherwise agreed or required by applicable law, payments will be applied first to any accrued unpaid interest; and then to principal. The annual interest rate for this Note is computed on a 365/360 basis; that is, by applying the ratio of the annual interest rate over a year of 360 days, multiplied by the outstanding principal balance, multiplied by the actual number of days the principal balance is outstanding, unless such calculation would result in a usurious rate, in which case interest shall be calculated on a per diem basis of a year of 365 or 366 days, as the case may be. Borrower will pay Lender at Lender’s address shown above or at such other place as Lender may designate in writing. Notwithstanding any other provision of this Note, Lender will not charge interest on any undisbursed loan proceeds. No scheduled payment, whether of principal or interest or both, will be due unless sufficient loan funds have been disbursed by the scheduled payment date to justify the payment.

VARIABLE INTEREST RATE.  The interest rate on this Note is subject to change from time to time based on changes in an independent index which is the Sovereign Bank, N.A. Prime Rate as determined, currently equal to Wall Street Journal Prime Rate as quoted in the Southwestern Addition of the Wall Street Journal (the “Index”). The index is not necessarily the lowest rate charged by Lender on its loans. If the index becomes unavailable during the term of this loan, Lender may designate a substitute index after notice to Borrower. Lender will tell Borrower the current index rate upon Borrower’s request. The interest rate change will not occur more often than each Day. Borrower understands that Lender may make loans based on other rates as well. The index currently is 6.500% per annum. The interest rate to be applied prior to maturity to the unpaid principal balance of this Note will be at a rate of 1.000 percentage point over the index, resulting in an initial rate of 7.500% per annum. NOTICE: Under no circumstances will the interest rate on this Note be more than the maximum rate allowed by applicable law. For purposes of this Note, the “maximum rate allowed by applicable law” means the greater of (A) the maximum rate of interest permitted under federal or other law applicable to the indebtedness evidenced by this Note, or (B) the “Quarterly Ceiling” as referred to in Section 303.006 of the Texas Finance Code.

PREPAYMENT.  Borrower may pay without penalty all or a portion of the amount owed earlier than it is due. Prepayment in full shall consist of payment of the remaining unpaid principal balance together with all accrued and unpaid interest and all other amounts, costs and expenses for which Borrower is responsible under this Note or any other agreement with Lender pertaining to this loan, and in no event will Borrower ever be required to pay any unearned interest. Early payments will not, unless agreed to by Lender in writing, relieve Borrower of Borrower’s obligation to continue to make payments of accrued unpaid interest. Rather, early payments will reduce the principal balance due. Borrower agrees not to send Lender payments marked “paid in full”, “without recourse”, or similar language. If Borrower sends such a payment, Lender may accept it without losing any of Lender’s rights under this Note, and Borrower will remain obligated to pay any further amount owed to Lender. All written communications concerning disputed amounts, including any check or other payment instrument that indicates that the payment constitutes “payment in full” of the amount owed or that is tendered with other conditions or limitations or as full satisfaction of a disputed amount must be mailed or delivered to: Sovereign Bank, N.A., 7301 North State Highway 161 Irving, TX 75039.

POST MATURITY RATE.  The Post Maturity Rate on this Note is the lesser of the maximum rate allowed by law or the variable interest rate in effect at the time of final maturity. Borrower will pay interest on all sums due after final maturity, whether by acceleration or otherwise, at that rate.

DEFAULT.  Each of the following shall constitute an event of default (“Event of Default”) under this Note:

Payment Default.  Borrower fails to make any payment when due under this Note.

Other Defaults.  Borrower fails to comply with or to perform any other term, obligation, covenant or condition contained in this Note or in any of the related documents or to comply with or to perform any term, obligation, covenant or condition contained in any other agreement between Lender and Borrower.

Default in Favor of Third Parties.  Borrower or any Grantor defaults under any loan, extension of credit, security agreement, purchase or sales agreement, or any other agreement, in favor of any other creditor or person that may materially affect any of Borrower’s property or Borrower’s ability to repay this Note or perform Borrower’s obligations under this Note or any of the related documents.

False Statements.  Any warranty, representation or statement made or furnished to Lender by Borrower or on Borrower’s behalf under this Note or the related documents is false or misleading in any material respect, either now or at the time made or furnished or becomes false or misleading at any time thereafter.

Insolvency.  The dissolution or termination of Borrower’s existence as a going business, the insolvency of Borrower, the appointment of a receiver for any part of Borrower’s property, any assignment for the benefit of creditors, any type of creditor workout, or the commencement of any proceeding under any bankruptcy or insolvency laws by or against Borrower.

Creditor or Forfeiture Proceedings.  Commencement of foreclosure or forfeiture proceedings, whether by judicial proceeding, self-help, repossession or any other method, by any creditor of Borrower or by any governmental agency against any collateral securing the loan. This includes a garnishment of any of Borrower’s accounts, including deposit accounts, with Lender. However, this Event of Default shall not apply if there is a good faith dispute by Borrower as to the validity or reasonableness of the claim which is the basis of the creditor or

forfeiture proceeding and if Borrower gives Lender written notice of the creditor or forfeiture proceeding and deposits with Lender monies or a surety bond for the creditor or forfeiture proceeding, in an amount determined by Lender, in its sole discretion, as being an adequate reserve or bond for the dispute.

Events Affecting Guarantor.  Any of the preceding events occurs with respect to any guarantor, endorser, surety, or accommodation party of any of the indebtedness or any guarantor, endorser, surety, or accommodation party dies or becomes incompetent, or revokes or disputes the validity of, or liability under, any guaranty of the indebtedness evidenced by this Note.

Change In Ownership.  Any change in ownership of twenty-five percent (25%) or more of the common stock of Borrower.

Adverse Change.  A material adverse change occurs in Borrower’s financial condition, or Lender believes the prospect of payment or performance of this Note is impaired.

Insecurity.  Lender in good faith believes itself insecure.

LENDER’S RIGHTS.  Upon default, Lender may declare the entire indebtedness, including the unpaid principal balance on this Note, all accrued unpaid interest, and all other amounts, costs and expenses for which Borrower is responsible under this Note or any other agreement with Lender pertaining to this loan, immediately due, without notice, and then Borrower will pay that amount.

ATTORNEYS’ FEES; EXPENSES.  Lender may hire an attorney to help collect this Note if Borrower does not pay, and Borrower will pay Lender’s reasonable attorneys’ fees. Borrower also will pay Lender all other amounts Lender actually incurs as court costs, lawful fees for filing, recording, releasing to any public office any instrument securing this Note; the reasonable cost actually expended for repossessing, storing, preparing for sale, and selling any security; and fees for noting a lien on or transferring a certificate of title to any motor vehicle offered as security for this Note, or premiums or identifiable charges received in connection with the sale of authorized insurance.

GOVERNING LAW.  This Note will be governed by federal law applicable to Lender and, to the extent not preempted by federal law, the laws of the State of Texas without regard to its conflicts of law provisions. This Note has been accepted by Lender in the State of Texas.

CHOICE OF VENUE.  If there is a lawsuit, and if the transaction evidenced by this Note occurred in Dallas County, Borrower agrees upon Lender’s request to submit to the jurisdiction of the courts of Dallas County, State of Texas.

DISHONORED CHECK CHARGE.  Borrower will pay a processing fee of $30.00 if any check given by Borrower to Lender as a payment on this loan is dishonored.

RIGHT OF SETOFF.  To the extent permitted by applicable law, Lender reserves a right of setoff in all Borrower’s accounts with Lender (whether checking, savings, or some other account). This includes all accounts Borrower holds jointly with someone else and all accounts Borrower may open in the future. However, this does not include any IRA or Keogh accounts, or any trust accounts for which setoff would be prohibited by law. Borrower authorizes Lender, to the extent permitted by applicable law, to charge or setoff all sums owing on the indebtedness against any and all such accounts.

COLLATERAL.  Borrower acknowledges this Note is secured by Assignment of Accounts Receivables and General Intangibles.

LINE OF CREDIT.  This Note evidences a revolving line of credit. Advances under this Note, as well as directions for payment from Borrower’s accounts, may be requested orally or in writing by Borrower or by an authorized person. Lender may, but need not, require that all oral requests be confirmed in writing. Borrower agrees to be liable for all sums either: (A) advanced in accordance with the instructions of an authorized person or (B) credited to any of Borrower’s accounts with Lender. The unpaid principal balance owing on this Note at any time may be evidenced by endorsements on this Note or by Lender’s internal records, including daily computer print-outs. Lender will have no obligation to advance funds under this Note if: (A) Borrower or any guarantor is in default under the terms of this Note or any agreement that Borrower or any guarantor has with Lender, including any agreement made in connection with the signing of this Note; (B) Borrower or any guarantor ceases doing business or is insolvent; (C) any guarantor seeks, claims or otherwise attempts to limit, modify or revoke such guarantor’s guarantee of this Note or any other loan with Lender; (D) Borrower has applied funds provided pursuant to this Note for purposes other than those authorized by Lender; or (E) Lender in good faith believes itself insecure.  This revolving line of credit shall not be subject to Ch. 346 of the Texas Finance Code.

RENEWAL AND EXTENSION.  This Note is given in renewal and extension and not in novation of the following described indebtedness:  The Promissory Note dated April 26, 2005 in the amount of Five Hundred Thousand & 00/100 ($500,000.00), from Borrower to Lender.

SUCCESSOR INTERESTS.  The terms of this Note shall be binding upon Borrower, and upon Borrower’s heirs, personal representatives, successors and assigns, and shall inure to the benefit of Lender and its successors and assigns.

GENERAL PROVISIONS.  If any part of this Note cannot be enforced, this fact will not affect the rest of the Note. Borrower does not agree or intend to pay, and Lender does not agree or intend to contract for, charge, collect, take, reserve or receive (collectively referred to herein as “charge or collect”), any amount in the nature of interest or in the nature of a fee for this loan, which would in any way or event (including demand, prepayment, or acceleration) cause Lender to charge or collect more for this loan than the maximum Lender would be permitted to charge or collect by federal law or the law of the State of Texas (as applicable). Any such excess interest or unauthorized fee shall, instead of anything stated to the contrary, be applied first to reduce the principal balance of this loan, and when the principal has been paid in full, be refunded to Borrower. The right to accelerate maturity of sums due under this Note does not include the right to accelerate any interest which has not otherwise accrued on the date of such acceleration, and Lender does not intend to charge or collect any unearned interest in the event of acceleration. All sums paid or agreed to be paid to Lender for the use, forbearance or detention of sums due hereunder shall, to the extent permitted by applicable law, be amortized, prorated, allocated and spread throughout the full term of the loan evidenced by this Note until payment in full so that the rate or amount of interest on account of the loan evidenced hereby does not exceed the applicable usury ceiling. Lender may delay or forgo enforcing any of its rights or remedies under this Note without losing them. Borrower and any other person who signs, guarantees or endorses this Note, to the extent allowed by law, waive presentment, demand for payment, notice of dishonor, notice of intent to accelerate the maturity of this Note, and notice of acceleration of the maturity of this Note. Upon any change in the terms of this Note, and unless otherwise expressly stated in writing, no party who signs this Note, whether as maker, guarantor, accommodation maker or endorser, shall be released from liability. All such parties agree that Lender may renew or extend (repeatedly and for any length of time) this loan or release any party or guarantor or collateral; or impair, fail to realize upon or perfect Lender’s security interest in the collateral without the consent of or notice to anyone. All such parties also agree that Lender may modify this loan without the consent of or notice to anyone other than the party with whom the modification is made. The obligations under this Note are joint and several.

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PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO THE TERMS OF THE NOTE.

BORROWER ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THIS PROMISSORY NOTE.

BORROWER:

TGC INDUSTRIES, INC.

LENDER:

SOVEREIGN BANK, N.A.

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NOTICE OF FINAL AGREEMENT

References in the shaded area are for Lender’s use only and do not limit the applicability
of this document to any particular loan or item.

Any item above containing “* * *” has been omitted due to text length limitations.

THE WRITTEN LOAN AGREEMENT REPRESENTS THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

As used in this Notice, the following terms have the following meanings:

Loan. The term “Loan” means the following described loan: B non-precomputed Variable Rate Nondisclosable Revolving Line of Credit Loan to a Corporation for $3,500,000.00 due on September 16, 2006. The reference rate (Sovereign Bank, N.A. Prime Rate as determined, currently equal to Wall Street Journal Prime Rate as quoted in the Southwestern Addition of the Wall Street Journal, currently 6,500%) is added to the margin of 1.000%, resulting in an initial rate of 7,500. This is a secured renewal of the following described indebtedness: The Promissory Note dated April 26, 2005 in the amount of Five Hundred Thousand & 00/100 ($500,000.00), from Borrower to Lender .

Loan Agreement. The term “Loan Agreement” means one or more promises, promissory notes, agreements, undertakings, security agreements, deeds of trust or other documents, or commitments, or any combination of those actions or documents, relating to the Loan, including without limitation the following:

LOAN DOCUMENTS

Parties.  The term “Parties” means Sovereign Bank, N.A. and any and all entities or Individuals who are obligated to repay the loan or have pledged property as security for the Loan, including without limitation the following:

This Notice of Final Agreement is given by Sovereign Bank, N.A. pursuant to Section 26.02 of the Texas Business and Commerce Code. Each Party who signs below, other than Sovereign Bank, N.A., acknowledges, represents, and warrants to Sovereign Bank, N.A. that it has received, read and understood this Notice of Final Agreement. This Notice is dated September 16, 2005.

BORROWER:

TGC INDUSTRIES, INC.

LENDER:

SOVEREIGN BANK, N.A.

[ILLEGIBLE]

Exhibit 10.2

BUSINESS LOAN AGREEMENT

References in the shaded area are for Lender’s use only and do not limit the applicability
of this document to any particular loan or item.

Any item above containing “* * *” has been omitted due to text length limitations.

THIS BUSINESS LOAN AGREEMENT dated September 16, 2005, is made and executed between TGC Industries, Inc. (“Borrower”) and Sovereign Bank, N.A. (“Lender”) on the following terms and conditions. Borrower has received prior commercial loans from Lender or has applied to Lender for a commercial loan or loans or other financial accommodations, including those which may be described on any exhibit or schedule attached to this Agreement (“Loan”). Borrower understands and agrees that: (A) in granting, renewing, or extending any Loan, Lender is relying upon Borrower’s representations, warranties, and agreements as set forth in this Agreement; (B) the granting, renewing, or extending of any Loan by Lender at all times shall be subject to Lender’s sole judgment and discretion; and (C) all such Loans shall be and remain subject to the terms and conditions of this Agreement.

TERM.  This Agreement shall be effective as of September 16, 2005, and shall continue in full force and effect until such time as all of Borrower’s Loans in favor of Lender have been paid in full, including principal, interest, costs, expenses, attorneys’ fees, and other fees and charges, or until September 16, 2006.

CONDITIONS PRECEDENT TO EACH ADVANCE.  Lender’s obligation to make the Initial Advance and each subsequent Advance under this Agreement shall be subject to the fulfillment to Lender’s satisfaction of all of the conditions set forth in this Agreement and in the Related Documents.

Loan Documents.  Borrower shall provide to Lender the following documents for the Loan: (1) the Note; (2) Security Agreements granting to Lender security interests in the Collateral; (3) financing statements and all other documents perfecting Lender’s Security Interests; (4) evidence of insurance as required below; (5) together with all such Related Documents as Lender may require for the Loan; all in form and substance satisfactory to Lender and Lender’s counsel.

Borrower’s Authorization.  Borrower shall have provided in form and substance satisfactory to Lender properly certified resolutions, duly authorizing the execution and delivery of this Agreement, the Note and the Related Documents. In addition, Borrower shall have provided such other resolutions, authorizations, documents and instruments as Lender or its counsel, may require.

Payment of Fees and Expenses.  Borrower shall have paid to Lender all fees, charges, and other expenses which are then due and payable as specified in this Agreement or any Related Document.

Representations and Warranties.  The representations and warranties set forth in this Agreement, in the Related Documents, and in any document or certificate delivered to Lender under this Agreement are true and correct.

No Event of Default.  There shall not exist at the time of any Advance a condition which would constitute an Event of Default under this Agreement or under any Related Document.

REPRESENTATIONS AND WARRANTIES.  Borrower represents and warrants to Lender, as of the date of this Agreement, as of the date of each disbursement of loan proceeds, as of the date of any renewal, extension or modification of any Loan, and at all times any Indebtedness, exists:

Organization.  Borrower is a corporation for profit which is, and at all times shall be, duly organized, validly existing, and in good standing under and by virtue of the laws of the State of Texas. Borrower is duly authorized to transact business in all other states in which Borrower is doing business, having obtained all necessary filings, governmental licenses and approvals for each state in which Borrower is doing business. Specifically, Borrower is, and at all times shall be, duly qualified as a foreign corporation in all states in which the failure to so qualify would have a material adverse effect on its business or financial condition. Borrower has the full power and authority to own its properties and to transact the business in which it is presently engaged or presently proposes to engage. Borrower maintains an office at 1304 Summit Avenue, Ste. 2, Plano, TX 75074. Unless Borrower has designated otherwise in writing, the principal office is the office at which Borrower keeps its books and records including its records concerning the Collateral. Borrower will notify Lender prior to any change in the location of Borrower’s state of organization or any change in Borrower’s name. Borrower shall do all things necessary to preserve and to keep in full force and effect its existence, rights and privileges, and shall comply with all regulations, rules, ordinances, statutes, orders and decrees of any governmental or quasi-governmental authority or court applicable to Borrower and Borrower’s business activities.

Assumed Business Names.  Borrower has filed or recorded all documents or filings required by law relating to all assumed business names used by Borrower. Excluding the name of Borrower, the following is a complete list of all assumed business names under which Borrower does business: None.

Authorization.  Borrower’s execution, delivery, and performance of this Agreement and all the Related Documents have been duly authorized by all necessary action by Borrower and do not conflict with, result in a violation of, or constitute a default under (1) any provision of (a) Borrower’s articles of incorporation or organization, or bylaws, or (b) any agreement or other instrument binding upon Borrower or (2) any law, governmental regulation, court decree, or order applicable to Borrower or to Borrower’s properties.

Financial Information.  Each of Borrower’s financial statements supplied to Lender truly and completely disclosed Borrower’s financial condition as of the date of the statement, and there has been no material adverse change in Borrower’s financial condition subsequent to the date of the most recent financial statement supplied to Lender. Borrower has no material contingent obligations except as disclosed in such financial statements.

Legal Effect.  This Agreement constitutes, and any instrument or agreement Borrower is required to give under this Agreement when delivered will constitute legal, valid, and binding obligations of Borrower enforceable against Borrower in accordance with their respective terms.

Properties.  Except as contemplated by this Agreement or as previously disclosed in Borrower’s financial statements or in writing to Lender and as accepted by Lender, and except for property tax liens for taxes not presently due and payable, Borrower owns and has good title to all of Borrower’s properties free and clear of all Security Interests, and has not executed any security documents or financing statements relating to such properties. All of Borrower’s properties are titled in Borrower’s legal name, and Borrower has not used or filed a financing statement under any other name for at least the last five (5) years.

Hazardous Substances.  Except as disclosed to and acknowledged by Lender in writing, Borrower represents and warrants that: (1) During the period of Borrower’s ownership of the Collateral, there has been no use, generation, manufacture, storage, treatment, disposal, release or threatened release of any Hazardous Substance by any person on, under, about or from any of the Collateral. (2) Borrower has no knowledge of, or reason to believe that there has been (a) any breach or violation of any Environmental Laws; (b) any use, generation, manufacture, storage, treatment, disposal, release or threatened release of any Hazardous Substance on, under, about or from the Collateral by any prior owners or occupants of any of the Collateral; or (c) any actual or threatened litigation or claims of any kind by any person relating to such matters. (3) Neither Borrower nor any tenant, contractor, agent or other authorized user of any of the Collateral shall use, generate, manufacture, store, treat, dispose of or release any Hazardous Substance on, under, about or from any of the Collateral; and any such activity shall be conducted in compliance with all applicable federal, state, and local laws, regulations, and ordinances, including without limitation all Environmental Laws. Borrower authorizes Lender and its agents to enter upon the Collateral to make such inspections and tests as Lender may deem appropriate to determine compliance of the Collateral with this section of the Agreement. Any inspections or tests made by Lender shall be at Borrower’s expense and for Lender’s purposes only and shall not be construed to create any responsibility or liability on the part of Lender to Borrower or to any other person. The representations and warranties contained herein are based on Borrower’s due diligence in investigating the Collateral for hazardous waste and Hazardous Substances. Borrower hereby (1) releases and waives any future claims against Lender for indemnity or contribution in the event Borrower becomes liable for cleanup or other costs under any such laws, and (2) agrees to indemnify and hold harmless Lender against any and all claims, losses, liabilities, damages, penalties, and expenses which Lender may directly or indirectly sustain or suffer resulting from a breach of this section of the Agreement or as a consequence of any use, generation, manufacture, storage, disposal, release or threatened release of a hazardous waste or substance on the Collateral. The provisions of this section of the Agreement, including the obligation to indemnify, shall survive the payment of the indebtedness and the termination, expiration or satisfaction of this Agreement and shall not be affected by Lender’s acquisition of any interest in any of the Collateral, whether by foreclosure or otherwise.

Litigation and Claims.  No litigation, claim, investigation, administrative proceeding or similar action (including those for unpaid taxes) against Borrower is pending or threatened, and no other event has occurred which may materially adversely affect Borrower's financial condition or properties, other than litigation, claims, or other events, if any, that have been disclosed to and acknowledged by Lender in writing.

Taxes.  To the best of Borrower’s knowledge, all of Borrower’s tax returns and reports that are or were required to be filed, have been filed, and all taxes, assessments and other governmental charges have been paid in full, except those presently being or to be contested by Borrower in good faith in the ordinary course of business and for which adequate reserves have been provided.

Lien Priority.  Unless otherwise previously disclosed to Lender in writing, Borrower has not entered into or granted any Security Agreements, or permitted the filing or attachment of any Security Interests on or affecting any of the Collateral directly or indirectly securing repayment of Borrower’s Loan and Note, that would be prior or that may in any way be superior to Lender’s Security Interests and rights in and to such Collateral.

Binding Effect.  This Agreement, the Note, all Security Agreements (if any), and all Related Documents are binding upon the signers thereof, as well as upon their successors, representatives and assigns, and are legally enforceable in accordance with their respective terms.

AFFIRMATIVE COVENANTS.  Borrower covenants and agrees with Lender that, so long as this Agreement remains in effect, Borrower will:

Notices of Claims and Litigation.  Promptly inform Lender in writing of (1) all material adverse changes in Borrower’s financial condition, and (2) all existing and all threatened litigation, claims, investigations, administrative proceedings or similar actions affecting Borrower or any Guarantor which could materially affect the financial condition of Borrower or the financial condition of any Guarantor.

Financial Records.  Maintain its books and records in accordance with GAAP, applied on a consistent basis, and permit Lender to examine and audit Borrower’s books and records at all reasonable times.

Financial Statements.  Furnish Lender with the following:

Interim Statements.  As soon as available, but in no event later than 45 days after the end of each fiscal quarter, Borrower’s balance sheet and profit and loss statement for the period ended, prepared by Borrower.

Tax Returns.  As soon as available, but in no event later than ninety (90) days after the applicable filing date for the tax reporting period ended, Federal and other governmental tax returns, prepared by Borrower.

All financial reports required to be provided under this Agreement shall be prepared in accordance with GAAP, applied on a consistent basis, and certified by Borrower as being true and correct.

Additional Information.  Furnish such additional information and statements, as Lender may request from time to time.

Financial Covenants and Ratios.  Comply with the following covenants and ratios:

Other Requirements.  Monthly Accounts Receivables aging due within 10 days of month end.

Monthly borrowing base certificate due within 30 days of month end.

Eligible Accounts Receivable: Accounts less than 90 days past due; entire Accounts Receivables with any portion over 90 days is excluded from eligible Accounts Receivables.

Revolving Line of Credit shall be rested for a minimum of 30 consecutive days every 12 months.

Borrower shall maintain minimum liquidity of $500,000.00.

Borrower shall have a maximum debt/worth ratio of 1.50X.

Except as provided above, all computations made to determine compliance with the requirements contained in this paragraph shall be made in accordance with generally accepted accounting principles, applied on a consistent basis, and certified by Borrower as being true and correct.

Insurance.  Maintain fire and other risk insurance, public liability insurance, and such other insurance as Lender may require with respect to Borrower’s properties and operations, in form, amounts, and coverages reasonably acceptable to Lender and by insurance companies authorized to transact business in Texas. BORROWER MAY FURNISH THE INSURANCE REQUIRED BY THIS AGREEMENT WHETHER THROUGH EXISTING POLICIES OWNED OR CONTROLLED BY BORROWER OR THROUGH EQUIVALENT COVERAGE FROM ANY INSURANCE COMPANY AUTHORIZED TO TRANSACT BUSINESS IN TEXAS. Borrower, upon request of Lender, will deliver to Lender from time to time the policies or certificates of insurance in form satisfactory to Lender, including stipulations that coverages will not be cancelled or diminished without at least thirty (30) days prior written notice to Lender. Each insurance policy also shall include an endorsement providing that coverage in favor of Lender will not be impaired in any way by any act, omission or default of Borrower or any other person. In connection with all policies covering assets in which Lender holds or is offered a security interest for the Loans, Borrower will provide Lender with such lender’s loss payable or other endorsements as Lender may require.

Insurance Reports.  Furnish to Lender, upon request of Lender, reports on each existing insurance policy showing such information as Lender may reasonably request, including without limitation the following: (1) the name of the insurer; (2) the risks insured; (3) the amount of the policy; (4) the properties insured; (5) the then current property values on the basis of which insurance has been obtained, and the manner of determining those values; and (6) the expiration date of the policy. In addition, upon request of Lender (however not more often than annually), Borrower will have an independent appraiser satisfactory to Lender determine, as applicable, the actual cash value or replacement cost of any Collateral. The cost of such appraisal shall be paid by Borrower.

Other Agreements.  Comply with all terms and conditions of all other agreements, whether now or hereafter existing, between Borrower and any other party and notify Lender immediately in writing of any default in connection with any other such agreements.

Loan Proceeds.  Use all Loan proceeds solely for Borrower’s business operations, unless specifically consented to the contrary by Lender in writing.

Taxes, Charges and Liens.  Pay and discharge when due all of its indebtedness and obligations, including without limitation all assessments, taxes, governmental charges, levies and liens, of every kind and nature, imposed upon Borrower or its properties, income, or profits, prior to the date on which penalties would attach, and all lawful claims that, if unpaid, might become a lien or charge upon any of Borrower’s properties, income, or profits.

Performance.  Perform and comply, in a timely manner, with all terms, conditions, and provisions set forth in this Agreement, in the Related Documents, and in all other instruments and agreements between Borrower and Lender. Borrower shall notify Lender immediately in writing of any default in connection with any agreement.

Operations.  Maintain executive and management personnel with substantially the same qualifications and experience as the present executive and management personnel; provide written notice to Lender of any change in executive and management personnel; conduct its business affairs in a reasonable and prudent manner.

Environmental Studies.  Promptly conduct and complete, at Borrower’s expense, all such investigations, studies, samplings and testings as may be requested by Lender of any governmental authority relative to any substance, or any waste or by-product of any substance defined as toxic or a hazardous substance under applicable federal, state, or local law, rule, regulation, order or directive, at or affecting any property or any facility owned, leased or used by Borrower.

Compliance with Governmental Requirements.  Comply with all laws, ordinances, and regulations, now or hereafter in effect, of all governmental authorities applicable to the conduct of Borrower’s properties, businesses and operations, and to the use or occupancy of the Collateral, including without limitation, the Americans With Disabilities Act. Borrower may contest in good faith any such law, ordinance, or regulation and withhold compliance during any proceeding, including appropriate appeals, so long as Borrower has notified Lender in writing prior to doing so and so long as, in Lender’s sole opinion, Lender’s interests in the Collateral are not jeopardized. Lender may require Borrower to post adequate security or a surety bond, reasonably satisfactory to Lender, to protect Lender’s interest.

Inspection.  Permit employees or agents of Lender at any reasonable time to inspect any and all Collateral for the Loan or Loans and Borrower’s other properties and to examine or audit Borrower’s books, accounts, and records and to make copies and memoranda of Borrower’s books, accounts, and records. If Borrower now or at any time hereafter maintains any records (including without limitation computer generated records and computer software programs for the generation of such records) in the possession of a third party, Borrower, upon request of Lender, shall notify such party to permit Lender free access to such records at all reasonable times and to provide Lender with copies of any records it may request, all at Borrower’s expense.

Environmental Compliance and Reports.  Borrower shall comply in all respects with any and all Environmental Laws; not cause or permit to exist, as a result of an intentional or unintentional action or omission on Borrower’s part or on the part of any third party, on property owned and/or occupied by Borrower, any environmental activity where damage may result to the environment, unless such environmental activity is pursuant to and in compliance with the conditions of a permit issued by the appropriate federal; state or local governmental authorities; shall furnish to Lender promptly and in any event within thirty (30) days after receipt thereof a copy of any notice, summons, lien, citation, directive, latter or other communication from any governmental agency or instrumentality concerning any intentional or unintentional action or omission on Borrower’s part in connection with any environmental activity whether or not there is damage to the

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environment and/or other natural resources.

Additional Assurances.  Make, execute and deliver to Lender such promissory notes, mortgages, deeds of trust, security agreements, assignments, financing statements, instruments, documents and other agreements as Lender or its attorneys may reasonably request to evidence and secure the Loans and to perfect all Security Interests.

LENDER’S EXPENDITURES.  If any action or proceeding is commenced that would materially affect Lender’s Interest in the Collateral or if Borrower fails to comply with any provision of this Agreement or any Related Documents, including but not limited to Borrower’s failure to discharge or pay when due any amounts Borrower is required to discharge or pay under this Agreement or any Related Documents, Lender on Borrower’s behalf may (but shall not be obligated to) take any action that Lender deems appropriate, including but not limited to discharging or paying all taxes, liens, security interests, encumbrances and other claims, at any time levied or placed on any Collateral and paying all costs for insuring, maintaining and preserving any Collateral. All such expenditures paid by Lender for such purposes will then bear interest at the Note rate from the date paid by Lender to the date of repayment by Borrower. To the extent permitted by applicable law, all such expenses will become a part of the Indebtedness and, at Lender’s option, will (A) be payable on demand; (B) be added to the balance of the Note and be apportioned among and be payable with any installment payments to become due during either (1) the term of any applicable insurance policy; or (2) the remaining term of the Note; or (C) be treated as a balloon payment which will be due and payable at the Note’s maturity.

NEGATIVE COVENANTS.  Borrower covenants and agrees with Lender that while this Agreement is in effect. Borrower shall not, without the prior written consent of Lender:

Indebtedness and Liens.  Sell with recourse any of Borrower’s accounts, except to Lender.

Continuity of Operations.  (1) Engage in any business activities substantially different than those in which Borrower is presently engaged, (2) cease operations, liquidate, merge, transfer, acquire or consolidate with any other entity, change its name, dissolve or transfer or sell Collateral out of the ordinary course of business, or (3) pay any dividends on Borrower’s stock (other than dividends payable in its stock), provided, however that notwithstanding the foregoing, but only so long as no Event of Default has occurred and is continuing or would result from the payment of dividends, if Borrower is a “Subchapter S Corporation” (as defined in the Internal Revenue Code of 1986, as amended). Borrower may pay cash dividends on its stock to its shareholders from time to time in amounts necessary to enable the shareholders to pay income taxes and make estimated income tax payments to satisfy their liabilities under federal and state law which arise solely from their status as Shareholders of a Subchapter S Corporation because of their ownership of shares of Borrower’s stock, or purchase or retire any of Borrower’s outstanding shares or alter or amend Borrower’s capital structure.

Agreements.  Borrower will not enter into any agreement containing any provisions which would be violated or breached by the performance of Borrower’s obligations under this Agreement or in connection herewith.

CESSATION OF ADVANCES.  If Lender has made any commitment to make any Loan to Borrower, whether under this Agreement or under any other agreement, Lender shall have no obligation to make Loan Advances or to disburse Loan proceeds if: (A) Borrower or any Guarantor is in default under the terms of this Agreement or any of the Related Documents or any other agreement that Borrower or any Guarantor has with Lender; (B) Borrower or any Guarantor dies, becomes incompetent or becomes insolvent, files a petition in bankruptcy or similar proceedings, or is adjudged a bankrupt; (C) there occurs a material adverse change in Borrower’s financial condition, in the financial condition of any Guarantor, or in the value of any Collateral securing any Loan; or (D) any Guarantor seeks, claims or otherwise attempts to limit, modify or revoke such Guarantor’s guaranty of the Loan or any other loan with Lender; or (E) Lender in good faith deems itself insecure, even though no Event of Default shall have occurred.

RIGHT OF SETOFF.  To the extent permitted by applicable law, Lender reserves a right of setoff in all Borrower’s accounts with Lender (whether checking, savings, or some other account). This includes all accounts Borrower holds jointly with someone else and all accounts Borrower may open in the future. However, this does not include any IRA or Keogh accounts, or any trust accounts for which setoff would be prohibited by law. Borrower authorizes Lender, to the extent permitted by applicable law, to charge or setoff all sums owing on the Indebtedness against any and all such accounts.

DEFAULT.  Each of the following shall constitute an Event of Default under this Agreement:

Payment Default.  Borrower fails to make any payment when due under the Loan.

Other Defaults.  Borrower fails to comply with or to perform any other term, obligation, covenant or condition contained in this Agreement or in any of the Related Documents or to comply with or to perform any term, obligation, covenant or condition contained in any other agreement between Lender and Borrower.

Default in Favor of Third Parties.  Borrower or any Grantor defaults under any loan, extension of credit, security agreement, purchase or sales agreement, or any other agreement, in favor of any other creditor or person that may materially affect any of Borrower’s or any Grantor’s property or Borrower’s or any Grantor’s ability to repay the Loans or perform their respective obligations under this Agreement or any of the Related Documents.

False Statements.  Any warranty, representation or statement made or furnished to Lender by Borrower or on Borrower’s behalf under this Agreement or the Related Documents is false or misleading in any material respect, either now or at the time made or furnished or becomes false or misleading at any time thereafter.

Insolvency.  The dissolution or termination of Borrower’s existence as a going business, the insolvency of Borrower, the appointment of a receiver for any part of Borrower’s property, any assignment for the benefit of creditors, any type of creditor workout, or the commencement of any proceeding under any bankruptcy or insolvency laws by or against Borrower.

Defective Collateralization.  This Agreement or any of the Related Documents ceases to be in full force and effect (including failure of any collateral document to create a valid and perfected security interest or lien) at any time and for any reason.

Creditor or Forfeiture Proceedings.  Commencement of foreclosure or forfeiture proceedings, whether by judicial proceeding, self-help, repossession or any other method, by any creditor of Borrower or by any governmental agency against any collateral securing the Loan. This includes a garnishment of any of Borrower’s accounts, including deposit accounts, with Lender. However, this Event of Default shall not apply if there is a good faith dispute by Borrower on to the validity or reasonableness of the claim which in the basis of the creditor or forfeiture proceeding and if Borrower gives Lender written notice of the creditor or forfeiture proceeding and deposits with Lender monies or a surety bond for the creditor or forfeiture proceeding. In an amount determined by Lender, in its sole discretion, as being an adequate reserve or bond for the dispute.

Events Affecting Guarantor.  Any of the preceding events occurs with respect to any Guarantor of any of the Indebtedness or any Guarantor dies or becomes incompetent, or revokes or disputes the validity of, or liability under, any Guaranty of the Indebtedness.

Change in Ownership.  Any change in ownership of twenty-five percent (25%) or more of the common stock of Borrower.

Adverse Change.  A material adverse change occurs in Borrower’s financial condition, or Lender believes the prospect of payment or performance of the Loan is impaired.

Insecurity.  Lender in good faith believes itself insecure.

EFFECT OF AN EVENT OF DEFAULT.  If any Event of Default shall occur, except where otherwise provided in this Agreement or the Related Documents, all commitments and obligations of Lender under this Agreement or the Related Documents or any other agreement immediately will terminate (including any obligation to make further Loan Advances or disbursements), and, at Lender’s option, all Indebtedness immediately will become due and payable, all without notice of any kind to Borrower, except that in the case of an Event of Default of the type described in the “Insolvency” subsection above, such acceleration shall be automatic and not optional. In addition, Lender shall have all the rights and remedies provided in the Related Documents or available at law, in equity, or otherwise. Except as may be prohibited by applicable law, all of Lender’s rights and remedies shall be cumulative and may be exercised singularly or concurrently. Election by Lender to pursue any remedy shall not exclude pursuit of any other remedy, and an election to make expenditures or to take action to perform an obligation of Borrower or of any Grantor shall not affect Lender’s right to declare a default and to exercise its rights and remedies.

MISCELLANEOUS PROVISIONS.  The following miscellaneous provisions are a part of this Agreement:

Amendments.  This Agreement, together with any Related Documents, constitutes the entire understanding and agreement of the parties as to the matters set forth in this Agreement.  No alteration of or amendment to this Agreement shall be effective unless given in writing and signed by the party or parties sought to be charged or bound by the alteration or amendment.

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Attorneys’ Fees; Expenses.  Borrower agrees to pay upon demand all of Lender’s costs and expenses, including Lender’s reasonable attorneys’ fees and Lender’s legal expenses, incurred in connection with the enforcement of this Agreement. Lender may hire or pay someone else to help enforce this Agreement, and Borrower shall pay the costs and expenses of such enforcement. Costs and expenses include Lender’s reasonable attorneys’ fees and legal expenses whether or not there is a lawsuit, including Lender’s reasonable attorneys’ fees and legal expenses for bankruptcy proceedings (including efforts to modify or vacate any automatic stay or injunction), appeals, and any anticipated post-judgment collection services. Borrower also shall pay all court costs and such additional fees as may be directed by the court.

Caption Headings.  Caption headings in this Agreement are for convenience purposes only and are not to be used to interpret or define the provisions of this Agreement.

Consent to Loan Participation.  Borrower agrees and consents to Lender’s sale or transfer, whether now or later, of one or more participation interests in the Loan to one or more purchasers, whether related or unrelated to Lender. Lender may provide, without any limitation whatsoever, to any one or more purchasers, or potential purchasers, any information or knowledge Lender may have about Borrower or about any other matter relating to the Loan, and Borrower hereby waives any rights to privacy Borrower may have with respect to such matters. Borrower additionally waives any and all notices of sale of participation interests, as well as all notices of any repurchase of such participation interests. Borrower also agrees that the purchasers of any such participation interests will be considered as the absolute owners of such interests in the Loan and will have all the rights granted under the participation agreement or agreements governing the sale of such participation interests. Borrower further waives all rights of offset or counterclaim that it may have now or later against Lender or against any purchaser of such a participation interest and unconditionally agrees that either Lender or such purchaser may enforce Borrower’s obligation under the Loan irrespective of the failure or insolvency of any holder of any interest in the Loan. Borrower further agrees that the purchaser of any such participation interests may enforce its interests irrespective of any personal claims or defenses that Borrower may have against Lender.

Governing Law.  This Agreement will be governed by federal law applicable to Lender and, to the extent not preempted by federal law, the laws of the State of Texas without regard to its conflicts of law provisions. This Agreement has been accepted by Lender in the State of Texas.

Choice of Venue.  If there is a lawsuit, and if the transaction evidenced by this Agreement occurred in Dallas County, Borrower agrees upon Lender’s request to submit to the jurisdiction of the courts of Dallas County, State of Texas.

No Waiver by Lender.  Lender shall not be deemed to have waived any rights under this Agreement unless such waiver is given in writing and signed by Lender. No delay or omission on the part of Lender in exercising any right shall operate as a waiver of such right or any other right. A waiver by Lender of a provision of this Agreement shall not prejudice or constitute a waiver of Lender’s right otherwise to demand strict compliance with that provision or any other provision of this Agreement. No prior waiver by Lender, nor any course of dealing between Lender and Borrower, or between Lender and any Grantor, shall constitute a waiver of any of Lender’s rights or of any of Borrower’s or any Grantor’s obligations as to any future transactions. Whenever the consent of Lender is required under this Agreement, the granting of such consent by Lender in any instance shall not constitute continuing consent to subsequent instances where such consent is required and in all cases such consent may be granted or withheld in the sole discretion of Lender.

Notices.  Any notice required to be given under this Agreement shall be given in writing, and shall be effective when actually delivered, when actually received by telefacsimile (unless otherwise required by law), when deposited with a nationally recognized overnight courier, or, if mailed, when deposited in the United States mail, as first class, certified or registered mail postage prepaid, directed to the addresses shown near the beginning of this Agreement. Any party may change its address for notices under this Agreement by giving formal written notice to the other parties, specifying that the purpose of the notice is to change the party’s address. For notice purposes, Borrower agrees to keep Lender informed at all times of Borrower’s current address. Unless otherwise provided or required by law, if there is more than one Borrower, any notice given by Lender to any Borrower is deemed to be notice given to all Borrowers.

Payment of Interest and Fees.  Notwithstanding any other provision of this Agreement or any provision of any Related Document. Borrower does not agree or intend to pay, and Lender does not agree or intend to charge, collect, take, reserve or receive (collectively referred to herein as “charge or collect”), any amount in the nature of interest or in the nature of a fee for the Loan which would in any way or event (including demand, prepayment, or acceleration) cause Lender to contract for, charge or collect more for the Loan than the maximum Lender would be permitted to charge or collect by any applicable federal or Texas state law. Any such excess interest or unauthorised fee will, instead of anything stated to the contrary, be applied first to reduce the unpaid principal balance of the Loan, and when the principal has bean paid in full, be refunded to Borrower.

Severability.  If a court of competent jurisdiction finds any provision of this Agreement to be illegal, invalid, or unenforceable as to any circumstance, that finding shall not make the offending provision illegal, invalid, or unenforceable as to any other circumstance. If feasible, the offending provision shall be considered modified so that it becomes legal, valid and enforceable. If the offending provision cannot be so modified, it shall be considered deleted from this Agreement. Unless otherwise required by law, the illegality, invalidity, or unenforceability of any provision of this Agreement shall not affect the legality, validity or enforceability of any other provision of this Agreement.

Subsidiaries and Affiliates of Borrower.  To the extent the context of any provisions of this Agreement makes it appropriate, including without limitation any representation, warranty or covenant, the word “Borrower” as used in this Agreement shall include all of Borrower’s subsidiaries and affiliates. Notwithstanding the foregoing however, under no circumstances shall this Agreement be construed to require Lender to make any Loan or other financial accommodation to any of Borrower’s subsidiaries or affiliates.

Successors and Assigns.  All covenants and agreements by or on behalf of Borrower contained in this Agreement or any Related Documents shall bind Borrower’s successors and assigns and shall inure to the benefit of Lender and its successors and assigns. Borrower shall not, however, have the right to assign Borrower’s rights under this Agreement or any interest therein, without the prior written consent of Lender.

Survival of Representations and Warranties.  Borrower understands and agrees that in extending Loan Advances, Lender is relying on all representations, warranties, and covenants made by Borrower in this Agreement or in any certificate or other instrument delivered by Borrower to Lender under this Agreement or the Related Documents. Borrower further agrees that regardless of any investigation made by Lender, all such representations, warranties and covenants will survive the extension of Loan Advances and delivery to Lender of the Related Documents, shall be continuing in nature, shall be deemed made and redated by Borrower at the time each Loan Advance is made, and shall remain in full force and effect until such time as Borrower’s Indebtedness shall be paid in full, or until this Agreement shall be terminated in the manner provided above, whichever is the last to occur.

Time is of the Essence.  Time is of the essence in the performance of this Agreement.

DEFINITIONS.  The following capitalized words and terms shall have the following meanings when used in this Agreement. Unless specifically stated to the contrary, all references to dollar amounts shall mean amounts in lawful money of the United States of America. Words and terms used in the singular shall include the plural, and the plural shall include the singular, as the context may require. Words and terms not otherwise defined in this Agreement shall have the meanings attributed to such terms in the Uniform Commercial Code. Accounting words and terms not otherwise defined in this Agreement shall have the meanings assigned to them in accordance with generally accepted accounting principles as in effect on the date of this Agreement:

Advance.  The word “Advance” means a disbursement of Loan funds made, or to be made, to Borrower or on Borrower’s behalf on a line of credit or multiple advance basis under the terms and conditions of this Agreement.

Agreement.  The word “Agreement” means this Business Loan Agreement, as this Business Loan Agreement may be amended or modified from time to time, together with all exhibits and schedules attached to this Business Loan Agreement from time to time.

Borrower.  The word “Borrower” means TGC Industries, Inc. and includes all co-signers and co-makers signing the Note.

Collateral.  The word “Collateral” means all property and assets granted as collateral security for a Loan, whether real or personal property, whether granted directly or indirectly, whether granted now or in the future, and whether granted in the form of a security interest, mortgage, collateral mortgage, deed of trust, assignment, pledge, crop pledge, chattel mortgage, collateral chattel mortgage, chattel trust, factor’s lien, equipment trust, conditional sale, trust receipt, lien, charge, lien or title retention contract, lease or consignment intended as a security device, or any other security or lien interest whatsoever, whether created by law, contract, or otherwise.

Environmental Laws.  The words “Environmental Laws” mean any and all state, federal and local statutes, regulations and ordinances relating to the protection of human health or the environment, including without limitation the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, 42 U.S.C. Section 9601, et seq. (“CERCLA”) the Superfund Amendments and Reauthorization Act of 1986, Pub. L. No. 99-499 (“SARA”), the Hazardous Materials Transportation Act, 49 U.S.C. Section 1801, et seq., the Resource Conservation and Recovery Act, 42 U.S.C. Section 8801, et seq., or other applicable state or federal laws, rules, or regulations adopted pursuant thereto.

Event of Default. The words “Event of Default” mean any of the events of default set forth in this Agreement in the default section of this Agreement.

4

GAAP.  The word “GAAP” means generally accepted accounting principles.

Grantor.  The word “Grantor” means each and all of the persons or entities granting a Security Interest in any Collateral for the Loan, including without limitation all Borrowers granting such a Security Interest.

Guarantor.  The word “Guarantor” means any guarantor, surety, or accommodation party of any or all of the Loan.

Guaranty.  The word “Guaranty” means the guaranty from Guarantor to Lender, including without limitation a guaranty of all or part of the Note.

Hazardous Substances.  The words “Hazardous Substances” mean materials that, because of their quantity, concentration or physical, chemical or infectious characteristics, may cause or pose a present or potential hazard to human health or the environment when improperly used, treated, stored, disposed of, generated, manufactured, transported or otherwise handled. The words “Hazardous Substances” are used in their very broadest sense and include without limitation any and all hazardous or toxic substances, materials or waste as defined by or listed under the Environmental Laws. The term “Hazardous Substances” also includes, without limitation, petroleum and petroleum by-products or any fraction thereof and asbestos.

Indebtedness.  The word “Indebtedness” means the indebtedness evidenced by the Note or Related Documents, including all principal and interest together with all other indebtedness and costs and expenses for which Borrower is responsible under this Agreement or under any of the Related Documents.

Lender.  The word “Lender” means Sovereign Bank, N.A., its successors and assigns.

Loan.  The word “Loan” means any and all loans and financial accommodations from Lender to Borrower whether now or hereafter existing, and however evidenced, including without limitation those loans and financial accommodations described herein or described on any exhibit or schedule attached to this Agreement from time to time.

Note.  The word “Note” means the Note executed by TGC Industries, Inc. in the principal amount of $3,500,000.00 dated September 16, 2005, together with all renewals of, extensions of, modifications of, refinancing of, consolidations of, and substitutions for the note or credit agreement.

Permitted Liens.  The words “Permitted Liens” mean (1) liens and security interests securing indebtedness owed by Borrower to Lender; (2) liens for taxes, assessments, or similar charges either not yet due or being contested in good faith; (3) liens of materialmen, mechanics, warehousemen, or carriers, or other like liens arising in the ordinary course of business and securing obligations which are not yet delinquent; (4) purchase money liens or purchase money security interests upon or in any property acquired or held by Borrower in the ordinary course of business to secure indebtedness outstanding on the date of this Agreement or permitted to be incurred under the paragraph of this Agreement titled “Indebtedness and Liens”; (5) liens and security interests which, as of the date of this Agreement, have been disclosed to and approved by the Lender in writing; and (6) those liens and security interests which in the aggregate constitute an immaterial and insignificant monetary amount with respect to the net value of Borrower’s assets.

Related Documents.  The words “Related Documents” mean all promissory notes, credit agreements, loan agreements, environmental agreements, guaranties, security agreements, mortgages, deeds of trust, security deeds, collateral mortgages, and all other instruments, agreements end documents, whether now or hereafter existing, executed in connection with the Loan.

Security Agreement.  The words “Security Agreement” mean and include without limitation any agreements, promises, covenants, arrangements, understandings or other agreements, whether created by law, contract, or otherwise, evidencing, governing, representing, or creating a Security Interest.

Security Interest.  The words “Security Interest” mean, without limitation, any and all types of collateral security, present and future, whether in the form of a lien, charge, encumbrance, mortgage, deed of trust, security deed, assignment, pledge, crop pledge, chattel mortgage, collateral chattel mortgage, chattel trust factor’s lien, equipment trust, conditional sale, trust receipt, lien or title retention contract, lease or consignment intended as a security device, or any other security or lien interest whatsoever whether created by law, contract, or otherwise.

BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS BUSINESS LOAN AGREEMENT AND BORROWER AGREES TO ITS TERMS. THIS BUSINESS LOAN AGREEMENT IS DATED SEPTMBER 16, 2005.

BORROWER:

LENDER:

SOVEREIGN BANK, N.A.

5

Exhibit 10.3

*LOAN5404*

PROMISSORY NOTE

9–2–05

(Date)

FOR VALUE RECEIVED, TGC Industries, Inc. a corporation located at the address stated below (“Maker”) promises, jointly and severally if more than one, to pay to the order of General Electric Capital Corporation or any subsequent holder hereof (each, a “Payee”) at its office located at 16479 Dallas Parkway # 300, Addison, TX 75001-2512 or at such other place as Payee or the holder hereof may designate, the principal sum of Two Hundred Eighty Six Thousand Two Hundred Thirty Five Dollars ($286,235.00), with interest on the unpaid principal balance, from the date hereof through and including the dates of payment, at a fixed per annum simple interest rate of Seven and 25/100 percent (7.25%).

Subject to the other provisions hereof, the principal on this Note is payable in lawful money of the United States in Thirty Six (36) consecutive monthly installments as follows:

each (“Periodic Installment”) and a final installment which shall be in the amount of the total outstanding unpaid principal.  The first Periodic Installment shall be due and payable on October 2, 2005 and the following Periodic Installments and the final installment shall be due and payable on the same day of each succeeding period (each, a “Payment Date”).  In addition to the payments of principal provided above, accrued interest shall be payable on the Payment Date.

All payments shall be applied first to interest and then to principal.  Each payment may, at the option of the Payee, be calculated and applied on an assumption that such payment would be made on its due date.  The acceptance by Payee of any payment which is less than payment in full of all amounts due and owing as such time shall not constitute a waiver of Payee’s right to receive payment in full at such time or at any prior or subsequent time. Interest shall be calculated on the basis of a 365 day year (366 day leap year).

The Maker hereby expressly authorizes the Payee to insert the date value is actually given in the blank space on the face hereof and on all related documents pertaining hereto.

This Note may be secured by a security agreement, chattel mortgage, pledge agreement or like instrument (each of which is hereinafter called a “Security Agreement”).

Time is of the essence hereof.  If any installment or any other sum due under this Note or any Security Agreement is not received within ten (10) days after its due date, the Maker agrees to pay, in addition to the amount of each such installment or other sum, a late payment charge of five percent (5%) of the amount of said installment or other sum, but not exceeding any lawful maximum.  If (i) Maker fails to make payment of any amount due hereunder within ten (10) days after the same becomes due and payable; or (ii) Maker is in default under, or fails to perform under any term or condition contained in any Security Agreement, then the entire principal sum remaining unpaid, together with all accrued interest thereon and any other sum payable under this Note or any Security Agreement, at the election of Payee, shall immediately become due and payable, with interest thereon at the lesser of eighteen percent (18%) per annum or the highest rate not prohibited by applicable law from the date of such accelerated maturity until paid (both before and after any judgment).

The Maker may prepay in full, but not in part, its entire indebtedness hereunder upon payment of the entire indebtedness plus an additional sum as a premium equal to the following percentages of the original principal balance for the indicated period:

Prior to the first annual anniversary date of this Note: Three percent (3%)

Thereafter and prior to the second annual anniversary date of this Note: One percent (1%)

Thereafter and prior to the third annual anniversary date of this Note: One percent (1%)

 and zero percent (0%) thereafter, plus all other sums due hereunder or under any Security Agreement.

It is the intention of the parties hereto to comply with the applicable usury laws; accordingly, it is agreed that, notwithstanding any provision to the contrary in this Note or any Security Agreement, in no event shall this Note or any Security Agreement require the payment or permit the collection of interest in excess of the maximum amount permitted by applicable law.  If any such excess interest is contracted for, charged or received under this Note or any Security Agreement, or if all of the principal balance shall be prepaid, so that under any of such circumstances the amount of interest contracted for, charged or received under this Note or any Security Agreement on the principal balance shall exceed the maximum amount of interest permitted by applicable law, then in such event (a) the provisions of this paragraph shall govern and control, (b) neither Maker nor any other person or entity now or hereafter liable for the payment hereof shall be obligated to pay the amount of such interest to the extent that it is in excess of the maximum amount of interest permitted by applicable law, (c) any such excess which may have been collected shall be either applied as a credit against the then unpaid principal balance or refunded to Maker, at the option of the Payee, and (d) the effective rate of interest shall be automatically reduced to the maximum lawful contract rate allowed under applicable law as now or hereafter construed by the courts having jurisdiction thereof.  It is further agreed that without limitation of the foregoing, all calculations of the rate of interest contracted for, charged or received under this Note or any Security Agreement which are made for the purpose of determining whether such rate exceeds the maximum lawful contract rate, shall be made, to the extend permitted by applicable law, by amortizing, prorating, allocating and spreading in equal parts during the period of the full stated term of the indebtedness evidenced hereby, all interest at any time contracted for, charged or received from Maker or otherwise by Payee in connection with such indebtedness; provided, however, that if any applicable state law is amended or the law of the United States of America preempts any applicable state law, so that it becomes lawful for the Payee to receive a greater interest per annum rate than is presently allowed, the Maker agrees that, on the effective date of such amendment or preemption, as the case may be, the lawful maximum hereunder shall be increased to the maximum interest per annum rate allowed by the amended state law or the law of the United States of America.

The Maker and all sureties, endorsers, guarantors or any others (each such person, other than the Maker, an “Obligor”) who may at any time become liable for the payment hereof jointly and severally consent hereby to any and all extensions of time, renewals, waivers or modifications of, and all substitutions or releases of, security or of any party primarily or secondarily liable on this Note or any Security Agreement or any term and provision of either, which may be made, granted or consented to by Payee, and agree that suit may be brought and maintained against any one or more of them, at the election of Payee without joinder of any other as a party thereto, and that Payee shall not be required first to foreclose, proceed against, or exhaust any security hereof in order to enforce payment of

this Note.  The Maker and each Obligor hereby waives presentment, demand for payment, notice of nonpayment, protest, notice of protest, notice of dishonor, and all other notices in connection herewith, as well as filing of suit (if permitted by law) and diligence in collecting this Note or enforcing any of the security hereof, and agrees to pay (if permitted by law) all expenses incurred in collection, including Payee’s actual attorneys’ fees.  Maker and each Obligor agrees that fees not in excess of twenty percent (20%) of the amount then due shall be deemed reasonable.

THE MAKER HEREBY UNCONDITIONALLY WAIVES ITS RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF, DIRECTLY OR INDIRECTLY,  THIS NOTE, ANY OF THE RELATED DOCUMENTS, ANY DEALINGS BETWEEN MAKER AND PAYEE RELATING TO THE SUBJECT MATTER OF THIS TRANSACTION OR ANY RELATED TRANSACTIONS, AND/OR THE RELATIONSHIP THAT IS BEING ESTABLISHED BETWEEN MAKER AND PAYEE.  THE SCOPE OF THIS WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES THAT MAY BE FILED IN ANY COURT (INCLUDING, WITHOUT LIMITATION, CONTRACT CLAIMS, TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW AND STATUTORY CLAIMS.) THIS WAIVER IS IRREVOCABLE MEANING THAT IT MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING, AND THE WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS NOTE, ANY RELATED DOCUMENTS, OR TO ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS TRANSACTION OR ANY RELATED TRANSACTION.  IN THE EVENT OF LITIGATION, THIS NOTE MAY BE FILED AS A WRITTEN CONSENT TO A TRIAL BY THE COURT.

This Note and other Debt Documents constitute the entire agreement of the Maker and Payee with respect to the subject matter hereof and supercedes all prior understandings, agreements and representations, express or implied.

No variation or modification of this Note, or any waiver of any of its provisions or conditions, shall be valid unless in writing and signed by an authorized representative of Maker and Payee.  Any such waiver, consent, modification or change shall be effective only in the specific instance and for the specific purpose given.

Any provision in this Note or any of the other Debt Documents which is in conflict with any statute, law or applicable rule shall be deemed omitted, modified or altered to conform thereto.

Exhibit 10.4

*MULT1000*

AMENDMENT

THIS AMENDMENT is made as of the 09th day of September, 2005, between General Electric Capital Corporation, together with its successors and assigns, if any, and TGC Industries, Inc. in connection with Schedule Number 003 of that certain Master Security Agreement, dated or dated as of October 22, 2004 (“Agreement”). The terms of this Amendment are hereby incorporated into the Agreement as though fully set forth therein. The Agreement is hereby amended as follows:

The 35 Periodic Installment Amount on the Promissory Note is changed from $8,870.86 to $7,950.97.

TERMS USED, BUT NOT OTHERWISE DEFINED HEREIN SHALL HAVE THE MEANINGS GIVEN TO THEM IN THE AGREEMENT. EXCEPT AS EXPRESSLY AMENDED HEREBY, THE AGREEMENT SHALL REMAIN IN FULL FORCE AND EFFECT.

IN WITNESS WHEREOF, the parties hereto have executed this Amendment by signature of their respective authorized representative set forth below.

Exhibit 10.5

PROMISSORY NOTE

9–12–05

(Date)

FOR VALUE RECEIVED, TGC Industries, Inc. a corporation located at the address stated below (“Maker”) promises, jointly and severally if more than one, to pay to the order of General Electric Capital Corporation or any subsequent holder hereof (each, a “Payee”) at its office located at 16479 Dallas Parkway #300, Addison, TX 75001-2512 or at such other place as Payee or the holder hereof may designate, the principal sum of Two hundred eighty six thousand two hundred thirty five and 00/100 Dollars ($286,235.00), with interest on the unpaid principal balance, from the date hereof through and including the dates of payment, at a fixed per annum simple interest rate of Seven and 25/100 percent (7.25%).

Subject to the other provisions hereof, the principal on this Note is payable in lawful money of the United States in Thirty six (36) consecutive monthly installments as follows:

each (“Periodic Installment”) and a final installment which shall be in the amount of the total outstanding unpaid principal.  The first Periodic Installment shall be due and payable on November 2, 2005 and the following Periodic Installments and the final installment shall be due and payable on the same day of each succeeding period (each, a “Payment Date”).  In addition to the payments of principal provided above, accrued interest shall be payable on the Payment Date.

All payments shall be applied first to interest and then to principal.  Each payment may, at the option of the Payee, be calculated and applied on an assumption that such payment would be made on its due date.  The acceptance by Payee of any payment which is less than payment in full of all amounts due and owing at such time shall not constitute a waiver of Payee’s right to receive payment in full at such time or at any prior or subsequent time. Interest shall be calculated on the basis of a 365 day year (366 day leap year).

The Maker hereby expressly authorizes the Payee to insert the date value is actually given in the blank space on the face hereof and on all related documents pertaining hereto.

This Note may be secured by a security agreement, chattel mortgage, pledge agreement or like instrument (each of which is hereinafter called a “Security Agreement”).

Time is of the essence hereto.  If any installment or any other sum due under this Note or any Security Agreement is not received within ten (10) days after its due date, the Maker agrees to pay, in addition to the amount of each such installment or other sum, a late payment charge of five percent (5%) of the amount of said installment or other sum, but not exceeding any lawful maximum.  If (i) Maker fails to make payment of any amount due hereunder within ten (10) days after the same becomes due and payable; or (ii) Maker is in default under, or fails to perform under any term or condition contained in any Security Agreement, then the entire principal sum remaining unpaid, together with all accrued interest thereon and any other sum payable under this Note or any Security Agreement, at the election of Payee, shall immediately become due and payable, with interest thereon at the lesser of eighteen percent (18%) per annum or the highest rate not prohibited by applicable law from the date of such accelerated maturity until paid (both before and after any judgment).

The Maker may prepay in full, but not in part, its entire indebtedness hereunder upon payment of the entire indebtedness plus an additional sum as a premium equal to the following percentages of the original principal balance for the indicated period:

Prior to the first annual anniversary date of this Note: Three percent (3%)

Thereafter and prior to the second annual anniversary date of this Note: One percent (1%)

Thereafter and prior to the third annual anniversary date of this Note: One percent (1%)

 and zero percent (0%) thereafter, plus all other sums due hereunder or under any Security Agreement.

It is the intention of the parties herein to comply with the applicable usury laws; accordingly, it is agreed that, notwithstanding any provision to the contrary in this Note or any Security Agreement, in no event shall this Note or any Security Agreement require the payment or permit the collection of interest in excess of the maximum amount permitted by applicable law.  If any such excess interest is contracted for, charged or received under this Note or any Security Agreement, or if all of the principal balance shall be prepaid, so that under any of such circumstances the amount of interest contracted for, charged or received under this Note or any Security Agreement on the principal balance shall exceed the maximum amount of interest permitted by applicable law, then in such event (a) the provisions of this paragraph shall govern and control, (b) neither Maker nor any other person or entity now or hereafter liable for the payment hereof shall be obligated to pay the amount of such interest to the extent that it is in excess of the maximum amount of interest permitted by applicable law, (c) any such excess which may have been collected shall be either applied as a credit against the then unpaid principal balance or refunded to Maker, at the option of the Payee, and (d) the effective rate of interest shall be automatically reduced to the maximum lawful contract rate allowed under applicable law as now or hereafter construed by the courts having jurisdiction thereof.  It is further agreed that without limitation of the foregoing, all calculations of the rate of interest contracted for, charged or received under this Note or any Security Agreement which are made for the purpose of determining whether such rate exceeds the maximum lawful contract rate, shall be made, to the extent permitted by applicable law, by amortizing, prorating, allocating and spreading in equal parts during the period of the full stated term of the indebtedness evidenced hereby, all interest of any time contracted for, charged or received from Maker or otherwise by Payee in connection with such indebtedness; provided, however, that if any applicable state law is amended or the law of the United States of America preempts any applicable state law, so that it becomes lawful for the Payee to receive a greater interest per annum rate than is presently allowed, the Maker agrees that, on the effective date of such amendment or preemption, as the case may be, the lawful maximum hereunder shall be increased to the maximum interest per annum rate allowed by the amended state law or the law of the United States of America.

The Maker and all sureties, endorsers, guarantors or any others (each such person, other than the Maker, an “Obligor”) who may at any time become liable for the payment hereof jointly and severally consent hereby to any and all extensions of time, renewals, waivers or modifications of, and all substitutions or releases of, security or of any party primarily or secondarily liable on this Note or any Security Agreement or any term and provision of either, which may be made, granted or consented to by Payee, and agree that suit may be brought and maintained against any one or more of them, at the election of Payee without joinder of any other as a party thereto, and that Payee shall not be required first in foreclose, proceed against, or exhaust any security hereof in order to enforce payment of

this Note.  The Maker and each Obligor hereby waives presentment, demand for payment, notice of nonpayment, protest, notice of protest, notice of dishonor, and all other notices in connection herewith, as well as filing of suit (if permitted by law) and diligence in collecting this Note or enforcing any of the security hereof, and agrees to pay (if permitted by law) all expenses incurred in collection, including Payee’s actual attorneys’ fees.  Maker and each Obligor agrees that fees not in excess of twenty percent (20%) of the amount then due shall be deemed reasonable.

THE MAKER HEREBY UNCONDITIONALLY WAIVES ITS RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF, DIRECTLY OR INDIRECTLY. THIS NOTE, ANY OF THE RELATED DOCUMENTS, ANY DEALINGS BETWEEN MAKER AND PAYEE RELATING TO THE SUBJECT MATTER OF THIS TRANSACTION OR ANY RELATED TRANSACTIONS, AND/OR THE RELATIONSHIP THAT IS BEING ESTABLISHED BETWEEN MAKER AND PAYEE.  THE SCOPE OF THIS WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES THAT MAY BE FILED IN ANY COURT (INCLUDING, WITHOUT LIMITATION, CONTRACT CLAIMS, TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW AND STATUTORY CLAIMS.) THIS WAIVER IS IRREVOCABLE MEANING THAT IT MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING, AND THE WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS NOTE, ANY RELATED DOCUMENTS, OR TO ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS TRANSACTION OR ANY RELATED TRANSACTION.  IN THE EVENT OF LITIGATION, THIS NOTE MAY BE FILED AS A WRITTEN CONSENT TO A TRIAL BY THE COURT.

This Note and other Debt Documents constitute the entire agreement of the Maker and Payee with respect to the subject matter hereof and supercedes all prior understandings, agreements and representations, express or implied.

No variation or modification of this Note, or any waiver of any of its provisions or conditions, shall be valid unless in writing and signed by an authorized representative of Maker and Payee.  Any such waiver, consent, modification or change shall be effective only in the specific instance and for the specific purpose given.

Any provision in this Note or any of the other Debt Documents which is in conflict with any statute, law or applicable rule shall be deemed omitted, modified or altered to conform thereto.

Exhibit 10.6

*MULT1000*

AMENDMENT

THIS AMENDMENT is made as of the 09th day of September, 2005, between General Electric Capital Corporation, together with its successors and assigns, if any, and TGC Industries, Inc. in connection with Schedule Number 004 of that certain Master Security Agreement, dated or dated as of October 22, 2004 (“Agreement”). The terms of this Amendment are hereby incorporated into the Agreement as though fully set forth therein. The Agreement is hereby amended as follows:

The 35 Periodic Installment Amount on the Promissory Note is changed from $8,906.59 to $7,950.97.

TERMS USED, BUT NOT OTHERWISE DEFINED HEREIN SHALL HAVE THE MEANINGS GIVEN TO THEM IN THE AGREEMENT. EXCEPT AS EXPRESSLY AMENDED HEREBY, THE AGREEMENT SHALL REMAIN IN FULL FORCE AND EFFECT.

IN WITNESS WHEREOF, the parties hereto have executed this Amendment by signature of their respective authorized representative set forth below.

Exhibit 10.7

*MULT1000*

AMENDMENT

THIS AMENDMENT is made as of the twelfth day of September, 2005, between General Electric Capital Corporation, together with its successors and assigns, if any, and TGC Industries, Inc. in connection with Schedule Number 004 of that certain Master Security Agreement, dated or dated as of October 22, 2004 (“Agreement”). The terms of this Amendment are hereby incorporated into the Agreement as though fully set forth therein. The Agreement is hereby amended as follows:

The first Periodic Installment on the Promissory Note is changed from November 2, 2005 to October 12, 2005.

TERMS USED, BUT NOT OTHERWISE DEFINED HEREIN SHALL HAVE THE MEANINGS GIVEN TO THEM IN THE AGREEMENT. EXCEPT AS EXPRESSLY AMENDED HEREBY, THE AGREEMENT SHALL REMAIN IN FULL FORCE AND EFFECT.

IN WITNESS WHEREOF, the parties hereto have executed this Amendment by signature of their respective authorized representative set forth below.