X0306 4 2021-12-01 0000866609 ION GEOPHYSICAL CORP IO 0001799422 LAMBERT DALE J 2105 CITYWEST BLVD., SUITE 100 HOUSTON TX 77042 1 EVP, E&P Technology & Services Common Stock 2021-12-01 4 F 0 5965 1.74 D 96351 D These shares were not sold, but were withheld by ION Geophysical Corporation upon the vesting of restricted stock shares to satisfy tax withholding obligations. /s/ Rebecca F. Sacco, attorney-in-fact 2021-12-03