Interplay of Fold Growth and Faulting, Walker Ridge Structures, Deep-Water Gulf of Mexico
Recent high-resolution seismic imaging of the Chinook and Cascade folds, southwest of the Green Knoll diapir and basinward of the Sigsbee Escarpment in Walker Ridge, allow detailed reconstruction of the relationship between fold development and crestal faulting in the deep-water Gulf of Mexico. Using 3-D seismic and biostratigraphic data, we have found the following. (1) Early short wavelength (~ 2300 m), small amplitude (~ 540 m) folds restricted to the Campeche (Cretaceous) and Challenger (Upper Jurassic) stratigraphic sequences that presumably took place no later than the Late Jurassic. (2) Early Cretaceous growth of the Chinook and Cascade masks these earlier folds. (3) A significant portion of the amplification of these larger folds was achieved by bed thickening.
4 Fold amplification and fault slip are closely linked.
Although the dominant stage of a long wavelength, large amplitude fold growth started around Early Cretaceous, episodes of increased amplification occurred at estimated rates of 240, 360 and 750 m/Ma within the Upper Mexican Ridges stratigraphic sequence at 14.8 Ma, 12.8 Ma and 5.54 Ma. Synchronous with folding was the development of high displacement (~1500 m) normal faults, perpendicular to the fold trend. Relatively smaller displacement faults occur afterwards in a radial pattern around the anticlines. The highest rates of fault slip are estimated at 85, 130 and 90 m/Ma within the Middle Mexican Ridges (21.9 Ma) and Upper Mexican Ridges (14.8 Ma, 5.54 Ma) stratigraphic sequences, respectively. The overall development of the Chinook and Cascade folds was continuous, punctuated by episodes of increased amplification.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009