Abstract: Forced Regressive and Lowstand Deposit, and Multiple Sequence Boundary Formation Based on High-Resolution Seismic and Borehole Data, Northeast Gulf of Mexico

KOLLA, V., P.BIONDI, B. LONG, R. FILLON

We have identified six major and many minor sequence boundaries, and maximum flooding surfaces associated with oxygen isotope stages 13 to 1 ( since 500 KY BP) within the late Pleistocene shelf-margin Lagniappe delta complex in the NE Gulf of Mexico. We discuss here in detail a portion of this delta complex that prograded seaward for several tens of miles during the last, fourth-order glacial-interglacial cycle since stage 5.The delta complex consists of many lobes that were deposited during several, fifth-order, sealevel drops within the falling and maximum lowstand-early rise stages of sealevel of the cycle. Each significant fifth-order sealevel drop caused an unconformity updip with incised valleys that became conformity downdip on which a delta lobe was deposited. Each of these prograding lobes onlaps and pinches updip below or close to the offlap break of a previous lobe. During the maximum lowstand, deep erosion with incised valley occurred on the top of the prograding wedges of the falling stage. This incised valley became filled with channel deposits, bay-head deltas etc. during the early and late rise of sealevel. Downdip, the base of the incised valley and the unconformity became a conformity on which the last part of the delta complex was deposited. The base of the incised valley and the unconformity-conformity surface form the main and final sequence boundary. Thus, during the last fourth-order cycle, several fifth-order and one fourth-order sequence boundaries formed. The recognition of these different-order sequence boundaries has impact on reservoir architecture in subsurface exploration.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria