ABSTRACT: Basal Yegua Shelf Margin Failures Along the Texas Gulf Coast

SWENSON, DAVID R.

Along the middle and upper Texas coast the updip Yegua has abundant sand in the Anomalina umbonatus interval yet the downdip expanded Yegua is largely an Eponides yeguaensis sand play. The expanded Anomalina umbonatus section is spottily developed along the trend with a Jackson County depocenter being the only one where the entire Anomalina umbonatus sand section is present. An erosionally oversteepened shelf margin and upper slope of basal Yegua age is present updip of all studied downdip Yegua sections except the Jackson County depocenter and accounts for the dearth of expanded Anomalina umbonatus sands. This steeper slope was eroded into the Cook Mountain shelf resulting in bypassing of lowermost Yegua sands beyond the later developed expanded Yegua trend. These sands were likely deposited in slope mini-basins and basin floor fans during sea level fall and lowstand. Slightly younger Anomalina umbonatus sands (middip Yegua play) were deposited just downdip of the shelf margin escarpment during sea level rise.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana