Abstract: South Texas Ingleside Barriers: Sediment Cycles and Vertebrate Fauna. Late Pleistocene Coastal Stratigraphy Revised

Ervin G. Otvos, Wade E. Howat

Three sedimentary cycles that include alluvial, inshore, and nearshore units were identified in the top Beaumont sequence. Unconformities, marked by oxidized and caliche-rich zones, lithologic, and biotope changes separate them. The youngest pre-barrier unit uncomformably underlies and continues landward of Ingleside barrier sectors. Thin muddy sands of the Encinal and Ingleside sectors rest unconformably on the pre-barrier surface. This surface is not a lagoon plain. The Aransas and Seadrift barrier sectors overlie a thicker transgressive sequence. In contrast with south Live Oak, barrier-correlative, multistage Sangamonian Interglacial alluvium and the prograding barrier sequence filled a broad, shallow embayment. Contrary to the suggested Wisconsinan age, amino acid ra emization data confirm the Sangamonian age of these mainland, not "island," barriers that are correlatives of the Gulfport barrier trend on the NE Gulf.

Core data refuted two theories of barrier thickness. One suggested a thick and "multistory" character; the other, extreme thinness. Alleged fossil indicators of sea- (olagoon-o) levels do not support tectonic upwarp. Wisconsinan deflation processes reduced or eliminated the strandplain morphology. Few groups of large dunes and thousands of pimple mounds of eolian origin cover the barriers. Ponds occupied blowout hollows in three barrier sectors. Sands with bones of radiometrically updatable Rancholabrean vertebrates filled them during a warmer, wetter post-Sangamonian lowstand phase.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas