FORAMINIFERA OF THE EARLY MIOCENE UPPER PART OF THE ANAHUAC FORMATIONFROM A WELL IN VERMILION PARISH, LOUISIANA, USA

The Anahuac Formation in the United States Gulf of Mexico coastal plai n has been previously placed in the middle to late Oligocene based on larger benthic foraminifera. In the subsurface of Vermilion Parish, Lo uisiana, the upper part of the Anahuac Formation of the #1 J.W. Steen well is assigned an early Miocene age based on planktic foraminifera. More precisely, both the Globigerinoides primordius Interval Subzone ( M1a) and Globorotalia kugleri/Globoquadrina dehiscens Concurrent Range Subzone (M1b) of the Globorotalia kugleri Total Range Zone (M1) and t he Catapsydrax dissimilis Partial Range Zone (M2) are represented. The benthic foraminiferal Heterostegina and Discorbis zones are present a nd the Oligocene-Miocene boundary probably occurs within the Heteroste gina Zone but beneath the studied interval, Paleoenvironmental reconst ructions based on benthic and planktic foraminifera indicate that the Anahuac Formation in the #1 J.W, Steen well was deposited at outer ner itic depths (100-250 m) during the earliest Miocene. Deposition shallo wed to middle neritic depths (50-150 m) within Zone Mlb, The uppermost studied section within the Catapsydrax dissimilis Zone (M2) was depos ited in slightly shallower (20-100 m), but still middle neritic condit ions. Three candidate maximum flooding surfaces are identified. Sevent y three planktic and benthic taxa are illustrated via scanning electro n micrographs.