Foraminiferal Biostratigraphy and Paleoenvironmental Analysis of the Anahuac Formation (Late Oligocene-Early Miocene) from a Deep Well in Vermilion Parish, Louisiana

• Main Author: Orndorff, Audrey Lynne
• Format: Text
• Language: unknown
• Published: ODU Digital Commons 1988
• Subjects: Stratigraphic; Foraminifera; Vermilion Parish (La.); Geology; Paleontology; Stratigraphy; Steen; Planktonic foraminifera
• Online Access: https://digitalcommons.odu.edu/oeas_etds/270; https://doi.org/10.25777/bb3w-pj22; https://digitalcommons.odu.edu/context/oeas_etds/article/1270/viewcontent/Orndorff_ForaminiferalBiostratigraphyAnd_1988_Redacted.pdf

In the subsurface of Vermilion Parish, Louisiana, sediments from the Anahuac Formation in the #1 J. W. Steen well are assigned an Upper Oligocene-Lower Miocene age based on planktonic foraminifera. Previous age determinations for sediments from this formation elsewhere range from Middle to Late Oligocene based on the presence of larger foraminifera contained within these strata. Planktonic foraminifera in Anahuac formation sediments in the #1 J. W. Steen well permit their assignment to an established worldwide zonation scheme and indicate that the age ranges from the Globorotalia kugleri Interval Zone (Upper Oligocene) to the Catapsydrax dissimilis Zone (Lower Miocene). Benthic foraminiferal assemblages indicate the presence of the Heterostegina and Discorbis Zones in the Anahuac Formation with the Oligocene-Miocene boundary level occuring within the Discorbis Zone. Paleoenvironmental reconstructions based upon benthic foraminifera indicate that the sediments of the Anahuac Formation within the well were deposited in marine waters ranging from 100 to 200 meters depth and decreased up section to depths of 20 to 100 meters. Possible explanations for this shallowing upwards sequence include, but are not limited to, eustatic sea level fall, increased regional sediment supply, or local variation in sedimentation and subsidence rates