Neogene stratigraphy and geologic history, Apalachicola Embayment, Florida

• Other Authors: Schmidt, Walter.
• Format: Others
• Language: English
• Subjects: Geology
• Online Access: http://purl.flvc.org/fsu/lib/digcoll/etd/3086792

Neogene units lie near the surface in the Florida Panhandle in a narrow band extending from twenty miles west of Tallahassee, Leon County, northwest to Oak Grove in north-central Okaloosa County. Downdip towards the Gulf of Mexico these units thicken and change in lithologic character. These contemporaneous lithologic packages, although subsurface, can be defined and mapped throughout the region using stratigraphic core tests, water well cuttings, and geophysical well logs. The Bruce Creek Limestone and Intracoastal Formation are two, predominantly subsurface, units mapped from this area. The Chipola and Jackson Bluff formations are younger downdip in the subsurface than where they are exposed updip. Pleistocene quartz sands and gravels, and massive silty clay beds are mapped in Gulf, Franklin, and southern Liberty counties. These units were deposited in brackish and fluvial environments as the Apalachicola delta system advanced south. === The Neogene and Pleistocene sequence of sediments thickens and dips around a gently plunging axis that decends gulfward through central Gulf County. This thickened sequence of sediments is called the Apalachicola Embayment. === The Apalachicola Embayment resulted from a graben in Triassic to Early Jurassic times. This graben slowly filled with sediments until it ceased to exist as an embayment at the end of the Early Cretaceous. From Early Cretaceous through Early Eocene a "low" or depression occurred eastward of the Jurassic axis. During Early through Late Eocene the axis of the "low" shifted northwest until, during the Oligocene, it was repositioned once again over the Jurassic axis. This Late Cretaceous-Tertiary feature is considered to be due to slow deposition in a current swept strait similiar to the present Florida straits. During the Early Miocene-Middle Miocene the strait apparently began to fill in as carbonates from the Florida platform on the southeast infringed into the shallow current, and clastics from the northwest spilled over onto the shallow shelf. During the Late Miocene to Pleistocene the strait completely filled in and the prograding coastal plain migrated over the area. The feature is not extant now because the Apalachicola River and its delta have prograded over the feature. === Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0674. === Major Professor: Ramil C. Wright. === Thesis (Ph.D.)--The Florida State University, 1983.