A Study of the Lithological and Petrographical Changes Across the Eocene-Oligocene Transition of the Ocala and Suwannee Formations in Northern Florida and Southern Georiga

• Other Authors: Smith, Kayla (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Geology
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-9686

With so few Eocene outcrops throughout Florida, it is difficult to study the Eocene-Oligocene boundary between the Ocala and Suwannee Limestone. This study provides a more detailed lithological description of the differences of rocks on either side of that boundary. In this study, core samples from seven wells throughout northern Florida and Southern Georgia were examined across what is believed to be the Gulf Trough. Samples were cut from the core of each well every six inches for approximately 1.5 feet and then every 1 foot for another 3 feet above and below Eocene-Oligocene boundary picks. The samples were then made into thin sections, stained with Alizarin Red S, examined using a petrographic microscope, described by using both Folk's (1959) and Dunham's (1962) carbonate classification schemes, and fossils were identified where possible. From this information, interpretations of the depositional environment were made. The Ocala Limestone variably consists of biomicritic and pelbiomicritic mudstones, biomicritic packstones, biosparitic grainstones, and dolostones. It consists primarily of white to cream to dark grey and variably fossiliferous limestone. Dolostones are grey to brown and chert is sparse. Fossil assemblages include echinoids, the foraminifera Lepidocyclina sp., Lepidocyclina ocalana, Nummulities sp., and rhodoliths. The Suwannee Limestone wells variably consist of pelmicritic and pelbiomicritic mudstones, pelbiomicritic wackestones, biomicritic packstones, pelbiosparritic grainstones, and dolostones. Dolomite is often grey to brown and chert is common. Fossil assemblages contained in the core from these wells include echinoid fragments and benthic foraminifera such as Lepidocyclina sp. and Nummulities sp. as well as rhodoliths. These findings show that there is minimal variation between the Ocala and Suwannee Limestone aside from the disappearance of the benthic foraminifera Lepidocyclina ocalana, suggesting that a change in environmental conditions was not significant at the Eocene-Oligocene boundary. Based on the lithological descriptions and contained fossil assemblages the Ocala and Suwannee Limestones were deposited in shallow marine environments within the photic zone of the middle marine shelf, such as a Wilson Zone 7 (Wilson, 1975). === A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. === Summer Semester 2015. === June 24, 2015. === Diagenesis, Lepidocyclina Ocalana, Ocala Limestone, Suwannee Limestone === Includes bibliographical references. === William Parker, Professor Directing Thesis; Stephen Kish, Committee Member; James Tull, Committee Member.