Pleistocene stratigraphy and optical dating of surficial sands in Florida's coastal plain and central highlands: Implications for sea-level and shoreline ages

Optical dating of siliciclastic sediments in various locations throughout Florida was conducted to obtain a better understanding of Cenozoic climates and sea-level fluctuations.;Merritt Island is located just west of Cape Canaveral, and the eastern part of the island is composed of a sand ridge set. Four and a half kilometers of ground penetrating radar (GPR) and 10 OSL ages were combined to determine the depositional history of these beach ridges. Direct-push electrical conductivity was tested in two locations to determine the effectiveness of this new technique as a quick stratigraphic tool. Also a new graphical way to illustrate grain size distribution was utilized. Particle size distribution (PSD) plots allow the reader to visualize any minute changes in grain size such as a slight increase in clay content that may be overlooked if just using mean grain size. These changes are very important for interpretation of luminescence characteristics. Radar facies indicate that the ridges at Merritt Island are a classic example of beach ridges with an approximately 1-2 m aeolian cap on them. A new OSL model was used for the first time in an attempt to obtain more accurate luminescence ages on the ridges.;Five direct-push cores, five vibracores, and twenty-eight OSL ages (using the ACRM) were collected, as well as seven kilometers of GPR, in an attempt to determine the depositional history of the Gulfport Formation. The GPR data clearly defined the Gulfport Formation and the Biloxi Formation, but the OSL ages suggest that the Biloxi was deposited before MIS-5, possibly MIS-7 or MIS-9. Sitting directly above the Biloxi Formation is a mica rich sediment that was deposited during MIS-6, a contradiction to previous works. It is believed that as sea level dropped the paleo-Apalachicola River began depositing this sediment as it meandered through the area. As sea levels began to rise again, beach ridges (the Gulfport beach ridges) were deposited in the field area. LiDAR was used for the first time in the area to determine high resolution elevations. These elevations coupled with the precision of the GPR allowed us to conclude that MIS-5e sea levels were approximately 3.5 m above present.;ESROD, a new optical dating technique, was used at 10 locations across north-central and peninsular Florida in an attempt to better understand Pleistocene sea-level fluctuations and establish age constraints on three regional scale geomorphic sequences characterized by ridges and terraces at distinct elevation ranges. These are believed to have formed at the different elevations in connection with past higher sea levels. A total of twenty-two ESROD samples were collected in these three sequences: the Trail Ridge Sequence, the Effingham Sequence, and the Chatham Sequence. ESROD was conducted for the first time in Florida and on marine sediments. Our results indicate that Trail Ridge began depositing on the Hawthorn Group around 2.2 Ma and continued in several stages until 6 ka. The Effingham Sequence, which contains the Osceola Cape, was deposited around 1.5 Ma. The Chatham Sequence is a multi-depositional terrace with at least three events preserved. The majority of the sequence was deposited between 0.86 Ma and 1.09 Ma, with surficial aeolian features deposited between 0.41 Ma and 0.61 Ma. (Abstract shortened by UMI.);The Anastasia Formation is a coquina ridge that is believed to be deposited during the marine isotope stage (MIS) 5. It is culturally very important because the first Spanish fort, Castillo de San Marcos, in built completely out of the coquina. Three OSL samples were collected to determine the validity of this hypothesis and to begin to understand the relationship of the Anastasia Formation to the lowest terrace. OSL dating of a coquina has only been performed a handful of times around the world and never in Florida. The results support the hypothesis that the Anastasia was formed during MIS-5 and contributed by confirming the Anastasia is in fact not a single depositional event but multiple events cemented together post-deposition. Associated fossils also support the OSL results.