ELECTRON SPIN RESONANCE OPTICAL DATING OF SILICICLASTIC SEDIMENTS IN FLORIDA, USA

Electron spin resonance optical dating (ESROD) of quartz was conducted for the first time on littorally transported and aeolian siliciclastic sediments in Florida. ESROD utilizes radiation-sensitive defects at silicon sites which have been replaced by aluminum and titanium atoms, to give rise to a time-dependant signal. These defects have the ability to absorb a larger amount of radiation dose, compared to optically stimulated luminescence, and can therefore extend the optical dating range back millions of years. Samples were collected at ten locations in northeastern Florida in an attempt to determine the depositional ages of the terraces described by Winker and Howard (1977). Eight samples were collected and dated from the Trail Ridge Sequence. Six samples were collected from the Chatham Sequence and eight samples were collected from the Effingham Sequence. Our results show that the Trail Ridge sequence is a multi-depositional unit that began depositing around 2.2 Ma and continued until 6 Ka. The Osceola Cape, of the Effingham Sequence, was deposited around 1.5 Ma, and the Chatham Sequence was a multi-depositional terrace with at least three events preserved. The majority of the Chatham Sequence was deposited between 0.86 Ma to 1.09 Ma, with aeolian features being deposited between 0.41 Ma to 0.61 Ma. The youngest feature in the Chatham sequence is the Atlantic Ridge and the Atlantic Barrier Chain which were deposited between .07 Ma and .12 Ma.