Late Oligocene Sequence Stratigraphy (Lower Arcadia Formation) of Southwest Florida

By

MISSIMER, THOMAS M.,

CDM Missimer, Fort Myers, FL

A single supersequence occurs within the late Oligocene mixed carbonate and siliciclastic sediments of southwest Florida. This supersequence was deposited beginning in Chron C8n.2n and ending in either Chron C7n or Chron C6Cr with an estimated age ranging between 26.5 and 24.2 Ma. The chronostratigraphy was established by using strontium isotope stratigraphy and magnetostratigraphy within three continuous cores through the sediments. The supersequence correlates to third order cycles 1.2 and 1.3 within supercycle TB1 (Haq et al., 1988). The supersequence is bounded by regional disconformities with a hiatus of 2 M.Y. at the base and 4 M.Y. at the top.

Detailed descriptions of three continuous cores, including core and thin section microscopic examination and correlation with a continuous seismic reflection section were used to define the sequence stratigraphy. From north to south in cores W-16242, W-16523, and W-17115, the number of stacked parasequences increases from 7 to 12. The thickness of the parasequences ranges from 1.2 to 12.2 m. The depositional environments represented within all of the parasequences are all rather shallow water environments from open shelf (less than 10 m of water depth) to peritidal. Most of the parasequences are capped with an exposure horizon or a laminated peritidal dolomite. There is a general increase of siliciclastic sediment within each parasequence from bottom to top.

The late Oligocene sediments of southwest Florida are a shallow-water ramp deposit. No sediments were deposited below the wave orbital depth of 20 m. These late Oligocene sediments are located within the lower part of the Arcadia Formation (Hawthorn Group).