Abstract
Ages of the geologic formations underlying Lee County, Florida have been in dispute for the last century. A new, unified chronostratigraphy (age analysis) was developed for the upper Paleogene and Neogene sediments of the Southwest Florida region. The age constraints were determined from analysis of samples collected from continuous cores and from compilation of existing age-data collected by a number of investigators. The ages of the sediments were determined by the combined use of calcareous nannofossils, planktonic foraminifera, diatoms, strontium isotope stratigraphy, and magnetostratigraphy. Based on these integrated dating techniques, the following age constraints using the Berggren et al. (1995) time scale were placed on the formations underlying Lee County: the Suwannee Limestone ranges from 33.7 (?) to 28.5 Ma, the Arcadia Formation of the Hawthorn Group from about 26.5 to 12.4 Ma., the Peace River Formation of the Hawthorn Group from 11(?) To 4.3 Ma, the Tamiami Formation from 4.3 to 2.1 Ma, and the Caloosahatchee Formation from 1.8 to 0.6 Ma. Based on these ages, the Suwannee Limestone was deposited in the early Oligocene, the Hawthorn Group was deposited from the late Oligocene to the early Pliocene, the Tamiami Formation was deposited from the early to the late Pliocene, and the Caloosahatchee Formation was deposited within the late Pliocene and early Pleistocene.