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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 50 (1966)

Issue: 10. (October)

First Page: 2322

Last Page: 2322

Title: Stratigraphy of Upper Miocene Deposits in Sarasota County, Florida: ABSTRACT

Author(s): Herbert C. Eppert, Jr.

Article Type: Meeting abstract

Abstract:

The presence of undisputed upper Miocene sedimentary rocks in Sarasota County, Florida, is not widely known. Most authors have stated that the middle Miocene Hawthorn Formation is overlain by Pliocene to Recent deposits. The upper Miocene is represented in southern Florida by the Tamiami Formation. The late Miocene age determination is based on the characteristic faunal assemblage, Ostrea disparalis, Chione ulocyma, and Ecphora quadricostata umbilicata. Fossil mollusks, echinoderms, and bryozoans collected from outcrops, quarries, and sinkholes in this area definitely confirm the presence of upper Miocene sedimentary rocks in Sarasota County. Typical upper Miocene species include Anadara cf. A. idonea, Chione ulocyma, Ostrea cf. O. tamiamiensis, O. tamiamiensis monroensis and Encope macrophora tamiamiensis.

In the upper Miocene deposits, an impermeable but porous bed is present and is characterized by a decrease in radioactivity and electrical resistivity. These characteristics are indicative of the presence of clay and the interpretation of X-ray diffraction patterns verified the predominance of clay minerals in the aquiclude. Montmorillonite is the dominant clay mineral with lesser amounts of attapulgite and alpha sepiolite.

Based on evidence presented in this paper, the upper Miocene deposits in Sarasota County are considered to be a lithosome of the Tamiami Formation.

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Copyright 1997 American Association of Petroleum Geologists