Abstract Introduction Material & Methods Lithostratigraphy Petrography, Biostratigraphy & Sr-isotope Analysis Collier-Seminole Old Pump Road F.S.-Ranger Station F.S.-Gate 12 >F.S.-Jones Grade Picayune Strand Southern States Conclusions References Figures Tables Appendix 1 Appendix 2 PDF version

Fakahatchee Strand-Jones Grade core

The Fakahatchee Strand-Jones Grade corehole site (fig. 1, table 1) is in the driveway of the first house on the south side of Jones Grade, west of State Route 29, about 1/2 mile south of the intersection of I-75 and Rte. 29 (Miles City). The core was drilled to 200 ft in July 1996. This core (fig. 7) has been sampled for thin sections, X-ray diffraction, strontium analysis of shells, and for mollusk, dinocyst, pollen, ostracode, and foraminifer content.

The unnamed formation occurs from the bottom of the core at 200 ft to 70.9 ft and consists of an unconsolidated, medium to coarse quartz and phosphatic sand with scattered quartz pebbles. The sand is dolomitic from 150 to 140 ft. The Ochopee Member of the Tamiami Formation is present from 70.9 to 3 ft and is a poorly recovered, moldic molluscan limestone and sandy limestone, which is partially unconsolidated. The upper 3 ft of this core is clay and quartz sand that is probably artificial fill brought in for the residence.

Semi-quantitative X-ray diffraction data for this core are shown in table 10. Within the unnamed formation, the unconsolidated quartz sands were assumed to be primarily quartz: quartz is the predominant mineral, and calcite is absent, in both samples analyzed (174.5 and 141.4 ft). Only a trace of dolomite was detected at 141.4 ft and no aragonite was detected. Calcite is the dominant mineral in samples from the Ochopee Limestone Member of the Tamiami Formation (53.0 to 3.1 ft), where no dolomite or aragonite was detected.

Petrography. Two thin sections were made from the Ochopee Limestone Member of the Tamiami Formation in this core at 15.2 and 11.0 ft. Each is a molluscan packstone with a trace to 15 percent quartz sand and skeletal grains that include molluscan molds and fragments, benthic foraminifers, bryozoans, and echinoid fragments. Cements are minor dogtooth spar on surfaces.

Lithologic and Petrographic summary. As in the Fakahatchee Strand-Ranger Station and Fakahatchee Strand-Gate 12 cores, there is no lithified carbonate depositional unit in the lower part of the Fakahatchee Strand-Jones Grade core. Samples from the Ochopee in the Jones Grade core are similar to samples from the Ochopee in other cores, except that they lack a planktonic foraminifer horizon, preserved aragonite, and early (now-leached) fibrous cement.

Biostratigraphy. Six samples were examined for dinocysts (appendix 2, table 3). The sample at 185 ft is late Miocene, and contains Erymnodinium delectabile, Invertocysta lacrymosa, Selenopemphix brevispinosa brevispinosa, and Trinovantedinium ? xylochoporum. The sample at 142 is late in the late Miocene, based on the overlap of S. armageddonensis and E. delectabile. The sample at 72 ft is barren. The sample at 57 ft contains Achomosphaera andalousiensis, Dapsilidinium pseudocolligerum, and Invertocysta sp. Like the samples from the Ochopee in the Collier-Seminole core, this sample is late Miocene or Pliocene, and because it is above the highest occurrence of E. delectabile, it is likely to be Pliocene. Higher samples were barren.

Ten samples were examined for molluscan faunal content. Four samples from 67 to 10 ft contained mollusks identified for this report (table 4). Turritella perattenuata (67 ft) is reported from late Pliocene or early Pleistocene units, but data gathered in this study indicate a longer range than previously discovered. Mollusks identified from 66.3 to 10 ft are Pliocene. The questionable identification of Chione cortinaria indicates a probable early Pliocene age (molluscan zone M6), but the presence of Chione procancellata (66.3 ft) indicates a probable late Pliocene age (Mansfield, 1932). As in other cores, the overlap of these species may suggest an age near the early/late Pliocene boundary.

Strontium-isotope stratigraphy. No samples from this core are included in the present study.

Age summary. The unnamed formation (200-70.9 ft) in the Fakahatchee Strand-Jones Grade core is late Miocene. Dinocysts near the base of the unit are late Miocene, and the assemblage is clearly the same as in the other cores where late Miocene strontium-derived ages are available. At 142 ft, the dinocysts indicate a late late Miocene age. Above this, the unit is undated.

The Ochopee Limestone Member of the Tamiami Formation (70.9-3 ft) is late late Miocene or Pliocene. Mollusks above 66.3 ft suggest an age near the early/late Pliocene boundary.