Upper Paleocene and lowermost Eocene angiosperm pollen biostratigraphy of the eastern Gulf Coast and Virginia

Strata comprising most of the upper Paleocene in eastern North America are divided into two new pollen zones, the Carya and Platycaryaplatycaryoides Interval Zones. Pollen data have proven to be important for correlations between Alabama-western Georgia and eastern Mississippi and between the eastern Gulf Coast and Virginia. Migration of tropical plant taxa from the Caribbean to the Gulf Coast began at least 4 m.y. before the end of the Paleocene. The Terminal Paleocene Extinction Event, accompanied by a distinct pulse of plant immigration from Europe, began several hundred thousand years before the end of the Paleocene. INTRODUCTION Correlation of coastal and terrestrial lower Tertiary strata is difficult because marine fossils are sparse or lacking. Pollen biostratigraphy is an excellent method for correlation of coastal and terrestrial strata, but it is highly desirable to calibrate the pollen data using standard marine nannoand microfossil zonations. The eastern Gulf Coast is an ideal region for creating a calibrated pollen biostratigraphy for the lower Tertiary of eastern North America because in this region pollen-rich coastal and terrestrial strata are interstratified with pollen-bearing strata rich in calcareous nannofossils and microfossils. The purpose of this paper is (1) to compile a composite pollenstratigraphic standard section (Composite Section A) for the upper Paleocene of Alabama and western Georgia, based on outcrop and core samples, including many new samples; (2) to calibrate this standard section by means of published nannofossil and microfossil age determinations for the strata; (3) to examine pollen assemblages from several outcrop and cored sections in Mississippi, comparing these sections with the standard section from Alabama and Georgia; (4) to combine all the data and create a composite pollen-stratigraphic section for the upper Paleocene of the eastern Gulf Coast (Composite Section B); and (5) to correlate upper Paleocene strata from the eastern Gulf Coast with those in the Oak Grove core of Virginia based on previously published calcareous nannofossil and pollen data from that core (text-fig. 1). During the course of the investigation, important new data were obtained about plant immigrations from the Caribbean and Europe to eastern North America and about plant taxon extinctions near the end of the Paleocene. Appendix 1 provides geographic and stratigraphic information about the 59 samples whose pollen assemblages are the main source of eastern Gulf Coast pollen data for this paper. Sample localities are shown in text-figure 2. PREVIOUS POLLEN WORK Papers on upper Paleocene pollen from the eastern Gulf Coast (including the upper Mississippi Embayment and central Georgia) have been published by Fairchild and Elsik (1969), Tschudy (1973a, 1973b, 1975), Tschudy and Patterson (1975), Christopher et al. (1980), Frederiksen (1980a, 1980b, 1991), Cofer and Frederiksen (1982), and Frederiksen et al. (1982). This paper completes the summary of Paleocene pollenstratigraphic research in the eastern Gulf Coast that was begun with my article of 1991 on the Midwayan Provincial Stage, which includes the Clayton Formation, Porters Creek Clay, and Naheola Formation of the eastern Gulf Coast and correlatives on the Atlantic Coastal Plain; these rocks are equivalent to the Danian and lower part of the Selandian European Stages, or lower Paleocene and lowermost part of the upper Paleocene. The emphasis here is on the upper Paleocene Nanafalia and Tuscahoma Formations, representing the upper Selandian(?) and Thanetian European Stages and the lower part of the Sabinian Provincial Stage. This article draws together information mainly from samples that I have examined that can be placed at reasonably accurate stratigraphic levels. Some of these upper Paleocene data have previously been published (Frederiksen 1980a, 1991; Frederiksen et al. 1982), but most of the samples discussed here are new. At least 80 angiosperm pollen taxa are known from the Nanafalia and Tuscahoma Formations of the eastern Gulf Coast; they are listed in table 1. Most of these taxa are well known and have been well illustrated in papers on early Tertiary palynology of the eastern United States. However, some taxa are also illustrated here (plates 1-2). The emphasis in this paper is on taxa having restricted stratigraphic ranges, defined as taxa that do not range both above and below the combined Nanafalia and Tuscahoma Formations. LITHOSTRATIGRAPHIC AND CHRONOSTRATIGRAPHIC UNITS Murray (1955) divided the Paleocene and certain lower Eocene strata of the Gulf Coast into the Midwayan and Sabinian Provincial Stages (text-fig. 3). The base of the Midwayan Stage is the base of the Paleocene section in the region. The boundary between the Midwayan Stage and the overlying Sabinian Stage was defined by Murray as the base of the "Ostrea thirsae beds" that he de cribed as forming the base of the Marthaville Formation in T xas and Louisiana and the base of the Nanafalia Formation in the eastern Gulf Coast (Mississippi, Alabama, and western Georgia). However, in the eastern Gulf Coast the provincial stage boundary and the base of the Nanafalia Formation micropaleontology, vol. 44, no. 1, pp. 45-68, text-figures 1-14, plates 1-2, 1998 45 This content downloaded from 207.46.13.113 on Wed, 05 Oct 2016 04:41:44 UTC All use subject to http://about.jstor.org/terms Norman 0. Frederiksen: Upper Paleocene and lowermost Eocene angiosperm pollen biostratigraphy of the eastern Gulf Coast and Virginia