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Abstract Detail


Baghai-Riding, Nina [1], Starnes, James [2], Hotton, Carol [3], Axsmith, Brian [4], Leard, Jonathan [2].

Implications for Climate and Plant Communities Based on Palynomorphs from the Early Oligocene Forest Hill Formation, Mississippi, U.S.A.

Oligocene floras of the Gulf Coast region of the southeastern United States remain poorly known. As part of a larger study of floras of the late Paleogene and Neogene of Mississippi and Alabama, palynological samples were collected from the early Oligocene Forest Hill Formation by J. Starnes and J. Leard in Yazoo County and Smith County, Mississippi. The Forest Hill Formation (Vicksburg Group) is a nearshore terrestrial unit consisting of laminated sands and dark carbonaceous clays with lignite beds. The Yazoo County sample was collected at the most northern and up-dip limit exposure of the formation along the axis of the Mississippi Embayment. Both samples possess well-preserved and diverse palynomorphs of pollen, spores, and algal cysts indicating a warm temperate climate. However, the two samples differ in taxonomic composition. Palynomorphs from the Smith County sample represent an oak-hickory-willow coastal forest bordering freshwater riverbanks and a storm surge zone flanking the eastern side of the Mississippi Embayment. In a 300-point count, angiosperms comprised 59%, conifers 11.4%, pteridophyte spores 20.5%, freshwater algal forms 9% and marine cysts 1.5% of the assemblage. This sample is associated with a rich and diverse assemblage of well-preserved plant macrofossils, including palm fronds. In contrast, the Yazoo County sample indicates a backwater, enclosed bay setting, based on the higher quantity of Anemia (22%) and Dictyophyllidites (7%) spores. In this 300-point count, angiosperms comprised 49%, conifers 3%, pteridophyte spores 40% and freshwater algal forms 9% of the assemblage. Seventeen taxonomic plant families represented by palynomorphs have been documented from these two samples. Families/orders common to both localities include Anemiaceae, Lycopodiaceae, Polypodiaceae, Cupressaceae, Pinaceae, Aquifoliaceae, Arecaceae or Liliales, Betulaceae, Cornaceae, Fabaceae, Fagaceae, Juglandales (including Normapolles, which may be reworked), Platanaceae, and Ulmaceae. Families/orders noted only in the Yazoo County site included Gleicheniales and Sphagnaceae and Ericaceae, Onagraceae, Sapotaceae, Symplocaceae, and possibly Myrtales. In contrast, families noted only in Smith County site include Ophioglossaceae, Osmundaceae, and Polypodiales,?Chenopodiaceae, ?Oleaceae, Salicaceae, and the pollen type Tetracolporites (a eudicot of uncertain affinities). A dinoflagellate cyst of ?Trithyrodinium and algal cysts of Zygnemataceae and Maculatasporites also occur in this sample.

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Related Links:
Detailed Cenozoic Chronostratigraphic Chart of Mississippi
Bulletin 116: Smith County Geology and Mineral Resources
Surface Geologic Map of Mississippi

1 - Delta State University, Division Of Math And Sciences, Walters Hall Room 116A, Cleveland, MS, 38733, United States
2 - MDEQ, MS Dept. of Environmental Quality (MDEQ), 700 North State St., Jackson, MS, 39202, USA
3 - National Institutes Of Health, National Center For Biological Information, 45 Center Dr Msc 6510, Building 45, Rm 6an.18, Bethesda, MD, 20892, United States
4 - Biology Department, 5871 USA Drive North, Room 124, Mobile, AL, 36688, United States

none specified

Presentation Type: Poster
Session: P3, Paleobotany Posters
Location: Virtual/Virtual
Date: Wednesday, July 21st, 2021
Time: 5:00 PM(EDT)
Number: P3PB007
Abstract ID:309
Candidate for Awards:None

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