Abstract Detail


Baghai-Riding, Nina [1], Hotton, Carol [2], Starnes, James (Jim) [3], Leard, Jonathan [4], Axsmith, Brian [5].

Implications of plant communities based on palynomorphs from three Early Oligocene Forest Hill Formation sites, 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, palynological samples were collected from the early Oligocene Forest Hill Formation by J. Starnes and J. Leard in Yazoo, Smith and Madison Counties. 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 geographical location and represents an up-dip limit exposure of the formation along the axis of the Mississippi Embayment. The Smith County sample is associated with a freshwater riverbank setting that is adjacent to a storm surge zone along the eastern side of the Mississippi embayment. The Madison County site is associated with a coastal environment and is an outlier outcrop on the north flank of the Jackson Dome. All three samples possess diverse palynomorphs of pollen, spores, and algal cysts indicating a warm temperate climate. The samples also differ in taxonomic composition. Palynomorphs from the Yazoo County sample indicate 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. Palm stumps are close to this locality. The Smith County sample represents an oak-hickory-willow coastal forest. 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 Madison County site displayed poorer recovery of identifiable palynomorphs. In a 200-point count, angiosperms comprised 35%, conifers 19.5%, trilete spores 24.5%, and algal cysts 42%. The preponderance of algal cysts suggests a coastal, freshwater environment. Thirty taxonomic plant families represented by palynomorphs were documented from these three samples. Families/orders common to both localities include Anemiaceae, Lycopodiaceae, Polypodiaceae, Cupressaceae, Pinaceae, Arecaceae or Liliales, Betulaceae, Fagaceae, Juglandales, and Platanaceae. Families/orders noted only in the Yazoo County site included Gleicheniales, Sphagnaceae, Ericaceae, Onagraceae, Sapotaceae, Symplocaceae, and possibly Myrtales. Families/orders noted only in Smith County site include Ophioglossaceae, Osmundaceae, Polypodiales, ?Oleaceae, Salicaceae, and Tetracolporites (a eudicot of uncertain affinities). Families found only in the Madison County site include Equisetaceae, Asteraceae, Poaceae, and ?Sapindaceae, ?Selaginella, Retisyncolporites (of uncertain affinity) and probable algal cysts (leiospheres) are also present.

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1 - Delta State University, Division Of Biological & Physical Sciences, Box 3262, Cleveland, MS, 38733, United States
2 - National Institutes Of Health, National Center For Biological Information, 45 Center Dr Msc 6510, Building 45, Rm 6an.18, Bethesda, MD, 20892, United States
3 - Mississippi Department of Environmental Quality, Office of Geology, Jackson, MS, USA
4 - Mississippi Department of Environmental Quality, Office of Geology, Jackson, MS, 39201, USA
5 - Biology Department, 5871 USA Drive North, Room 124, Mobile, AL, 36688, United States

none specified

Presentation Type: Poster
Number: PPB001
Abstract ID:157
Candidate for Awards:None

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