Abstract Detail

Paleobotanical Section

Baghai-Riding, Nina [1], Hotton, Carol [2], Davidson, Taylor [3], Baria, Lawrence R [4], Niemeyer, Patrick [5].

Marine and Terrestrial Palynomorphs from the Late Jurassic Smackover Formation, South Central Alabama, U.S.A.

The marine, late Oxfordian age Smackover Formation is an important oil- and gas-producing carbonate unit that subcrops in the northern Gulf of Mexico. The formation was deposited along the slope and shelf of the Gulf Coast embayment and consists of three carbonate dominated units, termed Smackover A, Smackover B and Smackover C, interspersed with thin (up to 15 m), black, laminated shales and siltstones containing abundant woody fragments and leafy plant debris. The siliciclastic units are thought to represent fluvial influx from short term regressional excursions during deposition of the Smackover carbonates. Here we report on the first palynological assemblages from the Smackover Formation. They were collected from four sampled intervals of a shale unit separating Smackover C and B, derived from cores drilled in the Little Cedar Creek Oil Field (T4N, R13E, Conecuh County, Alabama). Samples from the lower, more carbonate rich part ofthe shale are dominated by a rather impoverished dinoflagellate flora consisting primarily of Pareodinia ?ceratophora and Gonyaulacysta complex species, but also containing terrestrial elements, including abundant Classopollis spp. (Cheirolepidiaceae) and bisaccate pollen grains as well as diverse spores. Samples from the upper, more terrigenous unit contain only rare marine elements, and are dominated by bisaccate pollen (stem Pinaceae, ?Podocarpaceae) and Araucariacites australis and Callialasporites spp. (Araucariaceae), and also include Classopollis spp. Spores include representatives of Lycopodiaceae, Selaginellaceae, Osmundaceae, Schizeaceae, Matoniaceae, Dicksoniaceae or Cyatheaceae, and Gleicheniaceae, as well as probable fresh water algal cysts. Pollen morphospecies are largely comparable to those reported elsewhere from comparable strata, reflecting the relatively cosmopolitan nature of Late Jurassic floras, but a significant percentage of spore species lack exact matches to assemblages described from Europe, Britain and Canada, suggesting some degree of endemism. In particular, surprisingly little taxonomic overlap is seen between these assemblages and the palynoflora of the only slightly younger Morrison Formation (upper Oxfordian-?middle Tithonian). Spores are relatively abundant and diverse, suggesting a relatively humid climate, which supports an imputed plate position for the Conecuh embayment below 30 degrees north latitude. The Smackover palynoflora represents some of the few such assemblages reported from low latitude regions of North America during the Jurassic, and contribute to our knowledge of Late Jurassic floristics, climate, tectonics and stratigraphy of this region.

Broader Impacts:

1 - DELTA STATE UNIVERSITY, Division Of Biological & Physical Sciences, Caylor Hall Room 235, CLEVELAND, MS, 38733, USA
2 - NIH/NLM/NCBI - BLDG 45, 45 CENTER DR MSC 6510, Building 45, Rm 6an.18, BETHESDA, MD, 20892-6510, USA
3 - Delta State University, Biological and Physical Sciences, Cleveland, MS, 38733, USA
4 - Jura-Search, Inc., Flowood, MS, 29232, USA
5 - Hess Corporation, 1501 McKinney Street, Houston, TX, 77010, United States

Keywords:
Jurassic
Smackover Formation
palynology
terrestrial
dinoflagellates
Morrison Formation.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM
Number: PPB008
Abstract ID:554