A Leaiid Conchostracan Zone (Permian) in the Ohio Range, Horlick Mountains, Antarctica1

  1. Jarvis B. Hadley
  1. George A. Doumani1 and
  2. Paul A. Tasch2

Published Online: 3 APR 2013

DOI: 10.1029/AR006p0229

Geology and Paleontology of the Antarctic

Geology and Paleontology of the Antarctic

How to Cite

Doumani, G. A. and Tasch, P. A. (2013) A Leaiid Conchostracan Zone (Permian) in the Ohio Range, Horlick Mountains, Antarctica1, in Geology and Paleontology of the Antarctic (ed J. B. Hadley), American Geophysical Union, Washington, D. C.. doi: 10.1029/AR006p0229

Author Information

  1. 1

    Institute of Polar Studies, Ohio State University, Columbus

  2. 2

    Department of Geology, University of Wichita, Kansas

Publication History

  1. Published Online: 3 APR 2013
  2. Published Print: 1 JAN 1965

ISBN Information

Print ISBN: 9781118655733

Online ISBN: 9781118668528

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Keywords:

  • Gondwana leaiids and correlation;
  • Horlick mountains;
  • Leaiid conchostracan zone;
  • Ohio range;
  • Paleontology and stratigraphy

Summary

Fossil conchostracans were collected from the coal measures at Mercer Ridge in the Ohio Range, Horlick Mountains, Antarctica. The described conchostracans are represented by two new species: Leaia gondwanella, n. sp., and Cyzicus (Lioestheria) doumanii, n. sp. Both species occur in a thin, 10- to 15-cm zone of black, carbonaceous shale intercalating with sandstones, shales, and coal, which constitute the Mount Glossopteris Formation. The Leaia zone is near the diabase sill that caps the stratigraphic section of the Ohio Range. The section comprises a granitic basement overlain by the Devonian Horlick Formation, the Buckeye Tillite, the Discovery Ridge Formation, and the Mount Glcssopteris Formation in ascending order. The restricted biofacies represents isolated patches of water of puddle-to-pond size, and the presence of a Glossopteris flora, carbonized wood, as well as carbonized leaiid valves, suggests swamp conditions and deposition in shallow, still water. A study of sediment intervals between six conchostracan generations reveals a sedimentation rate of 0.68 mm per year for the Antarctic Leaia zone. The size of the conchostracans indicates a 1- to l½-month lifespan and suggests short-lived ponds or pools. This is also applicable to Leaia zones of equivalent age in Brazil, New South Wales, and South Africa, reflecting comparable weather (not climatic) cycles in these areas. The restricted occurrence of the Leaia zone in Antarctica is similar to such restrictions in Brazil and South Africa; its wider range in Australia appears to be the result of climatic control. The genus Leaia has not been reported in beds younger than Permian. The occurrence of leaiid conchostracans in the Lower Beaufort (M.-U. Permian) of South Africa and its equivalents in Australia and South America, appears to be a distinguishing feature. Similarly, the absence of Leaia species above this horizon in known Gondwana deposits assumes considerable significance. The similarities of the lealid species among Gondwana deposits, the association of leaiids with the Glossopteris components, and the many identical species of the Glossopteris flora in these localities establish a Lower Beaufort age for the Ohio Range leaiid zone. This also shows that the Leaia zone is neither Carboniferous nor Triassic.