Lower Devonian Fauna of the Horlick Formation, Ohio Range, Antarctica1
- Jarvis B. Hadley
Published Online: 3 APR 2013
Copyright © 1965 by the American Geophysical Union.
Geology and Paleontology of the Antarctic
How to Cite
Doumani, G. A., Boardman, R. S., Rowell, A. J., Boucot, A. J., Johnson, J. G., McAlester, A. L. G., Saul, J. G., Fisher, D. W. and Miles, R. S. (1965) Lower Devonian Fauna of the Horlick Formation, Ohio Range, Antarctica1, in Geology and Paleontology of the Antarctic (ed J. B. Hadley), American Geophysical Union, Washington, D. C.. doi: 10.1029/AR006p0241
- Published Online: 3 APR 2013
- Published Print: 1 JAN 1965
Print ISBN: 9781118655733
Online ISBN: 9781118668528
- Horlick Formation;
- Lower devonian fauna;
- Ohio range;
The Horlick Formation is a succession of sandstones and shales containing a marine faunal assemblage of brachiopods, bryozoans, gastropods, pelecypods, criccconarids, trilobites, and a fish plate. The brachiopods are the most abundant forms and are dominated by Pleurothyrella antarctica; other species include Australospirifer cf. iheringi, Cryptonella? sp., Lingula sp., Orbiculoidea cf. bainii, and Tanerhynchia doumanii, sp. nov. Biometric analyses reveal a small meristie variation and a high percentage of similar or equivalent values that justify close correlation particularly with South African specimens.
The new cricoconarid species Tentaculites antarcticus is assigned a pre-Givetian and post-Gedinnian age; a probable Lower Devonian age is also indicated by the new trilobite species Burmeisteria (Digonus) antarcticus. The fish plate belongs to an arctolepid (dolichothoracid) placoderm, a member of a group of fishes that flourished in the Early Devonian. Gastropods and pelecypods occur in profusion, the gastropods being ahnost exclusively the bellerophontid Plectonotus derbyi, a characteristic element of the Horlick community and of other Malvinokaffric assemblages. Among the ten bivalve species, Modiomorpha baini, Nuculites africanus, and Nuculoidea musculosa are indistinguishable from South American and South African species.
The elements of the Horlick Formation fauna are closely related to those of other southern hemisphere Lower Devonian communities, and the assemblage as a whole is considered an integral part of the Malvinokaffric fauna of Early Devonian age. Other features of the fauna characteristic of southern hemisphere Lower Devonian deposits are the absence of cephalopods, the paucity of aviculids and pterineids, the concentration of spiriferids on bedding surfaces, the absence of limestone, and the presence of a coarse basal sandstone and limy concretions. These characteristics indicate an unusual similarity in sedimentary conditions and suggest a close correlation between the Horlick Formation and the Tibají of South America and the Bokkeveld of South Africa.