Low grade metamorphic rocks of the Ruppert and Hobbs coasts of Marie Byrd Land, Antarctica



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Texas Tech University


Low grade metamorphic rocks exposed on the Ruppert Coast and Hobbs Coast are classified into two lithostratigraphic units. Herein the lower portion is named the Wilkins Nunatak Group and the upper portion is termed the Mount Pearson Group. The Wilkins Nunatak Group consists of a basal sequence of carbonate rocks conformably overlain by continental sediments. The Mount Pearson Group is composed of geosynclinal graywackes and subgraywackes.

During the late Precambrian and early Paleozoic a shallow epicontinental sea covered the Ruppert and Hobbs coasts. Shelf carbonate beds which form the basal portion of the Wilkins Nijinatak Group were deposited upon an eroded complex of amphibolite gneiss. As the Ruppert Coast and areas farther west were uplifted, the sea retreated eastward and subgraywackes, protoquartzites and arkose conglomerates were deposited, with seeming conformity, upon the carbonate banks. Basinward, the continental sediments graded into thin-bedded sequences of sandstone and shale. By the Ordovician Period, the entire area was emergent and was subjected to widespread erosion which formed the regional unconformity at the top of the Wilkins funatak Group. Subsequently, areas west of the Ruppert Coast were uplifted and lithic graywackes, feldspathic graywackes and subgraywackes of the Mount Pearson Group accumulated in a rapidly subsiding basin. As subsidence continued, possibly to depths approaching 10 kilometers, the basal portion of the Wilkins Nunatak Group was metamorphosed. Granite plutons were emplaced during the Cretaceous Period. Block faulting occurred during early Tertiary time,



Metamorphic, Stratigraphic, Rocks, Geology, Geology -- Antarctica -- Marie Byrd Land