Chapter 21: Structure of the Sentinel Range, Ellsworth Mountains, West Antarctica

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Abstract
The 5,500+-m Paleozoic succession of the Sentinel Range includes the Heritage Group (Cambrian), the Crashsite Group (Cambrian and younger, including Devonian), the Whiteout Conglomerate (Carboniferous?), and the Polarstar Formation (Permian). All these predominantly clastic rocks were strongly folded during the early Mesozoic (?) Ellsworth (Gondwanide) Orogeny, and the folds formed mainly by a flexural-slip mechanism. Axial planar cleavage is abundant throughout the range; it may be a solution cleavage in the massive diamictite beds of the Whiteout Conglomerate. One major, eastward-dipping reverse (?) fault cuts Crashsite quartzite beds along the west side of range. The Sentinel Range succession was subjected to mild burial metamorphism, and later dynamothermal metamorphism reached lower greenschist facies. The folds in the range plunge gently northward, and the entire Sentinel Range block may be slightly tilted eastward. Stratigraphic similarities with rocks of the Transantarctic Mountains make it likely that the Ellsworth Mountains have moved and rotated away from the margin of East Antarctica, but the sense of such a rotation cannot be determined at present. In addition, similarities exist between the Sentinel Range younger rocks and those in the Cape Fold Belt of southern Africa, as foretold by Du Toit (1937), but the Cambrian System of the Sentinel Range lacks a definite counterpart in Africa.

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