Ellsworth-Whitmore Mountains Crustal Block, Western Antarctica: New paleomagnetic results and their tectonic significance

Grunow, A. M.; Dalziel, I. W. D.; Kent, Dennis V.

Preliminary paleomagnetic study of granitic and sedimentary rocks from the Ellsworth-Whitmore Mountains crustal block (EVH), Vest Antarctica, leads to the following conclusions: (1) The EVH has a paleogole for the Middle Jurassic located at 235°E, 41°S, (α₉₅ = 5.3, N = 8 sites) assuming that no widespread regional tilting has occurred since the magnetization measured was acquired. A Middle Jurassic paleolatitude of 47°S is indicated for the sites and precludes an original location for the EVH block south of the Antarctic Peninsula crustal block (AP). (2) This pole is not significantly different from the previously published Middle Jurassic paleopole obtained from rocks of the northern Antarctic Peninsula. The combined AP-EVH paleopole, compared to the Middle Jurassic mean paleopole obtained from igneous rocks of the Ferrar Supergroup in East Antarctica, suggests about 15° tectonic clockwise rotation of the AP and EVH. Since the AP and EVH poles coincide, these two crustal blocks may have moved as one unit since the Middle Jurassic. ( 3) The new data are compatible with two different Gondwanaland reconstructions. The first considers the AP and EVH as separate entities. The second is based on the movement of the AP and EVH as one block. For the Middle Jurassic, both reconstructions would locate the EVH west of Coats Land and south of the Falkland Plateau, with the adjacent AP located south of southernmost South America. (4) Enigmas concerning the structural trend and isolation of the thick Ellsworth Mountains Paleozoic succession persist.

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Gondwana Six: Structure, Tectonics, and Geophysics
American Geophysical Union

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