31. BASEMENT ROCKS OF THE SOUTH-CENTRAL ROSS SEA
Calcareous metamorphic rocks of a continental-type crystalline basement were recovered by drilling at Site 270 in the south-central Ross Sea. Calcareous basement gneiss is of amphibolite-facies metamorphic rank and may correlate with calcareous meta-sedimentary rocks of similar rank in the early Pal...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.617.7030 http://www.deepseadrilling.org/28/volume/dsdp28_31.pdf |
| Summary: | Calcareous metamorphic rocks of a continental-type crystalline basement were recovered by drilling at Site 270 in the south-central Ross Sea. Calcareous basement gneiss is of amphibolite-facies metamorphic rank and may correlate with calcareous meta-sedimentary rocks of similar rank in the early Paleozoic(?) Skelton Group near McMurdo Sound. The basement rocks are overlain by 25 meters of coarse, angular, poorly sorted sedimentary breccia, the upper 3 meters of which is a deeply weathered regolith. The regolith is overlain unconformably by a thick sequence of mainly glacio-marine sediments of Oligocene and younger age. The breccia is interpreted as a probable talus or solifluction deposit derived from a nearby topographic high of basement rocks. Abundant fragments of marble and calc-silicate gneiss similar to the cored basement rocks, and numerous fragments of highly varied granitic and other metamorphic rocks in the breccia indicate that the basement terrane near Site 270 is a granitic and metamorphic com-plex probably similar to that of coastal parts of south Victoria Land near McMurdo Sound. Sedimentary rocks similar to those of the Devonian to Jurassic Beacon Supergroup and mafic-igneous rocks similar to those of the Jurassic Ferrar Dolerite were not observed in the breccia, suggesting that these widespread Victoria Land units do not extend to this region. |
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