Cretaceous-Paleogene tectonic reconstructions of the South Scotia Ridge and implications for the initiation of subduction in the Scotia Sea

Riley, T. and Burton-Johnson, A. and Hogan, K.A. and Carter, Andrew and Leat, P.T. (2023) Cretaceous-Paleogene tectonic reconstructions of the South Scotia Ridge and implications for the initiation of subduction in the Scotia Sea. Journal of the Geological Society 180 (4), pp. 1-10. ISSN 0016-7649.

Abstract

TheCenozoicdevelopmentoftheScotiaSeaandtheopeningofDrakePassageledtothedispersalofcrustalblocks of the North and South Scotia ridges, which today have a strong influence on the pathway of the Antarctic circumpolar current. The pre-translation positions of the crustal fragments of the Scotia ridges are uncertain, with correlations to both the Antarctic and South American plates. We present direct geochronology results (40Ar/39Ar) from the Bruce and Jane banks of the South Scotia Ridge that yield Late Cretaceous–Paleogene ages, indicating a pre-translation magmatic history. The basaltic magmatism from Bruce Bank is calc-alkaline, akin to the Cenozoic magmatism of the South Orkney microcontinent and the South Shetland Islands, and agrees with pre-translation tectonic models that place the crustal blocks of the South Scotia Ridge adjacent to the northern Antarctic Peninsula arc. The intra-oceanic arc magmatism at Jane Bank is Late Cretaceous in age (97.2 ± 1.1 Ma) and is therefore inconsistent with models suggesting a Miocene origin as part of the ancestral South Sandwich arc. The development of westwards-directed subduction adjacent to Jane Bank is predicted in some tectonic models as a consequence of Late Cretaceous plate dynamics that developed prior to the Oligocene–Miocene ancestral arc.

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