Provenance of Triassic – Cretaceous sandstones in the Antarctic Peninsula: implications for terrane models during Gondwana breakup
The Antarctic Peninsula is the largest of ~ twelve micro-continental fragments between southern South America, East Antarctica, and New Zealand. Their original positions and movement history following Gondwana breakup are poorly constrained. Recent work on the Antarctic Peninsula fore-arc/arc/back-arc suggests it consists of two suspect terranes that originated elsewhere and collided with the Pacific margin of Gondwana in the Cretaceous. This study reviews provenance models for three laterally extensive, kilometers-thick sedimentary units in the Antarctic Peninsula using previous studies, and new sandstone detrital modes and chemistry. 1) The Trinity Peninsula Group accretionary complex (Triassic) was possibly derived from a glaciated continental margin and may consist of several accreted tracts. The deformed, quartzose View Point and Legoupil formations were eroded from a deeply eroded, stable continental margin containing an old arc and mature quartzose sandstones, with provenance ages suggesting sources in north Patagonia and local Antarctic Peninsula basement. The weakly deformed and more feldspathic Hope Bay Formation was derived from an eroded arc, possibly the early Permian arc of the North Patagonian massif. 2) The LeMay Group accretionary complex (middle Triassic-middle Cretaceous) is dominated by arkoses derived from an eroded continental margin of Carboniferous and Permian age, possibly in the Marie Byrd Land sector, with several belts of volcanilithic sandstones representing episodes of arc magmatism. The youngest part of the LeMay Group contains abundant metamorphic detritus derived from basement uplifted during mid-Cretaceous terrane docking. 3) The Latady Formation in the southern Antarctic Peninsula has a completely different petrology, comprising mature sublitharenites (~ 190 Ma) of Gondwanan provenance, deposited in restricted rift basins. Younger volcanic litharenites (180 Ma) are dominated by REE-enriched low Eu/Eu* rhyolitic material, eroded from silicic calderas associated with Gondwana breakup. Abundant dacitic to andesitic detritus in the youngest LF (160-145 Ma) was derived from a contemporaneous arc, possibly on the Thurston Island block, as the Latady evolved into a back-arc basin.