Sedimentological and Geochemical Analysis of Deep-Water Deposits in the Mojón De Hierro Formation at Arroyo Garrido, Tepuel-Genoa Basin, Patagonia, Argentina

• Main Author: McNall, Natalie Beatrice
• Format: Text
• Language: unknown
• Published: UWM Digital Commons 2019
• Subjects: Chemical Index of Alteration; Deep-water deposits; Late Paleozoic Ice Age; Mojon de Hierro Formation; Paleo-oxygenation; Permian; Climate; Geochemistry; Geology; Patagonia; Argentina; South Pole; Ellsworth Mountains; Garrido; Mojón; Ice Sheet; South pole
• Online Access: https://dc.uwm.edu/etd/2226; https://dc.uwm.edu/context/etd/article/3231/viewcontent/McNall_uwm_0263m_12505.pdf

The Earth has had multiple Phanerozoic glacial intervals but the Late Paleozoic Ice Age (LPIA) was its longest and most extensive, lasting from the Late Devonian (~372 Ma) until the Late Permian (~254 Ma). The LPIA is the last complete climate shift from a greenhouse to icehouse and back to a greenhouse state and the only one to occur on a biologically complex Earth. Therefore, it provides perspectives on deep-time climatic transitions, the parameters controlling them, and the Earth’s physical, chemical and biological responses to such climate changes. Research on mid to high-latitude deposits in Gondwana provides evidence that the LPIA had a highly dynamic climate, with multiple ice sheets and ice caps, that fluctuated asynchronously and diachronously across the supercontinent as it drifted across the paleo South Pole. Numerous questions remain on the spatial and temporal extent of the ice centers, the timing of expansion and contraction of the ice sheets and the distribution of ice across Gondwana through time. The Tepuel-Genoa Basin, in Patagonia, Argentina, was situated within the paleo South Polar Circle as part of Gondwana and contains a nearly continuous sedimentary succession of Carboniferous to Lower Permian strata. The Mojón de Hierro Formation has been described as both non-glacial and glacial in origin. This study investigates a unit within the Mojón de Hierro Formation which was used in a detrital zircon analysis which implies a large ice sheet covered the basin at the time of deposition, which extended from an ice center in the Ellsworth Mountains all the way to the Panthalassan Margin in west-central Gondwana. These strata contain mudrocks, some with outsized clasts, diamictites and sandstones. Five stratigraphic sections were measured at Arroyo Garrido and the strata were categorized into five lithofacies associations; 1) laminated mudrock, 2) laminated mudrock with dispersed clasts, 3) graded rhythmites, 4) laminated and bedded diamictites, and 5) deformed bedded sandstones. The strata were ...