Testing the Late Paleozoic Ice Volume Paradox in the Southernmost Paraná Basin, Brazil
The late Paleozoic ice age (LPIA; ~372-259 Ma) was the last complete transition from icehouse to greenhouse conditions on a fully vegetated Earth, making it a relevant analog for modern Earth systems. High frequency glacioeustatic fluctuation of ~100-200 m during the late Paleozoic are described by...
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UWM Digital Commons
2019
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| Online Access: | https://dc.uwm.edu/etd/2066 https://dc.uwm.edu/context/etd/article/3071/viewcontent/Fedorchuk_uwm_0263D_12390.pdf |
| Summary: | The late Paleozoic ice age (LPIA; ~372-259 Ma) was the last complete transition from icehouse to greenhouse conditions on a fully vegetated Earth, making it a relevant analog for modern Earth systems. High frequency glacioeustatic fluctuation of ~100-200 m during the late Paleozoic are described by some authors in low paleolatitude basins and attributed to the orbitally-driven, waxing and waning of a massive (~20-35 x 106 km2) hypothetical ice sheet. This massive ice sheet is traditionally interpreted to have covered much of southern Gondwana for >100 m.y. Meanwhile, recent studies of high-paleolatitude glacial deposits imply a much more complex pattern of glaciation with distinct, smaller ice centers that persisted for <10 m.y. Seemingly in support of these more recent studies, climate models indicate that a massive ice sheet would be too stable to produce glacioeustatic fluctuations on a time scale generated by orbital forcing. However, numerous smaller ice sheets of equal spatial coverage would not contain enough water volume to produce glacioeustatic amplitudes like those reported by some authors. To address this ice-volume paradox, the southernmost margin of the Paraná Basin, Brazil was chosen for a detailed sedimentologic, stratigraphic, and geochemical study since it has an unaltered record of Permo-Carboniferous glaciation and since several contradictory hypotheses have been proposed regarding the nature of the glaciation in this region. Sedimentological and geochemical analyses of glacial deposits on the southernmost margin of the Paraná Basin indicate that the glacier covering this region was warm-based or polythermal and it experienced repeated fluctuations in ice-marginal positions during the Carboniferous. The glacial foreland was as a temperate, transitional, lacustrine to estuarine environment. Paleovalleys on the southern margin of the Paraná Basin were previously viewed as fjords that drained an ice center over northern Namibia, which is also thought to have supplied ice to the eastern ... |
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