Understanding Secular Changes In Earth’s Surface Through Deep Time
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Authors
Seraine Fernandes de Souza, Marina
Date
2024-09-19
Type
thesis
Language
eng
Keyword
Precambrian sedimentary rocks , Paleoproterozoic glaciation , Neoproterozoic glaciation , Triple oxygen analysis in shales
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Abstract
In this thesis, radiogenic and stable isotopes are evaluated to assess the transition between the Archean-Paleoproterozoic and Neoproterozoic, known for recording irreversible and dramatic changes in Earth’s history. One dramatic event that has occurred at various times in Earth history is global glaciation, with specific episodes clustered during the Siderian and Cryogenian. During the Paleoproterozoic, all cratons reconstructed as part of the Superia supercraton record the presence of glacial deposits, which are absent in the Sclavia supercraton.
In chapter 3 of this thesis, divergent provenance patterns in each supercraton reveal the contrasting effects of glacial erosion. One potential explanation for the lack of preservation of glacial deposits in Sclavia is associated with the diachronous emergence of the continents from 2.4 to 2.2 Ga. In chapter 4, provenance signatures from glacial units related to the Cryogenian glaciation indicate a more complex depositional history, where the detrital zircon contribution is most likely controlled by tectonic processes (e.g. rifting of Rodinia/assembly of Gondwana supercontinents). Hafnium and oxygen isotope signatures at 690 Ma suggest a major input of old sediment into subduction zones that might be related to tectonic processes coupled and deep glacial erosion of continental crust during the Sturtian glaciation.
In chapter 5, depleted δ’18O in fine-grained siliciclastic rocks provide evidence that the Huronian Glaciation (2.4-2.2 Ga) was established between 2.4 to 2.2 Ga. In chapter 6, new triple oxygen analysis performed in Fennoscandian and Huronian successions raises questions regarding the relationship between Δ′17O values and continental emergence during the Archean-Paleoproterozoic boundary, as previously proposed. The systematic analysis in the Zaonega Formation suggests an increase in Δ′17O values towards the deeper portions of the 11A core, which coincides with the increase of secondary catagenetic fluids in siliciclastic rocks.
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Attribution-NonCommercial-NoDerivatives 4.0 International