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The role of fault reactivation in the development of tropical montane lakes |
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| Authors: | Pedro Walfir M Souza-Filho Roberto Vizeu L Pinheiro Francisco R Costa José Tasso F Guimarães Prafulla K Sahoo Marcio S Silva Cleverson G Silva |
| Institution: | 1. Instituto Tecnologico Vale, Belém, PA, Brazil;2. Geosciences Institute, Universidade Federal do Pará, Belém, PA, Brazil;3. Geosciences Institute, Universidade Federal do Pará, Belém, PA, Brazil
Geosciences and Engineering Institute, Universidade Federal do Sul e Sudeste do Pará, Marabá, PA, Brazil;4. Instituto Tecnologico Vale, Belém, PA, Brazil Department of Environmental Science and Technology, School of Environmental and Earth Sciences, Central University of Punjab, Bathinda, India;5. Department of Geology, Universidade Federal Fluminense, Niterói, RJ, Brazil |
| Abstract: | This work details the role of fault reactivation in the development of tropical montane lakes by using basin morpho-structural analysis and seismostratigraphic studies. The upland lakes are severely faulted sinkholes, whose faults penetrate the Quaternary sedimentary units. Four main stages are related to the lake formation: (i) an Early Proterozoic tectonic deformation of the rocks along the southern border of the Carajás Structure, where the lake is placed; (ii) differential erosion by – and building of – the formation of the South Carajás Hill; (iii) Fe-rich crust formation by weathering and gravitational collapse faults following the E–W plateau border and the start of Violão Lake formation during the Pliocene–Pleistocene; and (iv) episodic fault-fracture reactivation by gravitational collapse causing pulses of subsidence in the lake and outlining its faulted borders. Dissolution of the lateritic crust and erosion by runoff drainage under wet climate conditions were coeval with fault activities, which allowed the deposition of relatively thick clastic deposits organized in three main seismostratigraphic units associated with major lake-level fluctuations. Initial fault reactivation under low-level water started lacustrine basin development with deposition of prograding fan deltas related to the main drainage. A second fault reactivation by gravitational collapse increased the lake accommodation space and resulted in the deposition of fine-grained sediments from dilute interflows or overflows until 36 000 cal year BP. At about 31 000 cal year BP, rapid decreases in the lake water level under redox conditions at the sediment/water interface allowed widespread siderite formation. A third gravitational collapse episode was responsible for the increase in the lake area and depth and the returning of clastic/organic deposition up to the present. This tropical montane lake can be seen as a representative example for understanding the formation of other upland lakes controlled by fault reactivation. © 2020 John Wiley & Sons, Ltd. |
| Keywords: | geomorphology seismostratigraphic facies structural geology bathymetry tropical lake Quaternary iron ore mountains |