Please use this identifier to cite or link to this item: http://library.iigm.res.in:8080/xmlui/handle/123456789/1775
Title: Red clays indicate sub‑aerial exposure of the Rio Grande Rise during the Eocene volcanic episode
Authors: Srivastava, Priyeshu
Murton, Bramley J.
Sant’Anna, Lucy Gomes
Florindo, Fabio
Hassan, Muhammad Bin
Guerra, Julia Taciro Mandacaru
Janasi, Valdecir de Assis
Jovane, Luigi
Keywords: Eocene volcanic episode
Rio Grande Rise
Sub-aerial exposure
Red clays
Issue Date: Nov-2023
Citation: Scientific Reports, 13, 19092 (2023). https://doi.org/10.1038/s41598-023-46273-y
Abstract: Autonomous underwater vehicle (AUV) mapping of the western Rio Grande Rise (RGR), South Atlantic, and subsequent exploration and photography of horizontal lava flows exposed in near vertical, faulted escarpments, showed occurrences of red clays/weathered volcanic tops trapped between successive alkaline lava flows. These red clays indicate a hiatus in successive volcanic eruptions. Here, we report detailed mineralogical, geochemical, and rock magnetic characteristics of one such distinct red clay dredged from ~ 650 m water depth in the western RGR. The mineral constituents of the red clay are kaolinite, magnetite, oxidized magnetite (/maghemite), hematite, and goethite, with biogenic calcite and halite occupying voids or precipitated on the surface of the red clay. The chemical index of alteration (CIA) has a value of 93, showing that red clay is a product of extreme chemical weathering of the lava flows. The alkaline volcanic rocks recovered from nearby show an age of ~ 44 Ma, indicating an Eocene age for the volcanism. We show that the red clays are a product of sub-aerial chemical weathering of these Eocene volcanic rocks, in a warm-wet climate, before the thermal subsidence of the RGR to its modern-day bathymetric depth.
URI: http://library.iigm.res.in:8080/xmlui/handle/123456789/1775
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