Late Toarcian continental palaeoenvironmental conditions: An example from the Cañadón Asfalto Formation in southern Argentina
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UNIL restricted access
State: Public
Version: Final published version
License: All rights reserved
Serval ID
serval:BIB_96D7A51628DB
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Late Toarcian continental palaeoenvironmental conditions: An example from the Cañadón Asfalto Formation in southern Argentina
Journal
Gondwana Research
ISSN
1342-937X
Publication state
Published
Issued date
01/2021
Peer-reviewed
Oui
Volume
89
Pages
47-65
Language
english
Abstract
The Cañadón Asfalto continental Basin preserves terrestrial deposits interbedded with volcanic rocks, providing a unique opportunity for palaeoenvironmental reconstructions of the Jurassic continental realm. This study presents a sedimentological, mineralogical, and geochemical analysis of three lacustrine successions in the Cerro Cóndor area of the Cañadón Asfalto Basin, Argentina. New CA ID-TIMS U–Pb data from tuffaceous deposits indicate a late Toarcian age (179.481 ± 0.059, 179.41 ± 0.13, and 177.27 ± 0.40 Ma), suggesting that the palaeolakes developed contemporaneously to the Chon Aike volcanic activity. The sedimentary successions are composed of carbonate, organic matter-rich mudstone — with up to 8 wt% total organic carbon (TOC) content — sandstone and conglomerate, all with an important contribution of volcanic and volcanogenic material. The clay mineral assemblage dominated by corrensite (chlorite-vermiculite mixed layers), smectite and vermiculite is likely related to hydrothermal activity and alteration of volcanic material, rather than to change in weathering processes and climate. Organic matter preserved in the sedimentary successions has a lacustrine and terrestrial/reworked origin. Changes in the source of carbon dioxide (CO2) and in the type and/or degree of preservation of the organic matter had a major impact on the δ13Corg values. This further exemplifies the necessity to evaluate the influence of the depositional environment before interpretation of the organic carbon isotope records. The combined high phosphorus and TOC contents suggest that episodes of increased nutrient availability into the basin enhanced lacustrine primary productivity, which favoured the development of oxygen-depleted conditions bottom waters and ultimately organic matter preservation and burial. High Corg/Ptot ratios indicate that phosphorus was likely released back into the water column in a positive feedback loop, further sustaining primary productivity. This study provides an important clue to understand the palaeoenvironmental conditions prevailing on land during the late Toarcian and on how volcanism exerted a control on the depositional conditions.
Keywords
Late Toarcian, Cañadón Asfalto Formation, U–Pb geochronology, Palaeoenvironment, Argentina
Funding(s)
Swiss National Science Foundation
Create date
18/10/2020 9:02
Last modification date
01/06/2024 6:18