Evolution of continental weathering conditions during the Albian-Santonian interval: influences of tectonics, eustatism and climate on the formation and recording of clay minerals - Sorbonne Université Access content directly
Conference Papers Year : 2023

Evolution of continental weathering conditions during the Albian-Santonian interval: influences of tectonics, eustatism and climate on the formation and recording of clay minerals

Abstract

The Albian-Santonian interval (113-83 Ma) is considered as a “hothouse” period characterized by volcanism episodes, high sea-level and low tectonic activity. This 30 Myr-longed interval is characterized by a gradual increase of temperature in oceanic domain, which culminates during the mid-Cretaceous thermal maximum, at the end of the Cenomanian (~ 94 Ma). The evolutions of continental weathering and climatic conditions have been documented by 50 years of research on clay mineral assemblages, mainly based on studies in the north hemisphere and in low latitudes of the south hemisphere. The compilation of all the data from more than 75 boreholes and continental sections and the acquisition of new ones at high latitudes of the southern hemisphere provides a better comprehension of the variations observed in the clay mineral assemblages at this period. During Albian, illites are abundant on the Western African and North American margins and are gradually substituted by smectites from the Turonian. The decrease of illites in favour of smectites indicates the major influence of the differential settling of clay minerals associated to the global sea-level rise. These variations also characterize the decrease of tectonic activity on the Western African and North American margins by the decrease of the physical dismantling of the massifs and the development of pedogenetic processes. The Cenomanian and Turonian times are characterized by high proportions of kaolinites recorded in low latitudes and middle to high latitudes of the Northern Hemisphere. These clay minerals form nowadays in tropical climatic belt and thus are thought to reflect strong hydrolysis conditions especially at low latitudes. The high proportions of kaolinites in sectors, like the Benue Trough and the Ivorian Basin, where tectonic activity was active a short time before kaolinite increase, also demonstrates the influence of high reliefs on the formation of kaolinites. The well-drained steep slopes allow the removal of the cations in solution during hydrolysis which leads to the formation of kaolinites. In the Northern Hemisphere, the decrease in palygorskite proportions at low latitudes coupled to the increase in the kaolinite proportions at mid- and high-latitudes reflects a warmer and wetter climate during the Turonian. In contrast, in the Southern Hemisphere, the Turonian is characterized by a decrease in the proportions of kaolinites and the appearance of palygorskites. These differences can illustrate a driest climate in the southern hemisphere. It could also reflect poorly-drained relief without evacuation of leachate solutions which prevent the formation of kaolinites. These flat landmasses are also favourable to the formation of peri-oceanic basins, subject to marine incursions, evaporation and the formation of palygorskites. During Coniacian and Santonian, the low proportion with respect to smectites indicate reduced hydrolysis conditions compared to the Turonian and poor drainage conditions, associated with the absent of any tectonic activity and flattened landmasses. Clay mineral assemblages recorded in marine sediments demonstrate a decrease in physical weathering and an increase in hydrolysis conditions from the Albian to the Turonian at low latitudes. At the same time, the enrichment in smectites at high latitudes reflects a reduced chemical alteration and poor drainage conditions due to the lack of major landforms. Finally, the high sea-level and the low reliefs lead to the formation of smectites during Coniacian and Santonian times.

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Earth Sciences
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Dates and versions

hal-04198479 , version 1 (07-09-2023)

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  • HAL Id : hal-04198479 , version 1

Cite

Thomas Munier, Laurent Riquier, François Baudin. Evolution of continental weathering conditions during the Albian-Santonian interval: influences of tectonics, eustatism and climate on the formation and recording of clay minerals. Euroclay 2023, Jul 2023, Bari, Italy. ⟨hal-04198479⟩
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