Clay Mineralogy of the Zhada Sediments: Evidence for Climatic and Tectonic Evolution Since ~9 Ma in Zhada, Southwestern Tibet

Abstract

The clay mineralogy of the Zhada sediments was investigated, using X-ray diffraction and scanning electron microscopy, to obtain a better understanding of climatic change and uplift of the Himalayas in the Zhada region of Tibet. The sediments of Zhada basin in the late Miocene to Pliocene consist of lacustrine and fluvial deposits >800 m thick and can be subdivided into five clay assemblage zones based on their clay-mineral composition. The upward zonation is as follows: (1) smectite-kaolinite;(2) illite-chlorite; (3) chlorite-illite-kaolinite; (4) illite-chlorite; and (5) smectite, illite, and kaolinite. The ratio of chlorite + illite to kaolinite + smectite (Ch+I/K+S) and the Kü bler index indicate a warm and humid climate from 9.5 to 8.4 Ma, a cold and dry climate from 8.4 to 7.2 Ma, a warm and seasonal arid climate from 7.2 to 4.5 Ma, a cool and humid climate from 4.5 to 3.6 Ma, and a warm and seasonally humid climate from 3.6 to 3.0 Ma. Intense fluctuations in the Kü bler index and in the quantities of evaporite minerals dolomite, aragonite, and gypsum, during the period 7.2À4.5 Ma suggest strong climatic fluctuations between humid and seasonally humid conditions in the Zhada basin. Rapid uplift around the Zhada basin occurred at 8.4 and 3.6 Ma, with sharp subsidence at 7.2 and 4.5 Ma. Evolution of the climate at Zhada showed a different model from that of global climate change, and tectonics-led climate change was the major contributor to climate evolution in the area.

Elevated physical weathering exceeds chemical weathering of clays during the Paleocene-Eocene Thermal Maximum in the continental Bighorn Basin (Wyoming, USA)

“…Tectonic activity can affect the clay mineral assemblages and proportions by intensifying the denudation and recycling of parent rocks from the hinterland, while this process is anticipated to have an impact at relatively long time scales (eg. Hong et al, 2010Hong et al, , 2012b. No change in provenance has been observed across the Fort Union to Willwood formations and so tectonics are not related to the shifts in clay mineralogy during the PETM (May et al, 2013;Welch et al, 2022).…”

“…Increased physical weathering and erosion on the other hand could be the cause of the smectite increase during the PETM. Factors including tectonic activity and climate change driving hydrological conditions and transportation may control detrital clay mineral assemblages and proportions (Hong et al, 2012b;Liu et al, 2016;Zhao et al, 2018). Tectonic activity can affect the clay mineral assemblages and proportions by intensifying the denudation and recycling of parent rocks from the hinterland, while this process is anticipated to have an impact at relatively long time scales (eg.…”

Tectono-stratigraphic and sedimentological analysis of the Early to Middle Devonian Floresta Formation: Insights from the Floresta Massif, Northern Andes, Colombia

“…In the samples analyzed (Fig. 10), clay minerals usually occur as particles that exhibit irregular and rounded outlines, indicating a detrital origin (e.g., Jouanneau and Latouche, 1981;Hong et al, 2012;Turner and Huggett, 2019;Virolle et al, 2019). In general, clay minerals show a flaky morphology with a bent shape and relatively smooth basal (001) planes, and their lateral surfaces are very uneven, with irregular outlines or ragged edges.…”

“…In general, clay minerals show a flaky morphology with a bent shape and relatively smooth basal (001) planes, and their lateral surfaces are very uneven, with irregular outlines or ragged edges. According to Hong et al (2012), the lateral dimensions of the clay flakes are poorly defined, with particularly thin plates and well-developed fissures, suggesting an origin in detrital clasts. Both illite and illite/smectite may also occur with a ragged or platy morphology, developing sometimes lath-shaped overgrowths (e.g., Pollastro, 1985;Inoue et al, 1988;Hugget, 1995).…”

Early middle Miocene tectonic uplift of the northwestern part of the Qinghai–Tibetan Plateau evidenced by geochemical and mineralogical records in the western Tarim Basin

“…These uplifts potentially caused regional aridification reducing chemical weathering. The dating is indirect via magnetostratigraphically dated ostracod biostratigraphy and detrital zircon chronology and currently not good enough to compare the shift accurately in time with the onset of the global middle Miocene Climate Plateau, such as the Qaidam, Xining, Linxia, Girong, and Zhada basins (Dettman et al 2003;Dupont-Nivet et al 2008;Graham et al 2005;Hong et al 2007Hong et al , 2010Hong et al , 2012Rieser et al 2009). The relationship between uplift of the QTP and climate change remains scarcely documented in the Tarim Basin.…”