Phased evolution and variation of the South Asian monsoon, and resulting weathering and surface erosion in the Himalaya–Karakoram Mountains, since late Pliocene time using data from Arabian Sea core

Abstract

We investigate the phased evolution and variation of the South Asian monsoon and resulting weathering intensity and physical erosion in the Himalaya–Karakoram Mountains since late Pliocene time (c. 3.4 Ma) using a comprehensive approach. Neodymium and strontium isotopic compositions and single-grain zircon U–Pb age spectra reveal the sources of the deposits in the east Arabian Sea, and show a combination of sources from the Himalaya and the Karakoram–Kohistan–Ladakh Mountains, with sediments from the Indian Peninsula such as the Deccan Traps or Craton. We interpret shifts in the sediment sources to have been forced by sea-level changes that correlate with South Asian monsoon rainfall variation since late Pliocene time. We collected 908 samples from the International Ocean Discovery Program Hole U1456A, which was drilled in the east Arabian Sea. Time series of hematite content and grain size of the sediments were examined downcore. We found South Asian monsoon precipitation and weathering intensity experienced three phases from late Pliocene time. Lower monsoon precipitation, with a lower variability and strong weathering intensity, occurred during 3.4–2.4 Ma; an increased and more variable South Asian monsoon rainfall, along with strengthened but fluctuating weathering intensity, occurred at 1.8–1.1 Ma; and a reduced rainfall with lower South Asian monsoon precipitation variability and moderate weathering intensity marked the period 1.1–0.1 Ma. Maximum entropy spectral analysis and wavelet transform show that there were orbital-dominated cycles of periods c. 100 and c. 41 ka in these proxy-based time series. We propose that the monsoon, sea level, global temperature and insolation together forced the weathering and erosion in SW Asia.

Climate–tectonic interactions in the eastern Arabian Sea

“…They noted that sandy turbidite deposits tended to be associated with high 87 Sr/ 86 Sr ratios and low ɛ Nd values, likely linked to erosion from the Himalayas and delivered by the Indus River. As in the Kumar et al (2019) and Lu et al (2020) studies, they propose that sea level plays a critical role in controlling sediment flux into the basin.…”

“…Change in the source of siliciclastic material to the submarine fan was reconstructed since 3.4 Ma by Lu et al (2020) using a combination of neodymium and strontium isotopes, together with single-grain zircon U–Pb age data. These authors show that the sediments represent a combination of erosion from the Himalayas, Karakoram and Kohistan–Ladakh, as well as some sediment flux from the peninsula of India, including the Deccan Traps and Indian Craton.…”

Variability of indian monsoon and its forcing mechanisms since late quaternary

“…In addition, the glacial-interglacial cycles lead to sea level fluctuations, such as the extensive exposure of marginal sea shelf during the glacial period, which may affect the spatial distribution pattern of precipitation in the provenance (Cai et al, 2015). Moreover, the changes of local ocean currents and shelf material transport in glacial-interglacial cycles may also lead to local environmental variations in marine sediments (Wang et al, 2014;Lu et al, 2020). Thus, how to effectively separate the temperature signals from the geological record of the summer monsoon is still worthy of further study.…”

“…The influence of Earth orbital forcing on the long-term evolution of Indian monsoon has been recorded in deep-sea cores, lake sediments and stalagmites (Ziegler et al, 2010a;Cai et al, 2010;An et al, 2011). Previous researches demonstrated that the climate evolution of Indian monsoon is dominated by precession (~23 ka), obliquity (~41 ka) and eccentricity (~100 ka) cycles (e.g., Clemens et al, 1996;Clemens and Prell, 2003;Kelly et al, 2005;Kunkelova et al, 2018;Lindhorst et al, 2019;Lu et al, 2020). Previous orbital-scale studies of the ISM mainly used proxies of phytoplankton (G. bulloides) from the northern Arabian Sea (Prell et al, 1984;Prell and Van Campo, 1986;, grain size (Clemens and Prell, 1990;Krissek and Clemens, 1992), Ti/Al and excess Ba MAR (Shimmield et al, 1990), biogenic opal and organic carbon MAR (Murray and Prell, 1991).…”

Monsoon‐Enhanced Silicate Weathering as a New Atmospheric CO2 Consumption Mechanism Contributing to Fast Late Miocene Global Cooling

“…Thus, the East Asian monsoon region provides an ideal case for revealing intriguing and complex tectonic-climate interactions. For example, many previous studies have investigated Asian monsoon development with changes in Neogene mountain exhumation, silicate weathering, and the associated CO 2 consumption (e.g., Clift et al, 2008Clift et al, , 2014Lu et al, 2020;Van Hoang et al, 2010;Wan et al, 2012). In particular, the Chinese Loess Plateau (CLP) in north China, an area that is very sensitive to variations in the East Asian summer and winter monsoons, has accumulated long, continuous eolian sequences within the large platforms on the eastern portion of the plateau (An et al, 2001).…”