Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

Abstract

The climate variability over western India has been significantly influenced by the perturbations in the Indian summer monsoon (ISM) and thus, provides a crucial platform to investigate the paleomonsoon variations, weathering intensity, and sediment source. The mudflats of southern Saurashtra, western India are deprived of perennial rivers, but the region receives terrestrial contribution exclusively due to activation of seasonal rivers during the monsoon. In the present study, an attempt has been made to investigate the paleomonsoon and palaeoweathering using various geochemical proxies (detrital, productivity, redox, and weathering) on the mudflat sediment core of southern Saurashtra, western Gujarat. The core is chronologically constrained by 14 C, 210 Pb, and 137 Cs dating techniques. The study suggests ISM strengthening during 2000-1800 cal yr BP with intermittent marginal ISM weakening during 1950-1970 cal yr BP and 1930-1890 cal yr BP associated with the reduced solar irradiance. Further, ISM weakening has been invoked during Dark Age Cold period (1800-1300 cal yr BP) and Little Ice Age (800-200 cal yr BP) interrupted by a marginal ISM strengthening during Medieval Warm period and the last two centuries witness climate warming. Based on historical rainfall data and Al 2 O 3, an intermittent strengthening of ISM during 90-30 cal yr BP has been suggested while a gradual increase in the weathering intensity synchronous to the rise in sea surface temperature (SST) during the last 200 cal yr BP revealed the role of temperature on the intensity of chemical weathering in the study area. In spite of changes in the geochemical proxies as a function of ISM fluctuations, the palaeoweathering intensities has remained nearly consistent wherein the chemical weathering was less operative and accompanied by the deposition of texturally immature sediments. The sediments of Diu mudflat indicate mafic signatures thereby underscoring a major contribution of the Deccan basalts along with other variable sources.

Geochemistry of meta‐sediments from Neoproterozoic Shimla and Chail Groups of Outer Lesser Himalaya: Implications for provenance, tectonic setting, and paleo‐weathering conditions

“…The rock/sediment geochemistry, U–Pb isotopes from accessory minerals (zircon, monazite, titanite, etc.) and mineral inclusions within zircon have been widely used to distinguish the rock/sediment source (Banerji et al, 2021a; Bruand, et al, 2016; Basu, Bickford, & Deasy, 2016; Joshi, Goswami, Banerji, & Shankar, 2021a; Slabunov et al, 2017). Studies have demonstrated that the chemical composition of fine‐grained sediments is related to that of their source regions (Dey, Rai, & Chaki, 2009; Manikyamba, Kerrich, González‐Álvarez, Mathur, & Khanna, 2008).…”

“…Mixing and homogenization of compositionally diverse source rocks due to the combined processes of erosion, transportation, deposition, and diagenesis render Post‐Archean sedimentary rocks with a certain degree of geochemical uniformity (McLennan & Taylor, 1991; Taylor, Rudnick, McLennan, & Eriksson, 1986). However, previous studies (Absar, Raza, Roy, Naqvi, & Roy, 2009; Banerji, Bhushan, Joshi, Shaji, & Jull, 2021a; Basu, Dandele, Kumar, Achar, & Umamaheswar, 2017; Bhat & Ghosh, 2001; El‐Bialy, 2013; McLennan, Hemming, Taylor, & Eriksson, 1995; Shukla, George, & Ray, 2020) have suggested that the geochemical characters of sediments and sedimentary rocks can yield reliable insights into the provenance, prevalent weathering conditions, secondary processes (K‐metasomatism), and tectonic setting of the depositional basin.…”

“…The rock/sediment geochemistry, U-Pb isotopes from accessory minerals (zircon, monazite, titanite, etc.) and mineral inclusions within zircon have been widely used to distinguish the rock/sediment source (Banerji et al, 2021a;Bruand, et al, 2016;Basu, Bickford, & Deasy, 2016; Joshi, Goswami, Banerji, & Shankar, 2021a; Slabunov F I G U R E 8 (a) Th/Sc versus Zr/Sc plot for Shimla and Chail meta-sediments (McLennan, 1993) and (b) A-CN-K plot (Nesbitt & Young, 1984, 1989 illustrating weathering trend of Shimla and Chail meta-sediments. Extrapolation of weathering trend (green) to the feldspar join reveals a granodioritic provenance et al, 2017).…”

The geochemical and pedogenic signatures of Shantisagara lake sediments, southern India: Implications for weathering, terrigenous influx, and provenance during the Holocene

“…Several studies of lacustrine sediments from China suggest that chemical weathering proxies are ideal tools to reconstruct the monsoonal strength in the region (Huang, Wei, & Li, 2018; Liu et al, 2014; Wang et al, 2019; Zhang, Ming, & Shi, 2016). The geochemical proxies from lacustrine sediments of the northern (Babeesh, Achyuthan, & Resmi, 2019; Bhushan, Sati, & Rana, 2018; Shah, Achyuthan, & Lone, 2020) and northwestern India (Banerji, Bhushan, Joshi, Shaji, & Jull, 2021; Roy, Smykatz‐Kloss, & Morton, 2008; Sinha, Smykatz‐Kloss, & Stüben, 2006) were employed to infer the past changes in rainfall. However, only a few studies have been done on the geochemical properties of lake sediments from southern India.…”

“…The geochemical proxies from lacustrine sediments of the northern (Babeesh, Achyuthan, & Resmi, 2019;Bhushan, Sati, & Rana, 2018;Shah, Achyuthan, & Lone, 2020) and northwestern India (Banerji, Bhushan, Joshi, Shaji, & Jull, 2021;Roy, Smykatz-Kloss, & Morton, 2008;Sinha, Smykatz-Kloss, & Stüben, 2006) were employed to infer the past changes in rainfall. However, only a few studies have been done on the geochemical properties of lake sediments from southern India.…”