Be Isotope in Ross Sea Sediment core

Hypothesized oceanographic conditions in the Ross Sea over the past 773 ka, illustrated alongside representative X-ray images corresponding to key time intervals. Please note that the thickness of the (10Be/9Be)reac “reaction rim” conceptually represents the efficiency of Be isotope scavenging under different environmental conditions. (a) Ice-sheet distal depositional setting during the interglacial period from 250 ka to the present. This interval is characterized by a strengthened inflow of Circumpolar Deep Water (CDW). As the ice sheet retreated, sediment transit time to continental rise increased, allowing for greater accumulation of (10Be/9Be)reac in open marine conditions. Enhanced surface productivity is evident, reflecting the dominance of interglacial conditions. In contrast, Deep Shelf Water (DSW) production declines due to reduced sea-ice coverage. (b) Relatively warm interval between 550 and 250 ka with partial sea-ice advance. CDW influx remains moderately high, and sediment particles acquire moderate levels of (10Be/9Be)reac , though lower than the 250 ka–present interval due to shorter sediment transit times. Primary productivity is also moderately elevated. (c) Ice-sheet proximal depositional setting during 750–550 ka. This period is marked by intensified DSW production and reduced CDW influx. Strong DSW formation initiates gravity-driven sediment flows, redistributing shelf sediments to the outer continental margin. The (10Be/9Be)reac ratio is relatively low, indicating that when the ice sheet advanced to the shelf edge, sediment transit time in open marine settings was limited, leading to reduced scavenging of Be isotopes.

ROSS SEA, ANTARCTICA

Environmental Magnetic Study on Chilika Lagoon Sediment Core

Core sediments from the Chilika Lagoon in the eastern part of the Core Monsoon Zone (CMZ) of India have provided a record of local environmental changes and catchment processes during the past 7800 cal. years B.P. Variations in the rock magnetic parameters (, , and IRM's at varying field strengths) of sediment samples reflect climate-induced changes in the Chilika Lagoon catchment. The down-core variations in the concentration-dependent magnetic parameters indicate an intensified summer monsoon and enhanced terrigenous input to the lagoon during the Early to Mid-Holocene (∼7.8 ka to ∼ 5.5 ka B.P.). In contrast, the Mid- to Late Holocene period witnessed a weaker Indian Summer Monsoon Rainfall (ISMR) and less terrigenous input to the lagoon, with an intermediate phase of strengthened monsoon around 2 to 1 ka B.P. Spectral analysis of sedimentary magnetic susceptibility () data show significant periodicities (at 95 % significance level) of 2523, 573, 147, 93, 59, and 55 years, which are in agreement with the periodicities shown by other paleoclimatic proxies from the region.

Indian Summer Monsoon and Sediment Dynamics

Climate-induced denudation of the Eastern Ghat during the Holocene: A multi-proxy study from Chilika Lagoon (India)

A Holocene sediment record from Chilika Lagoon, India, suggests that changes in climate control denudation and weathering rate change. We assessed climate variability in the region and through time using multiproxy data comprising biotic and abiotic proxies. Mangrove and its associate assemblages suggest a backwater estuarine environment between ∼7.8 and 6 ka B.P. Depleted δ13Corg values during ∼7.8 to 5.5 ka B.P. indicate dominance of C3 vegetation, suggesting a warmer climate and strengthened monsoon. Enhanced δ13Corg and absence of pollen/spores are observed in the sediment layers deposited after ∼5 ka B.P., indicating arid climatic conditions with a dominance of C4 photosynthesizing plants and a relative lowering of sea level. Paleodenudation rates estimated using 10Be/9Be ratios varied between 556 ± 35 to 242 ± 15 t.km−2.yr−1. Phases of intense denudation occurred during 7.8–6.7 and 2.2–1 ka B.P., corresponding to Holocene Climatic Optimum and Medieval Climatic Anomaly, respectively. The degree of chemical weathering appears to have gradually increased from the early to late Holocene and correlates well (negatively) with the denudation rate. A gradual increase in the degree of chemical weathering from the early to late Holocene suggests an increase in the residence time of minerals in the weathering zone as the monsoon weakened.

Eastern Ghat Weathering and Erosion

Mechanism of formation of terminal fans. Terminal fan associated with (A) normal fault (B) reverse fault, (C) Jharni terminal fan (JTFn) (D) Gandak terminal fan-I (GTFn-I) in the Rapti–Gandak block.

Neotectonism in Ganga Plain

Segmentation and fan building episodes in the upper and middle Gangetic plains. The figure shows a transitional shift of tectonic front from the upper to the middle Gangetic plain. Circles A, B, and C are the minor (in magnitude of 500 years) tectonically stable periods.

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