Integrating multiproxy results (geochemistry, mineral magnetism, grain size, and C/N ratio variability supported by 14C AMS dating), obtained from a 1.4-m sediment core retrieved from high-altitude ...Anchar Lake, Kashmir Valley, NW Himalaya, we present a 6000-years record of paleoenvironmental and paleolimnological shifts. Phase 1 (6000–4700 cal. yr BP) revealed a wetter climate with a significant terrestrial input corresponding to the gradual strengthening of the westerlies. Phase 2 (4700–3900 cal. yr BP) reflects an overall improved westerly precipitation and autochthonous sources of organic matter (OM). Magnetic parameters also indicate higher lake levels and reducing conditions during this phase. Phase 2 was followed by a gradual diminishing pattern of the westerlies as also represented by phase 3 (3900–2500 cal. yr BP) and phase 4 (2500–1600 cal. yr BP) indicating moderate precipitation conditions, catchment stability, and temperate and/or cold-dry climatic conditions. Phase 5 (1600–500 cal. yr BP) revealed the prevalence of moderately cold/dry and further subdued westerly precipitation. Phase 6 (500 cal. yr BP to present) is represented by reduced westerly precipitation, shrinking lake margins, and significant terrestrial/anthropogenic controls over the lake basin. Mineral magnetic parameters indicate reducing lake bottom water conditions and eutrophication during this phase due to anthropogenic activities. These paleoenvironmental shifts reveal near synchronous changes (within dating uncertainties) with other regional paleoclimate records close to the present Anchar Lake location and reflect the gradual late-Holocene diminishment of the amount of winter/early summer moisture provided by the mid-latitude westerlies.
Gangotri glacier located in the Uttarkashi District of the Garhwal Himalaya, is one of the longest valley glacier. It exhibits Lateral Moraines (LM), Recessional Moraines (RM), Kame Terraces (KT) and ...Outwash Plains (OWP) as important landforms. The sediments coded in these landforms, provide the information about sedimentary characteristics, and the evolutionary history of the Gangotri Glacier Region (GGR). The Gangotri is a well studied glacier, however the sedimentological characteristics and evolution of many landforms are yet to be understood. Therefore, present paper aimed to explain the sedimentological characteristics and the evolutionary history of the outwash plain deposits.The OWP deposits were studied by making a trench near Bhujbas and collecting the samples from it. The granulometric analysis explain that the mean grain size of the OWP sediments varies from 0.258 φ to 2.006 φ indicate coarse to medium sand. The skewness, varies from 0.138 φ to 0.427 φ indicate dominance of fine grained sediments. The kurtosis varying from 0.839 φ to 1.067 φ explain the dominance of finer sediments. The standard deviation varies from 1.210 φ to 1.633 φ thus indicating poor sorting of the OWP deposits and fluctuation in the energy of the depositional environment. Five sedimentary facies identified are gravel sandy facies, ripple laminated silty sand facies, sandy facies, poorly sorted sandy facies and silty sand facies.The study describes that the OWP deposits are stratified, consolidated to semi-consolidated, coarse to fine grained silt, sand and gravels with primary sedimentary structures, which are evolved by glacio-fluvial environment under fluctuating energy conditions during the late Holocene period.
•Six habitation-flooding timelines are recognized from the Vaigai River Basin.•Continuum of multiple stages of civilization since microlithic-recent times.•Origin and demise of habitation sites ...controlled by climatic and fluvial dynamics.•Coexistences of multiple groups that practiced varied cultural customs.•Preexistent practice of burning-burial of deceased than many other civilizations.
Recent studies have unearthed and recovered multiple sites with evidences of past human habitations in terms of ceramic, metal, precious stone, jewel, and stone tool industries and places of varied methods of burial and worship are being unearthed at different stratigraphic levels from floodplains of the Vaigai River Basin, Southern India. In this contribution, we present high-resolution 14C chronology of the archaeological artefacts, cultural evidence and the textural characteristics of sediments collected from the excavated pits. These data along with the information on regional geology, geomorphology, sedimentary facies, texture, petrography, and mineralogy constrain the older phase of the Vaigai River Basin Civilization to be microlithic in age, followed by affirmative evidence of ca. 5511-5147 BCE (7455-7091 cal yr BP). This was followed by few more colonization/cultural/habitation sites/surfaces at ca. 2976-2961 BCE (4938-4908 cal yr BP), 1860-1489 BCE (3543-3503 cal yr BP),530-390 BCE (2435-2314 cal yr BP), 596-629 CE (1353-1321 cal yr BP) and post 1225-1312 CE (729-619 cal yr BP). These are designated as habitation sites/surfaces namely HS-1, HS-2, HS-3, HS-4, HS-5 and HS-6, respectively. Evidences of urbanism, industrial and leisure activities besides cohabitation of at least three groups that practiced mutually exclusive burial customs are documented. Microlithic tools and buried habitation stages, together with the prevalence of modern habitations, make this basin unique with human occupation at least since the mid-Holocene. Major shifts of the trunk channel of the Vaigai River, perhaps associated with flood events, marooned/buried/destroyed the ancient habitation sites that forced the inhabitants to abandon old sites and led to the reestablishment of newer ones. Inevitable dependence of the ancient societies on the riverbanks and the flood plains for settlements and livelihood compounded with the lack of knowledge on extreme climatic events possibly caused the decimation of several settlements of this important civilization from south India.
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The semi-arid Ladakh region in the Trans Himalaya forms an environmental boundary between North Atlantic and monsoon forcings. Its location in the transient setting of these two climate systems ...enables to attest slight changes in the dynamics of these components of atmospheric circulation. Variation in climatic conditions from 19.6 to 6.1 ka using multi-proxy investigation (mineral magnetism, stable carbon isotope, palaeoprecipitation, sediment grainsize end member analysis, clay mineralogy and TOC) is studied from Khalsi palaeolake deposit in Ladakh. Considering the inherent uncertainty of radiocarbon chronology, the present study provides millennial to multi-centennial scale resolution of climate variation from the sediment sequence. The results indicate cold arid climate influenced by Westerly circulation for the last 19.6 to 11.1 ka, thereafter from 11.1 to 7.5 ka, monsoon forcings dominated the climate of the region, following the orbitally controlled solar insolation that influenced the position of ITCZ and formed the key driver of the variability of these atmospheric circulations. A short wet phase from ∼17.4 to 16.5 ka within the dominant Westerly period is attributed to the early wet phase of two-fold H1 event. Westerly regained strength from 7.5 to 6.1 ka during the mid-Holocene coinciding with decreasing insolation, weakening monsoon and enhanced El Niño activities.
•Palaeoclimate variations reconstructed from palaeolake record, Ladakh•Westerly dominated from 19.6 to 11.1 ka and from 7.5 to 6.1 ka.•A short wet phase from ∼17.4 to 16.5 ka attributed to early wet phase of H1 event.•ISM dominant from 11.1 to 7.5 ka.
Landform geomorphology and glacial lake deposits in the largest drainage basin of the Ladakh Range i.e. Chang La-Tangtse basin were studied to infer their palaeoclimatic significance. The grain size, ...mineral magnetism, percentage loss on ignition (%LOI) and organic carbon stable isotope (δ13C) data in combination with total organic carbon (TOC) supported by AMS 14C (calibrated) dates of a 190 cm long section from the Chang La-Tsoltak palaeolake provides a climatic record since the last ∼ 7075 cal yr BP. The χlf, χARM, and SIRM values suggest that the catchment-derived palaeolake sediments predominantly contain magnetically “soft” minerals like magnetite and maghemite. The δ13C values range between −21 and −24 ‰ with an average of –22 ‰ which suggests a mixed C3-C4 plant signature and water stressed ecosystem. The relatively small variations in the δ13C values of organic matter in the entire lake profile suggest a stable climatic condition. The prominent effect of westerlies is seen between 7075 and 6040 cal yr BP with huge detrital influx at the lake bottom indicating a glacial advancement in the region. The affect of Mid-Holocene warm period is evident at 6040 cal yr BP with the advent of ISM. Paradigm shifts in the proxy values are observed at 5710, 4890, 3435, and 2800 cal yr BP. The influence of westerlies gradually reduces at 2800 cal yr BP. The landscape evolution and the climatic variations in the Trans-Himalaya are primarily governed by westerlies and do not correspond to the Indian monsoon variability records, particularly during the Mid-Holocene Thermal Maxima. Several other regions of the Ladakh Range also record similar climatic variations, indicating that the palaeolake sediments also reflect regional climate variations.
•Spatial distribution of CO2ff and Δ14C across India using crop plants have been studied.•Δ14C values in the year 2017 are ranging from 29.33‰ to -34.06‰ across India.•CO2ff mole fractions are ...varying from 4.85 ppm to 26.59 ppm across India in the year 2017.•Sampling of storage organs in place of leaves in crop plants can induce a difference of 2.30 ppm in CO2ff values.•Radiocarbon in crop plant can be utilized in India to asses the CO2ff emissions in the absense of proper monitoring stations.
Examining the contribution of fossil fuel CO2 to the total CO2 changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe, specifically developing countries. Atmospheric radiocarbon represents an important observational constraint and utilized to trace fossil fuel derived CO2 (CO2ff) in the atmosphere. For the first time, we have presented a detailed analysis on the spatial distribution of fossil fuel derived CO2 (CO2ff) over India using radiocarbon (Δ14C) measurements during three-year period. Analysis shows that the Δ14C values are varying between 29.33‰ to -34.06‰ across India in the year 2017, where highest value belongs to a location from Gujarat while lowest value belongs to a location from Chhattisgarh. Based on the Δ14C patterns, spatial distributions of CO2ff mole fractions have been determined over India and the calculated values of CO2ff mole fractions are varying between 4.85 ppm to 26.59 ppm across India. It is also noticed that the highest CO2ff mole fraction is observed as 26.59 ppm from a site in Chhattisgarh. CO2ff mole fraction values from four high altitude sites are found to be varied between 4.85 ppm to 14.87 ppm. Effect of sampling different crop plants from the same growing season and different crop plant organs (grains, leaves, stems) on the Δ14C and CO2ff have been studied. Annual and intra seasonal variations in the Δ14C and CO2ff mole fractions have also been analyzed from a rural location (Dholpur, Rajasthan).
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This paper presents a review of Late Quaternary climatic changes and glacier variability in the Himalaya and East Africa, focusing on the role of Indian Summer Monsoon (ISM), East African monsoon, ...and Westerlies monsoons. Multi-proxy studies which are based on five different archives (lakes, peat bogs, speleothems, marine sediments, and ice cores) including sixty-six records from India and nearby regions, particularly in the Himalaya and in addition to six archives from the equatorial Eastern part of Africa encompasses with high-resolution published and unpublished records for the last 50 ka BP. The proxy data is discussed towards REMO-ESM model Coupled Model Intercomprasion Project phase 5 (CMIP5 Project) results. Our results indicate that both Western Himalaya and East Africa had undergone mega-droughts from ~17.0–15.0 ka BP, and precipitation had increased during the Early Holocene (10.0–7.0 Ka BP) during the time span when the Westerlies dominated regions. The model results suggest that the Westerlies monsoon has significantly contributed to the Northwestern Himalaya and somewhat to a lesser degree to the Western Himalaya and lower solar insolation in the winters did support the glacier advance during the LGM. The time series from the proxy data are compared with glacier fluctuations in different valleys to understand the response of the aforementioned monsoon system including other forcing factors which drive these variabilities. The review results indicate that the Westerlies was the main driver of the climate and glacier fluctuations in Northwestern Himalaya during the Late Quaternary. The Early and Late Holocene glacier fluctuation was mainly controlled by Westerlies precipitation in Northwestern Himalaya and the ISM controlled the glacier fluctuations in the Western Himalaya during Late Quaternary.
We present a comprehensive record of Holocene (11,590–628 cal. yr BP) climate and hydrographic changes around the Wular Lake located in Kashmir Valley, India. Based on the multi-proxy investigations, ...we have identified three phases of wet climate conditions that prevailed from the commencement of the Holocene Epoch – 9000 cal. yr BP, 8100–6650 cal. yr BP and 6350–5000 cal. yr BP, whereas periods of dry climate were observed during 9000–8100 cal. yr BP, 6650–6350 cal. yr BP and ~5000 to 4000 cal. yr BP. The results also suggested that the lake widened and deepened significantly around 6350–5000 cal. yr BP. The results indicated desiccation and the exposure of the lake margin around 5000–4500 cal. yr BP. The sedimentation rate since 4500–628 cal. yr BP was quite low for detailed paleoclimate interpretations. Oscillations in lake extension and deepening appear to be due to changing intensity of westerly moisture in the region, and we correlate several of the low lake-level phases to the Bond events caused by North Atlantic ice rafting events.
Multiproxy data of pteropods and planktic foraminifera from Core SK291/GC17 suggest significant surface paleoceanographic shifts from ∼25,000 to 3500 calibrated years before present (cal yr BP) in ...the eastern Arabian Sea (EAS). Increased values of the global ice-volume free stable oxygen isotope ratio of seawater (δ18Osw IVF) and stable oxygen isotope ratio in pteropod (δ18OH. inflatus IVF), as well as lower percentages of planktic foraminifer Globigerina bulloides from ∼22,000 to 18,000 cal yr BP, correspond to the weak Indian summer monsoon (ISM) during the Last Glacial Maximum (LGM). In the early Holocene, the EAS witnessed an increase in upwelling driven by strong summer monsoon winds, and a decrease in salinity corresponding with enhanced precipitation in the Western Ghats region. From ∼4800 to 4000 cal yr BP, including the 4.2 ka event, a prominent increase in the δ18OH. inflatus IVF values suggest an enhanced intrusion of the Arabian Sea High Saline Water (ASHSW) to the relatively deeper part of the mixed layer. In the same interval, the low representations of G. bulloides and thermocline dwelling planktic foraminifera indicate weakening of the coastal upwelling and a reduction in surface productivity due to weak ISM across the Arabian Sea, with more severe conditions in the EAS.
•During the Last Glacial Maximum, upwelling decreased in the eastern Arabian Sea.•Pronounced upwelling and freshening of surface waters in the early Holocene off the coast of Goa.•Weakening of the Indian summer monsoon was more severe during 4.2 ka event than Last Glacial Maximum.
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