Holocene environmental magnetic records of Indian monsoon fluctuations

Basavaiah, N.; Seetharamaiah, J.; Appel, Erwin; Juyal, Navin; Prasad, Sushma; Rao, K. Nageswara; Khadkikar, Aniruddha S.; Nowaczyk, Norbert R; Brauer, Achim

doi:10.1016/b978-0-323-90085-0.00004-8

Cited by 3 publications

(2 citation statements)

References 56 publications

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“…The S-ratio of 0.81 indicates that a small proportion of antiferromagnetic minerals are present in sample 2V of rock varnish (Table S1). A ratio of 1 indicates that the ferrimagnetic mineral magnetite is the primary remanence carrier, and as the proportion of hematite in a mixture increases , the S-ratio decreases (Basavaiah and Khadkikar, 2004;Bloemendal et al, 1992;Liu et al, 2012). Temperature variation magnetic susceptibility scans (χ-T) in samples RV1, RV2, and RV3, on varnish and host rock are less resolvable.…”

Section: Resultsmentioning

confidence: 99%

Ladakh's Rock Varnish: A potential Geomaterial for astrobiological studies

Chaddha,

Sharma,

Singh

et al. 2023

Preprint

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Rock varnish, a dark-coloured natural feature rich in manganese (Mn), iron (Fe), and clay minerals, is believed to provide nutritional support to microbiota. Thus, rock varnish is considered a unique substrate for potential microbial life to thrive in the extreme environments on Earth that are comparable to their planetary analogues. However, little is known about the occurrence of microbiota in rock varnish, as the microbes found on the varnish are quite diversified. We present here the new morphological and chemical results of microbial forms found in rock varnish samples from Ladakh, a potential site for hosting life in extreme environments. Our results demonstrate the presence of putative magnetofossils type biological entities in the form of nanochains present in the rock varnish layer that coincide with high magnetic susceptibility values of varnish samples. Further, the higher concentrations of oxidised fractions of Mn 4+ , and carboxylic acid functionality on the varnish surface revealed the signatures of organic entities. These collective results point towards the enriched concentration of magnetic minerals on the varnish layer that are possibly sourced through biotic forms. Consequently, the rock varnish can serve as a "black box" of ancient environmental records, as well as a potential geomaterial for astrobiological studies from the Martian analogue field location of Ladakh, which needs to be explored further for extensive biogeochemical studies.

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Section: Resultsmentioning

confidence: 99%

Ladakh's Rock Varnish: A potential Geomaterial for astrobiological studies

Chaddha,

Sharma,

Singh

et al. 2023

Preprint

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“…The reconstructed climatic variables were further compared to the environmental geomagnetic data of the profile sediments. The study of the mineral magnetic properties of sediments has become an increasingly useful tool to understand the input of sediment flux in different depositional environments containing iron mineral particles [89][90][91][92][93]. The technique is useful for reconstructing climate and environment because the mineral magnetic characteristics of sediments are sensitive to variations in climate, transport medium, and environmental conditions [90,91,[94][95][96].…”

Section: Introductionmentioning

confidence: 99%

Revisit the Medieval Warm Period and Little Ice Age in Proxy Records from Zemu Glacier Sediments, Eastern Himalaya: Vegetation and Climate Reconstruction

Mehrotra¹,

Basavaiah

Shah³

2023

Quaternary

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The Late Holocene fossil pollen records from the Zemu glacier, located in Yabuk, North Sikkim, in the eastern Himalayas, effectively generated quantitative climate reconstructions based on the transfer function model. The transfer function model was developed by establishing a modern pollen–climate calibration set from the temperate alpine belt of North Sikkim. A redundancy analysis was carried out to detect the pattern of variation of climatic variables in the modern pollen datasets. The mean annual precipitation (MAP) and mean temperature of the warming month (MTWA) had the strongest influence on the composition of the modern pollen samples among the climatic variables considered in the analysis. Proxy data in the form of fossil pollen records were analyzed for reconstructing past climate based upon the relationships between modern pollen vegetation assemblages and climatic patterns. Transfer functions for MAP and MTWA were developed with the partial least squares (PLS) approach, and model performance was assessed using leave-one-out cross-validation. The validated model was used to reconstruct MAP and MTWA for the last 2992 cal years BP (1042 BC) in North Sikkim. The variability observed in the reconstructions was analyzed for past global climatic events. It was further compared with the available regional and hemispheric proxy-based climate reconstructions. The reconstructions captured comparable Medieval Warm Period (MWP) and Little Ice Age (LIA)-like events from the Zemu glacier region. The fossil pollen data and climate reconstructions were further compared with the mineral magnetism data of the subsurface sediment profile.

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