Geoscience

 

During the past decade, Indian geoscientists from different institutions and universities have been playing an active role in carrying out research in the different fields of study pertaining to Antarctic geosciences. The leading institutes being the Geological Survey of India (GSI), National Centre for Antarctic and Ocean Research (ESSO-NCAOR), National Geophysical Research Institute (CSIR-NGRI), BirbalSahni Institute of Paleobotany (BSIP), Survey of India (SOI), Wadia Institute of Himalayan Geology (WIHG), Rajasthan University, Jadavpur University etc. The different themes of research being mapping of the outcrops to understand the crustal evolution, reconstructing the tectono-metamorphic history, genesis of petrological features and rock types, past climate reconstruction using lake sediments from Schirmacher Oasis and Larsemann Hills etc.

Significant Achievements (for last 10 years)

·      The annual recessional pattern of DakshinGangotri Glacier snout indicates that major recession follows a peak in every five years. Since 1996, nearly 4800 m2 area has been vacated by the shrinking snout of this glacier. This recession has led to the disappearance of about 672 x 103 m3 ice, which is equivalent to 576 x 103 m3 of water. The average annual recession of DakshinGangotri Glacier does not show any linear correlation with average annual surface air temperature, average annual ground temperature and average annual wind speed (Shrivastava et al., 2011a).

·      GPS data were collected at different sites and analyzed to estimate the site coordinates, baselines and velocities. Horizontal velocities of the glacier sites lie between 1.89±0.01 and 10.88±0.01 ma-1 to the north-northeast, with an average velocity of 6.21±0.01 ma-1. The principal strain rates provide a quantitative measurement of extension rates, which range from (0.11±0.01) x 10-3 to (1.48±0.85) × 10-3 a-1, and shortening rates, ranging from (0.04±0.02) × 10-3 to (0.96±0.16) × 10-3 a-1. (Sunil et al., 2007, 2010).

·      The oligotrophic lakes of Larsemann Hills area, owe their existence to accumulation of seasonal snow. All these lakes, in spite of their close proximity to sea, are fresh water lakes with uniform chemical characteristics and point towards the lithology as the dominant controlling factor along with weathering pattern, drainage, precipitation and to some extent evaporation. The marine influence, mixing of two kinds of water and evaporation took place in varying proportions (Shrivastava et al., 2011b).

·      The overall characteristics and composition of the sediments in the epi-shelf lakes of the Schirmacher Oasis, are a function of source rock compositions, sediment transportation, depositional processes, and weathering, with additional minor influence of the marine environment. SEM imaging of quartz grains selected at random, reveals a very high degree of mechanical abrasion characterized by features originating from glaciofluvial transport processes. Lattice shattering observed in some grains hints at the possible effects of high cryostatic pressure on the grains. The lake sediments indicates changing conditions in the transporting medium (or transfer from one medium to another, e.g., glacier to stream), and/or the contribution of sediments from multiple different provenances (Shrivastava et al., 2012). 

·      The glacial diamicts of the Jutulsessen area of East Antarctica show basal transportation in the glacier. These sediments were derived mainly from disintegration of the gneissic country rock. The reworking of sediments by water led to the relative enrichment of the coarser fraction of the sediments. The unaltered nature of the clay minerals shows their derivation by mechanical disintegration. The subordinate role of chemical alteration was observed within the sediments at the glacial fan site, and signifies the localized effect of water. The allochthonous glacial diamicts indicate extremely limited organic productivity (Shrivastava et al., 2014). 

·      Suturing of east and west Gondwana is a significant geological event and is well marked in African continent by the East African Orogen (EAO). However, its southward continuation is still not well understood as its projection in east Antarctic shield divides this craton into two distinct geological entities. Our recent work using petrological and geochronological data shows landward extension of EAO in east Antarctica in the Wohlthat Mountains in central Dronning Maud Land (Pant et al., 2013). The anorogenic magmatic association of EAO have been investigated and its geological significance in time and space has been provided (Joshi and Pant, 2008). Besides these, two publications from India were directed at understanding the supercontinent assembly (Santanu et al., 2011; Mahapatro et al., 2012).

·      In inaccessible areas (e.g. sub-ice areas in east Antarctica) ocean sediments reflect the geology of the provenance as well as the processes that leads to sediment formation and deposition. Using mineralogical proxies, the following conclusions have been inferred a) sourcing of sediments from Cambro-Ordovician Trans Antarctic Mountain domain and Proterozoic cratonic domain of the east Antarctic shield and b) describe the processes (including climate variability’s) leading to the deposition and infer the fluctuations of the East Antarctic Ice Sheet (EAIS) during Pliocene and late Miocene (Pant et al., 2013; Verma et al., 2014).

·      Ravikant (2009) and Ravikant et al. (2011) established first evidences of Neoproterozoic tectonothermal events from the central Dronning Maud Land Mountains of Payer and Weprecht and Filchnerfjella. Ravikant et al. (2007) and Ravikant (2006) established a detailed geochronology of the granulite-facies rocks from the Schirmacher Oasis that for the first time proposed a direct continuity of the East African Orogen into this segment of East Antarctica. Application of U-Pb and Sm-Nd geochronology to texturally distinct phases of monazite, sphene and garnet, to constrain the age of the metamorphism(s) in this polymetamorphosed and deformed East African Orogen segment was done for the first time. The major geological evolution in the Schirmacher Oasis was traditionally considered as Mesoproterozoic (1Ga). Ravikant (2008) studied the geochronology and geochemistry of metamorphosed mafic and ultramafic granulitic enclaves from the Schirmacher Oasis and central Dronning Maud Land mountains, East Antarctica. This resulted in constraints for tight Neoproterozoic supercontinent correlation across SE Africa and East Antarctica. Ravikant et al. (2015) interpreted for the first time, the high-grade metasedimentary rocks from the Schirmacher Oasis as Neoproterozoc basins, which were tectonically controlled.

·      Geophysical data such as airborne gravity and magnetic anomalies over the Schirmacher Oasis region recorded by other researchers have been interpreted for deep subsurface lithology. During the 23rd Indian Scientific Expedition to Antarctica, absolute gravity measurements (AG) were made at Maitri Station. This was first AG in the Dronning Maud Land, Antarctica coincidentally just before the Finnish Geodetic Institute (FGI) measurements at Novolazarevskaya, Russian station near Maitri. Measurements were initiated with two major objectives: (i) establishing reference gravity station for future gravimetric surveys, (ii) for studying temporal gravity changes related to Antarctic ice mass loss (Tiwari et al., 2006).

·      The permanent Seismological Observatory and GPS were established in 1997 at Maitri in Central Dronning Maud Land, East Antarctica (70°45י south 11°43' east) primarily to monitor the seismicity in and around Antarctica, the space and time distribution of earthquake occurrences and obtain hypocentral parameters, velocity structure, earthquake source mechanism, internal deformation, plate motion and other glacial and climate related processes. In 2013, the observatory has been upgraded with the new generation Geotech KS-2000M Seismometer and Smart 24R digitizer. Uninterrupted good quality digital Broad Band Seismic data was acquired.

·      GPS data have been analyzed from Maitri station from 1998 to 2002 including the permanent GPS stations of the IGS global network available on the Antarctic plate to define an optimal reference frame. For the period after 2002, there was frequent change in instrument setup leading to shifts in the time series of the coordinates and the monument appears to have become unstable after 2002. In February 2013, NGRI established a new GPS site in Maitri with Met sensor. Using the data from 1998 to 2002, a site velocity of 4.6 mm/year towards N345at Maitri is estimated, which represents the plate velocity at this site (Sapna et al., 2015). Both the observatories are now working fine and the data is being sent to NCAOR on daily basis.

 

·      The lake water from Fischer Island, Larsemann Hills, East Antarctica is slightly acidic to weakly alkaline conditions, whereas, water samples from the Lakes onBroknes Peninsula have feebly acidic to weakly alkaline conditions. In general, the lakes on Fisher Island have lower EC and TDS than the lakes on Broknes Peninsula. This difference can be attributed to the greater freshwater input to the Fischer Island lakes, or to the longer time elapsed since deglaciation on Broknes Peninsula, which is thought to have remained exposed during the Last Glacial Maximum. The paucity of sediments in the catchment areas and within the lake systems can be attributed to the combined effects of the relatively low volume and availability of sediments, transportation and deposition by ice, and paraglacial processes that redistribute and concentrate deposits during and after deglaciation. The sediments from Fischer Island showed a lithic arenite to arkosic composition, indicating slight to moderately weathered source rocks. Sediments on Fisher Island show intense mechanical textures characteristic of glacial transport. Several stages of crushing, grinding, and mechanical weathering were noted (Asthana et al., 2013). Lake sediments from Schirmacher Oasis and Larsemann Hills offer great potential to reconstruct the past climate/environmental conditions on different temporal scales. Environmental magnetic (Warrier et al., 2014), sedimentological and mineralogical (Warrier et al., 2016) and organic geochemical (Mahesh et al., 2015) data from different lakes in Schirmacher Oasis reveal that Schirmacher Oasis have been ice-free for the past 50,000 years and relatively warm periods during this period have been inferred. Warrier et al. (2014) reported for the first time glacial-interglacial climatic conditions in the Schirmacher Oasis based on the rock magnetic properties of lacustrine sediments. In other significant studies, Holocene climatic variations have been reconstructed by studying the paleo-lake deposits present in Schirmacher Oasis (Phartiyal et al. 2011; Phartiyal 2014). Based on productivity-related proxies like the total organic carbon and biogenic silica, climate variability in the Larsemann Hills during the Holocene has been reconstructed (Govil et al., 2011). Variations in the total diatom population and the abundance of salt crystals suggest the weakening of the seawater influence (which was high during the Early Holocene) after ~5000 years BP till date (Mazumder et al., 2013). Based on the abundance Fragilariopsiscurta(diatom species indicating sea-ice conditions)along with other diatom assemblages (using unweighted pair group averaging method of Q-mode Cluster Analysis), it can be concluded that Vestfold Hills experienced relative warmer conditions during the Late Holocene (Mazumder and Govil, 2013).

·      Based on the geological and topographical mapping carried out by the Geological Survey of India and the Survey of India, several high-resolution maps of key importance were published whose details are given below:

a)      Special Series Map on Schirmacher Oasis (Scale 1:10,000) published by the Survey of India in 2014 (Survey of India, 2014a).

b)      Special Series Map on Larsemann Hills (Scale 1:5,000) published by the Survey of India in 2014 (Survey of India, 2014b).

c)      Special Series Map on Larsemann Hills (Scale 1:2,500) published by the Survey of India in 2007 (Survey of India, 2007).

d)      Geological Map of Orvinfjella, Central Dronning Maud Land, East Antarctica (Scale 1:150,000) published by the Geological Survey of India (Geological Survey of India, 2006).

e)      Geological Map of MuhligHofmannfjella, East Antarctica (Scale 1:150,000) published by the Geological Survey of India (Geological Survey of India, 2010).

 

·      Oxygen and carbon isotopic studies on water and sediment samples: Paleoclimatic implications

·         Centennial scale sea surface temperature (SST) and salinity related to summer monsoon precipitation since mid-Holocene (the past ~5000 years) reconstructed from the southeastern Arabian Sea indicates that overall the precipitation has declined since mid-Holocene following solar activity. On shorter timescales, we find that the precipitation declined concurrently with the recent periods of strong solar minima (e.g. Maunder, Spörer, Oort, Wolf), but lagged by a couple of hundred years beyond 1300 years before present indicating competing influence of other forcing factors like coupled ocean-atmosphere phenomenon (Tiwari et al., 2015a).

·         Around 13,000 to 20,000 years ago, the SST decrease between 17 °S and 20 °S in the central Great Barrier Reef region was 1 to 2 °C more than present. It implies northward expansion of cooler subtropical waters due to a weakening of the East Australian Current and shows that coral reefs can withstand large temperature changes provided sufficient time of the order of thousands of years is provided for adaptation (IODP Expedition 325; Felis et al., 2014).

·         More accurate oxygen isotope-salinity relationships for surface waters of the Southern Ocean and southern Indian Ocean has been determined that would aid in studying hydrographic features and more precise past salinity quantification in these regions (Tiwari et al., 2013).

·         We find signatures of a warm-core eddy extending from 40 to 44 °S and 56 to 59.5 °E in Southern ocean during austral summer of 2013 based on oxygen isotope and salinity of the intermediate water (till 1000 m). Such mesoscale eddies have been reported as one of the factors leading to freshening/salinification of the Antarctic Intermediate Water (AAIW) on decadal time scale resulting in shoaling up of the AAIW. We also observed the AAIW at relatively shallow depth of 500 m (Tiwari et al., 2015b).

·         A 9000 year record of monsoon precipitation during part of Marine Isotope Stage (MIS) 5d-c, from ~108,000 to ~99,000 years ago based on speleothem data from Southern India indicates a step-like increase during the transition from the cooler stadial MIS 5d to warmer interstadial MIS 5c, signifying an abrupt reduction in monsoon rain. It also highlights divergent trends between the Indian and the East Asian Summer Monsoons for a time period for which not many high-resolution comparisons are available (Allu et al., 2015).

·         Stable isotopic studies carried out on planktic foraminiferal samples of plankton net and core top sediments collected during the first Indian expedition to the Southern Ocean show that the oxygen isotope values of planktic foraminifera in this region is mainly governed by SST fluctuations: the samples become isotopically heavier polewards. The carbon isotope values appear to be governed mostly by productivity fluctuations, which also increase polewards (both in the plankton net and sediment samples) possibly due to influx of nutrients via melting ice (Tiwari et al., 2011).

·         Carbon isotope variability of foraminifera in eastern Arabian Sea can act as an excellent indicator of productivity, which in turn is governed not only by wind induced mixing but also by the nutrient influx via surface runoff. Productivity is intrinsically linked with the Southwest (SW) monsoon strength; low productivity occurs during periods of aridity (Tiwari, 2013).

·         Study on sediment samples from the western Arabian Sea finds decoupling between the summer monsoon and insolation on sub-milankovitch timescales highlighting the importance of internal feedbacks (Tiwari et al, 2010).

 

·      Polar Satellite Remote Sensing and its applications in land cover classification, glaciology and extraction of Lake Bathymetry.

Designed a first generation accurate digital elevation models (DEMs) for Larsemann Hills and Schirmacher Oasis, East Antarctica, using interferometric and photogrammetric techniques (Jawak and Luis, 2011). Synthesized a precise DEMs by synergistic use of multitemporal RAMP, Cartosat-1 (Indian satellite) ICESat and ground reference data (GPS) (Jawak and Luis, 2012). These indigenous DEMs gained a significant attention internationally, as they had improved vertical accuracies compared to existing Antarctic DEMs.Utilization of Indian satellite RISAT-1 C-band imagery for geospatial mapping of cryospheric surface features in the Antarctic environment (Jawak et al., 2015a); Geospatial mapping of vegetation in the Antarctic environment using very high resolution WorldView-2 data (Jawak and Luis, 2013a); Employed very high resolution satellite imagery for object-oriented mapping of supra-glacial debris in the Antarctic environment (Jawak et al., 2015b). Shorelines of more than 100 lakes in Larsemann Hills and 10 lakes in Schirmacher Oasis were mapped as a reference data for validation of algorithms for semi-automatic extraction of lake features using satellite data (Jawak and Luis, 2013b). Developed three new geospatial methods for geo-information extraction in the cryospheric environment, viz. (1) spectral index ratio method (Jawak and Luis, 2013c) (2) ensemble classification method (Jawak and Luis, 2013a) (3) customized normalized difference water index (cNDWI) for lake feature extraction (Jawak and Luis, 2014).

 

References

1.      Allu, N.C., Manish Tiwari, M.G. Yadava, N.C. Dung, C.-C. Shen, S.P. Belgaonkar, R. Ramesh, A.H. Laskar (2015). Stalagmite δ18O variations in southern India reveal divergent trends of Indian Summer Monsoon and East Asian Summer Monsoon during the last interglacial. Quaternary International, v. 371, pp. 191-196.

2.      Asthana R., Beg M. J, Swain A K., Dharwadkar A., Roy S. K. and Srivastava H. B. (2013) Sedimentary processes in two different polar periglacial environments: Examples from Schirmacher Oasis and Larsemann Hills, East Antarctica, Geological Society of London, Special Publications, 381, 411-427.

3.      Felis, T., H.V. McGregor, B.K. Linsley, A.W. Tudhope, M.K. Gagan, A. Suzuki, M. Inoue, A.L. Thomas, T.M. Esat, W.G. Thompson, Manish Tiwari, D.C. Potts, M. Mudelsee, Y. Yokoyama, J.M. Webster (2014). Intensification of the Meridional Temperature Gradient in the Great Barrier Reef Following the Last Glacial Maximum. Nature Communications, 5, 4102, doi: 10.1038/ncomms5102.

4.      Geological Survey of India (2006). Geological Map of Orvinfjella, Central Dronning Maud Land, East Antarctica (Scale 1:150,000), published by the Director General, Geological Survey of India, Government of India.

5.      Geological Survey of India (2010). Geological Map of MuhligHofmannfjella, East Antarctica (Scale 1:150,000), published by the Director General, Geological Survey of India, Government of India.

6.      Govil, P., Mazumder, A., Tiwari, A. and Kumar, S. (2011). Holocene climate variability from lake sediment core in Larsemann Hills, Antarctica. Journal of the Geological Society of India, v. 78, pp. 30-35.

7.      Jawak, S. D. and Luis, A. J. (2011). Applications of WorldView-2 satellite data for Extraction of Polar Spatial Information and DEM of Larsemann Hills, East Antarctica, 2011 International Conference on Fuzzy Systems and Neural Computing, IEEE, vol 2, pp 148-151.

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16.  Mahapatro, S.N., Pant, N.C., Bhowmik, S.K., Tripathy, A.K. and Nanda, J.K. (2012). Archaean granulite facies metamorphism at the Singhbhum Craton–Eastern Ghats Mobile Belt interface: implication for the Ur supercontinent assembly. Geological Journal, v. 47, pp. 312-333.

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26.  Ravikant, V. 2008. Late Neoproterozoic Orogenesis in the central Dronning Maud Land, East Antarctica: a review of tectonothermal events affecting rocks of the Schirmacher Oasis (~660–580 Ma) and Filchnetfjella (~570–530 Ma). Geological Survey of India Special Publication No.91, Pan–African event in India and Antarctica, pp. 156–170.

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45.  Tiwari, M., Nagoji, S.S., Kartik, T., Drishya, G., Parvathy, R.K. and Rajan, S. (2013). Oxygen Isotope-Salinity relationships of discrete oceanic regions from India to Antarctica vis-à-vis surface hydrological processes. Journal of Marine Systems, v. 113-114, pp. 88-93.

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