- S. M. Ahmad
- A. M. Dayal
- V. M. Padmakumari
- J. R. Trivedi
- M. N. Balasubrahmanyan
- S. K. Ray
- C. Anjaneya Sastry
- N. Kochhar
- K. Pande
- S. N. Sarkar
- T. R. Venkatesan
- R. Ramesh
- S. K. Bhattacharya
- M. Santosh
- N. G. K. Nair
- A. B. Chakranarayan
- K. B. Powar
- Anil Kumar
- R. Srinivasan
- D. J. Patil
- B. V. Oleinikov
- A. F. Korobeinikov
- O. V. Koroleva
- P. Krishnamurthy
- S. Das Sharma
- R. Murari
- G. V. Nesterenko
- D. Rameshwar Rao
- Kewal K. Sharma
- A. K. Choudhary
- A. Naik
- D. Mukhopadhyay
- S. Sarangi
- A. B. Roy
- B. Sreenivas
- G. Anil Babu
- K. R. P. Rao
- S. S. Nayak
- Asru K. Chaudhuri
- Somnath Dasgupta
- Goutam Bandyopadhyay
- Subir Sarkar
- P. C. Bandyopadhyay
- R. Soundar Rajan
- K. S. Valdiya
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Gopalan, K.
- Evolution of Strontium Isotopes in Seawater During the Middle Miocene: New Results from ODP Site 758A
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 55, No 3 (2000), Pagination: 307-316Abstract
Thc 87Sr/86Sr ratio of seawater has increased significantly over the last 40 Ma. This increase was marked by very high rate of increase in 87Sr/86Sr and almost zero growth rate. The middle Miocene is one such period when considerable changes in the slope of 87Sr/86Sr curve have been reported. This study tests and improves on previously published strontium isotopic records for this period.We report 34 high precision strontium isotopic analyses of well preserved planktonic foraminifera from Ocean Drilling Program (ODP) site 758A in the eastern Indian Ocean. This site was selected because of the high quality magnetostratigraphy, suitable sedimentation rate (0.3 to 1.5 cm/ka) and excellent preservation of calcareous microfossils in sediments. Samples studied represent the period from 15.2 Ma to 10.3 Ma with approximately one sample per 100-200 ka.
The results show that the seawater 87Sr/86Sr ratio during this period increased from 0.70881 to 0.70892. The rare of increase in 87Sr/86Sr during 15.2 Ma to 14.3 was -31 x 10-6/m.y., whereas significantly from 14.3 to 12.8 Ma it was about a factor of two higher (-59x10-6/ m.y.). High rate of growth in seawater 87Sr/86Sr during this time interval indicates exceptionally high rates of continental weathering. However, during 12.8 to 10.3 Ma the growth in 87Sr/86Sr of seawater remained almost constant with an average value of 0.708914. This constant value may he due to decrease in weathering rates of continents as a result ofextensive glaciation. It is suggested that the tectonicuplift and denudation of Himalayas coupled with climatic changes have resulted in the variations of seawater strontium isotopes during this period. The inflection points in the curve may be used as event marker for stratigraphic corretation of marine sediments.
Keywords
Marine Geology, Stratigraphy, Strontium Isotopes, Miocene, Planktonic Foraminifera.- Rb-Sr Chronology of the Khetri Copper Belt, Rajasthan
Authors
1 Physical Research Laboratory, Ahmedabad 380009, IN
2 Geological Survey of India, 29, Jawaharlal Nehru Road, Calcutta 700 016, IN
3 Geological Survey of India, Bhutan Circle, Samchi, BT
4 Geological Survey of India, Geochronology and Isotope Geology Division, 29, Jawaharlal Nehru Road, Calcutta 700016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 20, No 9 (1979), Pagination: 450-456Abstract
Rubidium and strontium determinations are reported for the Udaipur and Saladipura granites from the Khetri copper belt. The whole-rock data define a Rb-Sr isochron corresponding to an age of 1480 ± 40 m.y. and initial Sr ratio of 0.7131 ± 0.006. This age is older than previously believed, but consistent with the generally high age of post-Delhi intrusive rocks so far dated in the region. Biotites associated with these rocks give younger ages around 700 m.y, This indicates mobilisation of Sr isotopes in a later metamorphic event. It is significant that this secondary event is almost synchronous with the intrusion of granites to the west and south of the Aravalli mountains.- Physics and Chemistry of the Earth
Authors
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 20, No 12 (1979), Pagination: 626-626Abstract
No Abstract.- Prof. V. S. Venkatasubramanian (1930-1984)
Authors
1 Physical Research Laboratory, Ahmedabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 9 (1984), Pagination: 614-615Abstract
No Abstract.- Rb-Sr Age of the Tusham Ring Complex, Bhiwani, India
Authors
1 Department of Geology, Punjab University, Chandigarh 160014, IN
2 Physical Research Laboratory, Navrangpura, Ahmedabad 380009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 26, No 3 (1985), Pagination: 216-218Abstract
Acid volcanics and associated granites from the Tusham Ring Complex in northwestern India yield a well defined Rb-Sr isochron corresponding to an age of 754±20 Ma (λ=1.42 x 10-11 yr-1 ) and an initial Sr composition of 0.7131±0.0025. This is in good agreement with the age of the Malani suite of igneous rocks of western Rajasthan.- Professor V. S. Venkatasubramanian (1930-1984) - An Appreciation
Authors
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 1 (1986), Pagination: 1-7Abstract
No Abstract.- Rb-Sr whole-Rock and Mineral Isochron Ages of the Tirodi Gneiss, Sausar Group, Rhandara District, Maharashtra
Authors
1 Indian School of Mines, Dhanbad 826 004, IN
2 Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 1 (1986), Pagination: 30-37Abstract
Six whole rock samples of the Tirodi gneiss belonging to the basal part of the Sausar Group rocks in the Dongri Buzurg area yield a good Rb-Sr isochron corresponding to an age of 1525±70 Ma and an initial Sr ratio of 0.7148±0.0033. Mineral isachrons for two of these rocks give concordant but younger ages at 860 Ma in good agreement with the previously reported K/Ar ages on minerals separated from the Sausar Group rocks. The 1525 Ma event is interpreted to mark the main phase of regional metamorphism of the Sausar Group of rocks including the granitization of the basal Tirodi unit. The deposition of the sediments of the Sausar Group and their basement must therefore be even older. The good agreement of the RblSr and K/Ar mineral ages at about 860 Ma indicates the latest thermal overprint on the Sausar - rocks, The regional metamorphism of the Tirodi gneiss at about 1500 Ma ago is also reflected in the Rb/Sr and K/Ar mineral ages of the Amgaon gneiss and Dongargarh granite to the east of the Tirodi gneiss.- 40Ar-39Ar Darting of Deccan Basalts
Authors
1 Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 1 (1986), Pagination: 102-109Abstract
The feasibility of dating igneous rocks by the 40Ar-39Ar method in India using the Apsara nuclear reactor at BARC, Bombay is reported, based on measurements on two tholeiitic basalts and one alkali basalt associated with the Deccan volcanism. The ages of the tholeiitic basalts are 71±4 Ma and 65±4 Ma, respectively and that of the alkali basalt is 682 Ma. Apart from the low neutron flux requiring long irradiation times, the neutron fluence within the sample irradiation volume is somewhat anisotropic. The latter needs to be minimised to achieve the higher precision the method is capable of.- Stable Isotope Systematics in Tree Cellulose as Palaeoenvironmental Indicators - A Review
Authors
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 National Geophysical Research Institute, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 1 (1986), Pagination: 154-167Abstract
Stable isotope ratios of hydrogen, carbon and oxygen in tree cellulose have been recently demonstrated as potential indicators of past climate, However, a number of problems remain to be solved before isotope dendroclimatology can be used for routine reconstruction of palaeoclimate. Here we review the existing Literature, with a special reference to the Indian context and identify key problems that deserve immediate attention.- Rb-Sr Geochronology of the Ambalavayal Granite, Kerala
Authors
1 Centre for Earth Science Studies, P. B. 2235, Sasthamangalam, Trivandrum 695 010, IN
2 Physical Research Laboratory, Navarangpura, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 3 (1986), Pagination: 309-312Abstract
Rubidium and strontium determinations are reported for seven whole-rock samples of the Ambalavayal granite of northern Kerala. The data yield a well defined Rb-Sr isochron, corresponding to an age of 595 ± 20 Ma and initial 87Sr/86Sr ratio of 0.7171 ± 0.0022. The age marks a regime of Late Precambrian-Early Palaeozoic granite magmatism in the southwestern Indian shield. The agreement of the Rb/Sr age with the previously measured K/Ar age of 560± 30 Ma indicates no significant secondary thermal event in the region. The evolved initial Sr ratio suggests either an exclusive origin or significant crustal contamination of magma derived from a deeper source.- Rb-Sr Age of the Belka Pahar Granite, Sirohi District, Rajasthan
Authors
1 Department of Geology, University of Poona, Pune 411 007, IN
2 Physical Research Laboratory, Ahmedabad 380 009, IN
3 National Geophysical Research Institute, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 28, No 4 (1986), Pagination: 325-327Abstract
At Belka Pahar, in the Sirohi district of Rajasthan, metasediments of the Delhi Super Group are associated with a medium-grained, leucocratic, alkali granite. Whole rock isotopic data for this granite define a Rb-Sr isochron corresponding to an age of 860±25 Ma and an initial 87Sr/86Sr ratio of 0.7059 ±0.0032.- Plea for an Annual National Conference on Earth Sciences
Authors
1 National Geophysical Research Institute Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 35, No 2 (1990), Pagination: 129-130Abstract
No Abstract.- Geochronology at N.G.R.I. Hyderabad
Authors
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 36, No 3 (1990), Pagination: 331-331Abstract
No Abstract.- A Reappraisal of an Archaean Carbonatite of Nellore Schist Belt, South India
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 40, No 2 (1992), Pagination: 169-174Abstract
Field observations, trace element and isotopic results are reported for rocks classified as carbonatites from Vinjamur area in the Nellore schist belt. These carbonate rocks occur either inter-bedded with metasedimentary quartzites and pelites or in association with calc-alkaline rather than alkaline volcanic rocks. No fenitised contacts are seen. Their Nb and REE contents are too low for carbonatites. Samples free from baryte veins have less than 150 ppm of Sr with an isotopic ratio greater than 0.7100 δ13CPDB range from -1.58 to - 0.56 ‰ and δ18OSMOW from +14.00 to +16‰ , All these features, individually and collectively, show that the carbonate rocks of Vinjamur are most probably sedimentary and not igneous in origin.Keywords
Carbonatite, Nellore Schist Belt, Andhra Pradesh.- The Gold Content of Deccan Basalts Western Ghats, India
Authors
1 Yakut Institute of Geological Sciences, Siberian Branch, Russian Academy of Science, Yakutsk - 677 891, RU
2 Atomic Minerals Division, Hyderabad-500 016, IN
3 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 42, No 3 (1993), Pagination: 243-246Abstract
Sixty nine (69) samples of Deccan basalt flows from the Western Ghats representing the Wai, Lonavala and Kalsubai subgroups average 3.7 ppb of gold. Gold content shows limited variation from 3.0 to 5.8 ppb in 62 samples whereas they range from 1.4 to 2.7 ppb in 7 samples. Flows of the Wai subgroup show the maximum variation in gold abundances (1.4 - 5.8 ppb) and which may be related to the presence of primitive uncontaminated basalts (Ambenali)- lowest value-crust-contaminated basalts (Poladpur) and basalts derived from enriched-mantle sources (Mahabaleshwar). Gold appears to be insensitive to crystal fractionation or differentiation as basalts of different types such as the picritic, porphyritic, aphyric and giant plagioclase-bearing types found within a subgroup or formation have similar avcrages (3.6-3.8 ppb).
Deccan Tholciitic basalts contain higher amounts of gold than dome of the occean island (Hawaii) tholciitic basalts island are (Kurile-Kamchatka) tholciites, but contain values similar to those found in the Columbia River basalt province.
Keywords
Gold, Deccan Basalts, Western Ghats, Economic Geology.- Oxygen Isotope Systematics of Siberian Basalts
Authors
1 National Geophysical Research Institute, Uppal Raod, Hyderabad-500007, IN
2 Vernadsky Institute of Geochemistry, Kosygin Street 19, Moscow-117075, RU
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 44, No 3 (1994), Pagination: 327-330Abstract
No Abstract.- Granitoid Rocks of Wangtu Gneissic Complex, Himachal Pradesh: An Example of In situ Fractional Crystallisation and Volatile Action
Authors
1 Wadia Institute of Himalayan Geology, General Mahadeo Singh Road, Dehradun-248001, IN
2 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 1 (1995), Pagination: 5-14Abstract
The Wangtu Gneissic Complex (WGC) of Himachal Himalaya represents the basement rocks which remained more or less in its original realm. The unique feature of this complex is that the various phases of deformed and undeformed granitoids are exposed in the area. The complex has a peripheral zone of augen gneisses and core of non-foliated granitoids comprising of Coarse Porphyritic Granites (CPG) and Fine Grained Granites (FGG).
In the field the FGG rocks have sharp intrusive contacts with CPG rocks. At places they are entrapped or have protrusions into CPG rocks. Compositionally they represent syenogranites. They are peraluminous to meta-aluminous with Sr initial ratio of 0.705. The major and trace elements of these rocks show unimodal distribution pattern on different variation diagrams. They along with rare earth elements show marked fractionation trends, with a significant negative Eu anomaly. The rocks more or less define an isochron, representing Rb-Sr age of 1895±64 Ma.
The petrochemical studies favour a fractionated rather than multiple intrusions of magma. The studies suggest that fractional crystallisation of parental magma gave rise to early formed CPG rocks and the residual melts resulted in the crystallisation of FGG rocks. The last formed granitoids, the FGG rocks are interpreted as the final residue which crystallised rapidly after build-up and loss of fluids and volatiles which migrated to higher levels to form pegmatite phase in the aureol zone. The Rb-Sr systematics in the present case indicate that the granite have primary crystallisation melts derived from the deep crustal levels around 1895±64 Ma.
Keywords
Granites, Igneous Petrology, Himachal Pradesh.- Geochemistry and Rb-Sr Chronology of Upper Jurassic A-type Granite, Tangmarg region, Kashmir Himalaya
Authors
1 Wadia Institute of Himalayan Geology, 33 General Mahadeo Singh Road, Dehra Dun - 248001, IN
2 National Geophysical Research Institute, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 3 (1995), Pagination: 225-233Abstract
The present paper deals with petrochemistry and geochronology of granite pluton that intrudes the Agglomerate Slate-Panjal Trap sequence in Tangmarg region of Baramulla district, Kashmir Himalaya. This granite body henceforth called 'Tangmarg Granite' contains biotite, amphibole and rare pyroxene as mafic minerals and shows higher abundances of Zr, Nb, Ga, Y and REE, and lower AI, Mg and Ca contents. The geochemical signatures suggest the granite to be chemically distiIict from most of the orogenic granites (M-, I- and S-types) and points to their Anorogenic nature.The six point whole rock Rb-Sr isochron of the Tangmarg granite gives an age of 161 ± 5 Ma, with Sr ratio of 0.714. The small size of the pluton points to limited melt generated from a partial fusion 'event' of short duration. Such a melt is attributed to pressure release due to reactivation of the faults that were formed during Permo-Triassicrifting event.
Keywords
Geochemistry, Geochronology, Granites, Kashmir Himalaya- Rb-Sr Dating of Sambalpur Granodiorite, Western Orissa
Authors
1 Department of Physics, Samastipur College, Samastipur, Bihar, IN
2 Department of Earth Sciences, Sambalpur University, Orissa, IN
3 Department of Geology, Calcutta University, Calcutta, W.B., IN
4 National Geophysical Research Institute, Hyderabad, A.P., IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 47, No 4 (1996), Pagination: 503-506Abstract
The wholerock Rb-Sr isochron age of 2380 ± 44 Ma (Sr<SUB>i</SUB> = 0.70492 ± 14) obtained for the Sambalpur granodiorite indicates an Early Proterozoic granitic activity in this region younger than Singhbhum Granite (ca. 3.3 to 3.1 Ga). Comparable Rb-Sr ages have also been reported for different granites from Mandhya Pradesh.- Pb-Pb Age of Carbonates of Jhamarkotra Formation: Constraints on the Age of Aravalli Supergroup, Rajasthan
Authors
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 Jai Narayan Vyas University, Jodhpur - 342 00 1, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 67, No 4 (2006), Pagination: 442-446Abstract
Pb-Pb isochron age of carbonate rocks of the Jhamarkotra Formation of the Aravalli Supergroup from the Udaipur sector in Rajasthan has been measured for the first time as 1921±67 Ma (2σ). We consider this as a reset age, as it is indistinguishable from the earlier reported Rb-Sr isochron age of 1900±8O Ma for the Darwal Granite formed synkinematically with the Aravalli deformation. The depositional age of the Jhamarkotra carbonates could be 200-300 Ma older as suggested by the positive δ13C anomalies noted in these carbonate rocks.Keywords
Pb-Pb Isochron Age, Carbonates, Aravalli Supergroup Rajasthan.- Changes in Seawater 87Sr/86Sr Curve during Early Miocene to Early Late Miocene: Implications of ODP Site 758A Record
Authors
1 National Geophysical Research institute, Uppal Road, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 65, No 2 (2005), Pagination: 147-157Abstract
A seawater 87Sr/86Sr record is generated for early Miocene to early late Miocene based on measurements of 114 samples of cleaned planktonic foraminifera from Ocean Drilling Program site 758 (Hole 758A) in the eastern Indian Ocean. Age model for this Site is based on nannofossil events and interpolated numerical ages are compared with Sr Isotopically-Derived ages, There is a fairly good agreement between the two stratigraphic tools (<±1.5 Ma). 87Sr/86Sr ratio during ∼23.7 Ma to ∼8.1 Ma increased from 0.70828 to 0.70895, with variations in the rate of 87Sr/86Sr increase. Seventh-Order polynomial fit curve shows the 87Sr/86Sr increase rates of 44 ×10-6m .y.-1 for -23.7 to ∼19.2 Ma, 41 × 10-6 m.y.-1 for -18.2 to - 10.8 Ma, and 25 × 10-6 m.y.-1 for ∼10.8 to ∼8.1 Ma. These rates are broadly consistent with the growth rates of 87Sr/86Sr reported from other DSDP and ODP sites with some minor differences.A composite Sr isotope curve constructed for the 24-8 Ma is broken into three linear segments with a different linear regression equation. The overall rate of 87Sr/86Sr increase for ∼24-8 Ma at site 758A (40 x 10-6 m.y.-1) is in agreement with the rate of 87Sr/86increase of the composite curve (42 x 10-6 m.y.-1).
Keywords
Sr Isotopes, Miocene, Stratigraphy, Planktonic Foraminifera, Eastern Indian Ocean.- Rb-Sr Age of Kimberlites and Lamproites from Eastern Dharwar Craton, South India
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
2 Geological Survey of India, Bandlaguda, Hyderabad - 500 068, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 58, No 2 (2001), Pagination: 135-141Abstract
Acid-Leached phlogopite Rb-Sr isochron ages of the Kotakonda and Mudalbid kimberlites in the Narayanpet kimberlite field northwest of the Cuddapah basin, south India are 1085±14 and 1099±12 Ma, respectively. These concordant ages are much younger than the recently reported K-Ar and 40Ar-39Ar ages of 1363±48 and 1402±5 Ma, respectively for the former kimberlite, and support our earlier conclusion that the south Indian kimberlites erupted episodically close to 1090 Ma ago. Three lamproites-one each from Ramannapeta at the northeastern margin and Chelima and Zangamarajupalle within the Cuddapah basin-give distinctly different Rb-Sr ages of 1224±14, 1354±17 and 1070±22 Ma, respectively. While the Rb-Sr age of the Ramannapeta lamproite is also younger than an earlier reported K-Ar age of 1381±18 Ma, it is the same as that of many spatially close alkaline complexes like at Elchuru and Kunavaram. The ages for the Chelima and Zangamarajupalle rocks are only tentative, as these rocks contain a large secondary carbonate component with its Sr isotopic composition genetically unrelated to that of their phlogopites.Keywords
Kimberlites, Lamproites, Narayanpet Kimberlite Field, Rb-Sr Ages, Dharwar Craton.- Stratigraphy of the Penganga Group Around Adilabad, Andhra Pradesh
Authors
1 Geological Studies, Unit, Indian Statistical Institute, Calcutta, IN
2 Department of Geological Sciences, Jadavpur University, Calcutta 700032, IN
3 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 34, No 3 (1989), Pagination: 291-302Abstract
The Proterozoic sequence around Adilabad, Andhra Pradesh comprises a distinct lithostratigraphic unit of 'Group' status and has been given the name Penganga Group. The Penganga Group has been classified into three Formations which are, in order of younging, Pranhita Sandstone, Chanda Limestone and Sat Nala Shale. The sequence is dominated by limestones and shales which were deposited in relatively deep water environment and, thus, contrast sharply with the conglomerate, sandstone and shallow water limestones of the Pakhal Group. Radiometric dating of fresh glauconites from middle part of the Penganga Group gives an age of 770 ± 30 Ma. Thus, the Penganga Group is the youngest of all other Proterozoic sequences in Pranhita-Godavari Valley.- Seawater Neodymium Isotopic Composition in the Northeastern Indian Ocean during the LGM to Holocene: Response to Glacial and Monsoonal Weathering in Himalaya-Tibet
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
2 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 68, No Spl Iss 3 (2006), Pagination: 425-432Abstract
Neodymium isotopic composition (εNd) of authigenic marine sediments is an important tracer of the continental input of Nd to the oceans As the residence time of neodymium in seawater 1s short when compared to the mixing time of the oceans, its isotopic composition shows regional variations In this paper, we present the surface seawater Nd isotopic record from a deep-sea sediment core (SK-72) from the Bay of Bengal Our results support the inference of Vance and Burton (1999) that thoroughly cleaned foraminifera can be used to infer glacial-to-Interglaciacl hanges ln the Nd isotopicc omposition of surface seawater The striking feature of this record is a sharp shift in εNd (˜ 4 epsilon units) from the Last Glacial Maximum (LGM) to Holocene In addition, the variations documented in εNd, show a remarkable correspondence with those of the oxygen isotopic composition of planktonic foraminifera,indicating a process that controls the Nd isotopic compoition, which responds in phase with climate We infer that the shift in εNd from the LGM to Holocene is due to a change in the weathering pattern in the Himalaya-Tibet and the Indo-Burman Ranges glacial erosion during the LGM and a strong monsoonal effect durtng the Holocene.Keywords
Neodymium Isotopes, LGM, Holocene, Weathering, Monsoon, Riverine Input, Oxygen Isotopes, Planktonic and Benthic Foraminifera.- Rb-Sr Ages of Granitic Rocks Within the Lesser Himalayan Nappes, Kumaun, India
Authors
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 Geology Department, Kumaun University, Nainital 263 001, IN