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The 1000 Ma felsic tuffs that occur near the top of both the Chhattisgarh and Indravati Basins in peninsular India have been attributed to a "rhyolite flare-up" occasioned by the collision of parts of East Antarctica with India, in what is now the Eastern Ghats Mobile Belt, and the suturing of the North and South Indian cratonic blocks along the Central Indian Tectonic Zone, all during the assembly of Rodinia. In this study we present (1) new U-Pb SHRIMP ages of zircons from the granitic basement; (2) Hf isotopic compositions (laser ablation multicollector ICP-MS) from previously dated zircons from a number of tuff samples and a sample of the Archean basement (Bastar craton); and (3) major, minor, trace, and rare earth element compositions of these and a randomly collected additional set of samples from the Bastar craton basement. We have used these data to infer the petrogenesis of the tuffs. The Hf isotopic data preclude derivation of the parent magmas of the tuffs from simple melting of the basement rocks; geochemical data constrain the source to include garnet, a titanium mineral, and in some cases plagioclase. It is likely that the source was a mafic granulite, possibly in the lower crust, and that the triggering mechanism was farfield stress release during collisional orogenies to the southeast and to the north. [ABSTRACT FROM AUTHOR]

Abstract: We report the results of a preliminary paleomagnetic study on well-dated 1.9Ga dykes from the Bastar craton, India. This suite of NW–SE trending dykes was linked to similarly-aged magmatic activity in the Dharwar craton and Cuddapah basin in India as part of a large igneous province. This igneous activity may have extended across many cratons in the “Columbia” supercontinent including the North China craton, Laurentia, Baltica, Australia, Siberia and the Kaapvaal and Zimbabwe cratons (southern Africa). The Bastar dykes along with the Cuddapah traps and dyke yield a dual-polarity magnetization with D=126°, I=+15.2° (k=27, α95 =11.9°) and a corresponding paleomagnetic pole at 31° N, 330° E (dp=6.3°, dm=12.2°). The relatively robust paleomagnetic and geochronologic database at 1.85–1.90Ga allow us to test one of the configurations of the supercontinent “Columbia”. There are some critical differences between our paleomagnetically-based reconstruction and the archetypal and geologically-based “Columbia” configuration of Zhao et al. (2004). Most notably, Siberia, India and Australia cannot be linked to Laurentia in the archetypal Columbia fit. Proposed links between western Australia and the Kaapvaal and Zimbabwe cratons are possible as is the fit between Baltica and Laurentia. The robust paleomagnetic data reported in this paper require that either the Columbia supercontinent did not exist at 1.9Ga or requires major modification. Given that our data provide only a snapshot on the Paleoproterozoic, we conclude that the Columbia supercontinent remains a viable possibility although relationships between individual elements should be re-evaluated as more data become available. [Copyright &y& Elsevier]

Abstract: The paleogeographic position of India within the Paleoproterozoic Columbia and Mesoproterozoic Rodinia supercontinents is shrouded in uncertainty due to the paucity of high quality paleomagnetic data with strong age control. New paleomagnetic and geochronological data from the Precambrian mafic dykes intruding granitoids and supracrustals of the Archean Bundelkhand craton (BC) in northern Peninsular India is significant in constraining the position of India at 2.0 and 1.1Ga. The dykes are ubiquitous within the craton and have variable orientations (NW–SE, NE–SW, ENE–WSW and E–W). Three distinct episodes of dyke intrusion are inferred from the paleomagnetic analysis of these dykes. The older NW–SE trending dykes yield a mean paleomagnetic direction with a declination=155.3° and an inclination=−7.8° (κ =21; α 95 =9.6°). The overall paleomagnetic pole calculated from these 12 dykes falls at 58.5°N and 312.5°E (dp/dm =6.6°/7.9°). The overall mean direction calculated from four ENE–WSW Mahoba dykes has a declination=24.7° and inclination=−37.9° (κ =36; α 95 =15.5°). The virtual geomagnetic pole (VGP) for these four dykes falls at 38.7°S and 49.5°E (dp/dm =9.5°/16.3°). A third, and distinctly steeper, paleomagnetic direction was obtained from two of the NE–SW trending dykes with a declination=189.3° and inclination=64.5°. U–Pb geochronology generated in this study yields a U–Pb Concordia age of 1979±8Ma for the NW–SE trending dykes and a mean 207Pb/206Pb age of 1113±7Ma for the Mahoba suite of ENE–WSW trending dykes, confirming at least two dyke emplacement events within the BC. We present global paleogeographic maps for India at 1.1 and 2.0Ga using these paleomagnetic poles. These new paleomagnetic results from the ∼2.0Ga NW–SE trending Bundelkhand dykes and the paleomagnetic data from the Bastar/Cuddapah suggest that the North and South Indian blocks of the Peninsular India were in close proximity by at least 2.5Ga. The paleomagnetic and geochronological data from the Mahoba dyke is significant in that it helps constrain the age of the Upper Vindhyan strata. The pole coincides in time and space with the Majhgawan kimberlite (1073Ma) and the Bhander–Rewa poles from the Upper Vindhyan strata. The most parsimonious explanation for this coincidence is that the age of the Upper Vindhyan sedimentary sequence is >1000Ma. [Copyright &y& Elsevier]

Abstract: The Precambrian history of the Earth is punctuated by a number of supercontinental assemblies and their disintegration. New paleomagnetic and geochronologic results from the Dharwar, Bundelkhand and Marwar cratons of the Indian subcontinent are presented here in an attempt to constrain the paleogeographic position of India within various proposed Precambrian supercontinents. Our paleomagnetic results from the Paleoproterozoic Gwalior traps of the Bundelkhand craton, all of a single polarity, yielded a combined tilt-corrected mean declination=73.9° and an inclination of +4.4° (k =22, α95=11.2°). The paleomagnetic pole was calculated using a site location of 26°N, 78°E and is located at 15.4°N, 173.2°E. The U–Pb isotopic studies on the zircons obtained from the alkaline mafic dyke sample from Anantapur dyke swarm of the Dharwar craton, southern India, yielded a concordant age of 1027.2±13Ma (2σ; MSWD=5.0). An overall mean of our paleomagnetic studies combined with previously published results yielded a VGP at 10°N and 211°E with a mean declination=65° and inclination=−57° (k =31, α95=10). In an effort to constrain the lower age limit of the Malani Igneous Suite (MIS) we report new U–Pb isotopic ages for the Harsani granodiorite. The granodiorite forms the basement for the Malani igneous province in NW India. The zircon U–Pb analyses from Harsani granodiorite yielded and age of 827.0±8.8Ma that we interpret as the age of intrusion and the 786.4±5.6Ma may relate to a disturbance marking onset of Malani volcanism. Along with these new data, we also review the paleomagnetic results from our previous studies on the Harohalli alkaline dykes, Upper Vindhyan sequence, Majhgawan kimberlite, and a widespread paleomagnetic overprint that we interpret to be of ∼580Ma in an attempt to constrain the paleogeography of the Indian subcontinent from 1.8Ga to 580Ma. [Copyright &y& Elsevier]

Just as modern nation-states struggle to manage the cultural and economic impacts of migration, ancient civilizations dealt with similar external pressures and set policies to regulate people's movements. In one of the earliest urban societies, the Indus Civilization, mechanisms linking city populations to hinterland groups remain enigmatic in the absence of written documents. However, isotopic data from human tooth enamel associated with Harappa Phase (2600-1900 BC) cemetery burials at Harappa (Pakistan) and Farmana (India) provide individual biogeochemical life histories of migration. Strontium and lead isotope ratios allow us to reinterpret the Indus tradition of cemetery inhumation as part of a specific and highly regulated institution of migration. Intra-individual isotopic shifts are consistent with immigration from resource-rich hinterlands during childhood. Furthermore, mortuary populations formed over hundreds of years and composed almost entirely of first-generation immigrants suggest that inhumation was the final step in a process linking certain urban Indus communities to diverse hinterland groups. Additional multi disciplinary analyses are warranted to confirm inferred patterns of Indus mobility, but the available isotopic data suggest that efforts to classify and regulate human movement in the ancient Indus region likely helped structure socioeconomic integration across an ethnically diverse landscape.