Palaeoproterozoic of India: an introduction

Abstract

A relatively rapid change in the Earth’s surface processes has been anticipated across the Archaean– Palaeoproterozoic boundary as a consequence of changes in the crust–mantle system and tectonic regime (Condie 1989, 1997; Eriksson et al. 2004; Reddy & Evans 2009). The Palaeoproterozoic era (2500–1600 Ma: Plumb 1991) represented perhaps the first supercontinent cycle, from the amalgamation and dispersal of a Neoarchaean supercontinent to the formation of the 1.9–1.8 Ga supercontinent Nuna (Reddy & Evans 2009), and encompasses one or more global tectonic event that coincides with fundamental changes in the integrated system of core, mantle, lithosphere, hydrosphere, atmosphere and biosphere (i.e. an integrated Earth System). An integration of seemingly disparate geoscience disciplines is therefore an essential prerequisite to understand these changes (Reddy & Evans 2009); and that was the aim of the UNESCOIGCP 509 project (2005–2009) on Palaeoproterozoic Supercontinents and Global Evolution. The fifth and final conference and postconference field workshop (in the Singhbhum Craton) related to the UNESCO-IGCP 509 project was organized by the Indian Statistical Institute (ISI), Kolkata with financial support from the UNESCO, the ISI, and the Council of Scientific and Industrial Research, Government of India during the period 26 October–3 November 2009. An entire session was devoted to the Palaeoproterozoic geology of India, as the Indian Shield represents a vast repository of the Palaeoproterozoic geological record. While most of the papers presented in this session were essentially on Palaeoproterozoic geology of the Indian Shield, a few were on the geological record during the Archaean– Palaeoproterozoic and Palaeo-Mesoproterozoic transitions. Some clues to the tectonic regime changes during these transitions also add to our understanding of the Palaeoproterozoic Earth processes, and how they connect with earlier or later periods of Earth’s evolutionary history. A thematic set of 13 papers on various regional as well as broader issues of the Indian Palaeoproterozoic geology and their global context constitute the present Special Publication. Built over the four major amalgamated Archaean nucleii, the major and minor Palaeoproterozoic sedimentary basins and supracrustal sequences in India contain potential information comparable only in scales to those of North America, Africa, Australia and Brazil. The deformation of these supracrustal sequences, attendant metamorphism and emplacement of plutonic bodies hold important clues to their connection with major orogenies, and facilitate investigations into global correlations. The latter has a direct bearing on refining models of Palaeoproterozoic supercontinent assembly and break-up. This volume begins with an overview of the Palaeoproterozoic geological records of the Indian Shield by Saha & Mazumder, wherein the key stratigraphic and tectonic issues are highlighted. Major Palaeoproterozoic sedimentary systems, according to these authors, developed in an intracratonic to marginal-marine setting. In significant contrast to the presence of banded iron formations (BIFs) in the Archaean of Singhbhum and Dharwar, the Indian Palaeoproterozoic supracrustals are devoid of BIFs. This article also provides a brief overview of the fold belts that straddle the suture between major Archaean nuclei, and the attendant tectonic processes. A comprehensive tectonic model for the amalgamation of the major Archaean nuclei of Dharwar, Bastar, Singhbhum and Aravalli–Bundelkhand, according to these authors, is yet to emerge and is of paramount importance to further our understanding of Palaeoproterozoic supercontinent development. An updated critical analysis of the Mesoarchaean–Palaeoproterozoic stratigraphic record of the Singhbhum Craton and a synthesis thereof has been undertaken by Mazumder et al. According to these authors, the stratigraphic record of the Singhbhum Craton across the Archaean–Palaeoproterozoic boundary implies a changing tectonic scenario. They have pointed out problematic and controversial regional stratigraphic issues that need to be resolved through further geochronological studies in order to understand the relationship between Singhbhum and other cratonic provinces of India, Australia and South Africa. In a complementary paper, Mazumder et al. have presented a critical analysis of the Singhbhum Palaeoproterozoic supracrustals, and compared the northern and southern Singhbhum successions, and their possible relationship with global-scale events and those identified on Kaapvaal. Abbott et al. have reported native Fe, native Si and (Fe, Mn)S