Tectonic Framework for Precambrian Sedimentary Basins in India

1 1 The Archean and Proterozoic History of Peninsular India: Tectonic 2 Framework for Precambrian Sedimentary Basins in India 3 4 Joseph G. Meert1 and Manoj K. Pandit2 5 1Department of Geological Sciences, 241 Williamson Hall, University of Florida, Gainesville, FL 32611 USA 6 2Department of Geology, University of Rajasthan, Jaipur 302004, Rajasthan, India 7 2 8 Abstract 9 The Precambrian geologic history of peninsular India covers nearly 3.0 billion years of time. The Peninsula 10 is an assembly of five different cratonic nuclei known as the Aravall-Bundelkhand, Eastern Dharwar, Western 11 Dharwar, Bastar and Singhbhum cratons along with the Southern Granulite Province. Final amalgamation of these 12 elements occurred either by the end of the Archaean (2.5 Ga) or the end of the Paleoproterozoic (~1.6 Ga). Each of 13 these nuclei contains one or more sedimentary basins (or metasedimentary basins) of Proterozoic age. This paper 14 provides an overview of each of the cratons and a brief description of the Precambrian sedimentary basins in India 15 that form the focus of the remainder of this book. In our view, it appears that basin formation and subsequent clo- 16 sure can be grossly constrained to three separate intervals that are related to the assembly and disaggregation of the 17 supercontinents Columbia, Rodinia and Gondwana. The oldest Purana-I basins developed during the 2.5-1.6 Ga in- 18 terval, Purana-II basins formed during the 1.6-1.0 Ga interval and the Purana-III basins formed during the 19 Neoproterozoic-Cambrian interval. 20 21 Introduction 22 Peninsular India represents an amalgam of ancient cratonic nuclei that formed and 23 stabilized during Archaean to Paleoproterozoic (3.8-1.6 Ga). Modern-day Peninsular India 24 is comprised of five Archaean nuclei known as the Banded Gneiss Complex (Aravalli re- 25 gion), Bundelkhand, Singhbhum, Bastar and Dharwar cratons (figure 1). The southern 26 granulite province is a polycyclic region that also contains Archaean-age crustal elements 27 that are dissected by younger orogenic belts. This review paper will focus on the Archean- 28 Paleoproterozoic history of each of the major cratonic elements of Peninsular India on 29 which large sedimentary basins were formed. 30 We make every effort to provide updated geochronologic data for each of the re- 31 gions, but note that there is still a paucity of reliable U-Pb, Pb-Pb, Ar-Ar and Sm-Nd ages. 32 Older K-Ar and Rb-Sr ages are used only when there are no other data available and only to 33 provide some constraints on the development of the region in question. The paper begins 34 with an overview of the Aravalli-Bundelkhand sectors and then moves eastward to the 35 Singhbhum craton; the central Indian Bastar craton and concludes with a look at the east- 36 ern and western Dharwar and regions. 37 Each of the aforementioned cratonic elements contains Precambrian- Early Paleozo- 38 ic sedimentary (or metasedimentary) sequences that form the basinal infrastructure of 39 Peninsular India. Among the best-preserved sedimentary sequences are the so-called 40 “Purana” or ancient basin. These include the large Cuddapah, Chhattisgarh and Vindhyan 41 basins along with several smaller regional basins known as the Indravati, Khariar, 42 Prahnita-Godavari, Kaladgi, Bhima, Kunigal, Kurnool and Marwar. There appear to be sev- 3 43 eral key intervals of basinal development (and closure) within Peninsular India. Purana-I 44 basins began development in the Paleoproterozoic (2.5-1.6 Ga); Purana-II basins formed 45 during the Mesoproterozoic (1.6-1.0 Ga); and the development of Purana-III basins is con- 46 fined to the Ediacaran-Cambrian interval. Basinal development and closure may be tempo- 47 rally related to the formation/breakup of the supercontinents Columbia (fig 2a; Purana-I), 48 Rodinia (fig. 2b; Purana-II) and Gondwana (fig. 2c; Purana-III). As a general reminder, we 49 note that the present-day basinal outcrops/areal extent of the sedimentary sequences and 50 may not accurately reflect the extent of those sequences at the time of deposition. We also 51 wish to note that we use the term ‘closure’ to indicate a period of time when the basin 52 stopped receiving sediments. Defining the cause of basinal closure in Proterozoic basins 53 can be difficult and may be related to the creation of tectonic barriers to sedimentation, 54 burial by younger (and now eroded) sedimentary sequences, sea-level change and many 55 other factors. If discussed in our overview, we provide only a best estimate for when clo- 56 sure occurred and offer some speculation for why sedimentation ceased. 57 Aravalli Banded Gneiss Complex and Bundelkhand Cratons 58 The Aravalli Banded Gneiss Complex (BGC)-Bundelkhand protocontinent occupies 59 the north-central region of the Indian sub-continent (Fig. 1). The Great Boundary Fault 60 (GBF) marks a present-day physiographic divide between the two blocks with the BGC 61 cratonic block to the west of the GBF and the Bundelkhand-Gwalior block to the east of the 62 GBF. These cratons are bounded to the Northeast by the Mesoproterozoic-aged Vindhyan 63 basin and the Indo-Gangetic alluvium and to the south by the northern edge of the Deccan 64 Traps volcanic rocks. The Western Margin Fault forms the wester boundary of the BGC. 65 The Bundelkhand and BGC regions are also separated from the Bastar and Singhbhum 66 cratons by the Central Indian Tectonic Zone (Fig. 1; Goodwin, 1991; Naqvi and Rogers, 67 1987; Meert et al., 2010). 68 There is considerable debate regarding the nature and age of the basement rocks in 69 the BGC. In part this was due to a lack of high-quality geochronological data for the differ- 70 ent metamorphic complexes and in part due to the obscured nature of the contacts be- 4 71 tween the separate regions (Ramakrishan and Vaidyanadhan, 2008; Buick et al., 2006; Roy 72 et al., 2012). The current status of this debate is described below. 73 The Banded Gneiss Complex was a catch-all term for the gneissic rocks that were lo- 74 cated to the west of the Great Boundary Fault (Heron, 1953) although Gupta (1934) had 75 recognized some differences between the eastern and western side of the Banas lineament 76 (Fig. 3). Gupta subdivided these two regions into the BGC-1 and BGC-2 domains (see also 77 Roy and Kroner, 1996; Wiedenbeck and Goswami, 1994; Gopalan et al., 1990). BGC-1 met- 78 amorphic basement included the Mewar gneisses whereas the BGC-2 region is composed of 79 rocks known as the Sandmata and Mangalwar Complexes. 80 The gneissic rocks of the BGC are dated to between 3300-2900 Ma (Roy and Kroner, 81 1996; Wiedenback and Goswami, 1994; Gopalan et al., 1990) and are dominated by 82 tonalite-trondjhemite gneisses (TTG’s) that are intruded by late Archaean granitoids dated 83 to between 2600-2500 Ma (i.e. the Untala, Gingla and Berach granites; Wiedenbeck et al., 84 1996a,b; Roy and Kroner, 1996; Meert et al., 2010). 85 Deb (1999) reported a 2075-2150 Ma Ga Pb-Pb age for galena, presumably 86 syngenetic with the basal Aravalli volcanics. In the absence of any direct geochronologic ev- 87 idence this age is taken to represent the initiation of Aravalli sedimentation. Further sup- 88 port is provided by Pandit et al. (2008) and de Wall et al. (2012) who describe the paleosol 89 below the Aravalli Supergroup to have developed during the Great Oxidation Event (GOE). 90 Intrusion of 1850 Ma Darwal Granite has generally been accepted as the closing age for 91 deposition of the Aravalli Supergroup. 92 The Mangalwar Complex (BGC-2) is located between the Banas & Delwara linea- 93 ments (Fig. 3). It has been subdivided into a number of formations (Ramakrishan and 94 Vaidyanadhan, 2008), but the relationships between the various formations that make up 95 the Mangalwar are very poorly known. The rocks of the Mangalwar Complex include 96 TTG’s, gneisses, migmatites, schists, amphibolites and quartzites. Commonly cited ages for 97 the Mangalwar Complex ranged between 2900-2600 Ma (Ramakrishan and Vaidyanadhan, 98 2008). 99 The Sandmata Complex (BGC-2) is sandwiched between the Delwara and Kaliguman 100 lineaments (Fig. 3) and is composed of TTG’s, metapelites, metapsammites, metagabbros, 101 charnockites and granulites (Buick et al., 2006). Ages from the Sandmata Complex also 5 102 cluster between 1.7-1.8 Ga (Buick et al., 2006). Roy et al. (2012) reported older ages from 103 the Sandmata Complex between 2.9-1.9 Ga. Those authors reaffirmed the problematic 104 metamorphic history recorded in both the Sandmata and Mangalwar Complexes, but ar- 105 gued that an Archaean-age component was present in the BGC-2 rocks albeit considerably 106 younger than the oldest ages recorded in the Mewar gneisses to the southeast. 107 Bhowmik et al. (2012) attempted to synthesize the available geochronological data 108 into a plate-tectonic framework for the development of the BGC region that we have modi- 109 fied slightly. During the interval from 3.3-2.5 Ga, the basement rocks of the craton were 110 formed that included both the BGC-1 rocks (TTG gneisses) and the BGC-2 rocks 111 (Mangalwar and Sandmata Complexes). The basement gneisses were then intruded by a 112 series of granitoid rocks that completed the stabilization of the craton (Sinha-Roy et al., 113 1998; Roy and Jakhar, 2002). Between 2.4-2.1 Ga an ocean basin formed and the Aravalli 114 Supergroup sediments were deposited (Deb and Thorpe, 2004, Deb, 1999).

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