Extending Darwin with Ediacaran and Small Shelly Fossils (?) In > 1000 Ma Rocks from Peninsular India

The Ediacaran Period (635 Ma to 543 Ma) is characterized by a burst of biotic diversification in the aftermath of the global Marinoan glaciation. Typical and arguably Ediacaran and early Cambrian (presumably Tommotian; 530 Ma to 525 Ma) acritarchs, soft-bodied metazoans, and small shelly fossils (Anabarites, Beltanelliformis, Conophyton, Colonnella, Cyclomedusa, Ediacaria, Eoporita, Girvanella, Hiemalora, Hyolithelus, Kaisalia, Kussiella, Medusinites, Megasphaera, Michrystridium, Nimbia, Obruchevella, Paliela, Protohertzin, Renalcis, Rugatotheca, Spriggina, Tribachidium, Zinkovoidies, etc.) have been found in units of (a) the Semri Group (Lr Vindhyan Supergroup), (b) the Bhander Group (Up Vindhyan Supergroup), and (c) the Tarenga and Charmuria Formations (Chhattisgarh Supergroup) in peninsular India (e.g., Azmi et al., 2006; De, 1999, 2003, 2007; Moitra, 2003; Prasad, 2007). U-Pb age dates of magmatic zircon from ash beds, detrital zircon from sandstones, provenance arguments, and compatibility of paleopole positions, however, date the deposition of these units at approximately (a) 1630 Ma, (b) ≥1000 Ma, and (c) very slightly younger, if not altogether older, than 1000 Ma respectively (Ray et al, 2002; Rasmussen et al., 2002; Sarangi et al. 2004; Ray, 2006; Patranabis-Deb et al., 2007; Chakrabarti et al, 2007; Malone et al., 2008). The age-contradiction can be resolved if it is hypothesized that (1) life forms reported from the Vindhyan, Chhattisgarh and equivalent sedimentary rocks of peninsular India evolved much earlier in the Paleoproterozoic (cf. Bengtson et al., 2007), (2) in early times, these life forms were far fewer in number and were not preserved as gorgeously as in the Ediacaran, and, (3) the rate of biotic diversification and the rate of preservation were not coupled. The hypothesis, at this point, provides an ad hoc explanation for inferred explosive biotic radiation between ~650 Ma and ~520 Ma at excessively high rates (cf. Blair and Hedges, 2005; Donoghue and Benton, 2007).