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Palaeogeography and Continental Reconstruction of the Proto-Eastern Gondwana and the Occurrences of Proterozoic Oil

Vibhuti Rai and Neetima Sateeja
Centre Of Advanced Study in Geology University of Lucknow, Lucknow 226007, U.P., India

In the post-Rodinia times, the disintegration of several Rodinian blocks assembled in a framework which constitute the basis of a regional terrain called as Proto Eastern Gondwana. Although, the geomagnetic signatures vividly support this new assembly, the regional geotectonic framework authenticates the assembly to a larger extent.

The culmination of various fragments of Rodinia derived blocks (continents) into Afro-Asian region supports the idea that a regional assembly of India (including Pakistan), Madagascar, Oman, Arabia, Afghanistan (Lut) and Iran juxtaposed each other in such a way that during the later part of Neoproterozoic, a large depositional basin developed near the equator. The basin evolved for almost 100 Ma up to the end of Early Cambrian (including the Precambrian- Cambrian Boundary) and in a few areas, the deposition further continued.

The occurrence of large carbonate deposits alongside evaporites, followed by phosphogenic events provided crucial inputs in deciphering the depositional realm in a geotectonic framework. An assessment of the basin using palaeobiological evidences suggests that Varanger equivalent glaciation marked by diamictite, followed by a cap-carbonate, occurs as the marker of Ediacaran period and later in the stratigraphic sequence we get the Ediacaran biota, microfossils of cyanobacterial affinity, other algal fossils, acritarchs, calcareous algae, sponges, typical bedding plane traces (grazing) and small shelly fossils heralding the beginning of the Early Cambrian period.

The occurrence of phosphorite deposits, evaporites and the Terminal Proterozoic oil from the strata (named differently in different parts of the region) suggests regional depositional system in which marine phytoplanktons got deposited, accumulated and later matured to generate hydrocarbons (Heavy Oil) triggering the development of Ediacaran play in the region. In addition to the Proterozoic oil occurrences, huge limestone deposit provides major input to cement industry which is currently required for resource development.

We propose here a geotectonic model comprising the palaeogeography and evolution of the Post Rodinia-Pre Gondwana continental setup which is also the Proterozoic play for hydrocarbon occurrences in the region.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery