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The Century-Old Problem of the Pali-Parsora-Tiki Stratigraphy and its Bearing on the Gondwana Classification in Peninsular India

1993; Springer Science+Business Media; Volume: 42; Issue: 1 Linguagem: Inglês

10.17491/jgsi/1993/420102

0974-6889

Prodip K. Dutta, S. Ghosh,

Geological and Geophysical Studies

The stratigraphic relationship between the Pali-Parsora-Tiki formations in the South-Rewa Gondwana basin remains unresolved after more than a century. We believe that this is primarily related to the flawed methodology used in addressing Ihe problem. The stratigraphic soIulion was, exclusively, lied to fossil-based age data which is an interprelative element in any stratigraphic analysis. Field relationships such as lithological associations, petrological character and order of superposition that contradicted the fossil-based stratigraphy were ignored. The contradictions, however, were explained by Conjectual faults, also an interpretative criterion that was invoked to explain the stratigraphy. The conventional hierarchical approach to stratigraphy, beginning with physical criteria followed by biostratigraphy and chronostratigraphy, was missing. The sequence encompassing the Pali, Tiki, and Parsora formations can be divided into two well defined lithostratigraphic units. A feldspathic sandstone-red mudstone association characterizes both the Pali and Tiki formations and is considered, in this paper, as a single lithostratigraphic unit. Tentatively and informally, the unit is named as Pali-Tiki Formation. The second unit, a quartzose sandstone-conglomerate and variegated clay association typifies the Parsora Formation. The Pali-Tiki Formation can be traced almost continuousIy from the Pali area to Tiki village. The field relation clearly demonstrates that the Parsora unconformably overlies the Pali-Tiki. Based on vertebrates, plants and palynological criteria, the Pali-Tiki formation has been assigned latest Permian/Early Triassic to Middle Norian age. The Parsora Formation spans from a little above Middle Norian to well within Early Jurassic. The Glossopteris flora that flourished in the Permian continues across the Permo-Triassic boundary into the Pali-Tiki Formation. The Dicroidium flora appears at the base of the Pali-Tiki Formation and demarcates the Permo-Triassic transition. In the Parsora Formation both Glossopteris and Dicroidium floral assemblages are present and extend, at least, up to the Early Jurassic. These observations go against the fundamental tenet of a two-fold classification scheme for the Gondwana System in peninsular India. This work supports a three-fold classification for the Gondwana system, solely based on floral content. If the floral elements are taken away, the physical straligraphers can make a strong case for a two-fold division based on lithology, petrography and the widespread unconformity throughout peninsular India. A unified classification scheme using both biological and physical pilrameters does not seem to work.