Reappraisal of palaeofloristics of Himmatnagar Sandstone vis-à-vis palaeogeographic significance

Abstract

The state of Gujarat physiographically comprises three distinct zones–the Gujarat Mainland, the Saurashtra and the Kachchh. The sedimentary deposits of Himmatnagar Sandstone (23°36'00": 72°57'45") are mainly exposed in Gujarat Mainland. Palaeobotanical study reveals occurrence of plant fossils Matonidium, Weichselia, Cladophlebis, Gleichenia, Sphenopteris, Dictyophyllum, Pachypteris, Pagiophyllum and Araucarites. Bennettitales are absent. Numerically pteridophytes are represented by 61%, pteridosperms are represented by 7% and cyacads are represented by 7% while conifers are represented by 24%. The assemblage is compared and correlated with contemporaneous deposits in India and other Gondwanic continents and found that it is coeval to fossil floral assemblage of Dharangdhara Formation, (Saurashtra) and Bansa Formation of South Rewa (in central part of India) and Athgarh Formation on east–coast of India, in having common occurrence of Wealden frond Weichselia with dominance of pteridophytic fronds and conifers of family Araucariaceae. Due to common occurrence of pteridophytes and conifers (at generic level) the flora also resembles to Bluff flora of Alexander Island (Antarctica) and Barcó flora of Baqueró Formation of Patagonia (South America) indicating that the dispersal of biota might have taken place through Kerguelen Plateau or Gunners ridge via Antarctica.