The fossil floras of Kachchh. III - Tertiary megafossils

Abstract

A complete account of plant megafossils described so far from the Eocene, Miocene and Pliocene beds of Kachchh District has been given. The megafossils belong to Algae and Phanerogams. The algal remains comprise the calcareous red algae assigned to the family Corallinaceae. Out of eight species belonging to five genera, three species representing the two genera: Lithothamnium and Lithophyllum, have been reported from the Eocene and five species belonging to the genera Lithophyllum, Mesophyllum, Archaeoporolithon and Aethesolithon are from the Lower Miocene deposits. The phanerogamous megafossils have been described from the Lower Eocene, Miocene and Pliocene beds. The Eocene megafossils consist of leaf-impressions belonging to eight species of dicotyledons and one species of monocotyledons. The Miocene assemblage is based on leaf impressions, seeds and petrified woods assigned to 14 genera and 15 species of dicotyledons and a palm. The megafossils recovered from the Pliocene deposits are all petrified woods belonging to seven families (5 dicotyledons, 1 palm and I gymnosperm) represented by 14 genera. Besides, two palm woods and a graminaceous stem reported from unknown Tertiary horizons have also been included.

In the light of distribution of their modern comparable forms, all the components of the Tertiary flora of Kachchh are tropical. Because of the occurrence of moist evergreen as well as deciduous taxa, the flora can be placed under the category of "moist tropical semi-evergreen to deciduous forests". The environment of deposition seems to have been mainly lacustrine and fluviatile. The overall vegetation of Kachchh during the Tertiary period was more luxuriant than the scrubby vegetation thriving there today. Obviously the present xeric conditions are a result of post-Pliocene changes in the climate in this area. Even during the Tertiary, Kachchh witnessed periodic changes in climate. It was moist during the early Eocene, gradually becoming comparatively drier during early Miocene and again turning moist towards the end of Miocene.

The occurrence of marine algae in the Eocene and Miocene deposits indicates that there was transgression of sea in Kachchh during Eocene and Miocene epochs.