Early Permian palaeofloras from southern brazilian Gondwana: a Palaeoclimatic approach

Abstract

In evaluating the parameters supplied by the taphofloras from different sedimentary facies in the Early Permian sedimentary sequences of the southern part of the Parana basin, Brazil, it has become evident that the palaeofloristic evolution was related to palaeoecological and palaeoclimatic evolution. The homogeneous composition of Early Permian floral assemblages, which are characterized mainly by herbaceous to shrub-like plants considered to be relicts from the rigorous climate of an ice age (e.g. Botrychiopsis plantiana) suggest the persistence of the cold climate. The dominance of Rubidgea and Gangamopteris leaves with palmate venation associated with glossopterids with penate venation seems to indicate a gradual warming of climate. In roof-shales of coalbearing strata pinnate glossopterids related to are common, while Gangamopteris and Rubidgea (palmate forms) are poorly represented. The sudden enrichment of herbaceous articulates and filicoids fronds is characteristic of this stage and trunks of arborescents lycophytes become important elements. These antrocophilic paleofloras are characterized by typical elements of the Glossopteris flora associated to tree lycophytes and ferns communities. Therefore, the cool seasonal climate of Early Permian changed into the moist seasonal interval during the Artinskian-Kungurian. This climatic change was significant to the meso-hygrophitic to hygrophitic vegetation registered in roof-shale ferns of the Gondwana Southern Brazilian coalbearing strata.