Reconstruction of Late Paleozoic Climatic Changes in Angaraland According to Phytogeographic Data

Abstract

A brief description of the Carboniferous and Permian floras of the Angara (northern extratropical) paleofloral province is given. The latter includes lepidophyte flora from the Early Carboniferous, postlepidophyte flora from the beginning of the Middle Carboniferous, and cordaite flora from the second half of the Carboniferous-Permian, comprising three geofloras. Analysis of the compositions of floras and their geographical distributions allows the climates of the different Carboniferous and Permian epoches to be reconstructed: a warm and frost-free climate during the Early Carboniferous, a cold climate at the beginning of the Middle Carboniferous, and a temperate one during the second half of the Carboniferous and Permian. Abrupt cooling at the Early-Middle Carboniferous boundary (replacement of the frost-free climate by the cold one) and the synchronous Gondwanaland glaciation of the southern hemisphere suggest the onset of a contrasting climate and the formation of subpolar ''refrigerators,'' which evidently existed by the end of the Late Permian. One epoch of relative cooling (the Early Permian-beginning of the Late Permian) is distinguished from the generally temperate climate of the second half of the Carboniferous-Permian. It separates two relatively warm epoches: the late Bashkirian-Late Carboniferous and the Late Permian epoches.