PHANEROZOIC STRIATE MIOSPORES AS INDICATORS OF BIOTIC EVENTS AND STAGES OF PALEOFLORA EVOLUTION

Abstract

The development history of striate miospores is considered. These miospores appeared first by the end of the Silurian-the beginning of the Devonian. During the existence period of striate miospores that lasted more than 400 m.y., the number of "striate genera" varied and was different in every geological epoch of the Middle-Late Phanerozoic. The variations in abundance of "striate genera" distinctly depended on and, probably, were controlled by major phases of orogenesis, transgressions, regressions, glaciations, aridity fluctuations, and humidification of climate. These oscillations can be used for recognition of homeostasis periods, critical events, and transitional stages in the Phanerozoic evolution flora, the most characteristic of which are briefly described. Plants with striate miospores apparently filled the ecological niches vacated after extinction of their predecessors and, therefore, the striate miospores can be used as indicators of biotic events and stages in the paleoflora evolution. Permian paleoflora from southwestern Caspian depression is considered as a particular example elucidating such events and stages. Two important biotic events are recorded in this region in the boundary intervals separating the lower and upper Artinskian substages and the Ufimian and Kazanian stages. These events divide the Permian flora history into three periods corresponding to the Lower, Middle and Upper series of the Permian System.