PENNSYLVANIAN FUSULINID DISTRIBUTION ON THE EASTERN PANGEAN MARGIN AND RESPONSE TO TECTONIC UPLIFT AND LONG-TERM CLIMATE CHANGE
The assemblage (A) inhabited proximal parts of large eperic basins during early transgression (ETST), when alpine glaciers periodically, with an interval of ~1,000,000 y, were accumulated in the high mountains. Situated near the equator these glaciers were melting fast. Large volume of water and sediments loading into the basins, which were surrounding the uplands, was one of the factors for their isostatic subsidence documented in appearance of complete fusulinid cycles (A, B, C) in sedimentary successions. The cyclic occurrence of late Moscovian fusulinids coincides with expansion of moist-like vegetation in the terrestrial deposits of the Western Europe (WE) during Westphalian D.
During early Kasimovian, which coincides with dry episode in WE (Cantabrian – early Stephanian), all genera from A and B assemblages become extinct, only C assemblage (incomplete fusulinid cycle) indicating persistence of very shallow marine condition occurs in the epicontinental seas in the eastern Pangean margin.
A cyclic repetition (A, B, C) represented by morphologically variable Triticites is recovered again in the late Kasimovian – Gzhelian time and coincides with another wet episode in WE (late Stephanian).
High-elevated mountains especially capped by alpine glaciers might increase monsoonal circulation resulting in wet climate in the northern slope of Variscan orogenic front.
Due to high denudation rate during Moscovian, mountains were partly eroded to the end of Moscovian. Alpine glaciers were absent in early Kasimovian time, resulting in an isostatic uplift of the Pangean continent and shoaling of surrounding seas. As mountains were not high, the monsoonal circulation decreased, moisture-bearing atmospheric currents could easily overcome this barrier and precipitation might be scattered over larger geographic areas reducing wetness in WE basins.