Sedimentary evidence of Early–Late Permian mid-latitude continental climate variability, southern Bogda Mountains, NW China

Abstract

A preliminary Early–Late Permian mid-latitude continental climatic record in NW China was interpreted mainly from sedimentary climate indicators and type and stacking pattern of depositional systems and cycles in a 1178-m fluvial–lacustrine section. Depositional systems analysis delineated five types of primary fluvial and lacustrine depositional cycles, which were grouped into three (high, intermediate, and low) orders. Semi-arid, subhumid, and humid climate types in terms of relative precipitation/evaporation ratio were interpreted and climate variability was identified at sub-cycle and high, intermediate, and low-order cycle scales. Early Kungurian climate fluctuated between subhumid to humid and middle–late Kungurian climate shifted gradually from subhumid/semi-arid to semi-arid. Roadian climate fluctuated widely from humid to semi-arid with strong precipitation seasonality at sub-cycle and high-order cycle scales. Wordian climate was dominantly humid with short subhumid intervals and ended with a peak semi-arid condition. Capitanian climate was mainly subhumid to humid, as the start of a long interval of dominantly humid, strongly wet–dry conditions into the Wuchiapingian time. The late Kungurian–Wordian semi-arid condition is incompatible with modern mid-latitude east-coast humid climate, suggesting different mechanisms operating in Pangea and Panthalassa. The highly variable Roadian–Wordian climate may have started terrestrial mass extinction that climaxed at the end of Permian.