Late Palaeozoic–Early Triassic deposition and climates between Samfrau and Tethys: A review

Abstract

AbstractIn the period between the Westphalian and the Early Triassic, climatic conditions across Gondwana changed from the Gondwana-wide glaciation in the Late Carboniferous–Early Permian to warm to hot, semi-humid to arid conditions by the Late Permian–Early Triassic. In Afro-Arabia, glaciers advanced to 40° palaeolatitude creating a steep gradient between them and the temperate-humid environment in the vicinity of the equator. Synchronous deglaciation associated with a eustatic rise of sea level in the Early Sakmarian was followed by a flattening of the climate gradient and increased humidity, expressed by blackwater rivers and coal swamps between the South Pole and about 50° palaeolatitude and increasing aridity towards the equator. Brief poleward advances of hot aridity are evident around the Kungurian. Expansion of the hot climate zone to the south took place in the Middle Permian, commencing with a humid to semi-humid phase in the south and semi-arid to arid conditions towards the north. A short pluvial event is locally indicated at the beginning of the Triassic, but warm semi-arid to semi-humid conditions prevailed in the south and hot aridity near the equator. There are variations of that general theme in eastern Gondwana, but the fundamental changes in climate-controlled depositional environments occurred almost synchronously over the whole of Gondwana, including Antarctica. The slight drift of Gondwana towards the equator is therefore an unlikely cause for these changes, as are modifications of ocean–continent geometries or of atmospheric composition. As the main driver was temperature it is suggested that governing control, not only of global temperature but also of the intensity of geotectonic activities, was imposed on the solar system by forces emanating from our galaxy (cosmic ray flux, magnetic intensity, gravitational vectors) and their variation over the course of a galactic year (the time for the solar system to orbit the core of the galaxy).