HUMID AND ARID STATE OF THE WARM BIOSPHERE

Abstract

The warm biospheres of the Late Cretaceous and Early Triassic interglacials existed alternately in the humid or arid state. The stages of humid and arid climate differed considerably in their paleogeography and sedimentation regimes and showed dissimilar climatic zonation. The Late Cretaceous humid belts covered up to 75% of the land. The climate humidity was caused by the opening of oceans, large-scale transgression, and formation of large shelf and epicontinental seas, as well as by the fact that the land occupied a small area and included intracontinental lowland peneplain. The global spread of warm humid climate in the Late Cretaceous was favored by the existence of the Tethys and circum-global western currents in the tropic latitudes of the Northern Hemisphere. The Early Triassic climate was mostly arid (arid and semiarid belts occupied up to 80% of the land) because of the existence of the Pangea supercontinent, with its high hypsometric level, marginal and intracontinental mountain systems, and elevated plateaus separated by undrained areas. Investigation of geological, geochemical, and biological consequences of humid and arid climate stages may provide better understanding of the geologic and climatic history of the Earth.