GLOBAL WARMING EVENT AND THE CHANGEOVER OF TERRESTRIAL ECOSYSTEMS DURING THE PERMIAN-TRIASSIC TRANSITION
At the end of the Permian,ca.252 million years ago,intense volcanic activities released a massive amount of CO2,CH4 and other greenhouse gases,resulting the surface seawater temperature rapid rising by 8～10 ℃,and the temperature rise may be greater in the terrestrial ecosystem.This global warming event had a devastating impact on both Marine and terrestrial ecosystems.However,the pattern of response of terrestrial ecosystems to this global warming event has been relatively poorly studied.Evidence of this warming event is preserved in the terrestrial Permian-Triassic transitional sedimentary sequence,including:terrestrial floras suffered a worldwide catastrophic die off of many plant groups in different geographical zones and followed by an Early-Middle Triassic'coal gap';the Permian gymnosperm-dominated floras in the Angara flora realm in the middle and high paleolatitudes of the Northern Hemisphere,the tropical rainforest-type Gigantopteris flora in the Cathaysia flora realm in the low paleolatitudes,and the coal-forming Glossopteris flora in the Gondwana flora realm in the middle and high paleolatitudes of the southern hemisphere all experienced catastrophic losses at the end of the Permian,and replaced by the flora dominated by dwarf Lycopodium at the beginning of the Triassic,which is adapted to the drought environment.The enrichment of charcoal fossils and polycyclic aromatic hydrocarbons from combustion sources in the latest Permian terrestrial strata suggests that the wildfire events occurred frequently on a global scale,resulting in rapid deforestation of terrestrial ecosystems during the Permian-Triassic transition period and global'coal-gap'in the Early Triassic.The Lopingian(Upper Permian)gray-green/yellow-green coal-bearing sediments is covered by the Lower Triassic purplish-red sediments,which contains numerous syngenetic soil breccia without any sorting and grinding,as well as freshwater calcareous nodules and gypsum deposited in evaporative environments,indicating arid climatic conditions and soil collapse during the Permian-Triassic transition and the Early Triassic periods.The collapse of terrestrial vegetation system aggravated the abnormal fluctuation of global carbon cycle and continental weathering,and huge amount terrestrial materials were imported into the ocean,which led to the rapid expansion of eutrophication and anoxic area in the ocean,and the development of microbial rocks and dolomites in the marine sedimentary sequence.The catastrophic processes of Earth's surface ecological environment at the end of the Permian provide an important geological analogous for the current rapid warming of the Earth.
万方数据
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