Resumen
The end of the Permian period is marked by global warming and the biggest known mass extinction
on Earth. The crisis is commonly attributed to the formation of large igneous provinces because continental volcanic
emissions have the potential to control atmospheric carbon dioxide (CO2
) levels and climate change. We propose that in
southwestern Gondwana the long-term hothouse Permian environmental conditions were associated with the development
of the Choiyoi magmatism. This large igneous province was developed between the Cisuralian and the early Triassic.
It covers an area estimated at 1,680,000 km2
with an average thickness of 700 m, so that the volume of effusive and
consanguineous rocks is estimated at 1,260,000 km3
. Towards the western sector of the study region, a major overlap
exists between the regional development of the Choiyoi magmatism and the Carboniferous sedimentary basins, which
include paralic and continental deposits with intercalations of peat and coal beds. Commonly, these upper Palaeozoic
deposits accumulated on a thick substrate composed of Cambro-Ordovician carbonates and Ordovician to Devonian
terrigenous sedimentary rocks characterised by a large proportion of dark organic-rich shales and turbidite successions.
While extensive volcanism released large masses of carbon dioxide into the Permian atmosphere, the heating of Palaeozoic
organic-rich shales, peat and carbonates by ascending magma led to CO2
and CH4
gas generation in sufficient volumes
to amplify the major climatic change. The analysis of the almost continuous record of Permian redbeds in the Paganzo
basin, where the Choiyoi magmatism is not recorded, allowed us to recognize two main pulses of strong environmental
desiccation, one at the Cisuralian and the second around the end-Permian. These two drastic climatic crisis are attributed
to peaks of CO2
and CH4
outbursts to the atmosphere and related collateral effects, such as acid rain, impoverishment of
soils and increase in forest-fire frequency. We propose that the combination of these multiple mechanisms triggered the
decline of biodiversity in southwestern Gondwana and caused the end-Permian extinction of most of the Glossopteridales.