T247 Volcanism, Impacts, and Phanerozoic Mass Extinctions: Discovering a Common Cause and Planning for the 6th Mass Extinction I

Wednesday, 25 September 2019
8:00 AM - 12:00 PM
Room 227ABC, North Building

INTEGRATING THE LARGE IGNEOUS PROVINCE (LIP) RECORD WITH BIOLOGICAL AND ENVIRONMENTAL CHANGES RECORDED IN THE SEDIMENTARY RECORD

Paper number: T247-1
Program: Technical Sessions
Time: 8:00 AM – 8:15 AM

Authors

Abstract

Large Igneous Provinces (LIPs) are a significant driver of global climatic and ecological changes including, in some cases, mass extinction events. Correlations of the magmatism-global climate change nexus have been extended into the Precambrian, and LIPs are potential markers for Precambrian time boundaries. Recent developments have created an opportunity for more systematic integration of major magmatic events such as LIPs with the sedimentary record.

LIP RECORD: High-precision U-Pb dating of LIPs is essential for meaningful correlation with the sedimentary record. Many factors control the climatic and ecological effects of LIPs. Whether a LIP is continental or oceanic matters, because oceanic LIPs do not drive mass extinctions. The magnitude of volatile release probably matters, and the original areal extent of flood basalts can be used to estimate this, but constraints are also needed for atmospheric inputs related to degassing from mafic sills emplaced into volatile-rich sedimentary basins. Silicic magmatism from calderas can have a stratospheric effect (global cooling). Faster erosion of flood basalts can cause cooling (weathering and CO2 drawdown; nutrients (e.g. P) carried into the ocean causing a productivity increase). Continental configuration at the time of emplacement can also be an important factor determining LIP lethality. Also important is how close the background climate is to a tipping point.

SEDIMENTARY RECORD: High precision dating of ash layers allows precise correlation of sedimentary sequences far removed from the site of LIP emplacement if that LIP is also precisely dated. Sharp eustatic sea level changes can be linked to glaciation / deglaciation (which can have a LIP cause). Sudden changes in regional topography including unconformities can identify regional uplift and rift zones associated with plume-generated LIPs. Sudden lithological changes can be linked with LIPs, including deposition of black shales (often associated with extinctions), diamictites (glacial event), and iron formations (link with oceanic plateaus). Other potential responses to LIP events in the sedimentary record include major changes in stable isotopic composition (sensitive to temperature, carbon fixing, mafic sedimentary input, pH, oxidized/reduced level), and trace elements such as Hg.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-332571

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