AN OCEAN ACIDIFICATION EVENT LINKED TO THE CENTRAL ATLANTIC MAGMATIC PROVINCE DETERMINED THROUGH DIRECT MEASUREMENTS OF CO2 FROM FLUID INCLUSIONS IN DEEP SEA CHERTS DURING THE END-TRIASSIC EXTINCTION

The Central Atlantic Magmatic Province (CAMP) has been proposed as the most temporally conspicuous trigger for the marine and continental end-Triassic extinction (ETE), ~201.6 Ma. The CAMP may have caused the ETE via short-term but intense volcanic winters from SO₂ and long-term global warming and ocean acidification from CO₂. Previous work has demonstrated a doubling of atmospheric pCO₂ following the initial emplacement of the CAMP. However, the extent of ocean acidification in the deep ocean at the ETE has not been quantified. We use fluid inclusions from bedded cherts (Inuyama, Japan) to reconstruct the deep ocean volatile content through the onset of the ETE and test the ocean acidification hypothesis. Volatiles in chert fluid inclusions were quantified by crushing under high vacuum into a quadrupole mass spectrometer. Our results show a tripling of CO₂ mol% and [CO₂]_aq as well as a decrease in pH and Ω_arag through the extinction interval followed by a return to pre-event values after the ETE. The maximum CO₂ values, minimum pH, and Ω_arag values in the deep ocean coincides with the onset of the oldest known CAMP lava flows in Morocco, based on the alignment with the continental and marine biotic extinction. However, an increase of CO₂ before the earliest of the preserved lava flows suggests a significant unknown earlier eruptive phase or degassing of CO₂ before the initial eruptive phase of the CAMP. The gradual pH and Ω_arag decrease following the event is consistent with model predictions of the continental silicate weathering response to the emplacement of continental flood basalts. The calculated pH and saturation, based on the fluid inclusion data, suggests that the deep ocean experienced intense and protracted acidification prior to and during the initial extrusive phase of the CAMP. This observation is consistent with previous work showing surface ocean acidification and a coral gap at the onset of the ETE. Intense ocean acidification and warming was likely the driver for the marine extinction, causing calcifiers to perish and other organisms that depend on them to follow suit, whereas the pattern of the terrestrial extinctions is most consistent with volcanic winters that favored survival of insulated forms capable of surviving.