Flood basalt weathering has a limited role in driving global cooling during the Mesozoic

The emplacement of large igneous provinces (LIPs) is known to be a driver of climate change in Earth’s past. However, the balance of climate warming through CO₂ emission and cooling through weathering is poorly understood.

Our study is focussed on the period between 300 and 150 million years ago (Ma), when the supercontinent Pangaea began to rift and break apart, a process which initiated many of the Earth system and evolutionary upheavals that led to the planet’s current configuration. During this time some of the largest LIPs in Earth history were emplaced, sometimes coinciding with mass extinctions. For example, the Siberian Traps (252 Ma), which is the largest continental LIP by volume, and widely thought to be the driver of the End-Permian Mass Extinction7,16–18. Later in the Mesozoic, the Central Atlantic Magmatic Province (CAMP; 201 Ma), the largest continental LIP by area, has been linked to the end-Triassic. Further, the Karoo and Ferrar LIPs (183 Ma) have been implicated in the end-Pliensbachian extinction, and Toarcian anoxic event respectively. To determine if major LIPs could have led to cooling on multimillion year timescales, and to investigate the cumulative impact of numerous LIP emplacements, we use a long-term climate-biogeochemical model (SCION) integrated with the record of LIP emplacement between 300 and 150 Ma. SCION uses a 3D emulated climate, which allows us to move beyond simple consideration of latitude bands to consider intersections of LIPs with local temperature, relief and hydrology, which is essential for estimating weathering—especially considering the prevalence of extensive aridity in Pangaea.

Of the seven LIPs during the breakup phase of Pangea, only the Central Atlantic Magmatic Province (CAMP) drives noticeable long-term cooling in the model, a minor effect (around 1°C) despite emplacement of a very large surface area in the humid tropics. Similarly, only the CAMP imparts a significant change in the long-term Sr isotope record whereas the other LIPs of this period do not. Due to limited areal extents, and emplacement outside tropical weathering zones, we conclude most LIPs have no significant global cooling effect on multimillion year timescales.