Meteorites that produce K-feldspar-rich ejecta blankets correspond to mass extinctions

Abstract

Meteorite impacts load the atmosphere with dust and cover the Earth's surface with debris. They have long been debated as a trigger of mass extinctions throughout Earth history. Impact winters generally last <100 years, whereas ejecta blankets persist for 103–105 years. We show that only meteorite impacts that emplaced ejecta blankets rich in K-feldspar (Kfs) correlate to Earth system crises (n = 11, p < 0.000005). Kfs is a powerful ice-nucleating aerosol, yet is normally rare in atmospheric dust mineralogy. Ice nucleation plays an important part in cloud microphysics, which modulates the global albedo. A conceptual model is proposed whereby the anomalous presence of Kfs post impact is posited to have two key effects on cloud dynamics: (1) Kfs reduces the average albedo of mixed-phase clouds, which leads to a hotter climate; and (2) Kfs weakens the cloud albedo feedback mechanism, which increases climate sensitivity. These mechanisms offer an explanation as to why this otherwise benign mineral is correlated so strongly with mass extinction events: every Kfs-rich ejecta blanket corresponds to a severe extinction episode over the last 600 myr. This model may also explain why many kill mechanisms only variably correlate with extinction events through geological time: they coincide with these rare periods of climate destabilization by atmospheric Kfs.Supplementary material: Extended Fig. 1 from main text is available at https://doi.org/10.6084/m9.figshare.c.5690646