Abstract
Potassium feldspar present in global mineral aerosol (<5%) plays a disproportionate role in modulating the microphysics of mixed-phase cloud. Via exceptional ice nucleation properties, it is capable of changing cloud properties and behaviour. Here we identify times of substantial and abrupt change in the global availability of potassium feldspar since 600 Ma. Normally, weathering and vegetation cover contribute to low availability, with clay dominating mineral aerosol. Periods of maximum availability are reasoned to follow the emplacement and remobilization of ejecta blankets from major meteorite impact events, before returning to background after some hundreds to thousands of years. We review the 44 largest confirmed craters and evaluate the potassium feldspar content of their target rocks, which range from c. 0 to >30%. By combining crater size and tectonic reconstructions, we are able to provide a quantitative and self-consistent assessment of changes to global potassium feldspar availability. Considerable differences in potassium feldspar availability following meteorite impact events are revealed. Different impact events generated dust containing different amounts of potassium feldspar. Differing levels of influence upon climate are hypothesized, and should now be tested by looking at stratigraphic records of these events to reveal the sensitivity of climate to different dust mineralogy. Supplementary material: Figures showing palaeolatitude determinations using various methods and reconstruction models, and estimates of alkali feldspar abundance and distribution across contemporary continental landmasses for meteorite impact events are available at: https://doi.org/10.6084/m9.figshare.c.4253312
Highlights
Kfs availability to the atmosphere, at a global scale, is buffered at low levels owing to chemical weathering and heterogeneous distribution of both high- and low-Kfs rock types
Placing upper limits on Kfs availability is more challenging to attempt with any useful degree of accuracy
A subset of these ejecta blankets were high in Kfs; they hold the greatest potential to change the global atmospheric ice nucleation regime so far recognized in geological history
Summary
Kfs availability to the atmosphere, at a global scale, is buffered at low levels owing to chemical weathering and heterogeneous distribution of both high- and low-Kfs rock types (Pankhurst 2017). We show here that global-scale dust-producing events can be quantified, and time-stamped, which implies that a way forward is possible. Rapid ice-sheet retreat has the potential to increase the abundance and proportion of Kfs available to the atmosphere by exposing fresh, finely milled rock powder (Pankhurst 2017). Compared with the timescales of these terrestrial processes, meteorite impact events are instantaneous, and have the potential to effect more dramatic change in surface KFF by distributing local rocks over global scales
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
