Stratigraphic record of the asteroidal Veritas breakup in the Tortonian Monte dei Corvi section (Ancona, Italy)

Abstract

The discovery of elevated concentrations of the cosmogenic radionuclide 3He in deep- sea sediments from Ocean Drilling Program (ODP) Site 926 (Atlantic Ocean) and ODP Site 757 (Indian Ocean) points toward ac- cretion of extraterrestrial matter, probably as a result of the catastrophic disruption of a large asteroid that produced the Veritas fam- ily of asteroids at ca. 8.3 ± 0.5 Ma, and which may have had important effects on the global climatic and ecologic systems. Here, we in- vestigated the signatures possibly related to the Veritas event by performing a high- resolution multiproxy stratigraphic analysis through the late Tortonian–early Messinian Monte dei Corvi section near Ancona, Italy. Closely spaced bulk-rock samples through a 36-m-thick section, approximately spanning from ca. 9.9 Ma to ca. 6.4 Ma, show an ~5- fold 3He anomaly starting at ca. 8.5 Ma and returning to background values at ca. 6.9 Ma, con rming the global nature of the event. We then analyzed, at 5 cm intervals, bulk-rock samples for sedimentary and environmen- tal proxies such as magnetic susceptibility, calcium carbonate content, total organic carbon, and bulk carbonate d18O and d13C, through a 21-m-thick section encompassing the 3He anomaly. Available high-resolution sea-surface temperature data (via alkenone analyses) for this site show a temperature decrease starting exactly at the inception of the 3He anomaly. Cyclostratigraphic fast- Fourier-transform spectral analyses of the proxies indicate an age of 8.47 ± 0.05 Ma for the inception of the 3He anomaly. A search for impact ejecta (analogous to what is pres- ent in the late Eocene, where both a 3He anomaly and large-scale impact events are recorded) was not successful. Detailed cy- clostratigraphic analyses of our data suggest that the changes in the stable isotope series and environmental proxy series through this late Tortonian time interval had a common forcing agent, and that perturbations of or- bitally forced climate cycles are present ex- actly through the interval with the enhanced in ux of extraterrestrial 3He. Thus, the che- mostratigraphic evidence for a collisional event that created the Veritas family of aster- oids, coinciding with climate perturbations on Earth, suggests yet another form of inter- action between Earth and the solar system.