Mass wasting of Atlantic continental margins following the Chicxulub impact event

Abstract

The Chicxulub impact 65 Ma triggered massive submarine failure of continental margins around the North Atlantic. Slumped sediments associated with impact ejecta and geochemical tracers of the bolide are present on the Blake Plateau, the midAtlantic continental slope and rise, Bermuda Rise, and the Iberian Abyssal Plain more than 6000 km from the impact crater. Evidence from deep-sea drilling and seismic stratigraphy suggests that much of the eastern seaboard of North America and at least parts of the eastern margin of the North Atlantic must have failed catastrophically because of the ϳ10-13 magnitude earthquake associated with the impact event, and created one of the largest, composite mass-wasting deposits on Earth. We infer that mass failure of the eastern margin of North America can account for elevated extinction rates and delayed recovery of North American invertebrates compared to other places during the Cretaceous-Paleogene mass extinction. Slumping on the margins also redeposited large volumes of carbonates into the deep sea below the Cretaceous carbonate compensation depth (CCD), giving the false impression of a drop in the CCD during the Maastrichtian.

Late Devonian Alamo Impact, southern Nevada, USA: Evidence of size, marine site, and widespread effects

“…unstable, impact-shattered carbonate-platform margin could have rapidly transported large quantities of debris to the deep-water setting, generating additional tsunami as a result. The importance and widespread effects of post-impact submarine mass wasting are well documented for other marine impact events (e.g., Bralower et al, 1998;Norris and Firth, 2002;Dypvik and Jansa, 2003).…”

Bolide summer: The Paleocene/Eocene thermal maximum as a response to an extraterrestrial trigger

“…Although we chose to use a large comet in our model, a similar perturbation to atmospheric pCO 2 could be obtained with a smaller bolide impact triggering release of terrestrial carbon stores. Effects resulting from a high energy impact that might release carbon to the atmosphere include 1) superheating of the atmosphere from the shock wave preceding the bolide as well as dispersion of melted material excavated at the site of impact and from the bolide itself, which have been implicated in widespread fires at the K/T boundary (but see Belcher et al, 2003) and could account for fires that have been more firmly documented coincident with the CIE Kaiho et al, 2003); 2) a large tsunami in the event of an oceanic impact, which has been implicated at the K/T boundary in slope failures along the North American Atlantic continental margin and widespread turbidite deposits (Norris and Firth, 2002;Olsson et al, 2002) and could account for slope failure at the P/E boundary documented along the North American Atlantic continental margin (Katz et al, 2001), potentially releasing methane and/or hydrocarbon reserves (although we note that there was no whole-ocean δ 13 C decrease at the K/T boundary); 3) vaporization of the impactor and target rock (e.g., O'Keefe and Ahrens, 1989); and 4) in the event of an oceanic impact, the initial warming would have been enhanced by rapid venting of much of the excess deep ocean CO 2 to the atmosphere and enhanced atmospheric H 2 O. In fact, our choice of a large comet minimizes the initial perturbation to the carbon cycle: reducing the size of the comet, or assuming a non-carbon-rich bolide, would force us to add more carbon from a less 12 C-enriched source in order to account for the initial decrease in δ 13 C values.…”

The Obolon impact structure, Ukraine, and its ejecta deposits

“…In the upper part of the sequence, large blocks of the fractured Triassic red clays and sandstones are present those accumulated through their sliding from the crater rim. Submarine sliding processes play an important role at forming shallow marine impact structures (e.g., Claeys et al 2002;Norris and Firth 2002;Dypvik et al 2004). …”