Extinction of Dinosaurs: Consensus Reached . . . mostly

Hi kbertsche,
I've been getting into the impact field a fair bit as of late and of the P-T, T-J, and Eocene-Oligocene extinction events, only the Eocene-Oligocene event seems to have any really good evidence. The Eocene-Oligocene event has a crater (2 actually, Chesapeake Bay, Popigai), with distributed impact glasses (the bediasites). That said, the Eocene-Oligocene extinction was much smaller in scale compared to the K-T/Pg extinction, and may be due to other things instead of an impact.The T-J impact has some evidence of impact, but it's not found throughout the T-J boundary. There are about 3 craters that correspond roughly to the T-J boundary in terms of age, but none of them really match the T-J boundary date. The shocked quartz associated with this layer has also been dismissed as tectonic in origin. The iridium enrichment is about 1/10th-1/20th the enrichment of the K-T/Pg layer, which can be attributed to a slow-down in sedimentation rates. So the good evidence, like that found at the K-T/Pg layer, isn't there for the T-J layer.The P-T impact evidence is really poor. Bedout "crater", which is claimed to be impact-derived, is more likely volcanic in origin. The various impact evidences linked to that crater are also very dubious. While the presence of chondritic impactors in Antarctic rocks associated with the P-T boundary have been claimed (Basu et al., Science 2003), the claim is based on a small amount of metal in these rocks. Metal is rare in geologic samples, but is known to form during lightning strikes (see for instance: Lightning-induced reduction of phosphorus oxidation state | Nature Geoscience ), some of these can have a fair bit of nickel in them.