evolution: another asteroid may have helped kill dinosaurs (Introduction)

by David Turell , Wednesday, October 16, 2024, 22:07 (36 days ago) @ David Turell

Off West Africa:

https://www.nature.com/articles/s43247-024-01700-4

"The Nadir Crater offshore West Africa is a recently proposed near K-Pg impact structure identified on 2D seismic. Here we present 3D seismic data that image this crater in exceptional detail, unique for any such structure, which demonstrates beyond reasonable doubt that the crater-forming mechanism was a hypervelocity impact. Seismic mapping reveals a near-circular crater rim of 9.2 km and an outer brim of ~23 km diameter defined by concentric normal faults. An extended damage zone is evident across the region, well beyond the perceived limit of subsurface deformation for impact craters, except in a ‘sheltered zone’ to the east. The paleo-seabed shows evidence for widespread liquefaction because of seismic shaking, and scars and gullies formed by tsunami wave propagation and resurge. Deformation within the ~425 m high stratigraphic uplift and annular moat allows us to reconstruct the evolution of the crater, with radial thrusts at the periphery of the uplift suggesting a low-angle impact from the east. Structural relationships are used to reconstruct the deformation processes during the crater modification stage, with the central uplift forming first, followed by centripetal flow of surrounding sediments into the evacuated crater floor in the seconds to minutes after impact."

Here is another report on the paper:

https://mail.google.com/mail/u/0/#inbox/FMfcgzQXJkQwcBGpvjXhJPqXVSxsqrpr

"Geologists from the University of Edinburgh, U.K., report that a second large asteroid impacted Earth at around the same time as the large one that has been held responsible for the extinction of dinosaurs. The dinosaurs are believed to have fallen victim to the aftermath of the impact of an asteroid with a diameter of about 10 kilometres that left a crater in Middle America about 66 million years ago. The new crater is just off the West Coast of Africa, stems from an asteroid with approximately half a kilometre in diameter, and has been dated to around the same time. It’s unclear how much this made things worse for dinosaurs, but it probably didn’t help."

Comment: looks like Chixculub had help.