Asteriod collision 65 million years ago in the Mexican Gulf

[John Justice]

At the time of asteroid impact 65 million years ago wiping out the dinosaurs and 50 % of all life on Earth - presuming all but the smallest mammals or sea creatures suggests that humans most likely wouldn't be here today if not for that event because the tiny mammals which then existed would not have had opportunity to evolve, and reptiles would still be the dominant species on earth. No civilizations and humanity. God works in mysterious ways!

 

[berkeman]

Welcome to the PF.

Did you have a question, or just wanted to share?

 

[BillTre]

Here are some recent, very detailed reports of what happened during this impact at both ends of the event, the actual impact (described geologically) and a series of events that resulted in the North Dakota findings.
Both of these events were revealed in:

• a series of thick, rapidly deposited sedimentary layers,
• showing a succession of different events,
• yielding a high temporal resolution in both events in the hours after the impact and the series of events involved in the mass entombment event.

The impact site in Yucatan was described based upon cores drilled through select locations of the peak ring located off shore in the Gulf of Mexico. This yielded 180 m of sediment for a single day! Differences in these sediments revealed a sequence of events immediately after the impact.
The first results from these cores were published ScienceMagNews and ResearchArticle (maybe behind paywall). More recently additional results were reported in a NYTimes and the PNAS article ($10 paywall, original article).
Series of events:

1. impact: crater: 60 miles diameter, 20 miles deep
2. this launched a lot of stuff out of the crater (including water) which came down in different places
   1. sulfur containing sediments vaporized by the impact reduce the Earth's temperature for 30 years​
3. The interior of the impact crater rebounded (rock materials are now fluid) to a central peak which then collapses into a peak ring between the center and crater edge. This is where the cores in these studies were taken.
   1. water returns to the crater in hours resulting in sediments​
   2. more water returns via tsunami leaving different sediments​
4. The impact is considered by some to have made magnitude 10 or 11 earthquakes.
5. Strong seizmic waves arrived in North Dakota first and caused seitches making dying fish in mud
6. Tektites pelted down on the mud mix (having taken a a ballistic path out of the atmosphere and back in),
7. tsunami deposits hours after the impact (North Dakota had a coast on the Gulf which went way north at that time).

Earlier this year, a site (~3,000 miles away from the impact) in North Dakota was described where animals were killed and quickly entombed in sediments showing a bizarre sequence of events as described in 5, 6, and 7. PNAS article (free) and NYTimes article, The New Yorker article (good).

 

[DrStupid]

Does the new data allow to decide whether this impact affected the Réunion hotspot (resulting in the Deccan Traps) or not?

 

[BillTre]

The Deccan Trap flows were spread out over a long period both before and after the impact.

Here is a Science Mag News article on a couple of recent studies.

The researchers’ dates suggest the eruptions began 400,000 years before the impact, and kicked into high gear afterward, releasing 75% of their total volume in the 600,000 years after the asteroid strike.

suggest that the Deccan Traps erupted in four intense pulses rather than continuously, as Sprain suggests. One pulse occurred right before the asteroid strike. That suggests the impact did not trigger the eruptions, he says.

Another issue concerns weather or not the impact actually killed off the dinosaurs. This means no (non-avian) dinosaurs after (above in the sediments) the impact layer but dinosaurs existing up to immediately prior to the impact.
The lack of non-avian dinosaurs after the impact seems to be pretty well accepted (none have been found).
Dinosaurs up to immediately before the impact was often questioned due to the statistical nature of finding relatively small numbers of large fossils at particular sediment levels (such as immediately before the impact). There are reports that some busted up dinosaur pieces were found in the North Dakota deposits. These have not yet been published (first article was to describe the site geologically) but are expected to be in a subsequent paper. If so, they would provide strong evidence of non-avian dinosaurs immediately before the impact.

To me, a more interesting antipodal relationship is that between the monster Martian impact crater, Hellas Basin (7,000 meters deep, 1,400 km wide) and the approximately antipodal location of the Martian region of volcanoes (Alba Mons, Tharsis Mons, and Olympus Mons).