Pretty clear both via depth maps showing the ejecta ring and center mound from "back slap", looking like other craters on dry land that have the little rise around lip of crater then center coming up again halfway or even to the former surface, example there is Crater Lake in the US, as well as gravity maps that show density in the area, posted below.








Compared to Crater Lake, much smaller size, and rotated a bit (˜120° CW) as well:

No citation you would "accept" has that information.  Once any geology, archaeology, or other science career topic drifts into those areas, the people are quickly removed from their scholarly work and become "para-" doctors and scientists.  Same way people believing in ESP and UFOs were "para-science" but now that the .gov is out in the open discussing these "para-scientists" proofs and results, things are being said more and papers are actually being published instead of kept on the down low.

Archeologists are the worse.  Their version of history changes by centuries every 10 years and not always in the same direction even for the same location.   In short, "Official Sources" or "Valid Sources" are restricted sources since too much information in the hands of people who didn't get a doctorate is dangerous, same way a president who wasn't part of the club was "Dangerous".

There is plenty of evidence around especially in Mayan calendars and their shared ancestors back to the Inca Gods where the number of "cycles" is disputed but argued at a low of 4-6 and more, and those cycles are 26000 years each.  Similar calendars are in India and Sumaria.  They don't match up numerically due to different lengths of measurement units of day/month/year/etc, but on celestial events and other records of major geological or meteorological change, some approximation to the current definition of years can be made.  However, this is all "para-science" since nothing existed prior to 50,000 years ago that resembled modern humans, and people refuse to accept existence of other extinct creatures being our ancestors, not in the Darwinian profile, but the dinosaurs were the king of their age, smaller and smarter beings became kings after peaks of intelligence causing wasteful things settled down again (depending on how you call genocide as peaceful or not).  Inuit tribes kept records, they've all kept and shared records and they've all managed to save some information in a safe place, as their history includes the disaster and reborn events so attempts are made to try and secure something for the future survivors of whatever lies next.  Were doing it now with the Seed Vault in Norway and Clock of the Long Now in Nevada (temporarily paused at the moment, IIRC), as well as other places not publicized but rumored, lots of nuclear defense bunkers and constructions to hold tens of thousands for a while with everything needed to come out and kickstart life once safe again, or until they run out of some resource, anyway.

TL;DR - There is none other than supposition and doing piecewise match ups of known celestial events, Magnetic Creep of North Pole and possible rotation changes from asteroid strikes, and other indicators can be copied and pasted together to create many alternative histories, each as valid as our own mainstream history held so dear by The Professionals.

Very true, but first they whittled 87 million rock grills out of the asteroid, which is why the asteroid is no longer sitting in the impact hole - its science. I saw the documentary on it.