That would put it at least some 300 million years ago.

along with the rock surrounding it. How much that extends out from the crater rim is something geologists would know, I don't. My geology courses were ages ago, when plate tectonics was just a theory.

That doesn't mean that there aren't deep deposits under the level of vaporization at the impact site, thrust deeper by the shock wave.

The dinosaurs were on their way out when that thing hit, thanks to the massive vulcanization in India plus disease brought on by slow starvation. That asteroid just finished them off.

and ejecta is found mostly in the Caribbean basin, but the vapors and ash made it all around the earth.

There are a few disputes about the single asteroid strike. You still have Keller who wants to say different, but it is shaping up fairly clearly that she's probably wrong. The iridium spike is exactly at the K/T boundary, dinos below, no dinos above. Pretty much says it all.

The dinos in decline evidence is also explained by selection biases in the fossil beds that have nothing to do with actual decline. So that is also in dispute.

My source is Skeptics Guide to the Universe who interview paleontologists regarding these matters. But I am sure that an expert would say it differently.

and in any case there isn't a huge deposition of dinosaur skeletons right at the KT extinction boundary. That's why so many think the population was probably stressed almost to the point of extinction before the impact. Likely the slow decline had been happening from anything for tens of thousands to a million years, a slow-mo extinction that left little evidence.

Speculation is great fun and let's be honest, after 65 million years, it's about all we have.

However, the energy released from the gas and oil it contacted was miniscule compared to the energy of the asteroid itself.
500 meters of andesite glass and breccia make up the interior of the crater, rock instantly melted to glass with the heat.
any organic (like oil, coal etc.) would have been vaporized, and and the crater looked like a huge cauterization scar.

would it not be likely that beyond the cauterization/vaporization zone, cracks in the earth's crust could have occurred, releasing oil?

but finding evidence of that would be quite improbable.

Here's a great animation that explains the forces and the reactions of the rock around it

How long ago....was that part of the earth, where the Deepwater Horizon deposits formed, above groud/not under water?

It was above water and covered with vegetation, then covered with h2o as the seas rose and fell repeatedly. Top layers weren't oil yet when the asteroid hit.

The impactor was ten kilometers wide; anything for a huge distance around the impact point would have been vaporized, driven deep into the crust (if not the mantle), or blown into space.

On that sort of scale, things like oil reservoirs (and there would still have been one then) would mostly have been irrelevant compared to the impact, the firestorms, the megatsunami, the acid rains and the nuclear winter. The Gulf of Mexico and neighboring areas would probably have been completely sterilized, and a lot of the rest of the planet wasn't that much better off for awhile.

the precise oil reserves released by Deepwater Horizon, were they already in place when the asteroid hit, or did they form after? I know they are separated by hundreds of miles.

My question isn't so much about the life that was wiped out... but what happened inside the earth, underground. If oil deposits were released, did they flow out for hundreds of years until depleted? Is there even any way of knowing?

The majority of the oil reserves these days would have been laid down pre-dinosaurs.

Nearly any that were directly affected by the impact would have been vaporized (and then ignited), or would have been re-sealed under the molten rock as it resolidified. It wouldn't have been a case of mere cracks forming at all, not with that kind of force. Some probably did leak for awhile afterwards for sure, but there wouldn't be much left in the oceans to notice, and a Deepwater Horizon-scale spill is probably way too small to notice in the geological records that far back anyway. That goes double in an area that got as disrupted as the gulf did by the K-T impact.

so at most a case of some insignificant bleeding around a gaping, cauterized wound.

Living on the gulf, the oil spill was a scary time. A lot of wild theories were floating around, including the possibility of part of the gulf coast collapsing into the water. The consensus seemed to be: stopping the oil leak was really important.

Everyone agreed that oil continuing to flow into the ocean for years would be a bad thing. I don't think anyone is disputing that. But how bad? Had the leak never been plugged, had it kept leaking for years... would that actually poison the entire ocean eventually, as people warned back then? If so.... if an oil leak is capable of poisoning the entire ocean now, how many previous oil leaks impacted the world's oceans? No one seemed to know how many years the Deepwater well would have leaked had it not been capped.

The impactor gouged a hole almost 200 kilometers wide and probably ten or fifteen deep before the rocks began to stabilize and collapse into a less ridiculous profile. Absolutely nothing that's happened to the planet since then could even begin to attempt to consider coming close to the violence of what happened there. We're talking North and South America largely on fire for days, earthquakes above 10.0 on the Richter scale, and a 25,000-square-kilometer hole in the ground.

Completely draining a major oil reservoir right into the ocean wouldn't even get noticed alongside something like that. That happening to us would suck, but as bad as it would be the Earth - and even the Gulf of Mexico specifically - have taken some real hits before and come back from them.

You all make me feel a little smarter for reading...something that doesn't happen alot in online forums