I think someone like Clive Oppenheimer would say both
Neither! Space rocks or earth hiccups never destroyed anything. the k-pg line is the flood line. the flood killed all biology, except on the ark or gods preservation in the water, and this fossil segregation is only because of unique fossilization oprocesses due to the flood or a few minor later events.
They insist its the space rock and only a few say volcanoes.
They are funny myths.
Who are the few?
I have read that a few still say it was volcanic action that brought the big die off and not meteors.
On youtube or wiki etc.
A flood line with Iridium in it?
Obviously, the iridium was divinely placed there to test our faith. (kidding)
Another topic. however yEC would see the iridium layer, where found, as just the front of what was behind. That is volcanic debris or ash from events after the flood.
its not from a space rock but massive volcanic eruptions all at once about a few centuries after the flood.