Neptunism was on its way out through the late 1600s to 1700s, and was pretty much gone (among geologists) by 1800. Mind you, people before 1650 were frequently skeptical that the fossils could be old enough to be from the flood, given how well-preserved they were, as compared to ancient buildings.
The Flood consisting of a series of megatsunamis caused by giant asteroid impacts is directly contradicted by scripture, as scripture rules out the ark getting repeatedly flipped by tsunamis in a boiling opaque slurry (formerly known as the oceans), and the animals inside getting cooked by said slurry. Also, if one is trying to have the megatsunamis deposit fossils, one runs into all the tiny, fragile shells in numerous different layers, each layer with its own set of tiny, fragile shells. Many of said shells are fragile enough to break if I were to set a 10 gram weight on them, let alone place them in a violently churning slurry ocean. Also, a violently churning slurry cannot deposit mud (or, given the violence invoked, anything smaller than boulders).