I came across this rock east of Austin, Nevada.
I don’t recall ever seeing anything just like it. This was at a small quarry and the material appeared to be useful for fill or maybe road surfacing. My first impression was this was fossiliferous limestone. However, when I looked closely, the features that I imagined to be shell fragments gave no evidence of being shells. Instead, they appeared to be shards of limestone in a matrix of gritty limestone. The outcrop was a limestone breccia. (I spent a little while scouring the area looking for fossils. I did not find any fossils.)
There is a story here. My read: Limey mud was deposited. This requires still water, not flowing water. The mud was exposed to air and through evaporation began hardening into limestone–a process that would work its way from the surface downward. After the surface (millimeters to a centimeter) hardened, a flood shattered the surface and swept the mixture of limey mud and limestone shards together into another slack water area where the material settled. Again, it was exposed to air and through evaporation began again the process of turning into the rock we see today.
Polemic Note: When Sean Pittman writes that the carbonate interdune deposits (these are limestones containing varying proportions of sand) form by “settling” from the waters of the flood he is ignoring the limey breccias that are sometimes found on these interdune deposits. These breccias are evaporite deposits–skins of hard carbonate that formed over soft mud, skins that there then broken up by wind action and pushed to the lee side of the interdune surface where they resumed their drying and hardening. This is not readily reconciled with Flood geology.