The sedimentary walls of the crater progressively slumped in, widened the crater, and formed a layer of huge blocks on the floor of the ring-like trough.
The slump blocks were then covered with the rubble or breccia.
The entire bolide event, from initial impact to the termination of breccia deposition, lasted only a few hours or days.
In the perspective of geological time, the 0.75 mi (1.2 km) breccia is an instantaneous deposit.
The crater was then buried by additional sedimentary beds that have accumulated during the 35 million years following the impact.
Hope this helps!
