High Quality Content by WIKIPEDIA articles! The Yacoraite Formation is a largely Mesozoic geologic formation. The deposits of this formation mainly date from the Maastrichtian of the Upper Cretaceous, but the K–T boundary runs right through this formation near its top, and the uppermost parts are consequently from the Danian (Lower Paleocene). It was probably deposited around the intertidal zone, as the sedimentary rocks of this formation alternate according to sea level changes between deposits of muddy beaches and of shallow ocean.