What geological period are the rocks in the Pelona Schist dated to?

The rocks in the Pelona Schist are primarily dated to the Cretaceous period, which is a significant geological era that lasted from about 145 to 66 million years ago. This period is known for its diverse array of marine and terrestrial life, as well as the presence of extensive sedimentary deposits.

The Pelona Schist itself represents a unit of metamorphic rock found in California that has undergone considerable geological transformation. During the Cretaceous, tectonic activity was pronounced, leading to the conditions that resulted in the formation of metamorphic rocks like the Pelona Schist. The processes of subduction and plate tectonics during this time are critical to understanding the metamorphism of these rocks.

This context is important when considering the other listed periods, which do not align with the dating of the Pelona Schist. The Jurassic period, preceding the Cretaceous, and the Triassic period, even earlier, are associated with different geological formations and conditions. The Paleogene period, which followed the Cretaceous, marks a time of significant evolutionary change and recovery after the mass extinction at the end of the Cretaceous, and it does not include the formation of the Pelona Schist.