What is the age of the rocks that the North Branch of the San Gabriel Fault is cutting through?

The age of the rocks that the North Branch of the San Gabriel Fault is cutting through is classified as Mesozoic. This time period, which spans from approximately 252 to 66 million years ago, is known for significant geological changes, including the formation of major mountain ranges and the presence of diverse fauna and flora, particularly the dinosaurs.

In the context of faulting and geological mapping, the Mesozoic rocks are significant because they often contain evidence of tectonic activity, which can help geologists understand the history of fault movements and the forces that shaped the region. Faults such as the North Branch of the San Gabriel Fault are often active in regions with older rock types, which have been subjected to tectonic forces over millions of years.

The other time periods mentioned — Quaternary, Paleozoic, and Proterozoic — represent different geological epochs that do not accurately reflect the age of the rocks associated with the fault in question. Quaternary refers to the most recent geological time, while Paleozoic and Proterozoic represent much earlier timeframes, with the Paleozoic ending around 252 million years ago and the Proterozoic preceding it significantly. Therefore, the Mesozoic designation