This is a spectacular exposure that can be seen along the Farmer Ridge trail about 2.5 miles from the start of the Day 3 hike. Here the dark gray slate in the left and upper center parts of the photo has been intruded by a very light gray, intrusive igneous granodiorite. Based on the age of the granodiorite in Griffith Park, this event occurred about 100,000,000 years ago and very deep within the crust of the Earth. Overlying the slate and the granodiorite at the top of the photo is a brown conglomerate and sandstone rock unit called the Monterey Formation. It is about 12,000,000 years old. In order for these relationships to exist, the slate and granodiorite had to be uplifted and very deeply eroded before the conglomerate and sandstone were deposited on top of them. Note the light-colored boulders of granodiorite in the conglomerate that prove that the granodiorite was eroding and being incorporated into the conglomerate.
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