Middle Topanga/quartz diorite contact


Overlying the quartz diorite (on the left side of this photo) are sandstone beds of the Middle Topanga Formation (right side of the photo). Because the quartz diorite cooled into a rock deep below the surface of the Earth, a long period of uplift and erosion of the quartz diorite is required before the sandstone can be deposited on top of it.

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