Rock Formations

Rocks at the Reserve

Geological Map of Torrey
Pines State Natural Reserve

All of the rock layers at Torrey Pines are sedimentary, made up of pieces of older rocks. The layers are divided into formations that are different enough from each other to be told apart and are big enough to be seen on a geologic map. Starting with the oldest, they are the Delmar Formation, the Torrey Sandstone, the Lindavista Formation, and the Bay Point Formation.

The ages of the four formations are determined from the fossils found in each. The Delmar Formation and the Torrey Sandstone are both middle Eocene (48,000,000 years old), the Lindavista Formation is middle Pleistocene (1,000,000 years old), and the Bay Point Formation is upper Pleistocene (120,000 to 400,000 years old). The absolute year ages come from radioactive dating of igneous rocks found elsewhere near sediments with the same fossils. The radioactive clocks start when crystals are formed in the cooling molten rock.

The Reserve has been cut by the sea into several marine terraces. The steps of the terraces are hard to see because erosion has covered them with mud and cut canyons into them. The terraces have also been cut by several faults that cut across the Reserve. The faults are easily seen in the beach cliffs and in the road cut for Torrey Pines Road.


Next topic: Cliffs