The stratigraphy of SD County’s coastal region contains seventeen formations that range from the Pleistocene to Late Jurassic. Between these bedrock layers, there are several unconformities that separate these strata.
The rock formations that are exposed at Torrey Pines bluffs show only the Bay Point Formation, Torrey Sandstone, and Delmar Formation. This means that between the Bay Point Formation and the Torrey Sandstone, there are nine formations that should exist between these strata, yet they are not found.
Bay Point Formation (120,000 years)
The Bay Point formation is a deposition of sandstone that has resulted from a marine terrace from during the Pleistocene. The sandstone was originally deposited partially in the ocean, …show more content…
Thus preserving the cracks. Concretions that can be found within the sandstone contain calcite and iron oxide that had run through the cracks within the sandstone.
The sandstone contains canyon features from the eroding rains.
Delmar Formation (45-50 million years)
Barrier islands and mud filled lagoons over eons of time turned into the green-grey shale that makes up the Delmar formation. Yet ten feet thick sandstone can also be found within the Delmar formation along with mudstone. You find these two rocks deposited in the same formation because the sand and base rock was deposited in a lagoon during middle Eocene. The lagoon depositions allow for marine fossils and cross bedding to be found. The cross bedding features can be seen in different directions, the current at the time was switching directions and thus piling sand up in different directions.
Age
The age of these strata is able to be determined due to the fossils that are found within the rock layer. Along with radioactive dating the igneous rocks that can be found near sediments that contain the same …show more content…
Torrey Sandstone is a deposit of rock resulting from a tidal flat. The Delmar Formation is a deposition of rock that has resulted from a lagoon.
Why We See Missing Layers Where we live in Southern California the land has been rising for the past million years due to faulting. With more ice at our polar regions we have lower sea level, and as that ice melts - the sea level rises. This back and forth pattern of rising and falling sea levels affects the coastal environments, as neither are steady processes. Numerous unconformities can be found between these layers of rock bed. The missing strata formations and unconformities that do not appear in the Torrey Pines bluffs have been eroded by multiple events. The wide open gap between the Bay Point Formation and Torrey Sandstone is missing millions of years worth of rock bed.