The sedimentary basins both onshore and offshore, including the Outer Santa Cruz basin, were formed along the California margin during the transition period between subduction and transformation. These basins were then enlarged, elongated, filled and deformed during the transform movement, and transported on the Pacific plate to their present location. During their evolution many of these basins underwent a depositional and thermal history that favored the generation and concentration of hydrocarbons. Today, onshore seeps of tar sands are present along the coast between Santa Cruz and Davenport (Phillips 1990). Offshore, a concentration of shallow hydrocarbons, including natural seepage of thermogenic hydrocarbons into the oceanic water column, occurs near the southern terminus of the outer Santa Cruz basin (Nagel 1983, Nagel et al. 1986). Several oil fields have been developed in the region, including the Half Moon Bay, La Honda and Moody Gulch fields (Wright 1990). All are located along structures that resulted from Neogene and Quaternary tectonic movement (McCulloch 1987).
With the exception of jade, no economically important deposits of minerals have been located within the MBNMS. Phosphate coating has been identified on rocks in Monterey Canyon (Greene 1977, Galliher 1932), but are not of the concentration to warrant mining.
Jade and jadeite exist along the Big Sur coast, and have been mined for years. They are eroded from Franciscan rocks during periods of severe storms and heavy winter rains. An especially large block (9000 lbs) of nephrite jade was taken from the nearshore seafloor in 1971 (Wobber 1975). Amateur mineralogists and gem collectors regularly comb the Big Sur coast for jade, and much jade is still believed to occur offshore.
C. Building materials
Though sand and gravel are mined from the Santa Margarita Formation in the Santa Cruz Mountains (Phillips 1981) and limestone and dolomites are mined from the Santa Cruz, Gabilan, and Santa Lucia Mountains, these materials have not been mined along the coast or within the MBNMS. However, mining of fine-grained quartzose sands used in porcelain making has taken place in the nearshore regions of southern Monterey Bay (Arnal et al. 1973, Galliher 1932). Only one sand mine operation exists (in Marina).Historically, as many as three or four sand mining operations exported these sands all over the world.
Section VI. Coastal Erosion