Understanding Geohydrology

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Research Goal 1-Central California Coast Ranges basins

Understanding any geohydrologic system requires characterization of the geometry and properties of geologic materials and structures at the surface and in the subsurface. Cenozoic basin-fill can have great lithologic diversity and large variation in hydrologic behavior.  Surficial deposits that may not be representative of the basin-filling history often cover deeper basin fill units. In order to provide a useable framework for hydrologic flow models, it is necessary to add the third dimension; geologic maps of surficial materials alone are not sufficient to characterize the basin fill and basin depositional history. Digital and conceptual models of the hydrogeologic framework must describe the surficial and subsurface stratigraphy, lithology, structural heterogeneity, and the spatial and depth variability of these elements.

The central Coast Ranges, between Monterey and Point Arguello, form a large, but poorly understood region of central California between the very urban San Francisco Bay and Los Angeles areas along the plate margin boundary.  Fundamental questions about the tectonic framework and geologic development of this area remain unanswered, such as the relationship between thrust and strike-slip faults (i.e. are the thrust faults bounding crustal flakes that root into the major strike-slip San Andreas and Hosgri faults or do these strike-slip faults sole into a detachment at depth?), the nature of the junction between two sub-parallel pairs of strike-slip faults near the La Panza range (La Panza knot), and how slip is transferred from the clockwise rotation of the western Transverse Ranges into this region.  Basins and valleys, such as Salinas Valley, Cuyama Valley, Jolon Valley, and the Santa Maria basin, record much of this tectonic history as well as contain important aquifers.  These areas are where the population resides and like most of the western U.S., are growing.  Salinas Valley is an important agricultural region (the “salad bowl” of the country) that depends heavily on groundwater.  Many of these basins also host oil and gas fields, such as the San Ardo field in Salinas Valley.  Understanding of the basin infrastructure is key to predicting whether oil and gas will mingle with aquifers. 

As part of our characterization of the faults that traverse the central California Coast Ranges, we flew an aeromagnetic survey.  Aeromagnetic data can be used to map the location of faults concealed beneath water and young sediments and project them to great depth, such as that depth where earthquakes nucleate.  These faults can also influence groundwater flow.

Research Abstracts for Goal 1

Watt, J.T., Johnson, S.Y., Langenheim, V.E., Scheirer, D.S., Rosenberg, L.I., Graymer, R.W., Kvitek, R., 2009, Geologic mapping in the central California coastal zone: Integrating geology, geophysics, and geomorphology, GSA Annual Meeting, Paper No. 101-36.

Jachens, R.C., Langenheim, V.E., Wentworth, C.M., Simpson, R.W., and Graymer, R.W., 2009, Defining fault offsets from aeromagnetic anomalies: Central California Coast Ranges: Geological Society of America Abstracts with Programs, v. 41, no. 7, p. 281.

Graymer, R.W., Langenheim, V.E., Rosenberg, L.I., Colgan, J.P., and Roberts, M.A., 2010, New insights into the tectonics of the central california coast ranges from cross-sections based on digital geologic mapping and potential-field geophysics: Geological Society of America Abstracts with Programs, v. 42, no. 4, p. 82.

Langenheim, V.E., Jachens, R.C., Graymer, R.W., Wentworth, C.M., Colgan, J.P., and Stanley, R.G., 2010, Implications of cumulative offsets along the San Gregorio-Hosgri Fault, California: Why the Santa Maria Basin Matters: Geological Society of America Abstracts with Programs, v. 42, no. 4, p. 81.

Nishenko, S.P., McClaren, M.K., Page, W.D., Langenheim, V.E., Watt, J.T., Greene, H.G., Rietman, J.D., Lettis, W.R., Angell, M., and Kvitek, R., 2010, Shoreline fault zone, south-central coastal California: Geological Society of America Abstracts with Programs, vol. 42, no. 4, p.82.

ytuba, James, J., 2010, Geothermal systems in the Paso Robles groundwater basin, central Coast Ranges, California, Geological Society of America, Cordilleran Section Meeting Anaheim.

Sweetkind, D.S., Langenheim, V.E,, and Shumaker, L.E., 2010, Configuration and lithology of Mesozoic basement beneath the Santa Maria basin, CA from analysis of borehole data: Geological Society of America Abstracts with Programs, v. 42. no. 4, p. 79.

Scheirer, D.S., Sweetkind, D.S., Langenheim, V.E., and Stanley, R., 2010, Can Gravity Anomalies be used to Delimit Pre-Pliocene Sedimentary Basins in the Central Coast Ranges, California?: Geological Society of America Abstracts with Programs, v. 42. no. 4, p. 80.

Taylor, E.M., Sweetkind, D.S., Garcia, A.G., and Shumaker, L.E., 2010, Terrain analysis and geologic field investigations used to constrain drainage evolution and basin-filling history within and near the northern Salinas Valley groundwater basin, Central California Coast Range: Geological Society of America Abstracts with Programs, v. 42. no. 4, p. 79.

Watt, J.T., Morin, R.L., and Langenheim, V.E., 2010, Using potential fields to refine basin and fault geometry in Salinas Valley, California: Geological Society of America Abstracts with Programs, vol. 42, no. 4, p.78.

Langenheim, V.E., Jachens, R.C., and Moussaoui, K., 2009, Aeromagnetic survey map of the central California Coast Ranges:  U.S. Geological Survey Open-File Report 2009-1044, scale 1:250,000 and database [http://pubs.usgs.gov/of/2009/1044/].

Sweetkind, D.S., Tennyson, M.E., Langenheim, V.E., and Shumaker, L.E., 2010, Digital tabulation of stratigraphic data from oil and gas wells in the Santa Maria Basin, central California coast: U.S. Geological Survey Open-File Report 2010-1129, 11 p., 3 tables. Available at: http://pubs.usgs.gov/of/2010/1129/