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Understanding Geohydrology - Research Goal 3

The Sonoma Volcanics of northern California, a very heterogeneous package of volcanic rocks, provide a field laboratory in which to conduct volcanic aquifer studies and to evaluate which conclusions may have widespread relevance in volcanic terranes. These rocks are being tapped as a source of groundwater in the wine country. Geologic mapping currently is being conducted here as part of the 3D Geologic Maps and Visualization Project <>, although detailed characterization of the volcanic rocks is not part of the present effort.

We will revisit existing geologic mapping of the Sonoma volcanics to predict their material properties for the lithologies (flows, breccias, tuffs, etc.), the distribution of these units, and the role of structure in promoting or hindering groundwater flow. Detailed mapping in the Calistoga area will be done to promote understanding of one of the sources of the widespread volcanic units, allowing for predictions of the kinds and distribution of deposits that emanated from the center. Analysis of the aeromagnetic data with the context of the derivative maps will allow mapping of the volcanics into the subsurface.

Geohydrologic map of the northern San Francisco Bay region
This is a gravity map of the North Bay region that was created from more than 5800 gravity measurements which are the black and blue dots.  The blue dots are data that we’ve collected in the past 5 years.  This map tells us about density of the underlying rocks and we use these data to model the geometry of the Sonoma Volcanics and young sedimentary deposits--the main aquifers-- in the region.
We have made nearly 2000 new gravity measurements in the northern San Francisco Bay area to delineate potential volcanic sources (calderas) and to estimate the thickness of the valley-fill and volcanic aquifers.  We are compiling maps of ground water quality based on hydrothermal alterantion within the volcanic rocks using faults and other structures as a template for predicting the patterns of hydrothermal alternation in the subsurface.  We are also closely working with USGS hydrologists to produce a hydrogeologic model of the Santa Rosa Plain for ground-water flow modeling and have recently collected 13 km of seismic-reflection data in the Santa Rosa area to examine the subsurface structure and the Rodgers Creek fault with Rob Williams (USGS Golden).  Preliminary seismic-reflection results confirm the presence of a buried basement ridge that bisects the Santa Rosa Plain.  This basement ridge not only is important for understanding ground-water flow, but also appears to have helped focus earthquake energy into downtown Santa Rosa, explaining why this area is prone to high shaking and damage.

Geohydrologic map showing the location of a basinal depression beneath the Santa Rosa area in a vicinity coincident with earthquake damage Oblique views to the northeast across the Santa Rosa Plain towards Taylor Mountain
(TM) and the city of Santa Rosa.  (A).  Topography with draped simplified geology, which
illustrates the flat surface of  the Santa Rosa Plain.  (B)  Simplified surficial geology draped on the basement surface as defined by inversion of gravity data, which illustrates variation of basin thickness beneath the Plain and the local depression that coincides with the 1906 and 1969 earthquake damage shown in the orange and gold colors.  Gray, young deposits; yellow and brown, Tertiary (2-65 million years old) sedimentary rocks; magenta, Tertiary volcanic rocks; green, Mesozoic (older than 65 million years old) basement rocks

Langenheim, V.E., Graymer, R.W., Jachens, R. C., McPhee, D.K., Schmidt, K.M., 2003, The West Napa Fault as defined by gravity and magnetic data, northern California: Eos, Trans. AGU, v. 84, no. 46, abstract T11D-0429, p. 1337.

Sweetkind, D.S., Langenheim, V., , Rytuba, J., McLaughlin, R., Wagner, D., and Farrar, C.D., 2004, Geologic and geophysical mapping of the Sonoma Volcanic Field, California:  A progress report on hydrogeologic applications in the Napa and Sonoma Basins:  Geological Society of America Abstracts with Programs, Vol. 36, No. 5, p. 579.

Langenheim, V.E., Wagner, D.L., Farrar, C.D., and Sweetkind, D.S., 2005, Structure of Sonoma Valley, California revealed by geologic and geophysical mapping:  a fault-bend basin within the Rodgers Creek and Bennett Valley Fault zones?:  Geological Society of America Abstracts with Programs, v. 37, No. 4, p. 84.

Sweetkind, D.S., Rytuba, J.J., and Langenheim, V.E., and Sarna-Wojcicki, A.M., 2005, Contrasting styles of volcanism along the eastern side of Napa Valley, CA:  Geological Society of America Abstracts with Programs, Vol. 37, No. 4, p. 84.

McLaughlin, R.J., Sarna-Wojcicki, A.M., Fleck, R.J., Langenheim, V.E., McPhee, D.K., Jachens, R.C., Wagner, D.L., and McCabe, C.A., 2006, Neogene Structural Basins Beneath Santa Rosa Plain: Strike-Slip Basins Formed in Wake of the Mendocino Triple Junction During Initiation of the Rodgers Creek-Healdsburg Fault Zone: Eos, v. 87(52), Fall Meet. Suppl., Abstract T21B-0407.

Langenheim, V.E., McLaughlin, R.J., and Jachens, R.C., 2006, Insights into the evolution of faulting along the Rodgers Creek-Healdsburg-Maacama fault zones, as revealed by gravity and magnetic data [abs.]:  Seismological Research  Letters, v. 77, no. 2, p. 166.

McPhee, D.K., Langenheim, V.E., Hartzell, S., McLaughlin, R.J., Aagaard, B.T., Jachens, R.C., and McCabe, C.M., 2007, Basin structure beneath the Santa Rosa Plain, Northern California:  Implications for damage caused by the 1969 Santa Rosa and 1906 San Francisco earthquakes:  Eos, Trans. AGU, v. 88, no. 52, abstract NS24A-02.

Erickson, G., Kelsey, H., Langenheim, V., and Furlong, K., 2007, Evolution of an intermontane basin along the northern San Andreas system:  Evidence from basin structure of Little Lake Valley (Willits), northern California inferred from gravity and geologic data: Eos, Trans. AGU, v. 88, no. 52, abstract T43A-1098.

Langenheim, V.E., Jachens, R.C., Morin, R.L., McCabe, C.M., and Page, W.D., 2007, Implications of preliminary gravity and magnetic surveys to the understanding of the Bartlett Springs fault zone, northern California: Eos, Trans. AGU, v. 88, no. 52, abstract S21A-0246.

Williams, R.A., Langenheim, V.E., McLaughlin, R.J., Odum, J.K., Worley, D.M., Stephenson, W.J., Kent, R.L., McCullough, S.M., Knepprath, N.E., and Leslie, S.R., 2008, Seismic reflection profiles image the Rodgers Creek fault and Trenton Ridge beneath urban Santa Rosa, California:  Seismological Research Letters, v. 79, no. 2, p. 317.

Research Products

Sweetkind, D.S., Rytuba, J.J., Langenheim, V.E., Sarna-Wojcicki, A.M., and Alan Deino, 2005,  Day 3--Franz Valley, Petrified Forest, Napa Valley, in Late Neogene Transition from Transform to Subduction Margin east of the San Andreas fault in the wine country of the northern San Francisco Bay Area, CA, Fieldtrip 10, Calvin Stevens and John Cooper, eds., Pacific Section Society for Sedimentary Geology Book 98, p.82-112.

McLaughlin, R.J., Wagner, D.L., Sweetkind, D.S., Sarna-Wojcicki, A.M., Rytuba, J.J., Langenheim, V.E., Fleck, R.J., Jachens, R.C., and Deino, Alan, 2005, Late Neogene transition from transform to subduction margin east of the San Andreas fault in the wine country of the northern San Francisco Bay area, California:  Fieldtrip Guidebook and Volume for the Joint Meeting of the Cordilleran Section-Geological Society of America and Pacific Section AAPG, Book 98, 112 p.

Langenheim, V.E., Graymer, R.W., and Jachens, R.C., 2006, Geophysical setting of the 2000 M5.2 Yountville earthquake:  Implications for seismic hazard in Napa Valley, California: Bulletin of Seismological Society of America, v. 96, no. 3, p. 1192-1198.

Langenheim, V.E., Roberts, C.W., McCabe, C.A., McPhee, D.K., Tilden, J.E., and Jachens, R.C., 2006, Preliminary isostatic gravity map of the Sonoma Volcanic Field and vicinity, Sonoma and Napa Counties, California:  U.S. Geological Survey Open-File Report 2006-1056  [available on the World Wide Web at URL].

Langenheim, V.E., 2006, Appendix A.  Basement rock configuration interepreted from gravity data in Farrar, C.D., Metzger, L.F., Nishikawa, Tracy, Koczot, K.M., and Reichard, E.G., Geohydrologic characterization, water-chemistry, and ground-water flow simulation model of the Sonoma Valley area, Sonoma County, California, with a section on basement rock configuration interpreted from gravity data, USGS Scientific Investigations Report SIR  2006-5092, p. 110-115.  [available on the World Wide Web at URL:]

McPhee, D.K., Langenheim, V.E., Hartzell, S., McLaughlin, R.J., Aagaard, B.C., Jachens, R.J., and McCabe, C., 2007, Basin Structure beneath the Santa Rosa Plain, northern California:  Implications for damage caused by the 1969 Santa Rosa and 1906 San Francisco earthquakes:  Bulletin of the Seismological Society of America, v. 97, no. 5, p. 1449-1457.

Thurber, C. H., T. M. Brocher, H. Zhang, and V. E. Langenheim, 2007, Three-dimensional P wave velocity model for the San Francisco Bay region, California, Journal of Geophysical Research, v. 112, B07313, doi:10.1029/2006JB004682.

Langenheim, V.E., Jachens, R.C., Morin, R.L., and McCabe, C.A., 2007, Preliminary gravity and magnetic data of the Lake Pillsbury region, northern California Coast Ranges:  U.S. Geological Survey Open-File Report 2007-1368, 24 p., [available on the World Wide Web at URL: ].

McLaughlin, R.J., Langenheim, V.E., Sarna-Wojcicki, A.M., Fleck, R.J., McPhee, D.K., Roberts, C.W., McCabe, C.A., and Wan, Elmira, 2008, Geologic and geophysical framework of the Santa Rosa 7.5’ quadrangle, Sonoma County, California:  U.S. Geological Survey Open-File Report 2008-1009, 3 sheets, 51 p.  [available on the World Wide Web at URL:].

Sweetkind, D.S., and Taylor, E.M., 2010, Digital tabulation of geologic and hydrologic data from water wells in the northern San Francisco Bay region, northern California: U.S. Geological Survey Open-File Report 2010-1063, 125 p. (available at


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