Field Sites: Lockshaw Ranch

Hydrogeology & Hydrogeophysics ("hydrogeolophys") in an exposure of Salinian Block Granite in Paso Robles, CA. Official webpage for the Lockshaw Ranch Field Site and Project Resources.

Electrical Resistivity Data

Data file naming scheme¹.

• LR_ERT_01 → Archive Folder

• LR_ERT_02 → Archive Folder

• LR_ERT_03 → Archive Folder

• LR_ERT_04 → Archive Folder

• LR_ERT_05 → Archive Folder

• LR_ERT_06 → Archive Folder

• LR_ERT_07 → Archive Folder

• LR_TDEM_01 → Archive Folder

Other Data

• ... other miscellaneous profiles gathered at Lockshaw Ranch may make an appearance ...

Maps

• Lockshaw Ranch Master KMZ File.kmz

• Dibblee 2004 Paso Robles Geologic Map

• Dibblee 2006 Adelaida Geologic Map

• ... GIS files ...

• ... surfer / rockware / leapfrog ...

Selected Literature on Hardrock Aquifers

• Dewandel 2006 | A generalized 3-D geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase weathering.

• Lachassange 2011 | The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes.

• Belle 2018 | Characterization and location of the laminated layer within hard rock weathering profiles from electrical resistivity tomography: implications for water well siting.

Salinian Block References

As background for the exposure at Lockshaw Ranch:

• Mattison 1990 Petrogenesis and Evolution of the Salinian Block

• Seiders and Fox 1992 - USGS | Place of Origin of the Salinian Block, California, as Based on Clast Compositions of Upper Cretaceous and Lower Tertiary Conglomerates.

• Colgan 2012 Salinian Block Deformation]

• Hall and Saleeby 2013 Salinia Revisited

Resistivity Data Images

• Slide set of selected electrical resistivity images at Lockshaw Ranch.

Well Logs

• CPW1: Driller Report | Well Completion Report | Well Water Test)

• CPW2: Well Completion Report | Shallow material cuttings (not sure what shallow means - I was sent this picture later by Curtis. I am guessing it is into the soft granite).

• Other drilling reports in the region:

  • Adjacent property (NW) three well drilling reports

General Questions

• What is the relationship to the surface geomorphology and the:

  • Shear-zones/faults in the subsurface?

  • What resistivity values appear to predict permeable fractures? How does this compare among CPW1 and CPW2?

  • Are the densest permeable fractures always situated between (interpreted) fault zones?

  • Do you interpret any of the data to contain a laminated layer?

  • How well, or not, do the ERT results conform to the commonly cited hardrock aquifer model shown in Lachassagne, 2011?

  • Does any of the resistivity data detect unweathered/competent, granite in our data?

  • Are the assumptions of Lachassagne 2011 met at our field site?

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