. Early geophysical papers of the Society of Exploration Geophysicists . Fig. 34.—Results of four resistivity traverses (single-probe method) and corre- sponding geologic section in San Fernando Valley, California. (Plotted from data pub- lished by J. J. Jakosky.) As stated by Lundberg and Zuschlag (ref. list No. IVB) apparent re- sistivities may also be readily computed from the potential-drop ratios. In Figure 34, the results obtained by Jakosky are shown, plotted in millivolt units which are directly proportional to the apparent re- sistivity. The geologic conditions are as follows. The lar
. Early geophysical papers of the Society of Exploration Geophysicists . Fig. 34.—Results of four resistivity traverses (single-probe method) and corre- sponding geologic section in San Fernando Valley, California. (Plotted from data pub- lished by J. J. Jakosky.) As stated by Lundberg and Zuschlag (ref. list No. IVB) apparent re- sistivities may also be readily computed from the potential-drop ratios. In Figure 34, the results obtained by Jakosky are shown, plotted in millivolt units which are directly proportional to the apparent re- sistivity. The geologic conditions are as follows. The larger part of the area is covered by a blanket of alluvial strata with a maximum thickness of nearly 80 feet. Below, in the eastern part of the area, are inclined strata of the Fernando group of the Pliocene. These forma- tions are cut off by a fault in the western part of the area which has brought strata of the Cretaceous Chico formation in contact with the Pliocene in the east. These Cretaceous strata do not contain water, but the upper parts of the Pliocene are filled with highly conductive waters down to a depth where the impervious strata indicated as 1 J- J- Jakosky, "Geophysical Examination of Meteor Crater, Arizona," Geophysi- cal Prospecting (Amer. Inst. Min. Met. Eng., 1932), pp. 63-98. 481
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