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At least 37 records · Page 2Linked to original sources

Water-quality data for the Santa Clara-Calleguas hydrologic unit, Ventura County, California, October 1989 through December 1993

More than 700 water samples were collected from 232 wells and 34 surface-water sites in the Santa Clara-Calleguas Hydrologic Unit, Ventura County, California, from October 1989 through December 1993 as part of the U.S. Geological Survey's Southern California Regional Aquifer-System Analysis study. Most samples were analyzed for major ions, nutrients, selected trace elements, oxygen-18, and deuterium. Selected samples were analyzed for one or more of the following isotopes: carbon-13/12, carbon-14, strontium-87/86, sulfur-34/32, and tritium. Other samples were analyzed for one or more of the following dissolved gases: hydrogen, methane, oxygen, and freon-11. Location of sampling sites is shown on maps and the results are presented in tables.

Open-File Report↗

Localized alteration of the paintbrush nonwelded hydrologic unit within the exploratory studies facility

The mound-like feature in the lower part of the PTn, composed of highly disrupted strata and open-system alteration were the result of intense water-rock interaction. This feature was formed by fumarolic activity during cooling of the 12.8 Ma Topopah Spring Tuff and prior to deposition of the pre-Pah Canyon bedded tuff. Evidence of vapor phase crystallization, commonly observed in fumaroles, is not pervasive but may have been destroyed by subsequent low-temperature water-rock interaction. The ESF has provided a unique opportunity to view the internal morphology and to sample the compositional variability of this feature, however, outcrop and borehole studies suggest that such localized occurrences of alterative are not uncommon phenomenon within the PTn Hydrology Unit.

Conference Paper↗