STRUCTURAL DEVELOPMENT OF THE LIVERMORE VALLEY AND ITS EFFECTS ON STRATIGRAPHY AND GROUNDWATER, ALAMEDA COUNTY, CALIFORNIA

The Zone 7 Water District sponsored a pilot study to evaluate the aquifer framework and groundwater flow patterns in the central part of the Livermore-Amador Groundwater Basin using sequence stratigraphic analysis techniques. As part of that study, the regional geology and structure of the basin and surrounding area were evaluated to understand the development and structural framework of the basin and how basin development affected stratigraphy and groundwater flow. The Livermore Valley formed between the southward movement of Mt. Diablo and the northward movement of the Diablo Range. The Diablo Range exerted the primary control on the structure and stratigraphy in the Livermore Basin. Large north flowing streams from the Diablo Range contributed the majority of groundwater basin sediments. The northward range movement created oblique slip and thrust faults within the southern part of the basin. Development of these faults controlled stream and groundwater flow patterns within the basin. The southward growth of the Mt. Diablo frontal thrusts overrode the northern part of the original Livermore basin but created few structures within the remaining basin. Mt. Diablo was not a significant source of basin sediments. The primary effect of Mt. Diablo growth was the deflection, blocking, and rerouting of the streams that flowed north out of the Diablo Range.