Helicopter electromagnetic and magnetic survey data and maps, northern Bexar County, Texas


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Publication Date

January 2005


This open-file report is a data release for a helicopter electromagnetic (HEM) and magnetic geophysical survey flown in early December 2003, in Northern Bexar County, Texas (fig. 1). The U.S. Geological Survey (USGS) contracted the survey to Fugro Airborne of Toronto, Canada. Fugro flew a similar survey under contract to the USGS in the Seco Creek area (fig. 1) of the Edwards aquifer (Smith and others, 2003). The objective of these surveys was to collect geophysical data to map and image subsurface features important in understanding ground-water resources in the area (Smith and others, 2003). In particular, the survey has refined the location of mapped faults in the survey area and suggested many unmapped faults exist. These faults can control ground-water flow and storage. New lithologic variations in the Edwards Recharge were mapped in both the shallow and deep subsurface. Images of the subsurface in the confined zone demonstrated a structural complexity not previously appreciated. Geophysical mapping in the Trinity aquifer also showed previously unmapped structures and lithologic variations.

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USGS, Vol. 5, no. 1158 (2005).