Investigations of ground water flow associated with the Saratoga warm springs and the Tecopa Hot Springs near Death Valley, California, using magnetic and conductivity methods Antony M. Wamalwa, Laura F. Serpa ⁎, Diane I. Doser Department of Geological Science, University of Texas at El Paso, El Paso, TX 79968, United States abstract article info Article history: Received 13 May 2010 Received in revised form 30 November 2010 Accepted 3 December 2010 Available online 13 December 2010 Keywords: Geophysics Ground water Death Valley Hot springs Magnetics Conductivity Electrical and ground magnetic surveys at Saratoga Springs and Tecopa Hot Springs in the vicinity of Death Valley reveal intersecting faults that appear to control the spring locations. Faults striking east–west and north–south intersect at Saratoga Springs. High electrical conductivity along imaged faults at Saratoga Springs implies shallow ground water channels between 5 and 20 m deep. Regions of high conductivity correlate with water saturated zones or clays. Gradients in magnetic and conductivity data at Saratoga are interpreted as faults. Similarly northwest- and northeast-trending faults are inferred to intersect at Isolated Spring in Tecopa Valley. Our data suggest that ground water flow along deep structures allows water to be heated and could account for the water temperature of about 41 °C at the Springs at Bath in Tecopa Valley. However, we hypothesize that cold water from the Amargosa River percolates downward and mixes with hot water rising at the fault intersections. The river water accounts for the lower water temperatures at Saratoga and at the Isolated Spring as compared to the Spring at Bath in Tecopa Valley. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The study of ground water distribution in the vicinity of Death Valley, California is challenging (Hunt et al., 1966; Miller, 1977; Belcher et al., 2001, 2002) because Death Valley and the nearby Tecopa Valley receive only 5 cm/yr rainfall on average but both have abundant flowing springs. Numerical inter-basin ground water flow modeling and geochemical analysis of the water in the numerous springs suggest a distant source outside the Death Valley region (Hunt and Robinson, 1960; Steinkampf and Werrell, 2001; Winograd et al., 1985; Davisson et al., 1999; Nelson et al., 2001; Miner et al., 2007). The water traverses numerous faults in this region to the spring sites (Faunt, 1997). Inter-basin ground water flow from the Amargosa Desert to Furnace Creek south of the Funeral Mountain has been proposed (Anderson et al., 2006). On the other hand, Davisson et al. (1999) advocated for a north–south ground water flow rather than an east–west flow. Nevertheless it is believed that the source of the spring waters at the Tecopa Valley and Death Valley is the Spring Mountains in nearby Nevada (Larsen et al., 2001; Miller, 1977; Nelson et al., 2001; Sperry and Larsen, 2007; Sperry, 2008). Water is transported along underground aquifers that are inferred to consist of interconnected porous sediments as well as fractures and faults in the bedrock (Hunt et al., 1966; Hunt and Robinson, 1960; Miller, 1977). The water may be heated during transport but the locations and the temperature variations of the springs across the region do not appear to reflect a simple pattern of deep circulation (Steinkampf and Werrell, 2001; Nelson et al., 2001). In this study, we investigate the geologic and structural controls on the springs' locations. In particular, we use magnetic and resistivity data to investigate Saratoga Springs in southern Death Valley and Isolated hot springs in the Tecopa Valley, southeast of Death Valley. Saratoga Springs is a warm spring with water temperatures of about 28 °C located nearly 100 km from the Spring Mountains while the Isolated Spring with water temperatures of about 42 °C is located in Tecopa and is only about 70 km from the putative source region as shown in Table 1 (Sperry, 2008; Steinkampf and Werrell, 2001). Water discharging at the Saratoga Springs in Death Valley may share the same source, the Spring Mountain, with the water from springs in Tecopa Valley, for example, the Tecopa Hot Springs (Grimshaw, Isolated and Springs at Bath) as suggested by Hunt et al. (1966) and Larsen (2000). The travel path to Saratoga Springs is significantly longer than the path to Tecopa Springs and in the model proposed by Mifflin (1988), it is expected that the water would be hotter at Saratoga than at Tecopa if it continues to travel along a deep path (Morrison, 1999; Steinkampf and Werrell, 2001). However the water at Saratoga is 13 °C colder than the water at the Springs at Bath in Tecopa Valley. Our study indicates that intersecting normal faults may be the key to the location of these springs. We hypothesize that the orientation of the intersecting faults relative to the regional stress field in Death Valley, in particular, produces open fractures that act as a conduit for the rising hot Tectonophysics 502 (2011) 267–275 ⁎ Corresponding author. Tel.: +1 9157476085. E-mail address: lfserpa@utep.edu (L.F. Serpa). 0040-1951/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2010.12.001 Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto