Geochemical data from Valle Trinidad, Baja California, Mexico, suggested a relation between faulting and geochemical anomalies. In addition, published accounts of a major gravity anomaly in the valley implied a complex structure. An integration of gravity, magnetics, and electrical resistivity techniques was used to help define the subsurface structure of Valle Trinidad. A sphenochasm is proposed, based on detailed gravity modeling with a digital computer. Additional normal faulting in the graben, trending at right angles to the Agua Blanca fault, is defined by gravity, magnetic, geochemical, and resistivity data. Computer modeling of resistivity data suggests the main aquifer in the valley is a sandy unit at a 80-100 m depth, overlain by a clay 40 - 60 m thick. Thickening of these near-surface units next to faults suggest faulting is still active in Valle Trinidad.
