Geophysical investigations for the location of a proposed dam in Al Bishriyya (Al Aritayn) area, northeast Badia of Jordan

Vertical electrical sounding and seismic refraction geophysical surveys wer e conducted on the northeast Badia of Jordan over the location of a propose d dam, as part of a national project to develop the Jordan Badia at the sam e national level. The objective of the study was twofold: (1) to evaluate t he possibility of mapping of volcanic medium in areas where little is known about the subsurface geology and to infer a shallow geological structure f rom the geophysical data interpretation, (2) to identify formations that ma y be present, and (3) subsequently estimate the relationship between ground water resources and geological structures. Geoelectrical data collected alo ng two profiles were interpreted utilizing both manual and automatic techni ques. Vertical electrical sounding data were pieced together along the surv ey lines to make a geoelectrical cross section. From the surface down, the cross sections reveal a thin layer of alluvial and wadi sediments, alluvial fans, alluvial mudflats and soils of Holocene to Recent age with high resi stivity values. A layer of dense basalts of medium resistivity values, 100- 400 Omegam, was recognized beneath the upper unit. Porous and fracture volc anic tuff bodies that have high resistivity value signatures were resolved at different depths along the eastern and western flanks of Wadi Tahawi. Th e seismic refraction data reveal three different units. From the surface do wn, the upper unit was 20-35 m thick and the velocity was 3,710-3,800 m/s u nderlain by a 20-m-thick low velocity unit of similar to1,560-2,000 m/s and lower dense basalt unit with a velocity ranging from 4,400 to 4,580 m/s.