| This research was undertaken to test the hypothesis that abnormal fluid pressure is generated in basins under tectonic compression. The site chosen for this study was the Peshawar Basin, in the Himalayan foreland in northwest Pakistan, which is experiencing a tectonic compression of 90 MPa. The study area extends from MKT and MMT in the north, through MCT and MBT in the center to SRT in the south. Springs with normal and anomalously high temperatures are abundant in the northern part of the study area. The southern part is divided into isolated basins with a number of drilled wells and dug-wells. A total of 71 springs and water wells were surveyed and sampled for analysis of major and trace elements. The research addresses three aspects of the groundwater from the study area: field characteristics, hydrochemical signatures, and model hydrodynamic behavior.; Field measurements of water surface temperature show an overall surplus over the mean annual air temperature. Analyzed water compositions, measured water temperatures, and calculated reservoir temperatures from several samples all point to waters that are anomalous in both chemistry and temperature. Water samples from one shallow well and three deeper wells, all located in the immediate vicinity of major thrust zones (MMT and MBT), exhibit clear imprints of oil-brine admixture. Hydrochemical signatures of strontium (Sr), silica (SiO2), boron (B) - and the geothermometric signatures - all indicate a deep circulation of the emerging groundwater. Spatial clustering of thermally and hydrochemically anomalous waters along major mapped faults suggests that these waters ascended from greater depths along the faults.; The basin has been divided into several hydrostratigraphic units in order to perform numerical simulations using the FEMWATER module of Groundwater Modeling System (GMS v. 5.1). Pressure head data generated by the numerical simulations have been compared with the field measurements of hydraulic heads. Results of the transient simulations indicate that topography alone is not sufficient to induce the pressure heads observed in the field. Instead, transient simulations indicate the presence of positive residuals over the topography-driven flow, which indicate the additional effect of tectonic compression on subsurface water flow. |
