The drainage pattern of the Reynosa Plain area from the Guadalupe River to the windblown sand area south of Hebronville, Duval County, shows a peculiar series of straight north-south, northeast-southwest, and northwest-southeast stream courses, which indicate corresponding series of erosion-etched fracture lines. The north-south series is the dominant one. The fracturing affected the sulphur mineralization at the Palangana sulphur mine, produced an impervious zone through the sulphur rock, and a little, but not much, displacement of the cap rock. The dip of the fracture planes has not been determined satisfactorily. The trends of the fractures correspond with deep basement trends which are manifest in the Paleozoic and Pre-Cambrian rocks of the Llano Burnet uplift, the Pa eozoic rocks of the Marathon Mountains, the alignment of the salt domes, the elongation of the salt domes, and the Sierra Madre. The immediate cause of the surface fractures of South Texas is the ease with which the weak caliche limestone and the Goliad sandstone fracture. The fundamental cause of the fractures presumably is shearing along old basement fractures, possibly supplemented by gulfward tension from the seaward flowage of the sediments and from vertical shear of the coastal subsidence.