A basaltic dike cuts Paleozoic strata and a Cenozoic landslide breccia in the southern Franklin block of the Franklin Mountains. Strike-slip displacement of this dike records mostly right lateral but some left lateral movements along major faults in the range. These major faults are genetically related with the boundary faults of the range. The dike has been emplaced following exogenic gravity gliding of large masses of west-dipping strata on the western dip slope of the range, thus indicating the following general geologic history: contemporaneous uplift and tilting of the range, with some internal faulting and gravity gliding of large blocks, dike emplacement, and strike-slip displacement along the internal faults. The Franklin Mountains are bounded by the Texas lineament on the southern end and by the Rio Grande trench on their westerly side, hence this strike-slip displacement in major faults of the range is of significance in the analysis of the regional tectonics of these two major lineaments.