The writers report the results of geologic field work, drilling, chemical and petrographic examinations, and other tests on the deposits of asphaltic substances in southeastern Turkey. The veinlike features attain lengths up to 3,500 m and, locally, widths up to 80 m. Their formation is attributed to tectonic events, such as upthrusts and overthrusts, which caused the opening of generally irregular systems of deep, broad, gaping fissures. In particular, tilt of strata below the overthrusts was observed, whereas diagonal fissures are a very striking feature of the hanging walls of the thrust zones. Soft masses of asphalt originated from a former oil-bearing zone and became intricately mixed with the simultaneously deposited mineral substance. These masses were squeezed int the fissures up to the surface as a result of pressure of the overlying rock masses. An "asphaltic pyrobituminous shale" zone in the so-called "Cudi Group," a limestone-dolomite sequence of Middle Triassic to middle or Late Cretaceous age, was recognized in the field, and by comparison of the infrared spectrograms of crude oil and CS₂ extracts of the asphaltic materials, as the original oil-bearing rock and source of the veinlike deposits.