Lithologic column of the “Arkoma” Drillhole and its relation to the Cajon Pass Deep Drillhole



The 1795 m "Arkoma" Federal 1-26 well, 48.5 m from the Cajon Pass Deep Drillhole (CPDDH), provides additional lithologic and structural data pertinent to that project. Basement surface was encountered 158 m deeper than in the CPDDH. Rock units correlate well between the holes; the offset persists to 1128 m. Below this depth both lithologic unit thicknesses and fault zones correlate between holes on subhorizontal projections. A combination of previously unrecognized high-angle and low-angle faults of several ages are required to explain the structures. Blind low angle faults may be regionally important.