Recent field investigations have made it clear that a Caledonian nappe system, consisting of four tectonostratigraphic units, covers wide expanses of central Rogaland. The three lowest units of the system are, in ascending order: The Lower Nappe Sheet, the Boknfjorden Nappe Complex, and the Jæren Nappe Complex. All three nappe sheets have probably their root area in the Precambrian basement off the west coast of Norway. The uppermost part of the allochthon, the Karmsund Nappe, consists mainly of low-grade greenschist facies metabasites of supposed Early Ordovician age.
The geology of Jæren and adjacent districts. A contribution to the Caledonian nappe tectonics of Rogaland, southwest Norway