The heritage of Tethyan oceanic transform faults within Alpine orogens: The Shkoder-Peja transverse zone (SPTZ) of Northern Albania

The Shkoder-Peja transverse zone (SPTZ) of Northern Albania marks the boundary between the Dinarides and the Albano-Hellenides chains and corresponds to a ~100 km SW-ward shift of the ophiolitic nappe front. Over the last sixty years, it has been variably interpreted as an inherited paleogeographic feature, a dextral strike-slip fault, the hinge of the clockwise (CW) rotating Albano-Hellenides system, and a Miocene-to-recent normal fault. Here we report on the paleomagnetism of 27 Triassic-Cretaceous sites from the Krasta-Cukali and the High Karst domain, both within and north of the SPTZ. Two sites yielded only a pre-tilting magnetization, 15 sites were found to be remagnetized after mid-Eocene-lower Miocene tilt, while 8 sites showed both pre- and post-tilt magnetizations. Both pre- and post-tilt paleomagnetic directions yielded a 60-70° clockwise (CW) rotation with respect to Adria/Africa, except 9 sites from the Koman zone at the ophiolitic nappe boundary showing a smaller 38°±15° CW rotation. Thus, the well-known regional CW rotation of the Albano-Hellenides extends northward in the southern Dinarides, and the SPTZ is not a rotation boundary as previously assumed. The ~70° CW rotation is consistent with available data from the nearby ophiolitic nappe complex, and is assumed to represent the sum of a 30° lower Miocene rotation during thrusting of the Kasta-Cukali over Kruja nappe plus the 40° Miocene-Pleistocene rotation well documented in the external zones of Albania. We suggest that the SPTZ is the heritage of a mid-Triassic transform fault of the Maliac Tethyan ocean, later overprinted by the lower Cretaceous obduction of the Vardar ocean, replacing Maliac since the middle-Jurassic.