GEOLOGY, November 2007 963 Geology, November 2007; v. 35; no. 11; p. 963–966; doi: 10.1130/G23378A.1; 3 figures; Data Repository item 2007240. © 2007 The Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or editing@geosociety.org. INTRODUCTION Extrusions of diapiric salt onto continental and marine basins have been described by a number of authors (see GSA Data Repository Table DR1 1 ). Active salt glaciers (namakiers) are spectacularly exposed on the flanks salt moun- tains as high as 300 m in the Zagros fold belt of onshore Iran in a system dominated by tec- tonic shortening. Today, outside of the Dead Sea depression, there are no terrestrial namakiers in regions of extensional tectonics (see the footnote of Table DR1). Even in the Dead Sea depression, the tectonic setting is not regional extension; rather, it is a local-scale rapidly subsiding tran- stensional pull-apart basin situated on a regional transform fault (Al-Zoubi and Ten Brink, 2001). In this paper, using cross sections and variance attribute analysis from three-dimensional (3D) seismic data, we present the first (to our knowl- edge) documentation of a subsurface example of a tiered set of namakiers in an extensional ter- restrial (redbed) setting. It is the preserved rem- nant of a number of ancient salt glaciers extruded onto a Late Triassic redbed landscape within the subsiding Triassic Northwest German Basin. The structural regime in the Late Trias- sic of the intracontinental Northwest German Basin of Central and northern Europe reflects incipient North Atlantic rifting and extension that locally formed graben structures (Ziegler, 1990). Rifting in the study area triggered salt movement and near-surface responses, includ- ing reactive, active, and passive diapirism (Mohr et al., 2005). The depositional surface in Late Triassic (Keuper) time was made up of a series of salt-filled low-relief playas and pans surrounded by desert redbeds, salt-filled domes, and occasional namakiers. GEOLOGICAL EVOLUTION OF THE EAST FRISIA AREA The investigated salt structure is one of a number of similar structures in the east Frisia area of northwestern Germany, located near the Germany-Netherlands border (Fig. 1A). The salt structures are arranged in a series of elongated NNW-trending diapirs, spaced at intervals of ~10 km (Fig. 1B). Late Paleozoic sedimentation in the east Frisia area (Fig. 1C) deposited upper Rotliegend sedi- ments in a series of playa mudflat–sandflat set- tings in an extensional regime. Approximately 800 m of bedded sulfate and halite were depos- ited in this area during the hydrographic isolation and drawdown of the Late Permian Zechstein evaporite basin (Jaritz, 1973; Warren, 2006). Triassic sedimentation changed from continental clastics during the Early Triassic Buntsandstein to shallow-marine sequences of carbonates and evaporites in the Middle Triassic Muschelkalk, to continental clastics with intercalated saline- pan evaporites during Keuper time. Several phases of Triassic rifting influenced the area and triggered its multiphase salt tec- tonics (Figs. 1D, 1E). Kinematic restoration modeling shows that decoupled extension in the late Early (middle Buntsandstein) and Middle Triassic (middle Muschelkalk) initi- ated salt diapirism and lateral salt flow with growth of a pillow-like salt structure (Mohr et al., 2005). Subsequent formation of a base- ment graben in the early Late Triassic triggered 1 GSA Data Repository item 2007240, Table DR1, summary table of selected worldwide salt extrusion occurrences, is available online at www.geosociety. org/pubs/ft2007.htm, or on request from editing@ geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA. *Current address: RWE Dea AG, Überseering 40, 22297 Hamburg, Germany. Subsurface seismic record of salt glaciers in an extensional intracontinental setting (Late Triassic of northwestern Germany) Markus Mohr* Geological Institute, RWTH Aachen University, Wüllnerstrasse 2, 52056 Aachen, Germany John K. Warren Shell Chair in Carbonate Studies, Sultan Qaboos University, Muscat, Oman Peter A. Kukla Janos L. Urai Geological Institute, RWTH Aachen University, Wüllnerstrasse 2, 52056 Aachen, Germany Anton Irmen Gaz de France Produktion Exploration Deutschland GmbH, Lingen (Ems), Germany ABSTRACT In the Northwest German Basin of Central Europe, Late Triassic interaction of normal faulting and salt diapirism during regional extension in subsalt basement locally initiated lat- eral flow of surface-piercing salt in namakiers (salt glaciers). Using seismic sections and vari- ance attribute maps derived from high-resolution three-dimensional seismic data, we show that when a syndepositional fault cuts a near-emergent diapir crest, the caprock carapace was breached, opening a pathway for salt extrusion. The fault escarpment and the adjacent fault-induced depression allowed focused gravity-driven downward flow of salt across the land surface (a namakier) and its subsequent preservation and encasement in continental (arid redbed) sediments. Geodynamically there is an apparent distinction between the com- pressional setting of modern namakiers in the arid deserts of Iran and the fault-intersected extensional setting of stacked Keuper namakiers. Stacked namakiers preserved in thicknesses that are seismically resolvable are interpreted to indicate hyperarid conditions in Keuper time. The climate was typical of the highly continental Late Triassic Pangaean supercontinent as it rifted and sagged to form the incipient Atlantic Ocean. Keywords: salt glacier, diapirs, Northwest German Basin, continental redbeds, extension.