Abstract The allochthonous Tertiary salt of the Garmsar salt nappe extruded from where the most southerly point of the Alborz Mountain front is offset by the Zirab–Garmsar strike-slip fault. We used eleven descending Advanced Synthetic Aperture Radar (SAR) images, acquired by the European Space Agency's ENVISAT satellite from 2003 to 2006, to map surface displacement over 23 increments ranging in time from 30 to 2 months. A 30 month SAR interferogram of the area shows that the regional folds and faults are active south of the mountain front, but are dampened by the allochthonous salt that otherwise appears to be merely degrading at rates that vary with the season. Interferograms for shorter epochs display different patterns of fault blocks in the country rocks that rose and fell with the seasons. By relating surface displacements mapped in these interferograms to the contemporaneous seismic record, we find that seismic faults reactivate repeatedly while their kinematics may have inverted on remarkably short timescales. Seismic disturbances propagate very slowly and faults are longer than expected for earthquakes with ML<3.5, indicating that the regional strains are more aseismic than anticipated by earlier studies.

Abstract Kuh-e-Jahani is one of the largest extrusions of salt currently active in the Zagros mountains. Salt rises from about 4 km below sea level to nearly 1.5 km, above, where, unable to support its own weight, it spreads over the surrounding scenery in a process responsible for present and past allochthonous salt sheets elsewhere. We report vertical movements and apparent horizontal displacements of 43 markers dispersed over this mountain of salt for 4.5 years in three consecutive intervals, the first of 18 months and two others of 12 months. The geometry and inferred flow rate of the salt changed between surveys emphasizing that the gravity spreading is not steady. Our field readings of the dimensions and velocities of the salt at Kuh-e-Jahani are used to tune a simple numerical model and constrain the viscosity of the salt to between 10 16 and 10 17 Pa s −1 , its rate of surface dissolution to 2–3 cm a −1 , and its rate of rise out of its orifice at 2–3 m a −1 for c. 55 ka. These results imply that vigorous extrusion of salt at Kuh-e-Jahani is probably close to evacuating its deep source and that this mountain will soon begin to waste as salt dissolution overtakes extrusion. This progress report is warranted because our results have significant implications for sophisticated engineering in salt.

Abstract Salt structures in the northeastern Nordkapp subbasin are interpreted on reflection seismic profiles. Thickness variations indicate localized accumulation of the mother salt in Late Carboniferous-Early Permian time. Rapid sedimentation in the Early Triassic accompanied rise of salt into asymmetric salt pillows during regional extension. These pillows domed the prekinematic Permian sediments and became diapiric during the late Early-Middle Triassic, perhaps as a result of thin-skinned normal faulting decoupled by the salt from old basement faults reactivated by thick-skinned regional (northwest-southeast) extension. Variations in size, maturity, and evolution history of individual salt structures can be attributed to local differences in thickness of the initial salt layer and its burial history. Salt structures form three rows concentric to the basin margins and cover ~ 20% of the basin area. Some salt stocks appear to overlie basement faults. Asymmetric primary, secondary, and in places tertiary, peripheral sinks indicate that salt was withdrawn mainly from the basin side of most diapirs throughout Triassic downbuilding. The ratio of net salt rise rate to net aggradation rate (R/Å) increased slowly from <1 to >1 during Middle Triassic time and increased markedly during slow sedimentation in the Late Triassic and Jurassic. By Jurassic time, more than 18 enormous salt fountains extruded downslope and spread a partial salt canopy in the central and northern parts of the northeastern subbasin. Larger and more widely spaced salt extrusions in the northeastern subbasin spread significantly farther than their equivalents in the southwestern subbasin, where Triassic subsidence or downbuilding was slower. Salt extrusion (and perhaps dissolution) ceased during Cretaceous burial but probably resumed locally in the late Tertiary. Salt loss during Cretaceous-Tertiary reactivation of salt rise reduced the area of the salt canopy. Surviving remnants of the salt canopy may still trap any pre-Jurassic hydrocarbons despite hydrocarbon venting throughout the Arctic during Tertiary uplift.