Short-distance variability in slope bed-forms along the southwestern Adriatic Margin (Central Mediterranean)

The slope of SW Adriatic Margin (SAM) is impinged today by two bottom-water masses, of thermohaline origin, that interact constructively along a preferred path: the Levantine Intermediate Water (LIW), generated in the eastern Mediterranean through intense evaporation and flowing along the contour, and the North Adriatic Dense Water (NAdDW), formed on the shallow north Adriatic and cascading episodically off the shelf. These two southward-flowing bottom-water masses impact the upper slope, which is characterized by an irregular physiographic setting, and together create the bottom-current deposits (e.g. fine-grained contourite drifts and sediment waves) and related erosional features (e.g. furrows, scours, comet marks). This study is focussed on a small open-slope area of the SAM (ca. 35 X 25 km), where high-resolution seismic data allow observe elongated contour-parallel scours, widespread erosion surfaces (accompanied by wide crescent-shape scours and furrow fields) and giant comet-marks spatially associated and genetically linked along a common current path. Further downslope, and away from this highly energetic current path, a field of sediment waves migrates upcurrent and shows bifurcated crests. In some cases the downcurrent limbs of the sediment waves display a well-defined erosional character on seismic profiles and furrows on side scan sonar mosaics. All bottom-current features observed are in equilibrium with the present day oceanographic regime, as documented by the available current-metre data. Moreover, sediment cores suggest that the sediment waves are actively migrating during the present interglacial, possibly implying that bottom waters formation was enhanced after the shallow Adriatic shelf was drowned during the late-Quaternary eustatic rise. The SAM slope represents, therefore, an ideal site to improve our understanding of the depositional impact of bottom currents along the Mediterranean margins and may provide useful hints on the activity of bottom currents elsewhere on the Mediterranean margins. (c) 2006 Elsevier B.V. All rights reserved.