The complex relationship between currents flowing around capes and related contourite deposits is an interesting topic to confront, both from a sedimentologic and oceanographic perspective. We analyze here the relationship between the spatial distribution of contourite drifts, observed at intermediate depths off promontories in the southern Tyrrhenian Sea and in the southern Adriatic Sea (Italy) and contour currents flowing around the offshore projection of the capes. These contourites are located slightly upstream from the tip of the cape (e.g. Cape Vaticano and Cilento Promontory) while they occur both upstream and downstream, in the lee wave region, of the Gargano Promontory and slightly downstream of Cape Suvero. We therefore analyze tank and numerical simulations of contour-following flows, with particular attention to turbulent phenomena that may occur in the lee region. Moreover, we provide physical justification for some aspects we recognized in the study experiments, discussing the stream-tube model (i.e., a thin vein of dense water flowing around a cape). The comparison between morphological characteristic of capes and numerical, tank and analytic results, provides new insights on the influence of cape morpho-structures on the position of contourite drifts. We found that the presence of turbulence, and thus of erosive condition in the lee of a cape, can be generally envisaged by using dimensionless numbers (Ref, Ek and Bu) related to large-scale morphology of the cape and ocean current features. For Cape Suvero the analyses is more complex since contourites are buried deposits, infilling a topographic depression (i.e. a slide scar). However it indicates that at the time of contourite formation a wider paleocape morpho-structure should have existed. Moreover, the classical hydrodynamic conservation of marine water potential vorticity suggests the occurrence of a anticlockwise eddy, trapped by the scar.
Effect of topography on contour currents and contourite drifts off italian promontories (Mediterranean Sea)
Eleonora Martorelli;Federico Falcini;
2012
Abstract
The complex relationship between currents flowing around capes and related contourite deposits is an interesting topic to confront, both from a sedimentologic and oceanographic perspective. We analyze here the relationship between the spatial distribution of contourite drifts, observed at intermediate depths off promontories in the southern Tyrrhenian Sea and in the southern Adriatic Sea (Italy) and contour currents flowing around the offshore projection of the capes. These contourites are located slightly upstream from the tip of the cape (e.g. Cape Vaticano and Cilento Promontory) while they occur both upstream and downstream, in the lee wave region, of the Gargano Promontory and slightly downstream of Cape Suvero. We therefore analyze tank and numerical simulations of contour-following flows, with particular attention to turbulent phenomena that may occur in the lee region. Moreover, we provide physical justification for some aspects we recognized in the study experiments, discussing the stream-tube model (i.e., a thin vein of dense water flowing around a cape). The comparison between morphological characteristic of capes and numerical, tank and analytic results, provides new insights on the influence of cape morpho-structures on the position of contourite drifts. We found that the presence of turbulence, and thus of erosive condition in the lee of a cape, can be generally envisaged by using dimensionless numbers (Ref, Ek and Bu) related to large-scale morphology of the cape and ocean current features. For Cape Suvero the analyses is more complex since contourites are buried deposits, infilling a topographic depression (i.e. a slide scar). However it indicates that at the time of contourite formation a wider paleocape morpho-structure should have existed. Moreover, the classical hydrodynamic conservation of marine water potential vorticity suggests the occurrence of a anticlockwise eddy, trapped by the scar.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
