This data set include (1) the detailed petrographic description of the diagnostic rock types used to infer the source areas of the material recovered from the Mar del Plata Canyon area (Western South Atlantic at 38° S) at Sites GeoB13830, GeoB22712, GeoB22717 and L45; and (2) the Acoustic Doppler Current Profiler (ADCP) data obtained from Sites GeoB22716, GeoB22717 and GeoB22732.
A variety of gravel- to cobble-sized rocks, recovered from the Mar del Plata Canyon area and interpreted as ice-rafted debris, represents the first evidence that large icebergs have floated in the Falkland (Malvinas) Current from the southern polar high latitudes far northward. Detailed petrographic analyses identified the Antarctic Peninsula, sub-Antarctic islands in the Scotia Sea, and Tierra del Fuego as plausible source areas. In the Mar del Plata Canyon, a combination of local slope instability and strong and persistent contouritic bottom currents, favored local enrichment in dropstones in the form of a loose, coarse sediment drape inside morphological depressions. The bottom current velocity would be locally strong enough to rework this sediment, leaving coarse rafted debris as a lag deposit.
Microscopic petrograohic determinations were done on thin sections to identify the mineralogical composition of the rocks. During cruise SONNE SO260-1, the hull mounted Ocean Surveyor Teledyne RDI Acoustic Doppler Current Profiler (ADCP) with a doppler shift of 38 kHz provided real-time current velocity profiles over a range from 38 to 1,200 m water depth. ADCP data from the lowest 10-15 % of the water column have been removed due to possible scattering caused by strong seafloor echo. Doppler shifts were converted into current velocities using real water sound velocities by means of Conductivity-Temperature-Depth (CTD) and Expendable Sound Velocimeter (XSV) profile calibration.
Water depth (m), current velocity (cm sec-1) and direction (degrees) measured with ADCP at Site GeoB22732 (La Plata Terrace Moat), at Site GeoB22717 (Ewing Terrace Channel), and at Site GeoB22716 (Ewing Terrace Moat) for water depths greater than 500 m. Current directions: 0º=North; 90º=East; 180º=South and 270º=West.
