The main focus of Leg 172 was to recover thick Pliocene to Holocene sedimentary sequences from sediment drifts in the western North Atlantic that document rapid changes in climate and ocean circulation. These sediments were also thought to contain other valuable information, including high-resolution records of geomagnetic field behavior, records of mud wave formation and migration, sedimentary microstructures that reflect a combination of downslope and along-slope depositional processes, and geochemical signatures that might help assess the lateral distribution of the Blake hydrate field and the role of hydrates in diagenetic processes (Shipboard Scientific Party, 1998a).
Leg 172 succeeded in reaching all the coring objectives, with recovery of 5.8 km of core from 42 holes cored at 11 sites (Tables T1, T2). Two of the sites were located on the Carolina Rise, seven on the Blake-Bahama Outer Ridge (BBOR), one on the Bermuda Rise, and one in the Sohm Abyssal Plain (Figs. F1, F2). Sediments recovered at all 11 sites were younger than ~3 Ma. Ten of the sites were part of a depth transect, spanning 1300 to 4800 m water depth, that sought to document changes in the depth distribution of water masses since the latest Neogene (Fig. F3) (pp. 8-9 in Shipboard Scientific Party, 1998a). At each of these sites, three to eight holes were cored to ensure recovery of complete stratigraphic sections (Table T2). The sediments were dominated by alternations between clay-rich and carbonate-rich intervals generally related to glacial and interglacial periods, respectively (Fig. F4). Sedimentation rates at the nine deepest sites of the transect averaged 100-300 m/m.y. (10-30 cm/k.y.) over the past 1 m.y.
Besides observations made from core and logging studies, Leg 172 collected an atypically large amount of seismic and echo-sounder (3.5 kHz) data for an ODP cruise. The data, which are available from the ODP data bank at Lamont-Doherty Earth Observatory, were gathered along criss-crossing survey lines over each site, providing an abundance of information for subsurface investigations and regional correlation of sedimentary sequences.