Of the many discoveries made during the expedition, the following are among the most noteworthy:
One of the most interesting discoveries, in the context of diagenesis, was the realization that layers of dolomite hard rock form within the soft organic-rich sediment. These layers extend over large areas and greatly impact the ability of sediments to reflect sound. Logging proved the case for the abundance of dolomite layers, which, because of their hardness, were difficult to sample.
In addition, some of the most extreme values for the intensity of sulfate reduction and the production of ammonia ever measured in sediments retrieved by drilling were encountered in a number of holes, especially at Site 1084.
An important result, and a pleasant surprise to many of the scientists on board, is the fact that so many of the sections recovered show continuous sedimentation at high rates of accumulation. Several conditions are responsible for this finding: high rates of supply from high productivity and terrigenous contributions, favorable sites of deposition through salt tectonics (north of WR), and a tectonically quiet setting (in the Cape Basin). This does not imply that, as a rule, sediments are undisturbed along this margin. They are not. A crucial ingredient of finding stratigraphically useful sections is well-prepared site selection. Optimal site selection was possible thanks to high-resolution air-gun profiles collected during two 4-week expeditions mounted for this purpose (the Sonne Expedition SO86 in 1993 [Bleil et al., 1995] and the Meteor Expedition 34/1 in 1996 [Bleil et al., 1996]). These preparatory expeditions were carried out by the Geosciences Group at Bremen University; processing was done at the Alfred-Wegener Institut for Polar and Marine Research at Bremerhaven.
Stratigraphic continuity also relies on drilling multiple holes using APC technology and on matching the records using detailed core-core correlation. The most important records for splicing proved to be magnetic susceptibility and spectral reflectance, as measured by the Minolta spectrophotometer.
In most cases, the measurement of physical properties was influenced by the high abundance of gas, which produced sediment expansion and created voids and cracks. Consequently, logging had an unusually important role in providing ground truth. Six sites were logged during Leg 175 (Sites 1077, 1081, 1082, 1084, 1085, and 1087). Many different types of measurements were made, including gamma ray, porosity, density, acoustic velocity, electrical resistivity, and magnetic susceptibility. The stability and shape of most of the logged holes were of excellent quality.
Although the high gas content made handling of the cores and measuring physical properties difficult, it also kept sediments from compacting as quickly as they might have otherwise, thus allowing much faster drilling than anticipated. This ultimately resulted in 13 sites being occupied, rather than the planned eight sites. The high rate of core recovery placed special demands on all Leg 175 participants. The stratigraphers, in particular, were called upon to deliver age estimates at an unusual pace. With coccolithophorids as a backbone, as well as magnetic reversals (fortunately still recognizable, despite the high intensity of diagenesis), it was possible to satisfy the demand for operationally relevant information. Backup information came from the other microfossils in due time. Unsurprisingly, diatoms proved to be especially valuable indicators of changes in upwelling intensity.