ALBERT

Description: Twenty four core samples from CRP-1, seven from Quaternary strata (20-43.55 meters below sea floor or mbsf) and seventeen from early Miocene strata (43.55 to 147.69 mbsf), have been analysed for their grain-size distribution using standard sieve and Sedigraph techniques. The results are in good agreement with estimates of texture made as part of the visual core description for the 1 :20 core logs for CRP-1 (Cape Roberts Science Team, 1998). Interpretation of the analyses presented here takes into account the likely setting of the site in Quaternary times as it is today, with CRP-1 high on the landward flank of a well-defined submarine ridge rising several hundred metres above basins on either side. In contrast, seismic geometries for strata deposited in early Miocene times indicate a generally planar sea floor dipping gently seaward. Fossils from these strata indicate shallow water depths (〈 100 m), indicating the possibility that waves and tidal currents may have influenced sea floor sediments. The sediments analysed here are considered in terms of 3 textural facies: diamict, mud (silt and clay) and sand. Most of the Quaternary section but only 30% of the early Miocene section is diamict, a poorly sorted mixture of sand and mud with scattered clasts, indicating little wave or current influence on its texture. Although not definitive, diamict textures and other features suggest that the sediment originated as basal glacial debris but has been subsequently modified by minor winnowing, consistent with the field interpretation of this facies as ice-proximal and distal glaciomarine sediment. Sediments deposited directly from glacier ice appear to be lacking. Mud facies sediments, which comprise only 10% of the Quaternary section but a third of the early Miocene section, were deposited below wave base and largely from suspension, and show features (described elsewhere in this volume) indicative of the influence of both glacial and sediment gravity flow processes. Sand facies sediments have a considerable proportion of mud, normally more than 20%, but a well-sorted fine-very fine sand fraction. In the context of the early Miocene coastal setting we interpret these sediments as shoreface sands close to wave base.

Description: Analyses of spatial structure of hydrophysical fields and its vertical evolution in the Northeast Atlantic in a layer from the surface down to 2-2.5 km are carried out based on results of measurements in a testing area (31°-36°N, 20°-26°W) southeast of the Azores in autumn 1993. A description of an anti-cyclonic lens (ACL) of Mediterranean water (MW), which was found in the eastern part of the testing area from data of sets of sequential surveys, is presented. Analysis of CTD and XBT measurements in an area west of the lens allows to conclude that despite some contraction of width of the Azores Current directed eastward (from 60-80 km to 50-60 km) its total eastward volume transport for a period of time from October to November does not vary much. It is shown that intermediate salinity maxima in the northern part of the testing area formed by advection of MW and meddy destruction weakens while intersecting the Azores frontal zone (AFZ) from north to south, displacing itself to larger depth, and increases in thickness. Analysis of data shows that the number of lenses observed within the selected area north of the AFZ is two times more than that observed south of it. North of the AFZ observed salinity maximum and local temperature maxima may be associated with accumulation of heat and salt because of the fact that the AFZ is not only a southern boundary of penetration of MW into the North Atlantic, but also is a "semitransparent" boundary for Mediterranean lenses.

Description: Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the warm peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5° to 1°C, less than the 4° to 4.5°C estimated during times of ice growth and the 3°C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature.

Description: Sediment cores recovered during ODP drilling operations are commonly scanned using a Minolta CM-2002 spectrophotometer to obtain spectral data. Core processing procedures aboard the JOIDES Resolution require that these spectral data be measured on wet cores. However, the effects of changing water content on the spectra of marine sediments is unknown. We examined the effects of changing water content on visible light (VIS) diffuse refiectance spectra for core samples composed of clay to foraminiferal ooze. The spectra of dry powdered samples were measured, then the samples were completely saturated (~35% water content) and spectra were measured at set time intervals as the samples progressively dried. The fully saturated samples were appreciably darker than the initial dry samples. The samples continued to darken during the initial phases of drying until the water content had decreased from 35% to ~20%. As the water content continued to decrease below 20%, the samples became progressively lighter and attained spectral values similar to the fully saturated samples at water contents of ~ 17%. Samples continued to lighten until they were totally dry; however, values never became as light as those of the dry samples prior to initial wetting. Changes in refiectance with decreasing water content are not uniform across the VIS. If the water content is greater than 5%, the refiectance decrease relative to a dry sample is greater at the red end of the spectrum. However, at water contents of less than 5%, the spectral curves of the wet and dry sediments are similar in shape, but the wet sediments are still darker. Comparison of these data with data obtained from similar saturation experiments using a coarse-grained beach sand suggest that the initial darkening of the saturated carbonate sediments apparently results frorn changing of the physical properties of the sediment; decreasing the water content apparently rearranges the grains. These studies suggest that maximum information will be obtained when spectral measurements are taken on samples that are allowed to dry as much as possible.