ALBERT

Description: Bedding dips in the CRP-3 drillhole were determined in three ways: (1) analysis of a dipmeter log, (2) identification of bed boundaries on borehole televiewer log images, and (3) identification of bed boundaries on digital images of the outer surfaces of oriented cores. All three methods determine both dip magnitude and downdip azimuth of bedding. Dipmeter results document variations in bedding dip throughout the logged interval (20-902 mbsf), whereas core and televiewer results are available at present only for selected depth intervals. Dipmeter data indicate that structural dip is remarkably constant, at 21° dip to azimuth 65°, throughout the Tertiary shelf section, except for the top 100 m where dips appear to be 5-10° shallower. This pattern, in conjunction with the systematically increasing dips throughout CRP-2A, suggests that the growth faulting active during CRP-2A deposition began during the final period of deposition at CRP-3. Normal faults at 260 and 539 mbsf in CRP-3 exhibit neither drag (localized dip steepening) nor significant changes in structural dip across them. Oriented core and televiewer analyses, covering a total of 200 m in the interval 400-900 mbsf, indicate bedding patterns that confirm the dipmeter results. The doleritic breccia at the base of the Tertiary section has steeper dips than overlying structural dips, possibly indicating a sedimentary dip to ENE in these fan sediments. Dip directions in the underlying Devonian Beacon sandstone are surprisingly similar to those in the overlying Tertiary section. Superimposed on the average Beacon dip of 22° to the ENE are localized tilts of up to 20°, probably caused by Tertiary fracturing and brecciation rather than original sedimentary dip variations.

Description: Bedding dips in the CRP-2A drillhole were determined in two ways (1) analysis of a dipmeter log, and (2) identification of bed boundaries on digital images of the outer core surface. The two methods document the downhole increase in structural dip, to a maximum of 15° in the lowest 150 m of the hole. Dipmeter data, which are azimuthally oriented, indicate a 75° azimuth for structural tilting, in agreement with seismic reflection profiles. Core and log dips indicate that structural dip increases by 5-7° between 325 and 480 mbsf. Both, however, also exhibit high dip inhomogeneity because of depositional (e.g., cross bedding) and post-depositional (e.g., softsediment deformation) processes. This variability adds ambiguity to the search for angular unconformities within the CRP-2A drillhole. Dip directions of different lithologies are generally similar, as are dip directions for the four kinds of systems tracts. Downdip azimuths of sands and muds are slightly different from those of diamicts, possibly reflecting the divergence between ENE offshore dip and ESE glacial advance.

Description: CRP-3 cores were not orientated with respect to North during coring operations. However, borehole televiewer (BHTV) logging did obtain azimuthally orientated images of the borehole wall, and core processing included digital imaging of the outer surface of 85% of the cores. Images of many individual core segments can be digitally joined, or stitched, by rotating them to match the shapes of their adjoining surfaces and then closing the gap. By aligning features (fractures, bedding, and clasts) on stitched-core images with correlative features on orientated BHTV images, we reorientated 231 m of core, or 25% of the cored interval. We estimate that the orientation uncertainty is ±10° for entire stitched-core intervals, and ±15° for individual features such as a single fracture or palaeomagnetic sample. Reliability of core orientations was confirmed by comparing azimuths of bedding and fractures measured directly within these reorientated cores to those measured within orientated borehole televiewer images.

Description: Holocene climate variability is investigated in the North Pacific and North Atlantic realms, using alkenone-derived sea-surface temperature (SST) records as well as a millennial scale simulation with a coupled atmosphere-ocean general circulation model (AOGCM). The alkenone SST data indicate a temperature increase over almost the entire North Pacific from 7 cal kyr BP to the present. A dipole pattern with a continuous cooling in the northeastern Atlantic and a warming in the eastern Mediterranean Sea and the northern Red Sea is detected in the North Atlantic realm. Similarly, SST variations are opposite in sign between the northeastern Pacific and the northeastern Atlantic. A 2300 year long AOGCM climate simulation reveals a similar SST seesaw between the northeastern Pacific and the northeastern Atlantic on centennial time scales. Our analysis of the alkenone SST data and the model results suggests fundamental inter-oceanic teleconnections during the Holocene.

Description: Sediments and rocks recovered in CRP-3 coring operations contain minute amounts of organic matter (average 0.3% TOC). TOC contents and C:N ratios are zoned systematically: those rocks encountered at depths greater than 330 meters below sea floor (mbsf) contain less organic matter and have higher TOC:N ratios (after correcting for inorganic N) than do shallower rocks. The only two samples that have TOC values greater than 1% also contain abundant granule to silt-sized particles of coal. The total sulphur contents of these rocks is very low and indicates either that only small amounts of deposited organic matter were labile, or that no source of reactive iron was present during diagenesis.