Drilling on Transect EG65 successfully recovered core at 55 sites over a distance of ~32 km. Forty holes reached volcanic basement. Continental basement (granitic gneiss) was recovered from Hole SEG32A located on the basement high immediately landward of the seismically imaged basin at the northwestern end of Transect EG65 (Fig. F2). In contrast, sites located on the seaward escarpment of this basin recovered friable sandstone (Sites SEG38 and SEG80) and Paleogene lavas, including a distinctive suite of highly to moderately olivine (± plagioclase and clinopyroxene) phyric basalt from Sites SEG77, SEG79, SEG37, SEG75, SEG76, SEG36, SEG74, SEG40, SEG41, SEG42, SEG44, SEG47, and SEG45 (ordered from west to east). Lavas recovered seaward of Site SEG45 are typically aphyric to moderately clinopyroxene-plagioclase phyric. These striking petrographic differences of lavas in the transect area were used to define a lower and upper series, with the boundary placed between Sites SEG45 and SEG51 (~36°17´W) (see Fig. F2).
All igneous units were analyzed by shore-based X-ray fluorescence (XRF). These results show volatiles between 0.5 and 1.5 wt% for most units, whereas the highly olivine phyric flows have volatiles as high as 4 wt%. All of the basalts are olivine and hypersthene normative. A few lavas from the upper series have normative nepheline. The highly to moderately olivine phyric basalts of the lower series have MgO contents as high as 11 wt%, Mg numbers of ~0.68, and TiO2 contents as low as 0.8 wt%. The basalts are also elevated in Cr and Ni, consistent with their high modal proportion of olivine. In contrast, the plagioclase-clinopyroxene basalts of the upper series have Mg numbers below 0.52 and TiO2 content reaching 3.8 wt%. Overall, the covariations of major and minor elements are typical of tholeiitic differentiation controlled by olivine, plagioclase, and clinopyroxene fractionation.
The highly to moderately olivine phyric basalts of the lower series commonly have the most calcic plagioclase phenocrysts (An87 –An76), Mg-rich clinopyroxene (Mg number = 0.85–0.77), and olivine (Fo75 – Fo68) phenocrysts. The sparsely to aphyric upper series reach more evolved phenocryst compositions (plagioclase An86 –An63; augite Mg numbers = 0.81–0.71; olivine Fo75 –Fo61), despite showing large compositional overlap with the lower series. The most iron-rich olivine (Fo54) was analyzed from the groundmass of Unit I-1 in Hole SEG61B. Spinel is often found in the lower series and is commonly Cr rich (Cr/[Cr + Al + Fe3+] = 0.42–0.59).
All igneous units for which the paleomagnetic polarity could be determined are reversely magnetized. Two samples were deemed suitable for 40Ar-39Ar dating. A plagioclase separate from the upper series (Section 163X-SEG58A-1-1) yields an isochron age of 55.1 ± 0.7 Ma. A whole-rock sample (Section 163X-SEG47A-1-1) of the lower series gives an imprecise isochron age of 51.9 ± 2.3 Ma (C. Tegner, unpubl. data).
The glaciomarine sediments recovered from most of the holes are accumulations of pebble-sized clasts and massive sandy or fine-grained bioturbated diamicton. The contact between the volcanic basement and the overlying glaciomarine sediments was never preserved. Glacial striations and glacially polished surfaces of volcanic basement were recovered from Holes SEG27A and SEG40A, whereas weathering of fractured surfaces is common. These observations suggest that the basement surface was locally barren, glacially eroded, and weathered before being covered by glaciomarine silt and mud containing pebbles and boulders.
The discovery of sandstone at two locations within the lower series is particularly noteworthy. The sandstone recovered from Hole SEG80B is a sulfate-rich, coal flaser–laminated, highly bioturbated, calcite-cemented sandstone containing fossil wood fragments. We interpret this sandstone as a subaqueous deposit formed in the sulfate reduction zone of a calm, shallow basin. A quartzwacke was recovered from Hole SEG38B. Although this material occurs as a 19-cm-long, well-indurated clast, its size, angularity, and the presence of lapilli fragments suggests that it may be Paleogene in age. Furthermore, the presence of rip-up clasts suggests that this unit may have been deposited in a high-energy environment, possibly as fallout from a concentrated turbidite suspension. The structure and age relations of these sediments to the associated lavas are unclear, but it is worth noting the close similarities between the sandstone from Hole SEG80B and sediment recovered from the bottom of ODP Hole 917A, which are stratigraphically below the lower series and interpreted as prebreakup in age (Larsen, Saunders, Clift, et al., 1994), and sediments of the Paleocene Ryberg Formation underlying the Paleogene basalts of the Blosseville Kyst, East Greenland.