Site 1267 (proposed Site WALV-11B) is located in the Angola Basin near the base of the northwestern flank of Walvis Ridge. At a water depth of 4356 m, the site is 100 m shallower than Deep Sea Drilling Project (DSDP) Site 527 just 10 km to the east, where previous drilling recovered a 341-m-thick section of Neogene, Paleogene, and Maastrichtian sediment. Sediments at Site 527 vary from clays to carbonate-rich oozes and chalks. The Pliocene–Pleistocene section consists of nannofossil oozes and extends to ~100 meters below seafloor (mbsf). The Oligocene–Miocene sequence, primarily carbonate-poor clays, is condensed and contains an unconformity. The Paleocene–Eocene sequence appears complete and consists of nannofossil oozes and chalks and a clay layer. However, only a portion of the Paleocene/Eocene Thermal Maximum (PETM), including a 70-cm-thick clay layer, was recovered at this site (Thomas and Shackleton, 1996; Thomas et al., 1999). A continuous Cretaceous/Paleogene (K/P) boundary was also recovered at DSDP Site 527 (Moore, Rabinowitz, et al., 1984). The basal Parvularugoglobigerina eugubina Zone in the Tertiary is well represented (25 cm), and faunas are well preserved. The sediments immediately above basement are of late Maastrichtian age. Site 527 was rotary cored, and, as a consequence, recovery was poor (25%–75%) and much of the core suffered from severe drilling disturbance, particularly the unlithified Neogene and Paleogene oozes.
Our main objective for this site was the recovery of undisturbed sediments recording critical intervals in the early Cenozoic, specifically the K/P boundary, and the following recovery of biota from the mass extinction, the PETM, and the period of global cooling and growth of polar ice caps across the Eocene/Oligocene (E/O) boundary into the earliest Oligocene (early Oligocene Glacial Maximum). We planned to recover 100% of the sedimentary section in multiple holes to make it possible to establish a cyclostratigraphy and develop an astronomically tuned timescale. We aimed to fully document events across the critical intervals as well as short-lived events such as the mid-Paleocene biotic event (PBE) and episodes of climate fluctuation during the early Eocene Climatic Optimum. Site 1267 is located in water ~400 m shallower than at Site 1262, the deep anchor of the Leg 208 depth transect, and is located close to the calcite compensation depth (CCD), making the site suitable to document fluctuations in the depth of the CCD over the early Cenozoic.
We chose a location where the Neogene section is thin (estimated at ~100 m) to facilitate recovery of much of the Paleogene section using the advanced piston corer (APC) rather than the extended core barrel (XCB). Site 1267 is located on a slightly elevated area on the basin floor where the Paleogene sequence appears to be thickest (GeoB 01-039; common depth point 3566) (Figs. F1, F2). Seismic profiles show two distinct packages of reflectors in the basin, a thin upper package (0–105 ms two-way traveltime [TWT] below seafloor) with low-amplitude reflectors and a thicker lower package of slightly higher-amplitude reflectors (105–280 ms TWT below seafloor) (Fig. F2). The upper package is interpreted as a moderately condensed interval of Neogene calcareous oozes and clays, and the lower package is interpreted as upper Maastrichtian to lower Eocene calcareous oozes and chalks. Two prominent reflectors dissect the lower package. The upper reflector, RP/E (240 ms TWT below seafloor), represents the Paleocene/Eocene (P/E) boundary clay layer estimated at ~216 mbsf (velocity = 1.8 m/ms), whereas the deeper reflector, RK/P (310 ms TWT below seafloor), represents the K/P boundary contact at an estimated depth of ~279 mbsf.
In two holes at Site 1267, we used the APC and XCB systems to obtain nearly 100% of a 330-m-thick sequence of upper Maastrichtian to Pleistocene sediment (see "Leg 208 Summary" chapter). The APC system produced less distorted core than was obtained with the rotary coring system during drilling of Site 527. The upper Maastrichtian and Paleocene–lower Eocene sections are moderately expanded. The middle–upper Eocene, upper Oligocene, and middle Miocene are represented by condensed clay-rich layers. The P/E boundary was recovered using the APC in both holes at ~205 mbsf with no obvious coring disturbance. The K/P boundary was recovered using the XCB in both holes at 283.5 mbsf with minimal coring disturbance (i.e., minor biscuiting).
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