Two holes were cored at Site 1267. Hole 1267A was cored to a depth of 348.8 mcd (311.9 mbsf), and Hole 1267B was cored to 367.8 mcd (329.0 mbsf). The major lithologies consist of various proportions of nannofossil ooze and clay with minor components including foraminifers, volcanic ash, and hematite. Near the bottom of the hole, chalk and porcellanite were encountered. The lithostratigraphic units and subunits at Site 1267 are very similar to those defined at Site 1262, as these sites differ in water depth by only 400 m; however, Site 1267 is marked by less dissolution and congruently higher sedimentation rates than those found at Site 1262.
On the basis of variations in lithologic observations and physical property measurements, we divided the sequence into three major lithostratigraphic units, with Units II and III further subdivided based on additional lithologic characteristics (Table T4; Fig. F6). These observations and measurements are summarized in plots illustrating variation with depth: whole-core magnetic susceptibility, natural gamma radiation (NGR), and sediment density from the multisensor track (MST) (Fig. F7); sediment L*, chromaticity (a* and b*), and carbonate content (Fig. F8); smear slide components (Fig. F9); split-core measurements of grain and bulk density, porosity, and compressional wave (P-wave) velocity (Figs. F10, F11); and interstitial water Mn and Fe contents (Fig. F12).
Unit I consists dominantly of nannofossil ooze with 92.6 wt% carbonate, which is reflected by relatively low MS and NGR, and light-colored sediments (Figs. F7, F8). Sediments are light brown to very pale brown or light gray, and color alternates on scales of 10–50 cm (Fig. F13). Darker-colored sediment is generally associated with more clay rich lithologies, reflecting periods characterized by a shallower lysocline and CCD in the South Atlantic Ocean. Unit I at Site 1267 is lithologically similar to Unit I at Site 1262 except that the unit thickness at Site 1267 is almost twice that of Site 1262. Difficulties in stratigraphic correlation between Cores 208-1267A-7H and 208-1267B-8H suggest disturbance, although we observed no obvious evidence of downslope transport in these cores.
Physical properties in the uppermost 50 mcd of Unit I differ from the interval below (50–100 mcd). Downhole, increasing bulk density and decreasing porosity in the upper 50 m of Unit I reflect sediment compaction (Fig. F10). Grain density shows a steplike increase from ~2.6 to 2.7 g/cm3 at ~50 mcd. Below this level, Unit I is marked by relatively high grain density and porosity and low bulk density. In the lower part of Unit I (~82–102.3 mcd), sediments become slightly more clay rich, as indicated by a small increase in MS and a decrease in L* (Fig. F6). Discrete measurements of density (moisture and density bulk density) correlate well with gamma ray attenuation bulk density measured with the MST (Fig. F11). A weak correlation exists between bulk density and grain density and, similar to Site 1262, a good linear correlation (r2 = 0.8) exists between increasing bulk density and decreasing porosity. A relatively good correlation (r2 = 0.69) exists between bulk density and P-wave velocity.
Unit II consists of an upper and lower subunit dominated by clay and separated by a middle subunit of nannofossil ooze. Similar to Site 1262, MS and NGR values are high, whereas L* is low in the clay-rich subunits (Subunits IIA and IIC), reflecting low carbonate content (48.0 and 54.6 wt%, respectively). Subunit IIB is marked by high carbonate concentration (83.5 wt%), which gives rise to lower MS and NGR and higher sediment L* values (Fig. F6). Unlike the sequence at Site 1262, carbonate concentration in Unit II at Site 1267 never decreases to 0 wt%, indicating less dissolution at the shallower water depth of Site 1267. Unit II is thicker at Site 1267 (55.5 mcd) than at Site 1262 (44.2 mcd), but nonetheless, biostratigraphy at both sites suggests that Unit II is a highly condensed interval with pervasive downslope transport, reworking, and dissolution (see "Biostratigraphy").
The contact between Unit I and Subunit IIA is abrupt and marked by a pronounced increase in MS and NGR and a decrease in sediment L*. Subunit IIA consists of clay-rich lithologies oscillating on a decimeter scale: dark brown hematite-bearing clay with abundant pinkish blebs of clay-bearing nannofossil ooze, light brown clay-bearing nannofossil ooze, and brown nannofossil clay. Carbonate content is low, averaging 48.0 wt%. Color variations in Subunit IIA reflect alternating concentrations of clay, nannofossils, hematite, and zeolite. Braarudosphaera is present in the clay-bearing nannofossil ooze of Core 208-1267A-10H (94.4–103.9 mbsf).
Subunit IIB is more carbonate rich than Subunits IIA and IIC (average = 83.5 wt%). Lithologies vary among light brown to gray nannofossil ooze, foraminifer-bearing nannofossil ooze, and medium brown to gray clayey nannofossil ooze. Unlike Site 1262, where clear evidence of turbidites was found in Subunit IIB, Site 1267 appears to have been less affected by downslope transport. Nonetheless, biostratigraphy indicates intensive downslope transport and reworking. The E/O boundary, although not clearly defined at this site, likely occurs near the base of Subunit IIB and is marked by an upward transition from brown clay to light brown nannofossil ooze (Fig. F14). Across the boundary interval, MS, NGR, and bulk density exhibit an upward decrease, whereas sediment L* increases from the Eocene into the Oligocene.
Subunit IIC is composed of clay-bearing and clayey nannofossil ooze at the top and bottom of the subunit, with ash-bearing clay more prominent in the center of the subunit. Subunit IIC is distinguished from Subunit IIB by its lower carbonate content (average = 54.6 wt%), higher MS, NGR, and bulk density, and decreased sediment L*.
Unit III is a carbonate-rich lithology composed primarily of nannofossil ooze with varying abundances of clay, foraminifers, and volcanic glass. It was divided into two subunits based mainly on clay content and degree of induration. Subunit IIIA has higher carbonate and lower clay content than Subunit IIIB. Sediments become progressively indurated downhole from ooze to chalk, with the first chalk occurring at ~300 mcd.
Subunit IIIA consists predominantly of nannofossil ooze with variable, although generally low, clay content. Lithologies oscillate on a decimeter to meter scale between light gray-brown nannofossil ooze and medium gray clay-bearing nannofossil ooze, with attendant variations in MS and color parameters. In the upper part of this unit, nannofossil clay is present in some of the thin dark horizons. Similar to Subunit IIA at Site 1262, large pinkish white blebs, which may be associated with burrowing or diagenetic alteration, occur sporadically throughout the unit. Cyclicity is apparent macroscopically and in records of MS and color reflectance, especially in the upper part of Subunit IIIA (Fig. F13).
Subunit IIIA contains the P/E boundary, a carbonate-free interval formed during a severe dissolution event in response to a shoaling of the lysocline and CCD in the earliest Eocene (Fig. F15). This boundary interval, similar in lithologic and physical properties to the boundary sequence at Site 1262, was recovered at 231.6 mcd in both Holes 1267A and 1267B (Sections 208-1267A-22H-7, 33 cm, and 208-1267B-23H-3, 102 cm). Carbonate content decreases from ~85 wt% in a nannofossil ooze to 0 wt% immediately above the contact, where the lithology changes to a 15-cm-thick dark red clay layer. Chromaticity a* (green-red) increases sharply above the boundary toward greater red values and then decreases gradually to baseline values over a 35-cm interval (Fig. F15). This is followed by a stepped increase in carbonate and decrease in MS as sediment gradually grades back to nannofossil ooze. P-wave velocity also changes across this interval, yet not in concert with other measures (Fig. F16). The maximum P-wave velocity lags behind the increase in MS and decrease in carbonate, with the velocity maximum occurring at 10 cm above the MS maximum.
A similar but less intense early Eocene dissolution event is represented by a thin reddish clay layer ~25 m above the P/E boundary (Fig. F17). This interval was recovered in Sections 208-1267A-20H-3 and 208-1267B-20H-7 and 20H-CC, but it is clearly incomplete in Hole 1267B. In addition to macroscopic characteristics, it is recognized in physical property records by an increase in MS and a* (Fig. F17). This clay-rich interval was observed at all of the Leg 208 sites except Site 1264, where sediments of this age were not recovered.
Subunit IIIB is composed of nannofossil ooze, nannofossil clay, ashy clay, and nannofossil chalk with variable nannofossil, foraminifer, clay, and ash content. Subunit IIIB is similar to Subunit IIIB at Site 1262 but with slightly more varied clay, ash, and chalk content. This variability is also observed in physical properties such as MS, NGR, and P-wave velocity (Figs. F6, F10).
The K/P boundary was recovered in both holes (intervals 208-1267A-31X-3, 75 cm, and 208-1267B-32X-4, 80 cm). Despite disruption and biscuiting by XCB coring and slight rotation directly at the K/P boundary, the transition is well represented in both physical property measurements and lithologic characteristics. Below the boundary, light reddish brown and brown clay-bearing nannofossil chalk alternate on a 0.5-m scale, a cyclicity that is recorded in both sediment lightness and chromaticity. Within the darker lithology, bioturbational features are well preserved with both subhorizontal and vertical structures present. In addition, rare foraminifer-nannofossil–bearing ashy clays are present as isolated blebs in some of the darker layers. At the boundary (Fig. F18), light reddish brown clay-bearing foraminifer nannofossil chalk grades upward into a distinctive 3- to 4-cm light gray nannofossil foraminifer chalk that contains minor amounts of ash (or is slightly silicified). This layer is abruptly overlain by a 2- to 3-cm-thick dark red to reddish brown Fe oxide–bearing foraminifer nannofossil chalk that is not bioturbated. A light reddish brown clay-bearing nannofossil chalk, which is mottled by dark red burrows, overlies this thin transition interval. The MS values increase abruptly across the K/P boundary (320.5 mcd) as sediment L* decreases, reflecting a higher abundance of Fe oxide in the overlying Paleocene sediments. This does not appear to correlate directly with clay content, which does not change dramatically at the boundary; however, clay does increase progressively upsection, as does the abundance of foraminifers. Clay content then decreases again toward the upper boundary of Subunit IIIA.
Lithification increases in the lower part of Subunit IIIA, leading to a dominance of nannofossil chalk. Rarely, nannofossil ooze is partially silicified with the development of porcellanite. In addition, discrete ash layers are present that are composed of abundant Fe oxides and highly altered volcanic glass. These layers are represented by spikes in the NGR record (e.g., interval 208-1267A-32X-3, 123 cm) (Fig. F6).