RESULTS

The CIE is recorded by bulk sediment at each site. At Sites 1209, 1210, 1211, and 1212, the magnitude of the excursion is ~2.5. The negative excursion covers an interval of several centimeters at and above the lithologic contact. The return to stable values, or the "recovery interval," shows a depth-dependent pattern with the recovery spanning ~80 cm at Site 1209 and ~50 cm at Site 1212. At Site 1211 the recovery is clearly truncated.

As the onset of the CIE at the base of the PETM is a "golden spike" that formally defines the P/E boundary; trends in all other records are described relative to this horizon (0 cm).

Weight percent coarse fraction trends vary significantly between the four sites despite their relative proximity. At Site 1209, coarse fraction increases at the base of the CIE (0 cm), reaches a maximum between 5 and 11 cm above the CIE, and then steadily decreases to background levels at about +22 cm (Fig. F5). This is similar to the coarse fraction at Site 1210, which begins to increase at 0 cm, reaches a maximum at +2 cm, then declines to background levels at +14 cm (Fig. F6).

The abrupt increases in coarse fraction at Sites 1209 and 1210 are not observed at the deeper Sites 1212 and 1211. Coarse fraction at Site 1212 is relatively low until about +2 cm, where it steadily increases and remains high through +16 cm (Fig. F7). At Site 1211, coarse fraction decreases slightly beginning just below 0 cm, then increases at +4 cm (Fig. F8).

At Site 1209, CaCO₃ decreases from 97 wt% at –3 cm to 86 wt% at +2 cm and then increases in an irregular fashion to 97 wt% at +17 cm (Fig. F5). At Site 1210, CaCO₃ decreases from 93 to 86 wt% from –3 to 0 cm, remains low (<91 wt%) until +10 cm and then remains relatively constant at >90 wt% to +92 cm. Samples with decreased CaCO₃ at Sites 1209 and 1210 correspond to the interval with elevated coarse fraction (Figs. F5, F6).

CaCO₃ decreases from 98 to 83 wt% at –1 cm at Site 1212 and remains mostly <90 wt% up to +10 cm, where it increases to >95 wt% (Fig. F7). CaCO₃ is more variable at Site 1211 (Fig. F8). There is a general decline in CaCO₃ content from >95 wt% at –4 cm to 70 wt% at +3 cm. CaCO₃ content increases at +3 cm from 70 to 92 wt%. Lowest recorded CaCO₃ occurs at the deepest site, Site 1211.

Foraminiferal fragmentation is the percentage of foraminifers that are broken in each sample. At Site 1209, fragmentation increases from 33% at –4 cm to 63% at 0 cm and then decreases to 27% at +5 cm (Fig. F5). At Site 1210, fragmentation is also highest (77%) at the base of the CIE but remains above 40% from –3 cm to +6 cm (Fig. F6). At Site 1212, fragmentation begins to increase from 10%–15% below –2 cm to 25% at –1 cm, peaks (70%) at +2 cm and then decreases to ~35% above +5 cm (Fig. F7). Fragmentation begins to increase at 0 cm at Site 1211, peaks (66%) at +3 cm (Fig. F8) and then decreases to ~30% above +5 cm.

At the two sites with records that extend well above the dissolution horizon (Sites 1209 and 1210), fragmentation drops to levels below preexcursion values.

A high benthic/planktonic foraminiferal ratio (B/P) has often been used as an indicator of dissolution (e.g., Corliss and Honjo, 1981). In all examined Shatsky Rise samples, benthic foraminifers are relatively rare. At Site 1209, the highest B/P (0.04) was found at 0 cm (Fig. F5). The highest B/P at Site 1210 (0.11) was at –12 cm, with a second maximum at –1 cm (0.09) (Fig. F6). The B/P is >0.02 from 0 to +1 cm at Site 1212 (Fig. F7). At the deepest site, Site 1211, the B/P is highest (0.06) at +2 cm (Fig. F8).

Pyrite was observed as coatings on foraminifers and as discrete particles. At Site 1209, pyrite content peaked (3%) at the CIE onset (Fig. F5). At Site 1210, pyrite abundance increased in the interval below the CIE and peaked at the onset (9%) (Fig. F6). Very little pyrite was recovered above base of the CIE at Sites 1209 and 1210. At Site 1212, pyrite abundance increased significantly at the CIE onset and reached a maximum at +1 cm (8%) (Fig. F7). At Site 1211, significant pyrite was confined to samples from +1 to +3 cm, and maximum content (28%) occurred at +2 cm (Fig. F8). Pyrite abundance steadily increases from the shallowest to deepest sites.

Fish debris includes fish teeth, scales, and bones. At Site 1209, maximum fish debris (4%) was recovered at the onset of the CIE coincident with the maxima in fragmentation, pyrite, and B/P ratio (Fig. F5). The peak in fish debris at Site 1210 extends from –4 to 0 cm and is centered (17%) at –2 cm (Fig. F6). At Site 1212, the peak in fish debris (40%) lies at +1 cm (Fig. F7). At Site 1211, fish debris is concentrated between +1 and +3 cm, with a peak (35%) at +2 cm (Fig. F8). The two deeper sites have a much higher abundance of fish debris than the two shallower sites.

An extensive survey of pore infilling and secondary calcite precipitation on foraminifers was conducted. Trends in visual foraminiferal preservation were correlated to the quantitative variables. Extensive micrographs documenting foraminiferal preservation can be found in Colosimo (2004); we present a summary of micrographs showing preservation across the base of the PETM in Hole 1209B in Plates P1, P2, P3, P4, P5, P6, and P7. We indicate the interval of poorest preservation in Figures F5, F6, F7, and F8.

Preservation is moderate before and after the PETM interval at Site 1209 but deteriorates at 0 cm and remains poor until +15 cm (Pls. P1, P2, P3, P4, P5, P6, P7; Fig. F5). Blocky secondary calcite is observed throughout the entire interval of poorest preservation with infilling of chambers and extensive overgrowth on muricae and walls. At Site 1210, foraminiferal preservation is moderate below and above the lithologic contact. Preservation deteriorates abruptly at 0 cm and remains poor until about +10 cm (Fig. F6). In this interval, extensive pore infilling with secondary calcite was observed. Euhedral calcite blades 5–10 µm long have also been observed on chamber walls in the interval of poorest preservation.

Foraminifers are generally more overgrown with secondary calcite at Site 1212 than at Site 1210. Preservation deteriorates significantly at the lithologic change and remains poor for much of the studied record (Fig. F7). Euhedral calcite blades were observed on chamber walls throughout this entire studied section. Less calcite overgrowth is observed on foraminifers at Site 1211, although preservation is poor from 0 to +5 cm (Fig. F8).