Foraminiferal assemblages and stable isotopes across the early Paleogene carbonate facies of Perth Abyssal Plain off Western Australia

A prominent Benthic Foraminiferal Extinction Event (BFEE) occurs across the clay-rich horizon, with an influx of large Acarinina immediately above. The delta13C records of bulk carbonate and N. truempyi exhibit trends similar to those observed in upper Paleocene–lower Eocene (~57–52 Ma) sediment from other locations. Two successive decreases in bulk carbonate and N. truempyi delta13C of 0.5 and 1.0‰ characterize the interval at and immediately above the BFEE.

Despite major changes in carbonate content, foraminiferal assemblages and carbon isotopes, the mineralogy of the non-carbonate fraction consistently comprises expanding clay, heulandite (zeolite), quartz, feldspar (sodic or calcic), minor mica, and pyrolusite (MnO2). The uniformity of this mineral assemblage suggests that Site 259 received similar non-carbonate sediment before, during and after pelagic carbonate deposition.

The carbonate plug at Site 259 probably represents a drop in the CCD from ~57 to 52–51 Ma, as also recognized at other locations.