IMPROVING THE CRETACEOUS BENTHIC FORAMINIFERAL OXYGEN ISOTOPE COMPILATION WITH NEW DATA FROM SHATSKY RISE (IODP EXPEDITION 324)

Deep-sea benthic foraminiferal oxygen isotope data provide a crucial paleoclimatological reference curve. The Cenozoic interval as well as the latest Cretaceous (late Campanian–Maastrichtian) part of the benthic oxygen isotope curve is well-established and serves as a foundation for integrating various paleoenvironmental and geological observations with Earth’s paleoclimatic evolution. By contrast, compilation of a benthic oxygen isotope record for much of the Cretaceous (from pre-late Campanian dating back to 115 Ma) has been hampered by a number of difficulties such as poor core recovery, relatively high levels of diagenetic alteration, presence of widespread unconformities at certain age-intervals, and/or restricted paleoceanographic conditions the Atlantic sites that have been most studied. To establish a better global paleoclimatic record through the Cretaceous, it is necessary that the available benthic oxygen isotope data are strengthened and extended further by additional high-quality data that are not influenced by local paleoceanographic effects. High quality samples from the central Pacific would be ideal for this purpose because of the central Pacific represents a fully open-ocean setting. However, technological, diagenetic and/or primary sedimentological issues mentioned above have long impeded data collection from this region.

Situated in the central Pacific during the Cretaceous, Shatsky Rise is the only place where a pelagic sediment cover potentially dates back to the earliest Cretaceous. Recent IODP Expedition 324 (Sites U1348 and U1349) recovered some unique suites of Cretaceous pelagic carbonates that are unconsolidated (described as ooze) and yield generally well-preserved benthic foraminifera. The recovered sedimentary records are limited in stratigraphic extent, but they give important insights that allow for improvement of the Cretaceous deep-sea benthic oxygen isotopes record. New data fill the significant data gap across the Santonian–Campanian transition interval and extend the isotope compilation to the early Aptian (~120 Ma).