Paleoclimate investiations on sediment core MD01-2378

We present a high-resolution (not, vert, similar 60-110 yr) multi-proxy record spanning Marine Isotope Stage 3 from IMAGES Core MD01-2378 (13°04.95'S and 121°47.27'E, 1783 m water depth), located in the Timor Sea, off NW Australia. Today, this area is influenced by the Intertropical Convergence Zone, which drives monsoonal winds during austral summer and by the main outflow of the Indonesian Throughflow, which represents a key component of the global thermohaline circulation system. Thus, this core is ideally situated to monitor the linkages between tropical and high latitude climate variability. Benthic d18O data (Planulina wuellerstorfi) clearly reflect Antarctic warm events (A1-A4) as recorded by the EPICA Byrd and Dronning Maud Land ice cores. This southern high latitude signal is transferred by deep and intermediate water masses flowing northward from the Southern Ocean into the Indian Ocean. Planktonic d18O shows closer affinity to northern high latitudes planktonic and ice core records, although only the longer-lasting Dansgaard-Oeschger warm events, 8, 12, 14, and 16-17 are clearly expressed in our record. This northern high latitude signal in the surface water is probably transmitted through atmospheric teleconnections and coupling of the Asian-Australian monsoon systems. Benthic foraminiferal census counts suggest a coupling of Antarctic cooling with carbon flux patterns in the Timor Sea. We relate increasing abundances of carbon-flux sensitive species at 38-45 ka to the northeastward migration of the West Australian Current frontal area. This water mass reorganization is also supported by concurrent decreases in Mg/Ca and planktonic d18O values (Globigerinoides ruber white).

(Table 3) Stable isotope record of Cretaceous foraminifera from DSDP Hole 44-392A

Mid-Cretaceous (Barremian-Turonian) plankton preserved in deep-sea marl, organic-rich shale, and pelagic carbonate hold an important record of how the marine biosphere responded to short- and long-term changes in the ocean-climate system. Oceanic anoxic events (OAEs) were short-lived episodes of organic carbon burial that are distinguished by their widespread distribution as discrete beds of black shale and/or pronounced carbon isotopic excursions. OAE1a in the early Aptian (~120.5 Ma) and OAE2 at the Cenomanian/Turonian boundary (~93.5 Ma) were global in their distribution and associated with heightened marine productivity. OAE1b spans the Aptian/Albian boundary (~113-109 Ma) and represents a protracted interval of dysoxia with multiple discrete black shales across parts of Tethys (including Mexico), while OAE1d developed across eastern and western Tethys and in other locales during the latest Albian (~99.5 Ma). Mineralized plankton experienced accelerated rates of speciation and extinction at or near the major Cretaceous OAEs, and strontium isotopic evidence suggests a possible link to times of rapid oceanic plateau formation and/or increased rates of ridge crest volcanism. Elevated levels of trace metals in OAE1a and OAE2 strata suggest that marine productivity may have been facilitated by increased availability of dissolved iron. The association of plankton turnover and carbon isotopic excursions with each of the major OAEs, despite the variable geographic distribution of black shale accumulation, points to widespread changes in the ocean-climate system. Ocean crust production and hydrothermal activity increased in the late Aptian. Faster spreading rates [and/or increased ridge length] drove a long-term (Albian-early Turonian) rise in sea level and CO2-induced global warming. Changes in ocean circulation, water column stratification, and nutrient partitioning lead to a reorganization of plankton community structure and widespread carbonate (chalk) deposition during the Late Cretaceous. We conclude that there were important linkages between submarine volcanism, plankton evolution, and the cycling of carbon through the marine biosphere.