Correlating the Pleistocene Sediment Stratigraphy Across the Arctic Ocean

An extensive sediment coring program was carried out during the Healy-Oden Trans-Arctic Expedition in 2005 (HOTRAX) from USCGC Healy. In total, 29 piston cores, on average 12 m long, were retrieved along a transect from the Alaskan margin, across the Arctic Ocean, to the Yermak Plateau off Svalbard. One of the purposes for the expedition was to establish the Pleistocene sediment stratigraphy for the Arctic Ocean and to resolve the issue of determining sedimentation rates in the central Arctic. Here, we present an attempt to correlate the cores along the HOTRAX transect in order to set a base for the chronostratigraphy. The cores taken from the Mendeleev Ridge and the Alpha Ridge can readily be correlated using gamma density and magnetic susceptibility measurements from the onboard Multi Sensor Core Logger as well as grain size measurements. The stratigraphic ties between the Alpha Ridge cores and the Mendeleev Ridge cores north of 80°N are detailed with many similar features. The most useful feature is an interval of five peaks in the magnetic susceptibility record. However, a correlation between the Mendeleev Ridge cores located further to the south and closer to the shelf edge was less straightforward, possibly indicating that depositional processes here are affected by other factors than in the central Arctic Ocean. Bridging the Amerasian and Eurasian Basin stratigraphies through the cores retrieved from the Lomonosov Ridge proved to be far less straightforward. None of the prominent physical property features that occur in the Mendeleev Ridge and Alpha Ridge cores are recognized in the Lomonosov Ridge stratigraphy. This may imply that the Lomonosov Ridge sediments predominantly originated from a different source area during the Pleistocene than the Alpha and Mendeleev Ridge sediments. Applying this as a working hypothesis, we focus on linking the cores within the Eurasian Basin for further correlation. However, the presence of alternating dark and light brown layers in all cores seem to indicate that the climatic signal should be recorded in all of them. Although no correlation across the entire Arctic Ocean has been achieved, the present results suggest that accurate core-to-core correlations are possible over large areas in the Amerasian Basin and that the depositional environment in the central Amerasian Basin has not varied significantly.