TOWARD AN UNDERSTANDING OF MID-LATITUDE NORTHWEST PACIFIC PLEISTOCENE CLIMATIC AND OCEANIC VARIABILITY: INSIGHTS FROM X-RAY FLUORESCENCE CORE SCANNING AND ICE-RAFTED DEBRIS

The mid to Late Pleistocene is characterized by a time of transition in the duration and amplitude variability of glacial to interglacial cycles. During the Mid-Pleistocene climate transition (MPT) (1.0-0.8 Ma), the periodicity of glacial to interglacial cycles shifted from 41-kyr to 100-kyr. The MPT is punctuated by interglacial periods that are interpreted from high-latitude records to have been exceptionally warmer than typical Pleistocene interglacial periods and are referred to as “super interglacials”. Some of the best dated super interglacials occur during Marine Isotope Stage (MIS) 31 as it aligns with the Jaramillo polarity reversal. The Mid-Brunhes Event (MBE) at ~430 ka marks an amplitude shift in glacial cycles. The MBE is best characterized from Antarctic ice core records but is identified globally in a variety of proxy records.

We present a high resolution (<3 ka sample resolution) x-ray fluorescence (XRF) core scanning data set and ice-rafted debris (IRD) record from a mid-latitude, mid to Late Pleistocene marine sediment record recovered from Ocean Drilling Program (ODP) Site 1207 on the Shatsky Rise plateau in the northwest Pacific Ocean. Located near the Kuroshio Extension, the ODP 1207 record can be used to test for regime changes in surface ocean circulation during MPT, super interglacials and the MBE. XRF core scanning data demonstrates glacial to interglacial lithological variability in sediment composition. Biogenic indicators of Ca/Ti and Si/Ti potentially relate to meridional shifts in surface ocean currents. Terrigenous proxies (Ti, Fe, K) demonstrate a baseline shift of input during the Late Pleistocene. Furthermore, IRD demonstrates periodic input of icebergs during the early to mid-Pleistocene and provides a direct record of glacial variability in the northwest Pacific Ocean during the MPT and MIS 31. XRF results and time series analysis are used to better identify the timing of the MPT from a non-orbitally tuned record. We then develop an orbitally tuned age model for comparison with terrigenous Arctic records to better understand teleconnections between mid to high latitude regions surrounding MIS 31 and the MBE.