The Late Quaternary Northwest Pacific: Palaeoenvironmental change and development of regional marine chronostratigraphy

The Northwest (NW) Pacific contains a significant, but poorly constrained and poorly understood ice-rafted debris (IRD) belt extending from the subarctic to the mid-latitudes. While these deposits point to substantial glacial ice in the Kamchatka-Koryak region during the last glacial period, the timing and dynamics of glacial change are not well constrained. This thesis updates the Late Quaternary marine core record with a high resolution and multi-faceted study of environmental change. The thesis begins with a review of the state of knowledge relating to Late Quaternary glacial and climatic change in the NW Pacific. I present a high resolution, ~175 kyr study of site ODP 1207A (37.79ºN, 162.75ºE), encompassing IRD, 14C dating, benthic δ18O, tephrochronology and planktic foraminifera counts. The southern limit of ice-rafting is revealed to be further south than previously thought. This discovery, in conjunction with a new high resolution age model reveals new information about the scale and timing of large magnitude ice-rafting events from NE Siberia. Ice-rafting does not show synchronicity with other major Northern Hemisphere ice sheets. A second IRD analysis is presented for DSDP 580 (41.37ºN, 153.59ºE) where icebergs are known to have reached. I present an updated age model for DSDP 580 derived from both pre-existing age tie points and new tephrochronological data. Together, these new IRD records reveal periods of widespread glacial collapse and possible synchronous collapse of NE Siberian glacial ice ~40 ka BP. Chapter 6 presents a comprehensive analysis of XRF core scanning data of Late Quaternary sections of nine North Pacific cores. This analysis extracts palaeoenvironmental signals from element intensities and log ratios, which identify episodes of palaeoproductivity change and terrigenous input. The palaeoproductivity indicators Ba and Ca are used to identify inter-core stratigraphic tie-points at multiple N Pacific sites, particularly around the last deglaciation. Chapter 7 presents the results and analysis of coupled climate-iceberg model experiments, which explores the most likely source points for icebergs into the N Pacific. The model experiments are important indicators of IRD provenance and provide a foundation for future geochemical provenance studies.