Glaciations and climate in the Cenozoic Arctic:evidence from microtextures of ice-rafted quartz grains

• Main Author: Immonen, N. (Ninna)
• Other Authors: Strand, K. (Kari), Lunkka, J. (Juha Pekka)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Oulun yliopisto 2014
• Subjects: arctic; climate; glaciation; icebergs; quartz; sea ice; arktinen alue; ilmasto; jäätiköityminen; jäävuoret; kvartsi; merijää; Arctic; Arctic Ocean; Arktinen alue; Ice Sheet; Iceberg*; Sea ice
• Online Access: http://urn.fi/urn:isbn:9789526206080

Abstract Numerous efforts have been made in recent decades to recover the climate history of the Arctic region. The present PhD study is one of them, focusing on terrestrial sediments which were deposited in the Arctic Ocean during the Cenozoic. The Arctic Ocean, surrounded by land on all sides, is among the most important marine archives of sediments that record information of palaeoclimates, including cold climates with extensive glaciation. Evidence of ancient glaciations is generally retraced by observing widespread terrestrial ice-rafted debris (IRD) deposits on the seafloor, as large amounts of IRD are transported by icebergs during deglacial phases. However, it has been shown that sea ice also transports abundant IRD from shallow continental shelves. What is worth noticing is that glaciers and sea ice influence climate variables differently, and therefore, to model climate in past glaciations, IRD released from these factors should be differentiated. The relative proportions of glacial IRD and non-glacial IRD were determined in this study from two central Arctic Ocean expedition site recoveries: the Integrated Ocean Drilling Program’s (IODP) Arctic Coring Expedition (ACEX) 302 composite core recovery and the Swedish Polar Research Expedition’s Arctic Ocean 1996 (AO96) piston core 96/12-1pc. The main objective was to characterise and quantify the process- and environment-related microtextures of quartz sand grain surfaces. The data were subjected to statistical methods and a multiproxy approach, and the results were used to define the dynamics and timing of palaeoglaciations. The results indicate that the signals of glacial and non-glacial continental processes and the involvement of iceberg versus sea-ice rafting can be distinguished by microtextural and statistical analyses. Improvements in the general interpretation of late Pleistocene Eurasian ice sheet distribution and dynamics are provided: late MIS 4 (ca. 62–67 ka) reflects a deglacial phase with increased fluvial activity, whereas MIS 3 at ca. 45 ...