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Based on a close relationship between ice-sheet evolution, ice rafting and sedimentation, quartz grain microtextures and clay minerals of the Central Arctic Ocean sediments were studied to find evidence of the earliest glacial influences in the Arctic Ocean since Middle Miocene when the Earth's climate started cooling dramatically. Only recently, the very first deep sediment cores from the Arctic Ocean basins are recovered to focus on these objectives. In this study the IODP Exp 302 Site M0002 (Lomonosov Ridge) for the first 200 meters below sea level was sampled extending from the Miocene through to the present. The sediments consist predominantly of siliciclastic sediments characterized by low organic carbon concentrations.
The continental glacial crushing and abrasion produces general angularity, high relief and certain microtextures like conchoidal fractures, crescentic gouges and arcuate steps in quartz grains. Surface texture analyses can therefore be used to identify characteristics of the ice-rafted debris originating from glacial environment. Scanning electron microscopy (SEM) has proved to be successful method for high resolution microtextural surface picturing of quartz grains because of great depth of field and resolution. At least 30 randomly selected grains from up to 24 representative samples in grain fractions between 0.6-0.125 mm were analyzed at the Institute of Electron Optics (University of Oulu). Preliminary results with evident continental ice indicators from middle and late Miocene samples correlate well with kaolinite occurrence related to increased glacial erosion on land which is also consistent with higher chlorite and illite contents. These results present the value of microtextural characteristics of ice rafted quartz grain material and reworked kaolinite and illite for recognizing an initiation of glaciation. The periodically high smectite contents seem, however to indicate turns to more open marine conditions and general interglacial periods.
In generally, the microtextural study of quartz sand grains when compared with the clay assemblages can provide additional information about sediment source area environmental conditions including possible ice sheet initiations in this case the periodical existences of the earliest Northern Hemisphere ice sheets.
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