A new insight of 3-D microfabric analysis of unconsolidated marine sediments: Examples from north atlantic 300-meter long cores

摘要

Detailed three dimensional microfabric images of deep-sea sediments were revealed from Anisotropy of Magnetic Susceptibility (AMS) measurements, Scanning Electron Microscope (SEM) observations and micro Xray CT analyses. Studied specimens of -300 meter composite depth (mcd) were collected from Sites U1302, 04, 05, 06, 07, and 08, in the North Atlantic during the Integrated Ocean Drilling Program (IODP) Expedition 303. The sediments from Sites U1302, 05, 06 and 07 were mainly composed of silty clay, those from Sites U1304 and 08 were composed of mainly pelagic sediments. The microfabric observation indicates that the sedimentary particles of silty clay re-arrange gradually from non-directional orientation to preferred horizontally orientation due to burial consolidation. In contrast, the sedimentary particles of pelagic sediments does not re-arrange well throughout the cores. The AMS and X-ray CT results are supported by detailed microfabric observations. Thus, the silty clay from the North Atlantic develops gradually into a shaly structure during burial, whereas similar fabrics in the pelagic sediments are not well developed.