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ABSTRACT

A system has been developed allowing the direct storage on disc of size data from the X-ray scanning settling tube SediGraph 5000ET. Processing of the cumulative percentage data output to produce smooth frequency curves is described. This allows rapid (15 min) and precise (±M 0.1ø) discrimination of size modes, peak heights, median and silt and clay percentages of fine-grained sediments. An example of a mud turbidite is given showing systematic changes in bulk and modal properties, not visible by eye. Lack of size segregation in the > 1 m thickness of this turbidite shows that it may have been deposited from a highly concentrated flow, rather than from a dilute, waning turbidity current. Such flows may explain ungraded/poorly graded, muddy sediments also known as homogenites, unifites or megaturbidites by other authors.