Monitoring sedimentation

Spatial and temporal variations in sedimentation rate and the formation of cyclic and event types of stratification have been identified by the correlation of sedimentation units between sediment cores, which were sampled on the same day during different seasons and years, as well as before and after specific events. The cores were X-rayed, the uppermost part in stereo, and the optical data obtained from the radiographic images were then quantified by the use of X-ray densitometric methods.

Radiographic comparison between the uppermost part of sediment cores 510, 514, and 513. The arrows mark the positions of the sediment surface on 18 October 1978 and 15 May 1979, i.e. just before and after a period of dredging and dumping operations. From Axelsson 2002 (Geo-Marine Letters 21/4).

Parts of a marker layer formed during the winter of 1978 - 1979, when dredged material was transported to and dumped in the deepest part of Hallsfjärden, a bay at the east coast of Sweden, are shown by the radiographs above. Coring sites 510, 514, and 513 were situated at depths of 20, 23, and 22 m, and about 150 m west of, 800 north of, and 400 m south of the disposal area respectively.

The use of X-ray radiographic techniques, especially stereo-radiography and X-ray densitometry simplifies the core-to-core correlation as well as the determination of sedimentary properties and the quantification of sedimentation rates. See further Axelsson, V., 2002: Monitoring sedimentation by radiographic core-to-core correlation (Geo-Marine Letters 21/4). However, the tonal range of the published X-ray radiographs is bad in relation to that of the originals, and observe that the publisher has added a point after html in the source code of the link to my homepage in the online version of my paper. Delete that point in the address, the link will work, and you can study better X-ray radiographs).

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