Echographiekartierung und physikalische Eigenschaften der oberflächennahen Sedimente in der Laptevsee (Teil 2, Laborarbeit)

• Main Author: Benthien, Albert
• Format: Thesis
• Language: German
• Published: 1994
• Subjects: Arctic; Laptev Sea; The Shoals; laptev
• Online Access: https://oceanrep.geomar.de/id/eprint/50437/; https://oceanrep.geomar.de/id/eprint/50437/1/Dipl_Benthien_A_1994.pdf

The Laptev Sea, one of the three epicontinental seas in the Siberian arctic, was the destination of the expedition TRANSDRIFT I during summer 1993. On the expedition at 47 stations sedimentcores were taken (boxcorer, 'kastenkorer'). In addition, during the whole expedition subbottom profiling (30/210 kHz) was carried out to get a continuous net of profiles. Three echotypes could be defined which show a different penetration of acoustic waves into the sediment. The penetration depends on the sediment composition. The mapping of these echotypes documents a significant distribution pattern. In the western region, the shoals, and the near shore areas the penetration is medium or low indicating sandy silt sediments. In the eastern region the penetration is in general very high due to silty clay sediments. The echo-sounding data show that the bottom of the Laptev Sea is disrupted by ice gouges. Most of them occur in water depths between 18 and 38 m. lt is suggested that most of the ice gouging in the Laptev Sea is caused by grounded ice during summer after ice break-up. The results of physical property measurements of near surface sediments (upper 15 cm) in the Laptev Sea show in general high porosities (60 to 70 %) and low shear strengths ( 4 to 8 kPa). Porosities correlate in general with grain size. Local variations due to an higher consolidation of the sediment are explained by interaction between ice and seafloor. The comparison of the echotype distribution pattern with porosities in the Laptev Sea proves that penetration of acoustic waves into the sediment extends with increasing porosities.