Preface The expedition ARK XIX/3 with the German icebreaking RV ...

material via the Transpolar Drift through the Fram Strait into the Nordic Seas. The goal
during this cruise leg was to reconstruct the origin of the icebergs that released icerafted
debris (IRD) from the study of gravel-sized clasts in sediments of the
“Hausgarten” area during the Holocene and late Pleistocene.
Materials and Methods
Sediment samples taken during expedition ARK XIX/3c from which IRD was analysed
are listed in the contribution of Matthiessen et al. (chapter C. 3). The content of gravel
grains (>2 mm) in surface sediments was estimated from photos of sediments
recovered with a Giant Box Corer (GKG). The uppermost 20 to 40 cm of sediments
recovered with a GKG were sieved through a 2 mm mesh for epi- and endobenthos
studies (see Budaeva (C. 9), and Urban-Malinga & Jankowska (C. 10)). Gravel
collected from these sediments could be analysed for petrography and grain size. Also
gravel from the upper 33 cm of sediment from several tubes of a multicorer (MUC)
was studied. A total number of 1061 gravel- (and bloc-) sized clasts from 29 stations
recovered at 15 locations was analysed.
Clasts of the gravel (and bloc) fraction were studied under 10-fold magnification with a
lense. The material was classified into plutonic, volcanic, sedimentary and
metamorphic rocks. A further subclassification into 28 different rock types was
performed and rock colors were noted. When incrustation or scratching was
observable this was also registered. With a micrometer scale the longest, shortest and
intermediate diameter of the clasts was measured, values were rounded to 0.5 mm
length. The sphericity was calculated by dividing the shortest through the longest
diameter. For determination of the roundness of the material three groups were
classified: well-rounded, marginally-rounded and unrounded (with sharp edges). When
gravel grains are only partly well-rounded and partly sharp as they were broken they
are classified as well-rounded.
The detailed grain size and petrographic data can be retrieved online under
http://www2.uni-jena.de/chemie/geowiss/angeol/start.html;
the gravel content in surface sediments under http://www.pangaea.de.
- 252 -