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

ounding processes as well. One possibility is that coastal wave activity rounded the
clasts, as it can be actually observed e.g. at the Isfjorden coast near Longyearbyen.
Another possibility is that glaciers advanced over extensive sander plains and this
sandy and gravelly material was entrained in moraines during later glacier
readvances. Today this is not observable on Spitsbergen. During the lowstand of the
last glacial maximum (ca. 18 kyr BP) this may have occurred on the shelf around
Svålbard. In southern Scandinavia this was a widely active landscape forming
process.
17 % of the clasts are incrusted by bryozoa, serpulid tubes, calcareous sponges or
rare foraminifers. Most of these clasts are siliciclastic sediments (90 %), less frequent
are metamorphics (7 %, mainly fine quartzites), volcanics (1 %) and bituminous
siltstones, limestones and chalk (2 %), but none are plutonic rocks. Some clasts show
incrustation on all sides of the clasts, indicating low sedimentation rates and
occasional rotation of the clasts by bioturbation or sediment reworking. Most bryozoa
shells are damaged and only the part in contact with the clast is preserved, except
when the bryozoa were protected from abrasion in small cavities.
The surface of many clasts, most of them incrusted, is often entirely or partly darker
than the interior due to Mn-oxide and Fe-hydroxide precipitation. On these Mn-oxide
covered clasts the skeletons of bryozoa and the tubes of serpulids have orange
colours (siderite?) whereas on other clasts they are white (calcite). Probably the Mnoxides
and Fe-hydroxides were formed in the upper part of the sediments under
suboxic or changing oxic and reducing conditions.
On average the material consists of 4 % plutonic %, 1 % volcanic, 73 % sedimentary
and 22 % metamorphic rocks and this distribution does not vary much between
sampling sites (Fig. C5-1). Description of various rock types:
Plutonic rocks: unrounded quartz, unrounded feldspar, granite /
granodiorite, diorite / gabbro.
Volcanic rocks: basalt with or without bubbles, pumice.
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