 |
| Titel |
Ice-internal and sedimentary structures in the Ekströmisen grounding line region detected with multi-offset seismics |
| VerfasserIn |
C. Hofstede, G. Uenzelmann-Neben, U. Nixdorf, O. Eisen, B. Kulessa |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022964
|
|
|
|
|
|
| Zusammenfassung |
| Ekströmisen is a small catchment area in coastal Dronning Maud Land, Antarctica,
terminating in the Ekström ice shelf, which is bounded by a narrow embayment
formed by two ice ridges. A seismic survey has been performed along a flow line on
Ekströmisen over about 22 km, crossing the grounding line between ice sheet and shelf
approximately midway of the profile. The measurements were performed with
explosive in shallow firn holes as seismic sources and a 60 channel 1.5 km snow
streamer for data recording. The data has been resorted to form a virtual 120 channel 3
km streamer, consisting of 150 shots. The maximum shot-receiver offset is thus
about three times larger then the ice thickness, yielding wide angle information for
intra-ice and bedrock reflections. Standard seismic data processing yields 862 common
depth points in total, with an increment of 25Â m. This provides a 20-fold coverage
of each common depth point. In addition to yielding the distribution of seismic
velocity within the firn, ice and sediment, the data clearly images ice and sedimentary
layers. Within the bottom part of the ice, a number of continuous internal layers
are visible upstream of the grounding line. Currently, our favorite explanation is
abrupt changes in the crystal orientation fabric caused by a combination of laterally
compressional flow and vertical shear, as observed with radio-echo sounding at
other places in Antarctica. Upstream of and at the grounding line, structures are
visible within the bedrock, which we interpret as sedimentary deposits related to
glacial activity. The data provide the base for interpretations of the ice-dynamic and
sedimentary processes occurring in the basal ice layer and at the ice-bedrock boundary, of
relevance for further understanding details of the ice sheet-to-shelf transition area. |
|
|
|
|
|
|