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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
ABSTRACT: Comparison Of Glacial Geomorphic Features In
Antarctic Peninsula Fjords Based On Multibeam Swath
Bathymetry Data
A distinctive suite of subglacial geomorphic features, representing the grounding of an ice sheet and its subsequent retreat, has been welldocumented
as occurring on many parts of the Antarctic continental shelf. Elements that characterize this suite include meltwater
channels, drumlins, mega-scale glacial lineations, and gullies. Many of these same elements occur in more recently deglaciated fjords,
but at different scales and in different combinations. Bathymetric soundings have been collected during transit onboard the RV/IB
Nathaniel B. Palmer in various expeditions to the Antarctic Peninsula. Multibeam swath bathymetry data were acquired using a Simrad
EM120 hull-mounted swath profiler consisting of 120 beams of 12 kHz data. The data were edited for anomalous readings by the scientific
party of each cruise while onboard; later the data were gridded and processed to create relief maps. The vertical and horizontal resolution
of the data is 10 meters. The study includes ten fjords on the north and west side of the Antarctic Peninsula, from the Graham Land
Coast around to Hope Bay as well as on Anvers Island. The multibeam data has been reprocessed using different software packages
including MB Systems, ArcGIS, Fledermaus, and CARIS resulting in high-resolution images. The different methods used to plot the
bathymetric data complement each other as the capabilities of each
method
vary. Diverse measurements, including dimensions of the
different morphological features, and calculations like slope, ice drainage area, and sediment volumes were made using these acoustic
techniques. Comparison of the geomorphic features from the ten fjords show certain trends. Meltwater channels are much more prevalent
within the fjords than on the open shelf. Mega-scale glacial lineations within the fjords have much shorter average lengths than those on
the open shelf; this is attributed to the irregular seafloor topography that characterizes the fjord floor. Finally, some fjords are characterized
by a series of back-stepping grounding zone wedges, which mark times during which ice was stabilized during retreat. The locations of
these pauses in retreat correlate to narrow and/or shallow parts of the fjord and demonstrate the control of pre-existing bathymetry on
ice retreat. The multibeam data provide a better understanding of the geomorphic features in each fjord and thus a clearer interpretation
of the retreat history in each of them.