HR: 1340h
AN: SF13A-0707    [Abstracts]
TI: High Resolution Visualizations of Lake Floor Structures in Lake Superior.
AU: * Wattrus, N J
EM: nwattrus@d.umn.edu
AF: University of Minnesota, Large Lakes Observatory, 10 University Dr., Duluth, MN 55812 United States
AU: Cartwright, J
EM: joe@ocean.cf.ac.uk
AF: University of Cardiff, School of Earth Sciences, P.O.Box 914, Cardiff, CF10 3YE United Kingdom
AU: Rausch, D
AF: University of Minnesota, Large Lakes Observatory, 10 University Dr., Duluth, MN 55812 United States
AB: High resolution visualizations of acoustic data collected in Lake Superior reveals that the lake floor is not a featureless basin, rather that it possesses fine-scale features. These are the "fingerprints" of processes that have shaped the development of the basin. Some of these are no longer active while others continue today. Some of the most interesting lake floor features observed in Lake Superior are the ring shaped depressions that are widely developed in areas below wave-base, where fine-grained sediments are preserved. These features are typically 100-300m across, 25-50m wide and up to 5m deep. They occur both as interconnected clusters and also as isolated structures. Multibeam imagery reveals that rings are composed of chains of pockmarks. They are believed to be the product of dewatering of the Holocene glacio-lacustrine clays that compose the lake floor. High resolution seismic reflection data, collected with a 28 kHz echosounder, shows evidence of a layer bound system of small extensional faults that is widely developed in the very fine grained glacio-lacustrine clays. They exhibit a polygonal plan form geometry with a large range of strikes and oblique to orthogonal intersection geometries. They have been interpreted to be an immature polygonal fault system. Discrete horizons exhibiting lateral variations in thickness and zones of acoustic blanking are interpreted to be evidence of post-depositional remobilization of the lake floor sediments.
DE: 9345 Large bodies of water (e.g., lakes and inland seas)
DE: 9350 North America
DE: 3025 Marine seismics (0935)
DE: 3045 Seafloor morphology and bottom photography
DE: 0850 Geoscience education research
SC: Special Focus: Advances in Data Acquisition, Management, Analysis and Display [SF]
MN: 2004 AGU Fall Meeting