High-Resolution Seafloor Mapping off the Cap de Creus Canyon Head, West Gulf of Lion

Matt D. Levey¹, Daniel Lewis Orange¹, Ana Garcia-Garcia², Mike Todd³, Joan Fabres⁴, and Andy Gardner^3
1 AOA Geophysics Inc, Moss Landing, CA
² U.C. Santa Cruz, Santa Cruz, CA
³ Fugro Survey Ltd, United Kingdom
⁴ Universitat de Barcelona, Barcelona, Spain

During July 2004 Fugro Survey Ltd. and AOA Geophysics Inc. mapped the Cap de Creus Canyon head off the northeast coast of Spain as part of an ongoing EuroSTRATAFORM study supported by the European Community and the U.S. Office of Naval Research. Data were acquired with a hull-mounted Simrad 30 kHz EM300 system (1x1 degree configuration) aboard Fugro's M/V Geo Prospector. Northwest-southeast lines were run approximately parallel to the canyon axis at speeds from 6.5 to 8 knots. The resultant bathymetry was processed without interpolation or smoothing at grid spacings of three, five, or ten meters depending on bottom depth. Sub-sampled backscatter mosaics of the field area have a pixel size of one meter for all water depths. ESRI's ArcGIS 9.0 with the Spatial Analyst extension was used to manipulate and display remote sensing data and create imagery.

Data clearly show a wide range of active geologic processes and a ship wreck. Furrows in the east-central part of the field area are approximately 20-50 cm deep, and 20-50 m apart. Backscatter data show significant variations throughout the field area and appear to be related to changes in seafloor sediment type. Laterally restricted high backscatter zones are related to seafloor outcrops of over-consolidated sediment and to possible gas seeps. Visualization of the data in Fledermaus assisted evaluating the active processes. The resulting imagery provided a very helpful high-resolution basic map for the current EuroSTRATAFORM program off the Gulf of Lion, where the Cap de Creus Canyon is a key feature.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005