HR: 1340h
AN: B13A-0161    [Abstracts]
TI: Cross-Correlation of High-Resolution Sonar Imagery and Fine-Scale Seafloor Volcanic and Tectonic Terrains: Applications to Ridge2000 Integrated Study Sites
AU: * Tyler, S
EM: st1@soc.soton.ac.uk
AF: Southampton Oceanography Centre, European way , Southampton, SO14 3ZH United Kingdom
AU: Smith, D K
EM: dsmith@whoi.edu
AF: Woods Hole Oceanographic Institute, Department of Geology & Geophysics, Woods Hole, MA 02543 United States
AU: Fornari, D J
EM: dfornari@whoi.edu
AF: Woods Hole Oceanographic Institute, Department of Geology & Geophysics, Woods Hole, MA 02543 United States
AU: Soule, A
EM: ssoule@whoi.edu
AF: Woods Hole Oceanographic Institute, Department of Geology & Geophysics, Woods Hole, MA 02543 United States
AB: Sidescan sonar data acquired at low ($\sim$12 kHz) and high ($\sim$120 kHz) frequencies have been used to map seafloor terrains in many tectonic environments over the past $\sim$40 years. However, the degree to which sidescan sonar data can be used to interpret fine-scale seafloor fabrics (for example, lava morphologies, sediment thickness and tectonised regions) has not been examined in detail. Here we examine how representative the variability in the acoustic return (the sonograph) is with respect to seafloor morphology. At mid-ocean ridges, for example, where a diversity of volcanic forms, are often complexly inter-fingered, can we identify the boundaries between them? Can sheet flows be reliably identified as areas of smooth acoustic texture? The regions for this study include the East Pacific Rise (EPR) crest between $1\deg$30'N and $1\deg$52'N, $3\deg$09'N and $3\deg$31'N, the Ridge 2000 EPR ISS site near $9\deg$50'N, and four sites along the Puna Ridge Hawaii, between $19\deg$31'N and $19\deg$51'N. We use 120 kHz DSL-120 sidescan sonar data, with an effective spatial resolution of 2m to produce detailed interpretations of acoustic facies resulting from volcanic, tectonic and variably sediment covered areas. We identify three main and five sub-categories of acoustic facies: regions of lumpy terrain on a scale of hundreds of meters (with differentiated tectonised and sedimented seafloor), smooth terrain, tectonised regions (with differentiation of fault scarps and fissured seafloor) and sedimented regions (with differentiated tectonised regions). From the electronic stills camera (ESC) images we identify a number of seafloor types: brecciated (with differentiated sedimented and tectonised seafloor), volcanic pillow lavas, lobates and sheet flows (with differentiation between high and low bathymetric gradients, tectonised and sedimented seafloor) and sedimented (with differentiation of tectonised regions). A comparison of these two datasets within Geographical Information System (GIS) software allows an assessment of how well these datasets are correlated. The results show a general agreement between interpreted acoustic facies and seafloor type, however, differences between the two datasets highlight the difficulty in extracting fine-scale information from sonar data. A particular disagreement between the datasets was identified with respect to smooth acoustic textures which are observed from regions of different seafloor types including pillows, variably sedimented seafloor and sheet flow. We have found that GIS compilation and analysis is important for the correlation of multi-scalar and high-resolution deep-sea data sets such as those being acquired at the Ridge 2000 ISS, where time-series relationships will be revealed by careful comparison between a wide range of multidisciplinary data.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3035 Midocean ridge processes
DE: 3045 Seafloor morphology and bottom photography
DE: 3094 Instruments and techniques
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting