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Table of Contents:

OF 2004-1014

Disc Contents

Geologic
    Discussion

• Introduction

• Field Program

• Field Equipment

• Interpretation

• Discussion

• Summary

• Acknowledgments

Data/GIS

Metadata/Data
    Catalog

References Cited

Contacts

Field Program

Geophysical data and ground-truth information were collected from the John Day Reservoir during 2000 and 2002. The first aspect of the field program was to collect high-resolution seismic-reflection profiles and sidescan-sonar imagery of the reservoir floor.

Figure 2.

The geophysical survey was completed aboard the R/V ESTERO during the first part of a cruise conducted September 13-27, 2000. The survey tracks are shown in Figure 2, and resulted in nearly complete sidescan-sonar coverage of the reservoir floor and a grid of seismic reflection profiles in the western part of the reservoir. The parts of the reservoir that were not imaged were areas north of Crow Butte and the Blalock Islands. Surveying these areas was prevented by shallow water depths.

Ground-truth information was collected to verify the interpretation of the geophysical data. Ground-truth information included still photos and video imaging of short transects of the lake floor. In addition, bottom sediment samples were attempted at points along most of the video transects. Samples were not recovered from many stations because cobbles did not allow the sampler to close. The ground-truth data from the western part of the reservoir (still photos, video, and samples) were collected during the second part of the September, 2000, field program. Video images and samples from the eastern part of the lake were collected during April, 2002. Locations where bottom video images were collected are shown in Figure 2.