U.S. Geological Survey
Open-File Report 00-043, Version 2.0  

Bathymetric, Geophysical and Geologic Sample Data from Medicine Lake, Siskiyou County, Northern California

by

Jonathan R. Childs (1), Jacob B. Lowenstern (2) , R. Lawrence Phillips (1), Patrick Hart (1), James J. Rytuba (3), John A. Barron (2), Scott W. Starratt (2), and Sarah Spaulding (4)
    

Open File Report 00-043

2000

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 

 

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

 

(1) Mail Stop 999, 345 Middlefield Road, Menlo Park, CA 94025 USA

(2) Mail Stop 910, 345 Middlefield Road, Menlo Park, CA 94025 USA

(3) Mail Stop 901, 345 Middlefield Road, Menlo Park, CA 94025 USA

(4) California Academy of Sciences, Dept. of IZ&G, Golden Gate Park, San Francisco, CA 94118 USA
 

Contents: A. Introduction B. Bathymetric and geophysical program C. Sediment Coring program D. Mercury analysis E. Paleontologic analysis F. List of Tables G. List of Figures H. Contacts I. Acknowledgements Appendices: I. Bathymetric and geophysical program field notes (observer logs) II. Summary of seismic reflection profile lines III. ASCII bathymetric data file Figure A1: Location of Medicine Lake Volcano, California.

Figure A2: Aerial view of Medicine Lake from the northeast. Photo by Julie Donnelly-Nolan, USGS About Medicine Lake in September 1999: Perimeter of Lake 6213 m or 20,380 ft Area of Lake 1.65 square km = 408 acres Volume of lake 13,400,000 cubic meters = 3.5 billion gallons = 10,860 acre-feet Elevation of lake surface 2036m or 6680 feet Greatest depth 46.4 m or 152.2 feet Mean depth 7.3m or 23.9 feet Median depth 4.9m or 16.1 feet

Introduction
In September, 1999, the U.S. Geological Survey acquired high-resolution bathymetry, seismic reflection profiles, and geologic sample data from Medicine Lake, a high altitude (2,036 m) lake located within the summit caldera/basin at Medicine Lake volcano (MLV), a dormant Quaternary shield volcano located in the Cascade Range, 50 km northeast of Mt. Shasta. It last erupted less than 1000 years ago.The purpose of this work was to assess whether sediments in the lake might provide a high-resolution record of the climate, volcanic and geochemical (particularly mercury) history of the region. We are still working with our data to assess whether the sediments are appropriate for further study. This report provides a summary of what we have learned to date.

Selected data products include:

• A bathymetric map of the lake (in meters).
• Another map with depth in feet.
• Forty high-resolution seismic reflection profiles of the lake, including seventeen acquired along east-west tracks, and twenty-three acquired along northeast-southwest tracks (see map with track lines).
• A temperature profile of the lake at its deepest point.
• A perspective-view of the lake bathymetry.
• Descriptions of nine sediment cores, ranging in depth from 10 to 100 cm, from various locations within the lake and surrounding environ.
• Map of sampling/coring locations.
• Mercury analyses of lakewater and sediment samples from the lake bottom.
• Description of diatoms and other microfossils found in lake water and sediments.
• Data for Downloading

Tables include:

• Table 1. Information on core locations and characteristics.
• Table 2. Mercury and methyl mercury concentration in sediment from cores at Medicine Lake.
• Table 3. Analyses of mercury and methyl mercury in sediment samples from core number 6.
• Table 4. Analysis of mercury and methyl mercury in water from Medicine Lake.
• Appendix 2. Summary of seismic-reflection profile lines.
• Appendix 3. ASCII Bathymetric Data File.

Figures include:

• Figure A1. Location map of Medicine Lake Volcano.
• Figure A2. Photo of Medicine Lake from the northeast.
• Figure A3. Perspective view of the Medicine Lake highland and surrounding region.
• Figure A4. Perspective view of geology and topography around Medicine Lake.
• Figure B1: The Geopulse and Seistec sources towed behind boat.
• Figure B2: The Fast Eddy (Boston Whaler).
• Figure B3: Map 1: Bathymetric map of Medicine Lake contoured at 5-m intervals (also can be downloaded).
• Figure B4: Map 2: Bathymetric map of Medicine Lake contoured at 10-foot intervals (also can be downloaded).
• Figure B5: A 3-D perspective view of the lake bathymetry, as seen from the SW.
• Figure B6: Map 3: Track lines showing locations of seismic profiles.
• Figure B7: Representative seismic line (N-STrackline 210) near deep hole in lake.
• Figure B8: Highlight of Trackline 210.
• Figure B9: Profile of temperature with depth in Medicine Lake.
• Figure C1: Stratigraphy summary.
• Figure C2: Key to sedimentary structures.
• Figure C3: Map of sample locations (for sediment cores).
• Figure C4: Photo of hammer core #3.
• Figure C5: Photo of box core #6.
• Figures C7(1-18): Stratigraphy and texture diagrams for cores 1-9.
• Figure E1: Photo of the planktonic diatom Cyclotella.
• Figure E2: Photo of benthonic diatom Navicula.
• Figure E3: Photos of other planktonic diatoms.
• Figure E4: Photos of other benthonic diatoms.
• Figure E5: Photos of chrysophyte stomatocysts.

Geographic location, geologic setting, and physiographic environment of the Medicine Lake volcanic region are described at:

http://vulcan.wr.usgs.gov/Volcanoes/MedicineLake/framework.html
http://vulcan.wr.usgs.gov/Volcanoes/California/Maps/map_medlake_shasta.html
http://vulcan.wr.usgs.gov/Volcanoes/MedicineLake/Maps/map_lavabeds.html

Contacts 

Acknowledgements

We appreciate considerable logistical assistance from Jayne Biggerstaff, Dan Meza, Brad Reed and Randall Sharp of the U.S. Forest Service, Modoc National Forest. At the USGS, Julie Donnelly-Nolan and Duane Champion offered advice and geologic expertise. Gerald O'Brien and Larry Kooker kept the Fast Eddy and the geophysical surveying equipment in top working order and the field program running smoothly. This work was funded through the USGS Volcano Hazards, Mineral Resources, Earth Surface Dynamics and Coastal and Marine Surveys Programs as well as through a grant from the Office of the Chief Geologist.