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.
Description
Chief Scientist: Jon Childs. Bathymetric and Geophysical and Sampling data (GPS, YoNav, 2channelairgun, bathymetry, temperature, CTDmeter, Geopulse, seismic, seismic, gravitycore) of field activity F-2-99-NC in Medicine Lake, Siskiyou County, Northern California from 09/15/1999 to 09/20/1999
Location
Northern California
Summary
A bathymetric and geophysical survey was conducted over Medicine Lake in Siskiyou County, North Central California. A concurrent shallow-water sampling program was also conducted. JD 257 Tuesday, September 15 travel from Redwood City to Medicine Lake JD 258 Wednesday, September 16 Morning spent deploying Fast Eddie with Bimini top, cowling, and installing electronics. Boat launched about 1245 local (1945 GMT). Weather conditions excellent: v. light clouds, ~ 70-75_ F, sunny, light wind. SEACAT CDT instrument started logging approx. 1245 local; in the water 1300 GMT). First line consisted of a circumnavigation of the lake at 3.5 to 4 knot. Ran into shallow water twice. NW end of the lake very broad and shallow. Returned to the dock at 1400. Deployed geopulse and back in the water at 2215Z. Finished surveying at 259/0000 (1700 PST). 258/1945 start logging CDT. 258/2000 leave dock, commence circumnavigation of lake; CDT in water 258/2101 complete circumnavigation, arrive dock; CDT out of water 258/2241 leave dock, testing reflection system; CDT back in water JD 259/0000 arrive dock; CDT out; end of day Problems with geopulse power supply limited reflection profiling. Changed out the power supply at the end of the day for the EG the "b" lines south. Steering the lines accurately proved problematic because of wind conditions and the filter response of the YONAV line-following algorithm. 259/172800 start logging CDT 259/173000 leave dock, commence deploying geopulse and benthos streamer 259/173700 CDT in water 259/174600 commence acquisition of EW lines 259/182430 stop acquisition of EW lines 259/183000 CDT out of water 259/183300 CDT in water 259/183700 continue acquisition of EW lines 259/195400 stop acquisition of EW lines 259/195500 CDT out of water 259/200000 arrive dock, break for lunch 259/212500 leave dock, CDT in water 259/214900 continue acquisition of EW lines 260/000400 complete acquisition of EW lines 260/000500 CDT out of water JD 260 Friday, September 18 Weather conditions remain excellent: v. light clouds, ~ 70-75_ F, sunny, wind calm. Acquiring reflection data with geopulse source, benthos streamer and Seistec receiver (two-channels). Survey lines run approximately NNE-SSW along arbitrary lines chosen by line of sight. Lines at eastern end of lake spaced closer (approx. 25-50 meters), at western end of lake wider (approx. 50-100 meters). CDT data not logged. 260/173000 depart dock, deploying and tuning seistec at east end of lake 260/181200 commence acquisition of NS lines 260/211400 complete acquisition of NS line 260/212000 arrive dock JD 261 Saturday, September 19 Weather conditions remain excellent: v. light clouds, ~ 70-75_ F, sunny, wind calm. Sampling and temperature profiles acquired. Two sampling sites selected based on geophysical profiles: latitude longitude water depth profile day/time 1. 41d 34.9911 -121d 35.4420 37 m 259/1846 2. 41d.34.8866 -121d 35.5590 10 m 259/1916 261/1715:21 41d 34.866 N 121d 35.582 W ---> dropping core 1 here 261/1729:03 41d 34.880 N 121d 35.556 W ---> dropping again here 261/1738:46 41d 34.986 N 121d 35.438 W ---> core site 2 drop here ~38m 261/1801:34 41d 34.999 N 121d 35.419 W ---> drop long barrel core at 42.1 meter depth 261/1824:55 41d 34.996 N 121d 35.465 W ---> site 2 core 10 first try 261/1842:58 41d 34.991 N 121d 35.467 W ---> site 2 core 10 try 2 261/1853:06 41d 34.971 N 121d 35.503 W ---> CDT drop here 261/1857:42 41d 34.967 N 121d 35.526 W ---> start to pull up CDT here 261/1858:46 41d 34.962 N 121d 35.526 W ---> CDT at surface 261/1903:09 41d 34.995 N 121d 35.494 W ---> CDT drop 2 here 261/1903:46 41d 34.994 N 121d 35.492 W ---> CDT on bottom-was not on bottom long enough 261/1904:44 41d 34.992 N 121d 35.503 W ---> CDT at surface 261/1904:54 41d 34.991 N 121d 35.505 W ---> CDT drop 3 261/1905:49 41d 34.987 N 121d 35.512 W ---> CDT coming up 261/1906:27 41d 34.985 N 121d 35.513 W ---> CDT at surface 261/1915:53 41d 34.969 N 121d 35.449 W ---> drop core10 try 3 JD 262 Sunday, September 20 Demobilization and travel from Medicine Lake to Redwood City
Info derived
Bathymetric map, high-resolution seismic reflection profiles, temperature profile, a perspective-view of the lake bathymetry. Map of sampling/coring locations, mercury analyses of lakewater and sediment samples from the lake bottom.
Comments
Staff information imported from InfoBank
Jon Childs (USGS Western Region) - Geophysicist
Pat Hart (USGS Western Region) - Geophysicist
Larry Kooker (USGS Western Region) - Electronic Technician
Gerry O'Brien (USGS Western Region) - Boat Driver
Larry Phillips (sampling, , USGS Western Region) - Geologist
Jake Lowenstern (sampling, , , VHZ, , USGS Western Region) - Geologist
John Barron (VHZ, , USGS Western Region) - Geologist Climate Change Program
Scott Starratt (VHZ, , USGS Western Region) - Geologist Climate Change Program
Jim Rytuba (USGS Western Region) - Geochemist Western Geologic Mapping
