2007 Joint Assembly          
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Cite abstracts as Author(s) (2007), Title, Eos Trans. AGU,
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(23), Jt. Assem. Suppl., Abstract xxxxx-xx
Below are 3 abstracts that were presented at the Spring 2007 AGU Meeting by Scientists in the UC Davis Paleomagnetism Laboratory:

HR: 15:50h
AN: A43D-12
TI: New Perspectives on the Climatic Impact of the 1600 Eruption of Huaynaputina Volcano, Peru
AU: * Verosub, K L
EM: verosub@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: Lippman, J
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AB: A critical test of the new understanding of volcanic aerosols developed since 1982 is to determine if it can predict the effects of larger eruptions than those that have occurred since El Chichon. To do that, requires detailed information about the effects of specific large eruptions. We have been investigating the human and climatic impacts of the 1600 eruption of Huaynaputina volcano in Peru. The estimated Volcanic Explosivity Index for this eruption is 6, which is comparable to that of the 1815 eruption of Tambora volcano in Indonesia, which produced global cooling and led to crop failures, famine and social unrest. On the basis of tree-ring data, Briffa et al. (1998) suggested that the most severe short-term Northern Hemisphere cooling event of the past 600 years occurred in 1601, the year following the Huaynaputina eruption. In order gain a better understanding of the nature and extent of this cooling, we have been collecting annual time series that provide information about climatic conditions during time intervals that bracket the Huaynaputina eruption. Among the time series that we have examined (or plan to examine) are ice conditions in the harbors of Tallinn, Estonia, and Riga, Latvia and in Lake Suwa in Japan: cherry blossom blooming (sakura) dates from Kyoto, Japan; records of agricultural production from China and Russia; tithe records from the Spanish colonial empire; dates of the beginning of the wine harvest in France and the rye harvest in Sweden; prices of agricultural commodities in Europe; and river flows from the Nile and the Colorado. Often, in the records we have examined, 1601 shows up as one of the coldest years, if not the coldest year. In addition, the worst famines in Russian history took place between 1601 and 1603, which eventually led to the overthrow of Tsar Boris Gudonov. Thus, there is considerable evidence that the climatic impacts of the Huaynaputina eruption were comparable to those from the Tambora eruption. This result is important because it documents that significant global cooling events can be generated by South American volcanoes as well as Indonesian ones and that such events might occur with a return frequency of as little as 200 years.
DE: 0370 Volcanic effects (8409)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 8408 Volcano/climate interactions (1605, 3309)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly


HR: 0800h
AN: GP41B-04
TI: Paleomagnetic Determination of Pre-Mining Metal Flux Rates at the Iron Mountain Superfund Site, Northern California
AU: Alpers, C N
EM: cnalpers@usgs.gov
AF: United States Geological Survey, California Water Science Center 6000 J Street, Sacamento, CA 95819, United States
AU: Nordstrom, D K
EM: dkn@usgs.gov
AF: United States Geological Survey, 3215 Marine St., Boulder, CA 80303, United States
AU: * Verosub, K L
EM: verosub@geology.ucdavis.edu
AF: University of California - Davis, Dept. of Geology One Shields Ave., Davis, CA 95616, United States
AU: Helm-Clark, C
EM: helmcath@isu.edu
AF: Idaho State University, Dept. of Geosciences, Pocatello, ID 83209, United States
AB: Iron Mountain, located near Redding in northern California, hosts a group of mines that were active from the late 1870s to the early 1960s. The mineral deposit is classified as a type-I volcanogenic massive sulfide, similar to the Noranda deposit of Ontario, Canada. Three large, isolated blocks of sulfide mineralization contain 90-95 percent pyrite and a few percent chalcopyrite (CuFeS2) and sphalerite (ZnS). Prior to mining, weathering converted parts of the massive sulfide to gossan consisting of hematite, goethite, and silica. Mining further exposed the pyritic masses to water and air, creating optimal conditions for sulfide oxidation and production of acid mine drainage. Because the acidic, metal-rich effluent reached the Sacramento River, the site has been one of the highest priorities on the US EPA's Superfund list since the early 1980s. A crucial area of scientific uncertainty that needed to be resolved was the magnitude of natural background metal flux. We collected 25 paleomagnetic samples from the gossan to determine the polarity of the Earth's magnetic field during pre-mining sulfide weathering. Nineteen samples exhibited stable magnetic endpoints during thermal demagnetization; of these, four were of reversed polarity and the remainder were of normal polarity. This result established that the gossan was already forming 780,000 years ago, and this information made it possible to estimate natural, pre- mining flux rates of copper and zinc. These rates were three orders of magnitude lower than post-mining (pre- remediation) rates. Resolution of the question of the background flux led to one of the largest legal settlements in U.S. history for remediation of an inactive mine site.
DE: 1520 Magnetostratigraphy
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1886 Weathering (0790, 1625)
DE: 3665 Mineral occurrences and deposits
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly


HR: 11:40h
AN: GP22A-05
TI: Paleomagnetic and Environmental Magnetic Studies of Eltanin Core 27-21 from the Ross Sea Sector, Antarctica
AU: Jovane, L
EM: jovane@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: * Verosub, K L
EM: verosub@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: Florindo, F
EM: florindo@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Roma, 00143, Italy
AU: Acton, G
EM: acton@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AB: Due to low core recovery, stratigraphic discontinuities, and poor microfossil abundances, it has proven difficult to obtain high-resolution sedimentary records from Antarctica with unambiguous age-models and uncomplicated magnetostratigraphies. In addition, carbonate dissolution due to corrosive bottom waters makes it difficult to use the record of oxygen isotopes as a clear climatic proxy for variations in ice volume and/or temperature. We have been conducting new paleomagnetic and environmental magnetic studies of old cores from the Ross Sea sector of Antarctica. Here we present results from 682 discrete samples from Eltanin 27-21, an 18-meter long piston core recovered in 1968 by the USNS Eltanin as part of Operation Deep Freeze. We believe the discrete samples were collected by Norm Watkins and Jim Kennett shortly after the core was returned to the United States and that those samples which were measured for paleomagnetism were only demagnetized to 15 mT. We find that after removal of a low-coercivity overprint, most samples show a strong remanent magnetization that is stable between about 25-50 mT. The stable characteristic remanent directions of the samples define four normal and five reversed polarity zones. We have used these zones to develop a high-resolution magnetostratigraphy that encompasses all polarity intervals from the Brunhes Chron to the Reunion Subchron. This correlation is consistent with a low resolution study of radiolaria and foraminifera done by Fillon (1975). Average rates of sedimentation for individual polarity zones range from 0.39 cm/ky to 1.46 cm/ky. Various environmental magnetic parameters, including magnetic susceptibility, anhysteretic remanent magnetization and isothermal remanent magnetization, show features that are suggestive of orbitally-induced cyclicity. These parameters are being used to create an astronomically-tuned age model that encompasses the last 2.15 million years of sedimentation in the Ross Sea. The environmental magnetic data, coupled with the chronostratigraphic results, will provide new insights on the timing and nature of paleoclimate events in the Ross Sea sector, especially those that affect the availability of sediment and its transport into the basin. We also believe that this record can serve as a "Rosetta Stone" for correlation and dating of other old (and new) cores from the Ross Sea sector, even including cores that do not go back as far as the Brunhes/Matuyama boundary.
DE: 1512 Environmental magnetism
DE: 1520 Magnetostratigraphy
DE: 1540 Rock and mineral magnetism
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 9310 Antarctica (4207)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly