Kenneth Verosub - US grants

This project will continue the development of a master curve of geomagnetic secular variation for western North America during the last 12,000 years. The curve is derived from the paleomagnetic study of suites of overlapping cores from small lakes in the western United States. The records from each lake are correlated on the basis of ash layers from various Cascade volcanoes. The research will involve the measurement and analysis of samples already collected from five lakes as well as the collection of samples from several additional sites. These samples will be used to verify and refine a proposed master curve of secular variation as well as to develop a curve of geomagnetic intensity variation. These curves will be compared to those developed from lava flows and archaeological features as well as from lakes in other parts of North America. As the curves are being developed, they will be used to solve geologic problems relating to the distribution of volcanic ash layers, the assessment of volcanic hazards, and the dating of archae ological sites. In addition, the relationship between rock magnetic properties and various palynological and sedimen tological indicators o f climate and environment will be studies. The PI is at the forefront of this important area of paleo magnetism. Funding at the revised level is recommended.

In the United States archaeomagnetism has been used primarily as an archaeological dating technique and has seldom been used to study the Earth's magnetic field. This project will use well- dated archaeological sites to acquire archaeomagnetic data relating to three problems: 1) the direction and intensity of the field at spot locations in the Western Hemisphere between 1550 and 1800 A.D., 2) the continuous record of directional changes in the American Southwest from 200 B.C.. to 1800 A.D., and 3) the record of intensity changes over the past 10,000 years in North and South America. In each case archaeomagnetism can clarify important questions about the behavior of the Earth's magnetic field that have arisen from recent advances in the study of historical records, rapidly-deposited sediments and lava flows. Although standard archaeomagnetic procedures will be followed during the course of the investigation, an important additional component will be detailed studies of the magnetic mineralogy and rock magnetic properties of various samples. These studies, which have never been done systematically for archaeomagnetic materials, will provide a firmer paleomagnetic basis for the measurements which we make and will provide new insights into the relative merits of different archaeological materials and archaeomagnetic techniques.

Although soil scientist have been studying the chemistry of iron in soils for many years, there have been relatively few studies of the magnetic properties of soils. Most of the studies have focussed on the enhancement of the magnetic susceptibility in the upper portion of the soil. For the past year and a half, the Principal Investigator has been studying the rock magnetic properties of three soil chronosequences in California, noting that the rock magnetic properties vary within different horizons of the same soil profile or pedon and between pedons of different age developed in the same parent material. Results have also shown that the enhancement of the magnetic susceptibility is a more complex phenomenon than previously thought. This project investigates other chronosequences in California and extends work to include additional rock magnetic parameters. The goal of this research will be to gain new insights into the basic pedogenic processes involved in the translocation and transformation of iron in soils and to use that information to develop a relative, if not an absolute, method of dating soils. Such a dating technique would have wide applicability, not only for the dating of soils on stable geomorphic surfaces but also for the dating of various surficial processes such as hillslope development and landsliding.

The PI will examine the acquisition of thermoviscous remanent magnetization on geologically significant time scales. The accomplish this goal, he will study randomly-oriented cobble and boulders that have been exposed to the earth's magnetic field for known intervals of time. Thermal demagnetization techniques will be used to determine the unblocking temperature of the secondary magnetic component in these rocks. The paleomagnetic studies will be complemented by various rock magnetic studies. The varied geological landscape of California includes many suitable sites with exposure ages ranging from a few weeks to almost one million years. These sites include landslide deposits, glacial tills, and marine, fluvial and lacustrine deposits as well as cultural deposits. The work will provide critically-needed information about the relationship between time and temperature in the acquisition of a thermoviscous remanent magnetization. Such information is needed to increase our understanding of thermal magnetization processes and to aid in the interpretation of thermal demagnetization data.

One of the most difficult problems in stratigraphy is that of developing a global biostratigraphic framework based on zonations involving different faunal groups, different depositional environments, and different geographic regions. One way to deal with this problem is to find a stratigraphic marker horizon to link the different zonations. At the present time, the only common, global and non-time-transgressive phenomena in the geological record are reversals of the earth's magneticf field. The unique structure of the Magnetic Polarity Tiume Scale in the vicinity of the Santonian/Campanian boundary makes this boundary a particularly convenient place to use magnetostratigraphy to establish a global marker horizon. PI will conduct magnetostratigraphic studies of sedimentary sequences that cross the Santonian/Campanian boundary in Europe and in the Western Interior of North America. The sequences in Europe include the stratotype for the boundary as well as other sections which are believed to be equivalent to it. Those in North America represent marine, marginal marine, and terrestrial sequences, all of which are believed to contain the boundary. By studying these sections, PI will be able to establish a correspondence between Santonian/Campanian biostratigraphic zonations on two different continents and involving a variety of different fossil groups. In addition, the sections in the Western Interior contain bentonite beds that will be used to obtain an absolute age for the Santonian/Campanian boundary. The proposed project represents a continuation of work conducted under a prior NSF grant, which looked at the magnetostratigraphy of sedimentary sequences that crossed the Santonian/Campanian boundary on the West Coast of North America, and it represents the next step in a systematic program to study the magnetostratigraphy of the Santonian/Campanian boundary in sedimentary sequences throughout the world.

In order to promote international communication on tephrochronology, the Inter-Congress Commission on Tephrochronology of the International Quaternary Association (INQUA) will hold a field conference and workshop on tephrochronology in Yellowstone National Park from June 17, 1990 to June 26, 1990. The purpose of the conference, the first on its kind since 1980, is to determine the current status of tephra studies worldwide, to assess the impact that new developments in other fields will have on tephrochronology, and to underscore the role which tephra studies can play in solving problems in Quaternary stratigraphy. Funds are requested for support of promising graduate students, for transportation expenses associated with field trips and for travel costs of keynote speakers.

Sequences of paleosols and loess units throughout the world have been interpreted as geologic records of terrestrial climate change. Of particular significance has been the discovery of a correlation between variations in the magnetic susceptibility in the Chinese loess sequence and the oxygen isotope record of the deep sea. Using an approach that combines rock magnetic measurements with a soil chemistry extraction procedure, we have obtained new data that challenges previous interpretations about the origin and nature of the magnetic susceptibility signal. In this proposal we request support for a comprehensive, interdisciplinary study of the rock magnetism and soil chemistry of paleosol/loess sequences in China and elsewhere. The goals of our study are 1) to complete our determination of the general characteristics of the magnetic susceptibility signal using a combination of rock magnetic and soil chemistry techniques, 2) to compare our rock magnetic analyses of the Chinese loess/paleosol sequence with similar analyses of loess/paleosols sequences in Alaska and New Zealand, and 3) to obtain complete soil descriptions and detailed profiles of soil chemistry and rock magnetic properties from selected loess and paleosols units. The work for this last objective will be done in close collaboration with Chinese colleagues.

This award provides 50% funding for the acquisition of equipment for the Paleomagnetism Laboratory of the University of California at Davis. Equipment items include an alternating field gradient magnetometer, a Mossbauer spectrometer, a Curie balance system, a magnetic susceptibility bridge, and ancillary equipment. The laboratory supports the research of the PI, his students, and on-campus as well as off-campus collaborators. The PI's research program is concentrated in the behavior of the geomagnetic field throughout geologic time, applications of paleomagnetic techniques to plate tectonics and related geologic phenomena, the origin of rock and mineral magnetism, and environmental magnetism.

This project involves paleomagnetic and rock magnetic studies in support of research drilling of the moat deposits of the Creede caldera. These studies will provide information relevant to the dating and correlation of cores from the moat as well as information about the diagenetic conditions which affected the sediments and volcanic rocks after deposition in the moat. The project represent a collaboration between Kenneth L. Verosub of the University of California, Davis, and Richard Reynolds and Joseph Rosenbaum of the United State Geological Survey, Denver.

In each hemisphere at the core/mantle boundary, there are patches of magnetic flux with a polarity opposite to that of the dominant flux for that hemisphere. These patches account for most of the secular variation of the geomagnetic field and may provide an explanation for larger-scale, longer-term behavior. In this project, the behavior of the geomagnetic field will be modelled using flux patches at the core/mantle boundary. The interactions of the flux patches will be treated as a problem in Ising model theory.

9413732 Verosub This award provides one-half the funding required to construct an instrument system for making continuous high- resolution measurements of cores of lake and marine sediments and of soil profiles. The system will be installed and operated in the Department of Geology at the University of California-Davis. The University is committed to providing the remaining funds required to complete the project. When magnetic mineral grains are deposited as sediment at the bottom of water bodies under quiet conditions or become incorporated in developing soil profiles, the grains are aligned parallel to the geomagnetic field, and their alignment can later be used to decipher the past history of the magnetic field during the time represented by the accumulation of the sediment or soil profile. The primary goal of the new instrumentation will be to obtain continuous interpretations of climate change using the variation of magnetic parameters measured along the length of sediment cores. A complementary scientific goal of the facility will be to obtain a history of the behavior of the Earth's magnetic field, including variations in the direction and intensity of the field. ***

Abstract This award supports a project to lay the groundwork for development of a reliable magnetostratigraphic record from drill core collected by the international Cape Roberts Project (CRP). A reliable chronostratigraphic framework is a prerequisite for proper interpretation of the climatic and tectonic events that are the focus of the CRP. Magnetostratigraphy could play a major role in development of that framework, but previous paleomagnetic studies of sedimentary sequences from Antarctica have shown that extracting a reliable magnetostratigraphy from the CRP cores may not be easy and that sophisticated treatment of samples may be necessary. This project will undertake paleomagnetic and mineral magnetic investigations of the lower part (Eocene and/or Oligocene) of the CIROS-1 core, which was collected in 1984/85 from western McMurdo Sound. In addition to useful information bearing on paleoenvironments that can be extracted from this core, this work provides an opportunity to gain paleomagnetic experience with the lithologies present in the Cape Roberts region and to address problems encountered in previous attempts to recover paleomagnetic records. This project will also utilize Cretaceous to Paleocene drill cuttings from the Great South Basin near New Zealand. The results of this work will allow determination of the most appropriate strategy for dealing with samples during the drilling and basic characterization phase of the CRP, when time and resources will be very limited. In this way, the efficiency of on site paleomagnetic investigations in support of the basic characterization work on the core should be greatly enhanced.

Recent concern about the declining interest in science on the part of students and the need for increased science literacy on the part of the general public has led to recognition of the importance of making special efforts to reach non-science majors and future teachers. One possible approach to this problem is to develop courses that have a reduced emphasis on terminology and equations and a greater emphasis on those aspects of the science that are tangible and relevant to students' lives and experiences. For the past five years, I have been teaching a General Education course entitled Geology and People. The goal of the course is to draw students' attention to some of the many ways in which geologic factors have been and still are influencing societies, civilizations and cultures. The material in the course is drawn from a variety of fields including history, economics, political science, and archaeology as well as art, music and literature. I believe the material that I have gathered for the course can make a useful contribution to the development of new paradigms for introductory earth science courses for non-majors and teachers. The interconnections between different components make it inappropriate to disseminate the material through a text or a reader. To overcome this problem, I propose to establish an Internet site on the World Wide Web. The Website would be available free to anyone wishing to access the material pertaining to the influences of geology on people's lives.. The Website would be constructed in a way that emphasized pathways and linkages between information. Individuals would use the Website to find information that they could incorporate into their own courses. This approach represents a new paradigm for the dissemination of curricular material.

Verosub OPP 9526889 Wilson OPP 9527343 Abstract The goals of the Cape Roberts Project (CRP) are to elucidate the history of fragmentation of the Pacific margin of Gondwana and the history of Antarctic glaciation from Cretaceous through Oligocene time. The CRP will operate with an integrated science plan in which all of the initial scientific characterization of the cores will be done at McMurdo Station in the Antarctic during two drilling seasons over two successive years. The drilling seasons will each be of two months duration and will operate in much the same manner as two month cruises of the Ocean Drilling Program. The scientific activities associated with characterization of the cores will include magnetostratigraphy, biostratigraphy, petrography, mineralogy, and sedimentology. Age determination is of principal importance in such a project because a temporal framework is necessary to obtain a history of climatic and tectonic events. This award supports a program of research which will enable determination of a high-quality paleomagnetic stratigraphy, with the appropriate mineral magnetic studies, in support of the CRP. For the on-site magnetic studies this award will: undertake logging of the whole-core magnetic susceptibility which will assist in correlation of the several overlapping cores to be recovered during the CRP; determine a magnetostratigraphic framework for dating of the cores; undertake mineral magnetic and environmental magnetic studies to assess the reliability of the paleomagnetic signal; and determine if environmental magnetic properties yield information concerning changes in the tectonic, sedimentologic, diagenetic or climatic influences on the sedimentary record at Cape Roberts. Detailed environmental and mineral magnetic studies will also enable evaluation of the sediments as recorders of the geomagnetic field. The Cape Roberts records provide the potential to obtain rare high southern latitude constraints on geomagne tic field behavior. Paleomagnetic studies should also provide important data concerning crustal movements and rift development in the Ross Sea sector.

9709245 Verosub This grant provides three years of partial salary support for a technician to oversee operation and maintenance, service user requests and develop new analytical methods for the recently acquired 2-G Model 755-R long-core cryogenic magnetometer at the University of California-Davis. This is a Phase I Technician Support grant under the IF/EAR program. Support of a technician for this u-channel cryogenic magnetometer facility is intended to allow easy access to this "first-of-its-kind" instrument in the U.S. for both members of the U.S. paleomagnetic community and other geoscientists interested in environmental paleomagnetism and the secular variation of the geomagnetic field. Support of this position will also aid in the development of software to adequately treat the large volumes of high-resolution paleomagnetic data that can be easily generated with the Model 755-R. ***

Funds are being provided for a high-resolution geomagnetic paleointensity study of U-channel samples from ODP Leg 129, Site 769 in the Sulu Sea. A pilot study confirmed the exceptional magnetic quality of these sediments and demonstrated that the site is free of drilling-induced mangetic overprint or storage diagenesis that effects paleointensity. Samples also preserve millennial scale record and have excellent stable-isotopic stratigraphy. The study will allow a detailed understanding of the temporal evolution and high-rgrequency variability of geomagneic paleointensity record of the Brunhes age.

Verosub
9909468

Most of the methods currently used for studying the magnetic properties of natural and synthetic materials only provide information about the average size of the magnetic grains. The investigators are developing a new method that will actually provide information about the size distribution of the magnetic grains. This information is contained in contour plots (called FORC diagrams) that are generated from a set of partial hysteresis curves. Preliminary results indicate that it is possible to characterize a wide range of samples using FORC diagrams and to identify and discriminate between the different types of assemblages that have the same average grain size. The goals of this project are 1) to develop a simple and rapid means of producing a FORC diagram so that the method can be more widely used, and 2) to demonstrate how FORC diagrams can solve problems that can not be easily solved using other techniques.

EAR-0136498
Verosub

In environmental magnetic studies, the magnetic properties of sediments and soils are used as tracers of paleoclimatic and other environmental processes. The automated long-core cryogenic magnetometer in the Paleomagnetism Laboratory at UC-Davis has been designated by NSF as a national facility for environmental magnetic research. This grant will provide support for a laboratory manager whose primary responsibilities will be to oversee the operations of this facility, to develop new applications for the long-core magnetometer and new methods of analyzing the data generated by it, and to facilitate the use of the instrument by outside users.

***

0216346
Verosub

Researchers at UC-Davis have recently developed a technique that uses partial hysteresis curves to determine the distribution of magnetic properties within a material. The method probes the microscopic mechanisms of magnetic behavior in greater detail than is possible with major hysteresis loops or with conventional magnetometry. This Major Research Instrumentation grant will provide funding for a combined Alternating Field Gradient and Vibrating Sample Magnetometer with high magnetic field and low temperature capabilities. The instrument will allow researchers to look at a much wider variety of materials under a much broader range of conditions than can be done presently. These enhanced experimental capabilities will lead to new advances in paleomagnetism, rock and mineral magnetism and environmental magnetism as well as new insights into condensed matter physics, particularly synthetic magnetic materials and magnetic nanostructures.
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This award, provided by the Office of Polar Programs, provides support for a project to conduct magnetic investigations of sediments from ice covered lakes in the McMurdo Dry Valleys in concert with other paleoenvironmental work on the sediment cores.

INTELLECTUAL MERIT
This award facilitates an extraordinary opportunity to conduct paleomagnetic and environmental studies on a suite of cores from the Dry Valleys. The cores were collected in November 2002 by Dr. Peter Doran and his colleagues as part of the NSF-funded project: "Paleoclimate Inferred from Lake Sediment Cores in Taylor Valley, Antarctica". The magnetic studies will improve the correlation between cores from a given lake, will provide new information about past behavior of the McMurdo-Dry Valley ecosystem, and will contribute to the development of a robust chronology for the cores. The research will significantly augment and enhance planned research on the sedimentology, geochemistry, mineralogy, and biostratigraphy of the cores. Funding under the Small Grants for Exploratory Research (SGER) program is appropriate for this project because practical considerations dictate that sampling of the cores take place at the beginning of August, 2003, and because both research and logistical considerations require that the magnetic sampling be done before other samples are collected.

BROADER IMPACTS
The proposed research will contribute to a better understanding of the McMurdo-Dry Valley ecosystem, which is the focus of a Long-Term Ecological Research project. The proposed project will also advance the field of environmental magnetism by demonstrating how magnetic parameters can be used to identify different sources of sediment in a lake core. It will also provide new insights about the behavior of the geomagnetic field at high latitudes, which in turn will lead to development of a master curve of secular variation that can be used for dating Holocene sedimentary sequences in Antarctica. And the project will provide an opportunity for undergraduates to participate in research involving Antarctic materials.

0330784
Verosub

Last year, the University of California, Davis, received a grant (EAR-02-16346) from the NSF Major Research Instrumentation (NSF-MRI) program. The grant, entitled "Enhancing the Capabilities for Characterization of Magnetic Materials at the University of California, Davis", provided funds for the purchase of a combined alternating gradient and vibrating sample magnetometer (AGM/VSM). This instrument will be dedicated to research using first-order reversal curves (FORCs), a new technique for studying the magnetic properties of natural and synthetic samples. The high magnetic field and high and low temperature capabilities of new instrument make it possible to acquire FORC data over a greater range of temperatures and magnetic fields than has heretofore been possible. The FORC method uses partial hysteresis curves to obtain information about the distribution of magnetic grains in a sample, rather than just their average value. In addition, it can be used to study magnetic interactions within a sample. For these reasons, the method can probe the microscopic mechanisms of magnetic behavior in greater detail than is possible with major hysteresis loops or with many conventional forms of magnetometry. Although it was originally developed to study natural geologic samples, the FORC method has potential applications to other fields, and an interdisciplinary team of earth scientists, condensed matter physicists and material scientists at UC Davis has already used the method to study advanced magnetic media, spin glasses and magnetic nanostructures.

In order to disseminate information about the FORC method as effectively as possible, this grant will provide travel support for international and U.S. scientists to attend a workshop entitled "Magnetism, Hysteresis and the FORC Method". The workshop will take place April 25-27, 2003, on the Davis campus, and the organizing committee consists of Ken Verosub (a geophysicist), Kai Liu (a material scientist), and Richard Scalettar and Gergely Zimanyi (both condenses matter physicists). At the workshop, participants will have the opportunity to learn about the FORC method and its applications, to listen to invited papers on current issues in magnetism and hysteresis, to participate in discussions about the relationship between these issues and the FORC method, and to obtain hands-on experience at creating FORC diagrams.
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This Small Grant for Exploratory Research supports a paleomagnetic survey of previously collected sediment cores from Antarcticas continental margin. Many of these cores were originally interpreted with methods that, though advanced for their time, were barely adequate. Nonetheless, these results are still used to construct an overall stratigraphic record for marine sediments and major events related to the Southern Ocean, global climate, and Antarcticas glacial history. With the advances in paleomagnetic techniques over the intervening decades and the great interest and current work on Antarctic marine sediments by major projects such as ANDRILL and ShalDrill, a reassessment of these cores is needed. In addition, these new studies will offer insight into the behavior of the geomagnetic field within the Earths tangent cylinder, the region delineated by an imaginary cylinder parallel to the Earths rotation axis and tangent to the equator of the inner core boundary.

The broader impacts of this work include support of postdoctoral student research and improving societys understanding of global climate change through an improved understanding of the Antarctic marine sediment record.

Abstract



This project performs a paleomagnetic survey of sediment cores from Antarctica's continental margin. Its goal is to refine the magnetostratigraphy to improve regional stratigraphic correlations, help date cores that lack biostratigraphic indicators, and understand paleoenvironmental conditions and climate change. As well, these cores record the earth's magnetic field near the magnetic pole, which may offer important information to scientists modeling the geodynamo.

The broader impacts of this work include postdoctoral and undergraduate education. There are also implications for society's understanding of global climate change, since these techniques offer a different perspective on climate change from Antarctic marine sediment cores, which are critical to understanding the behavior of the ice sheets and their links to the global climate.

The proposed work will test whether the onset of the Younger Dryas (about 12,900 years ago) was caused by a cometary impact over the Laurentide Ice Sheet. In particular, the team will seek to determine 1) whether the magnetic properties of iron spherules found at the based of the Younger Dryas at many sites are consistent with formation from a cometary impact, 2) whether evidence for ejecta from the impact event can be found in lacustrine sequences in the western United States where the Younger Dryas boundary is already known to be present but where evidence for an impact has not yet been sought, and 3) whether a dark layer at the base of unit in Europe that has correlated with the Younger Dryas contains material that would be consistent with the hypothesis.

Scientific Merit: There is enough physical evidence for an impact at the onset of the Younger Dryas that careful additional work seems warranted. If the hypothesis is correct, it will produce such a fundamental change in our understanding of the causes of abrupt climate change.

Broader Implications: The causes and consequences of large-scale, global climatic change are still not well-understood. Finding a new mechanism for an important, recent, global climate event will significantly advance our knowledge of the processes that drive climatic variations. It will also provide fundamental insights into how modern climatic variations will be affected by similar processes.