Paul Mueller - US grants

This project is focused on two problems: the reconstitution and functional analysis of sodium channels and the mechanism of visual transduction. Sodium channels from muscle plasma membranes are isolated and purified in a functionally intact state and reconstituted into vesicular and planar lipid bilayers. Reconstituted channels are studied by patch clamp and conventional recording techniques. Gating kinetics, ion permeation mechanism and specificities are investigated. Single channel gating kinetics are correlated with multi-channel data obtained from reconstituted bilayers as well as native membranes. Chemical modification of the channel and its lipid environment combined with pharmacological studies of the effects of neurotoxins serve as further tools for the elucidation of the channel function. The visual transduction studied are designed to test the possible role of protons is the light-induced Ca++ release. The effects of protons directly injected into isolated rod outer segments on dark current and light responses is measured and correlated with measurements of protons generated through light-induced cyclic GMP hydrolyis. Proton-induced Ca++ release is investigated in broken rod outer segments and disks. The ion specificities of the Ca++ release pathway are determined through Ca++ ion exchange experiments. The role of phosphatidylinositol in the visual transduction cycle is investigated. In particular it will be determined if the observed light-induced phosphatidylinositol turnover is linked to Ca++ release via the formation of phosphatidic acid.

Photosynthetic reaction centers from bacteria are incorporated into planar and large vesicular membranes. In such membranes, the kinetic and steady state aspects of the electron flow generated by steady light and single turnover laser flashes are analysed through direct measurements of the electric currents and potentials, and compared with theoretical predictions based on model calculations. Externally applied potentials, replacement of the endogeneous ubiquinones by other quinones of known redox potentials, variations of the electron donor and acceptor in the aqueous phase and modification of the membrane lipids serve as additional tools for the analysis. Cyclic electron transport is reconstituted by the incorporation of reaction centers and mitochondrial b-c1 complex in to the same membrane. Densely packed monolayers of reaction centers are sandwiched between two transparent metal electrodes. Photo-induced currents and potentials generated in these devices are studied at normal and liquid helium temperatures and correlated with optical measurements. Cytochrome oxidase is incorporated into planar bilayers separating two aqueous phases. The kinetic and steady state aspects of transmembrane electron currents and potentials generated in these membranes through oxidation of reduced cytochrome c are measured by voltage and current clamp techniques. The absorption spectra of the electron transport proteins within the membrane are measured by attenuated total internal reflection of light entering the membrane parallel to its plane through a transparent support. Spectra are correlated with the membrane potential, redox state of the electron transport components and the pH. Methods are developed for the formation of planar crystals of reaction centers which are then used for structural analysis by diffraction and image reconstruction methods. It is expected that these studies will give new insights into the molecular mechanisms of vectorial charge separation across biological membranes involved in photosynthesis and metabolism.

Mechanoreceptors provide the inputs for the sensory modalities of touch, muscle tension, motion and hearing. This project is aimed at gaining insight into the process of mechano-sensory transduction at the molecular level. Methods are developed for the application of static and dynamic mechanical stress to planar lipid bilayers. Stress-strain relations are analyzed in these membranes with microsecond time resolution through voltage clamp measurements of the capacity currents. Applied stress patterns are steps, ramps and sinusoidal oscillations of different frequencies and amplitudes. Effects of lipid composition, solvent content and aqueous phase environment on the stress-strain relations are some of the parameters to be studied. Selected ion channels are incorporated into the bilayers. They include channels from lower organisms such as gramicidin, alamethicin or porin, as well as channels from higher organisms including sodium and potassium channels. Small membrane areas are isolated by a 30 Mu diameter patch pipette and changes of the channel gating kinetics, ion conductance and ion specificity in response to mechanical stress are investigated at the multi- and single channel level by current and voltage clamp. Mechanical sensitivity of the transduction is evaluated by determining the quantitative relations between stress-induced membrane strain and membrane conductance. The coupling between mechanical and inherent electrical oscillations is studied in membranes containing voltage-gated multichannel conductances. Channels from membranes of cochlear hair cells and stereocilia are inserted into lipid bilayers by fusion of membrane vesicles. The responses of these channels to mechanical stress are evaluated at the single- and multichannel level.

Significant progress in computational neuroscience and neuroengineering requires a multifaceted interdisciplinary research program in several interrelated areas: Mathematical modeling and analysis of neural nets to better understand their collective behavior and capabilities for practical applications. Neurophysiological studies to better understand how retinal information is processed by neuronal assemblies in the striate and extrastriate cortex. Neural vision systems and their VLSI implementation for scene analysis and primitive extraction. Architectures and opto-electronic implementations of self-organizing neural nets partitioned into input/output and internal neurons for supervised and unsupervised learning with stochastic and deterministic state update rules. Higher order processing, in interconnected neural net modules utilizing, sequential and cyclic storage and recall, generalization, for multisensory data fusion and knowledge aggregation. Smart sensing and recognition from sketchy information with emphasis on object recognition including study of object representations that produce distortion invariant recognition. Highly structured associative memory and processing of spoken language. Study of optical materials and devices suitable for realizing artificial plasticity and learning specially in nets with unipolar binary neurons and ternary synaptic weights that facilitate opto-electronic implementations. The present proposal deals with studies to be carried out by a group of faculty with extensive expertise in the above areas, from the schools of Engineering and Medicine. Results of this research are expected to contribute to the development of a new generation of neuromorphic cognitive systems and to outperform more conventional approaches to signal processing. outperform more conventional approaches to signal and

The southwest coastal region of Florida offers one of the richest sequences of shelly marine faunas representing the last five million years of biological evolution in the region. This interval is of great interest because of its fundamental environmental and biotic changes including closure of the Panamanian seaway, reorganization of the Gulf Stream, severing of the Pacific-Atlantic connection between marine faunas and the interchange of North and South American land faunas. Recent work by Florida State Museum parties has shown that potentially rich land animal samples interfinger with the well- known marine mollusk faunas in southwest Florida. These vertebrate samples will be enlarged and studied, and they are expected to greatly improve the precision of present dating of the entire late Neogene sequence in the region. At the same time, intensive analysis of the largely neglected gastropod mollusks in the marine faunas will be undertaken. A relatively new approach to checking the correlation of these same marine and non-marine faunas will be tried, using strontium isotope ratios, in comparison with the sequence based on world-wide marine readings. This work is urgent because the major excavations now open will be closed and forever buried in about two years.

The proposal describes a planned two-day workshop on "Hardware Implementation of Analog Neuron Nets". The computational methods employed by neuron nets have received recently considerable attention. Whereas most of the research effort in this area has been directed toward theoretical work, actual construction of analog neural machines is still very much in its infancy and is being pursued in only a few laboratories. This workshop is specifically intended to bring together key investigators in this field with the aim to discuss critically the feasibility of different approaches, to evaluate new technologies and to foster collaboration between workers in the field. The agenda will be restricted to analog designs and not include neural net simulation on digital architectures. The workshop shall focus on device implementation as well as system design. The format of the meeting would emphasize informal discussion.

This proposal seeks funds to support a collaborative petrologic, structural, chemical, and isotopic investigation of the growth and development of continental crust as recorded in rocks of the middle crust (roughly 125-25 km). The middle crust is a dynamic environment through which Earth materials are cycled both mechanically and chemically. Supracrustal rocks may be transported to mid-crustal levels through tectonic processes; juvenile additions to the crust may be emplaced from the mantle; fluid fluxes may initiate melting, possibly to produce charnockites, or leach LIL elements; melting in the middle crust may extract large volumes of melt through vapor-absent melting. Artifacts of many of these processes have been recognized in two distinct blocks of Archean crustal rocks in the northern Madison Range, SW Montana. Our integrated study of this segment of Archean continental crust will lead to a more comprehensive understanding of the geochemical processes that contribute to the growth and development of continental crust, as well as to the specifics of the tectonic and magmatic cycles controlling crustal evolution in the northern Wyoming Province.

This collaborative proposal with Robert D. Shuster aims to study the growth and evolution of the Middle Proterozoic Granite- Rhyolite Province. This terrane underlies the south central North American continent and except for three areas of outcrop, is buried by Phanerozoic sedimentary rocks. Age constrained samples from outcrops and from cores and cuttings housed at the University of Kansas will be used to determine their Pb and Nd isotopic compositions and chemical (major, trace, and REE) compositions. This study will be directed at constraining potential source areas, processes, and tectonic models for the formation and evolution of this large area of highly evolved and unique Proterozoic crust.

The Late Proterozoic-early Paleozoic rocks of the Tallahassee- Suwannee terrane may provide a critical link between the southern terminus of the Appalachians and the Mauritanides of west Africa, yet they are poorly understood because concealed beneath Mesozoic and Tertiary rocks of the Atlantic Coastal Plain. This study will examine the major and trace element and isotopic composition of a suite of drill cuttings from the basement rocks of northern Florida, southern Georgia and southern Alabama to determine the geochemical character of the continental crust in these regions. The data obtained will be used to compose the Tallahassee-Suwannee terrane with Avalonian and West African rocks. The results of this study will place constraints on late Proterozoic-early Paleozoic tectonic history of southeastern North America and will have broader tectonic implications for global plate reconstructions over this time interval.

The Wyoming Province exposes one of the most isotopically evolved Archean cratons. The Wyoming Province forms an early part of the north American Precambrian shield, to which younger terranes were accreted. However, the origin of the province is unclear, with some isotopic data suggesting that it was derived from an older reservoir that must have been older than 4.0 Ga if it U/Pb ratio was comparable to average crust. Determining the age and composition of this older reservoir is crucial for understanding the processes that lead to the transformation of this craton from an older, relatively high U/Pb system to a low U/Pb system by the end of the Archean. The work involves a detailed geologic and geochemical investigation, including SHRIMP U-Pb geochronology, of the Middle to Early Archean crust in the Beartooth Mountains where the evolved isotopic signature is best documented. Results will be important in constraining the processes involved in Earth's early geochemical differentiation.

0080086
Foster

This grant provides partial support for the acquisition of a noble gas mass spectrometer, a UV/IR dual laser system, high precision furnace, and associated vacuum equipment and electronics to construct a facility for 40Ar/39Ar geochronology and rare gas geochemical investigations at the University of Florida. The lead PI, David Foster recently (1998) joined the faculty at the University of Florida after spending several years as a senior researcher at La Trobe University in Australia. He joins Paul Mueller, Michael Perfit and Ann Heatherington in the geochemistry and petrology group. Establishment of a thermochronology facility at Florida will complement existing and successfully operated geochemical instrumentation in the Geology Department including a TIMS, ICP-MS and SIRMS and will add capacity to a limited U.S. geoscience analytical infrastructure for Ar/Ar geochronology. The noble gas mass spectrometer will facilitate research in tectonics, economic geology, basin studies, geomorphology and anthropology by providing for constraints on the timing and rates of geologic processes.

***

The long-term goals of this proposal is to understand how the various Cdc2 regulatory mechanisms contribute to the control of cell cycle progression in vertebrates. Entry into mitosis is controlled by the Cdc2 cyclin dependent kinase. Proper regulation of Cdc2 ensures that mitosis occurs only after earlier phases of the cell cycle have been completed. This strict control is largely post-translational with inhibitory phosphorylation playing a key role. In metazoans, two types of inhibitory Cdc2 kinases have been identified: the soluble Wee1 found in the nucleus and the membrane-associated Myt1 found in the cytoplasm. Understanding the regulation of Wee1 and Myt1 is required to understand how cell proliferation is controlled. While recent studies have begun to unravel the regulatory mechanisms modulating Wee1, very little is known about Myt1. Myt1 may play a unique role in cell cycle control. For example, because of its localization to the cytoplasm, Myt1 is the only inhibitory kinase available to directly inhibit the interphase pool of the Cdc2/Cyclin B complex. Furthermore, Myt1 is the only Cdc2 inhibitory kinase found in oocytes. Oocytes must remain arrested in G2 with inactive Cdc2 for proper development. Understanding the regulation of Myt1 will aid in our understanding of these processes and give us insights into the general mechanisms used to control cell division and to prevent disease such as cancer. The goals of this proposal are to understand how Myt1 is regulated to ensure proper progression through the cell cycle. To accomplish these goals, we will: (1) Characterize the regulatory pathways controlling Myt1. We will examine the regulation of Myt1 during the cell cycle, oocyte maturation, and checkpoint response. (2) Map the cis-acting regulatory domains of Myt1. To aid in our understanding of Myt1 regulation and cell cycle control, we will determine the regions of Myt1 required for activity as well as the regions responsible for regulation. (3) Identify and characterize trans-acting regulators of Myt1. In order to understand at the molecular level how the initiation of mitosis is signaled and triggered, we need to understand the upstream regulators of Myt1. We will use both genetic and biochemical approaches to identify and characterize the regulators of Myt1.

0106592
Mueller
The Great Falls tectonic zone is a NE-trending feature that extends from northeastern Idaho to the Montana - Saskatchewan border, and may represent the collisional suture between the Archean Wyoming province and the Hearne province of the Canadian shield. However, recent work has raised the alternative interpretation that the Great Falls tectonic zone is an intracontinental shear zone reactivated by the Trans-Hudson orogeny and another feature represents the Wyoming-Hearne suture. This project will examine newly documented 1.86 Ga meta-igneous rocks of the Great Falls tectonic zone that will address several fundamental issues associated with the assembly of southern Laurentia and the breakup of Rodinia. Results are expected to help clarify the interpretation of the significance of the Great Falls tectonic zone in relation to the development of the Pacific Northwest.

EAR-0418905
Mueller

This proposal seeks support for the appointment of a Ph.D. scientist to act as laboratory manager for a new ICP-based analytical facility at the University of Florida for an initial 3-year period. The University of Florida will assume 100% financial responsibility for this position on a permanent basis subsequent to this initial period. The construction of the ICP laboratory and the acquisition of two new ICP mass spectrometers (Finnegan-MAT Element-2 and Nu Plasma multicollector) are part of the recent relocation into >10,000 sq. ft. of new geochemical laboratories as part of an overall relocation of our Department into greatly expanded and renovated facilities (Williamson Hall). These instruments have been interfaced with newly acquired Excimer (193 nm) and Nd-YAG (213 nm) lasers, as well as a desolvating nebulizer and autosamplers. Financial support for both laboratory renovation and instrument acquisition involved cost sharing between the University of Florida and the NSF. The primary responsibilities of this person will include: 1) contribute to method development and participate in collaborative and independent research, 2) maintain quality control of the facility, which will be a challenge in light of the large number of users; 3) oversee and administer day-to-day activities such as maintenance and scheduling, in order for the facility to efficiently produce the highest quality data; and 4) make the instruments capabilities known to and accessible to a wide range of users inside and outside of the department, including students. In addition, the laboratory manager will be the primary instructor for students exposed to elemental and isotopic methods both in courses and via individual research projects at the graduate and undergraduate levels. Without an experienced laboratory manager, access to this facility for these students and other users will be very limited.
***

An EarthScope workshop in the northern Rocky Mountains (NRM) will provide an opportunity
for a diverse array of earth scientists to meet and discuss the opportunities that
EarthScope will provide to improve our understanding of the wide range of processes that
formed this segment of continental crust. The NRM (generally defined as northern Wyoming,
SW Montana, and eastern Idaho) is a unique environment that provides an excellent natural
laboratory for studying many critical phenomena associated with the evolution of the
continental crust-mantle system. We propose to hold a 2.5-day workshop in the early fall of 2005 in SW Montana. The meeting will begin with a general session to inform participants of the current status of EarthScope and provide overviews of the overarching scientific questions related to the
geology of the NRM. An organizing committee will be charged to set the meeting agenda and
participate in selection of speakers and participants. The workshop will provide the
opportunity for smaller working groups to meet and identify scientific objectives and
assess how EarthScope can help address these objectives. Possible working group topics and
lists of individuals who have expressed an interest in attending is provided. A concluding
session will focus on presentations from the individual working groups. Appropriate and timely announcements will allow ample opportunity for all interested parties to apply to attend.
The broader impacts of the workshop will be realized through comprehensive web development
that will support workshop logistics, pre- and post-workshop activities, posting of all
workshop products (e.g. talks, posters, discussion summaries, essays, plans), and will
begin to compile a region-wide digital resource collection. The workshop program will also
address the EarthScope Education and Outreach (E&O) objectives by establishing an E&O
working group in parallel with the research-oriented working groups. The workshop will
also serve to identify and recruit colleagues who are interested in contributing to
EarthScope E&O in the NRM.

This research is directed at improving our understanding of the formation and dispersal of the Laurentian (ancestral North America) supercontinent and the relationship between these events and the episodic generation and preservation of continental crust along its southwestern margin. The southwestern margin of Laurentia is globally unique because it contains remnants of a former Archean microcontinent (Wyoming province) and two distinct Paleoproterozoic orogenic events at 1.6-1.9 billion years ago and 2.2-2.5 billion years ago, which produced new continental crust. Formation of Laurentia in the Paleoproterozoic coincides with a global period of exceptionally rapid growth of juvenile crust and aggregation of existing micrcontinents and arcs during the late Paleoproterozoic (1.6-2.0 billion years ago). This period of rapid growth was preceded, however, by a global period (2.0-2.5 billion years ago) with a pronounced paucity of preserved crust. Crust generated during this interval is less commonly preserved than crust from periods preceding and succeeding it in the global rock record. In addition, such crust is unevenly distributed among the modern continents. It is more commonly preserved in modern southern hemisphere continents, making its presence along the southwest Laurentian margin unique. To complete this research scientists from the University of Florida are conducting a detailed and integrated geochemical and structural/tectonic investigation of both the early and late Paleoproterozoic rocks preserved along a part of the southwestern margin of Laurentia. This is being accomplished by geologic mapping in two critical areas, the Highland Mountains of Montana and the Wasatch Mountains of Utah, which form the basis for sampling this crust for chemical, isotopic, and petrologic studies. This work is leading to more complete understanding of the ages and origins of crust and lithosphere generated during the Paleoproterozoic and will provide critical and unique insight into the global scale problem of low crustal production rates in the early Paleoproterozoic vs. much higher rates characteristic of the late Proterozoic and late Archean. These data are also providing new constraints on the relationship between supercontinent cycles and changes in crustal growth rates and a specific test of Proterozoic geodynamic models based on assumptions that certain features such as the Diamantina lineament of Australia or Aekit terrane in Siberia share a common geologic history with the Great Falls tectonic zone and, therefore, represent a combined feature that transects the Neoproterozoic margin of Laurentia.

In addition to the core science objectives, project funds are supporting undergraduate, graduate, and post-doctoral students by providing opportunities for their participation in various aspects of the research that is enhancing their mapping, sample preparation, analytical, and interpretive skills important to their professional development and employability. The research is benefiting from an established cooperative agreement to aid in supporting new undergraduate field research program supported by both the Keck Foundation and the National Science Foundation. The research is also being coordinated with an ongoing a U.S. Geological Survey mineral resources project (Metallogenic Evolution of Mesoproterozoic Sedimentary Rocks in Idaho and Montana) that is dependent on an accurate assessment of the age and distribution on pre-existing continental crust, such as that targeted in this project. On a longer time frame, this research will provide valuable input to decisions made for the NSF-sponsored EarthScope research project. When complete, the results of the research will be integrated into an on-line map that will allow both technically oriented individuals as well as the general public to see how the results from this research related to existing data from this region and elsewhere. Results of this research also are being made available through peer-reviewed scientific journals, on-line global databases, and presentations at professional society meetings.

0545751
Mueller

In order to optimize current and future deployment of EarthScope (ES) resources in the northern Rocky Mountains/Great Plains, a group of earth scientists from the University of Florida, Montana State University, and the U.S. Geological Survey are conducting research directed toward development of an integrated temporal and spatial (i.e., 4-D) framework for crustal evolution in this region. In particular, this region contains one of the most enigmatic segments of continental crust in North America, the Great Falls tectonic zone (GFTZ). This long-lived crustal structure has the most temporally extensive rock record in North America (ages to 4 billion years) and has had a major impact on the geologic history of this region, including younger episodes of faulting and seismicity, distribution of magmatism and ore deposits, and the creation of resource-rich sedimentary basins. For example, the intersection of the GFTZ and Trans-Hudson orogen, which developed ~ 1.8 billion years ago, is now the site of a major petroleum resource province, the Williston basin. Similarly, Phanerozoic structural reactivation, magmatism, seismicity, and mineralization in the northern Rocky Mountains is concentrated in the GFTZ, which leads to additional possibilities of how ancient structures and events may control modern earth processes and the distribution of resources.

The research group is applying modern geochronologic (ion probe U-Pb), thermochronologic (multi-and single grain 40Ar-39Ar), and geochemical (major and trace elements) techniques to samples from outcrops, deep test wells, and xenoliths (pieces of the mantle and lower crust brought to the surface via volcanic eruptions). These results will be critical for both optimizing the deployment of ES resources and ultimately developing an integrated 4-D framework for the northern Rocky Mountain/northern Great Plains portion of North America. This 4-D framework is essential to: 1) unraveling one of the most intriguing episodes of continent formation in the geologic record, the formation of Laurentian North America; 2) understanding how the amalgamating collisional events were recorded in the crust and mantle; and 3) to what extent these ancient events affected subsequent crustal and lithospheric evolution in the northern Rocky Mountains/Great Plains. The research team is utilizing facilities from all three organizations (University of Florida, Montana State University, and the U.S. Geological Survey). Student participation at the graduate and undergraduate level is providing critical workforce training in geologic and analytical skills. The results of this research will be integrated into the evolving Montana GIS/DEM geologic map base being developed at Montana State University. All of the geochemical and geochronologic data will be numerically and spatially displayed in an interactive web format and accessible to geoscientists, educators, and the general public. Results will also be disseminated via meeting presentations and peer reviewed journals.

Intellectual Merit. Constraining the size, spatial distribution, and extent of elemental fractionation that characterized both depleted and enriched geochemical reservoirs in the early Earth has been a fundamental long-term goal of terrestrial and planetary geochemists. For the Sm-Nd and Lu-Hf systems, crust-mantle evolution subsequent to 2.5 Ga has been viewed in terms of a generally monotonic increases in the radiogenic daughter isotopes within the mantle that reflects extraction of continental crust to produce a 'melt'-depleted upper mantle reservoir characterized by parent/daughter ratios that are greater than the values for the bulk silicate earth. The complementary enriched reservoir over this interval is the continental crust. However, for the earliest 4.5 to 2.5 Ga of Earth history, the rock record is more difficult to decipher - in part owing to limited exposures of rocks this old. Available data indicate that crust-mantle evolution in this period may have been quite different in terms of melt-extraction processes, leading to 'anomalous' departures from the younger Nd-Hf isotopic record. Recently, analysis of Lu-Hf systematics in old, well-preserved zircons have provided a new approach to resolving isotopic records for early earth evolution. This approach will be used to gain insights into the development of Earth's early enriched reservoirs through analysis of a suite of 3.2 to 4.0 Ga zircons preserved in both metasedimentary and metaigneous rocks from the northern Wyoming Province. The proposed research will consist of 3 primary components: [1] U-Pb dating and trace element analyses via ion probe (SHRIMP-RG), [2] finer scale elemental analyses and imaging via electron probe, and [3] measurement of Lu-Hf systematics via LA-ICP-MS on dated portions of individual zircons. The PIs have previously documented the antiquity of the crust in this region, and argued that understanding its evolution will provide fundamental insights into the early geochemical differentiation of the Earth.

Broader Impacts. This project will involve training of graduate students and post-doctoral researchers in geologic and analytical skills that will serve in future research and/or private sector employment. Undergraduate students will also be involved in this project - introducing them to methods of geologic research. Prior research results of this group have been included in popular books and in educational displays at the American Museum of Natural History (e.g., "The Earth Inside and Out", Gottesman's Hall of Planet Earth exhibit). Likewise, the proposed research will also be incorporated into formal and informal education and outreach. An example is provided by the "pet rock" approach utilized for petrology instruction at LSU. All results of this research will be disseminated via traditional presentations at professional meetings and peer reviewed publications.

Two different hypotheses for the relationship between the Congo and
Kalahari cratons, during the Rodinia and Gondwana supercontinent cycles,
will be evaluated. Co-funding for this work has been provided by the
Office of International Science and Engineering.

Congo and Kalahari presently reside within Africa and are juxtaposed
across the Neoproterozoic-Cambrian Damara-Lufilian-Zambezi orogenic system.
The primary controversy surrounding the assembly of these two cratons
in the supercontinent cycle centers on the extent to which Congo and
Kalahari remained associated geographically throughout the cycle,
i.e., were the two cratons directly adjacent to one another in
Rodinia, and, did they remain so until amalgamated in Gondwana, or
was one (or both) not in Rodinia at all and were not joined until
Gondwana formed? The metamorphosed sedimentary detritus within the
Damara orogenic zone records the separation of these blocks from
Rodinia and accretion within Gondwana. The U/Pb age and Hf-isotopic
compositions of detrial zircons from the metasedimenatry rocks, along
with whole-rock Nd isotopes, will be measured to define the origin of the
continental detritus in the suture zone. The significance of the
alternative hypotheses relates to the configuration of Rodinia, the
amalgamation of Gondwana (E-W or N-S final suturing), and the degree
to which Rodinia was fragmented during break-up.

The accretion and dispersal of supercontinents remains one of the
most significant problems in understanding global dynamics and motions
of continents through time and the convection of rock in the mantle.
The growth and break-up of two supercontinents in late Precambrian
time ? Rodinia and Gondwana ? are particularly significant for
understanding the supercontinent cycle, because they overlap the
development and dispersal of complex life forms in the shallow oceans
along their margins. The hypotheses being tested in this project
have implications for the dispersal and source of sediment in the
shallow seas, the initiation and proliferation of early life in those seas,
the evolving paleoclimatic system of the planet, and the time that the
younger supercontinent cycle of Pangea initiated.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

Research in Yellowstone National Park (YNP) will characterize the geology, geochemistry and geochronology of the Precambrian rocks that underlie the northern part of the Park. REU students will participate in three major activities that will constitute a complete research experience: 1) Field studies, conducted in YNP will include geologic mapping and sampling of the Precambrian basement of YNP; formulation of testable research questions by smaller working groups; and mapping and sampling projects to address these research questions; 2) Analytical studies, starting with sample preparation immediately following field work at Montana State University; petrographic analysis at the students' home institutions; a week-long visit to analytical laboratories to conduct follow-up studies by small research groups during the academic year (University of Florida for geochemistry and geochronology; Louisiana State University for electron microprobe analysis); 3) Communicating results, each working group will submit an abstract to the following Geological Society of America Rocky Mountain sectional meeting as a first step towards formalizing the research results, including a writing workshop to encourage collaborative writing towards a peer-reviewed journal article. This REU site project will be conducted over two years with a focus on the anomalously low-grade metasedimentary rocks in the first year and (meta)igneous rocks in the second year. In aggregate, the research results will provide important insights into the petrogenesis, architecture, and evolution of the Precambrian rocks of YNP.

The research results will contribute to a more complete understanding of the natural history of YNP. The geologic maps and sampling locations will be GIS-based and will be transmitted to the YNP Research Office for inclusion in their database to help inform further research and management in YNP. Students who participate in this project will gain valuable research experience through participating in the full range of activities including hypothesis formulation and testing, field mapping and sampling, sample preparation, analytical studies on modern instrumentation, communicating results at a professional meeting and engaging collaborative writing towards a peer-reviewed journal article. A research on learning component will document the cognitive and affective impacts of the field experience on the participating students to help document best instructional practices in field instruction for use by the larger geoscience education community.

The combined Alleghanian-Hercynian-Variscan orogeny (approximately 300 million years ago) marks the culmination of Earth?s most recent example of the formation and dispersal of a supercontinent (Pangea). The southern Appalachian Mountains record a critical zone in the formation of Pangea because they mark the collision of the precursors of three modern continents (North America, South America, and Africa). Pangea's subsequent rupture produced these three continents and continues with the expansion of the Atlantic Ocean. The research team of faculty and students from the University of Florida and Mississippi State University are conducting detailed geochemical investigations into the spatial distribution, ages, and geochemical compositions of a suite of granitic igneous bodies that intruded crystalline rocks that formed up to one billion years earlier in the roots of the mountain belt and are now in Georgia, Florida, Alabama, and South Carolina. These granitic bodies are the only known magmatic manifestation of the destruction of two ancient oceans (Iapetus and Rheic). Understanding the age and origin of the granitic bodies is critical to understanding the growth of continents in general and, particularly, how continental crust was exchanged during the Pangean supercontinent cycle. In particular, they are focusing on identifying the boundary and the operative tectonic and magmatic processes that characterized convergence of the continents that ultimately formed Pangea. The convergent boundary has tentatively been identified on the basis of geophysical data to occur in a zone known as the Suwannee suture; the proposed suture lies sub-parallel to the Florida-Georgia border. A new boundary was established after the rupture of Pangea, which produced the modern Atlantic Ocean and the African, South American, and North American continents. The location of this rupture is not known, but is being further constrained by this project.

Faculty and students (graduate and undergraduate) involved in this project are sampling the granitic rocks derived from melting of the lower continental crust as part of an integrated geochronologic, thermochronologic, and geochemical study of the spatial and temporal relationships between Alleghanian tectonism and magmatism. These data will provide unique constraints on lithospheric structure and evolution in the Pangean collision zone. The region chosen contains numerous Alleghanian magmatic rocks that intrude a range of pre-Alleghanian terranes typically considered part of ancient North America, as well as some considered to be fundamentally Gondwanan or peri-Gondwanan (e.g., African or South American). The uranium-lead zircon geochronology and isotopic composition of the granitic bodies are being used to geochemically image both sides of the proposed Suwannee suture to better understand the juxtaposition of the different continental fragments in 4-D. This "geochemical imaging" of lithospheric structure is: 1) providing a critical complement to on-going geophysical studies in this region that are integral to the mission of the EarthScope Program in North America, 2) providing important insight into the global tectonic enigma of largely amagmatic ocean closures, and 3) contributing to our understanding of the basement architecture of the eastern Gulf of Mexico petroleum province. The project supports an important regional scientific collaboration between researchers at the University of Florida and Mississippi State University. It is contributing to the training of graduate and undergraduate students in a STEM discipline. Because of the demographics of the student populations at both universities, it has the potential to contribute to the broadening of participation of underrepresented groups in the geosciences. The ongoing results of this research are being communicated in guidebooks, professional meeting symposia, and refereed scientific publications.

This project is being supported by the NSF Tectonics and EarthScope Programs

Earth scientists from Louisiana State University and the University of Florida are collaborating on an investigation of a unique segment of Precambrian (>550 million years old, m.y.o.) continental crust brought to the earth?s surface by the ~50 m.y.o. Sawtooth batholith in eastern Idaho. This crust is unique because it lies between some of the oldest crust in North America (exposed in SW Montana) and some of the most recent additions to the North American continent in western Idaho (Blue Mountains). This research will test a wide range of hypotheses for the formation and evolution of this crust: Is it an independent terrane accreted to North America in the recent past, or does it show geochemical ties to the old (>3000 m.y.o.) crust exposed in SW Montana? Does it record evidence of a ?vanished? episode of mountain building similar in age to the Grenville orogeny that formed much of eastern North America 1000 m.y. ago? If accreted to North America in the Precambrian, does it provide insight the fragmentation of North America that occurred 500-700 m.y.o ago? Specifically, the team will investigate the origin of metamorphosed sedimentary rocks that carry information about the nature of continental crust exposed at the time they were deposited. The temperature and pressure history of this crust, which will constrain the time at which it was appended to North America and the mechanism by which it was appended. Elemental abundances in the metamorphosed igneous rocks will give important clues to the environment in which they formed, while isotopic compositions will constrain the amount of new crust vs. recycled crust that is preserved. A large fraction of the crust that lies between the Archean (>2500 m.y.o.) crust of SW Montana and the <200 m.y.o. crust of western Idaho is buried beneath younger rocks, making the Sawtooth terrane a very important window into crustal evolution in western North America.

This research will be carried out by a team that includes members from underrepresented groups and women who will be trained in important quantitative techniques applicable across a range of STEM disciplines. The team will also participate in the public-private partnership between LSU Geology & Geophysics and Marathon Petroleum Corporation (Geoscience Diversity Enrichment Program) that is focused on increasing STEM participation. The public will also benefit by our partnership with the Sawtooth National Recreational Area (U.S. Forest Service), leading to better educational materials distributed in the Sawtooth National Recreational Area. In detail, this team (faculty and students, undergraduate and graduate) will employ and provide training in the following: 1) We will conduct U/Pb radiometric dating of zircons to determine original crystallization ages of igneous rocks and the origin of sediment deposited in protoliths to the metasedimentary rocks using laser ablation to sample individual crystals in the ICP-MS laboratory at the University of Florida; 2) Elemental analyses by a combination of x-ray fluorescence and ICP methods at the University of Florida; 3) The electron microprobe laboratory at LSU will be used to measure elemental abundances in individual minerals, which can then be used to determine the burial conditions and pressure-temperature path of the Sawtooth crust (thermobarometry); 4) U-Th-Pb (radiometric) dating of texturally and petrologically constrained monazite and titanite will provide a definitive age for the metamorphic event(s) recorded in the Sawtooth crust needed to develop Pressure-Temperature-time path(s) and determine the tectonic setting of metamorphism using facilities at the University of Florida and the University of Massachusetts; and 5) Measurement of K-Ar systematics (40Ar/39Ar) will help assess the most recent, post-metamorphic, thermal history of the terrain. Students from both universities will cross-train in these techniques as part of their thesis and dissertation research, and will then be well prepared to meet the technologically challenging opportunities afforded members of the country?s STEM workforce.

This collaborative project between investigators at Columbus State University and the University of Florida aims to resolve conflicting interpretations of the tectonic origin and age of a number of metamorphosed granitoids in the Ashland-Wedowee-Emuckfaw belt (Eastern Blue Ridge) province of Alabama in the southernmost Appalachians. Traditionally attributed to latest Cambrian-Middle Ordovician magmatism associated with the Taconic orogeny, the Elkahatchee Quartz Diorite, Zana Gneiss, and Kowaliga Gneiss have been considered by some workers to be part of an obducted Taconic island or peri-Laurentian arc emplaced atop the subducting margin of North America. SHRIMP-RG results from the dominant quartz diorite component of the Elkahatchee, however, suggest an Upper Devonian emplacement age with considerable evidence for abundant xenocrystic inheritance which may have complicated the initial whole rock and multi-grain analyses completed over two decades ago. The potential for significant Acadian-aged magmatic components in the Elkahatchee calls into question its association with a Taconic arc; a question which can only be addressed by detailed isotopic analysis of the various lithologies typically assigned to this batholith. Furthermore, since both the Zana and Kowaliga gneisses were assigned ages using some of the same techniques as those used to assign a latest Cambrian age to the Elkahatchee, attribution of these plutons to Ordovician orogenesis is also suspect. Spatially resolved U-Pb analysis of these plutons will provide the best temporal context for examining the Lu-Hf systematics of zircon components and, in combination, will allow us to constrain the petrotectonic evolution of parental magma(s).

Results from this project will shed new light on the tectonic evolution of the North American margin and the development of the Appalachian Mountains through the Paleozoic. Significantly, it will provide new constraints on fundamental questions regarding evolution of the southern Appalachian orogeny because of its bearing on the continuity and nature of subduction along the eastern margin of North America during the closure of the Iapetus and Rheic oceans. These results will also afford an improved understanding of the role of important plutonic elements in the evolution of the southern Appalachians, which will be of advantage to many institutions in the region for undergraduate and graduate instruction. Integration of student and faculty expertise and opportunities at these universities will have a significant impact on training professional geoscientists, who are critical to developing a strong national STEM workforce, and will provide valuable support for a faculty research program at a predominantly undergraduate institution through the Research in Undergraduate Institutions program (RUI). Finally, this project will afford a group of geology undergraduates an invaluable experience (from field to analytical) through participation in a geological research program, greatly enhancing their undergraduate education and enhancing the nation?s STEM workforce.

This project is enabling the acquisition of a state-of-the-art multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) to support a team of researchers within the Department of Geological Sciences at the University of Florida to make significant advances for research applications in the Earth and Ocean Sciences. This instrumentation facilitates the research program of the lead investigator, who is an early career female with a research focus on Uranium-series geochemistry, a technique used widely to determine the age of materials in studies of past climate and sea level change on time scales from a human life to thousands of years. This MC-ICP-MS instrument allows the development of sea level reconstructions with high temporal accuracy and precision, to define the rates and tempo of ice sheet retreat and sea level rise during past warm climates. These reconstructions can be paired with climate data to inform future projections of sea level rise over the coming decades to millennia. Additional capabilities afforded by this instrument will significantly improve other existing research programs as well as enabling new lines of research in a wide range of Earth science applications.

The new MC-ICP-MS acquired through this project will enable the incorporation of new investigators and new research directions within our department, as will improve our analytical capabilities. Specifically, the primary new capabilities will allow for several ion-counting channels, including multiple high abundance sensitivity filters to facilitate the analysis of U-series measurements. The instrumentation will also allow for simultaneous measurement capability of U-Th-Pb-Hg during laser ablation analyses for U-Pb geochronology applications. These advances, among others, will impact research in a wide range of disciplines beyond earth and ocean sciences, including existing collaborations within anthropology, chemistry, agriculture, paleontology, biology, medicine, engineering, and forensic science. The instrumentation will be used to train students and post-doctoral scholars supported by a wide range of NSF programs.