Since the advent of plate tectonics, earth scientists have increasingly emphasized the importance of the lateral growth of continental crust by the processes of terrane accretion and magmatic arc development. The Cordilleran orogeny of North America is one of the prime examples of such crustal growth, and the Alaskan portion of this belt is considered to have been constructed almost entirely by the process of terrane accretion. This study will undertake an ambitious geological and geophysical transect across the northernmost portion of the Cordilleran orogeny in the BeringChukchi region of the Arctic, between mainland Alaska and Russia. The main goals of the research are to provide us with greater insight into the details of the creation, evolution and modification of the crust beneath Cordilleran-style orogenic belts, to give us a better understanding of the coupling between tectonic and petrologic processes at deep and shallow crustal levels, and to help us determine the general links between processes at the scale of the crust and those at the plate tectonic scale. The project is a collaborative effort by researchers at Stanford (Miller and Klemperer), Rice (Wright), Univeristy of CaliforniaSanta Barbara (Gans) and Western Washington (Engebretson). The project also involves scientists from the U.S. Geological Survey branches of Pacific Marine Geology (Scholl and Childs), Alaskan Geology (Grantz and Moore), and Seismology (Brocher), and three well-known Russian scientists from Khabarovsk (B. Natal'in), Yakutsk (L. Parfenov) and Magadan (M. Gelman).
The accretion of terranes to continental margins is the tectonic process believed by many geologists to have been responsible for continental growth along western North America in the last 60100 million years. Because of the complex geologic relationships produced by accretionary tectonics, the complete geologic history of this tectonic collage in western North America is still unknown. The proposed project aims to build upon the PI's previous research by investigating Silurian reef and reef-related carbonate deposits in southeastern Alaska to determine their geologic relationship to Silurian limestones in southwestern Alaska. Rocks exposed in southeastern Alaska belong to the Alexander terrane, which existed during the Early-Middle Paleozoic as volcanically active islands at an unknown site in the ancient Pacific Ocean, whereas deposits in southwestern Alaska (Nixon Fork terrane) represent an original, although dismembered, part of the North American continent. Strata in these two areas share distinctive Silurian sponge faunas preserved in unusual stromatolite reefs. In southeastern Alaska, Silurian carbonates have been examined in detail at scattered localities but mainly only in one small area in the southern part of the Alexander terrane. The research will enable detailed investigations of Silurian rocks that are exposed in other parts of the Alexander terrane, especially where reconnaissance studies have revealed well-preserved, but as yet unstudied biotas. Field work involving undergraduate research students will focus on describing rocks and collecting fossils systematically from measured and photographed stratigraphic sections. Compilation of petrologic, petrographic and paleontolgic data will form the basis for determining the paleoecology, environmental setting and faunal affinities of the preserved biotas and for identifying the degree of similarity in rock and fossil composition with Silurian rocks in southwestern Alaska. Demonstrating that a diversity of fossils from more than one small part of southeastern Alaska is shared with southwestern Alaska represents an important advancement in our understanding of the early geologic history of the Alexander terrane. These data will help to document evidence for the hypothesis that the Alexander terrane was in close proximity to northwestern North America, allowing faunal communication between the two localities. Such data would be important in providing a definitive paleogeographic link between the Alexander terrane and North America proper. Because similar Silurian sponge deposits also occur in the Ural Mountains, Russia, the study will lay critical groundwork for exploring the idea that a seaway enabled migration of organisms along the northern rims of North America (Laurentia) and Europe (Baltica) in the Late Silurian.
Our concepts concerning the stability of the Laurentide Ice Sheet (LIS) and its role in the global climate systems have been revised dramatically in the past five years, as high-resolution records have been compiled from the sea floor, ice cores and from deposits around the margin of the former ice sheet. Collectively, these records document rapid reorganization of oceanic and atmospheric circulation on time scales of a few years to a few decades, and rapid fluctuations of the ice margin that resulted in massive transfers of ice into oceans on time scales of decades to centuries. The rapid delivery of large volumes of ice from the land to the ocean may have altered thermohaline circulation, with subsequent reduction in high-latitude precipitation, effectively coupling the three systems. The Institute for Arctic and Alpine Research (INSTAAR) research effort of the last decade has focused on the glacial history at the mouth of Hudson Strait, the most direct connection of the ice sheet to the ocean. We have provided field evidence for rapid advance and retreat of the ice margin in Hudson Strait (sustained advances in excess of 100 km/century), and for ice movement independent of topography, with major advances sourced in Labrador/Ungava rather than Hudson Bay. A consequence of these advances was a major flux of icebergs into the Labrador Sea, and subsequently the North Atlantic, providing the first direct glacial geologic evidence of a mechanism to produce Heinrich layers observed in the North Atlantic. In this proposal, funding is requested to test three questions: (1) Are observed rapid ice stream advances triggered by inherent instabilities at the bed of the (LIS), or are they climatically driven? (2) Did an ice stream in Cumberland Sound contribute substantial sediment/meltwater/icebergs to the Labrador Sea? If so, were fluctuations in phase with the Hudson Strait advances? (3) Are the reconstructions interpreted from the field evidence compatible with glaciological theory? We proposed to address these questions by field observations of the glacial geology at the mouth of Cumberland Sound and by applying a three-glaciological model to the Labrador/Baffin region using our field-based boundary conditions. The Cumberland Sound region should preserve evidence that will clarify the timing and magnitude of a Foxe Basin ice stream, and to the north, provide an independent record of local glacier activity. Comparing the timing of advances for these ice masses with that in Hudson Strait will indicate whether or not forcing is primarily climate or ice-sheet instability. Modeling our field-base glacier reconstructions will test whether or not they are compatible with ice physics and will provide additional insights into ice sheet dynamics.
The two main goals of the proposed work are: (1) to reconstruct the change in thickness of all of the large ice sheets that once covered much of the Earth's surface during the last ice age, and (2) to explain sea-level changes and earth deformation that have occurred during late-glacial and postglacial time as a result of glacio-isostatic processes. The reconstruction of ice-age ice sheets has usually been attempted by glaciologists and Quaternary geologists who model the flow of ice sheets and assume that climate and other boundary conditions are known. Because the great weight of the ice sheets caused the earth to deform, an alternative approach is to use earth deformation data (e.g., sea-level data, tide-gauge data, geodetic/(GPS) data or proglacial and postglacial lake shoreline tilt data) and a numerical model of viscous flow within the Earth's mantle to infer the weight of the ice sheets as they advanced and then retreated. The success of initial attempts to perform this "inversion" for the North American Laurentide ice sheet have demonstrated the feasibility of performing the global calculation. To ensure that the predicted ice sheets are plausible, the numerical inversion procedure utilizes quadratic programming methods to provide physical constraints upon the predicted ice sheets. The predicted ice sheets can be constrained to be always nonnegative, less than a prescribed maximum thickness, with thickness profile thinning in the direction of glacier flow, and having a maximum rate of thinning or thickening. Errors can be determined for the resulting ice-sheet prediction. A recently implemented method uses a priori estimates of the most likely ice-sheet thickness history to "guide" the inversion process. Results are required to fit the deformation data using least-squares criteria, while the predicted ice-sheet thicknesses are still as close as possible to the a priori model. Prescribed errors of the a priori model control how strongly the predicted ice sheet is constrained by the a priori model, although the errors may be exceeded if the deformation data warrant it. This approach allows considerable spatial resolution in the inversion for ice-sheet history because the inverse problem is always overdetermined regardless of the number of unknown ice-sheet thicknesses. The number of equations always exceeds the number of unknowns. An additional benefit is that the procedure provides remarkable numerical stability in the determination of the matrix eigenstructure. As the ice sheets retreated, their meltwater filled the ocean basins resulting in a rise in sea level, which has been observed in the geological record and recently estimated through time. This "eustatic" sea level rise provides an important constraint upon the inversion process by indicating the volume change of the Earth's ice sheets during deglaciation, whereas deformation data provide an estimate of the spatial distribution of this volume. Meltwater loading of the ocean floor is an important factor contributing to variation in relative sea-level curves at sites distant from ice sheets. An important goal of the proposed work is to include this factor in the inverse procedure, together with the requirement that sea level remain on a gravitational equipotential surface.
The process of extensional deformation within orogenic belts is of considerable interest in the development of collisional mountain ranges. First well-documented in the Himalayas, these extensional structures appear to provide a mechanism for limiting the topographic relief and mean elevation when physical erosion is not sufficient to compensate for the compression-drives uplift. Commonly associated with these extensional features is an enigmatic metamorphic relationship in which the metamorphic grade is inverted, that is, increases upward. From thermal modeling it is clear that these inverted metamorphic gradients can be preserved only with rapid cooling. However, the temporal, spatial and mechanical relationships between deformation (compression with extensional unroofing accommodation) and the geothermal budget (metamorphic grade and pressure-temperature-time path) of these systems is not well understood. This project will study tectonic denudation and inverted metamorphism in the East Greenland Caledonides. This area exposes a much deeper part of an orogen, and the inverted metamorphic gradient is present in a different structural setting from analogous structures in the Himalayas. Technically, the high-precision geochronologic techniques to be used are capable of more closely tying deformation metamorphism in this older orogen. The expected results of this research include a better understanding of the thermal behavior of actively deforming orogens, particularly in response to episodes of extension in the overall compressional orogens.
Deep crustal features associated with continentcontinent collisions are difficult to study in most phanerozoic orogens because the exposure levels are seldom deep enough. The Nagssugtoqidian Orogen of West Greenland has attracted much attention as one of t he world's most completely exposed foreland-to-foreland transects of a deep Precambrian orogen. However, recent work has failed to confirm the presence of major displacement, crustal-scale shear zones and thrusts anywhere in the orogen that should mark a continentcontinent suture. This project, in conjunction with the Danish Lithosphere Centre, will attempt to date, characterize and interpret metamorphism of this belt, previously thought to be an example of a deep suture, and to develop a tectonic model for its formation. Results should determine whether or not the deformation was due to an intracontinental, or an intercontinental, tectonic setting.
The PI will collect brachiopod and conodont faunas of suspect terranes in central Alaska and compare these faunas with known faunas in southeastern Alaska and cratonic North America. The comparison of these faunas will help determine the history of terrane displacement in Alaska. The field effort will be coordinated with the U.S. Geological Survey.
PIs have found iridium (Ir) anomalies in ice cores associated with the 1908 Tunguska event and the 1783 Laki eruption. In collaboration with Robert Rocchia (Paris), they will extend these analyses to other ice cores with the following goals: (1) test and verify findings, (2) make systematic studies on ice core samples to clarify partitioning of Ir and (3) investigate temporal variability of background Ir deposition. Results have implications for debate over impact versus volcanic sources for Ir in the stratigraphic record, and also for linking volcanism and impacts to climatic changes.
Unstable ice-sheet behavior is now recognized as an important characteristic of the Laurentide Ice Sheet (LIS) during the last glaciation, and it played a crucial role in forcing abrupt climate change in the circum-North Atlantic region, and perhaps globally. In this collaborative work, we propose to evaluate mechanisms of unstable ice-sheet behavior based on the late-Pleistocene sedimentary record of the Des Moines and Lake Michigan lobes along the southern margin of the (LIS). This behavior is far better documented by well-dated records of these lobes than for any other sector of the ice sheet, thus providing the best opportunity to explore mechanisms of such behavior and its relationship to abrupt climate change. Results from this research will have significant application to other areas where unstable behavior of the (LIS) occurred, but which are less well-constrained by the geologic record (for example, Hudson Strait). Models of ice-sheet instability thus far have treated the sources of the instability as arising from internal ice-sheet dynamics involving saturated, deforming subglacial sediment. The Des Moines and Lake Michigan lobes advanced across fine-grained sediments that, when water saturated, would have deformed under the shear stress applied by the ice. Additional studies, however, suggest external (climate) forcing mechanisms for unstable ice-sheet behavior. We will continue our collaborative work of integrating field, experimental and modeling studies to investigate potential forcing mechanisms. Our field studies will center on those aspects of the sediment record that offer the most information on subglacial processes with respect to mechanisms of ice-sheet behaviors as well as for comparison to modeling studies. Our experimental work will involve using geotechnical analyses of fine-grained diamictons deposited by the lobes to define the range in rheological parameters of different till sheets that are needed in the constitutive sediment flow law we use in modeling studies. We will use a one-dimensional coupled ice-sediment numerical model that integrates results of experimental work to investigate mechanisms of unstable ice-sheet behavior due to internal ice-sheet dynamics or external climate forcing. Finally, we will focus on intercomparison of results from field and modeling studies of subglacial hydrology, subglacial sediment processes and sediment transport fluxes.
PI will investigate the Cantwell Basin strata in Alaska, addressing questions of depositional systems, basin development and paleoclimate. Strata in the basin may preserve the CretaceousTertiary boundary as well, offering opportunities to investigate fossil plant community changes at this time in a high-latitude basin. Analysis of the Cantwell Basin will be a key step in developing a regionally integrated database for strike-slip basins along the Denali fault system.
This award supports a project to study the late Pleistoceneglacial geology of the regions bordering the Bering Strait. Field work and laboratory analyses of fossil materials collected on Chukotka Peninsula over the last three years indicate that the late Cenozoic stratigraphic framework for Northeast Russia is in need of significant revision. The development of a unified stratigraphic scheme for those parts of Beringia on both sides of the Bering Strait requires that the Pleistocene stratigraphy of NE Russia be more firmly based upon modern concepts of glacial sedimentology, isostasy and eustasy and secured with better geochronology. Knowledge of glacial ice extent in the Russian Arctic is important for establishing accurate boundary conditions for paleoclimatic modeling. Likewise, knowledge of interglacial marine conditions in the region is important for understanding changes in the distribution of water masses and heat transport, as well as understanding the role of the Bering Strait in global ocean circulation models. Based upon past field work and a complete inventory of moraines and other glaciogenic deposits using European Space Agency synthetic-aperture-radar images across Northeast Russia, this project will revise the Late Cenozoic stratigraphy of the region and provide an opportunity for both U.S. and Russian researchers to compare and exchange field methods and laboratory techniques via joint study of crucial stratigraphic sections and moraine sequences on both sides of the Bering Strait. Special attention will be given to the paleoclimatic and paleoceanographic significance of similarities and contrasts in the Pleistocene records. The correlation and geochronology of the deposits will be based upon a variety of modern techniques, including amino acid geochronology of mollusks, soft sediment paleomagnetism, cosmogenic isotope surface exposure dating and quantitative geomorphology of moraines, along with traditional biostratigraphy. The results of this project will be important to developing a complete picture of paleoenvironmental conditions in this region.
This proposal requests funds for a pilot study applying cosmogenic nuclide exposure ages to glacial deposits in the Torngat Mountains, northern Labrador, that were deposited by the eastern margin of the Laurentide Ice Sheet. This sequence of moraines and drift represents at least two successively limited glaciations of the Torngat Mountains and is a "type area" for study of weathering zones in North America. Despite over a century of study, the chronology of this classic sequence of differentially weathered glacial deposits is highly uncertain. Furthermore, the glacial history of this region is a key component in reconstructing the past history of the Laurentide Ice Sheet, which exerted a major influence on global climate during the last glacial period. Examples for measurement of cosmogenic 10Be and other cosmogenic nuclides will be collected to evaluate the suitability of this region for exposure dating studies. The preliminary 10Be data will be used to create an absolute exposure age chronology for the region, and to evaluate the correlation of previously mapped and correlated deposits. Potential results of the proposed work and its possible extensions include: (1) absolute chronology for a largely undated glacial sequence in an area that is crucial for reconstructing the margins of the Laurentide Ice Sheet at the last glacial maximum (LGM); (2) age constraints for glacial deposits and ice-sheet limits related to pre-LGM Laurentide Ice Sheet advances in Labrador; and (3) constraints on erosion rates and weathering history of rock surfaces in sub-Arctic/Arctic regions.
The emergence of order from disorder is observed in a wide range of complex dynamical systems. Several geological features, including patterned ground, constitute some of the clearest and most accessible examples of abiotic self-organization in nature. It is proposed to investigate the spontaneous emergence and dynamics of patterned ground through a coordinated program of field measurement and computer simulation of discrete particle motion in soil subjected to freeze/thaw activity. The close bending of these two approaches promises to be synergistic, with the simulations guiding the investigations in formulating novel and more precise questions in the field and vice versa. A new and more fundamental view of patterned ground as a prime example of self-organization will be obtained through the integration of the following specific objectives: (1) to develop a three-dimensional computer simulation of discrete particle motion in soil subjected to recurrent freezing and thawing, and to use it to investigate the development of patterns in frozen ground; (2) to measure stone and soil displacements, document the formation of patterns and their reaction to disturbances, and monitor with automated instrumentation soil temperature, moisture and climate parameters in established study sites with well-developed sorted circles and stripes; (3) to construct a micro-mechanical model of sorting in patterned ground through computer simulation and laboratory experimentation; and (4) to develop a realistic heat and mass transfer model to investigate factors critical in the formation of sorted circles-active layer depth and three-dimensional geometry of propagating freezing and thawing fronts. An important practical benefit of developing a realistic near-surface heat transfer model for frozen ground is that it promises to contribute to a more precise understanding of both the anticipated impacts of climate change permafrost areas, and the record of recent climate change that is contained in permafrost temperatures. The goal of the proposed research is to understand the processes through which patterns such as these circles of stones in the Arctic arise from a disordered initial state-in this case, a wave cut platform covered with 12 m of assorted beach sediments.
The extent of arctic ice sheets during the last glaciation is among the most controversial issues in arctic glacial geology, paleoglaciology and paleoclimatology. One of the main reasons is our inability to accurately date terrestrial deposits that define ancient ice margins. The in situ accumulation of cosmogenic nuclides can be used to approach this problem. In this study, cosmogenic surface exposure dating methods will be used to reconstruct the history of the last arctic ice sheets. The main goals of the proposed integrated study are to provide clear evidence either for or against the existence of the Innuitian Ice Sheet in the late Quaternary, to reconstruct the history of the last ice sheets, from their birth until today, and to determine the duration of ice-free period before the last glaciation started. The investigation will obtain cosmogenic surface exposure ages for glacial deposits and polished bedrock in northwestern Greenland, eastern Ellesmere Island and several small islands between them, western Ellesmere and eastern Axel Heiberg Islands, Devon, Baffin, Cornwallis, Somerset, Bathurst, Prince Patrick and Ellef Ringness Islands. They will also obtain cosmogenic and radiocarbon ages for raised marine shorelines in order to reconstruct the history of sea-level changes at these locations. The results will provide the much needed chronologic control for the late Quaternary glaciations in arctic islands. The results will also have important implications for paleoclimatologic studies because of a possibility to establish whether or not there was a connection between the Arctic Ocean and Baffin Bay during the last glaciation.
This research is to measure the direction of polarization of the S-waves from local earthquakes recorded by most of the 12 three-component seismograph stations in the Alaska network. Emphasis will be placed on those stations where preferred mineral orientation is not likely to be responsible for the anisotropy. The derived stress directions will be compared to those estimated in previously funded NSF work based on inversion of fault-plane solutions. It is important to estimate stress directions from S-polarizations, where this can be done, because there is not enough information available concerning stress directions to understand the seismic hazard in central and southern Alaska. All stress direction estimates (from fault-plane solutions, volcanic dikes, hydrofracture and anisotropy) will be integrated to construct a seismotectonic model for central and southern Alaska. This research is a component of the National Earthquake Hazard Reduction Program.
This award supports a geophysical survey from a nuclear submarine during the operation of the SCICEX-95 cruise to the Arctic Ocean. The survey will result in a comprehensive map of bathymetry and gravity of the Chukchi Borderland and portions of the Lomonosov Ridge, Makarov Basin and Mendeleev Ridge. These areas are out of the normal operating range of aerogeophysics platforms, and data from the region that are available to western scientists are extremely sparse. The proposed survey is designed to test current hypotheses of the geologic structure and tectonic development of the main geographic features of the region. Whether or not the hypotheses prove to be true, the data will fill a conspicuous gap in the geophysical data coverage in the Arctic Ocean Basin. Hence, the data collected will be valuable in determining the geologic and tectonic structure of the region and, in turn, will also be useful for evaluating tectonic models for the development of the region.
The Canada Basin of the Arctic Ocean remains one of the least known regions of the Earth, yet understanding its evolution is important in understanding the history of ocean circulation and climate generation, as well as the fact that the Alaska margin of the Canada Basin contains one of the world's giant hydrocarbon fields. In order to complete the aerogeophysical coverage of the Canada Basin between the Alpha and Mendeleyev ridges and the Arctic Alaska/Canada and Far Eastern Siberia margins, two seasons of aerogeophysics are proposed. The three most important aspects of the proposed work are: (1) collect reconnaissance aerogeophysical data that will allow specific hypotheses to be formulated about the tectonic evolution of the Canada Basin of the Arctic; (2) combine the aerogeophysical data collected offshore with a high-resolution aeromagnetics survey of Arctic Alaska's continental shelf (these two datasets definitely should answer the question of the nature of the OceanContinent Boundary along Arctic Alaska); and (3) survey in detail, gravity over the Chukchi Plateau and onto the continental margin of what should be the buried North Chukchi Basin, to allow insight into the evolution of this margin. Present data does not allow reasonable interpretation of the evolution of this margin.
The aims of this continuing project are to: (1) characterize the chemical compositions of the pristine large rivers of Eastern Siberia and their fluxes to the Arctic Ocean; (2) investigate the factors controlling weathering rates in low-temperature environments as compared to those operating in similar geologic terrains in the Tropics; (3) constrain the effects that the large expansion of peri-glacial environments characteristic of the glacial maxima had on weathering fluxes; and (4) provide baseline data for the environment likely to be most impacted by future greenhouse warming. This work will provide insights into the biogeochemical effects that will result from the climatic and hydrologic changes to be expected from anthropogenic global warming. In addition, the results will allow estimates to be made of the effects of climatic deterioration (i.e., glacial maximum conditions) on global weathering fluxes, presently a topic of much controversy owing, mainly, to lack of data. Strong constraints will also be placed on the assumptions used in global climate models of the geologic past that invoke a pCO2-weathering feedback to stabilize the greenhouse effect. Extensive field work has been carried out in the basins of the Lena, Yana and Kolyma. Data from steams draining the igneous and metamorphic basement rocks of the Aldan Shield and Trans-Baikal Highland in the Lena headwaters give areal chemical fluxes comparable to those from the Guayana Shield in the drainage of the Orinoco, despite the fact that the latter has an annual average temperature that is ~50°C warmer and receives at least four times the amount of precipitation. While the chemical yields are comparable the severity of weathering, as indicated by Na/K ratios and the 87 Sr/86Sr values, is much less in the Siberian basins. In the Tropics weathering of basement is essentially complete, to kaolinite and gibbsite, but extremely sl ow, "transport limited." In cold climates frost action continually generates fresh reaction surfaces at all scales leading to essentially an "exposure limited" situation. In addition, rivers draining the complete range of sedimentary rock types give fluxes similar to those observed in lower latitudes (e.g., the large rivers of China). It is proposed to extend this work to the other important rivers of the region-the Anabar, Olenek, Indigirka and Anadyrs-and to make a complete characterization of the major, minor and trace element geochemistry and of the isotopic systematics of the dissolved and particulate organic carbon and nitrogen systems of the fluvial regimes in this unglaciated but cold-dominated environment.
Northern and central Alaska consist primarily of large blocks of continental crust that are locally overlain by oceanic crustal fragments. Gross similarities between them has led to speculation that they are all fragments of North America's continental margin. However, data to support or refute this hypothesis is particularly sparse in the Ruby terrane of central Alaska. This project will provide the necessary thermal and structural history of the area in order to reconstruct the subduction and exhumation events so that firm comparisons to other continental blocks can be made. Results should lead to a robust model of the Mesozoic paleogeography of the northern Cordillera and answer the questions of what the relative significance of strike-slip, thrust and extensional tectonics were in the history of the Ruby terrane, and also how it arrived at its current oblique angle to the regional trends in the northern Cordillera.
This project will conduct mapping and paleomagnetic studies of the East Greenland rifted margin along the northeast branch of the Atlantic Ocean, a uniquely uplifted and exposed area of rifted continental margin. The basaltic lavas of rifted margins are typically imaged on seismic reflection profiles as a series of seaward-dipping reflectors that record a progressive subsidence and flexure of the continental edge during the transition to sea floor spreading. Surface mapping will document the interaction of faulting and basalt intrusion, and the large fjords will afford natural cross sections of key parts of the major structures. The onshore data will be integrated with offshore data to provide a comprehensive view of the internal structure and composition of this continental margin. Logistical support is being provided by the Danish Geological Survey. The results of this project will provide a comprehensive view of the internal structure and composition of this continental margin, and will be applicable to other rifted margins in a variety of tectonic regimes.
The research bears on an outstanding issue of broad scientific interest: the rate of glacial erosion in a tectonically active area, and its implications for the development of mountain ranges as dictated by the interplay of tectonics, climate and erosion. The Bering Glacier section of the proposed study also promises to yield valuable new information on rapid glacial overriding of sediments and its implication regarding the dynamics of glaciers and the stability of calving glaciers. Objectives are to determine current erosion rates in the extensive (>5000 km2) and tectonically active region drained by Bering Glacier, including the Mt. St. Elias area with unsurpassed relief from sea level, by monitoring sediment accumulation in the proglacial Vitus Lake complex to examine considerable new data recently obtained by researchers in the fjords and inland passages of Southeast Alaska. These data promise to yield valuable information about Quaternary and Holocene sediment yields over a broad, heavily glacierized area that can be compared to longer term regional exhumation rates known to be high; to compile readily available data from other Southeast Alaska glaciers to improve the definition and understanding of factors controlling regional rates of glacial erosion and sediment transfer to fjords; to develop a quantitative framework for exploring the topographic and geodynamic implications of rapid glacial erosion and sediment transfer through a continuum mechanical model of crustal convergence coupled with a simple abstraction of erosion and sediment transfer by glaciers. The multifaceted research is deemed feasible, within the five-year proposed duration of the project. It is a group effort involving four established researchers and is founded on considerable data already available. It involves Lew Hunter of the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), and independently funded U.S. Geological Survey (USGS) researchers Bruce Molnia and Paul Carslon, as well as PI Bernard Hallet and research assistant Yann Merrand (both at the University of Washington). All members will participate in field work. The collective expertise of our team is ideally suited for the proposed work; it emanates from considerable field experience in fjords and coastal waters and on glaciers in Alaska, and from quantitative studies of glacial erosion and calving-margin processes, process geomorphology and geodynamics. We stress that the NSF resources requested herein strongly will be leveraged by the collaboration with the USGS and CRREL.
This award provides support to continue a cooperative research program between the University of AlaskaFairbanks, Michigan State University, the Yakut Science Center (Yakutsk, Russia) and the Northeast Interdisciplinary Scientific Research Institute (Magadan, Russia) which was initiated in 1990. The research program is interdisciplinary, using paleomagnetism, geochronology, geochemistry, seismology and structural geology to study the Mesozoic to Cenozoic tectonic history of northeas tern Russia from the edge of the Siberian platform up to, and including, the OkhotskChukotka volcanic belt (OCVB). The study area includes the zone of Mesozoic accretion of terranes of both Arctic and Pacific origins and the present-day plate boundary between North America (NA) and Eurasia (EU). So far, this cooperative project has detected an age progression among Mesozoic granites, identified a widespread paleomagnetic overprint in the northwestern Kolyma Structural Loop (KSL), and obtained previously published paleomagnetic data for the region. To expand understanding of the KSL, this project will focus on its southeastern end, where formations similar to those studied in the northeastern part of the loop turn from a southeasterly strike to a northeasterly one. This region also lies along the NA-OK plate boundary, and fault traces and seismically generated features are visible in low-resolution satellite images.
A multidisciplinary study of the Strand Fiord and related volcanics is planned to address several questions of Arctic tectonic evolution and global change, taking advantage of the exposed sections to obtain high-latitude paleomagnetic data. The following five questions will be addressed through the collection of new paleomagnetic, radiometric and geochemical data: (1) What is the exact age and duration of the Strand Fiord volcanics, and do these flood basalt correlate, as do others (Deccan and Siberian Traps), with a global extinction event? (2) What is the relationship between the Strand Fiord volcanics and the older Isachesen volcanics, and can any of these units be used to constrain the geomagnetic timescale? (3) What is the relationship between these volcanics and mantle plumes, such as Iceland, and a larger scale activity such as the "superplume?" (4) Can a paleomagnetic record from the Strand Fiord volcanics answer the Nares Strait problem? (5) Can the Strand Fiord volcanics provide geomagnetic paleointensity information for the Cretaceous Normal Polarity Superchron? The study of these geological and geophysical questions is linked through a common sampling scheme, the flow-by-flow sampling of long, continuous volcanic sections for paleomagnetic and geochemical analyses.
This award supports a project under the Earth System History (ESH) Program of the U.S. Global Change Research Program (USGCRP). The objective of this award is to improve the ability of models to simulate large changes in the Earth system and to understand the interactions and feedback among components of the system. The Earth's climate system with its vegetation, lakes, wetlands and oceans has changed dramatically in the past, and the data about these large changes provide "ground truth" for testing the accuracy of the Earth system models. The research team will develop an integrated equilibrium biosphere model, a lake/continental-hydrology model, and coupling procedures to link these models off-line to atmospheric general circulation models and an ocean general circulation model. A regional fine-mesh climate model will also be used for studying Earth system changes in regions of complex topography. With these coupled models, it will be possible to explore a wide variety of potential Earth system feedback including: (1) atmospherebiosphere interactions associated with boreal forest replacing tundra, or tropical savannah replacing desert; (2) atmosphere/land-surface-hydrology interactions associated with increases or decreases in the area extend of lakes and wetlands; and (3) atmosphere/ocean/terrestrial-vegetation interactions associated with changes in Arctic sea-ice, the North Atlantic thermohaline circulation and coastal and equatorial upwelling. Global paleovegetation and lake status data sets will be compiled for 6,000 and 21,000 years ago, and these data sets will be used along with data for ocean circulation and from previous interglacial data to make comparisons with the coupled earth system models.
The objective of this project is to make possible the participation of approximately seven researchers from the United States in the International Geological Congress ((IGC)). The 30th IGC will take place August 414, 1996, in Beijing, China. This venue will highlight the demands of massive populations and evolving economies on the resources of the earth and the environment. It also will offer unparalleled opportunities for U.S. scientists to learn about the unique geology of China and the progress made by Chinese geoscientists. The scientific contacts and new perspectives that U.S. scientists will find at the technical sessions and field trips of the (IGC) will be invaluable for advancing understanding of the dynamic earth system.
This grant provides $113,487 as one-half support of the costs of acquiring a stable isotope ratio mass spectrometer (SIRMS) with a dual inlet system and a Kiel device for automated carbonate sample introduction. The PI's research involves deciphering high-resolution records of climate change indicated by variations in the carbon and oxygen isotopic signatures recorded in biogenic carbonates including corals, foraminifera and mollusc shells. The primary focus of research to be conducted utilizing this mass spectrometer will be on analyses of the del 18-O recorded in massive, scleractinian coral skeletons as high-resolution indicators of variability in tropical sea surface temperatures. These corals grow rapidly and can live for periods as long as 800 years, and, thus, offer a unique, high-resolution record of climate variability over decadal-to-centurian time scales, and also can aid our understanding of coupled ocean-atmospheric systems, such as the El Niño/Southern Oscillation that has global significance in determining patterns of precipitation, and, thus, is relevant to worldwide agriculture and flooding hazard mitigation. To effectively and efficiently analyze the carbon and oxygen isotopic ratios recorded in biogenic carbonates a t sub-monthly resolutions requires a sensitive mass spectrometer capable of analyzing samples in the 100600 mg size range with high throughput. Analyses of upwards of 10,000 samples per year including sufficient replicates so as to ensure regional fidelity can be required for century-scale records. The inclusion of a Kiel device in this acquisition will allow unassisted and sequential sample introduction of up to 74 samples, thus allowing for nighttime operations which are essential for maintaining the high throughput necessary for these high-resolution studies.
This award supports a study of discontinuous permafrost in northern Alaska. Permafrost exists in arctic and subarctic regions where changes in climate are most likely to be largest and to occur first. Warm discontinuous permafrost will be the first to thaw in the event of any climatic warming. Climatic data indicate that Alaska is currently warming at a rate of about 2.4ºC per century. Data has been obtained which shows that the discontinuous permafrost south of the Yukon River in Alaska has recently warmed by as much as 1.5ºC and that some of it is already thawing. The objective of this research is to develop a better understanding of the response of discontinuous permafrost to changes in climate and human activities. The significance of permafrost in the context of climatic change studies is that permafrost can detect and record climatic changes in its thermal regime. In thawing, it can act as an agent of environmental changes that influences ecological and human communities, and it can amplify climatic change by feedback effects associated with the release of carbon stored in the permafrost. This research includes analyses and interpretations of an extensive long-term (18 years) data set obtained at more than a dozen sites representing a wide range of environmental conditions that span the discontinuous permafrost zone along a northsouth transect of Alaska, measurements of current conditions, and assessing changes that have occurred and those that are still occurring. Six sites will be instrumented to measure temperatures in the air and active layer, permafrost, moisture contents (including unfrozen water), thermal parameters, snow cover and active layer characteristics, and heave. Less detailed measurements will be made at eight other sites. This research also will include an investigation of temporal and spatial trends in the data, the flow of heat and moisture (including several existing hypotheses) and the application of an analytical model and of two existing numerical models for predicting the thermal regime and talik development in warm and thawing permafrost. A sensitivity analysis will be carried out on the effects of changes in climatic variables and active layer characteristics on the thermal regime of the discontinuous permafrost.
Deformation of water-saturated sediment (till) beneath glaciers may, in effect, lubricate glacier beds. Such deformation has been measured beneath a number of modern glaciers and also may have contributed to the fast flow of Pleistocene ice masses with a possibly profound effect on regional climate. Support is requested to study with a rotary (ring-shear) device that shears a water-saturated till sample. Because the device can deform a large sample to infinitely high strains, it can be used to test a much broader range of hypotheses than traditional soil testing devices. For example, it has been used successfully to study stress concentrations in shearing sediment and the consequent evolution of till grain size. Special features of the device allow continuous observation of the distribution of shear strain, measurement of local stresses normal to the direction of shear and isolation of wall effects. In experiments aimed at better understanding till rheology, both clay-rich and clay-poor tills will be sheared with the primary goal of determining the relation between deformation rate and the steady (residual) till strength. In some experiments the effective normal stress will be varied to investigate the role of transient pore-pressure gradients on the apparent till rheology. In a second set of experiments, the evolution of contacts, the preservation of structures (e.g., sublithified sand clasts) and the development of fabric will be studied to test field criteria for the identification of highly strained Pleistocene tills. In addition, grain communication will continue to be studied with the additional important goal of quantifying the progressive degradation of selected diatom species as a function of shear strain.
Permafrost is one of the primary components of the Arctic land-atmosphere-ice system. Recent unexpected discoveries of a large-amplitude temperature cycle in the permafrost and of large and systematic changes in active layer thicknesses (since 1986) indicate that the current understanding of climate-active layer-permafrost interactions needs improvement. These interactions are important because warmer air temperatures predicted in the Arctic from increases in greenhouse gases will cause permafrost to thaw as the active layer becomes thicker. A better understanding of the linkages between the atmosphere, soil surface, active layer and permafrost is required to answer questions regarding the rate and extent of permafrost degradation, modifications to its thermal regime, release of carbon and trace gases by thawing permafrost, changes in soil moisture, the biota, the hydrological cycle, how these changes will influence the use of polar lands and the development, calibration, and validation of small-scale numerical models (<2 km grids) of land-atmosphere interactions that are to be nested in larger scale models. A permafrost research program is proposed that combines field measurements, laboratory measurements and analyses and interpretation of data to be obtained at six long-term study sites along a transect from Prudhoe Bay across the coastal plain and foothills into the Brooks Range. These sites are in undisturbed areas, span a wide range of permafrost, climatic and environmental conditions, include drillholes in the permafrost (4 0 to 75 m in depth) and have a long-time series of data (since 1983).
The research supported by this award aims to take advantage of the recent discovery of information that describes the location and circumstances of late-19th-century soil samples from sites across Russia (across the East European Plain and in central and eastern Siberia). The study will: measure the accumulation of atmospheric contaminants in Russian soils by comparing the 1895 and 1996/1997 samples; measure the changes in soil carbon stocks; combine these analyses to assess the effect of climate and soil type on the presence of trace metals in the soil profiles; and provide data to constrain models of atmospheric emission of these elements during Russian industrialization. The samples have been carefully stored, and with the help of a pilot award from NSF (as well as some institutional and some personal funds), the PI has ascertained that 47 samples are in exceptionally good condition, and that the locational and attribute information is sufficient to locate and access the sites for current-day sampling. In addition, some of the sites are in environmentally protected or controlled locations. The PI has collected long-term weather records for some of the sites already. The current research will focus on four sites, which have been located exactly from the documentation of the original samples. Three of the sites have the same vegetative profile now as they did in the late 19th century. All four sites will be resampled, and all eight samples will be analyzed for organic matter, radiocarbon content, trace elements, base cations, pH and particular anthropogenic organic compounds. These data will be used to: measure the accumulation of radiocarbon and toxic metals, trace nutrients and other atmospheric inputs; model the rate and form in which these elements are processed in the different soils and ecosystems; and relate the storage, depth distribution and form of these constituents to climate and soil characteristics.