Marine and terrestrial geology and geophysics

Cretaceous-Paleogene foraminiferida of the Victoria Land Basin (Cape Roberts Project). Peter-Noel Webb, Ohio State University. We will characterize the foraminifera in drill core recovered during the Cape Roberts Project (CRP). As part of the CRP, investigators will drill four holes from a sea-ice platform in up to 500 meters of water in the southwest Ross Sea. Geophysical site surveys suggest that the four drill holes will provide an aggregate thickness of about 1,500 meters of core and span about 100 to about 30 million years (Cretaceous-Paleocene). This interval of geological time is not yet documented by in situ stratigraphic sections in either the Ross Sea or East Antarctica. The nearest comprehensive data sources for the Cretaceous and Paleocene occur in New Zealand, the northern Antarctic Peninsula and the southern oceans. We will use benthic and planktonic Foraminiferida from the core, together with data from other fossil groups, to provide on-site age and stratigraphic control as drilling progresses. Age correlations will be made with biostratigraphy from southern ocean sites where drilling was conducted during Deep Sea Drilling Project/Ocean Drilling Project cruises and also with New Zealand planktonic and benthic zonal/stage schemes. Our initial objective is to make a comprehensive accounting of foraminiferal material present and to document this in the project's initial report in order to assist others who are planning post-drilling investi-gations. Basic information to be recorded on the foraminifera include

These data will be used to address various geological problems. Disconformities and acoustic reflectors that extend across the rift system basins and are also expected to be encountered in the drill hole will be dated. Major basin subsidence/uplift trends resulting from compaction and/or rift-margin faulting will be deduced from benthic foraminiferal bathymetric indicators. We will use more subtle cyclicity in the stratigraphic distribution of benthic species to recognize and document phases of transgression and regression, which in turn may indicate a relationship between sea-level oscillation and terrestrial glacial events. During the Cretaceous-Paleocene, the final disintegration of Gondwanaland occurred, specifically the northward movement of New Zealand and Australia away from Antarctica. Foraminifera from the CRP drill holes will contribute to an understanding of the paleogeography and paleooceanography between the East Antarctic highlands and Pacific margin (the location of the proto-Transantarctic Mountains) and the West Antarctic rift system basins between this suspected island chain and the highlands of West Antarctica. This will help answer the question as to whether the marine margin of East Antarctica, near the planned drill holes, was located in a Cretaceous cul-de-sac or whether it occupied, at times, a position on a major oceanic circulation pathway between the southwest Indian, southwest Pacific, and southwest Atlantic Oceans. (S-049B)

Mapping and geodesy program. Jerry L. Mullions and Tony K. Meaner, U.S. Geological Survey. Accurate maps of Antarctica are essential for research and support of operational and logistical activities. They also provide a cartographic base for support of future antarctic scientific investigations and data collections. The U.S. Geological Survey (USGS) maps large portions of the continent to support U.S. research in Antarctica. Before publishing these maps, the USGS establishes geodetic control for topographic and satellite image-mapping at scales of 1:10,000 to 1:250,000.

USGS personnel will take aerial photography using airborne global positioning system (GPS) photogrammetry and geodetic surveys, operate GPS stations at various sites, support digital cartographic data applications, obtain absolute gravity measurement, and participate in the international GPS antarctic campaign. As part of the aerial photographic mapping program, we will photograph selected overland routes to South Pole Station, including the Leverett Glacier and Skelton Glacier. We will also do aerial-mapping photography in the Shackleton Glacier and McGregor Glacier areas in support of geologic research. Airborne GPS photogrammetry will provide mapping control for aerial photographs taken by a Wild RC-10 aerial mapping camera using the Twin Otter aircraft.

The GPS Continuous Operating Reference Station (CORS) will continue to operate year-round at McMurdo and Amundsen­Scott South Pole Stations. Data from these GPS base stations are used by other science groups to improve the accuracy of their GPS field observations. In addition, during the summer, we operate a CORS GPS receiver at the Crary Science and Engineering Center as a backup to the McMurdo system.

Digital cartographic data collection and application activities will continue both on and off the ice to support antarctic science. Applications will use data at scales ranging from 1:30,000,000 to 1:10,000. At McMurdo Station, USGS will provide access to the antarctic data through cooperative activities with individual scientists, production of graphic displays of selected research areas, data/analysis support to McMurdo logistic activities, and demonstrations of applications software packages with antarctic data.

Absolute gravity meter measurements will be obtained at McMurdo Station, Terra Nova Bay, along the McMurdo Dry Valley coast, and at one site inland along the coast. These measurements will be used to establish baseline gravity values in Antarctica. These data also support GPS technology by improving the vertical and horizontal geodetic control values.

The USGS maintains the U.S. Antarctic Map and Aerial Photography Collection at the USGS National Center in Reston, Virginia. This reference library is used by many antarctic scientists to obtain maps and aerial photographs used in planning their field activities each year. (S-052)

Tephrochronology applied to Late Cenozoic paleoclimate and geomorphic evolution of the central Transantarctic Mountains. David R. Marchant, University of Maine. Our project focuses on the geomorphic evolution of the McMurdo Dry Valleys. We will use isotopic ages and areal distribution of volcanic ash deposits to constrain the chronology and rates of landform development and to help quantify the age of geomorphic surfaces. The depositional setting and degree of weathering of the ash will help us to constrain regional paleoclimatic conditions during and after deposition of the volcanic ash. We will focus on the Quartermain Mountains, Asgard Range, Olympus Range, and McKelvey Valley because these regions are known to contain some volcanic ash deposits and because they contain a variety of geomorphic settings over a substantial elevation range. With the data collected in the field, we will attempt to test assumptions that underlie the hypothesis that the dry valleys region represents a relict, semiarid landscape that formed before the continental ice sheets developed during middle Miocene time and that subsequent slope modification has been limited to minor glacial scouring concentrated at valley heads, glacier confluences, and deep-valley troughs. Among these underlying assumptions are the following:

The isotopic-age information generated by this project will help constrain models of geomorphic evolution in cold-desert regions and will have implications for models of landscape development and uplift history of the Transantarctic Mountains. If the hypothesis of ancient semiarid erosion followed by minor glacial incision proves correct for the dry valleys region, then changes in base level, as defined by isotopically dated land surfaces in the McMurdo Dry Valleys, will provide a chronology of Late Cenozoic mountain evolution and uplift independent of thermochronological studies that have been completed. Answering these questions is important because the thermochronology studies, although well suited for determining long-term uplift rates, are not well suited for distinguishing early from Late Cenozoic uplift. The volcanic ash database developed during this study will also be useful for studies of the McMurdo volcanic province. (S-054)

Diatom biostratigraphy and paleoenvironmental history of Cape Roberts Project cores. David Harwood, University of Nebraska at Lincoln. This project will work to characterize the diatom fossils in drill core recovered by the Cape Roberts Project (CRP). The CRP is a major program within the international antarctic earth science community designed to sample antarctic continental margin strata of late Cretaceous through Paleogene age (30 million to 100 million years ago). Drilling operations will include continuous coring from a sea-ice platform at four sites on the flank of the Victoria Land basin in the western Ross Sea, during two drilling seasons. This particular project involves initial field-based paleontologic analysis of siliceous microfossils in Cape Roberts cores. Core sections will be ferried to the Crary Science and Engineering Center for immediate analysis. Diatoms and other siliceous microfossils will provide rapid age and paleoenvironmental information during drilling operations. Each season will include preparation of a preliminary biostratigraphic/ paleoenvironmental report based on siliceous microfossils. This report will become part of the CRP Initial Reports volume, which will include the preliminary results from other microfossil groups, lithostratigraphic, magnetostratigraphic, and other analyses.

Analysis of diatoms and other siliceous microfossils in CRP cores will greatly aid in the development of an integrated biostratigraphy for this poorly known interval in the southern high latitudes. Diatoms will provide evidence of, for example, environmental changes in water depth, primary productivity, and the presence or absence of sea ice. CRP cores will provide an excellent opportunity to study adaptation of diatoms to strong polar seasonality and diatom evolution. By integrating CRP studies with ongoing studies of Paleogene siliceous microfossils in Arctic strata (for example, Ocean Drilling Program Leg 151), the CRP cores will also offer the possibility of gaining a bipolar perspective on Paleogene high-latitude phytoplankton evolution. (S-051)

Downhole logging for the Cape Roberts Project. Richard Jarrard, University of Utah. Continuous-core and downhole logging will be done at the four planned Cape Roberts Project (CRP) scientific drill holes. The goal of CRP is to study the Early Tertiary and Cretaceous record of climate, tectonics, and sea-level change and to determine the time of onset of antarctic glaciation. Geophysical well logs will be converted into continuous records of variation, and these records can be interpreted as indicating variations in mineralogy and porosity. The detailed one-dimensional records at each hole will be integrated with available high-resolution seismic data to produce a two-dimensional interpretation of the stratigraphy. This geophysical logging program is an essential component of basic characterization of the drill site and is a fundamental part of the effort to produce a stratigraphic framework for interpretation of other scientific work on the core. (S-055)

Calcareous nannofossil biostratigraphy and paleoenvironmental history of Cape Roberts Cores. David K Watkins, University of Nebraska at Lincoln, and Sherwood Wise, Florida State University. The Cape Roberts Project (CRP), a major program within the international antarctic earth science community, is designed to sample the stratigraphic record, which spans the time interval 30 to 100 million years ago, by drilling four sites on the flank of the Victoria Land basin. Our effort focuses on basic characterization of calcareous nannofossils as part of the development of the biostratigraphic framework for drill core recovered during the project and will support the drilling program by providing rapid-age and paleoenvironmental information through the study of calcareous nannofossils. To accomplish this, we will systematically sample the recovered sedimentary cores and analyze their calcareous nannofossil content at the Crary Science and Engineering Center at McMurdo Station, Antarctica. Initial reports volume to be prepared at the end of each of the two drilling seasons will include the results of this work as part of the initial characterization of the cores. The calcareous nannofossil biostratigraphic record spans the entire interval to be cored during CRP. Recent work on calcareous nannofossils from ocean drilling sites around Antarctica has yielded a refined zonation for the Paleogene and Upper Cretaceous of the southern oceans that will provide a high-resolution biostratigraphic framework for hemipelagic and pelagic sediments recovered by Cape Roberts drilling. Data from this research, when combined with other fossil data, magnetostratigraphic data, and other age-dating methods, will provide integrated age control that is essential for other geological investigations. In addition, calcareous nannofossils are excellent paleoenvironmental indicators for surface-water temperature and productivity. We will use statistical analysis of quantitative population census data to infer paleoenvironmental variations during the Paleogene and Cretaceous. These data, in combination with data from other fossil groups and sedimentological studies, will be useful for assessing climate change during the critical period of 30-100 million years ago. (S-057)

Antarctic search for meteorites. Ralph Harvey, Case Western Reserve University. The Antarctic Search for Meteorites (ANSMET) will continue during the 1997­1998, 1998­1999, and 1999­2000 austral summer field seasons in Antarctica. Since 1976, ANSMET has recovered more than 7,800 meteorite specimens from locations along the Transantarctic Mountains.

Over the next 3 years, systematic searches will be conducted in regions known to contain meteorites, and reconnaissance work will be conducted to discover new concentrations. During the 1997­1998 field season, work will be done in the Pecora Escarpment-LaPaz Icefields region, where several small icefields remain unsearched and earlier reconnaissance located significant concentrations. During the 1998­1999 field season, the southern Walcott Névé region will be visited, where more than 1,500 meteorites have already been recovered and many more remain. During the 1999­2000 field season, several icefields in the Dominion Range-Grosvenor Mountains-Scott Glacier region will be visited, where previous reconnaissance and incomplete systematic searching promise significant meteorite recoveries.

Antarctica is the world's premier meteorite hunting ground for two reasons.

Continued recovery of antarctic meteorites is important for several reasons. ANSMET samples

Maestrichtian land mammals of Vega Island, Antarctic Peninsula. Michael Woodburne, University of California at Riverside. The Maestrichtian is considered to have been a key interval in the development of the land mammal fauna of southern Gondwanaland from Australia to Antarctica and South America. Until now, no Maestrichtian fossil land mammals have been found in any of these continents. The Lopez de Bertodano Formation of Vega Island, Antarctic Peninsula, shows the best potential of yielding remains of land mammals of Maestrichtian age in any southern Gondwanaland location. This project is designed to grasp that opportunity as a collaborative venture between St. Mary's University, University of California at Riverside, and Argentine scientists.

Current theory predicts that the presently unknown Maestrichtian-age land mammal fauna in Antarctica should consist of

Investigators will test this hypothesis in terms of the composition of the Maestrichtian land mammal fauna by conducting field research on Vega Island of the James Ross Island basin, Antarctic Peninsula. The location has been chosen on the basis of its known productivity in yielding Maestrichtian-age vertebrates (presbyornithid birds and hypsilophodont dinosaurs) in near-shore fine-grained shallow-water marine sandstones of the Lopez de Bertodano Formation that are amenable to dry or wet sieving collecting methods. Such methods have proven successful in obtaining fossil mammals from similar facies in the medial Eocene La Meseta Formation of Seymour Island. (S-061)

Initial Characterization of Organic Matter in Cretaceous-Paleogene Sedimentary Rocks, Cape Roberts, Antarctica. Richard M Kettler, University of Nebraska at Lincoln. Our project focuses on organic geochemical characterization of Cretaceous-Paleogene sedimentary rocks to be recovered during the Cape Roberts Project (CRP). The CRP proposes to core four 500-meter holes from a fast ice drilling platform in the Ross Sea. The core recovered will be described, curated, and sampled for scientific re-search. The CRP has the potential to answer significant questions regarding the history of the West Antarctic rift system, the development of continental ice sheets in Antarctica during the Cretaceous and Paleogene, and the response of biota to climatic deterioration and the development of seaways. Because organic geochemical measurements are relevant to these issues, they are included in the initial core characterization studies. Our will include measuring whole-rock carbonate carbon, total carbon, total nitrogen and total sulfur; analyzing the elemental composition of kerogen in selected samples; and using gas chromatographic analysis of the solvent-soluble organic matter in selected samples. These data will be collected in the Crary Science and Engineering Center (CSEC) at McMurdo Station and will be reported as part of the initial core characterization study of the CRP. (S-064)

Thermal and fluid state of the lithosphere beneath South Pole region, East Antarctica, from magnetotelluric measurements. Philip Wannamaker and John Stodt, University of Utah. Our objective is to extend knowledge of the thermal and physico-chemical state (fluids, melts) of the deep crust and upper mantle of Antarctica with magnetotelluric (MT) geophysical profiling of the South Pole area. In the MT method, temporal variations in the Earth's natural electromagnetic (EM) field are used as source fields to probe the electrical resistivity structure in the depth range of 1 to 100 kilometers or more. The effort will consist of about 16 sites over a length of 90 kilometers, offset from South Pole Station a few kilometers and oriented grid NE-SW, normal to the Transantarctic Mountains (TAM). The method will test the cratonic character of the lithosphere of this part of East Antarctica to depths of 100 to 150 kilometers and compare its resistivity structure with that imaged in central West Antarctica (CWA) by the same research group. Second, there has been only one successful broadband MT campaign in the antartctic interior. Conditions around South Pole differ from those at CWA, and this project should make MT surveying more feasible over the entire continent. Third, the results will provide the crustal response baseline for possible long-term MT monitoring to lower mantle depths at South Pole. (S-068)

Initial sedimentological characterization of the Late Cretaceous-Early Cenozoic drill cores from Cape Roberts, Antarctica. Lawrence Krissek, Ohio State University. An international initiative to collect 1,500 meters of drill core from offshore of Cape Roberts, McMurdo Sound, Antarctica, is intended to provide a better understanding of antarctic history through the late Cretaceous and early Cenozoic. Events during this period, which extends from before the final breakup of Gondwanaland through the onset of antarctic glaciation, are ill-defined by existing data. The Cape Roberts Project (CRP) aims to provide new data about the development of the west antarctic rift system, the subsidence history of the Ross Sea, and ice-sheet fluctuations on Antarctica through this critical time interval.

CRP is partly an extension of previous drilling efforts on the antarctic continental margin and is partly a new initiative to document more completely the developmental history of the Ross Sea sector of the Antarctic and southern Pacific region through the late Cretaceous-early Cenozoic. It will draw on the successes of previous drilling efforts to document regional and environmental development with good spatial and temporal resolution, and it will also draw upon newly compiled geophysical databases.

CRP is a collaborative endeavor and is currently being supported by six participating countries. Tasks involved in this segment of the project will include initial description and characterization of the stratigraphic successions; these results will be used as the fundamental database for other analyses. The stratigraphic sections will also be used as reference sections for modeling observed marine and geophysical events. Initial sedimentological characterization of the successions will allow the definition of facies, the construction of facies sequences, and the interpretation of depositional environments through time. The end result of the proposed work will be an Ocean Drilling Program-style initial report for each drilling season. These reports will include the stratigraphic log, initial facies and depositional system interpretations, sedimentary petrologic and petrogenetic analyses, and initial clay mineralogical analysis. Information provided by other specialists will also be included in the reports, including biostratigraphy, magnetostratigraphy, geophysical logs, and geochemical interpretations. The initial interpretations of regional history will be presented in these reports, and the regional and global ramifications of this history will be highlighted. (S-070)

Holocene paleoenvironment change along the Antarctic Peninsula: A test of the bipolar/solar signal. Eugene Domack, Hamilton College. This project is a multi-disciplinary, multi-institutional effort to elucidate the detailed climate history of the Antarctic Peninsula during the Holocene epoch (the last 10,000 years). The Holocene is an important, but often overlooked, portion of the antarctic paleoclimatic record because natural variability in Holocene climate on time scales of decades to millennia can be evaluated as a model for our present "interglacial" world.

This project builds on over 10 years of prior investigation into the depositional processes, productivity patterns, and climate regime of the Antarctic Peninsula. This previous work identified key locations that contain ultra-high-resolution records of past climatic variation. These data indicate that solar cycles operating on multicentury and millennial time scales are important regulators of melt water production and paleoproductivity. These marine records can be correlated with ice-core records in Greenland and Antarctica.

This project will focus on sediment dispersal patterns across the Palmer Deep region. The objective is to understand the present links between the modern climatic and oceanographic systems and sediment distribution. In particular, additional information is needed regarding the influence of sea ice on the distribution of both biogenic and terrigenous sediment distribution. Sediment samples will be collected with a variety of grab sampling and coring devices. Two additional objectives are the deployment of sediment traps in front of the Muller Ice Shelf in Lallemand Fjord and seismic reflection work in conjunction with site augmentation. The goal of sediment-trap work is to address whether sand transport and deposition adjacent to the ice shelf calving line results from melt water or aeolian processes. In addition, the relationship between sea-ice conditions and primary productivity will be investigated. The collection of a short series of seismic lines across the Palmer Deep basins will fully resolve the question of depth to acoustic basement. (S-072)

Paleomagnetic and mineral magnetic characterization of drill cores from the Cape Roberts Project. Kenneth Verosub, University of California at Davis. The goals of the Cape Roberts Project (CRP) are to elucidate the history of fragmentation of the Pacific margin of Gondwanaland and the history of antarctic glaciation from Cretaceous through Oligocene time. The CRP will operate with an integrated science plan in which all of the initial scientific characterization of the cores will be done at McMurdo Station during two drilling seasons over two successive years. The drilling seasons will each be 2 months long and will operate in much the same manner as 2-month cruises of the Ocean Drilling Program. The scientific activities associated with characterization of the cores will include magnetostratigraphy, biostratigraphy, petrography, mineralogy, and sedimentology. Age determination is of principal importance in such a project because a temporal framework is necessary to obtain a history of climatic and tectonic events.

This research will determine high-quality paleomagnetic stratigraphy, with the appropriate mineral magnetic studies, in support of the CRP. For the on-site magnetic studies, this project will

Detailed environmental and mineral magnetic studies will also enable evaluation of the sediments as recorders of the geomagnetic field. The Cape Roberts records provide the potential to obtain rare high southern latitude constraints on geomagnetic field behavior. Paleomagnetic studies should also provide important data concerning crustal movements and rift development in the Ross Sea sector. (S-075)

Jurassic floras of the Carapace Nunatak area: Evolution and paleoclimatic significance. Thomas Taylor, University of Kansas. This project will systematically collect and analyze the Jurassic fossil floras from three levels at Carapace Nunatak in southern Victoria Land and will complete reconnaissance for similar-aged deposits at Shapeless Mountain near the head of Wright Valley. These floras represent the most extensive deposits of Jurassic fossil plants that are known from the continental portion of Antarctica. They are poorly known, both from a biostratigraphic and floristic standpoint and, as such, are important not only to our understanding of floral changes in Antarctica but also to correlations with other Gondwanaland continents. In addition to impressions and compressions, the site also contains permineralized specimens. In this rare preservation type, cells and tissue systems are intact so that details about the anatomy and morphology of these Jurassic plants can be evaluated. The preservation of the permineralized floral elements at Carapace is identical to those of Permian and Triassic age that have been studied over the past 10 years. As a result, a continuum of structurally preserved plant fossils extending from the Permian into the Upper Jurassic of Antarctica is available for examination. In this context, it will be possible to examine details of seed plant growth, development, and evolution at high paleolatitudes during the latter stages of the Paleozoic and extending into the Jurassic.

The few specimens collected during an earlier reconnaissance at Carapace Nunatak suggest a flora rich in conifers and seed ferns. The conifer components will be important in evaluating basal character states within the major conifer families, whereas the seed ferns will be useful in evaluating the characters and relationships of these Mesozoic gymnosperms to the geologically younger flowering plants. The site also contains some woody specimens (small twigs, fragments of wood), in which the tree rings will be analyzed and compared with those from other high latitude sites, both older (Permian and Triassic) and younger (Cretaceous and Tertiary). (S-076)

Dry valleys seismograph project. Bob Reynolds, U.S. Geological Survey. The dry valleys seismograph project was established in cooperation with the New Zealand Antarctic Program to record broadband, high-dynamic-range digital seismic data at a remote site removed from the environmental and anthropogenic noise on Ross Island. The Wright Valley offers one of the few locations on the continent where bedrock can be accessed directly. The station consists of a triaxial broadband borehole seismometer at 100 meters depth and a vertical short-period instrument at 30 meters depth. These data are digitized at the remote location and then are radio-frequency telemetered via repeaters on Mount Newell and Crater Hill, eventually to the recording computer located in the Hatherton Laboratory at Scott Base. Although archived at Scott Base for backup purposes, the data do not stop flowing at this point. The data pass via a point-to-point protocol link to the Internet at McMurdo Station and then on to the Albuquerque Seismological Laboratory for distribution to the seismological community. This year's objectives are to refuel the remote station and the repeater site and to continue to enhance the performance of the radio link. Extra effort will go into the overhaul of the thermoelectric generators this season to improve their reliability over past seasons. This data set has beautifully complemented the data from the other seismic stations that the Albuquerque Seismological Laboratory operates on the antarctic continent at Amundsen-Scott South Pole Station, Palmer Station, and, next season, the Australian station, Casey. (S-078)

Stress field history, Cape Roberts, Antarctica. Terry Wilson, Ohio State University. This collaborative research program will obtain the first age-calibrated stress-field history within the west antarctic rift system of Antarctica. The opportunity to acquire the stress data is provided by the international drilling program planned at Cape Roberts, which is located along the margin between the uplifted Transantarctic Mountains and the rifted crust of the Victoria Land basin. Information on the paleostress history of the Mesozoic and Cenozoic rift-basin fill will be obtained from the core and downhole logging of natural fractures and faults.

To establish the contemporary stress state, the cores will be examined for coring-induced stress fractures and the borehole will be examined via downhole televiewer and dipmeter for any wellbore breakouts and fractures reactivated by the contemporary stress field. The stress data will be analyzed to address questions relevant to the paleo- and neotectonic evolution of the antarctic plate. The results will contribute to the resolution of outstanding questions such as the cause of the anomalous aseismicity of the continent, the geometry of stresses along the lithospheric boundary between the Transantarctic Mountains and the west antarctic rift system, and the evolution of the antarctic intraplate stress field and its relation to rifting episodes associated with Gondwanaland breakup. Contemporary stress data obtained from this research will be added to the global stress database and will help to fill the current void in the global stress coverage marked by the antarctic plate. (S-079)

Initial palynological characterization of Cape Roberts drill cores. John Wrenn, Louisiana State University. The Cape Roberts Project (CRP) is designed to core submarine deposits in the western Ross Sea that range in age from middle Late Cretaceous to early Miocene. Four 500-meter-long drill cores will be taken from a platform of annual sea ice floating in water depths ranging from 100 to 500 meters. The cores will sample a composite stratigraphic section 1,500 meters thick during two 45-day drilling seasons.

Shipboard geophysical surveys have identified a package of dipping sedimentary strata interpreted to be Cretaceous-Miocene. A thin blanket of younger sediments overlies these beds. Rocks of this age range are not known from the Ross Sea, the Transantarctic Mountains, or elsewhere in East Antarctica. Thus, recovered sediments of this age have prime importance for interpreting antarctic geologic, biologic, climatic, and tectonic history during the Cretaceous-Cenozoic. Objectives of CRP include

Core description and downhole experiments will be conducted at each drill site. An international team of biostratigraphers, sedimentologists, magnetostratigraphers, petrologists, and others will conduct initial characterization of the cores and their constituents during and immediately following drilling.

Palynomorphs have proven to be invaluable tools for biostratigraphic and paleoenvironmental interpretation of younger Ross Sea sequences drilled in the Ross Sea embayment. They include both marine (dinocysts) and nonmarine (spores, pollen) types, record extensive and diverse geologic information, and are preserved in a wide variety of lithofacies formed in various paleoenvironments. This project will provide initial palynological characterization of the CRP drillcores in collaboration with New Zealand palynologists. Analyses will focus on providing palynological input for an integrated biostratigraphic and paleoenvironmental framework based on all microfossil groups present. This critical framework is of fundamental importance to all future geologic, geophysical, and paleontologic studies conducted on the cores and in the drilling area. (S-080)

Mount Erebus Volcano Observatory. Philip R. Kyle, New Mexico Institute of Mining and Technology. Mount Erebus, the most active volcano in Antarctica, has been in a continuous eruptive state throughout the 20th century. The volcano is unique because it contains a persistent, convecting lava lake composed of highly alkalic anorthoclase phonolite magma. During the time that the volcano has been observed, eruptive activity from the lava lake and adjacent vents has consisted of minor strombolian eruptions that rarely eject volcanic bombs to heights exceeding 500 meters. Recent work has also shown that Mount Erebus is an important source of aerosols to the antarctic atmosphere and most likely contributes significant quantities of chlorine, fluorine, and other trace components to the snow falling on the east antarctic ice sheet. These data have important consequences for chemists who are trying to decipher paleoenvironments from snow and ice-core analyses. Our objective is to continue seismic observations using the Mount Erebus Volcano Observatory at McMurdo Station. Year-round observations using eight seismic stations on Mount Erebus and one at McMurdo Station allow near real-time observations of the ongoing volcanic activity. Additional observations of the gas emissions and surveillance of the activity from an observatory near the summit of Mount Erebus will expand scientific understanding of the degassing behavior of this "open vent" volcano. Radiometric dating of lava erupted from Mount Erebus will contribute to an understanding of the development of the volcano. (S-081)

Global Positioning System (GPS) measurements of crustal motion in Antarctica. Carol A. Raymond, Jet Propulsion Laboratory. The objective of this project is to establish a Global Positioning System (GPS) geodetic network in the Transantarctic Mountains to measure vertical and horizontal crustal velocities. The vertical crustal velocities measured by GPS reflect the viscous, elastic response of the solid earth to antarctic deglaciation. We will use data from this GPS network to test models of late Pleistocene-early Holocene versus late Holocene deglaciation of Antarctica. These data will also help constrain the length of time over which the antarctic ice sheet disintegrated and the distribution of the peak glacial load. A mid-Holocene deglaciation model produces a predicted uplift pattern near the Transantarctic Mountains that we can measure using high-precision GPS geodetic measurements within a 4-year period. We will also measure horizontal deformation induced by rebound to help constrain present-day changes in antarctic ice mass by monitoring the elastic deformation of the lithosphere resulting from ongoing glacial loading and unloading. The lithospheric response to ongoing ice mass changes is predicted to be an order of magnitude less than the viscoelastic response to late Pleistocene-Holocene deglaciation. Tectonic uplift rates are also predicted to be small compared to the predicted rebound signal for this region. Baselines across faults in the Transantarctic Mountains may capture co-seismic motion if an earthquake or a seismic slip were to occur. (S-082)

Timing of retreat of the west antarctic ice sheet. John B. Anderson, Rice University. Our objective is to examine the timing of ice-sheet grounding and retreat from the continental shelf in the Ross Sea region during the past glacial episode. This type of analysis is needed to improve the understanding of the past behavior of the ice sheet and to provide an important basis for testing glaciological models that attempt to predict the future behavior of the ice sheet­for example response to global warming and subsequent sea-level rise. To accomplish this objective we will acquire a variety of different data sets. High-resolution seismic data acquired with air guns will provide a stratigraphic framework for recognizing deposits of the last glacial maximum. Very high-resolution seismic records acquired with both hull-mounted and deep-towed chirper systems will enable us to link cores to seismic data; these systems provide stratigraphic resolution on the order of tens of centimeters. Sediment cores provide sample material for dating glacial events and for establishing the source of ice that grounded on the continental shelf. The multibeam system provides direct images of features formed at the base of the ice sheet when it was grounded on the continental shelf, such as glacial furrows and drumlins. These features provide information about flow direction of former ice streams and the extent to which deformation of the bed on which the ice sheet rested contributed to ice sheet flow and retreat. (S-083)

The GPS campaign to measure rock motion in the Transantarctic Mountains and related volcanics. Ian Whillans, Ohio State University. In close cooperation with the U.S. Geological Survey, we will begin taking global positioning system (GPS) measurements of rock motion in southern Victoria Land and nearby areas. We will use the results to test some of the leading models for ice-sheet change and tectonic movement, particularly whether the continent is rebounding because of reduced ice load from East or West Antarctica and whether Terror Rift or Transantarctic Mountain uplift is producing tectonic motion. A modest program to measure ice motion will be conducted as well. Our objective is to test models for ice flow in the Allan Hills meteorite concentration region and to determine whether small glaciers in the McMurdo Dry Valleys are thickening or thinning. We will set monuments into rock and ice and will use GPS receivers to determine their locations. Measurements will be taken again in later years to determine further motion. (S-084)

Scotia Arc Global Positioning System project. Lawrence A. Lawver and Ian W. Dalziel, University of Texas at Austin. Antarctica is Earth's most isolated continent. It is surrounded by actively spreading ridges except in the South American sector. The motion of South America with respect to Antarctica is latitudinal and left-lateral at approximately 22 millimeters per year and is distributed along the boundaries of the intervening Scotia Plate. A prominent but discontinuous bathymetric high, known as the Scotia Ridge, surrounds the Scotia Plate on three sides. This feature includes some continental material detached from South America and Antarctica, but its eastern closure is a volcanically and seismically active group of islands, the South Sandwich Arc, which is separated from the Scotia Plate by a vigorously spreading back-arc ridge. The entire east-closing, locally emergent bathymetric feature joining the two continents, is known as the Scotia Arc. The D-shaped Sandwich Plate and Arc appear to be moving rapidly east with respect to both South America and Antarctica, thereby for the first time introducing a subduction system into the otherwise rift-bounded South Atlantic Ocean basin. This motion may constitute the best evidence for mantle return flow from the closing Pacific Ocean basin to the expanding Atlantic Ocean basin. The Scotia Arc is nonetheless one of the most poorly constrained of the major tectonic systems on Earth, although it is a critical and enigmatic link in global plate-motion circuits.

The Scotia Arc GPS Project (SCARP) will use the global positioning system (GPS) to measure the plate motions between South America, Antarctica, and Africa and around the Scotia Arc using a newly developed geodetic strategy known as a multimodal occupation strategy (MOST). This strategy involves setting up permanent GPS receivers at a small number of sites in South America and Antarctica and using additional receivers to position numerous stations relative to this continuously operating network. Two seasonally occupied stations in the South Sandwich Islands will be tied to permanent GPS sites in South America, Antarctica, and Africa, and to intervening stations in the Falkland, South Georgia, and South Orkney Islands, which British collaborators will occupy occasionally. During the initial 3 years, the South Sandwich arc motion will be easily resolved. Using roving stations in the Antarctic Peninsula/South Shetland Islands area, we should be able to determine if extension is occurring across Bransfield Strait.

We will also construct a relatively dense subnetwork in Patagonia/Tierra del Fuego and a moderately dense subnetwork in the Antarctic Peninsula network. Although we do not expect these subnetworks to achieve submillimeter-per-year velocity resolution in the initial 3-year project, we will be able to establish the baseline necessary for a follow-on suite of measurements in perhaps 6 to 8 years. The follow-on project will allow characterization of the slow motions and deformations that occur across and within the boundaries of the Scotia Plate.

The objectives of SCARP are to determine

The results of these objectives in turn will

IRIS: Seismology at the South Pole and Antarctic Peninsula. Rhett Butler, Incorporated Research Institutions for Seismology (IRIS). The IRIS Global Seismographic Network (GSN) operates two stations in Antarctica­SPA at Amundsen­Scott South Pole Station and PMSA at Palmer Station. Both SPA and PMSA provide key seismological coverage in the Southern Hemisphere and are critical stations in the GSN. Located on Earth's rotational axis, SPA is uniquely situated to measure long-period oscillations of the Earth without the effects of rotational splitting of modes. The Antarctic Peninsula station has a unique vantage for studies of the tectonics and seismicity of the Peninsula, South America, Scotia Sea, and Drake Passage. Near real-time access to the data is important to the seismological community. IRIS, a nonprofit consortium of 87 U.S. universities, creates and manages research facilities for seismology. Currently, it provides funding to the University of California at Los Angeles to operate a long-period gravimeter at the South Pole. IRIS operates the SPA and PMSA seismic stations in cooperation with the Albuquerque Seismological Laboratory of the U.S. Geological Survey. (S-090 and S-091)

Collaborative investigation of earliest crayfish: Paleobiologic, paleoecologic, and paleoclimatic implications. John Isbell, University of Wisconsin at Milwaukee; Molly Miller, Vanderbilt University; Loren Babcock, Ohio State University. During the 1995­1996 austral summer field season, the oldest known fossil crayfish and one of the oldest known occurrences of fossil crayfish burrows were found in the Shackleton Glacier area of Antarctica. This collaborative, interdisciplinary study will expand on these discoveries.

The crayfish claw was found in the Upper Carboniferous to Lower Permian Pagoda Formation deposited in glacial environments 280 to 300 million years ago. The discovery pushes back the first occurrence of crayfish 65 to 75 million years. The crayfish burrows were found in the Lower Triassic Fremouw Formation deposited approximately 240 million years ago. Their abundance and complexity indicate that crayfish developed burrowing behavior early in their long history. The objectives of the study are to collect additional crayfish body and trace fossils from Antarctica, to use these fossils to develop further insight into the depositional conditions in parts of that continent during intervals of the Late Carboniferous-Early Permian and the Early Triassic, and to study the early evolutionary and burrowing history of freshwater astacoid decapods (crayfish). Specifically, the work plan is

This study will elucidate the evolutionary and behavioral history of crayfish. Modern crayfish exert an important control on parameters such as energy flow, biotic species composition, and biotic abundance in many different aquatic ecosystems. This study will yield information about how and when this environmental and behavioral diversification took place, as well as increase understanding of the late Paleozoic and early Mesozoic paleoclimates. (S-094)

Contrasting architecture and dynamics of the Transantarctic Mountains. Robin Bell, Columbia University. Continental extension produces a great variety of structures. The cause of variable rift width and crustal thinning is fairly well explained by variable initial heat flow and crustal thickness. Mechanical stretching of the lithosphere has been linked to rift shoulder uplift, but the cause of variable rift flank uplift remains poorly understood. The Transantarctic Mountains are an extreme example of rift flank uplift, extending over 3,500 kilometers across Antarctica and reaching elevations up to 4,500 meters and thus constituting a unique feature of Earth's crust. The range was formed in the extensional environment associated with the Mesozoic and Cenozoic breakup of Gondwanaland. Geological and geophysical work has shown that the Transantarctic Mountains developed along the long-lived lithospheric boundary between East and West Antarctica reactivated by a complex history of extensional and translational microplate motions.

The motivation for studying the Transantarctic Mountains is to try to understand the geodynamics of their extreme elevation rift flank. Are the geodynamics of the area unique, or does the history of glaciation and related erosion contribute to the extreme uplift? Using the existing data sets, researchers find that it is difficult to be confident about constraining the geological architecture across representative sections of the Transantarctic Mountains. Any effort to refine geodynamic mechanisms requires this basic understanding of the Transantarctic Mountains architecture. The goal of this project is to

This project will allow development of a generalized framework for understanding the development of rift flank uplift as well as address the question of the specific geodynamic evolution of the Transantarctic Mountains. (S-095)

A broadband seismic experiment for study of the tectonics and structure of the Antarctic Peninsula and Scotia Sea regions. Douglas Wiens and Dapeng Zhao, Washington University. The present-day tectonics and seismological structure of the Antarctic Peninsula and Scotia Plate region are among the most poorly understood of any location in the world. This region offers a unique and complex geodynamic setting, as illustrated by the recent cessation of volcanism along the South Shetland Trench and onset of volcanism and rifting in the Bransfield Strait, the possible presence of diffuse deformation and/or microplates in the Drake Passage region, and fast back-arc spreading behind the South Sandwich Arc. Our project is the U.S. component of an international effort to study the seismotectonics and seismic structure of the Antarctic Peninsula and Scotia Sea regions by using a large-scale deployment of broadband seismographs beginning during the 1996ñ1997 field season. We will deploy nine broadband PASSCAL seismographs for 2 years in the Antarctic Peninsula region, southernmost Chile, and South Georgia Island. Our research addresses the following questions:

Answering these questions will help to constrain important tectonic questions such as what causes plate motion changes, what processes initiate back-arc spreading, and what is the relationship between mantle flow and surface tectonics? (S-097)

Transantarctic Mountains aerogeophysical research activities (TAMARA). Terry Wilson, Ohio State University, and Carol Finn, U.S. Geological Survey, Denver. As part of the TAMARA program, we will conduct aeromagnetic surveying over the Transantarctic Mountains in the McMurdo region. Ground-based gravity measurements will be made near the Skelton Neve camp as time permits. The aeromagnetic data will be integrated with a GIS to be constructed as part of this program (geophysical and geologic data sets and satellite imagery) to obtain a comprehensive model of the Transantarctic Mountains architecture and evolution. The science objectives of this project focus on

Antarctic network of unattended broadband integrated seismometers (ANUBIS). Sridhar Anandakrishnan, Pennsylvania State University. The antarctic crust and mantle composition and geometry are poorly known. The primary methods for studying the crust, upper mantle, and the deeper asthenosphere is interpretation of seismic data: either by "active" methods acquired through use of explosives or by "passive" means, using natural sources and interpreting various earthquake phase arrival times and amplitudes. Integrating passive and active seismology can result in efficient use of resources to produce detailed images of the lithosphere. This project will develop a passive seismic network for the antarctic interior.

The Antarctic is a gaping hole in the rapidly improving field of global seismic imaging and tomography. On this huge continent (surface area of 14 million square kilometers), there are only eight broadband seismic observatories. Further, with the exception of South Pole, all of those stations are along the margins of the continent and none are in West Antarctica. By contrast, there are 200 permanent stations worldwide in the FDSN (Federation of Digital Seismograph Networks) and on the order of 1,000 in national networks not yet integrated into the FDSN.

This project will develop and deploy 11 long-term broadband seismic stations on the continent itself. Because 98 percent of the continent is ice covered, these stations will be installed at the surface of the ice sheet. The body-wave data thus recorded from regional and teleseismic earthquakes can be analyzed at each station for local crustal thickness, lamination, Poisson's ratio (a measure of crustal composition), crust and mantle anisotropy (a measure of current and former stress regimes), and identification of rift zones and crustal block boundaries. In addition, the data from all the stations (including the existing peripheral ones) can be used for seismic tomographic analysis to detail lateral variations in these properties. Six of the stations will be installed at existing Automatic Geophysical Observatory sites (in East Antarctica), which will provide heat and power for the data loggers. The remaining five stations will be in West Antarctica and will be powered and heated by wind turbines during the austral winter. (S-180)