Publications
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The Central African Republic Diamond Database—A geodatabase of archival diamond occurrences and areas of recent artisanal and small-scale diamond mining The Central African Republic Diamond Database—A geodatabase of archival diamond occurrences and areas of recent artisanal and small-scale diamond mining
The alluvial diamond deposits of the Central African Republic (CAR) are mined almost exclusively by way of informal artisanal and small-scale mining (ASM) methods. ASM sites range in diameter from a few meters to 30 meters or more, and are typically excavated by crews of diggers using hand tools, sieves, and jigs. CAR’s reported annual production has ranged from 300,000 to 470,000 carats...
Authors
Jessica DeWitt, Peter Chirico, Sarah Bergstresser, Inga Clark
The significance of dinoflagellates in the Miocene Choptank Formation beneath the Midlothian gravels in the southeastern Virginia Piedmont The significance of dinoflagellates in the Miocene Choptank Formation beneath the Midlothian gravels in the southeastern Virginia Piedmont
The Fall Line (formally "Tidewater Fall Line") separates the more resistant igneous, metamorphic, and consolidated sedimentary rocks of the Piedmont from the typically unconsolidated deposits of the Coastal Plain of Virginia. Widespread but now discontinuous patches of a deeply weathered sand and gravel are found west of the Fall Line, capping the highest hilltops. Near the community of...
Authors
Lucy Edwards, Robert Weems, Mark Carter, David Spears, David Powars
PRISM marine sites—The history of PRISM sea surface temperature estimation PRISM marine sites—The history of PRISM sea surface temperature estimation
For more than three decades, the U.S. Geological Survey (USGS) Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project has compiled paleoenvironmental data with the goal of reconstructing global conditions during the warm interval in the middle of the Piacenzian Age of the Pliocene Epoch (about 3.3 to 3.0 million years ago). Because this is the most recent interval of time...
Authors
Marci Robinson, Harry Dowsett, Kevin Foley, Christina Riesselman
Latitudinal limits to the predicted increase of the peatland carbon sink with warming Latitudinal limits to the predicted increase of the peatland carbon sink with warming
The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate...
Authors
Angela Gallego-Sala, Dan Charman, Simon Brewer, Sue Page, I. Prentice, Pierre Friedlingstein, Steven Morley, Matthew Amesbury, David Beilman, Svante Bjorck, Tatiana Blyakharchuk, Christopher Bochicchio, Robert Booth, Joan Bunbury, Philip Camill, Donna Carless, Rodney Chimner, Michael Clifford, Elizabeth Cressey, Colin Courtney-Mustaphi, Francois De Vleeschouwer, Rixt de Jong, Barbara Fialkiawicz-Koziel, Sarah A Finkelstein, Michelle Garneau, Esther Githumbi, John Hribjlan, James Holmquist, Paul Hughes, Chris Jones, Miriam Jones, Edgar Karofeld, Eric Klein, Ulla Kokfelt, Atte Korhola, Terri Lacourse, Gael LeRoux, Mariusz Lamentowicz, David Large, Martin Lavoie, Julie Loisel, Helen MacKay, Glen MacDonald, Markku Makila, Gabriel Magnan, R. Marchant, Katarzyna Marcisz, Antonio Martinez-Cortizas, Charly Massa, Paul Mathijssen, Dmitri Mauquoy, Timothy Mighall, Fraser Mitchell, Patrick Moss, J. Nichols, P.O. Oksanen, L. Orme, Maara Packalen, Stephen Robinson, Thomas Roland, Nicole Sanderson, A. Sannel, Noemi Silva-Sanchez, Natasha Steinberg, Graeme Swindles, T. Turner, Joanna Uglow, M. Valiranta, Simon van Bellen, Marjolein van der Linden, Guoping Wang, Zicheng Yu, Joana Zaragoza-Castells, Yan Zhao
Geologic map of the Timberville quadrangle, Virginia Geologic map of the Timberville quadrangle, Virginia
This map of the Timberville 7.5-minute quadrangle in Rockingham and Shenandoah counties, Virginia shows the distribution of Paleozoic-age sedimentary rocks in map and cross-section. Surficial deposits including alluvium and colluvium are also shown. The characteristics of each map unit are described and a brief report discusses the stratigraphy, structure and mineral resources of the...
Authors
Matthew Heller, Randall Orndorff, David A. Hubbard, Eugene Rader
Kinematic, deformational, and thermochronologic conditions along the Gossan Lead and Fries shear zones: Constraining the western-eastern Blue Ridge boundary in northwestern North Carolina Kinematic, deformational, and thermochronologic conditions along the Gossan Lead and Fries shear zones: Constraining the western-eastern Blue Ridge boundary in northwestern North Carolina
The fault boundary between the western and eastern Blue Ridge (WBR-EBR) in the southern Appalachians separates Mesoproterozoic basement rocks and their cover from Neoproterozoic to Paleozoic accreted rocks. Several northeast striking faults delineate the boundary, including the Gossan Lead shear zone in northwestern North Carolina. Varying tectonic interpretations of WBR-EBR boundary...
Authors
Jamie Levine, Arthur Merschat, Ryan McAleer, G. Casale, K. Quillan, K. Fraser, T. BeDell
Divisions of geologic time—Major chronostratigraphic and geochronologic units Divisions of geologic time—Major chronostratigraphic and geochronologic units
Introduction Effective communication in the geosciences requires a consistent nomenclature for stratigraphic units and, especially, for divisions of geologic time. A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and is calibrated in years. Geologists from the U.S. Geological Survey (USGS), State geological surveys, academia, and other...
Authors
Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes
Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today’s changing Arctic oceanography. This study compares 14C-dated late Holocene microfaunal assemblages of sediment cores SWERUS-L2-2-PC1, 2-MC4 and 2-KL1 (57 mwd), which record the last 4200 years in the Herald Canyon...
Authors
Julia Seidenstein, Thomas Cronin, Laura Gemery, Lloyd D Keigwin, Christof Pearce, Martin Jakobsson, Helen Coxall, Emily A Wei, Neal W. Driscoll
Paleoclimate Records: Providing context and understanding of current Arctic change Paleoclimate Records: Providing context and understanding of current Arctic change
At present, the Arctic Ocean is experiencing changes in ocean surface temperature and sea ice extent that are unprecedented in the era of satellite observations, which extend from the 1980s to the present (see sections 5c,d). To provide context for current changes, scientists turn to paleoclimate records to document and study anthropogenic influence and natural decadal and multidecadal...
Authors
Emily Osborne, Thomas Cronin, Jesse Farmer
Icebergs in the Nordic Seas throughout the Late Pliocene Icebergs in the Nordic Seas throughout the Late Pliocene
The Arctic cryosphere is changing and making a significant contribution to sea level rise. The Late Pliocene had similar CO2 levels to the present and a warming comparable to model predictions for the end of this century. However, the state of the Arctic cryosphere during the Pliocene remains poorly constrained. For the first time we combine outputs from a climate model with a...
Authors
Yvonne Smith, Daniel Hill, Aisling Dolan, Alan Haywood, Harry Dowsett, Bjorg Risebrobakken
Bedrock geologic map of the Littleton and Lower Waterford quadrangles, Essex and Caledonia Counties, Vermont, and Grafton County, New Hampshire Bedrock geologic map of the Littleton and Lower Waterford quadrangles, Essex and Caledonia Counties, Vermont, and Grafton County, New Hampshire
The bedrock geologic map of the Littleton and Lower Waterford quadrangles covers an area of approximately 107 square miles (277 square kilometers) north and south of the Connecticut River in east-central Vermont and adjacent New Hampshire. This map was created as part of a larger effort to produce a new bedrock geologic map of Vermont through the collection of field data at a scale of 1...
Authors
Douglas Rankin
Preliminary geologic framework developed for a proposed environmental monitoring study of a deep, unconventional Marcellus Shale drill site, Washington County, Pennsylvania Preliminary geologic framework developed for a proposed environmental monitoring study of a deep, unconventional Marcellus Shale drill site, Washington County, Pennsylvania
Background In the fall of 2011, the U.S. Geological Survey (USGS) was afforded an opportunity to participate in an environmental monitoring study of the potential impacts of a deep, unconventional Marcellus Shale hydraulic fracturing site. The drill site of the prospective case study is the “Range Resources MCC Partners L.P. Units 1-5H” location (also referred to as the “RR–MCC” drill...
Authors
Robert Stamm