Publications
Filter Total Items: 899
Reevaluation of the Piermont-Frontenac allochthon in the Upper Connecticut Valley: Restoration of a coherent Boundary Mountains–Bronson Hill stratigraphic sequence Reevaluation of the Piermont-Frontenac allochthon in the Upper Connecticut Valley: Restoration of a coherent Boundary Mountains–Bronson Hill stratigraphic sequence
The regional extent and mode and time of emplacement of the Piermont-Frontenac allochthon in the Boundary Mountains–Bronson Hill anticlinorium of the Upper Connecticut Valley, New Hampshire–Vermont, are controversial. Moench and coworkers beginning in the 1980s proposed that much of the autochthonous pre–Middle Ordovician section of the anticlinorium was a large allochthon of Silurian to...
Authors
Douglas W. Rankin, Robert D. Tucker, Yuri Amelin
Lateglacial and Holocene climate, disturbance and permafrost peatland dynamics on the Seward Peninsula, western Alaska Lateglacial and Holocene climate, disturbance and permafrost peatland dynamics on the Seward Peninsula, western Alaska
Northern peatlands have accumulated large carbon (C) stocks, acting as a long-term atmospheric C sink since the last deglaciation. How these C-rich ecosystems will respond to future climate change, however, is still poorly understood. Furthermore, many northern peatlands exist in regions underlain by permafrost, adding to the challenge of projecting C balance under changing climate and...
Authors
Stephanie D. Hunt, Zicheng Yu, Miriam C. Jones
Upper crustal structure of Alabama from regional magnetic and gravity data: Using geology to interpret geophysics, and vice versa Upper crustal structure of Alabama from regional magnetic and gravity data: Using geology to interpret geophysics, and vice versa
Aeromagnetic and gravity data sets obtained for Alabama (United States) have been digitally merged and filtered to enhance upper-crustal anomalies. Beneath the Appalachian Basin in northwestern Alabama, broad deep-crustal anomalies of the continental interior include the Grenville front and New York–Alabama lineament (dextral fault). Toward the east and south, high-angle discordance...
Authors
Mark G. Steltenpohl, J. Wright Horton, Robert D. Hatcher, Isidore Zietz, David L. Daniels, Michael W. Higgins
Where fast weathering creates thin regolith and slow weathering creates thick regolith Where fast weathering creates thin regolith and slow weathering creates thick regolith
Weathering disaggregates rock into regolith – the fractured or granular earth material that sustains life on the continental land surface. Here, we investigate what controls the depth of regolith formed on ridges of two rock compositions with similar initial porosities in Virginia (USA). A priori, we predicted that the regolith on diabase would be thicker than on granite because the...
Authors
Ekaterina Bazilevskaya, Marina Lebedeva, Milan J. Pavich, Susan L. Brantley, Gernot Rother, Dilworth Y. Parkinson, David Cole
A geological synthesis of the Precambrian shield in Madagascar A geological synthesis of the Precambrian shield in Madagascar
Available U–Pb geochronology of the Precambrian shield of Madagascar is summarized and integrated into a synthesis of the region’s geological history. The shield is described in terms of six geodynamic domains, from northeast to southwest, the Bemarivo, Antongil–Masora, Antananarivo, Ikalamavony, Androyan–Anosyan, and Vohibory domains. Each domain is defined by distinctive suites of...
Authors
Robert D. Tucker, J.Y. Roig, B. Moine, C. Delor, S. G. Peters
Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica
The late Pliocene, ~ 3.3–3.0 Ma, is the most recent interval of sustained global warmth in the geologic past. This window is the focus of climate reconstruction efforts by the U.S. Geological Survey's Pliocene Research, Interpretation, and Synoptic Mapping (PRISM) Data/Model Cooperative, and may provide a useful climate analog for the coming century. Reconstructions of past surface ocean
Authors
Christina Riesselman, R. B. Dunbar
On the identification of a Pliocene time slice for data–model comparison On the identification of a Pliocene time slice for data–model comparison
The characteristics of the mid-Pliocene warm period (mPWP: 3.264–3.025 Ma BP) have been examined using geological proxies and climate models. While there is agreement between models and data, details of regional climate differ. Uncertainties in prescribed forcings and in proxy data limit the utility of the interval to understand the dynamics of a warmer than present climate or evaluate...
Authors
Alan M. Haywood, Aisling M. Dolan, Steven J. Pickering, Harry J. Dowsett, Erin L. McClymont, Caroline L. Prescott, Ulrich Salzmann, Daniel J. Hill, Stephen J. Hunter, Daniel J. Lunt, James O. Pope, Paul J. Valdes
Proterozoic to Cenozoic geology above, within and beneath the Blue Ridge Composite Thrust Sheet as exposed along the Blue Ridge Parkway in the Peaks of Otter region, central Virginia Blue Ridge: Guidebook for the 43rd Annual Virginia Geological Field Con Proterozoic to Cenozoic geology above, within and beneath the Blue Ridge Composite Thrust Sheet as exposed along the Blue Ridge Parkway in the Peaks of Otter region, central Virginia Blue Ridge: Guidebook for the 43rd Annual Virginia Geological Field Con
No abstract available.
Authors
Mark W. Carter, C. Scott Southworth, John N. Aleinikoff
The Cambrian-Ordovician rocks of Sonora, Mexico, and southern Arizona, southwestern margin of North America (Laurentia) The Cambrian-Ordovician rocks of Sonora, Mexico, and southern Arizona, southwestern margin of North America (Laurentia)
Cambrian and Ordovician shelf, platform, and basin rocks are present in Sonora, Mexico, and southern Arizona and were deposited on the southwestern continental margin of North America (Laurentia). Cambrian and Ordovician rocks in Sonora, Mexico, are mostly exposed in scattered outcrops in the northern half of the state. Their discontinuous nature results from extensive Quaternary and...
Authors
William R. Page, Alta C. Harris, John E. Repetski
100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends 100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends
We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+ yr interval (~ 115–15 ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging...
Authors
Ronald J. Litwin, Joseph P. Smoot, Milan J. Pavich, Helaine W. Markewich, George Brook, Nancy J. Durika
40Ar/39Ar evidence for Late Devonian deformation in the Chester shear zone, east central Maine 40Ar/39Ar evidence for Late Devonian deformation in the Chester shear zone, east central Maine
No abstract available.
Authors
Hind Ghanem, Michael J. Kunk, Allan Ludman, David Bish, Robert Wintsch, Joseph Biasi
An evaluation of automated GIS tools for delineating karst sinkholes and closed depressions from 1-meter LIDAR-derived digital elevation data An evaluation of automated GIS tools for delineating karst sinkholes and closed depressions from 1-meter LIDAR-derived digital elevation data
LiDAR (Light Detection and Ranging) surveys of karst terrains provide high-resolution digital elevation models (DEMs) that are particularly useful for mapping sinkholes. In this study, we used automated processing tools within ArcGIS (v. 10.0) operating on a 1.0 m resolution LiDAR DEM in order to delineate sinkholes and closed depressions in the Boyce 7.5 minute quadrangle located in the...
Authors
Daniel H. Doctor, John A. Young