USGS ScienceSearch

Geology topics

Chad A. Wittkop

Publications and source records attributed to Chad A. Wittkop.

2 recordsLinked to original sources

A lacustrine carbonate record of Holocene seasonality and climate

Annually laminated (varved) Holocene sediments from Derby Lake, Michigan, display variations in endogenic calcite abundance reflecting a long-term (millennial-scale) decrease in burial punctuated with frequent short-term (decadal-scale) oscillations due to carbonate dissolution. Since 6000 cal yr B.P., sediment carbonate abundance has followed a decreasing trend while organic-carbon abundance has increased. The correlation between organic-carbon abundance and the sum of March-April-October-November insolation has an r 2 value of 0.58. We interpret these trends to represent a precession-driven lengthening of the Holocene growing season that has reduced calcite burial by enhancing net annual organic-matter production and associated calcite dissolution. Correlations with regional paleoclimate records suggest that changes in temperature and moisture balance have impacted the distribution of short-term oscillations in carbonate and organic-matter abundance superimposed on the precession-driven trends.

Michigan

Bedrock Geologic Map of New Hampshire, a Digital Representation of Lyons and Others 1997 Map and Ancillary Files

The New Hampshire Geological Survey collects data and performs research on the land, mineral, and water resources of the State, and disseminates the findings of such research to the public through maps, reports, and other publications. The Bedrock Geologic Map of New Hampshire, by John B. Lyons, Wallace A. Bothner, Robert H. Moench, and James B. Thompson, was published in paper format by the U.S. Geological Survey (USGS) in 1997. The online version of this CD contains digital datasets of the State map that are intended to assist the professional geologist, land-use planners, water resource professionals, and engineers and to inform the interested layperson. In addition to the bedrock geology, the datasets include geopolitical and hydrologic information, such as political boundaries, quadrangle boundaries, hydrologic units, and water-well data. A more thorough explanation for each of these datasets may be found in the accompanying metadata files. The data are spatially referenced and may be used in a geographic information system (GIS). ArcExplorer, the Environmental Systems Research Institute's (ESRI) free GIS data viewer, is available at http://www.esri.com/software/arcexplorer. ArcExplorer provides basic functions that are needed to harness the power and versatility of the spatial datasets. Additional information on the viewer and other ESRI products may be found on the ArcExplorer website. Although extensive review and revisions of the data have been performed by the USGS and the New Hampshire Geological Survey, these data represent interpretations made by professional geologists using the best available data, and are intended to provide general geologic information. Use of these data at scales larger than 1:250,000 will not provide greater accuracy. The data are not intended to replace site-specific or specific-use investigations. The U.S. Geological Survey, New Hampshire Geological Survey, and State of New Hampshire make no representation or warranty, expressed or implied, regarding the use, accuracy, or completeness of the data presented herein, or from a map printed from these data; nor shall the act of distribution constitute any such warranty. The New Hampshire Geological Survey disclaims any legal responsibility or liability for interpretations made from the map, or decisions based thereon. For more information on New Hampshire Geological Survey programs please visit the State's website at http://des.nh.gov/Geology/. New Hampshire Geographically Referenced Analysis and Information Transfer System (NH GRANIT) provides access to statewide GIS (http://www.granit.unh.edu/). Questions about this CD or about other datasets should be directed to the New Hampshire Department of Environmental Services.

Data Series