This is the digital data archive of the Northwest Durham 7.5-minute quadrangle geologic map, Orange and Durham Counties, North Carolina. The archive presents field photographs of outcrops and hand samples, photographs of sawn slabs of samples and photomicrographs of select samples. Plots of geochemistry data and structural data are also provided. This geologic database contains original North Carolina Geological Survey data collected by detailed field observations. Primary field activities occured from August 2002 through September 2003 by Philips, Witanachchi, Ward and Clark. Additional field work, data collection and interpretation was conducted by Bradley and Bechtel in 2005 through 2009.

The bedrock geology was mapped using standard techniques. Location information was provided by one of two methods: 1) data locations were approximated in the field using a paper copy of the Northwest Durham, North Carolina USGS 7.5-minute topographic map and a comparison to area topography or 2) by using a recreational grade GPS receiver to approximate the station location to an accuracy of 40 feet or less. Location specific field observation and structural data were manually entered into an ARCVIEW attribute table. Specific field station locations were assigned to distinct geologic units and/or rock types based on interpretations of field observations, thin section observations, and geochemical data. Geologic contacts lines were drawn by grouping station locations of similar rock types into unique polygon shapes to represent unique geologic units.

Purpose: The geologic map database for the Northwest Durham quadrangle has been created as a general-purpose data set that is applicable to land-related investigations in the earth, environmental and biological sciences. The digital data are intended for use by all government, academic, commercial, or other agencies in need of geologic map information. The Northwest Durham database is not suitable for site-specific geologic evaluations at scales greater than 1:24,000 (1 in = 2,000 ft). This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.

Disclaimer:
This digital data archive is preliminary and has not been reviewed for conformity with the North Carolina Geological Survey editorial standards. Further revisions or corrections to this data set may occur.

Comments or identification of errors or technical inaccuracies can be directed to Phil Bradley – Piedmont Geologist, North Carolina Geological Survey: pbradley@ncdenr.gov

D. Parker Sprinkle (Part-Time Geologist in 2009) contributed significantly to the construction of this data archive.