Airborne magnetic and radiometric survey, Virginia and North Carolina Fall Zone, 2021

This data release provides digital flight line data for a high-resolution airborne magnetic and radiometric survey over Virginia and North Carolina along and near the eastern U.S. 'Fall Zone', which represents the transitional area between Atlantic Coastal Plain sediments and Piedmont metamorphic and igneous rocks. The airborne data collection was funded by the U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI) and National Cooperative Geological Mapping Program (NCGMP). Goals include a gaining a better understanding of placer deposits containing critical mineral resources titanium, zirconium, and rare earth elements, assisting geologic mapping of the crystalline basement either exposed at the surface or buried beneath Atlantic Coastal Plain sediments, and imaging structures associated with the central Virginia seismic zone. The northwestern corner of the survey overlaps an airborne magnetic, radiometric, and gravity survey collected in 2012 over the 2011 Mw5.8 Mineral Virginia earthquake epicenter (Shah, 2014). The southern boundary of the survey is near the town of Rocky Mount, North Carolina.

Data for this survey were collected and processed by Eon Geosciences, Inc. via subcontract to Woolpert, Inc., who in turn were contracted by the USGS. Using a fixed wing aircraft with a magnetometer mounted in the tail stinger and a fully calibrated gamma ray spectrometer, data were collected along east-west flight lines spaced 275 meters (m) apart with north-south tie lines flown every 2500 m. A mean terrain clearance of 138 m was maintained. However, for safety reasons and/or regulations, nearly 15% of the survey data were collected at a flying height greater than 250 m, including more densely populated areas such as Richmond, Virginia, Roanoke Rapids, North Carolina, and Rocky Mount, North Carolina, or areas with tall-standing towers. The survey approximately covers a 232-kilometer x 70-kilometer semi-rectangular area; a total of 64,266 line-kilometers (km) of data were collected. The survey took place January-April 2021.

References:

Shah, A.K., 2014, Airborne Geophysical Surveys over the 2011 Mineral, Virginia, Earthquake Area: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F78K773V.