STRATIGRAPHIC DISTRIBUTION AND SOURCE OF RADON IN THE YORKTOWN FORMATION (VIRGINIA)

Radon is an odorless, colorless, radioactive gas and is the leading cause of lung cancer for nonsmokers worldwide. The primary control on radon emanation into air is local parent material mineralogy; felsic igneous rocks and black shales typically have high ²³⁸U, which is the ultimate source of radon. Historically, the sediments of the Virginia Coastal Plain have been characterized as low radon potential. However, research from the past few decades conflicts with this assessment, with many homes in southeastern Virginia recording radon levels above the EPA action limit of 4 pCi/L.

Recent research shows that high uranium (over 10x crustal average) has been measured in portions of the Pliocene Yorktown Formation. We hypothesize that phosphates, glauconite, and shell material within the Yorktown Formation are the source of elevated radon concentrations in homes in southeastern Virginia. Here, we describe, and sample four sediment cores drilled on the James-York Peninsula. The Banbury Cross, Bayville Park, Busch Gardens, and Newport News II cores were accessed from core repositories at the U.S. Geological Survey and Virginia Department of Environmental Quality. The Yorktown Formation and the Yorktown-Eastover contact were described in detail before sampling, including grain size, composition, angularity, sorting, fossil content, sedimentary features, and color. The approximate percentages of glauconite and phosphate were also described, ranging from 0% to up to 15%. We use gamma spectrometry to measure ²³⁸U, ²²⁶Ra, and ²¹⁰Pb in core sections and x-ray fluorescence to quantify phosphorous concentrations. We find ²²⁶Ra activities as high as 121 Bq/kg, which is more than double the crustal average of 50 Bq/kg. Preliminary results show that the presence of glauconite and/or phosphate correlates with high ²²⁶Ra and ²³⁸U, which could be the source of high radon in homes in this region.