Critical mineral resources titanium, zirconium, and rare earth elements occur in placer deposits
over vast parts of the U.S. Atlantic Coastal Plain. Key questions regarding provenance, pathways
of minerals to deposit sites, and relations to geologic features remain unexplained. As part of
a national effort to collect data over regions prospective for critical minerals, the first
public high-resolution aeroradiometric survey over the U.S. Atlantic Coastal Plain was conducted
over Quaternary sediments in South Carolina. The new data provide an unprecedented view of
potential deposits by imaging Th-bearing minerals in the heavy mineral assemblage. Sand ridges
show the highest radiometric Th values with localized, linear anomalies, especially along the
shoreface and in areas reworked by multiple processes and/or during multiple episodes. Estuarine
areas with finer-grained sediments show lower, distributed Th anomalies. Th values averaged over
geologic unit areas are similar for both environments, suggesting that heavy minerals are
present but have not been locally concentrated in the lower-energy estuarine environments.
Radiometric K highlights immature minerals such as mica and potassium feldspar. K is elevated
within shallow sediments younger than ca. 130 ka, an attribute that persists in regional data
from northern South Carolina to northern Florida. Both K and Th are elevated over the
floodplains of the Santee River and other rivers with headwaters in the igneous and metamorphic
Piedmont Terrane. The persistence of K anomalies for distances of more than 100 km from the
Santee River floodplain suggests that heavy minerals are delivered from the Piedmont to offshore
areas by major rivers, transported along the coast by the longshore current, and redeposited
onshore by marine processes.
Manuscript received 26 Apr. 2021. Revised manuscript received 26 July 2021.
Manuscript accepted 1 Aug. 2021. Posted 8 Sept. 2021.
© The Geological Society of America, 2021. CC-BY-NC.