2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)
Paper No. 118-3
Presentation Time: 9:00 AM-6:30 PM
GEOCHEMICAL LINEAMENTS AND TRENDS IN NURE GROUNDWATER DOMESTIC WELL DATA, AND THEIR GEOLOGICAL RELATIONSHIPS, NORTH CAROLINA COASTAL PLAIN
CARPENTER, Robert H., Retired, North Carolina Geological Survey, 749 Fairview Lane, Topton, NC 28781 and REID, Jeffrey C., North Carolina Geological Survey, Division of Energy, Mineral, and Land Resources, N.C. Department of Environment and Natural Resources (NC DENR), 1612 Mail Service Center, Raleigh, NC 27699, firstname.lastname@example.org
This study identifies several anomalous lineaments and trends in geochemical data from the National Uranium Resource Evaluation (NURE) database for the North Carolina Coastal Plain. Two of the lineaments (F, Groundwater pH, and Mg x Mg/Cl) are closely associated with the Carolina Fault (CF) and Graingers Wrench Zone (GWZ) delineated in previous work. The GWZ is characterized by block faulting over a width of 10-20 miles. The widths of the anomalous geochemical belts are comparable. Another anomalous lineament (Mg, Mg x Mg/Cl, and alkalinity), here termed the Beaufort Lineament, extends N 10 W from near Beaufort, NC to the Virginia state line. The southern portion of this Beaufort Lineament is located along the southern segment of the Suffolk Scarp, but there is no identified geochemical association with the segment of the Suffolk Scarp that extends N 22 E from Pinetown, NC. Another geochemical lineament (Na, Cl, Mg, conductivity, alkalinity), here termed the Bayview-Scranton Lineament trends ENE-WSW and extends across Beaufort and Hyde Counties. Infiltration of sea water has occurred along this lineament due to pumping from the Castle Haynes aquifer creating a large cone of depression. The chemical composition of water in the upper Cretaceous aquifers contrasts significantly with that of groundwater in the Castle Haynes aquifer. The Castle Haynes aquifer typically has a more alkaline pH, higher electrical conductivity, alkalinity, Mg, Na, and Cl. The boundary lies just east of the GWZ.
Comparison of the azimuths of geochemical lineaments with those of the CF-GWZ, the Surry, Suffolk, and Orangeburg Scarps, and faults delineated in the eastern Piedmont show a distinct pattern. North of the Bayview-Scranton Lineament, the trends are N 10 W and N 22 E. South of this lineament the trends are N 10 W and N 45 E. Questions remain about the occurrence of faults in the North Carolina Coastal Plain, and whether or not all of the geochemical lineaments identified here are faults. However, the identified patterns form a basis for future evaluations which will likely require drilling, trenching, and seismic work.