CLAY MINERAL ANALYSIS OF THE USGS CANNON PARK CORE (CHN-800) USING NEAR INFRARED REFLECTANCE SPECTRA, CHARLESTON, SOUTH CAROLINA

Clay mineral identification provides useful information regarding sediment provenance and correlation of strata. Commonly, clays are analyzed by x-ray diffraction, which requires expensive instrumentation and significant turnaround time. An alternative method that reduces analytical time without reduction of accuracy is infrared reflectance spectroscopy. This nondestructive analytical technique takes advantage of characteristic absorption and scattering of photons resulting from OH- and H2O vibrational processes. These processes, along with the combination metal-OH- bend plus OH- stretch near 2.2-2.3 microns, are very diagnostic of phyllosilicate mineralogy.

We identified clay minerals by analyzing infrared spectra above and below contacts of Paleocene to Pleistocene units in the Cannon Park (CHN-800) core, Charleston, South Carolina. The analyses were conducted using a portable ASD FieldSpec Pro Spectroradiometer which measures light over 0.4-2.5 microns in 2151contiguous channels. Characteristic spectra from samples were reduced to absolute reflectance by ratioing to a National Bureau of Standards halon plate. Prior to and following analyses, montmorillonite, kaolinite, and hallyosite standards were analyzed for comparison with those from U.S. Geological Survey Spectral Library.

Although montmorillonite is the dominant clay detected in many units, subordinate kaolinite was detected in spectra from the Wando Formation, upper Ashley Formation, lower Parkers Ferry Formation, and lower Cross Formation. In addition to clay minerals, calcite, glauconite, and apatite were also identified using the same technique. These results correlate favorably with gamma log data and descriptions of Coastal Plain units and demonstrate the utility of infrared spectroscopy for rapid, nondestructive analysis of clays in Coastal Plain units.