REGIONAL GEOCHEMISTRY OF ARKANSAS, A COMPLETION OF SAMPLING FOR THE NATIONAL GEOCHEMICAL SURVEY

The National Geochemical Survey is an on-going nationwide geochemical project of the USGS.

In December 2003, I was given the task of completing the sampling for Arkansas through USGS Grant Number 03 ERAG0057. Approximately half of the state remained to be sampled after the NURE sampling in the early 1960s. The areas to be sampled were nearly equally divided between the Gulf Coastal Plain and the Interior Highlands. Samples collected from the Coastal Plain consisted of both upper (0-8”) and lower (12-18”) soil horizons. Representative samples(~1.5 lbs.) for analysis were bagged. Repository samples (~12 lbs.) were also taken. All were labeled with a map grid code from the appropriate USGS 1 X 2 degree topographic. The entire Coastal Plain was completed by March 10th, 2004.

As sampling began in the Interior Highland Region, the location of sample sites immediately proved to be more difficult, due to USGS criteria. Each site was to be a 1st or 2nd order stream for which the entire watershed was within the given grid pattern. Sampling was completed on December 6th, 2005. Steam sediment samples consist of -2 mm fines screened from each location. Again, an ~1.5 lb. cut was bagged for analysis. A >10 lbs. repository sample was taken from the remaining screened fines.

A field sheet with geographic and culture data, and sample description and potential for contamination, was completed. Digital images of each site were taken. Data was transferred to a MSExcel® spreadsheet and digital images stored on a laptop computer each evening. All data was backed up daily from the laptop on a flash drive. The analytical samples were then shipped to the USGS Denver warehouse. These samples are scheduled for 55 element analysis. Repository samples were shipped later to Denver by truck.

Original field sheets and digital information were mailed to Dr. Andrew Grosz , USGS, in Reston, VA. The AGC retained copies of all of this information.

During the project 17,094 miles were driven, approximately 5,000 on the Coastal Plain.

The results of this project for Arkansas will be a series of elemental and ratio maps published by the AGC at a scale of 1:500,000. This work will define regional baseline chemical values and should be of value for those concerned with health, environmental, or mineral research in Arkansas. The data will give regional geochemical overview to specific topical studies within the state.