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Geologist Analyzes Soil Samples to Assist the Search for a Missing Person

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Earlier this year, U.S. Geological Survey (USGS) geologist Terry Edgar (St. Petersburg, FL) analyzed a set of soil samples to help the Sheriff of Lee County, FL, and his staff narrow the range of locations where they might search for a missing person. Terry was brought into the investigation last February when Michelle Barret, Chief of Communications for the USGS' Eastern Region, asked him whether he could assist. Terry replied that although forensic geology was not his specialty, he would have a go at it or would contact folks who could help.

According to Sheri Alfaro, Crime Scene Technician with the Lee County Sheriff's Office (southwest Florida), a young woman was reported missing from Fort Myers, FL, in early January. She was last seen with a male companion she had met on the Internet a year earlier and had invited down from Washington State to stay with her. The male friend, now "suspect," was picked up in Corpus Christi, TX, on a separate charge. He was driving her car, which contained most of her belongings. The victim was not with him and was still missing at press time.

The Texas authorities found soil samples in the trunk of the car and on the floor of the rear passenger side. In addition, a shovel was found in the trunk with a few grains of sand on it. The suspect used the victim's credit card on the trip from Fort Myers to Corpus Christi, leaving a trail from south Florida to Goodyear (near Phoenix), AZ, and back to Corpus Christi.

The three samples and a list of all the stops the suspect made, based on the credit-card records, were sent to Terry. The suspect followed Interstate Highway 75 northward through Florida, joined Interstate Highway 10 (I-10) in northern Florida, and took it all the way to Goodyear, AZ. The two soil samples found in the car consisted of calcium carbonate-cemented sand grains, rather typical Florida sediment. The few grains recovered from the shovel, however, are igneous, consisting of quartz, plagioclase, and a black mineral that looks like hornblende. This mineral assemblage is not typical of Florida or the southern Gulf Coast, including the part of Texas traversed by I-10. Granitic rocks of Precambrian age occur in the Llano Uplift, north of San Antonio, but those rocks contain abundant orthoclase, none of which was apparent in the shovel sample.

A call to the Arizona Department of Mines and Mineral Resources confirmed that the State has a lot of material similar to the sediment on the shovel. With this information, the Lee County Sheriff's investigators redirected their search for the victim from Florida to Arizona. At the time of publication, the victim had not been found.

Related Web Sites
St. Petersburg Science Center
U.S. Geological Survey (USGS)
Introduction to Forensic Geology
Southern Illinois University

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in this issue: Fieldwork
cover story:
Benthic Habitats in Glacier Bay

North Carolina Submarine Groundwater

Research Mucus-Hosted Microbial Communities

Gulf of Maine Mapping Initiative

Forensic Geology Assists Investigation

Submarine Groundwater Discharge

USGS Participates in Marine Quest X

Caribbean Tsunami Hazard Workshop

USGS wins Blue Pencil, Gold Screen Awards

June Publications List

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