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GeoCore Coring System

Information for these pages was prepared by
Michael Dega, a doctoral candidate in archaeology at U.H.

Go to a brief discussion of
sediment coring in archaeology

The GeoCore is a manual coring system developed by Vincent J. Vohnout, an engineer at the Ohio State University, to systematically acquire continuous, minimally disturbed sections of various sediment matrices. When compared to a hand auger or drill, a coring system generally provides a sample with better integrity than that recovered by an auger, which cuts sediment or rock in a helical motion, and thus disturbs the context of the material.

The GeoCore is a piston-type corer consisting of a hollow, aluminum core tube with a movable piston inside the tube. The piston creates a vacuum inside the tube as the device is manually introduced into the sediment, the vacuum holding the core contents within the tube. The GeoCore system's hammering mechanism allows coring personnel to easily cut through stiff and course sediments (e.g., clay, sand), and limestone, coral, and small rock concentrations.

The GeoCore System has been ideally designed to be used in waterlogged or fairly wet sediments, although its use may not be exclusive to a wet environment.

As with any coring system, the GeoCore is most profitably used in concert with a hand auger or other manual drill, which will allow researchers to cut through rocky matrices or highly compacted sediments which are a barrier to the corer.  Once boring has penetrated through the rocky matrix or compacted sediment, the GeoCore can be put back into use.

The GeoCore System, although relatively simple to use, has a number of components, and one should be familiar with all parts of the system prior to its use.

Drop-Hammer Set-Up

(Photographs of corer components
courtesy of Vincent Vohnout)

Coring is best accomplished using a crew of two to three persons. The time necessary to core a site depends on the depth of deposits, the size of the site, the ease with which the site matrix is cored (a function of the concentration of obstructions such as impenetrable bones, rocks, sherds, soils, and the dryness and composition of the fine-grained matrix), the type of sampler used, and the precision desired by the researcher.

• Select the proper coring location.
• If the site is non-waterlogged or contains fairly wet sediments, clear any surface or intrusive vegetation prior to coring.
• Place the plywood board (with a hole cut in center of the board) at the coring location for stability in coring and for keeping tools nearby for use.
• Set up the coring mechanism for use:
  • Insert cutting shoe at one end of coring tube
  • Insert piston mechanism
  • Tighten piston mechanism withn core
  • Tighten piston cord at base of corer
  • Add t-bar and mark with flagging tape
• Insert core into ground and retrieve sample.
• Upon completion of coring, remove the piston, etc.--the sediment sample should be contained within the tube.
• The tube should be measured for sediment accumulation then cut with a metal-blade saw.
• Capping the ends of the tube completes the process of acquiring a core.

To prevent rust which may render the system unusable, the GeoCore system should be thoroughly cleaned and dried after use.

Preparing Cores for Analysis

The tubes containing cores should be stored in a cold environment (ideally a freezer) until analysis can be done.

Samples to be sent for specialized analysis (radiocarbon, pollen samples, etc.) can be taken from the metal tube by cutting the tube with a tablesaw or another device. After cutting the metal tube, the sediment sample should be cleaned by scraping several centimeters of sediment from around the sides of the core to reduce sample contamination.

This page was last updated:
March 9, 1999