Using the calibrated temperature sonde, both absolute temperature and temperature gradient can be obtained. The density tool requires an active Cobalt-60 source. The Terrain Geophysics Section operates both sidewell-locking geophones and hydrophone arrays for measurement of compressional and shear wave velocities in overburden materials. These units have been constructed in-house using commercial hydrophone and geophone elements. Surface seismic sources commonly used are the . buffalo gun.
Recording is done on an multichannel engineering seismograph.
A depth capability of 300 m is possible for both wave velocities. All systems are operated in a cased borehole, preferably one which is not open or screened at the bottom. Sonde Descriptions Natural gamma Radioactive isotopes of potassium, uranium and thorium occur naturally in unconsolidated sediments and the decay of these elements produces gamma rays. Changes in the measured count rate of gamma rays emitted from a formation can be used in a qualitative manner to estimate grain size, and to indicate lithological boundaries. In modern sondes, a sodium iodide scintillation detector is used to detect gamma radiation.