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Introduction
Field Geophysics will be run to assist groups in mapping their areas. Various Geophysical techniques can be used to remotely sense rocktypes below alluvium and other overlying sediments. Dr Roger Henderson and Carina Simmat (Ph.D. Candidate) have designed, and will supervise this exercise.
Before you come on the trip please read through the following notes on the various techniques to be used. First read through the following overview of field geophysics:
General Aspects of Geophysical Field Work.pdf
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Magnetic Surveying
"The aim of a magnetic survey is to investigate subsurface geology on the basis of anomalies in the Earth's magnetic field resulting from the magnetic properties of underlying rocks." Kearey and Brooks, 1991.
Mag Notes
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Radiometric Surveying
"Radiometric surveys are of use un geological mapping as different rock types can be recognised from their distinctive radioactive sugnatures." Kearey and Brooks, 1991.
Rad N otes
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Electrical Surveying
"There are many methods of electrical surveying. Some make use of naturally-occurring fields within the Earth while others require the introduction of artificially-generated currents into the ground. The resisitivity method is used in the study of horizontal and vertical discontinuities in the electrical properties of the ground, and also in the detection of three-dimensional bodies of anomalous electrical conductivity." Kearey and Brooks, 1991.
"Electrical methods utilize direct currents or low frequency alternating currents to investigate the electrical properties of the subsurface, in contrast to the electromagnetic discussed in the next section that use alternating electromagnetic fields of higher frequency."Kearey and Brooks, 1991.
Introduction to Resistivity
More Resitivity Notes
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Electromagnetic Surveying
"Electromagnetic (EM) surveying methods make use of the response of the ground to the propagation of electromagnetic fields, which are composed of an alternating electric intensity and magnetising force. Primary electromagnetic fields may be generating by passing alternating current through a small coil made of many turns of wire or through a large loop of wire. The response of the ground is the generation of secondary electromagnetic fields and the resultant fields may be detected by the alternatibe currents that they induce to flow in a receiver coil by the process of electromagnetic induction." Kearey and Brokks, 1991.
EM31.pdf
EM34.pdf
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Your Results and Final Report
You will be asked to produce a poster showing the results from the Geophysical techniques used in your area. The following document will help you setout your poster.
Guidelines for writing a report
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REFERENCE
Kearey P & Brooks M, 1991, An Introduction to Geophysical Exploration. Blackwell Science Publications.
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