Geological Field Techniques
Angela L. Coe
Format: PDF / Kindle (mobi) / ePub
The understanding of Earth processes and environments over geological time is highly dependent upon both the experience that can only be gained through doing fieldwork, and the collection of reliable data and appropriate samples in the field. This textbook explains the main data gathering techniques used by geologists in the field and the reasons for these, with emphasis throughout on how to make effective field observations and record these in suitable formats. Equal weight is given to assembling field observations from igneous, metamorphic and sedimentary rock types. There are also substantial chapters on producing a field notebook, collecting structural information, recording fossil data and constructing geological maps. The volume is in a robust and handy size, with colour coded chapters for ease of use and quick reference in the field.
Geological Field Techniques is designed for students, amateur enthusiasts and professionals who have a background in geology and wish to collect field data on rocks and geological features. Teaching aspects of this textbook include:<ul type="disc">* step-by-step guides to essential practical skills such as using a compass-clinometer, making a geological map and drawing a field sketch;* tricks of the trade, checklists, flow charts and short worked examples;* over 200 illustrations of a wide range of field notes, maps and geological features;* appendices with the commonly used rock description and classification diagrams;* a supporting website hosted by Wiley Blackwell.
direction on the dial. 3. Transfer azimuth to the map Lower the compass and place it on the map with the N–S grid lines on the compass dial (ignore the compass needle) aligned with the N–S grid lines on the map. Retaining this orientation place one edge of the compass adjacent to the feature that you have sighted. Draw a feint line on the map using the edge of the compass that passes through the object that you used for sighting. Your position is somewhere along this line. 4. Repeat stages 2
providing a set-up for photographing specimens and field notebooks. Various colleagues have allowed us to reproduce their photographs in this book, for which we are grateful. These individuals are acknowledged in the figure captions. Andrew Whitehead and David DuPlessis with the help of Chris Hough and Jon Owen (The Open University) prepared the final version of the figures. Richard Howes is thanked for general assistance with the electronic files. We are grateful to Andrew Lloyd for help with
definition have been Figure 7.14 Unusually wellpreserved and easily distinguished pillow lavas. Oman, Arabia. (David A. Rothery, The Open University, UK.) Igneous 149 7 150 Igneous 7 (a) (b) Figure 7.15 Dyke chilled margins. (a) The chilled margin runs from top to bottom of this view parallel to the pen. Its location is indicated by the arrow drawn in the deliberately positioned field notebook. This exposure is weathered and fragmented, but there is a slight darkening on fresh surfaces
folded bands of different colour and grain size in rocks with slaty cleavage. Slaty cleavage in 178 Structural 8 (a) (b) (c) (d) (e) (f) 179 Fabric Typical setting Formed by Clues in the field Pressure solution cleavage Upper crust, outer zones of mountain belts Dissolution of soluble grains due to directed stress Dark/pale colour striping; partially dissolved fossils, clasts; stylolitic surfaces Slaty cleavage Upper crust, outer zones of mountain belts; fine-grained rocks
rocks have a planar tectonic fabric defined by aligned and/or flattened mineral grains, which has been termed ‘gneissosity’. However, the same term has also been applied to centimetre-scale compositional banding in gneisses (Figure 8.17), and so is best avoided. Gneissic banding may reflect processes other than deformation (e.g. partial melting, metamorphic segregation, transposition of original lithological layering), whereas gneissic foliation is simply a coarser form of schistosity. 8.3.2