Table of Contents

Cover

The Geological Field Guide Series

Title

Preface to The Fourth Edition

Preface to The Fifth Edition

Chapter 1: Introduction

1.1 Outline and Approach
1.2 Safety
1.3 Field Behaviour
1.4 A Few Words of Comfort

Chapter 2: Field Equipment

2.1 Hammers and Chisels
2.2 Compasses and Clinometers
2.3 Hand Lenses
2.4 Tapes
2.5 Map Cases
2.6 Field Notebooks
2.7 Scales
2.8 Protractors
2.9 Pencils, Erasers and Mapping Pens
2.10 Acid Bottles
2.11 Global Positioning System (GPS) and Mobile Phones
2.12 Other Instruments
2.13 Field Clothing

Chapter 3: Topographic Base Maps

3.1 Types of Geological Map
3.2 Topographic Base Maps
3.3 Geographic Coordinates and Metric Grids
3.4 Grid Magnetic Angle
3.5 Position Finding on Maps
3.6 Use of Air Photography as a Mapping Tool
3.7 Suitability of Images for Geological Mapping

Chapter 4: Methods of Geological Mapping

4.1 Strategy for the Mapping Programme
4.2 Mapping by Following Contacts
4.3 Traversing
4.4 Exposure Mapping
4.5 Mapping in Poorly Exposed Regions
4.6 Superficial Deposits
4.7 Drilling
4.8 Geophysical Aids to Mapping
4.9 Large-Scale Maps of Limited Areas
4.10 Underground Mapping
4.11 Photogeology

Chapter 5: Technological Aids to Mapping

5.1 Digital Terrain Models
5.2 Topographic Surveying Techniques

Chapter 6: Field Measurements and Techniques

6.1 Measuring Strike and Dip of Planar Structures
6.2 Plotting Strike and Dip
6.3 Recording Strike and Dip
6.4 Measuring Linear Features
6.5 Folds
6.6 Faults
6.7 Thrusts
6.8 Joints
6.9 Unconformities
6.10 Map Symbols
6.11 Specimen Collecting
6.12 Field Photography
6.13 Panning

Chapter 7: Mappable Rock Units and Lithology

7.1 Lithostratigraphy and Sedimentary Rocks
7.2 Sedimentary Formations
7.3 Rock Descriptions
7.4 Identifying and Naming Rocks in the Field
7.5 Fossils
7.6 Phaneritic Igneous Rocks
7.7 Aphanitic Igneous Rocks
7.8 Veins and Pegmatites
7.9 Igneous Rocks in General
7.10 Pyroclastic Rocks
7.11 Metamorphic Rocks
7.12 Economic Geology

Chapter 8: Field Maps and Field Notebooks

8.1 Field Maps
8.2 Field Notebooks

Chapter 9: Fair Copy Maps and Other Illustrations

9.1 Fair Copy Maps
9.2 Transferring Topography
9.3 Transferring Geology
9.4 Lettering and Symbols
9.5 Formation Letters
9.6 Layout
9.7 Colouring
9.8 Stratigraphic Column
9.9 Overlays
9.10 Computer Drafting of the Fair Copy Map

Chapter 10: Cross-Sections and 3D Illustrations

10.1 Cross-Sections
10.2 Method of Apparent Dips
10.3 Down-Plunge Projection Method
10.4 Balanced Cross-Sections
10.5 Columnar Sections
10.6 Block Diagrams
10.7 Models

Chapter 11: Geological Reports

11.1 Preparation
11.2 Revising and Editing
11.3 Layout
11.4 The ‘Introduction’
11.5 Main Body of the Report
11.6 The ‘Conclusions’ Section
11.7 Text Illustrations
11.8 References
11.9 Appendices
11.10 Some Final Thoughts

Appendix A: Adjustment of a Closed Compass Traverse

Appendix B: Field Equipment Checklist

Appendix C: Indicators of Stratigraphical Way-Up

Appendix D: Useful Chart and Tables

References

Index

Selected Map Symbols

Colour Plates

End User License Agreement

List of Tables

Chapter 1: Introduction

Table 1.1 Common safety hazards associated with geological mapping

Chapter 2: Field Equipment

Table 2.1 Equivalent bearings using quadrant and azimuth conventions

Chapter 4: Methods of Geological Mapping

Table 4.1 Equivalents of 1 mm on maps of different scales

Chapter 7: Mappable Rock Units and Lithology

Table 7.1 Division of aphanitic igneous rocks into felsites and mafites

Appendix D: Useful Chart and Tables

Table D.1 Spacing of bedding and jointing
Table D.2 Abridged grain-size scales

List of Illustrations

Chapter 2: Field Equipment

Figure 2.1 Tools for the field.(a) Traditional geologist's hammer in leather belt ‘frog’;(b) steel-shafted ‘prospecting pick’.(c) Bricklayer's ‘club’ hammer with a replaced longer shaft.(d)A 45 cm chisel with 2.5 cm cutting edge and(e) An 18 cm chisel with 2 cm edge. (After Cooper, G.R. and C.D. McGillem, 1967: Methods of Signal and System Analysis. Holt, Rinehart and Winston, New York, 432 pp.)
Figure 2.2 Compasses designed for the geologist. (a) Finnish Suunto compass, similar to the Swedish Silva Ranger 15 TDCL.(b) American Brunton ‘pocket transit’.(c) Swiss Meridian compass and(d) French Chaix-Universelle. The Brunton and Meridian can also be used as hand levels.
Figure 2.3 The mirror compass. (After Cooper, G.R. and C.D. McGillem, 1967: Methods of Signal and System Analysis. Holt, Rinehart and Winston, New York, 432 pp.)
Figure 2.4 The recommended way to use a Brunton compass when taking a bearing on a distant point.(Reproduced by courtesy of the Brunton Company, Riverton, Wyoming.)
Figure 2.5 Taking a bearing with a mirror compass: (a) sighting on a landmark; (b) view through the mirror and (c) rotating the azimuth ring until the orienting arrow aligns with the magnetic needle.
Figure 2.6 Ideas for home-made clinometers: (a) plumb-line type and (b) ball bearing in transparent plastic tube.
Figure 2.7 Japanese ‘universal clinometer’. Plunge direction can be measured directly from the compass, which always stays horizontal, and plunge is read by the pointer hanging below the compass box.
Figure 2.8 The hand lens is an essential tool for close-up study of rocks in the field.
Figure 2.9 A map case made from a Perspex sheet attached to a plywood base by a nylon or brass ‘piano hinge’ (DIY shop) and ‘pop’ rivets.
Figure 2.10 Pocket stereonet and scales (a) Home-made stereonet for the field; the upper rotating Perspex disc is slightly sandpapered so that it can be drawn on and easily cleaned off again. (b) Transparent combination of map scale and protractor (C-Thru Ruler Company). (c) Plastic scale with different graduations on both edges and both sides. (d) Triangular map scale, which is not recommended for field use but is excellent in the office.
Figure 2.11 Using a mirror-type compass as a protractor.
Figure 2.12 Some of the wide variety of hand-held GPS systems available on the market. (a) Basic rugged 12-channel Garmin GPS, which only provides locational coordinates but can be used with pocket PC (d). (b) Garmin GPS unit with ability to plot location onto a simple on-screen base map. (c) Mobile phone with GPS app installed. (d) Field-rugged Trimble pocket PC, which can take input from a GPS via cable or Bluetooth connection. A georeferenced air photo is shown on the screen. The software installed on the PC has the ability to log positional information along with field notes. Data can then be later automatically integrated into GIS software applications.
Figure 2.13 Stereo air photography or 3D terrain models can be viewed in the field (a) using a pocket stereoscope or (b) printed as a colour anaglyph and viewed using red/cyan 3D glasses.

Chapter 3: Topographic Base Maps

Figure 3.1 Principle of azimuthal projection of the Earth's curved surface onto a flat map. The map is absolutely accurate only at the point where the plane of projection touches the Earth's surface. (After Duchon, C.E., 1979: Lanczos filtering in one and two dimensions. J. AppliedMeteor., 18, 1016–1022.)
Figure 3.2 Finding a map reference. The figure shows coordinates of a portion of 100 km square SN of the British National Grid. The point referred to lies 0.72 km east of the 87 km coordinate and 0.15 km north of the 46 km coordinate (eastings are always quoted before northings). The map reference of the point is therefore SN87724615. (After Duchon, C.E., 1979: Lanczos filtering in one and two dimensions. J. AppliedMeteor., 18, 1016–1022.)
Figure 3.3 Adjusting a mirror compass for the grid magnetic angle. Turning the adjustment screw alters the angle between the orienting arrow and the orienting lines. These represent the directions of magnetic north and grid north respectively when the measurement is made. The angle is therefore equal to the grid magnetic angle (11°W in the figure). (After Duchon, C.E., 1979: Lanczos filtering in one and two dimensions. J. AppliedMeteor., 18, 1016–1022.)
Figure 3.4 Orienting a map. (a) Place the compass on the map so that the north mark on the orienting ring (N) is in the north direction on the map. (b Rotate the map and compass together until the magnetic needle becomes parallel to the orienting arrow on the compass. The map is now properly oriented with respect to the scenery and easier to read.
Figure 3.5 Plotting a bearing with the mirror compass. (a) A bearing is taken on a feature identified on the map, for example the hilltop of 176 m, and (b) without moving the azimuth ring, place the compass on the map with the orienting lines parallel to grid north and also with the north (N) on the azimuth ring in the map's north direction. Draw a line in a backward direction through the landmark using the long edge of the compass; this is the back-bearing.
Figure 3.6 Plotting a bearing by POP (the pencil-on-point method).
Figure 3.7 Locating points by offsets. A traverse (bearing 062°) is paced from the house, using the tree as an aiming point, until you reach A, directly opposite an exposure at A′. Mark A with your rucksack and then pace the offset A–A′ at right angles to the traverse line. Plot the position of A′; make your observations of the exposure at A′ and return to your rucksack. Resume pacing and repeat the process for points B′, C′ and so on.
Figure 3.8 Locating yourself on a road or similar curvilinear feature. Sight on points that give good intersections with the road.
Figure 3.9 Intersection of bearings: (a) relatively good, bearings well-spaced in terms of angle; (b) poor, and (c) shows triangle of error.
Figure 3.10 Levelling-in a contour using a level. Set the level to zero and then search for a feature within 0.5° of your level line.
Figure 3.11 Oblique air photograph taken in 1935 of a large-scale anticlinal structure in limestone, Luristan (Lorestân) Province, Iraq. Source: Cardiff University, School of Earth Sciences Air Photo Library
Figure 3.12 A typical block of three runs of aerial photographs, A, B and C. Photographs taken in each run overlap each other by around 60% so that the position on the ground of the principal point (a₁) of photo A-1 can also be found on photo A-2 and so on. Adjacent flight runs overlap by about 30% so that a complete ‘photo-montage’ of the study area can be created.
Figure 3.13 An example of a typical aerial photograph printed directly from the original film negative. Fiducial marks, used for finding the image's principal point, are at the corners (crosses) and midpoints of the sides (triangles). The flight and image number are clearly marked. Along the bottom, the title strip shows a circular bubble level, altimeter and clock, all photographed at the time of exposure. The title strip records the location, date and scale of the direct contact print from the negative. The photo covers the area around Mumbles Head, South Wales (see Figure 4.2).
Figure 3.14 Scale variations across a single aerial photograph taken in undulating country. Plane A–B is the notional plane of the photograph, which includes the principal point (pp). The nominal scale of an air photograph is f/H, where f is the focal length of the camera lens and H is the height above the principal point. However, in a rugged landscape an air photograph cannot produce a uniform scale as the 3D landscape is projected onto a flat negative. Points with higher elevation than the principal point (e.g. hill) are distorted radially outwards and will appear to be further from the principal point in an aerial photograph than on a map. Points at a lower elevation than the principal point (e.g. valley) are distorted radially inwards (appear to be nearer to the principal point compared with a map).

Chapter 4: Methods of Geological Mapping

Figure 4.1 Recording a traverse in a surveyor's chain book. The column down the centre of the page (often printed in red) represents the traverse or ‘chain line’. It has no actual width on the ground, it is merely to record the distance from the start of the traverse leg.
Figure 4.2 Form-line map of Mumbles Head, South Wales, based on bedding orientations in Carboniferous limestones.
Figure 4.3 Lines of convex and concave break-of-slope (b.o.s.). (a) Breaks-of-slope occur at contacts of resistant and less-resistant rock units. (b) Symbols to denote breaks-of-slope.
Figure 4.4 Feature mapping country, Fforest Fawr Geopark, Brecon Beacons, Wales. The course of limestone units is closely related to the geomorphology so that, even in areas of poor rock exposure, recording breaks-of-slope on your field slip is a useful method of mapping formation boundaries.
Figure 4.5 Use of structure contours to interpret a contact. (a) Strike and dip have been measured at point P; (b) contours are drawn parallel to strike through P at a spacing calculated by contour interval/tan (angle of dip); and (c) the predicted outcrop is where the calculated structure contours intersect the topographic contours.
Figure 4.6 Float in hillslope colluvium as an indicator of a contact; the contact is where the first signs of mixed float appear in the soil.
Figure 4.7 Digital infra-red image of the Mynydd yr Eglwys landslide in the upper Rhondda Fawr valley, South Wales, taken in 2005. Important elements of the landslide's morphology are indicated.
Figure 4.8 A cross-section of a rotational landslide, showing how the toe extends further out than the original base of the hill slope, resulting in a lower average gradient, and why the surface of the slide consists of small ridges and hummocks with small streams and ponds between them. There are other types of slide too.
Figure 4.9 (a) Wireline, waterflush, rotary, diamond drilling exploration at Dolaucothi gold mine, Mid-Wales. (b) Cores retrieved from drilling. (c) Cores sequentially stored in core boxes and indexed against depth.
Figure 4.10 Proton magnetometer survey being carried out to detect and map a buried gabbroic dyke at Rhoscolyn, Anglesey, North Wales.
Figure 4.11 GEM-2 electromagnetic instrument coupled with a dGPS positioning system being used to help map faulted geological boundaries in the Rhondda Valley, South Wales.
Figure 4.12 A compass-and-tape traverse to plot larger-scale geological features.
Figure 4.13 A closed traverse of several legs to plot in a number of exposures for a medium-scale sketch map.
Figure 4.14 Mapping a large exposed area by building up a rough grid.
Figure 4.15 A 4 m cord mesh, used as a grid to aid sketch mapping, laid over an exposure at Badcall, NW Scotland (see Figure 4.16).
Figure 4.16 Structures mapped in a deformed ‘Scourie’ dyke at Badcall, mapped using the 4 m cord mesh shown in Figure 4.15. courtesy of R.H. Graham
Figure 4.17 Students undertaking an underground geological mapping exercise at Dolaucothi gold mine, Mid-Wales. Note the tape measure laid out along the adit floor marking distances away from a mine survey point. Mine survey points are usually marked by bolts drilled into the adit roof.
Figure 4.18 (a) Aerial photograph from Iran compared with its photogeological interpretation, and (b) note that the symbols used are different from those used on ordinary geological maps.

Chapter 5: Technological Aids to Mapping

Figure 5.1 Visual representation of a Digital Terrain Model (DTM). The landscape is divided up into square cells and the average elevation of each cell calculated.
Figure 5.2 Three ways in which a Digital Terrain Model made up of a number of individual cell values (black dots) can be visualised using dedicated software.
Figure 5.3 A 20 × 13 km DTM of the Ardnamurchan Peninsula in NW Scotland, UK, displayed in shaded relief with an artificial illumination from the west. The ring-like topographic features are a consequence of a Tertiary igneous complex surrounding a central caldera. DTM data are derived from Ordnance Survey contour mapping (profile data) compiled using 2.6 million 10 × 10 m individual data cells at 1.5 m elevation precision. Being contour-derived elevation information, there is an element of smoothing already applied to the landscape model. Such DTM data are just sufficient in resolution for geological mapping in areas of high topographic relief. However, the 1.5 m vertical precision is not usually detailed enough to create accurate geological base maps in areas of low topographic relief. © Crown Copyright Ordnance Survey. All rights reserved
Figure 5.4 A 900 × 900 m LIDAR-derived Digital Surface Model (DSM) of Flatholm Island in the Bristol Channel, UK, captured at low tide. The DTM is displayed in shaded relief with an artificial illumination from the south. The uplifted Flatholm Island comprises Carboniferous limestone deformed by Variscan folding and thrusting. The island has a very thin soil cover. The LIDAR data are supplied by the UK Environment Agency (EA) as part of their ongoing UK mapping programme. LIDAR data are supplied at a 2 × 2 m ground cell resolution, with a vertical precision of around 15 cm. The image contains 0.2 million data points. Such high-quality LIDAR data can produce an excellent base map for geological mapping. For large study areas covering many square kilometres, LIDAR data files can be excessively large and expensive to obtain, even at educational rates. Copyright: Permission obtained from UK Environment Agency, 2011.
Figure 5.5 Terrestrial laser scanner being used by Terradat UK Ltd to make 3D scans of the geological cliff section at Nash Point, South Wales. Repeated scans are taken at regular time intervals and compared, to quantify rates of cliff erosion. Photo: Nick Russill, Terradat Ltd. Permission obtained from Terradat, UK.
Figure 5.6 View through the eyepiece of an optical level, showing a typical cross-hair system and centimetre graduated staff.
Figure 5.7 Principle of the levelling technique. See text for details.
Figure 5.8 A levelling survey in Cardiff Bay.
Figure 5.9 A total station in operation.
Figure 5.10 The principle of making measurements with a total station. See text for details.
Figure 5.11 The principle of differential GPS (dGPS) systems. The use of both of Ground-Based Augmentation Systems (GBAS) and Satellite-based Augmentation Systems (SBAS) are illustrated.
Figure 5.12 Adapted Trimble marine dGPS system being used for landslide mapping in South Wales. Note marine dGPS antenna housed in rucksack.

Chapter 6: Field Measurements and Techniques

Figure 6.1 Measuring the strike by the contact method.
Figure 6.2 Using a ‘Dr Dollar’-type clinometer to measure dip.
Figure 6.3 A simple aid for measuring strike and dip: an A4-sized plywood board permanently marked with a set of lines parallel to a fixed spirit level. These lines become strike lines once the board is levelled, and can be measured directly with the compass clinometer.
Figure 6.4 Measuring the strike of a veinlet on a rough horizontal surface by Method 2 (see text).
Figure 6.5 An ideal exposure for the end-on measurement of dip.
Figure 6.6 Measuring the strike of an uneven surface with a prismatic compass (Method 3; see text).
Figure 6.7 Measuring the dip of an uneven surface by Method 3 (see text).
Figure 6.8 Conventions for recording strike and dip. (a) Strike/dip/quadrant of dip direction, that is, 032/43 SE (or 212/43 SE). (b) Strike/dip; the strike direction is chosen that, when used as a viewing direction, gives a dip to the right, that is, 032/43. (c) Strike/dip; the strike corresponds to the direction in which the index finger of the right hand points when the thumb points down dip, that is, 212/43. (d) Dip direction/dip, that is, 122/43.
Figure 6.9 The definition of trend and plunge of a linear structure.
Figure 6.10 (a) Geometry of pitch of a linear structure present on a dipping surface, for example, a foliation plane. (b) How to record pitch in your notebook by a diagram; record its angle together with the strike and dip of the surface that the linear structure lies on.
Figure 6.11 Stretched conglomerate pebbles in SW Uganda; trend and plunge can be measured directly.
Figure 6.12 Measuring the plunge and trend of a linear structure. (a) Plunge is measured with the clinometer held vertically and (b) trend is measured with the compass held horizontally.
Figure 6.13 Parasitic folds and larger-scale folds share similar orientations of their hinge lines and axial planes. The parasitic folds have different shapes on opposite limbs of the larger fold.
Figure 6.14 Measuring minor folds. (a) The plunge of the hinge line and (b) the strike of the axial plane.
Figure 6.15 Asymmetrical minor folds in Precambrian banded gneisses, Gjeroy, Norway. These z-folds indicate a major antiform to the right of the outcrop.
Figure 6.16 Fold with axial plane cleavage in Devonian slates at Combe Martin, North Devon. North is to the left of the photograph.
Figure 6.17 Mapping out fold structures from cleavage and bedding. Make a notebook sketch of the dipping bedding and cleavage, hold it up to the outcrop and rotate until the cleavage appears to be vertical; the dip direction of the bedding now indicates the direction of the nearest synform.
Figure 6.18 Fold classes based on relative curvature of outer and inner arcs and layer thickness.
Figure 6.19 Separation: (a) map of fault with strike separation of dextral sense and (b) cliff section showing faulted units. In both cases the arrows are confusing because they suggest the sense of slip (true movement), which here is not known.
Figure 6.20 Mapping a thrust. Over much of its outcrop, the thrust forms flats where there is concordance with the formation boundaries making it difficult to recognise as a thrust. The presence of a ramp where the thrust plane cuts through the units at an angle and the repetition of units helps with its recognition.
Figure 6.21 An angular unconformity displayed (a) on a geological map and (b) in a block diagram.
Figure 6.22 An unconformity at Sully Island, South Wales. Triassic mudstones rest unconformably on dipping Carboniferous limestone.
Figure 6.23 Marking a specimen to record its in situ orientation.
Figure 6.24 A specimen register in a field notebook.
Figure 6.25 Example of a good field photograph; folded upper Jurassic-lower Cretaceous rocks, Stair Hole, Dorset. A 70 mm focal-length lens is used to avoid wide-angle distortion. The sun is shining directly on to the cliff face. People and a fence give the scale.
Figure 6.26 Single digital image of thrusted sediments exposed at Dinas Dinlle, North Wales coast. Note the use of a 3 m survey staff as a scale.
Figure 6.27 Dinas Dinlle photo mosaic constructed from six overlapping digital images with 10 m markers overlain. This mosaic can be used to construct a technically accurate sketch of the outcrop.
Figure 6.28 A simplified profile through stream gravels; the heavy-mineral sands accumulate at the base of the coarser material and may even penetrate cracks in the bedrock. Note the sands and gravels of the stream are in constant movement, which allows the ‘heavies’ to pass downwards through them.
Figure 6.29 A geologist panning in the Euphrates Valley.

Chapter 7: Mappable Rock Units and Lithology

Figure 7.1 Calculation of stratigraphic thickness, t, from down-slope exposure distance, s, or width of outcrop, W. α and β are the angles of ground slope and formation dip, respectively. The values of s and W are measured at right angles to the strike.
Figure 7.2 A graphic sedimentary log. The horizontal scale is a measure of grain size. Divisions are unequal because the ϕ-scale range for silt is only four-fifths of that for sand (see Appendix D). The vertical triangles to the right indicate coarsening and fining in the sequence. courtesy of A.R. Gardiner
Figure 7.3 Part of a complex pegmatite in Buganda Province, Uganda, redrawn from a notebook sketch of a prospecting pit. Note the large radiating sheaves of ‘cleavelandite’ albite, massive microcline, granular topaz (not gem form) and large books of zinnwaldite (a lithium-bearing form of biotite).
Figure 7.4 Oxidation of sulphide ore deposits, showing how some ore minerals are oxidised and carried downwards; some to re-precipitate above the water-table; some to be reduced again to deposit as new sulphides, or as native metal, just below it, enriching sulphide ores already there. The insoluble iron oxides remain at surface as a mass of rather cellular insoluble iron oxide gossan.
Figure 7.5 The water profile of soil and rocks.
Figure 7.6 Wells. Well no. 1 penetrates to an aquifer and the water must be pumped. Over-pumping will draw down the rest-level and locally deplete until it is re-charged. Well no. 2 has penetrated through the aquiclude, which confines the water within the aquifer, and because the well-head is below the piezometric surface (the level of the water-table in the aquifer where it crops out), the well is artesian and water flows without pumping. Well-head no. 3, however, is above the piezometric surface and needs to be pumped. Note that the piezometric surface slopes downwards towards the centre of the artesian basin. WT, water-table.

Chapter 8: Field Maps and Field Notebooks

Figure 8.1 Reverse side of a field slip with the information it should carry. Note the index showing how this slip relates to those that make up the whole mapping area.
Figure 8.2 Symbols for field and fair-copy maps compared. (a) Strike and dip, plunge and azimuth are shown on the field map, though the quadrant of the dip is omitted because this is clear from the tick on the strike symbol. (b) Only dip and plunge are shown on the fair copy.
Figure 8.3 Styles of line used for contacts. The type of line used depends on the degree of certainty of the position of a contact.
Figure 8.4 Page from a field notebook (John Barnes). The column on the left shows the registered number of specimens collected. The observation number referring to the locality (Ravange, Iran) appears in the same column on the previous notebook page. The cross-section on the lower part of the page needs no locality/observation number as the section line is shown on the field slip and on the map.
Figure 8.5 Another example notebook page (RJL). Note the comment on the weather and the reason for the re-examination. There is both a locality number (179), and a grid reference (567 129) given, plus a description, that is, ‘S of bathing huts’. The cross-section has been cleaned up in the office later for inclusion in a report.
Figure 8.6 Poor and good sketches. (a) Photo of exposure of thrusted sandstones and shales, N of Widemouth Bay, Devon. (b) Poor sketch with no scale, orientation, indefinite linework, and lack of labelling. (c) Good sketch with attempt to trace individual bedding planes and faults as continuous features and representing cross-cutting relationships.

Chapter 9: Fair Copy Maps and Other Illustrations

Figure 9.1 Layout of a fair copy map, showing the arrangement of explanatory matter. Note the terminations to the cross-section lines so there is no ambiguity over the exact positions where the section lines end.
Figure 9.2 Scales and north symbols for fair copy maps. (a,b) Graphic scales. (c) Scale expressed as a representative fraction. (d) Composite north symbol shows the declination and grid magnetic angles diagrammatically.
Figure 9.3 Stratigraphic column. Sometimes brief descriptions of the rock-types, fossil content and ages are given on the right of the column.
Figure 9.4 Geological map draped onto a 3D LIDAR digital terrain model, Mynydd Yr Eglwys, Rhondda Fawr Valley, South Wales.

Chapter 10: Cross-Sections and 3D Illustrations

Figure 10.1 Structural interpretations. (a) Data consisting of contact positions and apparent dips. (b) Interpretation assuming maintenance of dips at depth. (c) Interpretation assuming constant thickness of units. Relationships on the geological map will help decide between these alternatives.
Figure 10.2 (a–c) Drawing a cross-section from apparent dip information. See text for details.
Figure 10.3 Drawing a cross-section using the down-plunge method. See text for details.
Figure 10.4 Serial cross-sections, in which each columnar section is constructed by oblique projection.
Figure 10.5 (a) Isometric cube; (b) a fold drawn using the isometric cube as a guide and (c) oblique projection of a cube.
Figure 10.6 Oblique projection of serial cross-sections. Each cross-section is a true (undistorted) cross-section but the distance between them is foreshortened by one-third.
Figure 10.7 Simple block diagram, split, with two halves separated, and with steps.
Figure 10.8 Fence, or panel, diagram illustrating stratigraphic variations in a region. It gives a better spatial impression than a columnar section (cf. Figure 10.4).
Figure 10.9 Photograph of an egg-crate model (by courtesy of S.J. Matthews)
Figure 10.10 3D computer-generated geological model of the central South Wales coalfield created from subsurface geological information (from Brabham, 2009).

Appendix A: Adjustment of a Closed Compass Traverse

Figure A.1 Adjustment of a closed compass traverse.

Wiley-Blackwell is an imprint of John Wiley & Sons, formed by the merger of Wiley's global Scientific, Technical and Medical business with Blackwell Publishing.

Registered office: John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex,

Editorial Offices: 9600 Garsington Road, Oxford, OX4 2DQ, UK

The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK

111 River Street, Hoboken, NJ 07030-5774, USA

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell.

The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

Library of Congress Cataloging-in-Publication Data

Lisle, Rixhard J.

Basic geological mapping.– 5th ed. / Richard J. Lisle, Peter J. Brabham, and John W. Barnes.

p. cm.

Rev. ed. of: Basic geological mapping / John W. Barnes, with Richard J. Lisle. 4th ed. Includes index.

ISBN 978-0-470-68634-8 (pbk.)

1. Geological mapping. I. Brabham, Peter. II. Barnes, J. W. (John Wykeham), 1921- III. Barnes, J. W. (John Wykeham), 1921- Basic geological mapping. IV. Title.

QE36.B33 2011

550.22'3–dc23

2011022844

ISBN: 978-0-470-68634-8

A catalogue record for this book is available from the British Library.

This book is published in the following electronic format: ePDF 978-1-119-97402-4;ePub 978-1-119-97751-3; MOBI 978-1-119-97752-0

Preface to The Fourth Edition

This book is a basic guide to field techniques used in geological mapping. It is meant to be kept in camp with you and even carried in your rucksack in the field. In addition, because no piece of geological mapping can be considered complete until the geology has been interpreted and explained, chapters are provided on drawing cross-sections, on preparing and presenting ‘fair copy’ maps, and on presenting geological diagrams from your fieldwork suitable for inclusion in your report. A report explaining the geology is an essential part of any field project, and a brief chapter on the essentials for writing and illustrating it concludes this book. Some emphasis, too, is given to field sketch-mapping because many reports lack those large-scale detailed maps of small areas that can often explain complex aspects of the geology that cannot be shown on the scale of the field map being used, and that are difficult to describe in words. Attention is also given to field notebooks, which are, in many cases, deplorable.

It is assumed that readers of this book have already had at least one year of university or equivalent geology, and have already been told what to look for in the field. Geological mapping cannot, however, be taught in lectures and the laboratory: it must be learnt in the field. Unfortunately, only too often, trainee geologists are left largely to their own devices, to sink or swim, and to learn to map for themselves with a minimum of supervision on ‘independent’ mapping projects. It is hoped that this book will help in that task.

John W. Barnes and Richard J. Lisle

2003

Preface to The Fifth Edition

This fifth edition of Basic Geological Mapping was revised without the help of John Wakeham Barnes who sadly passed away in 2007. On the suggestion of referees we have updated the text by including mention of modern technological aids and data that are used in modern geological mapping, such as applied geophysics, digital terrain models, and optical and GPS-based surveying. There has also been more emphasis given to structural geology and cross-section construction. Whilst making these additions we have been conscious of the need to maintain John's successful formula; to offer a practical guide for the student undertaking a mapping project with a minimum of resources and academic supervision.

We are grateful for the advice of Jim Hendry and Rob Strachan (University of Portsmouth), Chris Berry and Alun Rodgers (Cardiff University) and the book's reviewers.

Richard J. Lisle and Peter J. Brabham

January 2011