Geological Field Techniques

Dr Angela L. Coe specializes in sedimentology and stratigraphy and has over 20 years of experience of collecting geological field data in Europe, Asia, North and South America. Over this time, she has also designed and taught field geology courses for several UK universities and has led many field trips for international conferences and petroleum companies. Dr Tom W. Argles is a geologist who has conducted structural and metamorphic fieldwork in several mountain belts (Alps, Himalaya, Betic Cordillera, Caledonides, Basin and Range) for 20 years. He has set up and taught field courses in a range of locations across the UK and Europe Dr David A. Rothery is a volcanologist and planetary scientist. He has taught geology in the field for 30 years and has research experience of igneous rocks (including active volcanoes) in the Oman, Cyprus, Italy, the Andes, central America, NW USA, Hawaii and Western Australia. Professor Robert A. Spicer is a palaeobotanist and sedimentologist with over 30 years field experience working in remote regions of Northern Alaska and northeastern Russia, China and Tibet, India, Australia, New Zealand, and Mexico.

Preface x Acknowledgements xi 1 INTRODUCTION 1 1.1 A selection of general books and reference material on geology 2 1.2 Books on geological fi eld techniques 3 2 FIELD EQUIPMENT AND SAFETY 4 2.1 Introduction 4 2.2 The hand lens and binoculars 5 2.3 The compass-clinometer 6 2.3.1 Orientation of a dipping plane 11 2.3.2 Orientation of a linear feature 16 2.3.3 Triangulation: Determining location using a compass 20 2.4 Global positioning systems and altimeters 25 2.5 Measuring distance and thickness 26 2.5.1 Standard thickness and distance measurements 26 2.5.2 Use of the Jacob staff to measure the thickness of inclined strata 27 2.6 Classifi cation and colour charts 28 2.7 Hammer, chisels and other hardware 31 2.8 The hardcopy fi eld notebook 33 2.9 The laptop, netbook or PDA as a notebook 34 2.10 Writing equipment, maps and relevant literature 35 2.10.1 Writing equipment 35 2.10.2 Maps and relevant literature 35 2.11 Comfort, fi eld safety and fi eld safety equipment 36 2.11.1 Clothes, backpack/rucksack and personal provisions 36 2.11.2 Field safety 36 2.11.3 Field safety equipment 39 2.12 Conservation, respect and obtaining permission 40 2.13 Further reading 41 3 INTRODUCTION TO FIELD OBSERVATIONS AT DIFFERENT SCALES 42 3.1 Introduction: What, where and how? 42 3.1.1 Defining the fi eldwork objectives 42 3.1.2 Deciding where to do the fi eldwork 43 3.1.3 Locating your position 45 3.2 Scale of observation, where to start and basic measurements 45 3.2.1 Regional context 45 3.2.2 Whole exposure 46 3.2.3 Hand specimens 49 3.3 Overview of possible data formats 51 4 THE FIELD NOTEBOOK 53 4.1 Introduction: The purpose of fi eld notes 53 4.2 Field notebook layout 54 4.2.1 Preliminary pages 54 4.2.2 Daily entries 54 4.2.3 General tips 56 4.3 Field sketches: A picture is worth a thousand words 57 4.3.1 General principles: Aims, space and tools 59 4.3.2 Sketches of exposures 63 4.3.3 Sketching metre- and centimetre-scale features 67 4.3.4 Sketch maps 68 4.4 Written notes: Recording data, ideas and interpretation 72 4.4.1 Notes recording data and observations 72 4.4.2 Notes recording interpretation, discussion and ideas 72 4.5 Correlation with other data sets and interpretations 77 5 RECORDING PALAEONTOLOGICAL INFORMATION 79 5.1 Introduction: Fossils are smart particles 79 5.1.1 Why are fossils important? 79 5.1.2 Collecting fossil data 80 5.2 Fossil types and preservation 82 5.2.1 Body fossil classifi cation 82 5.2.2 Body fossil preservation 82 5.2.3 Trace fossils 85 5.2.4 Molecular fossils 87 5.3 Fossil distribution and where to fi nd them 87 5.3.1 Transported or life position? 88 5.4 Sampling strategies 90 5.4.1 Sampling for biostratigraphic or evolutionary studies 90 5.4.2 Sampling of bedding surfaces and palaeoecology 92 5.5 Estimating abundance 95 5.5.1 Presence/absence and qualitative abundance estimates 96 5.5.2 Quantitative measures of abundance 96 5.5.3 How many samples are required? 99 5.6 Summary 100 5.7 Further reading 101 6 RECORDING FEATURES OF SEDIMENTARY ROCKS AND CONSTRUCTING GRAPHIC LOGS 102 6.1 Introduction 102 6.2 Description, recognition and recording of sedimentary deposits and sedimentary structures 104 6.2.1 Recording sedimentary lithology 104 6.2.2 Recording sedimentary structures 109 6.3 Graphic logs 117 6.3.1 Conventions for graphic logs 119 6.3.2 Constructing a graphic log 121 6.4 Rocks in space: Reconstructing sedimentary environments and their diagnostic features 127 6.5 Using sedimentary rocks to interpret climate change and sea-level change 133 6.5.1 Climate change 134 6.5.2 Sequence stratigraphy and relative sea-level change 134 6.6 Further reading 137 7 RECORDING FEATURES OF IGNEOUS ROCKS 139 7.1 Equipment, basic tips and safety 139 7.2 Field relationships of igneous rocks 140 7.2.1 Relationships with surrounding rocks 140 7.2.2 Internal architecture: Joints and veins 144 7.2.3 Internal architecture: Other exposure-scale fabrics 146 7.3 Mineralogy and small-scale textures of igneous rocks 154 7.3.1 Petrologic type 155 7.3.2 Mineral texture and fabric 155 7.4 Recent and active volcanoes 159 7.4.1 Equipment and safety 159 7.4.2 Access 160 7.4.3 Observations 160 7.5 Further reading 161 8 RECORDING STRUCTURAL INFORMATION 163 8.1 Equipment and measurement 164 8.1.1 Structural measurements and notations 164 8.2 Brittle structures: Faults, joints and veins 165 8.2.1 Planar brittle features - orientation 165 8.2.2 Determining past motion on brittle structures 170 8.3 Ductile structures: Shear zones, foliations and folds 176 8.3.1 Orientation of ductile planar features 176 8.3.2 Direction of shear/stretching: Stretching lineations 180 8.3.3 Sense of shear: Kinematic indicators 182 8.3.4 Magnitude of shear strain 185 8.3.5 Fold analysis 185 8.4 Further reading 191 9 RECORDING FEATURES OF METAMORPHIC ROCKS 192 9.1 Basic skills and equipment for metamorphic fi eldwork 192 9.1.1 Field relations and context 192 9.2 Textures 194 9.2.1 Banding 194 9.2.2 Grain textures 196 9.2.3 Reaction textures 197 9.3 Mineralogy 198 9.3.1 Identifying common metamorphic minerals 198 9.3.2 Using mineral assemblages 198 9.3.3 Classifi cation of metamorphic rocks 200 9.4 Unravelling metamorphism and deformation 201 9.4.1 Pre-kinematic features 202 9.4.2 Syn-kinematic features 202 9.4.3 Post-kinematic features 203 9.5 Further reading 205 10 MAKING A GEOLOGICAL MAP 206 10.1 Principles and aims 206 10.2 Preparation and materials 207 10.2.1 Base maps and other aids 207 10.2.2 Equipment for mapping 212 10.3 Location, location, location 214 10.3.1 Equipment 214 10.3.2 Using base maps 214 10.4 Making a fi eld map 216 10.4.1 Information to record on fi eld maps 216 10.4.2 The evolving map 218 10.4.3 Sketch cross-sections 221 10.5 Mapping techniques 222 10.5.1 Traverse mapping 223 10.5.2 Contact mapping 225 10.5.3 Exposure mapping 226 10.5.4 Using other evidence 228 10.6 The geological map 233 10.6.1 Inking in the fi eld map 233 10.6.2 Cross-sections 235 10.6.3 Fair copy maps 235 10.6.4 Digital maps and GIS 239 10.7 Further reading 240 11 RECORDING NUMERICAL DATA AND USE OF INSTRUMENTS IN THE FIELD 241 11.1 Data collection 241 11.1.1 Instrument calibration and base stations 244 11.1.2 Survey grids 244 11.2 Transport and protection of the instruments 245 11.3 Correlation with other data sets 245 11.4 Further reading 246 12 PHOTOGRAPHY 247 13 SAMPLING 250 13.1 Selecting and labelling samples 250 13.1.1 Samples for thin-sections 251 13.1.2 Orientated samples 251 13.1.3 Samples for geochemical analysis 253 13.1.4 Samples for mineral extraction 253 13.1.5 Samples for fossils 253 13.1.6 Sampling for regional studies 254 13.1.7 High-resolution sample sets 254 13.1.8 Labelling samples and their packaging 255 13.2 Practical advice 256 13.2.1 Packing and marking materials 256 13.2.2 Extraction of samples 257 14 CONCLUDING REMARKS 259 14.1 Further reading on scientifi c report writing 260 REFERENCES 261 APPENDIX A1: GENERAL 263 APPENDIX A5: FOSSILS 265 APPENDIX A6: SEDIMENTARY 273 APPENDIX A7: IGNEOUS 293 APPENDIX A8: STRUCTURAL 296 APPENDIX A9: METAMORPHIC 302 APPENDIX A10: MAPPING 306 Index 310