Geological Field Techniques is a welcome addition to this specialized subject. The book is well-illustrated with colour photographs, sketches, tables, flowcharts, cartoons and worked examples. It also contains varying colour coded tabs at the upper section of the pages for ease of finding each chapter.
Chapter 1, ‘Introduction’, outlines reasons for field geology and notes the main intellectual challenges that a field geologist may encounter. ‘Equipment’ (Chapter 2) discusses the way various items of field equipment are utilized. Various compasses, hammers, chisels, tape measures, notebooks (both electronic and traditional hardcopy) and various charts are the key equipment detailed and comprehensively highlighted. Different choices of writing equipment (e.g., pens, pencils, colour pencils) are discussed, noting the different conditions under which each is effective. Safety, hazard awareness and respect for property, property owners and locals are also expounded.
‘Introduction to field observations at different scales’ discusses a systematic way to do fieldwork. Other than the delineation of the field area, the chapter discusses the most fundamental, but sometimes most difficult field decision, that is, the determination of rock types. By listing various questions that have to be asked, the author shows how to draw out the right conclusion.
‘The field notebook’ examines the reasons for a notebook, and various ways to use and keep one. This enlightening chapter encourages good ethics, emphasizing the need for space to record planning information, things to do, field discussions scale and orientation of page. Reasons for revisiting exposures are expounded on, along with the need to correlate between yourself and other workers.
‘Recording palaeontological information’ explains the importance of fossils, along with the various specialized tools necessary for palaeontological fieldwork. For me, the highlight in this chapter was the inclusion of a good section on trace fossils, so often ignored, and their importance. Distribution of and where to find fossils, ways to determine whether a fossil was transported or remained in life position and sampling strategies are discussed, all summarized by a flow chart.
‘Recording features of sedimentary rocks and constructing graphic logs’ is introduced by distinguishing five reasons for recording features of sedimentary rocks and constructing graphic logs, apart from the general requirements for mapping and reconstruction of geological history, such as understanding sedimentary processes and depositional environments, reconstruction of past periods of environmental change and refining the geological timescale. Visual aids include classification flowcharts for siliciclastics and carbonates, tables summarizing sedimentary structures and features are associated with various rock types (with suggestions for observing, describing and identifying the structures), the way to record and summarize data on sedimentary rock succession using graphic logs, and methods used to reconstruct sedimentary environments.
‘Recording features of igneous rocks’ gives four main reasons for this: hazards volcanoes pose to life, understanding processes beneath the Earth's surface, understanding the distribution of ore minerals and chronology. Field safety and the necessary equipment needed to examine ancient versus active systems are emphasized. Field relationships of igneous rocks with surrounding rocks, joints and veins, exposure-scale fabrics, chilled and chilling margins, and pyroclastic rocks are detailed, as are the measurements/observations to be made on these bodies. A welcome worked example of chilling statistics in Oman was outlined, with a schematic diagram of an east–west traverse across sheet dykes, although the (misleading) title of this section was ‘Chilling statistics in Cyprus’. Mineralogy and small-scale textures of igneous rocks were stressed, along with suggestions for types of features to look for in the field. Recommended observations on active volcanoes, only where safe to do so, include examination of lava flow morphology, seeking volcanic bombs, risk assessment of recent pyroclastic flow, fresh fall-out ash and checking for accessibility of vents.
‘Recording structural information’ introduces itself with discussion of the reasons why it is important and reminders of the equipment necessary. The use of the various types of notations for strike, etc., are tabulated. The determination of brittle structures includes a table detailing landscape clues to the presences of faults will be found useful to many users. A worked example, ‘Investigating a fault zone in Andalućia’, shows how slickenside lineations, minor fractures and slickenfibres are used to highlight past motions. A further useful visual aid is a flowchart for discrimination of different foliations in the field. Another flowchart explains how to discriminate between different lineations, along with a worked example.
‘Recording features of metamorphic rocks’ outlines the basic skills and equipment needed to undertake specialist metamorphic fieldwork. A worked example, ‘Mineral identification in southern Spain’, shows how clues that were used to identify minerals on an excursion. It is rightfully pointed out that the ‘study of metamorphic texture should not be left until you access to a petrographic microscope’; with careful field observations, an early understanding of complex rocks can be made which will help to avoid unnecessary assumptions. Various strategies for collection of information on the identification of minerals are tabulated, detailing common metamorphic rock types and their P/T conditions. Finally, the chapter discusses the observations needed to unravel metamorphism and deformation, ending with a worked example from a field excursion in the western Alps, showing how diverse observations can be made and data collected, and used, to reconstruct a metamorphic history.
‘Making a geological map’ examines the principles and aims of geological mapping. Although traditional and non-traditional (electronic) tools for mapping are discussed, the latter are considered outside this book's scope. Pros and cons of using aerial photography and satellite imagery are tabulated. A worked example shows how the use of satellite imagery may be used to produce a geological map after ‘ground-truthing’. After a discussion of the equipment used in the field for mapping, a worked example shows how location by compass in a remote area is effective after the GPS fails. The next section, on making a map, examines what data to put on it and how to do so, and the importance of sketching cross-sections in the field as an aid to understanding subsurface behaviour. Three methods, traverse, contact and exposure mapping, are discussed; of course, no method can be used in isolation and any map must utilize other evidence, such as topographic features, drainage, soil and vegetation.
‘Recording numerical data and use of instruments in the field’ serves as a reminder about the problems associated with carrying equipment, their calibration and their clearance through customs, and, therefore, the need to have proper backup documentation of data sets. A list of common equipment, their use and relevant examples are included. The next chapter, ‘Photography’, emphasizes the old maxim that photographs are a necessity for the majority of geological fieldwork, but that it should not be used as a replacement for sketches.
Nine key points are given with respect to ‘Sampling’. The amount of samples needed for various tasks (for example, mineral analyses, 1–2 kg of rock) is documented. Various ways of packaging and labelling of samples, especially fossils that may be rare, are examined for the novice. ‘Concluding remarks’ lists 17 points to be considered before, during and after geological fieldwork.
Geological Field Techniques is a well-illustrated, reader-friendly and logically organized guide to field geology. It will be attractive and relevant to all geologists, whether amateurs, undergraduate students (one which I would recommend) and postgraduates.