He conducts research on the development of sedimentary basins in Europe, Africa and Asia and teaches sedimentology, basin analysis, ichnology as well as historical geology. Skip to main content Skip to table of contents. Advertisement Hide. This service is more advanced with JavaScript available. Pocket Guide Geology in the Field. Authors view affiliations Tom McCann. Lecture 21 Notes PDF.
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Lisle p. Geological mapping. Lisle, Richard J. It is hoped that this book will help them in that task. John W. Barnes, Richard J. Among those who deserve special mention with the text or diagrams are the late D. Ager, M. Coulson, F. Cross, A. Gar- diner, R. Graham, S. Matthews, the late T. Owen, P. Styles, and C.
Tomlinson, all at that time of the University of Wales Swansea; also P. Brabham and A. Rogers of Cardiff University; M. Bailey of the United States Geological Survey. Jenkins who typed the original drafts and to my late wife for reading the typescript and original proofs. I also wish to thank Richard Lisle for his help in preparing this fourth edition. Here, however, we are concerned only with the rudiments of geological mapping.
The intention is to provide basic knowledge which can be built upon. As a geologist, you must also remember that accurate geological maps are the basis of all geological work, even laboratory work, for it is pointless to make a detailed investigation of a specimen whose provenance is uncertain. There never was and there never will be. First it describes the equipment you will need; then you are introduced to the many types of geological map you may have to deal with some time during your professional career.
Methods to locate yourself on a map are also described and advice is given on what to do if no topographic base maps at all are obtainable. The next three chapters describe methods and techniques used in geo- logical mapping, including a brief description of photogeology; that is the use of aerial photographs in interpreting geology on the ground.
Barnes with Richard J. However, a geological map is not, as is sometimes supposed, an end in itself. The whole purpose is to explain the geology of the area and your map is only a part of that process: a report is also needed to explain the geological history of the area and the sequence of geological events.
Chapter 10 is a guide on how to present this important part of any geological mapping project. It avoids theoretical considerations. What those conclusions are is up to you, but bear in mind what the geologist Lord Oxburgh has said; that making a geological map is one of the most intellectually challenging tasks in academia Dixon So, do not leave gates open, climb dry-stone walls or trample crops, and do not leave litter or disturb communities of plants and animals.
When you are collecting specimens do not strip or spoil sites where type fossils or rare minerals occur. Take only what you need. Bear in mind that upset landowners can inhibit geological activities in an area for years to come, and this has already happened in parts of Britain. Many other countries are less populated and have more open space, and the situation may be easier, but every country has some land where owners expect people to consult them before working there.
If in doubt, ask! Experience is the best teacher but common sense is a good substitute. Field safety is more fully discussed in Appendix I from both the standpoint of the student or employee and his supervisor or employer.
A ford often proves deeper than you thought and not all natural water is quite as pellucid as poets would have us believe. Such accidents happen to most of us sometime. If you are faced by something risky, play it safe, especially if you are on your own.
Geologists should also be able to drive. They sometimes have to ride, too. Horses, donkeys, and especially mules, are still used in some mountainous areas. They can save a great deal of tedious walking and backpacking, and mules in particular can clamber up astonishingly steep and rocky slopes. Field geologists spend a great deal of their time getting from place to place. Do not lose heart: this is quite normal and the map will suddenly begin to take shape. A hammer sometimes two is essential and some chisels.
Also essential are a compass, clinometer, pocket steel tape, and a handlens, plus a map case, notebook, map scales, protractor, pencils and eraser, an acid bottle and a jack-knife. A camera is a must and a small pair of binoculars can be most useful at times, as is a GPS instrument if it can be afforded see Section 3. Sometimes a 30 m tape may be needed and a stereonet. If using aerial photographs you will need a pocket stereoscope; very occasionally a pedometer can be useful, although not essen- tial.
A more detailed description of the essentials is given in Figure 2. Generally, a hammer weighing less than about 34 kg 1 12 lbs is of little use except for very soft rocks; 1 kg 2—2 12 lbs is probably the most useful weight.
The commonest pattern still used in Europe has one square- faced end and one chisel end. Geologists working on igneous and metamorphic rocks may opt for heavier hammers. Hammering alone is not always the best way to collect rock or fossil specimens. Its size depends on the work to be done. A 5 mm 14 inch chisel may be ideal to delicately chip a small fossil free from shale, but to break out large pieces of harder rock a 20—25 mm 34 inch chisel is required Figure 2.
This is a steel bar, usually a piece of drill steel, 25—30 cm long, sharpened to a point and tempered. One thing which you must never do is to use one hammer as a chisel and hit it with another. They can be bought or easily made from heavy leather Figure 2. Climbing shops stock them for piton hammers although some may be too small to take a geological hammer handle. Courts would probably take a less than liberal view of claims for compensation for eye injuries suffered if goggles were not being worn.
All are expensive. All the above have built-in clinometers. The Silva Figure 2. However, like the Brunton, a b c d Figure 2. Like the Suunto, an excellent and reasonably priced instrument the Silva and Suunto are needle compasses and are not as easy to take bearings with on distant points as are prismatic compasses which have a graduated card to carry the magnetic needle.
Silva do make a prismatic card-compass No. The Brunton is induction-damped. A compromise may be made by using a separate clinometer and a cheaper compass, such as the Japanese Europleasure Lensatic compass. This is liquid- damped and can be read like a prismatic available from sports and camping shops.
Another alternative is to buy a hand-bearing compass such as the Meridian or the very robust former British army compass second-hand shops. The latter suffers from having no straight edge with which to mea- sure strike with, but is excellent if you need to survey-in numerous distant points accurately. The basic choice is between the traditional degrees and the continental grads to a full circle.
Comparisons are made in Table 2. A mirror compass can be read in two ways. As the Brunton is undamped, do not wait until the needle has stopped swinging, wait until the swing is only a few degrees and read the average of the swing; it takes practice.
Some prefer to read a Brunton in the same way. Mirror compasses have a distinct advantage over prismatics in poor light such as underground. Clinometers can be bought separately and a few types, such as the Finnish Suunto, have the advantage that they can also be used as a hand-level. Some hand-levels, such as the Abney Figure 2. The Burgess level and angle indicator, designed for do-it-yourself handymen, makes a cheap and effective clinometer and it is sold under other names.
These DIY instruments Figures 2. Remove it for obvious reasons. Although not accurate enough for normal dip measurements, they are useful for measuring lineations Section 5. The Figure 2. It is effective in even the Trend can be measured directly most awkward places Figures 2. The maker is read by the pointer hanging be- Nihon Chikagasko Shaco, Kyoto.
To ensure that it does last a lifetime, attach a thin cord to hang it round your neck. A 3 m tape takes up no more room than a 1 m tape and is much more useful. You can use it to measure everything from grain size to bed thickness, and if the tape has black numbering on a white background, you can use it as a scale when taking close-up photographs of rock surfaces or fossils.
You might not need it every day but keep one in camp for when you do. Treat a tape with respect. Wind it back into its case only when clean, for dirt will wear off the graduations. If a long tape is muddy, coil it into loops between measurements. A map case must have a rigid base so that you can plot and write on the map easily; it must protect the map; and it must open easily, otherwise it will deter you from adding information to the map.
The best map cases are probably home-made Figure 2. Pencil holders make mapping easier, whether attached to your map case or your belt. Make your own. It will have to put up with hard usage, often in wet and windy conditions. Even simpler, use adhesive carpet tape for the hinge, but it will need frequent renewing vulnerable. A hard cover is necessary to give a good surface for writing and sketching. Try to buy a book with squared, preferably metric squared, paper; it makes sketching so much easier.
Half-centimetre squares are quite small enough. Scales are not expensive for the amount of use they get. Many are thinly oval in section and engraved on both sides to give four different graduations. The most convenient combination is probably , , and In the USA scales with and are needed.
Colour code scale edges by painting each with a different coloured waterproof ink or coloured adhesive tape, even nail varnish, so that the scale you are currently using is instantly recognisable. They are easily obtainable and relatively cheap. The harder alternatives are for warmer climates, the softer for cold. Do not be tempted into using soft pencils, they smudge and they need frequent sharpening. Attach a larger good quality eraser to your buttonhole or your mapcase with a piece of string or cord, and always carry a spare.
Coloured pencils should also be of top quality; keep a list of the make and shade numbers you do use so that you can replace them with exactly the same shades again. Waterproof ink and only waterproof ink should ever be used on your map is impossible to erase without damaging the surface of the map. They have the advantage that they deliver only one drop at a time, are small, do not leak and will not break.
GPS is a nav- igational method operated by the US government. A hand-held device, little bigger than a mobile phone Figure 2. It cannot be used in forest because it requires a clear view of several satellites. It also does not function well in icy conditions distance to be calculated. By simultaneously using signals from several satel- lites, the position of the receiver on the ground can be determined.
Noise errors, including those deliberately introduced by the system operators, are determined by putting a receiver at a base station with a known location, then using a rov- ing receiver to communicate with the base station to obtain the necessary corrections.
Instruments weigh between and g and there are several makers. Functions vary with makes and models: some give latitude and longitude, and grid references for different national grid systems.
Keep track of your route by constantly referring to your base map. In this way you will always have a general idea of where you are relative to the alignment of the geological features of the terrain. Plunge and trend can be calculated on the spot from strike and pitch measurements made on bedding and foliation planes, or from the intersection of planes Lisle and Leyshon Make one by glueing a 15 cm Wulff or Schmidt net to a piece of Perspex or even thin plywood, leaving a margin of 1 cm or so around edge of the net.
Cut a slightly smaller piece of Perspex and attach to the net by a screw or any other method so that one can rotate over the other. It will give you a three-dimensional image from stereopairs with a much exaggerated topographic relief; a great advantage, as minor topographic features controlled by geology, such as faults, joints and dykes stand out more clearly. However, also learn to get a 3D image from a stereo-pair of photos without a stereoscope; it just takes practice.
It does not actually measure distance directly: it counts paces and expresses them in terms of distance after it has been set with your own pace length.
Make allowances for your shorter paces on slopes, both up and downhill. It is better to keep them in your hand baggage when travelling by air, in case the baggage com- partment is not pressurised.
As most instruments read only to m above sea level, they are not likely to function properly if repeatedly exposed to the 10 or 15 m of modern air travel. In warm or hot climates, bad sunburn will not lead to full concentration on your work, nor will being covered in insect bites.
Even when the weather appears warm, carry a sweater in your rucksack in hilly country, and when buying an anorak, choose bright oranges or yellows: they are more easily seen by search parties!
In some countries you can rely on the weather but not in Britain, and nights can be very cold if you get lost. Clothing in warmer and tropical climates is at least less bulky. Wear long-sleeved shirts and long trousers until acclimatised. And note, it can still get cold at night on higher ground even in the tropics. Boots in temperate, wet and cold climates should be strong and waterproof, with well-cleated soles. Rubber Wellingtons can be worn when working in boggy ground, such as in parts of Scotland, and some have excellent soles, but they can be uncomfortable if you have to walk long distances in them.
Heavier boots, however, are still advisable in mountains, wherever you are. In Britain, geologists have a wide selection of Ordnance Survey OS maps at their disposal, from a scale of to even larger scales in many areas. In other countries the maps available are usually of much smaller scales. You may even have to make your own topographic base — if you know how. Any geologist, especially one who intends to enter the mineral industry, is well advised to learn at least the rudiments of map making.
It will stand them in very good stead later Appendix III. These are: reconnaissance maps; maps made of regional geology; large-scale maps of limited areas; and maps made for special purposes. Small-scale maps covering very large regions are usually compiled from information selected from one or more of these groups.
They are usually made at a scale of or smaller, sometimes very much smaller. Some reconnais- sance maps are made by photogeology, that is by interpreting geology from aerial photographs, with only a minimum of work done on the ground to identify rock types and to identify dubious structural features, such as lin- eaments. Basic Geological Mapping, Fourth Edition. Regional geological maps should be plotted on a reliable base.
An accurate geological map loses much of its point if superimposed on an inadequate topographic base. Regional geological mapping done on the ground may be supported by systematic photogeology, and it should be emphasised that photogeological evidence is not inferior to information obtained on the ground although it may differ in character.
Some geological features seen on aerial photographs cannot even be detected on the ground while others can even be more conve- niently followed on photographs than in surface exposures see Section 4. All geological mapping should incorporate any techniques which can help in plotting the geology and which the budget will allow, including geophysics, pitting, augering, drilling and even the use of satellite images where available.
Few countries match this detail for their regional topographic and geological map coverage. This is also the scale most commonly used by British students for their own mapping projects.
Some are for research, others for economic purposes, such as open pit mine plans at scales from to ; underground geological mine plans at or larger; and engineering site investigations at similar scales.
They include geophysical and geochemical maps; foliation and joint maps; and sampling plans. Most are superimposed over an outline of the geology, or drawn on transparencies to be superimposed on geological maps, to study their relationship with the solid geology.
The scales are: Urban areas printed as m squares Rural areas printed as 1 or 2 square km areas Uncultivated areas and moorland also covers above areas The two larger scales are uncontoured, the maps are contoured at 5 or 10 m vertical intervals VI depending on the steepness of the topography. The Superplan Service will print up to AO size at any scale from to , or can provide the data on a 3. There are also educational and recreational maps at , and They are coloured and so are not useful for mapping geology, but can be used for planning.
A summary of the maps in the countries students are most likely to choose for mapping projects is given below. The problem is that, although maps may be available at these scales, they may not be suitable as base maps. Many may be coloured with geographic information, such as forest areas, or colour- layered to indicate contour intervals, or contour-shaded and even worse hachured to emphasise topography.
Again refer to Parry and Perkins If you work on an overlay, tape it on one edge only, so that it can be lifted if necessary to examine the map beneath more clearly. Note also that some countries can be most sensitive over who uses their maps, a problem which can sometimes be eased by cooperating with their geological survey or a local university. There is a wide range of digital products and local authorities may be able to provide larger scales.
Some of the maps have relief shading or four-colour layering with VI at Maps at VI 10 m in outline monochrome are available. There are too many agencies to outline here. Digitised maps with 20 m VI are available. Maps at with a 5 m VI are available and there are orthophoto editions. Digitising is expected to be completed by Scales are and Digitisation is probably now complete. There are also Pixelkarten unshaded digital maps.
Scales of maps vary depend- ing on the area: some are some There are also smaller scale maps at with metric contours and at There is also a profusion of sources, both state and federal. Canada Canada has two mapping agencies, federal and provincial, the former respon- sible for and smaller scales and the latter for and even larger scales, but basically for economic purposes. This may result in one or both sets of coordinates being shown as curved lines, depending on the type of projection being used.
This results in some distortion because, of course, in reality lines of longi- tude converge towards the poles, but on any single map-sheet the distortion is negligible. Hence the use of metric grids. The grid covering Britain is numbered from an origin 90 km west of the Scilly Isles and extends km eastwards and km to the north. The whole grid is divided into km square blocks, each designated by two reference letters.
This is merely a convenience so that the map reference of a point far from the origin, for example Lerwick in the Shetland Isles, does not become an unwieldy multi-digit number. Other countries have other origins for their grids; some use other systems. The metric grid is a useful device for describing a point on a map.
SN if in southwest Wales. This is followed by the easting, i. This is good enough to indicate the general area of the town. The point referred to lies 0. These references are measured from the British OS sheet No. At larger scales, even more accurate references can be given.
Map or grid references are a convenient way of referring in a report or notebook to places on a map. They can designate areas, exposures, sample localities and geological observations.
Ensure that you do adjust your compasses against the proper variable Section 3. Where maps of poorer quality must be used, a geologist may have to spend several days surveying in the positions of a network of cairns and other useful points to work off when mapping the geology.
But GPS may not always be available for a number of reasons: deep valleys, forest, you have run out of batteries, or perhaps you just cannot afford one. With practice he should be able to pace with an error of less than 3 m in m even over moderately rough ground.
This means that when using a map he should be able to pace m and still remain within the 1 mm allowable accuracy, and over half a kilometre if using a map. However, pacing long distances is not to be recommended unless it is essential. Pace the distance twice in each direction counting double paces, for they are less likely to be miscounted when pacing long distances. Look straight ahead so that you do not unconsciously adjust your last few paces to get the same result each time.
Every measurement should be within two double paces of the average of the four. Prepare a table of paces and photocopy it Table 3. Tape one copy into the back of your notebook and one in your map case. When using this table, remember that you shorten your pace when going both up and downhill, so you must make allowances to avoid overestimating; this is a matter of practice. If very long distances do have to be paced, pass a pebble from one hand to another, or from pocket to pocket, at the end of every paces to save losing count.
A pedometer is dubiously useful for measuring moderate-to-long distances but you must still establish your pace length to set it. Its a waste of time for short distances. Then, pace the distance, providing it lies within the limits of accuracy for the scale of map you are using; plot the back-bearing from the feature; convert the paced distance to metres and measure it off along the back-bearing with a scale.
It is particularly useful where a large number of points are to be plotted in one small area. Drop your rucksack and then pace to the exposure at right angles to your main bearing line: this line is an offset. Plot the exposure and return to your rucksack and resume pacing towards the tree until opposite the next exposure.
Carry on until you have completed plotting all the exposures Figure 3. A variation of this method can be used on maps which show fences and walls. Use the fence as your chain line. If the fence is long, take an occasional compass bearing to a distant point and plot the back bearing. It should intersect the wall where you are standing. Students seldom make as much use of walls and fences as they should, although they are printed on many maps; certainly they are on British maps.
Check your GPS instrument against map features, too. Sight points which give good intersections with the road: a bearing to barn D, for instance, is not satisfactory 3. Plot the back-bearing from this point to intersect the road, river, etc. Where possible, check with a second bearing from another point. Ideal intersections are, unfortunately, seldom pos- sible, but every attempt should be made to approximate to them Figure 3.
All too frequently bearings do not intersect at a point but form a triangle of error. If larger, check your bearings and your plotting. If the error persists, it may be that you have set the wrong correction for magnetic declination on your compass Section 3. At the worst, perhaps your compass is just not up to the job. When plotting, do not draw bearing lines all the way from the distant sighted point, but just long enough to intersect your supposed position; do not scribe the lines, just draw them lightly; and when your point has been established, erase them.
The Suunto clinometer can also be used as a hand-level. Establish your position by a back-bearing from any point which will give a good intersection with the contour you have determined you are standing on.
Although not precise, this may be all you can do in some places Figure 3. Petroleum geology of the Devonian and Mississippian black shale of eastern North America:. Olsen, P. Parker, R. This field guide focuses on the geologic history of Ogden Canyon, which provides a remarkable natural Lowe Mesozoic rift basins of eastern North America and their gravity Pennsylvania: Geological Society of.
Centennial Field GuideNortheastern Section, p. Berg, T. Field Guides- Your own classroom or school library may have some similar and wonderful examples too! Prentice Hall School Division. Lesley was impressed with the 15foot square map and is quoted Thornbury,.
The correlation of parts was very fine ina geological sense. Geological Society of America. Field Guide 8. Geology of the Gettysburg battlefield: How Mesozoic events and processes impacted American history.
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