Field work in geology courses by different science
- 1. Chapter 1: History of Geology Field Geology and Report writing
- 2. • Development of Geology as independent science • Field expeditions and geological sciences • Field work and Field data in Geology Chapter 1
- 3. The importance of raw materials and ores cannot be ignored. In recent years it has become vital to discover new metallic ore deposits and the search for these has involved the use of increasingly sophisticated techniques and for these field techniques are the basics and crucial, and the success of such search depends on the field prospector to a large extent. 1.1 Introduction
- 4. To be a good geologist, one should be good field geologist. To the geologist, field is one where rocks or soil can be observed in place and, field Geology consists of the methods used to examine and interpret structures and materials at the outcrops.
- 5. Geologic field work usually involves: 1) the study and interpretation of rocks, structures and topography 2) determination of the location of points or outcrops 3) plotting of these sites on a map. Scope of geologic field work
- 6. After setting up the base camp, at the chosen site, make contact with the various authorities, government, local administration, police, labor officer, post office etc to request their assistance. Then make arrangements for the long–term labor and daily wage labors in consultation with the labor officer. Discuss the wages, work hours, rest-time over-time, allowances, porter load etc. Select the labors having no health problems. 1.6 Expedition activities
- 7. Setting up the camp is first thing. For this ground must be cleaned, and arrange the toilet and rubbish pits far away and take care of camp safety issues. Since local people know animals, water and power supply better to take the assistance of these. 1.6.1 Activities in the camp
- 8. Recording on map Precise route taken Entry of location of samples Entry of location of geochemical samples Entry in the note books –the details Duties of a Group Leader
- 9. • Selection of possible samples (petrography study) • Selection of possible samples for thin sections • Selection of possible samples for polished sections • Transfer of geological data to a map on 1:200,000 scale e.g., Geology work Name No of petro samples collected No. of geochem. samples collected Distance covered in km Field days X 25 34 42 7 Y 46 12 120 15 Z 21 8 19 10 Total 92 54 181 32
- 10. Geological mapping is a field work or part of it. These maps and sections are used in presenting large amounts of data or information to other person. Before this mapping outcrop is a must which provides information on the structures and rock types. Hence, geological field work is a combination of: • outcrop studies, • sampling and, • geological mapping.
- 11. Because geologist continuously observes the relations and making interpretations in the field, his general methods may be compared with the classical scientific methods which consist of several steps. • The investigation first collects and observes the data, • then formulate the hypothesis to explain these observations, • then tests the hypothesis. 1.7 Field studies as a scientific method
- 12. Thus field studies must go far beyond a mere mapping and collecting individual sample and structural data. Geologic processes are complex which are to be studied in the field and tested in lab or vice-versa.
- 13. Generally, geological investigations are split into 1) Field and 2) Laboratory studies. Unlike other studies experiments in the strict sense of the word are not possible in geology. However, the geological investigations are in the nature of identification of a rock, fossil, or structure, ultimately documenting the “space-wise” distribution of a rock or structural features in the form of a map, is the main objective of a field work. 1.7.2 Planning a field work
- 14. Geological field projects generally proceed in three stages, viz., •The stage of planning •The stage of mapping, observing and collecting, and •The stage of preparing a report The effectiveness of the project is largely determined during the planning stage. There are few cases where the geologist can study all kinds of data and relations thoroughly and he must therefore select the scope of his study and plan his work so that the most pertinent data are collected. It is essential to know clearly the purpose of a given project.
- 15. • Following recommendations should be considered in planning: • Determine if other geologists are working in that area, by inquiring at state and federal agencies, • Accumulate, and study reports and maps of the region in order to gain an understanding of the broader features of the geology and geography. • Visit the area in order to reconnoiter (advance knowledge) its topography, and geology and to obtain permission for camping, mapping and collecting samples. • Determine the scales and quality of maps and aerial photographs of the area. If these do not adequate base for geological mapping consider what means will be used to construct a map.
- 16. • Evaluate the probable schedule and costs of the project. To do this effectively, consider not only the mapping procedures, but how well the rocks are exposed, how accessible the area is from base camp and to what degree the weather is likely to interfere with the field work. • Order maps, aerial photographs and various other field and office equipment, allowing plenty of time for delay. • Read critically all reports that pertain to the area, as well as books or papers, that present basic ideas and methods pertinent to the project. Planning a field work contd…
- 17. Maps used for plotting geological features and note numbers in the field are called as “Base Maps”. These are two types 1) Planimetric base maps show drainage, culture and perhaps, scattered elevations and 2) Topographic base maps show contours as well. Accurate topographic maps are ideal base maps; for cross sections can be made from them in any direction and their contours provide several means of plotting outcrops accurately 1.8. Selecting and preparing a base map
- 18. The portion of the rocks exposed at the surface of the earth is called as “outcrop”. Generally, hard and resistant rocks occur as outcrop. Unnatural outcrops are made by man such as quarry or rail or road cuttings. Whatever might be the cause of the outcrops; such places assume importance, in ascertaining the nature of the rocks composing that part of the crust of the earth. Traverse should include these. The dam sites and rock quarries also are the best sites because vertical sections are available at such points. Study of Outcrops
- 19. Among the “natural outcrops”, the courses of streams are very promising ones,. The valley sides especially the gorges are very good sites. General data to be collected are as follows: Rock types, various structures, contacts of rocks, details of faults and folds, like: a) trend and plunge of the axis, b) the strike and dip of the axial plane c) the plunge of small scale folds, d) trend of cleavages, e) petrographic features of the outcrops
- 20. Definition: A rock unit or a lithologic unit is a rock body distinctive enough to be delineated from adjacent rock bodies along surfaces called contacts. Mapping the traces of these contacts is important. Rock units large enough to plot on maps are knows as “cartographic units” provide the practical basis for geologic survey. There is a great variety of genetic characteristics that may make a given rock body distinctive. 1.10.1. Rock units for mapping
- 21. In structurally confusing or lithologically monotonous terrains, distinctive beds that are too thin to plot to scale, should be mapped as “single unit” or “line”. Examples of such key beds are tuff or ash layers, carbonaceous beds, glauconite-rich layers, thin fossiliferous beds. In many cases, unit of such type is nearly synchronous over a large area, it can therefore serve as an approximate time horizon. 1.10.2 Key beds
- 22. Before mapping in a region, where rock units have been established, published definitions and descriptions of the units and their contacts should be marked. Lithologic (unit) details can often be used to match the units, however, these details becomes less reliable as the distance from the type areas increases. Moreover, nearly identical rocks can occur at more than one stratigraphic position or in more than one igneous body. 1.10.3 Matching or correlating rock units
- 23. Fossils provide another means of identifying units. Ideally, a given unit is characterized by an assemblage of fossils that are closely related ecologically. A sandstone unit, for example, might be recognized widely by its suite of neritic fossils.
- 24. Quiz-1 5% 1) define: a) rock/lithologic unit b) cartographic unit 2) Geological field projects generally proceed in three stages namely: ______________ _____________ and ____________