Geological field mapping is the process of selecting an area of interest and identifying all the geological aspects of that area with the purpose of preparing a detailed geological report and a map to summarize the report. A geological map will thus show the various rock types of the region, the structures, geological formations, geothermal manifestations, age relationships, distribution of mineral ore deposits and fossils etc. and all these features may be super imposed over a topographic map or a base map.
OBJECTIVES OF GEOLOGICAL FIELD MAPPING
PHASES OF GEOLOGICAL MAPPING
Phases of geological field mapping
A report is as good as its data and thus the need to collect good accurate data cannot be overemphasized. Ultimately when all possible available data has been collected it is taken back to the office or laboratory for sorting, interpretation and analysis. This phase is the most challenging of all three as wrong analysis or misinterpretation of data can lead to an inaccurate report and in consequence misinformation.
TOOLS AND EQUIPMENT USED IN GEOLOGICAL FIELD MAPPING
- Aerial photographs and stereoscope
- Brunton compass
- GPS (Geographic Positioning System)
- Geological hammer
- Hand held lens
- Sample bags
- Measuring tape
- Field camera
- First aid kit
- Observing and recording field data selectively and systematically for the construction of a detailed geological map at a given scale for determining the geological contacts of the stratigraphic units, their lateral and vertical extents, thickness of the units and their truncations by faults.
- Making careful observations of rock types, textures, structures, measurement of orientation of structures/contacts etc.
- Recording and describing the lateral and vertical distribution of lithofacies of stratigraphic units in the defined area.
- Constructing detailed field stratigraphic log covering lithology, biota, bedding pattern, sedimentary structures.
- Constructing a representative geological section across the mapped area.
Geological Map at 1:50000 scale.
- Measuring the stratigraphic section of the selected formation in the field.
- Samples collection is made keeping in view lithological and faunal changes at variable intervals.
- Making detailed log of the measured section covering its total thickness, sample depth and lithologic characteristics including grain size, shape, orientation, etc.
- Correlation of the different stratigraphic sections for understanding the lateral and vertical facies variations of the rock units within the basin.
- Classifying the rock according to a certain category
- Deducing the provenance
- Interpreting environment of deposition of the rock unit
- Evaluating visual porosity and permeability
- For geological field mapping to be carried out efficiently, it is essential that proper planning is executed.
- Once in the field, it is also important to be as detailed as possible in all descriptions, and to be keen as well as observant.
- Measurements must be performed meticulously and, if necessary, more than once for confirmation purposes.
- Team work must be adhered to, throughout the entire process.