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#*#*# Place the Jacob stick perpendicular with bedding. Use the clinometer to measure dip, so that Jacob stick can be perpendicular with the bedding. [[PIC 1]]
#*#*# Place the Jacob stick perpendicular with bedding. Use the clinometer to measure dip, so that Jacob stick can be perpendicular with the bedding. [[PIC 1]]
#*#*# Every Jacob stick has 10 cm interval every red-white line. It’s used to measure the width of bedding. Keep place perpendicular with the bedding [[PIC 2]]
#*#*# Every Jacob stick has 10 cm interval every red-white line. It’s used to measure the width of bedding. Keep place perpendicular with the bedding [[PIC 2]]
==Post-mapping stage (reading a geologic map==
After collecting geological data (such as lithology, geological structure, and geomorphology) from field observation, the next step that should be done is the poster which consists of points of observation’s map, geological map, geomorphological map, stratigraphic column, geological history, and photos and diagrams from petrography, paleontology and structural geology analysis. Those data and maps should represent your field geologically.
The first thing that you need to make is the poster. The poster is consist of:
# Cover Page (with title and your name)
# Points of Observation’s Map
# Geological Map with Profile and Legends
# Geomorphological Map with Profile
# Stratigraphic Column and Its Information
# Geological History that’s arranged based on the stratigraphy and structure of the area
# Photos and Diagrams from Laboratory Observations or Analysis
# Bibliography
# Validity Sheet
# Attachments (photos, sketches and diagrams that are optional)
Poster must be arranged with a logical line of reasoning and neatly structured. Below is the explanation about each components of the poster:
#; Cover Page: The cover page is consist of the title of poster (includes the village, town, city and country of the mapping area), name of the writer (full name and student id number), symbol of university/college or institutions, and date of published.
#; Traverse Map: The procedure about how to make this map have been mentioned in the pre-mapping phase. This map explains about the route that you’ve observed in mapping. Each points symbolize an area that you’ve visited to do some field work such as lithology descriptions, measured sections and strike/dip measurements. There will be some tracks which connect points that are nearby. The component of this map is almost the same as geological map, but with addition of the number of points and tracks in the legend and also the body of the map. From every point of stop side, we can see the lithology of every stop site by the lithology symbol.
#; Geological Map with Profile and Legends: From this map, you will know the information about distribution of rocks, the relationship between the rock units, the geological structure and the order of the rocks. The map is consist of title, scale, legend, coordinate, lithological symbol, contour, geological structure symbol, strike/dip, river and administrative location. And also a geological profile by making section in the body of the map.
#; Geomorphological Map with Profile
This map explains about the distribution of geomorphology. It’s consist of title, scale, legend, geomorphological symbol, contour, coordinate and also the used classification of geomorphology. And also a geomorphological profile by making section in the body of the map.
#; Stratigraphic column and its information: This column explains about the order of lithology based on the geological age and also the relationship between the rocks unit. From this column, we can know the depositional environment of the rocks.
#; Geological History: From all geological data that you’ve got, you will make interpretation of the geological processes and depositional environment of the mapping area. From the interpretation, you will make a narration that’s full of facts that you’ve got from your work in field and laboratory. The narration will explain about the geological processes and the change of depositional environments from the oldest age to now.
#; Photos and Diagrams: Photos from petrography and paleontology observation in laboratory may be put in the poster to support the map and interpretation that you’ve made. Diagrams from geological structure analysis also may be put on a show on the map.
#; Bibliography: All of the literature and books, papers, and other publications that support your work during mapping should be written in Bibliography page.
#; Validity Sheet: Before the poster is shown to public, it must be signed by the advisor or the lecturer to inform that this poster is able and good enough to be published.
#; Attachments: This page is optional. If there’s some data such as sketches, or other photos and diagrams that you want to add. You can add it in attachment page.
To make geological map and geomorphological map correctly and based on the data that we got from field observation, there are some rules that we need to apply in making the map. Below is the rules and the right procedure about how to make map:
# The accuracy and precision of geological map is mainly based on the scale of the map that you want to make. The greater scale means the more accurate the map that you make. For example, 1 : 25000 scale is more accurate than 1 : 50000 scale. Also the greater scale will make you get more geological information than the smaller scale.
# To make a boundary between two different rock units, we need to measure strike and dip in field observation. And also we need to pay attention closely to any contact between two different rock units that we found in the field. More value of strike and dip means the more accurate the geological structure construction and more rocks variance.
# To decide the boundary, we can apply the “V Rule”, which has these principle points below:
#* If the dip of bedding is 0° or <5°, the boundary will be drawn by following the contour line.
#* If the dip of bedding is > 5°, if the direction is the same as the dip of slope from topography, then the boundary will be drawn by cutting off the contour line but a bit inclined to downward. And if the direction is the opposite of the dip of slope from topography, then the boundary will be drawn by cutting of the contour line but a bit inclined to upward. Both appearances will be seen if the boundary is cutting of the river line.
#* This rule is not applicable in a field where there’s fault.
#* This rule is also not applicable in a field that has igneous and metamorphic rocks.
# To make cross sections, we need to make a line for a cross section which will show the appearance of the distribution of all rock units in the field and also the geological structure. Usually, the direction of the cross section is from north to south with a low or steep dip.
==Conclusion==
Geological mapping is a basic stage in the more complex geology analysis. The final results of geological mapping is a geological map that contains important information such as variation of litology, geological structure and stratigraphy. Stage in geological mapping is pre mapping, mapping, and post mapping. Each stage has an important role so that the geologic skills is needed to produce awasome geological maps.
==References==
Sukanndarumidi. 2011. Pemetaan Geologi. Yogyakarta : Gadjah Mada Press Pramumijoyo, Subagyo. 2014. Metode Geologi Lapangan. Yogyakarta : Unpublished