Virtual Geological Field Trip to Jhalawar
As a pre-field orientation program, I welcome all my B.Sc. VI semester students to this Virtual Field Trip to Jhalawar and surrounding areas in southern Rajasthan. This virtual trip has been designed as a pre-field exercise to help you understand the Vindhyans exposed in the southern part of Rajasthan – their geology, tectonics, structure, and economic potential. It will also show you the most important sites of geologic (and other) interest in and around the town of Jhalawar and the neighboring district of Kota in Rajasthan state which we shall visit during February 2019. I'd appreciate if you were to read an account of the geology and mineral resources of Jhalawar and the neighboring Kota district (parts of which are included in our survey), as documented by the Department of Mines and Geology, Government of Rajastan.
This virtual geological trip to Jhalawar is offered through Google Earth. Google Earth is a virtual globe browser, arguably the most popular of those available for free on the Internet. Virtual globes allow users to interactively display and investigate geographic data (primarily satellite and aerial images and terrain models, but also 2- and 3-D vector data such as earthquake locations, water bodies, and buildings). One of the most useful aspects of Google Earth from a geoscience education point of view is the availability of a variety of geoscience-related datasets for free on the web. Google Earth allows users to perform some basic measurements (latitude and longitude, elevation, and size), which has led some users to consider it a variety of GIS software.
Virtual Geological Mapping
Virtual geological mapping of the Vindhyan terrain around Jhalawar has been accomplished by interpretation of satellite imagery in conjunction with existing geological maps and other data, particularly the geological map of Ramasamy and Bakliwal*. Major geological formations comprising Semri, Kaimur, Rewa and Bhander groups of Vindhyan Supergroup, Deccan Trap and recent fluvial sediments and Aeolian sands have been studied for their contrasting spectral characteristics in high-resolution, true colour images in Google Earth, and studied in the field to establish relationships between spectral chatacteristics and field data. The DigitalGlobe data of November 2018 currently available on Google Earth for the Jhalawar region shows a panorama of contrasts which may be interpreted in terms of geology and structure. Superimposition of the aforesaid georeferenced geological map of Ramasamy and Bakliwal on Google Earth allows the interpretation of major lithological contacts and structural features in satellite images. To learn about superimposing maps in Google Earth, see the note at the end of this paragraph. Notice that the satellite image shows a variety of lineaments which may be interpreted (in conjunction with the geological map) in geological terms. Stone quarrying, particularly in the west and northwest of Jhalawar, with all its evident degradation of land, is also decipherable in satellite images.
Interpretations of satellite images need to be verified through field work. During the field trip, checks will be made in places by conventional field mapping for part of the area. A comparative assessment of the data producing capability and accuracy of these methods will be made from this study.
Whereas it may not be possible to characterize the petrological and mineralogical characteristics through interpretation of available satellite data, the variation in the spectral characteristics of all mappable units are apparent. Apply your knowledge of interpretation of satellite imageries to visualize all such variations, and use the Add Path tool in Google Earth to demarcate boundaries between contrasting lithounits. Save your drawings in your map folder, so that we may add/modify these during later sessions of the virtual geological field trip. Mark all features which you think will require detailed investigations in the field. Note the locations (in in decimal degrees) of all places you may want to visit in the field in order to verify your interpretations, and to collect other ground truth data and take photographs. When in the field, use the navigation function of Maps – Navigate and Explore, an android app installed in your smartphone, to take you to the exact location.
Geology of the area around Jhalawar: Geology of the area around Jhalawar has been mapped by taking into consideration the lithological types as identified and depicted in the geological map of the area published by Ramasamy and Bakliwal (1988) and the DigitalGlobe images of the area in Google Earth. For instance, the Jhalrapatan Sandstone in the geological map is seen as a clear, yellow to light brown, barren (devoid of vegetation) areas in the satellite imagery. Similarly, as can be seen in the geological map and the imagery, the areas of exposure of Suket Shales are under agriculture. Therefore whereas the lithology has been identified through published geological maps, geological contacts between lithounits have been deciphered and marked using mltispectral imagery available through Google Earth.
View the geological map of Jhalawar area in Google Earth and see if you can recognize the spectral/land cover signatures of different rock types. Can you identify some finer distinctions within the identified lithounits?
View the localities map of the area around Jhalawar town in Google Earth: The locations of villages have been digitized from the Survey of India topographic sheet No. 54D/2. Notice that most villages are located along the contact of Jhalrapatan Sandstone and Jhalrapatan Shale. Do you think this is just a coincidence? Or can there be some geological reasons? What, if any, could be the reason? Can you, on the basis of your observation, suggest areas suitable for industrial development?
Can you decipher any faults in the area? Take a closer look at the Kali Sindh River channel as it flows in the north and east of Jhalawar town. Do you notice that the river, which is generally flowing towards north, takes a series of sharp bends towards NW? Could this be a coincidence, or do you think the drainage here is influenced by a series of parallel faults? Note the coordinates (Lat/Long) of sharp bends in the course of the river; visit these locations to look for evidences of faulting when you are out there in the field (read about the criteria for recognizing faults in the field).
In the area around Jhalawar, note the relationship of geology with:
1. Cultivated and uncultivated areas
2. Human settlements
3. Density of forest cover
5. Drainage patterns
6. Natural and man-made lakes
Keep a detailed record of all your observations; you'll need to corroborate these with other data. When you're out there in the field you will need to use your GPS Receiver a lot. Go through these tutorials in order to familiarize yourself with the objectives of geological fieldwork, field procedures and practices, equipment that you are expected to carry with you in the field, important instructions and the code for geological fieldwork, rock types likely to be encountered around Jhalawar and how to recognize them, and a suggested format for the field report you are expected to submit on your return to Aligarh.
* S.M.Rarnasamy and P.C.Bakliwal, "Use of Remote Sensing in lineament analysis for tectonic evolution and resource study of a part of Vindhyan Basin, Jhalawar area, India,". Journal of the Indian Society of Remote Sensing Vol. 16, No. 1, pp. 63-71,1988.
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Department of Geology
Aligarh Muslim University, Aligarh - 202 002 (India)