Some Basics of Mapping
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Geological MappingGeological Mapping
n.k. agarwal
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The Mind Likes a Strange Idea as Little as the Body likes a Strange Protein and Resist it With Similar Energy.It Would Not Perhaps Be Too Fanciful to Say That a New Idea Is Most Quickly Acting Antigen Known to Science. If We Watch Ourselves Honestly We Shall Often Find That We Have Begun to Argue Against New Idea Even Before it Has Completely Started
- Wilfred Trotter
Innovation Means New Idea
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Relative Dating: Putting geologic events into proper order (oldest to youngest), but without absolute ages. We use a number of principles and laws to do this:
Law of Original Horzontality - Sedimentary units and lava flows are deposited horizontally.
Law of Superposition - the layer below is older than the layer above.
Principle of fossil succession - life forms succeed one another in a definite and determinable order and therefor a time period can be determined by its fossils.
Law of Cross-cutting Relationships - A rock is younger than any rock across which it cuts.
Geologic Time
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4 degree x 4 degree Sheets of Uttarakhand and Adjoining Areas
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53 - Million Sheet(28o-32o ; 76o-80o)
1:1000000
53 J - Degree Sheet(30o-31o ; 78o-79o)
1:250,000
53 J/7 - Toposheet Sheet(30o 15´-30o 30´ : 78o 15´-78o 30´)
1:50,000
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4o x 4o SheetScale 1: 1000000(1cm = 10,000m)
or1cm = 10km
Example Sheet No. 53
Each Million Sheet has 16 Degree Sheets (A,B,C……P)Scale 1: 250,000(1cm = 2500m) or1cm = 2.5km
Example Degree Sheet 53 J
Each Degree Sheet has 16 Toposheets (1,2,3….16)Scale 1:50,000(1 cm = 500m) or1 cm = 0.5km
Example Toposheet No. 53 J/3
Base Maps and Scales
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India – Areal Spread Latitudes 8o to 37o
and Longitudes 68o to 97o
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Spread of UttarakhandSpread of Uttarakhand
Area : 53,483sq.km, Districts 13nos.Area : 53,483sq.km, Districts 13nos. 2828oo 43´- 31 43´- 31oo 27´ : 77 27´ : 77oo 34´- 81 34´- 81oo 02´ 02´
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Toposheet No. 53 J/71:50,000 scale15’ X 15’
30o 15´-30o 30´ : 78o 15´-78o 30´
P1Coordinates of Point P130o 28´ 40” : 78o 16´ 20”
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1:25,000 Toposheet
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Geopetal Fabric
Top and Bottom Criteria
• Current BeddingCurrent Bedding
• Graded BeddingGraded Bedding
• Oscillatory Ripple MarksOscillatory Ripple Marks
• Load castLoad cast
• Fossil AssemblageFossil Assemblage
• Grade of MetamorphismGrade of Metamorphism
• Cleavage Bedding RelationshipCleavage Bedding Relationship
• Cross Cutting RelationCross Cutting Relation
Order of SuperpositionOrder of Superposition
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Important Information to be IncludedImportant Information to be Included
Depth of weathering
Landslide/landslide prone areas/
Avalanche routes
RBM/ Debris differentiation and demarcation
Geothermal Signatures
Mineralization, Mining activity
Agriculture/Arable land/ Forest Cover, Settlements.
Shrines, Heritage etc.
Springs
Geomorphic Escarpments/bluffs
Any unusual feature etc.
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Data Matrix
Activity Scale Resolution
Data Acquisition1:50,000/ 1:25,000 Small Scale data
1:10,000 / 1:5,000/4,000 Large Scale data
1:2,000/1,000 to 1:100 Detailed data
Data Plotting Manual & Digital
Small Scale – Low Large Scale – High
Cartographic Representation
Manual & Digital
Precision and Accuracy As Per Scale
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Basic RequirementsBasic Requirements
• Topographic or Contour Map Topographic or Contour Map
• Brunton CompassBrunton Compass
• Geological HammerGeological Hammer
• Hunter ShoeHunter Shoe
• Water BottleWater Bottle
• Field LensField Lens
• Streak PlateStreak Plate
• MagnetMagnet
• Grain Size ChartGrain Size Chart
• Field Diary, Pencils, Pen, Rubber, Field Diary, Pencils, Pen, Rubber, Cello Tape etc.Cello Tape etc.
• HaversackHaversack
• Dilute HClDilute HCl
• BinocularBinocular
• CameraCamera
• Video-CameraVideo-Camera
Special RequirementsSpecial Requirements
Total StationTotal StationPrismatic CompassPrismatic CompassGPS SystemGPS SystemPocket stereoscopePocket stereoscopeAreal PhotographsAreal Photographs
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How to Proceed ?How to Proceed ?Select a point of observationSelect a point of observationLocate the Point on Map and suitably label the pointLocate the Point on Map and suitably label the point•Record the observations in field diary with date and reference no.
•Lithology (Rock/Overburden/ Soil, Attributes (Dip/Strike, Plunge etc.)
•Collect Samples for laboratory studies
•Structural Data – Fold, Fault, direction, throw, displacement, slicken sides, Joint sets –attributes etc.
•Hydrological Conditions
•Signs of de-stressing
•Neotectonic signatures
•Landslides-type, size, active/old, cracks, water saturation conditions, Landslide Micro-Zonnation Data Sheet
•Density of data point would depend upon scale on mapping/data acquisition and purpose.
In case of geological mapping, trace the mutual formational/lithological In case of geological mapping, trace the mutual formational/lithological contact and/or the fault/thrust tracecontact and/or the fault/thrust trace
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Geological Component:
GEOLOGICAL INPUTSGEOLOGICAL INPUTS
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Important Observations
Weathering GradesWeathering Grades
Symbol Degree Weathering Extent Remarks
WO 0% Fresh No sign of weathering
W1 <25% Slightly Discoloration along discontinuities
w2 25-50% Moderately <50% rock is decomposed and disintegrated to soil, Fresh or discolored rock present
W3 50-75% Highly >50% rock is decomposed and disintegrated to soil, Fresh or discolored rock present
W4 >75% Completely Majority of rock material decomposed, original structure intact.
W5 100% Residual Soil No trace of rock
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Actual Ground ConditionsSoil with fragments of rocks
500
525
535
NN
ScaleScale
LEGEND
800
810
820
830
400
410
420
430
= Quartz Mica Schist+ ~ Quartz Biotite Gneiss
525
535
500
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800
810
820
830
400
410
420
430
LEGENDLEGEND
Overburden Overburden
525
535
500
N
Scale
Geological Map -2
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800
810
820
830
400
410
420
430
NN
LEGEND
= Quartz Mica Schist+ ~ Quartz Biotite Gneiss Lineaments
Geological Map -2
Scale
525
535
500
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nk. agarwalex-director, gsi