Geological MappingGeological Mapping

n.k. agarwal

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

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

4 degree x 4 degree Sheets of Uttarakhand and Adjoining Areas

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

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

India – Areal Spread Latitudes 8o to 37o

and Longitudes 68o to 97o

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´

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”

1:25,000 Toposheet

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

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.

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

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

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

Geological Component:

GEOLOGICAL INPUTSGEOLOGICAL INPUTS

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

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

800

810

820

830

400

410

420

430

LEGENDLEGEND

Overburden Overburden

525

535

500

N

Scale

Geological Map -2

800

810

820

830

400

410

420

430

NN

LEGEND

= Quartz Mica Schist+ ~ Quartz Biotite Gneiss Lineaments

Geological Map -2

Scale

525

535

500

nk. agarwalex-director, gsi