Field Geology Lecture 4

7/28/2019 Field Geology Lecture 4

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Field Geology2010-2011

Ibrahim M.J. Mohialdeen,MSc,PhD

Lecture 4



• Subject: Field measurements and Techniques ( Part II)

* lecturer’

s name: Ibrahim M.J. Mohialdeen* Contacts: Tel: 0770 142 6262, Email: [email protected]*Subject objective :The techniques required in the field also include sample collecting fromdifferent rocks and sediments. In this lecture you will learn about collectingsamples and how to determine fossils. The field photography is one of the mostimportant techniques too. What are the subjects to be photographed and whatare not necessary?*Scientific content of the subject:Reviewing strike and dipQuizSample collecting in the field*Subject references:

-Tucker,MC., 1988, Techniques in sedimentology, Blackwell scientific publ., 394p.-Stow, D.A.V., 2005, Sedimentary Rocks in the Field: A color Guide.-Barnes, J.W., 1995, Basic Geological Mapping, 3rd ed., John Wiley and Sons, Chichester, 133p.-Compton, R.R., 1962, Manual of Filed Geology, John Wiley and Sons, New York, 378p.-Lahee, F.H., 1961, Field Geology,6th ed., McGraw-Hill Book Company, New York, 926p.-Mikhailov,A.Ye.,1987, Structural geology and geological mapping, Mir Publishers, Moscow,

535p.

Field Geology 2010-2011

mailto:[email protected]



Lecture 4:

Field measurements and techniquesPart II

• Reviewing the ideas of the attitude ofbeds.

• Quiz on the plotting the data of strikeand dip on the map

• Any question you may have.• Measurement of stratigraphic section




Discussion on the first field trip .

Any suggestion you may have.




Measurement of stratigraphic sectionsMeasurement of strata on a slope by reference to stretched

tape.Note the projection of contact between units 2 and 3 to thetape(after Compton , 1962, Tucker, 1988).1-Measure the slope of the surface along with the strike and

dip of the beds.2-read the apparent thickness of beds, bedsets or faciesunits from the stretched tape.




3-correct for both slope anglesand oblique sections4-keep readings separatebetween changes of slope.(a ) correction of slope distance

that was measured oblique tothe dip of the beds.(b)Formulae used for variouscombinations of direction andamount of ground slope and

dip of beds.(after Compton, 1962)




In the case of steeplyinclined strata relativeto the surface ofmeasurement, the tapecan be used as small

Jacob staff withreasonable accuracy.An alternative to theuse of a tape, whereterrain permits, is to

use a graduated poletermed Jacob staff.(After Tucker, 1988)




Specimen collecting

Collecting samples from different rocks, fossils and soils isanother process in the field. Not necessary the numberof samples be big, sometimes the a few number will beenough to representative the rock unit.

The size of specimen is depended on the purpose you wishto put it to, not on what you think you can carry.See your rock cutter before you go into the field to see

what it needs for thin-sectioning. Try to collect bothtypes of samples weathered and fresh surfaces.

Mark sedimentary rock specimens to show which is theirtop. Metamorphic specimens may need to be oriented sothat directional thin sections can be cut.




Marking specimens:

Rock specimens are best marked with a waterproof felt-tipped pen or, for dark rocks , a yellow timber crayon or anumbered piece of sticking plaster.

Wrap specimens in newspaper to protect them frombruising and to spare your rucksack.In camp, scrub your specimens, dry them and then add a

spot of white paint, later number the spot with the blackpaint , not Indian ink, which easily rubs off.




Booking specimens

Log specimen in your notebook immediatelyyou have collected them. Preferably write

their number in the left-hand margin, sothat their details can be easily relocated.




Shipping specimens

Geological specimens are heavy and if shipped ina box which is too large can only accepted asfreight. Smaller boxes, which one man can lift,can go much more quickly by passengertransport.

Mark your name and address on the top and sides,and add ROCK SPECIMENS FOR SCINTIFICRESEARCH.

Never write ore specimens or mineral specimens.




Good photo




Bad photo


Field Geology Lecture 4

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