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Basics of Field Geology Rex A. Crouch

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Copyright 2008 by Rex A. Crouch

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Preface

This text addresses the basics of field geology for the amateur geologist

and prospector with the assumption that the reader has an introduction

to earth systems, mineralogy, petrology, and structural geology.

Observation and data collecting, using the transit compass, plotting

features on a map, and the geologic report are addressed herein.

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Chapter 1 - Observing and Collecting Data

The purpose of field geology

Planning the field project

Taking field notes

Collecting hand samples

Chapter 2 - Using a Transit Compass and Global Positioning System

The transit compass

Taking a bearing

Strike and dip

Global Positioning System

Chapter 3 - Plotting Geologic Features on a Map

Color standardization

Symbol standardization

Preparation

The field map

The mapping story

Chapter 4 - The Geologic Report

Purpose of geologic reports

Report format

Target audience

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Chapter 1 - Observing and Collecting Data

Purpose of Field Geology.

Field studies are the main

method of obtaining geologic

data. Field studies should have

a purpose, even if it be strictly

academic. The study may be as

simple as a single outcrop of

interest or an open pit quarry.

These simple studies may

include a sketch, some digital

photos, GPS coordinates, making

notes on relations between

rocks, and/or collecting some

hand samples. Other field

studies may be complex

requiring extensive time in the

field utilizing systematic

sampling methods of rocks, soil,

and even water with detailed

mapping in computer

applications.

Geologic mapping is the

backbone of the field study and

is frequently referred to as field

geology. Mapping finds

relations between rocks and

other geologic interests. Despite

our advanced technology many

geologic features of importance

such as folds and faults can only

be found by geologists with their

boots on the ground, in the field,

mapping an area. Some ore

deposits may be found with

airborne geophysics but in

reality, few are, it is the

geologist in the field that makes

the discovery. Ultimately, maps

convey more than words ever

will.

Mapping comes down to the

observations at the individual

outcrops as being the

fundamental principle of field

geology. The observation and

an interpretation is made, a

hypothesis is developed, and

tested by any means available.

The individual outcrop will be

the most rudimentary aspect of

mapping. As the map develops

complex relations are revealed.

Complex relations may occur

when multiple processes act

simultaneously or through

overprinting of multiple geologic

events. Sometimes geologic

features may be so complex that

no distinct conclusion can be

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found. Upheaval Dome in

Canyonlands National Park is

believed to be a collapsed salt

dome by one camp of geologists

and a meteorite impact site by

another. Other complex

features are understood only

when detailed field mapping has

been conducted and

interpreted.

Planning the Field Geology Project.

Field projects have three phases:

Planning/Research

Observing/Mapping/Collecting

Reporting

While each phase leads into the next, the writing of the report should

actually begin during the planning and research phase.

Planning/Research – This is as

critical as the other two phases.

Here, the scope of the project

must be determined. One

specific location is identified and

purpose for being there is clearly

stated. Without a place and a

purpose the geologist becomes

a free-range chicken. The

research is also critical. A lot of

the work may have already been

completed and available

through aggressive research;

some field mapping may have

already been done and drill

cores with chemical assays may

be available. Judging the data

recovered from research may be

difficult. Many brilliant

professors and research teams

have been wrong on multiple

occasions. Sometimes the

original researcher simply wasn’t

objective. The world was

considered flat for a longtime,

then considered round, and now

we know that was wrong too.

Over time techniques and

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technology change and allow

geologists to see datum under a

different light. Be prepared to

accept the researched data and

test it to ensure its validity.

Observing/Mapping/Collecting –

This phase is what geologists call

“Boots on the ground.”

Outcrops are observed. The

rock type is identified.

Distinctive items such as crystals

or fossils are scrutinized.

Besides the fine details,

geologists look for the obvious

such as slicken slides, big granite

boulders setting on top of mafic

bedrock, valleys or flowing

water bodies across the strike.

The primary school of thought is

to map what is in-place or

geologic bodies that are part of

the bedrock but what about that

huge granite boulder setting on

top of mafic bedrock. Some

geologists will annotate this

boulder on their maps as they

may encounter the granite

bedrock it originated from 10s

or 100s of kilometers away—this

is a great example of glacial

activity.

Taking Field Notes.

As geologic features are

encounter they should be

annotate in the notebook. The

geologist makes the notes at the

location of interest to ensure all

data is properly collected. The

field notes complement the

geologic map and will serve as

the basis for writing the report.

Good notes are clear and do not

have unexplained abbreviations.

Sloppy abbreviated shorthand of

a geologist who made critical

observations decades could

leave the work done as useless.

The notes a geologists takes may

be instrumental in the

development of a current

project or a project years or

even decades later. Geologists

develop systematic approaches

for taking notes ensuring all of

the datum are collected at each

outcrop or geologic feature

encountered. An example of

topics to cover:

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Numeric that correlates the notes to the features drawn on the

map

Name of formation – if known

Specific location

Characteristics such as thickness

Name of rock

Description of rock – the description should also be systematic

addressing rock and mineral properties

o Color

o Type (igneous/sedimentary/metamorphic)

o Texture

o Foliation (as appropriate)

o Folds (as appropriate)

o Cleavage (as appropriate)

o Luster

o Hardness

o Streak (as appropriate)

o Magnetics (as appropriate)

o Luminance (as appropriate)

A sketch of the geologic feature may be made or a digital photo

taken. In either case, ensure that a ruler is included in the sketch

or photograph and annotate in the notes the orientation of the

image. Photographs using coins or local items for scale from the

country where the photo was taken lose meaning outside of that

country and locally even after time; pesos change size every year.

A ruler is a good scale because a centimeter is a centimeter

around the world.

A small insert map may also be prudent if macro view would add

value to the description.

If a hand sample is taken ensure the number identifying the

sample is annotated in the notes.

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Collecting Hand Samples.

The reason for collecting hand

samples is to give the geologists

the opportunity to further

examine the rock at camp or in a

lab. Much more can be

discerned with Petrographic

polarizing microscope and even

more may be learned X-ray

crystallography and

geochemistry testing.

Standardization of hand sample

collecting should be established

prior to going to field—subjects

to standardize are:

Numbering method - When multiple geologists are involved a

scheme to identify the collecting geologist is also of importance

The rough size of the collected sample

That is represents the formation as a whole

Marking orientation

Numbering method – The

numbering method for hand

samples should correspond to

the notes as closely as possible

and have a scheme for relating

the rocks to the study area.

Finding boxes of rocks in the lab

each labeled 1, 2, 3 will lack

meaning. If the samples are

collected at “Example Creek” a

possible numbering scheme

would be EC 2d. The letter “d”

may represent the 4th sample,

collected at outcrop “2”, at

“Example Creek.” The number

should be annotated with a

permanent marker. Whiteout

can be used on dark colored

rocks with the number placed on

the whiteout. Rocks with

phaneritic textures may simply

need to be bagged; a number is

later written on a label and

glued to the rock.

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Size – Rocks with homogenous

matrices may be fist sized.

Rocks with large crystals or

coarse grains may warrant a

larger sample.

Representing the formation –

Taking one large pyrite crystal

would poorly represent the

limestone formation that

contained a few crystals. In this

case taking a hand sample of

limestone would be prudent and

of course take a representation

of the crystals that the

limestone contains.

Marking orientation – Rocks

having folds and foliations need

to have to have their orientation

annotated. Clearly mark which

side is up. If this is difficult mark

a band around the rock showing

the level line and annotate one

side as “TOP” and indicate the

bearing from when the rock fit

into the outcrop

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Chapter 2 - Using the Transit Compass and Global Position System

Geology curriculums typically

contain to two summer field

courses but these courses have

seen changes through the years.

One of these courses was

dedicated to surveying and may

have included the use of an

alidade and the second field

course was geology. The

surveying course has been

removed from most geology

curriculums which was a tool

geologists could use to locate

themselves. This handbook will

introduce the Global Positioning

System or GPS and how to

employ it in concert with a

transit compass.

Transit Compass.

A transit compass includes a

magnetic compass, clinometers

(Long Level), and hand level

(Round Level) in one package.

The transit compass most widely

used by geologists today is

called the Brunton. The

Brunton we know and use was

designed by Canadian geologist

D.W. Brunton in the early

1890’s. Although the Brunton

Company makes a variety of

equipment, the word Brunton is

widely accepted to mean transit

compass.

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The various parts of the Brunton are depicted below.

1. Bearing Needle 2. Graduated Circle 3. Zero Pin 4. Large Sight with Peep Sight 5. Small Sight

6. Mirror 7. Long Level 8. Adjusting Screw 9. Lift Pin 10. Vernier 11. Round Level

Depressing the Lift Pin stops the

motion of the compass needle

and when the box is closed the

Lift Pin protects the needle. The

Round Level is used to level the

compass when taking bearings.

The Long Level is used to take

clinometers (dip angle)

readings—the lever on the back

of the compass manipulates the

Long Level. The dip angle

reading is made on the Vernier.

The Graduated Circle may be

moved east or west by turning

the Adjusting Screw and is

observed using the Zero Pin.

Because true north and

magnetic north are not in the

same location, the compass will

have to be adjusted to point

toward true north; this will

change from location to

location. The field maps used

will have a section called

“Declination”. The declination

states how many degrees east or

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west the compass will point

away from true north. Turn the

Adjusting Screw until the

graduated circle has

corresponds to the declination

on the map. In Maine the

compass will have to be

adjusted about 18 degree west

whereas in Washington the

compass will have to be

adjusted about 18 east. Along

the Mississippi River there may

be no need to adjust the

compass.

Taking a Bearing.

A bearing is the direction the

compass needle is pointing. In

geology there is a specific

format for reporting a compass

bearing—this report will never

be greater than 90 degrees. As

an example, if the bearing reads

35 degrees then the report

would be annotated as N35E. If

the bearing was 91 degrees we

must remember that the report

will never be greater than 90

degrees; subsequently a bearing

of 91 degrees will be reported as

S89E. The east and west

indicators on the compass seem

to be reversed however this

orientation assists in reporting in

the correct format.

There are many methods for

taking a bearing. The transit

compass may be mounted on a

tripod or alidade mount for the

greatest accuracy. In rugged

terrain the tripods can be very

cumbersome. The compass to

cheek method using the peep

sights is a fast method for taking a

bearing.

This handbook recommends the

waist level measurements

technique.

Ensure there are no metallic objects such as belt buckles that may

affect the compass needle

Open the compass housing to about the 2/3 point

Hold the compass at waist level

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While looking down at the compass, sight the objective in the

mirror, ensure the system is level using the round level

Depress the Lift Pin locking the needle in place

Observe and record the bearing

In the following example:

There are four basic principles of geology being:

Principle of faunal succession – This principle is based on the observation that fossils succeed each other in a vertical manner

Principle of cross-cutting relationships – Rocks that have cut through other rocks such as dikes or sills are younger than the surrounding rock

Principle of lateral continuity – Sedimentary rocks extend laterally in all directions

Principle of original horizontality – Sediments that form sedimentary rock are deposited horizontally

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This final principle brings us to

strike and dip. Geologic

activities rarely leave rock in a

horizontal position and it is

critical for us to measure the

strike and dip to discern what

has happened at the site as well

as the region.

Strike and Dip.

Measuring the strike and dip of a

geologic feature uses all three

functions of the transit compass

being the magnetic needle,

Round Level, and Long Level.

The strike is found by placing the

edge of the compass against the

inclined rock and adjusting the

compass position until the round

level is center.

With the edge of the compass

flush to the rock and the round

level center observe and record

the bearing.

For this example the bearing is

N35E.

The dip angle will always be

orthogonal to the strike.

A trick for finding the strike is to

pour some water on the rock.

The water will flow in the

direction of the dip and the

strike is orthogonal as stated.

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The dip is found by placing the compass flat against the rock orthogonal

to the strike.

Adjust the lever on the back of

the compass until the Long Level

is flat. Observe and record the

measurement seen on the

Vernier. For this example it is 45

degrees.

This may be written as N35E 45

This may also be annotated on a

geologic map with a long line

pointing toward N35E and an

orthogonal line pointing in the

direction of dip with the dip

angle annotated adjacent to the

symbol.

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Global Positioning System.

The GPS is a ground based

receiver which uses a series of

satellite signals and triangulates

itself based on these signals.

There are two different varieties

of GPS units being the

commercial and the profession

version. The commercial version

is typically accurate to within 4 –

9 meters on the X Y axis and

about 15 meters on the Z axis.

The professional version is

accurate to within a meter on

the X, Y, and Z axis. This

accuracy is even further refined

with special antennas and base

units.

For most field geology

applications a commercial unit is

adequate. When accuracy

becomes critical is when gravity

measurements will be taken.

Accurate gravity measurements

are dependent upon elevation

making the professional version

of the GPS essential.

Whether using the commercial

or professional version of a GPS

there are two measuring

schemes- These are Latitude

and Longitude or Universal

Transverse Mercator UTM.

Latitude and Longitude uses

degrees, minutes, and seconds,

and is a projection of grid lines

on sphere. This results in

measurements being made with

degrees, minutes, and seconds.

The UTM system was designed

by the military and is a flat grid

based system. A flat system

becomes distorted in the Polar

Regions but warfare in the arctic

is unlikely. The system of

measurement uses zones

ranging from 01 to 60

horizontally and letters

vertically. The letters “I” and

“O” were omitted as they could

be confused with numbers.

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All GPS units have similar

features allowing the user to

select UTM or Latitude and

Longitude. UTM is used for

most applications today to

including modern geology tasks.

Most computer applications and

even maps use UTM. When

selecting UTM there are two

additional selections to be made

being the database and the

spheroid. Because the earth

does not remain stationary nor

is it a perfect sphere there are

different reference frames and

spheroid models in use. The

World Geodetic System (WGS)

allows us to define the Earth’s

reference frame. As we learn

more about the earth we update

the reference frame and

spheroid models. Select the

most current WGS when setting

up the GPS unit. The earth is

not even a perfect oval; it has

varying degrees of roundness at

different locations. The

spheroid of Earth changes

locally. In the United States we

use North American Datum or

NAD 83.

A word of caution, because

there are so many different

coordinate systems available

from Range and Township,

Latitude and Longitude, State

Plane, and many variations in

UTM dependent upon the age of

the data and spheroid location,

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geologists must ensure that any

data or maps used have been

converted into the same

coordinate system. The

difference between UTM NAD

27 and UTM NAD 83 may be on

the order of 10s of meters

dependent upon location. A

failure to ensure the correct

spheroid is in used compounded

by a commercial GPS unit’s

potential error of 4 – 9 meters

could become a significant

distance.

Another important function of

most GPS units is the ability to

establish Way Marks. Geologists

mark important locations on

their GPS units and enter

detailed data about the location.

Good geologists also ensure that

data and location of any

observation is entered into their

geology notes.

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Chapter 3 - Plotting Geologic Features on a Map

Color Standardization.

Maps used in the field for

documenting geologic features

and referred to as base maps or

geologic maps. Other map types

may show drainage which are

called planimetric maps. Culture

maps show manmade features

and topographic maps show

contour.

Some people prefer to use

topographic maps as their base

map. As a benefit of this

method, the user will have

reference points such as roads,

trails, and topography. The

drawback is that it convolutes

the data collected making the

map difficult to read. This

handbook recommends grid

paper for mapping. Grid paper

may also be found in a water

resistant variety.

To limit the size of the legend

geologists use accepted geologic

symbols and colors. The

following represents the

accepted color coding for rock

ages as presented by the USGS:

Precambrian RGB 178/134/83

Archean RGB 153/173/172

Eoarchean RGB 128/144/144

Paleoarchean RGB 153/151/145

Mesoarchean RGB 203/205/200

Proterozoic RGB 204/216/145

Paleoproterozoic RGB 179/178/94

Mesoproterozoic RGB 221/194/136

Neoproterozoic RGB 202/165/149

Tonian RGB 203/164/108

Cryogenian RGB 220/171/170

NeoproterozoicIII RGB 234/216/188

Phanerozoic RGB 179/226/209

Paleozoic RGB 128/181/213

Cambrian RGB 251/128/95

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Ordovician RGB 249/129/166

Silurian RGB 177/114/182

Devonian RGB 153/153/201

Carboniferous RGB 153/189/218

Permian RGB 103/198/221

Mesozoic RGB 127/173/81

Triassic RGB 103/195/183

Jurassic RGB 77/180/126

Cretaceous RGB 127/195/28

Cenozoic RGB 225/225/0

Paleogene RGB 255/179/0

Neogene RGB 253/204/138

Quaternary RGB 255/255/77

Symbol Standardization.

The following page presents some of the most commonly used geologic

symbols. A complete list may be derived from the Federal Geographic

Data Committee which standardizes all geologic symbols.

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Preparation.

Before mapping, the geologist conducts a walkthrough of the selected

area.

The geologist looks for and finds

any general trend in the strike.

The purpose of looking for a

trend in the strike is to assist the

geologist in establishing traverse

lines. Traverse lines are straight

lines that traverse the working

area in a parallel manner. The

traverse lines should be

perpendicular to the general

trending strike if there is one.

This will reveal as much geology

as possible during the mapping.

Simply following the trend of the

strike would be boring. For

small areas, geologists may

simply walk the area but for

large detailed projects it may be

necessary to emplace stakes at

the beginning and end of each

traverse line and run a line

between the stakes. The

distance between the lines

depends on how much accuracy

is needed as well as the visibility

between the lines. In wooded

areas, traverse lines may be as

close as 5 meters apart. The

geologist is not locked into

walking on the line; this is a

guide to ensure the area is

properly studied.

The geologist should be equipped with at least the following items:

Transit compass

GPS

Grid line paper

Number 2 pencils

Marker

Protractor

Clip board

Pocket knife

Hand lens

Rock hammer

Eye protection

Sample bags

Backpack

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Adequate food, water, sun screen, insect repellent, flash light, extra

batteries for everything, and rain gear should also be available.

In the example map on the

following page, the geologist

found that there is a trend in the

strike of N54E during the

walkthrough. Because of this

traverse lines were ran N36W to

ensure they were perpendicular

to the trend of the strike. If a

trend was not found it is

reasonable to conduct traverse

lines in a grid.

The field map should have the minimum information:

Map name – should be related to the area of study

Person developing map

Purpose of the study

Date

Legend

Scale

North arrow

While mapping, the geologist carefully draws each geologic feature and

annotates it with a number. This number corresponds to the notes and

samples taken.

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The Field Map.

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The Mapping Story

The geologist begins in the northwest corner of the mapping area and

proceeds southeast along the A to A’ route as shown on the map- This A

to A’ line is not really a route but a line drawn on the map by the

geologist that is orthogonal to the general strike of the geology and will

be used in the lab to visualize the subsurface geology. The geologist first

finds a schist outcrop. Pulling a slightly rusted rock hammer from its

sheath, the geologist looks for and finds a section of rock that may be

easily removed. Hitting the outcrop several times sent a sharp piece of

rock up and into the air; a subtle reminder to put on the safety glasses.

Removing the sample and examining it through a hand lens revealed tiny

garnets that had been sheared in a counterclockwise direction. This was

interesting. The geologist labeled the sample “FMN 1a” to mean “Field

Map Name”, outcrop 1, “a” being first sample from outcrop 1. Because it

was a foliated rock with some folding the geologists carefully put the rock

sample back on the outcrop and marked its orientation so the foliation

and folding could be understood when the rock was returned to the lab.

After the specimen was properly marked and documented in the note it

was safely bagged. The uneven surface of the foliated rock was difficult

to take a strike a dip on. At last, a small section was found smooth

enough for the task. Thinking, “Am I a pretzel or a geologist?” The

geologist had to contort to new forms to read the dip angle on the

Vernier. The notes were begun with “1. Schist outcrop - Green colored

metamorphic rock with a greasy luster bearing garnets 2 mm in diameter

exhibiting counterclockwise shearing. The garnets are spaced

sporadically. The sample shows a gentle2 cm folding with a regular

rhythm orthogonal to the foliation. Strike and dip is N54E 25.” The

location from where the sample was removed was observed with the GPS

and also recorded in the notes. After finishing the note, the geologist

thumbed through several screens on the GPS to the Way Marks. A way

mark was entered on the GPS itself; this would later be downloaded to a

computer. While scrolling through the screen keyboard the battery low

screen came on. Business as usual; a couple of minutes were spent

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changing the batteries. The outcrop was paced off several times and

while setting on the outcrop, the geologist drew a scale drawing of the

outcrop on the geologic map and labeled it with “1”. Then using a

protractor the geologist made a line on the map to represent the N54E

strike, a triangle for the foliation was added to the symbol and the dip of

25 was written. Thinking for a couple of minutes which way to put the

swirl to show counterclockwise motion in the shear the first outcrop was

complete.

Walking just one more meter the geologist encountered another

outcrop. This was a basalt outcrop, about 1 meter high and somewhat

flat on the top. Once again a sample is sought. Finding a suitable piece

and striking it with the hammer sent the tool recoiling and vibrations up

the arm. Yeap, this was a much harder rock. More effort was involved in

freeing the sample. The sample was examined under the hand lens,

bagged, and labeled. The geologist climbed on top of the rock. The

heavy lugged boats clung to the rock as it was ascended. From atop the

outcrop it was observed that the basalt had a general trend but stopped

in the southwest direction, off set, and began again. Thinking, “How odd,”

taking a compass bearing in each direction, a GPS reading, and pacing the

outcrop off, the geologist was able to accurately draw the outcrop on the

map. A note was also entered. “2. Basalt outcrop protrudes from

ground about 1 meter. Black dark grey aphaneritic igneous rock. Has a

uniform body that trends N54E. The outcrop stops, off sets, and begins

again in the southwest.” The coordinates of the sample were

documented on the sample bagged, and annotated in the notes.

Climbing down off the rock was much easier then climbing up and within

a meter the geologist encountered another outcrop. Examining the

outcrop closely showed that it was the same schist as seen before. It had

same gentle folding and the garnets were the same size. While pacing off

the outcrop to annotate it on the map the geologist found that the

outcrop is in contact with a banded iron outcrop. This is exciting, the

geologists starts to draw conclusions about the previous environment

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where the rocks formed, imagining a sea floor near the end of the

Precambrian but the geologist stopped. Think, “I haven’t learned enough

about the area to start drawing conclusions." The banded iron outcrop

looked rather ugly with the red oxidation coating. A lot of effort was

involved in collecting a sample. The rock that ultimately separated from

the outcrop was much larger than wanted but after examining it under a

hand lens it was found to be a gem worth weighting down the backpack.

Silver to black colored banded iron with metallic luster and narrow bands

of chert with waxy luster. Small vugs containing various metallic crystals

demanding further examination under a microscope with some calcite

and a larger vug was also present containing dark grey botryoidal iron.

The sample was labeled as “FMN 3a” and a detailed note was lovingly

entered for this metallic specimen. As banded iron is a sedimentary rock

a dip angle was sought. While taking the strike a lot of care was taken to

ensure the metallic content of the rock did not disturb the compass

bearing. Moving the compass closer and closer to the rock did not

change the bearing. This probably indicated that there was little to no

magnetite in the banded iron. The strike and dip were found to be N54E

25. This and the UTM coordinates were also entered into the notes.

While sitting on the outcrop and drawing it to scale on the map sheet the

mosquitoes insisted that the geologist should feed them. Applying some

repellent seemed to serve as a restraining order as they buzzed around

the face and ears but didn’t land. This was a low point in the topology

and there was some standing water between here and the next outcrop.

Moving through the smelly stagnate water the geologist came to the next

outcrop some two meters away. This was the same banded iron except it

was dipping in the opposite direction. This meant that the area of

standing water was obviously the low point in a syncline and the top of

the basalt outcrop was probably an anticline. Although there was an

urgency to move away from t he mosquito breeding ground the geologist

mapped the outcrop with as much care as the previous outcrops—and

then moved out quickly. The geologist continued to move along the A to

A’ route carefully mapping another basalt outcrop of equal in height to

the previous basalt outcrop, another schist outcrop, and another banded

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iron formation. There were three additional outcrops to the east side of

this traverse and all three were inferred with dotted lines to connect to

those mapped on the traverse.

The two segments of basalt that were disconnected and offset needed a

closer examination. The geologist found that each of these two segments

of basalt were about the same thickness as those mapped on the traverse

and seemed to be the same rock. Each was found to be about a half

meter shorter in elevation than the basalt outcrops to the east and their

offset was about 1.5 meters trending S36W. Both were accurately

mapped. The geologist was confident that this was a left lateral slip fault.

Drawing it on the map and labeled it as “4” there was a personal tug of

war as to whether the fault could be continued to the southeast on the

map even though there was no visual evidence to support that it had

continued to fault. Ultimately the geologist continued the fault on the

map but annotated it as inferred and labeled it as “5.” The fault was

described in the notes and the reasoning why it was believed to be a fault

were carefully detailed and why the other segment was presented as

inferred was detailed.

As the tops of the basalt were relatively flat they were given geologic

symbols showing them as flat. The geologist also believed that the two

basalt outcrops were dikes but represented the hinge of two anticlines—

the dikes were possibly the cause of the syncline between them.

The geologist stopped for lunch and reviewed the field notes and the

map. After enjoying a sandwich the geologist crisscrossed the area to

ensure nothing was missed. All outcrops were mapped. A good rock

sample was obtained, labeled, and entered into the notes at each

outcrop. The geologist was already mentally preparing the geologic

report.

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Chapter 4 - The Geologic Report

Without a report, all of the effort the geologist puts forth in the field is lost. It is much more than simply writing a report, the observations made and the data collected must convey

information in a meaningful manner. Scientific Technical Communication are keywords in writing for all fields of science. This field of writing requires the document to communicate.

Purpose of Geologic Reports.

The purpose of the report was predefined when the geologic project was planned. The purpose may have been academic or required in support of an engineering or mining project. Geologic reports have many purposes and no one purpose is better than the other

however the purpose may dictate an emphasis. There may be special emphasis on metallic minerals or on salt. Other projects may focus on faults to help discern the structural integrity of a possible waste disposal site.

Report Format.

Presentation does matter. The presentation of the report matters as much as the accuracy of the content. The data, tables, graphs, diagrams, photographs, and maps should be presented throughout the report.

The format should be established during the project planning. Having the format established during the planning phase allows the geologist to

focus on subject material in field that is relevant to the purpose.

The format is not to be taken for granted. The geologic report may be just a small part of a much larger presentation. The source requiring the report may have a predetermined format, specific font choice, preference in the paper’s weight, and even what media will be used to convey the report.

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The following is offered as a guideline if no format is defined:

Title of Project Name of Geologist(s)

Date

Abstract

1) Introduction

a) The Project’s Purpose b) Geographic Location c) Methodology Used

2) Local Geology

3) Regional Geology

a) Rock Unites b) Fossils c) Lithology

4) Structure

a) Faults b) Folds c) Unconformities

5) Summary

6) References

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Target Audience.

Target Audience is a term that

applies to Scientific Technical

Communication and means who

the document or report is

prepared for. In some aspects

target audience analysis is nearly

a field of science of its own.

Here teams identify the target

audience’s vulnerabilities,

susceptibilities, and even what

forms of media the target

audience best relates. The

target audience may be a team

of geologists, other scientists,

venture capitalists, executives,

or even politicians. The

document or report prepared

should be for the specific target

audience—the people who will

be reading the report and

making decisions. There are

large cumbersome dictionaries

dedicated to the field of

geology. There is probably no

other field of science that

fabricates so many complex and

entirely unnecessary words. If

the target audience is not a

group of geologists the use of

geologic terms prevents the

document from communicating

the content to the reader. Many

reports ultimately end up in

presentations for executives or

politicians who have to make a

decision on whether a project

will be funded or not. Ensure

the report communicates to the

reader. If necessary develop

more than one report, one that

serves as a presentation that

anyone can understand and

another made available for

those who understand the

jargon of a particular field of

science and want detailed

information that may bore

someone else. It has been said

here once but cannot be

overstated, presentation

matters.

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Bibliography.

FGDC Digital Cartographic Standard for Geologic Map Symbolization, 2008

USGS Color Code, 2005

Manual of Field Geology, Compton, 1962

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