G E O L O G I C A L M A P P I N G

O F

T I B B I T TT I B B I T T

L A K E L A K E

R E G I O NR E G I O N

JAC K R O B I N S O N

TIBBITT LAKE

1km

Area mapped

Ingraham Trail

LOCATION

Great Slave Lake

Ingraham Trail

Tibbitt Lake

30km

Great Slave Lake

1000km

INTRODUCTION

AND AIMS

I am a third year student at Queens’ college Cam-

bridge studying Natural Sciences and during the

summer I carried out a geological mapping project

as part of my course for the coming academic

year. The aim of the project was to map an area of

15-20 square kilometres of bedrock at a scale of

1:10,000 over 28 days. I was part of a four person

group made up of Cathy Smith, Max Winchester

and Sophie Lawson.

The area was within the Archean Slave province in

the Northwestern Canadian shield, approximately

65km Northeast of Yellowknife, where the Ingra-

ham Trail terminates at Tibbitt Lake (62.554 deg.

N 113.350 deg W). We stayed at Reid Lake camp-

site which was a modern camp ground with

shower and toilet facilities and was run by a very

friendly old Welsh couple.

Before the project began we knew some informa-

tion about what type of rocks to expect and we

had some contacts in the Geoscience office in Yel-

lowknife who had advised us on where to map.

Apart from that and a campsite reservation, we

didn’t know what to expect from the area or the

project. It was exciting!

Team Tibbitt in Yellowknife

Our camp-site with a sleepy Sophie taking a break.

Amphibolite on the right lies next to a layer of pale, baked sandy sediments. We believe the amphibolites here originally in-

truded the sediments as an igneus sill.

2013

OCT NOV DEC JAN

2012

FEB

JUL

Canada decided as target

country for mapping

project.

Valerie Jackson from GeoScience

office replied to email offering

advice about mapping in NWT.

Province decided. Further

planning and research required.

Tibbitt lake region decided as mapping area.

Begun to apply for grant money

July 10th- Flight leaves

Heathrow 11:05am arrives at Yellowknife at 23:02pm (but feels like 6am next day due to 7 hour time difference). Car hired and B&B found thanks to a friendly local.

First car hired, a sporty number

July 13th

Drive to

Campsite,

check in and

pitch tents.

Gravel sites…

July 14th- Day 1

of 28 mapping

days

Some spectacular views whilst mapping

July 18th

Encounter with a

black bear in the

field!

July 30th

Borrowed a canoe

to improve access

to remote

locations

TIMELINE

FEB MAR APR MAY JUN

AUG SEP

Begun to apply for grant money

Flights booked- trip beginning to feel like reality.

Campsite booked from 13th July until 18th August

2 week preparation mapping trip to the isle of Skye with university

August 16th - Last day

of mapping

August 19th – Return car and depart

Yellowknife

Aug 7th - Mapping

interrupted by punctured tire.

After a cautious journey back

to Yellowknife we got a new

car!

The spare tire was a bit thinner than the old one.

A hardened mapping team by the end.

TIMELINE

GEOLOGICAL

FINDINGS

Starting with the basics, geological mapping is the

process where you go into an area with a copy of

a topographic map (like an ordinance survey map

in the UK), locate your position on that map, using

a hand held GPS then identify the rock type that

you can see and mark it on the map. Additionally I

would make a note in my notebook about

interesting details of the rock and make a sketch if

it is particularly interesting. At every location I

would try to take the strike and dip of the rocks, if

they were sedimentary and were well exposed.

These measurements tell you what the strata or

sedimentary beds look like in 3D space and are

extremely useful for understanding any

deformation that has happened on a larger scale.

The red lines here

show the top of the

sedimentary beds.

Decreasing grain

size produces a

gradual colour

change in the beds.

The topographic

maps for our area

were digitally

available online so

we printed them out

on to card and took them out in to the field with

us every day. They were our field slips and for

each ‘locality’ that I made, there is a precise dot

on my field slip with a number next to it.

The number corresponds to the same number in

my notebook that has a greater description of the

rocks that I could see and any other interesting

features, as well as the important data and

labelled diagrams of relevance.

The area that I studied has been mapped before at

a very large scale of 1:250,000. I have mapped at

1:10,000 and will be able to produce a more

detailed map than anything available so far.

Classic turbidite beds of the

Burwash formation.

My field slips and notebooks at the end of the project.

An example page from

my notebook: The top

page is reserved for

labelled diagrams of

interesting features.

The bottom page

contains data on the

left, observations in

the middle and

interpretations of the

observations on the

right.

Over the course of 28 days

mapping (usually 9am-5pm) in the

field I managed to map an area of

roughly 10km2. One aspect of the

environment that made things

surprisingly difficult was the high

level of exposure. Because a lot of

the rocks were so excellently

exposed I initially found it difficult

to map at the right scale because

previous work has been in

Scotland where rocks might only

be exposed once every 100m or

so.

Rock Types

We found three major rock types

in our area, all of which had their

interesting features and

intricacies which made them

fascinating to map. There was the

Burwash formation, comprised of

Archaen meta-sediments,

including some pristine turbidite

sequences with flame structures,

graded bedding and cross bedding

preserved nicely in places. This

presented a challenge because it

has been greatly deformed, by

two major deformation events

that have led to both small and

large scale folding. Measuring the

strikes and dips of this unit was

thus of crucial importance.

The second major rock type was

the amphibolite- a dark, more

resistant unit composed of

amphibole and plagioclase

crystals that was sometimes

foliated, sometimes not and had

varying crystal sizes. Often it was

‘sill-like’, following the strike of

the surrounding Burwash

sediments and has been

interpreted as an intrusive

igneous rocks that has been

metamorphosed in a similar way

to the sediments around it.

Plotting the contacts of the

amphibole with the surrounding

sediments was challenging

because often it did not display

classic sill-like contacts but often

emerged, disappeared then re-

emerged at the surface. A

successful technique found

towards the end of the project to

map this well exposed but

complex unit was ‘traverse

mapping’ where I would traverse

across the whole unit, marking

contacts and which way the

contacts were going, then move

south 100m then traverse again.

Then at the end I could easily

connect the contacts measured

during the different traverses.

The final unit was a small area of

white granite that was exposed in

a sporadic way within the

Burwash formation,

uncharacteristic of granite which

is usually found in large plutons.

This exposure pattern suggested

to me that this could be the top of

a much larger body of granite that

lies beneath the surface. This

hypothesis however would need

more research to confirm or

refute.

CONCLUSIONS

Overall I thoroughly enjoyed the trip and I

believe I have developed a few skills along

the way:

Planning: We had to find an area by

ourselves, get there, get accommodation,

find topographic maps and all of the

equipment we would need.

Teamwork: In a group of four you have to

work together, especially with organisation in

order to make all of the different aspects

work. It is also important to get along well

which can be difficult when living in such

close quarters. Luckily there were no punch

ups!

Geological mapping skills: with only 2 weeks

of mapping experience before I have mapped

10km2 independently and will be able to

contribute new scientific information to the

world.

I loved camping and working in such a remote

part of the world. During the whole of our

mapping time, we did not see a single person

out in the field when we were working. The

worst part of being in the Northwest

Territories at that time of year were the

mosquitoes, especially just after it had rained

- they were everywhere so a combination of

bug spray and full body bug jacket were

needed to help reduce the number of bites.

I would highly recommend this type of

project to anybody doing geology, the more

remote and wild the better!

Max crosses the river using the bridge we built. Dedication.

Canoeing to the other side of the lake saved a lot of walking!