Paleogeography and paleoenvironments of southwestern Baffin Island (Nunavut, Canada):

post-glacial isostatic uplift and isolation of Nettilling Lake from marine influence

Biljana Narancic¹ (biljana.narancic.1@ulaval.ca), Reinhard Pienitz¹, Pierre Francus², Bernhard Chapligin3 and Hanno Meyer3

1 Geography Department, Centre for Northern Studies (CEN) Laval University, Quebec, Canada; 2 Institut National de la Recherche, Eau-Terre-Environnement, Quebec, Canada; 3 Alfred Wegener Institute (AWI) for Polar and Marine Research, Potsdam, Germany.

Ni4-7

Ni2-B

RESULTS OF MULTIPROXY SEDIMENT CORE ANALYSIS

Upper facies (0-16cm )

GENERAL CONTEXT AND STUDY OBJECTIVES

Here we present a pioneer study with respect to ecosystemic

postglacial succession that has never been completed before

in this remote region of the Canadian Arctic.

This multiproxy study will generate new paleolimnological and

paleoenvironmental data by reconstructing the history of

postglacial isostatic uplift and isolation of the lake basin from

marine influence.

It will provide further evidence for the usefulness of multiproxy

analysis (biological and geochemical indicators) in

reconstructing sea-level changes and land-uplift in formally

glaciated landscapes.

The paleolimnological record from the study will enable

ice-sheet modelers to accurately reconstruct the past and

better predict the future contribution of polar ice sheets to

global sea-level change.

Core Ni4-7

Diatoms (Lagoon)

0

5

10

15

20

25

30

35

40

45

50

Ag

e (

ca

l yr

BP

)

De

pth

(cm

)

X-RayOptical

image

5275

5779

6053

6510

0 3 2 644816

Ca/TiSi/Ti

0.15 0.75 1.35

Biogenic silicaCarbonates

Cl

0.0025 0.005 0.0075 0.01 0.01250

Salinity

1000

!"#$%&#'(%)*+,LOI (%)

1.2 3.6 6.0 8.4 10.8 1 10 100-4 4 12 20 28

Magnetic suseptibility

0 40 80 120

I Marine littoral

Cluster analysis

Zones Paleoenvironment

II Brackish interdital

IIIb Freshwater

IIIc Freshwater

IIIa Freshwater

12 24 36 48 60

Water content (%)

Relative abundance (%)

Polyhalobous Mesohalobous Oligohalobous Halophobous

Rha

bdon

ema minutum

Plagiog

ramma stau

roph

orum

Gra

mmatop

hora

oce

anica

Gra

mmatop

hora

arcua

ta

Coc

cone

is scu

tellu

m var. p

arva

Ope

phor

a mar

ina

Ehr

enbe

rgiulva ga

nulosa

Diatomella m

inutum

Elle

beck

ia are

naria

Tabu

laria

fasc

iculata

Pinnu

laria

qua

dratar

ea

Ach

nanthe

s cf. d

elicatula va

r. ha

uckian

a

Ope

phor

a olse

nii

Licm

opho

ra sp.1

Calon

eis ba

cillu

m

Nav

icula digitora

diata

Amph

ora cf. c

opulata

Pse

udos

taur

osira

bre

vistria

ta

Staur

osire

lla pinna

ta

Staur

osira

con

stru

ens va

r. ve

nter

Staur

osira

con

stru

ens

Amph

ora pe

dicu

la

Ach

nanthe

s minutissima

Den

ticula cf. ten

uis

0 1 2 0 000 1 2000 1 20 0 10 20 30 00 1 20 00 1 00 1 00 1 00 1 20 00 1 20 0 01 20 30 40 50 60 70 80 90 01 20 30 40 50 60 01 20 30 40 50 60000 1 00 1 00 1 00 1 00 1 00 1 00 1 00 1 20 00 0 0 1 200 100 1 00 1

Chironomids ( Lagoon)

Taxa inclus (Walker 1995)

Cricocopus

Orthocladius

Chironomus

Procladius

Psectrocladius

Cric

otop

us

Cor

ynone

ura

Stic

htoch

irono

mus

Parakiefferiella

fen

nica-typ

e

Pse

ctrocladius so

rdidellu

s-group

Tanytarsus sp

.

Micropse

ctra radialis

-typ

e

Tanytarsus with

spur

Microsp

ectra sp.

Oliv

erdia

Orthoclad

ius

Coryn

oce

ra oliv

eri-typ

e

Tanytarsus with

out sp

ur

Chironomini s

p.

Paratanytarsus

Micropse

ctra in

signilo

bus

-typ

e

Heterotrisso

cladius grimsh

awi-type

Procladius

Coryn

oce

ra ambigua

-typ

e

Paracladius

Chironomus an

thracinus-type

Cladotanytarsus

Sergentia

Zalutsch

ia sp. B

Abisko

myia

Heterotrisso

cladius marcidus-type

Heterotrisso

cladius su

bpilo

sus-type

Lim

nophye

s

Heterotrisso

cladius maeaeri-typ

e

Heterotrisso

cladius sp

.

Protanyp

us

Chironomid salin

ity tolerance

0 15 30 45 60 75 0 20 0 0 0 15 0 15 0 20 0 0 15 0 0 0 15 30 0 15 0 0 0 0 0 0 20 40 60 0 15 0 0 0 0 0 0 0 0 0 15 0 15 0 0 15 30 45 60 75 0 5 10

°C

Chironomid-inferred A

ugust air temperature

Shifts in the composition of fossil

diatom assemblages document the

marine-brackish-freshwater transition.

Fossil chironomid larvae started to

appear in the lake only after basin

isolation and the establishment of

freshwater conditons.

Paleosalinity and paleoproductivity

changes are reflected in the

sediment core geochemistry, as

shown by shifts in Ca/Ti, Si/Ti and

Cl profiles that coincide with the

diatom-inferred basin isolation.Relative abundance (%)

BIOLOGICAL INDICATORS PHYSICAL AND GEOCHEMICAL INDICATORS

Marine inferenceProductivity inferences

Isolation of lake basin end of postglacial marin influence

METHODS

A multi-proxy paleolimnological approach is used to study the sedimentary records

preserved in Nettilling Lake.

Physical properties:

- LOI and magnetic susceptibility

Chemical properties:

- Relative concentration of chemical elements by high resolution micro-fluorescence

(µ-XRF) core scanner

- Isotope analysis

Biological properties:

- Chironomid, diatom and foraminifer assemblage analyses

Two sampling areas were chosen based on the hypothesis that post-glacial marine

transgression and the establishment of the freshwater lake would be preserved in the

sediment records from the extreme opposite (west-east) parts of Nettilling Lake.

!"#$%&#'(%)*+,

-50 50 150 250 3500 4 8 12 16

LOI %Water content % Magnetic suseptibility

16 24 32 40 48 56 1 10 100 1000

-8 0 8 16 24

De

pth

(cm

)

X-RayOptical

image

Redox layerForams rich layersSalinity

0.000 0.001 0.002 0.003 0.004

Cl/k

cps

0 1 2 3 4

Ca/

Fe

0.0 0.1 0.2 0.3

Mn/

kcps

1 3 5 7 9 11

Fe/kc

ps

0.0 0.2 0.4 0.6

Mn/

Ti

0 8 16 24 32

Fe/Ti

0.00 0.03 0.06 0.09 0.12

Mn/

Fe

IV Freshwater

Cluster analysis

I Marine intertidal

II Brackish intertidal

0 50 150

III Brackish-Freshwater

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

PHYSICAL AND GEOCHEMICAL INDICATORS

0.1 0.2 0.3 0.4

Si/T

i

0 2 4 6 8 10

Ca/

Ti

0.07 0.08 0.10 0.11 0.12 0.13

Si/K

0.0000 0.0002 0.0004 0.0006

Ca/

K

Productivity inferencesMarine inferences

Isolation of lake basin end of postglacial marin influence

Ag

e (

ca

l yr

BP

)

2523

5410

5051

4118

Shifts in Ca/Ti, Si/Ti, and Cl reflect the

end of marine influence and the

establishment of the brackish-freshwater

conditions.

Diatom fraction used > 10 µm

Difference in fractination factor between

fresh and marine layer confirms the

marine influence in the Nettilling Lake

basin.

CONCLUSION

Glacio-isostatic submergence of the Earth crust moved the Foxe-Basin

coastline inland by hundreds of km for much of the Holocene.

Glacio-isostatic rebound resulted in the formation of a meromictic saline lake

system.

Sea water trapped in the lake during the isolation process was preserved in a

dense saline and anoxic hypolimnion that lasted for several hundred years.

Nettilling Lake basin remained under marine influence until the Mid-Holocene

(5000 yr cal. BP), followed by freshening and fluvial processes that supplied

sediment and fresh water until the present-day.

Precise radiocarbon dating of the transitional zone in the Ni2-B sediment core

will allow to refine the history of post-glacial sea extent and duration of

glacio-isostatic uplift.

Studies of the diatom assemblages from the Ni2-B sediment core will further

refine our interpretations of changes in diatom species in response to the

effects of decreasing salinity in the lake.

diatoms

21,24‰

diatoms

22,92‰

diatoms

27,31‰

water

-17,53‰

High Mn/Fe rations indicate strong

anoxic conditions in the lower water

columne during saline to freshwater

transition.

The clear difference in geochemistry of upper facies compared with lower facies:

1. Higher Ca peaks area in the low marine facies are indicative of endogenic calcite precipitation in the postglacial sea

2. Shifts in sediment source from carbonate terrain to Precambrian granites/gneiss terrain

Lower facies (70-82cm)

GEOCHEMICAL INDICATORS

Core Ni2-B

Core Ni2-B Core Ni2-BBIOLOGICAL INDICATORS

Dep

th (c

m)

Troch

amm

ina sp.

Polym

orph

inidae

uniden

tified

Foram

s

Polyc

haet

e m

outh

par

ts

Hyd

rozo

a tu

bes

Spicu

les (s

traight

and

sim

ple)

Tintin

nops

is ri

odelap

late

nsis

Chiro

nom

ids

Difflugia

oblong

a

Difflugia

oblong

a "g

lans

"

Cen

tropy

xis ac

ulea

ta

Cen

tropy

xis co

nstri

cta

?Pon

tigulas

ia com

pres

sa

Paleo

zoic E

chinod

erm

s & B

ryoz

oas

| | | | | | | | | | | | | |

33 X X X

43 X X X X X X

53 X X X X X

61 X X X X X

68 X X X X

77 X X X X X X X

brackishmarine/brackish freshwater

ThecamoebaeForaminifers

In this diagram, we present 63-1000 µm fractions.

We found fossil fragments from paleozoic carbonate terrain at 77 cm core depth. This confirms the shift in sediment

source from carbonate terrain to Precambrian granites/gneiss terrain.