Post on 07-Feb-2021
Evidence of Holocene climate change in northeastern Baffin Baybased on sedimentological analyses and dinoflagellate cyst assemblages
Myriam Caron1,2, André Rochon1, Guillaume St-Onge1, Jean-Carlos Montero-Serrano11 Ins�tut des sciences de la mer de Rimouski, Canada Research Chair in Marine Geology, Université du Québec à Rimouski et GEOTOP, 310 allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada
2 myriam.caron03@uqar.ca
INTRODUCTION
OBJECTIVES1) Track changes in sediment inputs and transport pathways2) Es�mate the evolu�on of sea surface condi�ons (temperature, salinity, sea-ice cover dura�on, produc�vity)3) Document ocean, ice sheet and climate interac�ons in Baffin Bay during the Holocene
• Two major ocean currents meet in the north of Baffin Bay (Tang et al., 2004): → Baffin Island Current (Arctic waters) → West Greenland Current (mixture of Atlantic and Arctic waters)
• Climatic and oceanographic changes occurred since the last glaciation, and through the Holocene.
Ice Sheet
Glacialmargin
Sea iceIceberg
Turbidity current
Debris flow
MeltwaterplumeIce Rafted Debris
Sea surface productivity
Iceberg calving
Hemipelagicsedimentation
Eolian input
Dinoflagellates
Deposition on the sea floor
Cysts
Dinocysts record sea-surface condi�ons
when they fossilize in the sediment
Mul�ple sediment transport processes on the con�nental shelf and slope when associated to ice
sheets
• During the last glacial maximum, Baffin Bay was surrounded by three large ice sheets: the Laurentian, Innuitian and Greenland ice sheets (Dyke et al., 2002).
• Presence of cross-shelf troughs on the continental shelves (Aksu and Piper, 1987).
• Sub-glacial erosion transports sediments across the continental shelf → recording of sediment provenance.
• Glacial erosion triggers different transport and depositional processes (O’Cofaigh et al., 2013)
72°N
74°N
76°N
78°N
80°N
82°N
80°W 70°W 60°W 50°W
Oce
an D
ata
View
2500 m
2000 m
1500 m
1000 m
500 m
300 m
200 m
100 m
80 m
60 m
40 m
20 m
5 m
GreenlandIce sheet
Karrat Group
Rinkian mobile belt
Thule Group
Upernavik
Melville Bugt
Uummannaq
Kane Basin
Baffin Island
EllesmereIsland
Lancaster sound
Nares
Strai
t
Age
Basalts (mafic)Limestone and
dolomite
Silicoclastic rocks(Quartzarenites)
Gneiss andsilicoclastic rocks
Granitesand orthogneiss
Gneisses Archaean
Prec
ambr
ian
Shie
ld
Arch
ean
Prot
eroz
oic
Pale
ozoi
c
BaffinBay
Kane2B
210
204
Did the sediment record the major climatic variations of the deglaciation and the Holocene?
What werethe impacts of these changes on the sediment input?
Simplified geological mapmodified a�er Simon et al. (2014)
METHODS• Three sedimentary cores collected on the northwestern Greenland margin (2014 Arc�cNet expedi�on - Leg1b)• The chronology of the sediment cores was constrained by combining paleomagne�c analyses with AMS-14C ages• Physical proper�es acquired with CT-Scan (X-ray digital image) and MSCL (high-resolu�on images, sediment color, magne�c suscep�bility)• Grain size (laser granulometry) and magne�c proper�es (cryogenic magnetometer) analyses • Quantitative X-ray diffrac�on (qXRD) and X-ray fluorescence (XRF): bulk mineralogical and geochemical sediment proper�es• Palynological analyses using the modern analog technic (MAT) to reconstruct the sea-surface condi�ons based on dinoflagellate cyst assemblages
AMD14-210AMD14-204
0 2 4 6 8 10
600
400
200
0
cal ka BP
Dep
th (c
m)
0 2 4 6 8 10
600
500
400
300
200
100
0
cal ka BP
Dep
th (c
m)
0 2 4 6 8 10
400
300
200
100
0
cal ka BP
Dep
th (c
m)
RESULTS
DISCUSSION
DeglacialHolocene
1
2a
2b
2c
3a
3b
1
2a
2b
3
2
3a
3b
Coarse sandsSandsCoarse siltsMedium siltsFine siltsClaysLithology
Dep
th (c
m)
0
100
200
300
400
428
CTScan
0
100
200
300
400
500
577
CTScan
Lithology%
0 50 1000
100
200
300
400
500
600
700
743
CTScan
Lithology%
0 50 100
Lithology%
0 50 1000 200 400
Magnetic susceptibility
(x10-5 SI)
0 275 550
Magnetic susceptibility
(x10-5 SI)
0 2 4a*
- green-red +
0 1 2a*
- green-red +
-1 0 1 2a*
- green-red +
0 100 200
Magnetic susceptibility
(x10-5 SI)
0 1000 2000
Density(CT number)
0 750 1500
Density(CT number)
300 550 800
Density(CT number)
AMD14-Kane2B AMD14-210 AMD14-204
• A significant downcore variability is observed on these three cores and different units are determined based on this variability: Unit 1: Glaciomarine sedimenta�on, ice-proximal Unit 2: Massive to laminated hemipelagic sedimenta�on, ice-distal Unit 3: Hemipelagic sedimenta�on, ice-distal
24
68
10
1214
16
Cal
cite
(%)
0 5 10 15 20 25Plagioclase (%)
141516171819202122
Qua
rtz (%
)
25 26 27 28 29 30 31 32 33Plagioclase (%)
AMD14-Kane2B AMD14-210 AMD14-204
Postglacial Deglacial
9 10 11 12 13 14 15 16 17K-Feldspar (%)
14
16
18
20
22
24
26
Qua
rtz (%
)
0
10
20
30
40
50
Ran
ge %
Quartz K-Feldspar Plagioclase Calc. + Dol. Micas Clay
Kane 2B
204
210
Distribution of minerals within the cores:
AMD14-Kane2B
Dep
th (c
m)
0
100
200
300
400
428
CTScan 0 5000 10000
Dinocyst concentration(cyst/cm3)
HeterotrophAutotroph
0
100
200
300
400
500
600
700
743
CTScan 0 12500 25000
Dinocyst concentration(cyst/cm3)
AMD14-204
I
I
II
III
II
III
Cyst of Pentapharsodinium
dalei
Operculodiniumcentrocarpum
Spiniferiteselongatus/frigidus
Islandinium minutum
Brigantediniumsp.
Echinidiniumkaraense
Islandiniumminutum
• Sediment provenance (detrital inputs): AMD14-Kane2B: mainly derived from Paleozoic carbonate-bearing rocks and more Proterozoic granitic sources in unit 2 (2a and 2B) AMD14-210 and AMD14-204: mainly derived from granite and gneiss from the Precambrian Shield
• Palynological results → three dinocyst assemblage zones determined: Assemblage I: low dinocyst concentra�on, heterotrophs dominate Assemblage II: marked by Operculodinium centrocarpum and Spiniferites elongatus dominance (AMD14-204) or occurrence (AMD14-Kane2B) and increasing dinocyst concentra�on Assemblage III: marked by Pentapharsodinium dalei dominance (AMD14-204) or occurrence (AMD14-Kane2B) and a decreasing concentra�on at the top of the cores
AM
D14
-Kan
e2B
War
m a
nd c
old
dino
cyst
s
0
10
20
0 2 4 6 8 10
% Gonyaulacal
Age cal ka BP
0
35
70
% Brigantedinium sp.
0
35
70% O. centrocarpum
0
17,5
35
% Islandinium minutum
AM
D14-204
Warm
and colddinocysts
1
2
3
4
Quartz/Plagioclase22
27
32
Quartz (%
)
AM
D14-K
ane2B
0,45
0,65
0,85
Qua
rtz/
Plag
iocl
ase
12
17
22
Qua
rtz
(%)
AM
D14
-204
0,1
0,4
0,7
Cla
y/Si
ltA
MD
14-2
10
0,45
0,6
0,75
Quartz/Plagioclase14
20
26
Quartz (%
)
AM
D14-210
Age cal ka BP
-32
-29,5
-27
0 2 4 6 8 10
18O
Cam
p Ce
ntur
y
-35
-34
-33
-32
-31
-30
-29
-28
-27
0 2000 4000 6000 8000 10000
18O
(‰) C
amp
Cent
ury
DeglaciationHolocene ThermalMaximumNeoglaciation
warmer
surfacewaters
warmer
surfacewaters
0
2
4
6
8
10
Age cal BP
Moro
s et a
l. (20
16)
Jenn
ings e
t al. (
2011
)St
-Ong
e and
St-O
nge (
2014
)
Leva
c et a
l. (20
01)
Pern
er et
al. (2
012)
Jenn
ings e
t al. (
2014
)
0 10 200
2
4
6
8
10
AMD14-Kane2B% Gonyaulacals
Age
cal B
P
Knud
sen e
t al. (
2008
)
Kraw
czyk
et al
. (201
7)
14 20 26
AMD14-210Quartz (%)
0 50 100
AMD14-204Heterotroph (%)
WEST GREENLANDSMITH SOUND / NARES STRAIT
Deglaciation
Holocene Therm
alM
aximum
Neoglaciation
-32 -29,5 -27
-35
-34
-33
-32
-31
-30
-29
-28
-27
02
00
04
00
06
00
08
00
01
00
00
18O (‰) Camp Century
Ag
e (ca
l BP
)
Vinther et al. (2009)18O Camp century (‰)
• Lithological units 1 and 2 show a mainly deglacial (glaciomarine) sedimenta�on strongly affected by meltwater inputs and ice-ra�ing. This units are correlated to the dinocyst assemblage zone I, characterized by cold sea-surface temperature and an extended sea-ice cover. Thus, this period is associated to the Deglacia�on.
• Finally, the dinocyst assemblage III suggests the establishment of modern sea-surface conditions and a cooling trend after 3 cal ka BP. This period is associated to the Neoglaciation.
• Holocene Thermal Maximum occurs earlier in the northernmost part of Baffin Bay compared to other parts of the Arctic (e.g., Moros et al., 2016; Jennings et al., 2014)
• Lithological unit 3 is characterized by hemipelagic sedimenta�on which indicates more stable condi�ons than units 1 and 2. Dinocyst assemblage II suggests higher produc�vity and generally warmer sea-surface condi�ons. This period is associated to the Holocene Thermal Maximum.
ACKNOWLEDGMENT & REFERENCESWe thank the captain, officers, crew and scientists on board the CCGS Amundsen for the recovery of cores AMD14-204, AMD14-210 and AMD14-Kane2B. We also thank Quentin Beauvais and Marie-Pier St-Onge for their technical support. This study was supported by the CREATE ArcTrain program (NSERC). © Q. Duboc for the background photo.REFERENCES: Aksu and Piper, 1987, Late Quaternary sedimentation in Baffin Bay. Can. J. Earth Sci. 24, 1833–1846. Dyke et al., 2002, The Laurentide and Innuitian ice sheets during the Last Glacial Maximum. Quat. Sci. Rev. 21, 9–31. Jennings et al. 2014, Paleoenvironments during Younger Dryas-Early Holocene retreat of the Greenland Ice Sheet from outer Disko Trough, central west Greenland. J. Quat. Sci. 29, 27–40. Moros et al., 2016, Surface and sub-surface multi-proxy reconstruction of middle to late Holocene palaeoceanographic changes in Disko Bugt, West Greenland. Quat. Sci. Rev. 132, 146–160. Ó Cofaigh et al., 2013, Glacimarine lithofacies, provenance and depositional processes on a West Greenland trough-mouth fan. J. Quat. Sci. 28, 13–26. Simon et al., 2014, North-eastern Laurentide, western Greenland and southern Innuitian ice stream dynamics during the last glacial cycle. J. Quat. Sci. 29, 14–26. Tang et al., 2004, The circulation, water masses and sea-ice of Baffin Bay. Prog. Oceanogr. 63, 183–228. Vinther et al., 2009, Holocene thinning of the Greenland ice sheet. Nature 461, 385–388.
CONCLUSIONSThe specific varia�ons of almost all proxies measured in this study are synchronous with other regional records, suppor�ng the following hypotheses: (1) the Greenland Ice Sheet fluctua�ons are mainly driven by changes in the intensity of the West Greenland Current, themselves related to Holocene climate variability and; (2) the Holocene is subdivided into three main clima�c periods: the end of the deglacia�on, the Holocene Thermal Maximum and the Neoglacia�on.