Evidence of Holocene climate change in northeastern Baffin Bay based on sedimentological analyses and dinoflagellate cyst assemblages Myriam Caron 1,2 , André Rochon 1 , Guillaume St-Onge 1 , Jean-Carlos Montero-Serrano 1 1 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 [email protected] INTRODUCTION OBJECTIVES 1) Track changes in sediment inputs and transport pathways 2) 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 Glacial margin Sea ice Iceberg Turbidity current Debris flow Meltwater plume Ice Rafted Debris Sea surface productivity Iceberg calving Hemipelagic sedimentation 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 Ocean Data View 2500m 2000m 1500m 1000m 500 m 300 m 200 m 100 m 80 m 60 m 40 m 20 m 5 m Greenland Ice sheet Karrat Group Rinkian mobile belt Thule Group Upernavik Melville Bugt Uummannaq Kane Basin Baffin Island Ellesmere Island Lancaster sound Nares Strait Age Basalts (mafic) Limestone and dolomite Silicoclastic rocks (Quartzarenites) Gneiss and silicoclastic rocks Granites and orthogneiss Gneisses Archaean Precambrian Shield Archean Proterozoic Paleozoic Baffin Bay Kane2B 210 204 Did the sediment record the major climac variaons of the deglaciaon and the Holocene? What werethe impacts of these changes on the sediment input? Simplified geological map modified 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- 14 C 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 AMD14-210 AMD14-204 0 2 4 6 8 10 600 400 200 0 cal ka BP Depth (cm) 0 2 4 6 8 10 600 500 400 300 200 100 0 cal ka BP Depth (cm) 0 2 4 6 8 10 400 300 200 100 0 cal ka BP Depth (cm) $0'í.DQH% RESULTS DISCUSSION Deglacial Holocene 1 2a 2b 2c 3a 3b 1 2a 2b 3 2 3a 3b Coarse sands Sands Coarse silts Medium silts Fine silts Clays Lithology Depth (cm) 0 100 200 300 400 428 CT Scan 0 100 200 300 400 500 577 CT Scan Lithology % 0 50 100 0 100 200 300 400 500 600 700 743 CT Scan Lithology % 0 50 100 Lithology % 0 50 100 0 200 400 Magnetic susceptibility (x10 -5 SI) 0 275 550 Magnetic susceptibility (x10 -5 SI) 0 2 4 a* - green-red + 0 1 2 a* - green-red + -1 0 1 2 a* - 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 2 4 6 8 10 12 14 16 Calcite (%) 0 5 10 15 20 25 Plagioclase (%) 14 15 16 17 18 19 20 21 22 Quartz (%) 25 26 27 28 29 30 31 32 33 Plagioclase (%) AMD14-Kane2B AMD14-210 AMD14-204 Postglacial Deglacial 9 10 11 12 13 14 15 16 17 K-Feldspar (%) 14 16 18 20 22 24 26 Quartz (%) 0 10 20 30 40 50 Range % Quartz K-Feldspar Plagioclase Calc. + Dol. Micas Clay Kane 2B 204 210 Distribution of minerals within the cores: AMD14-Kane2B Depth (cm) 0 100 200 300 400 428 CT Scan 0 5000 10000 Dinocyst concentration (cyst/cm 3 ) Heterotroph Autotroph 0 100 200 300 400 500 600 700 743 CT Scan 0 12500 25000 Dinocyst concentration (cyst/cm 3 ) AMD14-204 I I II III II III Cyst of Pentapharsodinium dalei Operculodinium centrocarpum Spiniferites elongatus/frigidus Islandinium minutum Brigantedinium sp. Echinidinium karaense Islandinium minutum • 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 AMD14-Kane2B Warm and cold dinocysts 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 AMD14-204 Warm and cold dinocysts 1 2 3 4 Quartz/Plagioclase 22 27 32 Quartz (%) AMD14-Kane2B 0,45 0,65 0,85 Quartz/Plagioclase 12 17 22 Quartz (%) AMD14-204 0,1 0,4 0,7 Clay/Silt AMD14-210 0,45 0,6 0,75 Quartz/Plagioclase 14 20 26 Quartz (%) AMD14-210 Age cal ka BP -32 -29,5 -27 0 2 4 6 8 10 į 18 O Camp Century Deglaciation Holocene Thermal Maximum Neoglaciation warmer surface waters warmer surface waters 0 2 4 6 8 10 Age cal BP Moros et al. (2016) Jennings et al. (2011) St-Onge and St-Onge (2014) Levac et al. (2001) Perner et al. (2012) Jennings et al. (2014) 0 10 20 0 2 4 6 8 10 AMD14-Kane2B % Gonyaulacals Age cal BP Knudsen et al. (2008) Krawczyk et al. (2017) 14 20 26 AMD14-210 Quartz (%) 0 50 100 AMD14-204 Heterotroph (%) WEST GREENLAND SMITH SOUND / NARES STRAIT Deglaciation Holocene Thermal Maximum Neoglaciation -32 -29,5 -27 Vinther et al. (2009) į 18 O 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 & REFERENCES We 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. CONCLUSIONS The 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.