barnett rl, bernatchez p, garneau m and juneau m-n. (2017) reconstructing late holocene relative sea...

Reconstructing late Holocene relative sea-level changes at theMagdalen Islands (Gulf of St. Lawrence, Canada) using multi-proxyanalyses

ROBERT L. BARNETT,1,2* PASCAL BERNATCHEZ,1 MICHELLE GARNEAU2 and MARIE-NOËLLE JUNEAU1

1Research Chair in Coastal Geoscience, D�epartement de Biologie, Chimie et G�eographie, Centre d’�etudes Nordiques etQu�ebec-Oc�ean, Universit�e du Qu�ebec �a Rimouski, 300 all�ee des Ursulines, C.P. 3300, Rimouski, QC, G5L 3A1, Canada

2D�epartement de G�eographie and Geotop Research Centre, Universit�e du Qu�ebec �a Montr�eal, 201 Pavillon Pr�esident-Kennedy,Montr�eal, QC, H2X 3Y7, Canada

Received 19 September 2016; Revised 22 November 2016; Accepted 28 November 2016

ABSTRACT: Proxy records of late Holocene relative sea-level changes are important for our understanding ofmechanisms that drive contemporary sea-level trends. In the Gulf of Saint Lawrence (eastern Canada), theMagdalen Islands currently experience higher than global average rates of relative sea-level rise. This articlepresents original reconstruction data of sea-level changes from the Magdalen Islands over the past few millenniacollected from a variety of coastal deposits and proxy records including salt-marsh foraminifera, testate amoebaeand plant macrofossils. Reconstructed late Holocene relative sea-level trends are between 1.3 and 2.0mm a�1 forthe past 2000 years. When combined with contemporaneous trends in tide-gauge data from Cap-aux-Meules(Magdalen Islands), multi-proxy data show acceleration in the rate of relative sea-level rise to over 4mm a�1 duringthe 20th century. This signal corresponds to similar inflexions also registered in salt marshes and tide-gauge dataalong the east coast of North America. Copyright # 2017 John Wiley & Sons, Ltd.

KEYWORDS: foraminifera; late Holocene; Magdalen Islands; proxy records; sea level; testate amoebae.

Introduction

Proxy-derived sea-level data that extend back in time beyondthe industrial era are valuable for investigating past andcontemporary sea-level rise. Understanding of regional toglobal patterns of sea-level variability relies on these proxyrecords that span the past few centuries and millennia(Nakada et al., 2013; Kopp et al., 2016). Such records arenow being used to investigate the role of ice-sheet dynamicsand vertical land motion (Gehrels et al., 2004; Long et al.,2010; Barlow et al., 2012), ocean circulation (Kemp et al.,2014, 2015), eustasy (Woodroffe et al., 2015), global temper-ature changes (Gehrels et al., 2005; Kemp et al., 2011) andwind stress (Saher et al., 2015) on local and regional patternsof sea-level rise. As a result, we know that certain regions ofthe globe are at greater risk of future relative sea-level (RSL)rise than others (Church et al., 2013; Stammer et al., 2013),like the Atlantic coast of North America (Slangen et al., 2012,2014). The Magdalen Islands, in the southern sector of theGulf of St. Lawrence, eastern Canada (Fig. 1), show higherthan global average rates of RSL rise (Church et al., 2013;Han et al., 2015; Watson et al., 2015), largely driven by highrates of glacio-isostatic land subsidence (Koohzare et al.,2008; Peltier et al., 2015) resulting from deglaciation (Milneand Mitrovica, 1998) and associated mechanisms such asocean siphoning (Mitrovica and Peltier, 1991; Mitrovica andMilne, 2002). In addition, sea-surface height in the region isalso sensitive to meltwater from the Antarctic Ice Sheet(Mitrovica et al., 2001), increased ocean heat storage (Churchet al., 2008, 2013; Levitus et al., 2012), changes in thestrength of the Atlantic Meridional Overturning Circulation

(Rahmstorf et al., 2015) and, consequently, modes of theAtlantic Multidecadal Oscillation and North Atlantic Oscilla-tion (McCarthy et al., 2015). Despite the sensitivity of theMagdalen Islands to important sea-level drivers, little hasbeen published on the Holocene sea-level history of theregion (R�emillard et al., 2016). The aim of this contribution istherefore to reconstruct late Holocene RSL changes at theMagdalen Islands (Gulf of St. Lawrence) using multi-proxyanalyses supported by robust 14C and 210 Pb chronologies toinvestigate how sea-level variations have evolved over thepast few thousand years. This study will aid ongoinginvestigations into the main drivers of contemporary andfuture sea-level rise in the North Atlantic.

Regional setting

The archipelago of the Magdalen Islands in the Gulf ofSt. Lawrence is formed of nine islands composed of Carbonif-erous to Permian bedrock, mostly sandstone, siltstone andvolcanic rock (Brisebois, 1981; Barr et al., 1985; Giles,2008). Seven of them are connected by late Quaternary sandbarriers (Dredge et al., 1992) that produce sheltered embay-ments and tidal lagoons (Fig. 1B). Extensive beach ridgesystems were formed since 2600 cal a BP in a context of RSLrise (Giles and King, 2001; R�emillard et al., 2015). Theislands experience a microtidal regime with small spring andneap tidal ranges (<1m). Tide-gauge data are available fromCap-aux-Meules for the past few decades (Canadian Hydro-graphic Service; tides.gc.ca), although significant data hia-tuses exist. Offshore significant wave height in the regionincreases from 4 to 5m from east to west, although thepresence of sea ice attenuates wave height size during wintermonths (Ruest et al., 2016). With greater exposure to stormevents in the west of the archipelago, historical displacementrates of tombolo for 1968 to 2008 were as high as �0.5

�Correspondence to: R. L. Barnett, Geography, College of Life and Environ-mental Sciences, University of Exeter, Amory Building, Rennes Drive, ExeterEX4 4RJ, UK.E-mail: [email protected]

Copyright # 2017 John Wiley & Sons, Ltd.

JOURNAL OF QUATERNARY SCIENCE (2017) ISSN 0267-8179. DOI: 10.1002/jqs.2931

to �2.0m a�1. (Bernatchez et al., 2012) With mean erosionrates between �0.3 and �1.5m a�1, the Magdalen Islandsexperience some of the highest rates of retreat for rocky cliffsin the estuary and Gulf of St. Lawrence (Bernatchez andDubois, 2004). Indications of the impact of RSL rise is evidentthroughout the islands and includes shoreline migration,coastal fringe forest deterioration, coastal wetland coloniza-tion and, significantly, the presence of submergedpalaeo-forests and tree stumps found in the intertidal andsubtidal zones (Dubois and Grenier, 1993; Juneau, 2012).

Methods

RSL changes are reconstructed using several proxies includingpalaeo-forest and peat horizons from the intertidal zone,salt-marsh plant macrofossils, foraminifera and testate amoe-bae, buried coastal (basal) peat deposits and geochemicalanalyses. Tide-gauge records are used to complete theanalysis of recent sea-level changes.Coastal surveys were first carried out in 2007 and 2008 to

study stratigraphic sections and submerged forests that pro-vide evidence for water level changes across the MagdalenIslands (Juneau, 2012). Palaeo-forest, palaeo-peat depositsand submerged tree stumps were used to infer maximumpossible altitudes of former sea level by subtracting theinferred (minimum) indicative elevation of mean higher highwater (0.43m) from the height of the sample relative to theCanadian Geodetic Vertical Datum of 1928 (CGVD28)

(Shennan, 2015). Survey data were collected with a TrimbleR8 RTK differential global positioning system base station andTrimble R10 rover system (�0.015m vertical uncertainty)relative to the Canadian Spatial Reference System NAD83.Elevations were recorded as height (m) above CGVD28following a correction from the geoid model HT2.0. Saltmarshes at Les Sillons and Basin (Fig. 1) were revisited in2014 for further sampling. Coring using an Eijkelkamp gougeauger was undertaken to create sub-surface transect profiles.Lithologies were described following Long et al. (1999) basedon 17 cores taken from Les Sillons (Fig. 1C) and 10 fromBassin (Fig. 1D). Selected sediment cores with long andcontinuous sections of salt-marsh peat were retrieved fromeach marsh, wrapped in cellophane, transferred into polyvi-nyl chloride tubes and stored at 4 ˚C before analyses.The relict foredune plain at Les Sillons (Giles and King,

2001) was also visited to sample freshwater peat deposits thatoccupy the swales running parallel to the relict beach ridges.A Russian sampler (7.5 cm diameter) was used to collect peatsections overlying basal sand at eight locations. A Solinstwater-level logger was installed within the groundwater tableof one of the swales to estimate hydrological balancebetween the tidal range at the coast and groundwater level inthe swales and the elevation of contemporary peat formationwas surveyed using differential global positioning system.In the laboratory, one salt-marsh core from Les Sillons and

one from Bassin (Fig. 1) were subsampled for plant macrofos-sil, foraminifera, testate amoebae and geochemical analyses.

Figure 1. Location map of the Magdalen Islands in the Gulf of St. Lawrence, eastern Canada (A). Field sites mentioned in the text are highlightedin blue (B) and the location of the salt-marsh sites at Les Sillons (C) and Bassin (D) are also shown.

Copyright # 2017 John Wiley & Sons, Ltd. J. Quaternary Sci. (2017)

JOURNAL OF QUATERNARY SCIENCE

Plant macrofossil preparation followed Barber et al. (1994)and macrofossil classification followed Garneau (1998) andMauquoy and van Geel (2007). Preparation for foraminiferaanalysis followed Gehrels (2002) after Scott and Medioli(1980) and identification followed the taxonomy of Murray(1971, 1979). Testate amoebae were prepared according toBarnett et al. (2013) after Charman et al. (2000). Taxonomyprimarily followed Charman et al. (2000), as described inBarnett et al. (2016). Loss-on-ignition was used to estimatechanges in organic matter concentration, related to carboncontent through time (Ball, 1964). Sediment subsamples ofknown (dry) weight were burned at 550 ˚C for 4 h to calculatethe percentage of organic mass loss. Bulk density wascalculated to reconstruct stratigraphic changes through thecore and detect possible auto compaction through overbur-den (Tovey and Paul, 2002; Brain et al., 2011). Sand contentwas also measured following Barnett et al. (2016).

Quantitative sea-level reconstructions

Intertidal testate amoebae and foraminifera transfer functionsfrom the Magdalen Islands (Barnett et al., 2016) were used toreconstruct palaeo-marsh surface elevations (PMSEs) fromfossil assemblages with C2, v.1.7.2 (Juggins, 2003). Aweighted averaging regression model with classical deshrink-ing was used to predict PMSEs from testate amoebae usingthe published surface training set (n¼62 samples) fromBarnett et al. (2016). PMSEs from foraminifera were derivedusing the published surface training set of samples (n¼ 74)from the Magdalen Islands (Barnett et al., 2016) andNewfoundland (Wright et al., 2011) using a weighted

averaging regression model with classical deshrinking(Barnett et al., 2016). Former sea-level was calculated bysubtracting the indicative meaning (cf. Shennan, 2007, 2015),in this case the PMSE, from the elevation of the fossilsubsamples relative to the tidal frame (cf. Gehrels, 1999). Atthis point, no correction was made for sediment compactiondue to overburden of overlying sediments (Brain et al., 2011,2012) as an incompressible substrate occurred at 0.70mdepth at Les Sillons and only the topmost 0.30m was used atBassin. Screening for fossil assemblages lacking a modernanalogue was carried out to improve reconstruction robust-ness (Barlow et al., 2013). A squared chord distancedissimilarity measure (minDC) was applied using the modernanalogue technique in C2. Fossil assemblages located beyondthe 20th percentile of the minDC were considered to have‘poor’ modern analogues (Simpson, 2007; Watcham et al.,2013) and were dismissed from the reconstructions. This ledto the omission of eight fossil testate amoebae assemblagesfrom Les Sillons and six fossil testate amoebae plus fiveforaminifera assemblages from Bassin.

Chronology

Material collected for radiocarbon analysis were sent forconventional accelerator mass spectrometry (AMS) 14C dating(Stuiver and Polach, 1977) at the Keck Carbon Cycle AMSLaboratory, University of California, Irvine. Radiocarbon ageswere calibrated using either the IntCal09 calibration curve(Reimer et al., 2009) in CALIB v.7.1 (Stuiver and Reimer,1986) or the post-bomb NH1 calibration curve (Hua andBarbetti, 2004) where appropriate. Radiocarbon ages from

Table 1. Radiocarbon data from Les Sillons and Bassin plant macrofossils.

Lab. code(UCIAMS)

Core(depth, m)

Material Radiocarbon age (14C a BP)(2s)

Calibrated age (cal a BP)(2s)

144898 Sil (0.025) Ericaceae (leaves/bark) 140�20 143�135144899 Sil (0.055) Schoenoplectus (seeds), Ericaceae

(leaves/stem)135�20 142�133

144900 Sil (0.075) Schoenoplectus (seeds) 175�20 143�143144901 Sil (0.105) Schoenoplectus (seeds), Pinaceae (needles) 175�20 143�143144902 Sil (0.125) Schoenoplectus (seeds), Eleocharis (seeds) 120�20 141�127146207 Sil (0.145) Schoenoplectus (seeds), Ericaceae

(leaves/stem)115�25 141�128

144903 Sil (0.165) Eleocharis (seeds), Pinaceae (needles) 125�20 141�129144904 Sil (0.205) Schoenoplectus (seeds) 100�20 143�116144905 Sil (0.245) Schoenoplectus (seeds), Ericaceae

(leaves/stem)150�30 142�142

144906 Sil (0.285) Schoenoplectus (seeds), Potentilla (seeds) 200�20 148�148144907 Sil (0.325) Carex (seeds), Ericaceae (leaves/stem) 150�30 142�142144908 Sil (0.365) Myrica (leaves) 230�25 155�155146204 Sil (0.425) Carex (seeds), Myrica (leaves/seeds) 360�25 408�91146205 Sil (0.525) Myrica (leaves) 365�25 409�91146206 Sil (0.685) Myrica (leaves/buds) 350�25 403�88149787� Bas (0.055) Carex (seeds), Alnus (bark) �545�20 �33�27149788� Bas (0.085) Eleocharis (seeds), Alnus (bark) �3855�20 �18�4149789 Bas (0.115) Herbaceae (stem), Alnus (bark), Larix (needles) 155�35 143�143149790 Bas (0.145) Eleocharis (seeds), Alnus (stem), Larix (needles) 75�20 144�112149791 Bas (0.175) Eleocharis (seeds), Lignose (stem) 80�20 144�112149792 Bas (0.205) Eleocharis (seeds), Carex (seeds), Lignose

(stem)165�20 142�142

149793 Bas (0.225) Alnus (stem/bark) 120�25 141�129149794 Bas (0.255) Myrica (buds), Alnus (stem/bark) 95�20 194�164149795 Bas (0.265) Larix (needles), Myrica (leaves), Sphagnum

(stem)120�20 141�127

149796 Bas (0.295) Larix (needles), Myrica (leaves), Sphagnum(stem)

125�20 141�129

�Samples calibrated using the NH1 post-bomb calibration curve.


LATE HOLOCENE RELATIVE SEA-LEVEL CHANGES AT THE MAGDALEN ISLANDS

salt-marsh cores from Les Sillons and Bassin were plotted indepth sequence order against the calibration curve to investi-gate the possibility of reversals (Marshall et al., 2007). Age–depth models were developed in R (R Core Team, 2016)using Bacon, a Bayesian statistical approach that appliesa priori information for developing accumulation rate histo-ries via Markov chain Monte Carlo iterations (Blaauw andChristen, 2011).The upper sediments of the reconstruction cores underwent

210Pb radionuclide analysis. Downcore 210Pb activity wascalculated by measuring activity of the daughter product210Po (Schell and Nevissi, 1983; Sanchez-Cabeza et al.,1998). Chemical procedures for 210Po extraction followedNot et al. (2008) after Baskaran and Naidu (1995) and activitywas measured on an EGG-Ortec Type 576A alpha spectrome-ter at the Geotop Radiochronology Laboratory, UQAM,Montreal. Age–depth predictions based on diminishing 210Pbactivity were constructed using the constant rate of supply(CRS) model from Appleby (2001) with 1s uncertainty basedon root-mean-square errors.During collection, the core from Les Sillons suffered a

limited degree of compaction in the upper surface sedi-ments. This compaction was also evident in the 210Pbprofile, which reached equilibrium (cf. Appleby, 2001) at0.04m depth, and in bulk density results. In an attempt tocorrect these values and retain palaeoecological value, thesurface sediments were artificially decompacted using the210Pb profile from Bassin by assuming that sedimentationrates at the two sites are analogous for the past ca.100 years. This adjustment resulted in lowering samplesfrom the Les Sillons core by between 0.01 and 0.04m; wehave made clear in the text where these adjustments havebeen applied.

Tide-gauge data

Tide-gauge data are available for Cap-aux-Meules (gaugeno. 1970) from 1964 to 2014, with a significant datahiatus between 1976 and 2006. Hourly observed waterlevels (relative to CGVD28) were imported from theanadian Tides and Water Levels Data Archives (Fisheriesand Oceans Canada; available online: www.isdm-gdsi.gc.ca/isdm-gdsi/twl-mne/index-eng.html). Hourly datawere smoothed to obtain monthly mean tidal levels,and months containing <90% of data were rejected.Stated rates of RSL rise were obtained using linearregression.

Results

Salt-marsh chronologies

Radiocarbon results from Les Sillons are presented in Table 1.The lowest age is from 0.69m depth at the upper contact ofthe basal sand unit and has a radiocarbon age of 350� 2514C a BP (Table 1). Above this, 14 additional dates documentover 400 years of sediment accumulation. The illusion ofmultiple reversals suggested in Table 1 is an artefact of theplateau in the radiocarbon calibration curve between 350and 0 cal a BP and only two samples appear to representpossible outliers (Fig. 2a). The ten radiocarbon ages from theBassin core document ca. 200 years of sediment accretionand do not extend beyond the radiocarbon plateau (Table 1).When aligned against the calibration curve (Fig. 2b), thesamples are able to be plotted in depth sequence orderassuming slight changes in accumulation rate (i.e. the depthaxis is assumed to be non-linear).The 210Pb analyses on the Bassin core reveal that unsup-

ported 210Pb activity reaches equilibrium with supportedactivity at 0.10m depth (Fig. 3a). Using the CRS model,inferred ages extend back to ca. 50 cal a BP (Fig. 3b). Incontrast, unsupported 210Pb activity in the Les Sillons corereaches equilibrium at 0.04m depth (Fig. 3c). We contendthat this is a result of compaction in the upper sediments ofthe core that occurred during collection (see Methods). Effortsto correct these data, based on the assumption that the depthof activity equilibrium at Les Sillons is analogous to that atBassin, result in lowering sample depths by up to 0.04m(Fig. 3).

Les Sillons: lithology and subfossils

The salt marsh at Les Sillons is backed by freshwater shrubsand herbaceous plants such as Myrica gale, Chamaedaphnecalyculata and Typha cf. angustifolia that colonize a relictbeach ridge above 0.7m CGVD28. High marsh flora suchas Schoenoplectus spp. and Juncus gerardii extend down to0.3m CGVD28 where the low marsh is sand-rich andsparsely vegetated. The lowest extent of the marsh isactively eroding at around 0.0m CGVD28. Lithologycomprises a shallow basal sand unit associated with thelate Holocene relict beach ridge system (Giles and King,2001; R�emillard et al., 2015). This basal unit slopesseaward and is overlain by organic-rich ligneous peat thatgrades into salt-marsh deposit as the amount of silt andsand increases (Fig. 4a).

Figure 2. Radiocarbon dates from the reconstruction cores from Les Sillons (a) and Bassin (b) plotted against depth (bottom axis) and radiocarbonage (vertical axis) versus the IntCal09 (Reimer et al., 2009) radiocarbon calibration curve following Marshall et al. (2007). Two possible outliersfrom the sediment core from Les Sillons are highlighted in red.



http://www.isdm-gdsi.gc.ca/isdm-gdsi/twl-mne/index-eng.html

http://www.isdm-gdsi.gc.ca/isdm-gdsi/twl-mne/index-eng.html

The basal sand unit in the core from Les Sillons isencountered at 0.74m below the surface. Plant macrofossilsabove this contact include Potamogeton sp. (pondweed) andNymphaea sp. (waterlilies), which provide evidence of afreshwater aquatic environment (Fig. 4c). Ligneous and herba-ceous tissues increase between 0.70 and 0.40m depth wherefreshwater sedges (e.g. Carex rostrata), algae (Chara spp.),water fleas (e.g. Daphnia spp.) and deciduous shrub macro-fossils are common. Above 0.40m, ligneous tissues arereplaced by increasing quantities of herbaceous remnants andclastic material. Between 0.40m and the present-day surface,halophytic bulrushes (Schoenoplectus spp.) and rushes (Juncusgerardii) increase while the top of the core contains remnantsof low intertidal flora such as Salicornia maritima (Fig. 4c).Subfossil testate amoebae and foraminifera were also

analysed along the same core (Fig. 5a). At the base, fewtestate amoebae tests (<1000ml�1) were encountered. The

lignose-rich peat between 0.60 and 0.40m contains low-diversity assemblages with predominantly Centropyxis spp.and Cyclopyxis arcelloides type. Above 0.40m, testateamoebae diversity increases and high marsh taxa are preva-lent (e.g. species of Centropyxis, Cyclopyxis, Euglypha andHeleopera). Halophytic low marsh taxa, including species ofArcella and Difflugia, are recorded in the upper section of thecore. Subfossil foraminifera were only encountered in con-centrations exceeding 30 tests ml�1 above 0.15m. Assemb-lages lack diversity and the salt-marsh species Balticamminapseudomacrescens and Jadammina macrescens dominate,whereas the low marsh species Miliammina fusca becomesmore abundant in the top 0.05m of the core (Fig. 5a).

Bassin: lithology and subfossils

The salt marsh at Bassin is more expansive than the one atLes Sillons. Here, the marsh is backed by well-establishedfreshwater shrubs (Alnus rugosa, Myrica gale) and tallgrasses (Spartina pectinata, Calamagrostis canadensis). Thehigh marsh is colonized by Schoenoplectus spp. and Juncusgerardii and extends from the terrestrial ecotone down to0.2m CGVD28 where low marsh vegetation (e.g. Spartinaalterniflora) is more dominant. Spartina patens is presentacross the entire marsh surface. The lithology at Bassin ischaracterized by a deep lignose-rich organic unit encoun-tered below thin (ca. 0.3m) salt-marsh deposits that cap theunit (Fig. 4b). Coring during earlier field surveys (Juneau,2012) established a basal sand unit at 3.1m belowCGVD28. The ligneous-rich peats underlying the surfaceare exposed at the lowest extent of the marsh and activeerosion is evident.Testate amoebae from the Bassin core show a clear

transition from supratidal species, such as Amphitrema andNebela, to high marsh taxa at ca. 0.26m below the surface(Fig. 5b). A shift to low intertidal genera (e.g. Psammono-biotus, Pseudocorythion and Pseudohyalosphenia) is appar-ent at the top of the core. Subfossil foraminifera (exceedingconcentrations of 30 tests ml�1) are evident from 0.13m tothe present-day surface. Only five foraminifera species wereencountered and J. macrescens, B. pseudomacrescens andTiphotrocha comprimata dominated the assemblages. Thelow marsh species M. fusca is encountered at the top of thesequence but only in very low abundance (Fig. 5b).

Reconstructing relative sea level

Transfer function root-mean-square prediction uncertaintiesare used to generate 2s vertical uncertainty bounds for eachreconstruction point (Table 2). Age–depth models based onradiocarbon and 210Pb-derived ages provide horizontal (i.e.chronological) constraints for each data point based on the 2srange of iterative model runs (Table 2). Radiocarbon dates aremodelled using Student’s t-test distributions with wide tails inBacon, negating the need to remove potential outliers (Chris-ten and P�erez, 2009; Blaauw and Christen, 2011). At LesSillons and Bassin, age–depth profiles show average accretionrates of 1.4 and 1.0mm a�1, respectively (Fig. 6). Assemblagesof foraminifera and testate amoebae from Les Sillons documentcontinuous RSL rise over the past ca. 500 years at a (linear)rate of 1.3� 0.6mm a�1 (Fig. 7c,d). RSL trends reconstructedfrom the upper sediments in the core corroborate contempora-neous tide-gauge data from Cap-aux-Meules. The reconstruc-tion core from Bassin documents a linear RSL rise rate of1.3� 1.2mm a�1 for the past ca. 300 years (Fig. 7e,f). Sea-level data reconstructed from the individual sites are represen-tative of local environmental changes. However, similarities inthe trends shown by the two proxies at Les Sillons and Bassin

Figure 3. Downcore 210Pb activity (a,c) and age–depth models (b,d)for the reconstruction cores from Bassin (a,b) and Les Sillons (c,d)based on the CRS model of Appleby (2001). The 210Pb profile fromBassin is used to ‘decompact’ the upper sediments of the reconstruc-tion core from Les Sillons (d) to correct for 0.04m of compaction thatoccurred during core collection (see text for details).



imply the presence of a regional signal in the records (Fig. 7).Records from both salt-marsh sites demonstrate the possibleoccurrence of non-linear trends. For example, potentialinflexions are seen at Les Sillons shortly after 300 and 100 cala BP (Fig. 7d) and at Bassin near 150 cal a BP (Fig. 7f). Thestrongest inflexion is identified around 0 cal a BP (i.e. 1950AD) in the testate amoebae record from Bassin when RSL riseappears to accelerate and exceed pre-industrial rates. This partof the record suggests that ca. 0.20m of RSL rise occurred overthe past 60 years, equating to a rate of 3.3mm a�1. At thispoint, the proxy-based reconstructions align (to within uncer-tainty) with tide-gauge data from Cap-aux-Meules, whichpresents a linear RSL rise rate of 4.3mm a�1 since 1964.

Les Sillons: swale peats

The elevation of the peat surface within the swales at LesSillons tends to decrease in the direction of the lagoon (Fig. 8;Giles and King, 2001; R�emillard et al., 2015). The oldestradiocarbon ages obtained from the contact between dunesand and overlying peat originate from the north-easternsector and correspond with the lowest contact elevations(Table 3). The youngest ages correspond generally to thehighest contact elevations (e.g. samples 9, 16 and 17) exceptfor samples 14 and 15 (Fig. 8). The upper boundary ofcontemporary peat formation occurs at 0.52�0.16mCGVD28 (mean� 2s; n¼ 20). The lower boundary occurs at

Figure 4. Lithology profiles of the salt-marsh sites at Les Sillons (a) and Bassin (b). Also shown are results from plant macrofossil analyses on thereconstruction core from Les Sillons (c).



0.45� 0.17m CGVD28 (mean� 2s; n¼ 20). We contendthat the elevation of contemporary coastal peat formation is aresult of tidally controlled groundwater height. Data from thewater-level logger installed in a swale proximal to the lagoon(Fig. 8) have shown a teleconnection between groundwaterand the tidal prism (Fig. 9). Over a 48-h window, groundwa-ter height oscillates (period: 25.9 h; amplitude: 0.02m) incoordination with tidal fluctuations (period: 25.1 h) followinga lag of 4.8 h (Fig. 9). The initial fall in groundwater heightbetween 5 and 15 h may be a combined result of the hightide that occurred �5 h prior and a response to precipitationthat occurred 5 days before the logger was installed (Fig. 9).No precipitation or alternative water source contributed togroundwater levels during the monitoring period. Conserva-tively, we take the higher and lower confines of contempo-rary peat formation to provide an indicative range of0.48� 0.20m CGVD28 for the basal peat deposits. Thisrange is centred close to the level of MHHW (0.43mCGVD28) for the Magdalen Islands and accords with thetypical indicative range (mean high water�0.20m) assignedto coastal dune peat (e.g. Berendsen et al., 2007). The ninesea-level index points from the basal radiocarbon dates fromthe swale peats at Les Sillons (Table 3; samples 9–17) hencedocument approximately 1.5m of RSL rise over the past1500 years (ca. 1.3� 0.3mm a�1) although a non-linear trendmay be apparent (Fig. 7b).

Palaeo-forest deposits

A total of 14 sites (Fig. 10) with palaeo-forest deposits in theintertidal zone were investigated originally and full descrip-tions of the field surveys are provided in an unpublished

thesis (Juneau, 2012). Here we summarize results from fivesites for which radiocarbon dates were obtained (Table 3).The beach at La Petite �Echouerie on Cap-aux-Meules is

composed of a sandy foreshore strewn with gravel andpebbles (Fig. 10a). This beach is migrating landward and actsas a barrier to supratidal coastal wetlands, which are beingactively eroded. Remnants of a submerged coastal forest arevisible across the foreshore (Fig. 10a) and an inventory of 231fossil tree stumps (Fig. 10b) reveals an elevational range ofbetween �0.18 and 1.98m CGVD28. Radiocarbon datingfrom a stump at 0.56m CGVD28 returned an age of 930� 1514C a BP. A second age of 805� 20 14C a BP is providedfrom a second stump of which the elevation was notrecorded.A second palaeo-forest is found in the intertidal zone at

Anse aux Renards on Pointe-aux-Loups (Fig. 10d). Aninventory of 44 fossil stumps provides an elevational range of�0.04 to 0.76m CGVD28 and a radiocarbon date on onestump at 0.10m CGVD28 returned an age of 625� 1514C a BP. Stratigraphic analysis from sediments at the upperedge of the intertidal zone shows basal sand at �0.16mCGVD28 overlain by 0.13m of organic-rich silt dated to585� 15 14C a BP with a palaeo-forest horizon above whichgrades into organic-rich peat towards the surface (Fig. 10e).The elevation of the palaeo-forest in the stratigraphy (�0.03to 0.50m CGVD28) corresponds with the elevation of theexposed fossil forest in the foreshore.The beach at Cap �a Isaac on Grande Entr�ee is protected by

an outcropping red sandstone headland and is backed byvegetated sand dunes (Fig. 10h). A fossil forest outcrop isfound on the lower foreshore (Fig. 10g). An inventory of81 stumps (Fig. 10h) gives an elevational range of �0.36 to

Figure 5. Salt-marsh proxy (testate amoebae and foraminifera) assemblage data from Les Sillons (a) and Bassin (b) with associated geochemistryanalyses (bulk density, loss-on-ignition and sand content). Results from the application of the transfer functions to assemblage data are given aspalaeo-marsh surface elevation (PMSE) predictions with 1s uncertainties and samples lacking modern analogues are highlighted in red.



Table 2. Estimations of former sea level derived from the Les Sillons and Bassin cores.

Sample height (h)(m CGVD28)

PMSE (i)(m CGVD28)

Sea level (s)(m CGVD28)

Vertical uncertainty(m�2s)

Modelled age(cal a BP)

Horizontal uncertainty(years�2s)

Les Sillons foraminifera0.305 0.32 �0.02 0.14 �42 160.275 0.35 �0.08 0.14 �15 190.255 0.35 �0.10 0.14 3 280.245 0.36 �0.12 0.14 3 280.235 0.41 �0.18 0.14 10 290.225 0.40 �0.18 0.14 17 300.215 0.40 �0.19 0.14 24 350.205 0.42 �0.21 0.14 30 450.195 0.40 �0.20 0.14 37 510.185 0.41 �0.22 0.14 46 470.175 0.43 �0.25 0.14 56 430.145 0.43 �0.28 0.14 79 41Les Sillons testate amoebae0.195 0.40 �0.21 0.19 17 300.155 0.38 �0.23 0.19 46 470.135 0.41 �0.28 0.20 64 410.115 0.45 �0.33 0.19 79 410.095 0.48 �0.39 0.19 93 400.075 0.46 �0.38 0.20 108 370.055 0.43 �0.37 0.20 122 360.035 0.42 �0.39 0.21 137 330.015 0.42 �0.41 0.21 156 41�0.005 0.45 �0.46 0.21 175 40�0.025 0.47 �0.50 0.20 192 39�0.045 0.45 �0.50 0.21 209 33�0.085 0.42 �0.50 0.23 247 46�0.105 0.44 �0.54 0.21 266 42�0.125 0.48 �0.60 0.21 285 35�0.185 0.45 �0.63 0.22 327 47�0.225 0.42 �0.65 0.20 352 59�0.26 0.39 �0.65 0.22 377 71�0.305 0.39 �0.70 0.21 402 79Bassin foraminifera0.295 0.35 �0.06 0.14 �55 40.245 0.34 �0.10 0.14 �10 100.235 0.35 �0.11 0.14 1 100.225 0.38 �0.15 0.14 15 140.205 0.36 �0.15 0.14 46 260.195 0.42 �0.22 0.14 58 320.185 0.42 �0.23 0.14 71 320.175 0.40 �0.23 0.14 82 32Bassin testate amoebae0.295 0.30 0.00 0.19 �55 40.285 0.32 �0.03 0.19 �45 60.275 0.35 �0.07 0.19 �37 80.265 0.43 �0.16 0.19 �28 80.255 0.45 �0.20 0.19 �19 80.245 0.45 �0.20 0.19 �10 100.235 0.47 �0.23 0.19 1 100.225 0.44 �0.21 0.19 15 140.215 0.42 �0.21 0.20 32 200.205 0.44 �0.23 0.19 46 260.195 0.45 �0.25 0.19 58 320.185 0.44 �0.26 0.19 71 320.175 0.46 �0.29 0.19 82 320.165 0.40 �0.23 0.19 93 320.155 0.47 �0.31 0.19 105 320.145 0.47 �0.33 0.19 115 300.135 0.50 �0.37 0.19 126 260.125 0.48 �0.35 0.19 136 240.105 0.51 �0.41 0.19 162 280.095 0.52 �0.43 0.19 177 260.085 0.49 �0.40 0.19 189 300.075 0.50 �0.43 0.19 200 300.065 0.47 �0.41 0.19 211 320.055 0.46 �0.41 0.19 222 30



0.01m CGVD28 and a radiocarbon date from one at�0.28m CGVD28 provided an age of 860� 15 14C a BP.Coring of the lower foreshore revealed basal sand at �1.05mCGVD28 overlain by an organic-rich peat unit to �0.45mCGVD28 and a palaeo-forest horizon up to the surface(�0.15m CGVD28). Dating of coniferous needles from theforest unit at �0.82m CGDV28 provided an age of1135� 15 14C a BP.A stratigraphic section at Cap de l’Eglise, also on Grande

Entr�ee, was taken from an eroding scarp at the back of anarrow foreshore beach with coastal wetland vegetationbehind (Fig. 10c). Basal sand is found at �0.22m CGVD28and is also overlain by a palaeo-forest horizon to 0.14mCGVD28. The elevation of fossil stumps located in situ withinoutcrops of the unit range from �0.36 to 0.08m CGVD28and a date from one at 0.13m CGVD28 returned a radiocar-bon age of 930� 15 14C a BP. Ericaceous peat overlies thepalaeo-forest horizon from 0.14 to 0.55m CGVD28 and istopped with 0.20m of Sphagnum peat (Fig. 10c).Finally, a coastal forest is found in the intertidal zone at

Baie du Bassin, the tidal lagoon located on Havre Aubert(Fig. 1). Submerged tree stumps outcrop at the erodingfringe of the intertidal marsh (Fig. 10f). An inventory of 156stumps reveal an elevational range of �0.34 to 0.9mCGVD28 and a date from one at �0.16m CGVD28returned a radiocarbon age of 625� 15 14C a BP. Stratigra-phy reveals basal sand at �3.10m CGVD28 that is overlainby a freshwater peat and palaeo-forest unit to 0.33mCGVD28. At this location, the terrestrial deposit is toppedby 0.20m of intertidal marsh and the contact between theseunits is dated to 120� 15 14C a BP.Due to the imprecise relationship between palaeo-forest

deposits and sea level, the palaeo-forest horizons (Table 3;samples 3, 5 and 8) and submerged tree stumps (Table 3;samples 1, 2, 4, 6 and 7) are used here as limiting sea-leveldata (cf. Shennan, 2015). Radiocarbon dates from thesedeposits provide 2s chronological constraints for the indexpoints (Table 3). The eight reconstruction points document atleast 3m of RSL rise at the Magdalen Islands between 2000and 500 cal a BP (Fig. 7a), which equates to an approximatetrend of 2.0mm a�1.

Discussion

Multi-proxy sea-level indicators from the Magdalen Islandsdocument continuous RSL rise throughout the late Holoceneat rates of between ca. 1.3 and 2.0mm a�1 (Fig. 7). Thisvalue closely resembles trends registered in Prince EdwardIsland (1.9mm a�1; Scott et al., 1981), the Atlantic coast ofNova Scotia (2.2mm a�1; Scott et al., 1995; Gehrels et al.,2004) and the southern coast of Newfoundland (ca. 2mma�1; Daly et al., 2007). It appears that sea level at theMagdalen Islands may have risen at a slightly reduced ratebetween ca. 1000 and 500 cal a BP (Fig. 11), which alsocoincides with a period of deceleration along the east coastof North America (Kemp et al., 2011, 2013, 2015). Theserecords, alongside other sea-level histories of the

Figure 6. Age–depth models using Bacon (Blaauw and Christen,2011) for Bassin (a) and Les Sillons (b). Calibrated radiocarbon agesare shown in dark blue and include possible outliers shown in Fig. 9.210Pb-based ages and uncertainties (following decompaction adjust-ments for Les Sillons) are shown in light blue. The shaded regionshows model iterations and the bounds represent 1s uncertaintyranges that are used to develop 2s horizontal uncertainties in thesea-level reconstructions.

Figure 7. Late Holocene sea-level reconstruction data based onsubmerged tree stumps and palaeo-forest horizons (a), coastalfreshwater peat deposits (b) and salt-marsh proxies from Les Sillons(b,c) and Bassin (d,e). Horizontal and vertical uncertainties are givenat the 2s range. Recent tide-gauge data from Cap-aux-Meules areshown in red.



Table 3. Radiocarbon data from submerged forests, palaeo-forest horizons and coastal peat deposits throughout the Magdalen Islands. Samplenumbers correspond to samples that are used to generate sea-level data for the past two millennia. Sea level (s) is calculated by subtracting theindicative elevation (i) from the elevation of the fossil sample (h) after Gehrels (1999).

Lab. code(UCIAMS)

Sampleno.

Location (island) Material (deposit) Radiocarbonage

(14C a BP)

Calibratedage (cal aBP) (2s)

h� sampleelevation (mCGVD28)

i� indicativeelevation (mCGVD28)

s� inferred sealevel (mCGVD28)

39583 1 Petite Echouerie(Cap-aux-Meules)

Stump fragment(submerged

forest)

930�20 854�61 0.56 >0.43 <0.13

39584 – Petite Echouerie(Cap-aux-Meules)


forest)

805�20 713�32 ? – –

39580 2 Anse aux Renards(Pointe-aux-Loups)


forest)

625�15 606�50 0.10 >0.43 <�0.33

41191 3 Anse aux Renards(Pointe-aux-Loups)

Conifer needles(organic-rich silt)

585�15 591�49 �0.14 >�0.07 <�0.07

41192 – Anse aux Renards(Pointe-aux-Loups)

Lignose fragment(organic rich

peat)

145�20 143�138 0.34 – –

45696 – Anse aux Renards(Pointe-aux-Loups)

Lignose fragment(peaty soil)

110�20 144�122 0.50 – –

39577 4 Cap �a Isaac (GrandeEntr�ee)


forest)

860�15 761�28 �0.28 >0.43 <�0.71

41190 5 Cap �a Isaac (GrandeEntr�ee)

Conifer needles(palaeo-forest

horizon)

1135�15 1024�45 �0.82 >0.43 <�1.25

39582 6 Cap de l’�Eglise(Grande Entr�ee)


forest)

930�15 853�58 0.13 >0.43 <�0.30

39585 – Cap de l’�Eglise(Grande Entr�ee)

Sphagnum stems(Sphagnum peat)

460�15 513�12 0.55 – –

57266 – Cap de l’�Eglise(Grande Entr�ee)

Sphagnum stems(Sphagnum peat)

350�15 399�81 0.80 – –

39578 7 Baie du Bassin(Havre Aubert)


forest)

625�15 606�50 �0.16 >0.43 <�0.59

? – Baie du Bassin(Havre Aubert)

Lignose fragment(palaeo-forest

horizon)

120�15 144�123 0.31 – –

41188 8 Baie du Bassin(Havre Aubert)

Plant fragments(organic-rich

peat)

1885�15 1812�69 �3.10 >0.43 <�3.53

144889 9 Les Sillons(Havre-aux-Maisons)

Ericaceaeleaves/bark(coastal peat)

90�20 144�113 0.31 0.49�0.20 �0.18�0.20


Ericaceaeleaves/stems(coastal peat)

1425�20 1324�28 �0.77 0.49�0.20 �1.26�0.20


Ericaceae stems(coastal peat)

1255�20 1186�89 �0.84 0.49�0.20 �1.33�0.20


Pinus needles(coastal peat)

1235�20 1168�93 �0.94 0.49�0.20 �1.43�0.20


Ericaceaeleaves/Pinusneedles

830�20 738�44 �0.37 0.49�0.20 �0.86�0.20



170�20 143�143 �0.30 0.49�0.20 �0.79�0.20



670�20 617�54 0.51 0.49�0.20 0.02�0.20


Ericaceae leaves(coastal peat)

155�20 142�141 0.56 0.49�0.20 0.07�0.20


Ericaceaeleaves/bryophyte

stems

145�20 144�139 0.68 0.49�0.20 0.19�0.20



St. Lawrence region (Dionne, 1988, 2001), contain significantisostatic components from residual glacio-isostatic adjustment(GIA). Absolute GIA solutions for the Magdalen Islandsremain imprecise. Measurements of land subsidence arelimited to GPS solutions at Cap-aux-Meules from 1996 to2010 by the Canadian Base Network, Natural ResourcesCanada (nrcan.gc.ca/earth-sciences/geomatics/geodetic-refer-ence-systems/data/10923), which provide trends of�1.48mm a�1 with significant uncertainties (�1.29mm a�1).Levelling data predict higher rates of subsidence of between�3 and �4mm a�1 (Koohzare et al., 2008) and the ICE-6G_C (VM5a) GIA model from Peltier et al. (2015) alsopredicts subsidence rates (�3.73mm a�1) that exceed the

bounds of GPS-measured uncertainty. The high rate ofsubsidence predicted by ICE-6G causes the GIA model toover-predict rates of RSL rise at the Magdalen Islands byapproximately 2mm a�1 for the past few millennia (Fig. 11).More accurate measurements of local GIA, such as thoseprovided by the global navigation satellite system solutionsapplied in Nova Scotia, ca. 100 km away from Cap-aux-Meules (Canadian Active Control System, NaturalResources Canada), would aid future GIA modelling attempts.Constraining contemporary vertical land motion and furtherdeveloping the Holocene RSL history at the Magdalen Islandsis necessary for better understanding GIA mechanisms (suchas forebulge migration) throughout eastern Canada, which

Figure 8. Surface topography of the foredune plain and associated swales at Les Sillons after R�emillard et al. (2015) and calibrated radiocarbonages from the basal peat contacts (left). The location of the water-level data-logger is highlighted (star). Inset: elevation of the dated basal peatsamples against calibrated age. On the right are images of six of the contacts cored in 2014 showing basal dune sand with coastal freshwater peatdeposits above.

Figure 9. Groundwater eleva-tion at Les Sillons, measuredby the water-level data-logger,versus the corresponding tide-gauge record from Cap-aux-Meules over a 48-h period. Inset:local precipitation for the31 days before installation of thedata-logger. Note the differenty-axis scales.



have been complicated by the presence of local ice domes inNewfoundland, Nova Scotia, eastern New Brunswick andQuebec during deglaciation (Shaw et al., 2006; Stea et al.,2011).At the Magdalen Islands, an RSL inflexion during the

middle of the 20th century signifies a departure from lateHolocene trends (Fig. 12). The conservative 2s uncertaintybounds of the proxy data preclude the precise timing of theinflexion, or indeed whether there have been multipleinflexions over the past few centuries. However, it is clearthat the local record, generated from our two sediment coresand supported by multiple proxies, conforms to regional andglobal patterns of 20th century RSL rise. Similar inflexion

signals have been recorded at the regional scale along theeast coast of North America in salt-marsh sediments (Kempet al., 2011, 2013, 2014, 2015) and by tide gauges (Boon,2012). Recent acceleration in global sea-level rise during the(late) 19th and 20th centuries is also evident from satellitealtimetry (Church and White, 2011), global tide-gauge net-works (Jevrejeva et al., 2014) and globally averaged proxyreconstructions (Kopp et al., 2016). The rate of 4.3mm a�1

recorded by the Magdalen Islands tide gauge since 1964exceeds significantly the linear trend of global average sea-level rise of 1.9mm a�1 between 1961 and 2009 (Churchand White, 2011). It is also higher than the rate of3.2mm a�1 calculated by satellite altimetry or 2.8mm a�1 by

Figure 10. Submerged tree stumps and palaeo-forest horizons found in the intertidal zone across the Magdalen Islands. The sandy foreshorebeach at La Petite �Echouerie on Cap-aux-Meules showing submerged fossil stumps (a) and locations of these stumps within the intertidal zone (b);eroding scarp at Cap de l’Eglise on Grande Entr�ee with palaeo-forest horizon between �0.22 and 0.14m CGVD28 (c); submerged tree stumps inthe foreshore beach (d) and palaeo-forest horizon at Anse aux Renards on Pointe-aux-Loups (e); fossil tree stumps fringing a coastal marsh in theintertidal zone at Bassin (f); fossil tree stump on the beach at Cap �a Isaac on Grande Entr�ee (g) and the locations of fossil stumps found in theintertidal zone (h); locations of submerged palaeo-forest deposits and submerged peat deposits found throughout the Magdalen Islands (i)described by Dubois and Grenier (1993) and Juneau (2012).



tide-gauge data since 1993 (Church and White, 2011;Rahmstorf et al., 2012). Without knowing the contributions

from different mechanisms, it is difficult to determine whetherthis trend will continue into the future. This issue is crucialfor establishing reliable projections of rising sea level on aregional scale. Quadratic regression and extrapolation ofthe available tide-gauge data for the Magdalen Islands(Boon, 2012) projects a median rise of 0.20m by 2050, but itcould be as large as 0.40m (Fig. 12). These values areconsistent with those modelled in the southern part of the Gulfof St. Lawrence from the Intergovernmental Panel on ClimateChange AR4 A1B special report emission scenarios andAtmosphere–Ocean General Circulation Models that includeGIA and ice-sheet meltwater effects (Han et al., 2014).Defining the mechanisms responsible for driving RSL

trends at the Magdalen Islands (and beyond) is an importanttask. Mechanisms such as meltwater from land-based iceand steric expansion, which have increased ocean volumeover the past few decades (Cronin, 2012; Church et al.,2013; Llovel et al., 2013), are likely to continue contribut-ing to long-term RSL rise in a warming world. Mechanismsthat redistribute ocean mass, such as the Atlantic Meridio-nal Overturning Circulation and other dynamic ocean–atmosphere processes (e.g. Scafetta, 2014), are capable ofdriving high rates of RSL rise at specific locations, such asthe east coast of North America, over shorter and cyclicalperiods (e.g. Goddard et al., 2015; McCarthy et al., 2015).The sustained and significant downturn in the strength ofthe Atlantic Ocean Overturning Circulation (Rahmstorfet al., 2015) coincides with late 19th and early 20thcentury sea-level inflexions seen in the western NorthAtlantic. This raises questions relevant to locations such asthe Magdalen Islands over the relative influence, impor-tance and longevity of processes concerned with oceanmass redistribution versus ocean mass addition.

Conclusions

The late Holocene sea-level history for the Magdalen Islandsin eastern Canada has been reconstructed using proxyevidence from submerged tree stumps and palaeo-foresthorizons, coastal peat deposits and salt-marsh testate amoe-bae and foraminifera. Local RSL has risen over the past fewmillennia at a rate of ca. 2mm a�1. The rate of RSL riseaccelerated during the 20th century to above 4mm a�1. Thissignal is similar to inflexions reproduced from salt-marshsediments along the east coast of North America and seen inregional and globally averaged tide gauge and proxy-basedrecords. This new record from the Magdalen Islands contains

Figure 11. Sea-level data developed in this study shown against theRSL prediction for Cap-aux-Meules from the latest GIA model ofPeltier et al. (2015) (a). Also shown is the change in RSL elevation forthe Gulf of St. Lawrence based on the ICE-6G(C)_VM5 GIA model forthe past two millennia, which shows rapid RSL rise centred on theMagdalen Islands (data from: atmosp.physics.utoronto.ca/�peltier/data.php; Peltier et al., 2015).

Figure 12. Proxy sea-level data developed in the study from 1900AD (blue) shown against the Cap-aux-Meules tide-gauge data (red)and quadratic regression of the tide-gauge data with extrapolation to2050 AD following Boon (2012).



a significant negative isostatic component, which remainsimprecisely defined. Recent trends in RSL rise are probably aconsequence of additional ocean volume from land-based icemelt and steric expansion and dynamic ocean–atmosphereprocesses (such as Atlantic Meridional Overturning Circula-tion and correlative mechanisms) driving ocean massredistribution.

Acknowledgements. This study was funded by the CoastalGeoscience Chair at the Universit�e du Qu�ebec �a Rimouski (UQAR)as part of the Qu�ebec government initiative on natural risksprevention. Radiocarbon analyses were funded by the PeatlandEcosystem Dynamics and Climate Change Research Chair(D�ECLIQUE) at the Universit�e du Quebec �a Montr�eal (UQAM). Thework was carried out in the Geotop research centre at UQAM. Thanksgo to Audrey R�emillard for the production of Fig. 8. We also thankBassam Ghaleb, Julien Gogot and Steve Pratte from Geotop (UQAM)for laboratory assistance and Gabriel Ladouceur, Audrey R�emillardand Francis Bonnier Roy of UQAR for field assistance.

Abbreviations. AMS, accelerator mass spectrometry; CRS, constantrate of supply; GIA, glacio-isostatic adjustment; PMSE, palaeo-marshsurface elevation; RSL, relative sea level.

References

Appleby PG. 2001. Chronostratigraphic techniques in recent sedi-ments. In Tracking Environmental Change Using Lake Sediments.Volume 1: Basin Analysis, Coring and Chronological Techniques,Last WM, Smol JP (eds). Kluwer Academic Publishers: Dordrecht.

Ball DF. 1964. Loss on ignition as an estimate of organic matter andorganic carbon in non-calcareous soil. Journal of Soil Science 15:84–92 [DOI: 10.1111/j.1365-2389.1964.tb00247.x].

Barber KE, Chambers FM, Maddy D et al. 1994. A sensitive high-resolution record of Late Holocene climatic change from a raisedbog in northern England. The Holocene 4: 198–205 [DOI: 10.1177/095968369400400209].

Barlow NLM, Shennan I, Long AJ et al. 2013. Salt marshes as LateHolocene tide gauges. Global and Planetary Change 106: 90–110[DOI: 10.1016/j.gloplacha.2013.03.003].

Barlow NLM, Shennan I, Long AJ. 2012. Relative sea-level responseto Little Ice Age ice mass change in south central Alaska:reconciling model predictions and geological evidence. Earth andPlanetary Science Letters 315–316: 62–75 [DOI: 10.1016/j.epsl.2011.09.048].

Barnett RL, Charman DJ, Gehrels WR et al. 2013. Testate amoebae assea-level indicators in northwestern Norway: developments insample preparation and analysis. Acta Protozoologica 52:115–128.

Barnett RL, Garneau M, Bernatchez P. 2016. Salt-marsh sea-levelindicators and transfer function development for the MagdalenIslands in the Gulf of St. Lawrence, Canada. Marine Micropaleon-tology 122: 13–26 [DOI: 10.1016/j.marmicro.2015.11.003].

Barr SM, Brisebois D, Macdonald AS. 1985. Carboniferous volcanicrocks of the Magdalen Islands, Gulf of St. Lawrence. CanadianJournal of Earth Sciences 22: 1679–1688 [DOI: 10.1139/e85-176].

Baskaran M, Naidu AS. 1995. 210Pb derived chronology and thefluxes of 210Pb and 137Cs isotopes into continental shelf sediments,east Chukchi Sea, Alaskan Arctic. Geochimica et CosmochimicaActa 59: 4435–4448.

Berendsen HJA, Makaske B, van de Plassche O et al. 2007. Newgroundwater-level rise data from the Rhine-Meuse Delta �implications for the reconstruction of Holocene relative mean sea-level rise and differential land-level movements. NetherlandsJournal of Geosciences 86: 333–354 [DOI: 10.1017/S0016774600023568].

Bernatchez P, Drejza S, Dugas S. 2012. Marges de s�ecurit�e en�erosion coti�ere: �evolution historique et future du littoral des les dela Madeleine. Rapport remis au minist�ere de la S�ecurit�e publiquedu Qu�ebec. Laboratoire de dynamique et de gestion int�egr�ee deszones coti�eres, Universit�e du Qu�ebec �a Rimouski.

Bernatchez P, Dubois JMM. 2004. Bilan des connaissances de ladynamique de l’�erosion des cotes du Qu�ebec maritime laurentien.

G�eographie Physique et Quaternaire 58: 45–71 [DOI: 10.7202/013110ar].

Blaauw M, Christen JA. 2011. Flexible paleoclimate age-depthmodels using an autoregressive gamma process. Bayesian Analysis6: 457–474 [DOI: 10.1214/ba/1339616472].

Boon JD. 2012. Evidence of sea level acceleration at U.S. andCanadian tide stations, Atlantic Coast, North America. Journal ofCoastal Research 285: 1437–1445 [DOI: 10.2112/JCOASTRES-D-12-00102.1].

Brain MJ, Long AJ, Petley DN et al. 2011. Compression behaviour ofminerogenic low energy intertidal sediments. Sedimentary Geology233: 28–41 [DOI: 10.1016/j.sedgeo.2010.10.005].

Brain MJ, Long AJ, Woodroffe SA et al. 2012. Modelling the effects ofsediment compaction on salt marsh reconstructions of recent sea-level rise. Earth and Planetary Science Letters 345–348: 180–193[DOI: 10.1016/j.epsl.2012.06.045].

Brisebois D. 1981. Lithostratigraphie des strates Permo-Carbonif�eresde l’archipel des Iles de la Madeleine. Minist�ere de l’�Energie et desRessources de Qu�ebec. DPV-796, 48.

Charman DJ, Hendon D, Woodland WA. 2000. The Identification ofPeatland Testate Amoebae. Technical Guide No. 9. QuaternaryResearch Association: London.

Christen JA, P�erez ES. 2009. A new robust statistical model forradiocarbon data. Radiocarbon 51: 1047–1059.

Church JA, Clark PU, Cazenave A et al. 2013. Sea level change. InClimate Change 2013: the Physical Science Basis. Contribution ofWorking Group I to the Fifth Assessment Report of the Intergovern-mental Panel on Climate Change, Stocker TF, Qin D, Plattner GK,et al. (eds). Cambridge University Press: Cambridge.

Church JA, White NJ. 2011. Sea-level rise from the late 19th to theearly 21st century. Surveys in Geophysics 32: 585–602.

Church JA, White NJ, Aarup T et al. 2008. Understanding global sealevels: past, present and future. Sustainability Science 3: 9–22[DOI: 10.1007/s11625-008-0042-4].

Cronin TM. 2012. Rapid sea-level rise. Quaternary Science Reviews56: 11–30 [DOI: 10.1016/j.quascirev.2012.08.021].

Daly JF, Belknap DF, Kelley JT et al. 2007. Late Holocene sea-levelchange around Newfoundland. Canadian Journal of Earth Sciences44: 1453–1465 [DOI: 10.1139/E07-036].

Dionne JC. 1988. Holocene relative sea-level fluctuations in the St.Lawrence estuary, Qu�ebec, Canada. Quaternary Research 29:233–244 [DOI: 10.1016/0033-5894(88)90032-4].

Dionne JC. 2001. Relative sea-level changes in the St. Lawrenceestuary from deglaciation to present day. In Deglacial History andRelative Sea-Level Changes, Northern New England and AdjacentCanada, Weddle TK, Retelle MJ. (eds). Geological Society ofAmerica: Denver; 271–284.

Dredge LA, Mott RJ, Grant DR. 1992. Quaternary stratigraphy,paleoecology, and glacial geology, Iles de la Madeleine, Quebec.Canadian Journal of Earth Sciences 29: 1981–1996 [DOI: 10.1139/e92-154].

Dubois JMM, Grenier A. 1993. The Magdalen Islands, Gulf of SaintLawrence. Coastlines of Canada. Proceedings of the 8th Sympo-sium on Coastal and Ocean Management. American Shore andBeach Preservation Associations: New Orleans, Louisiana;170–182.

Garneau M. 1998. Pal�eo�ecologie d’une tourbi�ere littorale de l’estu-aire maritime du Saint Laurent, Isle-Verte, Qu�ebec. Commissiong�eologique du Canada, Bulletin 514.

Gehrels WR. 1999. Middle and Late Holocene sea-level changes ineastern Maine reconstructed from foraminiferal salt marsh stratigra-phy and AMS 14C dates on basal peat. Quaternary Research 52:350–359 [DOI: 10.1006/qres.1999.2076].

Gehrels WR. 2002. Intertidal foraminifera as palaeoenvironmentalindicators. In Quaternary Environmental Micropalaeontology,Haslett SK (ed.). Oxford University Press: London.

Gehrels WR, Kirby JR, Prokoph A et al. 2005. Onset of recent rapidsea-level rise in the western Atlantic Ocean. Quaternary ScienceReviews 24: 2083–2100 [DOI: 10.1016/j.quascirev.2004.11.016].

Gehrels WR, Milne GA, Kirby JR et al. 2004. Late Holocene sea-levelchanges and isostatic crustal movements in Atlantic Canada.Quaternary International 120: 79–89 [DOI: 10.1016/j.quaint.2004.01.008].



Giles PS. 2008. Windsor Group (Late Mississippian) stratigraphy,Magdalen Islands, Quebec: a rare eastern Canadian record of LateVisean basaltic volcanism. Atlantic Geology 44: 167–185 [DOI:10.4138/5932].

Giles PT, King MC. 2001. Les Sillons: a relict foredune plain.Canadian landform examples. Canadian Geographer/LeG�eographe Canadien 45: 437–441 [DOI: 10.1111/j.1541-0064.2001.tb01193.x].

Goddard PB, Yin J, Griffies SM et al. 2015. An extreme event of sea-level rise along the Northeast coast of North America in 2009–2010. Nature Communications 6: 6346 [DOI: 10.1038/ncomms7346] [Pubmed:25710720].

Han G, Ma Z, Bao H et al. 2014. Regional differences of relative sealevel changes in the northwest Atlantic: historical trends and futureprojections. Journal of Geophysical Research: Oceans 119:156–164.

Han G, Ma Z, Chen N et al. 2015. Changes in mean relative sea levelaround Canada in the twentieth and twenty-first centuries. Atmo-sphere-Ocean 53: 452–463 [DOI: 10.1080/07055900.2015.1057100].

Hua Q, Barbetti M. 2004. Review of tropospheric bomb 14C data forcarbon cycle modelling and age calibration purposes. Radiocarbon46: 1273–1298 [DOI: 10.1017/S0033822200033142].

Jevrejeva S, Moore JC, Grinsted A et al. 2014. Trends and accelera-tion in global and regional sea levels since 1807. Global andPlanetary Change 113: 11–22 [DOI: 10.1016/j.gloplacha.2013.12.004].

Juggins S. 2003. C2: A Microsoft Windows Program for Developingand Applying Palaeoecological Transfer Functions and for Visual-ising Multi-Proxy Stratigraphic Datasets, 1.7.2 edn. University ofNewcastle, Newcastle Upon Tyne.

Juneau MN. 2012. Hausse r�ecente du niveau marin relatif aux Iles-de-la-Madeleine. MSc Thesis. Universit�e du Qu�ebec �a Rimouski,Canada.

Kemp AC, Bernhardt CE, Horton BP et al. 2014. Late Holocene sea-and land-level change on the U.S. southeastern Atlantic Coast.Marine Geology 357: 90–100 [DOI: 10.1016/j.margeo.2014.07.010].

Kemp AC, Hawkes AD, Donnelly JP et al. 2015. Relative sea-levelchange in Connecticut (USA) during the last 2200 yrs. Earth andPlanetary Science Letters 428: 217–229 [DOI: 10.1016/j.epsl.2015.07.034].

Kemp AC, Horton BP, Donnelly JP et al. 2011. Climate related sea-level variations over the past two millennia. Proceedings of theNational Academy of Sciences of the United States of America108: 11017–11022 [DOI: 10.1073/pnas.1015619108] [Pubmed:21690367].

Kemp AC, Horton BP, Vane CH et al. 2013. Sea-level changeduring the last 2500 years in New Jersey, USA. QuaternaryScience Reviews 81: 90–104 [DOI: 10.1016/j.quascirev.2013.09.024].

Koohzare A, Vanı�cek P, Santos M. 2008. Pattern of recent verticalcrustal movements in Canada. Journal of Geodynamics 45:133–145 [DOI: 10.1016/j.jog.2007.08.001].

Kopp RE, Kemp AC, Bittermann K et al. 2016. Temperature-drivenglobal sea-level variability in the Common Era. Proceedings of theNational Academy of Sciences of the United States of America113: E1434–E1441 [DOI: 10.1073/pnas.1517056113] [Pubmed:26903659].

Levitus S, Antonov JI, Boyer TP et al. 2012. World ocean heat contentand thermosteric sea level change (0–2000 m), 1955–2010.Geophysical Research Letters 39: L10603.

Llovel W, Fukumori I, Meyssignac B. 2013. Depth-dependenttemperature change contributions to global mean thermosteric sea-level rise from 1960 to 2010. Global and Planetary Change 101:113–118 [DOI: 10.1016/j.gloplacha.2012.12.011].

Long AJ, Innes JB, Shennan I et al. 1999. Coastal stratigraphy: a casestudy from Johns River, Washington, USA. In The Description andAnalysis of Quaternary Stratigraphic Field Sections, Jones AP,Tucker ME, Hart JK (eds). Technical Guide No 7. QuaternaryResearch Association: London.

Long AJ, Woodroffe SA, Milne GA et al. 2010. Relative sea levelchange in west Greenland during the last millennium. Quaternary

Science Reviews 29: 367–383 [DOI: 10.1016/j.quascirev.2009.09.010].

Marshall WA, Gehrels WR, Garnett MH et al. 2007. The use of‘bomb spike’ calibration and high-precision AMS 14C analyses todate salt-marsh sediments deposited during the past three centuries.Quaternary Research 68: 325–337 [DOI: 10.1016/j.yqres.2007.07.005].

Mauquoy D, van Geel B. 2007. Mire and peat macros. In Encyclope-dia of Quaternary Science, Elias SA (ed.). Elsevier: Oxford.

McCarthy GD, Haigh ID, Hirschi JJ-m et al. 2015. Ocean impact ondecadal Atlantic climate variability revealed by sea-level observa-tions. Nature 521: 508–510 [DOI: 10.1038/nature14491] [Pubmed:26017453].

Milne GA, Mitrovica JX. 1998. Postglacial sea-level change on arotating Earth. Geophysical Journal International 133: 1–19 [DOI:10.1046/j.1365-246X.1998.1331455.x].

Mitrovica JX, Milne GA. 2002. On the origin of Late Holocene sea-level highstands within equatorial ocean basins. QuaternaryScience Reviews 21: 2179–2190 [DOI: 10.1016/S0277-3791(02)00080-X].

Mitrovica JX, Tamisiea ME, Davis JL et al. 2001. Recent mass balanceof polar ice sheets inferred from patterns of global sea-level change.Nature 409: 1026–1029 [DOI: 10.1038/35059054] [Pubmed:11234008].

Mitrovica JX, Peltier WR. 1991. On postglacial geoid subsidence overthe equatorial oceans. Journal of Geophysical Research: Solid Earth96: 20053–20071 [DOI: 10.1029/91JB01284].

Murray JW. 1971. An Atlas of British Recent Foraminiferids. Ameri-can Elsevier Publishing Company, Inc: New York.

Murray JW. 1979. British Nearshore Foraminiferids. Academic Press:London.

Nakada M, Okuno J, Ishii M. 2013. Twentieth century sea-level riseinferred from tide gauge, geologically derived and thermostericsea-level changes. Quaternary Science Reviews 75: 114–131 [DOI:10.1016/j.quascirev.2013.06.010].

Not C, Hillaire-Marcel C, Ghaleb B et al. 2008. 210Pb–226Ra–236Thsystematics in very low sedimentation rate sediments from theMendeleev Ridge (Arctic Ocean). Canadian Journal of EarthSciences 45 210: 1–13.

Peltier WR, Argus DF, Drummond R. 2015. Space geodesy constrainsice age terminal deglaciation: the global ICE-6G_C (VM5a) model.Journal of Geophysical Research: Solid Earth 120: 450–487 [DOI:10.1002/2014JB011176].

R Core Team. 2016. R: A language and environment for statisticalcomputing. R Foundation for Statistical Computing, Vienna. www.r-oroject.org.

Rahmstorf S, Box JE, Feulner G et al. 2015. Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation.Nature Climate Change 5: 475–480 [DOI: 10.1038/nclimate2554].

Rahmstorf S, Perrette M, Vermeer M. 2012. Testing the robustness ofsemi-empirical sea level projections. Climate Dynamics 39:861–875 [DOI: 10.1007/s00382-011-1226-7].

Reimer PJ, Baillie MGL, Bard E et al. 2009. IntCal09 and Marine09radiocarbon age calibration curves, 0–50,000 years CAL BP.Radiocarbon 51: 1111–1150 [DOI: 10.1017/S0033822200034202].

R�emillard AM, Buylaert J-P, Murray AS et al. 2015. Quartz OSLdating of Late Holocene beach ridges from the Magdalen Islands(Quebec, Canada). Quaternary Geochronology 30: 264–269 [DOI:10.1016/j.quageo.2015.03.013].

R�emillard AM, St-Onge G, Bernatchez P et al. 2016. Chronologyand stratigraphy of the Magdalen Islands archipelago from thelast glaciation to the Early Holocene: new insights into theglacial and sea-level history of eastern Canada. Boreas 44:604–628.

Ruest B, Neumeier U, Dumont D et al. 2016. Recent wave climateand expected future changes in the seasonally ice-infested watersof the Gulf of St. Lawrence, Canada. Climate Dynamics 46:449–466 [DOI: 10.1007/s00382-015-2592-3].

Saher MH, Gehrels WR, Barlow NLM et al. 2015. Sea-level changesin Iceland and the influence of the North Atlantic Oscillationduring the last half millennium. Quaternary Science Reviews 108:23–36 [DOI: 10.1016/j.quascirev.2014.11.005].



http://www.r&x2010;oroject.org

http://www.r&x2010;oroject.org

Sanchez-Cabeza JA, Masque P, Ani-Ragolta I. 1998. 210Pb and 210Poanalysis in sediments and soils by microwave acid digestion.Journal of Radioanalytical and Nuclear Chemistry 227: 19–22.

Scafetta N. 2014. Multi-scale dynamical analysis (MSDA) of sea-levelrecords versus PDO, AMO and NA indexes. Climate Dynamics 43:175–192 [DOI: 10.1007/s00382-013-1771-3].

Schell WR, Nevissi A. 1983. Sedimentation in Lakes and Reservoirs.Guidebook on Nuclear Techniques in Hydrology. TechnicalReports Series No. 91. IAEA: Vienna.

Scott DB, Brown K, Collins ES, et al. 1995. A new sea-level curvefrom Nova Scotia: evidence for a rapid acceleration of sea-levelrise in the late mid-Holocene. Canadian Journal of Earth Sciences32: 2071–2080 [DOI: 10.1139/e95-160].

Scott DB, Medioli FS. 1980. Quantitative studies of marsh foraminif-eral distributions in Nova Scotia: implications for sea level studies.Cushman Foundation for Foraminiferal Research. Special Publica-tion No. 17.

Scott DB, Williamson MA, Duffett TE. 1981. Marsh foraminifera ofPrince Edward Island: Their recent distribution and application forformer sea level studies. Atlantic Geology 17: 98–129 [DOI: 10.4138/1380].

Shaw J, Piper DJW, Fader GBJ et al. 2006. A conceptual model of thedeglaciation of Atlantic Canada. Quaternary Science Reviews 25:2059–2081 [DOI: 10.1016/j.quascirev.2006.03.002].

Shennan I. 2007. Sea level studies. In Encyclopedia of QuaternarySciences, Ellias SA (ed.). Elsevier: Oxford.

Shennan I. 2015. Handbook of sea-level research: framing researchquestions. In Handbook of Sea-Level Research, Shennan I, Long AJ,Horton BP (eds). Wiley: Chichester; 3–25.

Simpson GL. 2007. Analogue methods in palaeoecology: using theanalogue package. Journal of Statistical Software 22: 1–29.

Slangen ABA, Carson M, Katsman CA et al. 2014. Projecting twenty-first century regional sea-level changes. Climatic Change 124:317–332 [DOI: 10.1007/s10584-014-1080-9].

Slangen ABA, Katsman CA, van de Wal RSW et al. 2012. Towardsregional projections of twenty-first century sea-level change based

on IPCC SRES scenarios. Climate Dynamics 38: 1191–1209 [DOI:10.1007/s00382-011-1057-6].

Stammer D, Cazenave A, Ponte RM et al. 2013. Causes forcontemporary regional sea level changes. Annual Review ofMarine Science 5: 21–46 [DOI: 10.1146/annurev-marine-121211-172406] [Pubmed:22809188].

Stea RR, Seaman AA, Pronk T, Parkhill MA, Allard S, Utting D.2011. The Appalachian Glacier Complex in Maritime Canada. InQuaternary Glaciations - Extent and Chronology, Part II:North America, Ehlers J, Gibbard PL (eds). Elsevier: New York;631–659.

Stuiver M, Polach HA. 1977. Discussion reporting of 14C data.Radiocarbon 19: 355–363 [DOI: 10.1017/S0033822200003672].

Stuiver M, Reimer PJ. 1986. A computer program for radiocarbon agecalibration. Radiocarbon 28: 1022–1030 [DOI: 10.1017/S0033822200060276].

Tovey KN, Paul MA. 2002. Modelling self-weight consolidation inHolocene sediments. Bulletin of Engineering Geology and theEnvironment 61: 21–33 [DOI: 10.1007/s100640100126].

Watcham EP, Shennan I, Barlow NLM. 2013. Scale considerations inusing diatoms as indicators of sea-level change: lessons fromAlaska. Journal of Quaternary Science 28: 165–179 [DOI: 10.1002/jqs.2592].

Watson CS, White NJ, Church JA et al. 2015. Unabated global meansea-level rise over the satellite altimeter era. Nature ClimateChange 5: 565–568 [DOI: 10.1038/nclimate2635].

Woodroffe SA, Long AJ, Milne GA et al. 2015. New constraints onLate Holocene eustatic sea-level changes from Mah�e, Seychelles.Quaternary Science Reviews 115: 1–16 [DOI: 10.1016/j.quascirev.2015.02.011].

Wright AJ, Edwards RJ, van de Plassche O. 2011. Reassessingtransfer-function performance in sea-level reconstruction based onbenthic salt-marsh foraminifera from the Atlantic coast of NE NorthAmerica. Marine Micropaleontology 81: 43–62 [DOI: 10.1016/j.marmicro.2011.07.003].



barnett rl, bernatchez p, garneau m and juneau m-n. (2017) reconstructing late holocene relative sea...

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