Quaternary Science Reviews 29 (2010) 2799e2820
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Quaternary Science Reviews
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Isotopic characterization of rapid climatic events during OIS3 and OIS4 in Villars
Cave stalagmites (SW-France) and correlation with Atlantic and Mediterranean
pollen records
Dominique Genty a, *, Nathalie Combourieu-Nebout a, Odile Peyron b, Dominique Blamart a,
Karine Wainer a, Fatima Mansuri a, Bassam Ghaleb c, Lauren Isabello c, Isabelle Dormoy b,
Ulrich von Grafenstein a, Stefano Bonelli a, Amaelle Landais a, A. Brauer d
a
Laboratoire des Sciences du Climat et de l’Environnement, UMR 8212 CNRS/CEA/UVSQ, l’Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France
UMR CNRS 6249 Laboratoire de Chrono-Environnement, Faculté des Sciences, 16 route de Gray, Université de Franche-Comté, France
c
GEOTOP, Université du Québec à Montréal, C.P. 8888, succ. Centre-Ville, H3C 3P8 Montréal, Canada
d
Deutsches GeoForschungsZentrum GFZ, Sektion 5.2 Klimadynamik und Landschaftsentwicklung, Potsdam, Germany
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 15 February 2010
Received in revised form
17 June 2010
Accepted 22 June 2010
We present a new mid-latitude speleothem record of millennial-scale climatic variability during OIS3
from the Villars Cave that, combined with former published contemporaneous samples from the same
cave, gives a coherent image of the climate variability in SW-France between w55 ka and w30 ka. The
0.82 m long stalagmite Vil-stm27 was dated with 26 TIMS UeTh analyses and its growth curve displays
variations that are linked with the stable isotopes, both controlled by the climatic conditions. It consists
in a higher resolved replicate of the previously published Vil-stm9 and Vil-stm14 stalagmites where
DansgaardeOeschger (DO) events have been observed. The good consistency between these three
stalagmites and the comparison with other palaoeclimatic reconstructions, especially high resolution
pollen records (ODP 976 from the Alboran Sea, Monticchio Lake record from southern Italy) and the
nearby MD04-2845 Atlantic Ocean record, permits to draw a specific climatic pattern in SW-France
during the OIS3 and to see regional differences between these sites. Main features of this period are: 1)
warm events corresponding to Greenland Interstadials (GIS) that are characterized by low speleothem
d13C, high temperate pollen percentages, warm temperatures and high humidity; among these events,
GIS#12 is the most pronounced one at Villars characterized by an abrupt onset at w46.6 ka and
a duration of about 2.5 ka. The other well individualized warm event coincides with GIS#8 which is
however much less pronounced and occurred during a cooler period as shown by a lower growth rate
and a higher d13C; 2) cold events corresponding to Greenland Stadials (GS) that are clearly characterized
by high speleothem d13C, low temperate pollen abundance, low temperature and enhanced dryness,
particularly well expressed during GS coinciding with Heinrich events H5 and H4. The main feature of
the Villars record is a general cooling trend between the DO#12 event w45.5 ka and the synchronous
stop of the three stalagmites at w30 ka 1, with a first well marked climatic threshold at w41 ka after
which the growth rate and the diameter of all stalagmites slows down significantly. This climatic
evolution differs from that shown at southern Mediterranean sites where this trend is not observed. The
w30 ka age marks the second climatic threshold after which low temperatures and low rainfalls prevent
speleothem growth in the Villars area until the Lateglacial warming that occurred at w16.5 0.5 ka. This
15 ka long hiatus, as the older Villars growth hiatus that occurred between 67.4 and 61 ka, are linked to
low sea levels, reduced ocean circulation and a southward shift of the Polar Front that likely provoked
local permafrost formation. These cold periods coincide with both low summer 65 N insolation, low
atmospheric CO2 concentration and large ice sheets development (especially the Fennoscandian).
Ó 2010 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ33 169082866.
E-mail address: [email protected] (D. Genty).
0277-3791/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.quascirev.2010.06.035
2800
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
1. Introduction
Marine Isotope Stage 3 (OIS3, w59 to w28 ka) is a key period in
Europe for several reasons: first, it is characterized by abrupt
climatic warmings, the DansgaardeOeschger events (DO1), with
temperature amplitudes exceeding 10 C, at least in Greenland
(Dansgaard et al., 1993; Huber et al., 2006); secondly, it coincides
with a major human migration whose consequence was the
disappearance of the Homo neanderthalensis (Mellars, 2006;
Tzedakis et al., 2007). Some authors therefore believe that the
specific climatic conditions of this period might have played a role
in human culture changes such as the Homo sapiens migration and
the Neanderthalian disappearance (d’Errico and Sánchez Goñi,
2003; Mellars, 1998).
Recently, the Antarctic and Greenland ice core records have
been synchronized using the methane concentration of the air
trapped in the ice (EPICA, 2006), confirming a one-to-one coupling
between the Antarctic warmings (Antarctic Isotope Maximum:
AIM) and the Greenland stadials confirming the bipolar seeesaw
mechanism (Blunier et al., 1998; Stocker and Johnsen, 2003). The
observation that the longer the stadials (in the northern hemisphere) the warmer the AIM suggests that the meridian overturning circulation (MOC) plays a central role in the distribution of
Southern Ocean heat accumulation: reduced MOC causes a heat
accumulation in the Southern Ocean, thus warm events in the
Antarctic. This mechanism where the MOC instability plays
a central role was also simulated by an Earth system model of
intermediate complexity (EMIC) that took into consideration the
atmosphere, ocean, sea ice, land surface, continental ice and
vegetation components on a 5 5 grid over Eurasia at least (Wang
and Mysak, 2006).
Besides Greenland, DO events have been recognized in
numerous Northern hemisphere archives and even in the tropical
zone, demonstrating their large impact on the ocean, the continent,
on the atmospheric circulation and on the monsoon intensity
(Cacho et al., 1999; Kiefer et al., 2001; Wang et al., 2001; Spötl and
Mangini, 2002; Burns et al., 2003; Cruz et al., 2005; Bard et al.,
2006). However, their consequences on the European continent
are still not well known because of the scarcity of well-preserved,
well dated and highly resolved records. Among the most complete
records we find: pollen records, especially from Central France and
from Italy, (Guiot et al., 1993; Allen et al., 1999; Beaulieu de et al.,
2001; Brauer et al., 2007); pollen sequences from Atlantic and the
Mediterranean Sea marine cores (Sánchez Goñi et al., 2000a;
Combourieu Nebout et al., 2002; Fletcher and Sanchez-Goni,
2008; Sánchez Goñi et al., 2008) and the Villars Cave speleothems (SW-France) (Genty et al., 2003, 2005; Wainer et al., 2009).
The later site is ideally located because it is close to the Atlantic
Ocean and therefore directly influenced by any North Atlantic
circulation changes. A 1.47 m long stalagmite from the Villars Cave
(Vil-stm9) has already shown large isotopic changes that were
correlated with DansgaardeOeschger events #5 to #20 (Genty
et al., 2003). The d13C variation measured on the calcite was
interpreted as changes in the vegetation density, soil activity and
hydrology: the lower the d13C the more active the vegetation and
the higher the drip rate. This record was characterized by: 1) a long
stop in the growth rate between 61.1 and 67.4 ka, coinciding, for
a large part, to the cold OIS4 period and H6 event, and 2) by a high
growth rate between 45.5 and 42.1 ka, coinciding with low d13C
values and correlated with GIS#12, the most pronounced warm
1
In the following we use DO event to characterize the rapid warmings as defined
initially, but introduce the term DO oscillation to describe the period between one
DO event and the next which consequently includes the following GIS and GS.
event of this record. From GIS#12 on, a general cooling trend,
punctuated by GIS, was observed until the definitive stop of the
stalagmite 31.8 ka ago. This pattern is slightly different to the one
observed in the Greenland isotopic records where small GIS events
appear more individualized (especially GIS#9, 10 and 11) and the
general trend between GIS#12 and the end of the OIS3 is less
pronounced. Because well dated and higher resolved continental
records that cover this period are rare, we do not have a clear vision
of what happened during stadial-interstadial successions in
Europe. This is the reason why we study the regional differences
between the Villars speleothem records and the other palaeoclimatic archives recording DO events of OIS 3.
The climatic reconstruction closest to the Villars Cave is the
pollen record of the Le Bouchet Lake, about 200 km east and at the
same latitude (Fig. 1). This record clearly shows temperature and
rainfall changes associated with the stadial/interstadial events
(Guiot et al., 1993). For example, an annual temperature drop of
about 10 C/present is observed during the H5 period, and
a warming of about þ7.5 C occurred between H5 and GIS#12. The
cooling that characterizes stadial events is generally accompanied
by a reduction of precipitation (i.e. 450 mm/present of deficit
during the H5 at Le Bouchet, while the GIS12 optimum has a rainfall
deficit of only 370 mm/present w100). This early work is
corroborated by the climatic pollen reconstructions made on marine
cores located southernmost of the Villars Cave, around the Iberian
peninsula: cold stadial events are associated with dryness while
warm interstadials (GIS) are more humid (Combourieu Nebout et al.,
2002; Sanchez Goni et al., 2002; Bout-Roumazeilles et al., 2007),
with regional differences between the Mediterranean and Atlantic
side, the later being more humid (Sanchez Goni et al., 2002).
The objective of this paper is to better characterize the Villars
speleothem records and to interpret, in terms of temperature and
rainfall changes, the climatic events recorded in the isotopic signals
of the Villars Cave stalagmites between w50 and w30 ka. This is
done here, not only by analysing a new stalagmite from the Villars
Cave, called Vil-stm27, that replicates the Vil-stm9 and the Vilstm14 samples (Genty et al., 2003; Wainer et al., 2009), but also by
comparing the isotopic and growth rate changes with the closest
palaeoclimatic reconstructions based on terrestrial and marine
cores pollen analyses that have a comparable time resolution. The
detailed comparison with the ODP 976 marine core (Alboran Sea),
one of the rare palaeoclimatic record that experiences a similar
high resolution as the Villars one (Combourieu Nebout et al., 2002),
brings information about the climatic conditions that prevailed
during these abrupt events of OIS3 in South Western Europe. It
helps better understanding the isotopic Villars record. However,
important regional differences exist in the expression of DO events,
which can be revealed by comparing with other pollen records
from the Atlantic Ocean even if their resolution is lower, and from
other continental records especially the high resolution Monticchio
Lake one from southern Italy (Allen et al., 1999; Brauer et al., 2000).
2. Sites settings
2.1. Villars Cave (SW-France; 45 300 N, 0 500 E, elevation 175 m)
The Villars Cave is located on the SW border of the Massif
Central, France, in sedimentary rocks overlying metamorphic ones
that crop out at about 3 km to the northeeast (Fig. 1). It is a shallow
cave whose w13 km long galleries developed in Bajocian oolithic
limestone in two levels (10e15 m/surface and 30e50 m/surface,
respectively). Most of the cave is nowadays covered by an oak,
hornbeam, and hazel forest. The soil cover is very thin and irregular
comprising less than 20 cm of brown earth containing occasional
weathered clasts of limestone (Baker et al., 2000; Genty et al.,
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
2801
Fig. 1. Localization of the studied sites: The Villars Cave (45.30 N, 0.50 E, 175 masl); cave records: Kleegruben, Germany (Spötl and Mangini, 2002), Soreq, Israel (Bar-Matthews
et al., 2000); Lake records: Le Bouchet, France (Guiot et al., 1993), Monticchio, Italy (Allen et al., 1999; Brauer et al., 2007); Greenland ice core records (NorthGRIPmembers,
2004); marine core records from the Mediterranean Sea (Combourieu Nebout et al., 2002; Sanchez Goni et al., 2002) and the Atlantic ocean (Sánchez Goñi et al., 2000b;
Sepulchre et al., 2007; Sánchez Goñi et al., 2008).
2001). Some root extremities appear at the roofs of the upper
galleries, suggesting that typical soil processes (i.e. root respiration,
vegetation-water exchange) may occur also in the epikarstic zone.
The climate around Villars is typically temperate maritime, with
mild winters (mean winter temp. ¼ 6.4 C) and relatively cool
summers (mean summer temp. ¼ 18.6 C; Table 1). Annual rainfall at
the closest meteorological station (Nontron) is 1033 mm for the
period from 1984 to 2004 with statistically slightly higher precipitation during the cold season. However, seasonality is much more
expressed for temperature and water excess (Fig. 2). Mean external
annual temperature for the 1984e2004 period is 11.9 C which is
slightly lower than the present day cave temperature of the upper
galleries (12.5 C for the last ten years), but higher than those of the
lower galleries (11.3 C for the last ten years). We observe a warming
trend, in both deep and shallow places, for the last ten years, i.e. since
we have started Cave monitoring. It is likely due to the thermal wave
conduction through the limestone and which might explain the
lower temperatures of the lower galleries (work in progress).
Studied stalagmites are situated in these lower galleries.
The stalagmite Vil-stm27 comes from the same chamber as the
Vil-stm9 stalagmite where DO events have been observed (Genty
et al., 2003). The room is located in the lower galleries of the Villars Cave at about 30 m below the surface. It is a 82 cm-long candlelike calcitic stalagmite. It is composed of columnar palissadic fabrics
and characterized, like for the other two Villars stalagmites, by
translucent calcite that contains, near the central axis, large voids,
which sometimes contains large fluid inclusions. We noted that the
tip of Vil-stm27 sample that grew after w40 ka has more compact
fabrics, a decreasing diameter and opalescent calcite parts. Similar
features were found on the Vil-stm9 and Vil-stm14 samples.
2.2 Ocean drilling program (ODP) site 976 (36120 N, 4180 W, 1108 m
water depth)
This ODP site has been drilled in the Alboran Sea, the westernmost Mediterranean Sea basin close to the Gibraltar Strait
(Combourieu Nebout et al., 2002). Present day climate in the Alboran
Sea region is Mediterranean with long and dry summer and mild
Table 1
Meteorological settings of the studied sites (see Fig. 2 legend). ETP ¼ evapotranspiration. Meteorological data for the Villars Cave come from the Nontron station (w10 km far);
and, for the ODP 976 site come from an interpolated calculation with the New LocClim software that considered the following stations: Malaga, Granada, Gibraltar, Ceuta; VillaSanjuro, Rincon-Medik, Rio-Martin, Uad-Lau, Malaien.
Site
Villars Cave 45.44 N, 0.78 E (Nontron, 1984 / 2004)
ODP 976 36.12 N, 4.18 W
Rann, mm
Rnove>apr, mm
Rmaye>oct, mm
Tann, C
Winter Tjfm, C
Sum. Tjas, C
ETPann, mm
1033
581
568
468
464
112
11.9
17.9
6.4
12.9
18.6
24.3
712
1147
2802
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
Fig. 2. Meteorological records provided by the closest meteorological stations from the sites studied: Nontron z15 km from Villars Cave. PET ¼ Potential Evapotranspiration.
rainy winter (Walter et al., 1975). Annual rainfall is about 581 mm
with a large deficit during the MayeSeptember period. Mean annual
temperature is 17.9 C with hot summer period (24.3 C) and mild
winter (12.9 C) as interpolated from the closest meteorological
stations using New LocClim software (Grieser et al., 2006). These
climate data express the average meteorological conditions from
relatively low altitude stations around the Alboran Sea. However, we
must keep in mind that marine pollen data are also controlled by all
the surrounding ecosystems, including high elevations (i.e. the
Sierra Nevada in Spain and the Rif massif in Morocco).
Modern environments vary from the coast to high elevations
with a thermomediterranean belt with Olea, Pistacia and some semidesert representatives (Artemisia, Chenopodiaceae, Ephedra) going
to a mesomediterranean belt, represented by a sclerophyllous oak
forest then a humid-temperate oak forest (eurosiberian trees as
Quercus, Betula and Ericaceae), and a supramediterranean belt with
a cold-temperate coniferous forest (Pinus, Abies, Cedrus) at the
higher altitudes (Ozenda, 1975; Rivas Martinez, 1982).
3. Methods
3.1. Villars stalagmite chronology and stable isotope measurements
The new Villars stalagmite Vil-stm27 was dated with 26 thermal
ionization mass spectrometry (TIMS) UeTh measurements at the
GEOTOP, UQAM, Montreal (Table 2). Samples were dissolved with
nitric acid and spiked with 229The236Ue233U. Uranium and thorium
fractions were separated on anion exchange columns using standard
techniques (Edwards et al., 1987; Marshall et al., 2009). Both
uranium and thorium were loaded onto graphite-coated Re filaments and analyses carried out using a VG Sector mass spectrometer.
The latter is equipped with an electro-static analyser and an ioncounting Daly detector. Errors were propagated from the in-run
statistics and the uncertainties on the spike isotopic composition.
Ages were calculated using the standard equation and the decay
constants used for 234U, 238U, and 230Th were 2.826 106,
1.55125 1010 and 9.1577 106 respectively. Except the base
sample that comes from a clayey part, all analysed samples have
a high 230Th/232Th activity ratio (i.e. >1000) and no detrital correction was necessary. The base sample was corrected with a 232Th/238U
activity ratio of 1.1 (Wainer et al., 2009), which corresponds to the
Villars cave clay isotopic ratio, close to the one already used in other
studies (Genty et al., 2003). Although this correction puts the base
sample in a consistent stratigraphic order, the lowermost part of the
stalagmite, below a discontinuity at 1.5 cm from base, is not
considered here due to the great uncertainty in the age. The uranium
content of the samples is relatively low with an average value of
108 ppb. The final error (given at 2s,) is, for most samples, lower than
2%, which is between w400 yrs to more than 1000 yrs (supplementary material). The chronology of Vil-stm14 relies mainly on
UeTh ages that were performed by MC-ICP-MS. This instrument
requires smaller samples, allows enhanced ionization efficiency for
Th and has a much greater sensitivity. The already published Vilstm9 chronology has been updated with the new decay constants
and the new Villars detrital 232Th/238U activity ratio (Supplementary
material); new ages do not differ significantly and rest within the 2s
error margin with respect to the previously published ages.
Stable isotope samples were taken at the centre of the growth axis
with a micro-drill (0.5 mm diameter). The samples were analysed
with a VG OPTIMA mass spectrometer (LSCE, Gif-sur-Yvette) after
orthophosphoric acid reaction at 90 C. The data are expressed in the
conventional delta notation relative to the V-PDB and the analytical
error is 0.08& for both d18O and d13C. In order to check the isotopic
equilibrium of speleothems, we used the classical Hendy’s test
(Hendy, 1971) that should indicate the existence of kinetic fractionation due to evaporation or rapid CO2 degassing: 1) a significant
correlation between the d18O and the d 13C along the growth axis and
along single laminae; 2) an enrichment in the d13C or d18O towards the
edges of the stalagmite. We also tested the present day isotopic
equilibrium by comparing the measured cave temperature with the
theoretical equilibrium fractionation temperature estimated with the
present day water and calcite d18O (O’Neil et al., 1969).
3.2. ODP 976 chronology, pollen extraction and interpretation and
quantitative reconstructions
The chronology of ODP Site 976 is based on 13 14C AMS ages
completed by a few tie points obtained from to the correlation
between the ODP 976 oxygen isotope curve and the core MD95-2042 reference curve from Portugal (von Grafenstein et al.,
1999; Shackleton et al., 2000, 2003; Combourieu Nebout et al.,
2002). The age model was refined by the correlation between
pollen and NorthGRIP d18O ice record down to 120,000 yrs
(NorthGRIPmembers, 2004). Time resolution between the 380
samples studied varies from 20 to 500 yrs depending of the
period and reaches rarely 1000 yr close to the base of the
Table 2
Uranium series results of stalagmites Vil-14 (Wainer et al., 2009) and Vil 9 (Genty et al., 2003) and the new Villars stalagmite Vil-stm27 (this study, GEOTOP, UQAM, Montreal). 2s error are shown. Decay constants used are
9.1577 106 yr1 for 230Th, 2.826 106 yr1 for 234U (Cheng et al., 2000), and 1.55125 1010 yr1 for 238U (Begemann et al., 2001). Only the age of the basis needed a correction for initial Thorium although all the values were
corrected to have a consistent data set. Age, error and corrected data are calculated thanks to ISOPLOT3, provided by Kenneth Ludwig, Berkley Geochronological Center (Ludwig, 2003).
a
Position/
basis (cm)
“”
(cm)
[238U]
ppm
“”
A(234/238)
activity ratio
“”
A(230/232)
activity ratio
“”
A(230/234)
activity ratio
“”
Uncorr
age (yrs)
“”
(yrs)
Corr age
(yrs)
“”
(yrs)
Laboratorytechnique
Vil9A
Vil9M
Vil9G
Vil9H
Vil9U
Vil9V
Vil9P
Vil9I
Vil9J
Vil9W
Vil9X
Vil9K
Vil9B
Vil9C
Vil9Z
Vil9A1
Vil9D
Vil9A3
Vil9A5
Vil9A4
Vil9A6
Vil9A7
Vil9L
Vil9A8
Vil9R
Vil9F
1.55
5.2
15.65
16.95
23.5
31.6
34.5
38.8
40.2
44.6
46.4
50.2
51.4
67.6
79.55
88.15
92.15
109.5
126.9
127.6
131.45
133.35
136.45
139.5
141.8
145.9
0.35
0.2
0.35
0.65
0.4
0.4
0.3
0.6
0.4
0.4
0.4
0.4
0.4
0.3
0.45
0.45
0.35
0.5
0.3
0.4
0.45
0.45
0.45
0.5
0.3
0.3
0.12874
0.10367
0.06295
0.06700
0.06128
0.05922
0.06634
0.06995
0.04942
0.05748
0.04540
0.04419
0.04773
0.06718
0.04347
0.05401
0.06266
0.04774
0.05102
0.04994
0.08924
0.05256
0.05641
0.05344
0.07427
0.04545
0.00038
0.00013
0.00012
0.00015
0.00007
0.00009
0.00013
0.00011
0.00020
0.00009
0.00008
0.00012
0.00016
0.00017
0.00006
0.00008
0.00013
0.00008
0.00007
0.00010
0.00018
0.00009
0.00017
0.00008
0.00013
0.00016
1.1566
1.1304
1.1377
1.1400
1.1256
1.1378
1.1513
1.1691
1.1997
1.1853
1.1849
1.1941
1.1655
1.1774
1.1730
1.1629
1.1457
1.1758
1.1985
1.1813
1.2011
1.2121
1.1998
1.2124
1.2306
1.2145
0.0080
0.0038
0.0086
0.0070
0.0033
0.0064
0.0083
0.0043
0.0119
0.0047
0.0055
0.0090
0.0090
0.0075
0.0049
0.0051
0.0055
0.0050
0.0056
0.0077
0.0077
0.0057
0.0092
0.0043
0.0064
0.0046
77.05
144.3
1163.8
280.8
1273.0
1100.1
2173.7
2282.3
966.0
1341.6
2250.5
2627.8
349.3
1012.4
496.9
659.6
293.0
1592.7
165.3
47.4
343.2
1374.1
570.0
5657.4
1433.0
975.0
1.4
2.0
21.8
3.9
16.6
16.1
36.2
42.8
14.2
19.8
59.4
42.2
7.3
23.8
7.3
9.8
4.5
24.3
2.9
0.8
4.7
20.0
10.5
82.7
42.8
28.7
0.5426
0.5327
0.5228
0.5041
0.5019
0.4862
0.4850
0.4706
0.4344
0.4222
0.4157
0.4072
0.3831
0.3744
0.3610
0.3550
0.3452
0.3343
0.3239
0.3262
0.3156
0.3148
0.3133
0.3053
0.2845
0.2619
0.0057
0.0033
0.0057
0.0030
0.0025
0.0031
0.0044
0.0043
0.0029
0.0028
0.0026
0.0031
0.0050
0.0056
0.0024
0.0026
0.0025
0.0024
0.0032
0.0031
0.0018
0.0020
0.0033
0.0019
0.0059
0.0039
83510
81553
79293
75232
74884
71537
71192
68191
61092
58908
57734
56179
52067
50552
48311
47338
45785
43938
42242
42638
40941
40793
40583
39331
36159
32853
1360
767
1328
688
551
688
945
875
594
523
497
582
882
967
415
438
421
400
509
508
294
314
524
302
887
576
82497
80867
78928
74755
74542
71204
70882
67895
60801
58639
57482
55936
51749
50310
48044
47093
45485
43739
41880
41796
40686
40605
40365
39166
35992
32694
1816
956
1779
1156
698
1043
1371
984
1277
671
690
960
1127
1110
542
562
568
506
608
765
535
446
737
380
930
606
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
OU-TIMS
b
Sample
name
Position/
top (cm)
“”
(cm)
[238U]
ppm
“”
A(234/238)
Activity ratio
“”
A(230/232)
Activity ratio
“”
A(230/238)
Activity ratio
“”
Uncorr
Age (yrs)
“”
(yrs)
Age corr (yrs)
(Vill. Clay)
Th/U ¼ 1.1
“”
(yrs)
Laboratorytechnique
Vil14-C
Vil14-G
Vil14-H
Vil14-I
Vil14-E
Vil14-J
Vil14-K
Vil14-L
Vil14-M
Vil14-N
Vil14-F
Vil14-O
Vil14-P
Vil14-Q
Vil14-R
0.7
5.45
10.9
16.75
21.2
21.85
26.6
31.3
36.65
41.7
46
49.15
54.25
57.8
61.9
0.7
0.25
0.2
0.25
0.4
0.25
0.2
0.2
0.25
0.2
0.5
0.25
0.25
0.3
0.4
0.05779
0.05463
0.04498
0.02816
0.03500
0.02369
0.03029
0.03607
0.03321
0.02915
0.04139
0.02633
0.02792
0.03142
0.02957
0.00008
0.00026
0.00021
0.00315
0.00005
0.00192
0.00236
0.00287
0.00022
0.00019
0.00066
0.00015
0.00016
0.00248
0.00021
1.0606
1.0345
1.0329
1.0349
1.0241
1.0360
1.0289
1.0299
1.0290
1.0261
1.0841
1.0344
1.0281
1.0254
1.0236
0.0054
0.0034
0.0034
0.0040
0.0060
0.0040
0.0042
0.0030
0.0035
0.0040
0.0297
0.0028
0.0027
0.0035
0.0023
28.6
26.8
156.9
126.2
120.5
147.8
67.9
85.6
126.9
73.0
72.1
52.3
21.8
18.3
21.4
0.3
0.2
1.6
1.8
1.5
2.4
0.9
0.8
1.3
0.7
0.6
0.4
0.2
0.2
0.2
0.2537
0.3369
0.3354
0.3401
0.3544
0.3481
0.3540
0.3560
0.3602
0.3642
0.4085
0.3787
0.3887
0.3926
0.3948
0.0025
0.0021
0.0030
0.0031
0.0042
0.0045
0.0038
0.0028
0.0031
0.0036
0.0033
0.0025
0.0028
0.0032
0.0029
29773
42929
42775
43409
46297
44597
45955
46202
46949
47778
51281
49632
51735
52595
53093
377
381
496
528
775
751
660
486
544
644
1963
453
507
595
524
28943
41732
42572
43154
46012
44375
45458
45806
46678
47301
50766
48946
50026
50523
51317
561
650
504
541
787
757
697
517
556
677
1965
543
908
1116
944
LSCE-TIMS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
LSCE-TIMS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
LSCE-TIMS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
SGS-MC-ICP-MS
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
Sample name
(continued on next page)
2803
2804
Table 2 (continued)
c
Position/top
(cm)
“”
(cm)
[238U]
ppm
“”
A(234/238)
Activity ratio
“”
A(230/232)
Activity ratio
“”
A(230/234)
Activity ratio
“”
Uncorr
Age (yrs)
“”
(yrs)
Age corr
(yrs) (Vill. Clay)
Th/U ¼ 1.1
“”
(yrs)
Laboratorytechnique
Vil27-L
Vil27-beta
Vil27-alpha
Vil27-Z
Vil27-Y
Vil27-K
Vil27-X
Vil27-W
Vil27-V
Vil27-J
Vil27-U
Vil27-I
Vil27-H
Vil27-T
Vil27-G
Vil27-S
Vil27-R
Vil27-Q
Vil27-F
Vil27-P
Vil27-O
Vil27-E
Vil27-N
Vil27-M
Vil27-D
Vil27-C
Vil27-B
Vil27-A
81.6
80.175
78.65
76.75
75.175
72.95
71.275
68.8
66
61.8
56.55
51.4
49.5
47.55
44.8
38.55
34.25
28.1
24.3
20.65
17.08
14.45
11.88
8.1
6.5
5.1
2.35
0.7
0.4
0.325
0.35
0.3
0.375
0.45
0.475
0.6
0.7
0.5
0.65
0.5
0.5
0.55
0.5
0.55
0.75
1
0.5
0.65
0.7
0.45
0.63
0.5
0.3
0.4
0.5
0.5
0.11419
0.12841
0.12511
0.13574
0.11645
0.14213
0.13327
0.13223
0.10003
0.11896
0.06202
0.10911
0.13450
0.07981
0.14190
0.09588
0.08565
0.11381
0.11512
0.05566
0.09011
0.06299
0.08081
0.08766
0.12056
0.15333
0.10437
0.03783
0.00064
0.00108
0.00073
0.00081
0.00085
0.00083
0.00102
0.00082
0.00088
0.00067
0.00038
0.00062
0.00076
0.00047
0.00083
0.00068
0.00056
0.00071
0.00063
0.00032
0.00049
0.00036
0.00047
0.00053
0.00069
0.00087
0.00058
0.00021
1.2185
1.2123
1.2237
1.2183
1.2238
1.1991
1.1845
1.1858
1.1815
1.1882
1.1493
1.1901
1.1843
1.1662
1.1636
1.1529
1.1505
1.1682
1.1543
1.1550
1.1558
1.1446
1.1409
1.1532
1.1513
1.1612
1.1558
1.1361
0.0069
0.0087
0.0109
0.0102
0.0158
0.0069
0.0121
0.0099
0.0171
0.0075
0.0129
0.0094
0.0080
0.0098
0.0080
0.0097
0.0115
0.0108
0.0116
0.0099
0.0091
0.0109
0.0067
0.0085
0.0167
0.0107
0.0088
0.0091
118.0
1242.2
455.9
976.4
1357.9
431.5
1341.8
1784.2
1002.8
280.4
589.4
1019.6
1522.3
1630.4
1104.1
1354.4
960.4
419.4
532.2
411.2
629.0
1042.2
744.4
947.6
1624.6
417.7
510.9
2.6
1.7
26.0
7.5
20.8
26.4
4.5
28.0
33.8
20.0
3.0
7.8
21.0
25.4
17.1
21.5
20.3
12.8
5.2
6.5
5.9
8.1
17.7
13.6
14.6
61.9
7.5
5.0
0.1
0.2543
0.2636
0.2635
0.2745
0.2853
0.3042
0.3134
0.3135
0.3174
0.3184
0.3353
0.3207
0.3297
0.3363
0.3350
0.3420
0.3455
0.3383
0.3409
0.3431
0.3470
0.3470
0.3472
0.3495
0.3484
0.3514
0.3613
0.4103
0.0031
0.0044
0.0043
0.0053
0.0055
0.0026
0.0063
0.0056
0.0060
0.0030
0.0047
0.0059
0.0051
0.0033
0.0059
0.0043
0.0044
0.0039
0.0045
0.0044
0.0043
0.0059
0.0054
0.0049
0.0131
0.0063
0.0033
0.0101
31752
33095
33079
35035
36281
39182
40632
40636
41253
41395
44172
41762
43198
44287
44085
45238
45825
44598
45057
45411
46056
46072
46117
46462
46289
46757
48415
56969
692
654
632
823
837
403
1000
884
968
484
781
950
827
549
968
728
745
654
752
741
726
987
903
833
2185
1069
579
1862
31541
33074
33023
34663
36261
39113
40609
40619
41223
41284
44116
41732
43177
44267
44055
45213
45790
44520
44995
45330
46002
46040
46072
46426
46268
46675
48346
40589
700
792
702
863
939
556
1119
974
1141
623
908
1023
918
707
1054
908
906
809
858
863
842
1075
1008
958
2206
1153
745
9084
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
GEOTOP-TIMS
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
Sample
name
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
record. The pollen record presented here is based on the
previously published record but was considerably condensed in
order to have a more detailed record around DO#8 and #12 (i.e.
we added samples below the H5 down to 80 kyr; for the H4D0#8 period (25 additional samples) and the beginning H5DO#12 phase (11 additional sampled) that increase in these two
parts of the ODP 976 the sampling resolution from 10 to 2e3 cm
corresponding to a time resolution from 100e200 yrs
to 20e50 yrs between samples) (Combourieu Nebout et al.,
2002; Genty et al., 2005).
3.2.1. Pollen data
Pollen extraction from marine sediments follows a standard
method already described in Combourieu Nebout et al. (2002).
Palaeoenvironmental interpretation of the downcore pollen
assemblages is built on the assumption that the primary pollen
contribution to AlboranSea sediments comes from west Mediterranean borderlands. The pollen diagram has been based on the
determination of 120 pollen taxa and counts of at least 100 pollen
grains per sample excluding Pinus. Pollen percentages are calculated with respect to a sum excluding Pinus pollen because its overrepresentation in such marine sediments generally masks all the
other taxa variations (Heusser and Balsam, 1977).
Fossil pollen spectra range from semi-desert to mountain
deciduous and coniferous forest. Their interpretation follows the
modern climatic-plant relationships in Eurasia and Northern Africa
(Woodward, 1987; Peyron et al., 1998).
Here, we only present variations of the two main associations:
- the mediterraneanetemperate association composed of Eurosiberian trees like Quercus, Fagus, Carpinus, Corylus, Alnus, Betula,
Tilia, Ulmus, ..., associated with mediterranean taxa such as
Quercus Ilex type, Olea, Phillyrea, Pistacia, cistus that reflects
warmer and moist climate characteristic of interstadials;
- the steppe to semi-desert association, composed of Artemisia,
Amaranthaceae-Chenopodiaceae and Ephedra, whose high
representations in pollen spectrum indicate dry and cold
climatic conditions of stadials.
3.2.2. Climate reconstructions deduced from pollen data
The modern analogue technique (MAT), firstly developed by
(Overpeck et al., 1985), was applied to the ODP 976 pollen sequence.
The MAT uses the squared-chord distance to determine the degree
of similarity between samples with known climate parameters
(modern pollen samples) to a sample for which climate parameters
are to be estimated (fossil pollen sample). The smaller the chord
distance is, the greater the degree of analogy between the two
samples. To calculate the climate parameter for the unknown
sample it is common practise to calculate the climate parameter as
the weighed mean of the closest n samples or “analogues”.
A minimum “analogue” threshold is often established beforehand
using a Monte Carlo method. For this analysis we retain the eight
nearest analogues with a distance inferior to this minimum. If less
than 8 analogues are found, no climate reconstruction is attempted
for that sample. The dispersion of the analogues around the
reconstructed value provides a partial estimate of the uncertainty,
which is related to the tolerance of the proxy to a relatively large
range of climatic. The MAT, like most of the approaches which aim
to quantitatively reconstruct the past climate from fossil assemblages, is based on the present day environment, and therefore
requires high-quality, taxonomically consistent modern datasets. In
this study, the method is based on an updated modern pollenclimate dataset which comprises 3530 pollen data sampled from
a wide variety of biomes (Bordon et al., 2009). Among these 3530
samples, more than 2000 taken from mosses samples, soil or core
2805
samples are located in the Mediterranean basin (Spain, Morocco,
Italia and Turkey). As in marine sediments, we removed Pinus from
the modern spectra as well as from the fossil spectra.
For each sample, the pollen percentages and the associated
biome are available, and the monthly climate variables have been
interpolated at each site using the high resolution climatic database of (New et al., 2002). Several bioclimatic parameters
controlling the plant distribution after Prentice et al. (1992a,b)
have been calculated for each modern pollen sample. For this
study, we have selected the mean temperature of the coldest
months (MTCO) and the ratio of actual over potential evapotranspiration (E/PE) which is calculated by a soil moistureebalance
model. In addition, we have reconstructed the annual precipitations (PANN) and the annual temperature (TANN) to allow
comparisons with published studies.
4. Results and discussion
4.1. Vil-stm27 stalagmite record
4.1.1. Vil-stm27 growth rate (GR)
The Vil-stm27 stalagmite chronology is anchored on 26 TIMS
UeTh ages which gives among the best dated European records for
the OIS3 period. There is a remarkable similarity between growth
rate curves of Vil-stm27, Vil-stm9, and Vil-stm14, with, however,
a better resolution for Vil-stm27 (Fig. 3). The millennial events in
Vil-14 are slightly offset towards older ages, but still within error
bars, compared the two others stalagmites records. Vil-14 was
dated with the MC-ICP-MS measurements while the other two
stalagmites were dated by TIMS. Theoretically this should only
change the accuracy, due to the smaller samples and a better
ionization efficiency, but not the absolute ages. The slight offset
thus remains still unexplained.
The Vil-stm27 growth curve is characterized by a relatively slow
growth (0.017 mm/yr) beginning between 49.9 and 46.6 ka followed
by a very high growth rate (0.28 mm/yr) between 46.6 and 44.1 ka. In
the same way than Vil-stm9 and Vil-stm14, the stalagmite growth
rate (GR) declined (to 0.014 mm/yr for Vil-stm27) from 40.4 ka to the
definitive growth at 31.5 ka. The Vil-stm9 stalagmite also had a very
fast growth rate between 50.3 ka and 40.3 ka, but its resolution is
lower and some small GR changes, showing up in Vil-stm27, are not
recorded (Fig. 3). Vil-stm14 GR is more monotonous and displays
a significant GR variation only at the top.
Relative GR changes, especially those occurring in several
contemporaneous stalagmites, already may point to hydroclimatic
changes, because they are mainly controlled by the drip rate and by
the Ca2þ seepage water content (Dreybrodt, 1988; Baker et al.,
1998). The GR variations in Vil-stm27 and companions indicate:
- three dry and cold periods between 48.2 and 46.6 ka, between
44.1 and 41.6 ka and between 40.4 and 31.9 ka;
- two main warm and humid periods between 46.6 and 44.1 ka
and between 41.6 and 40.4 ka.
This climatic pattern is confirmed by the stable isotope record.
Beside the climatic information, GR changes have an impact on
the time resolution of equidistant samples. For example, the time
represented of one sample varies from w600 yr to less than 10 yr in
Vil-stm27, with an average resolution of 53 yr during most of its
growth (from 20 mm to 713 mm from basis, representing the
period between 48.5 ka and 40.5 ka). After 40.5 ka, the average time
resolution is lower (203 yr) due to the GR slowing down. Similar
changes are observed on the other two Villars stalagmites: on Vilstm14, between 52.2 and 41.7 ka, the average time resolution is
81 yrs; it increases to 1066 years on the top part (41.7e28.9 ka). On
2806
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
Fig. 3. Vil-stm27 growth rate (GR) curve (blue), comparison with Vil-stm9 (red) and Vil-stm14 (brown) growth curves. Error bars display 2s errors. The growth model uses all Vilstm27 ages within error margin. The four ages, excluded from the age curve, show a slight age inversion and whose error bar is the largest. Note the good parallelism between all
three stalagmites, with high GR between w46 ka and w41 ka, and a significant GR slowing down from w41 ka until the synchronous definitive stop of all stalagmites at about 30 ka
1. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Vil-stm9, the average time resolution is 91 years, between 51.8 and
40.4 ka, it is 195 yrs on the last part between 40.4 and 31.8 ka.
4.1.2. Vils-tm27 stable isotope record
Along the Vil-stm27 profile, oxygen and carbon records display
a relatively similar behaviour characterized by a large isotopic
“bump” towards a decreasing d13C and d18O that occupies more
than one half of the stalagmite height (Fig. 4).
Measurements within single laminae carried out at different
isotopic level along the growth axis (4.6; 21; 43; 76 cm/basis;
Supplementary material), in order to test the isotopic equilibrium,
do not show any significant enrichment from the growth axis center
towards the edges. The only regular trend is very small: a 0.3&
increase at 76 cm/basis, during the slow growth rate period at about
35.4 ka 0.8. In addition, there is no significant d18O/d13C correlation
for this single laminae measurement suggesting that the deposits
formed in isotopic equilibrium. However, it is recognized that
neither a positive Hendy test nor a lack of correlation between d18O/
d13C can definitely exclude disequilibrium, as found in many modern
deposits, from Villars and from numerous other caves (Mickler et al.,
2006; Genty, 2008). A D47 test which consists in performing clumped isotope measurements on the carbonate and which is sensitive
to kinetics should certainly be a useful complement as recently
shown (Daeron et al., 2008). However, the possible isotopic
disequilibrium is not crucial for the present discussion, because we
do not attempt a quantitative reconstruction of temperatures.
We have attributed interstadial (GIS) numbers to the Vil-stm27
isotopic record by comparison with the published records from Vilstm9 and Vil-stm14, on a common time scale and based on the d13C
records which are less noisy than those of d18O. If the two main
isotopic “bumps” can be correlated with the GIS#12 and GIS#8 relatively easily, it is less obvious for the other events (GIS#9, 10 and 11)
but we have kept these GIS attributions for simplicity of the
discussion. Actually, we can observe that the more prominent DO
events recorded in the Villars isotopic records are those following
Heinrich events (H4 before GIS#8 at w39 ka and H5 for GIS#12 at
w48 ka). While the Greenland ice cores do not clearly record the
Heinrich events and thus exhibit similar amplitudes for the temperature changes associated with the different DO events, lower latitudes
records such as the Villars records are very sensitive to Heinrich
events so that some DO events preceded by H events are prominent.
Due to the strong variation of the growth rates, the aspect of the
record plotted against age differs significantly with respect to that
plotted against distance from base: GIS#8 is stretched due to the
low growth rate, and, more surprisingly, GIS#10 and GIS#11 are
contracted giving a confuse pattern with large isotopic variations in
a short duration (Fig. 5). The fact that the same accordion effect was
observed in Vil-stm9 and Vil-stm14 samples gives more confidence
in the timing of this period. However, the pattern is quite different
from what is recorded in ice core records where DO succession is
more regularly paced (NorthGRIPmembers, 2004). Several specific
features can be seen on the isotopic time series (Fig. 5, isotope scale
reversed):
- An isotope enrichment in both d13C and d18O between 48.6 and
46.6 ka: almost 3& in d13C and 0.8& in d18O; it is situated in
clean dark compact calcite between 2 and 5 cm from base,
above the basic discontinuity that shows clayey layers;
- An isotopic excursion between 46.6 and 42.6 ka (the large
isotopic “bump” of Fig. 4) marked by a d13C decrease of about
4.5& and a d18O decrease of about 1.4&;
- An unstable period between 41.6 and 40.5 ka where growth
rate is fast and stable isotopes records very variable;
- An other isotopic excursion between 38.5 and 34.6 ka characterized by smaller negative amplitude and low growth
rate;
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
2807
Fig. 4. Vil-stm27 stalagmite polished section and stable isotope record. Note the more regular d13C signal showing a large “bump” decrease that occupies more than one half of the
stalagmite. DO ¼ DansgaardeOeschger events associated with isotopic bumps. The top right d18O vs d13C graph shows the non significant correlation between both isotopes
(R2 ¼ 0.38).
- At the end of the growth, between 34.5 and 31.5 ka, the d18O record
displays a general increasing trend punctuated by w0.5& amplitude events while the d13C record also shows an increasing trend
towards the end but is characterized by an abrupt increase event
between 32.7 and 32.4 ka with very high d13C values (3.4&).
An important point is that the Vil-stm27 isotopic record is very
similar to the Vil-stm9 and the Vil-stm14 records found at different
locations in the same cave (Genty et al., 2003; Wainer et al., 2009). The
fact that both the growth rate and the stable isotopic records are very
close in the three stalagmites makes more solid the chronology and the
climatic interpretation which is a key point in order to compare these
records with other well dated records like NGRIP and other speleothems.
The isotopic signals are interpreted here in the same way as for
the published Villars records covering OIS3 and the last deglaciation (Genty et al., 2003, 2006): schematically, the calcite d18O
decreases during climate improvement because of a complex
combination of source, precipitation and temperature changes and
the d13C also decreases during warm episodes because of an
increase in the soil (and epikarst) microbial activity and in the soil
vegetation activity. Hydrology might have played a role in the d13C
changes too, especially during dry periods where prior calcite
precipitation might have occurred (Fairchild et al., 2000; McMillan
et al., 2005), but this is not demonstrated here.
The fact that the stalagmite started to grow while the isotopic
signal increases (2e5 cm/basis) may suggest that the basic discontinuity, which is contaminated with detrital layers and thus poorly
dated, coincides with a warm period (leading to low d13C values)
which in addition was humid and provoked a flooding in the Villars
cave. This flooding occurring during GIS#14, could have prevented
any speleothem growth in the lower galleries, exactly like it was
observed and suggested for the Vil-stm9 sample (Genty et al., 2003).
Following this decrease, the transition into the first long warm event
was measured with a much higher resolution than previously. It
occurred between 46.6 and 46 ka giving an average time resolution
of 12 yrs where a well marked plateau in the d13C signal and a YD like
event in the d18O record are recorded (Fig. 5).
4.2. ODP 976 pollen record and quantitative climate reconstruction
The ODP site 976 pollen record shows repetitive climate fluctuations during OIS4 and OIS3 (Fig. 6). The climate signal reconstructed from ODP 976 reflects two features:
- Four warm periods (80e66 ka, 60e48 ka, 46.2e39.5 ka,
38e30.5 ka) (Figs. 6 and 7). Temperate vegetation development was largely driven by rainfall as expressed by the similar
annual rainfall (PANN or Precipitation Annual) variations
related to the DO climate changes. These fluctuations clearly
depict the short-time DO oscillations with alternation
between warm interstadials and cold stadials. Thus temperate
trees curves may be easily annotated according to the chronology of the DO succession (Johnsen et al., 1992; Grootes
et al., 1993).
2808
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
-12
DO#8
-4.4
DO#10 DO#11
-8
-4
-6
-3.6
-4
-3.2
cm/basis
-2
80
70
60
50
40
30
20
b -12
DO#12
DO#8
-10
-2.8
10
-4.8
-4.4
-8
-4
-6
-3.6
-4
-3.2
-2
35000
-2.8
45000 U/Th age, year/2000
40000
-4.8
-9
-4.4
-8
-4
-7
-3.6
-6
-3.2
13C
-10
-5
18O
13C
DO#10 DO#11
c
18O
13C
-10
-4.8
DO#12
18O
a
-2.8
46000
13
47000
U/Th age, year/2000
18
Fig. 5. Stable isotopic record of Vil-stm27 stalagmite. a) d C and d O profile on a cm scale; b) d13C and d18O on the UeTh time scale, diamonds indicate dated points with 2s error
bars; c) details of the H5/GIS#12 transition; note that both d13C and d18O show asynchronous change to this major transition at w46.6 ka, but that they react differently afterwards,
possibly because of their different sensitivity to temperature, humidity and vegetation changes.
- Four drastic dry events (65e60 ka, 48e46.5, 39.5e38 ka,
30.5e29.2 ka) shown by the semi-desert pollen curve. These
large increases in semi-desert environments (more than 50%
in semi-desert taxa) illustrate a drastic decrease in the annual
rainfall (PANN) by more than 500 mm/yr, which is corroborated by a strong E/PE decrease. Very low E/PE values (18%)
typical of semi-desert conditions (Prentice et al., 1992b) are
reconstructed during each Heinrich events while the DO
oscillations are characterized by more temperate conditions
with E/PE values from 30 to 65%. This rainfall and E/PE
decrease is synchronous with annual mean temperature
drop (TANN or Temperature Annual) anomalies of 10e15 C.
This strong temperature decrease is mostly driven by a MTCO
(temperature of the coldest month) decrease. Enhanced
intense dryness in the west Mediterranean have been previously correlated to North Atlantic Heinrich events (e.g.
Combourieu Nebout et al., 2002; Sanchez Goni et al., 2002;
Moreno et al., 2002; Bout-Roumazeilles et al., 2007) and
ODP pollen record draws H6eH3. Even if the Heinrich events
strength is similar, H6 (65e60 ka) appears to be two times
longer than the other Heinrich events.
4.3. Vil-stm27 isotopic record in comparison to other “continental”
records
We compare the pollen records from core ODP 976 (Alboran Sea)
and from Lake Monticchio with the Villars isotopic record because
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
-12
H4
H3
H5
H6, OIS4
DO#12
DO#20
-10
Villars stalagmites
13
C
a
2809
DO#17
DO#8
DO#19
-8
-6
-4
U/Th age, year/2000
-2
60
4 0000
30000
50000
60000
70000
80000
0.03
DO#14
DO#17
40
0.01
DO#12
0
DO#8
20
-0.01
-0.02
0
ODP 976
temperate medit. forest
pollen grain, %
c
-0.03
30000
Monticchio woody taxa
pollen grain, %
4 0000
50000
60000
70000
80000
80
80
60
60
40
40
20
20
0
0
30000
d
Precession index
0.02
4 0000
50000
60000
70000
80
20
80000
PAZ 17c
PAZ 11
60
40
ODP 976
semi-desertic pollen grain, %
MD-04-2845, Atlantic forest
pollen grain, %
b
PAZ 7PAZ 9
PAZ 15
PAZ 5b
PAZ 13c
PAZ 5a
0
30000
40000
50000
60000
70000
80000
Fig. 6. Comparison between Vil-stm27 isotopic record (red curve), Vil-stm9 (purple) and Vil-stm14 (grey) stalagmite records (a) (Genty et al., 2003; Wainer et al., 2009). Diamonds
are UeTh dated points with 2s error bars, DO ¼ DansgaardeOeschger events, H ¼ Heinrich events. Comparison with: b) at the same latitude than Villars, the Atlantic forest record
from the Atlantic MD-2845 marine core (Sánchez Goñi et al., 2008) superimposed with the precession index curve; c) the Alboran Sea ODP 976 pollen record (Combourieu Nebout
et al., 2002) and d) northern Italy pollen record from the Monticchio Lake (Allen et al., 1999; Huntley et al., 2003; Brauer et al., 2007), PAZ ¼ Pollen Assemblage Zone. (For
interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
these records have a similar time resolution and are close to the
Villars site and situated in Europe more or less distant to the
northern ice sheets and the North Atlantic area.
4.3.1. Comparison with the ODP 976 pollen record, Alboran Sea
(36.12 N; 4.19 W)
The chronology of the ODP 976 record is mainly based on
wiggle matching with NGRIP oxygen isotope record (ss09sea
timescale, (Combourieu Nebout et al., 2002)), whereas the time
scale of Vil-stm27 is based on absolute UeTh ages. A peak to peak
correlation between both records therefore is not always perfect
and shows offsets related to the different dating methods. Average
time offset between Vil-stm27 and ODP 976 chronologies is
355 yrs, with minima up to 1000 yrs (around H6) and maxima up
to þ1500 yrs (around GIS#12) (Fig. 6). If we apply the last NGRIP
chronology GICC05 based on annual layer counting (Svensson
2810
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
-12
H3
H4 DO#12 H5
H6
DO#20
DO#19
-10
DO#17
Stalagmite
13
C
DO#8
-8
-6
-4
-2
a
30000
40000
50000
60000
70000
80000
U/Th age, year/2000
30000
40000
50000
60000
70000
80000
30000
40000
50000
60000
70000
80000
30000
40000
50000
60000
70000
80000
E/PE, %
80
60
40
20
0
rainfall, mm
b 1200
800
400
0
temperature, °C
c
20
10
0
-10
-20
d
Fig. 7. Comparison between Vil-stm27 and Vil-stm9 isotopic record (a) and climatic reconstructions from ODP 976 pollen record: OPD 976 E/PE reconstruction, mm and 1s error
curves (b); OPD 976 mean annual precipitation reconstruction, mm and 1s error curves (c); OPD 976 mean annual temperature C (dark brown) and mean temperature of the coldest
month (light brown, bottom) (d). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
et al., 2008), we observe that the H5-GIS#12 transition age is
getting younger by w500 yrs compared to the ss09sea chronology,
giving a better match with the Villars chronologies (Fig. 8). The
most pronounced offset occurred around the end of the H5 event
which is at w46.6 ka in the Vil-stm27 sample and at w47.9 ka in
the ODP record.
A first comparison between ODP 976 temperate pollen and the
Villars d13C records shows a relatively good correlation (Fig. 6). The
Villars cold phase (OIS4) marked by the stalagmite growth stop
shows a low temperate pollen abundance (i.e. <10%), especially
between 61 and 62.6 ka which coincides with the H6 event. This
growth stop occurred during a period where the d13C reached high
values (i.e. 6.5 to 5&; curve going down on the reverse scale
graph (a), Fig. 6). The same pattern is observed for the following
Heinrich events, H5 and H4, where low temperate tree abundances
are associated with high d13C values. Correlation around GIS#14 is
also difficult due to the growth stop in Vil-stm9 sample. The pollen
records lower resolution (i.e. GIS#12), but also the highly variable
Villars record in this time interval, makes the attribution of the
smaller warm events (i.e. GIS#9-11, Fig. 6) somewhat arbitrary;
a slow growth rate combined with a lower soil activity might be the
main cause. The correlation between semi-desert taxa abundance
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
a
-12
2811
DO#12
DO#20
DO#19
-10
DO#17
13
C
DO#8
Stalagmite
-8
-6
H4
H3
H5
H6
-4
U/Th age, year/2000
-2
30000
NGRIP temperature, °C
b
40000
50000
-30
60000
12
-35
5 6
7
11
8
10
-40
17
14
70000
19
80000
20
13
9
-45
-50
-55
30000
c
40000
50000
60000
70000
80000
0
0
DO#12 (?)
-200
DO#8 (?)
-4
-8
-400
-12
-600
d
20
30000
50000
60000
70000
80000
60000
70000
80000
DO#12
16
MD04-2845
Planktic SST, °C
40000
LE BOUCHET
rainfall anomaly, mm
LE BOUCHET
temperature anomaly, °C
200
4
DO#8
12
8
4
0
-4
30000
40000
50000
Fig. 8. Comparison between Vil-stm27 and Vil-stm9 isotopic record (a) and NGRIP temperature reconstruction (Huber et al., 2006) (b); Le Bouchet Lake temperature (red) and
rainfall (black) pollen reconstructions (Beaulieu de and Reille, 1992; Guiot et al., 1993) (c), foraminifera sea surface temperature reconstructions from MD04-2845 marine core
(black ¼ Summer temperature; orange ¼ Winter temperature) (Sánchez Goñi et al., 2008) (d). (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
in ODP 976 and high d13C in Villars stalagmites appears much
clearer (Fig. 6). Cold periods, especially the Heinrich events, are
characterized by a large increase in semi-desert pollen percentages.
H6 is marked by a peak of 58%, with a long duration from 63.2 ka to
60.0 ka. H5 and H4 events are very well marked with semi-desert
taxa reaching 70% while the stalagmite d13C increased up to 5.8&
and 6.4& respectively. Vil-stm27 has several other abrupt d13C
increases (41.2 ka, 40.6 ka, and 32.5 ka; Fig. 6) which, despite their
large amplitude, are not correlated with Heinrich events but rather
Table 3
Heinrich events age and duration from semi-desert pollen data and Villars UeTh
chronology. Ages are in ka.
Heinrich event
UeTh age begin/end
Duration, ka
H4
H5
H6
39.35 / 38.23 0.62
47.74 / 46.68 0.8
63.27 / 60.94 0.8
1.12 1.2
1.06 1.6
2.33 1.6
2812
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
with less marked cold events in the OPD 976 and Monticchio
records. Vil-stm7 and Vil-stm9 growth stopped just before the H3,
which is very well marked in the ODP 976 record by a huge semidesert extension coupled to a large temperate tree retreat. The Vilstm14 seems to have stopped slightly later, during the H3 event
within dating error margins.
It is tempting to estimate the duration of the Heinrich events
with the help of the d13C Vil-stm9 and Vil-stm27 profiles (Fig. 6).
The duration of Heinrich event 6 is less accurate because the
stalagmite growth likely stopped before its beginning. Results show
that the duration of the H4 and H5 events varies from a few years
and 2 ka (considering the dating errors, Table 3). The H4 event age
deduced from UeTh datings is in agreement with estimations from
Roche et al. (2004) and its w1 ka duration is close to the duration
found in the MD-95-2042 marine core, from south of the Iberian
Peninsula (Sepulchre et al., 2007). The later study raised a time
delay between the ice rafted debris and the pollen records of about
1 ka. A possible time delay between the d13C and the pollen record
might exist here too. In fact, the d13C is mainly controlled by the soil
pCO2 which itself is linked with the atmospheric temperature via
soil and vegetation activity. A Large amount of rafting ice at low
latitudes in the North Atlantic likely influenced the temperature
above the VillarsCave, thus the soil and the vegetation activity and
then the d13C. Similarly, the vegetation change from temperate to
semi-arid might have taken up to a century in the continental
regions around site ODP 976, leading to a possible time offset
between both records. A time offset is also possible due to the NeS
distance between Villars and ODP 976. However, we here reach the
limit of a comparison between two different archives with
distinctly independent chronologies and the duration of such
a delay remains in the error margin of the absolute ages of the
studied records (supplementary material).
4.3.2. Comparison with the Monticchio pollen record, southern Italy
(40 560 ; 4000 N; 15 360 3000 E, 656 masl)
The Monticchio Maar Lake is among the best resolved continental
paleaoclimatic record in Europe. Although still under the influence
of the Atlantic depression pathway it should be significantly less
influenced by the northern ice sheets and by the North Atlantic
circulation compared to the Villars site (Allen et al., 1999, 2000;
Brauer et al., 2000, 2007) and more dominated by variations of the
subtropical system. The time resolutions in Monticchio and Villars
records are comparable: w200 yr for Monticchio and in average
w90 yr for Villars. The time scale of the Monticchio record is constrained by two independent chronologies: varve counting and the
40
Ar/39Ar ages of clearly identifiable tephra layers (Brauer et al.,
2002; Wulf et al., 2004). During the period coinciding with the Vilstm27 growth (w50 ka to w31), three dated tephra layers where
found (TM-17f, TM-18 and TM-19). Varve dating is in very good
agreement with calibrated radiocarbon ages for TM-17f (Pererino
Albano Tephra), but for the Campanian Ignimbrite (TM-18) the varve
age of ca 36.7 ka BP is at the lower limit of an Ar/Ar date of tephra
material from the LM core (37.1 0.4 ka BP; (Deino et al., 1994)) and
particularly of Ar/Ar dates on proximal material ranging from 38.5 to
41.0 (weighted mean: 39.28 0.11) ka BP; (De Vivo et al., 2001)). This
would indicate an underestimation of varve counts between TM-17f
and TM-18, which in turn is not unlikely due to poor varve preservation within the H4 interval of the LM core. Therefore, the largest
age discrepancy appears for H4, probably enhanced by an imprecise
attribution of the cold event to the pollen record (Wulf et al., 2004).
In general, apparent differences between the Monticchio and other
records (Fig. 6) are likely the consequence of the different methods
used to construct the chronologies and also due to sometimes
imprecise attribution to H-events where the dating error margins
are larger.
Main vegetation features observed at the ODP 976 sites are also
observed in the Monticchio record: forest and open wooden steppe
developed during interstadials, steppe and tundra characterize
stadials (Fig. 6c). Interestingly, there is striking similarity between
the woody taxa percentage of Monticchio and the d13C Villars
stalagmites profile of (Fig. 6): between 50 ka and 30 ka, the two d13C
troughs can be correlated with pollen assemblage zones (PAZ). In
a first publication PAZ 11 was associated with GIS#11,12,13 in GISP2,
the “Pile” and the “Moershoofd Glinde” events in Central and
Northern Europe palynostratigraphy respectively (Allen et al.,
2000). However, the most recent chronology shifts this period
towards older ages which makes it match with the GIS#14 event
(Brauer et al., 2007). Consequently, the large isotopic bump of Villars that includes GIS#12 can be associated with the PAZ 9 in
Monticchio (Fig. 6). GIS#12 was likely warm and humid with fast
growth rate and low d13C, consequence of intense soil and vegetation activity. This is consistent with the PAZ 9 characteristics
where a high percentage of woody taxa (w55% with Quercusw20%,
Betula, Ulmus, Fagus) testifies a woody steppe with relatively warm
and humid climate suggesting a similar climate around the Villars
Cave and around Monticchio Lake (Allen et al., 2000). Between H5
and H4, both records show a high variability, making sometimes
difficult the identification of individual DO events, especially GIS#9,
10 and 11 (Fig. 6). By continuing the correlation between both
records, GIS#8 in Villars is correlated with the PAZ5b (Fig. 6). It is
also characterized by a woody steppe in Monticchio (w45% of
woody taxa) with less Quercus (w10%) so a climate similar to PAZ9,
but with less woody taxa and thus likely a dryer and colder climate.
This is consistent with the Villars record where the growth rate
decreased significantly since 40 ka and where d13C decreased,
suggesting a dryer and colder period (Fig. 6). Finally, the synchronous stop of the three Villars stalagmites at w30 ka coincides with
the end of the PAZ 5a where woody taxa decreased to the advantage of herbaceous taxa (i.e. Artemisia) characterizing a cold steppe
(Allen et al., 2000) and a much drier climate both at Villars and
southernmost at Monticchio too.
One of the most striking patterns found in the Villars isotopic
record is the pronounced isotopic trend observed between the GIS#12
optimum at w45 ka and the stalagmites growth stop at w30 ka
(Fig. 6). The general d13C increase, coupled with a growth rate
decrease in all three stalagmites, suggests that a general cooling is the
main cause of this trend (see discussion Section 4.3.5). This trend is
not clearly marked in ODP 976 where a cooling trend is observed only
after 39e37 ka with a general decrease in the woody taxa percentages.
It is much more pronounced on the Monticchio record where the
woody taxa decrease significantly between PAZ 9 and PAZ 5b.
At the same latitude than the Villars Cave, the closest studied
marine core MD04-2845 from the Biscaye Bay displays, despite its
lower resolution, a well marked Atlantic forest decreasing trend
(Betula, Corylus, Quercus deciduous type, Carpinus and Fagus)
between the GIS#14, GIS#12 and the GIS#8 (Sánchez Goñi et al.,
2008). These observations suggest that a general climatic deterioration occurred at the 45 N latitude since at least about 45 ka (and
possibly earlier as shown by the former marine pollen record),
punctuated by warm interstadial events (Fig. 6). At Monticchio,
about 5 south, the cooling trend seems to start also at around
45 ka. However, at our southernmost site (ODP 976, at 36 N), this
deterioration trend seems to occur later, i.e. after 39e37 ka (Fig. 6).
Thanks to rainfall and temperature reconstructions that cover this
period, especially in the ODP 976 record, more light is given to this
climatic change and to the observed regional differences.
4.3.3. Rainfall pattern between 50 ka and 30 ka
4.3.3.1. Stadials and Heinrich events. Rainfall reconstruction from
the ODP 976 record (Fig. 7) shows that Heinrich events are much
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
dryer (i.e. < w500 mm/year) than all the other periods of the
record, which is in the order of magnitude of the reconstructions
made from the nearby marine core MD95-2043 (Sanchez Goni
et al., 2002). This is also in agreement with the pollen-based
reconstruction from the Lake Le Bouchet (Guiot et al., 1993), which,
despite its lower resolution, dating uncertainties and the fact that
this pollen reconstruction was based on a restricted modern pollen
dataset, yields a rainfall difference between GIS and Heinrich
events between 150 and 300 mm (Fig. 8). These dry periods,
observed at the Alboran Sea, are also detected northward, at Villars
Cave where the dryness is testified by the high stalagmite d13C
values (Figs. 7 and 8) which are due to the vegetation density
decrease (leading to a higher calcite d13C), and to a possible prior
calcite precipitation that is likely to occur during such dry periods
(Fairchild et al., 2000).
ODP 976 record shows that rainfall also decreased significantly
(by w500 mm) during other stadials between H5 and H4 and
between H4 and H3 (Fig. 7). Their durations appear to be shorter
than the Heinrich-associated events and some of them seem to
coincide with the sharp increases of d13C already mentioned on the
Vil-stm27 stalagmite at 41.2 ka, 40.6 ka and at 32.5 ka (Fig. 5). Other
short events are not recorded on the speleothem d13C record
because of either regional differences or because of their lower
amplitude and shorter duration.
During at least one of these cold periods (Heinrich event H4), it
was suggested that an important rainfall gradient occurred
between NW (Atlantic side) and SE (Mediterranean side) Iberia
suggesting that the Villars site was more humid than ODP site
during Henrich events (Sepulchre et al., 2007). Modelling Heinrich
event conditions using an atmospheric general circulation model
(LMDz with a high resolution over the western part of Europe,
(Sepulchre et al., 2007)) suggests that absolute mean annual rainfall
was w600 mm in Villars while it was w50 mm near ODP site 976
(Sepulchre et al., 2007). This simulated value seems to be underestimated with respect to the rainfall reconstruction from ODP 976
which shows less dry Heinrich events with 150e200 mm/yr for H3,
H4 and H5 events (Fig. 7); this is also the case for the nearby MD952043 core where annual precipitation values are around 300 mm
(Sanchez Goni et al., 2002). Rainfall anomalies from today obtained
from the ODP 976 for H4 (300/400 mm) are consistent with the
values inferred from pollen for the last glacial maximum period in
Padul (south of Spain) with other palaeoclimatic reconstruction
methods as the plant functional type method or the inverse
modelling method (Peyron et al., 1998; Wu et al., 2007; Guiot et al.,
2008). However, annual precipitation anomalies close to 150/
200 mm are reconstructed for the Mediterranean region when
the lowering of the atmospheric CO2 to 200 ppmv is taken into
account in the inverse modelling reconstruction (Guiot et al., 2008).
4.3.3.2. Interstadials. Interstadials (GIS) are generally humid with
an annual rainfall between 600 and 800 mm/yr in the ODP 976 site
(Fig. 7). These values are slightly higher than the present day ones
(580 mm; Table 3) but are in the same order of those obtained in
the nearby MD95-2043 core. Although the GIS#12 event is the
most prominent warm and humid event recorded in the Villars
stalagmites (characterized by low d13C values and high growth
rates), it does not show a particularly well marked rainfall increase
in the ODP 976 pollen record (w744 mm/yr for GIS#12) compared
to the other interstadials. Several DO events are more humid like
the GIS#8 which reaches 920 mm/yr (Fig. 7). In the marine core
MD95-2043 the rainfall reconstructions displays a similar pattern
than the nearby ODP 976 record with a DO#8 slightly more humid
than the GIS#12 and in the same range (between 700 and 800 mm/
yr). Rainfall reconstruction from the Lake Le Bouchet record reveals
no significant trend in the rainfall reconstruction between GIS#12
2813
and GIS#8, instead a cooling trend is well visible despite its much
lower resolution than the other records (Fig. 8). Note that the
pollen-based rainfall reconstructions might have limits in distinguishing such decreasing trends inside the humid periods
probably due to the Mediterranean ecosystems sensitivity, and to
the fact that the difference in the temperate taxa is too small to
produce significant rainfall changes because the modern pollen
analogues taken in the Mediterranean biomes cover today a relatively wide rainfall amount.
Dry periods can be associated with low growth rates because of
a decrease in the flow rate feeding the stalagmite and because of its
consequence on the limestone dissolution due to a lower soil and
vegetation activity (less Ca2þ in the seepage water is a major cause
for slowing down the speleothem growth; (Dreybrodt, 1988)). It is
interesting to note that the Vil-stm27 growth rate is low, not only
during the Heinrich event H5, which coincides with the growth
beginning, and at the growth end, which covers H4 and GIS#8
events, but that there is a significant growth rate decrease in the
middle of the stalagmite just after the d13C peak of GIS#12, when
the climate started to deteriorate (Fig. 8). This suggests that, at least
at Villars the climate is getting dryer from w44.3 to w41.7 ka and
that the vegetation activity was reduced during this period. The
upper part of the stalagmite, from w70 cm/basis to the top, is also
characterized by a reduction of its diameter (as observed in the
other two Villars stalagmites) demonstrating that water seepage
was strongly reduced at that time despite the occurrence of an
important GIS event (GIS#8), characterized by a high humidity in
the Mediterranean area (Fig. 4). These differences between Villars
and ODP 976 could be related to the forest cover differences
observed between Atlantic and Mediterranean pollen marine
records. During the GIS#8, the forest cover amplitude can be linked
to the humidity and appears more developed in the Mediterranean
sites than in the Atlantic ones as revealed in former studies too
(Sánchez Goñi et al., 2008).
4.3.4. Temperature and evapotranspiration pattern between 50 ka
and 30 ka
Contrary to the rainfall record, the temperature reconstruction
from the OPD976 core does not show significant changes all along
the record and only the Heinrich events are well marked by
a temperature drop of w10 C (Fig. 7). Winter temperature values
agrees well with the signal obtained for the last glacial maximum in
south of Spain with the plant functional type method (Peyron et al.,
1998; Jost et al., 2005) but are 5e8 C lower than those inferred
with the inverse vegetation modelling method with a glacial level
of CO2 (Wu et al., 2007; Guiot et al., 2008).
Situated at same latitude as the Villars Cave and about 300 km to
the west, the MD04-2845 marine core records the vegetation
changes of hydrographical basins (Loire, Gironde, Adour) in western
France. The sea surface temperatures estimated from planktic
foraminifera assemblages in MD04-2845, which is rather close to
Villars, revealed that august SST increased by w14 C 2 C between
H5 and GIS#12 (Fig. 8d) while the February SST increased by w12 C
(Fig. 8d) (Sánchez Goñi et al., 2008). During the next important
climatic transition, between H4 and GIS#8, summer and winter
temperature changes were from 12 C to 10 C 2 C respectively.
Consequently, during warm phases (GIS), the Quercus, Betula forest
expanded in SW-France, while during cold and dry periods (stadials
and H) steppic plants developed (i.e. Artemisia). The Villars Cave
area is part of the Gironde hydrographical basin, thus it is very likely
that the d13C variations observed in the stalagmites is the direct
consequence of the temperature changes acting on the vegetation
type and density and on the soil microbial activity.
The Lake Le Bouchet pollen record, at about 200 km east from
the Villars Cave, yields a temperature reconstruction that mimics
2814
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
also the Vil-stm27 d13C record (Fig. 8) (Beaulieu de and Reille, 1992;
Guiot et al., 1993). GIS#12 and GIS#8 events display a temperature
anomaly increase (between the coldest and warmest phases) of
about 8 and 4 C respectively which is in the order of the Atlantic
SST and ODP 976 records. These continental stadials/interstadials
temperatures changes are of the same order of magnitude than
temperature changes that mark the onset of the GIS 12 and 8 in
Greenland (Huber et al., 2006). From the NGRIP record, the DO
warming appear to have been extremely rapid with rates from
0.3 C/decade up to 1 C/decade which make abrupt transitions at
the onset of the GIS in about 200 years. The abrupt d13C changes
observed in the Villars d13C record between H5 and GIS#12
(between 46.6 and 46.5 ka) seems to be in agreement with this
value (Fig. 7). This shift may coincide with the 12.5 C temperature
increase above Greenland and to the w12 C abrupt temperature
increase observed in the BiscayBay record (Fig. 8).
It is interesting to note that the best correlation between the
stalagmite d13C and the ODP 976 pollen reconstruction data is
obtained with E/PE (ratio of actual over potential evapotranspiration) which serves as a moisture availability index showing to
which extent the soil moisture supply satisfies atmospheric moisture demand (Fig. 7). The E/PE anomalies (15%) reconstructed
here for the Heinrich events are consistent with the values reconstructed for south Spain in Padul during the last glacial maximum
(Peyron et al., 1998; Jost et al., 2005; Wu et al., 2007).
Except for a part of the OIS4, cold and dry periods can be correlated to low E/PE while warm/wet ones correlate with high E/PE
values. The E/PE curve illustrates clearly the ecosystems shift from
steppe/desert to temperate ecosystems: following Prentice et al.
(1992a) low E/PE values (below 18) characterize desert or semidesert ecosystems. The E/PE value of 15e20% reconstructed in the
Alboran Sea for the Heinrich events agree well with the Prentice et al.
study. Transitions between Heinrich and GIS are particularly well
marked showing an E/PE mean increase of w50%. Note that Holocene (unpublished results) E/PE values are close to those during
interstadials suggesting that water availability was similar during
GIS than at present days. Beside the fact that ODP 976 is located in
a warmer and dryer area, relative changes between stadial/interstadial successions in E/PE at Villars were likely similar to the ones
observed at the ODP site. Because the E/PE parameter is close to the
soil water quantity that is used by the vegetation to grow above the
VillarsCave, it has a great impact on the vegetation growth and
development, thus, on the biogenic CO2 production and finally on
the calcite d13C. Future comparison with closer pollen/speleothem
sites will be of great interest to see the impact of the infiltrated water
on the speleothem isotopic records. The main unknown factor here
is the role of dry periods in the d13C increase because in such a case,
both vegetation activity and hydrological conditions like prior
calcite precipitation will control the d13C in the same way (d13C
increases when the climate is colder and dryer).
To resume, based on the comparison between isotopic Villars
record and vegetation and climate reconstructions from marine
core ODP 976, MD04-2845 and Lake Monticchio we confirm that
low calcite d13C values in Villars are mainly linked with high
temperature and development of the temperate forest while high
isotopic values coincide with low temperature and dryness.
continues to increase (warming marked by a decreasing d13C) while
the NGRIP cools down. The end of the warm periods is marked by
an abrupt cooling recorded in both archives. This contrasting trend
between NGRIP and South France speleothem records has been
noted previously for the BøllingeAllerød period (Genty et al., 2006)
and in the Ammersee lake record (von Grafenstein et al., 1999)
however in a deglaciation context, different from OIS3 DO events.
More recently, such opposition has also been noted over GIS events
12 and 8 between the surface temperature reconstruction at GRIP
and vegetation reconstruction on the Iberia margin (Goni et al.,
2009). Here, the same pattern is recorded but with climatic
reconstructions for higher latitudes in Europe suggesting that the
temperature evolution recorded in the Greenland ice core during
the GIS is actually specific to Greenland. Hereafter, we present
a possible explanation for the differences of behaviours between
Europe and Greenland involving the role of oceanic currents and
the ice sheet dynamics. We distinguish 4 phases (Fig. 9):
- phase 1 (Greenland Stadial e GS): the North Atlantic area
undergoes a cold period while Antarctic is warming, and heat
accumulates in the South. During this period, the MOC is
reduced (EPICA, 2006);
- phase 2 (transition between GS and GIS): at the end of phase 1,
temperature abruptly increases in the North Atlantic associated
with the resumption of MOC and probably a decrease of North
Atlantic sea ice cover (Renssen and Vandenberghe, 2003). The
onset of MOC explains also why temperature in Antarctica
begins its decrease at this time through a simple bipolar
seeesaw mechanism (Stocker, 1998; Stocker and Johnsen,
2003);
- phase 3 (GIS): This time period is characterized by a continuously slow cooling in Greenland while the temperature
continues growing until half of the GIS in south-west France
and in the Mediterranean regions (Fig. 9). This temperature
decreases in Greenland can be induced by the ice sheet growth
isolating Greenland from lower latitudes (Shackleton et al.,
2000; Siddall et al., 2003; Rohling et al., 2008). Another
possibility would be that melting of sea ice or of ice sheet at the
edges induced by the strong warming at the beginning of the
GIS shifts deep water convection zone and thus the polar front
southward (von Grafenstein et al., 1999; Goni et al., 2009);
- phase 4 (onset of the GS): At a certain point, temperature in the
Northern Atlantic and in our lower latitudes records drops
3
warm
4
cold
4.3.5. Different DansgaardeOeschger expressions at high and
temperate latitudes
While the GIS recorded in ice core d18O have a typical saw-tooth
shape with an abrupt warming at the beginning followed by
a gentle cooling until an abrupt cooling at the end (Fig. 8), the GIS
recorded in Villars stalagmites d13C is different: after the abrupt
increase synchronous with the NGRIP one within dating uncertainties, the optimum is not reached and the climatic signal
2
1
time
Fig. 9. Schematic DansgaardeOeschger phases (glacial stadial/glacial interstadial/
glacial stadial succession) in Groenland (NGRIP, thin continuous line), Antarctica
(EPICA, dashed thin line) and in Villars records (thick line) showing the opposite
timing between north and south ice records (bi-polar seeesaw) and the specificity of
the Villars record compared to the ice core ones. Note that the main difference
between NGRIP ice record and the lower latitude Villars record is the shape of the
phase 3, suggesting local influences on the former record (see text for details).
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
within several hundreds of years (i.e. abrupt cooling after
GIS#12, GIS#8 in Villars, Fig. 8). This shift is associated with
a shutdown of the MOC, the Polar Front reaches its southernmost position and the Antarctica displays the onset of a slow
warming.
DO#12
-11
24.5
C
23
13
23.5
DO#17
DO#8
-9
-8
Stalagmite
24
-7
500
460
480
-6
440
-5
-4
H5
-3
22.5
480
DO#20
-10
H6
-1
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
O
-12
DO#8
-10
-1
-5
0
-4
1
-3
2
-2
0.02
0.04
-14
-15
10000
20000
30000
40000
50000
60000
70000
80000
Soreq,
90000
520
DO#8
DO#16
DO#12
DO#14
500
Hulu
480
-8
460
Dongge
-6
440
-8
Santana
-6
-4
500
490
480
470
460
450
440
-4
-2
Botuvera
0
10000
20000
30000
40000
50000
60000
70000
80000
0
90000
30°N inso. (JJA)
30°S inso. (DJF) Chineese Caves
0
-13
O, per mil
0
-10
18
-0.02
-12
18
18
Sokotra,
-0.04
O, per mil
b
Kleegruben,
-6
-11
O
-2
O
-7
-7
-10
18
-8
DO#14
DO#12
-3
-9
18
-11
-6
440
400
Brazilian Caves
C
13
U/Th age, year/2000
0
a
Sofular,
460
420
-2
22
Precession
45°N JJA
insolation
Obliquity
65°N Jul.
insolation
that explains this difference because we know very little about what
happened exactly during these interstadials phases that followed H5
and H4 events (did the NH ice sheets melt or develop? Did both the
Laurentide and Fennoscandian ice sheets react in a similar way or in
opposite? How evolved the sea-ice cover and ocean circulation
around Greenland and Iceland?). The possibility of ice-melting may
have increased the East Greenland current width, the polar front
moved then from the Greenland coasts towards south-east provoking
The main difference between Greenland and Villars DO patterns
occurs during the phase 3 (GIS) (Fig. 9). There is no certain mechanism
-12
2815
Fig. 10. South France speleothem isotopic record compared with other contemporaneous speleothem records. a) speleothem isotopic records from Villars Cave (45.44 N, 0.79 E)
and Chauvet Cave (44.23 N,4.26 E) (red: Vil-stm27; purple:Vil-stm9; orange: Vil-stm11; pink: Chau-stm6) superimposed with the Earth obliquity (blue), 65 N insolation (yellow)
and 45 N insolation (black); b) light bleue: Kleegruben Cave record (47.08 N,11.67 E)., Austria (Spötl and Mangini, 2002), orange: Sokotra record (12.5 N, 53.5 E) (Burns et al., 2003;
Burns, 2004), black: Soreq Cave record (31.45 N,35.03 E) (Bar-Matthews and Ayalon, 2002), Sofular Cave record (Fleitmann et al., 2009); c) chinese speleothem records: Hulu
(32 300 N,119 100 E; dark green) and Dongge (2517N, 108 5E; light green) caves records (Wang et al., 2001; Dykoski et al., 2005), and Brazilian speleothem records: Santana Cave
(24.51 N,48.72 W) and Botuvera Cave (27.22 N,49.15 W) (Cruz et al., 2006). Superimposed: 30 N summer insolation (grey), 30 S winter insolation (black), precession index (red).
(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
2816
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
a regular cooling in Greenland as long as the East Greenland current
develops while, in middle latitude of Western Europe (Villars), the
warming continued as long as the MOC was active enough. Sea ice
cover in the Greenland and Iceland Sea possibly increased until the
polar front reached an other threshold, close to the Norwegian
Atlantic current, blocking again the MOC in this region provoking an
abrupt cooling which makes the end of the GIS (phase 4). Indeed, this
hypothesis should be tested with coupled climatic models but
unfortunately, up to now, difficulties exist in simulating the regional
climate evolution over the DO events and to properly predict the
different evolutions of the Fennoscandian and of the Laurentide ice
sheets.
Fig. 11. South France speleothem isotopic record compared with the sea level, north hemisphere insolation, atmospheric CO2 concentration and the north hemisphere ice sheets
extension. a): speleothem isotopic records (red: Vil-stm27; purple: Vil-stm9; orange: Vil-stm11; pink: Chau-stm6) (Genty et al., 2003; Genty et al., 2005) and the sea level: (light
blue: sea level reconstruction from (Waelbroeck et al., 2002) on the SPECMAP timescale; dark blue: part of the oxygen isotope composition of benthic stack (Lisiecki and Raymo,
2005) that can be explained by ice-sheet contribution (Bintanja et al., 2005) and matched on the recent EDC3 timescale (Parrenin et al., 2007); b): 65 N July insolation (Berger and
Loutre, 1991), atmospheric CO2 concentration from Vostok (black) (Cuffey and Vimeux, 2001) and from Greenland (green) (Indermuhle et al., 2000); bottom: numerical simulations
of the ice sheets extents from (Bonelli et al., 2009). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
4.3.6. A cooling trend between w45 ka and w31 ka
A general cooling is found in the three studied Villars stalagmites that cover OIS3, it is testimonied by: 1) an isotopic trend
towards enriched isotopes from w45 ka to w31 ka (Fig. 6); 2)
a growth rate decrease from 40 ka to the 31 ka synchronous speleothem stop (Fig. 3).
Similarly to the Villars record, the nearby Le Bouchet Lake
temperature reconstructions (and if we trust the chronology)
display a GIS#8 significantly colder than the GIS#12 (Fig. 8). At the
same latitude, the marine core MD04-2845 also displays
a temperature decrease of about 4 C between GIS#12 and GIS#8
maxima (Sánchez Goñi et al., 2008) (Fig. 8). But, contrary to Villars,
the cooling after 30 ka is not so well expressed and there are still
significant warm events after the Villars stalagmites stopped
growing (i.e. GIS#7) (Fig. 8). Such a cooling trend is suggested in the
NGRIP water isotopic record too, with a slight decrease of the mean
d18O levels over GIS and GS over OIS3. However, caution is needed
in interpreting such a record in term of Greenland temperature
because (1) it is strongly affected by seasonality of the precipitation
and (2) the saturation effect may affect the d18O of Greenland
precipitation during cold periods (Krinner et al., 1997; MassonDelmotte et al., 2005). Southernmost, around the AlboranSea, the
pattern is different: there is no significant decreasing trend in the
ODP 976 temperature reconstructions (Fig. 7). A slight decreasing
trend between GIS#12 and GIS#8 is observed on the E/PE reconstruction suggesting possible dryer conditions towards the end of
OIS3 (Fig. 7).
Most of other mid-latitudes speleothems do not cover continuously this period, as the high resolution record from Austria
centered around the GIS#14 (Spötl and Mangini, 2002) or, southernmost, the Sokotra records (Burns et al., 2003; Burns, 2004)
(Fig. 10b). In contrary, at lower latitude the Chinese and South
American stalagmites display continuous records that fit well into
the local summer insolation changes, mainly controlled by the
precession and where the DO events are superimposed (Wang
et al., 2001, 2008; Cruz et al., 2005) (Fig. 10). Contrary to Villars
stalagmites, these records do not show large differences between
DO optima but they appear much more regular in terms of isotopic
amplitude. On the Eastern side of the Mediterranean Sea, the Soreq
cave record (Israel) shows humid periods, linked to Sapropel events
and more or less paced by the precession variation (Fig. 10b) (BarMatthews et al., 2000). However, the DO events superimposed on
this variation are not clearly marked between 80 and 30 ka. Close to
the former site, a very recently published stalagmite isotopic series
from the Sofular Cave (northwestern Turkey) displays a remarkable
record where most of DO events are clearly visible (Fleitmann et al.,
2009) (Fig. 10b). Beside Villars records, this is the only speleothem
record that shows a high d13C-sensitiveness to climate which is
explained by the soil and vegetation changes. There is no
decreasing trend between GIS#12 and GIS#8 optima as observed in
Villars record, but, in contrary, the GIS#8 appears warmer than the
GIS#12 (assuming that the vegetation response to the climate is
similar at both sites).
Differences between Villars (Atlantic climate) and low latitude
or Mediterranean records could be due to their different sensitivity
in the precession and obliquity signals (Sánchez Goñi et al., 2008).
The Villars d13C record seems beyond doubt to follow the obliquity
with minima close to the observed hiatuses and maximum close to
the GIS#12 optimum, while the monsoon-related speleothems
clearly follow the precession (Fig. 10). However, looking closely,
there is a significant time offset between obliquity and the isotopic
signal that ranges from w10 ka to w5 ka and a better fit occurs with
the 65 N July insolation which is much more sensitive to the
precessional signal (Fig. 10a). Consequently, a simple duality
between a Mediterranean climate, linked to the precession
2817
variation, and an Atlantic middle latitude climate, mainly
controlled by the obliquity remains unsatisfactory here. As suggested by the new eastern Mediterranean Solufar record, a NWeSE
gradient might also have a significant influence on these regional
climate differences.
4.3.6.1. A local ice sheet influence? An interesting feature is that the
Villars climatic hiatus during which no speleothem grew coincide
with low CO2 level (<200 ppmv) and relatively low 65 N July
insolation (<445 W/m2) (Fig. 11): between w67 and 61 ka which is
the previously called “Cold Villars phase” and between w30 and
w16 ka called the “Villars Glacial Maximum” (the 52e56 ka hiatus
which is not accompanied with d13C changes was interpreted as
a possible flooding in the cave) (Genty et al., 2003). Both Villars
hiatus periods also coincide with sea levels lower than w80 m
suggesting a closed link between the speleothem growth period
and the ice sheet development. A recent numerical simulation
(Bonelli et al., 2009) performed with the climate intermediate
complexity model (CLIMBER, (Petoukohov et al., 2000)) fully
coupled with a 3D ice sheet model (GREMLINS, (Ritz et al., 1997))
demonstrated that at about w70 ka (coinciding with the first Villars
hiatus) and, above all, just after 30 ka (coinciding with the second
Villars hiatus and all three stalagmites stops), the Fennoscandian
Ice Sheet experienced a large expansion phase (Figs. 11 and 23 ka
and 65 ka maps). This ice sheet increase is linked with specific low
CO2 concentrations periods linked with low insolation (Bonelli
et al., 2009). Thus, extreme cooling in Villars area can be
explained by a stop in the heat brought by the North Atlantic
Current and its sub-branches, with consequences on the development of the Fennoscandian Ice Sheet and continental glaciers in the
Alps and in the Massif Central about 200 km east from Villars Cave.
A general mean annual temperatures decrease over the Western
and Northern Europe occurred with permafrost more or less
continuous at Villars as testimonies the maximum permafrost
extension in France during the LGM (Texier and Bertran, 1996; Van
Vliet-Lanoë, 2000). Westerlies depression pathways went southward yielding a dryer climate that, superimposed on general
atmospheric cooling, blocked the water infiltration and produced
hiatuses in stalagmite growth (“Villars Cold Phase” and “Villars
Glacial Maximum”, Fig. 11). Consequently, the observed cooling
trend between the GIS#12 optimum at about 45 ka and the
stalagmite growth stop, 31 ka ago, can be due to northern ice
sheets local influence (i.e. ice shelves that are not simulated by the
model) and by the development of the nearby glaciers. The Sofular
speletothem record, located much farther to the Fennoscandian ice
sheet and to the north Atlantic than Villars, does not display
a similar cooling trend and its glacial hiatus is much shorter
highlighting the importance of the regional cooling impact on
westernenorthwestern Europe (Fig. 10).
5. Concluding remarks
The former millennial-scale climate record of Villars Cave is here
confirmed by a new stalagmite record that displays similar growth
rate behaviour and isotopic signatures. The interpretation of the
d13C record is improved by the comparison with pollen records
from continental and marine cores, especially from ODP 976 and
Monticchio, whose resolutions are comparable to the Villars record.
This allows us to attribute with confidence high d13C and low
growth rate to cold and dry conditions while low d13C and fast
growth rate are related to warm and humid interstatials.
The well dated Villars records are combined with pollen
records for which the modern analogue technique provides
quantified records and give a specific climatic pattern of the
South France climate for the time period between 53 ka and
2818
D. Genty et al. / Quaternary Science Reviews 29 (2010) 2799e2820
30 ka. Firstly, the OIS3 climate is marked by an abrupt warming
at 46.6 ka 1 ka which is the onset of the major GIS#12
interstadial. The pollen-based temperature estimates suggest
a warming of about 8e10 C at both Villars latitude and at
southernmost Mediterranean sites. This warm period lasted
about 2.5 ka 0.5 ka, until w43. In the Villars record, between
the GIS#12 and GIS#8, climatic events are less well individualized possibly because of their shorter duration (GIS#11eGIS#9).
Then, after w40 ka, the climate is getting much dryer and colder
as shown by a significant slowing down in the all the studied
stalagmites growth rate by a d13C increase. An important feature
of Villars record is a cooling gradient from the GIS#12 optimum,
at w45 ka until the stalagmites stop w30 ka years ago. This
later date anchors a climatic threshold in SW-France, after which
extreme cooling and likely a more or less continuous permafrost
blocked the water infiltration and stopped speleothem formation
for several millennia. It is interesting to note that the first
climatic threshold in Villars (w40 ka) coincides, within dating
error margins, with the first major decline of the Neanderthals
in Europe about 34 ka BP (w39 cal BP, INTCAL09)(Svoboda,
2005; Herrera et al., 2009). This threshold is synchronous with
the Heinrich 4 cold event which may have had important
consequences on the environment of human cultures (Sepulchre
et al., 2007). But our Villars records also suggest that, after
40 ka, the climate in SW-France was likely dryer: in all studied
stalagmites, growth rate and diameter decrease significantly, and
the general increase of d13C indicates a slowing down of vegetation activity until an ultimate stage at w30 ka when low
temperature and low humidity prevented speleothem growth
(Fig. 3). This later threshold is close to the generally accepted
estimates of the age of the last Neanderthal remains
w24e28 ka BP (w28e33 ka cal BP, INTCAL09) found in southIberia (Finlayson et al., 2006) suggesting, here too, a possible
role of the climate, combined with other factors, in their
disappearance. Indeed, a more detailed study of the relationship
between well dated UeTh speleothems in which climatic variability is seen, and calibrated 14C results from archaeological
sites at a regional scale (now possible for this time period with
the new INTCAL09 calibration curve (Reimer et al., 2009)),
would certainly help in understanding the causes of the Neanderthal migrations and demise, whose paradigm is still debated
(d’Errico and Sánchez Goñi, 2003; Tzedakis et al., 2007; Zilhao
et al., 2010). However there are limits in looking at such
correlations as, until now, the 2s dating errors (on both
archaeological material and climatic records) vary from several
hundreds to more than 1 ka, which is in the order of the
duration of the rapid climatic variability for this period.
Regional differences between Villars area (strong Atlantic
influence; 45 N latitude) and Mediterranean sites from the Alboran
Sea, highlight differences in the individual expression of DO events
(i.e. GIS#12 and GIS#8, the later being better marked in the
southern sites). However, it appears that more data from similar
archives (i.e. pollen and speleothem records) are necessary to
confirm these observations.
At a more global scale, a clear link is seen between the sea level
changes and the hiatuses observed in Villars speleothem growth
periods demonstrating the great influence of the ice sheets development and its consequences on the MOC and on the North Atlantic
current changes. The 65 N July insolation decrease that coincides
with low CO2 level seems to favour the Fennoscandian Ice Sheet
development with large perturbations on ocean and atmospheric
circulation in the North Atlantic area. It provoked extreme cold
periods that are coincident with OIS4 and OIS2 and during which
speleothem growth stopped in Villars Cave. At southern most
latitudes, these cold periods were recorded in speleothems as
weaker summer monsoon in China, and stronger one in Brazil
because of the ITCZ southward movement (Wang et al., 2001; Cruz
et al., 2005). Going back in time, in the former climatic cycle (i.e.
during OIS6), a strong link between 65 N July insolation and the
Asian monsoon intensity is confirmed, but, overall, it was observed
that, during glacial periods, the DO durations decreased while their
frequency increased demonstrating the role of the ice sheet size
(Wang et al., 2008). This suggests that ice sheet dynamics play
a central role in pacing the occurrence of interstadials and it also
affects their amplitude as shown by our interpretation of the Villars
records.
Acknowledgements
We thank the Versaveau Familly, owner of the Villars Cave for
the authorization of sampling and monitoring in the cave. We also
thank Ocean Drilling Project for sending us ODP Site 976 samples. JP
Cazet and MH Castera help us for the pollen sample processes.
Analyses were funded by CNRS/INSU programs (ECLIPSE, PNEDC)
and ANR program PICC. Thanks to O. Mestre from (Météo France)
for the meteorological data from Nontron, to D. Fleitmann for the
Sofular data and to M. Sanchez Goni for MD04-2845 data. Finally
we are grateful to the two anonymous reviewers whose detailed
comments were very helpful.
Appendix. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.quascirev.2010.06.035.
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