ArticlePDF Available

Evidence of a prolonged drought ca. 4200 yr BP correlated with prehistoric settlement abandonment from the Gueldaman GLD1 Cave, N-Algeria

Authors:

Abstract and Figures

Middle Holocene cultures have been widely studied round the E-Mediterranean basin in the last 30 years and past cultural activities have been commonly linked with regional climate changes. However, in many cases such linkage is equivocal, in part due to existing climatic evidence that has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and E-Mediterranean basin, however, the scarcity of such records in the western part of the Mediterranean prevents us from correlating past climate evolutions across the basin and deciphering climate–culture relation at fine time scales. Here we report the first decadal-resolved Mid-Holocene climate proxy records from the W-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in N-Algeria. Comparison of our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yr BP across the Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave, which allows the comparison between in situ evidence of human occupation and of climate change. This approach shows that the timing of a prolonged drought at ca. 4400–3800 yr BP blankets the onset of cave abandonment shortly after ca. 4403 cal yr BP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption.
Content may be subject to copyright.
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Clim. Past Discuss., 11, 2729–2762, 2015
www.clim-past-discuss.net/11/2729/2015/
doi:10.5194/cpd-11-2729-2015
© Author(s) 2015. CC Attribution 3.0 License.
This discussion paper is/has been under review for the journal Climate of the Past (CP).
Please refer to the corresponding final paper in CP if available.
Evidence of a prolonged drought
ca. 4200 yr BP correlated with prehistoric
settlement abandonment from the
Gueldaman GLD1 Cave, N-Algeria
J. Ruan1,5, F. Kherbouche2, D. Genty1, D. Blamart1, H. Cheng3,4, F. Dewilde1,
S. Hachi2, L. R. Edwards4, E. Régnier1, and J.-L. Michelot5
1Laboratoire des Sciences du Climat et de l’Environnement, Gif-sur-Yvette, France
2Centre National de Recherches Préhistoriques, Anthropologiqes et Historiques, Algiers,
Algeria
3Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, China
4Department of Geological Sciences, University of Minnesota, Minnesota, USA
5Laboratoire Géosciences Paris Sud, UMR 8148, Université Paris-Sud, Orsay, France
Received: 12 June 2015 – Accepted: 15 June 2015 – Published: 03 July 2015
Correspondence to: J. Ruan (jiaoyangruan@gmail.com)
Published by Copernicus Publications on behalf of the European Geosciences Union.
2729
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Abstract
Middle Holocene cultures have been widely studied round the E-Mediterranean basin
in the last 30 years and past cultural activities have been commonly linked with regional
climate changes. However, in many cases such linkage is equivocal, in part due to ex-
isting climatic evidence that has been derived from areas outside the distribution of5
ancient settlements, leading to uncertainty from complex spatial heterogeneity in both
climate and demography. A few high-resolution well-dated paleoclimate records were
recently established using speleothems in the Central and E-Mediterranean basin,
however, the scarcity of such records in the western part of the Mediterranean pre-
vents us from correlating past climate evolutions across the basin and deciphering10
climate–culture relation at fine time scales.
Here we report the first decadal-resolved Mid-Holocene climate proxy records from
the W-Mediterranean basin based on the stable carbon and oxygen isotopes analyses
of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in N-Algeria. Com-
parison of our records with those from Italy and Israel reveals synchronous (multi)15
centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yrBP across the
Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the
age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated
inside the cave, which allows the comparison between in situ evidence of human oc-
cupation and of climate change. This approach shows that the timing of a prolonged20
drought at ca. 4400–3800 yr BP blankets the onset of cave abandonment shortly after
ca. 4403 cal yrBP, supporting the hypothesis that a climate anomaly may have played
a role in this cultural disruption.
1 Introduction
As drought in NW-Africa is a recurring phenomenon and prolonged dry conditions exert25
a significant impact on local social systems, it becomes important to accurately docu-
2730
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
ment the role of drought conditions on the area. For instance, the most recent drought in
Algeria began in 1998, as part of a widespread pattern of drying in the N-Hemisphere,
and brought considerable loss in regards to water resource and agricultural yields (Ho-
erling and Kumar, 2003). Increasingly dry sub-tropical conditions are predicted as one
potential consequence of anthropogenic climate change, but current general circula-5
tion models do not completely capture the magnitude and spatial extent of observed
drought conditions (Seager et al., 2007). To help understand recent climate anomalies,
paleoclimate studies are crucial to characterize the range of potential natural variability
in the past and to improve our understanding of the links between regional drought and
large scale forcing. Instrumental data from weather stations in NW-Africa report less10
than one hundred years. Tree ring based drought reconstructions in Algeria and Tunisia
have been extended back to the last nine centuries, which reveals large spatial hetero-
geneity of past climate evolutions in NW-Africa and concludes that the climate anomaly
1998–2002 appears to be the most severe in the last millennium (Touchan et al., 2008,
2011). Holocene paleoclimate studies in other regions, however, have suggested larger15
oscillations at centennial to millennial time scales highlighting the need for new records
from this area (Mayewski et al., 2004; Wanner et al., 2008).
A significant climate excursion ca. 4200 yr BP has been widely reported and is con-
sidered as an ideal case to study the causes and eects of a large-scale climate
anomaly that occurred against background conditions similar to those of today (Berkel-20
hammer et al., 2013; Booth et al., 2005; Roland, 2012). The climatic expression of the
4200 yr BP event diers around the world. For example, it has been documented as
droughts in much of mid-to-low latitudes, across Africa, Asia and N-America, wet and
stormy in N-Europe and cooler in N-Atlantic (Booth et al., 2005; Roland, 2012). More
recently, this climatic anomaly was characterized by extreme dry conditions on high-25
resolved speleothem isotope records from the Central (Drysdale et al., 2006; Zanchetta
et al., 2014) and E-Mediterranean basin (Bar-Matthews and Ayalon, 2011), but, until
now, such records have not available in the W-Mediterranean which prevents us the
correlation of past climate anomalies across the basin.
2731
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Aside from its climatic interest, such an episode likely influenced numerous human
cultures. Major societal changes have been observed across the Mediterranean basin
during the Mid-Holocene, and in particular, a catastrophic desiccation ca. 4200 yr BP
has been suggested to trigger the collapse of the Akkadian Empire in Mesopotamia,
the Old Kingdom in Egypt and the Early Bronze Age civilizations of Greece and Crete5
(Weiss and Bradley, 2000; Weiss et al., 1993; Wiener, 2014). These studies have
been stimulating an increasing number of debates on climate–culture relationship (e.g.,
Coombes and Barber, 2005). Uncertainty regarding the societal impact of such an
event is still large, due in part that climatic evidence, in many cases, has been de-
rived from regions far from the distribution of ancient settlements (e.g., Cullen et al.,10
2000). Although the 4200 yr BP dry event has been observed in several mid latitude
sites, the database remains incomplete and conflicting observations of climatic con-
ditions between seemingly adjacent regions exist (Magny et al., 2013; Staubwasser
and Weiss, 2006). Additionally, a recent study demonstrated that the climatic impact
on many agricultural settlements in ancient Near East was diverse even within spatially15
limited cultural units (Riehla et al., 2014).
In N-Algeria, the extinction of large mammal species (e.g., S. antiquus) during the
Mid-Holocene was correlated with regional climate aridity, likely due to the competition
with pastoralists and livestock for increasingly scarce water (Faith, 2014). Similarly, the
evidence of the aridity (i.e., the termination of the African Humid Period) that provoked20
this extinction has been derived from the Sahara and its surroundings (deMenocal
et al., 2000), which is several hundred kilometres away, leaving this assertion ambigu-
ous and stimulating the search for new high resolution paleoclimate records in the
area.
In this study, we document the Mid-Holocene climate history in the Western Mediter-25
ranean by decadal-resolved stable carbon and oxygen isotopes analyses of two U/Th
dated stalagmites from the Gueldaman GLD1 Cave of N-Algeria. We compare the
records with those established earlier in the Central and E-Mediterranean basin. In ad-
dition, we describe archaeological deposits layers inside the cave whose ages have
2732
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
been reasonably well constrained due to new radiocarbon dating. Finally we test the
links between cultural changes and climate anomalies with a particular emphasis on
the 4200 yr BP event.
2 Samples and methods
2.1 Study site5
Gueldaman GLD1 Cave is one of a series of karstic caves formed within the SE-ward
slope of the Adrar Gueldaman ridge, western part of Babor mountains in N-Algeria
(Kherbouche et al., 2014). It is located close to the large Soummam River, 5–6 km from
the Akbou town, and approximately 65km southern inland from the W-Mediterranean
Sea (36260N, 4340E, 507 ma.s.l.) (Fig. 1). Gueldaman GLD1 is a relatively short cave10
(total extension of 80 m) that developed in Jurassic limestone. The entrance, facing to
the SE, is a semi-circular 6 m large arch, leading to a dome-shaped 10 m high and
6 m wide corridor which ends with the main chamber “Grande Salle” at a depth of 30–
40 m. The area is covered by a thin layer (<10cm) of soil derived from the limestone
bedrock, wind-blown silicate dust, and organic matter from local vegetation such as15
Pistacia lentiscus, Quercus ilex, Buxus sempervirens, typical Mediterranean Garrigue
type plant assemblage (C3 dominated).
Local climate is Mediterranean semi-arid type, characterized by hot-dry summers
and mild-wetter winters. From the ERA-interim reanalysis data between 1979 and 2013
(http://apps.ecmwf.int/datasets/) the annual total rainfall is 516 mm, and the annual20
mean temperature is 17.2 C. Rainfall occurs rarely in the summer (37 mm) but rel-
atively evenly through the autumn (155 mm), winter (178 mm) and spring (147 mm).
Gueldaman GLD1 Cave is well ventilated with the outside atmosphere due to its larger
opening and shorter extension. Hobo logger data at 10 min resolution from Novem-
ber 2013 to April 2015 shows significant variations in cave temperature ranging from25
2733
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
13.7 to 19.5 C. The relative humidity varies from 56 to 94 %. Carbon dioxide has not
been measured, but it is likely to be close to the atmospheric value.
2.2 Stalagmites analyses
Two stalagmites and three modern calcites samples were collected in 2012 and 2013
from the main chamber of Gueldaman GLD1 Cave. Stalagmite GLD1-stm2 is 350mm5
long and 100–200 mm wide; GLD1-stm4 is 203 mm long with a diameter of 50–120 mm
(Fig. 2). They were halved and polished along the longitudinal axis. Both stalagmites
show well-marked laminae with several shifts in the drip apex of the lower parts (Fig. 2).
Black bandings, with visible incorporations of charcoal particles, are found throughout
both stalagmites profiles.10
U/Th dating
Seventeen powder samples were drilled from the two stalagmites and dated by a multi-
collector inductively coupled plasma mass spectrometer. The procedure to separate
uranium and thorium were referred to Edwards et al. (1987) and Cheng et al. (2013).
The dating work was carried out at the University of Minnesota (USA) and the Xi’an15
Jiaotong University (China). One dating from the base part of stalagmite GLD1-stm2,
for the exploration of preliminary age frame, was done at the Laboratoire des Sciences
du Climat et de l’Environnement (LSCE, France). The U/Th dates were reported in
years before 2000 AD. (Fig. 2, Table 1). The age model for both stalagmites was devel-
oped using the StalAge program (Scholz and Homann, 2011) where a linear interpola-20
tion between depth and age is made through each progressive triplet of adjacent U/Th
dates (Fig. 3). This procedure provides a quantitative estimate of age uncertainty con-
tinuously along the record despite having analytical constraints only at locations where
the U/Th dates exist. Stalagmite growth rates were calculated based on the StalAge
age model (Fig. 4).25
2734
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Stable isotopes
Four hundred and thirty samples were drilled every 1 to 2 mm along the stalagmite cen-
tral growth axis (Fig. 2). Stable carbon and oxygen isotopes compositions of both sta-
lagmites and modern calcites were measured using a VG-OPTIMA mass spectrometer
at the LSCE. For each analysis, 60 to 80 µg calcite powder is reacted with phosphoric5
acid at 90 C, and the resultant CO2is measured relative to a reference gas that has
been calibrated against a series of isotopic standards. Duplicates were run every 10
to 20 samples to check replicability. All values are reported in ‰ relative to the V-PDB
(Fig. 4). The error is 0.08 ‰ for δ18O and 0.05 ‰ for δ13C.
2.3 Archaeological analyses10
Archaeological excavations were carried out at two sectors S2 and S3 inside the Guel-
daman GLD1 Cave during the 2010–2012 campaign (Fig. 1). This work consisted
mainly in collecting, identifying, and referencing the archaeological materials found in
stratigraphic layers (refer to Kherbouche et al. (2014) for details). More than 7000 an-
thropogenic remains were collected, consisting mainly of faunal remains, ceramic, and15
lithic and bone tools. Besides, all sediments were water screened through 1.5 and 4mm
mesh and subjected systematically to flotation with collection in a 250 µm mesh yielding
a huge amount of charcoals. Initial radiocarbon dating of upper stratigraphic sequences
from S2 and S3 gave the median ages ranging from ca. 6800 to 1500cal yr BP (Kher-
bouche et al., 2014). In order to refine the chronology of these deposits, in this study,20
six new charcoal samples were collected from the key archaeological layers in exca-
vation area MN 47/48 of S2. These samples were dated using the AMS radiocarbon
method at the CEA Saclay (France). Detailed procedures of the chemical preparation
and the dating in the lab were referred to Cottereau et al. (2007). The dates were cal-
ibrated using the IntCal13 dataset (Reimer et al., 2013) and reported in years before25
2000 AD (Table 2).
2735
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
3 Results
3.1 Stalagmites U/Th dates and growth rates
The uranium contents of measured stalagmites samples are relatively high ranging
from 95 to 225 ppb (Table 1). The 2 sigma U/Th errors vary from 20 to 210 years with
an average of 77years (1.6 %). The U/Th date (5070 ±194 yr BP) of sample GLD1-5
stm4-47 was detected as a major outlier by the StalAge program, thus, it was not used
to calculate the final age model. Calculated StalAge age model for stalagmite GLD1-
stm4 shows large errors up to 500 years during ca. 4900–4200 yrBP (Fig. 3). Based
on individual StalAge age model, stalagmite GLD1-stm2 grew continuously from ca.
6200 to 4100 yr BP, whereas stalagmite GLD1-stm4 grew continuously from ca. 580010
to 3200 yr BP (Fig. 3).
Stalagmite GLD1-stm2 shows high and variable growth rates (mean =180 µm yr1)
with higher values 400 µm yr1at ca. 4800–4500 yrBP; whereas stalagmite GLD1-
stm4 shows relatively lower and less variable growth rates (mean =120 µm yr1) with
higher values 200 µm yr1at ca. 3800–3200 yrBP (Fig. 4).15
3.2 Stable carbon and oxygen isotopes
The isotopic compositions of modern calcite vary from 5.40 to 5.56 ‰ for the δ18 O
and from 8.43 to 10.34 ‰ for the δ13C. The δ18 O values from stalagmites GLD1-
stm2 and GLD1-stm4 range from 7.8 to 2.8 ‰ and from 7.3 to 0.6 ‰, respec-
tively; the δ13C values range from 10.6 to 3.3 ‰ and from 11.9 to 0.6 ‰, respec-20
tively. The δ18 O and δ13C significantly correlate in both stalagmites: R=0.87, P < 0.01
for GLD1-stm2 and R=0.92, P < 0.01 for GLD1-stm4. Albeit the dierent amplitudes,
the isotopic profiles of the two stalagmites show similarities during their common de-
velopment of ca. 5800–4100 yr BP: relatively elevated isotope values are found at ca.
5700–5400, ca. 5200, and ca. 4500 yr BP (Fig. 4). Two other isotopically enriched pe-25
riods in stalagmite GLD-stm2 are found at ca. 6200 and ca. 4900 yr BP (Fig. 4). There
2736
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
is a common isotopic enrichment trend since ca. 4800–4600 yrBP (depending on in-
dividual age model; abrupt in stalagmite GLD1-stm4 whereas more gradual in GLD1-
stm2). Toward the end of this trend, the most prominent anomaly occurs in stalagmite
GLD1-stm4 at ca. 4400–3800 yr BP during which the δ18O values are enriched by ap-
proximately 3.5 ‰ relative to the background values of that time as well as the modern5
calcite values for a period of 500 years (Fig. 4). Specifically within this anomalous
period, there is a mild depletion of δ18O at ca. 4200–4000 yrBP, followed by a second
enrichment toward its end during which stalagmite GLD1-stm2 stops growing (Fig. 4).
The last stage, ca. 3800–3200 yr BP, of GLD1-stm4, is characterized by a δ18O recov-
ery of about 3 ‰, synchronous with increased growth rates (Fig. 4).10
3.3 Anthropogenic deposits and 14C dates
Excavations inside Gueldaman GLD1 Cave revealed a large variety of archeological re-
mains and, among them, are numerous precious macro charcoals that have been used
for establishing the chronology of the deposits. In the 7 m2total excavated area of S2,
more than 7000 archaeological objects were identified and consisted of faunal remains,15
lithic artifacts and grinding equipment, potteries, bone tools, ornaments, and ochre. In
addition, a fragment of a human mandible and two isolated teeth were found during the
excavation 2010–2012 in Gueldaman GLD1 Cave (Kherbouche et al., 2014). These
deposits belong mainly to the Neolithic; only the top level of the sequence contains pot-
sherds of the historic period. In the lower Neolithic levels, identified domestic species20
(i.e. sheep and goats) represented 25 % of total faunal assemblages (N=2378) sug-
gesting a partly pastoral based economy. The potteries (N=825) are mostly related
to cooking vessels of 25–40 cm rim diameter. Hundreds of black charcoals (>1 cm)
were found and always associated with ceramic concentrations suggesting evidence of
cooking activities.25
Determined radiocarbon dates give the median ages of the sequence between 7002
and 1482 cal yrBP, with their 2σ-error intervals varying from 132 to 374 years (Table 2).
These dates provide a first chronology for the archaeological deposits excavated from
2737
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
sector S2 (Fig. 6) (Kherbouche et al., 2014): anthropogenic remains (i.e. charcoals,
bones, teeth and potteries) are numerous during ca. 7002–6003 cal yrBP (depths of
150–120 cm), decreased at ca. 6003–4918 calyrBP (depths of 120–105 cm), most
abundant in the period of ca. 4918–4403 cal yr BP (depths of 105–75 cm), significantly
diminished during the long interval of ca. 4403–1484 calyr BP (depths of 75–60 cm),5
and finally, numerous again from ca. 1484 cal yr BP (depths of 60–50 cm). With an
overall decrease in archeological materials, there are two levels clearly marked by their
poverty in charcoal and pottery during the periods of ca. 6003–4918 cal yr BP and ca.
4403–1484 cal yr BP (Fig. 6).
4 Discussions10
4.1 Climatic significance of stalagmites proxies
Stalagmite growth requires humid climates allowing sucient water infiltration into the
cave. In arid and semiarid areas, water availability is an essential controlling factor for
stalagmite growth, as well shown by Vaks et al. (2013) who correlated growth periods
with periods of eective rainfall regimes. The growth cessation of stalagmite GLD1-15
stm2 by ca. 4100 yr BP may suggest a phase of increased aridity, which is consistent
with the extreme dry condition inferred from the most elevated isotope values in sta-
lagmite GLD1-stm4 (see discussion in the following paragraphs) (Fig. 4). The fact that
stalagmite GLD1-stm4 does not stop growing at that time may be attributed to a dif-
ferent sensitiveness of the reservoir feeding the two speleothems (Fairchild and Baker,20
2012). Moreover, fast stalagmite growths together with wide diameters are usually as-
sociated with high drip rates suggesting humid conditions. A wetter period ca. 4800–
4500 yr BP is indicated by the high growth rates of stalagmite GLD1-stm2. The fact
that it is not seen in the growth rate change of stalagmite GLD1-stm4 is probably due
to the lack of dating between 5023 and 4197 yr BP (Fig. 4). Another wetter period ca.25
3800–3200 yr BP is suggested by fast growths of stalagmite GLD1-stm4 (Fig. 4).
2738
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Under isotopic equilibrium precipitation, stalagmite calcite δ18O depends mainly on
the temperature of calcite-water fractionation and on the δ18O of drip water that is
controlled by local rainfall δ18O (Genty et al., 2014). Observations from the IAEA net-
work show that the rainfall δ18O at many Mediterranean stations (including one in Al-
giers, Algeria) are partly controlled by the amount of rainfall (IAEA, 2005), which is5
coherent with previous studies that most stalagmite δ18O records from the Mediter-
ranean regions were interpreted to primarily reflect changes in rainfall amount (e.g.,
Bar-Matthews and Ayalon, 2011; Bar-Matthews et al., 1997, 2003; Drysdale et al.,
2004, 2006; Zanchetta et al., 2014). The temperature eect on calcite-water fractiona-
tion, on the other hand, is partly counteracted by the condensation temperature eect10
on rainfall δ18O (Drysdale et al., 2006). We note that this interpretation may particularly
hold true for the present study because the regional temperature seems to has been
relatively constant since the Mid-Holocene (Martrat et al., 2004).
The rainfall signal imprinted in the Gueldaman GLD1 stalagmite δ18O is probably
enhanced by two other processes - evaporation and disequilibrium isotopic fractiona-15
tion (Mickler, 2006), partly due to the large cave entrance. It has been recently shown
that evaporation in semiarid caves could cause 4–5 δ18 O enrichments of a wide
range of drip waters (Cuthbert et al., 2014). The Hendy test (i.e. studying the isotopic
variation in contemporaneous layer, Hendy, 1971) made on three dierent levels in sta-
lagmite GLD1-stm2 show that the δ18O and δ13C correlate (R=0.86, 0.89, and 0.93)20
and increase by up to 1 ‰ from the center toward the edge, suggesting that stalag-
mite calcites precipitate out of isotopic equilibrium. These two processes may partly
explain the significant correlation of δ18O and δ13C profiles (R=0.87 for GLD-stm2
and R=0.92 for GLD1-stm4). Moreover, the larger amplitudes of isotopic variations in
stalagmite GLD1-stm4 (Fig. 4) can be explained by the likelihood of suering from more25
evaporative and non-equilibrium enrichments due to lower drip rates, being indicated
by its smaller diameters (Fig. 2).
Stalagmite δ13C variations have several potential causes, the most likely, consider-
ing the studied location and time interval, being variations in soil CO2input and water
2739
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
flow rate (Genty et al., 2001; McDermott, 2004). Despite the fact that soil biogenic
CO2production varies according to both temperature and moisture level, moisture is
likely to be a major controlling factor due to low temperature variability of the consid-
ered time interval and limited water availability under semiarid climates. Moisture also
influences water flow rate and thus the CO2loss during the prior calcite precipitation5
(Fairchild et al., 2000). Low flow rate under diminished moisture condition enhances
CO2loss due to longer travel time and preferential 12C removing from solution, caus-
ing enrichments in stalagmite δ13C (Johnson et al., 2006; Mickler, 2004). Eventually,
atmospheric rainfall largely determines the moisture level and controls the δ13C vari-
ations. Therefore, the significant correlation between δ13C and δ18 O suggest not only10
a disequilibrium fractionation but a common control of rainfall.
Consequently, synchronous variations in two isotopes can be interpreted in terms
of water balance change: a prolonged severe drought can be inferred using the most
elevated δ18O and δ13C values during ca. 4400–3800 yrBP together with drier events
at ca. 6200, ca. 5700–5400, ca. 5200, and ca. 4500 yr BP (Fig. 4). The average δ18O15
value during ca. 4400–3800 yr BP is enriched by about 3.5‰ relative to the modern
calcite values, suggesting that the climatic conditions were likely drier during the Mid-
Holocene than at present. Thus, the current climate in N-Algeria appears to be within
the range of natural variability and the 4400–3800 yr BP climate anomaly may be con-
sidered analogous to end numbers of the most recent and ongoing drying.20
4.2 Mid-Holocene climate anomalies across the Mediterranean basin and their
dynamic implications
High-resolution absolute-dated Mid-Holocene climate records are rare in the W-
Mediterranean basin, however, there are a number of paleoenvironment studies using
sediment cores that documented large oscillations in vegetation ecology and indicated25
climate anomalies during the Mid-Holocene. A drying trend from ca. 4600 calyr BP on-
wards was inferred, based on the decreasing pollen ratio of deciduous broad-leaf vs.
evergreen sclerophyllous taxa at Capestang in the Mediterranean S-France (Jalut et al.,
2740
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
2000). At a nearby site in NE-Spain, the Mid-Holocene most arid condition at ca. 4800–
4000 cal yrBP was interpreted using maximum salinity values, more positive organic
carbon isotope values, and decreased algal productivity in Estanya Lake (Morrellon
et al., 2009). In the Mediterranean S-Spain, desertification phases at ca. 5200 calyrBP
and ca. 4100 cal yrBP were inferred using multiple palaeoecological indicators includ-5
ing pollen, microcharcoal, spores of terrestrial plants, fungi, non-siliceous algae, and
other microfossils in Siles Lake (Carrión, 2002). Similar environment changes have also
been observed in the Central Mediterranean basin, as shown by a synthesis study of
lacustrine palynological data which suggested a dryness peaking at ca. 4000 cal yr BP
(Sadori et al., 2011). Increasing aridity at ca. 5000–4000 calyr BP was suggested to10
explain the increases in non-tree pollen percentage and micro charcoal content in the
Lago di Pergusa Lake, Sicily (Roberts et al., 2011; Sadori and Giardini, 2007; Sadori
and Narcisi, 2001). Close to our site, a study at Preola Lake, in E-Sicily, documented
a significant low stand lake level at ca. 4500–4000 cal yrBP suggesting extreme arid-
ity (Magny et al., 2011). Although the sampling and dating resolutions in most of the15
above studies are low, they are in good agreement with the present study regarding the
5200 yr BP dry event, the drying trend from 4800–4600 yr BP onward, and the 4400–
3800 yr BP drought.
Recently, evidence of detailed Mid-Holocene climate change has been shown in
high-resolution U/Th-dated speleothem records from the Central and E-Mediterranean20
basin. Drysdale et al. (2006) demonstrated a severe Mid-Holocene drought through
multiproxy analysis on a flow stone from Renella Cave, Central Italy. The following
work at nearby Corchia Cave by Zanchetta et al. (2007) revealed similar climatic
condition during the Mid-Holocene (Fig. 5). In the E-Mediterranean, Bar-Matthews
and Ayalon (2011) explicitly discussed the Mid-Holocene climate by high-resolution25
dating and isotopic analysis on speleothems from Soreq Cave in Israel (Fig. 5).
Zanchetta et al. (2014) made comparisons between records from the Central and E-
Mediterranean; they identified coeval dry events at ca. 5600 and ca. 5200 yr BP based
on comparable enrichments in speleothem δ18O from Corchia Cave and Soreq Cave.
2741
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Detailed comparisons of these speleothem records with the Gueldaman GLD1 stalag-
mite records reveal similar variations. In particular, elevated δ18O values in the Guel-
daman GLD1 stalagmites at ca. 5700–5400, ca. 5200 and ca. 4400–3800 yr BP are all
identified in speleothems from the Renella, Corchia and Soreq suggesting that anoma-
lous dry conditions synchronously developed across the Mediterranean basin (Fig. 5).5
These observations indicate that climates across the Mediterranean might have been
under an identical regional scale climate regime during the Mid-Holocene.
It has been suggested that climate change in mid-latitude Europe and Mediterranean
might arise from a perturbation of the Westerlies from a high-latitude trigger (i.e. the
North Atlantic) (Bond et al., 2001; Drysdale et al., 2006; Zanchetta et al., 2014) or10
from dynamics within the tropics (Booth et al., 2005; Hoerling and Kumar, 2003). The
three dry periods in the Mediterranean are broadly in phase with the ice rafting events
in the subpolar North Atlantic (Bond et al., 2001), which suggests some links with
the N-Atlantic circulation. Based on the coincidence with the elevated wind strength in
Iceland (Jackson et al., 2005), Zanchetta et al. (2014) argued that the dry events at15
ca. 5700–5400 and ca. 5200 yr BP might be caused by reduction of vapor advection
into the Mediterranean, due to the intensification and northward displacement of the
N-Atlantic Westerlies. However, lacking evidence of strengthened wind in the fourth
millennium BP argues for a dierent forcing of the 4400–3800 yr BP drought. The con-
siderably lower amplitude of the Bond ice rafting event at ca. 4200 yr BP than at the fifth20
millennium BP also indicates a varied ocean–atmosphere circulation state. The mod-
ern mid-latitude droughts (1998–2002) have been linked to the increased warmth in
equatorial oceans (Booth et al., 2005). During this event, SST changes lead to persis-
tent high pressure over the Northern Hemisphere’s mid-latitudes, causing widespread
synchronous drought (Hoerling and Kumar, 2003). However, the challenge in apply-25
ing the dynamics under the 1988–2002 drought toward an understanding of the 440–
3800 yr BP climate anomaly is that while the mechanism operate eectively on short
time scales, it has never been tested as to whether they could produce an anomalous
climate mode for several centuries (Berkelhammer et al., 2013). General circulation
2742
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
model simulations that begin with realistic boundary conditions and are perturbed with
a variety of forcings have been successfully undertaken to understand potential mecha-
nisms that lead to the 8200 yrBP event (Tindall and Valdes, 2011). Similar eorts would
be a useful starting point to produce hypotheses for the dynamical underpinnings of the
4200 yr BP event.5
4.3 Possible relations between climate anomaly and cultural change
A regional drought ca. 4200 yr BP has been widely linked to ancient cultural changes
in the E-Mediterranean and the Asia (Staubwasser and Weiss, 2006), though, in many
cases, climatic inferences have been derived from sites that are distant to these human
settlements. For instance, evidence of reduced precipitation from elevated δ18O of Irish10
stalagmites and increased dust input into the Gulf of Oman sediment core has been
suggested to contribute to the collapse of the Akkadian imperial in Mesopotamia (Bar-
Matthews and Ayalon, 2011; Cullen et al., 2000; Weiss et al., 1993). Similarly, a dry
period inferred from reduced discharge of the Indus river and elevated δ18O of a NE-
Indian stalagmite has been linked with the Indus Valley de-urbanization (Berkelhammer15
et al., 2013; Staubwasser et al., 2003; Staubwasser and Weiss, 2006). A recent study
in ancient Near East, however, revealed that the regional impact of the drought on
ancient civilizations, being influenced by geographic factors and human technology,
were highly diverse even within spatially limited cultural units (Riehla et al., 2014). This
highlights the need for caution when linking human activities from a site to the evidence20
of climate oscillations from another one.
The present study in the Gueldaman GLD1 Cave provides an opportunity to test
climate–culture relations by comparing in situ archeological sequences and high res-
olution paleoclimate records, thereby avoiding the uncertainty of inter-site correlation
arising from complex spatial heterogeneity in climate and demography.25
To facilitate the comparison, stalagmite-inferred climate changes at the cave site
during ca. 6200–3200 yrBP are separated into four stages 1–4 (Table 3):
2743
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Stage 1 (6200–5100 yr BP): wet, superimposed by several centennial-scale
drier events;
Stage 2 (5100–4400 yr BP): wettest, ending with a 200-yr-long shift from the
wettest to extreme dry conditions;
Stage 3 (4400–3800 yr BP): a drought-like climatic anomaly;5
Stage 4 (3800–3200 yr BP): relatively wet.
In parallel, from the abundance of archaeological remains (especially bone, charcoal
and pottery) (Fig. 6), the temporal evolution of past cave occupations can be separated
into five phases 0–4 (Table 3):
Phase 0 (7002–6003 cal yrBP): permanent and intensive occupation;10
Phase 1 (6003–4918 cal yrBP): permanent but less intensive occupation;
Phase 2 (4918–4403 cal yrBP): permanent and most intensive occupation;
Phase 3 (4403–1484 cal yrBP): abandonment of the cave/occasional visits
Phase 4 (1484 cal yrBP–): re-occupation of the cave
Correlations can be identified when comparing the climatic and archaeological records,15
though this does not necessarily mean that occupation of the cave depends merely on
climate (Table 3; Fig. 7). When the climate was wet and variable ca. 6200–5100 yr BP
(Stage 1), the Gueldaman GLD1 Cave preserved a few bones and rare charcoals and
potteries (Phase 1) (Fig. 7). When the climate was wettest ca. 5100–4400 yr BP (Stage
2), the most abundance of bones, charcoals and potteries suggests a permanent and20
more intensive occupation of the cave (Phase 2) (Fig. 7). More striking is the drought-
like climate anomaly that has been establishing ca. 4400–3800 yr BP (Stage 3), in
which the cave was abandoned for ca. 3000 years (indicated by a dramatic decrease in
anthropogenic remains, especially charcoal and pottery) (Phase 3) (Fig. 7). The rarer
2744
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
bones seen in this period imply that the cave might have been occasionally visited until
its re-occupation at ca. 1484 cal yrBP (Fig. 7). These observations argue for links be-
tween climate and settlement activity especially during the 4200 yrBP climate anomaly.
Water availability was likely crucial to maintain the Neolithic community at Gueldaman,
N-Algeria and the prolonged severe drought ca. 4400–3800 yr BP might have played5
a role in triggering the settlement abandonment, indicating that the pastoral economy
may not be as resistant, as commonly assumed, to climate anomaly in semiarid area.
Moreover, the sole piece of the bone from large ungulate (supposed to be elephant
or rhinoceros) found at the depth of 110 cm (Kherbouche et al., 2014) was anchored
by two calibrated 14C dates from present study between 6003 and 4913 calyr BP, which10
is in line with the latest survival of large mammal species (S. antiquus, E. Mauritanicus,
and E. melkiensis) at the proximate sites of N-Algeria during the Mid-Holocene (Faith,
2014 and references wherein). The extinction of the Mid-Holocene large mammal in N-
Algeria was attributed to the competition with pastoralists and livestock for increasingly
scarce water, corresponding with an abrupt climatic shift toward extreme aridity in the15
Sahara region ca. 5500 cal yr BP (i.e. the end of the Humid Africa Period, deMenocal
et al., 2000; Faith, 2014). Recently, the timing of this climatic transition was refined to
ca. 4900 yr BP ±200 yr (McGee et al., 2013). In addition, a paleoenvironmental study in
the Sahara revealed that the Mid-Holocene deteriorations of terrestrial ecosystem and
climate culminated at ca. 4200–3900 cal yr BP (e.g., Kröpelin et al., 2006). Therefore, it20
is more likely based on evidence from the Gueldaman GLD1 Cave and the proximate
sites (Faith, 2014) that extinction of large mammal/ungulate in N-Algeria occurred dur-
ing the prolonged drought ca. 4400–3800 yr BP.
5 Conclusions
It is increasingly clear based on a growing number of records spanning across much25
of mid-to-low latitudes, N-Europe, and the Atlantic ocean that there was a significant
large scale climate anomaly at around 4200 yr BP (Booth et al., 2005). The 4200 yr BP
2745
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
aridity that had been suggested to aect the Early Bronze Age populations from the
Aegean to ancient Near East was recently characterized by high-resolution speleothem
records from the Central and E-Mediterranean basin (Bar-Matthews and Ayalon, 2011;
Drysdale et al., 2006; Zanchetta et al., 2014). The new record presented here from
the Gueldaman GLD1 Cave in N-Algeria provides increased evidence of a prolonged5
severe drought ca. 4400–3800yr BP, which suggests that the Mid-Holocene dryness
spread to the W-Mediterranean of N-Africa.
Radiocarbon dating made on charcoals constrains reasonably well the age of ar-
chaeological deposits excavated inside the cave (Kherbouche et al., 2014) and reveals
significant changes in human occupation during the last ca. 7000 years. Comparison10
of the stalagmite record with in situ archaeological sequence suggests synchronic-
ity between climate and settlement activity. Relatively wet/dry periods coincide with
the periods of more/less intensive human occupation. Particularly, the timing of the
prolonged drought at ca. 4400–3800 yr BP blanket the onset of the cave abandon-
ment event shortly after ca. 4403 cal yr BP, which argues a possible role of climate15
anomaly in this societal disruption. Further work on pollen-based reconstruction of
vegetation/environment change from the excavation sequence and on refinement of
the chronology of transitions between dierent occupation phases would potentially un-
cover the intrinsic relations among climate, environment and settlement. It is suggested
that the methodology and the findings from the present study at the Gueldaman GLD120
Cave be applied and tested at other sites.
Acknowledgements. Radiocarbon dating were analysed by Jean-Pierre Dumoulin at ARTEMIS
(LMC14, Saclay). We thank Edwige Pons-Branchu, Monique Pierre for the U/Th dating of
the base part of stalagmite GLD1-stm2 during the earlier stage of this study. We also thank
Lijuan Sha at the Xi’an Jiaotong University for assistance with the U/Th dating. Thanks25
to Cecilia Garrec for editing assistance. Funding is provided by the CNRS INSU program
PALEOMEX-ISOMEX, the NSFC grant 41230524 and the CSC scholarship.
2746
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
References
Bar-Matthews, M. and Ayalon, A.: Mid-Holocene climate variations revealed by high-resolution
speleothem records from Soreq Cave, Israel and their correlation with cultural changes,
Holocene, 21, 163–171, 2011.
Bar-Matthews, M., Ayalon, A., and Kaufman, A.: Late Quaternary paleoclimate in the eastern5
Mediterranean region from stable isotope analysis of speleothems at Soreq Cave, Israel,
Quaternary Res., 47, 155–168, 1997.
Bar-Matthews, M., Ayalon, A., Gilmour, M., Matthews, A., and Hawkesworth, C. J.: Sea–land
oxygen isotopic relationships from planktonic foraminifera and speleothems in the East-
ern Mediterranean region and their implication for paleorainfall during interglacial intervals,10
Geochim. Cosmochim. Ac., 67, 3181–3199, 2003.
Berkelhammer, M., Sinha, A., Stott, L., Cheng, H., Pausata, F. S. R., and Yoshimura, K.: An
abrupt shift in the Indian Monsoon 4000 years ago, in: Climates, Landscapes, and Civiliza-
tions, edited by: Giosan, L., Fuller, D. Q., Nicoll, K., Flad, R. K., and Clift, P. D., American
Geophysical Union, Washington, DC, 75–87, 2013.15
Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M. N., Showers, W., Homann, S., Lotti-
Bond, R., Hajdas, I., and Bonani, G.: Persistent solar influence on north Atlantic climate
during the Holocene, Science, 294, 2130–2136, 2001.
Booth, R. K., Jackson, S. T., Forman, S. L., Kutzbach, J. E., Bettis, E. A., Kreig, J., and
Wright, D. K.: A severe centennial-scale drought in midcontinental North America 4200 years20
ago and apparent global linkages, Holocene, 15, 321–328, 2005.
Carrión, J. S.: Patterns and processes of Late Quaternary environmental change in a montane
region of southwestern Europe, Quaternary Sci. Rev., 21, 2047–2066, 2002.
Cheng, H., Edwards, L. R., Shen, C. C., Polyak, V. J., Asmerom, Y., Woodhead, J., Hellstrom, J.,
Wang, Y., Kong, X., Spötl, C., Wang, X., and Alexander Jr., E. C.: Improvements in 230Th25
dating, 230Th and 234 U half-life values, and U-Th isotopic measurements by multi-collector
inductively coupled plasma mass spectrometry, Earth Planet. Sc. Lett., 371–372, 82–91,
2013.
Coombes, P. and Barber, K.: Environmental determinism in Holocene research: causality or
coincidence?, Area, 37, 303–311, 2005.30
2747
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Cottereau, E., Arnold, M., Moreau, C., Baque, D., Bavay, D., Cay, I., Comby, C., Dumoulin, J.-
P., Hain, S., Perron, M., Salomon, J., and Setti, V.: Artemis, the new 14C AMS14 in Saclay,
France, Radiocarbon, 49, 291–299, 2007.
Cullen, H. M., deMenocal, P. B., Hemming, S., Hemming, G., Brown, F. H., Guilderson, T., and
Sirocko, F.: Climate change and the collapse of the Akkadian empire: evidence from the deep5
sea, Geology, 28, 379–382, 2000.
Cuthbert, M. O., Baker, A., Jex, C. N., Graham, P. W., Treble, P. C., Andersen, M. S., and
Acworth, R. I.: Drip water isotopes in semi-arid karst: implications for speleothem paleocli-
matology, Earth Planet. Sc. Lett., 395, 194–204, 2014.
deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., and Yarusinsky, M.:10
Abrupt onset and termination of the African Humid Period: rapid climate responses to gradual
insolation forcing, Quaternary Sci. Rev., 19, 347–361, 2000.
Drysdale, R., Zanchetta, G., Hellstrom, J., Maas, R., Fallick, A., Pickett, M., Cartwright, I., and
Piccini, L.: Late Holocene drought responsible for the collapse of Old World civilizations is
recorded in an Italian cave flowstone, Geology, 34, 101–104, 2006.15
Drysdalea, R. N., Zanchetta, G., Hellstrom, J. C., Fallick, A. E., Zhao, J.-X., Isola, I., and Br-
uschi, G.: Palaeoclimatic implications of the growth history and stable isotope (δ18O and
δ13C) geochemistry of a Middle to Late Pleistocene stalagmite from central-western Italy,
Earth Planet. Sc. Lett., 227, 215–229, 2004.
Edwards, R. L., Chen, J. H., and Wasserburg, G. J.: 238U-234U-230 Th-232Th systematics and20
the precise measurements of time over the past 500 000 years, Earth Planet. Sc. Lett., 81,
175–192, 1987.
Fairchild, I. J. and Baker, A.: Speleothem Science – from Process to Past Environments, John
Wiley & Sons, Ltd, Chichester, UK, 2012.
Fairchild, I. J., Borsato, A., Tooth, A. F., Frisia, S., Hawkesworth, C. J., Huang, Y. M., McDer-25
mott, F., and Spiro, B.: Controls on trace element (Sr–Mg) compositions of carbonate cave
waters: implications for speleothem climatic records, Chem. Geol., 166, 255–269, 2000.
Faith, J. T.: Late Pleistocene and Holocene mammal extinctions on continental Africa, Earth-
Sci. Rev., 128, 105–121, 2014.
Genty, D., Baker, A., Massault, M., Proctor, C., Gilmour, M., and Pons-Branchu, E.: Dead car-30
bon in stalagmites: carbonate bedrock paleodissolution vs. ageing of soil organic matter.
Implications for 13C variations in speleothems, Geochim. Cosmochim. Ac., 65, 3443–3457,
2001.
2748
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Genty, D., Labuhn, I., Homann, G., Danis, P. A., Mestre, O., Bourges, F., Wainer, K., Mas-
sault, M., Régnier, E., Orengo, P., Falourd, S., and Minster, B.: Rainfall and cave water iso-
topic relationships in two South-France sites, Geochim. Cosmochim. Ac., 131, 323–343,
2014.
Hendy, C. H.: The isotopic geochemistry of speleothems – I. The calculation of the eects of dif-5
ferent modes of formation on the isotopic composition of speleothems and their applicability
as palaeoclimatic indicators, Geochim. Cosmochim. Ac., 35, 801–824, 1971.
Hoerling, M. and Kumar, A.: The perfect ocean for drought, Science, 299, 691–694, 2003.
IAEA: Isotopic Composition of Precipitation in the Mediterranean Basin in Relation to Air Cir-
culation Patterns and Climate: Final Report of a Coordinated Research Project, 2000–2004,10
International Atomic Energy Agency, Vienna, Austria, 2005.
Jackson, M. G., Oskarsson, N., Tronnes, R. G., McManus, J. F., Oppo, D. W., Gronvold, K.,
Hart, S. R., and Sachs, J. P.: Holocene loess deposition in Iceland: evidence for millennial-
scale atmosphre-ocean coupling in the North Atlantic, Geology, 33, 509–512, 2005.
Jaey, A. H., Flynn, K. F., Glendenin, L. E., Bentley, W. C., and Essling, A. M.: Precision mea-15
surement of half-lives and specific activities of 235U and 238U, Phys. Rev. C, 4, 1889–1906,
1971.
Jalut, G., Esteban Amat, A., Bonnet, L., Gauquelin, T., and Fontugne, M.: Holocene climatic
changes in the Western Mediterranean, from south-east France to south-east Spain, Palaeo-
geogr. Palaeocl., 160, 255–290, 2000.20
Johnson, K. R., Hu, C. Y., Belshaw, N. S., and Henderson, G. M.: Seasonal trace-element
and stable-isotope variations in a Chinese speleothem: the potential for high-resolution pa-
leomonsoon reconstruction, Earth Planet. Sc. Lett., 244, 394–407, 2006.
Kaufman, A., Wasserburg, G. J., Porcelli, D., Bar-Matthews, M., Ayalon, A., and Halicz, L.: U-Th
isotope systematics from the Soreq cave, Israel and climatic correlations, Earth Planet. Sc.25
Lett., 156, 141–155, 1998.
Kherbouche, F., Hachi, S., Abdessadok, S., Sehil, N., Merzoug, S., Sari, L., Benchernine, R.,
Chelli, R., Fontugne, M., Barbaza, M., and Roubet., C.: Preliminary results from excavations
at Gueldaman Cave GLD1 (Akbou, Algeria), Quatern. Int., 320, 109–124, 2014.
Kröpelin, S., Verschuren, D., Lézine, A.-M., Eggermont, H., Cocquyt, C., Francus, P., Cazet, J.-30
P., Fagot, M., Rumes, B., Russell, J. M., Darius, F., Conley, D. J., Schuster, M., Su-
chodoletz, H. v., and Engstrom, D. R.: Climate-driven ecosystem succession in the Sahara:
the past 6000 years, Science, 320, 765–768, 2006.
2749
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Magny, M., Vannière, B., Calo, C., Millet, L., Leroux, A., Peyron, O., Zanchetta, G., La Mantia, T.,
and Tinner, W.: Holocene hydrological changes in south-western Mediterranean as recorded
by lake-level fluctuations at Lago Preola, a coastal lake in southern Sicily, Italy, Quaternary
Sci. Rev., 30, 2459–2475, 2011.
Magny, M., Combourieu-Nebout, N., de Beaulieu, J. L., Bout-Roumazeilles, V., Colom-5
baroli, D., Desprat, S., Francke, A., Joannin, S., Ortu, E., Peyron, O., Revel, M., Sadori, L.,
Siani, G., Sicre, M. A., Samartin, S., Simonneau, A., Tinner, W., Vannière, B., Wagner, B.,
Zanchetta, G., Anselmetti, F., Brugiapaglia, E., Chapron, E., Debret, M., Desmet, M., Di-
dier, J., Essallami, L., Galop, D., Gilli, A., Haas, J. N., Kallel, N., Millet, L., Stock, A.,
Turon, J. L., and Wirth, S.: North–south palaeohydrological contrasts in the central Mediter-10
ranean during the Holocene: tentative synthesis and working hypotheses, Clim. Past, 9,
2043–2071, doi:10.5194/cp-9-2043-2013, 2013.
Martrat, B., Grimalt, J. O., Lopez-Martizez, C., Cacho, I., Sierro, F. J., Flores, J. A., Zahn, R.,
Canals, M., Curtis, J. H., and Hodell, D. A.: Abrupt temperature changes in the Western
Mediterranean over the past 250000 years, Science, 306, 1762–1765, 2004.15
Mayewski, P. A., Rohling, E. E., Stager, J. C., Karlén, W., Maasch, K. A., Meeker, L. D., Mey-
erson, E. A., Gasse, F., Kreveld, S. V., Holmgren, K., Lee-Thorp, J., Rosqvist, G., Rack, F.,
Staubwasser, M., Schneider, R. R., and Steig, E. J.: Holocene climate variability, Quaternary
Res., 62, 243–255, 2004.
McDermott, F.: Palaeo-climate reconstruction from stable isotope variations in speleothems:20
a review, Quaternary Sci. Rev., 23, 901–918, 2004.
McGee, D., deMenocal, P. B., Winckler, G., Stuut, J. B. W., and Bradtmiller, L. I.: The magnitude,
timing and abruptness of changes in North African dust deposition over the last 20 000 yr,
Earth Planet. Sc. Lett., 371–372, 163–176, 2013.
Mickler, P. J., Banner, J. L., Stern, L., Asmeron, Y., Edwards, R. L., and Ito, E.: Stable isotope25
variations in modern tropical speleothems: evaluating equilibrium vs. kinetic isotope eects,
Geochim. Cosmochim. Ac., 68, 4381–4393, 2004.
Mickler, P. J., Stern, L. A., and Banner, J. L.: Large kinetic isotope eects in modern
speleothems, Geol. Soc. Am. Bull., 118, 65–81, 2006.
Morrellon, M., Zvalero-Garces, B., Vegas-Vilarrubia, T., Gonzalez-Samperiz, P., Romero, O.,30
Delgado-Huertas, A., Mata, P., Moreno, A., Rico, M., and Corella, J. P.: Lateglacial and
Holocene paleohydrology in the western Mediterranean region: the Lake Estanya record
(NE Spain), Quaternary Sci. Rev., 28, 2582–2599, 2009.
2750
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Reimer, P. J., Bard, E., Bayliss, A., Beck, J. W., Blackwell, P. J., Bronk Ramsey, C., Buck, C. E.,
Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Haflidason, H.,
Hajdas, I., Hatté, C., Heaton, T. J., Homann, D. L., Hogg, A. G., Hughen, K. A., Kaiser, K. F.,
Kromer, B., Manning, S. W., Niu, M., Reimer, R. W., Richards, D. A., Scott, E. M.,
Southon, J. R., Sta, R. A., Turney, C. S. M., and van der Plicht, J.: IntCal13 and Marine13 ra-5
diocarbon age calibration curves 0–52 000years cal BP, Radiocarbon, 55, 1869–1887, 2013.
Riehla, S., Pustovoytov, K. E., Weippert, H., Klett, S., and Hole, F.: Drought stress variability in
ancient Near Eastern agricutural systems evidenced by δ13C in barley grain, P. Natl. Acad.
Sci. USA, 111, 12348–12353, 2014.
Roberts, N., Brayshaw, D., Kuzucuoglu, C., Perez, R., and Sadori, L.: The mid-Holocene cli-10
matic transition in the Mediterranean: causes and consequences, Holocene, 21, 3–13, 2011.
Roland, T. P.: Was there a “4.2kyr event” in Great Britain and Ireland? Evidence from the
Peatland Record, PhD thesis, University of Exeter, Exeter, UK, 2012.
Sadori, L. and Giardini, M.: Charcoal analysis, a method to study vegetation and climate of the
Holocene: the case of Lago di Pergusa (Sicily, Italy), Geobios-Lyon, 40, 173–180, 2007.15
Sadori, L. and Narcisi, B.: The postglacial record of environmental history from Lago di Pergusa,
Sicily, Holocene, 11, 655–672, 2001.
Sadori, L., Jahns, S., and Peyron, O.: Mid-Holocene vegetation history of the central Mediter-
ranean, Holocene, 21, 117–129, 2011.
Scholz, D. and Homann, D. L.: StalAge – an algorithm designed for construction of speleothem20
age models, Quat. Geochronol., 6, 369–382, 2011.
Seager, R., Ting, M., Held, I., Kushnir, Y., Lu, J., Vecchi, G., Huang, H. P., Harnik, N., Leet-
maa, A., Lau, N. C., Li, C., Velez, J., and Naik, N.: Model projections of an imminent transition
to a more arid climate in southwestern North America, Science, 316, 1181–1184, 2007.
Staubwasser, M. and Weiss, H.: Holocene climate and cultural evolution in late prehistoric–25
early historic West Asia, Quaternary Res., 66, 372–378, 2006.
Staubwasser, M., Sirocko, F., Grootes, P., and Segl, M.: Climate change at the 4.2 ka BP ter-
mination of the Indus valley civilization and Holocene south Asian monsoon variability, Geo-
phys. Res. Lett., 30, 1–4, 2003.
Tindall, J. C. and Valdes, P. J.: Modeling the 8.2 ka event using a coupled atmosphere–ocean30
GCM, Global Planet. Change, 79, 312–321, 2011.
2751
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Touchan, R., Anchukaitis, K. J., Meko, D. M., Attalah, S., Baisan, C., and Aloui, A.: Long
term context for recent drought in northwestern Africa, Geophys. Res. Lett., 35, L13705,
doi:10.1029/2008GL034264, 2008.
Touchan, R., Anchukaitis, K. J., Meko, D. M., Sabir, M., Attalah, S., and Aloui, A.: Spatiotemporal
drought variability in northwestern Africa over the last nine centuries, Clim. Dynam., 37, 237–5
252, 2011.
Vaks, A., Woodhead, J., Bar-Matthews, M., Ayalon, A., Cli, R. A., Zilberman, T., Matthews, A.,
and Frumkin, A.: Pliocene–Pleistocene climate of the northern margin of Saharan–Arabian
Desert recorded in speleothems from the Negev Desert, Israel, Earth Planet. Sc. Lett., 368,
88–100, 2013.10
Wanner, H., Beer, J., Bütikofer, J., Crowley, T. J., Cubasch, U., Flückiger, J., Goosse, H., Gros-
jean, M., Joos, F., Kaplan, J. O., Küttel, M., Müller, S. A., Prentice, C. I., Solomina, O.,
Stocker, T. F., Tarasov, P., Wagner, M., and Widmann, M.: Mid to Late Holocene climate
change: an overview, Quaternary Sci. Rev., 27, 1791–1828, 2008.
Weiss, H. and Bradley, R. S.: What drives societal collapse?, Science, 291, 609–610, 2000.15
Weiss, H., Courty, M.-A., Wetterstrom, W., Guichard, F., Senior, L., Meadow, R., and Curnow, A.:
The genesis and collapse of third millennium North Mesopotamian civilization, Science, 261,
995–1004, 1993.
Wiener, M. H.: The interaction of climate change and agency in the collapse of civilizations ca.
2300–2000 BC, Radiocarbon, 56, doi:10.2458/azu_rc.56.18325, 2014.20
Zanchetta, G., Drysdale, R. N., Hellstrom, J. C., Fallick, A. E., Isola, I., Gagan, M. K., and
Paresch, M. T.: Enhanced rainfall in the Western Mediterranean during deposition of sapropel
S1: stalagmite evidence from Corchia cave (Central Italy), Quaternary Sci. Rev., 26, 279–
286, 2007.
Zanchetta, G., Bar-Matthews, M., Drysdale, R. N., Lionello, P., Ayalon, A., Hellstrom, J. C.,25
Isola, I., and Regattieri, E.: Coeval dry events in the central and eastern Mediterranean basin
at 5.2 and 5.6 ka recorded in Corchia (Italy) and Soreq caves (Israel) speleothems, Global
Planet. Change, 122, 130–139, 2014.
2752
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Table 1. U/Th dates from MC-ICP-MS analyses of stalagmites GLD1-stm2 and GLD1-stm4
from the Gueldaman GLD1 Cave. Analytical errors are 2σof the mean. U decay constants:
λ238 =1.55125 ×1010 (Jaey et al., 1971) and λ234 =2.82206 ×106(Cheng et al., 2013).
Th decay constant: λ230 =9.1705 ×106(Cheng et al., 2013). aδ234U=([234U/238 U]activity
1) ×1000. bδ234Uinitial was calculated based on 230 Th age (T), i.e., δ234Uinitial =δ234Umeasured ×
eλ234×T. Corrected 230Th ages assume the initial 230 Th/232Th atomic ratio of 4.4 ±2.2 ×106.
Those are the values for a material at secular equilibrium, with the bulk earth 232Th/238 U value
of 3.8. The errors are arbitrarily assumed to be 50 %. cBP stands for “Before Present” where
the “Present” is defined as the year 2000 AD.
Sample 238U232Th 230 Th/232Th d234Ua 230Th/238U230 Th Age 230Th Age d234 UInitial
b 230Th Age Laboratory
(yr) (yr) (yrBP)c
Number (ppb) (ppt) (atomic ×106) (measured) (activity) (uncorrected) (corrected) (corrected) (corrected)
GLD1-stm2-7 169 ±0.1 396 ±0 136 ±1 863 ±2.3 0.105 ±0.001 6297 ±40 6228 ±72 863 ±2.3 6228 ±72 LSCE
GLD1-stm2-36 154 ±0.2 1922 ±39 137 ±3 910 ±2.2 0.103 ±0.000 6036 ±29 5848 ±136 925 ±2.3 5835 ±136 UM
GLD1-stm2-98 150 ±0.2 69 ±2 3077 ±73 776 ±2.4 0.086 ±0.000 5374 ±29 5366 ±29 788 ±2.5 5353 ±29 UM
GLD1-stm2-180 152 ±0.2 161 ±3 1157 ±25 644 ±2.0 0.074 ±0.000 5036 ±30 5018 ±33 653 ±2.1 5005 ±33 UM
GLD1-stm2-192 162 ±0.1 182 ±4 1158 ±24 807 ±1.7 0.079 ±0.000 4858 ±16 4840 ±20 818 ±1.7 4827 ±20 UM
GLD1-stm2-213 175 ±0.2 547 ±11 390 ±8 697 ±2.0 0.074 ±0.000 4841 ±33 4788 ±50 707 ±2.1 4775 ±50 UM
GLD1-stm2-286 169 ±0.2 207 ±4 980 ±21 756 ±1.8 0.073 ±0.000 4601 ±25 4581 ±28 765 ±1.9 4568 ±28 UM
GLD1-stm2-320 195 ±0.3 384 ±8 575 ±12 759 ±2.2 0.069 ±0.000 4321 ±26 4288 ±34 769 ±2.2 4276 ±34 Xi’an U
GLD1-stm2-340 194 ±0.3 354 ±7 612 ±13 800 ±2.9 0.068 ±0.000 4172 ±20 4142 ±29 809 ±2.9 4129 ±29 UM
GLD1-stm4-10 105 ±0.1 283 ±6 415 ±11 322 ±1.5 0.068 ±0.001 5734 ±90 5675 ±99 327 ±1.6 5662 ±99 UM
GLD1-stm4-24 126 ±0.1 983 ±20 135 ±3 347 ±1.9 0.064 ±0.001 5311 ±49 5143 ±128 352 ±1.9 5131 ±128 Xi’an U
GLD1-stm4-30 106 ±0.1 1362 ±27 80 ±2 298 ±1.9 0.062 ±0.001 5321 ±57 5035 ±210 302 ±1.9 5023 ±210 Xi’an U
GLD1-stm4-47 96 ±0.1 1104 ±22 88 ±2 290 ±1.9 0.062 ±0.001 5341 ±63 5082 ±194 294 ±1.9 5070 ±194 Xi’an U
GLD1-stm4-70 224 ±0.4 749 ±15 254 ±5 334 ±2.5 0.051 ±0.000 4282 ±27 4210 ±58 338 ±2.6 4197 ±58 UM
GLD1-stm4-113 155 ±0.2 130 ±3 910 ±20 363 ±2.1 0.046 ±0.000 3761 ±29 3743 ±32 367 ±2.1 3730 ±32 UM
GLD1-stm4-152 180 ±0.3 582 ±12 226 ±5 373 ±2.0 0.045 ±0.000 3590 ±25 3521 ±54 376 ±2.0 3508 ±54 UM
GLD1-stm4-195 175 ±0.1 929 ±19 131 ±4 369 ±1.7 0.042 ±0.001 3403 ±74 3290 ±108 372 ±1.8 3277 ±108 UM
2753
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Table 2. Radiocarbon dates from AMS analyses of charcoals from excavation sector S2 inside
the Gueldaman GLD1 Cave. * Kherbouche et al. (2014). Ages are reported in years before
2000 AD.
Depth Z Square Lab No. Material 14C Age Median Age Cal. Interval Note
(cm) (SacA#) (±σ; yr) (yr) (2σ; yr)
60 M48 39 408 Charcoal 1600 ±30 1482 1385–1604 This study
65 N48 29731 Charcoal 1610 ±25 1484 1415–1547 *
84 N48 39410 Charcoal 4020 ±30 4495 4411–4785 This study
86 N48 39411 Charcoal 3975 ±30 4416 4290–4569 This study
91 M48 39 409 Charcoal 3945 ±30 4403 4244–4522 This study
108 N47 36982 Charcoal 4355 ±30 4918 4851–5032 This study
124 L48 23 883 Charcoal 5250 ±35 6003 5924–6178 *
132 L48 23 884 Charcoal 4260 ±30 6025 5933–6178 *
147 M47 36 981 Charcoal 6120 ±35 7002 6907–7157 This study
2754
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Table 3. Summary of the features of climate and human activity in dierent climate stages and
occupation phases. Stages/phases 1–3 (bold) are presented in Fig. 7.
Climate stage Age Climate condition Occupation Age Human activity
(230Th yr) phase (14C cal yr)
0 7002–6003 Permanent and inten-
sive occupation
16200–5100 Wet & oscillatory 1 6003–4918 Permanent but less
intensive occupation
25100–4400 Wettest, ending with
a dramatic shift in
the last 200 years
24918–4403 Permanent and most
intensive occupation
34400–3800 Extremely dry 3 4403–1484 Abandonment of the
cave/occasional visit
43800–3200 Relatively wet 4 1484– Re-occupation of the
cave
2755
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 1. The Gueldaman GLD1 Cave (36260N, 4340E, 507 m a.s.l.). The top left shows the
location of the Gueldaman GLD1 Cave, in the N-Algeria of W-Mediterranean basin; the low left
shows a photo of cave entrance and local vegetation cover; the right panel shows maps of inner
cave where stalagmites and archaeological deposits are collected.
2756
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 2. U/Th dating of stalagmites GLD1-stm2 and GLD1-stm4 from the Gueldaman GLD1
Cave. U/Th dates and 2σerrors are shown next to sampling positions.
2757
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 3. Age models of stalagmites GLD1-stm2 and GLD1-stm4 from the Gueldaman GLD1
Cave. The age models were calculated using the StalAge program (Scholz and Homann,
2011). Note that the U/Th date of sample GLD1-stm4-47 was detected as a major outlier and
not used in the final age model of stalagmite GLD1-stm4. The 2σanalytical uncertainty of each
U/Th date (dot) is represented by the error bars, whereas the 95 % uncertainty assessed from
the model simulation is represented by thin curves.
2758
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 4. The δ18O,δ13 C and growth rate of stalagmites GLD1-stm2 and GLD1-stm4 from
the Gueldaman GLD1 Cave. U/Th dates with 2σerrors are presented at the top. The isotopic
ranges of modern calcites are also shown on the left (rectangles). Growth rates were calculated
from the StalAge age model. Note that the extraordinarily high and episodic growth rate at ca.
4600 yr BP in stalagmite GLD1-stm2 and at ca. 3800 yrBP in stalagmite GLD1-stm4 are likely
attributed to artificial simulations by the StalAge program and thus not discussed in terms of
climate in the text.
2759
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 5. Comparison of high-resolution Mid-Holocene stalagmite δ18O records across the
Mediterranean basin. From the top to bottom are stalagmite records from the Gueldaman GLD1
Cave in N-Algeria of W-Mediterranean basin (this study), the Corchia Cave (Zanchetta et al.,
2014) and the Renella Cave (Drysdale et al., 2006) in Central Italy of Central Mediterranean
basin, and the Soreq Cave (Bar-Matthews and Ayalon, 2011; Kaufman et al., 1998) in Israel of
E-Mediterranean basin. Dierent stalagmites from each area are represented in distinct colors.
U/Th dates with 2σerrors are shown at the top of each curve. Ages are reported in years before
2000 AD.
2760
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 6. Radiocarbon dating of anthropogenic deposits layers in excavation sector S2 in-
side the Gueldaman GLD1 Cave. From the left to right are 14C dates of charcoal samples,
anthropogenic deposit distribution, and a photo at depth across 75–88 cm showing a transi-
tion of layer from rich to rare anthropogenic deposits. Note that the gray colours highlight two
phases with diminished anthropogenic remains (especially pottery and charcoal) at ca. 4403–
1484 cal yr BP (depths of 75–60 cm) and ca. 6003–4918calyrBP (depths of 120–105 cm).
2761
CPD
11, 2729–2762, 2015
Evidence of
a prolonged drought
ca. 4200 yr BP
J. Ruan et al.
Title Page
Abstract Introduction
Conclusions References
Tables Figures
J I
J I
Back Close
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |
Figure 7. Comparison between evidence of ancient human occupation and of past climate
change from the Gueldaman GLD1 Cave. Stages/phases 1–3 are same to those defined in
Table 3.
2762
... (grains/g), f) Concentrations en TERRalcanes (ng/g, Jalali et al., 2016), h) Pourcentages de Fagus sp., i) Log du rapport de la forêt eurosibérienne sur la forêt méditerranéenne. j) Signal δ 18 O du spéléothème de la grotte de Gueldaman dans l'Atlas tellien au Nord de l'Algérie (Ruan et al., 2016). k) à o) : données Marge algérienne (MD04-2801) : k) Moyenne des longueurs de chaînes d'alcanes (ACL), l) Rapport Deutérium/Hydrogène sur les alcanes avec les n-C33 identifiés en bleu, les n-C31 en rouge et les n-C29 en vert, m) Concentrations en TERR-alcanes (ng/g), n) Log du rapport de la forêt eurosibérienne sur la forêt méditerranéenne, o) (Douguédroit, 1977 ;Xoplaki, 2002). ...
... c) à i) (sauf g)) : en TERR-alcanes (ng/g, Jalali et al., 2016), h) Pourcentages de Fagus sp., i) Log du rapport de la forêt eurosibérienne sur la forêt méditerranéenne. j) Signal δ 18 O du spéléothème de la grotte de Gueldaman dans l'Atlas tellien au Nord de l'Algérie (Ruan et al., 2016). et al., 2012). ...
Thesis
Ce travail de doctorat a pour objectif de comprendre les mécanismes et les réponses régionales de la variabilité climatique pendant la dernière déglaciation et l’Holocène en Méditerranée occidentale. Les environnements méditerranéens sont particulièrement vulnérables face aux aléas climatiques et à la pression anthropique. Il s'agit ainsi de discuter les forçages naturels et anthropiques à partir de signaux paléoenvironnementaux marins et continentaux couvrant les derniers 14 000 ans. Pour ce faire, deux séquences sédimentaires (Marge Algérienne et Golfe du Lion) ont fait l'objet d’études multiproxies principalement basées sur les études palynologiques (pollen, kystes de dinoflagellés et palynomorphes non-pollmiques), associées à des études sédimentologiques (MSCL, XRF, XRD), isotopiques, biomarqueurs moléculaires (alcénones et n-alcanes) ainsi que sur des quantifications climatiques et hydrologiques. L'analyse croisée de ces signaux, acquis avec une résolution moyenne de 150 ans sur l'Holocène et 30 ans sur l'évènement extrême du 4.2 ka BP, a permis de discuter des interactions océan-atmosphère-surfaces continentales, en questionnant l’évolution des biosphères marine et continentale au cours de l'Holocène. Ces études paléoenvironnementales s’appuient en amont sur l'étude des assemblages dinokystes et pollen reconstruits dans les sédiments modernes des deux zones d'étude. En synthèse, ce travail a permis de mettre en évidence de fortes disparités régionalisées à l’échelle orbitale et infra-orbitale selon des transects ouest-est et nord-sud. L’impact croissant des sociétés humaines, lié à une ouverture de plus en plus marquée des paysages, est discuté sur la marge algérienne depuis 5 000 ans BP, et dans le Golfe du Lion sur les derniers 1000 ans BP, avec une plus forte transmission des marqueurs d'anthropisation sur le plateau à partir de la mise en place des conditions hydrographiques modernes à partir d’environ 3 000 ans BP.
... While the better integration of archaeological and palaeoenvironmental data has been of interest to both research communities since the turn of the new millennium (Chapman and Gearey 2000), the attempt to better conciliate archaeology and palaeoenvironmental science is an area of research gaining even greater interest as of recent years (Arikan et al. 2016;Cremaschi et al. 2016;Holmgren et al. 2016;Izdebski et al. 2016;Mazzini et al. 2016;Morell on et al. 2016;Weiberg et al. 2016;Weiberg and Finn e 2018). While there is much evidence for the coincidence of shifts in climate system dynamics during the EBAC and LBAC, such as Mediterranean winter westerlies due to the NAO Wanner et al. 2008;L opez-Moreno et al. 2011;Di Rita et al. 2018;Isola et al. 2019;Katrantsiotis et al. 2019;Di Rita and Magri 2019), the northern winter-spring Siberian High (Rohling et al. 2002;Mayewski et al. 2004), and the southern-eastern African-Asian summer Monsoon (Neumann and Parpola 1987;deMenocal et al. 2000;Zhang et al. 2000;Hassan et al. 2001;Roberts et al. 2001;Gasse 2002;Magny et al. 2002;Russell, Johnson, et al. 2003;Roberts et al. 2004;Russell and Johnson 2005;Jones et al. 2006;Magny et al. 2007;Wanner et al. 2008;Cole et al. 2009;Baioumy et al. 2010;Vanni ere et al. 2011;Triantaphyllou et al. 2014;Ruan et al. 2016;Zanchetta et al. 2016;Katrantsiotis et al. 2019;Perşoiu et al. 2019), it has been shown that recognising the coincidence of broad scale climate shifts with broad scale societal trends does not allow for resolving the specific interactions between local climate changes and individual societal fluctuations at a site-by-site resolution Finn e et al. 2019). Due to this, there is a need to examine local case studies in an interdisciplinary approach to better understand the mechanisms of climate-society interrelations ; Finn e et al. 2019). ...
... From an archaeological perspective, (bi-)annual chronologies are ideal for identifying societal shifts, with sub-and multi-decadal records considered adequate and low resolution respectively (Knapp and Manning 2016). Most palaeoclimate records provide multi-centennial resolution, and sub-decadal palaeoclimate records are uncommon, typically restricted to speleothem/varved lake deposits (Wick et al. 2003;Ruan et al. 2016) (Supplementary 1). This makes direct correlation between climatic and societal shifts difficult from both chronological and geographical perspectives (Finn e et al. 2011;Butzer and Endfield 2012;Knapp and Manning 2016;Homsher and Cradic 2017). ...
Article
Full-text available
Bronze Age archaeological records from the eastern Mediterranean identify two periods of widespread so-called societal ‘collapse’ between ca. 4.50–ca. 4.20 cal ka BP and ca. 3.50–ca. 2.80 cal ka BP, respectively, which have been linked to a number of proposed causes, including climate change. However, the role of climate change in the ‘collapse’ of eastern Mediterranean Bronze Age societies has been questioned due to the resolution of climate proxy records. In this paper we present a regional synthesis of the highest resolution palaeoclimate records and compare these to archaeological evidence. By recalibrating radiocarbon dates onto a consistent timescale and using pollen, oxygen and carbon isotopes from both marine and terrestrial deposits, we reconstruct aridity at a 50-year resolution. Our results challenge a simple ‘climate destroyed society’ hypothesis. Instead, we find a more complex record of changing aridity and societal response and provide a nuanced perspective on climate versus non-climate causes of Bronze Age societal ‘collapse’ events. Our results have implications for the generation of palaeoclimate records aimed at exploring links between climate and societal change, emphasising the need for high resolution records proximal to archaeological sites.
... This camp site also followed a chronological occupation pattern similar to that of most mid-Holocene middens of the bay, exhibiting an occupational pause between circa 6585 BP and 2220 BP (Fujita, 2010;. The absence of archeological records during this period suggests a change in environmental and oceanographic conditions, and/or in the dietary strategies of natives, which led to the abandonment of the area, most likely in search of alternative food sources (Michelot, 2015). ...
Article
Oceanic characteristics of the Holocene are used to understand climatic patterns and phenomena that affect marine and human communities. Likewise, past marine conditions can be reconstructed from surface sea temperature (SST), using stable oxygen isotopes in bivalve shells. The objective of this study was to calculate Holocene summer SSTs for La Paz Bay, by analyzing δ18O of 14C dated bivalve shells (Chione californiensis) from a Holocene camp site located in Cañada de La Enfermería, Baja California Sur, México. Aragonite was extracted from the shells’ umbo, representing the summer growth season during the first year of life. δ18O value of C. californiensis is −1.9 ± 0.1‰ at present, and varied between −1.3‰ and −2.6‰ during the last 9 ky. In 9469 BP, 8396 BP, and 7708 BP, δ18O values were similar to those of the present. In 7857 BP, 7805 BP, and 7804 BP, δ18O was 18O depleted (0.6–0.9‰), indicating warmer summer SSTs versus the present. In 7070 BP, 6945 BP, and 2087 BP, δ18O was enriched in 18O (0.3–0.4‰), suggesting colder SSTs versus the present. This study coincides with other paleotemperature studies for the region and allows us to address the effect of changing SST on this marine resource, its use by human communities of the past, and its effects on human presence in the area with respect to climate variability.
... North Africa is one of the areas for which there is lack of data, despite attention having been paid to this region in recent decades to study climatic changes (Ruan et al., 2016) and model future scenarios. North Africa has been proposed as a possible refuge for warm-climate species during glacial periods (Carrión et al., 2010), but there is still a lack of empirical data on palaeovegetation in this region. ...
... North Africa is one of the areas for which there is lack of data, despite attention having been paid to this region in recent decades to study climatic changes (Ruan et al., 2016) and model future scenarios. North Africa has been proposed as a possible refuge for warm-climate species during glacial periods (Carrión et al., 2010), but there is still a lack of empirical data on palaeovegetation in this region. ...
Article
Vegetation dynamics during the Pleistocene–Holocene transition and the beginning of farming are major topics for palaeoenvironmental sciences, especially interesting in ecologically sensitive areas, such as in North Africa. However, there are still important geographic and chronological gaps of environmental information in this region. Archaeobotanical record from Gueldaman GLD 1 deals with these issues, as it presents the longest archaeobotanical sequence available nowadays for Algeria, which includes these moments of major changes in landscapes. This topic has been approached from an interdisciplinary point of view, focused on the analysis of various types of plant remains that result in the reconstruction of both environment and use of plant resources. Results reveal the existence of a postglacial phase of plant colonization with Cupressaceae formations, which are gradually integrating some elements of sclerophyllous vegetation, such as several species of Pistacia, well documented both in charcoal and seed records. Neolithic levels show a shift in vegetation composition, as Olea europaea dominates the spectra, accompanied by strawberry tree and evergreen Quercus, among others. The presence of Olea in earlier chronologies has resulted from intrusions from the Neolithic levels: a set of radiocarbon dates has made it possible to evidence this process and detect the extent of the intrusions, which are inherent to cave records.
... In the course of this period, the ~4.2 kyr cal. BP climate event [79] was likely expressed by drier hydrological conditions in the Western Mediterranean [94][95][96][97], in the context of high river alluviation [98] and more frequent summer rainfall [99]. Regarding the variety of the proxies, this climate event was likely a centennial-scale exacerbation of the Mediterranean climate, meaning a stronger seasonality of temperatures and precipitations [97]. ...
Article
Full-text available
We conducted palynological, sedimentological, and chronological analyses of a coastal sediment sequence to investigate landscape evolution and agropastoral practices in the Nao Cap region (Spain, Western Mediterranean) since the Holocene. The results allowed for a reconstruction of vegetation, fire, and erosion dynamics in the area, implicating the role of fire in vegetation turnover at 5300 (mesophilous forests replaced by sclerophyllous scrubs) and at 3200 calibrated before present (cal. BP) (more xerophytics). Cereal cultivation was apparent from the beginning of the record, during the Mid-Neolithic period. From 5300 to 3800 cal. BP, long-lasting soil erosion was associated with the presence of cereals, indicating intense land-use during the Chalcolithic and Bronze Age periods. The decline of the agriculture signal and vegetal recolonization is likely explained by land abandonment during the Final Bronze Age. Anthropogenic markers reappeared during the Iberian period when more settlements were present. A contingency of human and environmental agencies was found at 5900, 4200, and 2800 cal. BP, coinciding with abrupt climate events, that have manifested locally in reduced spring discharge, an absence of agropastoral evidence, and a marked decline in settlement densities. This case study, covering five millennia and three climate events, highlights how past climate changes have affected human activities, and also shows that people repeatedly reoccupied the coast once the perturbation was gone. The littoral zone remained attractive for prehistoric communities despite the costs of living in an area exposed to climatic hazards, such as droughts.
Article
Oceanic characteristics of the Holocene are used to understand climatic patterns and phenomena that affect marine and human communities. Likewise, past marine conditions can be reconstructed from surface sea temperature (SST), using stable oxygen isotopes in bivalve shells. The objective of this study was to calculate Holocene summer SSTs for La Paz Bay, by analyzing δ ¹⁸ O of ¹⁴ C dated bivalve shells ( Chione californiensis) from a Holocene camp site located in Cañada de La Enfermería, Baja California Sur, México. Aragonite was extracted from the shells’ umbo, representing the summer growth season during the first year of life. δ ¹⁸ O value of C. californiensis is −1.9 ± 0.1‰ at present, and varied between −1.3‰ and −2.6‰ during the last 9 ky. In 9469 BP, 8396 BP, and 7708 BP, δ ¹⁸ O values were similar to those of the present. In 7857 BP, 7805 BP, and 7804 BP, δ ¹⁸ O was ¹⁸ O depleted (0.6–0.9‰), indicating warmer summer SSTs versus the present. In 7070 BP, 6945 BP, and 2087 BP, δ ¹⁸ O was enriched in ¹⁸ O (0.3–0.4‰), suggesting colder SSTs versus the present. This study coincides with other paleotemperature studies for the region and allows us to address the effect of changing SST on this marine resource, its use by human communities of the past, and its effects on human presence in the area with respect to climate variability.
Article
Full-text available
L'Oued Mzi-Djedi, artère fluviale Sud-atlasique holocène en Algérie centrale Iddir Amara L'optique comportementale de cette étude étant dépendante d'un contexte environnemental humide quoiqu'instable et peu connu, souhaite attirer l'attention sur le potentiel holocène du réseau hydrographique de l'oued Mzi-Djedi, supposé maintenu entre les viii e et v e millénaires BC. Connecté aux bassins lacustres bordant au Nord et au Sud l'Atlas Saharien, ce sont les caractéristiques de leurs dépôts qui conduiront à préciser les périodes d'attractivité de ce territoire à travers les extensions spatiales des cours d'eau et les niveaux des plans d'eau. L'objectif de cette approche et de rassembler les données disponibles, les unes paléo climatiques tirées de l'étude de formations lacustres Sud-atlasiques, les autres provenant d'ensembles chrono-culturels holocènes. Ceux-ci étaient conservés dans des sites sous abri et des campements en plein air, aux traces nombreuses et enfouies, et d'autres gravées sur les parois rocheuses. Les occupations multimillénaires qu'elles attestent vont contribuer à préciser les périodes de présence et les motivations des populations ins-tallées près des fleuves, des sources et des lagunes. Les questionnements soulevés en contexte holocène rejoignent, mais à une échelle de moindre gravité, ceux que posent aujourd'hui les changements climatiques qui se manifestent en région méditerranéenne plus particulièrement. En Algérie, et dans le secteur géographique retenu ici, de nombreux chercheurs se sont penchés depuis plusieurs décennies sur l'actuel potentiel des eaux souterraines fossiles, capital exploité aujourd'hui (Kebiche 1994 ; Che-nafi 2013 ; Gonçalvès, Petersen, Deschamps, Hamelin, Baba-Sy 2013 ; Sellam, Zouggaghe, Vinolas, Moulai 2016). Certes l'emprise anthropique moderne qui caractérise ces territoires ne saurait être rapprochée de celle qui dut s'installer durant l'Holocène. Cependant, en s'appuyant sur cette tranche chronologique voisine de la nôtre, on détecte ce que furent les comportements des hommes et des faunes, à l'occasion notamment de deux événements climatiques majeurs, marqués par un dérèglement (cli-matique) et des périodes de sécheresse. Ces événements qui eurent un fort retentissement à travers le bassin méditerranéen n'épargnèrent pas les territoires atlasiques et sahariens. L'étude sera précédée d'un bref rappel
Article
Here we identify and analyze proxy data interpreted to reflect hydro-climatic variability over the last 10,000 years from the Mediterranean region to (1) outline millennial and multi-centennial-scale trends and (2) identify regional patterns of hydro-climatic variability. A total of 47 lake, cave, and marine records were transformed to z-scores to allow direct comparisons between sites, put on a common time scale, and binned into 200-year time slices. Six different regions were identified based on numerical and spatial analyzes of z-scores: S Iberia and Maghreb, N Iberia, Italy, the Balkans, Turkey, and the Levant, and the overall hydro-climate history of each region was reconstructed. N Iberia is largely decoupled from the five other regions throughout the Holocene. Wetter conditions occur in the five other regions between 8500 and 6100 yr BP. After 6000 yr BP, climate oscillated until around 3000 ± 300 yr BP, which seems to have been the overall driest period in the eastern Mediterranean and North Africa. In contrast, Italy and N Iberia seem to have remained wetter during this period. In addition, non-metric multidimensional scaling (nMDS) was applied to 18 long, continuous climate z-score records that span the majority of the Holocene. nMDS axes 1 and 2 illustrate the main trends in the z-score data. The first axis captures a long-term development of drier condition in the Mediterranean from 7900 to 3700 yr BP. Rapid shifts occur in nMDS axis 2 at 6700–6300 BP, 4500–4300 BP, and 3500–3300 BP indicating centennial-scale climate change. Our synthesis highlights a dominant south/east versus north/west Mediterranean hydro-climate dipole throughout the Holocene and therefore confirms that there was no single climate trajectory characterizing the whole Mediterranean basin during the last 10 millennia.
Preprint
The climatic controls on the stable carbon isotopic composition (d13C) of speleothem carbonate are less often discussed in the scientific literature in contrast to the frequently used stable oxygen isotopes. Various local processes influence speleothem d13C values and confident and detailed interpretations of this proxy are often complex. A better understanding of speleothem d13C values is critical to improving the amount of information that can be gained from existing and future records. This contribution aims to disentangle the various processes governing speleothem d13C values and assess their relative importance. Using a large data set of previously published records we examine the spatial imprint of climate-related processes in speleothem d13C values deposited post-1900 CE, a period during which global temperature and climate data is readily available. Additionally, we investigate the causes for differences in average d13C values and growth rate under identical climatic conditions by analysing pairs of contemporaneously deposited speleothems from the same caves. This approach allows to focus on carbonate dissolution and fractionation processes during carbonate precipitation, which we evaluate using existing geochemical models. Our analysis of a large global data set of records reveals evidence for a temperature control, likely driven by vegetation and soil processes, on d13C values in recently deposited speleothems. Moreover, data-model intercomparison shows that calcite precipitation occurring along water flow paths prior to reaching the top of the speleothem can explain the wide d13C range observed for concurrently deposited samples from the same cave. We demonstrate that using the combined information of contemporaneously growing speleothems is a powerful tool to decipher controls on d13C values ...
Article
Full-text available
The new facility Artemis was installed in 2003 in Saclay, France. This 3MV NEC Pelletron is dedicated to high-precision radiocarbon measurements for French 14C laboratories. We will present information on Artemis along with our sample preparation methods. Results from measurements on some intercalibration samples will be given along with the values of measured blanks. Finally, we report on some problems we have encountered when measuring sputter cathodes with high CH-outputs. © 2007 by the Arizona Board of Regents on behalf of the University of Arizona.
Article
Full-text available
Climate change has been suggested as a possible cause for the decline of urban centers of the Indus Civilization similar to 4000 yr ago, but extant paleoclimatic evidence has been derived from locations well outside the distribution of Indus settlements. Here we report an oxygen isotope record of gastropod aragonite (PO.) from Holocene sediments of paleolake Kotla Dahar (Haryana, India), which is adjacent to Indus settlements and documents Indian summer monsoon (ISM) variability for the past 6.5 k.y. A4% increase in delta O-18(a) occurred at ca. 4.1 ka marking a peak in the evaporation/precipitation ratio in the lake catchment related to weakening of the ISM. Although dating uncertainty exists in both climate and archaeological records, the drought event 4.1 ka on the northwestern Indian plains is within the radiocarbon age range for the beginning of Indus de-urbanization, suggesting that climate may have played a role in the Indus cultural transformation.
Article
Full-text available
We report the results of the first multi-year monitoring and modelling study of the isotopic composition of drip waters in a semi-arid karst terrane. High temporal resolution drip rate monitoring combined with monthly isotope drip water and rainfall sampling at Cathedral Cave, Australia, demonstrates that drip water discharge to the cave occurs irregularly, and only after occasional long duration and high volume rainfall events, where the soil moisture deficit and evapotranspiration is overcome. All drip waters have a water isotopic composition that is heavier than the weighted mean annual precipitation, some fall along the local meteoric water line, others trend towards an evaporation water line. It is hypothesised that, in addition to the initial rainfall composition, evaporation of unsaturated zone water, as well as the time between infiltration events, are the dominant processes that determine infiltration water isotopic composition. We test this hypothesis using a soil moisture balance and isotope model. Our research reports, for the first time, the potential role of sub-surface evaporation in altering drip water isotopic composition, and its implications for the interpretation of speleothem δO18 records from arid and semi-arid regions.
Article
We have developed techniques to measure the ^(230)Th abundance in corals by isotope dilution mass spectrometry. This, coupled with our previous development of mass spectrometric techniques for ^(234)U and ^(232)Th measurement, has allowed us to reduce significantly the analytical errors in ^(238)U-^(234)-^(230)Th dating and greatly reduce the sample size. We show that 6 × 10^8 atoms of ^(230)Th can be measured to ±30‰ (2σ) and 2 × 10^(10) atoms of ^(230)Th to ± 2‰. The time over which useful age data on corals can be obtained ranges from a few years to ∼ 500 ky. The uncertainty in age, based on analytical errors, is ± 5 y (2σ) for a 180 year old coral (3 g), ± 44 y at 8294 years and ± 1.1 ky at 123.1 ky (250 mg of coral). We also report ^(232)Th concentrations in corals (0.083–1.57 pmol/g) that are more than two orders of magnitude lower than previous values. Ages with high analytical precision were determined for several corals that grew during high sea level stands ∼ 120 ky ago. These ages lie specifically within or slightly postdate the Milankovitch insolation high at 128 ky and support the idea that the dominant cause of Pleistocene climate change is Milankovitch forcing.
Article
Speleothems (mineral deposits that formed in caves) are currently giving us some of the most exciting insights into environments and climates during the Pleistocene ice ages and the subsequent Holocene rise of civilizations. The book applies system science to Quaternary environments in a new and rigorous way and gives holistic explanations the relations between the properties of speleothems and the climatic and cave setting in which they are found. It is designed as the ideal companion to someone embarking on speleothem research and, since the underlying science is very broad, it will also be invaluable to a wide variety of others. Students and professional scientists interested in carbonate rocks, karst hydrogeology, climatology, aqueous geochemistry, carbonate geochemistry and the calibration of climatic proxies will find up-to-date reviews of these topics here. The book will also be valuable to Quaternary scientists who, up to now, have lacked a thorough overview of these important archives. Additional resources for this book can be found at: www.wiley.com/go/fairchild/speleothem.
Article
Human history has been marked by major episodes of climate change and human response, sometimes accompanied by independent innovations. In the Bronze Age, the sequencing of causes and reactions is dependent in part on dendrochronology and radiocarbon dating. This paper explores the interaction of a major, prolonged desiccation event between ca. 2300 and 2000 BC and human agency including migrations, the displacement of trading networks, warfare, the appearance of weapons made of bronze, and the first appearance of sailing vessels in the Mediterranean.
Article
Soreq (Israel) and Corchia (central Italy) Caves are located 2500 km far apart along the Mediterranean winter-storm track and are ideally suited for investigating past variations of winter rainfall in the Mediterranean region. Analyses of speleothem δ18O records from both caves for the period between ca. 7 to 4 ka BP show some striking similarities for the ca. 6 and 4 ka interval, but lack agreement between ca. 7 to 6 ka BP. Two prominent isotopic excursions, argued to reflect relatively drier conditions, are centred at ca. 5.6 and ca. 5.2 ka. The 5.2 ka event lasts less than a century, whereas the 5.6 ka event extends from ca. 5.7 to 5.4 ka. A period of progressive drying is also apparent from ca. 5 to 4 ka. Another prominent event, reflecting wetter conditions, is recorded in both records at ca. 5.8 ka and seems to last several decades. The 5.6 and 5.2 ka events occurred within a period of higher deposition of haematite-stained grains in cores of the sub-polar North Atlantic, and correlation with the wind strength proxy record from Hólmsá loess profile in Iceland suggests that rainfall reduction was related to a reduced vapour advection from Atlantic towards the Mediterranean connected to northward shift in the Westerlies. A comparison with Alpine records, including the Spannagel Cave isotope record, suggests that dry events recorded at Soreq and Corchia caves may correspond to wetter (lake high stands) and cooler (glacier expansion) conditions in the Alpine region, indicating complex regional climate re-organization.
Article
Speleothem growth requires humid climates sufficiently warm to stimulate soil CO2 production by plants. We compile 283 U/Th dates on 21 stalagmites from six cave systems in the NW coast of Spain to evaluate if there are patterns in stalagmite growth that are evidence of climatic forcing. In the oldest stalagmites, from marine oxygen isotope stage (MIS) 7–5, growth persists through the glacial period. Hiatuses and major reductions in growth rate occur during extreme minima in summer insolation. Stalagmites active during the last interglaciation cease growth at the MIS 5–4 boundary (74 ka), when regional sea-surface temperature cooled significantly. During MIS 3, only two stalagmites grew; rates were highest between 50 and 60 ka during the maximum in summer insolation. One stalagmite grew briefly at 41 ka, 36.5 and 28.6 ka, all during warm phases of the Dansgaard–Oeschger cycles. A pronounced Holocene optimum in stalagmite growth occurs from 9 to 6 ka. The cessation of most growth by 4.1 ka, coincident with broad increases in aridity over the Mediterranean and areas influenced by the North African Monsoon, suggest that regions such as NW Spain, with dominant Atlantic moisture sources, also experienced increased aridity at this time.