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Late Middle Pleistocene climate in southwestern China: inferences from the
stratigraphic record of Panxian Dadong Cave, Guizhou
Panagiotis Karkanas
a,
, Lynne A. Schepartz
b
, Sari Miller-Antonio
c
, Wang Wei
d
, Huang Weiwen
e
a
Ephoreia of Palaeoanthropology– Speleology of Southern Greece, Ardittou 34b, 11636 Athens, Greece
b
Department of Anthropology, Florida State University, 1847 West Tennessee Street, Tallahassee, FL 32306, USA
c
Department of Anthropology/Geography, California State University, Stanislaus, One University Circle, Turlock, CA 95382, USA
d
Natural History Museum of Guangxi, No. 1-1 East Renmin Road, Nanning 530012, China
e
Institute of Vertebrate Paleontology and Paleoanthropology, P.O. Box 643, Beijing, China
article info
Article history:
Received 8 February 2008
Received in revised form
13 Ma y 20 08
Accepted 21 May 2008
abstract
Panxian Dadong Cave, situated in the subtropical zone of southwestern China, preserves a fan-like
sedimentary sequence close to its entrance that spans the period between MIS 8 and 5 (300–130 ka).
The frequent alternation of flowstone formation, cementation, clastic deposition, and frost activity in
the depositional sequence makes it ideal for reconstructing the environmental conditions prevailing
during the later Middle Pleistocene on the Guizhou Plateau.
Macroscopic and microscopic sedimentary analyses determine that clastic deposits were entering
the cave in the form of intermittent cohesive debris flows and sheetflows during cold and relatively dry
climatic conditions when vegetation cover was reduced. Interlayered impure flowstones were forming
during wetter phases but still under glacial conditions. Seasonally freezing temperatures are deduced
from the frequent occurrence of cycles of well-developed freeze–thaw features affecting both the clastic
parts of the sequence and the flowstones as they were deposited. The described depositional processes
were responsible for lateral redistribution on the fan surface of bone remains and lithic artifacts that
were accumulating on the surface as a result of hominid activities. During the intervening interglacial
stages (MIS 7 and possibly MIS 5) clastic deposition was considerably reduced and only thin flowstone
caps and weathering manganese–iron crusts were forming. It is suggested that precipitation was much
higher during glacial intervals than interglacials under a predominantly cold climate. Dadong Cave
provides a good example of very cold and wet climatic conditions during glacials in the subtropics of
East Asia.
&2008 Elsevier Ltd. All rights reserved.
1. Introduction
Caves can act as perfect sedimentary traps as they are
protected from many post-depositional subaerial processes, and
their sedimentary facies have been used to interpret and
reconstruct depositional histories that can track changes in earth
system processes (Springer, 2005). These data also yield insights
into the climate and landscape evolution of the area. Speleothems,
in particular, are regarded as appropriate terrestrial analogs to the
deep sea and ice cores used in establishing a detailed terrestrial
climatic record (Bar-Matthews et al., 2003). Conversely, clastic
cave sediments have been more rarely used to infer climatic
signals. In most cases they are considered to be coarse proxies of
environmental changes. Many variables affect the formation of
clastic sediments, therefore the paleoclimatic significance of these
deposits is complex and open to interpretation (for a review see
Farrand, 2001;Woodward and Goldberg, 2001). However, there
are certain cave sedimentary features like cryogenic features that
are useful climatic proxies, and when their study is combined
with stratigraphic and field sedimentary facies analysis, these
features can provide important clues to the climatic and
geomorphological evolution of an area. Petrographic or micro-
morphological studies of cave sediments are particularly useful
for revealing features related to frost activity and ice segregation
(Gremaschi and Van Vliet-Lanoe
¨, 1990;Courty and Vallverdu,
2001;Karkanas, 2001). In addition, the study of sedimentary
facies at the microscopic level provides additional information on
the depositional processes (Knapp et al., 2004). The microscopic
approach to studying cave sediments has a wide application in
caves with archaeological remains (Goldberg and Sherwood,
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Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/quascirev
Quaternary Science Reviews
0277-3791/$- see front matter &2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.quascirev.2008.05.005
Corresponding author. Tel.: +30 21 07 5614 11; fax: +30 21 07 5614 38.
E-mail addresses: pkarkanas@hua.gr (P. Karkanas),lschepartz@fsu.edu
(L.A. Schepartz),smillerantonio@csustan.edu (S. Miller-Antonio),
wangwei12841@163.com (W. Wang),huangweiwen@ivpp.ac.cn (W. Huang).
Quaternary Science Reviews 27 (2008) 1555– 1570
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2006). Data from cave sediments provide contextual information
for the interpretation of archaeological remains and the human
role in formation of the deposits (Courty et al., 1989).
This study is concerned with a site located in an area with
meager climatic information, but the region is of major impor-
tance in understanding monsoon changes related to glacial and
interglacial stages. Panxian Dadong Cave lies in the western part
of the Guizhou Plateau that is part of the southeastern extension
of the Tibetan Plateau (Fig. 1). A preliminary study documented
that the cave deposits have a rich record of cyclical climatic
changes (Wang et al., 2004). Paleoclimate studies have been
conducted in central China using loess sequences (Kukla, 1987)
and on the Qinghai-Xizang (Tibetan) Plateau using lake and ice-
core records (Lister et al., 1991;Thompson et al., 1997), but few
paleoclimate records exist from southwestern subtropical China.
The majority of them are from the Holocene and the late
Pleistocene (Zheng et al., 2002;Yuan et al., 2004;Zhang et al.,
2004;Zhu et al., 2006). Therefore, our aim is to present a
combined microscopic and macroscopic sedimentary facies
analysis of a cave sequence within an established chronological
framework to infer climatic changes between ca 30 0–130 ka. As
these cave sediments also contain archaeological remains these
data can also be used to establish the implications for the human
use of the cave, and fill a critical gap in the climate record during
the time when humans were broadly dispersed across the East
Asian landscape.
2. Cave setting and environment
2.1. Cave formation
The Guizhou Plateau where Panxian Dadong Cave is located
(25137
0
38
00
N, 104144
0
E) is composed of Carboniferous and Permian
limestones, basalt, shale, sandstone, and coal formations. The
general elevation ranges between 1400 and 2000 m. Dadong is the
middle cave in a series of interconnecting karstic caverns within a
230 m hill. The hill itself is situated in a small karstic valley (polje)
that lies at an elevation of 1630m above sea level. The eastern
facing cave entrance is 55 m wide and 50 m high and located 32 m
above the valley floor (Fig. 2). The main chamber narrows slightly
to become an average 35 m wide and 30 m high phreatic passage
that runs over 220 m in length and covers an area of over 800 0 m
2
.
The area is a typical karst combination of peak clusters and
depressions (Fig. 2). The cave itself is a sinkhole formation, the
result of neotectonic uplift, where underground rivers with
phreatic features drained through (Xiong and Liu, 1997). The cave
walls bear large asymmetrical meter-sized scallops showing a
direction of flow towards the interior of the cave and evident of a
period when the cave was an active sinkhole. The continuous
uplift of the cave and lowering of the base level rendered the
Dadong passage dry. After that, clastic sedimentation alternating
with flowstone formations prevailed in the cave. A more recent
collapse at the back of the cave has produced a pitfall connecting
the cave with the top of the hill.
The entrance of the cave is dominated by a huge complex
columnar speleothem from which an extensive flowstone formation
spreads and covers the present floor of the cave (Figs. 3–5). Several
other flowstone formations intercalated within the studied clastic
deposits also spread down from the modern entrance along the
northern wall and the area of the columnar speleothem, forming a
gently sloping fan towards the interior of the cave.
2.2. Climatic data
The vegetation of the Dadong area is characterized by mixed
evergreen coniferous, broad leaf, and deciduous forest. Mean
annual temperature is about 14 1C and mean annual precipitation
is approximately 1400 mm. In summer, the monthly highest mean
temperature is observed during July (20–21 1C) and in winter the
lowest is in January (4–5 1C). The climate is subtropical (humid in
summer and dry in spring). From mid-May through the beginning
of October the area is influenced by summer monsoons. Toward
the end of fall and into winter, cold air from the north and warm
air from the south meet in this area forming a stationary front and
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Fig. 1. Map of China with the location of Dadong Cave (1) relative to Tongzi Cave (2) and the Dongge and Qixing caves (3).
P. Karkanas et al. / Quaternary Science Reviews 27 (2008) 1555–15701556
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establishing a regime of rainy weather. From February to early
May, the weather is very dry as a result of strong south-west
winds. In summary, precipitation during the summer season is
mainly controlled by the East Asian summer monsoon, while the
meteoric precipitation in the winter season is mainly controlled
by the cold fronts of the winter monsoon and the southwest
warm-wet air masses (Zhang et al., 2004).
2.3. Archaeology
Panxian Dadong contains an extensive record of human
activities during the late Middle Pleistocene. Stone tools of
limestone, basalt, and chert were recovered from the cave
excavation and there is some evidence that Rhinoceros sinensis
teeth were also flaked to produce small scrapers (Miller-Antonio
et al., 2000, 2004). The stone tools are associated with a rich
assemblage of the Middle Pleistocene southern Chinese Ailuropo-
da–Stegodon fauna predominated by R. sinensis and Stegodon
orientalis elements (Schepartz et al., 2003;Bekken et al., 2004).
Other taxa include a variety of ungulates (cervids, bovids,
rhinoceroses, pigs, giant tapirs, muntjak, and musk deer),
insectivores, rodents (white-toothed shrew, porcupine, and bam-
boo rat), and small numbers of carnivores (tiger, bear, hyena,
weasel, and tiger cat) and primates such as macaques. The
excavation also yielded five Homo sapiens teeth. Bones and
artifacts show very little indication of transport or subaerial
weathering so it is inferred that they were accumulating inside
the cave. The exact process of accumulation is thus of primary
interest for reconstructing the human use of the cave and
exploitation of faunal resources in the area.
3. Methods
The recent excavated part of the sedimentary sequence is
approximately 5 m deep. It runs from the northern wall to the
center of the cave at roughly the middle of the main chamber
(Fig. 3). Material was removed horizontally with artifacts and
bones larger than 2.5 cm piece-plotted with a total station as they
were uncovered and smaller material recovered with screening
and hand sorting.
In addition to field stratigraphic and sedimentological ob-
servations, 28 intact blocks of sediment were collected from the
profiles of the excavation for micromorphological and petro-
graphic study. Their locations are shown in Fig. 5. Strongly
cemented sediments were removed by cutting blocks of appro-
priate dimensions (ca (10–30) 10 10 cm) using an angle
grinder, while loose samples were first jacketed with plaster
of Paris to secure undisturbed samples. All samples were
impregnated with polyester resin under vacuum. In total 34
medium (3 5 cm) and 28 large format (5 7 cm) thin sections
were produced. They were studied under a stereomicroscope at
magnifications of 5–40 and a polarizing microscope at
magnifications ranging from 15 to 400 . Micromorphological
description follows the terminology of Bullock et al. (1985) as
modified by Stoops (2003), whereas certain features related to
calcite cementation were described according to the standard
petrographic terminology of carbonate rocks (Scholle and Ulmer-
Scholle, 2003).
The mineralogy of selective bulk samples was analyzed with
Fourier Transform Infrared Spectroscopy (FTIR) in an attempt to
decipher the mineralogical features identified in the thin sections.
About 0.5 mg of sediment was mixed with about 4 mg of KBr and
hand-pressed to produce a pellet that was introduced into the
chamber of a MIDAC Corporation (Costa Mesa, CA) infrared
spectrometer. Spectra were obtained at 4 cm
1
resolution and
interpreted using a built-in library (for more details, see Weiner
et al., 1993).
4. Stratigraphy
The deposits of the main chamber make a gently inclined slope
from the entrance. Some key stratigraphic markers can be roughly
followed in their full extension in the 1996–2005 excavation (the
area where detailed observation and analysis of the deposits
was conducted) as well as in the previous excavated trenches (see
Figs. 4 and 5). Therefore, continuity of strata can be determined
and reworking from the underlying layers (e.g. undermined
flowstones) is not observed—rendering the sequence reliable for
environmental interpretation (cf Moriarty et al., 2000).
A first generation of a series of complex speleothem formations
(bell canopies, after Hill and Forti, 1997) on the side walls of the
main cave passage is one of the earliest sedimentary phases that is
now partially buried by the clastic sedimentary sequence (Fig. 4).
These speleothems grew below a line representing a former water
level inside the cave at approximately 4.5 m above the present
floor. Below this line the walls are smoothly corroded overprinting
the scallop formations. The water-line corresponds to a period
when the entrance of the cave was close to the base of the valley
and the Dadong passage was seasonally flooded (Xiong and Liu,
1997). The canopies overprint the water-marks and thus have
been formed after the cave was abandoned by stream processes,
the passage was drained, and clastic sediment started entering
from the modern entrance. The sedimentary sequence is inclined
to the back of the cave, and from the northern wall to the center.
The sedimentary sequence comprises clastic sediments with
thin intercalating capping flowstones and a top thick flowstone. In
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Fig. 2. (a) Photograph of the area around Dadong Cave (with arrow) showing the
ragged karstic topography. Note the peak clusters on the very upper left edge of the
photograph. (b) The entrance of the cave in the hill above the karstic valley in front.
P. Karkanas et al. / Quaternary Science Reviews 27 (2008) 1555–1570 1557
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the lower parts, the clastic sediments are mainly massive silts
changing to alternating bedded gravels, clay-rich deposits, and
boulder lags. Field and microscopic observations of the individual
strata of the cave are described in Table 1 and stratigraphic
sections are shown in Figs. 5 and 6.
5. Interpretation of depositional facies and
post-depositional alterations
The great potential for reconstructing the environmental
conditions in Dadong warrants a fuller interpretation of the
depositional features. Although the actual sedimentary type may
not necessarily be diagnostic of surface environmental condi-
tions—because of large delays between surface processes and
final sedimentation in caves—the processes responsible for the
final deposition are directly linked with surface processes
(Moriarty et al., 2000). The Dadong deposits form a small low
angle fan that is directly connected to the entrance and the
outside environment. Thus, the main source of sediment input is
well defined. Furthermore, the sequencing of flowstones versus
clastic deposition is suggested to be excellent for reconstructing
environmental conditions in caves (Moriarty et al., 2000). Capping
flowstones preserve the integrity of the stratigraphy and prevent
post-depositional mixing and slumping. There are also several
other criteria that, in the case of Dadong, can constrain the
interpretation of the sediment, such as freeze–thaw features that
show a very well-developed cyclical pattern. In this respect,
depositional facies and their post-depositional evolution can be
used to deduce paleoenvironments. The main depositional facies
and post-depositional alterations (a total of six), as well as their
environmental significance, are as follows.
5.1. Massive silty calcite facies
The lower part of the clastic sequence, i.e. layers XII–VIII,
is characterized by massive moderately to well-sorted silty
calcitic sediment with some dispersed rounded calcareous clasts
and few soil lumps (Figs. 5 and 6;Table 1). Their massive
appearance is probably due to deposition from flash flood
episodes or hyperconcentrating flows dumping loess-like material
from the valley inside the cave. Although loess is not reported
from this area, the large amount of clastic silt sized calcite can be
considered to be typical dust sediment (Nickling, 1994)of
mostly local origin (limestone plateau). It is evident, however,
that the sediment is actually redeposited loess-soil as it has a
moderate content of clay and clay soil lumps. A temporarily
elevated water table is also suggested by the presence of organo-
metallic impregnative and iron–manganese aggregate nodules
(Table 1).
5.2. Alternation of bedded gravel, matrix-rich facies,
and boulder lags
Layers VII and VI and above mark a change to a different
sedimentation pattern characterized by alternating clast-
to matrix-supported gravel and matrix-rich beds (Figs. 5–8;
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Fig. 3. Panxian Dadong main chamber excavations. The excavation area designated as Area C consists of a long trench that was cleared of approximately one meterof
disturbed sediments. Controlled excavations then followed in the north portion of the trench, as shown in the inset.
P. Karkanas et al. / Quaternary Science Reviews 27 (2008) 1555–15701558
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Table 1). Their field and microscopic features suggest deposition
from episodic sediment gravity flows and water flows forming a
small fan-like feature from the present entrance to the center
of the main chamber. Sediment gravity flows are mainly in the
form of cohesive debris flows characterized by matrix to clast-
supported tabular beds with floating boulders, coarse ‘‘tails’’, and
imbrication of coarser particles (cf Blikra and Nemec, 1998). They
were formed when colluvium that had accumulated in the
entrance was destabilized by water saturation and failed under
the force of gravity. It was transformed into a high viscosity flow
that fanned down into the main chamber. Water flows are
restricted to sheetflows forming tabular beds of plane-parallel
stratified subrounded gravels (cf Blikra and Nemec, 1998). They
were formed by shallow unconfined (not channelized) water flow
washing the fan. Sediment feeding was from the modern entrance
and close to the northern wall as suggested by the general
geometry of the sequence, the lateral grading of the individual
layers, and the cementation pattern; all have a source from the
northern cave wall and the entrance.
What is of major interest is the content of reworked calcareous
clastic material with compound pisoid structure derived from
already deposited and cemented material inside the cave (Fig. 9).
These features are mostly associated with gravelly beds or impure
(clastic-rich) flowstone formations. In contrast, the clayey matrix-
rich beds normally do not contain complex pisoids, but instead are
enriched in decayed organic matter and concentric aggregate
organo-metallic nodules.
The formation of this alternation of clastic sediment requires
an open entrance that permits unconfined water flow down the
opening. These are regularly associated with frost action (see
below) and may derive from surges of sediment-laden water
related to snow melt during a predominantly cold climate with
reduced vegetation cover. Some of the thicker matrix-rich beds
might have been formed during a milder climatic regime given
their high organic content and reduced intensity of freeze–thaw
features.
5.3. Flowstones
Since all flowstones in Dadong Cave are contaminated with
clastic material, an open entrance is hypothesized permitting
episodic sediment and water flow (cf Moriarty et al., 2000).
Flowstone formation requires relatively continuous precipitation
of calcite from water films flowing over the surface, and they have
been interpreted as indicators of former warmer and wetter
climates in temperate zones or increased precipitation in arid
desert settings (e.g. Baker et al., 1993;Ayliffe et al., 1998). In the
case of Dadong, extensive flowstone formations are related to cold
and wet environmental conditions, as they are closely associated
with intensive freeze–thaw activity (see below). In particular,
layer I is an impressive thick impure flowstone (Figs. 4–6 and 10)
covering much of the present surface of the cave and containing
abundant evidence of ongoing frost action. The same activity,
but less extensively, can be seen in the impure flowstones of
layers VI, IV and II (Fig. 5). However, some thin massive impure
flowstone formations without evidence of freeze–thaw activity
are related with the crust formations found in layer VII and
probably layer VIa (Fig. 7) as well as in the capping crust of layer I.
These were presumably deposited during relatively wet but
warmer periods.
5.4. Calcite cementation
In Dadong cave calcite cementation of clastic layers is in the
form of phreatic and vadose calcite precipitation inside the pores
of the sediment (Figs. 11b and 12). Formation of bladed rims of
calcite and complete filling of the pores with blocky sparite (layers
XII, XI, IX, VIII, III, II and I: Table 1) requires a continuous
immersion of the sediment in water (Scholle and Ulmer-Scholle,
2003). It is most likely that occasionally the cave floor was
saturated by water with water-filled pools occupying the surface.
Cementation is always related with intensive frost action but
usually it post-dates it.
5.5. Frost action
Most of the layers in Dadong Cave are characterized by fissure
to incipient platy microstructures (Figs. 11a and 13) that in most
cases give way upwards to lenticular and finally granular
microstructures (Figs. 11, 12 and 14–17;Table 1). In several cases
laminated silty calcite link cappings support several granules
(Figs. 11 and 12) and loose sorted grains fill the voids (Fig. 16).
These types of microstructures are typical of frost activity and are
reproducible by experiments (Van Vliet-Lanoe
¨et al., 1984;
Gremaschi and Van Vliet-Lanoe
¨, 1990). It is well known that in
seasonally frozen soils when soil water is transformed into ice the
latter is crystallized outside the groundmass and takes the form of
ice lenses that are parallel to the soil surface. The stresses thus
produced bring about fragmentation and the production of
incipient fissures that with repeating freezing give way to platy
and lenticular aggregates known also as ice lensing. Further
fragmentation produces fine particles that are transported by the
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Fig. 4. Sketch section showing relationships between the canopy bell, water-line,
and dated speleothems (see also Table 2). Stratigraphy of flowstones is based on
observations in the old excavated Area A, northern wall.
P. Karkanas et al. / Quaternary Science Reviews 27 (2008) 1555–1570 1559
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melt water and accumulate as cappings on the upper part of the
aggregates (Courty et al., 1989, pp. 160–163). In particular the
complex granular structure observed in Dadong Cave sediments
enclosing several generations of pisoids (Figs. 14b and 9)is
attributed to gelifluction, resulting from an increasing slope or
water flow (Van Vliet-Lanoe
¨et al., 1984).
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Fig. 5. Stratigraphic sections of excavated area C (refer to Fig. 3) showing the location of the micromorphological samples (black rectangles; not to scale) and the location of
the dated fossil teeth (black dots with Arabic numbers: see Table 3).
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Table 1
Description of the stratigraphy of the Dadong Cave sedimentary sequence, including macroscopic and microscopic observations
Layer Thickness
(cm)
Field observations Micromorphological observations
XII 50–60 A thick massive yellowish brown and slightly
cemented sediment with very few floating
pebbles.
Under the microscope it has a sorted fine silty, mostly calcitic texture with
a few dispersed clay lumps. Very few fine silty quartz grains were also
identified. Organo-metallic impregnated and iron–manganese aggregate
nodules are widespread. A few very well-rounded to subrounded
calcareous aggregates with organic hypocoatings are visible. The
microstructure is fissure to incipient platy structure (Fig. 11a). Very few
voids show isopachous rims or complete filling of equant sparite.
XI 30 The same sediment as XII but moderately
cemented.
Stronger development of lenticular and granular microstructures (Fig. 11b)
and some clastic-rich calcite cappings. Most of the pores have isopachous
rims or are sealed with sparitic calcite of phreatic origin (Fig. 11b).
However, vadose laminated silty clay coatings in the form of pendants are
also observed (Fig. 11b). Secondary micritization is evident in the upper
part.
X 20 A massive yellowish brown layer with very few
floating rounded limestone fragments ranging up
to boulder size. The layer thins out towards the
center of the cave.
Moderate unsorted sandy silt calcitic sediment with some rounded
calcareous aggregates, limestone and speleothem fragments. Some of the
aggregates and fragments have organic and organo-metallic hypocoatings.
There are several cases where the clastic-rich calcareous aggregates have
an incipient pisoid structure (concentric nucleic to aggregate nodules).
The matrix also has organo-metallic impregnated and iron–manganese
aggregate nodules. Fissure and incipient platy microstructure is evident
towards the upper part. A few silty clay coatings were also identified.
IX 30 A massive reddish yellow to brownish locally
cemented layer.
A well-sorted calcitic silt with some clay and moderately developed
organo-metallic impregnated and iron–manganese aggregate nodules.
Some impure calcareous aggregates with pisoid structure and few
rounded limestone and speleothem fragments were identified. Well-
developed lenticular microstructure (Fig. 14a) that grades upwards into a
granular one. A few silty calcite cappings and some laminated dusty clay
coatings are observed. Most of the pores are lined with phreatic bladed
calcite with some of them completely sealed.
VIII 10–20 An unconsolidated reddish brown fine-grained
layer with subrounded limestone boulders
floated in the matrix. A thin calcareous surface
crust separates layer VIII from the overlying layer
VII. Bones and lithic artifacts are widespread
(prior to this layer, there was little bone
recovered and few lithic artifacts).
The matrix is more unsorted than that of the layer below as evidenced by
the presence of some angular sandy grains. The microstructure is
lenticular that upwards grades to granular. Laminated silty calcite link
cappings support several grains (Fig. 14b). Impure calcareous aggregates
with pisoid structures are regularly observed. Indeed, the characteristic of
this layer is a complex granular structure enclosing several generations of
pisoids (Fig. 14b). Thick laminated reddish dusty clay coatings are seen
everywhere. Organo-metallic hypocoating is widespread on the
aggregates. Towards the top there is phreatic calcite cementation in the
form of isopachous bladed calcite and infills of sparitic calcite.
A calcitic crust is developed on top of the granular microstructure
enclosing some of the granules within it. The crust is characterized by
compound clay and iron–manganese impregnative features (Fig. 18).
VII 10–30 A matrix-supported gravel with sizes ranging up
to boulders. The gravel is subangular to
subrounded. Close to the northern wall a
flowstone cap is evident.
Some of the finer clastic sediment in between the boulders displays
granular microstructure and complex pisoid structures. However, the
flowstone cap has a massive microstructure.
VI 30–40 VIb: A brownish lenticular fine-grained bed.
Some gravel is dispersed inside with subrounded
forms. It also contains a dense accumulation of
bone and lithic artifacts.
Lenticular and granular microstructures are widespread. Complex
redeposited pisoid structures are often encountered.
VIa: A boulder lag with a thin flowstone cap on
top (Fig. 7). It contains a dense accumulation of
bone and lithic artifacts.
Locally, both the matrix and the flowstone are characterized by lenticular
to granular microstructure.
V 40–50 A brownish fine-grained deposit with floating
boulders and fine gravel (Fig. 7). Bone and lithic
artifacts are less abundant.
An unsorted clayey loam containing many organo-metallic impregnative
nodules, some of them with concentric and dendritic structures.
Remnants of decayed organic matter are abundant. From the top to the
bottom the microstructure changes from lenticular, to platy and fissure,
and finally to massive (Figs. 15 and 16).
IV 10–20 A tabular bed of mostly clast-supported
subrounded to rounded gravel that is moderately
sorted and plane-parallel stratified (Fig. 7). It
thins out from the northern wall to the center of
the cave. It is also strongly cemented close to the
wall giving way to impure thin flowstone.
Contains bones and lithic artifacts.
The fine matrix in between the gravel is characterized by erratic
development of lenticular microstructures and a compound pisoid
granular structure. In some areas the lenticular microstructure continues
undisturbed in the underlying layer V.
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In the Dadong Cave sequence discrete frost events can be
recognized, as they are separated by cementation events not
affected by frost action or showing repeated cycles with increas-
ing intensity upwards from angular fissuring to planar, lenticular
and finally granular microstructures (Fig. 15). Freeze–thaw
features are observed both in fine-grained and gravelly layers.
However, some thick clayey layers do not show well-developed
features but only fissuring and incipient coarse platy microstruc-
ture (Fig. 13). This is probably due to a combination of high
sedimentation rate and low intensity of frost action. It is also clear
that some of these layers were affected after being deposited,
whereas others were affected during their formation. Never-
theless, on the basis of their recurring pattern and spatial
development, it appears that almost all sedimentary layers more
or less were affected by freeze–thaw activity during or shortly
after their formation. The only exception seems to be the crust
horizons in layers VI and VII and the capping surface of layer I. It is
also important to stress that ice lensing requires that the sediment
contains some water in order for ice to form.
5.6. Weathered crusts
The weathered crusts found in layers VI and VII (Table 1)
represent depositional hiatuses. They are characterized by weath-
ering iron–manganese rinds on boulder lags and complex
iron–manganese impregnative crust pedofeatures overprinting
impure flowstone formations (Figs. 7 and 18). The paucity of
clastic input implies stabilization of the soil on the hills above the
cave and thus the existence of a tree cover under probable humid
warm climatic conditions. However, under such conditions
extensive speleothem formations are expected—something not
observed in Dadong.
6. Chronological framework and summary of
sedimentary history
The regular interlaminated clastic sediment, impure flowstones,
phreatic and vadose cementation, and frost activity in Dadong is
related to a cold environment with fluctuating humidity but a
predominantly wet climatic regime. Major episodes of uncemented
clastic sedimentation are probably related to reduced humidity and
limited vegetation cover, whereas calcite cementation and flow-
stone formation are related to wetter phases. The exceptions to this
picture are probably the weathered crust–flowstone couplets that
should imply more stable periods with reduced erosion and
extensive vegetation cover.
Absolute age estimates for the sedimentary deposits of Dadong
Cave include U-series ages from speleothems (Table 2;Fig. 4)
ARTICLE IN PRESS
Table 1 (continued)
Layer Thickness
(cm)
Field observations Micromorphological observations
III (IIIa–c) 50–70 IIIb–IIIc: Matrix-rich tabular beds that are more
boulder-rich in the north and become more fine-
grained in the south. They contain floating
cobbles and boulders with occasionally clast-
supported ‘tails’ and crude imbrication (Fig. 7).
Cementation is locally intense towards the
northern profile where bouldery and gravelly
facies give way to flowstone formations (Fig. 5).
Reddish brown loam with microscopic organo-metallic nodules and
remnants of decayed organic matter. Platy and lenticular microstructures
are well-developed.
IIIa: A tabular bed with clast- to matrix-
supported gravel. The gravel is subrounded and
shows crude plane-parallel stratification and
weakly erosional contacts with the underlying
layer (Fig. 8). This layer also yields a relatively
dense concentration of fauna as well as lithic
artifacts with a conspicuously high proportion of
teeth towards its base (Schepartz et al., 2003).
Several phases of alternating platy, lenticular and granular
microstructures are observed. Widespread development of complex pisoid
structures. Thin impure flowstone formations also show lenticular
microstructures.
II (IIa–c) 100 IIc: A dark brown clayey bed that contains
floating boulders and finer gravel arranged in
clusters and lines. It also becomes cemented
towards the northern wall. Fragmentary bone
and lithic artifacts are abundant.
Alternating sorted and unsorted loamy increments. A high amount of
decayed organic matter and organo-metallic nodules are observed (Fig.
16). It is characterized by well-developed fissure to incipient platy
microstructure (Fig. 16).
IIa–IIb: A sequence of gravelly tabular beds that
become cemented towards the northern wall.
Layer IIb has a bouldery base and show local
crude stratification. It also thin out towards the
center of the cave.
The loamy matrix shows lenticular microstructure.
I 150 A thick laminated clastic-rich flowstone
formation (Figs. 6 and 10). Locally, in between the
calcareous laminae, there are thin uncemented
reddish clayey laminae. Bones and artifacts occur
in very high concentration.
Redeposited clastic material in the form of composite calcareous pisoid
structures (Fig. 9) that are welded in well- developed lenticular and
granular microstructures with calcitic link cappings (Fig. 12). The
structures are arranged in increments, with each one starting with coarse
lenticular microstructure giving way to fine lenticular and finally typically
capped by a laminated clastic-rich calcite crust (Fig. 17). On the crust fine
crystal fans, consisting of radial calcite, are occasionally developed. Each
increment is cemented with sparitic calcite filling the interaggregate
fissures (Fig. 12). On the contact with the underlying increment vadose
calcite coatings (pendants) are overlain by dusty clay coatings.
The top ca 10 cm is characterized by mesoscopic fenestral porosity and
microscopic vesicles.
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(Shen et al., 1997) and coupled ESR/uranium series ages for fossil
teeth (Table 3;Fig. 5)(Jones et al., 2004). Although both methods
produced a wide spread of ages, in general they are comparable
and the ages are in relatively good stratigraphic order. Some minor
discrepancies observed in the lower group of the coupled ESR/
uranium series ages (Table 3) can be explained by depositional
processes (see below). In the present work, we use the above age
estimates to produce a general chronological framework for
groups of layers and thus the resolution offered by the available
dating results is satisfactory. In addition, the observed frost action
puts further constraints on the age determination.
Preliminary U-Th dates obtained from two of the oldest
speleothem formations (bell canopies) on the cave walls that are
buried inside the clastic sequence are greater than 300 ka and
probably averaged to about 330 ka (Fig. 4;Table 2)(Shen et al.,
1997). The lower part of the clastic sequence, i.e. layers XII–IX,
accumulated during a glacial period when seasonal freezing
temperatures prevailed in the cave. Frost action was interrupted
by humid, probably milder periods where phreatic calcite was
deposited in frost cracks, and there was possibly a temporally
changing water table. There is a coupled ESR/U-Th date
on a mammalian tooth from layer IX giving an age of ca
296 ka (+31/24) (Jones et al., 2004)(Table 3). Based on the date
and the climatic conditions, it is reasonable to assume that
this part of the sequence was formed during the interval of glacial
MIS 8.
As noted above, layers VII and VI and above mark a change to a
different sedimentation pattern characterized by alternating clast
to matrix-supported gravel and matrix-rich beds. They are also
associated with the densest accumulations of anthropogenic
material inside the cave. Layers VII and VI also record three
prominent crusts on top of flowstone formations related to
bouldery lags. Weathering crusts on the boulders associated with
iron–manganese impregnation features in the cemented matrix
implies a long exposure and reduced sedimentation of these
layers on the floor of the cave (Gillieson, 1996, p. 155). It also
appears that these crusts were forming during periods without
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Fig. 6. General stratigraphy of the northern excavation profile. Note the fine-
grained nature of the lower part, the boulder- and gravel-rich middle part and the
flowstone formations of the upper part. The height is 5 m.
Fig. 7. Part of the stratigraphy of the eastern excavation profile. Note the crust on
top of layer VIa (with arrow), the floating boulders in layer V, and the coarse tails
and imbrication in layers IIIb and c. Height of photo is 1.5 m.
Fig. 8. Detail of layer III1 (between horizontal bars) with planar stratified gravel
and weakly erosional lower contact.
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Fig. 9. Microphotograph of complex pisoid structures in layer I. Note that the
upper left pisoid has a core of cemented calcite aggregate with lenticular and
granular microstructure; PPL.
Fig. 10. Resin-impregnated slab of laminated flowstone of layer I.
Fig. 11. Microphotographs of (a) homogeneous fine silty calcite with incipient
platy microstructure (defined by fissure pattern); layer XXII, plane polarized light
(PPL) and (b) lenticular and granular microstructure with grains having rims of
bladed calcite (Cc) and dusty clay meniscus coatings (with arrow); layer XXI,
crossed polarized light (XPL).
Fig. 12. Lenticular microstructure with link cappings (arrow) and completely filled
with sparitic calcite (Cc); layer I, XPL.
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frost action under rather humid and warm climatic conditions
when an extensive tree cover would have stabilized the
soils above the cave. However, the clastic content of the crusts
affected by this weathering process, and possibly even the major
part of the flowstones, were forming during previous cold periods,
as they are the product of being affected by frost action.
ARTICLE IN PRESS
Fig. 13. Microphotograph of incipient platy microstructure (defined by the fissure
pattern) and organo-metallic nodules (with arrow); layer II, PPL.
Fig. 14. Photographs of thin sections showing well-developed lenticular micro-
structure (a) and lenticular to granular microstructure with abundant laminated
silty calcite link cappings (b). Note also pisoid structures.
Fig. 15. Sequence of two thin sections. The arrow marks the contact between the
underlying loamy layer V and the overlying gravelly layer IV. Note that
freeze–thaw features in layer V increase towards the contact with layer IV which
shows only fissure microstructure.
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Conventional ESR and coupled ESR/U-series dates on mammalian
teeth from these layers assume a minimum age of ca 257737 ka
based on a linear uptake model (Jones et al., 2004)(Table 3). This
places them close to the end of MIS 8. However, the mean ESR
early uptake model ages for this group are 211731ka (Table 3).
Unfortunately, given the complex nature of these layers with
bouldery facies alternating with hard calcareous crusts in a thin
(20–50 cm) sediment slice, it was not possible to determine a
better approximation of their exact provenance inside these
two complex layers. In addition, a U-Th date from a flowstone
sample located 20 m away from the excavation, but linked to one
of these crusts on the basis of field stratigraphic correlations (see
Figs. 4 and 5), gave a corrected but inconclusive date of ca 260 ka
since it was highly contaminated with detrital material (Shen et
al., 1997)(Table 2). Nevertheless, given the complex nature of this
unit (with beds clearly affected by frost action and others
representing hiatuses under milder climatic conditions and
containing sediment frequently redeposited), layers VI and VII
should correspond to MIS 7 along with potentially redeposited
material from MIS 8. Some of the dated teeth that show a marked
deviation from the mean value (Table 3) might be also explained
in the same way. It is tempting to assume that the three crusts
might represent the three warm substages of MIS 7 (e, c and a)
(Pisias et al., 1984), but additional data are required before this is
substantiated.
Layers V–II show a similar depositional pattern with fluctuat-
ing frost intensity. There are thick matrix-rich layers with high
organic content that show evidence of freeze–thaw activity,
although some layers have only fissuring and incipient coarse
platy microstructure. However, sedimentation and frost action
were more or less contemporaneous processes throughout the
formation of the sequence, and it seems that the pattern is
consistent with sedimentation mainly produced under a glacial
climate, intensive hill erosion, and fluctuating humidity. It is also
evident that some flowstones accompany coarse gravel sheetflow
facies. This implies a wetter environment when episodic sediment
flows were accompanied by constant dripping and surface water
flows. Coupled ESR/U-Th dates on mammalian teeth from these
layers suggest a minimum age of 156717 ka (Jones et al., 2004)
(Table 3) placing their formation inside the glacial MIS 6 in
accordance with the observed freeze–thaw features. This is in
agreement with the two flowstone formations dated in the area to
the north of the excavation and correlated with the flowstone
formations inside the complex layers III and II close to the north
wall (see Figs. 4 and 5). They had corrected ages (due to their
contamination with clastic material) of 190 and 160 ka, respec-
tively (Shen et al., 1997)(Table 2).
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Fig. 16. Microphotograph of lenticular microstructure with voids infilled with
loose sorted grains; layer V, PPL.
Fig. 17. Photograph of a thin section from layer I showing an increment (between
arrows) with decreasing size of ice lensing upwards.
Fig. 18. Microphotograph of iron–manganese crust bridging coarse particles; layer
VII, XPL.
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Layer I is of special interest because it provides some more
detailed information on the conditions prevailing during the
formation of thick flowstones in Dadong. This flowstone is one of
the unique examples of calcite precipitation under intermittent
frost action inside a cave. It actually consists of consecutive
reworked clastic calcareous material deposited by low energy
sheetflow. One of the actual main sources of the clastic material
was the frost action that fragmented the previously deposited
moderately cemented sediments. Seasonal alternation of freeze
and thaw cycles might explain the unique characteristics of these
deposits. At the same time, calcite was precipitating in inter- and
intra-aggregate pores. Intraclast precipitation might have been
active seasonally during the thawing cycle since pisoids are
cemented inside the ice lenses, but interaggregate calcite is not
affected by frost action in contrast to what is seen in other layers
(e.g. XI, IV and III). It is actually the material that gives the overall
flowstone appearance of the deposit. The cementation was
followed with dusty clay and silty vadose features. The overall
structure of the flowstone is related to glacial humid climatic
conditions with some regularly intervening milder conditions.
The uppermost cap of the flowstone was dated with U-Th by
Shen et al. (1997) to ca 130 ka (Table 2;Fig. 4). Thus, the main part
of the flowstone should correspond to the lower part of MIS 6. A
sample from the uppermost preserved 10 cm of the flowstone is
not affected by frost action suggesting that flowstone formation
continued into the ensuing interglacial but with reduced intensity.
This seems to be the case with the stratigraphically lower
flowstones and particularly those related to the crusts in layers
VI and VII. During interglacials flowstone formation was con-
siderably reduced, probably due to limited water flow inside the
cave. However, we do not have information on the other type of
speleothem formations like stalagmites and stalactites that are
pure dripstones (but see Section 7).
7. Discussion
The clastic sequence of Dadong cave was formed predomi-
nantly during glacial periods. Impure flowstones and generally
enhanced calcite precipitation in the sediments were recorded at
the same time, but probably during wetter and milder periods.
Sedimentation rates and flowstone formation were reduced
during interglacial times. Today, water dripping and speleothem
formation in Dadong is minimal and flowstone formation is
actually absent. Although the modern constructions in the front of
the entrance do not seem to impede speleothem formation in the
interior, the considerable forest clearance and agricultural
activities on the hill above the cave might have disturbed the
karstic system. In addition, the modern configuration of the cave
with a widened entrance, the considerable dimensions of the cave
cross-section, and the formation of the pitfall in the back create a
strong air current that produces less than ideal humidity
conditions for speleothem formation. In any case, although the
configuration of the entrance and the back pitfall might have
changed through time, the large dimensions of the cave demand
enhanced water flow and humidity for flowstones to be formed.
Another explanation for the interruption in speleothem formation
is the large amount of organic cave sediments formed during
warm stages. The surface deposits of Dadong were a source of
nitrates for the production of gunpowder in the recent past.
Nitrates are formed on the surface of caves by evaporation in
warm, relatively dry and well-ventilated conditions. A major
source of nitrates is surface rich organic soils (Hill and Forti, 1997,
pp. 157–158;Onac, 2005). The deposition of nitrates may be
further aided by various nitrogenous bacteria (Culver, 2005). The
formation of iron and manganese crusts, observed in layers VI and
VII, is also partially attributed to bacterial activity and the
breakdown of organic material (Culver, 2005). Hence, we suggest
that during warmer interglacials, waters percolating through rich
organic densely vegetated soils were entering Dadong where
enhanced bacterial activity formed iron–manganese crusts and
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Table 2
U/Th dating of speleothems from Dadong Cave (after Shen et al., 1997)
Sample Description U (ppm)
230
Th/
232
Th
234
U/
238
U
230
TH/
234
U
230
Th age (ka) Corrected age
(
230
Th/
232
Th)
0
¼1
Corrected age
(
230
Th/
232
Th)
0
¼2
9311-6 Layer I 0.07 12.3 1.20770.031 0.78570.026 155
+13
/
11
149 14 2
9509-1 Layer I 0.11 73 1.21870.021 0.69470.016 122
+6
/
5
9509-3 Layers II–III 0.07 18.1 1.13470.017 0.86170.017 198
+13
/
11
193 189
9509-4 Layers II–III 0.05 17.2 1.17670.019 0.81470.017 169
+10
/
9
165 160
9311-3 Layers VI–VII 0.14 10.1 1.13570.019 0.96070.023 284
+44
/
31
274 264
9205-6 Bell canopy 0.07 37.6 1.06270.022 0.98370.016 360
+189
/
64
9209-4 Bell canopy 0.08 21.5 1.08870.017 0.96870.024 308
+65
/
40
In samples with
230
Th/
232
Th less than 20 the initial
230
Th contribution to the age result is corrected. Age results of samples with
230
Th/
232
Th less than 10 are not shown here
as they are considered unreliable (Shen et al., 1997). The stratigraphic assignment of the samples is based on field correlations during the present study (see also Fig. 4).
Table 3
ESR and U-series dating results form Dadong Cave (after Jones et al., 2004)
Sample Layer EU ESR age
(ka)
LU ESR age
(ka)
Coupled
ESR-
230
Th/
234
U
age (ka)
Upper group
PD4C II–IV 118714 131718
PD6A II–IV 160722 182725 208
+23
/
19
PD3a II–IV 124714 166 721
PD8A II–IV 144723 154726
PD10A II–IV 142715 149723
Mean 137715 156717
Lower group
ESR 26A VI–VII 159726 185731
ESR 22A VI–VII 158720 210728
ESR 20A VI–VII 184730 219734 231
+32
/
26
ESR 25A VI–VII 228739 274744
ESR 24A VI–VII 233734 296742 294
+35
/
30
ESR 24B VI–VII 296754 349758
PD17A VI–VII 247729 301742
PD18A VI–VII 195721 250732
PD16A VI–VII 199726 228717
Mean 211731 257737
PD15a IX 214724 268736 296
+31
/
24
Stratigraphic assignment to specific layers is based on sample projection onto the
profiles during the present study. Nevertheless, sample grouping and mean values
are as presented by Jones et al. (2004), except for sample PD15 that is separated
from the lower group. Sample PD6A shows a recent uptake or episodic uranium
gain and losses. For full discussion of the results see Jones et al. (2004).
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nitrate formations. Under these conditions speleothem formation
was considerably suppressed.
On the basis of the freeze–thaw features, during glacial periods
the mean temperature in Dadong cave through the winter months
was probably a few degrees below zero in order for ice to develop
and remain inside the sediment. The only available climatic data
in the region (Guizhou Province) come from the last part of the
penultimate glacial from two caves to the east, the Qixing
and Dongge caves (Fig. 1)(Yuan et al., 2004;Zhang et al., 2004).
Based on isotopic studies of speleothem formations, Zhang et al.
(2004) suggest a minimum temperature range from 0.65 to
1.431C during the coldest stage of the penultimate glacial
period. Given that the elevations of Qixing and Dongge are lower
(1000 and 680 m, respectively) than that of Dadong (1700 m), we
expect that the latter would have temperatures a few degrees
lower. This is consistent with the present temperature differences
between Dadong and the other caves (15.6 and 18.31Cvs.141C).
However, we have to stress that freezing temperatures are
frequently recorded in the Dadong sequence and are not restricted
to a certain layer that corresponds only to one glacial period. It is
important to note that freezing temperatures are apparent during
both MIS 6 and 8 in Dadong Cave. At least seven discrete episodes
of frost activity are recorded in the sequence representing MIS 6
and three in MIS 8. The latter, however, does not represent the
complete time span of this glacial period, as the excavation did not
reveal the full development of this part of the sequence. The type
of freeze–thaw activity recorded in Dadong, i.e. lenticular and
granular microstructures, is related to a long series of alternating
freezing and thawing (Van Vliet-Lanoe
¨et al., 1984) and is not the
product of a few extreme seasonal climatic excursions. For an area
with a subtropical climate at present, this is probably unexpected.
In any case, given that the mean temperature of the coldest month
today is ca 5 1C, it is certain that a seasonal drop of at least 6–7 1C
is expected for long portions of the glacial periods.
Pollen studies from coastal subtropical areas in China suggest a
cooler and wetter climate during parts of the last glacial but drier
conditions during the Last Glacial Maximum. However, in the
western highlands of Yunnan to the south of Dadong Cave, the
pollen studies show that rainfall should be higher in the glacial
than in the interglacial. A drop in temperature of 4–6 1C is also
estimated (Zheng, 2000). Yet contrasting evidence for the
distribution of C4 and C3 plants during the late part of the
penultimate glacial is recorded from the caves of Qixing and
Dongge (Zhang et al., 2004). Qixing Cave (Fig. 1), at the higher
elevation than Dongge, records a very high ratio of C3 to C4 plants
during part of the glacial, exceeding the value for the interglacial.
This should be interpreted as higher precipitation during glacial
intervals. Periods with high precipitation in cold stages of the
penultimate glacial are also reported from isotopic studies of
speleothems from caves in subtropical Guilin, Guangxi Province
(Zhang et al., 2006). Even so, the consensus is that during glacial
times in the subtropics, the climate was considerably drier due to
a weakened summer and a strengthened winter monsoon (Wang
et al., 2001;Yuan et al., 2004; for a review see also Wang et al.,
2005). Yuan et al. (2004) conducted oxygen isotopic analysis of
speleothems formed over the past 160,000 years in Guizhou. Their
sample includes Dongge Cave, already discussed above, situated at
a slightly more southern latitude (25117
0
N) and lower elevation
than Dadong (Fig. 1), with a comparable annual temperature
(15.6 1C) but higher precipitation (1753 mm). They suggest a
considerably drier climate during glacial times. In comparison, the
Dadong sedimentary record supports the scenario of high
effective precipitation during intervals of the glacial periods that
were also characterized by low temperatures and reduced
vegetation cover. This contrasts with the other speleothem studies
in the area that record enhanced precipitation only during very
warm interstadials (Zhang et al., 2004). A possible explanation
could be that Dadong, situated at 105 1E longitude at the boundary
between the Indian and East Asian monsoons (Wang et al., 2005),
belongs to a different precipitation regime than the rest of
subtropical southern China where these other sites are located.
Modeling experiments have shown that this is also roughly the
boundary between areas of contrasting precipitation during
different climatic stages (de Noblet et al., 1996). It is also in
agreement with the past climatic characteristics of several
Chinese regions during wet and dry monsoons in relation to the
snow cover in Eurasia (Yang and Xu, 1994). The possibility of a
strong monsoon under a glacial climate was also suggested by
simulation studies (Masson et al., 2000). Furthermore, Ju et al.
(2007) showed that the simulated annual precipitation during the
Last Glacial Maximum is higher in western China than present in
contrast with eastern China. As Wang et al. (2005) clearly pointed
out, monsoon variability is not a direct linear response to global
ice volume and thus should not be considered only in the context
of glacial–interglacial variability. The Dadong cave sequence
provides strong indications of enhanced monsoons under glacial
climate with temperatures much lower than today.
The faunal record at Dadong provides additional evidence for
the climatic conditions prevailing during the formation of the
deposits. The frequent intercalation of flowstones and calcified
and non-calcified clastics, with the former building extensive caps
on the underlying clastic deposits, assures that artifacts and bones
are more or less contemporaneous with the enclosing strata
(cf Moriarty et al., 2000). Formation processes of each layer,
however, include transport and reworking along distances
restricted to their lateral and horizontal extensions. Some crude
lateral sorting is evident from a preliminary analysis of the sizes of
the bone in each layer although taphonomic surface analysis of
the assemblage precludes major post-depositional alteration
of the fauna (Schepartz et al., 2003;Bekken et al., 2004).
Nevertheless, during interglacials the combination of reduced
sedimentation, enhanced bacterial activity, and the associated
production of acidic waters (Culver, 2005) would have resulted in
the dissolution of bones accumulated on the surface of the cave.
Interestingly, there are no indications of enhanced dissolution of
the carbonates (limestone clasts, flowstones, etc.). Furthermore,
widespread chemical alteration in the form of phosphate miner-
alization that normally occurs in cave environments and is partly
attributed to bone dissolution (Karkanas et al., 2000) is not
recorded in any of the Dadong layers. Some smaller bones that
accumulated during the formation of the weathering crusts might
have dissolved away, but the evidence does not support dissolu-
tion to any extent that would alter the faunal composition. Thus,
fauna in Dadong can be evaluated in the light of the environ-
mental conditions responsible for the accumulation of each layer.
A mixed woodland environment with two or three habitats
including bamboo forests and open rocky areas with abundant
grasses is suggested by the fauna composition. One of the striking
characteristics of the Dadong fauna is the consistency of
taxonomic representation over time (Bekken et al., 2004). Given
the environmental interpretation of the depositional sequence,
with the vast majority of the material being accumulated during
glacial times, this consistency is not entirely unexpected. Most of
the abundant Dadong species are highly adaptable forms with
fairly broad environmental ranges. However, indications of heavy
or closed canopy forests are not encountered in Dadong, unlike
the cave site of Tongzi in northern Guizhou (Olsen and Miller-
Antonio, 1992). The fauna of this site seems to be derived from a
layer dated to the interglacial MIS 7.
It is also important to note that the majority of the taxa found
in Dadong are not habitual cave dwellers. Carnivores were only
present in small numbers and indications of rodent and carnivore
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modifications of the fauna assemblage are not an important
taphonomic feature (Bekken et al., 2004). Hominin produced
bone modifications in the form of cutmarks, percussive damage
and burning are relatively scarce, but stone tools are found
throughout the deposits. In conclusion, combining all the
evidence above, it is not unreasonable to assume that hominins
are the primary agent of faunal accumulation in Dadong and
therefore may have been responsible for the relative consistency
of the assemblage over time. But it also appears that hominins
were probably not present during interglacials periods, and that
carnivore use of the cave did not increase during their absences, as
has been documented for many cave faunas (cf Stiner, 1991). One
explanation might be that the denser subtropical forests of the
interglacial could have resulted in lower prey densities of the large
animals such as Stegodon,Rhinoceros and many large bovids and
cervids that are frequently found in the Dadong depositional
sequence. Alternatively, the hominin use of the cave for shelter
and warmth might not have been necessary during the warmer
interglacials.
8. Conclusion
The frequent alternation of flowstone formation, cementation,
clastic deposition, and frost activity in the depositional sequence
of Dadong Cave is used to reconstruct the environmental
conditions prevailing during the later Middle Pleistocene on the
Guizhou Plateau. The sedimentary sequence was deposited
mainly during the glacial intervals of MIS 8 and 6.
Clastic deposits were entering the cave in the form of
intermittent cohesive debris flows and sheetflows. The sources
of the clastic sediment were soils and sediment in the vicinity of
the cave, transported under a cold and relatively dry climate when
vegetation cover was reduced. Interlayered impure flowstones
were forming during wetter phases but still under glacial
conditions. The frequent occurrence of cycles of well-developed
freeze–thaw features affecting both the clastic parts of the
sequence and the flowstones as they were deposited suggests
unexpectedly low seasonally freezing temperatures. At the same
time, remains of hominin activities in the form of faunal remains
and lithic artifacts were accumulating on the surface of the
fan-like sedimentary sequence and redistributed laterally along
the different depositional facies. During the intervening inter-
glacial of MIS 7 and possibly MIS 5, clastic deposition was minimal
and sedimentation was restricted to thin flowstone caps and
weathering manganese–iron crusts. Hominins were probably not
present during interglacials periods—perhaps due to lower prey
densities of the large animals in the denser subtropical forests of
the interglacial or a diminished need for the sheltering benefits
the cave offered. Consequently, a relative consistency of the faunal
assemblage over time is observed, with temperature-resistant
forms constituting the bulk of the taxa. Most notably, the primates
and suids that are typically associated with subtropical faunas are
only minimally represented.
Analysis of the Dadong sequence suggests that precipitation
was much higher during glacial intervals than interglacials
under a predominantly cold climate. Other paleoclimatic studies,
based on pollen or simulation studies, point toward the same
conclusion, although the current state of our knowledge of
climatic conditions in southern China from fauna and spe-
leothems indicates considerable diversity relating to elevation
and geographical position. Dadong Cave may present its dis-
tinctive signature of very cold and wet climatic conditions during
glacials in the subtropics of East Asia because it is situated
precisely in the area where the Indian and East Asian monsoon
effects converge.
Acknowledgments
The authors would like to thank the other members of the
Panxian Dadong Collaborative Project for their input toward the
field research that this analysis is based upon: Kanai Paraso, Liu
Jun, Si Xinqiang, Deborah Bekken, Hou Yamei and the fieldworkers
from Dadong. Our research was supported by the National
Geographic Society (2005–2006), The Henry Luce Foundation
(1998–2001), NSF (1997), the Wenner-Gren Foundation (1996)
and the LSB Leakey Foundation (1996).
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