JOURNAL OF QUATERNARY SCIENCE (2012) 27(9) 891–900
ISSN 0267-8179. DOI: 10.1002/jqs.2578
Reconstruction of environmental changes using a
multi-proxy approach in the Ulleung Basin (Sea of
Japan) over the last 48 ka
JIANJUN ZOU,1 XUEFA SHI,1* YANGUANG LIU,1 JIHUA LIU,1 KANDASAMY SELVARAJ2,3 and SHUH-JI KAO2,3
1
Key Laboratory of State Oceanic Administration for Marine Sedimentology and Environmental Geology, First Institute of
Oceanography, Qingdao 266061, China
2
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
3
Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan
Received 30 September 2011; Revised 6 May 2012; Accepted 26 July 2012
ABSTRACT: Based on elemental geochemical data, we reconstructed the sediment provenance, surface productivity
and bottom water redox conditions for the last 48 ka in the Ulleung Basin (Sea of Japan) and inferred the factors
controlling them. Al2O3/TiO2 ratio and chemical index of alteration (CIA) suggest that sediment provenance changed
during the glacial period (48–18 ka) compared to the deglacial (ca. 18–11 ka) and Holocene. Mass accumulation rates
of total organic carbon (TOC), CaCO3, phosphorus, cadmium and excess barium reveal low paleoproductivity during
low sea stand. During 18–11 ka, productivity increased due to increasing inflow of nutrient-rich water masses – the
Oyashio and the East China Sea coastal water – in tandem with the rising sea level. Maximum productivity occurred
during Younger Dryas and Pre-boreal periods when sea level was at 60 m and then gradually decreased as the
Tsushima Warm Current inflow kicked off at ca. 9.3 ka, consistent with other paleoredox proxies, which reveal the
presence of anoxic bottom water during ca. 12–9 ka. With the changes in paleoredox proxies and their ratios (TOC,
Mo, U, Mn, C/S ratio and Uauthigenic and Mo contents), we hypothesized that the redox changes were mainly ventilation
driven and were superimposed on the influence of circulation-induced productivity changes. The global climate and
sea-level changes on a millennial timescale play a major role in enhancing paleoproductivity and restrict bottom water
advection, subsequently driving the oxygenation of bottom water in the Ulleung Basin. Copyright # 2012 John Wiley
& Sons, Ltd.
KEYWORDS: sediment geochemistry; provenance; paleoproductivity; paleoredox; Ulleung Basin.
Introduction
Marginal seas are recognized as important contributors and
regulators of the global carbon cycle (Jahnke, 2010; Seitzinger
et al., 2005; Walsh et al., 1981) and are thus intimately linked to
climate change on a glacial–interglacial timescale. The Sea of
Japan, a typical semi-enclosed marginal sea in the northwestern
Pacific Ocean, is surrounded by the Eurasian continent and
North Pacific Ocean. Previous reports showed that the
laminated layers with alternate dark organic-rich and light
organic-poor sediment deposition were ubiquitous in the Sea of
Japan (Itaki et al., 2007; Oba et al., 1991; Tada, 1994). This
phenomenon was deemed to be correlated with the changes
in surface productivity and oxygen content in the bottom
water. Geochemical studies on sediment cores from the Ocean
Drilling Program further indicated that millennial-scale cyclic
dark–light layering was the consequence of fluctuating
physicochemical conditions of seawater that was associated
with Dansgaard–Oeschger (D-O) cycles (Tada and Irino, 1999).
The sedimentary record of various redox-sensitive
elements (e.g. U, Mn, Mo) may reflect the redox conditions
prevailing in the water column at the time of sediment
deposition (Elbaz-Poulichet et al., 2005) and therefore can be
used to discover paleoredox in the marine environment (Algeo
and Lyons, 2006; Nameroff et al., 2002; Russell and Morford,
2001; Tribovillard et al., 2006). This is mainly because these
trace elements tend to have significant solubility reduction
under reducing conditions, resulting in authigenic enrichment
in oxygen-depleted sedimentary facies (Tribovillard et al.,
2006). Furthermore, biogenic elements such as cadmium,
*Correspondence: Xuefa Shi, as above.
E-mail: xfshi@fio.org.cn
Copyright ß 2012 John Wiley & Sons, Ltd.
phosphorus and barium show significant correlation with
productivity changes, and have therefore been used to evaluate
past productivity changes in different ocean basins (Dymond
et al., 1992; Schenau et al., 2005; Tribovillard et al., 2006).
Based on the development of laminated layers in core KCES-1
retrieved from the Ulleung Basin, Liu et al. (2010) inferred that
basin-wide changes in surface productivity and oxygen content
in the bottom water occurred in the past. In this paper, using
high-resolution geochemical analysis with the well-defined age
model of core KCES-1, we reconstruct the paleoproductivity
and paleoredox history of the Ulleung Basin for the last 48 000
calendar years before the present (48 ka). Furthermore, we use
additional proxies such as chemical index of alteration and
degree of pyritization in core KCES-1 for the first time to
substantiate our inferences.
The Sea of Japan is composed of three deep basins – Ulleung,
Yamato and Japan – and exchanges water with other adjoining
seas and oceans through only four narrow and shallow
passages, namely Tartar (15 m), Soya (55 m), Tsugaru (130 m)
and Tsushima (140 m), from north to south (Piper and Isaacs,
1996) (Fig. 1a). The maximum sill depth for the four straits is
140 m in Tsushima Strait and the minimum depth is just 15 m
in Tartar Strait (Piper and Isaacs, 1996). Therefore, on a
millennial timescale, the past eustatic sea-level changes exert a
strong control on the oceanographic regime and environmental
history of the Sea of Japan (Kim et al., 2001; Oba et al., 1991;
Takei et al., 2002). Among the four straits, Tsushima plays
the most important role since the Tsushima Warm Current
(TWC), a branch of the Kuroshio Current (KC) flowing
northeastward from the East China Sea, is responsible for
major heat and water inflow to the Sea of Japan (Fig. 1b). The
total volume transport of the modern-day TWC through
the strait is 2.64 Sv (Sv ¼ 106 m3 s1) (Takikawa et al.,
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JOURNAL OF QUATERNARY SCIENCE
Figure 1. (a) Physiography of the Sea of
Japan and adjacent seas with four straits.
The dashed curve stands for the 120 m isobaths. (b) Location of sediment core KCES-1
(*), site 16 (&) and 97PC-19 (*) with dominant currents illustrated. Arrows denote simplified surface currents in the study region.
2005). This transport has a strong seasonal variation as the
inflow of low-salinity nutrient-replete water mass driven by
freshwater discharge from the rivers around the Yellow Sea and
East China Sea dominates from August to October every year.
The deep water in the basin, the Japan Sea Proper Water, is
formed in the northern part of the sea in winter due to surface
cooling and/or evaporation/freezing and then sinks toward the
bottom (Sudo, 1986). The formation of this deep water may
control the oxygen supply to deep and bottom water, which in
turn is responsible for basin-wide ventilation. Variable primary
production-induced oxygen consumption in the deep-water
column may thus regulate organic matter burial, sedimentary
and water column redox states. In addition, the environmental
condition in the Sea of Japan was influenced by river discharge,
the strength of Kuroshio and Oyashio currents, intensity of the
East Asian monsoon and global climate changes on a glacial–
interglacial timescale (Kido et al., 2007; Yokoyama et al.,
2007).
The studied site, Ulleung Basin, is situated beneath the
entrance of the TWC and is located at the southernmost margin
of the deep water. The sedimentary geochemistry retrieved
from this basin would reveal insightful information regarding
sediment provenance, productivity and redox history of the
Sea of Japan. Previous studies have suggested that the
paleoredox of bottom water in the Ulleung Basin has taken
place since the last deglacial, based on the record of
sedimentology and sedimentary geochemistry (Lim et al.,
2011; Liu et al., 2010). In this study, we illustrate more
comprehensive paleoenvironmental evolutional information
since the last glacial using multiple proxies.
Material and methods
Core KCES-1 (358 56.1500 N, 1308 41.9150 E; Fig. 1) recovered
at a water depth of 1464 m from the southeastern Ulleung Basin
in the Sea of Japan was provided by the Korean Ocean Research
and Development Institute (KORDI). The region is influenced
largely by the TWC in the present interglacial (Fig. 1). The
length of core KCES-1 is 10.2 m and mainly consists of clayey
silt and silt with occasional occurrence of plant debris at some
depth intervals. Liu et al. (2010) also observed four layers of
volcanic ash with different thicknesses. In the upper section of
core (0 400 cm), sediment is dominated by clayey silt and silt,
while alternate light and dark layers are seen in the middle
section (400 730 cm). Below 730 cm, the sediment texture
is foul-up and this is likely caused either by turbidity currents or
shelf collapse due to slumping. In the present study, we
therefore analyze the subsamples from the core top through
730 cm of core KCES-1, with the sampling interval ranging from
Copyright ß 2012 John Wiley & Sons, Ltd.
6 to 20 cm based on the sediment texture. In total, 71
subsamples were analyzed for total contents of organic carbon
(TOC), nitrogen (TN) and sulfur (TS), as well as selected major
and trace elements.
TOC, TN, TS and CaCO3
Each sediment subsample was oven dried at 608C for 2 h and
homogenized by grinding in an agate mortar. Total content of
carbon (TC), TN and TS were determined with an elemental
analyzer (EA; Vario EL III) at the First Institute of Oceanography,
State Oceanic Administration, China. In addition, 2 g of each
powdered sample was treated with 12 mL of 1 M HCl for 24 h at
608C to remove carbonate, and the residue was centrifuged and
oven dried. TOC in these decarbonated samples was
determined by using the same instrument. The content of
calcium carbonate (CaCO3) was calculated using the equation
CaCO3 ¼ ðTC TOCÞ 8:33
(1)
Quality assurance and control for the analytical process were
evaluated with the help of reference material (GSD-9) and
blank correction. The relative standard deviation of the GSD-9
for TC, TN, TOC and TS was 1.2%, 1.8%, 2.6% and 12%,
respectively.
Major and minor elements
For major and trace elemental analyses, each sediment
subsample was oven dried at 1058C for 3 h. 50 mg of each
aliquot transferred to Teflon beakers was digested with
ultrapure HF and HNO3. Selected major (Al, Ca, Fe, Mg,
Mn, Na, K, P and Ti) and minor (Ba, Cu, Ni, Sr, Th, V and Zn)
elements were determined by inductively coupled plasma
optical emission spectroscopy (ICP-OES; Thermo Scientific
iCAP 6000). In addition, specific redox-sensitive trace elements
including uranium (U), molybdenum (Mo) and cadmium (Cd)
were analyzed with inductively coupled plasma mass spectrometry (ICP-MS; Thermo Scientific XSERIES 2, located at the
Key Laboratory of State Oceanic Administration for Marine
Sedimentology and Environmental Geology, First Institute of
Oceanography, China). Precision for most elements at the
concentrations present in the reference material GSD-9 was
<5% relative standard deviation. The concentration of excess
barium (Baexcess) was calculated using the following normative
equation (Murray and Leinen, 1996):
Baexcess ¼ Batotal Al ðBa=AlÞsilicate
(2)
where Baexcess is biogenic barium, Batotal and Al are the bulk
concentrations, respectively, and (Ba/Al)silicate signifies the Ba
content associated with the detrital fraction of sediments.
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
PALEOENVIRONMENTAL CHANGES IN THE ULLEUNG BASIN
Age model and mass accumulation rate
893
The results show that three factors account for 83.2% of
variance (Table 2).
Factor 1 accounts for 34.4% of the variance, and TOC, TN,
Na2O, P2O5 and trace metals (Ba, Cd, Cu, Ni, V and U) as well
as U/Th, Cd/U and TOC/P ratios, Uauthigenic and Baexcess are
loaded in this factor (Table 2). Association of elemental forms of
C and N along with the calculated contents of Uauthigenic and
Baexcess reveals the association of Baexcess and Uauthigenic in
sedimentary C and N phases, suggesting that the changes in
productivity can be obtained by using a combination of these
proxies.
Factor 2 explains about 28.6% of variance and is
characterized by high loading for TS, Mo, CaO, Sr and
Moauthigenic as well as calculated ratios of Mo/TOC, Mo/U, CIA
and degree of pyritization (DOP) (Table 2). Since Mo, TS and
DOP, together with Mo/TOC and Mo/U, are ideal redox
proxies, changes in redox conditions can be obtained by using a
combination of these variables.
Factor 3 accounts for 20.2% of the variance (Table 2) and is
characterized by high loading for Ti, Al, Fe, Mg and K, along
with trace elements, Ni and Th. Since Al, Ti and Th are ideal
detrital indicators, association of Fe, Mg, K and Ni with these
detrital indicators may be suggestive that all these variables
were sourced by continental input via river discharge, or they
might have derived from the exposed shelf concurrently with
the sea-level rise during the transgression.
There is no significant overlap of these variables among the
factors explained, suggesting that the changes in productivity,
redox and detrital input can explain around 83% of the
sediment geochemical results in the studied core. Very
similarly, sea level, bottom water oxygenation and nutrient
input associated with kick-off of different currents through
different straits during the glacial–interglacial conditions might
be the principal processes for the last 48 ka in the Sea of Japan
responsible for productivity and redox changes seen in the
proxy records.
The age model was build on the basis of accelerator mass
spectrometry (AMS) 14C of plankton foraminifera and tephra
markers, as also published by Liu et al. (2010). Table 1 shows
AMS 14C and calendar ages converted using the CALIB 6.1.1
program with Marine09 age calibration curves (Reimer et al.,
2009). According to the age control points, the 7.6 m core
length contains the ca. 48 ka record. The calculated linear
sedimentation rate (LSR) was calculated, which varied
greatly from 5.5 to 28.3 cm ka1, with higher rates during
the Holocene period than in the last glacial stage (Table 1).
Recently, Yao et al. (2012 – this issue) compared lightness of
the KCES-1 core with that of the MD01-2407 core, and found
good correlations.
The mass accumulation rate (MAR) for parameters studied
was also calculated. For that, the conversion of weight percent
of the component to the MAR was accomplished using the
following formula (Murray and Leinen, 1996):
MAR ðmg cm2 ka1 Þ
¼ DBD ðg cm3 Þ LSR ðcm ka1 Þ CC ðwt%Þ 1000 (3)
where CC is the content of each component, DBD is sediment
dry bulk density and LSR is the linear sedimentation rate. Since
core KCES-1 was provided by KORDI, parameters such as water
content, porosity and wet density were not available for this
calculation. Kim and Kim (2001) reported that the sediment
physical properties of the Ulleung Basin can be divided into
two sections: slope and deep plain regions. Core KCES-1 is
located at the slope region and therefore we chose the physical
parameters available at site 16 (triangle in Fig. 1), located near
the core site of KCES-1, to calculate the DBD. Since the DBD
profile for site 16 changes insignificantly, a mean value of
2.3 g cm3 was taken as the DBD of core KCES-1.
Results
Discussion
All measured sedimentological and geochemical parameters
are listed in an online table (Supporting information, Table S1).
Since the studied elements in core KCES-1 cover a wide
spectrum of terrigenous, biogenic and redox-sensitive elemental characteristics, to decipher significant grouping of factors
and related geochemical controlling processes, the complete
geochemical data of the present study have been subjected to
factor analysis using SPSS software. The factors were extracted
using the Varimax rotation scheme with Kaiser normalization.
Sediment provenance
Aluminum is believed to be an index element for the
terrigenous source, and both Ti and Al are refractory elements
that are mostly immobile in the marine environment (Nath
et al., 1989). In core KCES-1, the Al2O3/TiO2 ratio ranges from
20.19 to 25.38 (Fig. 2), showing three distinct ranges, with
lower ratios (20.95–23.03) in sediments of the last glacial
period compared to the last deglacial period (20.19–25.12) and
Table 1. The age-controlling point for KCES-1.
Depth (cm)
Marker zone
150–156
179–181
252–254
260
402
466
493
636
AMS14C
K-Ah Tephra
U-Oki Tephra
TL-1
TOP TL-2
Bottom TL2
AT Tephra
SKP-1 Tephra
AMS
14
C age (ka)
5.09 0.04
Cal. age (ka)
Sedimentation rate (cm ka1)
Reference
5.46
7.30
10.69
11.41
17.67
24.31
29.24
40.50
28.3
14.7
21.5
8.3
22.7
9.6
5.5
12.7
Liu et al. (2010)
Machida (1999)
Tada and Irino (1999)
Oba et al. (1995)
Oba et al. (1995)
Oba et al. (1995)
Tada and Irino (1999)
Chun et al. (2007)
K-Ah, Kikai-Akahoya tephra; K-Ah ash is the most widespread Holocene tephra layer in the Japan region and originated from Kikai; a detailed
counting of annual layers suggests that the K-Ah tephra was ejected at 7324 cal. a BP (Machida, 1999). U-Oki, Ulleung-Oki tephra: a well-known ash
layer in the eastern Ulleung Basin, erupted from the Nari Caldera of Ulleung Island about 10.69 ka. AT, Aira-Tanzawa tephra: a prominent ash
layer was erupted from the Aira Caldera in southern Kyushu Island about 29.24 ka. SKP-I, a newly identified tephra; maximum thickness can be
observed at a location near the South Korea Plateau (SKP), which is present between the AT (29.24 cal. ka) and Aso-4 (88 ka) tephras in the southern
Ulleung Basin (Sea of Japan). TL, thinly laminated layers; depositional ages of TL1 and TL2 are around 10.5k 14C a BP and 14.5–23 14C ka BP (Ikehara
and Itaki, 2007), respectively.
Copyright ß 2012 John Wiley & Sons, Ltd.
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
894
JOURNAL OF QUATERNARY SCIENCE
Table 2. Varimax factor loading of elements in core KCES-1 from the
Ulleung Basin (Sea of Japan).
TOC
TN
TS
CaCO3
P2O5
Al2O3
Fe2O3
TiO2
CaO
MgO
Na2O
K2O
MnO
Ba
Cd
U
Th
Mo
Cu
Ni
V
Sr
Mz(F)
Moauthigenic
Uauthigenic
Baexcess
Mo/TOC
TOC/P
DOP
Mo/U
U/Th
Cd/U
CIA
Variance (%)
Cumulative variance (%)
F1
F2
F3
0.96
0.88
0.28
0.36
0.59
0.38
0.33
0.05
0.21
0.23
0.65
0.13
0.43
0.73
0.92
0.95
0.01
0.21
0.80
0.61
0.86
0.21
0.49
0.21
0.95
0.73
0.07
0.85
0.17
0.19
0.93
0.78
0.09
34.38
34.38
0.05
0.41
0.87
0.07
0.60
0.20
0.21
0.21
0.80
0.26
0.46
0.41
0.45
0.44
0.05
0.00
0.06
0.94
0.30
0.47
0.20
0.87
0.36
0.95
0.01
0.44
0.96
0.20
0.78
0.94
0.01
0.28
0.88
28.60
62.98
0.04
0.16
0.01
0.57
0.17
0.88
0.88
0.72
0.33
0.90
0.45
0.88
0.34
0.13
0.09
0.11
0.91
0.10
0.40
0.57
0.37
0.18
0.55
0.08
0.16
0.13
0.12
0.01
0.46
0.15
0.28
0.07
0.05
20.20
83.18
Holocene sediments (24.10–25.38). This reveals the changes in
sedimentary sources from the last glacial through the Holocene
as sediments of the former interval contain a lower content of
TiO2 compared to sediments of the latter interval, which are
dominated by more clayey sediments and thus contain slightly
higher Al2O3 content (Fig. 2). It is apparent that during the
initial stage of the last deglacial period (ca. 18–15 ka), the
Al2O3/TiO2 ratio was very low, coinciding with a very high silt/
clay ratio and higher sand content (Fig. 2). Such a prominent
drop in Al2O3/TiO2 ratio suggests an enhanced flux of silty
sediments likely dominated by Ti-bearing minerals relative to
Al-rich clay minerals. This could be attributable to either
aeolian transport or hemiplegic advection of riverine materials
deposited on the exposed shelf during the Last Glacial
Maximum (LGM) (Nagashima et al., 2007).
On the other hand, a continuous increase in Al2O3/TiO2 ratio
since ca. 15 ka mimics the deglacial rise in sea level, suggesting
hemiplegic advection of riverine materials from the SinoKorean craton through the TWC, which started to flow during
the Holocene. This is consistent with Bahk et al. (2004), who
reported a significant increase of detrital mineral input during
the last deglaciation, between 15 and 10 ka, in a piston core
(97PC-19) that was recovered from the southern lower slope of
the Ulleung Basin (368 20.30 N, 1318 20.90 E; water depth
1872 m) (black dot in Fig. 1).
The chemical index of alteration (CIA) is used to define the
weathering conditions of source rocks and sediment input
(Nesbitt and Young, 1982). The calculated CIA value for
core KCES-1 ranges from 46 to 62 from the last glacial to
Copyright ß 2012 John Wiley & Sons, Ltd.
Figure 2. Age versus concentrations of Al2O3, sand, Al/Ti, silt/clay,
CIA and CaO, and compared with d18O curves of cave stalagmite
(Wang et al., 2001) and GRIP ice core record (Dansgaard et al., 1993).
Gray bars indicate the duration of important climate events recorded in
the GRIP ice core. MIS 1, 2 and 3 represent Marine Isotope Stages 1, 2
and 3, respectively. YD, BA, OD and LGM refer to Younger Dryas,
Bølling–Allerød, Older Dryas and Last Glacial Maximum, respectively.
TS flow signifies the inflow of the TWC during the Holocene. Dashed
vertical line represents 6 ka, when the Sea of Japan attained its modern
oceanographic conditions.
Holocene (Fig. 2), suggesting low to moderate chemical
weathering conditions in the Sino-Korean craton for the last 48
ka. Lower CIA values (46–52) are mostly associated with
sediments of the last glacial period (ca. 48–20 ka), indicating a
weak hydrolysis of source rocks owing to low temperature and
rainfall. By contrast, the last deglacial and Holocene sediments
(since ca. 18 ka) are characterized by comparatively higher
CIA values (57–62). The content of silicate-associated
CaO (CaO ¼ total CaO content in wt% – wt% of CaO that
is associated with carbonate) ranges between 0% and 4.2%
(Fig. 2) and CaO content is approaching zero in the early
Holocene, implying the derivation of sediment from more
intensively weathered rocks during the Holocene, consistent
with higher CIA values (Fig. 2) during the Holocene. On the
other hand, a poor correlation between the contents of CaO
and Al2O3 (r2 ¼ 0.17) indicates either some changes in
sediment provenance or sediment sources through different
weathering states due to changing climate conditions (see
below). Within the last deglacial interval (18–11 ka), two
distinctly lower CIA values of 52 and 49 were found at ca.
11.87 ka and ca. 11.52 ka, respectively. This seems to be
attributed to increase in CaO content (1.08% and 0.87%) as
well as a decrease in Al2O3 content (11.76% and 9.64%) and
thus resembling the CIA values for sediments of the last glacial
period. These times further correspond to the Younger Dryas
(YD) cold event, reconfirming the weak hydrolysis of source
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
PALEOENVIRONMENTAL CHANGES IN THE ULLEUNG BASIN
rocks due to low temperature and precipitation in the
provenance that may have brought less fine sediments with
a relatively low Al content.
To address the shifts in terrigenous sources from the glacial
through Holocene intervals, we compared our data with the
published results of major element geochemistry of surface
sediments from the Ulleung Basin, Yellow Sea and South Sea,
as well as suspended particulate matter around the Korean
Peninsula (Cha et al., 2007) (Fig. 3). We calculated the CIA
value and Al2O3/TiO2 ratio for these different source sediments
reported by Cha et al. (2007). On a TiO2 versus Al2O3 plot
(Fig. 3), while we plot these source materials from the SinoKorean craton along with the samples of core KCES-1, coastal
and upper slope sediments from the Ulleung Basin and
suspended particulate matter from Huanghe fall in the center of
KCES-1 samples. Moreover, lower slope and basin sediments as
well as inner shelf sediments – all three from the Ulleung
Basin – also plot along and/or close to the regression line of
KCES-1 samples. Such a coincidence implies that sediments of
core KCES-1 were mainly sourced by Huanghe with substantial
influx from shelf and slope sediments from the Korea Strait, at
least during low sea stands. It is also evident that the influence
of Changjiang at the coring site is insignificant in terms of Al2O3
and TiO2 contributions as the Al2O3/TiO2 ratio of suspended
particulate matter from Changjiang plots away from the present
samples (Fig. 3). These are different from the bi-plot of Al2O3
versus K2O (Fig. 3), which shows a good correlation (R2 ¼ 0.93;
P < 0.0001) between these two major oxides, where coastal
and upper slope sediments and suspended particulate matter
from both Huanghe and Changjiang plot on the regression
trend along with deep-sea clay. Because of the different
behavior of these detrital ratios, it is difficult to ascertain the
source from Changjiang into the core site. We therefore
cautiously infer that the sediments of core KECS-1 contain
Al2O3/K2O ratios that are very similar to suspended particulate
matter of Huanghe as well as shelf and slope surface sediments
of the Ulleung Basin.
895
Paleoproductivity changes
It is apparent from Fig. 4 that the proxies reveal lower
productivity between 48 and 18 ka, whereas maximum
productivity occurred during the last deglacial–early Holocene
transition between ca. 14.6 and 7.5 ka.
We combined the oxygen isotope (d18O) time series from
Hulu Cave stalagmite in eastern China (Wang et al., 2001) and
GRIP2 ice core (Dansgaard et al., 1993) and insolation in June
at 308 N (Berger, 1978), as well as sea-level changes for the last
48 ka (Saito et al., 1998). The cave stalagmite d18O record
indicates the intensity of the East Asian monsoon, whereas the
GRIP2 d18O record reveals the changes in Greenland air
temperature. The lower productivity revealed by MARs of TOC,
CaCO3, P2O5, Cd, U and Baexcess in core KCES-1 during the last
glacial period from 48 to 18 ka could be attributed to lower sea
level (Fig. 4). Consistent with this, the cave stalagmite d18O
record shows enriched d18O values as an indication of weak
monsoon when Greenland air temperatures fluctuate minimally. During the last glacial period, since the sea level
was 80 m lower than that in the present day, the water mass
exchange between the Sea of Japan and other oceans was
mainly from the Tsushima and Tsugaru Straits (140 m and
130 m deep, respectively). This likely limited the inflow of
nutrient-rich water mass from the East China Sea and Oyashio
Current. The alkenone-based temperature reconstruction
shows that the climate was cold and moist in the Sea of Japan
during the last glacial period (Lee et al., 2008). The limited
water mass exchange and cold temperature conditions,
consistent with the GRIP2 d18O record (Fig. 4), may likely
inhibit the bloom of algae and thus productivity in the Sea of
Japan.
Productivity increased from 18 to 11.5 ka, with the maximum
occurring during 12.7 9 ka (Fig. 4). The increased productivity indicates that the bloom conditions were likely
favored by the increasing temperature and the input of nutrientrich water mass from the East China Sea. This is consistent with
Figure 3. Scatter-plots
of
Al2O3–TiO2,
Al2O3–K2O, CIA–Al2O3/TiO2, CIA-U/Th and
compared with Yangtze River, Yellow River,
Yellow Sea, and slope and plain of the Ulleung
Basin, reported in Cha et al. (2007).
Copyright ß 2012 John Wiley & Sons, Ltd.
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
896
JOURNAL OF QUATERNARY SCIENCE
Figure 4. Age versus mass accumulation
rates of TOC, TN, P2O5, CaCO3, Baexcess,
copper, uranium, cadmium and ratios of Cd/
U and U/Th, and compared with d18O curves
of cave stalagmite (Wang et al., 2001), GRIP
ice core record (Dansgaard et al., 1993), sealevel curve of East China Sea (Satio et al.,
1998) and sedimentation rate. Dashed vertical
line and gray bars are the same as in Fig. 2.
a rapid sea-level increase between 18 and 9 ka, as evident from
Fig. 4, although this interval in the cave record shows a weaker
meteoric precipitation in eastern China and low temperatures
in Greenland. Moreover, sea-level increase can extend the
width and depth of the straits and allow nutrient-rich water
mass flowing into the Sea of Japan, which in turn may induce
the productivity bloom. Benthic foraminiferal oxygen and
Copyright ß 2012 John Wiley & Sons, Ltd.
carbon isotopes and planktic foraminiferal assemblages
indicate that the Oyashio Current has flowed into the Sea of
Japan since 17.5 ka (Domitsu and Oda, 2006; Hoshiba et al.,
2006; Kuroyanagi et al., 2006). The Oyashio Current with cold
temperature sinks in the north of the Sea of Japan and decreases
the water stratification. The process would have increased
the exchange between deep- and surface-water masses and
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
PALEOENVIRONMENTAL CHANGES IN THE ULLEUNG BASIN
probably entrained lots of nutrients from the deep water to
the surface. Maximum productivity was observed during
12.3 – 9 ka, the period when the East China Sea nutrient-rich
water also contributed to higher productivity in the Sea of
Japan (Tada, 1994) because of the sea-level rise. The high
sedimentation and increased detritus input during this
interval in core KCES-1 support this inference (Fig. 4) (Zou
et al., 2010).
In the Holocene, the Tsushima Warm Current flowed into
the Sea of Japan through the Tsushima Strait and dominated the
environmental changes. Oba et al. (1991) suggested that
the paleo-Tsushima Warm Current started to flow through the
Tsushima Strait into the Sea of Japan ca. 11 ka. However, many
other researchers have proposed that the Ulleung Basin (Sea of
Japan) was fully influenced by the Tsushima Warm Current only
after 8.1 ka (Ijiri et al., 2005; Xu and Oda, 1999). In contrast to
the Oyashio Current and East China Sea Coastal Current, the
Tsushima Warm Current is poor in nutrients. Minimal changes
of TOC, Cd, P and Baexcess since 6 ka imply a steady state in
productivity, suggesting that the environment since 6 ka in the
Ulleung Basin was similar to the present day, further
corroborating cave and GRIP2 d18O records (Fig. 4).
Paleoredox history
The spatial and temporal persistence of dark and light layers in
the Sea of Japan can be observed on the basin scale, reflecting
the high-frequency changes in the depositional environment
(Bahk et al., 2001; Khim et al., 2007; Minoura et al., 1997;
Shibahara et al., 2007; Watanabe et al., 2007). Similar to other
cores, we also observed alternate dark and light layers in core
KCES-1 and attributed this phenomenon to the effects of high
surface water productivity and weak bottom water ventilation.
Figure 5 shows the proxy parameters from core KCES-1 to infer
the redox changes for the last 48 ka. All the proxies such as TS,
Moauthigenic, DOP and Mo/TOC show similar down-core trends.
DOP – one of the useful geochemical proxies for assessing
the redox state of the depositional environment locally –
quantifies the extent to which reactive iron converts into pyrite
(FeS2) and is calculated from the relative amounts of reactive to
non-reactive iron in the sediment (Raiswell and Berner, 1985;
Raiswell et al., 1988). According to Pearce et al. (2010), a good
approximation for DOP can be obtained using the total content
of Fe and S in sediments and is based on the assumption that all
sulfur in sediment is in the form of pyrite. In this study, the DOP
is thus calculated as DOPT (%) ¼ (TS 0.86)/FeT 100.
During the last glacial period between ca. 48 and 24 ka,
DOPT in core KCES-1 shows a narrow range between 24% and
27%. Since then, this proxy fluctuates largely with prominent
high values (>30%) at ca. 21, 17 and 11.5 ka, consistent
with similar high DOP values found in core MD012404 from
the Okinawa Trough (Kao et al., 2006). A distinct decrease of
DOPT from ca. 11.5 ka to 8.6 ka and a continuous decrease
since 6.8 ka to the present indicate a better ventilation of deep
waters in the coring site, mainly resulting from the inflow of the
warm Tsushima Current along with the East China Sea Coastal
Current during these intervals. Consistently, previous studies
have indicated that the Sea of Japan was dominated by cold
surface water and anoxic bottom conditions throughout the last
glacial period and by warm surface waters coupled with
oxidizing bottom conditions during the Holocene (Oba et al.,
1991).
Algeo and Lyons (2006) reported that Mo/TOC ratios are
useful for distinguishing degrees of restriction of the subchemoclinal water mass in anoxic marine environments, with
ratios of >35, 15–35 and <15 (104) associated with weak,
moderate, and strong restrictions, respectively. During the last
Copyright ß 2012 John Wiley & Sons, Ltd.
897
glacial period, Mo/TOC ratios varied between 15 and
30 104, which correspond to moderate restriction. After
18 ka, Mo/TOC ratios were less than 15 104 and correspond
to a strong restriction criterion proposed by Algeo and Lyons
(2006). Lower Mo/U ratios are recorded in sediments since ca.
17 ka and higher Mo/U ratios are mostly associated with
sediments between 48 and 18 ka, with intermittent lower ratios
at ca. 47.3, 43.2, 40, 31.5 and 27.5 ka. The present-day
seawater contains a range of Mo/U ratios 7.5–7.9 (Algeo and
Tribovillard, 2009). In deglacial and the Holocene sediments,
this ratio is lower than modern seawater and ranges from 0.62
to 2.65. Such lower Mo/U ratios since 17 ka indicate that
deposition occurred mostly under oxic conditions. Higher
Mo/U ratios, mostly above the present-day Mo/U ratios in
seawater, evident in the last glacial period, suggest the
occurrence of sediment deposition under suboxic or mildly
reducing conditions when the accumulation of Mo was
normally enhanced.
The geochemical behavior of Mo and Mn in anoxic water
differs, so a combination of these elemental behaviors can be
used to trace the redox history in the bottom water (Tribovillard
et al., 2006). During 12 8 ka, the down-core profiles for
Mn and Moauthigenic show different trends, with higher
Moauthigenic contents corresponding to lower Mn contents
(Fig. 5). The contents of Uauthigenic and Mo together with U/Th
and C/S ratios indicate that the ventilation activity increases
in the bottom water after 9.3 ka, and the bottom water is similar
to the modern conditions from 6 ka.
All redox proxies show that the ventilation of bottom water
changes significantly over the 48 ka. Before 15 ka, the
alterations between dark and light layers appear in the KCES-1
core, indicating a rapid change in the bottom-water dissolved
oxygen concentration. In fact, the redox variation reflects the
ventilation history in the bottom water, which is related to the
surface current and global climate change (Bahk et al., 2005).
Li et al. (2001), based on their study with piston core
DGKS9603 from Okinawa Trough, suggested the influence of
the KC since about 16 ka, weakening at ca. 2.8–5.3, 11.4 and
15.5 ka. Consistent with this, radiolarian assemblages showed
that the deeper zone was filled with static, anoxic water during
30 17 ka BP, while deep ventilation was abrupt at 14 ka (Itaki
et al., 2004). Further, they mentioned that deep convection
activity had stopped at ca. 12 11.5 ka. In the northern Sea of
Japan, the benthic foraminifera assemblage showed that
dysoxic taxa occurred during the Bølling–Allerød (B/A) and
the Preboreal intervals (the earliest Holocene), while suboxic
taxa mainly dominated during the last glacial period, YD and
Holocene (Shibahara et al., 2007).
Redox proxies such as TS, Moauthigenic content, DOP and Mo/
U ratio suggest that dissolved oxygen concentration in the
bottom water was very low during 12.3–8.2 ka (Fig. 5). This
phenomenon was likely caused by high surface-water
productivity and increasing stratification in the water column.
As mentioned above, during 14.6 7.5 ka high productivity
was recorded in the KCES-1 core. In fact, high productivity
during the last deglacial period in the Sea of Japan, Okhotsk Sea
and the subarctic Pacific Ocean has been widely reported
(Gorbarenko et al., 2004, 2007; Keigwin and Gorbarenko,
1992, Keigwin et al., 1992; Lee et al., 2003; Ono et al., 2005).
The high productivity in the Sea of Japan was attributed to the
nutrient-rich water inflow (Tada and Irino, 1999). A lot of
particulate organic matter accompanied by high productivity
will consume large amounts of oxygen in the water column. On
the other hand, with the rising sea level during 12.3 8.2 ka,
the low-saline and nutrient-rich waters flow into the Sea of
Japan. The low-salinity water influx raises the potential for
water stratification, slowing down the diapycnal dissolved
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
898
JOURNAL OF QUATERNARY SCIENCE
Figure 5. Time series of multi-proxies in
core KCES-1 used for the reconstruction of
paleoredox conditions and compared with
d18O curves of Cave stalagmite (Wang et al.,
2001) and GRIP ice core record (Dansgaard
et al., 1993). Dashed vertical line and gray
bars are the same as in Fig. 2.
oxygen exchange, resulting in a higher delivery flux of organic
carbon to deep sea that might elevate the oxygen consumption
rate.
Since 9.3 ka, the Tsushima Current with warm, high-salinity
water mass flows into the Sea of Japan, resulting in the
vertical convection increase between surface and deep waters
and also increasing the renewal rate of dissolved oxygen in
the bottom waters. The bioturbated, mud-dominated sediments
in the Holocene section of our core also support that the
depositional environment was under oxygenated bottom-water
conditions.
One of the pressing issues in the western Pacific paleoceanographic changes is to understand the re-entry of the warm KC in
the Okinawa Trough and subsequent re-entry of the TWC in the
Sea of Japan through the Korea Strait, especially during
the Holocene. The past two decades of studies reveal different
time periods for re-entry of these two currents at the Holocene
commencement. Oba et al. (1991) identified through elemental
and isotopic proxies that the TWC started to flow into the Sea of
Japan at ca. 10 ka to establish the modern oceanographic
conditions which have continued since 8 ka. By investigating a
core retrieved from the northern part of the East China Sea, Ijiri
et al. (2005) noted a wider transitional period from cold to
warm water masses from 14 to 8 ka, as indicated by the increase
of warm water species such as Pulleniatina obliquiloculata and
Globigerinoides ruber; however, they also found the presentCopyright ß 2012 John Wiley & Sons, Ltd.
day warm KC conditions after 8 ka, consistent with the finding
of Oba et al. (1991). On the other hand, the ODP site 1202
drilled beneath the Kuroshio was investigated for sediment
granulometry, mineralogy and elemental X-ray fluorescence
scanning by Diekmann et al. (2008). They found two pulsed
entrances of Kuroshio to the Okinawa Trough, with relative
current strengthening at ca. 11.2 and 9.5 ka, as documented by
stepwise increases of sortable silt in the lower Holocene
section. By comparing all these records, it is possible to place
the re-entry of both KC and TWC between 11.2 and 8 ka,
perhaps due to the different responses of different proxies used
in these studies as well as different age models which used a
range of AMS 14C calibration methods. According to our study,
when we use the updated Calib 6.1 program we are able to infer
the re-entry of the TWC into the Sea of Japan at 9.3 ka and this
age falls within the surface currents re-entry established in the
above-mentioned studies, although we need a systematic study
with representative proxies to re-evaluate the inconsistency of
KC and TWC re-entries in future.
Conclusions
The basin-wide redox condition in the Ulleung Basin (Sea of
Japan) varied significantly over 48 ka. Sea level exerts a major
control on renewal of the bottom waters for ventilation as well
as water exchange for surface productivity. With the rising sea
J. Quaternary Sci., Vol. 27(9) 891–900 (2012)
PALEOENVIRONMENTAL CHANGES IN THE ULLEUNG BASIN
level, increasing inflow of nutrient-rich water had resulted in a
high surface productivity during 18 9 ka, peaking during
the YD and Preboreal. The terrestrial nutrient input from
China and Korea may also contribute to this peak productivity.
The coexistence of high values in productivity and redox
proxies implies the dominance of dysoxic conditions during
12.3 – 8.2 ka, which was caused by high surface productivity
with enhanced water stratification. The intensified Tsushima
Current inflow starting from the early Holocene gradually
lowers the productivity peak until 6 ka and since then the
primary production was similar to modern conditions. The
entire redox history is governed by low-frequency sea-level
fluctuation superimposed with productivity impacts associated
with terrestrial input, water exchange and circulation change,
which are related to global climate conditions.
Supporting information
Additional supporting information can be found in the online
version of this article:
Table S1 The concentrations of TOC, TN, TS, CaCO3, major
and minor elements and calculated ratios at KCEs-1 Core in
East/Japan Sea.
Please note: This supporting information is supplied by the
authors, and may be re-organized for online delivery, but is not
copy-edited or typeset by Wiley-Blackwell. Technical support
issues arising from supporting information (other than missing
files) should be addressed to the authors.
Acknowledgements. We would like to thank the Korea Ocean
Research and Development Institute for providing the sediment core
KCES-1 for this study. Financial support was provided by the National
Natural Science Foundation of China (grant nos. 40906035,
40710069004) and by the Youth Foundation of the State Oceanic
Administration People’s Republic of China (2012301) and by the Basic
Research Science Foundation in the First Institute of Oceanography,
State Oceanic Administration (nos. 2010G24, 2007T09 and 2012G31).
We are grateful to two anonymous reviewers for their critical comments, which greatly improved our paper.
Abbreviations. AMS, accelerator mass spectrometry; CIA, chemical index of alteration; DBD, dry bulk density; D-O, Dansgaard–
Oeschger; DOP, degree of pyritization; ICP-MS, inductively
coupled plasma mass spectrometry; KC, Kuroshio Current;
KORDI, Korean Ocean Research and Development Institute;
LGM, Last Glacial Maximum; LSR, linear sedimentation rate;
MAR, mass accumulation rate; TC, total carbon; TN, total nitrogen; TOC, total organic carbon; TS, total sulfur; TWC, Tsushima
Warm Current; YD, Younger Dryas.
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