Quaternary Science Reviews 19 (2000) 1067}1085
Benthic foraminifer record of environmental changes in the Yellow Sea
(Hwanghae) during the last 15,000 years
Jung-Moo Kim, Michal Kucera*
Department of Geological Sciences, University of California, Santa Barbara, CA 93106, USA
Abstract
Latest Quaternary benthic foraminifer census counts in four cores from the Yellow Sea (Hwanghae) were analyzed to decipher
paleoenvironmental changes in this area since the Last Glacial Maximum. Principal component analyses of samples from two cores in
the central Yellow Sea indicate that the faunal variation in these cores re#ects a sequence of distinct assemblages divided by sharp
boundaries. The shifts between individual biofacies correspond to changes in geochemical and lithological composition of the
sediments, and stable-isotope ratios of foraminiferal shells, and most can be correlated between cores. The major faunal transition, at
a clear increase in bottom-water salinity, occurred between 8.47 and 6.63 ka, and may indicate the establishment of modern-type
circulation in the Yellow Sea. The inferred threshold size of the Yellow Sea Basin for the establishment of such circulation seems to be
rather close to its present-day extent. Faunal shifts at 10.6 and 4.67 ka probably re#ect changes in the intensity of river runo!,
associated sediment and organic carbon delivery, and bottom-water oxygenation. Changes in benthic foraminifer faunas between 12.9
and 11.75 ka may signal the Younger Dryas climatic oscillation in the Yellow Sea. The Lateglacial marine transgression reached the
central part of the Yellow Sea around 15.09 ka. Possibly, an uplift of the central and eastern Yellow Sea area during the late Holocene
can explain the discrepancy between the timing of the transgression in the Yellow Sea and the global sea-level curve. 2000
Published by Elsevier Science Ltd. All rights reserved.
1. Introduction
The Yellow Sea (Hwanghae) has undergone a whole
suite of dramatic environmental changes during the last
glacial cycle (e.g., Wang and Sun, 1994; Zheng et al.,
1998). Beginning as a subaerial plain cut by numerous
river channels at times of the Last Glacial Maximum
(LGM; &21 cal ka), the region has been gradually
#ooded during the Holocene marine transgression (Park
et al., 1994). Today, the Yellow Sea has an area of about
500,000 km; it is a relatively shallow (water depth
(100 m), semi-enclosed shelf sea with brackish water
(salinity: (32) originating from the mixture of oceanic
water and fresh water from major Asian rivers, including
the Yellow River (Fig. 1; Chough, 1983).
The dramatic environmental changes in this area had
a profound e!ect on sediment accumulation (e.g., Alexander et al., 1991), and have been recorded in the stable
isotope composition of foraminiferal shells (Kim and
* Corresponding author. Tel.: 001-805-893-3103; fax: 001-805-8932314.
E-mail address: [email protected] (M. Kucera).
Kennett, 1998a; Kim et al., 1999). Benthic foraminifera
are by far the most abundant fossil group found in the
sediments deposited during the marine transgression (e.g.
Wang et al., 1985). Kim and Kennett (1998a) provided
the "rst quantitative data from this area on changes in
benthic foraminifer assemblages throughout the Holocene marine transgression. Although they mostly used
stable isotopic evidence, they were also able to identify
a large reorganization of the benthic foraminifer communities, coinciding with inferred variations in bottomwater salinity.
Interpretations of Holocene paleoenvironmental
changes in the Yellow Sea (Kim and Kennett, 1998a; Kim
et al., 1999) placed much emphasis on changes in
salinity associated with the progression of the marine
transgression as well as changes in continental precipitation and runo!. Temperature changes during the Holocene were likely relatively small (Webb, 1985; COHMAP,
1988; Crowley and North, 1991). In contrast, the
in#uence of major Asian rivers in this shallow, semienclosed sea would have created large #uctuations
in salinity and in the transport of organic matter and
"ne-grained sediment into the basin. Relatively low
salinities occur in the northern Yellow Sea today, and
0277-3791/00/$ - see front matter 2000 Published by Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 3 7 9 1 ( 9 9 ) 0 0 0 8 6 - 4
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J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
are marked by typical benthic foraminifer assemblages, absence of planktonic foraminifera, and low
foraminifer oxygen isotopic values (Kim and Kennett,
1998a).
Here we present a detailed account of changes in
benthic foraminifer assemblages throughout the last
15 kyr (calendar yr) in four cores from two regions of the
Yellow Sea. The distribution of modern benthic
foraminifera in surface sediments of the Yellow Sea has
been studied by many authors (Polski, 1959; Kim, 1970;
Kim et al., 1970; Chang and Lee, 1984; Wang et al., 1985;
Cheong, 1991; Zheng and Fu, 1994). Before now, however, paleoenvironmental reconstructions in this region
have received little attention from quantitative studies of
benthic foraminifera. The main objective of this study
was to describe the response of benthic foraminifer
faunas to the Holocene marine transgression in the Yellow Sea using multivariate statistics, and to use this
information for a more detailed reconstruction of
paleoenvironmental changes.
2. Material and methods
This study is based on quantitative analysis of benthic
foraminifer assemblages in four cores at two locations in
the Yellow Sea. Piston cores CC02 and CC04 were collected in the Kunsan Basin in the central part of the
Yellow Sea, while vibracores DH1-4 and DH4-1 were
collected from a tidal #at close to the central part of the
Korean Peninsula (Fig. 1; Table 1). All cores were collected by the Korea Ocean Research and Development
Institute (KORDI).
Core CCO2 consists of light-to-dark gray marine sediments, with the lower part composed of laminated silty
sand and the upper part, above 120 cm, of less laminated,
bioturbated mud to silt (Fig. 2; cf. Kim and Kennett,
1998a). In core CC04, well-laminated silty mud in the
lower part of the core is replaced by less laminated sandy
mud at 148 cm; the upper 30 cm of Core CC04 consists of
a homogenous layer of mud with no obvious sedimentary
structures (Ministry of Environment, 1998). Core DH1-4
Fig. 1. Map of the Yellow Sea with locations of the four cores studied (CC02, CC04, DH1-4 and DH4-1). Schematic chart of regional circulation and
water masses was modi"ed after Beardsley et al. (1985) and Lie (1985, 1986), respectively. Water depth is shown in meters.
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
1069
Table 1
Location, water depth, length, and date of retrieval of the four cores analyzed in this study
Core
Latitude (N)
Longitude (E)
Water depth (m)
Core length (cm)
Date of retrieval
CC02
CC04
DH1-4
DH4-1
363743
3631800
373313
373124
12334913
12433000
12632918
12632810
77.5
83.0
2.0
1.8
278
225
470
350
August 1993
August 1993
October 1994
October 1994
consists entirely of marine sediments; the lower 170 cm of
the core is composed of silty mud to mud; the upper part
is composed of sandy mud to sand (Fig. 2). Core DH4-1,
350 cm long, has been divided into two parts (Kim and
Kennett, 1998a); the lower part, containing non-marine
deposits, is covered by a 270 cm thick, downward-"ning
sequence of marine muddy sand (Fig. 2). Foraminifera,
ostracods and shell fragments occur in the upper 220 cm
of this core only. The non-marine deposits consist of
semi-consolidated, upward-"ning sequence of oxidized
yellowish-brown clayey silt (KORDI, 1994). This facies,
named the &Kanweoldo' deposit, was formed during the
last glacial maximum (Park et al., 1994; Chun et al., 1995;
Kim and Kennett, 1998a).
In addition to previously published dates from cores
CC02 and DH4-1 (Table 2; Kim and Kennett, 1998a;
Kim et al., 1999), Accelerator Mass Spectrometer (AMS)
C ages of foraminifera and shell fragments from "ve
levels in core CC04 were measured at the Center for
AMS, Lawrence Livermore National Laboratory, California, USA. No reservoir correction has been made on
the measured radiocarbon ages. Although the reservoir
e!ect for the central part of the Yellow Sea has not been
studied in detail, benthic foraminifera from the core-top
sample in core DH4-1 yielded an AMS C age of 4 yr
(Table 2; Kim and Kennett, 1998a), suggesting that the
reservoir e!ects on radiocarbon ages in the Yellow Sea
are minimal (see also Kim et al., 1999). The measured
radiocarbon ages have been converted to calendar ages
using the calibration curves of Stuiver et al. (1991) and
Stuiver and Braziunas (1993) (Table 2). Throughout this
article, calendar years BP are used whenever referring
to age.
Samples were oven dried at 503C, weighed and washed
over a 63 lm Tyler screen. After further drying, the samples were reweighed. The '63 lm fraction was drysieved over a 150 lm sieve, and the '150 lm fraction
subdivided using a modi"ed Otto microsplitter until
aliquots of at least 300 benthic specimens remained.
Benthic foraminifer counts were made for samples taken
at 5 cm intervals (CCO2) and at 10 cm intervals (CC04,
DH1-4 and DH4-1). All specimens present within these
aliquots were identi"ed and counted. The data on the
distribution of 31 species in 56 samples from core CC02,
and 17 species in 23 samples from core DH4-1 were
published by Kim and Kennett (1998a). In core CC04, 13
Fig. 2. Lithology and AMS C ages (shown as calibrated ages BP) of
the four cores studied. A: dark-grey bioturbated mud to silt. B: lightgrey slightly laminated sandy mud. C: dark-grey homogenous silt to
mud. D: light-grey-well laminated silty mud. E: light grey silt to mud. F:
upward coarsening sequence of light grey silt to mud. G: terrigenous
yellowish brown oxidized mud to clayey silt. Mollusks include bivalves,
gastropods, and oysters. The lithology was modi"ed from Ministry of
Environment (1998) and Kim and Kennett (1998).
species were identi"ed in 22 samples (Table 3); in core
DH1-4, 18 species were found in 47 samples (Table 4).
The taxonomy of benthic foraminifera in this paper is
based upon that of Ellis and Messina (1940), Barker
(1960), Wang et al. (1985), Cheong (1991), Loeblich and
Tappan (1994), and Yassini and Jones (1995). A scanning
electron microscope was used to assist with the identi"cation of some smaller species using surface ultrastructural characteristics. Representative specimens of the
most abundant species are illustrated in Figs. 3 and 4.
Photographs of these specimens were taken with Akashi
ISI-SX-40 SEM at the Department of Geology, Chungnam National University, Korea.
1070
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Table 2
List of Accelerator Mass Spectrometer C dates used to construct the age models for cores CC02, CC04 and DH4-1
Sample no.
Depth (cm)
Analyzed material
Lab. no.
AMS C ages (years B.P.)
Calendar ages (ka)
CC02-1
CC02-2
CC02-3
CC02-4
CC04-1
CC04-2
CC04-3
CC04-4
CC04-5
DH4-1-1
DH4-1-2
DH4-1-3
DH4-1-4
DH4-1-5
15}25
95
170}180
275
70}80
110
140
160
210
0
50
100
240
270
Foraminifera (mixed)
Foraminifera
Foraminifera (mixed)
Foraminifera
Foraminifera (mixed)
Foraminifera (mixed)
Foraminifera
Shell fragments
Shell fragments
Foraminifera
Gastropod shell
Oyster shell
Peat
Peat
39659
24749
39660
24750
46599
46600
46601
46602
46603
5404
5405
5406
5661
5662
2200$100
5370$60
9840$200
11340$80
10670$80
9640$60
11100$60
11560$60
12740$70
4$73
4423$71
6730$110
7460$100
7550$100
1.80
5.72
10.60
12.91
12.13
10.33
12.45
13.34
15.09
0.00
4.55
7.21
7.89
7.94
Kim and Kennett (1998).
Kim et al. (1999).
Ammonia ketienziensis.
Ammonia beccarii.
Center for AMS, Lawrence Livermore National Laboratory, USA.
Institute of Geological and Nuclear Sciences Limited, New Zealand.
Calibrated using the data of Stuiver et al. (1991) and Stuiver and Braziunas (1993).
0.00
0.00
4.65
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.15
0.36
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.76
0.36
3.41
12.96
3.85
2.22
2.80
0.00
0.00
0.00
0.00
10.00
0.00
11.63
21.43
0.00
21.88
19.25
11.56
16.08
13.21
15.85
18.57
14.36
20.45
9.31
10.58
11.11
18.69
0.00
20.00
13.64
30.00
0.00
23.08
30.23
0.00
7.14
3.13
0.00
0.00
0.00
0.00
0.47
0.00
0.00
0.09
0.00
0.00
0.00
0.93
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
6.25
0.00
0.89
0.50
0.00
0.23
0.76
0.36
0.17
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Rotalinodes annectens
Lagena striata toddae
Hanzawaia nipponica
Elphidium etigoense
Elphidium advenum
Cribrononion subinecertum
0.00
0.00
0.00
7.14
7.14
9.38
9.62
9.78
14.57
12.89
6.53
7.46
4.73
9.62
12.55
9.62
8.89
11.21
0.00
20.00
9.09
10.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.94
0.93
2.44
1.45
1.22
0.40
0.00
0.00
0.00
6.67
3.33
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.47
0.76
1.09
0.00
1.01
0.00
0.00
0.00
0.00
3.33
0.00
0.00
20
13
43
14
14
32
239
225
199
318
429
657
550
1144
494
104
45
107
15
30
22
10
Foraminiferal number (specimens/g)
5.00
7.69
0.00
14.29
28.57
18.75
23.01
24.00
20.60
21.70
19.35
22.07
18.91
16.17
6.48
14.42
15.56
17.76
26.67
20.00
9.09
10.00
Bulimina marginata
Buccella frigida
Astrononion italicum
10.00
0.00
2.33
7.14
0.00
0.00
0.00
0.00
0.00
0.31
0.47
0.15
0.00
0.00
0.00
1.92
0.00
0.00
0.00
0.00
0.00
0.00
Total dry sample weight (g)
0.00
0.00
4.65
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
No of specimens
70.00
69.23
46.51
21.43
14.29
3.13
0.00
1.33
0.50
1.26
1.86
0.00
0.00
0.09
0.81
0.00
4.44
0.00
0.00
0.00
0.00
0.00
Reophax sp.
5.00
0.00
0.00
28.57
42.86
37.50
48.12
52.44
47.74
49.69
53.85
46.88
58.36
48.69
56.48
59.62
57.78
48.60
66.67
33.33
68.18
50.00
Augnlogerina semitrigona
8.01
8.24
8.47
8.70
8.94
9.17
9.40
9.63
9.87
10.10
10.33
11.04
11.74
12.45
12.90
13.34
13.69
14.04
14.39
14.74
15.09
15.44
Ammonia ketienziensis
Age (ka)
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
Ammonia beccarii
Depth (cm)
Table 3
Relative and absolute abundance data of benthic foraminifera in Core CC04
7.34
8.55
8.75
19.45
23.51
37.44
49.67
58.00
43.09
49.83
59.76
72.28
61.98
70.67
53.31
47.29
43.10
31.06
46.97
47.65
32.74
33.54
2.72
1.52
4.91
0.72
0.60
0.85
4.81
3.88
4.62
6.38
7.18
9.09
8.87
16.19
9.27
2.20
1.04
3.44
0.32
0.63
0.67
0.30
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
1071
5.68
4.02
10.35
4.85
7.58
2.95
3.59
0.00
0.94
7.84
4.95
13.51
17.33
3.03
6.04
0.80
14.57
7.67
7.86
7.21
4.67
4.73
13.61
4.77
0.93
19.39
7.52
9.28
7.11
4.20
1.68
4.64
8.86
8.11
0.72
1.91
4.36
11.11
0.00
50.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.25
0.00
0.00 405
0.00
0.45
0.00 224
0.00
0.00
0.00 193
0.00
0.00
1.39 144
0.00
0.00
0.00 317
0.59
0.00
0.00 170
0.00
0.00
0.00 167
0.00
0.00
0.00 39
0.00
0.00
0.00 212
1.12
0.00
0.00 179
0.00
0.83
0.00 364
0.71
0.00
0.00 141
3.01
0.00
0.00 133
0.00
0.00
0.00 66
0.00
0.00
0.00 116
0.00
0.00
0.00 124
0.00
0.00
0.00 124
1.53
0.00
0.00 130
0.00
0.00
0.00 140
0.51
0.00
0.00 194
0.67
0.00
0.00 150
0.79
0.00
0.00 127
0.52
0.00
0.00 191
0.60
0.00
0.00 168
0.00
0.00
0.00 107
0.00
0.00
0.00 134
0.00
0.00
0.00 146
0.00
0.00
0.00 140
0.44
0.00
0.00 225
0.00
0.60
0.00 167
0.00
0.00
0.00 179
0.00
0.00
0.00 129
0.00
0.55
0.00 181
0.00
0.00
0.00 173
0.00
0.00
0.00 139
0.00
0.00
0.00 367
0.00
0.10
0.00 1010
0.00
0.00
0.00
9
0.00
0.00
0.00 23
0.00
0.00
0.00
2
0.00
0.00
0.00
1
0.0
0.00
0.00 12
0.00
0.00
0.00
1
0.00 100.00 100.00
1
0.00
0.00
0.00
0
0.0
0.00
0.00
1
0.00
0.00
0.00
0
Foraminiferal number (specimens/g)
Total dry sample weight (g)
0.00
0.00
0.00
0.89
1.58
0.00
0.60
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.49
1.37
0.71
0.00
0.00
0.00
0.00
1.11
0.00
0.00
0.54
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
No of specimens
0.00
0.89
0.52
1.39
0.00
0.00
0.60
0.00
0.00
0.00
0.83
0.00
0.00
0.00
0.86
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.66
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Trochammina sp.
1.23
4.02
2.59
2.77
1.58
2.36
0.00
0.00
0.00
0.00
0.00
0.71
0.00
1.52
1.73
2.41
0.81
0.77
0.00
1.54
0.00
0.79
2.62
3.58
0.00
2.24
1.37
2.86
2.67
2.40
4.48
0.77
6.65
5.21
12.20
7.63
6.93
22.22
8.70
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Sigmomorphina gallowayi
0.49
0.00
0.52
1.39
1.90
2.95
1.20
0.00
0.94
0.56
1.38
0.00
2.26
1.52
1.73
3.22
1.62
0.00
1.43
5.66
2.00
0.79
1.57
0.00
0.00
1.49
1.37
0.71
1.33
1.20
1.12
0.00
1.11
4.63
1.44
0.27
1.68
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Q. serninulum
0.00
0.45
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Q. lamarcliana
0.25
2.68
1.55
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.28
0.00
0.00
0.00
0.00
2.41
0.00
0.00
0.00
0.00
0.00
0.00
1.57
1.19
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.54
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
100
0.00
Quinqueloculina aknerinus
12.10
12.95
13.97
13.87
9.48
2.95
0.00
0.00
0.00
2.24
0.00
0.00
0.00
6.06
6.90
7.24
5.66
2.30
2.14
8.75
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.44
5.18
2.57
0.00
0.00
0.00
100.00
0.00
100.00
0.00
0.00
0.00
0.00
Rotalinoides annectens
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.79
0.00
0.00
0.00
0.75
0.00
0.00
1.33
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.59
0.00
8.70
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Rosalina bradyi
0.25
0.00
0.00
0.00
0.63
1.18
1.20
2.59
0.47
0.00
0.28
0.71
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
2.37
0.52
0.00
0.00
0.75
0.00
0.00
0.00
0.00
0.00
0.77
0.00
0.00
0.00
0.27
0.49
0.00
0.00
0.00
0.00
8.16
0.00
0.00
0.00
0.00
0.00
Pararotalie nipponice
24.69
8.48
11.53
6.39
15.64
11.00
7.77
4.28
0.92
3.65
6.48
8.25
8.83
4.50
2.53
2.70
3.71
3.37
4.26
1.17
3.84
3.81
3.67
2.20
2.03
2.31
0.90
1.44
1.39
0.99
1.48
1.02
0.87
0.98
0.95
0.58
1.01
0.00
0.00
0.00
0.00
2.03
0.00
0.00
0.00
0.00
0.00
Henzewaia japonica
E.etigoense
0.25
0.00
1.55
0.69
0.95
2.95
5.39
5.17
8.02
5.60
8.80
0.00
0.00
1.52
0.86
1.61
1.62
0.00
2.86
2.06
1.34
2.37
0.00
2.98
1.87
1.49
0.68
0.71
1.33
1.20
1.12
0.00
1.11
1.74
0.00
1.38
1.09
0.00
4.35
0.00
0.00
8.16
0.00
0.00
0.00
0.00
0.00
Elphidium sp.
E.asiaticum
0.00
0.00
0.00
0.00
0.32
0.00
0.60
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0
0.93
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
E.hispidulum
Elphidium advenum
Buccella frigida
15.80
21.88
12.42
18.03
10.43
6.48
0.00
5.17
0.47
2.80
2.48
27.24
27.13
34.86
24.15
17.69
21.04
19.17
20.00
11.84
14.02
20.50
16.23
25.05
27.99
26.85
38.27
44.28
17.32
31.20
38.38
34.80
30.46
27.80
32.30
27.79
30.59
0.00
8.70
50.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Cribrononion subincertum
39.01
44.20
45.01
49.93
49.92
66.60
79.06
82.79
88.23
76.19
73.72
48.37
41.44
46.99
55.20
61.92
50.98
65.19
61.44
61.25
73.45
63.07
59.68
59.63
66.25
43.25
48.53
40.00
67.07
58.20
53.74
58.00
47.63
51.54
50.96
53.94
50.58
66.67
69.57
0.00
0.00
81.64
0.00
0.00
0.00
0.00
0.00
Cibicides sp.
8
18
28
38
48
58
68
78
88
98
108
118
128
138
148
158
167
178
188
198
208
218
228
238
248
258
268
278
288
298
308
318
328
338
348
358
368
378
388
398
408
418
428
438
448
458
468
Ammonia beccarii
Depth (cm)
Table 4
Relative and absolute abundance data of benthic foraminifera in Core DH1-4
40.00 10.13
57.00 3.93
48.00 4.03
70.00 2.06
72.00 4.40
57.00 2.98
63.00 2.65
43.00 0.90
43.00 4.93
58.00 3.08
48.00 7.57
57.00 2.47
60.00 2.21
82.00 0.80
62.00 1.87
59.00 2.11
51.00 2.42
46.00 2.83
51.00 2.74
50.00 3.89
63.00 2.38
62.00 2.05
64.00 2.98
44.00 3.81
49.00 2.19
50.00 2.68
32.00 4.57
43.00 3.28
43.00 5.24
38.00 4.39
48.00 3.72
30.00 4.31
43.00 4.20
52.00 3.32
51.00 2.73
43.00 8.54
66.00 15.31
49.00 0.18
64.00 0.36
59.00 0.03
57.00 0.02
52.00 0.24
59.00 0.02
51.00 0.02
62.00 0.00
53.00 0.02
46.00 0.00
1072
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Fig. 3. Representative specimens of benthic foraminifera from the latest Quaternary of the Yellow Sea. 1a}c. Ammonia beccarii (LinneH ) forma tepida
(Cushman) from sample CC02-275; 1a, umbilical view, X 100; 1b, apertural view, X 120; 1c, spiral view, X 100. 2a}c. Ammonia ketienziensis (Ishizaki)
from sample CC02-85; 2a, umbilical view, X 100; 2b, apertural view, X 120; 2c, spiral view, X 80. 3a}c. Rotalinoides annectens (Parker and Jones) from
sample DH4-1-30; 3a, umbilical view, X 45; 3b, apertural view, X 45; 3c, spiral view, X 45. 4a}c. Buccella frigida (Cushman) from sample CC02-190; 4a,
umbilical view, X 130; 4b, apertural view, X 150; 4c, spiral view, X 150. 5. Angulogerina semitrigona Galloway and Wissler from sample CC02-140; 5,
side view, X 100. 6a, b. Cribrononion subincertum (Asano) from sample CC02-265; 6a, side view, X 100; 6b, apertural view, X 100. 7a, b. Elphidium
advenum (Cushman) from sample CC02-230; 7a, side view, X 80; 7b, apertural view, X 100.
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
1073
Fig. 4. Representative specimens of benthic foraminifera from the latest Quaternary of the Yellow Sea. 1a}c. Ammonia beccarii (LinneH ) forma tepida
(Cushman) from sample CC02-275; 1a, umbilical view, X 80; 1b, apertural view, X 120; 1c, spiral view, X 80. 2a}c. Buccella frigida (Cushman) from
sample CC02-190; 2a, umbilical view, X 80; 2b, apertural view, X 85; 2c, spiral view, X 80. 3a}c. Pararotalia nipponica (Asano) from sample DH4-1-140;
3a, umbilical view, X 91; 3b, apertural view, X 100; 3c, spiral view, X 60. 4a, b. Elphidium asiaticum Polski from sample CC02-275; 4a, side view, X 120;
4b, apertural view, X 145. 5a, b Bulimina marginata d'Orbigny from sample CC02-35; 5a,b, opposite sides; 5a, X 150; 5b, X 200. 6a, b. Elphidium
etigoense Husejima and Maruhasi from sample CC02-265 cm depth; 6a, side view, X 120; 6b, apertural view, X 120. 7a, b. Elphidium hispidulum
Cushman from sample CC02-275; 7a, side view, X 101; 7b, apertural view, X 100.
1074
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Systematic changes in benthic foraminifer assemblages
occur in both cores from the deeper part of the Yellow
Sea (see also Kim and Kennett, 1998a). In order to
describe these changes quantitatively, R-mode Principal
Component Analysis (PCA) has been performed on the
data. Relative abundances, adding up to a unit value, are
subject to the constant sum constraint * a mathematical
property which may e!ectively conceal true relationships
between variables of any compositional dataset (Pearson,
1897). Thus the raw percentages were log-ratio transformed (Aitchison, 1986) with zero replacement of 0.01%
(see also Kucera and Malmgren, 1998). The PCA was
performed separately for each core. In the sequence from
core CC02, the 21 most abundant species (relative abundance '1% in at least 5 samples) and all 56 samples were
included in the analysis, while in core CC04 the analysis
was based on all 13 species (relative abundance '1% in
at least 2 samples) in 18 samples above 180 cm. The
signi"cance of the contribution of individual variables
(species) to the principal components has been determined using a bootstrap variety of PCA (Diaconis and
Efron, 1983) with 1000 replicates. A species loading on
a particular principal component was considered signi"cant if its con"dence interval did not contain the zero
value. An analysis performed in this way will circumvent
the constant sum constraint; it will enable us to discuss
the faunal changes on a rigorous basis, and to evaluate
statistically the signi"cance of individual species for the
observed patterns.
3. Results
3.1. Age models
Four C AMS ages (Table 2) were used as the basis of
the age model for core CC02 (Fig. 5). The model implies
relatively constant sedimentation rates (16}19 cm/kyr) in
the upper 175 cm of the core, following an interval of
rapid sedimentation (&43 cm/kyr) below 175 cm,
i.e. 10.6 ka (Fig. 5).
In core CC04, four C dates (Table 2) provide a "rm
basis for the age of the sediments below 110 cm (Fig. 5).
The "fth date, obtained from pooled benthic foraminifera
from samples between 70 and 80 cm, is considered unreliable; the age of this sample is greater than that of
the sample at 110 cm. The weight of the analyzed calcite
in this sample was much less than in the other samples
(see Table 2). Should we decide to discard the date
from 110 cm, the sediment between 140 and 75 cm would
Fig. 5. Age models for all cores studied. Control points, between which age was assigned to samples by linear interpolation, are shown together with
sedimentation rates for all intervals. `Faunal transitiona refers to the replacement of Ammonia becarrii by A. ketienziensis.
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
have to be deposited under as little as 320 years, implying
a mean sedimentation rate of 203 cm/kyr for this interval.
No radiometric dates are available for the upper
110 cm of core CC04. Assuming a constant sedimentation rate for this interval makes the correlation of faunal
events with those in core CC02 di$cult. The replacement
of A. beccarii by A. ketienziensis occurs at 140 cm in core
CC02 (Fig. 6), with an age of about 8.47 ka (Fig. 5). This
age model is constrained by a C age of 5.72 ka in the
sample from 95 cm (Table 2). Assuming constant sedimentation rate in the upper 110 cm of core CC04, this
faunal transition (Fig. 6) would occur around 3 ka. Using
stable oxygen isotopic data, Kim and Kennett (1998a)
showed that the invasion of A. ketienziensis into the
central Yellow Sea re#ects a major increase in bottom
water salinity. It is hard to envisage how such an event
would remain unnoticed by benthic assemblages recovered from core CC04, located in the immediate vicinity of core CC02 (Fig. 1, Table 1). Thus, instead of
assuming continuous sedimentation throughout the upper 110 cm of core CC04, we base the age model for this
part of the core on the assumption of synchroneity of the
major faunal transition (Fig. 5). This implies that core
CC04 probably only recovered the interval before 8 ka.
The occurrence of an unconformity would also explain
the lack in core CC04 of several distinct faunal shifts seen
in core CC02 (Fig. 6).
For core DH4-1, we adopted the age model in Kim and
Kennett (1998a) based on "ve C dates (Fig. 5). Only
a tentative age model can be constructed for core DH1-4
(Fig. 5). The "rst sample probably representing fully marine conditions in core DH4-1 is at 190 cm (based on the
abundance of benthic foraminifera; see data in Kim and
Kennett, 1998a) with a corresponding interpolated age of
7.65 ka. This event can be correlated to 368 cm in core
DH1-4, where benthic foraminifera for the "rst time occur
in signi"cant numbers (Table 4). Since no other stratigraphically useful events could be identi"ed in both cores,
the tentative age model for DH1-4 assumes a constant
sedimentation rate throughout the sequence (Fig. 5).
3.2. Faunal variation in cores CC02 and CC04, Kunsan
Basin
Relative abundances of the 12 most common species
of hyaline benthic foraminifera and of the sum of
porcellaneous and arenaceous taxa in all cores are displayed in Fig. 6. The assemblages in all four cores exhibit
relatively low diversity (Fisher's alpha index generally
(2), and are largely dominated by either Ammonia beccarii, characteristic of low salinity waters of the modern
Yellow Sea (Chang and Lee, 1984; Wang et al., 1985;
Cheong, 1991), or A. ketienziensis, which is presently
typical for deeper, more saline waters (Wang et al., 1985).
These two species alone account for almost one-half of all
the benthic foraminifera in the studied samples. Although
1075
we have carefully searched for planktonic foraminifera,
they were not found in any of the samples analyzed.
The results of PCAs for both cores are shown in Figs. 7
and 8 and Table 5. The analyses have revealed that for
both cores, more than a half of the variability in the
multidimensional faunal data can be expressed by few
principal components (Table 5). Plots of individual
sample scores along these components demonstrate the
presence of several distinct clusters (Fig. 7). The clusters
from core CC02 correspond exactly to the major faunal
assemblages discussed by Kim and Kennett (1998a).
However, two of these clusters can be further subdivided
(Fig. 7). In all cases, the clusters contain stratigraphically
adjacent samples (Fig. 8). Therefore, the major part of
the variability in benthic foraminifer faunas from both
cores can be interpreted as one re#ecting a succession
of distinct assemblages. The shifts between these assemblages divide the sequences in both cores into a series of
benthic foraminifer biofacies, which are henceforth referred to by capital letters A}E (Figs. 7 and 8). Two of the
biofacies (D and E) can be further subdivided into two
parts (Figs. 7 and 8). Positions of the biofacies in both
cores, as well as lists of typical species are summarized in
Table 6. We use same letters for corresponding biofacies
in the two cores. Both the inferred age of the faunal shifts
(Fig. 8) and the species variation (Fig. 6, Table 6) in the
two cores are similar suggesting that the sample clusters
in both cores (Fig. 7) represent the same succession of
faunal assemblages. Such a result can be expected given
the close location of the two cores (Fig. 1, Table 1).
3.3. Faunal variation in cores DH1-4 and DH4-1, Korean
tidal yats
In both cores from the tidal #ats o! central Korea, A.
beccarii dominates the benthic foraminifer fauna by
50}75% (Fig. 6); the assemblages show a low diversity
with only four additional species with relative abundances higher than 10% (B. frigida, C. subincertum, E.
advenum, and Pararotalia nipponica). Changes in the
composition of the benthic foraminifer faunas from cores
DH1-4 and DH4-1 with time are much smaller than in
Kunsan Basin (Fig. 6). The only distinct features are the
gradual trends in the relative abundance of some species,
which appears to be opposite in both cores. Thus, while
the relative abundance of C. subincertum and E. advenum
increased during the interval recovered in core DH1-4,
the same species show a decreasing trend in core DH4-1
(Fig. 6). Since the age model for core DH1-4 is only tentative, no conclusions can be drawn about detailed correlation of these features. Porcellaneous and arenaceous species are relatively rare in all samples from both cores,
with the exception of the coretop from DH4-1, where
a single agglutinated species, Trochammina rotaliformis,
constitutes over 14% of the benthic foraminifer fauna
(Fig. 6).
Fig. 6. Relative abundance of 12 most abundant species of benthic foraminifera and of the sums of porcellaneous and arenaceous taxa in the studied cores. Lines and shaded areas depict the position
of major faunal transitions as seen in Figs. 7 and 8.
1076
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
1077
3.4. Benthic foraminifer accumulation rate
Absolute abundance of benthic foraminifera, when expressed as number of shells per volume unit of sediment
re#ects both the rate of production of new shells, and the
rate of dilution of these by other sedimentary particles
(provided calcite dissolution e!ects are minimal, as is the
case with our material). Thus, if biological and environmental interpretations are to be drawn from the variation
in abundance of benthic foraminifera, these two
processes must be separated. With known sedimentation
rates the rate of accumulation of benthic foraminifera
(BFAR) can be calculated as BFAR " BGSHDHSR,
where BGS denotes number of benthic foraminiferal
shells per gram sediment, D denotes sediment density
(here set to 2.5 g/ccm for all samples), and SR denotes
sedimentation rate in cm/kyr (see Fig. 5). In open
ocean environments, BFAR is directly proportional to
the vertical #ux of organic matter (Herguera and Berger,
1991).
Fig. 9 shows the variations in BFAR for all four cores
studied, plotted against age in calendar years. In core
CC04, BFAR increased from about 20 shells/g/kyr in the
lowermost sample to almost 800 shells/g/kyr in the upper
part of the sequence (Fig. 9). A conspicuous minimum in
BFAR can be seen in three samples from around 9 ka (Fig.
9). Before 10.6 ka in core CC02, BFAR shows relatively
steady variation between 3000 and 4000 shells/g/kyr. After
this time, the values dropped below 1000 shells/g/kyr and
continued to decrease until about 7 ka (Fig. 9). During
the later part of the Holocene, the BFAR values in
core CC02 show only a moderate #uctuation around
1000 shells/g/kyr (Fig. 9).
After a remarkable peak immediately following the
arrival of the marine transgression, the BFAR values
remained stable in both cores from the Korean tidal #ats
(Fig. 9). In core DH1-4, prior to the #ooding datum,
BFAR values appear to be an order of magnitude lower
than those observed in core DH4-1. Also, the (tentative)
age model for this core seems to suggest that benthic
foraminifera were present in low numbers already shortly
after 10 ka (Fig. 9). Both of these apparent discrepancies
can be resolved if it is assumed that sedimentation rates
were much higher in the lower part of core DH1-4, at
about the time of the initial marine #ooding in this area,
as has been observed in core DH4-1 (Fig. 5).
4. Discussion
Fig. 7. A. Distributions of scores of the 56 samples from core CC02
along the "rst three principal component axes. These axes alone account for over 70% of the faunal variation in the dataset. Five major
clusters, corresponding to "ve benthic foraminifer biofacies (A}E) can
be distinguished among the samples. Cluster E can be further subdivided into two parts (see also Fig. 8). B. Scores of 18 samples from
core CC04 along the "rst two principal component axes. The distribution of the samples in the plane of the two PCs ('55% of the total
variation) reveals the presence of three major and two minor clusters.
4.1. Chronology of the Holocene marine transgression
Based on data from core CC02, Kim and Kennett
(1998a) concluded that the central part of the Yellow Sea
must have been #ooded before 12.9 calendar ka BP (the
age of the lowermost sample in this core). We provide an
1078
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Fig. 8. Scores of samples from both cores along the principal component axes plotted against age. Benthic foraminifer biofacies A}E, corresponding to
the clusters in Fig. 7, are indicated (see also Fig. 6).
improved estimate of the timing of the marine transgression in Kunsan Basin. Shell fragments collected at 210 cm
in core CC04 yield a calendar age of 15.09 ka (Table 2).
Since benthic foraminifera occur in abundances comparable to those of modern tidal-#at environments 30 cm
higher in core, this age probably re#ects the original
establishment of a transitional environment with only
a partial, perhaps periodical marine in#uence.
In broad terms, this age is in agreement with results of
earlier studies of sea-level change in the Yellow Sea area
Wang et al., 1985b; Geng et al., 1987; Park et al. 1994;
Chun et al., 1995). However, considering the present-day
water depth of 83 m (Table 1), a modern tidal range
between 8 and 9 m (taken as a maximum estimate of the
past tidal range), and sediment cover of 210 cm for the
15.09 ka level in core CC04, the transgression in Kunsan
Basin seems to lead the global sea-level curve of Fairbanks (1989) by about 15 m (Fig. 10). A similar situation
is encountered for the arrival of the marine transgression
to the Korean tidal #ats, which can be dated to about
7.65 ka (Kim and Kennett, 1998a). According to Fairbanks' (1989) curve, the global sea level at this time
should have been about !20 m.
Conspicuously, the di!erence of the inferred altitude at
the time of the transgression (based on the sum of the
present-day water depth, sediment cover and tidal range)
and the global sea-level curve (Fig. 10) appears to be
similar at both locations (slightly more than 10 m). Although this possibility has not been previously considered for this area (e.g. Park and Yi, 1995), we suggest
that the discrepancy between sea-level change in the
Yellow Sea and the global curve of Fairbanks (1989) can
be explained by a vertical uplift of the Yellow Sea area by
some 10}20 m during the last 7000 years. There is a circumstantial evidence corroborating this conclusion.
First, there are numerous though controversial reports in
the literature about sea-levels on the western margin of
Yellow and Bohai Seas and southeastern coast of Korea
Peninsula being higher than today at some point during
the last 6 kyr (e.g. Jo, 1980; IGCP Project No. 200 China
Working Group, 1986 and references therein). Second,
based on the present-day position of uplifted marine
terraces of the Shandong and Liaodong Peninsulas,
Wang and Wang (1982) calculated an emergence rate of
&3 mm/yr for the western Yellow Sea coast; if the same
rate of uplift occurred in the central and eastern Yellow
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Table 5
Loadings of the species onto the "rst three principal components in the
analysis of the data from core CC02 and the "rst two principal components in the analysis of the data from core CC04. Numbers in parenthesis refer to the portion of the total variation explained by each of the
principal components. Loadings in bold typeface were signi"cant at
95-% level.
Species
Principal component loadings
Core CC02
First PC
(50%)
Second PC
(11%)
Third PC
(9%)
Ammonia ketienziensis
Bulimina marginata
Astrononion italicum
Fissurina laevigata
Ammonia nakamurai
Hanzawaia nipponica
Lagena straita toddae
Lenticulina calcar
Bulimina exilis
Lagena striata inertia
Fissurina marginata
Dentalina costai
Angulogerina semitrigona
Elphidium etigoense
Rosalina isabelleana
Reophax di{ugiformis
Buccella frigida
Textularia mexicana
Cribrononion subincertum
Elphidium advenum
Ammonia beccarii
ⴚ0.285
ⴚ0.244
ⴚ0.243
ⴚ0.241
ⴚ0.228
ⴚ0.222
ⴚ0.217
ⴚ0.204
ⴚ0.197
ⴚ0.135
ⴚ0.117
!0.087
0.057
0.184
0.191
0.204
0.225
0.230
0.286
0.294
0.295
!0.076
!0.133
0.339
0.011
0.332
0.340
0.080
0.106
!0.292
!0.409
!0.212
!0.291
!0.342
0.202
0.005
!0.122
0.220
0.039
0.079
0.023
!0.080
!0.052
!0.204
0.041
0.126
0.032
!0.090
!0.141
0.257
!0.196
0.143
0.370
0.358
!0.506
!0.077
0.319
!0.163
!0.219
0.248
0.002
0.137
0.022
Core CC04
First PC
(37%)
!0.410
ⴚ0.307
ⴚ0.305
ⴚ0.304
ⴚ0.230
0.113
0.118
0.147
0.167
0.178
0.299
0.377
0.402
Second PC
(18%)
0.022
!0.142
!0.311
0.328
!0.048
0.078
!0.033
0.527
0.475
0.269
!0.343
!0.182
!0.197
Angulogerina semitrigona
Hanzawaia nipponica
Ammonia ketienziensis
Bulimina marginata
Astrononion italicum
Elphidium etigoense
Lagena striata toddae
Reophax di{ugiformis
Rotalinodes annectens
Elphidium advenum
Buccella frigida
Cribrononion subincertum
Ammonia beccarii
Sea, it would easily account for the 10}20 m di!erence
between the local and global sea-level changes. Alternatively, the apparent discrepancy may be explained
by imperfections of our age model. For example, the
reservoir e!ect in the early Yellow Sea may have been
much di!erent from the present situation.
4.2. Benthic Foraminifer Biofacies and environmental
changes
Faunal changes in both cores from the central Yellow
Sea, as revealed by the PCA analyses (Figs. 7 and 8) are
1079
similar and occur at the same levels as variations in
lithological and geochemical characteristics of sediments
in these cores (Fig. 11). If the age models in this study are
correct, the timing of the early Holocene faunal changes
can clearly be correlated between the two cores (Fig. 11).
Both pieces of evidence suggest that the successive
replacement of the benthic foraminifer biofacies was
caused by changes in the regional environment. The most
obvious of such environmental changes is the continuously increasing water depth and extent of the Yellow
Sea, resulting from the postglacial rise of the global
sea-level.
Both geochemical (Kim and Kennett, 1998a; Kim
et al., 1999) and biological data point at signi"cant
changes in salinity of the Yellow Sea. The major shift in
salinity occurred between 8.5 and 6.6 ka; it is recorded
in stable oxygen isotope values from benthic foraminiferal
shells, in C/S ratios of sediments, and in the major faunal
transition observed in both cores * the replacement of
the A. beccarii dominated biofacies (E-D) with A. ketiensiensis dominated biofacies (C-A) (Fig. 11). The abrupt
nature of this salinity increase, and its timing some
6}8 kyr after the initial arrival of the marine transgression, imply that the environment of the Yellow Sea did not
respond to the increasing water depth in a linear manner.
Thus, although the water depth in the Kunsan Basin
must have increased by some 40 m during the early
Holocene (cf. Fairbanks, 1989), the bottom water salinity
remained low. As a consequence, the benthic foraminifer
A. beccarii biofacies persisted throughout this interval,
although, in the present day Yellow Sea, species characteristic of this biofacies typically inhabit inner shelf environments, less than 20 m in depth (Wang et al., 1985b).
To explain the abruptness of this (as well as of other)
event one has to resort to the concept of oceanographic
thresholds. Prior to 8.5 ka, the early Yellow Sea was an
estuary with a large positive hydrographic balance resulting from major riverine freshwater input, preventing
higher salinity bottom waters from the East China Sea to
fully penetrate into the Yellow Sea Basin (see also discussion in Kim and Kennett, 1998a). In both cores from
the Kunsan Basin, the 8.5 ka transition in benthic fauna
coincides with a clear change in sediment composition,
characterized by the replacement of early Holocene sand
and muddy-sand with late Holocene mud (Figs. 2 and
11). Finer-grained sediments in the western and central
part of the modern Yellow Sea basin are primarily derived from the Yellow River discharge (Lee and Chough,
1989). Further to the east, coarser-grained sediments are
derived mainly from the Korean Peninsula; the boundary
between these sedimentary provinces is located in the
close vicinity of both cores studied Park et al. 1990. The
observed change of sediment composition at 8.5 ka
may thus be interpreted as an eastward shift of the
Yellow River discharge plume, facilitated by an areal
expansion of the Yellow Sea. Apparently, both surface
1080
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Table 6
Summary chart of the "ve biofacies recognized in the two cores from the Kunsan Basin on the basis of the R-mode PCAs (Figs. 7 and 8). Dashed lines
mark boundaries of the two subclusters.
Biofacies
Core CC02
Core CC04
Lowest sample
Lowest sample
Depth
Age
75 cm
4.67 ka
Ammonia ketienziensis
Hanzawaia nipponica
Astrononion italicum
110 cm
6.63 ka
Ammonia ketienziensis
A
B
Typical assemblage
Depth
Age
Angulogerina semitrigona
C
140 cm
8.47 ka
D
30 cm
Ammonia beccarii
Angulogerina semitrigona
Cribrononion subincertum
Buccella frigida
8.47 ka
Typical assemblage
Ammonia ketienziensis
Hanzawaia nipponica
Angulogerina semitrigona
Ammonia beccarii
Cribrononion subincertum
Buccella frigida
9.17 ka
10.33 ka
First Ammonia ketienziensis
130 cm
11.75 ka
Ammonia beccarri
Rotalinoides annectens
Elphidium advenum
Reophax sp.
12.90 ka
D
150 cm
Bottom not
recovered
water circulation and the bottom water circulation in the
basin reacted together towards the crossing of the threshold size of the Yellow Sea. The tidal #ats along the
central Korean coast were #ooded by 7.65 ka or earlier
(Fig. 10; see also Chun et al., 1995; Lee and Yoon, 1997;
Kim and Kennett, 1998a for more data), thus the threshold size of the Yellow Sea basin must be very close to
its modern extent.
The major faunal transition at 8.5 ka is preceded by
the replacement of Biofacies E by Biofacies D, dated
to 10.60 ka, in Core CC02 and to 10.33 ka in Core
CC04 (Figs. 8 and 11). This replacement is marked by
an increase in the relative abundance of B. frigida and C.
subincertum, a decrease in the relative abundance of E.
advenum, and, in core CC02, by the initial immigration of
A. semitrigona (Fig. 6). The event coincides with a
clear increase in organic carbon content of sediments in
core CC02 (Fig. 11; Kim et al., 1999), suggesting that
its origin may be sought in changes of organic matter
in#ux and/or the oxygenation of bottom waters. Based
on its general morphology, A. semitrigona is probably
a lower-oxygen species. Indeed, it closely tracked the
increasing trend of organic carbon content in sediments
from core CC02, reached its maximum abundance
('75%) in the middle of the major faunal transition,
and virtually disappeared thereafter (Figs. 6 and 11).
The low BFAR values in samples from Biofacies C (Fig.
9) indicate that the apparent bloom of A. semitrigona
occurred during a time of environmental conditions less
favorable to other species. Thus, it is tempting to interpret the behavior of this species in terms of ecological
opportunism and adaptation to environment with high
#ux of organic matter and low oxygen content. Once the
steady increase in organic carbon content terminated, the
population of this until-then blooming species rapidly
declined, being replaced by species of Biofacies B
(Figs. 6 and 11). On the basis of stable isotope data from
core DH4-1, Kim and Kennett (1998a) inferred a decrease in input of terrestrial carbon between 6.2 and
6.7 ka. It is possible that the decline of A. semitrigona in
the central Yellow Sea re#ects the same environmental
perturbation.
Since the end of the major faunal transition in core
CC02 (6.65 ka), the benthic foraminifer assemblages began to resemble the modern deep Yellow Sea fauna as
described by Wang et al. (1985). The high relative abundance of A. ketiensiensis at this time may signify the development of the Hwanghae Cold Water, with which this
175 cm
10.60 ka
E
60 cm
110 cm
Ammonia beccarii
Rosalina isabelleana
Elphidium advenum
225 cm
11.76 ka
Bottom not recovered
Max Elphidium advenum
Max Elphidium advenum
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
1081
Fig. 9. Benthic foraminifer accumulation rate calculated for all cores on the basis of the age models from Fig. 5. Also marked are the positions
in all cores of the inferred onset of marine conditions and the positions of the biofacies recognized in cores from the Kunsan Basin (Figs. 7 and 8,
Table 6).
species is typically associated in the modern Yellow Sea
(Wang et al., 1985; Cheong, 1991). At 4.67 ka, after the
replacement of Biofacies B by Biofacies A as observed in
core CC02, the transition towards the modern-type fauna
was completed. The coleval increase in relative abundance of H. nipponica and A. italicum (Fig. 6) at this time
may re#ect changes in the Hwanghae Cold Water pool.
According to Cheong (1991) both species typically inhabit muddy bottoms in the deepest parts of the modern
Yellow Sea, an environment characterized by low annual
#uctuations in salinity and temperature, and high #ux of
"ne-grained sediment transported into the basin by major Chinese rivers.
The benthic foraminifer records from both cores from
the western Korean tidal #ats show relatively stable
conditions throughout the late Holocene, both with respect to relative abundance of the dominant species (Fig.
6), and accumulation rate of benthic foraminifer shells
(Fig. 9). The only discernible pattern is the gradual increase and decrease in certain species (Fig. 6). This may
be related to the gradual reduction in river runo! associated with reduced rainfall over Korea (see Kim and
Kennett, 1998a and references therein), or alternatively, it
may re#ect changes in the relative sea-level along the
Korean coast. Since the inferred time of the marine
#ooding of the tidal #ats at 7.65 ka, the global sea-level
rose by some 20 m (Fairbanks, 1989). The gradual trends
in abundance of certain species may as well re#ect the
complex interplay between rising sea-level and the
coleval uplift of the area, as discussed above.
Planktonic foraminifera are absent in all the studied
cores almost certainly because of low surface-water salinities in the central Yellow Sea. Today, abundant planktonic foraminifera occur in the southern part of the
Yellow Sea associated with the Hwanghae Warm Current (KORDI, 1987) marked by salinities of '27
(Waller and Polski, 1959), while no planktonic foraminifera have been reported in sediments north of 353N
(Kim, 1970; Kim et al., 1970; Wang et al., 1985; KORDI,
1987). The lack of planktonic foraminifera in our cores
suggests that the Hwanghae Warm Current at no time
penetrated northwards into these latitudes during the
Holocene, which is also consistent with the conclusion of
Lie (1985).
1082
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
Fig. 10. Comparison of the inferred ages and depths of marine transgression in the Yellow Sea with the global sea-level curve of Fairbanks
(1989). Vertical error bars represent the mean present-day tidal range
(8}9 m) on the Korean tidal #ats (although this was probably di!erent
in the past); horizontal error bars depict the $2 sigma errors of the
radiocarbon ages (Table 2).
4.3. Possible record of the Younger Dryas climate
oscillation
One of the characteristics of the faunal variation in
core CC04 is the appearance of a benthic foraminifer
assemblage distinguishing samples of Biofacies E (Figs.
7 and 8) during a short interval in the lower part of
the core. This interval can be dated with a high level of
con"dence (on the basis of three C ages) to a 2600-year
long period between about 12.9 and 10.3 ka. Of the
four samples from this interval, the upper two seem to
di!er from the lower two by much higher scores along
the second PC (cf. Figs. 7 and 8). This transition can be
dated to about 11.7 ka. Although the record from core
CC02 does not span to more than 12.9 ka, a small but
distinct change in relative abundance of certain species
(Figs. 7 and 8; marked by dashed line) in this core
seems to be coleval to the transition in core CC04
(Figs. 8 and 11).
Between about 13.0 and 11.7 ka (based on the GISP
chronology), climate of the Northern Hemisphere has
been in#uenced by a short-lived climatic oscillation
known as the Younger Dryas (Alley et al., 1993; Severinghaus et al., 1998). Evidence of this abrupt reversal of the
deglacial warming trend has been found in many terrestrial and marine sedimentary environments both in the
North Atlantic and North Paci"c regions (see Kennett,
1990), including the East Sea (Japan Sea) (Kim and
Kennett, 1998b). Therefore, it is conceivable to propose
that this climatic oscillation also had some in#uence on
the environment of the Yellow Sea. We suggest that the
faunal changes at 150 and 130 cm in core CC04 and at
225 cm in core CC02 represent the "rst known record of
Younger Dryas from this area.
Paleoenvironmental interpretation of these faunal changes is inherently di$cult. Benthic foraminifer assemblages from both cores remained dominated by Ammonia
beccarii throughout the event (Fig. 6). Only a handful of
other species occurred in and around the interval in significant abundances, showing rather con#icting patterns.
Thus, B. frigida, a typical cold-water species, occurs
throughout the presumed Younger Dryas in core CC04,
while in core CC02 it "rst appears in large numbers after
the level corresponding to the end of the Younger Dryas
(Fig. 6). Nevertheless, in both cores, at the presumed
position of this event the relative abundance of E. advenum is conspicuously higher than below and above this
interval (Fig. 6), suggesting that this species may be
associated with Younger Dryas environmental conditions. Similarly, the end of the inferred Younger Dryas
interval is characterized by a maximum in the abundance
of R. annectens (CC04) and Rosalina isabelleana (CC02).
The climate oscillation during the Younger Dryas apparently did not lead to any reversal of the sea-level
rise in the Yellow Sea, or alterations in the temperature
and salinity of the bottom waters. Such changes would be
recorded in stable isotope signals and other geochemical
indices in core CC02 (Kim and Kennett, 1998a; Kim
et al., 1999). The onset of Biofacies E in core CC04
seems to correspond with a conspicuous change in mean
grain size of the sediment (Figs. 2 and 11). The apparent
coarsening of the sediment can be interpreted as a consequence of a large-scale shift in the hydrological balance
on land surrounding the Yellow Sea, which may have
resulted from cooler and drier climate of the Younger
Dryas time. A decrease in precipitation over the
area drained by the Yellow River may have caused a
temporary change in the con"guration of its discharge
plume so that mud particles transported in the river
waters did not reach the central part of the Kunsan
Basin. Subsequent changes in the input of organic matter
into the Kunsan Basin and the increased availability of
coarser sedimentary particles may have facilitated the
temporary occurrence of R. annectens and arenaceous
species in core CC04, as well as the increase in relative
abundance of E. advenum, observed in both cores (Fig. 6).
In the present-day Yellow Sea, both species are characteristic of the Korean Central Coast Biofacies of Cheong
(1991), an area controlled by an input of sedimentary
particles from Korean rivers.
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
1083
Fig. 11. A summary scheme of the biotic, geochemical, and lithological changes in the central Yellow Sea since the Last Glacial Maximum. B/A
" B+lling/Aller+d, YD " Younger Dryas. References: (1) Kim and Kennett (1998a); (2) Kim et al. (1999).
5. Conclusions
(1) Based on new radiocarbon dates from core CC04,
we conclude that the Holocene marine transgression
reached the central part of the Yellow Sea by about
15.09 ka. Both this date and the date from the Korean
tidal #ats (7.65 ka) indicate that the Yellow Sea leads
global sea-level rise by some 10}20 m. An uplift of the
area during the late Holocene is proposed as an explanation for this discrepancy.
(2) The major faunal transition occurs when the
A. beccarii assemblage in the lower part of cores
CC02 and CC04 is replaced during the middle and late
Holocene (between 8.47 and 6.63 ka) by an assemblage
dominated by A. ketienziensis. It indicates a sudden increase in bottom water salinity, which appears to result
from the establishment of the modern-type circulation in
the Yellow Sea. The inferred threshold size of the Yellow
Sea Basin for the establishment of such circulation seems
to be rather close to its present-day extent.
(3) Faunal, geochemical, and lithological #uctuations
before (10.60 ka in CC02; 10.33 ka in CC04) and after
(4.67 ka in CC02) this transition are probably related to
changes in the intensity of river runo!, associated sedi-
ment and organic carbon delivery, and bottom-water
oxygenation.
(4) Distinct changes in benthic foraminifer faunas can
be seen at 12.9 ka and 11.75 ka in both cores. Although
the temporal resolution of this study is not su$cient to
draw any ultimate conclusions, the striking similarity
in timing of these transitions with the Younger Dryas
climatic oscillation suggests that the observed faunal
variation in the Yellow Sea may be a re#ection of this
temporary reversal in deglacial warming.
Acknowledgements
This research was funded in part by the Korea Research Foundation as a postdoctoral fellowship to
J.M.K. Financial support was also provided by the Ministry of Environment and the Ministry of Science and
Technology, Korea through the G7 project on `Research
and Development on Technology for Global Environmental Monitoring and Climate Change Predictiona.
J.M.K. also thanks Dr. Yi, S. for technical assistance in
SEM photography. During the preparation of this article, MK has been supported by a postdoctoral fellowship
1084
J.-M. Kim, M. Kucera / Quaternary Science Reviews 19 (2000) 1067}1085
from STINT (The Swedish Foundation for International
Cooperation in Research and Higher Education). We
thank James P. Kennett, Ellen Thomas, and an anonymous reviewer for useful comments on an early version of
this manuscript.
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