Xuan et al. Progress in Earth and Planetary Science
https://doi.org/10.1186/s40645-020-00373-9(2020) 7:60

Progress in Earth andPlanetary Science

RESEARCH ARTICLE

Open AccessIntegrated Pliocene-Pleistocene
magnetostratigraphy andtephrostratigraphy of deep-sea sediments
at IODP Site U1424 (Yamato Basin, Japan
Sea)
Chuang Xuan1* , Yuxi Jin1, Saiko Sugisaki2, Yasufumi Satoguchi3 and Yoshitaka Nagahashi4

Abstract
Sediments from the semi-enclosed Japan Sea are sensitive to paleoclimatic perturbations and they offer great
opportunities for many regional and global paleoceanographic and paleoclimatic studies. These studies often
require a robust chronology. However, due to rare preservation of calcareous microfossils and drastic changes insurface water salinity during glacial lowstands, the construction of a traditional oxygen isotope stratigraphy forJapan Sea sediments is often difficult. Here, we use sediments recovered at Integrated Ocean Drilling Program(IODP) Expedition 346 Site U1424 to build an integrated Pliocene-Pleistocene reference magnetostratigraphy andtephrostratigraphy for sedimentary sequences from the region. Rock magnetic experiments indicate that magnetic
remanence of Site U1424 sediments are carried primarily by (titano)magnetite with small contributions from highcoercivity minerals (e.g., hematite) and possibly iron sulphides (pyrrhotite and/or greigite). Dark-colored sediments
appear to contain less (titano)magnetite probably due to reductive diagenesis under euxinic conditions. Natural
remanent magnetization (NRM) of u-channel samples covering a continuous ~ 167.6 m sediment sequence at Site
U1424 was repeatedly measured at 1 cm intervals before and after stepwise demagnetization. Despite lower NRM
intensity in dark-colored sediments, NRM directional data from both dark- and light-colored sediments are
considered suitable for the construction of magnetostratigraphy. Site U1424 sediments clearly recorded the majorityof the polarity chrons and subchrons within the last ~ 4.89 Myr, with the Cobb Mountain subchron, the end of
Kaena subchron, and the onset of Nunivak subchron less well preserved. Sixteen tephra layers from the site were
sampled for chemical composition analyses and the results were correlated to reference tephrostratigraphy of theregion. Ages of the identified tephras are consistent with and can be well integrated with the magnetostratigraphy.
The resulting age model suggests that sedimentation rates at Site U1424 range between ~ 1.7 and 7.6 cm/kyr withan average of ~ 3.3 cm/kyr. The acquired magnetostratigraphy and tephrostratigraphy at Site U1424 provide areference chronology that can be correlated with and transferred to other sediment sequences in the region to
study paleoceanographic and paleoclimatic changes of the region as well as their links to other regional and global(Continued on next page)* Correspondence: c.xuan@soton.ac.uk
1School of Ocean and Earth Science, National Oceanography Centre
Southampton, University of Southampton, Waterfront Campus, European
Way, Southampton SO14 3ZH, UK
Full list of author information is available at the end of the article© The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give
appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in this article are included in the article's Creative Commonslicence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commonslicence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain
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Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 2 of 19(Continued from previous page)changes.
Keywords: Paleomagnetism, Magnetostratigraphy, Tephrostratigraphy, Japan Sea, IODP Expedition 346, Site U1424

1 Introduction
The Japan Sea is a semi-enclosed marginal sea locatedon the eastern end of the Asian continent with an average depth of ~ 1350 m and it covers an area of about
one million square kilometers. It is connected to otherseas only through narrow and shallow straits withpresent sill depth of ~ 130 m (Fig. 1). The Japan Sea has
been responding to changes of global surface conditions
in sensitive manner at various time scales since it wasformed at ~ 20 Ma (Tada 1994). Deposition of sediments
and euxinic conditions in the Japan Sea were largely
modulated by paleoceanographic conditions which werestrongly influenced by factors such as sill depth, positionof channels, and the degree of closure of the sea. These

factors were controlled by local tectonism and/or global
eustatic sea level changes (Tada 1994). Sedimentary records from the Japan Sea provide great opportunity to
study paleoceanographic and paleoclimatic changes of
the region as well as their links to other regional andglobal processes. For example, studies on cores recovered by Ocean Drilling Program (ODP) Legs 127/128(Tamaki et al. 1990; Ingle et al. 1990; Tada et al. 1992)
show that Quaternary sediments in deeper part of theJapan Sea are characterized by centimeter- to meterscale alternations of dark organic-rich layers and lightorganic-poor layers. The alternations of dark and lightlayers were demonstrated to record wet and dry cycles
in central to eastern Asia that could be linked toFig. 1 Location of Site U1424 and other sites drilled during IODP Expedition 346. Arrows indicate flow directions of surface currents. TWC: Tsushimawarm current

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Dansgaard–Oeschger cycles with dark layers deposited
during interstadials (Tada et al. 1999; Tada 2005; Tada
2012). Marine sediments in the Japan Sea also hold great
potential to build long and continuous records that are
key to understanding land-ocean linkages and interrelationships between East Asian Summer/Winter Monsoon
and the Westerly Jet axis movement through the
Pliocene-Pleistocene (Tada et al. 2013).
In 2013, Integrated Ocean Drilling Program (IODP)
Expedition 346 (Asian Monsoon) drilled at seven sites in
the Japan Sea and two sites in the East China Sea (Fig.
1) (Expedition 346 Scientists 2014). The overall goal of
the Expedition was to test the relationship between uplift of the Tibetan plateau, Westerly Jet circulation, andevolution of the East Asian monsoon. A fundamental requirement for these studies is a robust chronology forthe recovered sediments so that timing, duration, andrates of change for events and processes revealed byvarious proxy records could be determined. However,construction of traditional oxygen isotope stratigraphy
for Japan Sea sediments is challenging due to rare preservation of calcareous microfossils and drastic changes
in surface water salinity during some glacial lowstands(Oba et al. 1991). The construction of chronology for
Pliocene-Pleistocene sediments from the Japan Sea often
relies on magnetostratigraphy and tephrostratigraphy(see Hamano et al. 1992; Tada 1994; Tada et al. 2018).
Magnetostratigraphy of ODP Leg 127/128 sedimentsfrom the Japan Sea mainly relied on shipboard half-core
section measurement made at low resolution (i.e., 10 cm
interval) and a very limited number of discrete cube
samples (see Hamano et al. 1992). However, reasonable
quality polarity records were acquired mostly for sediments within the last ~ 2.5 Myr cored using advanced
piston corer (APC) from a single hole (see Tada 1994).
Site U1424 drilled during IODP Expedition 346 wasused as a chronology reference record by Tada et al.
(2018) to build a “paleo-observatory network”, which
comprises sediment archives from six sites drilled in theJapan Sea during IODP Expedition 346. These sites
cover wide ranges of latitudes, longitudes, and water
depths and allow the reconstruction of temporal-spatialchanges in material fluxes in the Japan Sea. Detailed correlation of dark layers in the sediments guided by magnetostratigraphy and tephrostratigraphy was used by theauthors to project the Site U1424 chronology to fiveother sites. The site U1424 chronology used by Tada
et al. (2018) incorporated the best paleomagnetic andtephra data available at the time which covered the last
~ 3 Myr (see Table 1 in Tada et al. 2018), and was further tuned to the LR04 stack (Lisiecki and Raymo 2005)
using gamma ray attenuation density (GRA) and natural
gamma radiation (NGR) data. Polarity reversals in Site
U1424 sediments used by Tada et al. (2018) were

Page 3 of 19

determined based on partially demagnetized (using alternating fields with peak fields up to 30 mT) u-channel
sample data available at the time (i.e., for sediments
younger than ~ 3 Ma), and are more reliable and accurate than those acquired based on shipboard measurement (Tada et al. 2015).
In this paper, we report high-resolution magnetostratigraphy for Site U1424 sediments based on shore-based
measurement of u-channel samples with complete sequence of stepwise demagnetization (with peak fields up
to 100 mT). The analyzed u-channel samples continuously cover a total of ~ 167.6 m sediment sequence(spanning the last ~ 4.89 Myr) recovered at Site U1424.
We conducted rock magnetic experiments to investigate
the magnetic mineralogy of the sediments and to help
verify the fidelity of the reconstructed paleomagnetic records. Chemical compositions of sixteen tephra layers
from Site U1424 were analyzed and reported here, andthe studied tephra layers were correlated with PliocenePleistocene reference tephrostratigraphy of the region.
Note that an earlier version of the tephra correlation
was used by Tada et al. (2018) to support their chronology for Site U1424 sediments of the last ~ 3 Myr. We
compare and discuss results from the paleomagnetismand tephra studies conducted to form an integrated
magnetostratigraphy and tephrostratigraphy for the sediment sequence cored at IODP Site U1424.

2 Samples and methods
2.1 IODP Site U1424

IODP Site U1424 (40° 11.40′ N, 138° 13.90′ E, ~ 2808 m
water depth) was drilled at the same location as ODP Site
794 and is located in the eastern part of the Yamato Basin,
Japan Sea, ~ 200 km southwest of the Tsugaru Strait (Fig.
1). The site is mainly under the influence of the second
branch of the Tsushima Warm Current (TWC). A total of
41 cores from three holes were recovered at Site U1424
using the advanced piston corer (APC). The recovered
cores form a complete stratigraphic sequence of ~ 167.75
m of sediments (Tada et al. 2015).
Site U1424 sediments are dominated by clay and diatom ooze with minor component of pyrite and volcaniclastic materials (concentrated at numerous tephra
layers) throughout the sediment succession (Tada et al.
2015). These sediments are divided into two major lithologic units: units I and II, with the boundary at ~ 70 mcore composite depth below sea floor (CCSF-A). Unit I
sediments are characterized by alternating decimeterscale color-banded bedding with dark, organic-rich clay
intervals interspersed with lighter colored, organic-poorintervals. Unit I sediments are further divided into subunits IA and IB (boundary at ~ 47.7 m CCSF-A). Subunit IA is characterized by decimeter-scale alternationsof light and dark colored sediment intervals and subunit

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 4 of 19

Table 1 Major element composition of tephra samples from Hole U1424A based on EDS analysis
SampleID

Coresection

Offset(cm)

CCSFA (m)NK 371

1-1

135.5

1.355

NK 373

1-3

98.0

3.980

NK 375

1-4

26.0

4.760

NK 3802-6

117.0

16.240NK 3873-5

27.0

24.470NK 391

3-6

84.0

26.540NK 3974-4

28.0

33.880NK 4044-6

19.0

36.790NK 4135-4

58.0

44.380NK 4165-5

110.0

46.400NK 4185-6

112.5

47.925NK 424

6-6

103.5

57.905

NK 4318-5

32.0

74.740NK 4399-4

15.0

83.290NK 13912-5

79.0

114.670

NK 142

15-6

63.0

142.670

Major element composition by EDS analysis (mean wt.%)
SiO2

TiO2

Al2O3

FeO*

MnO

MgO

CaO

Na2O

K2O

Av

76.78

0.19

13.12

1.30

0.02

0.12

1.05

3.55

3.87

sd

0.77

0.10

0.34

0.42

0.04

0.08

0.21

0.15

0.55

Av

71.34

0.48

15.31

1.78

0.11

0.44

1.30

4.65

4.59

sd

0.75

0.09

0.28

0.27

0.11

0.09

0.20

0.16

0.20

Av

77.57

0.08

13.16

0.92

0.06

0.06

0.45

4.60

3.09

sd

0.49

0.07

0.28

0.11

0.07

0.05

0.06

0.24

0.10

Av

65.13

0.34

16.66

4.54

0.13

0.24

1.20

6.09

5.67

sd

0.58

0.11

0.17

0.32

0.09

0.07

0.13

0.20

0.18

Av

77.70

0.26

12.52

1.39

0.07

0.26

1.60

3.73

2.48

sd

0.24

0.08

0.16

0.20

0.07

0.08

0.09

0.17

0.10

Av

77.59

0.31

12.45

1.45

0.10

0.23

1.40

4.07

2.40

sd

0.42

0.10

0.19

0.15

0.09

0.06

0.13

0.18

0.12

Av

76.94

0.37

12.40

2.00

0.02

0.36

1.80

3.59

2.51

sd

0.28

0.11

0.15

0.15

0.04

0.09

0.07

0.12

0.06

Av

77.09

0.28

12.62

1.02

0.06

0.22

1.14

3.22

4.34

sd

0.34

0.08

0.15

0.11

0.08

0.06

0.11

0.19

0.15

Av

76.40

0.13

13.88

0.92

0.07

0.32

1.39

4.02

2.87

sd

0.27

0.06

0.13

0.15

0.10

0.07

0.08

0.13

0.10

Av

77.27

0.18

13.07

0.91

0.10

0.19

1.08

3.59

3.61

sd

0.15

0.08

0.14

0.15

0.10

0.06

0.05

0.07

0.11

Av

77.37

0.32

12.44

1.59

0.07

0.35

1.69

3.40

2.76

sd

0.82

0.09

0.34

0.20

0.10

0.10

0.09

0.19

0.18

Av

75.57

0.14

13.39

1.61

0.05

0.13

1.04

3.76

4.31

sd

0.26

0.08

0.18

0.22

0.07

0.07

0.08

0.19

0.12

Av

74.98

0.15

13.71

1.67

0.05

0.11

1.06

3.98

4.29

sd

1.07

0.09

0.47

0.45

0.07

0.06

0.36

0.32

0.72

Av

75.10

0.33

13.60

1.52

0.11

0.29

1.42

3.97

3.66

sd

0.31

0.10

0.13

0.18

0.10

0.06

0.11

0.12

0.18

Av

76.02

0.10

13.35

1.16

0.05

0.09

0.71

3.41

5.15

sd

0.20

0.10

0.07

0.16

0.05

0.06

0.07

0.14

0.18

Av

76.38

0.06

13.52

0.93

0.08

0.11

0.65

3.26

5.07

sd

0.24

0.07

0.15

0.16

0.08

0.05

0.08

0.13

0.11

n
=

Total
(raw)

Correlative
tephra

11

94.33

AT

0.94
12

95.74

Aso-4

1.18
12

94.84

Toya

0.70
15

94.00

B-Og

1.77
12

93.77

Ka1

0.76
12

94.93

Hkd-Ku

0.84
12

92.68

Yamada 1

0.62
12

94.24

Ss-Pnk

0.54
12

93.08

Yellow II or III

0.57
12

93.31

Yellow I

0.69
12

93.87

Ak-Kd18?

1.22
12

93.47

Eb-Fukuda

0.54
13

94.35

Msn-Jwg4

1.14
12

93.94

Ass-Tmd2

0.58
12

95.11

Sr-Ity

0.97
12

94.27

Znp-Ohta

0.44

FeO*: total iron recalculated as FeO, Av = average, sd = standard deviation

IB is identified by a decrease in the frequency of dark
and light color alternation and the dominance of lightgreenish gray and light gray clay (Tada et al. 2015). Unit
II is distinguished from unit I on the basis of the sediment color and a significant increase in diatom content
and is further divided into subunits IIA and IIB (boundary at ~ 85 m CCSF-A). Subunit IIA is dominated bybrownish and greenish diatom-bearing and diatom-richclay, and subunit IIB is defined by the consistent appearance of diatom ooze (Tada et al. 2015).

2.2 Paleomagnetic analysis of u-channel samples

A total of 143 continuous u-channel samples werecollected for paleomagnetism studies. Sampling of theu-channels followed the shipboard splice derived fromHoles U1424A and U1424B (see Table T18 in Tada
et al. 2015). All u-channel samples were taken fromthe center part of the half-core sections to avoid disturbed core margins that can influence the quality of
paleomagnetic records. Sample from core-section
U1424B-6H-5 was taken from the working-half of theXuan et al. Progress in Earth and Planetary Science(2020) 7:60

core-section. All other samples were taken fromarchive-half core-sections. Sediments in each uchannel sample were enclosed in plastic containerthat has the same length as the core-section (typically~ 150 cm) and an internal cross section of ~ 1.8 × 1.9
cm2, with a clip-on plastic cover that seals the sediments to minimize dehydration (Tauxe et al. 1983).
The collected u-channel samples cover a continuous
sediment sequence between 0 and 167.6 m CCSF-A
at IODP Site U1424.
Natural remanent magnetization (NRM) of the uchannel samples were measured on a 2G Enterprises liquid helium-cooled pass-through superconducting rockmagnetometer (SRM) at the University of Southampton.
The SRM has a narrow sample access bore (4.2 cm
diameter) designed for u-channel measurements and ishoused inside a magnetically shielded room. NRM measurements for each u-channel were made at 1 cm intervals over the sample length as well as over a 10 cm“leader” interval before the sample and a 10 cm “trailer”
interval after the sample. The “leader” and “trailer” measurements serve the dual functions of monitoring themeasurement background and allowing for future signal
deconvolution (see Oda and Xuan 2014; Xuan and Oda
2015). NRM of all samples were repeatedly measured
after progressive alternating field (AF) demagnetization
with peak fields of 20–50 mT in 5 mT increments, andat 60, 80, and 100 mT (10 steps in total). For a few uchannel samples, NRM measurements were also collected after AF demagnetization with additional peakfields of 55, 65, 70, and 90 mT.
The UPmag software (Xuan and Channell 2009) wasused to correct any flux jumps and spike noises in NRM
measurements. We normalized all u-channel measurements using a nine-term “effective length” matrix estimated for the SRM to gain more accurate NRM
intensity and directional data (see Xuan and Oda 2019).
For each 1 cm interval, component magnetization directions were calculated using principal component analysis(PCA, Kirschvink 1980) and the UPmag software (Xuanand Channell 2009). PCA calculations used NRM datafrom 9 common steps between 20 and 80 mT
demagnetization without anchoring the directions to theorigin of the orthogonal projections. PCA results are associated with maximum angular deviation (MAD) values
that monitor the quality of the definition of component
directions. In addition, we calculated mean declinations
and inclinations based on Fisher statistics for the same
NRM data used in the PCA calculations. These mean directions are accompanied with α95 values that estimate
the circle of 95% confidence about the mean directions.
The α95 values complement the PCA MAD values andprovide an additional check on NRM data quality. For
example, NRM demagnetization data that lie closely on

Page 5 of 19

a line in vector space but not cross near the origin
would yield a small MAD value, but such data would be
associated with large α95 values (see van Peer et al.
2017). Declination data from each core were correctedby uniform rotation of each core so that the circularmean of the corrected declinations is oriented north or
south for positive and negative inclination intervals, respectively. An additional 180° rotation was applied tocorrect declination data of the u-channel sample takenfrom the working-half of Core-section U1424B-6H-5.
2.3 Rock magnetic experiments

During u-channel sampling of some core-sections, excess sediments that stuck along the outside walls of theplastic u-channel containers were scraped and placed inplastic bags. The scrapings represent an average bulk
sediment sample of the core-section (typically ~ 1.5 mlong) from which the u-channel was taken. Selectedscraping samples were used for rock magnetic experiments on a Princeton Measurements Corp. (now Lakeshore Inc.) Model 3900 vibrating sample magnetometer(VSM) at the University of Southampton. Weight ofsamples used for all analyses on the VSM was measured
and used to normalize the measurement data.
Hysteresis loops for a group of samples were measured
using applied fields ranging between − 0.5 T and + 0.5 Twith steps of 4–5 mT and averaging time of 500–800
ms. For backfield experiments on the same samples, a
0.5 T field was first applied to the samples, remanenceof the samples was then monitored after applying (andturning off) an increasing field (with a 2.5 mT increment) in the opposite direction until zero remanence
was reached. Hysteresis loop data were processed, andslope corrected following the procedures of Jackson and
Solheid (2010) and using the HystLab program (Paterson
et al. 2018). The “Automatic” routine in HystLab wasused to decide most suitable methods for both drift andslope corrections of data (see Paterson et al. 2018). The
slope corrected hysteresis loop data and backfield curves
were used to determine ratios of hysteresis parameters:
Mr/Ms and Bcr/Bc, where Mr is saturation remanence,
Ms is saturation magnetization, Bcr is coercivity of remanence, and Bc is coercivity.
Selected bulk samples were used for isothermal remanent magnetization (IRM) acquisition experiments on
the VSM. IRM of the samples were acquired and measured (using averaging time of 500 ms) at 100 field steps
on a logarithmic scale ranging from 0.1 mT to 1 T. In
addition, two samples from Core U1424B-2H were used
for first order reversal curve (FORC) measurements(Pike et al. 1999; Roberts et al. 2000, 2014) on the VSM.
The FORC diagrams consist of 133 curves collected at 2
mT field increments with an averaging time of 200 ms.
FORC measurement data were analyzed using theXuan et al. Progress in Earth and Planetary Science(2020) 7:60

FORCinel software (Harrison and Feinberg 2008), which
incorporates VARIFORC smoothing (Egli 2013) andstatistical confidence intervals (Heslop and Roberts2012).
Two samples from the top part of Hole U1424A (i.e.,
1H-2W, 89–91 cm and 1H-4W, 94–96 cm) were measured on a low-temperature susceptometer (Quantum
design MPMS-XL-5) at the Center for Advanced Marine
Core Research (CMCR), Kochi University. The samples
were first dried, then saturation IRM (SIRM) was
imparted using a 3–T field at room temperature of 300
K. IRM of the samples were then monitored while thesamples were cooled to 10 K and subsequently warmed
to 300 K in zero field. The samples were then cooled
from 300 to 10 K in zero field, and an IRM was imparted
using a 3–T field at 10 K. The acquired IRM was thenmonitored while warming the samples to 300 K in zero
field.
2.4 Color data from half-core section photos

To check if any relationship exists between NRM dataand sediment color, we stacked half-core section image(using the “trimmed” version) scanned onboard JOIDES
Resolution during IODP Expedition 346 (Tada et al.
2015) for all sections from which u-channel samples
were collected. CCSF-A depth scales were assigned tostacked image for Holes U1424A and U1424B so thatstacked images could be directly compared with the uchannel paleomagnetic data. We extracted RGB values
from the images at every 2 mm resolution and calculated
mean RGB values for sediments from the same depth
level. The acquired RGB values were then used to estimate L*, a*, and b* data following the calibration andformulae provided by Irino et al. (2018). The calculated
L* values were then smoothed using 5-point moving
average. The smoothed L* curve was subsequently interpolated at 1-cm intervals that match the same depth
levels of the u-channel paleomagnetic data.
2.5 Tephra analyses

Chemical compositions of volcanic glass shards fromsixteen selected depth intervals in Hole U1424A (seeTable 1) were analyzed for major oxides on an energy
dispersive spectroscopy (EDS) type electron probe
micro-analyzer (EPMA) at the Fukushima University,
Japan. Tephra samples were mounted in an epoxy resinon a slide glass. Sample surfaces were polished until
glass shards were exposed. The samples then went
through ultrasonic washing and drying process before
they were carbon coated. Measurement conditions used
are 15 kV accelerating voltage, 0.5 nA electric current
on a faraday cup, and a 5 μm × 5 μm beam scanningarea. The obtained major element compositions were
further calibrated by X-ray fluorescence (XRF) analytical

Page 6 of 19

results of the well-characterized dacite to rhyolite representative volcanic glasses analyzed during the same analytical session (Nagahashi et al. 2003).
The correlation of each tephra was examined withones at other sites and/or with other known tephras interrestrial deposits characterized by their properties,
litho-, bio-, magneto-stratigraphy and estimated ages.
Tephrostratigraphy in the Pliocene to Holocene series
on the Japanese Archipelago is based on widespread
tephras (e.g., Machida 1999; Nagahashi et al. 2004; Satoguchi and Nagahashi 2012), with their characteristics described by both major and trace element compositionsof volcanic glass shards (e.g., Kimura et al. 2015; Nagahashi et al. 2003, 2004, 2015).

3 Results and discussion
3.1 Magnetic properties of the Site U1424 sediments

Representative results from rock magnetic experiments
using the scraping samples are shown in Fig. 2. Raw hysteresis loops of the samples are dominated by positive
slopes suggesting presence of significant amount of paramagnetic materials in the sediments. Slope corrected
hysteresis loops (Fig. 2a) and estimated saturation fields
by HystLab show that studied samples appear to bemostly saturated at applied fields of less than ~ 350–400
mT. Weight normalized saturation magnetization (Ms)of the samples (based on slope corrected loops) vary onorders of 10−4 to 10−2 Am2/kg (Fig. 2a). Sample fromcore-section U1424A-3H-4A (~ 23.5 m CCSF-A) thatcomprises predominantly dark colored sediments appears to have significantly lower Ms than other samples.
Coercivity of remanence (Bcr) of the samples is generally
low and ranges between ~ 30–60 mT (Fig. 2b). Hysteresis parameter ratios (i.e., Mr/Ms and Bcr/Bc) of thesamples are shown on a Day et al. (1977) plot in Fig. 2c.
Results from the samples fall into the “pseudo-single domain” (PSD) category in the area associated with magnetite particles with sizes of about a few microns to few
tens of microns (Dunlop 2002), although many issues including magnetic mineralogy and magnetic particle mixtures could potentially complicate the interpretation of
domain state based on a Day et al. plot (see Roberts
et al. 2018).
IRM acquisition and gradient data of the studied bulk
sediments are shown in Fig. 2d, e. Raw IRM acquisition
data were fitted using smoothing splines (with a smoothing parameter of 0.995) to suppress noise in the measurement data. IRM gradient curves were normalized sothat total area underneath each curve is equal to 1.
Weight normalized saturation remanence of these samples is on the order of 10−3 Am2/kg (Fig. 2d). Gradientsof the IRM data plotted on logarithmic field scale (Fig.
2e) generally follow normal distributions with mean coercivity of ∼ 50 mT, consistent with a generally low

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 7 of 19

Fig. 2 Room temperature rock magnetic analyses results of selected bulk sediment samples from Site U1424. Measurements were conducted ona vibrating sample magnetometer (VSM). a Slope corrected hysteresis loops. b IRM backfield curves. c Hysteresis parameters plotted on a Day
et al. (1977) plot. d IRM acquisition data. e Gradient of IRM acquisition. f, g FORC diagrams. Hysteresis loops, IRM backfield experiment, and IRM
acquisition data are weight normalized. Gradient of IRM curves are normalized so that total area underneath each curve is equal to 1. Color ofdata curves and points in (b) and (c) share the same key shown in (a), and data curves in (e) share the same key shown in (d). Depth of samples
listed is in m CCSF-A

coercivity magnetic mineral such as (titano)magnetite
being the primary remanence carrier. Some samples(e.g., those from ~ 3.8, ~ 7.1, ~ 23.5, and ~ 96.8 m CCSFA) appear to have slightly higher mean coercivity (~ 65–
70 mT), possibly due to finer magnetic particles in thosesamples. The IRM acquisition curves do not seem tohave completely saturated at higher fields suggesting asmall contribution from high coercivity magnetic
phases (e.g., hematite). FORC diagrams of the two samples show generally low coercivity (mostly centered at ~20–30 mT on the Bc axis) component with verticalspread between ~ ± 30–40 mT on the Bu axis, consistent
with presence of a predominantly PSD (titano)magnetite
phase in the sediments (Roberts et al. 2000, 2014).
The two samples used for low temperature magnetic experiments show similar behaviors during low temperature
cycling of the SIRM acquired at room temperature (RTSIRM), and warming of the SIRM acquired at low
temperature (LT-SIRM) following zero-field cooling(ZFC). Cooling curves of the RT-SIRM (Fig. 3a) firstundergo a gradual increase and then a large decrease between ~ 100 and 150 K. The warming curves of the RTSIRM generally overlap with the cooling curves below ~100 K. Both samples show significant loss (~ 11%) in RTSIRM after the cooling and warming cycles. Warming
curves of the LT- SIRM (after ZFC) for both samples (Fig.
3b) show abrupt drop at ~ 120 K, characteristic for (titano)magnetite due to Verwey transition around thistemperature range. The abrupt changes at ~ 120 K is evenmore evident on the derivatives of the LT-SIRM warming
curves (Fig. 3c).
Samples used for the hysteresis loops, backfield, andIRM acquisition experiments were taken from a large
range of depth levels and cover all four lithologic subunits at Site U1424. Weight normalized Ms and IRM
values of these samples vary significantly downcore, presumably due to varying concentration of ferrimagnetic
materials. But similarity in the shape of the hysteresis
loops, Bcr values, and mean coercivity from the IRM
gradient curves indicates that the samples are likely
dominated by a low coercivity magnetic mineral common in U1424 sediments with a small contribution ofhigh coercivity magnetic minerals (e.g., hematite). Although samples used for the FORC and the lowtemperature experiments were taken mostly from theupper part of the sediment sequence, results from theseXuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 8 of 19

Fig. 3 Low temperature rock magnetic experiment results of two samples from Site U1424. a Saturation isothermal remanent magnetizationacquired at room temperature (RT-SIRM) monitored on cooling from 300 to 10 K and subsequent warming back to 300 K; b SIRM acquired at low
temperature (LT-SIRM) after zero-field cooling monitored on warming; and c derivative of the LT-SIRM warming curves. Note that RT-SIRM and LTSIRM curves have been normalized to SIRM of samples at 300 K and at 10 K respectively. The derivatives of LT-SIRM were calculated based on asmoothed version of the raw data to avoid influence from occasional noisy measurements. Depth of samples listed is in m CCSF-A

samples suggest that (titano)magnetite is the dominant
low coercivity magnetic remanence carrier in the sediments. These results are consistent with previous work
done by Vigliotti (1997) on Brunhes aged sedimentsfrom ODP Site 794, which show that the sediments are
dominated by magnetite-type minerals with small contribution made by canted-antiferromagnetic minerals(hematite) and iron sulphides (pyrrhotite and/or greigite). Vigliotti (1997) also noted that the dark- and lightcolored sediments are mineralogically similar but are

different in terms of magnetic mineral concentrationand grain size. Lower concentration of (titano)magnetite
in the dark-colored sediments at Site U1424 is probably
related to reductive diagenesis during which (titano)magnetite dissolves and forms pyrite that is paramagnetic and does not carry remanence. This process istypically associated with euxinic conditions during glacial stages when the dark-colored sediments were deposited and is likely driven by sea level changes (Vigliotti
1997; Tada et al. 1999). Although our rock magnetic

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 9 of 19

Fig. 4 Representative orthogonal projections of NRM demagnetization data. Examples shown include results from selected 1 cm intervals in different
polarity zones recorded by Site U1424 sediment sequence. Circles (red) and squares (blue) indicate projections onto vertical and horizontal planes,
respectively (unit for axes are × 10−3 A/m). The 20 mT and 80 mT demagnetization steps are labeled. Hole-core-section and position (in cm) and depth(in m CCSF-A) information associated with each 1 cm interval data is also labeledXuan et al. Progress in Earth and Planetary Science(2020) 7:60

experiments could not directly suggest the presence oflarge amount of remanence carrying iron sulphides (e.g.,
pyrrhotite and/or greigite), it is possible that U1424 sediments contain some amount of pyrrhotite and/or greigite as a result of the reductive diagenesis.

3.2 U-channel NRM data and their fidelity

Typical NRM demagnetization behaviors of samples
from both normal and reversed polarity intervals at varying depths of Site U1424 are shown in Fig. 4. A stablesingle magnetization component can be clearly definedusing NRM data after demagnetization with peak fields
above ~ 20 mT. Majority of the NRM for all samples
were removed after AF demagnetization with peak fieldof 100 mT. This observation is consistent with the results from the rock magnetic experiments that (titano)magnetite is the main remanence carrier in Site U1424
sediments. Component inclination and corrected declination data together with MAD and α95 values for all uchannel samples from Site U1424 calculated using PCA
analysis and Fisher statistics on NRM data from 20 to 80
mT demagnetization steps are shown in Fig. 5. These
data are compared with NRM intensity after 35 mT
demagnetization (i.e., NRM35mT intensity) as well as
photos and estimated L* of core sections from which theu-channels were taken. Paleomagnetic data from any disturbed intervals due to coring or sampling, or fromtephra layers are shown in lighter color on Fig. 5 and are
not used for magnetostratigraphic interpretations. In
addition, NRM measurements from intervals within the
top and bottom 3 cm of each u-channel sample are subjected to convolution effect of the SRM’s sensor response (see Oda and Xuan 2014; Xuan and Oda 2015)
and are not shown on Fig. 5.
NRM35mT intensity of Site U1424 sediments ranges
between 10−5 and 10−2 A/m with majority of the values
in the order of 10−4 A/m. The highest intensity values
occur in the top ~ 15 m CCSF-A of the sediment sequence and are mostly in the orders of 10−3 to 10−2 A/
m. MAD values associated with the PCA analysis varyclosely (correlation coefficient ~ 0.48) with α95 estimatesfrom Fisher statistics (see Fig. 5) suggesting the two
types of NRM data quality measure generally yield consistent results. MAD and α95 values change significantly
down core and appear to follow opposite trend to the
NRM intensity data. Lowest MAD values occur in the
top ~ 15 m CCSF-A where NRM intensity is highest andare mostly a few degrees (mean ~ 3.6° and std. ~ 3.7°),
suggesting very well-defined paleomagnetic components.
MAD values for samples from below ~ 15 m CCSF-A
are higher (mean ~ 18.4° and std. ~ 10.7°) and reach a
few tens of degrees at intervals with low NRM intensities. Nevertheless, majority of these samples still yield

Page 10 of 19

reasonably well-defined directions that are suitable formagnetostratigraphic interpretations.
There appears to be a broad relation between sediment color and NRM intensity of the samples. Similarly, a broad relation seems to exist between
sediment color and MAD and α95 values as MAD
and α95 values show clear opposite trend to NRM intensity (Fig. 5). As an example, core image, estimatedL*, and NRM35mT intensity of Core U1424B-6H isshown in Fig. 6. Dark-colored sediment intervals between ~ 45.8–46.4 and between ~ 47.4–47.6 m CCSFA are apparently associated with lower NRM intensities (Fig. 6a). This is consistent with the rock magnetic experiment results which suggest that(titano)magnetite concentrations are lower in darkcolored sediments presumably due to reductive
diagenesis.
To check if the alternation of dark and light layers
might have debilitated the paleomagnetic signal (especially directional data) preserved in these sediments,
we compared histograms of NRM intensity and directional data from both dark- (with L* values < 25) andlighter-colored (with L* values > 45) sediments at Site
U1424. As alternation of dark and light layers mainly
occurred in unit I (see Fig. 5), the histograms mainly
count data from the top ~ 70 m of the sediment sequence. NRM intensity from lighter-colored sedimentsshows generally stronger NRM intensity than thatfrom dark-colored sediments (Fig. 6b). Occasionally,
there are dark-colored intervals that show high NRM
intensity possibly due to enhanced growth of authigenic greigite at some dark-colored intervals. However, corrected declination (Fig. 6c) and inclination(Fig. 6d) data from dark- and light-colored sediments
show very similar distributions. Corrected declinations
from both types of sediments show peak distributions
around 0° or 360° and around 180° that correspondto data from normal and reversed polarity intervals
respectively. Inclination data from both types of sediments show peak distributions close to expected inclinations of ± 59.4° at the latitude of Site U1424
assuming a geocentric axial dipole (GAD) field model.
Similarity in directional data distributions of the two
types of sediments is clear for results from normal
polarity and appears less strong for results from reversed polarity. Inclinations from reversed polarity intervals in both types of sediments show peak
distributions around the expected GAD inclination
but are more spread out (i.e., have larger standard deviation) than inclinations from normal polarity intervals. This “spread-out” could be caused by thegenerally weak NRM of the sediments (especiallythose from below ~ 15 m CCSF-A) combined with incompletely removed vertical drilling overprints at

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 11 of 19

Fig. 5 Down-core changes in Site U1424 sediment color and NRM data with interpreted magnetostratigraphy and tephrostratigraphy. From left to right:
image of core-sections used in this study, lithologic units and subunits, L* estimated from core images, NRM intensity data (35 mT demagnetization step), MADvalues (blue) and α95 (purple) associated with the PCA analyses and Fisher mean calculations, corrected PCA (green) and Fisher mean (gray) declinations, PCA(red) and Fisher mean (gray) inclinations, and interpreted magnetic polarity stratigraphy (black and white bars) and tephrochronology (horizontal red bars andlabels). Core names (e.g., A1, B2) and section breaks are marked next to the core-section images. Light and dark gray points on L* plot are values estimated at 2mm and 1 cm intervals respectively. Vertical gray dash-dotted lines on the inclination plot are expected inclinations during reversed and normal polarity
intervals at Site U1424 assuming a geocentric axial dipole (GAD) field. NRM data, MAD and α95 values from disturbed and tephra intervals are shown in lighter
color, and not used for magnetostratigraphy interpretations

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 12 of 19

Fig. 6 Comparison of NRM intensity and directional data from dark- and light-colored sediments at Site U1424. a Comparison of core-section
photo, L*, and NRM35mT intensity data from an example interval in Core U1424B-6H; and histograms of b NRM35mT intensity, c mean corrected
declination, and d mean inclination data from dark- (blue bars) and light-colored (orange bars) sediments. Dark- and light- colored sediments are
set to intervals with L* values < 25 and > 45, respectively. Data from disturbed intervals are not included in the histograms. Light and dark graypoints in (a) are L* values estimated using the core-section photos at 2 mm and 1 cm intervals, respectively. Vertical green dashed lines on (d)are expected inclinations during reversed and normal polarity intervals at Site U1424 assuming a GAD fieldoccasional intervals that induce more influences on
results from reversed intervals. In addition, the“spread-out” in reversed inclinations distribution ismore obvious in dark-colored sediments, possibly due
to smaller signal-to-noise ratios related to generally
weaker NRM intensity in dark-colored sediments.
Nevertheless, these results suggest that although darkcolored sediments often show lower NRM intensity
and Site U1424 sediments could have experienced
varying degrees of reductive diagenesis, the reductive
diagenesis does not seem to have debilitated recording of paleomagnetic directions in the sediments.

Both dark- and light-colored sediments appear tohave recorded paleomagnetic directions that can beused for magnetostratigraphic interpretations.
3.3 Magnetostratigraphy

Inclination and corrected declination data in Fig. 5 show
clear patterns that can be correlated to geomagnetic polarity time scale (e.g., GPTS2012 in Gradstein et al. 2012) ofthe last ~ 4.89 Myr. During normal and reversed intervals,
inclination data vary closely around the expected GAD inclinations of 59.4° and − 59.4° (dash-dotted lines in Fig. 5)
while corrected declinations vary around 0° (or 360°) andXuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 13 of 19

Table 2 Polarity boundaries identified in collected u-channel samples from Holes U1424A and U1424B
Polarity boundaries

Age (Ma) Hole-core-section Center position (cm) Uncertainty (cm) Depth CSF-A (m) Depth CCSF-A (m)(B) C1n (Brunhes/Matuyama)

0.781

B-4H-2

112

±5

24.32

27.54

(T) C1r.1n (Jaramillo)

0.988

A-4H-4

132

±8

31.62

34.92

(B) C1r.1n (Jaramillo)

1.072

A-4H-6

96

± 19

34.26

37.56

B-5H-3

52

± 18

34.18

37.58

(T) C1r.2n (Cobb Mountain)

1.173

B-5H-5

54

±5

37.20

40.60

(B) C1r.2n (Cobb Mountain)

1.185

B-5H-5

76

±5

37.42

40.82

(T) C2n (Olduvai)

1.778

B-7H-3

126

±5

54.46

59.69

(B) C2n (Olduvai)

1.945

B-7H-6

98

±5

58.68

63.91

(T) C2r.1n (Reunion)

2.128

A-7H-6

103

±7

62.83

67.96

B-8H-2

67

± 10

61.87

67.93

(B) C2r.1n (Reunion)

2.148

A-7H-6

137

±7

63.17

68.30

B-8H-2

118

± 10

62.38

68.44

(T) C2An.1n (Matuyama/Gauss) 2.581

B-9H-4

100

± 12

74.66

81.30

(T) C2An.1r (Kaena)

3.032

A-10H-5

115

± 15

89.95

95.81

(B) C2An.1r (Kaena)

3.116

B-11H-2

110

± 10

90.80

98.44

(T) C2An.2r (Mammoth)

3.207

A-11H-3

67

± 20

95.35

101.87

B-11H-5

7

±5

94.27

101.91(B) C2An.2r (Mammoth)

3.33

A-11H-5

50

± 25

98.18

104.70(T) C2Ar (Gauss/Gilbert)

3.596

A-12H-6

26±5

109.62115.67

B-13H-2

8±5

107.51115.64

A-16H-1110±5140.90149.06

B-16H-545± 15

142.15149.10(T) C3n.1n (Cochiti)

4.187(B) C3n.1n (Cochiti)

4.3

A-16H-533± 20

146.05154.21(T) C3n.2n (Nunivak)

4.493

B-17H-555± 10

151.75159.34(B) C3n.2n (Nunivak)

4.631

A-17H-3

92± 25

153.22

162.10(T) C3n.3n (Sidufjall)

4.799

A-17H-5150± 20

156.80165.68(B) = bottom; (T) = top. In bold are polarity boundaries that are defined with more confidence. Reversal ages are based on GPTS2012 (Gradstein et al. 2012)

180°, respectively. We use the following criteria/methods
to identify polarity reversals at Site U1424 based on the uchannel NRM data: (1) the reversals are accompanied byboth a sign switch in inclinations and an ~ 180° transitionin corrected declinations; (2) if reversals are recorded inoverlapping intervals of the two holes, CCSF-A depths of
the reversals should closely match each other; (3) center
position of a reversal is estimated by reviewing NRM datafrom individual u-channel samples that recorded the reversal, and averaging the closest positions on either side of
the reversal that clearly show normal or reversed
magnetization components (difference between the two
positions is halved and used as uncertainty for the center
position of the reversal); and (4) data used to define the reversals are not from disturbed intervals. Information about
identified polarity reversals are summarized in Table 2 including hole-core-section ID, center position and uncertainty, and depth of the reversals in m CSF-A and m

CCSF-A. Uncertainties of the reversal positions typicallyrange between a few cm to a few tens of cm. Identified reversals are also shown in the rightmost panel on Fig. 5
with their corresponding GPTS ages labeled.
The majority of geomagnetic polarity reversals in thelast ~ 4.89 Myr in the GPTS are clearly identified in theu-channel NRM data. These reversals are marked inbold in Table 2. The following six reversals were recorded in overlapping intervals of Holes U1424A andU1424B: onset of the Jaramillo subchron, onset and endof the Reunion subchron, end of the Mammoth subchron, the Gauss/Gilbert boundary, and end of the
Cochiti subchron. CCSF-A depths at which these reversals were recorded in the two holes are remarkably consistent, typically within a few cm to just over 10 cm (seeTable 2). The Cobb Mountain subchronozone, top of
the Kaena subchronozone, and bottom of the Nunivak
subchronozone are less well defined in the sediments

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

(labeled in grey on the rightmost panel of Fig. 5). There
are apparent transitions in inclinations and corrected
declinations associated with these four reversals, but theboundaries are less well defined than other recorded reversals. Inclination and corrected declination data appear
to be nosier during intervals with NRM35mT intensity
lower than ~ 10−4 A/m level (e.g., ~ 30, ~ 46, ~ 70–80, ~96, ~ 143–147 m CCSF-A). Inclination data during theseintervals sometimes show shallower values or even occasional values in opposite directions but they still averagearound the expected GAD values and provide support
for the interpreted magnetostratigraphy.
Correlation of Site U1424 polarity stratigraphy to
GPTS is mostly straightforward for boundaries between
the Brunhes, Matuyama, Gauss, and Gilbert Chrons, aswell as for most of the subchrons (except Cobb Mountain and Kaena) within the Matuyama and Gauss
Chrons. For the top ~ 100 m CCSF-A sediments at Site
U1424, a preliminary polarity stratigraphy based on partially demagnetized (up to 30 mT peak field) u-channel
NRM data was reported in Tada et al. (2018). Those results supersede that based on shipboard half-core section
NRM data (Tada et al. 2015) but are updated here using
u-channel NRM data with full demagnetization sequence(up to 100 mT peak field) for a total of ~ 167.6 m sediment sequence recovered at IODP Site U1424. Depth
levels of the identified reversals in sediments from thetop ~ 100 m CCSF-A from this study are very consistent
with those reported in Tada et al. (2018) with differences
typically around just a few cm. We tentatively revise the
top of Kaena subchronozone to ~ 95.81 m CCSF-A.
Magnetostratigraphic interpretation for Site U1424
sediments below ~ 100 m CCSF-A (i.e., mostly in the
Gilbert Chronozone) is less straightforward. Based on
shipboard NRM data which are low resolution, only partially demagnetized, and nosier, the Cochiti subchronozone was placed around 140 m CCSF-A (see Tada et al.
2015). Our results do not appear to support this. Theinterval between ~ 115.67 and 149.1 m CCSF-A is apparently dominated by negative inclinations, and do notshow clear evidence of a normal polarity zone (Fig. 5).
Although inclinations around 131.6 m CCSF-A in Hole
U1424A show a brief interval with positive inclinations,the overlapping interval in Hole U1424B however show
stable negative inclinations with low MAD values. Similarly, an apparent brief positive inclination interval in
Hole U1424B around 136 m CCSF-A is not replicated inoverlapping intervals in Hole U1424A. This interval occurs in the top of a core (i.e., U1424B-15H) that is often
prone to drilling induced disturbance. We interpret the
Cochiti subchronozone to be between ~ 149.1 and 154.2
m CCSF-A at Site U1424. This interpretation is supported by the identification of the Znp-Ohta tephra at ~142.7 m CCSF-A (see section below). The Nunivak

Page 14 of 19

subchronozone is recorded between ~ 159.3 and 162.1
m CCSF-A with a clearly defined top but a less welldefined bottom. Site U1424 sediments appear to have recorded the top of the Sidufjall subchronozone at ~ 165.7
m CCSF-A. The bottom of the studied Site U1424 sediment sequence should be within the Sidufjall subchronozone and close to (but not reaching) the bottom of the
Sidufjall subchronozone.
3.4 Tephra correlation

We correlate sixteen tephra layers identified at Site
U1424 to known tephras on the Japanese archipelago
based on their chemical compositions and stratigraphic
positions (see Tables 1 and 3). Major element compositions of volcanic glass shards from the studied tephras in
U1424A sediments are also compared with data fromthe corresponding known Japanese tephras in Fig. S1 todemonstrate the tephra correlations made. An earlier
version of the tephra correlation was utilized by Tada
et al. (2018) but detailed tephra properties supportingthe correlation were not reported. Here, we demonstrate
the tephra correlation based on the analyzed data andinclude two new correlations corresponding to the Yellow I and Yellow II/III tephras. Tephra correlations reported here were also checked by their petrographic
properties. These correlations allow us to transfer depositional ages of the widespread known tephras to Site U1424.
Ages for the known tephras were typically acquired throughstudies of formations on land using associated horizon of
the marine isotope stage with radiometric ages, fission trackage, and biostratigraphic markers (see Table 3).
Identified tephra layers at Site U1424 and their estimated ages are also listed on the rightmost panel of Fig.
5. Estimated ages of these identified tephras at Site
U1424 agree very well with the interpreted magnetostratigraphy. For example, the Hkd-Ku tephra with an estimated age of ~ 0.75 Ma (Suzuki et al. 2005) is identified
at ~ 26.54 m CCSF-A, just above the identified Brunhes/
Matuyama boundary. Similarly, the Ass-Tmd2 and Sr-Itytephras with estimated ages of ~ 2.62 and ~ 3.55 Ma respectively were identified at ~ 83.29 and ~ 114.7 m
CCSF-A, greatly supporting the interpreted Matuyama/
Gauss and Gauss/Gilbert boundaries. In addition, identification of the Yamada I and Ss-Pnk tephras at Site
U1424 with estimated ages of ~ 0.95 and ~ 1.053 Ma areconsistent with the interpreted top of the Jaramillo subchronozone (with an estimated age of ~ 0.988 Ma). Identification of the Yellow I and Yellow II/III tephras at ~46.4 and ~ 44.38 m CCSF-A with their estimated age
within MIS 35 (~ 1.2 Ma) is generally consistent with
the interpreted Cobb Mountain subchronozone (although not well defined in the U1424 sediments). The
Ak-Kd18 and Eb-Fukuda tephras identified at ~ 47.925
and ~ 57.9 m CCSF-A with estimated age of ~ 1.45 andXuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 15 of 19

Table 3 Summary of chemical composition of known tephras on the Japanese archipelago from the literature and this study
Tephra name(*reference)

Chemical composition (wt. %)
SiO2

TiO2

Al2O3

FeO*

MnO

MgO

CaO

Na2O

K2O

77.49

0.16

12.81

1.32

0.06

0.12

1.20

3.41

3.43

A-Tn

*2

Av
sd

0.32

0.08

0.09

0.17

0.07

0.08

0.09

0.15

0.09

Aso-4

*2

Av

71.70

0.41

15.44

1.67

0.10

0.41

1.27

4.47

4.52

sd

0.60

0.07

0.33

0.17

0.08

0.10

0.24

0.11

0.16

Toya

*1

Av

77.72

0.09

13.25

1.04

0.08

0.11

0.31

4.38

3.02

sd

0.30

0.08

0.21

0.12

0.11

0.06

0.09

0.20

0.23

B-Og

*1

Av

65.00

0.39

16.80

4.71

0.15

0.23

1.11

6.00

5.61

sd

0.53

0.15

0.17

0.28

0.12

0.11

0.12

0.17

0.14

Ka1

**

Av

77.63

0.21

12.53

1.50

0.06

0.27

1.67

3.69

2.44

sd

0.25

0.08

0.17

0.19

0.06

0.08

0.07

0.12

0.11

Hkd-Ku

*3

Av

77.20

0.27

12.45

1.55

0.08

0.28

1.43

4.32

2.43

sd

0.45

0.08

0.22

0.08

0.11

0.08

0.10

0.12

0.07

Yamada I

*3

Av

76.70

0.39

12.31

2.00

0.03

0.31

1.98

3.74

2.55

sd

0.30

0.05

0.14

0.10

0.03

0.09

0.08

0.16

0.10

Ss-Pnk

*3

Av

76.63

0.26

12.77

1.17

0.08

0.23

1.11

3.43

4.33

sd

0.23

0.09

0.09

0.07

0.08

0.09

0.07

0.16

0.14

Yellow III

*3

Av

76.05

0.20

13.68

1.07

0.07

0.32

1.44

3.94

3.22

sd

0.45

0.10

0.29

0.20

0.07

0.12

0.17

0.33

0.45

Yellow II

*3

Av

76.14

0.15

13.77

1.06

0.03

0.31

1.49

3.94

3.12

sd

0.38

0.08

0.15

0.07

0.03

0.09

0.05

0.22

0.26

Yellow I

*3

Av

76.93

0.21

13.05

0.95

0.06

0.24

1.02

3.72

3.81

sd

0.36

0.09

0.18

0.09

0.07

0.11

0.08

0.28

0.32

Ak-Kd18

**

Av

77.66

0.33

12.35

1.57

0.06

0.31

1.68

3.34

2.74

sd

0.45

0.16

0.26

0.21

0.07

0.06

0.10

0.11

0.11

Eb-Fukuda

*3

Av

75.48

0.10

13.42

1.62

0.05

0.11

0.99

3.87

4.35

sd

0.22

0.07

0.11

0.11

0.05

0.10

0.06

0.15

0.13

Msn-Jwg4

**

Av

74.40

0.13

13.91

1.86

0.02

0.10

1.08

3.90

4.59

sd

0.21

0.09

0.25

0.20

0.05

0.09

0.10

0.16

0.28

Ass-Tmd2

*3

Av

75.15

0.33

13.56

1.46

0.09

0.28

1.41

4.06

3.66

sd

0.47

0.10

0.16

0.15

0.11

0.09

0.10

0.17

0.12

Sr-Ity

*3

Av

75.97

0.08

13.46

1.18

0.05

0.10

0.61

3.58

4.96

sd

0.26

0.07

0.10

0.13

0.07

0.06

0.08

0.15

0.13

Znp-Ohta

**

Av

76.28

0.07

13.50

0.98

0.09

0.08

0.65

3.35

5.00

sd

0.21

0.12

0.18

0.22

0.15

0.08

0.09

0.18

0.27

n=

Age (Reference)16~ 30 ka (Smith et al. 2013)16~ 87 ka (Aoki et al. 2008)30~ 106 ka (Shirai et al. 1997)35~ 448 ka (Shirai et al. 1997)10

MIS 17, ~ 700 ka (Pickering et al. 1999)

15

MIS 19.1-18.4, ~ 750 ka (Suzuki et al. 2005)15~ 950 ka (Yoshikawa and Mitamura 1999)15~ 1.053 Ma (Tsuji et al. 2005)

15

MIS 35 (Yoshikawa and Mitamura 1999)

15

MIS 35 (Yoshikawa and Mitamura 1999)

15

MIS 35 (Yoshikawa and Mitamura 1999)

11~ 1.45 Ma (Satoguchi and Nagahashi 2012)15

MIS 62, ~ 1.75 Ma (Nozaki et al. 2014)12~ 2.3 Ma (Satoguchi and Nagahashi 2012)15~ 2.62 Ma (Kurokawa et al. 2008)15~ 3.55 Ma (Watanabe 2002)

15~ 3.95 Ma (Satoguchi et al. 2005)*1: Nagahashi et al. (2003), *2: Nagahashi et al. (2004), *3: Nagahashi et al. (2015), **: This study. FeO*: total iron recalculated as FeO, Av: average, sd:
standard deviation~ 1.75 Ma respectively provide extra constraint for theinterpreted top of the Olduvai subchronozone beneaththem. The Znp-Ohta tephra with an estimated age of ~3.95 Ma is identified at ~ 142.7 m CCSF-A, supporting
the interpretation that the Cochiti subchronozne should
be below it. All identified tephras also agree with magnetic polarity chrons and subchrons recorded in sections
on land (Niitsuma 1976; Hayashida and Yokoyama 1983;

Nakayama and Yoshikawa 1990), and can be integrated
with the magnetostratigraphy to add valuable age control
points within the polarity chrons and subchrons.
3.5 Age model and sedimentation rates of Site U1424
sediments

Depth to age tie points based on magnetostratigraphy
and tephrostratigraphy from this study are plotted inXuan et al. Progress in Earth and Planetary Science(2020) 7:60

Page 16 of 19

Fig. 7 Age model and sedimentation rates of Site U1424 sediments. Top panel: depth-age model of Site U1424 sediments between 0 and 167.6
m CCSF-A (~ 0–4.89 Ma) based on polarity reversals (black squares), tephra (red triangles) chronology, and tuning of U1424 GRA and NGR data toa global benthic oxygen isotope stack (green dots; see Tada et al. 2018). Bottom panel: Site U1424 sedimentation rate changes through time
estimated using tuned ages for the last ~ 3 Myr and magnetostratigraphy and tephra ages for intervals older than ~ 3 Ma

Fig. 7. For the last ~ 3 Myr, we compare our results withthe depth-age tie points acquired based on tuning of
gamma ray attenuation (GRA) density and natural
gamma radiation (NGR) of Site U1424 sediments (Tadaet al. 2018) to a global benthic oxygen isotope stack record (Lisiecki and Raymo 2005). The tuning is justified
because GRA density of Site U1424 sediments reflects
diatom contents which are higher during interglacial
high-stands (see Tada et al. 2018). Age tie points fromwithin the last ~ 3 Myr are very consistent with one another (upper panel in Fig. 7) and fall within the depthage relation range defined by biostratigraphic markers of
this interval (see Tada et al. 2015; Kamikuri et al. 2017).
For the interval prior to ~ 3 Ma, the u-channel data
based magnetostratigraphy agrees well with identification of the two tephras in this interval (i.e., Sr-Ity and
Znp-Ohta). These depth-age tie points are again broadly
in agreement with biostratigraphic marks available forthis interval. In particular, the preliminary interpretationof Cochiti subchronozone based on shipboard data wasin conflict with the Znp-Ohta tephra and a diatom event(i.e., the first occurance of Neodenticula Koizumii; see
Tada et al. 2015). The revised position of the Cochiti
subchronozone to ~ 149.1–154.2 m CCSF-A in thisstudy largely resolved this issue. According to this age
model, bottom of the Site U1424 sediment sequence
covered by the u-channel samples at ~ 167.6 m CCSF-A
is dated to ~ 4.89 Ma, assuming extrapolation of linear
sedimentation rate between the bottom of the Nunivak
and the top of the Sidufjall subchronozones.
Site U1424 sediment accumulation rates based on themagnetostratigraphy and tephrostratigraphy as well as
the tuned chronology (last ~ 3 Myr only) are shown inlower panel of Fig. 7. Sedimentation rates range between~ 1.7 and 7.6 cm/kyr with an average of ~ 3.3 cm/kyr.
The highest mean sedimentation rate of ~ 7.6 cm/kyr
occurred between ~ 3.6 and 3.95 Ma, while lowest mean
sedimentation rates of ~ 1.7–2 cm/kyr happened at ~ 2,
~ 3, and prior to ~ 4.5 Ma. There appears to be an overall increasing trend in sedimentation rates since ~ 2 Ma.
These changes in sedimentation rates likely reflect theamount and relative proportion of various source

Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

materials been transported and deposited at Site U1424,
including fluvial sediments from the Japanese island rivers, eolian dust from central Asia, as well as materials
from rivers in Russia, Korea, and China (see Irino andTada 2002; Milliman and Farnsworth 2011; Shen et al.
2017). The highest mean sedimentation rate of ~ 7.6
cm/kyr between ~ 3.6 and 3.95 Ma occurred in the middle of Subunit IIB (Fig. 5). Shipboard GRA density data
(Tada et al. 2015) show low values during this intervalsuggesting high diatom flux during this time period
which could have contributed to the elevated sedimentation rates. The integrated magneto- and tephrostratigraphy provide a robust chronology at Site U1424 covering
the last ~ 4.89 Ma. This chronology can be transferred
to other sites drilled during IODP Expedition 346
through detailed correlation of dark and light layers aswell as reversals and tephra layers, providing anchors toa “paleo-observatory network” (see Tada et al. 2018). In
addition, Site U1424 could serve as a regional stratigraphic reference site to facilitate the study of othersediment sequences in the Japan Sea as well as PliocenePleistocene formations on land (e.g., the Kazusa Groupwidely distributed in the central part of the Boso Peninsula; see Kazaoka et al. 2015) to investigate paleoceanographic and paleoenvironmental conditions in the region
and their links to global changes.

4 Conclusions
Rock magnetic analyses on bulk samples from IODP Site
U1424 indicate that magnetic remanence carriers in thesediments are primarily (titano)magnetite with small
contribution of high coercivity magnetic minerals (e.g.,
hematite) and possibly iron sulphides (e.g., pyrrhotite
and/or greigite). Concentration of (titano)magnetite appears significantly lower in dark-colored sediments,
probably due to reductive diagenesis under euxinic conditions during which (titano)magnetite dissolves andforms pyrite that is paramagnetic. Comparison of histograms of NRM intensity and directional data from darkand light-colored sediments suggest that although darkcolored sediments often show lower NRM intensity,
both dark- and light-colored sediments have recorded
paleomagnetic directional data that can be used to construct magnetostratigraphy.
Geomagnetic polarity boundaries between the
Brunhes, Matuyama, Gauss, and Gilbert Chronozones
are clearly recorded in Site U1424 sediments at ~ 27.54,~ 81.3, and ~ 115.67 m CCSF-A respectively. In addition,
the Jaramillo, Olduvai, and Reunion subchronozones
within the Matuyama Chronozone are well preserved between ~ 34.92–37.56, ~ 59.69–63.91, and ~ 67.96–68.3
m CCSF-A. The Cobb Mountain subchronozone is lesswell defined. The apparent inclination switch accompanied by ~ 180° shift in declination suggests its possible

Page 17 of 19

recording between ~ 40.6 and 40.8 m CCSF-A. Within
the Gauss Chronozone, the Mammoth subchronozone isclearly recorded between ~ 101.87 and 104.7 m CCSF-A.
The bottom of the Kaena subchronozone appears wellpreserved at ~ 98.44 m CCSF-A, but the top of the
Kaena subchronozone is less well defined and has beententatively placed at ~ 95.81 m CCSF-A based on patterns in both declination and inclination data. The
Cochiti and Nunivak subchronozones within Gilbert
Chronozone are recorded at ~ 149.1–154.21 and ~154.21–162.1 m CCSF-A respectively, with bottom of
the Nunivak subchronozone less well recognized. The
Sidufjall subchronozone is partly recorded at Site U1424
with its top located at ~ 165.68 m CCSF-A.
We analyzed and correlated sixteen tephra layers
in Site U1424 sediments to reference tephrostratigraphyof the region. Ages of these identified tephras agree very
well with the interpreted magnetostratigraphy, and canbe integrated with the magnetostratigraphy to add valuable age control points within the recognized polarity
chrons and subchrons. The integrated magneto- andtephrostratigraphy suggest that Site U1424 covered sediments deposited during the last ~ 4.89 Myr, with sediment accumulation rates range between ~ 1.7 and 7.6
cm/kyr with an average of ~ 3.3 cm/kyr. The robust age
model obtained at Site U1424 makes it possible to use
the site as a stratigraphic reference record for studies of
Pliocene-Pleistocene marine and land sections in theregion.

5 Supplementary information
Supplementary information accompanies this paper at https://doi.org/10.
1186/s40645-020-00373-9.
Additional file 1: Figure S1. Major element compositions of volcanic
glass shards from studied tephras in U1424A sediments compared withdata from correlated known Japanese widespread tephras. FeO* is thetotal iron recalculated as FeO. The pale bars indicate the standard
deviations.
Abbreviations
AF: Alternating field; APC: Advanced piston corer; CCSF: Core composite
depth below sea floor; CMCR: Center for Advanced Marine Core Research;
CSF: Core depth below sea floor; EDS: Energy dispersive spectroscopy;
EPMA: Electron probe micro-analyzer; FORC: First-order reversal curve;
GAD: Geocentric axial dipole; GPTS: Geomagnetic polarity time scale;
GRA: Gamma ray attenuation; IODP: Integrated Ocean Drilling Program;
IRM: Isothermal remanent magnetization; MAD: Maximum angular deviation;
NRM: Natural remanent magnetization; ODP: Ocean Drilling Program;
PCA: Principal component analysis; PSD: Pseudo-single domain; RGB: Red,
green, blue; SIRM: Saturation isothermal remanent magnetization;
SRM: Superconducting rock magnetometer; TWC: Tsushima warm current;
VSM: Vibrating sample magnetometer; XRF: X-ray fluorescence; ZFC: Zerofield cooled
Acknowledgements
We thank the captain, crew, and shipboard scientists of IODP Expedition 346
for their contributions to the recovery and preliminary analysis of sediments
used in this study. The authors are grateful to IODP Expedition 346 scientists
and staff at Kochi Core Center for their assistance with the sampling andXuan et al. Progress in Earth and Planetary Science(2020) 7:60

shipping of the u-channels. We thank two anonymous reviewers and theeditor for their helpful comments and suggestions that improved the manuscript. We also thank Benjamin Griffin and Michael Egbulefu who conducted
NRM measurement for some of the u-channel samples as part of their undergraduate dissertation work at the University of Southampton.
Authors’ contributions
CX proposed the topic, designed the paleomagnetism and rock magnetism
study, analyzed and interpreted the paleomagnetic and rock magnetic data,
and wrote the manuscript. YJ carried out the paleomagnetic experiments on
u-channel samples and room temperature rock magnetic experiments onbulk samples, analyzed the data, and contributed to the writing and editingof the manuscript. SS carried out the low temperature rock magnetic experiments, analyzed the results, and contributed to the writing and editing of
the manuscript. YS and YN conducted the tephra analyses, analyzed andinterpreted tephra related data, and wrote tephra work related sections. All
authors read and approved the manuscript.
Authors’ information
CX is associate professor at University of Southampton; YJ is researchtechnician at University of Southampton; SS is research scientist at National
Institute of Advanced Industrial Science and Technology (AIST), Japan; YS is
research scientist at Lake Biwa Museum; YN is professor at Fukushima
University.
Funding
Paleomagnetism work in this study was supported by UK Natural Environment
Research Council (NERC) grants NE/N004736/1 and NE/R011281/1 awarded to
CX. Low temperature rock magnetic work was supported by Japan Society for
the Promotion of Science (JSPS) KAKENHI grant JP17K14408 awarded to SS, andwas performed under the cooperative research program of Center for
Advanced Marine Core Research, Kochi University (Accept No.17A052, 17B052).
Tephra analyses work was supported by the JSPS KAKENHI grant JP25400493
and JP21340144 awarded to YS and YN, respectively.
Availability of data and materials
Please contact author for data requests.
Competing interests
The authors declare that they have no competing interest.
Author details
1
School of Ocean and Earth Science, National Oceanography Centre
Southampton, University of Southampton, Waterfront Campus, European
Way, Southampton SO14 3ZH, UK. 2Research Institute of Geology andGeoinformation, Geological Survey of Japan, AIST, Central 7, 1-1-1 Higashi,
Tsukuba 305-8567, Japan. 3Lake Biwa Museum, 1091 Oroshimo, Kusatsu,
Shiga 525-0001, Japan. 4Faculty of Symbiotic Systems Science, Fukushima
University, 1 Kanayagawa, Fukushima, Fukushima 960-1296, Japan.
Received: 19 March 2020 Accepted: 4 September 2020

References
Aoki K, Irino T, Oba T (2008) Late Pleistocene tephrostratigraphy of the sedimentcore MD01-2421 collected off the Kashima coast, Japan. The Quat Res(Daiyonki Kenkyu) 47:391–407 (in Japanese with English Abstract)
Day R, Fuller M, Schmidt VA (1977) Hysteresis properties of titanomagnetites:
grain-size and compositional dependence. Physics of the Earth and Planetary
Interiors 13(4):260–267.
Dunlop DJ (2002) Theory and application of the Day plot (Mrs/Ms versus Hcr/Hc)
1. Theoretical curves and tests using titanomagnetite data. J Geophys ResSolid Earth 107(B3):2056. https://doi.org/10.1029/2001jb000486
Egli R (2013) VARIFORC: An optimized protocol for calculating non-regular firstorder reversal curve (FORC) diagrams. Glob Planet Change 110:302–320.
https://doi.org/10.1016/j.gloplacha.2013.08.003
Expedition 346 Scientists (2014) Asian Monsoon: onset and evolution ofmillennial-scale variability of Asian monsoon and its possible relation with
Himalaya and Tibetan Plateau uplift. IODP Prel Rept 346. doi:https://doi.org/
10.2204/iodp.pr.346.2014

Page 18 of 19

Gradstein FM, Ogg JG, Schmitz M, Ogg G (2012) The Geologic Time Scale 2012.
Elsevier, Amsterdam
Hamano Y, Krumsiek KAO, Vigliotti L, Wippern JM (1992) Pliocene–Pleistocene
magnetostratigraphy of sediment cores from the Japan Sea. In Tamaki K,
Suyehiro K, Allan J, McWilliams M et al. Proc ODP Sci Results 127/128 (Pt. 2):
College Station, TX (Ocean Drilling Program), 969–982. doi:https://doi.org/10.
2973/odp.proc.sr.127128-2.216.1992
Harrison RJ, Feinberg JM (2008) FORCinel: An improved algorithm for calculating
first-order reversal curve distributions using locally weighted regression
smoothing. Geochem Geophys Geosyst 9:Q05016. https://doi.org/10.1029/
2008gc001987
Hayashida A, Yokoyama T (1983) Paleomagnetic chronology of the PlioPleistocene Kobiwako Group to the southeast of Lake Biwa, Central Japan.
Jour Geol Soc Japan 89:209–221
Heslop D, Roberts AP (2012) Estimation of significance levels and confidence
intervals for first-order reversal curve distributions. Geochem Geophys
Geosyst 13:Q12Z40 https://doi.org/10.1029/2012GC004115
Ingle JC, Suyehiro K, von Breymann MT et al (1990) Proc ODP Init Repts 128:
College Station. TX (Ocean Drilling Program). https://doi.org/10.2973/odp.
proc.ir.128.1990
Irino T, Tada R (2002) High-resolution reconstruction of variation in aeolian dust
(Kosa) deposition at ODP site 797, the Japan Sea, during the last 200 ka. Glob
Planet Change 35:143–156
Irino T, Tada R, Ikehara K, Sagawa T, Karasuda A, Kurokawa S, Seki A, Lu S (2018)
Construction of perfectly continuous records of physical properties for darklight sediment sequences collected from the Japan Sea during Integrated
Ocean Drilling Program Expedition 346 and their potential utilities as
paleoceanographic studies. Prog Earth Planet Sc 5:23 https://doi.org/10.1186/
s40645-018-0176-7
Jackson M, Solheid P (2010) On the quantitative analysis and evaluation ofmagnetic hysteresis data. Geochem Geophys Geosyst 11(4):Q04Z15. https://doi.org/10.1029/2009gc002932
Kamikuri S-I, Itaki T, Motoyama I, Matsuzaki KM (2017) Radiolarian Biostratigraphy
from Middle Miocene to Late Pleistocene in the Japan Sea. PaleontologicalResearch 21(4):397–421
Kazaoka O, Suganuma Y, Okada M, Kameo K, Head MJ, Yoshida T, Sugaya M,
Kameyama S, Ogitsu I, Nirei H, Aida N, Kumai H (2015) Stratigraphy of the
Kazusa Group, Chiba Peninsula, Central Japan: an expanded and highlyresolved marine sedimentary record from the Lower and Middle Pleistocene.
Quat Int 383:116–134
Kimura J, Nagahashi Y, Satoguchi Y, Chang Q (2015) Origins of felsic magmas inJapanese subduction zone: Geochemical characterizations of tephra from
caldera-forming eruptions <5 Ma. Geochem Geophys Geosyst 16:2147–2174
Kirschvink JL (1980) The least-squares line and plane and the analysis of
paleomagnetic data. Geophys J InT 62(3):699–718
Kurokawa K, Nagahashi Y, Yoshikawa S, Satoguchi Y (2008) Correlation of the
Asashiro Tephra Bed in the Osaka Group and the Tzw Tephra Bed in the
Niigata region in central Japan. Quat Res, 47:93-99. (Japanese with English
abstract)
Lisiecki LE, Raymo ME (2005) A Pliocene-Pleistocene stack of 57 globally
distributed benthic δ18O records. Paleoceanography 20(1):PA1003. https://doi.org/10.1029/2004PA001071
Machida H (1999) The stratigraphy, chronology and distribution of distal markertephras in and around Japan. Global Planet Change 21:71–94
Milliman JD, Farnsworth KL (2011) River discharge to the coastal ocean: a global
synthesis. Cambridge: Cambridge University Press. https://doi.org/10.1017/
CBO9780511781247.
Nagahashi Y, Nakai S, Kikkawa K, Okudaira T, Yoshikawa S, Yoshida T (2015)
Petrological properties of tephra beds based on the major and trace element
composition of volcanic glass shards - a case study of the Osaka Group andthe Takashima-oki drilling core sediments in Lake Biwa, Kinki district, Japan.
Earth Science (Chikyu Kagaku) 69:205–222 (in Japanese with English Abstract)
Nagahashi Y, Yoshida T, Nakai S, Okudaira T (2003) Evaluation and correction of
EDS results of the glass shards from some representative tephra bycomparison with XRF Analysis. The Quat Res (Daiyonki Kenkyu) 42:265–277(in Japanese with English Abstract)
Nagahashi Y, Yoshikawa S, Miyakawa C, Uchiyama T, Inouchi Y (2004) Stratigraphy
and chronology of widespread tephra layers during the Past 430ky in the
Kinki District and the Yatsugatake Mountains: major element composition of
the glass shards using EDS analysis. The Quat Res (Daiyonki-kenkyu) 43:15–35(in Japanese with English Abstract)Xuan et al. Progress in Earth and Planetary Science(2020) 7:60

Nakayama K, Yoshikawa Y (1990) Magnetostratigraphy of the late Cenozoic TokaiGroup in central Japan. Jour Geol Soc Japan 96:967–976 (in Japanese withEnglish Abstract)
Niitsuma N (1976) Magnetic stratigraphy in the Boso Peninsula. Jour Geol Soc
Japan 82:163–181 (in Japanese with English abstract)
Nozaki A, Majima R, Kameo K, Sakai S, Kouda A, Kawagata S, Wada H, Kitazato H(2014) Geology and age model of the Lower Pleistocene Nojima, Ofuna, andKoshiba Formations of the middle Kazusa Group, a forearc basin-fill sequenceon the Miura Peninsula, the Pacific side of central Japan. Island Arc 23:157–179
Oba T, Kato M, Kitazato H, Koizumi I, Omura A, Sakai T, Takayama T (1991)
Paleoenvironmental changes in the Japan Sea during the last 85,000 years.
Paleoceanography 6(4):499–518
Oda H, Xuan C (2014) Deconvolution of continuous paleomagnetic data frompass-through magnetometer: A new algorithm to restore geomagnetic andenvironmental information based on realistic optimization. Geochem
Geophys Geosyst 15:3907–3924 https://doi.org/10.1002/2014GC005513
Paterson GA, Zhao X, Jackson M, Heslop D (2018) Measuring, processing, andanalyzing hysteresis data. Geochem Geophys Geosyst 19(7):1925–1945.
https://doi.org/10.1029/2018gc007620
Pickering KT, Couter C, Oba T, Taira A, Schaaf M, Platzman E (1999) Glacio-eustatc
control on deep-marine clastic forearc sedimentation, Pliocene-midPleistocene (c. 1180-600 ka) Kazusa Group, SE Japan. J Geol Soc London 156:
125–136
Pike CR, Roberts AP, Verosub KL (1999) Characterizing interactions in finemagnetic particle systems using first order reversal curves. J Appl Phys 85(9):6660–6667
Roberts AP, Heslop D, Zhao X, Pike CR (2014) Understanding fine magnetic
particle systems through use of first-order reversal curve diagrams. Rev
Geophys 52(4):557–602. https://doi.org/10.1002/2014rg000462
Roberts AP, Pike CR, Verosub KL (2000) First-order reversal curve diagrams: a newtool for characterizing the magnetic properties of natural samples. J Geophys
Res 105(B12):28461–28475. https://doi.org/10.1029/2000jb900326
Roberts AP, Tauxe L, Heslop D, Zhao X, and Jiang Z (2018) A critical appraisal of
the “Day” diagram: J Geophys Res 123. doi: https://doi.org/10.1002/
2017JB015247
Satoguchi Y, Higuchi Y, Kurokawa K (2005) Correlation of the Ohta Tephra bed in
the Tokai group with a tephra bed in the Miura Group, central Japan. Jour
Geol Soc Japan 111:74–86 (in Japanese with English Abstract)
Satoguchi Y, Nagahashi Y (2012) Tephrostratigraphy of the Pliocene to Middle
Pleistocene Series in Honshu and Kyushu Islands, Japan. Island Arc 21:149–169
Shen XY, Wan SM, France-Lanord C, Clift PD, Tada R, Revillon S, Shi XF, Zhao DB,
Liu YG, Yin XB, Song ZH, Li AC (2017) History of Asian eolian input to the Sea
of Japan since 15 Ma: Links to Tibetan uplift or global cooling? Earth Planet
Sci Lett 474:296–308. https://doi.org/10.1016/j.epsl.2017.06.053
Shirai M, Tada R, Fujioka K (1997) Identification and chronostratigraphy of middle
to upper Quaternary marker tephras occurring in the Anden coast based oncomparison with ODP cores in the sea of Japan. Quat Res (Daiyonki-Kenkyu)
36:183–196 (in Japanese with English abstract)
Smith VC, Staff RA, Blockley SPE, Ramsey CB, Nakagawa T, Mark DF, Takemura K,
Danhara T, Suigetsu 2006 Project Members (2013) Identification andcorrelation of visible tephras in the Lake Suigetsu SG06 sedimentary archive,
Japan: chronostratigraphic markers for synchronising of east Asian/west
Pacific palaeoclimatic records across the last 150 ka. Quat Sci Rev 67:121–137
Suzuki T, Eden D, Danhara T, Fujiwara O (2005) Correlation of the HakkodaKokumoto Tephra, a widespread Middle Pleistocene tephra erupted from the
Hakkoda Caldera, northeast Japan. Island Arc 14:666–678
Tada R (1994) Paleoceanographic evolution of the Japan Sea. Palaeogeography
Palaeoclimatol Palaeoecol 108(3):487–508
Tada R (2005) Onset and evolution of millennial-scale variability in the Asian
Monsoon and its impact on paleoceanography of the Japan Sea. MillennialScale Variability in the Asian Monsoon, American Geological Union, U.S.A, pp
1–16
Tada R (2012) The Japan Sea sediments and variability of East Asian Monsoon:
toward the IODP drilling of the Japan Sea and East China Sea. Quat Res(Tokyo) 51(3):151–164
Tada R, Irino T, Ikehara K, Karasuda A, Sugisaki S, Xuan C, Sagawa T, Itaki T, Kubota
Y, Lu S, Seki A, Murray RW, Alvarez-Zarikian C, Anderson WT, Bassetti MA,
Brace BJ, Clemens SC, Gurgel MHD, Dickens GR, Dunlea AG, Gallagher SJ,
Giosan L, Henderson ACG, Holbourn AE, Kinsley CW, Lee GS, Lee KE, Lofi J,
Lopes CICD, Saavedra-Pellitero M, Peterson LC, Singh RK, Toucanne S, Wan
SM, Zheng HB, Ziegler M (2018) High-resolution and high-precision

Page 19 of 19

correlation of dark and light layers in the Quaternary hemipelagic sedimentsof the Japan Sea recovered during IODP Expedition 346. Prog Earth Planet Sc
5:19. https://doi.org/10.1186/s40645-018-0167-8
Tada R, Irino T, Koizumi I (1999) Land-ocean linkages over orbital and millennial
timescales recorded in late Quaternary sediments of the Japan Sea.
Paleoceanography 14(2):236–247. https://doi.org/10.1029/1998pa900016
Tada R, Koizumi I, Cramp A, Rahman A (1992) Correlation of dark and light layers,
and the origin of their cyclicity in the Quaternary sediments from the Japan
Sea. In Pisciotto, K. A., Ingle, J. C, Jr., von Breymann, M. T., Barron, J., et al. Proc
ODP, Sci results, 127/128, Pt. 1: 577–601 College Station(Ocean Drilling
Program)
Tada R, Murray RW, Alvarez Zarikian CA, Anderson WT Jr, Bassetti MA, Brace BJ,
Clemens SC, da Costa Gurgel MH, Dickens GR, Dunlea AG, Gallagher SJ,
Giosan L, Henderson ACG, Holbourn AE, Ikehara K, Irino T, Itaki T, Karasuda A,
Kinsley CW, Kubota Y, Lee GS, Lee KE, Lofi J, Lopes CICD, Peterson LC,
Saavedra-Pellitero M, Sagawa T, Singh RK, Sugisaki S, Toucanne S, Wan S,
Xuan C, Zheng H, Ziegler M (2015) Site U1424. In. Proc IODP. https://doi.org/
10.2204/iodp.proc.346.105.2015
Tada R, Murray RW, Zarikian CAA (2013) Asian Monsoon: onset and evolution ofmillennial-scale variability of Asian Monsoon and its possible relation with
Himalaya and Tibetan plateau uplift. IODP Sci. Prosp. 346. https://doi.org/10.
2204/iodp.sp.346.2013
Tamaki K, Pisciotto K, Allan J et al. (1990) Proc. ODP, Init Repts 127: College
Station, TX (Ocean Drilling Program). doi:https://doi.org/10.2973/odp.proc.ir.
127.1990
Tauxe L, Labrecque J, Dodso D, Fuller M (1983) "U" channels—a new techniquefor paleomagnetic analysis of hydraulic piston cores. EOS Trans AGU 64:219
Tsuji T, Miyata Y, Okada M, Mita I, Nakagawa H, Sato Y, Nakamizu M (2005) Highresolution chronology of the lower Pleistocene Otadai and Umegase
Formations of the Kazusa Group, Boso Peninsula, central Japan–
Chronostratigraphy of the JNOC TR-3 cores based of oxygen isotope,
magnetostratigraphy and calcareous nannofossil. Jour Geol Soc Japan 111: 120. (in Japanese with English Abstract)
van Peer TE, Xuan C, Lippert PC, Liebrand D, Agnini C, Wilson PA (2017)
Extracting a Detailed Magnetostratigraphy From Weakly Magnetized,
Oligocene to Early Miocene Sediment Drifts Recovered at IODP Site U1406(Newfoundland Margin, Northwest Atlantic Ocean). Geochem Geophys
Geosyst 18. doi: https://doi.org/10.1002/2017gc007185
Vigliotti L (1997) Magnetic properties of light and dark sediment layers from thejapan sea: Diagenetic and paleoclimatic implications. Quat Sci Rev 16(10):1093–1114 https://doi.org/10.1016/S0277-3791(96)00118-7
Watanabe M (2002) Revised diatom biostratigraphy and chronostratigraphy of
the Pliocene sequence in Himi-Nadaura area, Toyama Prefecture, central
Japan: With special reference to ages of widespread volcanic ash beds andNo.3 Globorotaliia inflata bed of planktonic foraminiferal biostratigraphy. J
Geol Soc Japan 108:499–509 (in Japanese with English abstract)
Xuan C, Channell JET (2009) UPmag: MATLAB software for viewing andprocessing u channel or other pass-through paleomagnetic data. Geochem
Geophys Geosyst 10:Q10Y07. https://doi.org/10.1029/2009gc002584
Xuan C, Oda H (2015) UDECON: deconvolution optimization software forrestoring high-resolution records from pass-through paleomagnetic
measurements. Earth Planets Space 67:183 https://doi.org/10.1186/s40623015-0332-x
Xuan C, Oda H (2019) Sensor response estimate and cross calibration of
paleomagnetic measurements on pass-through superconducting rockmagnetometers. Geochem Geophys Geosyst 20. https://doi.org/10.1029/
2019GC008597
Yoshikawa S, Mitamura M (1999) Quaternary stratigraphy of the Osaka Plain,central Japan and its correlation with oxygen isotope record from deep sea
cores. Jour Geol Soc Japan 105:332–340 (in Japanese with English Abstract)

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