Kajita et al.
Progress in Earth and Planetary Science(2022) 9:40
https://doi.org/10.1186/s40645-022-00499-y

PAPER WITH FULL DATA ATTACHED

Progress in Earth andPlanetary Science

Open Access

Long‑chain alkenones in the Shimosa Groupreveal palaeotemperatures of the Pleistocene
interglacial Palaeo‑Tokyo Bays
Hiroto Kajita1,2,3,4* , Tsutomu Nakazawa2, Masayuki Utsunomiya2, Naohiko Ohkouchi3, Miyako Sato3,
Naomi Harada3 and Hodaka Kawahata4

Abstract: The Shimosa Group, a Middle- to Late-Pleistocene sedimentary succession, has been the focus ofstratigraphic attention because it lies beneath the Tokyo metropolitan area of central Japan. It is also of palaeoclimatic significance because it contains important interglacial marine strata of the past 450,000 years. Because themarine strata of the Shimosa Group were formed in the shallow inner bay known as the Palaeo-Tokyo Bay, rareoccurrences of planktonic foraminifera make it difficult to quantitatively reconstruct the palaeo-sea surface temperatures (SSTs). Here, we extracted long-chain alkenones (LCAs) from the core GS-UR-1 penetrating the ShimosaGroup to Marine Isotope Stage (MIS) 11. We found that the alkenone unsaturation ratio appears to reflect theSST of the Palaeo-Tokyo Bay formed during the peaks of MISs 5e, 7e, 9, and 11, which was consistent with the
inflowing water mass changes inferred from the benthic foraminiferal assemblages. The palaeo-SSTs during eachinterglacial period were 2–3 °C higher than the pre-industrial levels of Tokyo Bay and seemed to reach a level similar to that of the Holocene thermal maximum. The findings of this study demonstrate that the LCA-based proxy,
which has not before been utilised in studies on the Shimosa Group, has strong potential to provide palaeoceanicand stratigraphic information.
Keywords: Alkenone palaeothermometer, Interglacial periods, Shimosa Group
1 Introduction
Modern increases in greenhouse gas concentrations in
the atmosphere and the weather catastrophes in recent
years have stimulated growing public and scientificinterest. Palaeotemperature reconstructions for pastinterglacial periods are particularly important in palaeoenvironmental studies because they provide a basis
for comparison with the present interglacial period (Holocene) and its future evolution under the influence of
global warming (Tzedakis et al. 2009, 2012). Of particular importance is the last 450,000 years, when the 100kyr eccentricity cycle characterising modern climate was*Correspondence: kajita322@frontier.hokudai.ac.jp
1
National Institute of Polar Research, Research Organization of Informationand Systems, 10‑3 Midori‑tyo, Tachikawa, Tokyo 190‑8518, Japan
Full list of author information is available at the end of the article

established (the so-called mid-Brunhes event) becausesome of the interglacial periods during this era are characterised by relatively high atmospheric ­CO2 concentrations and have potentially been warmer than the presentday (e.g. Droxler et al. 2003; Lüthi et al. 2008; Melles
et al. 2012; Uemura et al. 2018). The latest Intergovernmental Panel on Climate Change report states that thelast interglacial period, Marine Isotope Stage (MIS) 5e,
was 0.5–1.5 °C higher in surface temperature than the
pre-industrial period when assessed on a global averageand had a warmer environment approaching the current greenhouse effect on Earth (Six Assessment Report2021). However, there are large diversities among theseinterglacial periods in terms of the regional variation in
their intensity, which makes their climatic structure andcontrolling mechanism elusive (Lang and Wolff 2011;© The Author(s) 2022. 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 theoriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images orother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line
to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory
regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of thislicence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/.

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

Milker et al. 2013; Otto-Bliesner et al. 2013; Hoffman
et al. 2017; Turney et al. 2020).
The climate in central Honshu Island, Japan, is controlled by unique oceanic conditions (Fig. 1a). It faces theKuroshio extension and subarctic fronts, which generatea distinct sea surface temperature (SST) gradient in thelatitudinal direction (Kida et al 2016). It is also locatednear the northern limit of the westerly jet that bounds theEast Asian summer monsoon front, where temperaturesand precipitation vary greatly at its boundaries (Sampeand Xie 2010; Nagashima et al. 2013; Tada and Murray2016). Because of these oceanic and atmospheric conditions, the north–south anomaly in the climate of Honshu
Island is extremely large, meaning that it is sensitive toglobal climate change, and relatively large signals of palaeoclimatic and palaeoceanic changes at various chronological scales have often been observed (e.g. Haneda et al.
2020; Kajita et al. 2020b).
Despite their high palaeoclimatic significance, few
geological samples can be used for systematic and continuous palaeotemperature reconstructions for multiple
interglacial periods after the mid-Brunhes event. Continuous and accurately dated archives, such as lake andmarine sediments, are promising to provide comprehensive information. In the case of lakes, the sedimentcore recovered from Lake Biwa, the largest and oldest
lake in Japan, has been recorded to be up to approximately 450,000 years old, and provides palaeoclimate
information based on pollen indicators (Nakagawa et al.
2008; Tarasov et al. 2011). With respect to marine sediment cores, except for some sediment cores drilled in theJapan Sea and the East China Sea on Integrated Ocean
Drilling Program (IODP) Expedition 346 (Tada et al.
2018; Sagawa et al. 2018; Clemens et al. 2018) and off
the Shimokita Peninsula on D/V CHKYU CK06-06 (trial
voyage for IODP Expeditions) (Phillips and Harwood2017), there are a few promising archives, particularly on
the Pacific side.
In this study, we focused on marine strata situatedin the subducting coastal plains formed during past
sea-level highstands. Typical examples are distributedin the Osaka and Kanto Plains, which are called the
Osaka Group and Shimosa Group, respectively (Masuda 2007). They are characterised by the cyclic deposition of shallow-marine and terrestrial strata related toPage 2 of 13

glacial–interglacial sea-level changes during the Middle
to Late Pleistocene. Previous palaeoenvironmental studies using pollen-based proxies have provided important
information on climate change during past interglacial
periods (e.g. Okuda et al. 2002; Kariya et al. 2010; Kitaba
et al. 2013). However, information on the marine environment, especially quantitative palaeo-SSTs, is scarcebecause of the few occurrences of planktic foraminifera
in these successions.
Here, we found that organic biomarkers, long-chain
alkenones (LCAs), are preserved in the marine strataof the Shimosa Group. LCAs are composed of ­C35–C42
unsaturated methyl and ethyl ketones with two to four
double bonds and feature unique lipid biomarkers produced by Isochrysidales haptophytes inhabiting sea surface waters (Volkman et al. 1980; Marlowe et al. 1984),
brackish-saline lakes (Theroux et al. 2010; Plancq et al.
2019), freshwater lakes (Theroux et al. 2010; Longo et al.
2018; Richter et al. 2019), and sea ice (Wang et al. 2021).
Based on culture experiments, it has been confirmed thatthe degree of unsaturation in LCAs is strongly correlatedwith the growth in temperature of haptophytes (Prahl
et al. 1988; Sawada et al. 1996; Nakamura et al. 2014;
Araie et al. 2018). In marine settings, except where large
freshwater inflows or sea ice are distributed, the degreeof unsaturation in ­C37 methyl ketones, which mostly
originate from pan-global Gephyrocapsa spp. (including
G. huxleyi formerly known as Emiliania huxleyi), can beused as palaeo-SST proxies (Müller et al. 1998; Tierney
and Tingley 2018). Using this palaeotemperature proxy,
we attempted to quantitatively reconstruct the SSTs during the MISs 5e, 7e, 9, and 11 that were recorded in the
Shimosa Group.

2 Geological setting
The Kanto Plain, which covers the Tokyo metropolitan
area of Japan, was formed as part of the tectonic basin
developed in response to the subduction of the Pacificand Philippine Sea Plates beneath the North American
Plate. This tectonic setting has resulted in a continuously subsiding basin with an uplifting and tilting margin
relative to the basin centre. The Kanto tectonic basin is
now buried with Neogene to Quaternary sediments up
to 3,000 m thick, forming the widest plain (ca. 17,000­km2) in Japan (Suzuki 2002). The present-day Kanto Plain(See figure on next page.)
Fig. 1 Maps showing the overall setting of the drill site of core GS-UR-1. a The marine and atmospheric environment around the Japanese islands,
including the study site, is shown in this figure. The blue and red arrows represent the paths of the Oyashio and Kuroshio currents. The core sites
referred to in this study are also shown. This base map was generated using Generic Mapping Tools. (b) Topography and geology around the coresite. The sampling location of the core KT12-06-2B (Kajita et al. 2020b) is also shown. The base map was generated using the Seamless Digital
Geological Map of Japan (Geological Survey of Japan, AIST 2020)

Kajita et al. Progress in Earth and Planetary ScienceFig. 1 (See legend on previous page.)(2022) 9:40

Page 3 of 13

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

Page 4 of 13

3 Materials and methods
3.1 Core GS‑UR‑1

Fig. 2 Stratigraphic summary of the Pleistocene Shimosa Group andcorrelation with MISs. The stratigraphic framework and depositional
age summarised in Nakazawa and Tanabe (2011) are shown in the left
column. Among the widespread tephra beds in the Shimosa Group,
those detected in core GS-UR-1 (J4, Km2, Km4, and Hk-TP) are shownin bold (Nakazawa and Nakaszto 2005). The Yokota and Kiyokawa
formations shown in shaded boxes are lacking due to the erosion
during MIS 6 at the core site of GS-UR-1 (Nakazawa and Nakaszto2005). The marine oxygen isotope curve is adapted from Lisiecki andRaymo (2005)

is underlain by the Middle to Late Pleistocene ShimosaGroup, which consists of fluvial–coastal depositional
cycles (Tokuhashi and Kondo 1989) related to sea-levelchanges from MIS 12 to 5e (Nakazato and Sato 2001).
The marine strata heavily accumulated in the Kanto Plain(Palaeo-Tokyo Bay), when the relative sea level increased
during each interglacial period. They can be subdivided
into the Jizodo, Yabu, Kamiizumi, Kiyokawa, Yokota, andKioroshi formations in ascending order and are bounded
by a discontinuity formed during the sea-level lowstands(Tokuhashi and Endo 1984; Nakazawa and Nakaszto
2005; Nakazawa et al. 2006; Nakazawa and Tanabe 2011)(Fig. 2). The Kioroshi Formation, which was deposited during the last interglacial period (MIS 5e), can beobserved in the shallow subsurface part of the uplandareas that have not been subjected to fluvial erosion since
the latest Pleistocene (Fig. 1b).

The sediment core GS-UR-1 was obtained from
Saitama City, Saitama Prefecture, in the Omiya Upland(139°39′25′′ E, 35°51′13′′ N) from an elevation of 16.29 m(Fig. 1b). This core was drilled in 2004 and stored at room
temperature until our analysis. The core was recovered
using a triple-tube sampler with a diameter of 116 mm
and a total length of 101.95 m. The stratigraphy anddepositional age of GS-UR-1 have been described comprehensively by Nakazawa and Nakazato (2005) and areoutlined below.
The core comprises five depositional cycles bounded byunconformities formed at sea-level lowstands. The cycles
are composed of non-marine and marine beds accumulated under the influence of sea-level change, except for
the fluvial terrace deposits and the surface soil of theshallowest cycle. These depositional cycles in GS-UR-1
are correlated with the Jizodo, Yabu, Kamiizumi, andKioroshi formations of the Shimosa Group in ascending order, based on the sea-level change inferred fromthe depositional cyclicity and intercalated with several
marker tephra beds. These marker tephra beds, J4 (TE5a), Km2 (TCu-1), Km4, and Hk-TP, were detected in
GS-UR-1 (Fig. 2). Of these, J4 (TE-5a) is recognised in themarine bed of the lowest cycle in GS-UR-1. It is known asa marker tephra bed of the Jizodo Formation (Tokuhashi
and Endo 1984) and is correlated with ­A1Pm and Ty1
tephras (Nakazawa et al. 2009) intercalated at the stratigraphic level during or immediately following the peakof MIS 11 (Kameo et al. 2006; Tsukamoto et al. 2007; Itoand Danišík, 2020) (Fig. 2). These results indicate thatthe lowest cycle of GS-UR-1 corresponds to the Jizodo
Formation of MIS 11. Km2 (TCu-1) and Km4 are intercalated in a brackish/marine bed at two cycles above the
Jizodo Formation in GS-UR-1. They are known as marker
tephra beds of the Kamiizumi Formation (Tokuhashi andEndo 1984). The Km2 tephra is widespread in the Kanto
Plain (Naya et al. 2020), and believed to indicate the early
MIS 7e (Nakazato and Sato 2001; Naya et al. 2020). This
indicates that the depositional cycle intercalating Km2
and Km4 in GS-UR-1 corresponds to the Kamiizumi Formation of MIS 7e and that the cycle between the Jizodo
and Kamiizumi formations is correlative to the Yabu
Formation of MIS 9. Hk-TP is known as a tephra bed
indicating MIS 4 (66.0 ± 5.5 ka: Aoki et al. 2008) and isintercalated at the base of the surface soil overlying thefluvial terrace deposits in the shallowest part of GS-UR-1.
Therefore, the depositional cycles of marine beds below
the fluvial terrace deposits seem to correlate with theKioroshi Formation of MIS 5e.
Based on the tephra beds described above and comparing them with the stratigraphy in the stratotype of theKajita et al. Progress in Earth and Planetary Science(2022) 9:40

Page 5 of 13

Shimosa Group, the Jizodo (deposited in MIS 11), Yabu
(MIS 9), Kamiizumi (MIS 7e), and Kioroshi (MIS 5e) formations were identified in the core GS-UR-1. Of these,
the Yabu, Kamiizumi, and Kioroshi formations can bedivided into lower and upper parts, respectively, with bay
ravinement surfaces. While the lower parts are composed
mainly of fluvial gravels and mud containing plant rootlets, the upper parts consist of inner-bay sediments with
abundant marine microfossils. Such facies stacking patterns suggest a rising sea level and transgression during
each interglacial period.
Benthic and planktic foraminiferal assemblages werealso analysed for core GS-UR-1 (Kaneko et al. 2018).
In that study, a maximum of 20 g sediment was sampled from 98 levels covering almost the entire spanof Jizodo, Yabu, Kamiizumi, and Kioroshi formations.
The sediments were disaggregated by boiling and thenwashed with a sieve with a mesh size of 0.074 mm. For
specular examination, the residue was divided so thatthe foraminifera population reached 200, and individuals larger than 0.125 mm were selected for identification. Although a few foraminifers were detected fromthe lower part of the Kioroshi Formation and none fromthe lower parts of the Kamiizumi or Yabu formations,the marine bed above the bay ravinement surface of eachformation yielded enough benthic foraminiferal fossils
for palaeoenvironmental analysis, whereas the numberof planktic foraminifera was less than 20 individuals/g
at maximum, probably due to the shallow inner-bay
environments.

internal diameter 5% phenyl-dimethylpolysiloxane
liquid phase) and an Instant Connect Programmable
Temperature Vaporizing Injector (Thermo Fisher Scientific). Helium was used as the carrier gas, and thecolumn flow rate was 36 cm ­s−1. The oven temperature
was programmed with an initial temperature of 40 °C(held for 2 min), which was increased at 30 °C ­min−1
to 120 °C and then at 6 °C ­min−1 to 320 °C (held for
20 min). The samples were dissolved in 50 µL of hexane, of which 1 µL was injected. The detection limit
of LCAs was 0.8 ng, which was estimated by repeatedinjection of the external standard of 2-nonadecanone.
The samples in which LCAs were detected were thenquantified using an Agilent Technologies (Santa Clara)
model 6890A GC with a flame ionisation detector (FID)
using mid-polar VF-200 ms fused silica columns (J&W
Scientific, 60 m/0.25 mm internal diameter, trifluoropropylmethylsiloxane lipid phase), which exhibited
adequate LCA separation (Longo et al. 2013). Hydrogen was used as the carrier gas, and the column flowrate was maintained at 36 cm ­s−1. The oven temperature was then programmed with an initial temperature of 60 °C (held for 1 min), which was increased at
20° C ­min−1 to 250 °C (held for 48 min), and then at
20 °C ­min−1 to 310 °C (held for 15 min). The samples
were dissolved in 10–50 µL of hexane, of which 3 µL
was injected. The detection limit of LCAs was 1.4 ng,
which was estimated by the repeated injection of theexternal standard of 2-nonadecanone.

3.2 Organic geochemical analysis

3.3 Identification of coccolithophores

In this study, we obtained silty to sandy mud samples from stratigraphic levels similar to those of theforaminiferal analysis (Kaneko et al. 2018) and carriedout an organic geochemical analysis following the procedures of Ohkouchi et al. (2005). Approximately 6 gof the dried sediment were crushed into a fine powder, and lipids were extracted by sonification using amixed solvent of dichloromethane/methanol (70:30,
v/v). The lipids were saponified with 0.5 M KOH in
MeOH. The saponified samples were then extractedwith n-hexane to obtain the neutral components. The
neutral lipids were separated into four sub-fractions
by silica gel column chromatography. The N-1 fraction(hydrocarbons) and N-2 fraction (ketones, esters, andaldehydes) were extracted using a solvent mixture ofn-hexane and dichloromethane. For the identificationof LCAs by gas chromatography (GC), the N-2 fraction
was introduced into an Agilent Technologies (Santa
Clara, CA) model 7890A gas chromatograph connected
to a mass-selective detector with a non-polar VF-5 ms
fused silica column (J&W Scientific, 30 m/0.25 mm

To detect Gephyrocapsa spp., which is an ocean-dwelling
LCA producer, sandy mud samples collected from eachof the Jizodo, Yabu, Kamiizumi, and Kioroshi formations were suspended in tap water by gentle ultrasonication and then collected on a membrane filter with a poresize of 0.45 µm (HAWP04700, Millipore); subsequently,
the samples were dried for 12 h in a desiccator. The filters (approximately 5 × 5 mm) containing the dried samples were mounted onto the stub of a scanning electron
microscope (SEM) (JSM-6390LV, JEOL) coated withgold and gold–palladium using an E-1020 sputter coater(Hitachi High-Tech) for further observation.

4 Results
GC-mass spectrometry (MS) analysis showed that LCAs
were preserved in almost all the marine strata where
foraminiferal shells were found, whereas they were notdetected in strata without foraminiferal shells. In most
samples with LCAs, major components ­(C37–C39 unsaturated methyl and ethyl ketones with 2–3 double bonds)′
were quantified from GC chromatograms and then UK37

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

values (defined as = ­[C37:2Me]/[C37:2Me] + ­[C37:3Me],
where ­[C37:2Me] and ­[C37:3Me] represent the concentrations of di-unsaturated and tri-unsaturated C­ 37 methyl
ketones, respectively) were obtained (Fig. 3, Additional′
file 1: Table S1). However, in some cases, reliable UK
37values could not be obtained because of the small peakintensities or the co-elution of other substances on the
GC chromatogram.
The SEM images of each marine strata showed thatthe stratigraphic levels with high LCA concentrations
contained Gephyrocapsa coccoliths (Fig. 4). Gephyrocapsa coccoliths (4.0–5.5 µm long) with a bridge at ahigh angle to long axis were assigned as G. oceanica following the biometric subdivision of Young et al. (2003).
This species was detected in the Yabu (MIS 9), Kamiizumi (MIS 7e), and Kioroshi (MIS 5e) formations. Small(< 3 µm) placolith specimens from the Kioroshi Formation included gephyrocapsids, which lacked a bridge(probably assigned as G. huxleyi), and Gephyrocapsa sp.
1 (Fig. 4). Medium-sized (3.0–4.0 µm long) Gephyrocapsa coccoliths detected from the Yabu Formation witha bridge at a low angle to the long axis were assigned asGephyrocapsa sp. 2. Further, Gephyrocapsa sp. 1 and 2
resembled G. ericsonii and G. muellerae, respectively, butthese morphotypes were not assigned as extant species
based on our sporadic morphometric data, considering
their complicated phylogenetic relation in the Late Pleistocene (Bendif et al. 2019). In the Jizodo Formation (MIS11), coccoliths were dissolved, but coccoliths of Gephyrocapsa spp. with bridges were detected.

5 Discussion′

5.1 Assessment of the UK37‑SST

In this study, we showed for the first time that LCAs arepreserved in the marine strata of the Shimosa Group.
′
UK
37-SST is a useful tool for reconstructing quantitative
palaeotemperatures in the coastal shallow sea because
Gephyrocapsa spp., which specifically synthesises LCAs
in marine settings, reproduce even in coastal and inland
bay environments (e.g. Kawahata et al. 2009; Kajita et al.
2018). In low salinity seas, LCAs have been potentiallysynthesised by other Isochrysidaceae haptophytes living
in brackish water that have characteristics different fromthose of Gephyrocapsa spp. (e.g. Salacup et al. 2019; Kaiser et al. 2019). Based on field and culture studies, mostof these are characterised by the abundant synthesis of­C37:4Me and extremely low C­ 38:2Me and C­ 38:3Me (Nakamura et al. 2014; Araie et al. 2018; Plancq et al. 2019;
Zheng et al. 2019; Kajita et al. 2020a; Huang et al. 2021;′
Yao et al. 2022). In all samples where UK
37 was calculated
in this study, no distinct peak of ­C37:4Me was detected,
and ­C38 alkenones with a methyl group were detected(Fig. 3, Additional file 1: Table S1). Gephyrocapsa

Page 6 of 13

coccoliths were detected in all formations in the ShimosaGroup in this study (Fig. 4), and these have also been
detected in the present-day Tokyo Bay (Ogura and Sato
2001). Therefore, LCAs in the marine strata of the Shimosa Group are likely to be derived mostly from Gephyrocapsa spp.
Palaeo-SSTs of only samples with good chromatograms′
were calculated from UK
37 based on the culture experiments of G. oceanica, which was isolated from the inner
bay of Japan (Sawada et al. 1996), using the following
conversion formula:′

SST(◦ C) = (UK37 + 0.204)/0.044
As the evolutionary characteristics of extant Gephyrocapsa spp. after 600 ka are complex (Bendif et al.
2019), the following global core-top calibration formula,which is empirically applicable to Quaternary sedimentbased on comparisons with data from other SST proxies(McClymont et al. 2005), was also used to calculate palaeo-SSTs (Müller et al. 1998):′

SST(◦ C) = (UK37 + 0.044)/0.033′

In the present-day Tokyo Bay, the UK
37-SST of the surface sediment is approximately 2 °C higher than themeasured annual mean SST (Kajita et al. 2020b). There′
fore, we discuss that the UK
37-SSTs recovered in this study
may reflect the temperature range from annual mean tosummer temperatures of Palaeo-Tokyo Bays.
It is expected that the LCAs have been well-preserved
because of the small degeneracy of the Shimosa Group,
meaning it has not been subjected to strong compaction
or diagenesis since the time of deposition (Nakazawa
and Nakazato 2007). Well-preserved LCAs have also
been detected in the underlying Kazusa Group, which

Fig. 3 Partial GC chromatogram of LCAs detected from the core
GS-UR-1. The sample depth was 99.38–99.40 m, corresponding to the
Jizodo Formation

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

Page 7 of 13

Fig. 4 SEM images of Gephyrocapsa spp. obtained from core GS-UR-1. a G. oceanica and Gephyrocapsa sp. 1 obtained from a sample collected
at a depth of 29.20–29.22 m in the Kioroshi Formation. b G. oceanica obtained from a sample collected at a depth of 52.78–52.80 m in theKamiizumi Formation. c Gephyrocapsa sp. 2 obtained from a sample collected at a depth of 77.25–77.27 m, corresponding to the Yabu Formation. dGephyrocapsa gen et sp. indet obtained from a sample collected at a depth of 101.7–101.9 m in the Jizodo Formation

has experienced a deeper burial depth than the ShimosaGroup (Kajita et al. 2021). In the following sections, we
discuss the palaeotemperature variations during eachinterglacial period, especially in relation to foraminiferal
production proposed by Kaneko et al. (2018).

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

5.2 Comparison with the foraminifer assemblages

The stratigraphic levels, at which LCAs were detected,
are almost the same as those having a high relative
abundance ratio of planktonic foraminifera to benthic
foraminifera (P/T ratio) (Kaneko et al. 2018). Both thenumber of planktonic foraminifera per sediment weightand P/T ratio are positively correlated with distancefrom the shoreline (Gibson 1989). Therefore, when thetransgressions in the Palaeo-Tokyo Bays were sufficiently
advanced, LCA producers were dominant at the core site
(Fig. 5). Although benthic foraminiferal assemblages canbe used as indicators of the marine environment in Palaeo-Tokyo Bay, the corresponding information obtained
from these assemblages is limited as it is qualitative′(Kaneko et al. 2018). Here, we compare quantitative UK
37-SSTs with the benthic foraminiferal assemblages for the
strata in which the total number of benthic foraminifera
reached 200 individuals, which is a common requirement for environmental change analysis (Fig. 5). We
focused on the production of species that are relatively
abundant in the core, that is, Ammonia japonica, Pseudorotalia gaimardii (Rotalinoides gaimardi), Buccellafrigida, and Elphidium clavatum. Many of these species
can also be found in present-day Tokyo Bay (Kosugi et al.
1991). Of them, A. japonica and P. gaimardii are found ina wide range of areas along the coast of Japan but indicate a relatively warm water environment, including thatof the Kuroshio Current (Hasegawa 1993). In contrast,
B. frigida and E. clavatum, which are abundant in subarctic neritic faces under the influence of Oyashio Current water (Ishiwada 1964; Hasegawa 1993), suggest a
relatively colder environment. The benthic foraminiferal
assemblage is influenced not only by water temperature
but also by the nutrient and redox environment of thesea floor (Murray 2001); however, it is the rare proxy thatprovides information on continuous marine environmental change from the Shimosa Group. These fluctuations′
broadly support the UK
37-SST changes (Fig. 6); therefore,K′
we believe that U37-SSTs in the Shimosa Group are robust
and provide quantitative palaeotemperatures which may
be related to water mass structures between the Kuroshio
and Oyashio currents.
5.3 Interglacial environments of (Palaeo‑) Tokyo Bays

The examined samples were obtained from the marine
strata formed during the sea-level highstands of MIS
5e, 7e, 9, and 11. Assuming that the maximum sea-level
rise in the Palaeo-Tokyo Bay could be linked to global ice
sheet volume fluctuations, the LCA-based palaeotemperatures can be interpreted as reflecting SSTs aroundthe peak of each interglacial period. Within the marine
strata of the Jizodo Formation, the key tephra bed of
TE-5a accumulated during or immediately after the peak

Page 8 of 13

of MIS 11 (Kameo et al. 2006; Tsukamoto et al. 2007; Itoand Danišík, 2020) can be recognised above the stratum level where LCAs are detected, which supports ourinterpretation. As for the Kioroshi Formation, the stratigraphic level near the bay ravinement surface is considered to correspond to the sea-level highstand of MIS 5e(Nakazawa et al. 2006) and abundant LCAs are detected.
The lower part below the bay ravinement surface, withpoor preservation of LCAs and foraminifera, seems tohave been formed in a restricted inner-bay environment
as incised-valley fills where the salinity was too low for
oceanic plankton to thrive (Nakazawa et al. 2006).
′
UK
37-SSTs in each formation generally showed decreasing trends towards the upper section, which might indicate the SST decrease during and after each sea-levelhighstand. Although data were not available for the lower
part of the Jizodo Formation, which was out of the core′
GS-UR-1, UK
37-SSTs suggested that the Palaeo-Tokyo Baysin each interglacial period seemed to reach similar SSTs
around their sea-level highstand. These temperatures′are 2–3 ℃ higher than the UK
37-SSTs of the pre-industrial
level of Tokyo Bay recovered from the sediment core
KT12-06-2B (Kajita et al. 2020b) and possibly equivalent
to or warmer than the values of the Holocene thermal
maximum (5–7 ka), which was previously estimated tobe approximately 2 ℃ higher than that of the pre-industrial level (Matsushima and Ohshima 1974; Matsushima1979). High temperatures in MIS 5e compared to thepresent level have also been recorded in several cores(MD01-2421, MR97-04–1, MR99-04–2, MR00-05–2,
MR02-03–2) collected from the Kuroshio–Oyashio mixing zone (Yamamoto et al. 2004; Koizumi and Yamamoto 2010), the core from site U1429 in the East China
Sea under the influence of the branched Kuroshio Current (Lee et al. 2021), and the core from site C9001 off
the northern Honshu coastal region under the influenceof the Oyashio Current (Phillips and Harwood 2017). In
the high latitudes of the Northern Hemisphere, not onlyin the Pacific Ocean but also globally, 1–2 ℃ warmer
SSTs than the pre-industrial level have been recorded forthe peak of MIS 5e, which are considered to have beencaused by high summer insolation and positive feedback
related to ice distributions (Hoffman et al. 2017; Thomas
et al. 2020; Turney et al. 2020). Accordingly, we consider
that the north–south temperature gradient along thecoast of Japan formed by the Kuroshio–Oyashio interfrontal zone should have been shifted more to the norththan it is today, which causes the Japanese coastal region
to be generally warm. Our results suggest that MIS 9
seems to be the warmest interglacial since the mid-Brunhes event. These tendencies are comparable to the temperature records from cores U1429 and C9001 (Phillips
and Harwood 2017; Lee et al. 2021), the ­CO2 record inKajita et al. Progress in Earth and Planetary Science′(2022) 9:40

Page 9 of 13

Fig. 5 Results of LCA concentration and UK37-SST. The stratigraphic horizons examined in this study are shown in the left column with the columnar
section of core GS-UR-1 described in Nakazawa and Nakazato (2005). a–c Variations in the total number of benthic and planktic foraminifera′
along with their relative abundance (P/T ratio) (Kaneko et al. 2018). d–e Variations in the LCA concentrations and UK37-SSTs shown in this study.
The white dots represent the samples in which LCAs were identified by GC/MS analysis, but clearly separated peaks could not be obtained by the
GC chromatographKajita et al. Progress in Earth and Planetary Science(2022) 9:40

Page 10 of 13′

Fig. 6 Variations of UK37-SST and the abundance of benthic foraminifer in the present-day Tokyo Bay and Palaeo-Tokyo Bays. The left and right axes
show the calculation results after performing culture calibration (Sawada et al. 1996) and global core-top calibration (Müller et al. 1998), respectively.
′a Variation of UK37-SSTs in Tokyo Bay over the past 4200 years (late of MIS 1) recovered from the sediment core KT12-06-2B (Kajita et al. 2020b). The
11 points’ running average (black line) with standard error ranges (grey lines) is presented. The pre-industrial level obtained by averaging the values
from 1850 to 1950 CE is shown by the red dotted line. The benthic foraminiferal assemblage in the surface sediment is at almost the same location′
as the site of the KT12-06-2B core (K5 site in Kosugi et al. 1991). b–e Variations of UK37-SSTs (this study) and benthic foraminiferal abundances in
Palaeo-Tokyo Bays (Kaneko et al. 2018)

the Antarctic ice core (Uemura et al. 2018), and climate
modelling results of past interglacial periods (Yin andBerger 2010). Therefore, we consider that interglacial SST
variations in the Kuroshio–Oyashio boundary region
including the Palaeo-Tokyo Bays have been linked to
global climate changes via shifts in oceanic fronts.

when quantitatively comparing palaeorecords between
different sites and periods (e.g. Tarasov et al. 2011).
′
Compared to the pollen-based indices, UK
37-SST has theadvantage that it can show similar variations in a wide′
range of contemporaneous strata. Consequently, UK
37-SST
can be a new tool for elucidating the stratigraphy of the
Shimosa Group and for extracting palaeoenvironmental
information.

′

5.4 
UK37‑SSTs for stratigraphy of the Shimosa Group′The UK
37-SSTs revealed in this study provides useful infor-

mation not only for palaeoclimatology but also for stratigraphic studies in the Shimosa Group, which is important
for revealing the subsurface structure of the Kanto Plain,
where the capital of Japan is located (Nakazawa et al.
2017). Because the sequences of the Shimosa Group are
not always rich in interbedded key tephra beds, information on palaeoenvironmental changes mainly basedon pollen assemblages has been used to estimate stratigraphic correlations between cores and outcrops in otherregions (e.g. Nakazawa et al. 2006, 2017). However, pollen assemblages which have been preserved in coastal
sediments do not always accurately reflect the local climate of the catchment area because of the wide variety
of sedimentary processes involved (e.g. Igarashi et al.
2015). In addition, the quality of pollen-based palaeoenvironmental indices strongly depends on the current
reference pollen dataset; therefore, care should be taken

6 Conclusions
We detected LCAs in the marine strata of the ShimosaGroup and succeeded in reconstructing the SSTs of
Palaeo-Tokyo Bays formed during the past interglacial′
periods after the mid-Brunhes event. The UK
37 fluctuation in each interglacial formation was consistent
with the water mass structure estimated from previously published benthic foraminiferal assemblages andseemed to indicate SST variations during those peri′ods. UK
37-SSTs in the Palaeo-Tokyo Bays around thepeak of MIS 5e, 7e, 9, and 11 were estimated to be 2–3℃ higher than the pre-industrial levels of Tokyo Bay
with the highest temperature recorded in MIS 9. These
characteristics were similar to the trends shown by previous studies of the surrounding ocean, suggesting that′
the UK
37-SST recorded in the Shimosa Group reflects thetemperature variations associated with the shifts in the

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

northern limit of the Kuroshio Current during the pastinterglacial periods. This study demonstrates that LCAs
can act as novel indicators that are useful for palaeoceanographic and stratigraphic studies in the ShimosaGroup.
Abbreviations
IPCC: Intergovernmental Panel on Climate Change; LCAs: Long-chain alkenones; MIS: Marine Isotope Stage; SST: Sea surface temperature.

Supplementary Information
The online version contains supplementary material available at https://​doi.​
org/​10.​1186/​s40645-​022-​00499-y.
Additional file 1. Supplementary Table 1. Abundance of LCAs in thecore GS-UR-1.
Acknowledgements
We would like to thank the researchers at Japan Agency for Marine-Earth Science and Technology (Y. Takano, H. Suga, N.O. Ogawa, Y. Isaji, Y. Sasaki, and M.
Noguchi) for their helpful advice and in organising the analytical devices. We
also thank Y. Nishikura and K. Sakata who helped us with the laboratory work.
Author contributions
HK proposed the research topic and designed the study. N.T. drilled the coreand performed stratigraphic study. M.U. performed SEM analysis and identified coccoliths. HK carried out the geochemical experiments and wrote themanuscript. N.O., N.H., and HK organised the analytical devices and helpedwith the interpretations. M.S. assisted with the laboratory analysis. All authors
have read and approved the final manuscript.
Funding
This work was supported by Japan Society for the Promotion of Science (JSPS)
KAKENHI (Grant Numbers: 18J21788, 20H01981, and 21J00133) and the publication support program of National Institute of Polar Research (NIPR).
Availability of data and materials
The datasets supporting the conclusions of this article are included within thearticle and the additional file.

Declarations
Competing interests
The authors declare that they have no competing interests.
Author details
1
National Institute of Polar Research, Research Organization of Informationand Systems, 10‑3 Midori‑tyo, Tachikawa, Tokyo 190‑8518, Japan. 2 Geological Survey of Japan, National Institute of Advanced Industrial Scienceand Technology, 1‑1‑1 Higashi, Tsukuba, Ibaraki 305‑8567, Japan. 3 Japan
Agency for Marine-Earth Science and Technology, 2‑15 Natsushima, Yokosuka,
Kanagawa 237‑0061, Japan. 4 Atmosphere and Ocean Research Institute, The
University of Tokyo, 5‑1‑5 Kashiwanoha, Kashiwa, Chiba 277‑8564, Japan.
Received: 5 September 2021 Accepted: 4 July 2022

References
Aoki K, Irino T, Oba T (2008) Late Pleistocene tephrostratigraphy of the sediment core MD01-2421 collected off the Kashima coast, Japan. Quat Res(Daiyonki-Kenkyu) 47(6):391–407
Araie H, Nakamura H, Toney JL, Haig HA, Plancq J, Shiratori T, Leavitt PR, Seki O,
Ishida K, Sawada K, Suzuki I, Shiraiwa Y (2018) Novel alkenone-producing

Page 11 of 13

strains of genus Isochrysis (Haptophyta) isolated from Canadian saline
lakes show temperature sensitivity of alkenones and alkenoates. Org
Geochem 121:89–103
Bendif EM, Nevado B, Wong ELY, Hagino K, Probert I, Young JR, Rickaby REM,
Filatov DA (2019) Repeated species radiations in the recent evolutionof the key marine phytoplankton lineage Gephyrocapsa. Nat Commun
10:4234
Clemens SC, Holbourn A, Kubota Y, Lee KE, Liu Z, Chen G, Nelson A, Fox-Kemper B (2018) Precession-band variance missing from East Asian monsoon
runoff. Nat Commun 9(1):1–12
Droxler AW, Alley RB, Howard WR, Poore RZ, Burckle LH (2003) Unique andexceptionally long interglacial Marine Isotope Stage 11: Window into
Earth warm future climate. Geophys Monogr Ser 137:1–14
Geological Survey of Japan, AIST (ed.) (2020) Seamless digital geological mapof Japan 1: 200,000. June 9, 2020 version. Geological Survey of Japan,
National Institute of Advanced Industrial Science and Technology
Gibson TG (1989) Planktonic benthonic foraminiferal ratios: Modern patterns
and Tertiary applicability. Mar Micropaleontol 15:29–52
Haneda Y, Okada M, Kubota Y, Suganuma Y (2020) Millennial-scale hydrographic changes in the northwestern Pacific during marine isotope stage
19: Teleconnections with ice melt in the North Atlantic. Earth Planet Sci
Lett 531:115936
Hasegawa S (1993) Distribution of recent benthic foraminifers as an indicator of thermal conditions of the seas around the Japanese Islands: An
approach to reconstruction of Cenozoic oceanic condition. Fossils
55:17–33
Hoffman JS, Clark PU, Parnell AC, He F (2017) Regional and global sea-surface
temperatures during the last interglaciation. Science 355(6322):276–279
Huang Y, Zheng Y, Heng P, Giosan L, Coolen MJ (2021) Black Sea paleosalinity
evolution since the last deglaciation reconstructed from alkenoneinferred Isochrysidales diversity. Earth Planet Sci Lett 564:116881
Igarashi Y, Yamamoto M, Noda A, Ikehara K, Katayama H (2015) Deposition
pattern and sources of palynomorphs on the continental margin off Hokkaido Island, northwest Pacific. Mar Geol 368:58–65
Ishiwada Y (1964) Benthonic foraminifera off the Pacific coast of Japan referred
to biostratigraphy of the Kazusa Group. Rep Geol Sur Japan 205:1–45
Ito H, Danišík M (2020) Dating late Quaternary events by the combined U-Pb
LA-ICP-MS and (U-Th)/He dating of zircon: a case study on Omachi
Tephra suite (central Japan). Terra Nova 32(2):134–140
Kaiser J, Wang KJ, Rott D, Li G, Zheng Y, Amaral-Zettler L, Arz HW, Huang Y(2019) Changes in long chain alkenone distributions and Isochrysidales
group along the Baltic Sea salinity gradient. Org Geochem 127:92–103
Kajita H, Kawahata H, Wang K, Zheng H, Yang S, Ohkouchi N, Utsunomiya M,
Zhou B, Zheng B (2018) Extraordinary cold episodes during the midHolocene in the Yangtze delta: Interruption of the earliest rice cultivating
civilization. Quat Sci Rev 201:418–428
Kajita H, Nakamura H, Ohkouchi N, Harada N, Sato M, Tokioka S, Kawahata
H (2020a) Genomic and geochemical identification of the long-chain
alkenone producers in the estuarine Lake Takahoko, Japan: Implications
for temperature reconstructions. Org Geochem 142:103980
Kajita H, Harada N, Yokoyama Y, Sato M, Ogawa N, Miyairi Y, Sawada C, Suzuki
A, Kawahata H (2020b) High time-resolution alkenone paleotemperature
variations in Tokyo Bay during the Meghalayan: Implications for cold
climates and social unrest in Japan. Quat Sci Rev 230:106160
Kajita H, Maeda A, Utsunomiya M, Yoshimura T, Ohkouchi N, Suzuki A, Kawahata H (2021) Biomarkers in the rock outcrop of the Kazusa Group reveal
palaeoenvironments of the Kuroshio region. Commun Earth Environ
2(1):1–9
Kameo K, Okada M, El-Masry M, Hisamitsu T, Saito S, Nakazato H, Ohkouchi N,
Ikehara M, Yasuda H, Kitazato H, Taira A (2006) Age model, physical properties and paleoceanographic implications of the middle Pleistocene
core sediments in the Choshi area, central Japan. Isl Arc 15(3):366–377
Kaneko M, Ishikawa H, Nomura M, Nakazawa T (2018) Fossil foraminiferal
assemblages from the Pleistocene Shimosa Group in core GS-UR-1,
Urawa, Saitama City, central Japan. Bull Geol Surv Japan 69(4):211–232
Kariya C, Hyodo M, Tanigawa K, Sato H (2010) Sea-level variation during MIS
11 constrained by stepwise Osaka Bay extensions and its relation withclimatic evolution. Quat Sci Rev 29(15–16):1863–1879
Kawahata H, Yamamoto H, Ohkushi KI, Yokoyama Y, Kimoto K, Ohshima H,
Matsuzaki H (2009) Changes of environments and human activity at the

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

Sannai-Maruyama ruins in Japan during the mid-Holocene Hypsithermal
climatic interval. Quat Sci Rev 28(9–10):964–974
Kida S, Mitsudera H, Aoki S, Guo X, Ito SI, Kobashi F, Komori N, Kubokawa A,
Miyama T, Morie R, Nakamura H, Nakamura T, Nakano H, Nishigaki H,
Nonaka M, Sasaki H, Sasaki YN, Suga T, Sugimoto S, Taguchi B, Takaya
K, Tozuka T, Tsujimoto H, Usui N (2016) Oceanic fronts and jets around
Japan: a review. In: Nakamura H, Isobe A, Minobe S, Mitsudera H, Nonaka
M, Suga T (eds) “Hot Spots” in the Climate System. Springer, Tokyo, pp
1–30
Kitaba I, Hyodo M, Katoh S, Dettman DL, Sato H (2013) Midlatitude coolingcaused by geomagnetic field minimum during polarity reversal. Proc Natl
Acad Sci 110(4):1215–1220
Koizumi I, Yamamoto H (2010) Paleoceanographic evolution of North Pacificsurface water off Japan during the past 150,000 years. Mar Micropaleontol 74(3–4):108–118
Kosugi M, Kataoka H, Hasegawa S (1991) Classification of foraminifer communities as indicators of environments in an inner bay and its application toreconstruction of paleoenvironments. Fossils 50:37–55
Lang N, Wolff EW (2011) Interglacial and glacial variability from the last 800 ka
in marine, ice and terrestrial archives. Clim past 7(2):361–380
Lee KE, Clemens SC, Kubota Y, Timmermann A, Holbourn A, Yeh SW, Bae SW, Ko
TW (2021) Roles of insolation forcing and C­ O2 forcing on Late Pleistocene
seasonal sea surface temperatures. Nat Commun 12(1):1–13
Lisiecki LE, Raymo ME (2005) A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20(1):PA2003
Longo WM, Dillon JT, Tarozo R, Salacup JM, Huang Y (2013) Unprecedented
separation of long chain alkenones from gas chromatography with apoly (trifluoropropylmethylsiloxane) stationary phase. Org Geochem
65:94–102
Longo WM, Huang Y, Yao Y, Zhao J, Giblin AE, Wang X, Zech R, Haberzettl T,
Jardillier L, Toney J, Liu Z, Krivonogov S, Kolpakova M, Chu G, D’Andrea WJ,
Harada N, Nagashima K, Sato M, Yonenobu H, Yamada K, Gotanda K, Shinozuka Y (2018) Widespread occurrence of distinct alkenones from GroupI haptophytes in freshwater lakes: Implications for paleotemperature andpaleoenvironmental reconstructions. Earth Planet Sci Lett 492:239–250
Lüthi D, Le Floch M, Bereiter B, Blunier T, Barnola JM, Siegenthaler U, Raynaud
D, Jouzel J, Fischer H, Kawamura K, Stocker TF (2008) High-resolution carbon dioxide concentration record 650,000–800,000 years before present.
Nature 453(7193):379–382
Marlowe IT, Brassell SC, Eglinton G, Green JC (1984) Long chain unsaturated
ketones and esters in living algae and marine sediments. Org Geochem
6:135–141
Masuda F (2007) Paleoclimate of Interglacial Marine Isotope Stage 11 (MIS
11) from Strata in the Japanese Islands. Quat Res (Daiyonki-Kenkyu)
46(3):235–240
Matsushima Y, Ohshima K (1974) Littoral Molluscan Fauna of the Holocene Climatic Optimum (5,000–6,000 y. BP) in Japan. Quat Res (Daiyonki-Kenkyu)
13(3):135–159
Matsushima Y (1979) Littoral molluscan assemblages during the post-glacial
Jomon transgression in the southern Kanto, Japan. Quat Res (DaiyonkiKenkyu) 17:243–265
McClymont EL, Rosell-Melé A, Giraudeau J, Pierre C, Lloyd JM (2005) Alkenone
and coccolith records of the mid-Pleistocene in the south-east Atlantic:
implications for the ­UK’37 index and South African climate. Quat Sci Rev
24:1559–1572
Melles M, Brigham-Grette J, Minyuk PS, Nowaczyk NR, Wennrich V, DeConto
RM, Anderson PM, Andreev AA, Coletti A, Cook TL, Haltia-Hovi E, Kukkonen M, Lozhkin AV, Rosén P, Tarasov P, Vogel H, Wagner B (2012) 28
million years of Arctic climate change from Lake El’gygytgyn, NE Russia.
Science 337(6092):315–320
Milker Y, Rachmayani R, Weinkauf MFG, Prange M, Raitzsch M, Schulz M, Kučera
M (2013) Global and regional sea surface temperature trends during
Marine Isotope Stage 11. Clim past 9(5):2231–2252
Müller PJ, Kirst G, Ruhland G, Von Storch I, Rosell-Melé A (1998) Calibration of
the alkenone paleotemperature index U37K′ based on core-tops fromthe eastern South Atlantic and the global ocean (60 N–60 S). Geochim
Cosmochim Acta 62(10):757–1772
Murray JW (2001) The niche of benthic foraminifera, critical thresholds, andproxies. Mar Micropaleontol 41(1–2):1–7

Page 12 of 13

Nagashima K, Tada R, Toyoda S (2013) Westerly jet-East Asian summer
monsoon connection during the Holocene. Geochem Geophys Geosyst
14(12):5041–5053
Nakagawa T, Okuda M, Yonenobu H, Miyoshi N, Fujiki T, Gotanda K, Tarasov PE,
Morita Y, Takemura K, Horie S (2008) Regulation of the monsoon climate
by two different orbital rhythms and forcing mechanisms. Geology
36(6):491–494
Nakamura H, Sawada K, Araie H, Suzuki I, Shiraiwa Y (2014) Long chain alkenes,
alkenones and alkenoates produced by the haptophyte alga Chrysotila
lamellosa CCMP1307 isolated from a salt marsh. Org Geochem 66:90–97
Nakazato H, Sato H (2001) Chronology of the Shimosa Group and movementof the “Kashima” uplift zone, central Japan. Quat Res (Daiyonki-Kenkyu)
40(3):251–257
Nakazawa T, Nakaszto H (2005) Depositional cycles and tephrochronology ofPleistocene Shimosa Group in central Kanto Plain, central Japan. J Geol
Soc Jpn 111(2):87–93
Nakazawa T, Nakazato H (2007) Pleistocene Shimosa Group in central part of
Kanto Plain, central Japan: overview. Chishitsu News 634:50–59
Nakazawa T, Nakashima R, Ueki T, Tanabe S, Oshima H, Horiuchi S (2006)
Sequence stratigraphy of the Pleistocene Kioroshi Formation, ShimosaGroup beneath the Omiya Upland, central Kanto Plain, central Japan. J
Geol Soc Jpn 112(5):349–368
Nakazawa T, Nakazato H, Oshima H, Horiuchi S (2009) Boundary between the
Kazusa and Shimosa groups beneath the central Kanto Plain: Reconstruction of MIS 12 in the GS-KS-1 core (Koshigaya, Saitama Prefecture, central
Japan). J Geol Soc Jpn 115(2):49–63
Nakazawa T, Sakata K, Hongo M, Nakazato H (2017) Transition from incisedvalley to barrier island systems during MIS 5e in the northern Chiba area,
Kanto Plain, central Japan. Quat Int 456:85–101
Nakazawa T, Tanabe S (2011) Geology of the Noda District. Quadrangle Series
1:50,000, Geol Surv Japan
Naya T, Nakayama T, Suzuki T, Sakata K, Nakazawa T (2020) Stratigraphy of the
Pleistocene Tokyo Formation in the Kita-ku Central Park (Chuo-Koen) corein Kita-ku, Tokyo, central Japan. J Geol Soc Japan 126(10):575–587
Ogura H, Sato M (2001) A Bloom of Gephyrocapsa oceanica Kamptner in Tokyo
Bay in May 1995. J Jpn Soc Water Environ 24(2):115–119
Ohkouchi N, Xu L, Reddy CM, Montluçon D, Eglinton TI (2005) Radiocarbon
dating of alkenones from marine sediments: I. Isolation protocol. Radiocarbon 47(3):401–412
Okuda M, Okazaki H, Sato H (2002) Middle Pleistocene pollen assemblages
and their implications for the Yabu Formation, Boso Peninsula, Central
Japan. Quat Res (Daiyonki-Kenkyu) 41(5):403–412
Otto-Bliesner BL, Rosenbloom N, Stone EJ, McKay NP, Lunt DJ, Brady EC,
Overpeck JT (2013) How warm was the last interglacial? New model–datacomparisons. Philos Trans R Soc A:Math Phys Eng Sci 371(2001):20130097
Phillips MP, Harwood DM (2017) Marine diatom assemblage variation acrossPleistocene glacial-interglacial transitions from Integrated Ocean Drilling
Program Site C9001, Northwest Pacific. Palaeogeogr Palaeoclimatol
Palaeoecol 483:172–187
Plancq J, Couto JM, Ijaz UZ, Leavitt PR, Toney JL (2019) Next-generation
sequencing to identify lacustrine haptophytes in the Canadian Prairies:
significance for temperature proxy applications. J Geophys Res: Biogeosci
124(7):2144–2158
Prahl FG, Muehlhausen LA, Zahnle DL (1988) Further evaluation of long-chain
alkenones as indicators of paleoceanographic conditions. Geochim
Cosmochim Acta 52(9):2303–2310
Richter N, Longo WM, George S, Shipunova A, Huang Y, Amaral-Zettler L (2019)
Phylogenetic diversity in freshwater-dwelling Isochrysidales haptophyteswith implications for alkenone production. Geobiology 17(3):272–280
Sagawa T, Nagahashi Y, Satoguchi Y, Holbourn A, Itaki T, Gallagher SJ, SaavedraPellitero M, Ikehara K, Irino T, Tada R (2018) Integrated tephrostratigraphy
and stable isotope stratigraphy in the Japan Sea and East China Sea using
IODP Sites U1426, U1427, and U1429, Expedition 346 Asian Monsoon.
Prog Earth Planet Sci 5(1):1–24
Salacup JM, Farmer JR, Herbert TD, Prell WL (2019) Alkenone paleothermometry in coastal settings: Evaluating the potential for highly resolved
time series of sea surface temperature. Paleoceanogr Paleoclimatol
34(2):164–181
Sampe T, Xie SP (2010) Large-scale dynamics of the Meiyu-Baiu rainband:
environmental forcing by the westerly jet. J Clim 23(1):113–134

Kajita et al. Progress in Earth and Planetary Science(2022) 9:40

Sawada K, Handa N, Shiraiwa Y, Danbara A, Montani S (1996) Long-chain
alkenones and alkyl alkenoates in the coastal and pelagic sediments of
the northwest North Pacific, with special reference to the reconstructionof Emiliania huxleyi and Gephyrocapsa oceanica ratios. Org Geochem
24(8–9):751–764
Sixth Assessment Report (2021) The Intergovernmental Panel on Climate
Change (IPCC)
Suzuki H (2002) Underground geological structure beneath the Kanto Plain,
Japan. Report of the National Research Institute for Earth Science andDisaster Resilience 63:1–19
Tada R, Murray RW (2016) Preface for the article collection ‘Land–Ocean Linkages under the Influence of the Asian Monsoon.’ Prog Earth Planet Sci
3(1):1–5
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 Jr, Bassetti M, Brace BJ, Clemens SC, da Costa Gurgel MH, Dickens GR, Dunlea
AG, Gallagher SJ, Giosan L, Henderson ACG, Holbourn AE, Kinsley CW,
Lee GS, Lee KE, Lofi J, Lopes CIDD, Saavedra-Pellitero M et al (2018) Highresolution and high-precision correlation of dark and light layers in the
Quaternary hemipelagic sediments of the Japan Sea recovered during
IODP Expedition 346. Progr Earth Planet Sci 5(1):1–10
Tarasov PE, Nakagawa T, Demske D, Österle H, Igarashi Y, Kitagawa J, Mokhova
L, Bazarova V, Okuda M, Gotanda K, Miyoshi N, Fujiki T, Takemura K,
Yonenobu H, Fleck A (2011) Progress in the reconstruction of Quaternary
climate dynamics in the Northwest Pacific: A new modern analoguereference dataset and its application to the 430-kyr pollen record from
Lake Biwa. Earth Sci Rev 108(1–2):64–79
Theroux S, D’Andrea WJ, Toney J, Amaral-Zettler L, Huang Y (2010) Phylogenetic diversity and evolutionary relatedness of alkenone-producing
haptophyte algae in lakes: implications for continental paleotemperaturereconstructions. Earth Planet Sci Lett 300(3–4):311–320
Thomas ZA, Jones RT, Turney CS, Golledge N, Fogwill C, Bradshaw C, Menviel
L, McKay NP, Bird N, Palmer J, Kershaw P, Wilmshurst J, Muscheler R (2020)
Tipping elements and amplified polar warming during the Last Interglacial. Quat Sci Rev 233:106222
Tierney JE, Tingley MP (2018) BAYSPLINE: A new calibration for the alkenone
paleothermometer. Paleoceanogr Paleoclimatol 33(3):281–301
Tokuhashi S, Endo S (1984) Geology of the Anesaki District. Quadrangle Series
1:50,000, Geol Surv Japan
Tokuhashi S, Kondo Y (1989) Sedimentary cycles and environments in the
middle-late Pleistocene Shimosa Group, Boso Peninsula, central Japan. J
Geol Soc Jpn 95(12):933–951
Tsukamoto S, Murray AS, Huot S, Watanuki T, Denby PM, Bøtter-Jensen L (2007)
Luminescence property of volcanic quartz and the use of red isothermal
TL for dating tephras. Radiat Meas 42(2):190–197
Turney CS, Jones RT, McKay NP, Van Sebille E, Thomas ZA, Hillenbrand CD,
Fogwill CJ (2020) A global mean sea surface temperature dataset for theLast Interglacial (129–116 ka) and contribution of thermal expansion tosea level change. Earth Syst Sci Data 12(4):3341–3356
Tzedakis PC, Raynaud D, McManus JF, Berger A, Brovkin V, Kiefer T (2009) Interglacial diversity. Nat Geosci 2(11):751–755
Tzedakis PC, Wolff EW, Skinner LC, Brovkin V, Hodell DA, McManus JF, Raynaud
D (2012) Can we predict the duration of an interglacial? Clim past8(5):1473–1485
Uemura R, Motoyama H, Masson-Delmotte V, Jouzel J, Kawamura K, GotoAzuma K, Fujita S, Kuramoto T, Hirabayashi M, Miyake T, Ohno H, Fujita K,
Abe-Ouchi A, Iizuka Y, Horikawa S, Igarashi M, Suzuki K, Suzuki T, Fujii Y(2018) Asynchrony between Antarctic temperature and ­CO2 associatedwith obliquity over the past 720,000 years. Nat Commun 9(1):1–11
Volkman JK, Eglinton G, Corner EDS, Sargent JR (1980) Novel unsaturated
straight-chain C37–C39 methyl and ethyl ketones in marine sediments
and a coccolithophore Emiliania huxleyi. Phys Chem Earth 12:219–227
Wang KJ, Huang Y, Majaneva M, Belt ST, Liao S, Novak J, Kartzinel TR, Herbert
TD, Richter N, Cabedo-Sanz P (2021) Group 2i Isochrysidales produce
characteristic alkenones reflecting sea ice distribution. Nat Commun
12:15
Yamamoto M, Oba T, Shimamune J, Ueshima T (2004) Orbital‐scale anti‐phasevariation of sea surface temperature in mid‐latitude North Pacific margins
during the last 145,000 years. Geophys Res Lett 31(16)Yao Y, Zhao J, Vachula RS, Liao S, Li G, Pearson EJ, Huang Y (2022) Phylogeny,
alkenone profiles and ecology of Isochrysidales subclades in saline lakes:

Page 13 of 13

implications for paleosalinity and paleotemperature reconstructions.
Geochim Cosmochim Acta 317:472–487
Yin QZ, Berger A (2010) Insolation and ­CO2 contribution to the interglacial
climate before and after the Mid-Brunhes Event. Nat Geosci 3(4):243–246
Young JR, Geisen M, Cros L, Kleijne A, Sprengel C, Probert I, Østergaard JB(2003) A guide to extant coccolithophore taxonomy. J Nannoplank Res
1:1–132
Zheng Y, Heng P, Conte M, Vachula RS, Huang Y (2019) Systematic chemotaxonomic profiling and novel paleotemperature indices based on alkenones
and alkenoates: Potential for disentangling mixed species input. Org
Geochem 128:26–41

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.