Progress in Earth andPlanetary Science

Suganuma et al.
Progress in Earth and Planetary Science(2022) 9:9
https://doi.org/10.1186/s40645-022-00468-5

Open Access

PREFACE

Preface for the article collection“Stratigraphy and paleoclimatic/
paleoenvironmental evolution across the Early–
Middle Pleistocene transition in the Chiba
composite section, Japan, and other reference
sections in East Asia”
Yusuke Suganuma1,2*, Martin J. Head3 and Takuya Sagawa4
Keywords: Early–Middle Pleistocene transition, Marine Isotope Stage (MIS) 19, Matuyama–Brunhes reversal, Global
Boundary Stratotype Section and Point (GSSP), Chiba composite section
The Earth experienced dramatic and progressive changes
in oceanic and atmospheric circulation, ice sheet distributions, and biotic evolution from the Early to Middle
Pleistocene. This interval is now known as the “Early–
Middle Pleistocene transition (EMPT)” (Head and Gibbard 2015; Head 2019). Because East Asia is an importantregion for land–ocean–atmosphere heat and moistureexchange owing to its location at the boundary between
Eurasia and the Pacific Ocean (e.g., Tada and Murray,2016) (Fig. 1), understanding paleoenvironmental change
in this region will provide valuable insights into Earth’s
climate system. Continuous deep-ocean records acrossthis climatic transition are not rare, but constructing
detailed links between atmospheric circulation, terrestrial environmental change, and evolution of the biota
have been hampered by an inevitable scarcity of continuous and expanded sedimentary records from coastal,shallow-marine environments.
The Chiba composite section, including the Chiba
section itself which was recently ratified as the Global*Correspondence: suganuma.yusuke@nipr.ac.jp
1
National Institute of Polar Research, 10‑3 Midori‑cho, Tachikawa, Tokyo
190‑8518, Japan
Full list of author information is available at the end of the article

Boundary Stratotype Section and Point (GSSP) defining the base of the Middle Pleistocene Subseries/Subepoch and Chibanian Stage/Age (Head 2021; Head et al.
2021; Suganuma et al. 2021), is a continuous marine silty
sedimentary record from upper Marine Isotope Stage(MIS) 20 to lower MIS 18, representing one of the most
expanded and chronostratigraphically constrained sections yet documented across the Lower–Middle Pleistocene boundary (e.g., Kazaoka et al. 2015; Suganuma
et al. 2018). This composite section comprises five individual exposures cropping out along a 7.4 km transect, all
securely linked by a detailed framework of tephra beds.
Deposited on the continental slope and receiving substantial organic input from both marine and terrestrial
sources (Balota et al. 2021; Izumi et al. 2021; Suganuma
et al. 2018), it therefore provides a rare opportunity tocapture both terrestrial and marine environmental variability continuously across MIS 19 and hence the Lower–
Middle Pleistocene boundary.
This special issue focuses on sedimentary records fromthe Chiba composite section and its stratigraphic correlation with other reference sections in East Asia andacross the globe. It addresses terrestrial and marine paleoclimatic and paleoenvironmental co-evolution with anemphasis on the midlatitude westerly jet stream, East

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Fig. 1 Schematic representation of the climatic configurations in East Asia, and the Mediterranean and North Atlantic Ocean. Locations of the
Chiba composite section and other important sites discussed in this special issue are shown. Atmospheric systems are abbreviated as follows. SH
Siberian High, AL Aleutian Low, ITCZ intertropicalconvergence zone, AH Azores HighAsian monsoon, North Pacific Gyre, and the interplayof subtropical and subpolar settings across MIS 19 andthrough the Early–Middle Pleistocene transition. We
hope the articles collected in this issue within the Special
Call for Excellent Papers on Hot Topics (SPEPS) series
will stimulate and promote future research on stratigraphy and paleoenvironmental changes in this region.
Detailed comparisons between reference sections in East
Asia and the global record will help further our understanding of Earth’s climate system.
The Chiba composite section, located near the Pacificmargin of the central Japanese archipelago (Fig. 1),
belongs to the Kokumoto Formation of the Kazusa
Group, which is one of the thickest (~ 3000 m) and best
exposed Lower and Middle Pleistocene marine sedimentary successions in the world (e.g., Kazaoka et al. 2015;
Takao et al. 2020). It represents the infill of the Kazusa
fore-arc basin, developed in response to the west–
north–westward subduction of the Pacific plate beneaththe Philippine Sea plate along the Japan and Izu–Bonin
trenches (e.g., Seno and Takano 1989).
The stratigraphy of the Kazusa Group has been evaluated since the 1940s (e.g., Kanehara et al. 1949; Shinada
et al. 1951; Mitsunashi et al. 1961), with more recent
focus shifting to the depositional systems and glacioeustatic sea level changes (e.g., Ito and Katsura 1992; Pickering et al. 1999; Takao et al. 2020). In this issue, Takao
et al. (2020) report a detailed investigation into thedepositional processes responsible for deepwater massive sandstones (DWMSs) occurring in the middle toupper parts of the Kazusa Group. The authors suggestthat these DWMSs represent density flows developed in
response to prograding shelf-margin deltas or fan deltas during the falling and lowstand stages of relative sea
level. These sandstones contrast with the muddy deposits of the Chiba composite section which are interpreted
to have formed in the uppermost part of a transgressive

systems tract (Takao et al. 2020), explaining their suitability for high-resolution paleoceanographic and paleoclimatic studies.
The Matuyama–Brunhes (M–B) paleomagnetic boundary represents a clear and global isochronous marker andhence serves as the primary guide to the Lower–Middle
Pleistocene boundary (Head et al. 2008; Suganuma et al.
2021). A tightly defined M–B paleomagnetic polarity
boundary has been observed throughout the Chiba composite section and adjacent areas (Suganuma et al. 2015,2018; Hyodo et al. 2016; Okada et al. 2017; Haneda et al.
2020a), providing a precise tie point for global stratigraphic correlation. Haneda et al. (2020a) report in thisissue a detailed record of the geomagnetic field reversal
behavior over time. A clear drop observed in paleointensity is supported by the authigenic 10Be/9Be record(Simon et al. 2019). An astronomically estimated M–B
boundary age of 772.9 ± 5.4 ka at the Chiba composite section (Haneda et al. 2020a) is consistent with thatof paleomagnetic records (e.g., Channell et al. 2010,
2020; Channell 2017; Valet et al. 2019) and cosmogenic
nuclide records (Raisbeck et al. 2006; Suganuma et al.
2010; Simon et al. 2018; Valet et al. 2019), around theworld. This age is also consistent with a weighted mean
40
Ar/39Ar age of 773 ± 2 ka from new measurements andthe recalibration of all M–B transitionally magnetizedlava flow sequences (Singer et al. 2019), which facilitatesa robust chronostratigraphic framework for the Chiba
composite section.
In this special issue, Hyodo et al. (2020) report a
detailed paleomagnetic record across the M–B boundaryfrom a loess succession in Lingtai, central Chinese Loess
Plateau (CLP). Loess-paleosol sequences can be excellent
archives of past changes in the geomagnetic field not only
for polarity but also direction and intensity, although
the process leading to magnetization lock-in remains
unclear. Hyodo et al. (2020) have investigated more thanSuganuma et al. Progress in Earth and Planetary Science(2022) 9:9

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100 high-resolution paleomagnetic samples from thesuccession and found millennial-to-sub-centennial-scalepolarity flips around the M–B paleomagnetic boundary.
Although further investigations from adjacent sections in
the CLP, along with other expanded sedimentary sections
and lava sequences, are needed to confirm the natureof these high-speed polarity flips, their documentation
should yield new insights into the physical processes
leading to this geomagnetic reversal and improve global
correlation and age constraints for terrestrial sections.
Other polarity boundaries recorded in and around
the Japanese archipelago are similarly useful for understanding the dynamics of geomagnetic field reversals
and in refining their chronological framework. Konishi and Okada (2020), in this issue, reconstruct a highresolution paleomagnetic record of the lower part of the
Matuyama Chronozone from the Chikura Group in thesouthern part of the Boso Peninsula (Naruse et al. 1951;
Kotake 1988) which contains the Réunion Subchronozone and the lower Olduvai polarity reversal. Althoughthese sections have not been chronologically well constrained, they are thought to be the most expanded
records so far obtained. Thus, the timings and durationsof geomagnetic field variations obtained from the Chikura Group will help understand the general phenomenon of geomagnetic field reversals. Meanwhile, Xuanet al. (2020) present a Pliocene–Pleistocene magnetostratigraphy of deep-sea sediments at Integrated Ocean
Drilling Program (IODP) Expedition 346 Site U1424 in
the Yamato Basin, Japan Sea, based on the transitions ofpolarity chrons and subchrons coupled with a detailed
tephrostratigraphy. The integrated stratigraphy proposed
for Site U1424 offers an excellent chronological framework for both marine and terrestrial Pliocene–Pleistocene sections in the region.
The Chiba composite section has yielded a diverse
array of well-preserved marine and terrestrial microfossils and provides an ultra-high-resolution benthic andplanktonic foraminiferal isotope record that captures
centennial- to millennial-scale paleoceanographic andpaleoclimatic changes from late MIS 20 to early MIS 18(Suganuma et al. 2021). In this issue, Kameo et al. (2020),
Balota et al. (2021), and Itaki et al. (2022) document theassemblage changes of calcareous nannofossils, dinoflagellate cysts, and radiolarians, respectively, to explore
variations in the position of the Subarctic Front between
the subtropical Kuroshio and subarctic Oyashio currents.
Because the Subarctic Front is presently situated just eastof the Boso Peninsula (Qiu 2001), the Chiba composite
section is located at an ideal position to record the past
displacement of the front. Changes in marine microfossil assemblages and indicator taxa along with foraminiferal isotope data reveal millennial-scale fluctuations

superimposed on glacial–interglacial orbital-scale variability, in which the phenomenon is generally coherent
with detailed records from the North Atlantic and Mediterranean region (Haneda et al. 2020b; Head 2021). Basedon the abundant occurrences of a warm-water calcareous
nannofossil and radiolarian species, Kameo et al. (2020)and Itaki et al. (2022) respectively show periodic intensifications of the Kuroshio Current following the end of
MIS 19c and continuing into MIS 18, indicating repeatednorthward shifts of the Subarctic Front. In addition, thedinoflagellate cyst record reveals instability in the Kuroshio Extension system throughout MIS 19c and theabrupt influence of the Kuroshio–Oyashio Interfrontal
Zone in MIS 19b, signaling the first stadial of the latterpart of MIS 19 (Balota et al. 2021). This instability andsimilar rapid shifts are also seen in the cyclic appearanceof cold-water calcareous nannofossil and radiolarian taxa
from MIS 19b to MIS 18 (Kameo et al. 2020; Itaki et al.
2022).
The total organic carbon (TOC) values of the Chiba
composite section also show millennial-scale oscillationsin the latter part of MIS 19a (Izumi et al. 2021). Althoughthe δ13Corg and C/N records are generally modulated byglacial–interglacial orbital-scale variability, Izumi et al.
(2021) show that peaks of TOC at warmer intervals in
MIS 19a represent enhanced organic matter preservation
owing to water column stratification caused by the northward displacement of the Subarctic Front rather thanincreased surface water productivity. However, the radiolarian records infer that the warmer intervals are characterized by higher productivity, which may reasonably
be explained by a stratified Kuroshio–Oyashio structure(Itaki et al. 2022). The dinoflagellate cyst record, whichmight represent warm-season conditions rather than the
cold-season signal reflected by most of the other proxies,
includes increased cyst concentrations during the initialstadial following MIS 19c. This implies increased surface
water productivity resulting from a southward shift of the
Subarctic Front and increased influence of the nutrientrich waters of the Oyashio Current (Balota et al. 2021).
Also in this issue, Kubota et al. (2021) examine calcareous nannofossil and radiolarian assemblage records andgeochemical data from planktonic foraminifera (δ18O,
δ13C, and Mg/Ca) of the Chiba composite section andoffer new paleoceanographic insights based on theirquantitative analysis. Through the use of principal component analysis (PCA) to capture dominant patterns of
temporal variation in these records, the authors confirm
that the microfossil assemblages are consistent with thewater mass types inferred from the geochemical proxies.
They also show that oceanic conditions, including latitudinal shifts of the Subarctic Front, were closely linked
both to the East Asian Winter Monsoon and the orbitally

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modulated global climatic signal, as previously suggested
by Suganuma et al. (2018). This approach identifies independent signals in geological records, such as those generated by surface and subsurface ocean processes, andtherefore has great potential to advance our understanding of the ocean circulation and East Asian climate.
MIS 19c is of special relevance to our present interglacial (Holocene) owing to similar orbital configurations.
Both interglacials are characterized by low orbital eccentricity, and their precession and obliquity parameters arenearly in phase allowing their inception to be unambiguously aligned. For this reason, MIS 19c has been used as abaseline to understand the trajectory of our future interglacial under natural conditions (e.g., Tzedakis et al. 2012;
Suganuma et al. 2018; Head 2021). Detailed paleoclimaticrecords of MIS 19 are therefore particularly significant.
With this in mind, Head (2021) in this issue reviews theclimatic characteristics of MIS 19 on a global scale, incorporating records from East Asia with other key sites from
the Mediterranean and North Atlantic Ocean. A critical feature of MIS 19 is its pronounced millennial-scale
climate variability following the inception of glaciationthat terminates MIS 19c. Head (2021) covers key topics
including the interrupted deglaciation of Termination
IX, the length and amplitude of full interglacial condition within MIS 19c, the stadial–interstadial oscillations
during MIS 19b–c, and the teleconnections responsible
for the remarkable coherence observed in MIS 19 records
globally. The bipolar seesaw mechanism via Atlantic
meridional overturning circulation (AMOC) across the
Atlantic certainly played a major role in climatic oscillations, causing shifts in the intertropical convergence zone
(ITCZ). These oscillations were especially pronounced
during MIS 19b–a, with low-latitude monsoon dynamics likely having amplified responses regionally (Nomade
et al. 2019; Haneda et al. 2020b). Similarities between
high-latitude Asian and northern North Atlantic records
suggest the concurrent influence of high-latitude teleconnections (Head 2021). Therefore, the importanceof additional high-resolution studies from East Asia andnorthern Asia as well as from the southern hemisphere isneeded to fully understand the nature of these phenomena during MIS 19. In addition, a detailed history of the
Middle Pleistocene, from its first use as a term to its final
ratification along with the Chibanian Stage, is reviewed
by Head (2021).
This special issue encompasses a broad range of methodologies and demonstrates the importance of paleoclimaticinterpretation in Quaternary stratigraphy to understandglobal linkages in the climate system. It also highlights thevalue of paleomagnetic reversals for defining formal chronostratigraphic units. In focusing on MIS 19, with a duration of only around 30 kyr, the special issue exemplifies

the value of ultra-high-resolution stratigraphic analysis
for understanding climatic evolution on a global scale during an orbital configuration similar to the present and at atimescale relevant to the future of our planet.
Abbreviations
M–B boundary: Matuyama–Brunhes boundary; MIS: Marine isotope stage;
GSSP: Global Boundary Stratotype Section and Point; CLP: Chinese Loess
Plateau; AMOC: Atlantic meridional overturning circulation; ITCZ: Intertropicalconvergence zone.
Authors’ information
YS is an associate professor at the National Institute of Polar Research (NIPR)
and at the Graduate University for Advanced Studies (SOKENDAI), Japan. He
is an Advisory Board member of the INQUA Commission on Stratigraphy andChronology (INQUA- SACCOM) (2015–). He was also a member of International
Subcommission on Quaternary Stratigraphy Working Group on the Lower–
Middle Pleistocene Subseries Boundary (2017–2020). MJH is a professor of
Earth Sciences at Brock University, Canada. He was Chair of the International
Subcommission on Quaternary Stratigraphy and Co-Convener of its Working
Group on the Lower–Middle Pleistocene Boundary during the time the Chiba
section was proposed and ultimately ratified as the GSSP for the ChibanianStage and Middle Pleistocene Subseries. TS is an assistant professor at Kanaz‑
awa University, Japan. He is a committee member of Past Global Changes(PAGES)-JAPAN and Paleosciences Society.
Acknowledgements
We thank all members of the Chiba composite section research community.
We are also grateful to the PEPS staff for their support and patience during
the submission and revision of manuscripts and the PEPS editorial board
for its helpful and swift editorial handling of these contributions. This article
has been improved by helpful comments from Ryuji Tada. We are grateful toJun’ichi Okuno for drafting Fig. 1.
Authors’ contributions
YS wrote the draft of the manuscript, and MJH and TS rewrote and confirmed
the contents. All authors read and approved the final manuscript.
Availability of data and materials
Please contact the authors contributing to this special issue for data requests.

Declarations
Competing interests
The authors declare that they have no competing interests.
Author details
1
National Institute of Polar Research, 10‑3 Midori‑cho, Tachikawa, Tokyo
190‑8518, Japan. 2 Department of Polar Science, School of Multidisciplinary Sci‑
ences, The Graduate University for Advanced Studies, SOKENDAI, Midori‑cho
10‑3, Tachikawa, Tokyo 190‑8518, Japan. 3 Department of Earth Sciences, Brock
University, St. Catharines, ON L2S 3A1, Canada. 4 Institute of Science and Engi‑
neering, Kanazawa University, Kakuma‑machi, Kanazawa 920‑1192, Japan.
Received: 13 January 2022 Accepted: 13 January 2022

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