Memoir of the Fukui Prefectural Dinosaur Museum 14: 25–61 (2015)

REVIEW© by the Fukui Prefectural Dinosaur Museum

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUPIN CENTRAL JAPANShin-ichi SANO
Fukui Prefectural Dinosaur Museum
Terao, Muroko, Katsuyama, Fukui 911-8601, Japan

ABSTRACTThe stratigraphy of the Tetori Group (sensu lato) and other Early Cretaceous strata in the Hakusan Region in the Hida
Belt, northern Central Japan, is reviewed based on recent advances in ammonoid biostratigraphy, U-Pb age determinationof zircons using inductively coupled plasma-mass spectrometry with laser ablation sampling (LA-ICPMS), recognitionof marine inﬂuence, and climatic change inferred from the occurrences of thermophilic plants and pedogenetic calcareous
nodules. Four depositional stages (DS) are recognized: DS1 (Late Bathonian–Middle Oxfordian)̶mainly marine
strata characterized by the occurrences of ammonoids; DS2 (Berriasian–Late Hauterivian)̶mainly brackish strata
characterized by the occurrences of Myrene (Mesocorbicula) tetoriensis and Tetoria yokoyamai; DS3 (Barremian–
Aptian)̶fluvial strata characterized by the occurrence of abundant quartzose gravels and freshwater molluscs,
such as Trigonioides, Plicatounio and Nippononaia; DS4 (Albian–Cenomanian)̶volcanic/plutonic rocks which
unconformably covered or intruded into the Tetori Group. I here propose new interpretation that 1) the Tetori Group(s.l.) in the Hakusan Region in the Hida Belt is divided into Middle–Late Jurassic Kuzuryu Group (corresponding toDS1) and unconformably overlying Early Cretaceous Tetori Group (sensu stricto) (corresponding to DS2–3); and 2) the
Tetori Group (s.l.) in other areas is separated from the Tetori Group (s.s.), and divided into the Late Jurassic strata of theKuzuryu Group (corresponding to the upper part of the same group in the Hakusan Region) and the Early Cretaceous
Jinzu Group in the Jinzu Region in the Hida Belt, and the Late Jurassic–Early Cretaceous Managawa Group in the Hida
Gaien Belt.
Key words：Tetori Group, Kuzuryu Group, Jurassic, Early Cretaceous, Hakusan Region, Central Japan

佐野晋一（2015）手取層群の新しい見方̶時代論の見直しと再定義の提案̶．福井県立恐竜博物館紀要 14：25‒61．
白山区の飛騨帯上に分布する手取層群（広義）からの，アンモノイドの時代論，ジルコン粒子を用いた
LA-ICPMS年代測定，軟体動物化石などによる海水の影響，好熱性植物と土壌性炭酸塩ノジュールの存在に基づく気候変動などの新知見をレビューした結果，本地域のジュラ〜下部白亜系を４堆積ステージに区分する．すなわち，主に海成層からなるステージ１（後期バトニアン〜中期オックスフォーディアン），主に汽水成層からなるステージ２（べリアシアン〜後期オーテリビアン），豊富な石英質砂岩礫と淡水棲二枚貝化石の産出で特徴づけられるステージ３（バレミアン〜アプチアン），主に火成・深成岩からなるステージ４（アルビアン〜セノマニアン）である．また，手取層群（広義）は地域によって層序や時代が異なっており，
白山区の中部〜上部ジュラ系九頭竜層群（堆積ステージ１相当）と下部白亜系手取層群（狭義）（堆積ステー
ジ２と３相当），神通区の上部ジュラ系九頭竜層群と下部白亜系神通層群，飛騨外縁帯の上部ジュラ系〜下部白亜系真名川層群に区分することを提案する．

Received June 2, 2015. Accepted November 22, 2015.
Corresponding author̶Shin-ichi SANO
E-mail: ssano*dinosaur.pref.fukui.jp(The asterisk should be replaced by @)25

26

SHIN-ICHI SANO

Tetori Group (sensu lato)

Asahi area
A: Asuwa area
M:

Tochio area
Nyukawa areaA
M

Mana-Ono-NaganoKamihambara areas

D

50 km

FIGURE 1. Index map showing the distribution of the Tetori Group (sensu lato) (modiﬁed from Maeda (1961d) and Fujita (2003)). As for subdivision of theKuzuryu District, see Sano et al. (2013).

INTRODUCTION
The Middle Jurassic–Early Cretaceous Tetori (or Tedori)Group is thick marine to non-marine siliciclastic sequence, and issporadically distributed in northern Central Japan (Maeda, 1961d;
Yamada, 1988; Kusuhashi et al., 2002; Fujita, 2003; Matsukawa
et al., 2006, 2014a; Takeuchi et al., 2015a, b) (Fig. 1). It is oneof the most important targets to better understand Cretaceous
tectonic events and the evolution of terrestrial ecosystem in East
Asia (e.g., Manabe et al., 2000; Matsuoka et al., 2002; Hirano
et al., 2003; Matsukawa et al., 2006). However, contrary to theJurassic, generally marine, Kuzuryu Subgroup (lower part of
the Tetori Group), the age and stratigraphy of the generally nonmarine Itoshiro and Akaiwa subgroups (middle and upper partof the Tetori Group, respectively) are still debatable, becauseof the scarcity of good index fossils and volcanic rocks suitableto numerical age analysis, and also distinct lateral changeof lithofacies (e.g., Yamada et al., 1989; Sano et al., 2008;
Matsukawa et al., 2008a; Yamada and Uemura, 2008).
During the last three decades, marine strata have beenrecognized in the Itoshiro Subgroup, and some of them are
tuned by the finding of age-diagnostic ammonoid specimens(Tamura, 1990; Fujita et al., 1998; Kumon and Umezawa, 2001;
Sato et al., 2003, 2008; Sato and Yamada, 2005; Goto, 2007;
Matsukawa et al., 2007; Yamada and Uemura, 2008; Matsukawa
and Fukui, 2009; Matsukawa and Asahara, 2010; Kashiwagi,
2014; Kashiwagi et al., 2014). Recently, U-Pb age determinationof zircons using inductively coupled plasma-mass spectrometry
with laser ablation sampling (LA-ICPMS) is also applied to theTetori Group (Kusuhashi et al., 2006; Kawagoe et al., 2012, 2014;
Takeuchi et al., 2015a). These data strongly require the complete
revision of the age and stratigraphy of the Tetori Group.

27

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

Furthermore, the discoveries of the lapilli tuff of 124.6 ± 2.3
Ma (late Barremian–early Aptian: ICS, 2015) LA-ICPMS U-Pb
zircon age (Kawagoe et al., 2012), and a Tithonian ammonoid(Sano et al., 2013) from the putative Kuzuryu Subgroup in the
Ono area of the southern Kuzuryu District suggested the differenceof the age and stratigraphy between the Tetori Group in the Hida
Belt (a continental block/fragment, which is mainly composedof Hida Metamorphic Rocks, Permian to Middle Triassic metagranitoids, and Early Jurassic granitoids (e.g., Kunugiza et al.,2010)) and that in the Hida Gaien Belt (a narrow tectonizedzone, which is composed of Middle to early Late Triassic
shallow marine formations including their metamorphosed facies(Tsukada et al., 2004; Kawagoe et al., 2013)). Thus it is indicatedthat the stratigraphy of the Tetori Group in each belt should
be discussed separately (Sano et al., 2013). In addition, there
are recent proposals to distinguish the Cretaceous strata of theTetori Group in the Jinzu Region and also some formations of
the Tetori Group in the Asahi (or Tomari) area from the Tetori
Group in the Hakusan Region (Matsukawa et al., 2014a; Takeuchi
et al., 2015a).
In this paper, the age and correlation of the Tetori Group in allimportant distributional areas in the Hakusan Region in the Hida
Belt are reviewed, mainly focusing on the recent ﬁndings of theage-diagnostic ammonoids, detrital zircon U-Pb dating and thepresence or absence of marine and brackish molluscs. Historicalreview of the studies of the Tetori Group is beyond the scope of
this paper. Other articles have already described this topic in detail(e.g., Maeda, 1961c, d; Matsuo and Omura, 1966; Kusuhashi etal., 2002; Fujita, 2003; Matsukawa et al., 2003a, 2006, 2014a;
Takeuchi et al., 2015a). New view of the stratigraphy of theTetori Group is proposed here to contribute to future studies
of Cretaceous tectonic events and the evolution of terrestrial
ecosystem in East Asia.

Series) non-marine strata in Central Honshu Island (= Central
Japan) as the Tetori Group. He also mentioned that the Tetori
Series is relatively typically developed in the upper reaches of
the Tedorigawa River (the area along the Ushikubigawa Riverand southern foot of Mt. Hakusan) in Ishikawa Prefecture, andits stratigraphy provides the standard for the comparison withthose of the coeval strata in other areas (Oishi, 1933a, p. 619). It
is reasonably considered that the type locality/area of the Tetori
Group is probably located in the area along the Tedorigawa River,namely in the Shiramine area in this paper. In the case of threefold division of the Tetori Group, i.e., the Kuzuryu, Itoshiro andAkaiwa subgroups, in ascending order (Maeda, 1961d; Yamada,
1988; Kusuhashi et al., 2002)*1, type localities of the Kuzuryu andItoshiro subgroups are located in the Itoshiro area, and that of the
Akaiwa Subgroup is in the Shiramine area (Maeda, 1952a, 1961c, d).
METHODS
Stratigraphic interpretation and geological maps of the Tetori
Group in each distributional area are considerably different
among studies. Their detailed reviews are beyond the scope of thispaper. Here, marine inﬂuence, bio- and magnetostratigraphy, andnumerical age data are focused on, because they are important todiscuss the age of the Tetori Group and the change of sedimentary
environments in the Tetori Group. They are reported on the basisof the general idea of the stratigraphy in each area.
1 Marine influence
Presence or absence of marine and brackish molluscs in eacharea is used to recognize marine inﬂuence and correlation of strata
among depositional areas. Occurrences of freshwater molluscs arealso mentioned in some cases, to recognize the absence of marine
inﬂuence.

STUDY AREAS
2 Bio- and magnetostratigraphy
The Tetori Group is distributed in two regions: the western
Hakusan Region and the eastern Jinzu Region (Maeda, 1961a)(Fig. 1). Mainly discussed in this paper are the Tetori Group in
the Itoshiro, Uchinamigawa, Shokawa, Hida-Furukawa, Setono,
Shiramine and Takinamigawa areas in the Hakusan Region in
the Hida Belt (Fig. 1). The Tetori Group in the Hida Gaien Belt,such as that in the Mana–Ono–Nagano–Kamihambara areas in the
Kuzuryu District, is excluded here.
The name Tetori Series was proposed in Yokoyama (1894,
p. 212) for all those strata containing Middle Jurassic plants,
which are distributed only in the inner side of Japan, from thename of the valley of the Tetori river (= Tedorigawa River orTedori River) in Kaga (former name of southern part of Ishikawa
Prefecture), where these fossils were first discovered (Geyler,
1877; Yokoyama, 1889). Later, Oishi (1933a, b) re-defined theTetori Series as the whole Late Jurassic strata with both marine
and terrestrial environments, which are distributed in the Innerand Outer zones of Southwest Japan, and even in Northeast Japan(Oishi, 1933b, p. 693), and called the Late Jurassic (= Tetori

Stratigraphic ranges of ammonoids are mainly taken into
consideration. Age assignment using the composition of radiolarianassemblage is also discussed. Charophyte biostratigraphy andmagnetostratigraphy are referred to in the Takinamigawa andShiramine areas, respectively. In some cases, biostratigraphic valuesof bivalves and ostracods are also mentioned.
3 Numerical age data
Only the LA-ICPMS U-Pb ages of zircons are used for the
discussion. Fission Track (FT) dating method has been applied to*1

The Tetori Group consists of three subgroups and the latest Cretaceous
Omichidani Formation according to Maeda (1961c, d). However, it has almost
always been cited that Maeda (1961c, d) subdivided the Tetori Group into
three subgroups. This is inconsistent with Maeda s original deﬁnition in termsof exclusion of the Omichidani Formation. In this paper, the Omichidani
Formation is discussed separately from the Tetori Group following Yamada(1988) and Kusuhashi et al. (2002).

28

SHIN-ICHI SANO

the studies of the Tetori Group (e.g., Gifu-ken Dinosaur ResearchCommittee, 1993). However, recent zircon U-Pb dating of
tuffaceous rocks in the Tetori Group revealed that zircon grainsof Precambrian and Paleozoic age are very abundant in somesamples (Kusuhashi et al., 2006; Kawagoe et al., 2012), and thus
the reliability of the FT age data, which require a group of ages ofmany zircon grains, needs very careful review (e.g., Matsukawa etal., 2014a). Furthermore, FT age can be relatively easily affectedby secondary heating (e.g., Seike et al., 2013). Since the reliabilityof the FT age data of the Tetori Group in most literature seems
low, I do not use them here.
On the other hand, K-Ar age data of volcanic/plutonic rocks,
which cover or intrude into the Tetori Group, are mentioned todeﬁne the upper limit of the age of the Tetori Group.
AGE AND STRATIGRAPHIC DISTRIBUTION OF MARINE/
BRACKISH HORIZONS OF THE TETORI GROUP
In this paper, the stratigraphic scheme is mainly basedon Maeda (1961d) and Kusuhashi et al. (2002), because theoccurrences of molluscs were mentioned in these papers in detail.
In Figure 2, names of subgroups and formations are usually notmentioned to avoid confusion, because the names of formations
and their inclusion to each subgroup are different among studies.
1 Kuzuryu District
The Kuzuryu District (or Kuzuryugawa area/Region) is oneof the classic and important localities for discussion of thestratigraphy of the Tetori Group (e.g., Yokoyama, 1889, 1904;
Oishi, 1933a; Maeda, 1961d; Yamada, 1988; Kusuhashi et al.,
2002; Matsukawa et al., 2003c, 2006). The Tetori Group is widelydistributed in this district. Recently, Sano et al. (2013) proposed
the idea that the Tetori Group in this district can be divided into
three parts (Northern, Middle and Southern rows), which arebounded by east-trending faults and contain different stratigraphyof the Jurassic to Cretaceous strata in each part. The Northern
Row is located in the Hida Belt and other two rows in the Hida
Gaien Belt. In this chapter, the Tetori Group in the Itoshiro andUchinamigawa areas, which belong to the Northern Row of theTetori Group in this district, is discussed.
It should be noted that, in case that the records in previous
studies are referred to, not only the formation names but also the
locality names in these studies must be reviewed. For example,
Nagano, a classic Oxfordian ammonoid locality, is located in the
Middle Row of the Tetori Group in this district, and is probably
not assigned to the Yambarazaka Formation, contrary to theinterpretations in previous studies (see Sato, 2008 and references
therein) (Sano et al., 2013). Type locality of Vaugonia (Vaugonia)
fukuiensis of Maeda (1962d) is Aradani, south of Kurotodo in
the Middle Row, and should not be assigned to the Yambarazaka
Formation, contrary to the original paper.

1) Itoshiro area (Fig. 2A)
Maeda (1952b, 1957) first established the stratigraphic
framework of the Tetori Group in this area, and divided it into 11
formations: the Shimoyama, Oidani, Tochimochiyama, Kaizara,
Yambarazaka, Yambara, Ashidani, Obuchi, Itsuki (or Izuki),
Nochino and Chinaboradani formations, in ascending order.
Among them, the Chinaboradani Formation is distributed only ina small area, near the boundary between the Northern and Middle
rows of the Tetori Group (Sano et al., 2013), and is not discussed
in this paper.
The Kuzuryu Subgroup consists of lower five formations,and is overlain by the Yambara Formation with the Umagatani
Unconformity (Maeda, 1952b). The Itoshiro Subgroup iscomposed of Yambara to Itsuki formations, and the Akaiwa
Subgroup consists of only the Nochino Formation.
Marine/brackish horizons̶Marine molluscs, such as
ammonoids, belemnites, and inoceramid and trigoniid bivalves,
have been recovered from the Oidani, Tochimochiyama, Kaizara,
Yambarazaka, and Yambara formations (e.g., Yokoyama, 1904;
Kobayashi, 1947, 1956, 1957a; Maeda, 1952b, 1962d, 1963a;
Sato, 1962; Matsukawa et al., 2003c, 2006; Sano et al., 2010,2011; Handa et al., 2014; Goto and Handa, 2014). Hasegawa et al.
(2010) conﬁrmed the marine or brackish condition of the Kaizara
Formation based on a geochemical study using the ratio of total
sulfur (TS) to total organic carbon (TOC) of the sedimentaryrocks. On the other hand, brackish molluscs, such as oysters andcorbiculoids, are known from the Ashidani and Itsuki formations(Kobayashi and Suzuki, 1937; Maeda, 1952b; Matsukawa and Ido,
1993; Matsukawa et al., 2003c; Nishida et al., 2013). Freshwatermolluscs were also recovered from the Itsuki Formation(Kobayashi and Suzuki, 1937; Maeda, 1957; Matsukawa andIdo, 1993; Matsukawa et al., 2003c), and possibly co-occur withbrackish bivalves in some horizons of this formation (Kobayashi
and Suzuki, 1937; Matsukawa et al., 2003c).
Biostratigraphic age data̶Sato and Westermann (1991)
established three ammonoid zones of the upper Bathonian tolower Callovian in the Kaizara Formation. Handa et al. (2014)
conﬁrmed this ammonoid zonation and discussed the Bathonian/
Callovian boundary in the Kaizara Formation. Sano andKashiwagi (2014) and Kashiwagi and Hirasawa (2015: this issue)
reported a radiolarian fauna from the Kaizara Formation andassigned its age to the late Bathonian–early Callovian.
Sato and Westermann (1991) established Oxfordian ammonoid
zonation in the Yambarazaka Formation. This proposal is mainly
based on the ammonoid records from Nagano. Sano et al. (2013)
pointed out Nagano belongs to the Middle Row of the Tetori
Group, and in fact the Yambarazaka Formation is not distributed
there. However, some Oxfordian ammonoids were recoveredfrom the exact Yambarazaka Formation, and the Oxfordian age
assignment to the Yambarazaka Formation is probably still valid,
though Oxfordian ammonoid zone in the Yambarazaka Formationis dubious (see the discussion in Sano et al. (2013)).
The occurrence of terrestrial palynomorphs, such as fern
spores: Appendicisporites, Cicatricosisporites, Cyathidites,
Osmundacidites and Schizaeoisporites, and a gymnosperm pollen:29·30NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

L.

P E

Age
Cenomanian

Age
(Ma)

Depositional stage

Transgressive
stageA) Itoshiro area
Hayashidani Andesite

100.5B)Uchinamigawa area

99.4MaTanase et al. (1994)

DS4

AlbianUchinami
Quartz diorite
106.5Ma

C) Shokawa area

D)Hida-Furukawa area

Kitamatadani body102~104Ma

Awaradani body93.6~99.3Ma
97.3~107Ma

Makido body90.7~100Ma

E) Setono areaF) Shiramine areaG) Takinamigawa area

?

?

113

?

?

AptianCRGNR(1979)

?
?

PN

DS3

TPN

121.2Ma

125
Barremian
Hauterivian

129.4
132.9

Valanginian
139.8

?

? M 127.2Ma?

TS-IIb?

117.5Ma131.4Ma132.9MaM?

130.7Ma

?

MN
M

?

M

M

?

?

145

N
M
N

TS-IIIDS2

BerriasianM

125.6Ma
129.8Ma
130.0Ma
124.4Ma
130.2MaM?

M

Tithonian
152.1
Kimmeridgian
157.3
OxfordianCallovian
Bathonian
Bajocian

163.5
166.1
168.3
170.3

Kuzuryu Gp.

JURASSIC
M.
Late

pre Nohi Andesites?

Tetori GroupCRETACEOUS
Early

Tomioka et al. (2000) GDRC (1993) Shibata and Uchiumi (1995)

TS-Ib
DS1
TS-Ia
?

?

plutonic bodies

strata containing
brackish water molluscs

strata mainly composedof volcanic rocks

strata containing
marine molluscs
strata dated
by ammonoid fossils

fluvial deposits
without molluscan fossils
strata containing
freshwater molluscs

unconformable relationshiplast horizon of the records
of marine influence: Zircon U-Pb dating

characteristic bivalves: K-Ar dating

T : Trigonioides: magnetostratigraphic study

P : Plicatounio: pedogenetic calcareous nodulesN: thermophilic plants

M : Myrene (Mesocorbicula): Nippononaia

FIGURE 2. Stratigraphic distribution of marine and brackish horizons of the Kuzuryu and Tetori (sensu stricto) groups in each important distributional area in the Hakusan Region in the Hida Belt, and their possible correlation. Stratigraphic distribution of marine (e.g., ammonoids), brackish (e.g., Myrene) and freshwater (e.g., Trigonioides, Plicatounio andNippononaia) molluscs, and climatic indicators (pedogenetic calcareous nodules and thermophilic plants) is shown. Numerical age data and the horizon of magnetostratigraphic study in the Tetori Group and Albian–Cenomanian volcanic/plutonic rocks, Transgressive stages (TS(s)) of Sano et al. (2013) in the Tetori Group (sensu lato), and Depositional stages (DS(s):proposed here) are also mentioned. See the text for details. The numerical ages are based on ICS (2015). Abbreviation: GDRC̶Gifu-ken Dinosaur Research Committee; CRGNR̶Collaborative Research Group for the Nohi Rhyolite.

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUPClassopollis, from the uppermost part of the Tetori Group in thisarea were reported, and its Hauterivian–Aptian age was suggested(Umetsu and Matsuoka, 2003; Umetsu and Sato, 2007).
Numerical age data̶Kawagoe et al. (2012) obtained LAICPMS U-Pb ages of detrital zircons in sandstone recovered fromabout 100 m above the base of the Itsuki Formation along the
Itoshirogawa River, and revealed that its youngest zircon has theconcordant age of 127.2 ± 2.5 Ma (2 SD). The depositional ageof the Itsuki Formation is Barremian or younger (International
Commission on Stratigraphy (ICS)，2015). The Hayashidani
Andesite of 99.4 ± 5 Ma K-Ar cooling age (Tanase et al., 1994)
unconformably covers the Tetori Group in this area, and deﬁnes
the age of the upper limit of the Tetori Group in this area.
2) Uchinamigawa area (Fig. 2B)
Stratigraphy of the Tetori Group in this area is still debated, andthere is no consensus on its stratigraphy and correlation with thatof the Itoshiro area (Maeda, 1957; Kawai et al., 1957; Goto, 2007;
Matsukawa and Asahara, 2010). In this paper, only the Early
Cretaceous ammonoid record reported by Goto (2007) is focused,
and mentioned in Figure 2.
Marine/brackish horizons̶Goto (2007) reported theoccurrence of an ammonoid from the Tetori Group at Ikegahara
along Taniyamagawa River. In addition, several horizons ofbrackish molluscs are recognized in this area (e.g., Matsukawa
and Asahara, 2010). However, it is difficult to correlate them,or compare their stratigraphic position with ammonoid-bearing
horizon.
Biostratigraphic age data̶Goto (2007) described anammonoid Pseudothurmannia sp. and considered its age as late
Hauterivian to Early Barremian. Later Matsukawa and Asahara(2010) discussed the stratigraphic distribution of the species ofthis genus more strictly, and assigned the age of this ammonoid tothe late Hauterivian.
2 Shokawa area (Fig. 2C)
Maeda (1952a) divided the succession of the Tetori Group in
the Shokawa (or Shiokawa) area into eight formations: Ushimaru,
Akahoke, Mitarai (or Mitarashi), Otaniyama, Okurodani,
Amagodani, Okura, Bessandani (or Betsuzandani) formations, inascending order. Although he considered that the Okura Formation
overlies the Amagodani Formation with unconformity, subsequentstudies revised its relationship as conformity (e.g., Umezawa,
1997; Matsukawa and Nakada, 1999).
Marine/brackish horizons̶Diversiﬁed marine invertebrates,
such as bivalves, ammonoids, a belemnite, a glypheid lobster,
scalpellomorph barnacles, a crinoid, were described or reported
from the Mitarai Formation (Hayami, 1959a, b, 1960; Sato andKanie, 1963; Ito et al., 1999; Komatsu et al., 2001; Sato et al.,2003, 2008; Kato and Karasawa 2006; Nomura and Shimizu,
2008; Hunter et al., 2011; Yano, 2012; Sha and Hirano, 2012;
Sano et al., 2015). Kumon and Umezawa (2001) ﬁrst recognized
the marine bed in the lower part of the Otaniyama Formation fromthe discovery of belemnite specimens. Yamashita et al. (2011, ﬁg.

313) reported the marine horizon also occurs in the upper part of
the Otaniyama Formation. Hasegawa et al. (2010) conﬁrmed themarine or brackish condition of the Mitarai Formation and somehorizons of the lower part of the Otaniyama Formation based ongeochemical studies.
Maeda (1952a) reported the brackish bivalves from the
Ushimaru, Akahoke, Otaniyama and Okurodani formations.
Komatsu et al. (2002) described new oyster species Crassostrea
tetoriensis from the Ushimaru Formation. Brackish and freshwaterbivalves occur alternatingly in the Otaniyama and Okurodani
formations, indicating the frequent environmental changes
in this stratigraphic sequence (Gifu-ken Dinosaur ResearchCommittee, 1993; Matsukawa and Nakada, 1999; Matsukawa
et al., 2006; Yamashita et al., 2011). On the contrary, only the
freshwater molluscs have been recovered in the uppermost partof the Okurodani Formation, and no brackish molluscs have beenrecognized in younger Cretaceous strata in this area (Matsukawa
and Nakada, 1999; Yamashita et al., 2011).
Biostratigraphic age data̶Sato et al. (2003, 2008) assigned
the Mitarai Formation to the Berriasian based on the discovery
of Neocosmoceras sp. On the other hand, Sha and Hirano (2012)
pointed out that four bivalves of the Mitarai Formation occur also
in the Barremian–Aptian Qihulin and Yunshan formations of theLongzhaogou Group in eastern Heilongjiang Region, Northeast
China. Combining these occurrences with the numerical age
data mentioned below, they assigned the Mitarai Formation to
the Barremian–Aptian age. However, it should be noted that themarine bivalve fauna of the late Hauterivian Inagoe Formation(see the section of Hida-Furukawa area below) is very similar tothat of Yunshan Formation (Matsukawa and Fukui, 2009). Sinceammonoid assemblages of the Mitarai and Inagoe formations are
distinct, different ages are indicated for these two formations,though some similarity of the bivalve fauna is recognized. Thus
the hypothesis of age assignment of the Mitarai Formation using
these bivalves is not adopted here, and the similarity of bivalves
may be explained by another interpretation: for example, thesefore-mentioned taxa are long ranging species at least from the
Berriasian to Barremian–Aptian. A belemnite, Cylindroteuthis
aff. knoxvillensis was recently described from the Mitarai andpossibly Otaniyama formations (Sano et al., 2015). Since theupper limit of stratigraphic range of the genus Cylindroteuthis(sensu Dzyuba (2011)) is Valanginian (e.g., Doyle and Kelly,
1988; Dzyuba, 2005), this belemnite record probably supports theage assignment (Berriasian) by ammonoids.
Komatsu et al. (2003) described a charophyte gyrogonite:
Mesochara sp. from the Okurodani Formation for the first timein Japan, though more materials are necessary to discuss the
charophyte biostratigraphy in this area.
Numerical age data̶Kusuhashi et al. (2006) first reported
the zircon LA-ICPMS U-Pb age of tuffs of the Tetori Group in thisarea: 130.2 ± 1.7 Ma (errors of Kusuhashi et al. (2006) represent
2 SE) for the Ushimaru Formation; 130.0 ± 1.7 Ma and 129.8 ±1.0 Ma for the Mitarai Formation; 132.9 ± 0.9 Ma, 131.4 ± 0.9
Ma and 117.5 ± 0.7 Ma for the Okurodani Formation, excluding
less reliable data. They chose the youngest age data of each32

SHIN-ICHI SANO

formation for the age assignment, and concluded that maximum
ages of the Ushimaru, Mitarai and Okurodani formations arelate Hauterivian to Barremian, late Hauterivian to Barremianand Barremian to Aptian, respectively (using the time scale ofGradstein et al. (2004)).
The Tetori Group in this area was intruded by several midCretaceous plutonic bodies, such as Kitamatadani Diorite: K-Ar
cooling age 102~104 Ma (71.6 Ma of their data is dubious)(Shibata and Uchiumi, 1995), Awaradani Granodiorite: K-Ar age
93.6~99.3 Ma (Shibata and Uchiumi, 1995) and 97.3~107 Ma(84.9 Ma of their data is dubious) (Gifu-ken Dinosaur ResearchCommittee, 1993), and Makido Mafic Complex: K-Ar age
90.7~100 Ma (125 Ma of their data is dubious) (Shibata andUchiumi, 1995) (e.g., Kamiya and Harayama, 1982; Tanase etal., 2005). In addition, the pre-Nohi Andesites (Collaborative
Research Group for the Nohi Rhyolite, 1979) , which was also
intruded by the Kitamatadani Diorite, is distributed in this area,
and is correlated with the Hayashidani Andesite (ca. 100 Ma) in
the Kuzuryu District (Tanase et al., 2005). These data probably
deﬁne the upper limit of the age of the Tetori Group in this area.
Remarks̶There is a large discrepancy between the ammonoid
biostratigraphic and numerical age data of the Mitarai Formation.
Neocosmoceras is recovered also from the earliest Cretaceous
strata in the South Kitakami Region in Northeast Japan (e.g.,
Sato et al., 2011). Similarity of ammonoid assemblages among
coeval strata in the Tetori and South Kitakami regions suggests
the validity of the age assignment of the Mitarai Formation using
ammonoids. On the contrary, it is a bit dubious that very similar
numerical age data (ca. 130 Ma) were obtained from different
formations of the Tetori Group in this area, and different age data
(OK3: 117.5 ± 0.7 Ma and OK4: 132.9 ± 0.9 Ma) were recordedin almost the same horizons (OK3 is only several meters below
OK4) (Kusuhashi et al., 2006). Further numerical dating studies
are necessary to conﬁrm the validity of these data.
3 Hida-Furukawa area (Fig. 2D)
The Tetori Group in this area is divided into the Tanemura,Numamachi, Sugizaki, Taie, Inagoe formations in ascending order(Matsukawa et al., 2007). The Tochio Formation (Maeda, 1958a)in the Fukuji area is excluded from this study, because it belongs
to the Hida Gaien Belt (e.g., Otoh et al., 2003; Nakama et al.,2010).
Marine/brackish horizons̶ Matsukawa et al. (2007) andMatsukawa and Fukui (2009) reported the occurrences of marine
molluscs from Sugizaki, Taie and Inagoe formations, and those ofbrackish water molluscs from Numamachi and Taie formations.
In addition, some species of marine bivalves (inoceramid andtrigoniid) were described from this area (Hayami, 1960; Maeda,
1962b).
Biostratigraphic age data̶Matsukawa and Fukui (2009)
described ammonoids, Phyllopachyceras infundibulum,
Pseudothurmannia aff. baleare and Acrioceras (Paraspinoceras)
sp. from the Inagoe Formation, and assigned its age to theHauterivian–Barremian. This idea is re-mentioned in detailin Matsukawa and Asahara (2010). These three species wererecovered from two very nearby horizons (WT-03, 4) in thesame route (columnar section 7 in Matsukawa et al., 2007).
Stratigraphic ranges of Ph. infundibulum and Acrioceras(Paraspinoceras) sp. are Hauterivian to Barremian. Matsukawa
and Fukui (2009) mentioned Pa. jourdani as the related speciesof the Hida-Furukawa Acrioceras (Paraspinoceras) sp. The
former is recovered from very nearby horizons in the Hauterivian
succession in Southwest Romania with Ph. infundibulum
and Pseudothurmannia spp. (Avram, 1994), In addition,
Pseudothurmannia clearly indicates the late Hauterivian age(Matsukawa and Asahara, 2010). Thus the age of the Inagoe
Formation can be discussed more precisely, as around theHauterivian–Barremian boundary, or possibly the late Hauterivian,on the basis of these ammonoid records.
4 Setono area (Fig. 2E)
Distribution of the Tetori Group in this area is divided into
many fault bounded blocks, and its stratigraphy, especially thecorrelation with that of the Shiramine area, is still uncertain(Matsuoka et al., 2009; Sakai and Matsuoka, 2011). Thus only
the marine stratum near the conﬂuence of the Tedorigawa Riverand the Ozogawa River is focused on in this paper, because
Matsuoka et al. (2009) reported the occurrence of limuloid tracks(Kouphichnium isp.) there, and shows the distribution of relatively
thick marine strata in geological map and columnar section.
Marine/brackish horizons̶Maeda (1958b) mentioned
several localities of brackish bivalves. Tamura (1990) firstreported the occurrence of a marine bivalve, Isognomon, withother brackish bivalves from Setono (the place between Seto and
Setono in Tamura (1990, table 1)), though its exact locality is not
mentioned. Matsuoka et al. (2009) recognized relatively thickmarine strata near the conﬂuence of the Tedorigawa River and the
Ozogawa River. Recently, Kashiwagi et al. (2014) reported theoccurrence of sponge spicules and radiolarian tests from mudstonerich alternating beds of sandstone and mudstone in this locality.
They also reported the occurrence of a belemnite specimen in asandstone ﬂoat along the Ozogawa River, which was discovered
in upstream from the sponge and radiolarian locality discussed
here, and suggested the possible presence of another marine
horizon in the Setono area, though its stratigraphic relationshipwith above-mentioned marine strata is still ambiguous.
Biostratigraphic age data̶Marine horizon is recognized, but
no age-diagnostic fossil has been reported.
Numerical age data̶Matsumoto et al. (2006) obtained a
LA-ICPMS U-Pb zircon age of 130.7 ± 0.8 Ma (2 SE) from a
tuff bed covering the limuloid tracks bed, and indicated that themarine stratum is Hauterivian in age (ICS, 2015).
5 Shiramine area (Fig. 2F)
The type locality/area of the Tetori Series (Yokoyama, 1894)
and also the Tetori Group (Oishi, 1933a, b) is probably located inthis area, as mentioned above. Maeda (1958b, 1961d) divided theNEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

succession of the Tetori Group in this area into four formations:
the Gomishima (or Gomijima), Kuwajima (or Kuwashima),
Akaiwa and Kitadani formations, in ascending order. One of
the famous dinosaur localities of the Tetori Group (Kaseki-kabe(or Kasekiheki)) is assigned to the upper part of the Kuwajima
Formation (e.g., Matsuoka, 2000; Matsuoka et al., 2002; Isaji etal., 2005). Its age assignment was discussed in detail in Kusuhashi(2008: p. 380–381), and is basically followed in this paper. Since
the correlation between the stratigraphy of the Shiramine area andthat of the Setono area is uncertain, the stratigraphy of both areas
are discussed here separately.
Brackish horizons̶Brackish bivalves, Myrene (Mesocorbicula)tetoriensis and ostreoid are recovered only from the lower partof the Kuwajima Formation (Maeda, 1958b; Okazaki and Isaji,2008). Freshwater molluscs have been known from the upper partof the Kuwajima Formation and the Kitadani Formation (Matsuo
et al., 1976; Isaji, 1993, 2010).
It should be noted that at Yanagidani, east of Ichinose, brackish
and freshwater bivalves, such as Myrene and Nippononaia, cooccur in the same beds (Maeda, 1958b; Matsuura, 2001). The
assignment of this fossil-bearing stratum to either the Kuwajima(or Okurodani) Formation or the Akaiwa Formation has been
debated for a long time, and is still ambiguous (e.g., Maeda,
1958b; Matsukawa et al., 2000, 2003a; Matsuura, 2001; Hachiya,2011). Choristoderan remains, which have been known from the
Kuwajima Formation and not from the strata above the Kuwajima
Formation (Matsumoto et al., 2015), occur in the same outcrop(Matsuura, 2001), and may indicate the possible correlation
between this stratum and the Kuwajima Formation. Further
studies are clearly required to solve this problem, and to reveal the
paleoenvironmental signiﬁcances of this record.
Biostratigraphic age data̶Marine horizon is not recognizedin this area. Isaji (1993) reported the occurrence of Nippononaia
ryosekiana and Plicatounio sp. from the Kitadani Formation inthis area (see the discussion in the Takinamigawa area below).
Magnetostratigraphic age data̶Geomagnetic study
suggested that the deposition of the Akaiwa Formation did
not occur during the period of the Cretaceous Normal Polarity
Superchron (early Aptian to Santonian), because twice changes ofthe magnetic polarities were recognized in the outcrop at Yunotani(Kunugiza et al. 2002a). The age of the Akaiwa Formation in thislocality can be considered as the pre-Aptian time.
Numerical age data̶Sakai et al. (2015) obtained LA-ICPMS
U-Pb zircon age of 121.2 ± 1.1 Ma (95% conﬁdence interval, CI)(Aptian; ICS, 2015) from the tuff of the Akaiwa Formation in
Osugidani.
Remarks̶Age assignment of the Akaiwa Formation (preAptian) by the magnetostratigraphic data is considerably different
from recent numerical age datum (Aptian). Although precise
stratigraphic relationship between two outcrops where thesedata were obtained is uncertain, it is clearly indicated that theupperlimit of the age of the Akaiwa Formation is extended to the
Aptian, and this formation can be tentatively considered as theBarremian–Aptian age.

33

6 Takinamigawa area (Fig. 2G)The formation names, which were used to describe thestratigraphy of the Tetori Group in this area, are variable among
papers, because of the different interpretation of the correlation
with that of the Shiramine area (e.g., Maeda, 1958b; Tsukano,
1969; Omura, 1973; Tamura, 1990; Matsukawa et al., 2003a,
2006; Molnar et al., 2009; Nichols et al., 2010). However, theirrecognition of lithological changes of the Tetori Group in thisarea is usually identical. Sano et al. (2008) divided the Tetori
Group in this area into four lithostratigraphic units (Unit A to D inascending order), and this unit division is used here. Unit C andD correspond to the Kitadani Formation of Maeda (1958b). Oneof the famous dinosaur localities of the Tetori Group, the Kitadani
Dinosaur Quarry (Azuma, 2003), is assigned to Unit C.
Brackish horizon̶A brackish bivalve, Myrene sp. occurs in
the lowermost part of Unit A (Tsukano, 1969; Sano et al., 2008).
Biostratigraphic age data̶Since marine horizon is notrecognized in this area, the age assignment of the Tetori
Group in this area should be discussed based on non-marine
fossil biostratigraphy. Various freshwater molluscs including
Trigonioides, Plicatounio and Nippononaia occur in Unit C (e.g.,
Maeda, 1962e, 1963b, Tamura, 1990; Matsukawa and Ido, 1993).
Isaji (1993) discussed the age of Unit C as Late Barremian–
Early Aptian, according to the occurrence of a freshwater bivalve
Nippononaia ryosekiana, which is known from the Sebayashi
Formation in the Sanchu area, Kanto Mountains, in the Outer
Zone of Southwest Japan. This information has been used as
the grounds for the age of the Kitadani Formation. However, N.
ryosekiana-bearing horizon of the Sanchu area is now consideredas the Barremian in age (Terabe and Matsuoka, 2009; Matsukawa
and Tomishima, 2009). On the contrary, the age of Nakdong
Formation in Korea, where N. ryosekiana occurs (Yang, 1978),is re-assigned to the late Aptian (118 Ma) or younger, based on
LA-ICPMS U-Pb dating of detrital zircons (Lee et al., 2010).
Thus stratigraphic range of N. ryosekiana should be revised as
Barremian–Upper Aptian (or above).
On the other hand, according to recent summary of stratigraphic
range of Early Cretaceous non-marine bivalves in East Asia,
the stratigraphic range of Plicatounio is usually consideredas the Aptian–Albian (Sha et al., 2012), though the age of theMonomiyama Formation in South Kitakami Region in Northeast
Japan, where Plicatounio was reported, can be considered as preAptian (Ogasawara, 1988), and the stratigraphic range of thisgenus needs further conﬁrmation.
Kubota (2005) described 5 species of charophyte gyrogonites:
Clavator harrisii var. reyi, Mesochara harrisi and Mesochara
stipitata, Mesochara sp. and Stellatochara sp. from Unit C, andassigned its age to Barremian according to the co-ocurrence of
C. harrisii var. reyi, M. harrisi and M. stipitata. Among them,stratigraphic range of C. harrisii var. reyi is usually considered as
the Barremian–Early Aptian (Kubota, 2005; Vicente and MartínClosas, 2013). It was also reported from the Nakdong Formationin Korea of the Late Aptian or younger age (Choi, 1989; Kubota,
2005; Lee et al., 2010). M. harrisi and M. stipitata show relatively

34

SHIN-ICHI SANO

long stratigraphic ranges from the Kimmeridgian and Berriasian,respectively, and their youngest records were recognized in the
Barremian deposits (Kubota, 2005). In Europe, M. harrisi occurs
also in the Ascidiella cruciate–Pseudoglobator paucibracteatuscharophyte biozone of the Late Barremian–Early Aptian age
with C. harrisii var. reyi (Martín-Closas et al., 2009; Vicente andMartín-Closas, 2013). M. stipitata was known from the upper
part of the Jiufotang Formation to the Fuxin Formation (Wang etal., 2003). These formations were recently assigned to the Aptian(Sha et al., 2012). Thus the co-ocurrence of these three species
probably indicates the Barremian to Aptian in age instead of theBarremian.
Legrand et al. (2013) described rich palynoﬂora from Unit C,
but they concluded that the assignation of an accurate age to it was
difﬁcult. Recently, Legrand et al. (2015) reported the occurrenceof an angiosperm pollen Clavatipollenites hughesii from Unit C,
suggesting the possibility of future biostratigraphic study using
angiosperm pollen from the Kitadani Formation.
Cao (1996) described four ostracod species: Cypridea
angusticaudata, C. (Morinia) monosulcata zhejiangensis, C.
(Bisulcocypridea) sp. and Timiriasevia sp. from Unit C, andsuggest its close similarity to that of the Guantou Formation
in Southeast China. The age of Guantou Formation is now
considered as Aptian based on SHRIMP (sensitive highresolution ion-microprobe) zircon dating (Zhang et al., 2014).
Wang et al. (2012) discussed the age of Cypridea (Morinina)–
Bisulcocypridea–Mongolocypris assemblage is mainly Aptian–
Albian.
Numerical age data̶Arakawa et al. (2005) applied detrital
zircon SHRIMP dating to Unit C, and mentioned that youngest
detrital zircon from the Kitadani Formation is Hauterivian in age,and Unit C is assigned to Hauterivian or later. However, their
discussion is based on the datum of only a single grain of zircon,
and the detailed evaluation of the datum is not provided. The
reliability of this datum needs further conﬁrmation.
Remarks̶The age of the Kitadani Formation had beensometimes mentioned as the Aptian–Albian in literature. Thisage assignment is probably based on the figure showing thecorrelation of the Tetori Group in various localities published in
Maeda (1961d, table 1). However, the age of Kitadani Formation
was described as Lower Cretaceous or Eo-Cretaceous in
the subsequent papers (e.g., Maeda, 1962e, 1963b), and thus
the supposed Aptian–Albian age of the Kitadani Formation isprobably misinterpretation of the figures of Maeda (1961c, d).
Based on the above mentioned data, the age of Unit C (and also
the Kitadani Formation) can be considered as the Aptian at thismoment, though some discrepancies still exist among the age
assignment on each biota. Furthermore, the upper limit of the ageof the Kitadani Formation is still ambiguous.
Maeda (1958b) deﬁned the Kitadani alternation of sandstone,
shale and tuff , which is characterized by the presence of reddish
or greenish tuffaceous rock facies and also the occurrencesof non-marine molluscs, such as Trigonioides and Plicatounio.
Putative greenish tuffaceous rocks are in fact paleosol (e.g.,
Kubota, 2003), and unambiguous tuffaceous rocks are probably

absent in the Kitadani Formation, causing the difficulty ofnumerical dating study of this formation.
7 Asuwa area
Since purported occurrence of ammonoid from the Asuwa area
was reported, the presence of the Kuzuryu Subgroup in this area
has been supposed (e.g., Maeda, 1961b). The presence of marine
strata in this area is now questioned (Yamada and Uemura, 2008;
Yamada et al., 2008). Since age indicating data have not beenobtained, the stratigraphy of the Tetori Group in this area is notdiscussed in this paper.
CORRELATION BETWEEN THE STRATA IN EACH
DISTRIBUTIONAL AREA
1 Marine horizons in the Tetori Group
Alternating changes of marine and non-marine depositional
environments are recognized in the lower and middle part of
the Tetori Group. Three marine transgression stages in the
Tetori Group were recognized in Matsukawa et al. (2007), andslightly revised in Sano et al. (2013). Marine strata can be usedas key horizons for correlation in the Tetori Group. Stratigraphic
distributions of marine strata in the studied areas, which arereviewed in detail in previous chapter, are summarized as follows.
Bathonian–Callovian (transgression stage (TS)-Ia of Sano et al.
(2013), the same reference for TS hereafter) and Oxfordian (TSIb) marine strata occur only in the Itoshiro area. Tithonian (TS-IIa)
one has not been recognized in any part of the studied areas.
Berriasian (TS-IIb) one is recognized in the Shokawa area.
The marine Sugizaki Formation in the Hida-Furukawa area canbe considered as the older transgression than that of the late
Hauterivian Inagoe Formation, and to be correlated with the
Mitarai Formation and lower part of the Otaniyama Formation,
because of the occurrences of Inoceramus maedae and belemnite
specimens, and similar changes of depositional environments(Matsukawa et al., 2007). Thus TS-IIb transgression possibly
occurred also in the Hida-Furukawa area.
Occurrence of Vaugonia (Vaugonia) yambarensis from theYambara Formation suggests the marine influence on thelowermost pat of the Itoshiro Subgroup in the Itoshiro area
(Maeda, 1952a; Kobayashi, 1956). Age assignment of thishorizon is debatable (see discussion in Kawagoe et al. (2012)
and Sano et al. (2013)). It is possible that this marine horizon
is directly correlated with Mitarai Formation (corresponding
to TS-IIb) in the Shokawa area, because it is probably the lasttransgression below the Barremian Itsuki Formation, though thelithologies of the Mitarai and Yambara formations are different.
However, it should be noted that only a single specimen of V.
(V.) yambarensis was recovered, and this species was consideredas the youngest record of this genus in Japan (Kobayashi etal., 1959). Thus it is necessary to review the possibility that
this specimen was reworked from the lower strata such as the
Yambarazaka Formation, where abundant trigoniid specimens

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

including Vaugonia kuzuryuensis occur (Kobayashi, 1957a;
Maeda, 1963a). On the other hand, Inoceramus-bearing boulder
in the Yambara Formation suggests the deposition and subsequenterosion of Inoceramus-bearing marine stratum occurred in thisarea. Inoceramus is very abundant in the Mitarai Formation(e.g., Hayami, 1960; Komatsu et al., 2001). If this eroded marine
stratum is correlated with the Mitarai Formation, the age of the
Yambara Formation can be considered younger than that of
the Mitarai Formation. Another candidate of the Inoceramusbearing marine stratum is the Tithonian Kamihambara Formation(corresponding to TS-IIa) in the Kamihambara area of the Middle
Row of the Tetori Group in the Kuzuryu District. However, in thiscase, there is another discrepancy that marine horizon of TS-IIb(corresponding to the Mitarai Formation) cannot be recognizedin the Itoshiro area. Furthermore, marine horizon of TS-IIa is
not recognized in any other part of studied areas in the Hida
Belt. Thus the second hypothesis that the Yambara Formation is
younger than the Mitarai Formation is preferred, though further
dating studies of the Yambara Formation is required.
Late Hauterivian (TS-III) marine strata are recognized in the
Uchinamigawa, Hida-Furukawa and Setono areas. The former
two records are based on ammonoids, and the last one is dated byzircon U-Pb dating.
2 Disappearance of marine influence on the Tetori Group
Brackish environment characterized by the occurrences ofMyrene (Mesocorbicula) tetoriensis and Tetoria yokoyamai, isprevailed widely in the middle part of the Tetori Group (Maeda,
1955; Kondo et al., 2006; Nishida et al., 2013), though marine
horizons are limited to only a few horizons (Fig. 2). Kondo etal. (2006) supposed the presence of a huge brackish lake in the
Tetori Region. Nishida et al. (2013) recognized the Tetori Regionis one of the important areas to consider the evolution of brackishbivalve corbiculoids.
On the other hand, freshwater molluscs, such as Nippononaia,
were reported only from the upper formations of the Tetori Group:
the Kuwajima Formation in the Shiramine area, the Okurodani
Formation in the Shokawa area, and the Kitadani Formation in the
Takinamigawa area (e.g., Kobayashi and Suzuki, 1937; Maeda,
1952a, b, 1955; 1958b, 1961d, 1962a, e, 1963b; Matsuo et al.,
1976; Tamura, 1990, Matsukawa and Ido, 1993; Isaji, 1993, 2010;
Matsukawa and Nakada, 1999; Matsukawa et al., 2003b, 2006;
Komatsu et al., 2003; Goto, 2010; Kikuchi, 2011; Hachiya, 2011),
except for the Otaniyama Formation in the Shokawa area, where
the marine/brackish environments were predominant (Matsukawa
et al., 1998; Matsukawa and Nakada, 1999; Yamashita et al.,2011) (Fig. 2).
The faunal change from the lower brackish fauna to upper
freshwater fauna in the Kuwajima Formation and in the Shokawa
area was mentioned in Tamura (1990), though he discussed thestrata in the Shiramine and Setono areas together, contrary to thedescription in this paper. Quartzose gravel rich conglomerates arevery dominant in the upper part of the Tetori Group, and a ﬂuvial
environment prevails in these strata (e.g., Maeda, 1961d; Taira

35

and Matsuo, 1983, Masuda et al., 1991; Fujita, 2002; Yamagami
et al., 2003; Kim et al., 2007; Sano et al., 2008; Okazaki and Isaji,2008). Thus the distinct change of depositional environments frombrackish to ﬂuvial probably occurred in the Tetori Region and its
hinterland during the time of deposition of the middle to upper
part of the Tetori Group. The similar idea was already proposedby Matsukawa et al. (1997a).
If the same or related tectonic event(s) caused theseenvironmental changes in the whole Tetori Region, the transition
from the marine/brackish to freshwater environments in each
distributional area possibly occurs at almost same time or shorttime interval, and can be used as the approximate correlation toolin the middle and upper part of the Tetori Group. The last marine
strata of the Tetori Group (TS-III) are late Hauterivian basedon ammonoids and zircon U-Pb dating. On the other hand, lastappearance of brackish fossils in the Tetori Group are recognizedin the lowermost part of the Tetori Group in the Takimanigawa
area, within the Kuwajima Formation in the Shiramine area,
within the Okurodani Formation in the Shokawa area, and in
the Itsuki Formation in the Itoshiro area (Fig. 2). Among them, thenumerical age of the Itsuki Formation is 127.2 ± 2.5 Ma (Barremian)or younger. Those of the Okurodani Formation are Hauterivian toAptian (132.9 ± 0.9 Ma, 131.4 ± 0.9 Ma and 117.5 ± 0.7 Ma),though the validity of these numerical age data was questioned,
as mentioned above. In the Shiramine area, paleomagnetic
study and recent numerical age datum (121.2 ± 1.1 Ma) of the
Akaiwa Formation revealed that the Kuwajima Formation isprobably older than Aptian. Charophytes, freshwater molluscs andostracods indicate the Aptian age for the uppermost part of theTetori Group in the Takinamigawa area. Thus the disappearance ofmarine inﬂuence in the whole Tetori Region is supposed to occur
within the Barremian stage, and used as approximate correlation
tool in this paper.
Matsukawa et al. (1997a) already proposed the hypothesisthat the tectonic duplication of Jurassic–early Early Cretaceous
accretionary complexes in the Hauterivian caused the upheavalof the hinterland and the change of depositional environmentsof the Tetori Group at that time. However, their recent studies(e.g, Matsukawa et al., 2006, 2007; Matsukawa and Fukui, 2009)
interpreted the signiﬁcant hiatus (Berriasian–Valanginian) between
the Itsuki and Nochino formations in the Itoshiro area, because
they considered the age of Itsuki Formation as the Tithonian, andthus did not used the transition of depositional environment as thecorrelation tool in the whole Hakusan Region.
Compared with eustatic sea level curve (Haq, 2014), TS-IIb(Berriasian) and TS-III (late Hauterivian) probably correspondto the duration of relatively high sea level in the early to middle
Early Cretaceous. Although much higher sea level in global
scale is recorded in the Aptian–Albian time, transgressive
stage corresponding to it is not recognized in the Tetori Group.
A possible explanation is that the change of depositional
environment from the huge brackish lake to the fluvial
environment occurred in the Barremian, and then the marine
inﬂuence had not been recognized in the Tetori Group after that
time.

36

SHIN-ICHI SANO

3 Appearance of relatively warmer and dryer climate indicatorsin the Tetori GroupThe plant fossils of the Tetori Group (the Tetori Flora) represent
the Tetori-type flora, which flourished in the Tetori Region, north
China and Russia, where the temperate and moderate humid
climatic condition prevailed (e.g., Kimura, 1987; Ohana andKimura, 1995). Yabe et al. (2003) pointed out the presence ofthermophilic plant species, which characterize the Ryosekitype flora of Kimura (1987), and/or pedogenetic calcareous
nodules from the upper formations of the Tetori Group in the
Takinamigawa, Shiramine, and possibly Shokawa areas (Fig. 2).
The Ryoseki-type ﬂora was mainly distributed in the Outer Zoneof Southwest Japan, south China and Southeast Asia, and has
been interpreted to represent subtropical climatic condition with
continuous dry season (e.g., Ohana and Kimura, 1995; Yabe etal., 2003). Kubota (2003) described the paleosol in the Kitadani
Formation, focusing on the characters of pedogenetic calcareous
nodules, and discussed the depositional environments of theKitadani Formation and paleoclimatic (relatively dry) conditionat that time. Subsequently, Yabe and Kubota (2004) described
Brachyphyllum, a typical thermophilic species, from the Kitadani
Formation in the Takinamigawa area. Terada and Yabe (2011)
reported the siliciﬁed wood specimens of Xenoxylon latiporosum
and Podocarpoxylon sp. from the Kitadani Formation. The latteralso indicates that the climate with dry season occurred at thattime. Recently, Sakai et al. (2014a, b) and Sakai (2014) conﬁrmed
the presence of thermophilic plant species from the upper
formations of the Tetori Group in the Shokawa, Shiramine andalso Itoshiro areas (Fig. 2). In addition, Yabe and Shibata (2011)
discussed the paleoecology of Brachyphyllum from the Kitadani
Formation, and the difference of climatic conditions between the
Oguchi Flora of the Kuwajima Formation and the flora of theKitadani Formation (warmer and dryer in the latter). This idea
is clearly supported by the fact that some typical elements of the
Oguchi Flora, for example, Nilssonia, Otozamites, Podozamites
reinii, ginkgos and czekanowskias, which characterize the Tetoritype ﬂora, have not been found in the Kitadani Formation (Yabeet al., 2012). At this moment, neither thermophilic species nor
pedogenetic calcareous nodule is reported from the lower andmiddle parts of the Tetori Group. Thus the presence of theseclimatic indicators (and possibly absence of typical elementsof the Oguchi Flora) in upper stratigraphic sequence can beconsidered as the useful tool to recognize climatic change in the
Early Cretaceous.
Recently Matsumoto et al. (2015) discussed a climatic barrier
may have separated the distribution of choristoderes (North)and crocodyliforms (South) in Asia during the Early Cretaceous,and the faunal change from choristoderan occurrences without
crocodilyforms in the Okurodani and Kuwajima formations tocrocodilyform occurrence without choristoderes in the Kitadani
Formation is concordant with climatic change from cool to hot,which is recognized based on ﬂoral change in Yabe et al. (2003).
Since such climatic changes probably affected the whole Tetori
Region at almost the same time, the presence of these climatic

indicators in upper stratigraphic sequence can be used to divide
the upper part of the Tetori Group prevailing warmer and dryer
climate from its other parts.
4 About 100 Ma volcanic/plutonic activities
About 100 Ma or Albian–Cenomanian volcanic/pultonic
rocks, such as the Hayashidani Andesite in the Itoshiro area, theUchinami Quartzdiorite in the Uchinamigawa area (Tomioka et al.,2000), and the Kitamatadani Diorite, the Awaradani Granodiorite,
the Makido Mafic Complex and the pre-Nohi Andesites in the
Shokawa area, unconformably covered or intruded into the Tetori
Group in the Hakusan Region. Volcanic/pultonic rocks of similar
age are sporadically but widely distributed in the northern Central
Japan, and can be correlated with the volcanic episodes recordedin the Kwanmon (or Kanmon) and Sasayama groups in the Inner
Zone of Southwest Japan (Tanase et al., 1994; Yamada et al.,
2001; Yamada, 2005 and references therein). These volcanic
episodes in the Hakusan Region are important not only fordeﬁning the upper limit of the age of the Tetori Group, but also
for the possible correlation with those recorded in other regions inSouthwest Japan, or even in East Asia.
SUMMARY OF NEW STRATIGRAPHIC SCHEME
Three subgroup division of the Tetori Group (sensu lato)(e.g., Maeda, 1961d; Yamada, 1988; Kusuhashi et al., 2002)
has been generally used to discuss its correlation and change ofdepositional environments, though such a scheme has recently
been challenged (e.g., Matsukawa et al. 2006, 2007; Matsukawa
and Asahara, 2010). As discussed above, the timing of change ofdepositional environment is not concordant with subgroup and/or
formation boundaries (Fig. 2), and thus the subgroup division
is not appropriate to discuss the correlation and environmental
changes, as suggested by Matsukawa et al. (2003b, 2006).
Middle–Late Jurassic strata (lower part of the Tetori Group(s.l.)) are distributed only in the Itoshiro area, whereas those of
the Early Cretaceous (middle to upper part of the Tetori Group(s.l.)) are widely distributed in the Hakusan Region. The latteroverlies the former with unconformity. Since the age of the former
is at least late Bathonian to middle Oxfordian, the Kimmeridgian–Tithonian strata is probably absent. Thus the Jurassic strata(Kuzuryu Group of Maeda (1952a) = Kuzuryu Subgroup of
Maeda (1961d)) should be separated from the Early Cretaceous
ones (Tetori Group (sensu stricto))*2.
Oishi (1933a, b) probably used the term Tetori Group forthe ﬁrst time. He clearly separated ammonoid-bearing formation(Kaizara Formation) in the Kuzuryu District from the Tetori*2

In this paper, the term Tetori Group is revised from the previous generalusage for the Middle Jurassic–Early Cretaceous stratum (e.g., Maeda, 1961d;
Yamada, 1988; Kusuhashi et al., 2002) to that for the Early Cretaceous stratum.
In case of the necessity of the distinction of two usage, the Tetori Group (sensu
lato, or s.l.) is used for the former case, and the Tetori Group (sensu stricto,
or s.s.) for the latter case. From this chapter, the Tetori Group means the
Tetori Group (s.s.).

37

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

L.

P E

Age
Cenomanian

Age
(Ma)

Depositional stage

?

113

?
Trigonioides Plicatounio

AptianDS3

125
Barremian
Hauterivian

129.4
132.9
139.8

Tetori GroupCRETACEOUS
Early

Stratofloras and paleobotanical topics(Yabe et al., 2003, 2012;
Yamada and Uemura, 2008)

DS4

Valanginian?

start of abundant quartzose gravels supply

TS-IIITS-IIb
?

145

Nippononaia

FO of thermophilic plants

MyreneDS2

BerriasianMyreneFO of Onychiopsis in the Tetori Group

Tithonian
152.1
Kimmeridgian
157.3
OxfordianCallovian
Bathonian
Bajocian

163.5
166.1
168.3
170.3

Kuzuryu Gp.

JURASSIC
Late

Geological and Paleontological events

100.5

AlbianM.

Transgressive
stage

TS-Ib
DS1
TS-Ia
?

FIGURE 3. Summary of the Depositional stages (DS(s)) in the Hakusan Region in the Hida Belt. Transgressive stages (TS(s)), geological and paleontologicalevents, and stratofloras and paleobotanical topics in the Middle Jurassic to Early Cretaceous strata are shown. Abbreviation: FO̶First occurrence. The
numerical ages are based on ICS (2015).

Group , though he considered both of the Tetori Group andthe Kaizara Formation are almost coeval, and belong to the Tetori
Series (Late Jurassic). The usage of the Tetori Group (s.s.) in thispaper is almost identical to the original usage in Oishi (1933a,b). Omura (1973) and Kumon (1995) used the both terms of theKuzuryu and Tetori groups, and similar usage was also seen in
Tashiro (2000) and Kunugiza et al. (2002b). Following the usageof the Kuzuryu Subgroup in Maeda (1961d), the Kuzuryu Group,
re-proposed in this paper, includes Oxfordian marine strata in the
Jinzu Region.
The idea of depositional stage (DS) is introduced here for the
discussion of the paleoenvironmental changes in the Jurassic–
Early Cretaceous strata in the Hakusan Region in the Hida Belt
(Fig. 3). The Kuzuryu Group covers the basement in the Hida
Belt, such as the Hida Metamorphic Rocks, and represents the ﬁrst
depositional stage (DS1) of the Mesozoic non-metamorphic strata
in the Hida Belt. The Tetori Group covers the Kuzuryu Group in
the Itoshiro area. In other areas, it unconformably overlies, or in
fault contact with the constituents of the Hida Belt (e.g., Maeda,
1961d; Matsukawa and Nakada, 1999; Matsukawa et al., 2003a,
2007). It is almost continuous sequence, and no large time gap
is known during its depositional time, though the depositional
environmental change from brackish lake to ﬂuvial environmentis recognized. DS2 and DS3 are proposed here for the lower
brackish dominant part and the upper fluvial part of the Tetori
Group, respectively (see Fig. 3). Since TS-IIb and TS-III arerecognized in DS2, DS2 ranged at least from Berriasian to Late
Hauterivian, indicating the presence of significant stratigraphic
gap between the Kuzuryu and Tetori groups (see discussionin Sano et al., 2013). The Tetori Group showed much wider
distribution at the period of TS-III than that of TS-IIb, especiallyin northwestern part of the Hakusan Region, and such wider
distribution continues to DS3. The transition from DS2 to DS3
probably occurred within the Barremian stage. DS3 represents thestratigraphc range from the Barremian to Aptian, though its upper
limit is still ambiguous.
After the deposition of the Tetori Group, about 100 Ma or
Albian–Cenomanian volcanic/pultonic rocks unconformably
covered or intruded into the Tetori Group in the Hakusan Region.
These volcanic/plutonic rocks can be considered as DS4 in thispaper for the comparison with other Albian strata in Southwest
Japan, such as the Kwanmon and Sasayama groups (e.g.,
Kusuhashi et al., 2013; Aoki et al., 2014), or even in East Asia.
1 Comparison with previous stratigraphic schemes
The new stratigraphic scheme, here proposed, seems to bebasically similar to the classic scheme of Maeda (1961d), Yamada(1988) and Kusuhashi et al. (2002). However, the accumulationof recent age data revealed that marine strata is not limited to the
Kuzuryu Group, contrary to the Maeda s supposition, and a large
time gap between the Kuzuryu and Tetori groups is supposed

38

SHIN-ICHI SANO

in this paper. In addition, the transition from DS2 to DS3, here
proposed focusing on the disappearance of marine influence,is not concordant with the boundary between the Itoshiro andAkaiwa subgroups of Maeda (1961d). The upper limit of the ageof the Tetori Group is still uncertain. Instead of Maastrichtian
Omichidani (or Omitidani) Formation, DS4 is proposed above
the Tetori Group in this paper, and probably can be used to becorrelated with Albian strata in the Inner Zone of Southwest
Japan.
The stratigraphic scheme in this paper is generally similar also
to that of Fujita (2003). However, he used the FT data for theage assignment of each area, and interpreted that the base of theTetori Group in most distributional areas is tentatively assigned
to the base of Hauterivian (= the base of the Early Cretaceous
strata in the Outer Zone of Southwest Japan), because Berriasianammonoids had not been known from the Tetori Group at thattime. After recent accumulation of ammonoid data and U-Pb
dating in the Tetori Group, the age assignment of this group andcorrelation among each distributional area in Fujita (2003) arecompletely revised in this paper.
Omura (1973) proposed the complete different idea of thestratigraphy that the formations of the Tetori Group represent
different lithofacies of the same age. However, recent age data
mentioned in this paper revealed that different ages are usuallysuggested for the formations in each area.
Matsukawa and his colleagues scheme (see Matsukawa andAsahara (2010) and Matsukawa et al. (2014a, fig. 7) for recent
concept) is signiﬁcantly different in the correlations of the selected
formations/horizons in each distributional area and thus in theirage assignment from the new scheme here proposed: for example,
the correlation of the Itsuki Formation in the Itoshiro area andthe Tithonian ammonoid-bearing horizon in the Kamihambaraarea; that of Late Hauterivian ammonoid-bearing horizon in the
Uchinamigawa area to the Amagodani Formation in the Shokawa
area; that between the Okurodani Formation in the Shokawa
area and the Kitadani Formation in the Takinamigawa area. Suchideas of correlation are not supported by the recent age data, or
contradict those discussed in this chapter, and cannot be adopted
here.
IMPLICATION FOR THE AGES OF VERTEBRATE FAUNASAND FLORAS OF THE TETORI GROUP
1 Age of vertebrate fossil-bearing formations
In the Tetori Region, several important vertebrate fossil
localities are known. Their age assignment is still controversial,and discussed here based on new stratigraphic scheme of theTetori Group. The fossil-bearing stratum at Locality KO-2 in the
Shokawa area is the lowermost part of the Okurodani Formation(e.g., Hasegawa et al., 1995; Cook et al., 1998, Evans et al.,1998), and thus is assigned to Late Hauterivian or earlier, because
this horizon is lower than last brackish horizon (but later than
Berriasian, which is the age of the underlying Mitarai Formation).
At Kaseki-kabe in the Shiramine area, a vertebrate fossil-bearing

stratum is in the upper part of the Kuwajima Formation, andis assigned to Barremian, because it is younger than the age ofbrackish horizon, and earlier than Barremian–Aptian Akaiwa
Formation. A vertebrate fossil-bearing stratum at the Kitadani
Dinosaur Quarry in the Kitadani Formation can be considered
as Aptian, because it is younger than the age of the last brackishhorizon in this area (Unit A of Sano et al. (2008)), and overlies
also the thick sandstone dominant unit (Unit B of Sano et al.
(2008)), which is probably corresponding to the Barremian–
Aptian Akaiwa Formation in the Shiramine area. These ages ofvertebrate fossil-bearing formations are well concordant withthe recent turtle evolutionary hypothesis/biostratigraphy, namely
Okurodani, Kuwajima, Akaiwa and Kitadani turtle faunas inascending order (Hirayama, 2007, 2010; Hirayama et al., 2013).
2 Age of plant fossil-bearing formations and climatic change
Yabe et al. (2003) reviewed the floral composition of the
Oguchi, Akaiwa and Tamodani floras, in ascending order, anddiscussed the change of climatic conditions recorded in the Tetori
Group. Tamodani, a type locality of the Tamodani Flora, islocated in the Kamihambara area in the Middle Row of the Tetori
Group (s.l.) in the Kuzuryu District, and thus its stratigraphy andpossibly its age also need revision. It is better to use the name of
the Kitadani Flora (Yabe et al., 2012) instead of the Tamodani
Flora for the youngest stratoﬂora in the Tetori Group. Charactersof the youngest stratoflora discussed in Yabe et al. (2003) do
not change though the exclusion of the ﬂoral composition of the
Tamodani locality from the Kitadani Flora (A. Yabe personalcommunication, 2014. February). The Oguchi Flora is recoveredfrom the upper part of the Kuwajima Formation, and is assigned
to Barremian, as discussed in previous chapter. The Akaiwa Florais recovered from the Barremian–Aptian Akaiwa Formation, andthe Kitadani Flora from the Aptian Kitadani Formation. Thus
climatic change (warmer and dryer) recognized in Yabe et al.
(2003) probably occurred around the period of the Barremian–
Aptian boundary.
COMPARISON WITH CRETACEOUS STRATA FORMERLYASSIGNED TO THE TETORI GROUP (SENSU LATO)IN OTHER REGIONSThe Tetori Group (s.l.) is sporadically but widely distributed innorthern Central Japan (e.g., Maeda, 1961d; Yamada, 1988) (Fig.
1). The attribution of Late Mesozoic strata in most of these areas
to the Tetori Group (s.l.) is challenged recently (e.g., Sano et al.,2013; Matsukawa et al., 2014a; Takeuchi et al., 2015a). In thischapter, Late Mesozoic strata in the Jinzu Region in the Hida Belt,
and the Mana–Ono–Nagano–Kamihambara areas of the Kuzuryu
District, Tochio, Asahi (or Tomari) and Nyukawa areas in the
Hida Gaien Belt are focused on. Furthermore, the possible Early
Cretaceous stratum in the Katashina area of the Joetsu Belt, which
has been considered as the correlative of the Tetori Group (s.l.),is also brieﬂy mentioned. Marine inﬂuence, biostratigraphy, andnumerical age data (mainly LA-ICPMS U-Pb zircon age data) are39

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

Kurobegorodake
102Ma
Diorite?
?

Aptian125
Hauterivian

129.4

DS3
?

132.9

DS2
139.8

C) Mana Ono Nagano
Kamihambara areas
Hd

TS-III

?

145

Si

?

99.4MaSt

U
110.4Ma

110.1Ma?
In

Ku
120.0Ma

Io?

128.7Ma
ca.123Ma
123.4Ma

M?

?

TS-IIb?

Tithonian

TS-IIa152.1

uK

124.6MaIMyopholastanakai M?

Tetoria

T sanchuensis

?
?

KK
A

Kimmeridgian

M

157.3
163.5 DS1
166.1
168.3
170.3

Kuzuryu Gp.

?

OxfordianCallovian
Bathonian
BajocianD)Tochio areaO?

Berriasian

JURASSIC
LateB)Asahi area

106Ma

113

Barremian

A)Jinzu Region

89.7Ma96.6MaDS4

Valanginian

M.

Transgressive
stage

100.5

AlbianCRETACEOUS
Early

Hakusan Region

Managawa Group

Cenomanian

Age
(Ma)

Jinzu Group

Age

Tetori Group

L.

P E

Ng

TS-Ib

?

TS-Ia
?

plutonic bodies
strata mainly composedof volcanic rocks
fluvial deposits
without molluscan fossils
strata containing
freshwater molluscs

strata containing
brackish water molluscs
strata dated
by ammonoid fossils
unconformable
relationship: Zircon U-Pb dating: K-Ar dating

M : Myrene (Mesocorbicula): pedogenetic calcareous nodules: thermophilic plants

FIGURE 4. Comparison of stratigraphy, horizons of marine, brackish and freshwater molluscs and climatic indicators (pedogenetic calcareous nodules andthermophilic plants), numerical age data, and depositional and transgressive stages (DS(s) and TS(s)) of the Middle Jurassic to Early Cretaceous strata inthe each regions/areas in northern Central Japan. Myopholas tanakai and Tetoria sanchuensis are typical Hauterivian brackish bivalves in the Outer Zone ofSouthwest Japan. These strata except Albian volcanic/plutonic rocks were previously called as the Tetori Group (s.l.), but are divided into four different groups:
the Kuzuryu, Tetori (s.s.), Jinzu and Managawa groups in this paper. See the text for details. Abbreviation: Io̶Ioridanitoge Formation, In̶Inotani Formation,
Si̶Shiroiwagawa Formation for the Jinzu Group in the Jinzu Region (Matsukawa et al., 2014a); M̶Mizukamidani Formation, Ku̶Kurobishiyama
Formation, U̶Uchiyama Formation, St̶Shiritakayama Formation, O̶Oyashirazu Formation for the Asahi area (Takeuchi et al., 2015a); Ng̶ Nagano
Shale , A̶ Ashidani Formation in the Kamihambara area (Fujita, 2002) , KK̶Kurotodo and Kamihambara formations, I̶ Itsuki Formation in the
Kamihambara area (Fujita, 2002) , uK̶ Upper Formation of the Kuzuryu Subgroup (Yamada et al., 1989) , Hd̶Hayashidani Andesite for the Mana–Ono–
Nagano–Kamihambara areas in the Kuzuryu District (Tanase et al., 1994; Sano et al., 2013); T̶Tochio Formation for the Tochio area (Maeda, 1958a). The
numerical ages are based on ICS (2015).

reviewed in each area, and compared with those of the Kuzuryu
and Tetori groups (Fig. 4).
1 Jinzu Region in the Hida Belt (Fig. 4A)
Upper Mesozoic strata (= The Tetori Group (s.l.)) in the Jinzu
Region is divided into two parts: lower marine sequence andupper non-marine sequence (e.g., Maeda, 1961d; Hirasawa etal., 2010; Matsukawa et al., 2014a). The lower sequence is now
in fault contact with, but originally unconformably overlies theconstituent rocks of the Hida Belt, such as Hida Metamorphic
Rocks and granitoids (e.g., Matsukawa et al., 2014a). The upper
sequence unconformably overlies the lower sequence or theconstituents of the Hida Belt (e.g., Kashiwagi and Hirasawa,
2010; Matsukawa et al., 2014a).
The stratigraphy, correlation and age assignment of the upper

40

SHIN-ICHI SANO

non-marine sequence (= Jinzu Group of Matsukawa et al. (2014a))
is still debatable (e.g., Maeda, 1961d; Omura, 1973, 1974;
Matsukawa et al., 1997b, 2014a; Board of Education of Toyama
Prefecture, 2003; Hirasawa et al,, 2010), because of the absenceof marine index fossils and key beds/horizons. In this paper, thenames of the strata of the upper non-marine sequence basicallyfollow those of Matsukawa et al. (2014a): the Ioridanitoge, Inotani
and Shiroiwagawa formations, in ascending order.
Marine/brackish horizons̶The lower marine sequence
contains abundant marine ammonoids, other molluscs and trace
fossils (e.g., Kobayashi, 1956, 1957b; Sato, 1962, 2008; Maeda,
1962c; Maeda and Kawabe, 1963, 1966; Matsukawa et al., 2008b;
Hirasawa and Kashiwagi, 2010; Hirasawa et al., 2010; Hirasawa,
2012a, b, 2015; Sato et al., 2012; Sato and Yamada, 2014).
Abundant radiolarians and other microfossils were also recently
reported from this sequence (Kashiwagi and Hirasawa, 2010,
Hirasawa et al., 2010). It should be noted that marine inﬂuence
was supposed by the geochemical study in the Shiroiwagawa
Formation (Hasegawa et al., 2010), though further studies arenecessary to clarify this possible marine record. On the contrary,rare occurrences of possible freshwater bivalves are recently
reported from the Ioridanitoge and Inotani formations (Shigeno,
2003; Fujita, 2014; Matsukawa et al., 2014a, b).
Biostratigraphic age data̶The lower marine sequence isassigned to the Oxfordian age by the ammonoid biostratigraphy(e.g., Sato, 1962, 2008; Matsukawa et al., 2008b; Sato et al.,2012; Sato and Yamada, 2014). Such age assignment has been
conﬁrmed recently by the radiolarian biostratigraphy (Kashiwagi
and Hirasawa, 2010; Hirasawa et al., 2010).
Chemostratigraphy̶Hasegawa and Hibino (2006) alreadypublished the preliminary result of organic carbon isotope study
from the upper non-marine sequence. If reliable datum planes
can be established, carbon-isotope stratigraphy probably provides
a powerful tool for the correlation between the non-marine andmarine strata (e.g., Hasegawa, 2003; Hasegawa and Hibino, 2006;
Weissert et al., 2008). Attention should be paid to the applicationof this method to the stratigraphic study of Mesozoic non-marine
strata in future.
Numerical age data̶Kawagoe et al. (2014) reported 120.0± 1.2 Ma (2 SD) LA-ICPMS U-Pb zircon age for the tuff bed
possibly from the upper part of the Inotani Formation. Matsukawa
et al. (2014a) discussed the age of non-marine sequence as
Aptian–Albian based on their own new FT dating with best-fit
peak ages (112.5 (-11.0, +11.7) Ma, 102.6 (-6.1, +6.5) Ma, 121.0(-12.1, +11.7) Ma, 111.6 (-6.2, +6.6) Ma, in ascending order) of
the tuffaceous sandstone in the Inotani Formation. On the other
hand, Harayama et al. (1991) reported K-Ar age of 106 ± 5 Ma and102 ± 2 Ma from the Kurobegorodake Diorite, which intruded the
Jinzu Group in the easternmost part of its distribution. These
data probably represent the upper limit of the depositional ageof the Jinzu Group. In addition, such plutonic activities possibly
caused the thermal effects to the FT age data of the Jinzu Group.
Thus the age of the Jinzu Group is considered as the Aptian–early? Albian in this paper, and signiﬁcant hiatus (at least from theKimmeridgian to Barremian) is supposed to occur between thelower marine and upper non-marine sequences.
Correlation̶The Oxfordian marine sequence corresponds
to TS-Ib represented by the Yambarazaka Formation in the
Hakusan Region. The lower marine sequence is redeﬁned as thethe Kuzuryu Group in this paper, as mentioned before, though
the strata correlated with the middle to lower part of the Kuzuryu
Group (Kaizara Formation (corresponding to TS-1a) or lower
formations) in the Hakusan Region have not been recognized in
the Jinzu Region (Fig. 4).
Matsukawa et al. (2014a) considered their FT age data aresigniﬁcantly younger than the age of the Tetori Group, and thus
proposed new name: the Jinzu Group for the upper non-marine
sequence of the Mesozoic strata in the Jinzu Region. However,since DS3 in the Hakusan Region is assigned to the Barremian–
Aptian as discussed above, the uppermost part of the Tetori Groupcan be considered as the age equivalent to at least some part of the
Jinzu Group. The absence of DS2 equivalent in the Jinzu Region
suggest the difference of the geological histories of the Cretaceousbasins between the Hakusan and Jinzu regions, and support theidea of the separation of the Jinzu Group from the Tetori Group.
Difference of the river systems between the two groups has
already been pointed out by the detrital zircon geochronology(Kawagoe et al., 2014), and probably support that idea.
On the other hand, the Albian part of the Jinzu Group can
be correlated with DS4 in the Hakusan Region. Occurrenceof thermophilic plant species probably from the the Inotani
Formation (Yabe et al., 2003), and the presence of the red
beds with abundant pedogenetic calcareous nodules in the
Shiroiwagawa Formation (Shigeno et al., 2004; Matsukawa et al.,2014b) indicate that the warmer and dryer climatic conditions,which are comparable to those of the upper part of DS3 in the
Hakusan Region (e.g., Yabe et al., 2003) or much younger (Albian)strata, such as the Kwanmon and Sasayama groups (e.g., Yamada,2009; Horiuchi et al., 2009), prevailed there.
2 Hida Gaien Belt
1) Kuzuryu District (Fig. 4C)
The Tetori Group (s.l.) in this district is divided into threefault-bounded parts (Northern, Middle and Southern rows): theNorthern Row in the Hida Belt and the Middle and Southern rows
in the Hida Gaien Belt (Sano et al., 2013). Boundary between the
Northern and Middle rows is marked by the fault running southern
margin of the Hida Metamorphic Rocks, that of the Middle andSouthern rows by the Ono Thrust. Stratigraphy and age data of theTetori Group (s.l.) in the Middle and Southern rows were recently
reviewed in Sano et al. (2013), and now it is clear that they areprobably different from those of the Tetori Group (s.s.) in the
Itoshiro area in the Northern Row. Thus the Managawa Group,
named in Kobayashi (1954), is used here for the Late Mesozoic
strata in the Mana–Ono–Nagano–Kamihambara areas in the
Middle Row to avoid confusion with the Tetori Group (s.s.). In
this chapter, Late Mesozoic strata in the Middle Row are mainly
focused on, and those in the Southern Row is brieﬂy mentioned
in the Remarks section. The Managawa Group unconformably

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

overlies, or is in fault contact with the Carboniferous Fujikuradani
Formation, a constituent rock of the Hida Gaien Belt, in the
Mana–Ono areas (e.g., Maeda, 1961a; Yamada, 1967; Fukahori
et al., 1983). At present the stratigraphy of the Mesozoic strata in
the Middle Row await its complete revision (Sano et al., 2013).
Since the names of formations of the Tetori Group (s.s.) in the
Itoshiro area in the Northern Row had been usually applied to thesuccession in the Middle Row, the names of the formations of theManagawa Group are not fully established yet.
Marine/brackish horizons̶Many ammonoids, belemnites
and bivalves have been described or reported from theManagawa Group in the Mana–Ono–Nagano–Kamihambara
areas (Kobayashi, 1954; Hayami, 1960; Maeda, 1961a, 1962d;
Sato, 1962, 2008; Yamada et al., 1989; Fujita et al., 1998; Fujita,
2002; Matsukawa et al., 2003c; Sato and Yamada, 2005; Yamada
and Uemura, 2008; Sano et al., 2013). Marine strata are called
differently in each area, such as the Kurotodo Formation in
the Mana–Ono areas, the Nagano Shale in the Nagano area(see Sano et al., 2013), and the Kamihambara Formation in the
Kamihambara area (Fujita, 2002). At least two marine strata,
corresponding to TS-Ib (Oxfordian) and TS-IIa (Tithonian), aresupposed to be there, though the distribution of each stratum andtheir stratigraphic relationship are still ambiguous (Sano et al.,2013).
Brackish bivalves occur in several horizons in the Kamihambara
area (Fujita, 2002). For examples, Myrene (Mesocorbicula) were
known from the horizons above and below the Kamihambara
Formation (TS-IIa) ( Itsuki and Ashidani formations ,respectively; Fig. 4). Another brackish bivalve Myopholas tanakai
and freshwater molluscs were also reported from the horizon
above the Kamihambara Formation (= Itsuki Formation of
Fujita (2002); Fig. 4) (Fujita, 2002; Sano et al., 2013). Although
the occurrences of brackish and freshwater molluscs were also
reported from the southern part of the Mana area (e.g., Kobayashi,
1954; Maeda, 1961a; Yamada et al., 1989), their stratigraphic
position in the Managawa Group are uncertain.
Hasegawa et al. (2010) confirmed the marine or brackish
condition of the middle part of the Managawa Group in the
Kamihambara area (= Itoshiro and Akaiwa subgroups in
the Izumi Section (east) in Hasegawa et al. (2010)) based ongeochemical studies.
Biostratigraphic age data̶Sato and Westermann (1991)
established the Oxfordian ammonoid zonation in the Tetori Group(s.l.) mainly based on the ammonoid records from Nagano. This
ammonoid-bearing stratum was assigned to the Nagano Shalein the Nagano area (Sano et al., 2013). An Oxfordian ammonoid
specimen from the Mana area was also figured in Sato (1962).
A Tithonian ammonoid Parapallasiceras has been described orreported from the Mana, Ono and Kamihambara areas (Sato and
Yamada, 2005; Yamada and Uemura, 2008; Sano et al., 2013).
A brackish bivalve Myopholas tanakai has been known fromthe Hauterivian formations in the Outer Zone of Southwest
Japan (Tashiro, 1994). Its occurrence from the horizon above theTithonian Kamihambara Formation possibly contributes its age
assignment (Fujita, 2002; Sano et al., 2013).

41

Rare fern spores were reported from the Kamihambara area,
though age assignment based on these fossils is probably difﬁcult(Umetsu and Matsuoka, 2003; Umetsu and Sato, 2007).
Numerical age data̶Lapilli tuff from the upper part of theManagawa Group in the Mana area ( Upper Formation of theKuzuryu Subgroup ; Fig. 4) has 124.6 ± 2.3 Ma (2 SD) LAICPMS U-Pb zircon age (Kawagoe et al., 2012). The Hayashidani
Andesite of ca. 100 Ma, representing DS4 in the Hakusan Region,
directly covers also the Managawa Group in the Kamihambara
area with unconformity (Tanase et al., 1994). It means that the
Tetori Group in the Hida Belt and the Managawa Group in the
Hida Gaien Belt had juxtaposed before DS4.
Correlation̶Marine strata corresponding to TS-Ib and TSIIa have been recognized in the Managawa Group (e.g., Sato,
1962; Sato and Yamada, 2005; Sano et al., 2013), though theirstratigraphic relationship (belonging to a same formation or two
different formations) are still uncertain. It should be noted that
TS-IIa is known only in the Managawa Group, but not in the
Tetori Group.
The Managawa Group has the stratigraphic range at least fromthe Oxfordian to early Aptian, and corresponding to the upper
part of the Kuzuryu Group and the Tetori Group. No large time
gap has been known during its depositional time at this moment.
Even during the time of possible hiatus between the Kuzuryu
and Tetori groups, the Kamihambara and Kurotodo formations
representing TS-IIa, which has not been known in the Mesozoic
strata in the Hida Belt, were deposited. However, since the change
of depositional system in the sedimentary basin was supposed tooccur at the time between the Kurotodo Formation and overlying
non-marine strata (possibly during the time between Tithonian andHauterivian) in the Mana–Ono areas (Yamada et al., 1989; Sanoet al., 2013), stratigraphic gap in this horizon can be expected infuture studies.
Remarks̶In the Southern Row of the Tetori Group (s.l.)in the Kuzuryu District, its northernmost part contains possible
Tithonian–Berriasian ammonoids and inoceramids, which isequivalent in its age and fauna to the Managawa or Tetori (s.s.)Group, whereas the age of its most part is still uncertain (Sanoet al., 2013). The occurrence of Hausmannia (Maeda, 1961a),
usually recovered from Late Triassic to Early Jurassic strata, fromthis latter part indicates that this undated stratigraphic sequence
may be correlated with the Early Jurassic Kuruma Group or its
equivalents, which is distributed in the Asahi area in the Hida
Gaien Belt (T. Yamada written communication, 2013. August).
Attention should be paid to that the gravels of serpentine andcrystalline schist have been reported from this sequence (Sohma
et al., 1983, fig. 4; Sohma and Maruyama, 1989, fig. 4, 5), aswith the Kuruma Group (Kobayashi et al., 1957; Kumazaki andKojima, 1996; Takeuchi et al., 2006). Furthermore, Northeast–
Southwest directed lenticular distribution of the Tetori Group (s.l.)in the Southern Row indicates that these Mesozoic strata possibly
formed a dextral strike-slip duplex with the Permian–Triassic
formations (including the Motodo Formation, which had been
considered as a part of the Tetori Group (s.l.) (see Kawagoe etal. (2013) for the discussion of its attribution)) of the Hida Gaien

42

SHIN-ICHI SANO

Belt after its deposition (Sano et al., 2013). In this case, their age
deﬁnes the lower limit of the dextral movement, and they possibly
deposited faraway place (in the East) from the Managawa Groupand even from the Tetori Group (s.s) (Sano et al., 2013). Further
studies are necessary to conﬁrm these hypotheses.
2) Tochio area (Fig. 4D)
Maeda (1958a) established the Tochio Formation in the
Tetori Group (s.l.) in the Tochio area. Matsukawa et al. (2007)
considered the Tochio Formation is a time equivalent to the
Sugizaki Formation, both of which were possibly deposited in thesame or nearby basin(s). However, since the differences between
the Tetori Group in the Hida Belt and Late Mesozoic strata in the
Hida Gaien Belt were pointed out in the Kuzuryu District (Sanoet al., 2013), the Tochio Formation in the Hida Gaien Belt is
separately discussed from the Tetori Group in the Hida-Furukawa
area in the Hida Belt in this paper. The Tochio Formation is infault contact with the constituent rocks of the Hida Gaien Belt
(Harayama, 1990; Otoh et al., 2003). Otoh et al. (2003) pointed
out that the age of the Tochio Formation provides the clues torevealing the formation of the Hida Gaien Belt, constraining thetiming of the sinistral shearing there.
Biostratigraphic age data̶Maeda (1959) paid attention
to the occurrences of two brackish bivalves from the Tochio
Formation: Polymesoda (Isodomella) kobayashii sp. nov. andPolymesoda (Paracorbicula) sanchuensis, which are different
from brackish molluscs in other areas of the Tetori Group (s.l.),but probably similar to those of Lower Cretaceous in the Outer
Zone of Southwest Japan and the Yoshimo Formation of the
Toyonishi Group in the Inner Zone of Southwest Japan, andnamed the Kamitakara Fauna for them (Maeda, 1958a). Later
Hayami (1975) assigned these species to Crenotrapezium?
kobayashii and Tetoria sanchuensis, respectively. In addition,
Matsukawa et al. (2007) ﬁgured Crenotrapezium kobayashii andTetoria yokoyamai from this formation.
Tetoria sanchuensis has been recovered from the Hauterivian
strata (Kondo et al., 2006) or Hauterivian–Early Aptian strata(Kozai and Ishida, 2003; Kozai et al., 2005, 2012; Nishida et al.,2013) in the Outer Zone of Southwest Japan. T. yokoyamai has
been only known from DS2 in the Hakusan Region, and assigned
to Berriasian–Late Hauterivian. Thus the age of the Tochio
Formation is supposed to be the Hauterivian based on these
bivalves.
Correlation̶On the basis of the supposed Hauterivian ageof the Tochio Formation, it can be correlated at least partly to the
Early Cretaceous strata of the Managawa Group. Furthermore,
occurrences of Hauterivian (possibly corresponding to TS-III)brackish bivalves, which have been known only from the Outer
Zone of Southwest Japan, in the Managawa Group in the Kuzuryu
District and the Tochio Formation may suggest possible similarityof tectonic or paleoenvironmental settings between the two strata.
The Tochio Formation is tentatively included in the Managawa
Group in the following discussion.
Remarks̶Although numerical age data have not beenobtained directly from the Tochio Formation, sandstone samples

from the putative Ordvician Hitoegane Formation in the Fukuji
area in the Hida Gaien Belt, which is adjacent to the Tochio
area, contain detrital zircon of the Cretaceous or Paleocene LAICPMS U-Pb age (the youngest age is 123.2 Ma for NK-12, 59.7
Ma for NK-22) (Nakama et al., 2010). The former age is almost
coeval with the upper part of the Managawa Group in the Mana
area. Thus the distribution of Cretaceous strata in the Tochio–
Fukuji areas is possibly much wider than previously thought.
It should be noted that conspicuous shear zone runs along thesouthern boundary of the Tochio Formation (Otoh et al., 2003),
and complex geological structure is suggested for these areas.
Stratigraphic relationship among the Early Cretaceous Tochio
Formation, the Maastrichtian Oamamiyama Group (Kasahara,
1979; Takahashi and Shimono, 1982), and newly-recognized
Cretaceous–Paleocene strata in the Fukuji area remain unsolved,
and further studies are awaited.
3) Asahi area (Fig. 4B)
Although non-marine strata covering the Kuruma Groupin the Asahi area in the Hida Gaien Belt (e.g., Mizukamidani,
Kurobishiyama and Shiritakayama formations) have been
considered as the Tetori Group (s.l.) (e.g., Chihara et al., 1979; see
Takeuchi et al., 2015a for historical review), their age assignmenthas been controversial for a long time, because of the lack ofindex fossils. In this paper, the stratigraphy of Cretaceous nonmarine strata in this area are basically based on Takeuchi et al.
(2015a).
Biostratigraphic age data̶Marine or brackish horizon is
not recognized in this area. Sakai et al. (2013) recently reported
the occurrence of possible freshwater molluscs from theShiritakayama Formation of the Takeuchi et al. (2015a, b), which
was originally reported from the Mizukamidani Formation in
Sakai et al. (2012).
Numerical age data̶Takeuchi et al. (2015a) applied the
LA-ICPMS U-Pb zircon dating to these strata and related rocks,
and revealed that the youngest age of detrital zircon from the
Mizukamidani Formation is ca. 123 Ma; the age of a dacite
dyke intruding the Mizukamidani and overlying Kurobishiyama
formations is ca. 109 Ma; the youngest age of detrital zircon
from the Uchiyama Formation, which possibly covers the
Kurobishiyama Formation with unconformity, is ca. 110 Ma. Thus
the Mizukamidani and Kurobishiyama formations can be assigned
to the Aptian (–early Albian) (ICS, 2015).
On the other hand, both the Shiritakayama and Uchiyama
formations underlain the Oyashirazu Formation, where K-Ar agesof 96.6 ± 4.8 Ma and 89.7 ± 4.5 Ma were reported (Yamada et al.,2001). The youngest age of detrital zircon from the Shiritakayama
Formation is also ca. 110 Ma, though the reliability of this datum
needs further confirmation (Takeuchi et al., 2015a, b). Both the
Shiritakayama and Uchiyama formations show almost same age:
Albian (–early Cenomanian) (ICS, 2015), and can be consideredthat they are composed of contemporaneous heterotopic facies (theUchiyama Formation contains thick rhyolitic or andesitic lavas/
volcanic rocks) (Takeuchi et al., 2015a).
Correlation̶Aptian strata are distributed more widely

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

in the Hida and Hida Gaien belts than pre-Aptian strata. The
Mizukamidani and Kurobishiyama formations can be correlatedwith the upper part of the Managawa Group or the lower part of
the Jinzu Group, or the uppermost part of the Tetori Group or
DS3 in the Hakusan Region. The Uchiyama and Shiritakayama
formations are correlated with DS4 in the Hakusan Region, or
possibly to the upper part of the Jinzu Group, or even to the
Kwanmon and Sasayama groups.
Tomita et al. (2007) and Takeuchi et al. (2015b) recognized
the similarity of the characters of composition of clastics, theirstratigraphic change, and the occurrences of Permian and Triassic
radiolarian fossils in the gravels between the Mizukamidani and
Kurobishiyama formations and the Jinzu Group. On the other
hand, Takeuchi et al. (2015a, b) pointed out the difference ofthe published depositional age between these strata, and also thenecessity of the application of U-Pb zircon dating to the Jinzu
Group to reconfirm their possible correlation. As discussed
above, the Mizukamidani and Kurobishiyama formations can becorrelated with at least some part of the Jinzu Group. Thus the
Early Cretaceous strata in the Asahi area is most likely correlated
in age and clastic composition with the Jinzu Group. Since
the Uchiyama Formation overlies not only the Kurobishiyama
Formation but also the granite in the Hida Belt (Takeuchi etal., 2015a), it is indicated that the Hida Belt and Hida Gaien
Belt in this area had been juxtaposed before the deposition ofthis formation (probably Albian) at the latest, and possibly in
the Aptian, and thus similar lithofacies (e.g., the Jinzu Group)
probably deposited in both belts.
4) Nyukawa area
The Yokoo Conglomerate Formation (Kasahara, 1979) , or
Yokoo Conglomerate (Kojima, 1986) in the Nyukawa area
has been assigned to the Tetori Group (s.l.) (e.g., Nozawa et al.,
1975; Otoh et al., 2003). Matsukawa et al. (2007) included it in
the Tanemura Formation of the Tetori Group (s.s.) in the HidaFurukawa area. However, it is distributed near the boundary
between the Hida Gaien Belt (North) and the correlative of the
Ultra-Tamba Belt (South) (Kojima, 1986; Niwa et al., 2002), andprobably separated from the Tetori Group (s.s.). Although thestratigraphic position and age of this stratum is still uncertain,by the presence of reddish brown to yellowish brown tuffaceous
rocks (Kojima, 1986), it can be correlated with Albian volcanic
strata, such as the Hayashidani Andesite in the Kuzuryu District or
the Uchiyama Formation in the Asahi area both in the Hida Gaien
Belt.
3 Joetsu Belt
Very narrow distribution of the possible Early Cretaceousshallow marine to non-marine stratum has been known in the
Katashina area in the Joetsu Belt, which located about 140
km east from the Asahi area (Hayashi et al., 1965; Toya et al.,
1965; Hayama et al., 1969; Sudo, 1976). The occurrences ofMyrene (Mesocorbicula) tetoriensis, which characterizes the
Early Cretaceous Tetori Group (s.l.), and plant fossils similar

43

to the Tetori-type flora were reported from the Tokurazawa (orTokurasawa) Formation (Hayashi et al., 1965; Kimura et al.,
1979; Matsukawa et al., 2015). On the basis of these data, theTokurazawa Formation has been assigned to, or correlative with
the Tetori Group (s.l.) (Hayashi et al., 1965; Toya et al., 1965;
Kimura et al., 1979; Takenouchi and Takahashi, 2002; Matsukawa
et al., 2015).
Marine/brackish horizons̶The Tokurazawa Formationconsists of the Lower, Middle and Upper members (Toya et al.,
1965; Kimura et al., 1979). Marine belemnites were recoveredfrom the Lower Member, and a brackish bivalve Myrene and plantfossils from the Upper Member (Hayashi et al., 1965; Toya et al.,
1965; Kimura et al., 1979; Matsukawa et al., 2015). The Middle
Member is composed of an arkose and partly conglomeratic
sandstone (Toya et al., 1965; Matsukawa et al., 2015), andpossibly indicates the freshwater or terrestrial depositional
environment.
Biostratigraphic age data̶No good age-diagnostic fossil has
been reported at present. Thus the Tokurazawa Formation is notshown in Figure 4.
Correlation̶The Joetsu Belt is characterized by lowgrade schists indicating high-pressure type metamorphism,
metabasic rocks, ultrabasic rocks, Permian accretionary complex,
and Permian, Late Triassic, Early Jurassic and possible Early
Cretaceous shallow marine to brackish strata (the Oze-Takinosawa
Formation, the Okutone Group, the Iwamuro Formation, theTokurazawa Formation, respectively), and located in the innerside of the Jurassic accretionary complex (Ashio Belt) (Takenouchi
and Takahashi, 2002). The Tokurazawa Formation is surrounded
by, and in fault contact with the Tokura Metabasic rocks (e.g.,
Takenouchi, 1988; Takenouchi and Takahashi, 2002). Such
constituent rocks of the Katashina area are similar to those in the
Asahi area and the Southern Row of the Kuzuryu District, both in
the Hida Gaien Belt. Myrene, belemnites and plant fossils similar
to the Tetori-type flora were known not only from the Tetori
Group (s.s.), but also from the Managawa Group (for example,
the succession from the Kamihambara to the Itsuki formationsof Fujita (2002) in the Kamihambara area) (e.g., Maeda,
1961a; Kimura, 1975; Fujita, 2002; Sano et al., 2013). Thus the
Tokurazawa Formation is possibly correlated with the Managawa
Group, and not to the Tetori Group (s.s.). In this case, the marine
and brackish horizons of the Managawa Group and its correlatives
can be traced to the Katashina area, far east from the Tochio area.
4 Summary of the division of the Tetori Group (sensu lato)
The Tetori Group (s.l.) in northern Central Japan can bedivided into four different groups at this moment: Middle–LateJurassic (Bathonian–Oxfordian) Kuzuryu Group distributed in the
Hakusan Region in the Hida Belt, and only its Late Jurassic strata
in the Jinzu Region in the Hida Belt; Early Cretaceous (Berriasian–
Aptian) Tetori Group (s.s.) only in the Hakusan Region in the Hida
Belt; Early Cretaceous (Aptian–early? Albian) Jinzu Group in the
Jinzu Region and its possible correlatives in the Asahi area in the
Hida Gaien Belt; Late Jurassic–Early Cretaceous (Oxfordian–44

SHIN-ICHI SANO

early Aptian) Managawa Group in the Kuzuryu District and the
Tochio area both in the Hida Gaien Belt (Fig. 4).
The Kuzuryu Group shows only narrow distribution. At theperiod of TS-Ia, it is distributed only in the Itoshiro area of the
Hakusan Region, whereas, at the period of TS-Ib, it is distributed
not only in the Itoshiro area, but also in very narrow areas in
the Jinzu Region. On the contrary, the Tetori Group is widelydistributed in the Hakusan Region, indicating the possible
difference of the mode of development and size of the sedimentarybasins and/or tectonic setting between the periods of depositionof the Kuzuryu and Tetori groups. The size of basin(s) probably
became wider in the Hauterivian (before the period of TS-III at
the latest). Sedimentation continued in most parts of the Hakusan
Region to the period of DS3, but ceased before the period of DS4.
The Managawa Group is characterized by the occurrence ofrich Oxfordian ammonoid fauna representing the Kranaosphinctes
matsushimai assemblage zone of Sato and Westermann (1991),
which is corresponded to TS-Ib; the presence of marine strata
corresponding to TS-IIa and the possible absence of marine
strata corresponding to TS-IIb; the occurrences of the possible
Hauterivian brackish bivalves usually found in the Outer Zoneof Southwest Japan with typical brackish bivalves of the Tetori
Group; a clear evidence of volcanic activity of the age close to
the Barremian–Aptian boundary, which has not been known in
the Tetori Group, but possibly in the Jinzu Group (Fig. 4). Further
studies are necessary to reveal the stratigraphy of the Managawa
Group, and to clarify its difference from and/or similarity with theTetori Group.
The Aptian–early? Albian Jinzu Group is composed ofthe lithofacies reflecting alluvial fan, fluvial and flood-plain
environments (e.g., Matsukawa et al., 2014b), and deposited in
the period after the transition from DS2 to DS3 in the Hakusan
Region (Fig. 4). It is indicated that sedimentary basin(s) showedmuch wider distribution at that time than previous period in the
Hida Belt and possibly even in the Hida Gaien Belt. The presenceof Albian volcanic rocks, and red beds with abundant pedogenetic
calcareous nodules are characteristic lithofacies of the upper
part of the Jinzu Group and its possible correlatives in the Asahi
area. They can be compared in age and lithofacies to DS4 in
the Hakusan Region, possibly to the Yokoo Conglomerate
Formation in the Nyukawa area, and to the Kwanmon andSasayama groups, indicating that the warmer and dryer climate
and also volcanic activities prevailed in the Inner Zone ofSouthwest Japan at that time.
Omura (1973) already proposed the four-fold division of the
Mesozoic strata in the northern Central Japan: the Kuzuryu,
Tetori, Arimine and Asuwa groups. The Asuwa Group of Omura(1973) includes the Omichidani Formation and its coeval strata in
the Hakusan Region. Matsukawa et al. (2014a, p. 156) named the
Jinzu Group for almost same stratigraphic unit with the Arimine
Group to avoid the duplication of the group name and formation
name in the same region. Thus, in terms of the group division, theproposal of this paper is similar to that of Omura (1973), though
the correlation of the strata within the groups are completely
different, and DS4 is newly recognized in the time between the

Tetori and Asuwa groups in this paper.
5 Comments on the group divisions of the strata of the Tetori
Group (sensu lato) where radioralia-bearing gravels wererecoveredRadiolarian records from the gravels in the Tetori Group (s.l.)
attracted much attention for last three decades, because they
represent the clues to revealing the exhumation and denudation
process of the Jurassic accretionary complexes, such as those of
the Mino Belt, and also the juxtaposing of the Hida, Hida Gaien
and Mino belts (Kojima, 1986; Saida, 1987; Takeuchi et al., 1991;
Matsukawa and Takahashi, 1999; Tomita et al., 2007; Ito et al.,2012, 2014a, 2015; Takeuchi et al., 2015b). The Itoshiro andAkaiwa subgroups of the Tetori Group (s.l.) in Maeda (1961d)
have been used to describe geological setting in all these studies(e.g., Ito et al., 2012, table 1). As discussed above, recent age
data indicate that such subgroup division cannot be applied to theCretaceous strata in the Hida Gaien Belt and the Jinzu Region in
the Hida Belt. The group divisions of the strata, where radioraliabearing gravels were recovered, are brieﬂy mentioned here basedon the proposal of group division in this paper.
The radiolarian records from the gravels in the Tetori Group(s.s.) were reported from the Otaniyama Formation in the
Shokawa area (Matsukawa and Takahashi, 1999) and the Itsuki
Formation in the Itoshiro area (Ito et al., 2015). The radiolarian
records from the gravels in the Kurobegawa area (Takeuchi et al.,1991) represent the only record from the Jinzu Group in the Hida
Belt. The Mizukamidani and the Kurobishiyama formations in the
Asahi area in the Hida Gaien Belt contains the radiolaria-bearing
gravels (Tomita et al., 2007; Takeuchi et al., 2015b), and areprobably correlable to the Aptian part of the Jinzu Group. Ito et al.
(2012, 2014a) also reported the radiolaria-bearing gravels in the
Cretaceous stratum in the Asahi area. Although they considered
this stratum was the Mizukamidani Formation, it was re-assigned
to the Albian Shiritakayama Formation in Takeuchi et al. (2015a, b).
Another record of radioralia-bearing gravels was reported fromthe Yokoo Conglomerate in the Nyukawa area (Kojima, 1986),
which is possibly correlated with Albian volcanic strata, such as
the Hayashidani Andesite in the Kuzuryu District or the Uchiyama
Formation in the Asahi area both in the Hida Gaien Belt.
The records in the Kamihambara area (Saida, 1987) are thoseof the Managawa Group in the Hida Gaien Belt. It should be
noted that the studied conglomerate is found in the lower horizonin the stratigraphic sequence (= Ashidani Formation ) than
the Tithonian Kamihambara Formation (e.g., Fujita, 2002), andits pre-Tithonian age can be considered as the earliest record
indicating the exhumation and denudation process of the Jurassic
accretionary complex (Ito et al., 2014b). On the other hand,
Ito et al. (2014b) still questioned the stratigraphic position ofradiolarian-bearing gravels and also their age assignment.
The exhumation and denudation process of the Jurassic
accretionary complexes should be discussed in future research,
considering the paleogeographic relationships among the sedimentarybasins of each Early Cretaceous stratum in northern Central Japan.

45·46105Ma T

TPN

uS

102Ma
106Ma
106.4MalS

112.1Ma

Nk

118Ma TPN

Toyonishi Grp.
Y

125

Ki

Barremian
Hauterivian

125Ma
125Ma

129.4

110.4Ma

Ku

?
HHa
YH
MH
RT

ValanginianM

110.1Ma

?
HHo

138Ma

Berriasian

T

uK

M

124.6Ma

DS4

?

St

U

HF

132.9
139.8

Js

Huashan
Grp.

LW
Ny
Se

O

128.7Ma
ca.123Ma
123.4Ma

Si

?
?

In

TPN
120.0Ma

Io

DS3

?

?

?

I

121.2MaN

Longzhaogou Grp.

109Ma TPN

UW

Heilongjiang

89.7Ma96.6Ma99.4MaHd

Hakusan

Jinzu

Asahi area

Jinzu Group

AptianHa

106Ma TP

98Ma

Kuzuryu District

Managawa Group

113

Jj

Sm

Monobegawa GroupCRETACEOUS
Early

Albian98Ma

Hida Gaien Belt

Shikoku

Sasayama

Sasayama Grp.

100.5

KanmonGyeongsang

KwanmonGrp.

Cenomanian

Age
(Ma)
HayangAge

Sindong Grp. Grp.

L.

P E

Tetori GroupNEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

?
Ho

TP

D

?

?

DS2
?
?

145

?
plutonic bodies

strata containing
brackish water molluscs

strata mainly composedof volcanic rocks

strata containing
marine molluscs
strata dated
by ammonoid fossils

fluvial deposits: Zircon U-Pb dating: K-Ar dating

T : Trigonioides
P : Plicatounio
N : Nippononaia

FIGURE 5. Comparison of stratigraphy, marine and brackish horizons, volcanic/plutonic strata/rocks, numerical age data, and the occurrences of selected freshwater bivalves of the Early Cretaceous strata in the Inner Zone of Southwest Japan and adjacent regions. Data are based on the following studies: Gyeongsang Region in South Korea̶Chang and Park,
2003; Jwa et al., 2009; Lee et al., 2010, Kanmon Region in the Inner Zone of Southwest Japan̶Shiraishi and Yoshidomi, 2005; Kozai et al., 2005; Aoki et al., 2014, Sasayama Region in the Inner Zone of Southwest Japan̶Yoshikawa, 1993; Hayashi et al., 2010; Kusuhashi et al., 2013, Shikoku Region in the Outer Zone of Southwest Japan̶Kozai et al., 2005;
Matsukawa and Obata, 2015, Heilongjiang Region in Northeast China̶Sha, 2007; Sha et al., 2012. Note that about 97 Ma tuff bed of the Hayang Group in the Gyeongsang Region contains some accidental zircons of 107.9 Ma, which indicate the presence of Albian volcanic activity there (Jwa et al., 2009). Abbreviation: M̶Myogok Formation, Nk̶Nakdong
Formation, Ha̶Hasandong Formation, Jj̶Jinju Formation for the Gyeongsang Region (Lee et al., 2010); Ki̶Kiyosue Formation, Y̶Yoshimo Formation, Se̶Sengoku Formation, Ny̶Nyoraida Formation, LW̶Lower Wakamiya Formation, UW̶Upper Wakamiya Formation, Sm̶Shimonoseki Subgroup for the Kanmon Region (Kozai et al., 2005; Aoki
et al., 2014); lS̶ Lower Formation of the Sasayama Group, uS̶ Upper Formation of the Sasayama Group for Sasayama Region (Kusuhashi et al., 2013); RT̶Ryoseki and Tatsukawa formations, MH̶Monobe and Lower Hanoura formations, YH̶Yunoki Formation and Hiura Facies, HHa̶Lowermost part of Hibihara Formation and Upper Hanoura
Formation, HHo̶Lower part of Hibihara Formation and Hoji Formation, HF̶Upper part of Hibihara Formation and Fujikawa Formation for the Shikoku Region (Kozai et al., 2005); D̶Dongshan Formation, Ho̶Houshigou Formation, Js̶Jinsha Formation for the Heilongjiang Region (Sha, 2007; Sha et al., 2012); See abbreviation in Figure 4 for otherregions. The numerical ages are based on ICS (2015).

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUPCOMPARISON OF GEOLOGICAL EVENTS OF THE
TETORI GROUP WITH THOSE OF EARLY CRETACEOUS
STRATA IN THE INNER ZONE OF SOUTHWEST JAPANAND ADJACENT REGIONS
1 Correlation of geological events
Generally non-marine Early Cretaceous strata are sporadically
but widely distributed in the Inner Zone of Southwest Japan andadjacent regions, and their correlation with the Tetori Group has
been discussed frequently (e.g., Yang, 1979; Matsumoto et al.,
1982; Tamura, 1990; Matsukawa and Obata, 1992; Chang andPark, 2003; Kozai et al., 2005; Sha et al., 2012). Depositional ages
and marine/brackish horizons of these Early Cretaceous strata aresummarized in Figure 5, mainly based on the recent age data ofzircon U-Pb dating, and also age assignment using marine fossils
in the Shikoku and Heilongjiang regions. Occurrences of some
freshwater bivalves, Trigonioides, Plicatounio and Nippononaia,
which are typical to Early Cretaceous East Asia, are also shownin Figure 5, according to Sha et al. (2012) and Kozai et al. (2005),
to indicate the horizons of freshwater environments. In thischapter, geological events recorded in the Tetori and Jinzu groups
and other Early Cretaceous strata/rocks in the Tetori Region
are tentatively compared with those in other regions for future
research.
The marine/brackish strata of the Berriasian age are only
distributed in the Hakusan Region, though the early Valanginian
Myogok Formation with freshwater molluscs has been known
in the Gyeongsang (or Kyongsang) Region. The development of
sedimentary basins of the Monobegawa Group in the Shikoku
Region and the Longzhaogou Group in the Heilongjiang
Region started in the Hauterivian, almost concurrently with thewidening of sedimentary basin in the Hakusan Region. Possible
causal relationship of basin development in these regions in theHauterivian was already pointed out (e.g., Tashiro and Okuhira,
1993; Matsukawa et al., 1997a), and was ascribed to the tectonic
duplication of Jurassic–early Early Cretaceous accretionary
complexes at that time, proposed by Matsukawa et al. (1997a)(Matsukawa et al., 2007; 2008a; Matsukawa and Fukui, 2009).
However, its mechanism and timing should be reconfirmed
and re-discussed in future studies, considering the presence ofsubsequent other geological events discussed below.
The marine/brackish strata of the Hauterivian–Barremian age
are known mainly in the Kanmon and Hakusan regions in the
Inner Zone of Southwest Japan. Drastic change of the depositional
environment from the brackish lake (DS2) to ﬂuvial environment(DS3) possibly started at the early Barremian (after TS-III) andprobably completed within the Barremian in the Hakusan Region.
The youngest marine/brackish strata in the Kanmon Region is the
Yoshimo Formation of the Toyonishi Group, and was recently
assigned to the age around Barremian–Aptian boundary by zircon
U-Pb dating (Aoki et al., 2014), though such age is comparatively
younger than previous age assignment (Hauterivian) based onmolluscs (e.g., Kozai et al., 2005). Considering that the Sindongand Hayang groups in the Gyeongsang Region were deposited in47

the same or related basins with the Kwanmon Group (e.g., Okada
and Sakai, 2000), similar change of depositional environmentswith the Hakusan Region possibly occurred in the Early Aptian
after the end of the deposition of the Toyonishi Group, but
before the start of the deposition of the Sindong Group. Thus
the disappearance of marine influence, or distinct change ofdepositional environments from shallow marine/brackish lake toﬂuvial environments occurred in the Barremian–Early Aptian in
the Hakusan and Kanmon regions or in the whole intracontinental
basins in East Asia. Subsequently, no marine/brackish stratumof the Early Cretaceous age has been known there except for
Shikoku and Heilongjiang regions, though sedimentation usuallycontinued to the Albian in almost all regions. It should be notedthat almost at the same time (early Aptian), new sedimentarybasins started to develop in the Gyeongsang Region, theJinzu Region, and the Asahi area, and the deepening of thedepositional environment (= absence of brackish strata) is also
recognized in the Monobegawa Group. It is speculated that somecausal relationship might exist among also these geological eventsin the Barremian–Early Aptian: the disappearance of marine
influence, and the development of sedimentary basins in East
Asia, in addition to above-mentioned Hauterivian events.
The Albian time is characterized by the widespread andesitic
volcanic/plutonic activities across almost all regions (e.g., DS4 in
the Hakusan Region), now including the Sasayama Region andexcluding the Shikoku Region. Such activities possibly extended
to the Heilongjiang Region. These Albian volcanic strata/rocks areprobably related to the development of huge volcanic belt along
the continental margin of East Asia at that time (e.g., Takahashi,1983).
These Albian volcanic episodes in a continental arc wererecently interpreted as the ﬁnal stage of slab rollback after the ﬂatslab subduction during the Jurassic in East Asia (e.g., Kiminami
and Imaoka, 2013; Imaoka et al., 2014). Furthermore, a series ofgeological episodes, such as the basin development, uplift andvolcanism, in the continental margin of western North America
at the Paleogene (e.g., Smith et al., 2014) and of southeastern
China at the early to mid-Jurassic (e.g., Li and Li, 2007), wererecently recognized, and are ascribed to the ﬂat-slab rollback. It
is supposed that the series of above-mentioned geological events
in Southwest Japan and adjacent regions in the Early Cretaceous(for example, the lithofacies change from (at least the upper partof) DS2 to DS4 through DS3 in the Hakusan Region) can be
explained by the similar mechanism of the ﬂat-slab rollback.
On the other hand, a series of Jurassic–earliest Cretaceous
accretionary complexes is widely exposed in the Inner Zone ofSouthwest Japan (e.g., Wakita, 1988; Nakae, 2000). It contains
abundant Carboniferous–Jurassic oceanic plate material/rocks,
such as bedded chert, basalts and limestones, which clearly
indicates very old (more than 100 million years) oceanic plate(s)subducted along the eastern margin of the Asian Continent atthat time (e.g., Sano and Kojima, 2000; Imaoka et al., 2014).
According to the comparative studies of subduction zones (e.g.,
Uyeda, 1983), an old oceanic plate slab generally subducts at asteep angle, and an accretionary prism is not fully developed in

48

SHIN-ICHI SANOTABLE 1. Comparisons of Hauterivian freshwater and brackish bivalves among the Monobegawa, Managawa and Tetori groups. Occurrence of Trigonioides(Wakinoa) tetoriensis from the Tetori Group is not based on the records from the Okurodani Formation, but the Aptian Kitadani Formation.

Monobegawa GroupManagawa Group

Tetori Group

Tatsukawa Formation

Tochio Formation;"Itsuki Formation"in the Kamihambara area

Okurodani Formation(*Kitadani Formation)

Kozai et al. (2005, 2012)

Maeda (1959), Hayami (1975)
Tashiro (1994), Fujita (2002),
Matsukawa et al. (2007)

Kozai et al. (2005, 2012)

Unio ? ogamigoensis
Megasphaerioides okurodaniensis
Freshwater Batissa ? antiqua
Trigonioides (Wakinoa ) tetoriensis
bivalves

Unio ? ogamigoensis
Megasphaerioides okurodaniensis
Batissa ? antiqua
Trigonioides (Wakinoa ) tetoriensis *Sphaerium coreanicum
Nagdongia soni
Nippononaia tetoriensis

Sphaerium sp.

Myrene (Mesocorbicula) tetoriensis

Brackishbivalves

Crenotrapezium kitakamiense
Tetoria sanchuensis
Myopholas tanakai
Protocardia ibukii
Costocyrena otsukai
Hayamina naumanni
Isodomella shiroiensis
Pulsidis antiqua

Myrene (Mesocorbicula) tetoriensis
Tetoria yokoyamai
Crenotrapezium ? kobayashii
Tetoria sanchuensis
Myopholas tanakai

the subduction zone. Such a general idea is not concordant with
the Late Jurassic–Early Cretaceous case in East Asia, where theflat-slab or shallow angle subduction was supposed, and hugeaccretionary complexes were developed, as discussed above.
Further detailed studies are required to reconstruct the tectonic
model to explain Early Cretaceous geologic events in East Asia.
2 Comparison of the brackish bivalve fauna of the Managawa
Group with those of the Tetori and Monobegawa groups
Occurrence of the possible Hauterivian brackish bivalves,
usually found in the Outer Zone of Southwest Japan, is
one of important characters of the Managawa Group. The
comparison among almost coeval faunas from the Managawa
and Tetori groups in the Inner Zone of Southwest Japan, and theMonobegawa Group in the Outer Zone of Southwest Japan isbrieﬂy discussed here (Table 1).
Five brackish bivalve species have been described or reported
from the Managawa Group (Maeda, 1959; Tashiro, 1994;
Matsukawa et al., 2007). Among them, Tetoria sanchuensis
and Myopholas tanakai are known also from the Tatsukawa
Formation of the Monobegawa Group, but not from the Tetori
Group. Polymesoda (Isodomella) kobayashii Maeda, 1959 is now
considered to belong to Crenotrapezium, and this genus is also
known from the Tatsukawa Formation. On the other hand, thebivalve assemblage of the Tatsukawa Formation is characterized
by the typical Early Cretaceous brackish genera in East Asia,

Myrene (Mesocorbicula) tetoriensis
Tetoria yokoyamai

namely Hayamina, Isodomella and Pulsidis (Kozai et al., 2012),
and thus distinct difference and slight similarity exists between
the brackish bivalve faunas of the Managawa and Monobegawa
groups. On the other hand, the occurrences of typical brackishbivalves of the Tetori Group: Myrene (Mesocorbicula) tetoriensis
and Tetoria yokoyamai (e.g., Kondo et al., 2006; Nishida et al.,2013), are recently recognized in the Managawa Group (Fujita,
2002; Matsukawa et al., 2007). Thus the similarity of the brackishbivalve faunas between the Managawa and Tetori groups isalso strongly suggested. Occurrence of Sphaerium sp. from the
Kamihambara area in the Kuzuryu District (Fujita, 2002) may
suggest the presence of the typical freshwater bivalves of theTetori Group in the Managawa Group.
Freshwater bivalves are usually not recovered in the
Monobegawa Group (Tashiro and Okuhira, 1993), but several
species have been known from the Tatsukawa Formation (e.g.,
Kozai and Ishida, 2003; Shinomiya, 2011; Kozai et al., 2012).
Freshwater bivalve fauna of the Tatsukawa Formation is usuallycommon with that of the Tetori Group, though some elementsof the Tetori Group have not been known in the Tatsukawa
Formation (Table 1). Even in the brackish bivalves, Myrene(Mesocorbicula) tetoriensis was also common element between
the Tetori and Monobegawa groups (e.g., Kozai and Ishida, 2003;
Kozai et al., 2012).
In summary, some common bivalves are recognized among
two or three groups, and brackish bivalve fauna of the Managawa
Group represents intermediate composition between those of theNEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

Tetori and Monobegawa groups (Table 1). It is supposed thatsome geographical and/or environmental barrier(s) separated thecomposition of brackish faunas between the Monobegawa andTetori groups. Such geographical and/or environmental conditionsin the depositional area of the Managawa Group were possiblyintermediate between those of the Monobegawa and Tetorigroups, and may cause the intermediate composition of brackishbivalve fauna of the Managawa Group.
Recently, it is revealed that the bivalve faunas of the late
Hauterivian Inagoe Formation in the Hida-Furukawa area and the
Berriasian Mitarai Formation in the Shokawa area, both of which
belong to the Tetori Group, are similar to that of the Barremian–
Aptian Qihulin and Yunshan formations of the Longzhaogou
Group in the Heilongjiang Region, Northeast China (Matsukawa
et al., 2007; Matsukawa and Fukui, 2009; Sha and Hirano, 2012).
Thus the northern current probably influenced the Tetori Basin,
where the Tetori Group deposited, at that time.
On the contrary, shallow marine limestones containing
hermatypic fossils occur in the Early Barremian Lower Hanoura
and Monobe formations of the Monobegawa Group (e.g., Iba
and Sano, 2007; Iba et al., 2011), and thus tropical/subtropicalmarine condition are indicated for the depositional area of theMonobegawa Group. Different environmental conditions, suchas, temperature, salinity, oceanic current system, etc. (see thediscussion in Kozai et al., 2012) are inferred to exist between
the depositional areas of the Tetori and Monobegawa groups.
Such ideas may provide the clues to revealing the differences
and similarities of the Hauterivian brackish faunas of the Tetori,
Managawa and Monobegawa groups, or even those of marine
environmental conditions in the Hida Belt, the Hida Gaien Belt,
and the Outer Zone of Southwest Japan in the Early Cretaceous.
New view of the Tetori Group and related strata possibly
provides the basic standpoint to future studies of the interregionalcorrelation among the Early Cretaceous strata, paleogeographicaland paleoenviromental reconstruction, and also the evolution of
Late Mesozoic terrestrial ecosystem in East Asia.
ACKNOWLEDGMENTS
The parts of this paper were read at the International
Symposium on Asian Dinosaurs in Fukui (March, 2014) and theSecond International Symposium of International Geoscience
Programme (IGCP) Project 608 in Tokyo (September, 2014).
Thanks are extended to the conveners and participants ofsymposia for their fruitful discussion. I would like to thankAtsushi YABE for the fruitful discussion on the study of the Tetori
Group (s.l.) and its biota during almost twenty years, and forcommenting on the earlier draft of this manuscript. I am gratefulto Jingeng SHA, an anonymous reviewer, and the editors: Kenji
KONISHI and Hiroto ICHISHIMA for critical review and editing
works of the manuscript. I thank Yohei ARAKAWA, Oksana S.
DZYUBA, Masato FUJITA, Michiharu GOTO, Naoto HANDA,
Takashi HASEGAWA, Satoshi HIRASAWA, late Hiromichi
HIRANO, Ren HIRAYAMA, Yasuhiro IBA, Hiroto ICHISHIMA,
Shinji ISAJI, Tsuyoshi ITO, Katsutoshi JIJU, Kenji KASHIWAGI,

49

Yuta KAWAGOE, Naoki KIKUCHI, Yoshitsugu KOBAYASHI,
Toshifumi KOMATSU, Kenji KONISHI, Katsuhiro KUBOTA,
Nao KUSUHASHI, Yoshihito NARITA, Shigeru OTOH, Yusuke
SAKAI, Jingeng SHA, Teppei SONODA, Kasuo TERADA, Keita
UMETSU, Akemi WAKIMOTO and Toshihiro YAMADA for
their guidance, advice, discussion and encouragements during thecourse of this study.
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Yokoyama, M. 1894. Mesozoic Plants from Kozuke, Kii,
Awa, and Tosa. Journal of the College of Science, Imperial
University, Japan 7 (part 3): 201–231, pls. 20–28.
Yokoyama, M. 1904. Jurassic ammonites from Echizen andNagato. Journal of the College of Science, Imperial Universityof Tokyo, Japan 19: 1–17, pls. 1–4.
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*: in Japanese** : in Japanese with English abstract*** : in Russian with English summary

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SHIN-ICHI SANO＜
Akahoke Formation ……… 赤歩危層
Akaiwa ………………………… 赤岩
Akaiwa Formation …………… 赤岩層
Akaiwa Subgroup ……… 赤岩亜層群
Amagodani Formation … アマゴ谷層
Aradani ………………………… 荒谷
Arimine Group …………… 有峰層群
Asahi …………………………… 朝日
Ashidani Formation ………… 葦谷層
Ashio Belt …………………… 足尾帯
Asuwa …………………………… 足羽
Asuwa Group ……………… 足羽層群
Awaradani Granodiorite……………… アワラ谷花崗閃緑岩
Bessandani (or Betsuzandani) Formation…………………………… 別山谷層
Chinaboradani Formation………………………… 知那洞谷層
Dongshan Formation ………… 東山層
Fujikawa Formation ………… 藤川層
Fujikuradani Formation …… 藤倉谷層
Fukui …………………………… 福井
Fukuji …………………………… 福地
Fuxin Formation ……………… 阜新層Gifu-ken (= Gifu Prefecture) … 岐阜県
Gomishima (or Gomijima) Formation…………………………… 五味島層
Guantou Formation ………… 馆头層
Gyeonsang (or Kyongsang) Region……………………………… 慶尚区
Hakusan Region ……………… 白山区
Hasandong Formation …… 霞山洞層
Hayang Group …………… 河陽層群
Hayashidani Andesite …… 林谷安山岩
Heilongjiang ………………… 黒竜江
Heilongjiang Region ……… 黒竜江区
Hibihara Formation ……… 日比原層
Hida Belt …………………… 飛騨帯
Hida-Furukawa …………… 飛騨古川
Hida Gaien Belt ………… 飛騨外縁帯
Hida Metamorphic Rocks……………………… 飛騨変成岩類
Hitoegane Formation …… 一重ヶ根層
Hiura Facies ………………… 日浦相
Hoji Formation ……………… 傍示層
Honshu Island ………………… 本州
Houshigou Formation ……… 猴石沟層
Huashan Group …………… 桦山層群
Ichinose ……………………… 市ノ瀬
Ikegahara ……………………… 池ケ原
Inagoe Formation …………… 稲越層
Inotani Formation …………… 猪谷層
Ioridanitoge Formation …… 庵谷峠層

地名・地層名＞Ishikawa Prefecture ………… 石川県
Itoshiro ……………………… 石徹白
Itoshiro Subgroup …… 石徹白亜層群
Itoshirogawa River ………… 石徹白川
Itsuki (or Izuki) Formation …… 伊月層
Iwamuro Formation ………… 岩室層
Izumi …………………………… 和泉
Jinju Formation ……………… 晋州層
Jinsha Formation …………… 金沙層
Jinzu Group ……………… 神通層群
Jinzu Region ………………… 神通区
Jiufotang Formation ……… 九佛堂層
Joetsu Belt …………………… 上越帯
Kaga …………………………… 加賀
Kaizara Formation …………… 貝皿層
Kamihambara ………………… 上半原
Kamihambara Formation … 上半原層
Kamitakara ……………………… 上宝
Kanazawa ……………………… 金沢
Kanmon Region ……………… 関門区
Kanto Mountains ………… 関東山地
Kaseki-kabe (or Kasekiheki) … 化石壁Katashina ……………………… 片品
Kitadani ………………………… 北谷
Kitadani alternation of sandstone, shale
and tuff … 北谷砂岩頁岩凝灰岩互層
Kitadani Formation ………… 北谷層
Kitamatadani Diorite … 北俣谷閃緑岩
Kiyosue Formation ………… 清末層
Kurobegawa ………………… 黒部川
Kurobegorodake Diorite………………… 黒部五郎岳閃緑岩
Kurobishiyama Formation … 黒菱山層
Kurotodo …………………… 黒当戸
Kurotodo Formation ……… 黒当戸層
Kuruma Group …………… 来馬層群
Kuwajima (or Kuwashima) Formation……………………………… 桑島層
Kuzuryu District (or Kuzuryugawa area/
Region) ………………… 九頭竜地区
Kuzuryu Group ………… 九頭竜層群
Kuzuryu Subgroup …… 九頭竜亜層群
Kuzuryugawa River ……… 九頭竜川
Kwanmon (or Kanmon) Group…………………………… 関門層群
Longzhaogou Group …… 龍爪溝層群
Lower Hanoura Formation……………………… 下部羽ノ浦層
Lower Wakamiya Formation………………………… 下部若宮層
Makido Maﬁc Complex……………… 牧戸苦鉄質複合岩体
Mana …………………………… 真名Managawa Group ……… 真名川層群
Managawa River …………… 真名川
Mino Belt …………………… 美濃帯
Mitarai (or Mitarashi) Formation…………………………… 御手洗層
Miyagawa River ……………… 宮川
Mizukamidani Formation … 水上谷層
Monobe Formation ………… 物部層
Monobegawa Group …… 物部川層群
Monomiyama Formation … 物見山層
Motodo Formation …………… 本戸層
Mt. Hakusan …………………… 白山
Myogok Formation ………… 卯谷層
Nagano ………………………… 長野
Nagano Shale …………… 長野頁岩層
Nakdong Formation ………… 洛東層Nochino Formation …………… 後野層
Nohi Rhyolite …………… 濃飛流紋岩
Numamachi Formation ……… 沼町層
Nyoraida Formation ……… 如来田層
Nyukawa ……………………… 丹生川
Oamamiyama Group … 大雨見山層群
Obuchi Formation …………… 大淵層
Oguchi ………………………… 尾口Oidani Formation ………… 大井谷層
Okura Formation …………… 大倉層
Okurodani Formation ……… 大黒谷層
Okutone Group ………… 奥利根層群
Omichidani (or Omitidani) Formation…………………………… 大道谷層
Ono …………………………… 大納
Ono Thrust …………… 大納衝上断層
Osugidani …………………… 大杉谷
Otaniyama Formation …… 大谷山層
Oyashirazu Formation …… 親不知層
Oze-Takinosawa Formation……………………… 尾瀬滝ノ沢層
Ozogawa River ……………… 尾添川
Pre-Nohi Andesite …… 先濃飛安山岩
Qihulin Formation ………… 七虎林層
Ryoseki ………………………… 領石
Ryoseki Formation …………… 領石層
Sanchu ………………………… 山中
Sasayama Group ………… 篠山層群
Sasayama Region …………… 篠山区
Sebayashi Formation ………… 瀬林層
Sengoku Formation ………… 千石層
Seto …………………………… 瀬戸
Setono ……………………… 瀬戸野
Shikoku Region ……………… 四国区
Shimonoseki Subgroup … 下関亜層群
Shimoyama Formation ……… 下山層
Shiramine ……………………… 白峰

NEW VIEW OF THE STRATIGRAPHY OF THE TETORI GROUP

Shiritakayama Formation … 尻高山層
Shiroiwagawa Formation … 白岩川層
Shogawa River ………………… 庄川
Shokawa (or Shiokawa) ………… 荘川
Sindong Group …………… 新洞層群
South Kitakami Region … 南部北上区
Sugizaki Formation ………… 杉崎層
Taie Formation ……………… 太江層
Takaharagawa River ………… 高原川
Takinamigawa ……………… 滝波川
Tamodani …………………… 田茂谷
Tanemura Formation ………… 種村層
Taniyamagawa River ………… 谷山川
Tatsukawa Formation ………… 立川層
Tedorigawa (or Tedori/Tetori) River……………………………… 手取川
Tetori …………………………… 手取
Tetori (or Tedori) Group … 手取層群

Tetori Region ………………… 手取区
Tetori Series ………………… 手取統
Tochimochiyama Formation … 栃餅山層
Tochio …………………………… 栃尾
Tochio Formation …………… 栃尾層
Tokura Metabasic rocks………………… 戸倉変塩基性岩類
Tokurazawa (or Tokurasawa) Formation…………………………… 戸倉沢層
Tomari …………………………… 泊
Toyama ………………………… 富山
Toyama Prefecture …………… 富山県
Toyonishi Group ………… 豊西層群
Uchinami Quartzdiorite…………………… 打波石英閃緑岩
Uchinamigawa ……………… 打波川
Uchiyama Formation ………… 内山層
Ultra-Tamba Belt ………… 超丹波帯

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Umagatani Unconformity…… 馬ガ谷（または馬ヶ谷）不整合
Upper Hanoura Formation……………………… 上部羽ノ浦層
Upper Wakamiya Formation………………………… 上部若宮層
Ushikubigawa River ………… 牛首川
Ushimaru Formation ………… 牛丸層
Yambara Formation ………… 山原層
Yambarazaka Formation …… 山原坂層
Yanagidani ……………………… 柳谷
Yokoo Conglomerate ……… 横尾礫岩
Yokoo Conglomerate Formation………………………… 横尾礫岩層
Yoshimo Formation ………… 吉母層
Yunoki Formation ………… 柚ノ木層
Yunotani …………………… 湯ノ谷
Yunshan Formation ………… 云山層