Na t. His t. Res. , Vo l. 10 NO.1 : 1-8, March 2008

Comparative Study of Sedimentary Processes Forming Bone-bearing Beds between the Early Cretaceous Kuwajima Formation, Central J apan, and W onthaggi Formation, South Australia

Hiroko Hiroko Okazaki and Shinji Isaji

Natural Natural History Museum and Institute, Chiba 955-2 955-2 Aoba-cho, Chucト ku ， Chiba , 260-8682 ]apan E-mail: E-mail: [email protected];isaji@chiba-muse .or. jp

Abstract Abstract The Early Cretaceous Kuwajima Formation , Tetori Group , central ]apan, and Wonthaggi Formaｭ tion , southeastern Australia, have yielded abundant terrestrial and fresh-water vertebrate fossils. Boneｭ bearing bearing beds in the Kuwajima and Wonthaggi formations are observed in fluvial systems having different channel channel styles. In the Kuwajima Formation, var ied bone-bearing beds were preserved in the broad , stable flood-plain flood-plain deposits of a meandering river system. In the Wonthaggi Formation , fossils accumulated in a chanｭ nellag nellag because of rapid deposition of channel bars and easily eroded interchannel deposits in a braided river system. system. Consequently, the mode offossil accumulation and preservation is considered to ha ve been controlled by by channel styles

Key words: sedimentary environments, sedimentary processes, Cretaceous, Kuwajima Formation, Wonthaggi Wonthaggi Formation , bone-bearing beds

The purpose of this study is to deduce sedimentary Group, is distributed in Kuwajima, Hakusan City, environments environments and processes involved in the formation Ishikawa Prefecture (Fig. 1). The formation consists of of bone-bearing beds. The sedimentary condition that of shallow marine to fluvial deposits and has yielded cause cause terrestrial and fresh-water fossils to be accumuｭ abundant vertebrate fossils. A number of lated lated and preserved are discussed by comparing two paleontological and stratigraphical studies have been Cretaceous Cretaceous fluvial systems, the Kuwajima Formation, conducted and reviewed by Isaji et al. ( 2005) 目 The ]apan, and the Wonthaggi Formation, southeastern sedimentological results of the formation have also Australia. Australia. Se d.i mentary analysis of the two formations been described in some reports ( Taira and Matsuo, has has demons t.r ated that the channel style of a fluvial 1983; Kumon, 1991 ; Masuda et al., 1991) . The upperｭ system is an important factor in the accumulation and most part of the Kuwajima Formation is observed at preservation preservation of vertebrate fossils. Kaseki-kabe in Kuwajima, which is a well-known fossil The Early Cretaceous Kuwajima Formation, Tetori locality .At this locality, huge numbers of vertebrate fossils, including 五shes ， anurans, turtles, choristoderes, lizards, pterosaurs, sauropods, theropods, hypsilophodontian-grade hypsilophodontian-grade ornithopods, iguanodontids,

Fig .2 . Stratigraphy of the Hakusan area . ]apan ( from Sato et et al. , 2003: Kubota . 2005: Rougier et al., 2007) , and of the Gippsland Gippsland Basin. A u st ralia (from Holdgate and McN ico l. 1992: Fig. Fig. l. Location map showing the distribution of the Tetori Chiupka .1996 ) ( 女 indicating the formation including a boneｭ Gro up in central ]apan and fossil sites (*: Kaseki-kabe ) in bearing bed ) Hakusan Hakusan City.

可 EA Hiroko Hiroko Okazaki and Shinji Is aji

Facies Facies _ assocla 甘 on t- ac les Sedimentary st川 ctu r e & fossils Paleoe nvironments Blue-grey Blue-grey mudstone Akaiwa Akaiwa Fissi 除 Distal F. Alluvial Fan

g.r avel 回 aring c9.a目e ~ands~oneFin i flg l:I pward (Channe l) Sc Sc Shärp'tôSëö'u~d 回目 ， T剛 gh cross-bèd在 .....Plant fragments 且Iternation of Mン 品;z:?UfJJ;21;AfJtErne mnt S. C山er (Flood Plain ) C Bone-…回 aring Beds"

。。。、 5c Meande ring River

ち』 帽、 5a コ (Creva 田 e-5play) LL.: LL.: Con vex up.va rd sandst one ・ 。 F -distributary (I nte r-distributary 』 Mb Mb ~I:~~~a~o.~ _o!!~n_~_~~~~~:~~~~_ grey siltstone 一cω 何 B Ripple & Honzontallaminations - Rootlets , Coal layers channe l) E 巴問。。 Plant Plant fragments (Distributary channe l) -圃圃・.側主コ出

Bird ・foot Delta

G団 ded ， (Distribula 吋 Ho旧o ntallam i na tio n She t1 fragments mouth bar)

Dark .brown mudstone M問削曲附 s is ， Os t 間叩 Bay A Massi ve , Fissile (6ay bottom)

Fig .3. Columnar section of the Kuwajima Formation , This section is compiled from two outcrop sections (Nishijima-touge and Kas e ki ・ kabe ) birds. birds. a tritylodontid synapsid. and mammals have basically discriminated on feat u res observab le in the been been found .At Kaseki-kabe . the fossil assemblages are field, such as grain size, sedimentary structures, color, concordant concordant with the litho logic features of the boneｭ bounding -surface type and fossils bearing bearing beds (Isaji et al., 2005 ). suggesting that sed iｭ mentary processes contro ll ed their modes of 1. The K u wajima Formatio n occurrence. occurrence. The 400-m -thick Kuwajima Formation is composed The Early Cretaceous Wonthaggi Formation of alternating layers of arkosic sandstone and

( Holdgate and McNico l. 1992 ) in the Gipps l and Basin. mudstone, The precise age of the formation has not southeast southeast Victoria , Australia. has been compared in been determined, but it has been estimated to be order order to examine the relation between bone-bearing Neocomi an on the basis of stratigraphic corre lations beds beds and sedimentary processes in fluvial systems with other formations of the Tetori Group ( see sumｭ The Wonthaggi Formation contains a diverse verteｭ mary in Rougier et al., 2007 ) (Fig. 2). brate brate fauna in bone-bearing beds. The assemb l age inｭ Six sedimentary fac ies. Ma .Sa , Mb, Sb, Mc, and Sc, cludes cludes fish, turtles, a large temnospond yl amphibian, and three facies associations, A, B, and C, are distinｭ plesiosaurs, dinosaurs, birds, a tribosphenic mammal, guished in the Kuwajima Formation (Fig, 3). Facies and a monotreme (Rich and Rich , 1989; 1994). associations A, B and C are recognized in the lower, middle, and upper parts of the formation, respectively . Met hods and Res ul ts Facies Facies association A is composed of alternating layers Facies Facies analysis was conducted in the Kuwajima Forｭ of mudston e (Facies Ma) and sandstone (Facies Sa) , mation mation in the Hakusan area, and the Wonthaggi Forｭ with the mudstone dominant Facies Ma is 2 to 15 m mation mation at Flat Rocks. Sedimentar y facies were thick and consists of blue-grey to dark brown

- 2- Sedimentary Sedimentary processes forming bone-bearing beds a C

b

Fig. Fig. 4. a. massive mudstone including molluscan shells (Fac ies Mc): the hand points a brackish water molluscan hell: shell: b. trough cross-bedded fine sandstone that fines upｭ ward ward (Faci es Sb ): the pen is 1 50 mm lon g: c. alternating la ye rs of fin e sandstone a nd mudstone with rootlets (Fa cies Sb): the hamm e rhead is 100 mm long.

mudstone. mudstone. This facies is massive to fissile and contains greenis h- grey siltstone. The siltstone has numerous the the brackish-water molluscs My問問 ( Mesoco rbicula ) rootlets and plant fragments, and black coa ll ayers are tetoriensis tetoriensis and ostreo id (Fig. 4a). Brown , organic-rich intercalated. The sandstone la yers intercalated among la yers are occasionally intercalated. The thickness of the siltstone l ayers exhibit ripple and horizontal lamiｭ Facies Facies Ma decreases upward . Facies Sa is 2 to 5 m nation and include rootlets intruded from the s il tstone thick thick and composed of 五 ne- to medium-grained sandｭ (Fig. 4c). Facies Sb is posited to have formed in a river stone. stone. Above the sharp lower bounding surface of the channe l. Facies Mb indicates interchannel deposits. facies, granu l es are scattered . This facies is graded Therefore, these facies are interpreted as bay normally, or rarely inversely, with horizontal laminaｭ (prode lt a) (Ma) , river-mouth bar (Sa ). distributaryｭ tion tion in its upper par t. Facies Ma represents deposition chan nel 五 11 (Sb ) a nd inter-distributary channel depos- in in a bay envi ronmen t. Facies Sa indicates that a den- its (M b) of a tluvial-dominated delta . sity sity current deposited sand in a bay In Facies association C, Facies Sc alternates wit h In In Facies association B, Facies Sb alt巴 rnates with Facies Mc . Facies Sc is 2 to 6 m th i ck and composed of Facies Facies Mb. Facies Sb is 4 to 6 m thick and composed pebbly coarse- to very coarse -gr ained sandstone. It of of pebbly coarse- to very coarse -gra in ed sandstone fines upward s li ghtly. This facies has an apparent (Fig. (Fig. 4b) representing trough cross-stratification. erosional bas e on which pebbles and fragments of Facies Facies Mb is 2 to 5 m thick and comprises couplets of driftwoods are presen t. Trough cross-bedding is comｭ fine- to medium-grained sa ndstone and grey to monly observed in t he facies. Facies Mc. which is 2 to

- 3- Hiroko Hiroko Okazaki and Shinji Isaji

145 ・ 6 m thick . resembles Facies Mb. but the thicker siltstone siltstone is massive. poorly sorted. and b lue.grey to ark.grey. dark.grey. Slump structures are also visible in some beds beds of the siltstone . This facies common ly contains in situ situ sil icified woods. Bone.bearing beds have been found found in facies Mc . Facies association C is identified as a combination of river.channel (Facies Sc ) and flood. plain deposits (Mb).

2. The Wo nth aggi Fo rm atio n Bas s S trait The Wonthaggi Formation has been palyno logically 39 ・ dated as Aptian (Constantine et α 1. . 1 998 ) (Fig. 2). The bone.bearing bone.bearing beds crop out as coastal cliff exposures o 30km Eコ Stロelecki Gro叩 - at Flat Rocks. lnverloch. southeast Victoria (F ig. 5). Fig. Fig. 5. Locatiorl map showing the distribution of the The 200-m.th i ck Wonthaggi Formation is composed of S甘zelecki Group. や hich contains the Wonthaggi Formation. in alternating l ayers of sandstone and mudstone at F lat the the Gippsland Basih. southern Victoria. AustraJia. and the fos Rocks Rocks along 1 km of coastal cli妊 Three sedimentary siJ siJ site at In ve rloch ( ・ indicating FJat Rocks) facies. facies. Wa .Wb .and Wc . are distinguished in 出巴 For.

Facies Facies Sedimentary st ruct u re & il foss s Environment

Wa T rough cross.bed. Plants fragment Channel Irregular Irregular base

ここ

Alternation Alternation of sandstone sandstone & mudstone Wb Cryoturbation Flood Pla in

Coa llayer 比邑斗 Horizontal lamination

~ 1~1 ~ Wa Drifted woods Channel 8raided 何 工= Alteranation of 4回 .. Wb Flood Plain River C sandstone & mudstone s。 二二

Well.so円ed fine sandstone Wa Mud lenses Plants fragment Channe l rough Trough cross.bed ~

T 。 I亨手1 ポt Wa rough cross.bed "Sone bed " Chan nel tu同 les . 目的 . dinosaurs . birds .mammals

Fig .6. CoJumnar section of the Wonthaggi Formation at Flat Rocks す indicating bone.bearing bed

-4- Sedimentary Sedimentary pro cesses form in g bone-bearing beds

Fig.7.. Fig.7.. Trough cross-bedded fin e sandstone with an irregular erosional base (Faci es Wa). Numerous mud clasts are are observed in the sandstone . The cliff is about 10 m high mation mation (Fig. 6). or arid areas and on perig lacia l outwash plains (Mia l. Facies Facies Wa. 10 to 30 m thick. consists of well-sorted 1992 ) fine-grained fine-grained sandstone with homogeneous grain size (Fig. (Fig. 7a) .Ir regular erosional bases and trough crossｭ 3. Bone-bearing bed stratification stratification are commo nl y observed . This facies is inｭ The bone-bearing beds found in the uppermost part terpreted terpreted as channe l deposits. Boulder-sized or lensｭ of the Kuwajima Formation, Facies Mc , indicate three shaped shaped mudstones are conta ined in the sandstones. different facies (Subfacies 1 , II and III ) These mud clasts were originally flood-plain deposits, Subfacies 1 ( Carbonaceous sandstones ): all verteｭ which which fell into the channel by co ll apse of the flood-plain brate fossils are isolated bones and teeth, abraded to slope slope as the ri ver channel migrated laterally. The varying degrees and commonly fragmented or heavily bone-bearing bone-bearing beds, 1m thick , consist of pebble-sized weat hered .The most abundant elements are aquatic cong l omerates at the base of the channel deposits vertebrate remains, su ch as fish sca les and dermal These cong l omerate layers are replaced by wellｭ bones of turtles. This facies is rich in coa l. but l acks in rounded rounded mud clasts near the channel edges (Seegetsｭ situ plant remains. Molluscan fossils , including unionid Villiers, 2002) biva l ves and viviparid gastropods, are poorly preｭ Facies Facies Wb, 15 to 25 m thick , alternates with Facies served, due to post-burial diagenesis Wa and consists of couplets of fine-grained sandstone Subfacies II (Dark grey fine-grained silty and mudston 巴 (Fig. 7b). The mudstone contains coal sandstones ) :vertebrate fossi ls are well preserved but layers layers and cryoturbation structures (Fig. 7c ). genera ll y small . Large bones (more than 100 mm in Cryoturbation Cryoturbation structilres are characteristic of flood size ) are extre mel y rare and heavily fractured and plains plains in periglacial regions (Vandenberge, 1988: weathered where presen t. The fossil assemb l age is Constantine Constantine et al., 1998) . Fac ies Wb corresponds to characteriz ed by aquatic vertebrate remains simil ar to overbank overbank deposits Subfacies 1. but occasional associated or articu la ted Facies Facies W c is sometimes interbedded with Facies skeletons of turtles are also presen t. This facies a lso Wb. Facies W c is 1 to 3 m thick and is composed of contains fractured leaves and stems. which are not acｭ wedge-shaped wedge-shaped sandstone layers (Fig. 7b). Climbing cumu lated in layers, but in situ rootlets are rare. Nu ｭ ripple ripple lamination is often observed in Facies Wc . The merous viviparid gastropods and unio nid bivalves fac ies is interpreted as crevasse sp l ay deposits, The occur. with the latter commonly articu lated and often climbing climbing ripple lamination is formed by floodwat e rs found in life position ca r rying abundant suspended sand from a channel Subfacies III (Dark greenish-grey mudstones ):verｭ on on to the flood plain tebrate fossils are mostly isolated . Some articulated Thus, the facies correspond to channel (Fac ies Wa) specimens have also been found (Evans et al., 2006) and interchannel (Facies Wb and W c) deposits, sugｭ and sometimes heavily modified (i .e. abraded, fragｭ gesting gesting a sandy braided river system . Braided rivers mented and weathered) bones occur in association have have highly variab le discharge rates and l arge vo lｭ The fossil assemblage is characterized by the common umes of sedimen t. They are also common in semiarid occurre l1 ce of terrestria l lizards. tritylodo l1 tid

にd Hiroko Hiroko Okazaki and Shinji Isaji

synapsids synapsids and mammals, although aquatic elements are are also preserved .Hundreds of tritylodont teeth have been been found , despite the loss ofother skeletal elements. Mammals have been discovered only from this facies, and numerous ﾎn sﾎtu rootlets have been observed. Unionid Unionid bivalves and viviparid gastropods are exｭ tremely tremely rare but tiny pulmonate gastropods, ne v re er covered covered in Subfacies 1 and IT, are common In In the Wonthaggi Formation, the bone-bearing beds at at Flat Rock site have yielded fish, turtles, a temnospondyl temnospondyl amphibian, plesiosaurs, dinosaurs, birds, a tribosphenic mammal, and a monotreme . The site has has a huge concentration of fossil bones and teeth, with with fragments of turtle and fish as the most common element s. Vertebrate fossils are generally small and isolated, for ex ample mammal bones and dinosaur ). ). The fos Fig . 7b . Thin , altern at ing laye rs of fin e sa nd ston e and teeth a re less th an 30 mm in size (Kool, 2002 mud stone (Fac ies Wb ). W edg e-s haped sand ston e lay ers sils a re preserved in thin conglomerate layers, sandｭ Faci es Wb. Th e cliff is Facies (Facies Wc ) ar e interb edd e d within wiched between thick underlying mudstones and ab o ut 7 m hi gh) overlying overlying sandstone. The bon e-bearing bed is interｭ preted preted as part of a lag deposit in the base of a channel

Discussion Discussion

In In the Kuwajima and overlying Akaiwa formations, bay, ri v er-dominated delta, meandering river, and disｭ tal tal alluvial fan d eposits are found in ascending order and indicate a regressiv e sequence ( Okazaki and Isaji, 2002 ). In this sequence, a large f1 00d plain might have been been produced by extensive overbank deposition of muddy and sandy sedim e nts alongside a meandering rive r. Three bone-bearing beds with different fossil asｭ semblages semblages beenhave distinguished in the flood-plain deposits : carbonaceous sandstone containing rich plant fragm e nt and aquatic vertebrate remains, dark-grey silty silty fine-grained sandstones with aquatic vertebrate remains, and dark greenish-grey siltstone character ized ized mainly by terrestri a l lizards (Isaji, 2000; Isaji et al., 2005 ).Each bed corresponds to sub-environments of of the flood plain: peat marsh, shallow lake, and back swamp. These subenvironments were formed on a sta ble, humid and vegetated flood plain. The accumulaｭ tion tion of vertibrate remains on the flood plain occurred during during f1 00ding of the stream The Wonthaggi Formation at Flat Rocks consists of channel channel (Wa) and interchannel (Wb and Wc) deposｭ its its in a sandy braided river system. In the Wonthaggi Formation, the bone-bearing beds were preserved in Fig.7c. Fig.7c. (1) Climbing rippl e lamin ation of Fac ies Wc: (2) a the bas e of channel deposits. Abundant turtle and fish comp ose d of alt ern ating sand ston e cr yoturba tion s 甘 u c tur e fossils are found in a channel deposit because they had and and silt ston e beds with a thin coal layer, w hi ch ha ve be en de formed by seas on al m elting a nd refr eez ing (th e pen is lived there and th e bones of dinosaurs, birds and mamｭ 150 150 mm long ) mals were washed into the channel during periodic flooding flooding events (Kool, 2002 )

-6- Sedimentary Sedimentary processes forming bone-bearing beds

Meandering River 8raided River

"* "* Inter-channel

"* "* Kuw司 ima F. Wonthaggi F.

In ベchannel bar

Mud Mud Sa nd Gravel Mucf Sa nd "Gravel |女: bo 時bearing bed I Fig. Fig. 8. Schematic facies successions at Kaseki-kabe and Flat Rock

The sedimentary processes which fossils were deｭ comments. This research was supported by the Grantｭ posited posited in the systems of two formations suggest the in-Aid for Specially Promoted Research, awarded to following following (Fig. 8). The sediments of upper part of the MM (grant no. 12800018) , from th巴 ]apanese Ministry Kuwajima Formation, Facies Mc, were deposited by a of Education and Science, and the Grant-in-Aid for Sciｭ meandering meandering river system with a relatively restricted entific Research (C) (19540486) from the ]apan Sociｭ stream stream channel and a broad , stable flood plain. As a reｭ ety of the Promotion of Science. t. sul t. a varied terrestrial fauna has been preserved in References References the the flood-plain deposits. In contras t. the facies of the W onthaggi Formation at Flat Rocks indicate deposiｭ Chiupka, ]. W. 1996. Hydrocarbon play fairways of the tion tion by a braided river system. The thick, homogeneｭ onshore Gippsland Basin , Victoria. Department of ous ous channel deposits reflect the high sediment Natural Resources and Environment Victorian Iniｭ discharge discharge and the interchannel deposits easily erod巴 d tiative for Minerals and Petroleum Report 30. by lateral change of the streams. Therefore, in the Constantine, A., A. Chinsamy, P. Vickers-Rich and T. Wonthaggi Formation , fossil assemblages tended to H. 1998. Rick. Periglacial environments and polar di田 preserve preserve in the channel lag as a result of the rapid nosaurs. S. Af r. ]ou r. Sci. 94: 137-14 1. deposition deposition of bars. Consequently, the mode of fossil ac・ Evans , S. E.. M. Manabe, M. Noro, S. Isaji and M. cumulation cumulation and preservation in the two areas is conｭ Yamaguchi. 2006. A long-bodied lizard from the sidered sidered to have been controlled by channel styles. lower Cretaceous of ]apan. Palaeontology 49: 1143- From the observations in this study, sedimentary 1165 system system can be used to predict the likely locations and Holdgate, G. R. and M. D. McNico l. 1992. New direcｭ sedimentary sedimentary processes for deposition of terrestrial reｭ tions - old ideas, hydrocarbon prospects of the mains. mains. Taphonomic features such as disarticulation, Strzelecki Group onshore Gippsland Basin. In abrasion abrasion and the size of the remains, also represent Barton, C. M. and K. Hill (eds.) , Proceedings of the the the degree of fluvial transport and reworking. Thereｭ Gippsland Basin Symposium, pp. 121 - 13 1. fore, both sedimentological and taphonomic analyses Australasian Institute of Mining and Metallurgy, will will be able to contribute to the reconstruction of the Melbourne. paleodrainage paleodrainage and paleoclimate systems. Isaji , S. 2000. Depositiollal environments of the boneｭ bearing bearing strata with special reference to the Acknowledgements taphonomical taphonomical process of vertebrate fossil assemｭ The first author is deeply indebt to Prof. Tom Rich, blage. In Matsuoka, H. (edふ Scientific Report on a Monash University, for providing an opportunity of Neocomian (Early Cretaceous) Fossil Assemblage survey survey for the W onthaggi Formation at Flat Rocks from Kuwajima Formation, Tetori Group, and kindly comments on the original manuscrip t. We Shiramine. Ishikawa, ]apan. 277 pp. (in ]apanese) also also would like to acknowledge Prof. Susan E. Evans Isaji, S., H. Okazaki, R. Hirayama, M. Manabe, H and Ryoko Matsumoto , University College London , for Matsuoka , P. M. Barrett , S. E. Evans, G. W. Rougier, reviewing reviewing the manuscript and for 0任ering valuable T. Tsubamoto. Y. Yabumoto, M. Yamaguchi, 1

一 7 Hiroko Hiroko Okazaki and Shinji Isaji

Yamaguchi and T. Sakumoto. 2005. Depositional enｭ Mizunami Fossil Mus. 30: 151-167. (in ]apanese with vironments vironments and taphonomy of the bone-bearing English abstract and systematic descriptions) beds beds of the Lower Cretaceous Kuwajima Formation, Seegets-Villiers, D. 2002. Taphonomic repor t. In Flat Tetori Tetori Group, ]apan. Bull. Kitakyusyu Mus. Na t. Rocks Field Report 2002, pp. 17-20. His t. Hum. Hist., Se r. A (Na t. His t.) 3: 123-133. Taira, A. and H. Matsuo. 1983. New observations on Kubota, K. 2005. Charophyte gyrogonites from the the Tetori Group (J urassic to Lower Cretaceous) in Lower Cretaceous Kitadani Formation of the Tetori the Hakusan area. Conserv. Na t. Center 9: 1-1 1. (in Group in the Takinamigawa area, Katsuyama City, ]apanese) Fukui Fukui Prefecture , central ]apan. Paleonto l. Res. 9・ Vandenberghe , ]. 1988. Cryoturbations. In Clark, M. ]. 203 司 213 (edよ Advances in Periglacial Geomorphology, pp. Kumon, F. 199 1. A sedimentological study for the 179-198. ]ohn Wiley , Chichester. Tetori Tetori Group in the Shokawa Di strict Gifu Prefecｭ (Accepted 24 February 2007) ture , central ]apan. Science Report for the National Scientific Scientific Foundation. 58 pp. (i n ]apanese) Maeda , S. 196 1. On the geological history of the Mes。 下部白E系手取層群桑島層と zoic zoic Tetori Group in ]apan. ]ap. ]our. Geo l. Geogr. 32: 375-396. 375-396. 南部オーストラリア Wonthaggi 層の Mail, A. D. 1992. Alluvial models. In Walker , R. G. and 化石密集層形成過程の比較研究 N. N. P. ]ames. (eds.) , Facies Models Response to Sea Level Level Change, pp. 119-142. Geological Association of 岡崎浩子・伊左治銭司 Canada. Canada. Masuda, F., M. Ito, M. Matsuoka, M. Yokokawa and Y. 千葉県立中央博物館 Makino. Makino. 199 1. Depositional environments. In 干 260 ・ 8682 千葉市中央区青葉町955回2 Matsukawa, M. (e d.) , Lower Cretaceous Nonmarine E-mail kolùroko@clùba-muse.or お; isaji@cl�a-muse.or.jp and Marine Deposits in Tetori and Sanchu, Honshu, pp. pp. 11 -17. IGCP-245 Field Trip Guide Book, 1991 要旨 下部白亜系である中部日本の手取層群桑島層 Fukuoka International Symposium. と南部オーストラリアの Wonthaggi層は豊富な隆生お Matsukawa, H. (ed.). 2000. Fossil of the Kuwajima よび淡水生脊椎動物化石を産出する.桑島層と Wonth “ Kaseki-kabe" (Fossιbluff). Scientific Report on a aggi 層のボーンベッドは異なる河道形態をもっ河川シ Neocomian (Early Cretaceous) Fossil Assemblage ステム中に認められる.桑島層では，多様なボーンベッ from from the Kuwajima Formation, Tetori Group, ドが蛇行河川の広く安定した氾濫原に保存された .W Shiramine, Ishikawa. Shiramine Village Board of onthaggi層では，網状河川内での河道砂州、l の急速な堆 Education, Shiramine, 152 pp., 62 pls. (i n ]apanese) 積と河道関堆積物の容易な浸食のために，化石は河道 Okazaki, H. and S. Isaj i. 2002. Palecト environmental のラグ中に集積した.これらの結果から，化石の集積 change change of the Tetori Group in the Shiramine area, と保存は河道形態に支配されていたと考えられる. Ishikawa Ishikawa Prefecture, Central ]apan. Annual Meetｭ ing ing of The Sedimentological Society of ]apan, Abｭ stracts stracts 2002: 78-79. (i n ]apanese) Rich , H. T. and P. V. 1989. Rich. Polar dinosaurs and biotas biotas of the early Cretaceous of southeastern Ausｭ tralia. tralia. Natn. Geogr. Res. 5・ 15-53. Rich , H. T. and P. V. 1994. Rich. Neoceratopsians and ornithomimosaurs: ornithomimosaurs: dinosaurs of Gondwana origin. Res. Res. Exp l. 10: 129-13 1. Rougier, G. , S. Isaji and M. Manabe. 2007. An early Creｭ taceous taceous mammal 合om the Kuwajima Formation (Tetori (Tetori Group) , ]apan, and a reassessment of triconodont triconodont phylogeny. Ann. Carnegie Mus. 76: 73- 115 115 Sato, T., K. Hachiya and Y. Mizuno. 2003. Latest urassic-Early ]urassic-Early Cretaceous ammonites from the Tetori Tetori Group in Shokawa, Gifu Prefecture. Bul l.

。。