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Searching for a Non-Marine Jurassic/Cretaceous Boundary in Northeastern China

Searching for a Non-Marine Jurassic/Cretaceous Boundary in Northeastern China

Jour. Geol. Soc. , Vol. 121, No. 3, p. 109–122, March 2015 doi: 10.5575/geosoc.2015.0001

Review Searching for a non-marine / boundary in northeastern

Abstract Gang Li＊ and Atsushi Matsuoka＊＊ The well-developed Jurassic and Cretaceous strata of northeastern China are mostly of non-marine origin. The definition of the non- Received September 26, 2013 marine Jurassic/Cretaceous (J/K) boundary in northeastern China is Accepted January 6, 2015 based mainly on the age assignment of the well-known non-marine ＊ State Key Laboratory of Palaeobiology and Jehol Biota of eastern Asia. Although the Eosestheria–Ephemeropsis– Stratigraphy, Nanjing Institute of Geology Lycoptera-bearing strata in China, Mongolia, and Transbaikalia and Palaeontology, Chinese Academy of Sci- (Russia) were originally assigned to the in the ences, Nanjing 210008, China ＊＊ 1920s, the age of the entire Jehol Group of western , north- Department of Geology, Faculty of Science, eastern China, which contains the Jehol Biota in the lower part and Niigata University, Niigata 950-2181, Japan the Fuxin Biota in the upper part, was revised to Middle–Late Juras- Corresponding author: A. Matsuoka, sic during the early 1960s. This age revision was further supported by [email protected] the recovery of an apparent Bathonian (Middle Jurassic) Arctoceph- alites ammonite fauna and a Buchia fauna from east- ern Province in the middle 1980s. During the early 1990s, through revisions of the ages of the above-mentioned marine faunas of eastern Heilongjiang from Jurassic to Early Cretaceous, the Jehol Biota was re-dated as Early Cretaceous by some authors. At the same time, the recovery of feathered , early , , and angiosperms from the Yixian and Jiufotang forma- tions encouraged precise radiometric dating of the Jehol Group and its underlying strata in western Liaoning and northern . The new radiometric dating indicates that the non-marine J/K boundary in northern China falls within the contemporaneous Houcheng For- mation (northern Hebei) and Tuchengzi Formation (western Liaon- ing), which are stratigraphically much lower than the Jehol Group of western Liaoning. Key words: non-marine, stratigraphy, Jurassic/Cretaceous boundary, northeastern China

different J/K boundary interval biozones identified sepa- Introduction rately in the Tethyan and Boreal realms (Wimbledon et The definition of a global Jurassic/Cretaceous (J/K) al., 2011). We can imagine that the forthcoming final boundary, i.e. the choice of the last system Global decision for choosing a base GSSP would be Boundary Stratotype Section and Point (GSSP) for the very near to us, which would be of a great help for the Phanerozoic of the International Time Scale still re- definition of the non-marine J/K boundary in terrestrial mains an intractable problem because of the lack of a sequences. significant faunal overturn at the base of the Berriasian In China the Jurassic and Cretaceous strata are mainly and the extreme faunal provincialism caused by the Pur- of terrestrial origin. They are well developed and widely beckian regression (Remane, 1991; Zakharov et al., distributed in many Mesozoic basins, such as the 1996). However, the situation changed dramatically Songliao, Yanji, Fuxin-Yixian, Ordos, Junggar, Turpan, with the first magnetostratigraphic study of the J/K Tarim, Qaidam, Sichuan, Mengyin, Laiyang basins (Fig. boundary sequence in Russia (Houša et al., 2007), in 1) (Chen, 1979; Li et al., 2012). Scientists have made which the -Berriasian M19-M18 magneto- great efforts for defining a non-marine J/K boundary in chrons were identified in the J/K transition strata in the China since early 20th century. In the paper we would Nordvik Peninsula (the Laptev Sea), north . This like to review the research history and the great efforts great progress makes it possible to directly correlate the on searching for a non-marine J/K boundary in north- ©The Geological Society of Japan 2015 109 110 Gang Li and Atsushi Matsuoka 2015―3

Fig. 1. Late Mesozoic basins in China (revised after Chen, 1979; Sha et al., 2002; Li et al., 2012). H, Heilongjiang Prov- ince; J, Jilin Province; L, Liaoning Province; He, Hebei Province; Sh, Shandong Province.

Fig. 2. Correlation chart for Upper Jurassic and Lower Cretaceous sequences in northern Hebei and northeastern China (af- ter Sha, 2007; Wan et al., 2013). Jour. Geol. Soc. Japan 121（ 3 ） Searching for a non-marine Jurassic/Cretaceous boundary in northeastern China 111 eastern China. Japan and was assigned a Middle–Late Jurassic age. The Jehol Group is nowadays subdivided into the Yixi- Non-marine J/K strata subdivision in early time an and Jiufotang formations (yielding the Jehol Biota) The early geological investigations on the Chinese in the lower, the Shahai and Fuxin -bearing forma- non-marine Cretaceous strata began in 1920s. These re- tions (yielding the Fuxin Biota, Wang et al., 1989) in the searches included lithostratigraphical subdivision of upper (Chen, 1988, 1999a) (Fig. 2). As a result of these Cretaceous deposits in Shandong (eastern China) and studies the J/K boundary was placed above the Jehol Zhejiang provinces (southeastern China) (Tan, 1923; Group, i.e. at the base of the overlying Sunjiawan For- Liu and Chao, 1927) and mineral resources explora- mation (Kobayashi, 1942a, b; Oishi and Morita, 1943). tions, such as geological mapping of coal-bearing suc- This proposal for a non-marine J/K boundary delinea- cessions (Tan, 1924; Wang, 1929; Wang and Huang, tion in northeastern China was accepted by Chinese sci- 1929) and oil shale formations (Tan and Wang, 1929) in entists (Gu, 1962), and the well known Mengyin and Liaoning and Heilongjiang provinces, northeastern Chi- Laiyang groups of Shandong were also reassigned to na. Meanwhile, preliminary palaeontological studies the Jurassic. were also conducted on Cretaceous non-marine , Different opinion on delineating the such as plants from the Laiyang Group of Shan- non-marine J/K boundary dong (Chow, 1923), mollusks, clam shrimps “( conchos- tracans”), insects and fishes from Shandong, Liaoning, Palaeontological data on non-marine biota were in- Shanxi and Hubei provinces (Grabau, 1923a, b, c). Ac- creasingly accumulated since 1970s. Although these cording to these limited terrestrial fossil evidence Gra- new data fueled further discussions on the delineation bau (1928) came to the conclusion that the non-marine of the J/K boundary in the non-marine sediments of Jehol Fauna, i.e. the“ middendofii” (clam shrimp)– northeastern China, Gu (1982a, b, 1983) maintained the Ephemeropsis (insect)–Lycoptera (fish) fauna, was Middle–Late Jurassic age assignment for the whole Je- widely distributed in northern China, Mongolia and hol Group (Fig. 3) because of the occurrence of an al- Transbaikalia of Russia, and it was assigned an Early leged Jurassic bivalve Arguniella (=Ferganoconcha) Cretaceous age. This age assignment for the Jehol Fauna quadrata–Solenaia mengyinensis fauna, and delineated (Biota) was consistent with the research results of the the J/K boundary at the base of the overlying sequences fruitful Central Asiatic Expeditions led by Roy Chap- yielding an Early Cretaceous bivalve Trigonioides–Pli- man Andrews of the American Museum of Natural His- catounio–Nippononaia (TPN) fauna (Fig. 4). Various tory during 1922–1930 (Osborn, 1922; Morris, 1936). candidate horizons were chosen for defining the J/K Since late 1920s Japanese geologists began to carry boundary within the Jehol Group. Firstly, the "middend- out intensive investigations in northeastern China. In ofii" clam shrimp fauna of Jehol Biota was renamed as a addition to the description of fossil plants (Yabe and Oi- Late Jurassic Eosestheria fauna, which was widely shi, 1929, 1933; Oishi, 1933, 1935, 1941) and fossil found in the Yixian and Jiufotang formations of the vertebrates, such as splendens Endo, lower Jehol Group, as well as in the stratigraphically 1940, Yabeinosaurus tenuis Endo and Shikama, 1942, equivalent sequences of northern and northeastern Chi- Manchurochelys manchuensis Endo and Shikama, 1942, na, Mongolia and Transbaikal regions where the drain- the typical non-marine Mesozoic lithostratigraphic se- age system of the ancient Heilongjiang River was pres- quences were subdivided and nominated, and many ent (Chen, 1988). The Eosestheria fauna was also lithostratigraphic units are still maintained valid until discovered in several scattered basins in southern Jilin, now, such as the Lower Cretaceous Yixian, Jiufotang, in the northern foothills of the Dabie Mountains in Shahai and Sunjiawan formations in western Liaoning Henan and Anhui, and in the Mengyin Basin of Shan- (Fig. 2), the Huashan Group in eastern Heilongjiang, dong (Chen, 1988). The J/K boundary was moved etc. (Endo, 1934; Morita, 1939; Muroi, 1940; BG- downward and placed within the Jehol Group, i.e. at the MEDL, 1997; BGMRH, 1997; BGMRJ, 1997; Chen, base of the Shahai Formation (Fig. 3) because an Early 2000). Cretaceous Pseudestherites–Yanjiestheria–Diestheria– At the beginning of 1940s a general outline of the Eosestheria–Orthestheria（ PYDEO）clam shrimp as- non-marine Mesozoic sequences and biotas in the Kore- semblage was discovered in the formation (Fig. 4) an peninsula and northeastern China was summarized (Chen, 1988). So that the Early Cretaceous age was as- (Kobayashi, 1942a, b). The whole Jehol Group in west- signed to the contemporaneous coal-bearing sequences ern Liaoning was correlated with the of in northeastern China which contains a Ruffodia–Ony- 112 Gang Li and Atsushi Matsuoka 2015―3

Fig. 3. Different proposals for the definition of the non-marine J/K boundary in northeastern China in the 1980s (after Gu, 1982b; Hao et al., 1982; Chen, 1988).

Fig. 4. Biostratigraphic subdivision of Upper Jurassic and Lower Cretaceous strata in northern China used in the 1980s (af- ter Gu, 1982a; Hao et al., 1982; Chen, 1988). Jour. Geol. Soc. Japan 121（ 3 ） Searching for a non-marine Jurassic/Cretaceous boundary in northeastern China 113

Fig. 5. Marine bivalve Buchia biozones identified in the 1980s and early 1990s in eastern Heilongjiang Province by differ- ent authors (after Gu, 1982a; Gu et al., 1984; Chen and Sun, 1989; Sun et al., 1989; Sha, 1992). chiopsis flora, such as the Chengzihe and for- the Longzhaogou Group (including, in stratigraphically mations of the Group in eastern Heilongjiang. Then, ascending order, the Peide, Qihulin, Lower Yunshan, Hao et al. (1982) proposed to lower the J/K boundary Upper Yunshan and Zhushan formations) (Fig. 2). Be- further downwards to the base of the Jingangshan Beds cause the ammonites were recovered from the Qihulin (earlier called the Jingangshan Formation, Fig. 3) of the Formation of the Longzhaogou Group, and members of upper based on the occurrence of var- the Jehol Fauna were recovered from the Jixi Group (bi- ious Early Cretaceous faunas, such as a bivalve Arguni- valve Arguniella=Ferganoconcha and Sphaerium), the ella (=Ferganoconcha)–Sphaerium anderoni–S. je- correlation among these three lithological groups (i.e. holense assemblage, an ostracode Cypridea vitimensis– the Jehol, Jixi and Longzhaogou groups) seemed to C. sulcata–Limnocypridea subplana–Mongolianella have been very important for establishing the non-ma- palmosa assemblage (Fig. 4), an Ephemeropsis trisetalis rine J/K boundary in northeastern China. This stimulat- insect fauna and a Lycoptera fish fauna, etc. ed the great geological investigation campaigns carried out by three research groups during late 1970s and early Marine faunas from eastern Heilongjiang Province 1980s, thousands of farmers were also involved in dig- The disparity in defining the non-marine J/K bound- ging test trenches to disclose the study sections in the ary in northern China among research groups focuses forest of the Wanda Hills (Ju et al., 1981, 1982; Gu and on the geological age assignment of the Jehol Group of Chen, 1983; Li et al., 1986; RTMCF, 1986). western Liaoning. In order to date the non-marine Jehol Through intensive field investigations, marine macro- Biota using marine fossil evidence the eastern Hei- and microfossils have been recovered from the Jixi and longjiang area became a key region because a purported Longzhaogou groups, including ammonites, bivalves, Callovian (Middle Jurassic) ammonite Subkossmatia sp. gastropods (Yu and Zhu, 1983), brachiopods (Li and was reported from the Wanda Hills in 1958 (Chang in Gu, 1982; Sun, 1983), and ostracodes (Li and Zhang, Huang, 1963). There are two coal-bearing, alternating 1981; Zhang, 1982; Gou, 1983). The extremely com- marine and non-marine lithological groups in eastern pressed ammonites from the Qihulin Formation were Heilongjiang: i.e. in the west is the Jixi Group (includ- identified as a Middle Jurassic (Bathonian) Arctocepha- ing, in stratigraphically ascending order, the Didao, lites fauna. First, Liang (1982) identified ten specimens Chengzihe and Muling formations), and in the east is and described five new species, including Arctocepha- 114 Gang Li and Atsushi Matsuoka 2015―3 lites peideense Liang, 1982. Then, Wang (1983) de- Volgian–Valanginian or age assignment for scribed eight specimens and came to the conclusion that the Zhushan Formation (Chen and Sun, 1989) was still the fauna was dominated by a Boreal species Arcto- inconsistent with a Neocomian– age assignment cephalites (Cranocephalites) hulinensis Wang (Fig. 5). suggested by a palynomorph Gleicheniidites (66%)– The abundant and high diversity marine bivalve fau- Osmundacidites (11%) assemblage (Zhang, 1983). nas from the Jixi and Longzhaogou groups were as- While the discovery of another Buchia faunal locality signed to Middle–Late Jurassic (Fig. 5) (Li and Yu, at Dong’an of Raohe County of northeastern Heilongji- 1982; Gu et al., 1984). The identification of the index ang (Fig. 5) made it possible to delineate a more precise fossil Buchia tenuistriata from a borehole core in the marine J/K boundary horizon in eastern Heilongjiang Jixi Basin at a horizon of the lower Chengzihe Forma- (Sun et al., 1989; Sha, 1992). The continuous marine se- tion indicated a Kimmeridgian (Late Jurassic) age for quence of the Dong’anzhen Formation at the Dong’an the fossil bearing horizon, and the conformably overly- Town yields four Buchia assemblages, i.e. in ascending ing Muling Formation was assigned to the latest Juras- order: the middle Volgian Buchia russiensis–B. fischeri- sic. The correlation between the Chengzihe and Shahai ana assemblage, the late Volgian Buchia fischeriana–B. formations was supported by the non-marine bivalve unschensis assemblage, the Ryazanian (mostly Berria- evidence, such as the recovery of Neomiodon? yixianen- sian) Buchia volgensis–B. cf. subokensis–B. cf. okensis– sis (Gu, in Gu et al., 1976) from the Chengzihe Forma- B. unschensis assemblage and the early Valanginian B. tion in the coalfield, and the discovery of Ar- pacifica assemblage (Fig. 5). The base of the Buchia guniella (=Ferganoconcha) cf. quadrata–Unio cf. fischeriana–B. unschensis assemblage zone, correlated grabaui bivalve assemblage from the Chengzihe Forma- with that of the Boreal ammonite Craspedites exoticus tion in the Jixi Basin. The recovery of Sphaerium zone, was defined as the J/K boundary in eastern Hei- (Sphaerium) subplanum–S. (S.) selengiense bivalve as- longjiang (Sha, 2007). semblage (Fig. 5) in the Muling Formation supported its Since 1990s restudies of the marine fossils dramati- correlation with the Fuxin Formation of the upper Jehol cally changed the initial Jurassic age assignment for the Group (Gu et al., 1984; Sha, 2007). Thus, the alleged Jixi and Longzhaogou groups in eastern Heilongjiang. Bathonian ammonites and Kimmeridgian bivalve Bu- First, the above mentioned two Buchia biozones were chia fauna from eastern Heilongjiang seemed to indi- re-identified as two Aucellina assemblages (Sha, 1990), rectly support a Jurassic age for the whole Jehol Group i.e. the lower is the A. (A.) caucasica–A. (A.) aptiensis– (Gu, 1982b). A. jelezkii assemblage from the lower Chengzihe and Further investigation along the Qihulin River in the middle Upper Yunshan formations, and the upper is the Yunshan area of County made further Buchia A. cf. caucasica–A. cf. aptiensis assemblage from the specimens available. Chen and Sun (1989) identified Upper Yunshan Formation, with a consequent revision two biozones, i.e. the early Kimmeridgian Buchia con- of their geological age to late Early Cretaceous (latest centrica Zone from the middle Upper Yunshan Forma- middle Barremian–middle Albian) (Sha and Fürsich, tion, and the middle Volgian B. mosquensis–B. russien- 1993; Sha et al., 1994). Then, Kelly et al. (1994) indi- sis Zone from the top of the Upper Yunshan Formation cated that the original ammonite specimens reported (Fig. 5). At the same time Chen and Sun (1989) revised from the Qihulin Formtion are mainly desmoceratids the above mentioned B. tenuistriata Zone of the lower with subordinate tetragonitids, whereas Futakami et al. Chengzihe Formation to the B. concentrica Zone. Thus (1995) described the ammonites as a Barremian Pseu- the J/K boundary (i.e. the bottom of Ryazanian) was de- dohaploceras fauna. Thus, the Jixi and Longzhaogou lineated within the lower parts of the Muling and groups were reassigned to an Early Cretaceous age (Sha Zhushan formations, respectively. The base of the two et al., 1994; Gu et al., 1997; Sha et al., 2002). formations was believed to be the base of the upper Vol- Further lines of evidence from microfossils supported gian (Fig. 5). Although this was the first time to lower the Early Cretaceous age assignment for the Jixi and the J/K boundary downwards into the Jixi and Longzha- Longzhaogou groups. Firstly, a Berriasian–Valanginian ogou groups based on bivalve Buchia biozones, this brackish water dinoflagellate Vesperopsis didaoensis– boundary horizon was still higher than the J/K boundary Lagenorhytis granorugosa zone indicated that the Didao proposed based on macrofossil plant evidence, i.e. the Formation could not be older than Cretaceous (Cheng base of the Ruffordia–Nilssonia sinensis assemblage and He, 2001; Zhu and He, 2007). Secondly, a low di- bearing sequence (upper Chengzihe and Muling forma- versity radiolarian Novixitus?– Archaeodictyomitra– Xi- tions) (Zheng and Zhang, 1982). Meanwhile, the upper tus fauna and a relatively well-preserved agglutinated Jour. Geol. Soc. Japan 121（ 3 ） Searching for a non-marine Jurassic/Cretaceous boundary in northeastern China 115 foraminiferal Cribrostomoides nonioninoides– Haplo- age of 122±0.3 Ma for the lower Yixian Formation in phragmoides concavus– H. gigas minor fauna from the the Daxinfangzi section of Lingyuan, western Liaoning. Qihulin Formation support an Early Cretaceous age for Swisher et al. (1999) reported a laser 40Ar/39Ar study of the formation (Li and Yang, 2003; Li and Yu, 2004). single sanidine crystals from tuffs of the Jianshangou Beds that crops out in the Sihetun and Jianshangou sec- Discovery of extremely tions near Beipiao, and gave a mean age of 124.6±0.2 well-preserved fossil records (or 0.3) Ma. Wang et al. (2001) reported three ages from The recovery of the fossil Cathayornis yandica the Jianshangou Beds at Sihetun: a K–Ar age of 129.0± Zhou et al., 1992 from the Jiufotang Formation of Cha- 2.6 Ma for the base basalt-andesite, a zircon U–Pb age oyang, western Liaoning preludes the further important of 125.2±0.9 Ma for a middle tuff layer, and an Ar–Ar fossil discoveries of the Jehol Biota, like feathered dino- plateau age of 122.3±0.5 Ma for the cover diabase lay- saurs (Ji and Ji, 1996; Chen et al., 1998; Xu et al., 2000, er. He et al. (2004) reported 40Ar/39Ar step heating anal- 2003), birds (Hou et al., 1995; Hou and Chen, 1999), yses of K-feldspar and SHRIMP U–Pb zircon data indi- mammals (Hu et al., 1997; Ji et al., 1999, 2002; Li and cating a 120.3±0.7 Ma age for the Jiufotang Formation Luo, 2006; Luo et al., 2007) and angiosperms (Sun et (Fig. 6). al., 1998, 2002, 2011; Leng and Friis, 2003). These new The above mentioned radiometric ages, indicating a fossil records from the Jehol Group led to more exten- middle Early Cretaceous age for the Yixian Formation, sive discussions on its age assignment and the position are inconsistent with the Late or latest Jurassic–Early of the non-marine J/K boundary in northeastern China Cretaceous age assignment based on some fossil occur- (Gu et al., 1997; Batten, 1998; Chen and Wu, 1998; rences. Clam shrimps and ostracodes are important Wang et al., 1999; Xu et al., 1999). Of particular con- components of the Jehol Biota, and palynomorphs have cern is the geological age of the Yixian Formation, the also been recovered. In the Yixian Formation the clam lowest formation of the Jehol Group, which consists of, shrimps belong to a widely distributed Eosestheria fau- in stratigraphically ascending order, the Jianshangou, na, which has generally been regarded as Late Jurassic Zhuanchengzi, Dakangpu and Jingangshan beds (Chen (Kobayashi and Kusumi, 1953; Zhang et al., 1976; et al., 1980; Chen, 1999a, b, 2000; Chen et al., 2005; Chen et al., 1980; Wang, 1987; Wang, 1998; Chen, Wang et al., 2005). Smith et al. (1995) fixed a maximum 1999b). This older age determination has received fur-

Fig. 6. Correlation chart for Upper Jurassic and Lower Cretaceous sequences in northern Hebei and western Liaoning, in- corporating radiometric and biostratigraphic data (after Wan et al., 2013; Wang et al., 2013). 116 Gang Li and Atsushi Matsuoka 2015―3 ther support from a comparison made between the Chi- by K-feldspar 40Ar/39Ar age of 130.7±1.4 Ma (He et al., nese dragonfly species Aeschnidium heishankowense 2006), contains an early Jehol Biota, characterized by a from the Yixian Formation and A. densum from the Ti- Nestoria–Keratestheria clam shrimp fauna (Wang, thonian Solnhofen Limestone (Zhang, 1999). 1981), a Luanpingella–Eoparacypris–Darwinula ostra- Zhang (1985) recognized two ostracode assemblages code fauna, an Arguniella bivalve fauna, a Lymnaea from the Yixian Formation, i.e. a lower Cypridea (C.) websteri gastropod fauna and a Peipiaosteus fish fauna liaoningensis–C. (Ulwellia) muriculata–Djungarica ca- (Chen, 1999a). Although the radiometric dating of the marata assemblage from the Jianshangou Beds, which Zhangjiakou and Dabeigou formations show an Early was considered to be of a Tithonian age, and an upper Cretaceous age, the two formations have been assigned Cypridea (C.) veridica arquata–C. (C.) jingangshanen- to Late Jurassic based on the above mentioned fossil as- sis–C. (C.) zaocishanensis assemblage from the Jin- semblages (Tian et al., 2004a, b; Liu et al., 2003). The gangshan Beds, which was regarded as Berriasian in non-marine J/K boundary was defined at the basal part age. As a result, the J/K boundary was placed at the of the overlying four-membered Dadianzi Formation, a base of the Jingangshan Beds yielding the younger os- horizon at which ostracode Cypridea stenolonga first tracode assemblage. Later, a restudy of the biostratigra- occurs (Tian et al., 2004a, b). The correlation of the phy of the ostracode fauna of the Jianshangou Beds ex- Third and Forth members of the Dadianzi Formation posed in the Sihetun, Huangbanjigou and Jianshangou with the Jianshangou Beds of the Yixian Formation was sections near Beipiao arrived at an age determination of based on the finds of clam shrimp Eosestheriopsis late Tithonian or late Tithonian–early Berriasian (Cao, (=Clithrograpta) within the two successions, respec- 1999). This was based on a comparison of Cypridea (C.) tively (Figs. 2, 6) (Chen, 1999b; Niu et al., 2003; Li et liaoningensis liaoningensis Zhang and C. (Ulwellia) al., 2007). beipiaoensis Cao with C. granulosa (Sowerby) and C. Potential non-marine J/K boundary in dunkeri Jones from the middle and lower Purbeck suc- northern China cession of southern England, respectively (Horne, 1995). But a palynomorph assemblage recovered from The definition of a non-marine J/K boundary in north- the Jianshangou Beds at Huangbanjigou suggests an ern China is still problematic. Although Chinese scien- earliest Cretaceous (Berriasian) age (Li and Liu, 1999). tists previously proposed several J/K boundary ages, The Early Cretaceous age assignment for the Jianshan- such as 124 Ma (Wang et al., 2005), 125 Ma (Chen et gou Beds is consistent with the recovery of Cratos- al., 2005), 130 Ma (Liu et al., 2003), 135–137 Ma (Hao tracus? cheni Li and Batten, 2004 from the Yixian For- et al., 1982), recent research on the marine J/K transi- mation in western Liaoning (Li and Batten, 2004). As a tion sequences in the Gyangze–Nagarze areas of south- result, the J/K boundary was placed at the base of the ern Tibet indicates that the base of Hauterivian is not Yixian Formation (Li and Liu, 1999). Further study of older than 136±3 Ma (Wan et al., 2011), and 140– the palynomorph assemblage of the Jianshangou Beds 142 Ma SIMS zircon U–Pb ages for the mid-Berriasian in the Sihetun area indicates a not older than Valangin- (Liu et al., 2012) supported the 145 Ma for the J/K ian–Hauterivian or Barremian age for the Jianshangou boundary age proposed by Gradstein et al. (2012). Thus, Beds (Li and Batten, 2007). Thus, according to the new the potential J/K boundary should be lower than the palynomorph evidence the J/K boundary should be low- Yixian Formation, i.e. within the Tuchengzi Formation er than the base of the Yixian Formation of western Lia- in western Liaoning; and below the Dabeigou and oning. Zhangjiakou formations, i.e. within the Houcheng For- In northern Hebei, the“ standard strato-section” of the mation in northern Hebei (Ji et al., 2006; Sha, 2007; non-marine J/K boundary strata was measured in the Zhou et al., 2009; Wan et al., 2013). This new interpre- Luanping Basin (Tian et al., 2004a, b), where above the tation was supported by new radiometric ages (Fig. 6), Houcheng Formation are the Zhangjiakou, Dabeigou such as an 40Ar/39Ar age of 139±0.19 Ma (Swisher et and Dadianzi formations (Figs. 2, 6). The Zhangjiakou al., 2002), a zircon U–Pb age of 137.2±6.7 Ma (Zhang Formation, mainly composed of rhyolite and rhyolitic et al., 2009) and a zircon U–Pb age of 137.3±1.0 Ma tuff, yields a SHRIMP zircon U–Pb age of 135.4± (Wang, et al., 2013) for the upper Tuchengzi Formation 1.6 Ma from its top tuff layer at the Jingshang Village of of Beipiao, and a zircon U–Pb age of 147.4±2.2 Ma for Luanping County (Fig. 6) (Liu et al., 2003). The overly- the base of the Tuchengzi Formation at Batuyingzi of ing Dabeigou Formation, dated by zircon U–Pb ages of Beipiao, western Liaoning (Zhang et al., 2009). Mean- 133.9±2.5 Ma and 130.1±2.5 Ma (Liu et al., 2003) and while, further radiometric ages were also reported, such Jour. Geol. Soc. Japan 121（ 3 ） Searching for a non-marine Jurassic/Cretaceous boundary in northeastern China 117 as a 136.4±1.9 Ma age and a 139.6±1.5 Ma age for the non-marine J/K boundary in northeastern China. top tuff layer in the Houcheng Formation, the 156 Ma Correlation between Chinese and Japanese sequences (Davis, 2005) and 146.5±1.7 Ma (Zhang et al., 2009) would be one of good directions for establishing the ages for the base of the Houcheng Formation in north- non-marine J/K boundary in China. The Chinese late ern Hebei. Mesozoic deposits contain well developed non-marine The above mentioned radiometric ages from the biotas, whereas the Japanese upper Mesozoic sequences Tuchengzi and Houcheng formations are inconsistent contain many marine fossil assemblages, such as Mid- with their Middle–Late Jurassic age assignment based dle–Late Jurassic and Early Cretaceous ammonites from on the biostratigrphic evidence (Wang et al., 2004). the Tetori Group in central Japan (Sato, 1962, 2008; Firstly, a Middle Jurassic (Shen and Chen, 1984) or ear- Sato et al., 2003, 2012; Sato and Yamada, 2005; Goto, ly Late Jurassic (Chen et al., 2007) Pseudograpta clam 2007; Matsukawa et al., 2008; Matsukawa and Fukui, shrimp fauna was found from the lower Tuchengzi For- 2009; Sano et al., 2013), which would be a great help to mation; and a middle Late Jurassic Yanshanoleptesthe- constrain the geological age of the fossil bearing beds. ria–Pingquania–Lingyuanella assemblage was recov- At the same time recently new fossil assemblages were ered from the Upper Houcheng Formation and the upper also recovered from the Tetori Group, i.e. the Jurassic Tuchengzi Formation, respectively (Wang et al., 2013). plants (Yamada and Uemura, 2008) and radiolarians Secondly, two Late Jurassic ostracode assemblages (Kashiwagi and Hirasawa, 2010), the Early Cretaceous were recovered from the Tuchengzi or Houcheng For- charophytes (Komatsu et al., 2003; Kubota, 2005), paly- mation, respectively: i.e. a lower (early Late Jurassic) nomorphs (Umetsu and Matsuoka, 2003; Legrand et al., Cetacella substriata–Mantelliana alta–Darwinula ba- 2013), gastrapods (Isaji, 2010), (Hirayama, panxiaensis assemblage form the lower Tuchengzi For- 2002), dinosaurs (Kobayashi and Azuma, 2003; Azuma mation, and an upper (middle Late Jurassic) Djungarica and Shibata, 2010), pterosaurs (Unwin et al., 1996) and yangshulingensis–Mantelliana reniformis–Stenestro- mammals (Tsubamoto et al., 2004; Rougier et al., 2007; emia yangshulingensis assemblage from the upper Kusuhashi, 2008). In consideration the new data of bio- Houcheng Formation (Wang et al., 2004). stratigraphy and radiometric dating of the Tetori Group Thirdly, a Middle–Late Jurassic Brachyphyllum ex- (Fujita, 2002; Kusuhashi et al., 2006; Kawagoe et al., pansum–Pagiophyllum beipiaoense floral assemblage 2012), new interpretation has been proposed on the cor- was recovered from the Tuchengzi Formation. It con- relation scheme of late Mesozoic sequences between tains not only the Middle Jurassic elements, such as Co- China and Japan (Sha and Hirano, 2012). Thus, it would niopteris hymenophylloides, C. simplex, Brachyphyllum be very fruitful to carry out a joint work to correlate mamillare, Equisetites cf. sarrani, and Yanliaoa cf. si- Chinese non-marine J/K boundary sequences with Japa- nensis, but also yields Late Jurassic members, such as nese marine and non-marine transition sequences in the Equisetites cf. naktongensis, Leptostrobus marginatus, future. Carpolithus fabiformis, Pityolepis larixiformis, P. Acknowledgments pingquanensis, Schizolepis chilitica, and Pagiophyllum beipiaoense (Wang et al., 2004). This study was supported by the Major Basic Re- Fourthly, an early Late Jurassic Classopollis (86%) search Projects of the Ministry of Science and Technol- dominated palynomorph assemblage from the lower ogy, China (National 973 Project 2012CB822004), Tuchengzi Formation contains rare spores, such as Graduate School of Science and Technology of Niigata Deltoidospora, Cyclogranisporites, Osmundacidites, University, National Natural Science Foundation of and Punctatisporites; while a Late Jurassic palyno- China (41172010), Chinese Academy of Geological morph assemblage was recovered from the Houcheng Sciences (1212011120142, 1212011120116), and State Formation, which is dominated by Classopollis (91%), Key Laboratory of Palaeobiology and Stratigraphy, and yields 5% Callialasporites and rare Cicatricosi- Nanjing (20101104). The authors would like to express sporites and Schizaeoisporites (Wang et al., 2004). the great thanks for the critical reviews and the con- Although at the moment the non-marine J/K boundary structive comments from Dr. N. Kusuhashi (Ehime Uni- in northeastern China is delineated between the middle versity, Japan), Dr. T. Komatsu (Kumamoto University, and upper parts of the Tuchengzi Formation (Wan et al., Japan) and an anonymous reviewer. 2013), as shown in Fig. 6, further extensive biostrati- References graphical investigations on the Tuchengzi and Houcheng formations are needed in order to establish a Azuma, Y. and Shibata, M., 2010, nipponensis, a 118 Gang Li and Atsushi Matsuoka 2015―3

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（要 旨）

Li, G. and Matsuoka, A., 2015, Searching for a non-marine Jurassic/Cretaceous boundary in northeastern China. Jour. Geol. Soc. Japan, 121, 109–122．（李 罡・松 岡 篤，2015，中国東北部の非海成層におけるジュラ系・白亜系境界の探索．地質雑， 121, 109–122.） 中国東北部では，ジュラ系および白亜系は，主として非海成の地層からなる．中国東北 部における非海成層中のジュラ系・白亜系境界の認定は，遼寧省西部から産出する Jehol 生物群の年代決定に大きく依存している．同生物群の年代観は，幾多の変遷をたどっている． 中国，モンゴルおよびロシア・トランスバイカルの含 Eosestheria–Ephemeropsis– Lycoptera 層は，1920 年代には白亜紀古世に位置づけられていた．しかし，1960 年代以 降は，ジュラ紀中世ないし新世へと変更された．1990 年代前半以降，黒竜江省東部から産 する海生生物相の年代位置づけが修正されたことにより，Jehol 生物群の年代は，再び白 亜紀古世を示すと考えられるようになった．最近の放射年代の測定によれば，ジュラ紀・ 白亜紀境界は，Jehol 層群の層準よりもずっと下位に位置づけられる．

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