Jour. Geol. Soc. Japan, Vol. 121, No. 3, p. 109–122, March 2015 doi: 10.5575/geosoc.2015.0001 Review Searching for a non-marine Jurassic/Cretaceous boundary in northeastern China 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 Early Cretaceous in the ences, Nanjing 210008, China ＊＊ 1920s, the age of the entire Jehol Group of western Liaoning, 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 Late Jurassic Buchia fauna from east- ern Heilongjiang 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 dinosaurs, early birds, mammals, 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 Hebei. 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 Berriasian 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 Tithonian-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 Siberia. 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 coal-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 fossils, Different opinion on delineating the such as fossil 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 Monjurosuchus 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 Tetori Group 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.