- Email: [email protected]
Biostratigraphic and palaeoenvironmental implications of an Early Cretaceous miospore assemblage from the Muling Formation, Jixi Basin, northeast China
Cretaceous Research 28 (2007) 339e347 www.elsevier.com/locate/CretRes
Biostratigraphic and palaeoenvironmental implications of an Early Cretaceous miospore assemblage from the Muling Formation, Jixi Basin, northeast China Xiaoju Yang a,*, Wenben Li a, David J. Batten b a
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China b School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK Accepted 19 July 2006 Available online 23 February 2007
Abstract In the Jixi Basin, eastern Heilongjiang Province, China, the lower part of the Lower Cretaceous succession consists of coal-bearing strata including the Muling Formation, which, in addition to plant megafossils, yields abundant spores and pollen grains and a few dinoflagellate cysts. The spore-pollen assemblage consists of more than 42 species belonging to 34 genera. Most of these are derived from pteridophytes and gymnosperms. The association of Aequitriradites echinatus, Cicatricosisporites australiensis, C. imbricatus, C. mediostriatus, C. undosus, Contignisporites glebulentus, Crybelosporites punctatus, Foraminisporis asymmetricus, Gleicheniidites laetus, Impardecispora purverulenta, Kuylisporites lunaris, Pilosisporites trichopapillosus and Triporoletes singularis suggests that the formation is unlikely to be older than late Hauterivian and younger than Aptian, with emphasis placed on the Barremianeearly Aptian. The composition of the dinoflagellate cyst and plant megafossil assemblages is consistent with this determination. Based on palynofloral content, a comparison between the miospores recovered and the spores and pollen produced by extant plant taxa, the associated plant megafossils, and the sedimentary facies that characterize the Muling Formation, it is concluded that the source vegetation was dominated by ferns and that the climate was wet subtropical but seasonally dry. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Miospores; Early Cretaceous; Muling Formation; Heilongjiang; China
1. Introduction The Jixi Basin is situated in the southeast of Heilongjiang Province, China, at about 130 200 e31 350 E and 44 450 e 45 250 N. It contains good exposures of the late Mesozoic coal-bearing strata of the Jixi Group. This group is divided into, in ascending order, the Didao, Chengzihe
* Corresponding author. E-mail address: [email protected] (X. Yang). 0195-6671/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2006.07.008
and Muling formations. The name of the last of these is derived from the ‘‘Muleng Coal Series’’ of Wang (1929), which was used to refer to coal-bearing strata near the River Muling in Jixi City. It was erected by Gu (1962) based on the upper part of the ‘‘Muleng Coal Series’’. Its relationships with the underlying Chengzihe and overlying Dongshan formations are conformable. The fine-grained clastic deposits intercalated with greyish-green tuffs of which it is composed (Bureau of Geology and Mineral Resources of Heilongjiang Province, 1997) differentiates it from these two formations, the Chengzihe Formation containing more
340
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
coal and less tuff and the Dongshan Formation comprising coarse sandstones and other clastic deposits with fewer plant remains and no coal. Geological studies on the Muling Formation began during the 1920s. For the next 40 years it was considered to be Jurassic in age (Ahnert, 1925; Wang, 1929; Oishi and Takahashi, 1938; Chen, 1959; Shi, 1960; Gu, 1962), but from the mid 1960s it was increasingly regarded as Early Cretaceous (Zhang, 1965; Zhou et al., 1980; Ju et al., 1982; Pu and Wu, 1982; Zheng and Zhang, 1982), and during the past 15 years discoveries of angiosperms in the basin (Sun et al., 1993; Sun and Dilcher, 1996, 1997) and analyses of bivalves recovered from it (Sha, 1991; Sha et al., 1994, 2002), have led to the conclusion that the formation must have been deposited during the Early Cretaceous. Sun et al. (1999) and Yang (2003) dated it as middleelate Barremian or Barremianeearly Aptian. Sha et al. (2000) considered it to be possibly late Aptianeearly Albian. Until marine dinoflagellate cysts (dinocysts) were encountered recently (Wan et al., 2000; Yang et al., 2003) it had been regarded as an entirely non-marine succession. Plant microfossils from the Muling Formation were reported by Zhang (1965). He described and illustrated a considerable number of spore species, many new, from core samples, and recognized their Early Cretaceous age. Pu and Wu (1982) described abundant spores and pollen grains from surface samples and dated the formation as BarremianeAptian. Yang et al. (2003) based their more recent age determination of possibly Barremian on dinocyst evidence. These publications have provided general conclusions on the age of the formation. The main aim of the present paper is to review the composition of the spore-pollen flora of the
type locality of the Muling Formation and to use the data in conjunction with evidence from occurrences of dinocysts and plant megafossils as a basis from which to consider its age once more, and to draw palaeoenvironmental and palaeoclimatic conclusions. To this end, samples were collected from beds containing megafossils throughout the formation. However, despite the logic behind the collecting strategy, a disappointingly large proportion of these (see below), especially from the upper part of the section, proved to contain only poorly preserved palynomorphs of no biostratigraphic value; as a result, they have had to be omitted from consideration here. 2. Material and methods Twenty samples of mainly dark grey to black mudstones and siltstones were taken at irregular stratigraphic intervals from the coal- and plant-bearing beds at Qinglongshan, which is where the type section of the Muling Formation is exposed. This is situated along a railway line about 10 km to the west of the city of Jixi (130 210 E, 45 250 N; Fig. 1). Conventional physico-chemical procedures for processing samples for palynological analysis (Batten and Morrison, 1983; Phipps and Playford, 1984) were employed for extracting and concentrating palynomorphs from the samples. Unfortunately only six of them yielded well-preserved spores and pollen grains. All of the slides prepared were examined and specimens were photographed under a Nikon transmitted light microscope. They were then deposited, along with the unmounted residues, in the collections of the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPCAS). Labelling of the slides is as shown in the
Fig. 1. Map showing the location of the type section of the Muling Formation at Qinglongshan.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
341
following example: JM03-3: J, Jixi Basin; M, Muling Formation; 03, sample number; -3, third slide from this sample.
3. Results Most of the samples processed yielded palynomorphs but the only well-preserved assemblages were recovered from those taken from the mouth of a mine (Fig. 2). Selected examples of the taxa encountered are illustrated in Figs. 3e6.
3.1. Palynostratigraphy
Fig. 2. Lithological log of the Muling Formation at Qinglongshan showing the six horizons that yielded assemblages of well-preserved palynomorphs.
More than 42 miospore species referred to 34 genera were identified from the palynological preparations. A list of the genera recorded with their presumed or possible botanical affinities noted alongside is given in Table 1. Among the miospores, 22 genera (65) are derived from pteridophytes, six (18) from gymnosperms, five (15) from bryophytes and one (3) is an alga. Of the pteridophytes, the Schizaeaceae show considerable diversity. Spores attributable to the Lycopsida are also common, but conifers are comparatively poorly represented by members of the families Pinaceae, Podocarpaceae and Cheirolepidiaceae, and no angiospermous taxa were found. Many of the spore species, such as Aequitriradites echinatus Pu and Wu, Cicatricosisporites australiensis (Cookson) Potonie´, C. imbricatus (Markova) Singh, C. mediostriatus (Bolchovitina) Pocock, C. undosus Yu and Han, Contignisporites glebulentus Dettmann, Crybelosporites punctatus Dettmann, Foraminisporis asymmetricus (Cookson and Dettmann) Dettmann, Gleicheniidites laetus (Bolchovitina) Bolchovitina, Impardecispora purverulenta (Verbitskaya) Venkatachala, Kar and Raza, Kuylisporites lunaris Cookson and Dettmann, Pilosisporites trichopapillosus (Thiergart) Delcourt and Sprumont and Triporoletes singularis Mtchedlishvili have been reported mainly or only from Early Cretaceous deposits. Others are commonly found in midelate Mesozoic successions. Overall the total spore-pollen assemblage recovered is similar to that described by Zhang (1965) from the formation elsewhere in the basin but it differs from that recorded from beds apparently of the Muling Formation in the adjacent Boli Basin (Pu and Wu, 1982) in lacking species of Appendicisporites (e.g., A. auritus, A. bifurcatus, A. cristatus and A. insignis) and in the lower percentage occurrence of gleicheniaceous spores. The associated plant megafossils indicate that the flora is composed mainly of leptosporangiate ferns and gymnosperms that indicate mid Barremianeearly Aptian ages (Yang, 2003). Several species of marine dinoflagellate cyst have been recorded from the palynological preparations, including Circulodinium attadalicum (Cookson and Eisenack) Helby, C. cingulatum He, Wan and Yang, Oligosphaeridium totum Brideaux, Palaeoperidinium cretaceum Pocock and Sentusidinium sp. Their occurrence is consistent with a
Fig. 3. Examples of miospores recovered from the Muling Formation at Qinglongshan; all 800. For explanation of slide labelling, see under Section 2. AeD, Lygodiumsporites? sp., slides JM03-1, 03-3, 03-2, 03-1. EeH, Cibotiumspora dentata Lei, JM03-5, 03-9, 03-11. I, J, Stereisporites stereoides (Potonie´ and Venitz) Pflug, JM10-2, 10-1. KeM, Gleicheniidites laetus (Bolchovitina) Bolchovitina, JM04-2, 05-5, 10-4. N, O, Impardecispora purverulenta (Verbitskaya) Venkatachala, Kar and Raza, JM03-5. P, Concavissimisporites asper (Bolchovitina) Pocock, JM03. Q, Lygodiumsporites subsimplex (Bolchovitina) Gao and Zhao, JM03-5.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
midelate Early Cretacous age determination for the formation (cf. Helby et al., 1987; He et al., 1999; He and Sun, 2000).
3.2. Palaeocology and palaeoclimate Plant micro- and megafossil remains can provide information about the taxonomic composition of the former vegetation of a region from which, in turn, palaeoecological and palaeoclimatic conclusions can be drawn, though usually only in a general way. Comparisons of the morphology of the palynomorphs with the products of extant plant taxa with the aim of suggesting botanical affinities can assist in this respect, but they can also mislead. It helps to be able to base at least some of the relationships on connections with fertile fern fronds, gymnospermous cones and other megafossil remains. From such comparisons it may then be inferred, albeit tentatively, that the plants represented by a palynoflora occupied ecological niches similar to those of the extant taxa whose products they resemble. Plant megafossils have been described from the Muling Formation in the Dongning, Shuangyashan, Mishan and Baoqing basins in eastern Heilongjiang by Oishi and Takahashi (1938), Zhang et al. (1980) and Zheng and Zhang (1982). The flora from the Jixi Basin (Yang, 2003) comprises 38 species belonging to 31 genera, mainly of leptosporangiate ferns and gymnosperms, and all in a fragmentary state. Despite evidence, albeit limited, from the pollen record, no representatives of gymnosperms with needle-like leaves have been found. The abundant fern remains are of tropical or subtropical type; these include Acanthopteris, Athyrium, Coniopteris, Gleichenites, Gonatosorus, Hymenophyllites, Onychiopsis and Ruffordia. The composition of the flora indicates that the climate of the Jixi Basin and adjacent regions during much of the mid Early Cretaceous was warm and generally wet, but with seasonally dry periods. Evidence for a seasonal climate is apparent from, in particular, an abundance of Ginkgoites and two fossil woods that have been recovered from the formation: Glyptostroboxylon xidapoense Zheng and Zhang and Taxodioxylon szei Yang and Zheng, both of which have distinct growth rings (Yang and Zheng, 2003). Natural alliances of the dispersed miospore genera encountered in the Muling Formation are listed in Table 1. Some of these are more uncertain than others, with a few being little more than guesses. Pteridophyte spores dominate the palynomorph assemblages both numerically and taxonomically. The Schizaeaceae are strongly represented, as noted above; Cicatricosisporites species are abundant, with C. australiensis being especially numerous. Gleicheniidites laetus, attributable to the family Gleicheniaceae, is also very common. Representatives of these two families and of the Cyatheaceae and Dicksoniaceae thrive in both tropical and subtropical habitats (Tryon and Tryon,
343
1982). Bryophyte species constitute only a minor component of the assemblages. Extant bryophytes are most abundant in relatively moist terrestrial situations (Taylor and Taylor, 1993), but some inhabit dry locations and many are capable of withstanding periods of drought. The affinities of the dispersed pollen grains lie with the families Cycadaceae, Cheirolepidiaceae, Podocarpaceae and Pinaceae. Classopollis grains, produced by cheirolepidiaceous conifers, are consistently present in Early Cretaceous deposits over much of the Northern Hemisphere (e.g., Vakhrameev, 1991 and many other authors), but may occur only in relatively low numbers, as in the Muling Formation. The presence of representatives of the Cycadaceae and Podocarpaceae is consistent with a warm, predominantly humid but seasonally dry climate, with only representatives of the Pinaceae suggesting cooler conditions at higher elevations at some unknown distance from the depositional basin. Overall, despite the absence of any evidence of angiosperms, the palynoflora suggests a diverse source vegetation similar in composition to that described from other warm (tropicalesubtropical), generally humid parts of the mid Early Cretaceous world. In common with the megafossil record and with the composition of coeval palynofloras elsewhere in northeast China (Zhang, 1965; Pu and Wu, 1982; Li, 1992), it is clear that pteridophytes were the major components. Low numbers of Classopollis pollen grains tie in with a generally humid climate, as has been inferred previously from, for example, the changing sedimentary conditions and associated palynofacies of the English Wealden succession (Batten, 1975). Freshwater algae are rare in the assemblages, with only Concentricystes sp. having been recorded. This could be taken to imply that freshwater conditions were only intermittent and short-lived. On the other hand, the minor aquatic megafossil component that includes bivalves and rare conchostracans (Sun et al., 1999), and sedimentary analyses of the formation in the central part of the Jixi Basin suggest that the reverse is true, namely that it accumulated under predominantly fluvio-lacustrine to lacustrine conditions (Working group of the ‘‘Regional Stratigraphic Chart of Heilongjiang Province’’, 1979). Hence, the presence of poorly preserved marine dinoflagellates in two of the samples (JM03 and 20) suggests that marine transgressions in eastern Heilongjiang Province may have only ocasionally raised salinities in the Jixi Basin at the time of deposition of the Muling Formation.
Acknowledgements This work was supported by the National Basic Research Programme of China, grant 2006CB701400, the National Natural Science Foundation of China, grant NFSC 40572010, and the Pilot Project of the Knowledge Innovation Programme, Academia Sinica, grant KZCX2SW-129.
344
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
Fig. 5. Examples of miospores recovered from the Muling Formation at Qinglongshan, continued; all 800. A, Cicatricosisporites undosus Yu and Han, slide JM02-1. B, Cicatricosisporites australiensis (Cookson) Potonie´, JM05. C, Cicatricosisporites mediostriatus (Bolchovitina) Pocock, JM04-3. D, Cicatricosisporites sp., JM05-2. E, Laevigatosporites ovatus Wilson and Webster, JM05-5. FeH, Contignisporites glebulentus Dettmann, JM03-2. I, J, Kuylisporites lunaris Cookson and Dettmann, JM05-5. K, Crybelosporites punctatus Dettmann, JM05-4. L, Annulispora perforata (Leschik) Li and Shang, JM04-3. M, Polycingulatisporites reduncus (Bolchovitina) Playford and Dettmann, JM04-4. N, O, Triporoletes singularis Mtchedlishvili, JM05-3. P, Q, T, Foraminisporites asymmetricus (Cookson and Dettmann) Dettmann, JM05-1, 05-3. R, S, Aequitriradites echinatus Pu and Wu, JM05-3.
Fig. 4. Examples of miospores recovered from the Muling Formation at Qinglongshan, continued; all 800. AeC, Neoraistrickia variabilis Pu and Wu, slides JM042, 05-5. D, E, Verrucosisporites rotundus Singh, JM02-1, 05-1. FeH, Osmundacidites elegans (Verbitskaya) Xu and Zhang, JM05-5, 05-1. I, Neoraistrickia bayanhuaensis Yu, JM05-3. J, Acanthotriletes varispinosus (Pocock) Srivastava, JM05-5. K, Pilosisporites trichopapillosus (Thiergart) Delcourt and Sprumont, JM10-1. L, M, Lycopodiumsporites austroclavatidites (Cookson) Couper, JM05-3, 05-1. N, Klukisporites variegatus Couper, JM05-5. O, Foveotriletes subtriangularis Brenner, JM05-5. PeR, Cicatricosisporites australiensis (Cookson) Potonie´, JM10-3, 05-3, 10-2. S, Appendicisporites tricornitatus Weyland and Greifeld, JM03. T, Cicatricosisporites imbricatus (Markova) Singh, JM03. U, Cicatricosisporites sunjiawanensis Pu and Wu, JM10-3. V, W, Cicatricosisporites spiralis Singh, JM05-3, 05-1.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
346
Fig. 6. Examples of miospores recovered from the Muling Formation at Qinglongshan, continued; all 800. A, Classopollis classoides Pflug, slide JM10-2. B, Cycadopites sp., JM10-3. C, Concentricystes sp., JM05-4. D, Podocarpidites unicus (Bolchovitina) Pocock, JM05. E, Piceaepollenites sp., JM05-3. F, Podocarpidites biformis Rouse, JM05-5. G, Callialasporites trilobatus (Balme) Sukh Dev, JM05-5. HeJ, Pinuspollenites divulgatus (Bolchovitina) Qu, JM05-1.
References Table 1 Inferred botanical affinities of spore and pollen genera Division Algae Bryophyta
Pteridophyta
Spore or pollen grain Ricciaceae Sphagnaceae Lycopodiaceae Selaginellaceae Cyatheaceae Dicksoniaceae Gleicheniaceae Schizaeaceae
Marsileaceae Osmundaceae Polypodiaceae Cycadophyta Coniferophyta
Cycadaceae Cheirolepidiaceae Podocarpaceae Pinaceae
Concentricystes Triporoletes Annulispora, Foraminisporis, Stereisporites Polycingulatisporites Lycopodiumsporites, Foveotriletes Acanthotriletes, Aequitriradites, Neoraistrickia, Verrucosisporites Kuylisporites, Cyathidites, ?Leiotriletes Cibotiumspora Geicheniidites Lygodiumsporites, Impardecispora, Pilosisporites, Appendicisporites, Cicatricosisporites, Klukisporites, Concavissimisporites Crybelosporites Osmundacidites Laevigatosporites Contignisporites Cycadopites Classopollis Podocarpidites Piceaepollenites, Pinuspollenites, Callialasporites
Ahnert, E., 1925. Les nouvelles de´couvertes de la flore fossile dans la Manchurie du Nord. Bulletin of the Geological Society of China 4, 95e98. Batten, D.J., 1975. Wealden palaeoecology from the distribution of plant fossils. Proceedings of the Geologists’ Association 85 (for 1974), 435e458. Batten, D.J., Morrison, L., 1983. Methods of palynological preparation for palaeoenvironmental, source potential and organic maturation studies. In: Costa, L.I. (Ed.), Palynology-Micropalaeontology: Laboratories, Equipment and Methods. Norwegian Petroleum Directorate, Bulletin 2, 35e53. Bureau of Geology and Mineral Resources of Heilongjiang Province, 1997. Stratigraphy (Lithostratigraphy) of Heilongjiang Province. China University of Geosciences Press, Wuhan, pp. 198e206 (in Chinese). Chen, Guangya, 1959. The stratigraphy of coal-bearing beds in Jixi Basin. Geological Review 19, 216e219 (in Chinese). Gu, Zhiwei, 1962. The Jurassic and Cretaceous of China. Science Press, Beijing, 84 pp. (in Chinese). He, Chengquan, Sun, Xuekun, 2000. Late Hauterivian dinoflagellates from the lower part of the Chengzihe Formation in Jixi Basin, eastern Heilongjiang, NE China. Acta Palaeontologica Sinica 39, 46e62 (in Chinese, English abstract). He, Chengquan, Wan, Chuanbiao, Yang, Mingjie, 1999. Hauteriviane Barremian dinoflagellates from the Longzhaogou Group of the H87-3 well in Hulin Basin, eastern Heilongjiang, NE China. Acta Palaeontologica Sinica 38, 183e202 (in Chinese, English abstract). Helby, R., Morgan, R., Partridge, A.D., 1987. A palynological zonation of the Australian Mesozoic. Memoir of the Association of Australasian Palaeontologists 4, 1e94.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347 Ju, Ranhong, Zheng, Shaolin, Yu, Xihan, Pu, Ronggan, Zhang, Lijun, Yuan, Hong, 1982. Stratigraphy of Longzhaogou and Jixi groups in eastern Heilongjiang Province. Bulletin of the Shenyang Institute of Geology and Mineral Resources. Chinese Academy of Geological Sciences 5, 1e44 (in Chinese, English abstract). Li, Wenben, 1992. Early Cretaceous spore-pollen assemblages from eastern Heilongjiang. Acta Palaeontologica Sinica 31, 178e189 (in Chinese, English abstract). Oishi, S., Takahashi, E., 1938. Notes on some fossil plants from the Moulin and the Mishan coalfields, prov. Pinchiang, Manchoukuo. Journal of the Faculty of Science, Hokkaido Imperial University, Geology and Mines 4, 57e62. Phipps, D., Playford, G., 1984. Laboratory techniques for extraction of palynomorphs from sediments. Department of Geology, University of Queensland, Papers 11 (1), 1e23. Pu, Ronggan, Wu, Hongzhang, 1982. Spore-pollen from the late Mesozoic beds in eastern Heilongjiang Province. Bulletin of the Shenyang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences 5, 383e456 (in Chinese, English abstract). Sha, Jingeng, 1991. A different opinion on the geological ages of the Longzhaogou and Jixi groups of eastern Heilongjiang, China. Acta Geologica Sinica 4, 376e383 (in Chinese, English abstract). Sha, Jingeng, Cai, Huawei, Gu, Zhiwei, Jiang, Baoyu, 2000. Age of the bivalve fossil faunas from the Longzhaogou and Jixi groups. In: Committee of the Proceedings of the Third National Stratigraphical Conference of China (Ed.), Proceedings of the Third National Stratigraphical Conference of China. Geological Publishing House, Beijing, pp. 265e269 (in Chinese). Sha, Jingeng, Cai, Huawei, He, Chengquan, Gu, Zhiwei, Jiang, Jianhong, Yin, Deshun, Zhao, Xifeng, Liu, Zhixun, Jiang, Baoyu, 2002. Studies on the Early Cretaceous Longzhaogou and Jixi groups of eastern Heilongjiang, northeast China, and their bearing on the age of supposedly Jurassic strata in eastern Asia. Journal of Asian Earth Sciences 20, 141e150. Sha, Jingeng, Fursich, F.T., Grant-Mackie, J.A., 1994. A revised Early Cretaceous age for the Longzhaogou and Jixi groups of eastern Heilongjiang, China, previously considered Jurassic: palaeogeographic implications. Newsletters on Stratigraphy 31, 101e114. Shi, Tiemin, 1960. Division and correlation of Mesozoic from eastern Heilongjiang Province. Acta Geologica Sinica 40, 187e204 (in Chinese). Sun, Ge, Dilcher, D.L., 1996. Early angiosperms from Lower Cretaceous of Jixi, China and their significance for study of the earliest occurrence of angiosperms in the world. Palaeobotanist 45, 393e399. Sun, Ge, Dilcher, D.L., 1997. Discovery of the oldest known angiosperm inflorescences in the world from Lower Cretaceous of Jixi, China. Acta Palaeontologica Sinica 36, 135e142 (in Chinese, English summary). Sun, Ge, Guo, Shuangxing, Piao, Taiyuan, Sun, Xuekun, 1993. First discovery of the earliest angiospermous megafossils in the world. Science in China, Series B 36, 249e256.
347
Sun, Ge, Zheng, Shaolin, Jiang, Jianhong, He, Chengquan, Yin, Deshun, Piao, Taiyuan, Zhou, Qidao, Zhao, Xifeng, 1999. Recent advance in study of Early Cretaceous biostratigraphy from Jixi coal-bearing basin, Heilongjiang, China. Coal Geology and Exploration 27, 1e3 (in Chinese). Taylor, T.N., Taylor, E.L., 1993. The Biology and Evolution of Fossil Plants. Prentice Hall, Englewood Cliffs, NJ, 982 pp. Tryon, R.M., Tryon, A.F., 1982. Ferns and Allied Plants. With Special Reference to Tropical America. Springer-Verlag, New York, NY, xii þ 857 pp. Vakhrameev, V.A., 1991. Jurassic and Cretaceous Floras and Climates of the Earth. Cambridge University Press, Cambridge, xvii þ 318 pp. Wan, Chuanbiao, Qiao, Xiuying, Yang, Jianguo, Kong, Hui, Zhao, Chuanben, 2000. The sporopollen assemblage of the early Cretaceous in Jixi Basin, Heilongjiang Province. In: Zhu, Zhonghao, Zheng, Guoguang, Zhao, Chuanben (Eds.), Selected Papers of Palynology of Petroliferous Basins, China. Petroleum Industry Press, Beijing, pp. 83e90 (in Chinese). Wang, Hengsheng, 1929. The geology and mineral resources of Mishan and Muleng, Kirin. Bulletin of the Geological Survey of China 13, 25e31. Working group of ‘‘Regional Stratigraphic Chart of Heilongjiang Province’’, 1979. Regional Stratigraphic Charts of Northeast China e Heilongjiang. Geological Publishing House, Beijing, 338 pp. (in Chinese). Yang, Xiaoju, 2003. New material of fossil plants from the Early Cretaceous Muling Formation of the Jixi Basin, eastern Heilongjiang Province, China. Acta Palaeontologica Sinica 42, 561e584. Yang, Xiaoju, Zheng, Shaolin, 2003. A new species of Taxodioxylon from the Lower Cretaceous of the Jixi Basin, eastern Heilongjiang, China. Cretaceous Research 24, 653e660. Yang, Xiaoju, He, Chengquan, Li, Wenben, Piao, Taiyuan, 2003. Marine dinoflagellates from Lower Cretaceous Muling Formation of Jixi Basin, China and their palaeoenvironmental significance. Chinese Science Bulletin 48, 2480e2483. Zhang, Chunbin, 1965. Spores from the Muling Formation in Jixi, Heilongjiang Province and their stratigraphical significance. Memoir of the (Nanjing) Institute of Geology and Palaeontology. Academia Sinica 4, 163e198 (in Chinese, Russian summary). Zhang, Wu, Zhang, Zhicheng, Zheng, Shaolin, 1980. Plants. In: Shenyang Institute of Geology and Mineral Resources (Ed.), Paleontological Atlas of Northeast China (Mesozoic and Cenozoic volume). Geological Publishing House, Beijing, pp. 222e307 (in Chinese). Zheng, Shaolin, Zhang, Wu, 1982. Fossil plants from Longzhaogou and Jixi groups in eastern Heilongjiang Province. Bulletin of the Shenyang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences 5, 277e382 (in Chinese, English abstract). Zhou, Zhiyan, Chen, Guangya, Shan, Wen, Zhang, Chuanbo, Zhang, Qingbin, Zhang, Wu, Pu, Ronggan, 1980. Late Mesozoic stratigraphy and aspect of fossil plants of Jixi and Muling, Heilongjiang Province. Bulletin of the Nanjing Institute of Geology and Palaeontology, Academia Sinica 1, 56e75 (in Chinese).
Biostratigraphic and palaeoenvironmental implications of an Early Cretaceous miospore assemblage from the Muling Formation, Jixi Basin, northeast China Xiaoju Yang a,*, Wenben Li a, David J. Batten b a
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China b School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK Accepted 19 July 2006 Available online 23 February 2007
Abstract In the Jixi Basin, eastern Heilongjiang Province, China, the lower part of the Lower Cretaceous succession consists of coal-bearing strata including the Muling Formation, which, in addition to plant megafossils, yields abundant spores and pollen grains and a few dinoflagellate cysts. The spore-pollen assemblage consists of more than 42 species belonging to 34 genera. Most of these are derived from pteridophytes and gymnosperms. The association of Aequitriradites echinatus, Cicatricosisporites australiensis, C. imbricatus, C. mediostriatus, C. undosus, Contignisporites glebulentus, Crybelosporites punctatus, Foraminisporis asymmetricus, Gleicheniidites laetus, Impardecispora purverulenta, Kuylisporites lunaris, Pilosisporites trichopapillosus and Triporoletes singularis suggests that the formation is unlikely to be older than late Hauterivian and younger than Aptian, with emphasis placed on the Barremianeearly Aptian. The composition of the dinoflagellate cyst and plant megafossil assemblages is consistent with this determination. Based on palynofloral content, a comparison between the miospores recovered and the spores and pollen produced by extant plant taxa, the associated plant megafossils, and the sedimentary facies that characterize the Muling Formation, it is concluded that the source vegetation was dominated by ferns and that the climate was wet subtropical but seasonally dry. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Miospores; Early Cretaceous; Muling Formation; Heilongjiang; China
1. Introduction The Jixi Basin is situated in the southeast of Heilongjiang Province, China, at about 130 200 e31 350 E and 44 450 e 45 250 N. It contains good exposures of the late Mesozoic coal-bearing strata of the Jixi Group. This group is divided into, in ascending order, the Didao, Chengzihe
* Corresponding author. E-mail address: [email protected] (X. Yang). 0195-6671/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2006.07.008
and Muling formations. The name of the last of these is derived from the ‘‘Muleng Coal Series’’ of Wang (1929), which was used to refer to coal-bearing strata near the River Muling in Jixi City. It was erected by Gu (1962) based on the upper part of the ‘‘Muleng Coal Series’’. Its relationships with the underlying Chengzihe and overlying Dongshan formations are conformable. The fine-grained clastic deposits intercalated with greyish-green tuffs of which it is composed (Bureau of Geology and Mineral Resources of Heilongjiang Province, 1997) differentiates it from these two formations, the Chengzihe Formation containing more
340
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
coal and less tuff and the Dongshan Formation comprising coarse sandstones and other clastic deposits with fewer plant remains and no coal. Geological studies on the Muling Formation began during the 1920s. For the next 40 years it was considered to be Jurassic in age (Ahnert, 1925; Wang, 1929; Oishi and Takahashi, 1938; Chen, 1959; Shi, 1960; Gu, 1962), but from the mid 1960s it was increasingly regarded as Early Cretaceous (Zhang, 1965; Zhou et al., 1980; Ju et al., 1982; Pu and Wu, 1982; Zheng and Zhang, 1982), and during the past 15 years discoveries of angiosperms in the basin (Sun et al., 1993; Sun and Dilcher, 1996, 1997) and analyses of bivalves recovered from it (Sha, 1991; Sha et al., 1994, 2002), have led to the conclusion that the formation must have been deposited during the Early Cretaceous. Sun et al. (1999) and Yang (2003) dated it as middleelate Barremian or Barremianeearly Aptian. Sha et al. (2000) considered it to be possibly late Aptianeearly Albian. Until marine dinoflagellate cysts (dinocysts) were encountered recently (Wan et al., 2000; Yang et al., 2003) it had been regarded as an entirely non-marine succession. Plant microfossils from the Muling Formation were reported by Zhang (1965). He described and illustrated a considerable number of spore species, many new, from core samples, and recognized their Early Cretaceous age. Pu and Wu (1982) described abundant spores and pollen grains from surface samples and dated the formation as BarremianeAptian. Yang et al. (2003) based their more recent age determination of possibly Barremian on dinocyst evidence. These publications have provided general conclusions on the age of the formation. The main aim of the present paper is to review the composition of the spore-pollen flora of the
type locality of the Muling Formation and to use the data in conjunction with evidence from occurrences of dinocysts and plant megafossils as a basis from which to consider its age once more, and to draw palaeoenvironmental and palaeoclimatic conclusions. To this end, samples were collected from beds containing megafossils throughout the formation. However, despite the logic behind the collecting strategy, a disappointingly large proportion of these (see below), especially from the upper part of the section, proved to contain only poorly preserved palynomorphs of no biostratigraphic value; as a result, they have had to be omitted from consideration here. 2. Material and methods Twenty samples of mainly dark grey to black mudstones and siltstones were taken at irregular stratigraphic intervals from the coal- and plant-bearing beds at Qinglongshan, which is where the type section of the Muling Formation is exposed. This is situated along a railway line about 10 km to the west of the city of Jixi (130 210 E, 45 250 N; Fig. 1). Conventional physico-chemical procedures for processing samples for palynological analysis (Batten and Morrison, 1983; Phipps and Playford, 1984) were employed for extracting and concentrating palynomorphs from the samples. Unfortunately only six of them yielded well-preserved spores and pollen grains. All of the slides prepared were examined and specimens were photographed under a Nikon transmitted light microscope. They were then deposited, along with the unmounted residues, in the collections of the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPCAS). Labelling of the slides is as shown in the
Fig. 1. Map showing the location of the type section of the Muling Formation at Qinglongshan.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
341
following example: JM03-3: J, Jixi Basin; M, Muling Formation; 03, sample number; -3, third slide from this sample.
3. Results Most of the samples processed yielded palynomorphs but the only well-preserved assemblages were recovered from those taken from the mouth of a mine (Fig. 2). Selected examples of the taxa encountered are illustrated in Figs. 3e6.
3.1. Palynostratigraphy
Fig. 2. Lithological log of the Muling Formation at Qinglongshan showing the six horizons that yielded assemblages of well-preserved palynomorphs.
More than 42 miospore species referred to 34 genera were identified from the palynological preparations. A list of the genera recorded with their presumed or possible botanical affinities noted alongside is given in Table 1. Among the miospores, 22 genera (65) are derived from pteridophytes, six (18) from gymnosperms, five (15) from bryophytes and one (3) is an alga. Of the pteridophytes, the Schizaeaceae show considerable diversity. Spores attributable to the Lycopsida are also common, but conifers are comparatively poorly represented by members of the families Pinaceae, Podocarpaceae and Cheirolepidiaceae, and no angiospermous taxa were found. Many of the spore species, such as Aequitriradites echinatus Pu and Wu, Cicatricosisporites australiensis (Cookson) Potonie´, C. imbricatus (Markova) Singh, C. mediostriatus (Bolchovitina) Pocock, C. undosus Yu and Han, Contignisporites glebulentus Dettmann, Crybelosporites punctatus Dettmann, Foraminisporis asymmetricus (Cookson and Dettmann) Dettmann, Gleicheniidites laetus (Bolchovitina) Bolchovitina, Impardecispora purverulenta (Verbitskaya) Venkatachala, Kar and Raza, Kuylisporites lunaris Cookson and Dettmann, Pilosisporites trichopapillosus (Thiergart) Delcourt and Sprumont and Triporoletes singularis Mtchedlishvili have been reported mainly or only from Early Cretaceous deposits. Others are commonly found in midelate Mesozoic successions. Overall the total spore-pollen assemblage recovered is similar to that described by Zhang (1965) from the formation elsewhere in the basin but it differs from that recorded from beds apparently of the Muling Formation in the adjacent Boli Basin (Pu and Wu, 1982) in lacking species of Appendicisporites (e.g., A. auritus, A. bifurcatus, A. cristatus and A. insignis) and in the lower percentage occurrence of gleicheniaceous spores. The associated plant megafossils indicate that the flora is composed mainly of leptosporangiate ferns and gymnosperms that indicate mid Barremianeearly Aptian ages (Yang, 2003). Several species of marine dinoflagellate cyst have been recorded from the palynological preparations, including Circulodinium attadalicum (Cookson and Eisenack) Helby, C. cingulatum He, Wan and Yang, Oligosphaeridium totum Brideaux, Palaeoperidinium cretaceum Pocock and Sentusidinium sp. Their occurrence is consistent with a
Fig. 3. Examples of miospores recovered from the Muling Formation at Qinglongshan; all 800. For explanation of slide labelling, see under Section 2. AeD, Lygodiumsporites? sp., slides JM03-1, 03-3, 03-2, 03-1. EeH, Cibotiumspora dentata Lei, JM03-5, 03-9, 03-11. I, J, Stereisporites stereoides (Potonie´ and Venitz) Pflug, JM10-2, 10-1. KeM, Gleicheniidites laetus (Bolchovitina) Bolchovitina, JM04-2, 05-5, 10-4. N, O, Impardecispora purverulenta (Verbitskaya) Venkatachala, Kar and Raza, JM03-5. P, Concavissimisporites asper (Bolchovitina) Pocock, JM03. Q, Lygodiumsporites subsimplex (Bolchovitina) Gao and Zhao, JM03-5.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
midelate Early Cretacous age determination for the formation (cf. Helby et al., 1987; He et al., 1999; He and Sun, 2000).
3.2. Palaeocology and palaeoclimate Plant micro- and megafossil remains can provide information about the taxonomic composition of the former vegetation of a region from which, in turn, palaeoecological and palaeoclimatic conclusions can be drawn, though usually only in a general way. Comparisons of the morphology of the palynomorphs with the products of extant plant taxa with the aim of suggesting botanical affinities can assist in this respect, but they can also mislead. It helps to be able to base at least some of the relationships on connections with fertile fern fronds, gymnospermous cones and other megafossil remains. From such comparisons it may then be inferred, albeit tentatively, that the plants represented by a palynoflora occupied ecological niches similar to those of the extant taxa whose products they resemble. Plant megafossils have been described from the Muling Formation in the Dongning, Shuangyashan, Mishan and Baoqing basins in eastern Heilongjiang by Oishi and Takahashi (1938), Zhang et al. (1980) and Zheng and Zhang (1982). The flora from the Jixi Basin (Yang, 2003) comprises 38 species belonging to 31 genera, mainly of leptosporangiate ferns and gymnosperms, and all in a fragmentary state. Despite evidence, albeit limited, from the pollen record, no representatives of gymnosperms with needle-like leaves have been found. The abundant fern remains are of tropical or subtropical type; these include Acanthopteris, Athyrium, Coniopteris, Gleichenites, Gonatosorus, Hymenophyllites, Onychiopsis and Ruffordia. The composition of the flora indicates that the climate of the Jixi Basin and adjacent regions during much of the mid Early Cretaceous was warm and generally wet, but with seasonally dry periods. Evidence for a seasonal climate is apparent from, in particular, an abundance of Ginkgoites and two fossil woods that have been recovered from the formation: Glyptostroboxylon xidapoense Zheng and Zhang and Taxodioxylon szei Yang and Zheng, both of which have distinct growth rings (Yang and Zheng, 2003). Natural alliances of the dispersed miospore genera encountered in the Muling Formation are listed in Table 1. Some of these are more uncertain than others, with a few being little more than guesses. Pteridophyte spores dominate the palynomorph assemblages both numerically and taxonomically. The Schizaeaceae are strongly represented, as noted above; Cicatricosisporites species are abundant, with C. australiensis being especially numerous. Gleicheniidites laetus, attributable to the family Gleicheniaceae, is also very common. Representatives of these two families and of the Cyatheaceae and Dicksoniaceae thrive in both tropical and subtropical habitats (Tryon and Tryon,
343
1982). Bryophyte species constitute only a minor component of the assemblages. Extant bryophytes are most abundant in relatively moist terrestrial situations (Taylor and Taylor, 1993), but some inhabit dry locations and many are capable of withstanding periods of drought. The affinities of the dispersed pollen grains lie with the families Cycadaceae, Cheirolepidiaceae, Podocarpaceae and Pinaceae. Classopollis grains, produced by cheirolepidiaceous conifers, are consistently present in Early Cretaceous deposits over much of the Northern Hemisphere (e.g., Vakhrameev, 1991 and many other authors), but may occur only in relatively low numbers, as in the Muling Formation. The presence of representatives of the Cycadaceae and Podocarpaceae is consistent with a warm, predominantly humid but seasonally dry climate, with only representatives of the Pinaceae suggesting cooler conditions at higher elevations at some unknown distance from the depositional basin. Overall, despite the absence of any evidence of angiosperms, the palynoflora suggests a diverse source vegetation similar in composition to that described from other warm (tropicalesubtropical), generally humid parts of the mid Early Cretaceous world. In common with the megafossil record and with the composition of coeval palynofloras elsewhere in northeast China (Zhang, 1965; Pu and Wu, 1982; Li, 1992), it is clear that pteridophytes were the major components. Low numbers of Classopollis pollen grains tie in with a generally humid climate, as has been inferred previously from, for example, the changing sedimentary conditions and associated palynofacies of the English Wealden succession (Batten, 1975). Freshwater algae are rare in the assemblages, with only Concentricystes sp. having been recorded. This could be taken to imply that freshwater conditions were only intermittent and short-lived. On the other hand, the minor aquatic megafossil component that includes bivalves and rare conchostracans (Sun et al., 1999), and sedimentary analyses of the formation in the central part of the Jixi Basin suggest that the reverse is true, namely that it accumulated under predominantly fluvio-lacustrine to lacustrine conditions (Working group of the ‘‘Regional Stratigraphic Chart of Heilongjiang Province’’, 1979). Hence, the presence of poorly preserved marine dinoflagellates in two of the samples (JM03 and 20) suggests that marine transgressions in eastern Heilongjiang Province may have only ocasionally raised salinities in the Jixi Basin at the time of deposition of the Muling Formation.
Acknowledgements This work was supported by the National Basic Research Programme of China, grant 2006CB701400, the National Natural Science Foundation of China, grant NFSC 40572010, and the Pilot Project of the Knowledge Innovation Programme, Academia Sinica, grant KZCX2SW-129.
344
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
Fig. 5. Examples of miospores recovered from the Muling Formation at Qinglongshan, continued; all 800. A, Cicatricosisporites undosus Yu and Han, slide JM02-1. B, Cicatricosisporites australiensis (Cookson) Potonie´, JM05. C, Cicatricosisporites mediostriatus (Bolchovitina) Pocock, JM04-3. D, Cicatricosisporites sp., JM05-2. E, Laevigatosporites ovatus Wilson and Webster, JM05-5. FeH, Contignisporites glebulentus Dettmann, JM03-2. I, J, Kuylisporites lunaris Cookson and Dettmann, JM05-5. K, Crybelosporites punctatus Dettmann, JM05-4. L, Annulispora perforata (Leschik) Li and Shang, JM04-3. M, Polycingulatisporites reduncus (Bolchovitina) Playford and Dettmann, JM04-4. N, O, Triporoletes singularis Mtchedlishvili, JM05-3. P, Q, T, Foraminisporites asymmetricus (Cookson and Dettmann) Dettmann, JM05-1, 05-3. R, S, Aequitriradites echinatus Pu and Wu, JM05-3.
Fig. 4. Examples of miospores recovered from the Muling Formation at Qinglongshan, continued; all 800. AeC, Neoraistrickia variabilis Pu and Wu, slides JM042, 05-5. D, E, Verrucosisporites rotundus Singh, JM02-1, 05-1. FeH, Osmundacidites elegans (Verbitskaya) Xu and Zhang, JM05-5, 05-1. I, Neoraistrickia bayanhuaensis Yu, JM05-3. J, Acanthotriletes varispinosus (Pocock) Srivastava, JM05-5. K, Pilosisporites trichopapillosus (Thiergart) Delcourt and Sprumont, JM10-1. L, M, Lycopodiumsporites austroclavatidites (Cookson) Couper, JM05-3, 05-1. N, Klukisporites variegatus Couper, JM05-5. O, Foveotriletes subtriangularis Brenner, JM05-5. PeR, Cicatricosisporites australiensis (Cookson) Potonie´, JM10-3, 05-3, 10-2. S, Appendicisporites tricornitatus Weyland and Greifeld, JM03. T, Cicatricosisporites imbricatus (Markova) Singh, JM03. U, Cicatricosisporites sunjiawanensis Pu and Wu, JM10-3. V, W, Cicatricosisporites spiralis Singh, JM05-3, 05-1.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347
346
Fig. 6. Examples of miospores recovered from the Muling Formation at Qinglongshan, continued; all 800. A, Classopollis classoides Pflug, slide JM10-2. B, Cycadopites sp., JM10-3. C, Concentricystes sp., JM05-4. D, Podocarpidites unicus (Bolchovitina) Pocock, JM05. E, Piceaepollenites sp., JM05-3. F, Podocarpidites biformis Rouse, JM05-5. G, Callialasporites trilobatus (Balme) Sukh Dev, JM05-5. HeJ, Pinuspollenites divulgatus (Bolchovitina) Qu, JM05-1.
References Table 1 Inferred botanical affinities of spore and pollen genera Division Algae Bryophyta
Pteridophyta
Spore or pollen grain Ricciaceae Sphagnaceae Lycopodiaceae Selaginellaceae Cyatheaceae Dicksoniaceae Gleicheniaceae Schizaeaceae
Marsileaceae Osmundaceae Polypodiaceae Cycadophyta Coniferophyta
Cycadaceae Cheirolepidiaceae Podocarpaceae Pinaceae
Concentricystes Triporoletes Annulispora, Foraminisporis, Stereisporites Polycingulatisporites Lycopodiumsporites, Foveotriletes Acanthotriletes, Aequitriradites, Neoraistrickia, Verrucosisporites Kuylisporites, Cyathidites, ?Leiotriletes Cibotiumspora Geicheniidites Lygodiumsporites, Impardecispora, Pilosisporites, Appendicisporites, Cicatricosisporites, Klukisporites, Concavissimisporites Crybelosporites Osmundacidites Laevigatosporites Contignisporites Cycadopites Classopollis Podocarpidites Piceaepollenites, Pinuspollenites, Callialasporites
Ahnert, E., 1925. Les nouvelles de´couvertes de la flore fossile dans la Manchurie du Nord. Bulletin of the Geological Society of China 4, 95e98. Batten, D.J., 1975. Wealden palaeoecology from the distribution of plant fossils. Proceedings of the Geologists’ Association 85 (for 1974), 435e458. Batten, D.J., Morrison, L., 1983. Methods of palynological preparation for palaeoenvironmental, source potential and organic maturation studies. In: Costa, L.I. (Ed.), Palynology-Micropalaeontology: Laboratories, Equipment and Methods. Norwegian Petroleum Directorate, Bulletin 2, 35e53. Bureau of Geology and Mineral Resources of Heilongjiang Province, 1997. Stratigraphy (Lithostratigraphy) of Heilongjiang Province. China University of Geosciences Press, Wuhan, pp. 198e206 (in Chinese). Chen, Guangya, 1959. The stratigraphy of coal-bearing beds in Jixi Basin. Geological Review 19, 216e219 (in Chinese). Gu, Zhiwei, 1962. The Jurassic and Cretaceous of China. Science Press, Beijing, 84 pp. (in Chinese). He, Chengquan, Sun, Xuekun, 2000. Late Hauterivian dinoflagellates from the lower part of the Chengzihe Formation in Jixi Basin, eastern Heilongjiang, NE China. Acta Palaeontologica Sinica 39, 46e62 (in Chinese, English abstract). He, Chengquan, Wan, Chuanbiao, Yang, Mingjie, 1999. Hauteriviane Barremian dinoflagellates from the Longzhaogou Group of the H87-3 well in Hulin Basin, eastern Heilongjiang, NE China. Acta Palaeontologica Sinica 38, 183e202 (in Chinese, English abstract). Helby, R., Morgan, R., Partridge, A.D., 1987. A palynological zonation of the Australian Mesozoic. Memoir of the Association of Australasian Palaeontologists 4, 1e94.
X. Yang et al. / Cretaceous Research 28 (2007) 339e347 Ju, Ranhong, Zheng, Shaolin, Yu, Xihan, Pu, Ronggan, Zhang, Lijun, Yuan, Hong, 1982. Stratigraphy of Longzhaogou and Jixi groups in eastern Heilongjiang Province. Bulletin of the Shenyang Institute of Geology and Mineral Resources. Chinese Academy of Geological Sciences 5, 1e44 (in Chinese, English abstract). Li, Wenben, 1992. Early Cretaceous spore-pollen assemblages from eastern Heilongjiang. Acta Palaeontologica Sinica 31, 178e189 (in Chinese, English abstract). Oishi, S., Takahashi, E., 1938. Notes on some fossil plants from the Moulin and the Mishan coalfields, prov. Pinchiang, Manchoukuo. Journal of the Faculty of Science, Hokkaido Imperial University, Geology and Mines 4, 57e62. Phipps, D., Playford, G., 1984. Laboratory techniques for extraction of palynomorphs from sediments. Department of Geology, University of Queensland, Papers 11 (1), 1e23. Pu, Ronggan, Wu, Hongzhang, 1982. Spore-pollen from the late Mesozoic beds in eastern Heilongjiang Province. Bulletin of the Shenyang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences 5, 383e456 (in Chinese, English abstract). Sha, Jingeng, 1991. A different opinion on the geological ages of the Longzhaogou and Jixi groups of eastern Heilongjiang, China. Acta Geologica Sinica 4, 376e383 (in Chinese, English abstract). Sha, Jingeng, Cai, Huawei, Gu, Zhiwei, Jiang, Baoyu, 2000. Age of the bivalve fossil faunas from the Longzhaogou and Jixi groups. In: Committee of the Proceedings of the Third National Stratigraphical Conference of China (Ed.), Proceedings of the Third National Stratigraphical Conference of China. Geological Publishing House, Beijing, pp. 265e269 (in Chinese). Sha, Jingeng, Cai, Huawei, He, Chengquan, Gu, Zhiwei, Jiang, Jianhong, Yin, Deshun, Zhao, Xifeng, Liu, Zhixun, Jiang, Baoyu, 2002. Studies on the Early Cretaceous Longzhaogou and Jixi groups of eastern Heilongjiang, northeast China, and their bearing on the age of supposedly Jurassic strata in eastern Asia. Journal of Asian Earth Sciences 20, 141e150. Sha, Jingeng, Fursich, F.T., Grant-Mackie, J.A., 1994. A revised Early Cretaceous age for the Longzhaogou and Jixi groups of eastern Heilongjiang, China, previously considered Jurassic: palaeogeographic implications. Newsletters on Stratigraphy 31, 101e114. Shi, Tiemin, 1960. Division and correlation of Mesozoic from eastern Heilongjiang Province. Acta Geologica Sinica 40, 187e204 (in Chinese). Sun, Ge, Dilcher, D.L., 1996. Early angiosperms from Lower Cretaceous of Jixi, China and their significance for study of the earliest occurrence of angiosperms in the world. Palaeobotanist 45, 393e399. Sun, Ge, Dilcher, D.L., 1997. Discovery of the oldest known angiosperm inflorescences in the world from Lower Cretaceous of Jixi, China. Acta Palaeontologica Sinica 36, 135e142 (in Chinese, English summary). Sun, Ge, Guo, Shuangxing, Piao, Taiyuan, Sun, Xuekun, 1993. First discovery of the earliest angiospermous megafossils in the world. Science in China, Series B 36, 249e256.
347
Sun, Ge, Zheng, Shaolin, Jiang, Jianhong, He, Chengquan, Yin, Deshun, Piao, Taiyuan, Zhou, Qidao, Zhao, Xifeng, 1999. Recent advance in study of Early Cretaceous biostratigraphy from Jixi coal-bearing basin, Heilongjiang, China. Coal Geology and Exploration 27, 1e3 (in Chinese). Taylor, T.N., Taylor, E.L., 1993. The Biology and Evolution of Fossil Plants. Prentice Hall, Englewood Cliffs, NJ, 982 pp. Tryon, R.M., Tryon, A.F., 1982. Ferns and Allied Plants. With Special Reference to Tropical America. Springer-Verlag, New York, NY, xii þ 857 pp. Vakhrameev, V.A., 1991. Jurassic and Cretaceous Floras and Climates of the Earth. Cambridge University Press, Cambridge, xvii þ 318 pp. Wan, Chuanbiao, Qiao, Xiuying, Yang, Jianguo, Kong, Hui, Zhao, Chuanben, 2000. The sporopollen assemblage of the early Cretaceous in Jixi Basin, Heilongjiang Province. In: Zhu, Zhonghao, Zheng, Guoguang, Zhao, Chuanben (Eds.), Selected Papers of Palynology of Petroliferous Basins, China. Petroleum Industry Press, Beijing, pp. 83e90 (in Chinese). Wang, Hengsheng, 1929. The geology and mineral resources of Mishan and Muleng, Kirin. Bulletin of the Geological Survey of China 13, 25e31. Working group of ‘‘Regional Stratigraphic Chart of Heilongjiang Province’’, 1979. Regional Stratigraphic Charts of Northeast China e Heilongjiang. Geological Publishing House, Beijing, 338 pp. (in Chinese). Yang, Xiaoju, 2003. New material of fossil plants from the Early Cretaceous Muling Formation of the Jixi Basin, eastern Heilongjiang Province, China. Acta Palaeontologica Sinica 42, 561e584. Yang, Xiaoju, Zheng, Shaolin, 2003. A new species of Taxodioxylon from the Lower Cretaceous of the Jixi Basin, eastern Heilongjiang, China. Cretaceous Research 24, 653e660. Yang, Xiaoju, He, Chengquan, Li, Wenben, Piao, Taiyuan, 2003. Marine dinoflagellates from Lower Cretaceous Muling Formation of Jixi Basin, China and their palaeoenvironmental significance. Chinese Science Bulletin 48, 2480e2483. Zhang, Chunbin, 1965. Spores from the Muling Formation in Jixi, Heilongjiang Province and their stratigraphical significance. Memoir of the (Nanjing) Institute of Geology and Palaeontology. Academia Sinica 4, 163e198 (in Chinese, Russian summary). Zhang, Wu, Zhang, Zhicheng, Zheng, Shaolin, 1980. Plants. In: Shenyang Institute of Geology and Mineral Resources (Ed.), Paleontological Atlas of Northeast China (Mesozoic and Cenozoic volume). Geological Publishing House, Beijing, pp. 222e307 (in Chinese). Zheng, Shaolin, Zhang, Wu, 1982. Fossil plants from Longzhaogou and Jixi groups in eastern Heilongjiang Province. Bulletin of the Shenyang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences 5, 277e382 (in Chinese, English abstract). Zhou, Zhiyan, Chen, Guangya, Shan, Wen, Zhang, Chuanbo, Zhang, Qingbin, Zhang, Wu, Pu, Ronggan, 1980. Late Mesozoic stratigraphy and aspect of fossil plants of Jixi and Muling, Heilongjiang Province. Bulletin of the Nanjing Institute of Geology and Palaeontology, Academia Sinica 1, 56e75 (in Chinese).