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Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321 Potential Marine and Non-marine Jurassic−Cretaceous Boundaries in China: A Review 26 Jingeng Sha 1 , Bo Peng 1 , Xiaoqiao Wan 2 , R. Scott 3 1. LPS, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China (E-mail: jgsha@nigpas.ac.cnk) 2. LGM, China University of Geosciences, Beijing 100083, China 3. The University of Tulsa, 149 West Ridge Road, Cleveland, OK 74022, U.S. The Jurassic-Cretaceous boundary or the base of Berriasian Stage is estimated as 14.5±0.4 Ma age, and traditionally placed at the base of the ammonite Berriasella jacobi Zone. Although dozen international conferences and working groups dedicated to defining the base of the cretaceous system since 1974, the global Jurassic-Cretaceous boundary has yet not been established (http://www.stratigraphy.org). Such situa- tion is mainly caused by the separation of the world into various biogeographic realms during the late Jurassic – early Cretaceous interval, particularly the Tethyan and Boreal realms, complicating the international correlation (Sha, et al., 2006). In China, there are good Tethyan (in southern Tibet) and subboreal (in northeastern China) marine, and non-marine (in most part of China) Jurassic and Cretaceous deposits. The various previous works have implied that there potentially exist marine and non- marine boundaries which could be widely correlated. 1 Potential marine Jurassic-Cretaceous boun dary 1.1 Tethyan type There are sections spanning Jurassic−Cretaceous boundary in southern Tibet, particularly in Gyangze– Nagarze and Menkadun−Gucuo areas. In Gyangze– Nagarze area, the upper Jurassic is represented by the Wermei Formation, the lower Cretaceous includes Sangxiu and Jiabula Formations in Nagarze, and Jiabula Formation in Gyangze. The Weimei Formation consists of lightly grey thick-bedded coarse- to fine- grained quartzose sandstone, yielding rare ammonite including Haplophylloceras and Himalayites. The Sangxiu formation is composed of black shale, an- desite and basalt. The Jiabula Formation comprises black shale, siliceous mudstone and shale, and sandy limestone (Wan, et al., 2005). Both the lower Sangxiu Formation and Jiabula Formation yield ammonite Spiticeras, bivalve Ino- ceramus, and Berriasian and Valanginian nannofossil assemblages, i.e., Berriasian Nannoconus steimannii steimannii−Nannoconus steinmannii minor−Watz- naueria barnesae assemblage, and Valanginian Calci- calathina oblongata−Spoetonia colligate assemblage. The appearance of the ammonite Spiti- ceras and the nannofossil assemblage of Nannoconus steinmannii steinmannii−Nannoconus steinmannii minor− Watznaueria barnesae is the indicators of the base of Cretaceous or Berriasian, which has been indirectly conformed by the radiometric age 136±3.0 Ma of the Volcanic rock of the upper Sangxiu Formation (Wan, et al., 2010). In Menkadun−Gucuo area, particularly in Gucuo, the Gucuo section used to be seen as a good Jurassic−Cretaceous boundary section because there were recordings of late Jurassic and early Cretaceous ammonites including Blanfordiceras (see Yin and Enay, 2004). Although, Yin and Enay (2004) have confirmed the existence of Tithonian ammonites in the area, they concluded that the Berriasian ammonites are remained to be examined. 1.2 Subboreal type In eastern Heilongjiang of northeastern China, there also exist the potential Jurassic-Cretaceous boundary in Dong’An of Raohe country and Suibin of Suibin country. In Dong’an area, the Jurassic−Cretaceous boundary strata is represented by the Dong’Anzhen Formation consisting of yellowish-green silty shale in the lower part, and dark grey and greyish-green muddy siltstone, silty mudstone and greywacke in the upper part. The lower part of the formation yields lower Berriasian (= upper Volgian) bivalve Buchiarus- siensis − Buchia fischeriana assemblage, and the upper Tithonian (= middle Volgian) Buchia fischeriana−Buchia unschensis assemblage. The upper part contains early Valanginian Buchia pacifica bed. The base Berriasian or the Jurassic-Cretaceous boundary is signed to the base of Buchia russiensis−Buchia fischeriana assemblage or between the Buchia fischeriana−Buchia unschensis and Buchia russiensis− Buchia fischeriana assemblages. The Jurassic-Cretaceous boundary interval in Suibin area is represented by the Dongrong Formation from boreholes. It is mainly composed of dark fine- grained sandstone, siltstone and siliceous siltstone, intercalated with coarse- and medium-grained sand- stones, microconglomerates, and greyish-green tuffs. In ascending order, Dongrong Formation yields the uppermost Oxfordian−Kimmeridgian Buchia cf. con- centrica assemblage and the Oxfordian−upper Kim- meridgian Gonyaulacysta jurassica dianoflagellate cyst assemblage in lower part; Tithonian (= lower and middle Volgian) Buchia cf. mosquensis− Buchia cf. rugosa assemblage including Buchia ex gr. tai- myrensis, and Kimmeridgian−lower Berriasian Am-
Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321 phorala dilicata dinoflagellate cyst assemblage in the middle; Berriasian Buchia fischeriana bed and Ber- riasian−Valangimian Oligospaeridium pulcherrimum dinoflagellate cyst assemblage in upper. Consequently, there also probably exists a Jurassic− Cretaceous boundary interval between the middle and upper Dongrong Formation in Suibin area, indicated by the disappearance of Buchia cf. mosquensis - Buchia cf. rugosa bivalve assemblage and Amphorala dilicata dinoflagellate cyst assemblage, and the appearance of Buchia fischeriana bed and Oligosphaeridium pulcherrimum dinoflagellate cyst assemblage (Sha, 2007; Sha, et al., 2006, 2008, 2009). 2 Non-marine Jurassic-Cretaceous boundary There are numerous articles on Chinese non- marine Jurassic-Cretaceous boundary which have been published, but they are mainly involved in northeastern China. In northeastern China and Inner Mongolia, the terrestrial uppermost Jurassic and lower Lower Cre- taceous, including Tithonian, Berriasian, Valanginian and even part of Hauterivian are absent (Sha, 2007). However, judging from the radiometric age of 139.4 ± 0.19(ISD) ± 0.5(SE) Ma, corresponding to the Va- langinian obtained by Swischer, et al. (2002) from the Tuchengzi Formation of western Liaoning. Ji, et al. (2006) got a similar radiometric dating. The non- marine Jurassic-Cretaceous boundary is, therefore, probably within the Tuchengzi Formation in western Liaoning, though there is no fossil evidence (Sha, 2007; Zhou, et al., 2009). 3 Discussion Due to the bio-provincialism separation caused by the pronounced latitudinal segregation, even the pelagic ammonites cannot play the international correlation role. Furthermore, ammonites are often absent or ill-preserved in the Jurassic-Cretaceous boundary interval. The non-ammonite fossils, including bivalves, belemnites, crinoids, calcareous nannofossils, cali- pionellids, dinoflagellate cysts, foraminifers, radio- larians and ostracods become more and more useful in subdivision and correlation of stratigraphy, particularly when the ammonites are absent or ill- preserved. The main approach to define the non-marine Jurassic−Cretaceous boundary interval is probably to correlate non-marine with marine strata, mainly on the basis of the biostratigraphy and radiometric dating obtained from the strata concerned. Through correct taxonomic identification of both marine and non- marine fossils in alternating marine and non-marine strata, the concerned marine and non-marine strata could be both correlated within the international chronostratigraphic chart (http://www.stratigraphy.org) and, therefore to determine or constrain the age of the non-marine strata/fossils (chronostratigraphy). The intervening volcanic rocks including tuffs, tuffaceous rocks and lavas can also be radiometrically dated (geochronology), providing a basis for accurate age determinations of the associated sedimentary rocks and the fossils they contain (Sha, 2007). Such cor- rectly identified and dated (by marine fossils and non-marine fossils radiometric dating) non-marine fossils not only could be reliably date the widely distributed non-marine rocks, but also could correlate the terrestrial strata in the marine biostratigraphic framework. The principles of “Strict phylogenetic closeness” of fossil taxa are very important and useful in biostratigraphic correlation and boundary definition in both marine and non-marine strata (Zhou, et al., 2009). Key words: Marine and non-marine; Jurassic− Cretaceous boundary; China References: Ji Q., Liu Y.Q. Ji S.A., et al., On the terrestrial Jurassic−Cretaceous boundary in China. Geolo- gical Bulletin of China, 2006, 25:336-339. Sha J.G. Cretaceous stratigraphy of northeast China: Non-marine and marine correlation. Cretaceous Research, 2007, 28:146-170. Sha J.G., Chen S.W., Cai H.W., et al. Jurassic-Creta- ceous boundary in northeastern China: Placement based on buchiid bivalves and dinoflagellate cysts. Progress in Natural Science, 2006, 16 (Special Issue):39-49. Sha J.G., Hiromich H., Yao X.G., et al. Late Meso- zoic transgressions of eastern Heilongjiang and their significance in tectonics, and coal and oil accumulation in northeastern China. Palaeogeo- graphy, Palaeoclimatology, Palaeoecology, 2008, 263:119-130. Sha J.G., Wang J.P., Kirilova G., et al. Upper Jurassic and Lower Cretaceous of Sanjiang- Middle Amur basin: Non-marine and marine correlation. Scien- ce in China, Series D: Earth Sciences, 2009, 52:1873-1889. Swisher C.C. Ⅲ, Wang X.L., Zhou Z.H. Further sup- port for a Cretaceous age for the feathered- dinosaur beds of Liaoning, China: New 40 Ar/ 39 Ar dating of the Yixian and Tuchengzi Formations. Chinese Science Bulletin, 2002, 47:135-202. Wan X.Q., Gao L.F., Li G.B., et al. Jurassic-Creta- ceous boundary strata in Dyangze-Nagarze area, Tibet. Geoscience, 2005, 19: 479-487 (in Chin- ese with English abstract). Wan X.Q., Scott R., Chen W., et al. Early Cretaceous stratigraphy and SHRIMP U-Pb age constrain the Valanginian-Hauterivian boundary in southern Tibet. Lethaia, 2010 (in press). Yin J.R., Enay R. Tithonian ammonoid biostratigraphy in eastern Himalayan Tibet. Geobios, 2004, 37: 667-686. Zhou Z.H., He H.Y., Wang X.L. The continental Jura- ssic-Cretaceous boundary. Acta Palaeontologica Sinica, 2009, 48:553-555 (in Chinese with Eng- lish abstract). 27
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