Sedimentology of reefal buildups of the Xiannüdong Formation (Cambrian Series 2), SW China
Hao Tang1,2,3, Stephen Kershaw3, Xiu-Cheng Tan1, Hong Liu1, Fei Li1, Cheng Shen1, Fei-Fan Lu1, Xue-Fei Yang1,2
1 Division of Key Laboratory of Carbonate Reservoir of CNPC, Southwest Petroleum University, Chengdu 610500, Sichuan Province, China.; 2 Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Mineral, Shandong University of Science and Technology, Qingdao 266590, Shandong Province, China.; 3 Department of Life Sciences, Brunel University, Kingston Lane, Uxbridge, UB8 3PH, UK
Abstract The reefs in the Xiannüdong Formation (Cambrian Series 2) are the oldest archaeocyathan-microbial bioconstructions in China, but the details of their microbial structures have not been previously described. However, a new section at Tangjiahe site, northern Sichuan Province, contains very well-preserved microbial fabrics that provide these details, and is described in this study. The Tangjiahe section contains three levels of reefal buildups that were constructed by a consortium of archaeocyaths and calcimicrobes in varying proportions. The lowest (oldest) reefal buildup is a calcimicrobial biostrome, possibly in the form of a wide mound with a low relief (unconfirmed due to outcrop limitation), which was formed by Epiphyton with rare small archaeocyaths, and is sandwiched by flat-pebble conglomerates. The middle reefal buildup is a high-relief calcimicrobial mound, enclosed by oolites, that was built by intergrown Renalcis and Tarthinia. Archaeocyath fossils are uncommon, and were bound into the framework by microbial carbonates. The uppermost (youngest) reefal buildup is a low-relief archaeocyathan mound lacking calcimicrobes but partly having microbially-clotted textures attached on archaeocyaths. Calcimicrobes built or aided archaeocyaths to form the framework of Tangjiahe reefs. The three buildups formed in low-energy lagoons behind ooid shoals, and the environment was nutrient-rich due to terrigenous influx from adjacent lands. Tangjiahe reefs thus resemble most Early Cambrian reefs, in settings consistent with eutrophic, calm environments, and are characterized by the domination or aid of calcimicrobial components in framework construction.
Adachi N.,A. Kotani,Y. Ezaki, and J.B. Liu.2015. Cambrian Series 3 lithistid sponge-microbial reefs in Shandong Province, North China: Reef development after the disappearance of archaeocyaths.Lethaia 48(3): 405-416.
[2]
Adachi N.,T. Nakai,Y. Ezaki, and J.B. Liu.2014. Late Early Cambrian archaeocyath reefs in Hubei Province, South China: modes of construction during their period of demise.Facies 60(2): 703-717.
[3]
Brasier M.D.1996. The basal Cambrian transition and Cambrian bio-events (from terminal Proterozoic extinctions to Cambrian biomeres). In: Walliser, O.H. (Ed.), Global Events and Event Stratigraphy in the Phanerozoic. Berlin: Springer, pp. 113-138.
[4]
Chen J.,H.S. Lee.2013. Soft-sediment deformation structures in Cambrian siliciclastic and carbonate storm deposits (Shandong Province, China): Differential liquefaction and fluidization triggered by storm-wave loading.Sedimentary Geology 288: 81-94.
[5]
Chen J.T.,S.K. Chough,S.S. Chun, and Z.Z. Han.2009. Limestone pseudoconglomerates in the Late Cambrian Gushan and Chaomidian Formations (Shandong Province, China): soft-sediment deformation induced by storm-wave loading.Sedimentology 56(4): 1174-1195.
[6]
Debrenne F.,A. Gandin, and A. Zhuravlev.1991. Paleoecological and sedimentological remarks on some Lower Cambrian sediments of the Yangtse Platform (China).Bulletin de la Société Géologique de France 162: 575-583.
[7]
Debrenne F.,A. Gandin, and M. Debrenne.1993. Calcaires à archéocyathes du Membre de la vallée de Matoppa (Formation de Nebida), Cambrien inférieur du Sud-Ouest de la Sardaigne (Italie).Annales de Paléontologie 79: 77-118.
[8]
Gandin A.,F. Debrenne.2010. Distribution of the archaeocyath-calcimicrobial bioconstructions on the Early Cambrian shelves.Palaeoworld 19(3-4): 222-241.
[9]
Hicks M.,S.M. Rowland.2009. Early Cambrian microbial reefs, archaeocyathan inter-reef communities, and associated facies of the Yangtze Platform.Palaeogeography, Palaeoclimatology, Palaeoecology 281(1-2): 137-153.
[10]
Hong J.,J.-H. Lee,S.-J. Choh, and D.-J. Lee.2016. Cambrian Series 3 carbonate platform of Korea dominated by microbial-sponge reefs.Sedimentary Geology 341: 58-69.
[11]
Hong J.,S.-H. Cho,S.-J. Choh,J. Woo, and D.-J. Lee.2012. Middle Cambrian siliceous sponge-calcimicrobe buildups (Daegi Formation, Korea): Metazoan buildup constituents in the aftermath of the Early Cambrian extinction event. Sedimentary Geology 253-254: 47-57.
[12]
Kreisa R.D.1981. Storm-generated sedimentary structures in subtidal marine facies with examples from the Middle and Upper Ordovician of southwestern Virginia.Journal of Sedimentary Petrology 51(3): 823-848.
[13]
Lee J.-H.,R. Riding.2018. Marine oxygenation, lithistid sponges, and the early history of Paleozoic skeletal reefs.Earth-Science Reviews 181: 98-121.
[14]
Lee J.-H.,J. Hong,S.-J. Choh,D.-J. Lee,J. Woo, and R. Riding.2016. Early recovery of sponge framework reefs after Cambrian archaeocyath extinction: Zhangxia Formation (Early Cambrian Series 3), Shandong, North China.Palaeogeography, Palaeoclimatology, Palaeoecology 457: 269-276.
[15]
Lee J.-H.,J.T. Chen, and S.K. Chough.2015. The Middle-Late Cambrian reef transition and related geological events: A review and new view.Earth-Science Reviews 145: 66-84.
[16]
MacNeil, A.J., and B. Jones. 2008. Nutrient-gradient controls on Devonian reefs: Insight from the ramp-situated Alexandra Reef System (Frasnian), Northwest Territories, Canada. In: J. Lukasik and J.A. Simo (Eds.), Controls on Carbonate Platform and Reef Development. SEPM Special Publications, vol. 89, pp. 271-289.
[17]
Mount J.F.1984. Mixing of siliciclastic and carbonate sediments in shallow shelf environments.Geology 12(7): 432-435.
[18]
Munnecke A.,C. Samtleben.1996. The formation of micritic limestones and the development of limestone-marl alternations in the Silurian of Gotland, Sweden.Facies 34(1): 159-176.
[19]
Peng S.,L.E. Babcock, and R.A. Cooper. 2012. Chapter 19 — The Cambrian Period. In: F.M. Gradstein, J.G. Ogg, M.D. Schmitz and G.M. Ogg (Eds.), The Geologic Time Scale. Boston: Elsevier, pp. 437-488.
[20]
Pratt B.R.,B.R. Spincer, R.A. Wood, and A.Y. Zhuravlev. 2001. Ecology and evolution of Cambrian reefs. In: The Critical Moments in Paleobiology and Earth History Series. New York: Columbia University Press, pp. 254-274.
[21]
Purdy E.G.1963. Recent calcium carbonate facies of the Great Bahama Bank. 2. Sedimentary facies.The Journal of Geology 71(4): 472-497.
[22]
Riding R.,A.Y. Zhuravlev.1995. Structure and diversity of oldest sponge-microbe reefs: Lower Cambrian, Aldan River, Siberia.Geology 23(7): 649-652.
[23]
Rowland S.M.,R.A. Gangloff.1988. Structure and paleoecology of Lower Cambrian reefs.Palaios 3(2): 111-135.
[24]
Rowland, S.M.,R.S. Shapiro. 2002. Reef patterns and environmental influences in the Cambrian and earliest Ordovician. In: W. Kiessling, E. Flügel, and J. Golonka (Eds.), Phanerozoic Reef Patterns. Tulsa, OK: Society of Economic Paleontologists and Mineralogists. SEPM Special Publications, vol. 72, pp. 95-128.
[25]
Sepkoski Jr., J.J. 1982. Flat-pebble conglomerates, storm deposits, and the Cambrian bottom fauna. In: G. Einsele, and A. Seilacher (Eds.), Cyclic and Event Stratification. Springer, pp. 371-385.
[26]
Sepkoski Jr., J.J. 1992. Proterozoic-Early Cambrian diversification of metazoans and metaphytes. In: J.W. Schopf, C. Klein (Eds.), The Proterozoic Biosphere. Cambridge: Cambridge University Press, pp. 553-561.
[27]
Westphal H., Munnecke A., Böhm F., Bornholdt S.2008. Limestone-marl alternations in epeiric sea settings — Witnesses of environmental changes, or of rhythmic diagenesis?Geological Association of Canada, Special Paper 48: 389-406.
[28]
Wignall P.B.,R.J. Twitchett.1999. Unusual intraclastic limestones in Lower Triassic carbonates and their bearing on the aftermath of the end-Permian mass extinction.Sedimentology 46(2): 303-316.
[29]
Wood R.,A.Y. Zhuravlev, and C.T. Anaaz.1993. The ecology of Lower Cambrian buildups from Zuune Arts, Mongolia: Implications for early metazoan reef evolution.Sedimentology 40(5): 829-858.
[30]
Xiang L., Zhu Z., Li S., Zhou Z.1999. Stratigraphic Dictionary of China: Cambrian. Beijing: Geological Publishing House (in Chinese).
[31]
Yang A.H.,K.X. Yuan.2012. New archaeocyaths from the Early Cambrian of Shaanxi and Guizhou Provinces, South China.Geobios 45(6): 591-601.
[32]
Yang A.H.,M.Y. Zhu,A.Y. Zhuravlev,K.X. Yuan,J.M. Zhang, and Y.Q. Chen.2016. Archaeocyathan zonation of the Yangtze Platform: Implications for regional and global correlation of Lower Cambrian stages.Geological Magazine 153(3): 388-409.
[33]
Yu K.H.,Z.K. Jin,K. Su,X.D. Dong,W. Zhang,H.Y. Du,Y. Chen, and W.D. Zhang.2013. The Cambrian sedimentary characteristics and their implications for oil and gas exploration in north margin of Middle-Upper Yangtze Plate.Science China Earth Sciences 56(6): 1014-1028.
[34]
Yuan K.X.,S.G. Zhang.1981. Lower Cambrian archaeocyathid assemblages of central and southwestern China.GSA Special Papers 187: 39-54.
[35]
Yuan K.X.,M.Y. Zhu,J.M. Zhang, and H. Vaniten.2001. Biostratigraphy of archaeocyathan horizons in the Lower Cambrian Fucheng section, South Shaanxi Province: Implications for regional correlations and archaeocyathan evolution.Acta Palaeontologica Sinica 40(Suppl.): 115-129 (in Chinese with English abstract).
[36]
Zhang J.M.,K.X. Yuan.1994. Archaeocyath reefs from the Lower Cambrian Tianheban Formation at Wangjiaping, Yichang, Hubei and their diagenesis.Scientia Geologica Sinica 29: 236-245.
[37]
Zhang M.Q.,J.S. Hong,S.-J. Choh, and D.-J. Lee.2017. Thrombolite reefs with archaeocyaths from the Xiannüdong Formation (Cambrian Series 2), Sichuan, China: Implications for Early Paleozoic bioconstruction.Geosciences Journal 21(5): 655-666.
[38]
Zhuravlev A.Y.1986. Evolution of archaeocyaths and paleobiogeography of the Early Cambrian.Geological Magazine 123(4): 377-385.
[39]
Zhuravlev A.Y.1996. Reef ecosytem recovery after the Early Cambrian extinction. In: M.B. Hart (Ed.), Biotic Recovery from Mass Extinction Events. Geological Society, London, Special Publications, vol. 102, pp. 79-96.
[40]
Zhuravlev A.Y.2001. Paleoecology of Cambrian reef ecosystems. In: G.D. Stanley Jr. (Ed.), The History and Sedimentology of Ancient Reef Systems. New York: Kluwer Academic/Plenum Publishers, pp. 121-157.
[41]
Zhuravlev A.Y.,D.I. Gravestock.1994. Archaeocyaths from Yorke Peninsula, South Australia and archaeocyathan Early Cambrian zonation.Alcheringa: An Australasian Journal of Palaeontology 18(1-2): 1-54.
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