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This volume will draw the attention of everyone interested in the fascinating diversity of ancient ecosystems such as reefs and shell accumulations in the Palaeozoic, whose difficulty of study rests primarily on its multidisciplinary position crossing numerous geological disciplines. Their facies characterization is, like many other biosedimentary structures, a process that requires the acquisition and integration of a wide and multiscale diversity of observations, which include field (global geometries), sample (fabrics), and thin-section (textures) scales. One of the messages of this collection of papers is the wide diversity of sedimentary geometries and facies displayed by Palaeozoic reefs, shell accumulations, and transitional composite deposits. We have touched on some of the major issues at this stage of development in the field: the major climatic, environmental and evolutionary factors that controlled the Palaeozoic development of shell accumulations and reefs. Emmanuelle Vennin is professor at the Université de Bourgogne (France) and is carbonate sedimentologist. She is currently investigating the development of ancient (Ordovician to Miocene) reef deposits in term of geometry, biosedimentary processes, stratigraphy and palaeoclimatology. Markus Aretz holds a PhD from the Universität zu Köln (Germany). He previously worked at Liège (Belgium) and Brisbane (Australia) and is currently employed at the University of Köln as assistant professor. He is a carbonate sedimentologist and palaeobiologist who is specialised in Late Devonian and Carboniferous reefs and reef biota, especially corals. The interactions of very

edited by Emmanuelle Vennin, Markus Aretz, Frédéric Boulvain & Axel Munnecke

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Palaeozoic reefs and bioaccumulations

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Palaeozoic reefs and bioaccumulations

edited by Emmanuelle VENNIN, Markus ARETZ, Frédéric BOULVAIN & Axel MUNNECKE

different organisms in reef forming processes have been an important aspect of his research in the last years. Frédéric Boulvain graduated from the Brussels and Paris-XI universities, and obtained a Doctorat en Sciences from Brussels after five years research on Frasnian mud-mounds. He is now Professor at the University of Liège (Belgium) and Head of the Department of Geology. His main research interests are in sedimentology of Palaeozoic reefs and mounds and use of magnetic susceptibility in sedimentary dynamics reconstructions. Axel Munnecke is assistant professor at the Institute of Palaeontology in Erlangen (Germany), and is currently investigating the development of the Ordovician and Silurian climate by means of analysis of stable C/O-isotopes from brachiopod shells. In addition, he is working on the origin and diagenesis of limestone-marl alternations, and on the development of Palaeozoic calcareous micro- and nanofossils.

Mémoires du Muséum national d’Histoire naturelle

Tome 195 Mémoires du Muséum national d’Histoire naturelle, Tome 195

ISBN : 978-2-85653-593-6 ISSN : 1243-4442

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2007

Permian

Illustration page 277: Tubiphytes-Archaeolithoporella-bryozoan boundstone, Asselian, Urals (Russia).

Permian

LATEST PERMIAN CALCISPONGES OF LAREN, Guangxi Province, South China LOCALITY. — The ���������������������������������������������������������������������������������������������� Yangtze carbonate platform of South China constituted a stable palaeogeographic component from Late Proterozoic to the end of Middle Triassic with deposition of shallow-water carbonates during most of this time (Enos et al. 1995). ��������������������������������������������������������������������������������������������� Middle and Late Permian reef limestones are widely distributed and well preserved in eastern Yunnan, southwestern Guizhou and northwestern Guangxi (Sheng et al. 1985; Rigby et al. 1989a, b). The southern margin of the Yangtze platform was embayed by the Nanpanjiang Basin (sensu Lehrmann et al. 1998) which was widely opened southward and extended into central Guizhou. Dominant deep-water deposits surrounded various carbonate platforms dispersed within the basin. The Laren area lies on the margin of one of these isolated platforms (Fig. 85) and is located in the Fengshan District of the northwestern Guangxi Province.

Guizhou

Rongjiang

China Luodian

Hechi

Leye Laren

Fengshan Liuzhou

Lingyun Bose

Yunnan

Tiandong NANPANJIANG BASIN

23° N

Pingguo

Western Guangxi

Cao Bang

Nanning

VIETNAM

Qinzhou

Yangtze platform margin Isolated platforms

Gulf of Tonkin

200 km 105°E

107°E

109°E

FIG. 85. ��������������������������������������������������������������������������������� Geographic map of the West Guangxi Province, location of the studied area (black star) and distribution of the Permian platform (modified after Rigby et al. 1989b).

STRATIGRAPHY. —������������������������� ������������������������ I����������������������� n South China, largely because of post-sedimentary faulting, complete Late Permian-Early Triassic sections are often very rare.����������������������������������� The Laren profile is a particular exception. In fact, it illustrates an excellent outcrop straddling the Permo-Triassic Boundary apparently devoid of hiatuses (Galfetti et al. 2007). The latest Permian Wujiaping Formation is characterized by shallow-water reef limestones. These rocks are drastically overlain by a ~7.5 mthick unit of calcimicrobial limestones of earliest Triassic age (Griesbachian) (Fig. 86). The foraminifer assemblage (see below) within the beds preceding the Permian-Triassic boundary allows to attribute a late Changhsingian age, while the nearly total absence of index fossils immediately after the boundary does not consent to precisely date the base of the calcimicrobial unit. However the base of these beds is bed-parallel and the bottom surface does not show any evidence of erosion processes. The occurrence of foraminiferal “disaster forms” such as Earlandia sp., Rectocornuspira kalhori, Spirorbis phlyctaena, Cornuspira mahajeri as well as rare nodosarioids, two and seven meters above the latest Permian beds, leads to suggest a Griesbachian (earliest Triassic) age for the calcimicrobial unit.

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Early Triassic Late Permian

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89

90

91

92

93

FIGS 86-93. 86, The Permian-Triassic boundary at Laren (South-China), with the studied calcisponge reefs capped by calcimicrobial limestones of earliest Triassic age; scale = 5m. 87-90: Field photographs showing latest Permian (late Changhsingian) reef limestones associated with the calcisponge bioconstruction of Laren. 87, Calcisponges in life position; scale = 5 cm. 88, Longitudinal section of the calcisponges; scale = 5 cm. 89, Transverse sections of the same calcisponges; scale = 2,5 cm. 90, Rugose corals and silicified brachiopods; scale = 1,25 cm. 91-93: Microfacies of the bioclastic wacke/packstones associated with the calcisponge reefs. 91, Neosparitized, slightly silicified, bioclastic and peloidal wackestone showing Climacammina sp. and Nankinella sp. Thin section L6 (collection T. Galfetti); scale = 500 μm. 92, Neosparitized bioclastic limestone showing Paraglobivalvulinoides sp., Climacammina sp. and Neodiscus sp. Thin section L10b (coll. T. Galfetti); scale = 500 μm. 93, Similar microfacies showing Neodiscus sp., Climacammina sp. (several sections) and Tetrataxis sp. Thin section L10b (coll. T. Galfetti); scale 500 μm.

Permian

FACIES AND MICROFACIES (Figs 86-93). — Permian strata are easily recognizable in South China because of their typical, spectacular karst morphology. Macroscopically, Late Permian rocks are generally very massive, dark-colored and frequently accompanied by centimetric to decimetric black chert concretions. At Laren these beds display an extraordinarily, well preserved faunal assemblage (e.g., brachiopods, gastropods, rugose corals, very large calcareous algae and calcareous porifera) (Figs 87-90). Geometrical fossils orientation has not been observed excepting for a sphinctozoan colony which illustrates a planar setting (Fig. 87). Microfacies analysis on thin sections (Figs 9193) revealed that these skeletal, peloidal pack/grainstones are mainly associated with: rare gastropods, rare incertae sedis Tubiphytes (non Shamovella) obscurus Maslov, rare fusulinids Nankinella cf. inflata (Colani) emend. Sheng, and Reichelina simplex Sheng, as well as abundant and diversified small foraminifers, especially biseriamminids. Among foraminifers, the following taxa have been recognized: Eotuberitina spinosa (Lys in Lys et al.); Postendothyra micula (Sosnina in Sosnina & Nikitina); Globivalvulina curiosa Gaillot & Vachard in Gaillot et al.; G. kantharensis Reichel; G. vonderschmitti Reichel; G. bulloides (Brady); Septoglobivalvulina distensa (Wang in Zhao et al.); S. cf. guangxiensis Lin; S. sp. 1; Dagmarita chanakchiensis Reitlinger; D. altilis Wang in Zhao et al.; D.? cf. sharezaensis Mohtat-Aghai & Vachard; D. simplex Wang in Zhao et al.; Bidagmarita sinica Gaillot & Vachard in Gaillot et al. (with pseudo-fibrous inner layer); Siphodagmarita vasleti Gaillot & Vachard in Gaillot et al.; Louisettita ultima Gaillot & Vachard in Gaillot et al.; Retroseptellina decrouezae (Köylüoglu & Altiner); Retroseptellina nitida (Lin et al.); Paraglobivalvulinoides septulifer (Zaninetti & Altiner); Paradagmaritopsis kobayashii Gaillot & Vachard in Gaillot et al.; Paradagmaritopsis sp. and Paradagmarita sp. They are associated with relatively rare nodosarioids, such as Rectostipulina sp., Nodosinelloides sp., Geinitzina sp., Pseudotristix cf. solida Reitlinger, Pachyphloia pedicula Lange, P. ex gr. ovata Lange, and Ichthyofrondina palmata (Wang). Miliolids are very rare with some tubes of Pseudovermiporella nipponica (Endo in Endo & Kanuma). Phylogenetically older forms (early to late Mississippian), such as Climacammina (C. tenuis Lin) and Tetrataxis (T. lata Spandel) are relatively frequent (Figs 91-93). The latter aspect seems to be common in the late Changhsingian (Gaillot 2006). BIODIVERSITY AND TAPHONOMY. — As indicated by Rigby et al. (1989a, b), the biodiversity of the sphinctozoans is generally poor in these reefs, whereas the smaller foraminifers belong to diverse families. Here the biseriamminids are especially diversified with the genera and subgenera Globivalvulina, Dagmarita, Septoglobivavulina?, Louisettita?, Paradagmarita?, Paraglobivalvulinoides and Paradagmaritopsis n. gen. This diversity has been already pointed out in the Chinese literature (e.g., Lin et al. 1990). DISCUSSION. — The abrupt transition at the Permian-Triassic boundary, from bioclastic pack/grainstones containing foraminifers with sophisticated endoskeletons, to calcimicrobial limestones showing a total lack or extreme rarity of very simple, undivided foraminifers is known from Turkey to South China (e.g. Groves & Altiner, 2005). Nevertheless, the last Permian reefs in the late Changhsingian are very rare in this Neo- and Palaeo-Tethyan Provinces. Exceptions were described in Greece and South China (Flügel & Reinhardt 1989; Weidlich 2002; Weidlich et al. 2003; this study), and NW Caucasus (Théry et al. this volume); the sphinctozoan and inozoan bioconstructions (Rigby et al. 1989a, b) are especially famous.

References Enos P., Wei J.Y. & Lehrmann D.J. 1998. — Death in Guizhou - Late Triassic drowning of the Yangtze carbonate platform. Sedimentary Geology, 118: 55-76. FlügeL E. & Reinhardt J. 1989. — Uppermost Permian reefs in Skyros (Greece) and Sichan (China): implications for the Late Permian extinction event. Palaios 4: 502-518. Gaillot J. 2006. — The Khuff Formation (Late Permian, Middle East): highresolution biostratigraphy by means of foraminifers and algae, sequence

stratigraphy, depositional environments, and new approach of the Permian/ Triassic crisis. Thèse de 3ème cycle, Université de Lille, 3 vol., 687 p., 134 pl. (unpublished). Galfetti T., Bucher H., Brayard A., Martini R., Weissert H., CrasquinSoleau S., Goudemand N., Hochuli P. A. & Guodun K. 2007. — Early Triassic facies and microfacies evolution after the end-Permian mass extinction. Jinya area, South China, Earth and Planetary Science Letter 1004.1023.

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GROVES J. R. & ALTINER D. 2005. — Survival and recovery of calcareous pursuant to the end-Permian mass extinction. Compte-Rendus Palevol 4: 487-500. Lehrmann D. J., Wei J. Y. & Enos P. 1998. — Controls on facies architecture of a large Triassic carbonate platform: The Great Bank of Guizhou, Nanpanjiang Basin, South China. Journal of Sedimentary Research, 68, 311-326. Lehrmann D. J., Wan Y., Wei J. Y., Yu Y. Y. & Xiao J. F. 2001. — Lower Triassic peritidal cyclic limestone: an example of anachronistic carbonate facies from the Great Bank of Guizhou, Nanpanjiang Basin, Guizhou province, South China. Palaeogeography Palaeoclimatology, Palaeoecology 173: 103-123. Lin J. X., Li L. X. & Sun Q. Y. 1990. — Late Paleozoic foraminifers in South China. Science Publication House, Beijing, 269 p. [in Chinese]. Rigby J. K., Fan J. S. & Zhang W. 1989a. — Sphinctozoan Sponges from the Permian Reefs of South China. Journal of Paleontology, 63 (4): 404-439. Rigby J. K., Fan J. S. & Zhang W. 1989b. — Inozoan calcareous porifera from the Permian reefs in South China. Journal of Paleontology 63 (6): 778-800.

Sheng J., Rui L. & Chen C. 1985. — Permian and Triassic sedimentary facies and paleogeography of South China, in Sheng J., Rui L. & Chen C. (eds), The Tethys: Her Paleogeography and Paleobiography from Paleozoic to Mesozoic. Tokai University Press.: 133-181. THERY J. M., VACHARD D. & DRANSART E. — New biostratigraphic and geochemical data on the Late Permian reef at Nikitin (Kuban, Russia). Important biostratigraphic and geochemical correlative implications , in Alvaro J. J., ARETZ M., BOULVAIN F., MUNNECKE A., VACHARD D. & Vennin E. (eds), Palaeozoic Reefs and Bioaccumulations: Climatic and Evolutionary Controls. Geological Society, London, Special Publications 275: 255-274. Weidlich O. 2002. — Middle and Late Permian reefs – distributional patterns and reservoir potential, in Kiessling W., Flügel E. & Golonka J. (eds), Phanerozoic Reef Patterns. Society of Economic Paleontologists and Mineralogists Special Publications 72: 339-390. Weidlich O., Kiessling W. & Flügel E. 2003. — Permo-Triassic boundary interval as a model for forcing marine ecosystem collapse by long-term atmospheric oxygen drop. Geology 31 (11): 961-964.