Ce anomalies of the Yangtze Region, South China, through the Ordovician and Silurian Transition

Abstract

Systematic Ce anomalies for whole-rock have been obtained from the shale-dominated, continuous, and pelagic sedimentary sequences spanning the Ordovician/Silurian (O/S) boundary at the Tieshui (铁水) of Xiushan (秀山), Chongqing (重庆), South China. Ce anomalies across the O/S boundary are recognized in three intervals, Wufeng (五峰), Guanyinqiao (观音桥) and Longmaxi (龙马溪). The calculated Ce/Ce* values of Wufeng Formation range from 0.84 to 0.96 (avg. 0.90). In the Guanyinqiao Formation, the values of calculated Ce/Ce* range from 0.73 to 0.85 (avg. 0.79). The Ce/Ce* values of uppermost Longmaxi Formation range from 0.87 to 0.96 (avg. 0.91). All along the section, the magnitude of the Ce anomaly is always negative, but is more significant in the Guanyinqiao Formation. The relatively higher Ce/Ce* values in the Wufeng and Longmaxi shales are likely to be due to the sediments deposited under rather reducing conditions. The Ce anomaly apparently does play some regular roles in the anoxic events that accompany prominent mass extinctions, and this work provides new data of critical importance for constraining models on the end-Ordovician anoxic events and mass extinctions.

Keywords

Ce anomaly / redox / mass extinction / Ordovician/Silurian boundary / Yangtze platform

References

[1] Byrne R. H., Kim K. H.. Rare Earth Element Scavenging in Seawater. Geochim. Cosmochim. Acta, 1990, 54(10): 2645-2656.

[2] Catherine G., Christophe L. C.. Variations in Ce Anomalies of Conodonts through the Frasnian/Famennian Boundary of Poland (Kowala-Holy Cross Mountains): Implications for the Redox State of Seawater and Biodiversity. Palaeogeogr., Palaeoclimatol., Palaeoecol., 2002, 181(1–3): 299-311.

[3] Chen X., Xiao C., Chen H.. Wufengian (Ashgillian) Graptolite Faunal Differentiation and Anoxic Environment in South China. Acta Palaeontologica Sinica, 1987, 26(3): 326-344.

[4] Chen X., Rong J., Fan J., . Global Correlation of Biozones across the Ordovician-Silurian Boundary. Acta Palaeontologica Sinica, 2000, 39(1): 100-114.

[5] de Baar H. J. W., Bacon M. P., Brewer P. G.. Rare Earth Elements in the Pacific and Atlantic Oceans. Geochim. Cosmochim. Acta, 1985, 49: 1943-1959.

[6] de Baar H. J. W., German C. R., Elderfield H., . Rare Earth Element Distribution in Anoxic Waters of the Carioca Trench. Geochim. Cosmochim. Acta, 1988, 52: 1203-1219.

[7] Desprairies A., Courtois C.. Relation Entre la Composition des Smectites d Alteration Sous-Marine et Leur Cortege de Terres Rares. Earth Planet. Sci. Lett., 1980, 48(1): 124-130.

[8] Elderfield H., Greaces M. J.. The Rare Earth Elements in Seawater. Nature, 1982, 296: 214-219.

[9] German C. R., Elderfield H.. Rare Earth Elements in Saanich Inlet, British Columbia: A Seasonally Anoxic Basin. Geochim. Cosmochim. Acta, 1989, 53: 2561-2571.

[10] German C. R., Elderfield H.. Application of the Ce Anomaly as a Paleoredox Indicator: The Ground Rules. Paleoceanography, 1990, 5(5): 823-833.

[11] German C. R., Holliday B. P., Elderfield H.. Redox Cycling of Rare Earth Elements in the Suboxic Zone of the Black Sea. Geochim. Cosmochim. Acta, 1991, 55(12): 3533-3558.

[12] Goldberg E. D., Koide M., Schmitt R. A., . Rare-Earth Distributions in the Marine Environment. J. Geophys. Res., 1963, 68(14): 4209-4217.

[13] Hallam A.. The Case for Sea-Level Change as a Dominant Causal Factor in Mass Extinction of Marine Invertebrates. Philos. Trans. R. Sci., 1989, 325(1228): 437-455.

[14] Holser W. T., Magaritz M., Ripperdan R. L., Walliser O.. Global Events and Event Stratigraphy in the Phanerozoic: The Case for Sea-Level Change as a Dominant Causal Factor in Mass Extinction of Marine Invertebrates. Philos. Trans. R. Sci., 1995, 12: 205-243.

[15] Holser W. T.. Evaluation of the Application of Rare-Earth Elements to Paleoceanography. Palaeogeogr., Palaeoclimatol., Palaeoecol., 1997, 132(1–4): 309-323.

[16] Jiang S. Y., Zhao H. X., Chen Y. Q.. Trace and Rare Earth Element Geochemistry of Phosphate Nodules from the Lower Cambrian Black Shale Sequence in the Mufu Mountain of Nanjing, Jiangsu Province, China. Chem. Geol., 2007, 244(3–4): 584-604.

[17] Kajiwara Y., Yamakita S., Ishida K., . Development of a Largely Anoxic Stratified Ocean and Its Temporary Massive Mixing at the Permian/Triassic Boundary Supported by the Sulfur Isotopic Record. Palaeogeogr., Palaeoclimatol., Palaeoecol., 1994, 111(3–4): 367-379.

[18] Kato Y., Nakao K., Isozaki Y.. Geochemistry of Late Permian to Early Triassic Pelagic Cherts from Southwest Japan: Implications for an Oceanic Redox Change. Chem. Geol., 2002, 182(1): 15-34.

[19] Liu Y. G., Miah M. R. U., Schmitt R. A.. Cerium: A Chemical Tracer for Paleo-oceanic Redox Conditions. Geochim. Cosmochim. Acta, 1988, 52: 1361-1371.

[20] Metcalfe I.. Late Palaeozoic and Mesozoic Palaeogeography of Eastern Pangaea and Tethys. Can. Soc. Pet. Geol., Mem., 1994, 17: 97-111.

[21] Mu E., Li J., Ge M., . Late Ordovician Paleogeography of South China. Acta Stratigr. Sin., 1981, 5: 165-170.

[22] Murray R. W., Buchholtz B. M. R., Jones D. L., . Rare Earth Elements as Indicators of Different Marine Depositional Environments in Chert and Shale. Geology, 1990, 18: 268-271.

[23] Murray R. W., Buchholtz B. M. R., Brumsack H. J., . Rare Earth Elements in Japan Sea Sediments and Diagenetic Behavior of Ce/Ce*: Results from ODP Leg 127. Geochim. Cosmochim. Acta, 1991, 55(9): 2453-2466.

[24] Murry R. W., Buchholtz B. M. R., Gerlach D. C., . Interoceanic Variation in the Rare Earth, Major, and Trace Element Depositional Chemistry of Chert: Perspectives Gained from the DSDP and ODP Record. Geochim. Cosmochim. Acta, 1992, 56(5): 1897-1913.

[25] Piper D. Z.. Rare Earth Elements in Ferromanganese Nodules and Other Marine Phases. Geochim. Cosmochim. Acta, 1974, 38(7): 1007-1022.

[26] Racki G., Racka M., Matyja H., . The Frasnian/Famennian Boundary Interval in the South Polish-Moravian Shelf Basins: Integrated Event-Stratigraphical Approach. Palaeogeogr., Palaeoclimatol., Palaeoecol., 2002, 181(1–3): 251-297.

[27] Saltzman M. R., Davidson J. P., Holden P., . Sea-Level-Driven Changes in Ocean Chemistry at an Upper Cambrian Extinction Horizon. Geology, 1995, 23: 893-896.

[28] Sholkovitz E. R.. Rare Earth Elements in the Sediments of the North Atlantic Ocean, Amazon Delta, and East China Sea: Reinterpretation of Terrigenous Input Patterns to the Oceans. Am. J. Sci., 1988, 288(3): 236-281.

[29] Taylor S. R., McLennan S. M.. The Continental Crust: Its Composition and Evolution, 1985, Oxford: Blackwell 311

[30] Tlig S., Steinberg M.. Distribution of Rare Earth Elements (REE) in Size Fractions of Recent Sediments of the Indian Ocean. Chem. Geol., 1982, 37(3–4): 317-333.

[31] Wang K., Chatterton B. D. E., Wang Y.. An Organic Carbon Isotope Record of Late Ordovician to Early Silurian Marine Sedimentary Rocks, Yangtze Sea, South China: Implications for CO₂ Changes during the Hirnantian Glaciation. Palaeogeogr., Palaeoclimatol., Palaeoecol., 1997, 132: 147-158.

[32] Wang K., Orth C. J. Jr., Chatterton B. D. E., . The Great Latest Ordovician Extinction on the South China Plate: Chemostratigraphic Studies of the Ordovician-Silurian Boundary Interval on the Yangtze Platform. Palaeogeogr., Palaeoclimatol., Palaeoecol., 1993, 104(1–4): 61-79.

[33] Wright J., Schrader H., Holser W. T.. Paleoredox Variations in Ancient Oceans Recorded by Rare Earth Elements in Fossil Apatite. Geochim. Cosmochim. Acta, 1987, 51(3): 631-644.

[34] Yan D. T., Chen D., Wang Q., . Environment Redox Changes of the Yangtze Sea during the Ordo-Silurian Transition. Acta Geologica Sinica, 2008, 82(3): 679-689.

[35] Yan D. T., Chen D., Wang Q., . Carbon and Sulfur Isotopic Anomalies across the Ordovician-Silurian Boundary on the Yangtze Platform, South China. Palaeogeogr., Palaeoclimatol., Palaeoecol., 2009, 274(1–2): 32-39.

[36] Yan D. T., Chen D., Wang Q., Wang J.. Geochemical Changes across the Ordovician-Silurian Transition on the Yangtze Platform, South China. Science in China (Ser. D), 2009, 52(1): 38-54.