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Terminal Cambrian and lowest Ordovician succession of Mexican West Gondwana: biotas and sequence stratigraphy of the Tiñu Formation

Published online by Cambridge University Press:  01 August 2007

ED LANDING ,
STEPHEN R. WESTROP  and
JOHN D. KEPPIE
ED LANDING*
Affiliation:
New York State Museum, Madison Avenue, Albany, New York 12230, USA
STEPHEN R. WESTROP
Affiliation:
Oklahoma Museum of Natural History and School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73072, USA
JOHN D. KEPPIE
Affiliation:
Instituto de Geologia, Universidad National Automona de Mexico, Ciudad Universitaria, 04510 Coyoacan, D. F., México
*
*Author for correspondence: [email protected]
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Abstract

The Tiñu Formation of Oaxaca State is the only fossiliferous lower Palaeozoic unit between the Laurentian platform in northwest Mexico and Gondwanan successions in Andean South America. The Tiñu traditionally has been referred to the Lower Ordovician (Tremadoc) and regarded as having a provincially mixed fauna with Laurentian, Avalonian, and Gondwanan elements. Bio- and lithostratigraphic re-evaluation demonstrates that the Tiñu is a Gondwanan, passive margin succession. It includes a lower, thin (to 16 m), condensed, uppermost Cambrian Yudachica Member (new). The Yudachica nonconformably overlies middle Proterozoic basement as a result of very high late Late Cambrian eustatic levels. The Yudachica changes from storm-dominated, but slightly dysoxic, shelf facies (fossil hash limestone and shale) in the south to an upper slope facies with debris flows 50 km to the north. Three biostratigraphically distinct depositional sequences comprise the Yudachica. The Yudachica has Gondwanan-aspect trilobites with low-diversity conodonts characteristic of unrestricted marine/temperate facies. The upper Tiñu, or Río Salinas Member (new), is a Lower Ordovician (Tremadoc) depositional sequence that records strong early, but not earliest, Tremadoc eustatic rise marked by graptolite- and olenid-bearing dysoxic mudstones. Higher strata shoal upward into shell-hash limestones and proximal tempestite sandstones with upper lower Tremadocian unrestricted marine/temperate conodonts. New taxa include Orminskia rexroadae Landing gen. et sp. nov. from the Cordylodus andresi Zone; this euconodont is related to hyaline coniform genera best known from Ordovician tropical platform successions. Cornuodus? clarkei Landing sp. nov. resembles the coeval, upper lower Tremadoc tropical species Scalpellodus longipinnatus (Ji & Barnes).

Keywords

CambrianOrdovicianGondwanaMexicoconodontssequence stratigraphy
Type
Original Article
Information
Geological Magazine , Volume 144 , Issue 6 , November 2007 , pp. 909 - 936
Copyright
Copyright © Cambridge University Press 2007

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References

Adrain, J. M., Westrop, S. R., Chatterton, B. D. E. & Ramsköld, L. 2000. Silurian trilobite alpha diversity and the end-Ordovician mass extinction. Paleobiology 26, 625–46.Google Scholar
An, T.-X., Zhang, F., Xiang, W., Zhang, Y., Xu, W., Zhang, H., Jiang, D., Yang, C., Lin, L., Cui, Z. & Yang, X. 1983. The Conodonts of North China and Adjacent Regions. Beijing: Science Press, 223 pp.Google Scholar
Bagnoli, G., Barnes, C. R. & Stevens, R. K. 1987. Lower Ordovician conodonts from Broom Point and Green Point, western Newfoundland. Bolletino della Società Paleontologica Italiana 25, 145–58.Google Scholar
Bagnoli, G., Stouge, S. & Tongiorgi, M. 1988. Acritarchs and conodonts from the Cambro-Ordovician Furuhäll (Köpingsklint) section (Öland, Sweden). Bolletino della Societa Paleontologica Italia 26, 255–70.Google Scholar
Barnes, C. R. 1988. The proposed Cambrian–Ordovician global boundary stratotype and point (GSSP) in western Newfoundland, Canada. Geological Magazine 124, 381–414.Google Scholar
Barrande, J. 1868. Fauna silurienne des environs de Hof en Bavière, pp. 31–110. Prague.Google Scholar
Bronn, H. G. 1846. Lethaea geonostica. Stuttgart: E. Schweizerbart, 768 pp.Google Scholar
Bruton, D. L., Koch, L. & Repetski, J. E. 1988. The Nærsnes section, Oslo Region, Norway: trilobite, graptolite and conodont fossils reviewed. Geological Magazine 125, 451–5.Google Scholar
Bulman, O. M. B. 1950. Graptolites from the Dictyonema shales of Quebec. Quarterly Journal of the Geological Society of London 106, 63–99.Google Scholar
Bulman, O. M. B. 1954. The graptolite fauna of the Dictyonema shales of the Oslo Region. Norsk Geologisk Tidsskrift 33, 1–40.Google Scholar
Cabaleri, N. G. & Armella, C. 1990. Microfacies y paleoecología en la transgression tremadociana de la Formación Tiñu, Oaxaca, México. III Congreso Latinoamericano de Paleontología, Memorias, 3, pp. 42–51. Universidad Nacional Autónoma de Mexico, Instituto de Geologia, Mexico City.Google Scholar
Callaway, C. 1877. On a new area of Upper Cambrian rocks in south Shropshire with description of a new fauna. Quarterly Journal of the Geological Society of London 33, 652–72.Google Scholar
Cameron, K. L., Lopez, R., Ortega-Gutiérrez, F., Solari, L., Keppie, J. D. & Schulze, C. 2004. U–Pb geochronology and Pb isotope compositions of leached feldspars: constraints on the origin and evolution of Grenvillian rocks from eastern and southern Mexico. In Proterozoic tectonic evolution of the Grenville orogen in North America (eds Tollo, R. P., Corriveau, L., McLelland, J. B. & Bartholomew, G.), pp. 755–69. Geological Society of America, Memoir no. 197.Google Scholar
Centeno-Garcia, E. & Keppie, J. D. 1999. Latest Paleozoic–Early Mesozoic structures in the central Oaxaca Terrane of southern Mexico: deformation near a triple junction. Tectonophysics 301, 231–42.Google Scholar
Centeno-Garcia, E., Keppie, J. D., Sour-Tovar, F., Sanchez-Zavala, J. L. & Ortega-Gutierrez, F. 1998. October 20th, 1998: Field Stops 11–14. In Laurentia–Gondwana connections before Pangaea – Field trip in the Mixteco and Zapoteco terranes (ed. Keppie, J. D.), pp. 14–19. International Geological Correlation Program Project 376.Google Scholar
Chen, J.-Y. (ed.) 1986. Aspects of the Cambrian–Ordovician boundary in Dayangcha, China. Beijing: China Prospect Publishing House, 410 pp.Google Scholar
Clark, D. L., Sweet, W. C., Bergström, S. M., Klapper, G., Austin, R. L., Rhodes, F. H. T., Müller, K. J., Ziegler, W., Lindström, M., Miller, J. F. & Harris, A. G. 1981. Systematic descriptions. In Treatise on Invertebrate Paleontology, Part W, Miscellanea, Supplement 2 Conodonta (ed. Robison, R. A.), pp. 111–80. Geological Society of America and University of Kansas Press.Google Scholar
Cooper, R. A. 1979. Sequence and correlation of Tremadoc graptolite assemblages. Alcheringa 3, 7–19.Google Scholar
Cullison, J. S. 1938. Dutchtown fauna of southeastern Missouri. Journal of Paleontology 12, 219–28.Google Scholar
Dalziel, I. W. D., Dalla Salda, L. H. & Gahagan, L. M. 1994. Paleozoic Laurentia-Gondwana interaction and the origin of the Appalachian–Andean mountain system. Geological Society of America Bulletin 106, 243–52.Google Scholar
Dong, X., Repetski, J. E. & Bergström, S. M. 2004. Conodont biostratigraphy of the Middle Cambrian through lowermost Ordovician in Hunnan, South China. Acta Geologica Sinica 78, 1185–1206.Google Scholar
Druce, E. C. & Jones, P. J. 1971. Cambro-Ordovician conodonts from the Burke River structural belt, Queensland. Bureau of Mineral Resources, Geology and Geophysics, Canberra, A. C. T. Bulletin 110, 159 pp.Google Scholar
Dzik, J. 1976. Remarks on the evolution of Ordovician conodonts. Acta Palaeontologica Polonica 21, 395–455.Google Scholar
Dzik, J. 1994. Conodonts of the Mójcza Limestone. Palaeontologia Polonica 53, 43–128.Google Scholar
Eichenberg, W. 1930. Conodonten aus dem Kulm des Harzes. Paläontologisches Zeitschrift 12, 177–82.Google Scholar
Eichwald, E. von. 1840. Ueber das silurische Schichtensysstem in Esthland. Akademie der St. Petersburg, 240 pp.Google Scholar
Eichwald, E. von. 1855. Beiträge zur Geologie und Paläontologie Russlands. Bulletin du Societè Naturaliste à Moscou, 4.Google Scholar
Endo, R. & Resser, C. E. 1937. The Sinian and Cambrian formations and fossils of southern Manchoukuo. Manchurian Science Museum Bulletin 1, 1–474.Google Scholar
Epstein, A. G., Epstein, J. B. & Harris, L. D. 1977. Conodont color alteration—an index to organic metamorphism. United States Geological Survey Professional Paper 995, 27 pp.Google Scholar
Ethington, R. L. & Brand, U. 1981. Oneotodus simplex (Furnish) and the genus Oneotodus (Conodonta). Journal of Paleontology 55, 239–47.Google Scholar
Ethington, R. L. & Clark, D. L. 1964. Conodonts from the El Paso Formation (Ordovician) of Texas and Arizona. Journal of Paleontology 38, 685–704.Google Scholar
Ethington, R. L. & Clark, D. L. 1971. Lower Ordovician conodonts in North America. In Symposium on conodont biostratigraphy (eds Sweet, W. C. & Bergström, S. M.), pp. 63–82. Geological Society of America, Memoir no. 127.Google Scholar
Ethington, R. L. & Clark, D. L. 1981. Lower and Middle Ordovician conodonts from the Ibex area, western Millard County, Utah. Brigham Young University Geology Studies 28 (2), 155 pp.Google Scholar
Fåhraeus, L. E. 1966. Lower Viruan (Middle Ordovician) conodonts from the Gullhögen quarry, southern central Sweden. Sveriges Geologiska Undersökning Series C 610, 1–40.Google Scholar
Flower, R. H. 1968. Cephalopods from the Tiñu Formation, Oaxaca State, Mexico. Journal of Paleontology 42, 804–10.Google Scholar
Fortey, R. A. & Cocks, L. R. M. 2003. Paleontological evidence bearing on global Ordovician–Silurian continental reconstructions. Earth-Science Reviews 61, 245–307.Google Scholar
Fortey, R. A. & Owens, R. M. 2001. A trilobite fauna from the highest Shineton Shales in Shropshire, and the correlation of the latest Tremadoc. Geological Magazine 128, 437–64.Google Scholar
Furnish, W. M. 1938. Conodonts from the Prairie du Chien (Lower Ordovician) beds of the upper Mississippi valley. Journal of Paleontology 12, 318–40.Google Scholar
Gillis, R. J., Gehrels, G. E., Ruiz, J. & Flores de Dios-Gonzales, A. 2005. Detrital zircon provenance of Cambrian–Ordovician and Carboniferous of the Oaxaca terrane, southern México. Sedimentary Geology 182, 87–100.Google Scholar
Hahn, F. F. 1912. On the Dictyonema-fauna of Navy Island, New Brunswick. Annals of the New York Academy of Sciences 22, 135–60.Google Scholar
Harrington, H. J. 1938. Sobre las faunas del Ordoviciano del Norte Argentino. Revisita del Museo de La Plata, Nuevo Serie 1, Palaeontología 4, 109–289.Google Scholar
Harrington, H. J. & Kay, M. 1951. Cambrian and Ordovician faunas of eastern Columbia. Journal of Paleontology 25, 655–8.Google Scholar
Harrington, H. J. & Leanza, A. F. 1957. Ordovician trilobites of Argentina. Department of Geology, University of Kansas, Special Publication 1, 266 pp.Google Scholar
Henningsmoen, G. 1957. The trilobite family Olenidae. With description of Norwegian material and remarks on the Olenid and Tremadoc Series. Skrifter auf norsk Videnskaps-Akademie matematisk-naturvissen Klasse 1, 303 pp.Google Scholar
James, N. P. 1997. The cool-water depositional realm. In Cool-water carbonates (eds James, N. P. & Clarke, J. A. D.), pp. 1–20. SEPM Special Publication no. 56.Google Scholar
Jell, P. A. 1985. Tremadoc trilobites of the Digger Island Formation, Waratah Bay, Victoria. Memoirs of the Museum of Victoria 46, 53–88.Google Scholar
Ji, Z. & Barnes, C. R. 1994. Lower Ordovician conodonts of the St. George Group, Port au Port Peninsula, western Newfoundland, Canada. Palaeontographica Canadiana 11, 149 pp.Google Scholar
Kaljo, D., Borovko, N., Heinsalu, H., Khasanovich, K., Mens, K., Popov, L., Sergeeva, S., Sobolevskaya, R. & Viira, V. 1986. The Cambrian–Ordovician boundary in the Baltic Lagoda Clint area (north Estonia and Leningrad region), USSR). Proceedings of the Academy of Sciences of the Estonian SSR, Geology 35, 97–108.Google Scholar
Kayser, E. 1876. Beitrage zur Geologie und Paläontologie der Argentinischen Republik. Über primordiale und untersilurische Fossilien aus der Argentinischen Republik. Paläontographica, Supplement 3 (2), 1–33.Google Scholar
Kennedy, D. J. 1980. A restudy of conodonts described by Branson and Mehl, 1933, from the Jefferson City Formation, Lower Ordovician, Missouri. Geologica et Palaeontologica 14, 47–76.Google Scholar
Keppie, J. D. 1977. Plate tectonic interpretation of Palaeozoic world maps (with emphasis on circum-Atlantic orogens and southern Nova Scotia). Nova Scotia Department of Mines, Paper 77–3, 45 pp.Google Scholar
Keppie, J. D. 2004. Terranes of Mexico revisited: a 1.3 billion year odyssey. International Geology Review 46, 765–94.Google Scholar
Keppie, J. D., Nance, R. D., Murphy, J. B. & Dostal, J. 2003. Tethyan, Mediterranean, and Pacific analogues for the Neoproterozoic–Paleozoic birth and transfer of peri-Gondwanan terranes and their transfer to Laurentia and Laurussia. Tectonophysics 365, 195–219.Google Scholar
Keppie, J. D., Nance, R. D., Murphy, J. B., Dostal, J. & Miller, B. V. 2006. Birth of the Rheic Ocean, a 2-stage process on the southern (Mexican) margin. Geological Society of America Abstracts with Programs 38 (2), 21.Google Scholar
Keppie, J. D. & Ortega-Gutiérrez, F. 1995. Provenance of Mexican terranes – isotopic constraints. International Geology Review 37, 813–24.Google Scholar
Keppie, J. D. & Ortega-Gutiérrez, F. 1999. Middle American Precambrian basement: a missing piece of the reconstructed 1-Ga orogen. In Laurentia–Gondwana connections before Pangaea (eds Ramos, V. A. & Keppie, J. D.), pp. 199–210. Geological Society of America, Special Paper no. 336.Google Scholar
Keppie, J. D., Solari, L. A., Orgega-Gutiérrez, F., Elias-Herrera, M. & Nance, R. D. 2004. Field Trip 12: Paleozoic and Precambrian rocks of southern Mexico – Aclatlán and Oaxacan complexes. In Geological transects across Cordilleran Mexico. Guidebook for the Field Trips of the 99th Geological Society of America Cordilleran Section Annual Meeting, Puerto Vallarta, Jalisco, Mexico, April 4–10, 2003 (ed. Keppie, J. D.), pp. 281–314. Universidad National Autónoma de México, Instituto de Geología, Publication Especial 1.Google Scholar
Kobayashi, T. 1931. Studies of the stratigraphy and palaeontology of the Cambro-Ordovician formations of Hua-Lien-Chai and Nui-Hsin-tai, south Manchuria. Japanese Journal of Geology and Geography 8, 131–89.Google Scholar
Landing, E. 1983. Highgate Gorge: Upper Cambrian and Lower Ordovician continental slope deposition and biostratigraphy, northwestern Vermont. Journal of Paleontology 57, 1149–87.Google Scholar
Landing, E. 1993. Cambrian–Ordovician boundary in the Taconic allochthon, eastern New York, and its interregional correlation. Journal of Paleontology 67, 1–19.Google Scholar
Landing, E. 1995. Upper Placentian–Branchian Series of mainland Nova Scotia (middle–upper Lower Cambrian): faunas, paleoenvironments, and stratigraphic revision. Journal of Paleontology 69, 475–95.Google Scholar
Landing, E. 1996. Avalon – Insular continent by the latest Precambrian. In Avalonian and related peri-Gondwanan terranes of the circum-North Atlantic (eds Nance, R. D. & Thompson, M.), pp. 27–64. Geological Society of America, Special Paper no. 304.Google Scholar
Landing, E. 2005. Early Paleozoic Avalon–Gondwana unity: an obituary – response to “Palaeontological evidence bearing on global Ordovician–Silurian continental reconstructions” by R. A. Fortey and L. R. M. Cocks. Earth-Science Reviews 69, 169–75.Google Scholar
Landing, E., Barnes, C. R. & Stevens, R. K. 1986. Tempo of earliest Ordovician graptolite faunal succession: conodont-based correlations from the Tremadocian of Quebec. Canadian Journal of Earth Sciences 22, 1928–49.Google Scholar
Landing, E. & Bartowski, K. E. 1996. Oldest shelly fossils from the Taconic allochthon and late Early Cambrian sea-levels in eastern Laurentia. Journal of Paleontology 70, 741–61.Google Scholar
Landing, E., Benus, A. P. & Whitney, P. W. 1992. Early and early Middle Ordovician continental slope deposition: shale cycles and sandstones in the Quebec Reentrant and New York Promontory region. New York State Museum Bulletin 474, 40 pp.Google Scholar
Landing, E., Bowring, S. A., Davidek, K., Rushton, A. W. A., Fortey, R. A. & Wimbledon, W. A. P. 2000. Cambrian–Ordovician boundary age and duration of the lowest Ordovician Tremadoc Series based on U–Pb zircon dates from Avalonian Wales. Geological Magazine 137, 485–94.Google Scholar
Landing, E., Geyer, G. & Bartowski, K. E. 2002. Latest Early Cambrian small shelly fossils, trilobites, and Hatch Hill dysaerobic interval on the east Laurentian continental slope. Journal of Paleontology 76, 285–303.Google Scholar
Landing, E., Geyer, G. & Heldmaier, W. 2006. Distinguishing eustatic and epeirogenic controls on Lower–Middle Cambrian boundary successions in West Gondwana (Morocco and Iberia). Sedimentology 54, 899–918.Google Scholar
Landing, E., Ludvigsen, R. & von Bitter, P. H. 1980. Upper Cambrian–Lower Ordovician conodont biostratigraphy and biofacies, District of Mackenzie. Royal Ontario Museum Life Sciences Contributions 126, 44 pp.Google Scholar
Landing, E., Taylor, M. E. & Erdtmann, B.-D. 1978. Correlation of the Cambrian–Ordovician boundary between the Acado-Baltic and North American faunal provinces. Geology 6, 75–8.Google Scholar
Landing, E. & Westrop, S. R. 2006. Early Ordovician faunas, stratigraphy, and sea-level history of the middle Beekmantown Group, northeastern New York. Journal of Paleontology 80, 958–80.Google Scholar
Landing, E., Westrop, S. R. & Knox, L. 1996. Conodonts, stratigraphy, and relative sea-level changes of the Tribes Hill Formation (Lower Ordovician), east-central New York. Journal of Paleontology 70, 652–76.Google Scholar
Landing, E., Westrop, S. R. & van Aller Hernick, L. 2003. Uppermost Cambrian–Lower Ordovician faunas and Laurentian platform sequence stratigraphy, eastern New York and Vermont. Journal of Paleontology 77, 78–98.Google Scholar
Lindström, M. 1955. Conodonts from the lowermost Ordovician strata of south-central Sweden. Geologiska Föreningens i Stockholm Förhandlingar 76, 517–604.Google Scholar
Lindström, M. 1971. Lower Ordovician conodonts of Europe. In Symposium on conodont biostratigraphy (eds Sweet, W. C. & Bergström, S. M.), pp. 21–61. Geological Society of America, Memoir no. 127.Google Scholar
Löfgren, A. 1978. Arenigian and Llanvirnian conodonts from Jämtland, northern Sweden. Fossils and Strata 13, 129 pp.Google Scholar
Löfgren, A. 1993. Conodonts from the Lower Ordovician at Hunneberg, south-central Sweden. Geological Magazine 130, 215–32.Google Scholar
Löfgren, A. 1997. Conodont faunas from the upper Tremadoc at Brattefors, south-central Sweden, and reconstruction of the Paltodus apparatus. GFF 119, 257–66.Google Scholar
Löfgren, A. 1999. A septimembrate apparatus model for the Ordovician conodont genus Cornuodus Fåhraeus, 1966. Bolletino della Società Paleontologica Italiana 37, 175–86.Google Scholar
Löfgren, A., Repetski, J. E. & Ethington, R. L. 1999. Some trans-Iapetus conodont connections in the Tremadocian. Bolletino della Società Paleontologica Italiana 37, 159–73.Google Scholar
Lu, Y., Lin, H., Han, N., Li, L. & Ju, T. 1984. On the Cambrian–Ordovician boundary in the Jiangshan-Changshan area, western Zhejiang. In Stratigraphy and Paleontology of Systemic Boundaries in China. Cambrian–Ordovician Boundary, vol. 1 (compilers Nanjing Institute of Paleontology, Academica Sinica), pp. 285–408. Anhui Science and Technology Publishing House.Google Scholar
Ludvigsen, R. 1982. Upper Cambrian and Lower Ordovician trilobite biostratigraphy, District of Mackenzie. Royal Ontario Museum Publications in Life Sciences 134, 188 pp.Google Scholar
Miller, J. F. 1969. Conodont faunas and biostratigraphy of the Upper Cambrian and lowest Ordovician, House Range, Utah. Journal of Paleontology 43, 413–39.Google Scholar
Miller, J. F. 1980. Taxonomic revisions of some Upper Cambrian and lowest Ordovician conodonts with comments on their evolution. University of Kansas Paleontological Institute Paper 99, 39 pp.Google Scholar
Miller, J. F. 1984. Cambrian and earliest Ordovician conodont evolution, biofacies and provincialism. In Conodont biofacies and provincialism (ed. Clark, D. L.), pp. 43–68. Geological Society of America, Special Paper no. 196.Google Scholar
Miller, J. F. 1988. Conodonts as biostratigraphic tools for redefinition and correlation of the Cambrian–Ordovician boundary. Geological Magazine 125, 349–62.Google Scholar
Miller, J. F., Evans, K. R., Loch, J. D., Ethington, R. L., Stitt, J. H., Holmer, L. & Popov, L. E. 2003. Stratigraphy of the Sauk II interval (Cambrian–Ordovician) in the Ibex area, western Millard County, Utah, and central Texas. Brigham Young University Geology Studies 47, 23–118.Google Scholar
Mound, M. C. 1965. Two new conodont genera from the Joins Formation (lower Middle Ordovician) of Oklahoma. Biological Society of Washington Proceedings 78, 193–200.Google Scholar
Müller, K. J. 1981. Micromorphology of elements. In Treatise on Invertebrate Paleontology, Part W, Miscellanea, Supplement 2, Conodonta (ed. Robison, R. A.), pp. W20–41. Geological Society of America and University of Kansas Press, Lawrence.Google Scholar
Müller, K. J. & Hinz, I. 1991. Upper Cambrian conodonts from Sweden. Fossils and Strata 28, 153 pp.Google Scholar
Murphy, J. B., Keppie, J. D., Braid, J. F. & Nance, R. D. 2005. Geochemistry of the Tremadocian Tiñu Formation (southern Mexico): provenance in the underlying ∼1 Ga Oaxacan Complex on the southern margin of the Rheic Ocean. International Geology Review 47, 887–900.Google Scholar
Myrow, P. M. 1992. Bypass-zone tempestite facies model and proximality trends for an ancient muddy shoreline and shelf. Journal of Sedimentary Petrology 62, 99–115.Google Scholar
Nikolaisen, F. & Henningsmoen, G. 1985. Upper Cambrian and lower Tremadoc olenid trilobites from the Digermul peninsula, Finnmark, northern Norway. Norges Geologisk Undersögelese Bulletin 400, 1–49.Google Scholar
Nicholson, H. A. 1872. Monograph of the British Graptolitidae. London: Blackwood & Sons, 133 pp.Google Scholar
Nicoll, R. S. 1990. The genus Cordylodus and a latest Cambrian–earliest Ordovician conodont biostratigraphy. BMR Journal of Australian Geology & Geophysics 11, 529–58.Google Scholar
Nicoll, R. S. 1991. Differentiation of Late Cambrian–Early Ordovician species of Cordylodus with biapical basal cavities. BMR Journal of Australian Geology & Geophysics 12, 223–44.Google Scholar
Nielsen, A. T. 2004. Ordovician sea level changes: a Baltoscandian perspective. In The Great Ordovician Biodiversification Event (eds Webby, B. D., Paris, F., Droser, M. L. & Percival, I. G.), pp. 84–93. New York: Columbia University Press.Google Scholar
Nogami, Y. 1967. Kambrische Conodonten von China, Teil 2. Memoirs of the College of Science, University of Kyoto, Series B 33, 211–19.Google Scholar
North American Commission On Stratigraphic Nomenclature. 1983. North American Stratigraphic Code. American Association of Petroleum Geologists Bulletin 67, 841–75.Google Scholar
Nowlan, G. S. 1985. Late Cambrian and Early Ordovician conodonts from the Franklinian miogeosyncline, Canadian Arctic Islands. Journal of Paleontology 59, 96–122.Google Scholar
Pander, C. H. 1856. Monographie der fossilen Fische des silurischen Systems der russisch–baltischen Gouvernments. St Petersburg: Akademie der Wissenschaft, 91 pp.Google Scholar
Pantoja-Alor, J. 1970. Rocas sedimentarias paleozoicas de la region Centro-Septrional de Oaxaca. In Libro-Guia de la Excursion Mexico – Oaxaca (eds Segura, L.R. & Rodriguez-Torres, R.). Sociedad Geologica Mexicana, Mexico City, 173 pp.Google Scholar
Pantoja-Alor, J. & Robison, R. 1967. Paleozoic sedimentary rocks in Oaxaca, Mexico. Science 157, 1033–5.Google Scholar
Peng, S. 1984. Cambrian–Ordovician boundary in the Cili-Yaoyuan border area, north-western Hunan with descriptions of the trilobites. In Stratigraphy and Paleontology of Systemic Boundaries in China. Cambrian–Ordovician Boundary 1 (compilers, Nanjing Institute of Paleontology, Academica Sinica), pp. 285–408. Anhui Science and Technology Publishing House.Google Scholar
Peng, S. 1990 a. Tremadoc stratigraphy and trilobite faunas of northwestern Hunan. 1. Trilobites from the Nantsinkwan Formation of the Yangtze Platform. Beringeria 2, 3–53.Google Scholar
Peng, S. 1990 b. Tremadoc stratigraphy and trilobite faunas of northwestern Hunan. 2. Trilobites from the Panjiazui Formation and the Madaoyu Formation in the Jiangnan Slope Belt. Beringeria 2, 55–171.Google Scholar
Qian, Y. 1986. Trilobites. In Aspects of Cambrian–Ordovician Boundary in Dayangcha (ed. Chen, J.), pp. 255–313. Beijing: China Prospect Publishing House.Google Scholar
Repetski, J. E. 1982. Conodonts from El Paso Group (Lower Ordovician) of westernmost Texas and southern New Mexico. New Mexico Bureau of Mines & Mineral Resources Memoir 40, 121 pp.Google Scholar
Robison, R. & Pantoja-Alor, J. 1968. Tremadocian trilobites from the Nochixtlan region, Oaxaca, Mexico. Journal of Paleontology 42, 767–800.Google Scholar
Ross, C. A. & Ross, J. R. P. 1995. North American Ordovician depositional sequences and correlations. In Ordovician Odyssey: Short Papers for the Seventh International Symposium on the Ordovician System (eds Cooper, J. D., Droser, M. L. & Finney, S. C.), pp. 309–13. Society for Economic Paleontology and Mineralogy, Pacific Section, Fullerton, CA.Google Scholar
Ross, R. J., Hintze, L. F., Ethington, R. L., Miller, J. F., Taylor, M. E. & Repetski, J. E. 1997. The Ibexian, lowermost series in the North American Ordovician. In Early Paleozoic biochronology of the Great Basin, western United States (ed. Taylor, M. E.), pp. 1–50. U.S. Geological Survey Professional Paper 1579-A.Google Scholar
Ruiz, J., Tosdal, R. M., Restrepo, P. A. & Murillo-Muñetón, G. 1999. Pb isotope evidence for Columbia–southern México connections in the Proterozoic. In Laurentia–Gondwana connections before Pangaea (eds Ramos, V. A. & Keppie, J. D.), pp. 183–97. Geological Society of America, Special Paper no. 336.Google Scholar
Rushton, A. W. A. 1982. The biostratigraphy and correlation of the Merioneth–Tremadoc Series boundary in North Wales. In The Cambrian–Ordovician boundary: sections, fossil distributions, and correlations (eds Bassett, M. G. & Dean, W. T.), pp. 41–59. National Museum of Wales, Geological Series 3.Google Scholar
Sageman, B. B., Wignall, P. B. & Kauffman, E. G. 1991. Biofacies models for oxygen-deficient facies in epicontinental seas: tool for paleoenvironmental analysis. In Cycles and Environments in Stratigraphy (eds Einsele, G., Ricken, W. & Seilacher, A.), pp. 542–64. Berlin: Springer-Verlag.Google Scholar
Schovsbo, N. H. 2001. Why barren intervals? A taphonomic case study of the Scandinavian Alum Shale and its faunas. Lethaia 34, 271–85.Google Scholar
Scotese, C. R. & McKerrow, W. S. 1990. Revised world maps and introduction. Geological Society of London Memoir 12, 1–21.Google Scholar
Sedlock, R. L., Ortega-Gutiérrez, F. & Speed, R. C. 1993. Tectonostratigraphic terranes and tectonic evolution of Mexico. Geological Society of America Special Paper 278, 153 pp.Google Scholar
Sergeeva, S. P. 1964. Some new conodonts from Ordovician strata in the Leningrad region. Paleontology Suborny 1974, 79–84 (in Russian).Google Scholar
Shergold, J. H. 1972. Late Upper Cambrian trilobites from the Burke River structural belt, western Queensland, Australia. Australian Department of Minerals and Energy, Bureau of Mineral Resources, Geology and Geophysics Bulletin 112, 127 pp.Google Scholar
Shergold, J. H. 1975. Late Cambrian and Early Ordovician trilobites from the Gola Beds, western Queensland. Australian Department of Minerals and Energy, Bureau of Mineral Resources, Geology and Geophysics Bulletin 153, 221 pp.Google Scholar
Shergold, J. H. 1988. Review of trilobite biofacies distributions at the Cambrian–Ordovician boundary. Geological Magazine 125, 363–80.Google Scholar
Shergold, J. H. 1991. Late Cambrian and Early Ordovician trilobite faunas of the Pacoota Sandstone, Amadeus Basin, central Australia. Bureau of Mineral Resources Bulletin 237, 15–75.Google Scholar
Sour Tovar, F. 1990. Comunidades Cambrico–Ordovicicas de la Formation Tiñu, en el area de Santiago Ixtaltepec, Oaxaca. Implicaciones paleoambientales y paleogeographicas. Revista de la Societa Mexicana Paleontologica 3, 7–22.Google Scholar
Sour, F. & Buitrón, B. E. 1987. Los graptolitos del Tremadociano de Ixtaltepec, Oaxaca, consideraciones sobre el limite Cambrico–Ordovicico en la region. Revista de la Societa Mexicana Paleontologica 1, 380–95.Google Scholar
Szaniawski, H. 1980. Conodonts from the Tremadocian Chalcedony Beds, Holy Cross Mountains (Poland). Acta Palaeontologica Polonica 25, 101–21.Google Scholar
Szaniawski, H. & Bengtson, S. 1998. Late Cambrian euconodonts from Sweden. Palaeontologica Polonica 58, 7–29.Google Scholar
Taylor, M. E 1977. Late Cambrian of western North America: trilobite biofacies, environmental significance, and biostratigraphic implications. In Concepts and Methods in Biostratigraphy (eds Kauffman, E. G. & Hazel, J. E.), pp. 397–425. Stroudsburg, PA: Dowden, Hutchison and Ross.Google Scholar
Van Wamel, W. A. 1974. Conodont biostratigraphy of the Upper Cambrian and Lower Ordovician of north-western Öland, south-eastern Sweden. Utrecht Micropaleontological Bulletins 10, 126 pp.Google Scholar
Viira, V. 1970. Conodonts of the Varangu Member (Estonian upper Tremadoc). Eesti NSV Teaduste Akadeemia, Keemia-Geoloogia 19, 224–33 (in Estonian).Google Scholar
Viira, V. 1974. Konodonty ordovika pribaltiki. Tallinn: ‘Valgus’, 142 pp.Google Scholar
Westrop, S. R. & Adrain, J. M. 1998. Trilobite alpha diversity and the reorganization of Ordovician marine benthic communities. Paleobiology 24, 1–16.Google Scholar
Whittington, H. B. 1966. Phylogeny and distribution of Ordovician trilobites. Journal of Paleontology 40, 696–737.Google Scholar
Wolfart, R. 1970. Fauna, Stratigraphie und Palägeographie des Ordoviziums in Afghanistan. Beiheft zum Geologischen Jahrbuch 89, 169 pp.Google Scholar
Yochelson, E. L. 1968. Tremadocian mollusks from the Nochixtlán region, Oaxaca, Mexico. Journal of Paleontology 42, 801–3.Google Scholar
Zeballo, F. J. & Tortello, M. F. 2005. Trilobites del Cámbrico tardío-Ordovícico temprano del áreo de Alfarcito, Tilcara, Cordillera Oriental de Jujuy, Argentina. Ameghiniana, 42, 127–42.Google Scholar