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Acritarchs from the Hanford Brook Formation, New Brunswick, Canada: new biochronological constraints on the Protolenus elegans Zone and the Cambrian Series 2–3 transition

Published online by Cambridge University Press:  27 April 2016

TEODORO PALACIOS ,
SÖREN JENSEN ,
SANDRA M. BARR ,
CHRIS E. WHITE  and
RANDALL F. MILLER
TEODORO PALACIOS*
Affiliation:
Área de Paleontología, Facultad de Ciencias, University of Extremadura, 06006 Badajoz, Spain
SÖREN JENSEN
Affiliation:
Área de Paleontología, Facultad de Ciencias, University of Extremadura, 06006 Badajoz, Spain
SANDRA M. BARR
Affiliation:
Department of Earth & Environmental Science, Acadia University, Wolfville, NS, B4P 2R6, Canada
CHRIS E. WHITE
Affiliation:
Nova Scotia Department of Natural Resources, Halifax, NS, B3J 2T9, Canada
RANDALL F. MILLER
Affiliation:
New Brunswick Museum, 277 Douglas Avenue, Saint John, New Brunswick, E2K 1E5, Canada
*
†Author for correspondence: [email protected]
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Abstract

Diverse and well-preserved acritarchs are reported from the type section of the Cambrian Hanford Brook Formation at Hanford Brook, southern New Brunswick. This section fills an important gap in acritarch studies by providing the first detailed picture of changing acritarch associations close to the traditional lower–middle Cambrian boundary in Avalonia. Acritarchs from the St Martins Member, at the base of the succession, include Skiagia ciliosa, Heliosphaeridium notatum, H. longum and Liepaina plana and suggest attribution to Cambrian Stage 4. Acritarchs from the Somerset Street Member, in the middle of the formation, include Eliasum llaniscum and Comasphaeridium silesiense. This information adds new biochronological context to an ash bed in the Somerset Street Member previously dated as c. 510 Ma or 508 Ma, and to the endemic trilobites from the same member, including Protolenus elegans. It also places absolute ages on the basal range of stratigraphically important acritarchs. Both the acritarch assemblage and the radiometric age are consistent with a position very close to the traditional lower–middle Cambrian transition and likely within Cambrian Stage 5. Acritarchs from the Long Island Member, at the top of the succession, include additional taxa demonstrating assignment to Cambrian Stage 5. Both the Somerset Street and Long Island members probably correlate with the Morocconus notabilis Zone. The new acritarch species Retisphaeridium striatum Palacios is described. New data are presented on acritarchs from the upper part of the Hell's Mouth Formation, Wales, and correlation proposed with the Long Island Member.

Keywords

New BrunswickWalesacritarchsmiddle CambrianCambrian Series 3
Type
Original Articles
Information
Geological Magazine , Volume 154 , Issue 3 , May 2017 , pp. 571 - 590
Copyright
Copyright © Cambridge University Press 2016 

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References

Bassett, M. F., Owens, R. M. & Rushton, A. W. A. 1976. Lower Cambrian fossils from the Hell's Mouth Grits, St Tudwal's Peninsula, North Wales. Journal of the Geological Society, London 132, 623–44.CrossRefGoogle Scholar
Bowring, S. A. & Schmitz, M. D. 2003. High-precision U–Pb zircon geochronology and the stratigraphic record. In Zircon: Experiments, Isotopes, and Trace Elemental Investigation (eds Hanchar, J. M. & Hoskin, P. W. O.), pp. 305–26. Reviews in Mineralogy and Geochemistry 53.Google Scholar
Cobbold, E. S. 1910. On some small trilobites from the Cambrian rocks of Comley Shropshire. Quarterly Journal of the Geological Society of London 66, 19–51.CrossRefGoogle Scholar
Cobbold, E. S. 1921. The Cambrian horizons of Comley (Shropshire) and their brachiopoda, pteropoda, gasteropoda etc. Quarterly Journal of the Geological Society of London 76, 325–86.CrossRefGoogle Scholar
Cowie, J. W., Rushton, A. W. A. & Stubblefield, C. J. 1972. A correlation of Cambrian rocks in the British Isles. Geological Society Special Report 2, 1–42.Google Scholar
Cramer, F. H. & Díez, M. del C. R. 1972. Acritarchs from the upper Middle Cambrian Oville Formation of León, northwestern Spain. Revista Española de Micropaleontología, número extraordinario 30, Aniversario E. N. Adaro, 39–50.Google Scholar
Dean, W. T., Martin, F., Monod, O., Gunay, Y., Kozlu, H. & Bozdogan, N. 1997. Precambrian? and Cambrian stratigraphy of the Penbegli-Tut inlier, southeastern Turkey. Geological Magazine 134, 37–53.CrossRefGoogle Scholar
Dean, W. T. & Özgul, N. 1994. Cambrian rocks and faunas, Hudai area, Taurus Mountains, southwestern Turkey. Bulletin de l'Institut royal des Sciences naturelles de Belgique, Sciences de la Terre 64, 5–20.Google Scholar
Devaere, L. Clausen, S. & Álvaro, J. J. (eds) 2014. Stratigraphic Overview of the Ediacaran and Cambrian from the Anti-Atlas, Morocco. University Lille 1.Google Scholar
Downie, C. 1982. Lower Cambrian acritarchs from Scotland, Norway, Greenland and Canada. Transactions of the Royal Society of Edinburgh: Earth Sciences 72, 257–85.CrossRefGoogle Scholar
Downie, C. 1963. ‘Hystrichospheres’ (acritarchs) and spores of the Wenlock Shales (Silurian) of Wenlock, England. Palaeontology 6, 625–52.Google Scholar
Elicki, O. & Geyer, G. 2013. The Cambrian trilobites of Jordan – taxonomy, systematics, and stratigraphic significance. Acta Geologica Polonica 63, 1–56.CrossRefGoogle Scholar
Eklund, K. 1990. Lower Cambrian acritarch stratigraphy of the Bårstad 2 core, Östergötland, Sweden. Geologiska Föreningens i Stockholm Förhandlingar 112, 19–44.CrossRefGoogle Scholar
Evitt, W. R. 1963. A discussion and proposals concerning fossil dinoflagellates, hystrichospheres, and acritarchs I. Proceedings of the National Academy of Sciences of the United States of America 49, 158–64.CrossRefGoogle Scholar
Fletcher, T. P. 2003. Ovatoryctocara granulata: the key to a global Cambrian stage boundary and the correlation of the olenellid, redlichiid and paradoxidid realms. Special Papers in Palaeontology 70, 73–102.Google Scholar
Fletcher, T. P. 2006. Bedrock Geology of the Cape St. Mary's Peninsula, Southwest Avalon Peninsula, Newfoundland (includes parts of NTS map sheets 1M/1, 1N/4, 1L/16 and 1K/13). St. John's: Government of Newfoundland and Labrador, Geological Survey, Department of Natural Resources, Report 06-02, 117 pp.Google Scholar
Fombella, M. A. 1977. Acritarcos de edad Cámbrico medio-inferior de la Provincia de León, España. Revista Española de Micropaleontología 9, 115–24Google Scholar
Geyer, G. 1990 a. Revised Lower to lower Middle Cambrian biostratigraphy of Morocco. Newsletters on Stratigraphy 22, 53–70.CrossRefGoogle Scholar
Geyer, G. 1990 b. Die Marokkanischen Ellipsocephalidae (Trilobita: Redlichida). Beringeria 3, 1–363.Google Scholar
Geyer, G. 2015. Exotic trilobites from the Lower–Middle Cambrian boundary interval in Morocco and their bearing on the Cambrian Series 3 lower boundary. Paläontologische Zeitschrift 89, 749–81.CrossRefGoogle Scholar
Geyer, G., Buschmann, B. & Elicki, O. 2014. A new lowermost middle Cambrian (Series 3, Stage 5) faunule from Saxony (Germany) and its bearing on the tectonostratigraphic history of the Saxothuringian domain. Paläontologische Zeitschrift 88, 239–52.CrossRefGoogle Scholar
Geyer, G. & Landing, E. 2004. A unified Lower – Middle Cambrian chronostratigraphy for West Gondwana. Acta Geologica Polonica 54, 179–218.Google Scholar
Geyer, G. & Malinky, J. M. 1997. Middle Cambrian fossils from Tizi n'Tichka, the High Atlas, Morocco; Part 1, Introduction and trilobites. Journal of Paleontology 71, 620–37.CrossRefGoogle Scholar
Geyer, G. & Palmer, A. R. 1995. Neltneriidae and Holmiidae (Trilobita) from Morocco and the problem of Early Cambrian intercontinental correlation. Journal of Paleontology 69, 459–74.CrossRefGoogle Scholar
Gozalo, R., Dies Alvarez, M. E., Gamez Vintaned, J. A., Zhuravlev, A. Yu., Bauluz, B., Subias, I., Chirivella Martorell, J. B., Mayoral, E., Gursky, H. J., Andres, J. A. & Liñán, E. 2013. Proposal of a reference section and point for the Cambrian Series 2–3 boundary in the Mediterranean subprovince in Murero (NE Spain) and its intercontinental correlation. Geological Journal 48, 142–55.CrossRefGoogle Scholar
Hagenfeldt, S. E. 1989. Middle Cambrian acritarchs from the Baltic depression and south-central Sweden: taxonomy and biostratigraphy. Stockholm Contributions in Geology 41, 177–250.Google Scholar
Harvey, T. H. P., Williams, M., Condon, D. J., Wilby, P. R., Siveter, D. J., Rushton, A. W. A., Leng, M. J. & Gabbott, S. E. 2011. A refined chronology for the Cambrian succession of southern Britain. Journal of the Geological Society, London 168, 705–16.CrossRefGoogle Scholar
Hayes, A. O. & Howell, B. F. 1937. Geology of Saint John, New Brunswick. Geological Society of America Special Papers no. 5, 146 pp.CrossRefGoogle Scholar
Jachowicz-Zdanowska, M. 2013. Cambrian phytoplankton of the Brunovistulicum – taxonomy and biostratigraphy. Polish Geological Institute Special Papers 28, 1–150.Google Scholar
Landing, E. & Westrop, S. R. 1996. Upper Lower Cambrian depositional sequence in Avalonian New Brunswick. Canadian Journal of Earth Sciences 33, 404–17.CrossRefGoogle Scholar
Landing, E. & Westrop, S. R. 1998. Cambrian faunal sequence and depositional history of Avalonian Newfoundland and New Brunswick: Field Workshop. In Avalon 97 — The Cambrian Standard (eds Landing, E. & Westrop, S. R.), pp. 5–75. New York State Museum Bulletin 492.Google Scholar
Landing, E., Bowring, S. A., Davidek, K. L., Westrop, S. R., Geyer, G. & Heldmaier, W. 1998. Duration of the Early Cambrian: U–Pb ages of volcanic ashes from Avalon and Gondwana. Canadian Journal of Earth Sciences 35, 329–38.CrossRefGoogle Scholar
Lister, T. R. 1970. The Acritarchs and Chitinozoa from the Wenlock and Ludlow Series of the Ludlow and Millichope Areas, Shropshire. Monograph of the Palaeontographical Society no. 124 (issue 528), 100 pp.CrossRefGoogle Scholar
Martin, F. & Dean, W. T. 1983. Late Early Cambrian and Early Middle Cambrian acritarchs from Manuels River, eastern Newfoundland. In Current Research, Part B. Geological Survey of Canada, Paper 83–1B, 353–63.Google Scholar
Martin, F. & Dean, W. T. 1984. Middle Cambrian acritarchs from the Chamberlains Brook and Manuels River Formations at Randon Island, eastern Newfoundland. In Current Research, Part A. Geological Survey of Canada, Paper 84–1A, 429–40.Google Scholar
Martin, F. & Dean, W. T. 1988. Middle and Upper Cambrian acritarch and trilobite Zonation at Manuels River and Random Island, eastern Newfoundland. Geological Survey of Canada Bulletin 381, 1–91.Google Scholar
Matthew, G. F. 1890. On Cambrian organisms in Acadia. Transactions of the Royal Society of Canada 7 (4), 135–62.Google Scholar
Matthew, G. F. 1892. Protolenus—a new genus of Cambrian trilobites. Bulletin of the Natural History Society of New Brunswick 10, 34–7.Google Scholar
Matthew, G. F. 1895. The Protolenus Fauna. Transactions of the New York Academy of Sciences 14, 101–53.CrossRefGoogle Scholar
Moczydłowska, M. 1991. Acritarch biostratigraphy of the Lower Cambrian and Precambrian–Cambrian boundary in southeastern Poland. Fossils and Strata 29, 1–127.CrossRefGoogle Scholar
Moczydłowska, M. 1998.Cambrian acritarchs from Upper Silesia, Poland – biochronology and tectonic implications. Fossils and Strata 46, 1–121.CrossRefGoogle Scholar
Moczydłowska, M. 1999. The Lower–Middle Cambrian boundary recognized by acritarchs in Baltica and at the margin of Gondwana. Bollettino della Societa Paleontologia Italiana 38, 207–25.Google Scholar
Moczydłowska, M. 2011. The Early Cambrian phytoplankton radiation: acritarch evidence from the Lükati Formation, Estonia. Palynology 35, 103–45.CrossRefGoogle Scholar
Moczydłowska, M., Landing, E., Zang, W. & Palacios, T., 2011. Proterozoic phytoplankton and timing of Chlorophyte algae origins. Palaeontology 54, 721–33.CrossRefGoogle Scholar
Moczydłowska, M. & Vidal, G. 1986. Lower Cambrian acritarch zonation in southern Scandinavia and southeastern Poland. Geologiska Föreningens i Stockholm Förhandlingar 108, 201–23.CrossRefGoogle Scholar
Moczydłowska, M. & Vidal, G. 1988. Early Cambrian acritarchs from Scandinavia and Poland. Palynology 12, 1–10.CrossRefGoogle Scholar
Molyneux, S. G., Delabroye, A., Wicander, R. & Servais, T. 2013. Biogeography of early to mid Palaeozoic (Cambrian–Devonian) marine phytoplankton. In Early Palaeozoic Biogeography and Palaeogeography (eds Harper, D. A. T. & Servais, T.), pp. 365–97. Geological Society of London, Memoir no. 38.Google Scholar
Molyneux, S. G., Le Hérissé, A. & Wicander, R. 1996. Paleozoic phytoplankton. In Palynology: Principles and Applications (eds Jansonius, J., & McGregor, D. C.), pp. 493–529. College Station, Texas: American Association of Stratigraphic Palynologists Foundation.Google Scholar
Neltner, L. & Poctey, N. 1950. Quelques faunes géorgiennes du Maroc. Notes et Mémoires du Service Geologique, Maroc 74, 53–83.Google Scholar
Palacios, T. 2008. Middle Cambrian acritarch zones in the Oville Formation and their correlation with trilobite zones in the Cantabrian Mountains, Northern Spain. In Advances in Trilobite Research (eds Rábano, I., Gozalo, R. & Bellido, D. García), pp. 289–95. Cuadernos del Museo Geominero no. 9.Google Scholar
Palacios, T. 2014. A pilot proposal of a Middle Cambrian (Series 3) acritarch biozonation in northwestern Gondwana. In Stratigraphic Overview of the Ediacaran and Cambrian from the Anti-Atlas, Morocco (eds Devaere, L., Clausen, S. & Álvaro, J. J.), pp. 27–8. University Lille 1.Google Scholar
Palacios, T. 2015. Acritarch assemblages from the Oville and Barrios Formations, northern Spain: a pilot proposal of a middle Cambrian (Series 3) acritarch biozonation in northwestern Gondwana. Review of Palaeobotany and Palynology 219, 71–105.CrossRefGoogle Scholar
Palacios, T., Jensen, S., Apalategui, O. 2006. Biostratigrafía de acritarcos en el Cámbrico Inferior y Medio del margen septentrional de Gondwana (Área de Zafra, Suroeste de la Península Ibérica). In 22 Jornadas de la Sociedad Española de Paleontología, Libro de Resúmenes (ed. Fernández-Martínez, E.), pp. 156–61.Google Scholar
Palacios, T., Jensen, S., White, C. E. & Barr, S. M. 2012. Cambrian acritarchs from the Bourinot belt, Cape Breton Island, Nova Scotia: age and stratigraphic implications. Canadian Journal of Earth Sciences 49, 289–307.CrossRefGoogle Scholar
Palacios, T. & Moczydłowska, M. 1998. Acritarch biostratigraphy of the Lower–Middle Cambrian boundary in the Iberian Chains, province of Soria, northeastern Spain. Revista Española de Paleontología, Numero Extraordinario, Homenaje al Prof. Gonzalo Vidal, 65–82.Google Scholar
Peng, S., Babcock, L. E. & Cooper, R. A. 2012. The Cambrian. In The Geologic Time Scale 2012 (eds Gradstein, F. M., Ogg, J. G., Schmitz, M. & Ogg, G.), pp. 437–88. Amsterdam: Elsevier.CrossRefGoogle Scholar
Potter, T. L. 1974. British Cambrian acritarchs – a preliminary report. Review of Palaeobotany and Palynology 18, 61–2.CrossRefGoogle Scholar
Richter, R. & Richter, E. 1941. Die Fauna des Unter-Kambriums von Cala in Andalusien. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 455, 1–90.Google Scholar
Rudavskaya, V. A. 1973. Akritarkhi pogranichnikh otlozhenij rifeya i kembriya yuga vostochnoj Sibiri. In Mikrofossilii Drevnejshikh Otlozhenij (eds Vozzhennikova, T. F. & Timofeev, B. V.), pp. 17–21. Moskow: Nauka.Google Scholar
Rushton, A. W. A. 1974. The Cambrian of Wales and England. In Cambrian of the British Isles, Norden, and Spitsbergen (ed. Holland, C. H.), pp. 43–121. London: Wiley.Google Scholar
Rushton, A. W. A. & Molyneux, S. G. 2011. Welsh Basin. In A Revised Correlation of the Cambrian Rocks in the British Isles (eds Rushton, A. W. A, Brück, P. M., Molyneux, S. G., Williams, M. & Woodcock, N. H.), pp. 21–7. Geological Society of London, Special Report no. 25.Google Scholar
Sarjeant, W. A. S. & Stancliffe, R. P. W. 1994. The Micrhystridium and Veryhachium complexes (Acritarcha: Acanthomorphitae and Polygonomorphitae): a taxonomic reconsideration. Micropalaeontology 40, 1–77.CrossRefGoogle Scholar
Schmitz, M. D. 2012. Radiometric ages used in GTS 2012. In The Geologic Time Scale 2012 (eds. Gradstein, F. M., Ogg, J. G., Schmitz, M. & Ogg, G.), pp. 1045–77. Amsterdam: Elsevier.CrossRefGoogle Scholar
Schwarzbach, M. 1939. Die oberlausitzer Protolenus-fauna. Weiter funde aus dem schlesischen Kambrium und ihre allgemeine bedeutung. Jahrbuch der Preussischen Geologischen Landes-Anstalt Berlin 59 (for 1938), 769–85.Google Scholar
Sdzuy, K. 1972. Das Kambrium der acadobaltischen Faunenprovinz. Gegenwärtiger Kenntnisstand und Probleme. Zentralblatt für Geologie und Paläontologie, Teil II 1972, 1–91.Google Scholar
Siveter, D. J., Waloszek, D. & Williams, M. 2003. An early Cambrian phosphatocopid crustacean with three-dimensionally preserved soft parts from Shropshire, England. Special Papers in Palaeontology 70, 9–30.Google Scholar
Siveter, D. J. & Williams, M. 1997. Cambrian bradoriid and phosphatocopid arthropods of North America. Special Papers in Palaeontology 57, 1–69.Google Scholar
Stanevich, A. M. 2003. Relics of marine bacterial coenoses from Neoproterozoic Formations of the south margin of Siberian Platform. In Instruments, Methods, and Mission for Astrobiology 6 (eds Hoover, R. B., Rozanov, A. Yu. & Lipps, J. H.), pp. 28–37. Proceedings of SPIE 4939.CrossRefGoogle Scholar
Staplin, F. L., Jansonius, J. & Pocock, S. A. J. 1965. Evaluation of some acritarchous hystrichosphere genera. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 123, 167–201.Google Scholar
Tanoli, S. K. & Pickerill, R. K. 1988. Lithostratigraphy of the Cambrian–Lower Ordovician Saint John Group, southern New Brunswick. Canadian Journal of Earth Sciences 25, 669–90.CrossRefGoogle Scholar
Timofeev, B. V. 1959. Drevnejshaya Flora Pribaltiki. Leningrad: Trudy VNIGRl 129, 320 pp.Google Scholar
Vanguestaine, M. 1978. Criteres palynostratigraphiques conduisant a la reconnaissance d'un pli couche revinien dans le sondage de Grand-Halleux. Annales de la société géologique de Belgique 100, 249–76.Google Scholar
Vanguestaine, M. & van Looy, J. 1983. Acritarches du Cambrien moyen de la Vallee de Tacheddirt (Haut-Atlas, Maroc) dans le cadre d'une nouvelle zonation de Cambrien. Annales de la société géologique de Belgique 106, 69–85.Google Scholar
Vavrdová, M. & Bek, J. 2001. Further palynomorphs of Early Cambrian age from clastic sediments underlying the Moravian Devonian (borehole Nĕmčičky-3). Bulletin of the Czech Geological Survey 76, 113–26.Google Scholar
Vidal, G. 1988. A palynological preparation method. Palynology 12, 215–20.CrossRefGoogle Scholar
Volkova, N. A. 1968. Akritarkhi dokembrijskikh i nizhnekembrijskikh otlozhenij Estonii. In Problematiki Pogranichnykh Sloev Rifeja i Kembriya Russkoj Platformy, Urala i Kazakhstana (Volkova, N. A., Zhuravleva, Z. A., Zabrodin, V. E. & Klinger, B. Sh.), pp. 8–36. Moskow: Nauka.Google Scholar
Volkova, N. A. 1974. Akritarkhi iz pogranichnykh sloev nizhnego-srednego kembriya zapadnoj Latvii. In Biostratigrafiya i Paleontologiya Nizhnego Kembriya Evropy i Srednoj Azii (eds Zhuravleva, I. T. & Rozanov, A. Yu.), pp. 194–8. Moskow: Nauka.Google Scholar
Volkova, N. A., Kirjanov, V. V., Piskun, L.V, Pashkyavichene, L. T. & Jankauskas, T. V. 1979. Rastitel'nye mikrofossilii. In Paleontologiya Verkhnedokembrijskikh i Kembrijskikh Otlozhenij Vostochno-Evropejskoj Platformy (eds Keller, B. M. & Rozanov, A. Yu.), pp. 4–38. Moskow: Nauka.Google Scholar
Volkova, N. A, Kirjanov, V. V, Piskun, L. V., Paskeviciene, L. T. & Jankauskas, T. V. 1983. Plant microfossils. In Upper Precambrian and Cambrian Palaeontology of the East-European Platform (eds Urbanek, A. & Rozanov, A. Yu.), pp. 7–46. Warszawa: Wydawnictwa Geologiczne.Google Scholar
Westrop, S. R. & Landing, E. 2000. Lower Cambrian (Branchian) trilobites and biostratigraphy of the Hanford Brook Formation, southern New Brunswick. Journal of Paleontology 74, 858–78.2.0.CO;2>CrossRefGoogle Scholar
Yang, R. & Yin, L. 2001. Acritarch assemblages from the Early–Middle Cambrian Kaili Formation of east Guizhou province and biostratigraphic implication. Acta Micropalaeontologica Sinica 18, 55–69.Google Scholar
Yin, L., Yang, R., Peng, J. & Kong, F. 2009. New data regarding acritarch biostratigraphy from the Early-Middle Cambrian Kaili Formation in Chuandong, Guizhou Province, China. Progress in Natural Science 19, 107–14.CrossRefGoogle Scholar
Yin, L., Zhao, Y., Yang, R. & Peng, J. 2010. Acritarchs from the Early–Middle Cambrian Kaili Formation in the Wuliu–Zengjiaya section, eastern Guizhou Province, China. Acta Palaeontologica Sinica 49, 164–73.Google Scholar
Young, T., Martin, F., Dean, W. T. & Rushton, A. W. A. 1994. Cambrian stratigraphy of St Tudwal's Peninsula, Gwynedd, northwest Wales. Geological Magazine 131, 335–60.CrossRefGoogle Scholar
Zylinska, A. & Szczepanik, Z. 2009. Trilobite and acritarch assemblages from the Lower – Middle Cambrian boundary interval in the Holy Cross Mountains (Poland). Acta Geologica Polonica 59, 413–58.Google Scholar