New occurrence of rocky-coast facies near Ronov nad Doubravou (Kolín lithofacial development, Bohemian Cretaceous Basin)

 

Pavel Čáp, Radek Vodrážka, Lilian Švábenická, Markéta Chroustová

Geoscience Research Reports 55, 2022, pages 11–18

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Published online: 2022-05-04

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Abstract

A rocky-coast facies in the Bohemian Cretaceous Basin (BCB) are developed mainly in the Kolín lithofacial area at its southern margin. Ronov – the newly described locality – is situated south of Ronov nad Doubravou, on the right bank of the Doubrava river near the St. Kříž church. The outcrop located in a ditch was partially excavated in order to study the character and extent of Cretaceous sediments (Beds No. 1–3; see Figs. 1–3).

Bed 1 is composed of red clay with yellow streaks, representing lateritically weathered crystalline bedrock – likely amphibolites and garnet migmatites (Fig. 2). Overlying bed 2 consists of yellow to gray-green clay; in the lower part, the layer contains fragments of fossils that occur in the overlying layer, and sandy “intraclasts” interpreted as bioturbations. The most conspicuous bed 3 (25 cm in thickness) is represented by calcareous, coarse-grained sandstone to conglomerate with glauconite and abundant fauna (mainly fragmentary; Figs. 4 and 5). This type of rock in the wider area (between Ronov nad Doubravou and Žleby) was reported by Sejček (1982) who described three occurrences as scree or fragments on the surface but has not found any rock outcrops in situ despite excavation work.

The individual layers were sampled for the study of foraminifers, calcareous nannoplankton and macrofauna. Shells of Rhynchostreon suborbiculatum, which are always disarticulated, often fragmented and bioturbated (Entobia exogyrarum), represent the most prominent element of macrofauna. In addition, Rastellum diluvianum and Amphidonte halitoidea, unspecified large colonies of bryozoans, spines of the echinoids Cidaris vesiculosa, complete shells of brachiopods Cyclothyris aff. difformis and tiny teeth of sharks Otodus rarely occur.

Calcareous nannofossils were found only in bed 3. Isolated small, mostly difficult to identify fragments belong to long-range stratigraphic taxa (Fig. 6) and may indicate an interval from the uppermost Cenomanian to the lowermost Turonian. Similar poor nannofossil assemblages are known also in other rocky-coast facies of the BCB.

The refining indicator of stratigraphic classification is thus macrofauna. Similar communities with Rhynchostreon suborbiculatum and echinoderms are known from Upper Cenomanian and Lower Turonian in the area of Heřmanův Městec, Čáslav and especially Kutná Hora. However, brachiopods Cyclothyris aff. difformis and oyster Amphidonte halitoidea recorded from Ronov are typical representatives of Upper Cenomanian “rocky-coast” faunas, whereas typically Lower Turonian elements such as the oyster Exogyra reticulata, Exogyra sigmoidea, or the spines of the Cidaris sorigneti are missing in the studied community.

The study of macrofossil and nannofossil communities shows that the Upper Cretaceous rocks, represented by the calcareous glauconitic sandstones to conglomerates in Ronov locality, are most likely of the Upper Cenomanian age and represent the Korycany Member of the Peruc-Korycany Formation.


 

References

Bolli, H. (1952): Note on the disintegration of indurated rocks. – Micropaleontologist 6, 1, 46–48.

Burnett, J. A. (1998): Upper Cretaceous. In: Bown P. R., ed.: Calcareous nannofossil biostratigraphy, 132–199. – Cambridge Univ. Press. Cambridge.

Drahota, P. (1995): Rhynchostreon suborbiculatum (Lamarck) a jeho výskyt v kolínské oblasti české křídové pánve. – Bohemia cent. 24, 5–16.

Frič, A. (1911): Studie v oboru křídového útvaru v Čechách. Ilustrovaný seznam zkamenělin cenomanních vrstev Korycanských. – Arch. přírodověd. Výzk. Čech 15, 1, 1–101.

Holásek, O. – Fišera, M. – Štěpánek, P. – Klečák, J. – Tíma , V. (1998): Geologická mapa ČR 13-41 Čáslav. – Čes. geol. úst. Praha.

Kennedy, A. E. – Coe, A. L. (2014): Development of the freeze– thaw processing technique for disaggregation of indurated mudrocks and enhanced recovery of calcareous microfossils. – J. Micropalaeont. 33, 2, 193–203.

Novák, F. (1952): Příspěvek k paleozoologickému zhodnocení křídového útvaru u Markovic. – Čas. Nár. Muz., Odd. přírodověd. 121, 149–155.

Počta, P. (= Počta, F.) (1885): Beiträge zur Kenntniss der Spongien der böhmischen Kreideformation. III. Abtheilung: Tetractinellidae, Monactinellidae, Calcispongiae, Ceratospongiae, Nachtrag. – Abh. Kön. Böhm. Gesell. Wiss., Math.-naturwiss. Cl. 2, 1, 1–46.

Sejček, Z. (1982): Nová paleontologická lokalita. Tilia – leták pro ochranu přírody, č. 16 – 4 str. Městské muzeum. Čáslav.

Štědrá, V. – Čáp, P. – Stárková, M. – Vít, J. (2017): Základní geologická mapa České republiky 1 : 25 000, list 13-432 Vilémov. – MS Čes. geol. služba. Praha.

Štěpánek, P. – Fišera, M. – Hrubeš, M. (1997): Geologická mapa ČR 13-43 Golčův Jeníkov. – Čes. geol. úst. Praha.

Thomas, F. C. – Murney, M. G. (1985): Techniques for extraction of foraminifers and ostracodes from sediment samples. – Can. Tech. Rep. Hydrogr. Ocean Sci. 54, 1–24.

Vodrážka, R. (2006): Entobia exogyrarum (Frič, 1883) from the Upper Cretaceous of the Bohemian Cretaceous Basin. – Ichnos 13, 199–201.

Vodrážka, R. – Bubík, M. – Švábenická, L. – Žítt, J. (2013): Late Cretaceous (Upper Cenomanian–Lower Turonian) transgressive deposits near Kutná Hora and Kolín (Central Bohemia, Bohemian Cretaceous Basin). The Micropaleontological Society, Spring Meeting 2013, Excursion Guide. – 28 str. Faculty of Sci., Charles Univ. Prague.

Wentworth, Ch. K. (1922): A Scale of Grade and Class Terms for Clastic Sediments. – J. Geol. 30, 5, 377–392.

Young, J. R. – Bown, P. R . – Lees, J. A., ed. (2018): Nannotax 3 website. – International Nannoplankton Association. Febr. 2018. URL: http://ina.tmsoc.org/Nannotax3.

Zázvorka, V. (1946): Transgrese svrchní křídy v severozápadní části Železných hor. – Věst. Král. Čes. Společ. Nauk, Tř. mat.-přírodověd. 1944, 1–26.

Zázvorka, V. (1956): Hlavonožec Mammites nodosoides (Schlotheim) z české křídy a jeho stratigrafický význam pro stanovení spodního turonu. – Čas. Mineral. Geol. 1, 4, 353–360.

Ziegler, V. (1992): Stratigrafie a vrstevní sled křídových sedimentů v kolínské oblasti české křídové pánve. – Čas. Nár. Muz., Ř. přírodověd., 160, 29–46.

Žák, L. (1946): Příbojová facie křídového moře na žule u Chvaletic a problém transgrese křídy v sz. části Železných hor. – Věst. Stát. geol. Úst. ČSR 21, 377–384.

Žítt, J. – Nekvasilová, O. (1994): Běstvina u Ronova nad Doubravou – pozoruhodný výskyt spodnoturonských fosílií v příbřežních sedimentech České křídové pánve (kolínská litofaciální oblast). – Bohemia cent. 23, 23–30.

Žítt, J. – Nekvasilová, O. – Hradecká, L. (2002): Platidiid brachiopods from the Middle Turonian of the Bohemian Cretaceous Basin (Czech Republic). – Paläont. Z. 76, 251–255.

Žítt, J. – Vodrážka, R. – Hradecká, L. – Svobodová, M. – Šťastný, M. – Švábenická, L. (2015): Depositional and palaeoenvironmental variation of lower Turonian nearshore facies in the Bohemian Cretaceous Basin, Czech Republic. – Cretaceous Res. 56, 293–315.

Žítt, J. – Vodrážka, R. – Hradecká, L. – Svobodová, M. – Zágoršek, K. (2006): Late Cretaceous environments and communities as recorded at Chrtníky (Bohemian Cretaceous Basin, Czech Republic). – Bull. Geosci. 81, 1, 43–79.