Middle and Upper Jurassic bryozoan biota of the southern Poland – their diversity, palaeocology, evolution pattern and biogeography

• Autorzy: Hara U.
• Konferencja: International Congress on the Jurassic System (7 ; 06-18.09.2006 ; Kraków, Poland)
• Języki publikacji: EN

Abstrakty

EN

A few distinctive bryozoan assemblages have been recognized in the Middle and Upper Jurassic sediments of the southern Poland. The Upper Callovian to Lower Oxfordian of the hardground character, epibenthic, bryozoan community at Zalas (the Kraków-Wieluf Upland) is restricted to a few cyclostomes, which are dominated by undeterminated, tubuloporinids of the fan-shaped or discoidal, bereniciform colonies, respectively (Fig. 1: 1-2), as well as to well-known Jurassic Hyporosopora and Microeciella genera. Much rarer are vine-like, uniserial runners of Stomatopora dichotoma Bronn. A moderately rich, the Early Oxfordian bryozoan biota of amielów (NW margin of the Holy Cross Mts.) occurs in the sponge biohermal facies, where the majority of colonies acquire an erect encrusting, massive, fungiform, as well as the branched colony-forms, among which the following taxa have been distinguished: Oncousoecia sp., Radicipora radiciformis (Goldfuss), Idmonea sp., Reptomultisparsa(?) sp., Mecynoecia sp., Ceriocava corymbosa (Lamouroux), Theonoa chlatrata Lamouroux and Apsendesia cristata Lamouroux. The most prolific is Radicipora radiciformis typically present in the high-diversified bryozoan assemblages, amongst marly facies, and is often accompanied by the numerous sclerosponges. The Middle-Upper Oxfordian bryozoan fauna of Ba.tów (NW of the Holy Cross Mts.), which colonizes the soft-bodied substrate, consists entirely of small, delicate, erect colonies and abundant, bereniciform, tubular-shaped zoaria (Fig. 1: 3) of the Hyporosopora baltovensis (see Hara & Taylor 1996). Palaeoecological aspects of the studied bryozoan biotas are related to the nature and relative abundance of the colonial growth forms, as well as to a substrate type, the orientation to substrate and methods of attachment. Evolution of the bryozoan biotas of Poland, during the late Middle and Late Jurassic was undoubtedly connected with the development of the favourable Callovian transgressive mostly sandy limestone facies (Calloviense-Lamberti chrons) and the shelf carbonate facies, which became prevalent in the Early Oxfordian (Cordatum Chron) as an open shelf sponge biohermal facies (amielów bryozoan biota), and replaced later during the Middle-Late Oxfordian (Transversarium-Bifurcatus chrones) by the shallower, soft-bottom coral facies (Ba.tów bryozoan fauna). Taxonomically, the Middle/Upper Oxfordian Jurassic bryozoans at Zalas show the similarities with the palaeogeographically distant Middle Jurassic shallow-water bryozoan fauna of the Carmel Formation (Utah), and the Early Oxfordian amielów bryozoans bear much of resemblance to the Middle Jurassic fauna the Saone-Rhine Basin (France) and the Swabian Basin of Germany. The moderately rich occurrence of the bryozoans in the Middle/Upper and Upper Jurassic sequences of Poland, shows the different pattern of distribution, than the biotas of the northwestern Europe which display the greatest species diversity in the Middle Jurassic (Bathonian). This fact has a great significance for an answer, weather the bryozoans of the southern Poland originated and started to radiate in the Late Jurassic, or this event was mostly connected with a facies migration from west to east. The Middle/Upper and Upper Jurassic bryozoan fauna of Poland has a key biogeographical significance, however, there is still a great patchiness in the global distribution of the Jurassic cyclostomes.

Słowa kluczowe

EN

Jurassic; bryozoans; cyclostomes; diversity; palaeoecology; evolution; biogeography

• Wydawca: Państwowy Instytut Geologiczny - Państwowy Instytut Badawczy
• Czasopismo: Volumina Jurassica
• Rocznik: 2006
• Tom: Vol. 4, no. 1
• Strony: 234--235
• Opis fizyczny: Bibliogr. 1 poz.

Twórcy

autor

Hara U.

• Polish Geological Institute, Rakowiecka 4, PL-00975 Warszawa, Poland,

Bibliografia

• Hara U. and Taylor P. D. 1996. Jurassic bryozoans from Ba.tów (Holy Cross Mts., Poland). Bulletin of the Natural History Museum, 52: 91-102.