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Charakterystyka jurajskich mszywiołów południowej Polski w aspekcie warunków paleooerodowiska i biogeografii

Hara U.

Przegląd Geologiczny

2007

Vol. 55, nr 1

54-54, 60

A few distinctive bryozoan assemblages have been recognized in the Middle and Upper Jurassic sediments of southern Poland. The biota moderately rich in bryozoan taxa are generally restricted to a few cyclostome genera and dominated respectively by tubuloporines among which the majority form a fan-shaped or discoidal [bereniciform], encrusting colonies previously called "Berenieca", a bryozoan ubiquitous in the Jurassic. The Lower and Upper Callovian epifaunal bryozoan community of the vicinity of Cracow at Zalas in the Cracow Upland is represented by well-known Jurassic Stomatopora Bronn, Hyporosopora Canu & Bassler and Microeciella Taylor & Sequeiros, genera, as well as the other undeterminated, numerous bereniciform colonies. In terms of the species richness the most diversified is the Early Oxfordian bryozoan assemblage of the Ćmielów area [NW margin of the Holy Cross Mts], associated with an open shelf biohermal sedimentation, which was replaced later [during the transversarium and bifurcatues zones] by the shallow-water, soft-bottom coral buildups, among which the bryozoans are well-represented and described from Bałtów. The presence of the ?Late Tithonian–Berriasian bryozoan fauna has been documented in the thin-sections of the Stramberk limestones of the Polish Flysch Carpathians. Palaeoecological aspects of the studied bryozoan biotas are related to the nature and relative abundance of the colonial growth forms, the substrate type and other ecological factors. The moderately rich occurrence of the bryozoans in the Late Middle and Upper Jurassic sequences of Poland shows a different pattern of distribution than the biotas of the northwestern Europe which display the greatest species diversity in the Middle Jurassic [Bathonian]. The taxonomical and biogeographical studies of the Jurassic bryozoan biotas of Poland, in spite of the great patchiness in the global distribution of the Jurassic cyclostomes, has a key significance for the evolutionary radiation pattern and may add new data, whether this fauna originated and started to radiate in the Late Middle or the Upper Jurassic, or this event was mostly connected with the facies migration from west to east.

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

Hara U.

Volumina Jurassica

2006

Vol. 4, no. 1

234-235

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.