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Taxonomy and taphonomy of Cenomanian (Upper Cretaceous) nautilids from Annopol, Poland

Machalski M., Wilmsen M.

Acta Geologica Polonica

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2015

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Vol. 65, no. 4

495--506

EN

A nautilid faunule of seven specimens, comprising Eutrephoceras bouchardianum (d’Orbigny, 1840), Cymatoceras deslongchampsianum (d’Orbigny, 1840), and Cymatoceras tourtiae (Schlüter, 1876) is described from a condensed middle Cenomanian interval at Annopol, Poland. C. tourtiae is recorded for the first time in Poland. The studied material consists of reworked phosphatised internal moulds of phragmocones, which may be of early or middle Cenomanian age, given the stratigraphic range of the associated ammonites. The nautilid moulds vary in inferred mode of infilling, and in intensity of abrasion, bioerosion and mineralisation. The sediment entered the phragmocones in two ways: 1) through punctures in the shell, the result of bioerosion or mechanical damage; 2) through siphonal openings by intracameral currents. In contrast to the fossil moulds from the Albian phosphorites of Annopol, which originated via direct precipitation of apatite around and/or inside fossils, the present nautilid moulds seem to have originated through secondary phosphatisation of the initially calcareous moulds. Diversity of taphonomic signatures in nautilid material from the middle Cenomanian interval at Annopol is compatible with the complex, multievent depositional scenario proposed for this level.

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Geology and taphonomy of the base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil

Chahud A., Petri S.

Acta Geologica Polonica

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2015

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Vol. 65, no. 3

379--387

EN

The taphonomy of Early Permian vertebrates from a sandy facies at the base of the Taquaral Member, Irati Formation, was surveyed in order to acquire data for the interpretation of the sedimentary processes and paleoenvironment of deposition. Six outcrops from the Rio Claro municipality and surrounding areas, from the Brazilian State of São Paulo, were investigated. The vertebrate groups are Chondrichthyes (Xenacanthiformes, Ctenacanthiformes and Petalodontiformes), Osteichthyes (Actinopterygii and Sarcopterygii) and Tetrapodomorpha. They occur as loose teeth, scales, spines and bone remains. The sandy facies is characterized by fining upward deposition. The coarser sandstone immediately above the underlying Tatuí Formation is rich in Chondrichthyes. However, the fine sandstone above, immediately beneath the silty shale facies, is devoid of Chondrichthyes, though Osteichthyes scales, teeth and bones were present. The taphonomy is important for inferring sedimentary processes and then the paleoenvironments. The poor sorting of the sandstone and the presence of fossils that are mostly abraded or worn are indicative of a high energy environment. In contrast, the presence of fossils in a good state of preservation, some without abrasion and breakages are indicative of only limited transport. Differences of fossil spatial density, numbers of specimens and taxa may be explained by the dynamics of deposition, from details of the palaeoenvironment can be obtained.

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The usefulness of a taphonomic approach for studies of Pleistocene mammals

Pawłowska Kamilla

Geologos

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2010

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Vol. 16, No. 3

183--189

EN

The potential usefulness of taphonomical research for studies of Pleistocene mammal remains is detailed. The required taphonomical research involves two stages. The first one is the biostratinomical stage, which concerns the time between the death of the organism and its burial; for this time-span, the spatial distribution of the remnants is analysed, as well as the weathering marks, the activity of predators (i.e. gnawing and digestion), the influence of temperature, intentional human activity, rodent marks (i.e. gnawing), and trampling. in the second one is the diagenetic stage, which deals with the time-span from the burial of the remnants to their discovery; for this time-span, the influence of physical and chemical processes (including diagenetic alterations of the deposit, the influence of water, and plant-root marks) are considered. The application of taphonomical analysis provides the possibility of reconstructing the environmental conditions under which the skeleton or bone complex was preserved, as well as the depositional history of the bones (postconsumption remnants, flood remains, accumulation of bones by predators). This opens new possibilities for the study of Pleistocene bones in Poland.

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Unusual preservation of Ophiomorpha in middle Miocene rocks of Wadi Zablah, east Matruh area, northwestern Egypt

Gameil M., Sadek S.

Acta Geologica Polonica

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2010

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Vol. 60, no. 1

39-44

EN

Unusual biogenic structures in the form of hollow burrows are preserved in middle Miocene sandy limestones (calcarenites) exposed in Wadi Zablah, east of the town of Mersa Matruh along the Egyptian Mediterranean coast. This calcarenite unit is about 30 m thick and lies in the middle part of the Marmarica Formation. The burrows commonly are up to 2.5 m long and can reach a length of 3 m in some outcrops. The internal diameter ranges from 1 to 5 cm. In most cases there is a hard cemented zone surrounding the hollow burrows that ranges in thickness from 0.2 to 0.4 cm. In several burrows where the hard cemented zone is preserved, a knobby sculpture is visible on the internal surfaces of the burrows. This is considered to be a negative mold of the pelleted wall of Ophiomorpha. This inverted knobby sculpture is formed by the cemented zone, which permitted the trace fossils. preservation, the original Ophiomorpha wall having been dissolved away during or subsequent to lithification by subsequent weathering processes. The presence of these burrows in association with marine fossils suggests a littoral to very shallow shelf environment.

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Kopalne zygospory glonów Zygnemataceae (Chlorophyta) z osadów górnego miocenu KWB Bełchatów

Worobiec E., Worobiec G.

Przegląd Geologiczny

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2008

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Vol. 56, nr 11

1000-1004

EN

The Zygnemataceae are an extant family of freshwater filamentous green algae which produce acid-resistant zygospores. Palynomorphs of probable zygnematacean affinity occur in sediments of the Carboniferous to Holocene age (van Geel & Grenfell, 1996). These algae reproduce using four types of spores, but only zygospores and probably aplanospores are acid-resistant and can be preserved in the fossil record. The majority of recent species have zygospores of constant form of three types: elliptical (occurring in genera Debarya and Spirogyra), square (occurring in Mougeotia) or circular (occurring in Zygnema). The zygospores normally have a three-layered wall (exospore, mesospore and endospore), but only mesospore contains a decay and acid-resistant substance (most probably algaenans), so usually only this layer is preserved in fossil state, and is of interest to palynologists. The mesospore layer is smooth or ornamented with various sculptures (Kadłubowska, 1972; Grenfell, 1995). The shape and sculpture are very important features for determination of both the recent and fossil species. Two samples from the Bełchatów Lignite Mine were palynologically examined and two types of probable fossil zygnematacean zygospores, differing in shape, were encountered. The following species have been distinguished: Tetraporina sp., Spintetrapidites quadriformis Krutzsch & Pacltová as well as Ovoidites elongatus (Hunger) Krutzsch, and O. ligneolus Potonié ex Krutzsch. The fossil genus Tetraporina is usually related to the recent zygnematacean algae zygospores of Mougeotia genus, fossil Ovoidites is the nearest the recent zygospores of Spirogyra and Sirogonium, while Spintetrapidites is similar to both zygospores of Zygnemataceae and Tetraedron green algae. Species of recent genera Mougeotia and Spirogyra are usually found in shallow, freshwater, oxygen-rich environments such as ponds, lake margins (paludal or low gradient fluvial), ditches and very slowly moving streams (Kadłubowska, 1972). Occurrence of Tetraporina and Ovoidites zygnematacean zygospores in the material studied from Bełchatów points out at presence of water basin(s) during sedimentation time. That confirms the previous geological results that formation of examined sediments took place in the environment of a meandering river (including ox-bow lakes).

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Zespół skamieniałości a biocenoza - reprezentatywność zapisu paleontologicznego

Niedźwiedzki R.

Przegląd Geologiczny

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2002

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Vol. 50, nr 10/1

899-904

PL

Podczas przeobrażania się biocenozy w oryktocenozę największe znaczenie mają czynniki oddziaływujące na nekrocenozę, zwłaszcza rozkład organizmów bezszkieletowych, w rezultacie którego w tafocenozie nie zachowuje się przeciętnie od ok. 70% gatunków (w środowiskach morskich) do ponad 90% gatunków (w środowiskach lądowych) występujących w biocenozie. Wśród zwierząt szkieletowych podstawowymi czynnikami działającymi na etapie nekrocenozy jest dysartykulacja i fizyczne, chemiczne lub biologiczne niszczenie szkieletów. Procesy te działają często selektywnie w zależności od przynależności taksonomicznej, a także od wielkości okazów i niekiedy uniemożliwiają odtworzenie liczebności taksonów. Bardzo istotne jest uśrednianie czasowe, które zachodzi zarówno w obrębie nekrocenozy, jak i tafocenozy. Zjawisko to powoduje nadreprezentację wielu taksonów oraz niemożność obserwowania krótkoterminowych zmian biocenozy. Po utworzeniu się tafocenozy zachodzą dalsze zmiany zespołu skamieniałości, m.in. w wyniku rozpuszczania szkieletów aragonitowych oraz pokryw chitynowych. Dlatego w artykule używam terminu "oryktocenoza" dla zespołów skamieniałości zachowanych do czasów współczesnych.

EN

Most important for post-mortem modification of biocoenosis structure are processes which influenced the necrocoenosis, especially nonpreservation of soft-bodied organisms. This factor alone may eliminate from about 70% species in marine environments to more than 90% species in terrestrial environments. Shelly communities are changed post-mortem mainly by disarticulation and by physical, chemical or biological destruction. These factors are strongly selective and their importance depend on taxonomic position and size of specimens. Such processes can seriously hamper the recognition of abundance of specimens and proportions of taxa. Time-averaging is very important for modification both the necrocoenosis and the taphocoenosis. The consequences of this phenomenon are preservational bias favouring some taxa of the taphocoenosis and the fact, that short-term biologic phenomena are extremely rarely observed in the fossil assemblages. Many kind of taphocoenosis modifications are documented, e.g., dissolution of aragonite shells or chitinous integuments. Therefore, I use the term " orictocoenosis "for assemblages of fossil remains preserved to our times.