Stratigraphy, facies and geodynamic settings of Jurassic formations in the Bükk Mountains, North Hungary: its relations with the other areas of the Neotethyan realm.

Jurassic mélange complexes related to the subduction of the Neotethys Ocean occur in the Bükk Mountains, North Hungary. This paper characterizes the sedimentary sequence of basin and slope facies that occur in the southwestern part of the Bükk Mountains, placing special emphasis on the redeposited sedimentary rocks (olistostromes, olistoliths: Mónosbél Group) in order to obtain information on the provenance of the clasts, and the mode and time of their redeposition. The series of formations studied shows a general coarsening-upwards trend. Based on radiolarians and foraminifera, the Mónosbél Group formed in Early to Late Bathonian time. The lower part of the complex is typified by a predominance of pelagic carbonates, shale and radiolarite with andesitic volcaniclastic intercalations. The higher part of the succession is characterized by polymictic olistostromes. Large olistoliths that are predominantly blocks of Bathonian shallow marine limestone (Bükkzsérc Limestone) appear in the upper part of the sequence. Based on the biostratigraphic and sedimentological data, results of analyses of the redeposited clasts and taking into consideration the concepts of the development of the western Neotethys domain, the evolutionary stages of the sedimentary basins were defined. The onset of the compressional stage led to initiation of nappe stacking that led to the formation of polymict olistostromes and then to the redeposition of large blocks derived from out-of-sequence nappes of the former platform foreland

The palaeoecology of two Scottish encrinites: Jurassic crinoid assemblages from the Trotternish Peninsula, Isle of Skye, Scotland

Despite a long history of investigation, articulate crinoids from the Jurassic of Scotland have not received great attention compared to their counterparts in Southern England or continental Europe; this is thought to be largely due to poor preservation. Two examples of ‘local’ encrinites (rocks almost entirely composed of crinoids debris), one from the Pliensbachian and the other from the Aalenian/Bajocian from the Isle of Skye, are shown to consist of columnals of Hispidocrinus cf. schlumbergeri and Balanocrinus donovani respectively. They represent local encrinites that have been deposited parautochthonously; one in a proximal, and the other in a more offshore low energy environment. This demonstrates that even limited encrinite material can not only be assigned systematically, but can also be used to reconstruct the original palaeoenvironments that the crinoids inhabited

Sea surface temperature contributes to marine crocodylomorph evolution

During the Mesozoic and Cenozoic, four distinct crocodylomorph lineages colonized the marine environment. They were conspicuously absent from high latitudes, which in the Mesozoic were occupied by warm-blooded ichthyosaurs and plesiosaurs. Despite a relatively well-constrained stratigraphic distribution, the varying diversities of marine crocodylomorphs are poorly understood, because their extinctions neither coincided with any major biological crises nor with the advent of potential competitors. Here we test the potential link between their evolutionary history in terms of taxic diversity and two abiotic factors, sea level variations and sea surface temperatures (SST). Excluding Metriorhynchoidea, which may have had a peculiar ecology, significant correlations obtained between generic diversity and estimated Tethyan SST suggest that water temperature was a driver of marine crocodylomorph diversity. Being most probably ectothermic reptiles, these lineages colonized the marine realm and diversified during warm periods, then declined or became extinct during cold intervals

An effective palynological preparation procedure using hydrogen peroxide

Most pre-Quaternary palynology samples are currently prepared by demineralization of the sediment/sedimentary rock matrix using hydrochloric and hydrofluoric acids (HCl and HF respectively). If a consistently effective alternative to this procedure can be developed, palynological processing will be made significantly less hazardous to both laboratory personnel, and to the wider environment. Furthermore, most non-acid processing methods are normally quicker and cheaper than matrix dissolution using acid. Some authors have previously used hydrogen peroxide (H2O2) to extract palynomorphs by the physico–chemical disaggregation of the clay fraction. However, H2O2 is a powerful oxidizing agent and hence can potentially destroy sedimentary organic material, including palynomorphs. A new method using hot H2O2, where exposure of the sample material to the H2O2 is minimized, has been developed. Crushed sample material in a suitable vessel is placed on a hot plate for one minute, treated with 15–30% H2O2 for 10 minutes, then the residue is diluted with cold distilled water. Disaggregated sample material tends to float, and is decanted into a large vessel containing distilled water to further dilute the H2O2. If any undisaggregated sample remains, the procedure is repeated several times if necessary. Relatively indurated sedimentary lithotypes normally require several treatments. The reason for this stepwise treatment is that the organic material is not exposed to H2O2 for sustained periods, thereby reducing the possibility of palynomorph damage/degradation due to oxidation. When the sample matrix has been fully disaggregated, the residue can be further processed as appropriate. In this study, eight samples of Carboniferous, Jurassic, Paleogene, and Quaternary age were prepared quantitatively using the new H2O2 method. These were all prepared using 30% H2O2. For comparison, they were also prepared quantitatively using HCl/HF and/or sodium hexametaphosphate [(NaPO3)6]. Quantitative preparations allow the concentration of palynomorphs extracted to be determined, and therefore the effectiveness of the techniques used can be compared objectively. The palynomorph residues derived from these three techniques varied markedly. The H2O2 method does not consistently disaggregate all the sample material, particularly the older and more indurated lithotypes. Some evidence of oxidation effects was observed. Two samples of Mississippian mudstone from the U.S.A. were prepared using H2O2 and (NaPO3)6. Both methods produced abundant miospores, however the H2O2 procedure yielded far higher palynomorph concentrations than the (NaPO3)6 technique. Minor degradation of palynomorphs in the H2O2 preparation was noted. The H2O2 and HCl/HF methods were compared directly on a palynomorph-rich sample of Upper Carboniferous mudstone from offshore Scotland. Both preparations produced abundant miospores. The HCl/HF method had significantly higher recovery levels than the H2O2 procedure. It appears that the H2O2 method simultaneously macerates the matrix, and oxidizes any amorphous organic material (AOM) present. In this sample, the HCl/HF residue was relatively rich in AOM. By contrast, the H2O2 preparation is virtually clear of this phytoclast type, which partially obscures palynomorphs. Two samples of the Middle Jurassic Grantham Formation of eastern England were processed using H2O2 and HCl/HF. The two methods produced abundant palynofloras of similar palynomorph concentrations. Two dinoflagellate cyst acmes within the Danian (Paleogene) part of the López de Bertodano Formation of Seymour Island, Antarctica were also tested using H2O2, (NaPO3)6, and HCl/HF. TheH2O2 preparation completely destroyed the dominant taxon, Palaeoperidinium pyrophorum, in one sample. By contrast, the (NaPO3)6 and HCl/HF preparations produced abundant, fully representative palynofloras. In the other sample, the acme of Spinidinium spp. is completely unaffected by the H2O2 preparation procedure. The final sample of this study is an unconsolidated clay of Late Pleistocene age from offshore Scotland. Both the H2O2 and HCl/HF preparations proved similar in both taxonomic content and overall palynomorph yield. The new method of preparation using hot H2O2 has proved to be extremely effective. In particular, it appears to be superior to the (NaPO3)6 procedure for indurated lithotypes. However care should be taken because H2O2 can destroy certain dinoflagellate cysts and kerogen macerals which are especially susceptible to oxidation. Further development work, and more comparative testing of the H2O2, (NaPO3)6, and HCl/HF procedures, should be undertaken

Foraminiferal assemblages from the bajocian global stratotype section and point (GSSP) at Cape Mondego (Portugal)

A detailed study of the benthic foraminiferal assemblages at the Bajocian Global Stratotype Section and Point (GSSP— Murtinheira section, Lusitanian Basin, western Portugal) presented herein increases the correlation potential of this relevant global geological time reference. The recorded assemblages are relatively abundant and diverse, and are composed of wellpreserved taxa typical of the Boreal Realm. The most abundant suborders are Lagenina and Spirillinina. Representatives of the Suborder Textulariina are also abundant in some assemblages, while those of the suborders Robertinina and Rotaliina are scarce. Lenticulina specimens are the most abundant in all assemblages, but at the specific level, there are differences between Aalenian and Bajocian assemblages, with Lenticulina muensteri being most abundant in the former and Spirillina orbicula in the latter. Two biozones, based on calcareous foraminifers, have been established and calibrated to the standard ammonite zonation: 1) the Lenticulina quenstedti Zone, ranging from the upper part of the Gigantea Subzone, Bradfordensis Biozone, upper Aalenian, to the lower part of the Discites Biozone, lower Bajocian, and 2) the Ramulina spandeli Zone, beginning at the top of the preceeding zone and having an undefined upper boundary. In addition, 11 bioevents are defined on first occurrences, last occurrences, changes in abundances of some taxa, or changes in assemblage diversity. After a severe impoverishment at the Aalenian–Bajocian transition, an important foraminiferal turnover takes place in the early Bajocian, where some Lower Jurassic and Aalenian forms are replaced by typical Middle Jurassic tax

Ammonite-benthic Foraminifera turnovers across the Lower-Middle Jurassic transition in the Lusitanian Basin (Portugal)

This paper describes and characterises the co-occurrence of ammonite and benthic foraminiferal assemblages across the São Gião outcrop (Central Portugal), a reference section for the Lower-Middle Jurassic boundary in the Lusitanian Basin. The upper Toarcian-lower Aalenian marls and marly-limestones in this section provide a precise and detailed ammonite-based biostratigraphic zonation, with a mixed assemblage of northwest European and Mediterranean faunal elements, associated with benthic foraminifera assemblages with northern hemisphere affinities, both correlatable with the Aalenian GSSP at the Fuentelsaz section (Iberian Cordillera, Spain). A total of 447 well-preserved ammonite specimens and 13.116 foraminifera have been studied; no evidence was detected of any taphonomic processes that could have changed the original assemblages. From a biostratigraphic point of view, the ammonite record has enabled four biostratigraphic units to be recognised (the Mactra and Aalensis subzones of the Aalensis Biozone in the upper Toarcian, and the Opalinum and Comptum subzones of the Opalinum Biozone in the lower Aalenian). With regard to the benthic foraminifera, the taxa identified have enabled the Astacolus dorbignyi Zone and 11 bioevents to be identified, most of which representing local biostratigraphic proxies. However, the increase in the relative abundance of Lenticulina exgaleata Dieni from the upper part of the Opalinum Subzone to the lower part of the Comptum Subzone has a regional value. The constant and continuous ammonite record of northwest European taxa, together with typical Mediterranean taxa – namely Grammoceratinae – throughout the section, the high relative abundance of Miliolina representatives – generally interpreted as foraminifers typical of shallow waters – and the absence of foraminiferal forms typical of cool waters, do not support the inference of cool seawater temperatures attributed to the Early Aalenian, or the global character of the “Comptum cooling event”, at least with reference to the Lusitanian Basin

Early Jurassic (latest Toarcian) brachiopods from the northeastern margin of the Western Tethys (Central Iran) and their paleobiogeographical significance

Brachiopod fauna from central Iran, recorded in the upper part of the Shemshak Group and attributed to the upper Toarcian (Pseudoradiosa-Aalensis zones), are reported for the first time in Iran. The assemblage recognized includes six different taxa: Homoeorhynchia sepahanensis nov. sp., formally described in this paper, Globirhynchia subobsoleta, Pseudogibbirhynchia sp., Tetrarhynchiidae sp. indet., Monsardithyris? aff. haresfieldensis, and Zeilleria cf. leckenbyi. Analysis of faunal affinities with other paleobiogeographical regions shows a free connection the central Iranian brachiopod fauna with wide areas of the northern shelf margin of the Tethys Ocean. This is due to an apparent disruption of bioprovinciality inferred for the late Toarcian-earliest Aalenian, congruent with a connection through the northern seaway across the peri-Laurasian epicontinental platforms.The present research is partially supported by Research Group VIGROB-167 (University of Alicante)