Evolution of karst in Messinian gypsum (Monferrato,Northern Italy)

In the Tertiary Basin of Piedmont (Northern Italy) a 100-150 m thick Messinian sedimentary succession crops out, composed of pre-evaporitic clays, gypsum beds and post-evaporitic lacustrine-marine fine-grained sediments. In the Monferrato area the thickness of the evaporite sequence is highly variable (0-140 m) due to an important erosion surface formed at the end of the evaporite cycle and carved in the gypsum beds. Epigenic caves probably formed during this short intra-Messinian phase of emersion. Cave sediments contain benthonic and planctonic foraminiferal associations ranging in age from Burdigalian to Upper Pliocene. These sediments have probably been deposited in recent times, although it cannot be completely ruled out that they accumulated in caves developed in Upper Messinian times. The formation of the most important caves of this area probably started at the end of the Messinian under epigenic conditions. Possibly, those inherited caves enlarged slowly during the Quaternary in an intrastratal and confined hypogene karst system.     

Benthic foraminiferal assemblages from Moreton Bay, South-East Queensland, Australia: Applications in monitoring water and substrate quality in subtropical estuarine environments

We assess species composition, assemblage structure and distribution of the benthic foraminiferal assemblages from diverse substrates in Moreton Bay, South-East Queensland, Australia. Analysis of 47 surface sediment samples revealed 69 species, three distinct foraminiferal assemblages and six sub-assemblages. The assemblages from the western Bay are characterized by stress tolerant taxa and the lowest diversity, whereas the assemblages from the eastern Bay are characterized by symbiont-bearing taxa and high diversity. We found a correlation between foraminiferal assemblages and substrate conditions that was indicative of strong environmental gradients (substrate type, water quality and salinity), from an urban-impacted assemblage in the westernmost part of the Bay, to a hyposaline, estuarine-influenced assemblage in the western Bay to a nearly normal marine to hypersaline assemblage in the eastern Bay. The FORAM Index was consistent with the changes in water and sediment quality gradient, from the western shoreline to the eastern Bay. Thus the foraminiferal assemblages of Moreton Bay make excellent bio-indicators of environmental changes in a subtropical, estuarine setting in eastern Australia.     

白令海底栖有孔虫壳体镁钙比值对水团温度的响应

底栖有孔虫壳体Mg/Ca是重建深层水团古温度的主要指标。通过分析表层沉积物样品中底栖有孔虫Uvigerina peregrina壳体的Mg/Ca和δ18 O,探讨了"Mg/Ca古温度重建方法"在白令海低温水体中的可行性及其转换函数。结果表明,利用U.peregrina壳体δ18 O换算的"结壳温度"明显低于"现代水团温度",不能客观反映温度对Mg/Ca的控制作用;可能受季节性变化的影响,水深小于150m样品中U.peregrina壳体的Mg/Ca与"现代水团温度"之间并没有表现出明显的相关性,但是,在深海区两者之间却呈现出良好的指数关系:Mg/Ca=0.69*e0.43*T。该公式指出白令海低温水体中Mg/Ca对温度的敏感性约为43%℃-1,由其估算的温度误差约为0.2℃。     

Ecophenotypic responses of benthic foraminifera to oxygen availability along an oxygen gradient in the California Borderland

Spatial variation in environmental conditions can elicit predictable size and morphological responses in marine organisms through influences on physiology. Thus, spatial and temporal variation in marine organism size and shape are often used to infer paleoenvironmental conditions, such as dissolved oxygen concentrations. Benthic foraminifera commonly serve as a tool for reconstructing past ocean oxygen levels. For example, benthic foraminiferal species assemblages, within‐ and among‐species patterns of test morphology, and geochemical analyses of carbonate tests are often employed to reconstruct past marine conditions. In this study, we measured the sizes and shapes of modern foraminifera representing four species that inhabit a steep oxygen gradient in the Santa Monica Basin on the Southern California Borderland with the aim of quantifying the influence of oxygen availability on foraminiferal morphology, both within and among species. Most foraminifera rely on aerobic respiration, but the four benthic foraminifera from the Santa Monica Basin do not show the predicted size and morphological responses to variations in dissolved oxygen concentrations based on first principles of cell physiology: Bolivina spissa shows no volume or volume‐to‐surface area response, Uvigerina peregrina increases in both test volume and volume‐to‐surface area ratio with decreasing dissolved oxygen concentrations, and both Bolivina argentea and Loxostomum pseudobeyrichi decrease in test volume, but only L. pseudobeyrichi shows a decrease in test volume‐to‐surface area ratio with decreasing oxygen concentrations as expected from physiological predictions. These findings imply that the morphological responses of individual foraminiferal species are not necessarily representative of the responses of other foraminiferal species within the community. Our findings further suggest that these species use physiological strategies such as depressed metabolic rates and alternative energy metabolisms to persist in low oxygen environments and, therefore, cannot be used in any simple way as paleo‐oxygen indicators. Should Proterozoic (1,000–542 million years ago) protists have possessed metabolic strategies similar to foraminifera, the sizes and shapes of protists in the fossil record may not usefully constrain ambient oxygen conditions during the appearance and initial taxonomic radiation of heterotrophic eukaryotes.     

A new platypterygiine ichthyosaur rostrum from the Lower Cretaceous of the Lessini Mountains (Northern Italy)

An incomplete rostrum of a platypterygiine ichthyosaur (IGVR 94574) has recently been found near Tregnago (Verona, Italy), in the Lessini Mts. This is the first Cretaceous ichthyosaurian fossil found in Italy outside the northern Apennines, where fragmentary remains have been recovered since the 19^th century.IGVR 94574 is a mid-distal rostral fragment infilled by a white, fine-grained limestone matrix. It consists of the premaxilla, nasal, vomer, dentary, and splenial, together with 20 teeth.Even if the exact horizon of provenance is unknown, analysis of the microfossil content of the matrix (planktonic foraminifera and calcareous nannofossils) allowed us to assign it to the lower part of the upper Albian. This is also the first Cretaceous ichthyosaur in Italy with a precise age: all previously reported fossils from the Apennines could not be dated due to the complete absence of microfossils in the surrounding matrix.We assign IGVR 94572 to Platypterygiinae; generic specification is not possible pending the taxonomic revision of the genus Platypterygius.Finally, the Tregnago rostrum is strikingly similar to the specimen IPUM 30139 from Gombola (Modena, Italy), stored in the collections of the Paleontological Museum of Modena and Reggio Emilia University and also attributable to a platypterygiine ichthyosaur. The comparison between these two fossils reveals the teeth are very similar both in shape and size.     

Fissumella motolae n. gen. n. sp., a new soritoidean (Foraminifera) from the lowermost Albian carbonate platform facies of central and southern Italy

The Soritoidea (Foraminifera) represent an important component of Cenomanian microfossil assemblages of the central and southern Tethyan carbonate platforms and are widely used as biostratigraphic markers. In this paper a new taxon, Fissumella motolae n. gen. n. sp., is described from the Cretaceous carbonate platform facies of central and southern Italy. It is characterized by its small size, planispiral-involute arrangement of chambers, fissure-shaped single aperture and few and short radial septula subdividing the marginal lumen of the chambers. Fissumella motolae n. gen. n. sp. represents the first soritoidean in the fossil record showing internal subdivisions of the chamber lumen. Carbon isotope stratigraphy supports an earliest Albian age for this significant step in the evolution of the superfamily Soritoidea. The new subfamily Fissumellinae is established for soritoidean foraminifera with planispiral-involute lens-shaped shells, single aperture and chamber lumen subdivided by few and short septula.     

河北阳原盆地泥河湾组有孔虫来源的探讨

该文探讨河北阳原—蔚县盆地早更新世沉积的泥河湾组所含有孔虫化石是否与海侵有关等问题。通过对河北平原、阳原—蔚县盆地所在地的冀西北山地及北京西山在上新世一晚更新世的地质、构造、地貌等调查、研究与分析,认为阳原—蔚县盆地早更新世时并没有发生海侵,有孔虫来源与海侵无关,属于内陆湖泊非海相有孔虫。     

Geoheritage significance of three Pleistocene formations recording a succession of climates and sea levels on the Yalgorup Plain in southwestern Australia

The Yalgorup Plain of southwestern Australia is underlain by two limestone formations and a linear quartz-sand formation containing limestone lenses. These limestones record carbonate deposition in seagrass banks during the Pleistocene; they are capped either by a prograding beach-ridge system of small cuspate forelands or a quartz-rich shore-parallel coastal barrier. The cuspate forelands formed behind protective offshore limestone reefs within a given Pleistocene wind-and-wave field, while the quartz-rich coastal dune barrier formed under enhanced swell conditions. These formations record three different Pleistocene interglacial depositional events, separated by unconformities, each linked to a distinct climate and mean sea level. Foraminiferal assemblages within the two limestones and within the limestone lenses of the quartz-sand formation faithfully record changes in minimum seawater temperature, reflecting these changes in climate. They indicate a cycle of warm–cool–warm water accumulation of carbonates. Such a record of both climate and sea level history for southwestern Australia is unique, contributing greatly to the Pleistocene coastal sedimentary history of limestones within southwestern Australia. These formations occur within the globally unique setting of Western Australia and are conserved within a National Park and represent an outstanding record of Quaternary coastal geomorphic development in terms of both carbonate and siliciclastic sedimentation linked to both climate and sea level changes. Given their array of lithofacies, environmental setting, sea level and climate changes, as well as their biostratigraphy reflecting these changes, these formations form a sedimentary ‘package’ that is of global geoheritage significance, with many of its inherent geological features also of global to national geoheritage significance.     

Reassessment of historical sections from the Paleogene marine margin of the Congo Basin reveals an almost complete absence of Danian deposits

The early Paleogene is critical for understanding global biodiversity patterns in modern ecosystems. During this interval, Southern Hemisphere continents were largely characterized by isolation and faunal endemism following the breakup of Gondwana. Africa has been proposed as an important source area for the origin of several marine vertebrate groups but its Paleogene record is poorly sampled, especially from sub-Saharan Africa. To document the early Paleogene marine ecosystems of Central Africa, we revised the stratigraphic context of sedimentary deposits from three fossil-rich vertebrate localities: the Landana section in the Cabinda exclave(Angola), and the Manzadi and Bololo localities in western Democratic Republic of Congo.We provide more refined age constraints for these three localities based on invertebrate and vertebrate faunas, foraminiferal and dinoflagellate cyst assemblages, and carbon isotope records. We find an almost complete absence of Danian-aged rocks in the Landana section, contrary to prevailing interpretations over the last half a century(only the layer 1, at the base of the section, seems to be Danian). Refining the age of these Paleocene layers is crucial for analyzing fish evolution in a global framework, with implications for the early appearance of Scombridae(tunas and mackerels) and Tetraodontiformes(puffer fishes). The combination of vertebrate fossil records from Manzadi and Landana sections suggests important environmental changes around the K/Pg transition characterized by an important modification of the ichthyofauna. A small faunal shift may have occurred during the Selandian. More dramatic is the distinct decrease in overall richness that lasts from the Selandian to the Ypresian. The Lutetian of West Central Africa is characterized by the first appearance of numerous cartilaginous and bony fishes. Our analysis of the ichthyofauna moreover indicates two periods of faunal exchanges: one during the Paleocene, where Central Africa appears to have been a source for the European marine fauna, and another during the Eocene when Europe was the source of the Central Africa fauna. These data indicate that Central Africa has had connections with the Tethyian realm.     

The application of expert systems to the identification and use of microfossils in the petroleum industry

Development of an expert system for microfossil identification and their use in dating rocks demonstrates that such systems can be used in the evaluation and interpretation of basic geological data. Palaeontological data lends itself to this kind of approach because it is controlled to a greater extent than other geological data by internationally accepted rules and practice. Two fossil groups, planktonic foraminifera and conodonts, have been chosen for initial development, both groups having a long history of study.