Cenomanian radiolitid bivalves from Malchina, Karst of Trieste, Italy

A radiolitid fauna, rudist bivalves, composed of Durania acuticostata Caffau and Pleni?ar, Eoradiolites fleuriausus (d’Orbigny), Eoradiolites liratus (Conrad), Paronaites zuffardii (Parona), and Sauvagesia sharpei (Bayle) is described from the upper Cenomanian Monrupino Formation in the Malchina area, Karst of Trieste. The taxonomic part includes [1] the proposal of the new genus Paronaites and [2] neotypes for E. liratus, [3] the identification of several junior synonyms (Eoradiolites zucchii Caffau and Pleni?ar and Praeradiolites acutilamellosus Caffau and Pleni?ar for E. fleuriausus; Eoradiolites zizensis Astre and Eoradiolites adriaticus Caffau and Pleni?ar for E. liratus; and Eoradiolites carsicus Caffau and Pleni?ar for P. zuffardii), [4] the discrimination between E. liratus and Eoradiolites schweinfurthi Zittel, and [5] the identification in Europe of species so far only reported in North Africa, besides [6] illustrating the diagnostic characters and morphologic variability of the treated species. All this facilitates their proper identification and certainly helps the stratigraphic correlation of the Cenomanian shallow water carbonates deposited on the margins of the Tethys.     

Records of environmental and climatic changes during the late Holocene from Svalbard: palaeolimnology of Kongressvatnet

A multi-core, multidisciplinary palaeolimnological study of the partially varved sediment of a deep, meromictic, arctic lake, Kongressvatnet (Svalbard, Western Spitsbergen), provides a record of environmental and climatic changes during last ca. 1800 years. The chronology of sedimentation was established using several dating techniques (¹³⁷Cs, ²¹⁰Pb, varve counts, palaeomagnetic correlation). A multiproxy record of palaeolimnological variability was compiled based on sedimentation rates, magnetic properties, varve thickness, organic matter, geochemistry, pigments from algal and photosynthetic bacteria, mineralogy and biological assemblages (diatoms, Cladocera). The major features recognised in our master core K99-3 include a shift in sediment source and supply (magnetic measurements, geochemistry) probably caused by glaciological changes in the catchment around 38–32 cm core depth (AD 700–820). Additional environmental changes are inferred at 20–18, 8–4.5 and 3–2 cm (AD ca. 1160–1255; 1715–1880; 1940–1963, respectively). During the past ca. 120 years a prominent sedimentological change from brownish-grey, partly laminated silt-clay (varves) to black organic-rich deposits was observed. From AD 1350 to AD1880 the sediment is comprised of a continuous sequence of varves, whereas the earlier sediments are mostly homogeneous with only a few short intercalated laminated sections between AD 860 and 1350. Sedimentation and accumulation rates increased during the last 30 years (modern warming). Pigment concentrations are very low in the lower ca. 32 cm of the core (AD 820) probably because of the high turbidity high energy environment. The high sulphur content in the uppermost 32 cm of sediment has given rise to two horizontally stratified populations of sulphur anaerobic photosynthetic bacteria, as inferred from their specific carotenoids. These bacteria populations are much more abundant during the Little Ice Age (LIA) than during warmer periods (e.g., during the Medieval Warm Period and 20th century). Diatoms are lacking from the core base up to 18 cm (ca. AD 1255); at this level, species indicative of mesotrophic water are present, whereas from 17 cm to the top of the core, oligotrophic taxa such as Staurosira construens/S. pinnata complex dominate, indicating extended ice coverage and more oligotrophic waters during the LIA. The concentration of Cladocera subfossil remains (dominated by Chydorus) are relatively high in the deepest sections (54–32 cm), whereas the upper 32 cm are characterized by a very low concentration of remains, possibly because of the strongly anoxic conditions, and in this upper sediment section rotifer resting eggs become prevalent. We interpret these changes as responses to climate forcing through its impact on glacial melt water, lake ice cover duration and mainly redox conditions in deep water. The observed changes suggest that at least some of our recorded changes may parallel the Greenland Ice core, although our study added more details about the inferred climatic changes. Further aspects are discussed, such as catchment processes, glacial activity, duration of the Medieval Warm Period, the Little Ice Age, local human activity, and limnology.