Morphology and distribution of Pronoctiluca (Dinoflagellata, incertae sedis) in the Pacific Ocean

The diversity and distribution of Pronoctiluca, a marine dinoflagellate of enigmatic systematic position, was studied in the vicinity of the Kuroshio and Oyashio Currents, the Philippines, Celebes, Sulu and South China Seas, western and central equatorial and southeast Pacific Ocean. The abundance of Pronoctiluca was higher, with a wide vertical distribution, in eutrophic temperate regions, whereas it was nearly absent in surface waters of oligotrophic tropical regions. Most of the specimens corresponded to P. spinifera. Pronoctiluca pelagica, covered by hyaline layers and with no flagella, is considered as an encysted form. The bipartition was only observed in P. acuta-P. spinifera forms, that together with the occurrence of intermediate forms between P. spinifera and P. pelagica suggest that they may correspond to developmental stages of a single species. Pronoctiluca is essential to understanding the evolutionary history of the alveolates.     

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.     

A new method for processing clay-rich unconsolidated sediments for paleoecological investigations

A method is described for processing flocculated clay-rich sediments which avoids acetolysis and heavy liquid separation. Twin 80 (Merck index 1983) is used for deflocculation. Microsieves separate the recovered organisms according to size. Taxonomic identification and quantitative evaluation of the organisms can be performed in counting chambers or on permanent slides. Algae, cysts and exospores of dinoflagellates, pollen grains and zooplankton remains can be recovered.     

Multiproxy approach to understanding the origin of Cretaceous pelagic limestone–marl alternations (DSDP site 391, Blake-Bahama Basin)

Limestone–marl alternations are usually directly interpreted to reflect cyclic palaeoenvironmental signals. However, uncertainty in such interpretations stems from the differential diagenesis that most limestone–marl alternations have undergone. Differential diagenesis results in markedly different alterations between limestones and marls and in the loss of comparability of many measurable parameters. For an unequivocal interpretation of the origin of rhythmic alternations, diagenetically robust parameters or parameters that clearly indicate the degree of diagenetic bias are required. The present study uses a multiproxy approach (independent biotic, sedimentary and geochemical parameters) in order to unravel the palaeoenvironmental signal recorded in Valanginian (Early Cretaceous) limestone–marl alternations from the Blake‐Bahama Basin (DSDP site 391). Using this approach, terrestrial and marine influences can be distinguished, changes in nutrient levels estimated and prediagenetic differences in the non‐carbonate fraction constrained. Surprisingly, no systematic variations in any of these parameters were observed between limestone and marl layers, implying that none of these was directly responsible for the formation of the rhythmic alternation. Hence, none of the current models of sedimentary formation of limestone–marl rhythmites is applicable here. Calcareous nannofossils are equally well preserved in limestone and marl layers, ruling out their dissolution in marl layers as a source of the calcite cement in the limestone beds. Sr values of 700–900 p.p.m. indicate that aragonite may have been present in the original, pelagic sediment. The assumption of fine‐grained sedimentary aragonite imported from nearby carbonate platforms as the source of the cement would explain a number of otherwise enigmatic features in these rhythmites, including the source of the calcite cement observed in the limestones, the equally good preservation of calcareous nannofossils in limestones and marls and the higher concentration of calcareous nannofossils in marl layers. The study demonstrates that examination of diagenetically inert parameters or parameters in which diagenetic effects can be filtered can yield unexpected results. Clearly, careful analysis of such parameters needs to be undertaken in order to make reliable palaeoenvironmental interpretations from rhythmite successions.     

Lipid geochemistry of Lake Kinneret

Lake Kinneret, a relict lake from the Neogene, is characterised by the dominance among its phytoplankton of the dinoflagellate Peridinium cinctum. The lipid geochemistry of Lake Kinneret is discussed herein in terms of the biology, chemistry and hydrology of the lake. Lipids isolated from two sediment sections (surface and 15 cm deep), obtained from the deepest point of Lake Kinneret, include: (1) 4α-methyl-5α (H)-stanols and related derivatives characteristic of P. cinctum, the novel sterol 4a-methylgorgosterol, and peridinosterol and 4α-methylgorgostanol, not previously reported to occur in lacustrine sediments; (2) C₃₀ and C₃₂ alkane-1,15-diols, not previously reported to occur in contemporary lacustrine deposits, and (3) products of early diagenesis. Many similarities were observed with the more widely studied marine dinoflagellates and marine sediments with dinoflagellate input.     

Integrated microfossil biostratigraphy,Mid-Cretaceous (Albian to Saronian)

An attempt is made to integrate biozones based on planktic Foraminifera with those on calcareous nannofossils, mainly on first order correlation. An approximate correlation with ammonite zones, magnetic events and radiometric age values, partly on first-order data, partly from the literature, is added.     

Phosphorus status and sorption characteristics of some calcareous soils of Hamadan,western Iran

Phosphorus (P) application in excess of plant requirement may result in contamination of drinking water and eutrophication of surface water bodies. The phosphorous buffer capacity (PBC) of soil is important in plant nutrition and is an important soil property in the determination of the P release potential of soils. Phosphorus sorption greatly affects both plant nutrition and environmental pollution. For better and accurate P fertilizer recommendations, it is necessary to quantify P sorption. This study was conducted to investigate available P and P sorption by calcareous soils in a semi-arid region of Hamadan, western Iran. The soil samples were mainly from cultivated land. Olsen’s biocarbonate extractable P (Olsen P) varied among soils and ranged from 10 to 80 mg kg⁻¹ with a mean of 36 mg kg⁻¹. Half of the soils had an Olsen P > 40 mg kg⁻¹ and >70% of them had a concentration >20 mg kg⁻¹, whereas the critical concentration for most crops is <15 mg P kg⁻¹. Greater average Olsen P in soils occurred under garlic (56 mg kg⁻¹) and potato (44 kg kg⁻¹) fields than in dry-land wheat farming (24 mg kg⁻¹), pasture (30 mg kg⁻¹), and wheat (24 mg P kg⁻¹) fields. A marked increase in fertilizer P rates applied to agricultural soils has caused P to be accumulated in the surface soil. Phosphate sorption curves were well fitted to the Freundlich equation. The standard P requirement (SPR) of soils, defined as the amount of P sorbed at an equilibrium concentration of 0.2 mg l⁻¹ ranged from 4 to 102 mg kg⁻¹. Phosphorus buffer capacity was relatively high and varied from 16 to 123 l kg⁻¹ with an average of 58 l kg⁻¹. In areas of intensive crop production, continual P applications as P fertilizer and farmyard manure have been used at levels exceeding crop requirements. Surface soil accumulations of P are high enough that loss of P in surface runoff and a high risk for P transfer into groundwater have become priority management concerns.     

Calcareous nannofossils from the Santa Marta Formation (Upper Cretaceous), northern James Ross Island,Antarctic Peninsula

This study reports on the most stratigraphically extensive nannofloras yet recovered from the Lachman Crags Member of the Santa Marta Formation, James Ross Island, Antarctic Peninsula. The productive samples are dated as early Campanian. These ages are in accord with those provided by ammonites, foraminifera, ostracods and radiolarians from the same locality. The consistent and relatively abundant presence of Gephyrobiscutum diabolum throughout the productive part of the section, a species that has previously only been documented from the Falkland Plateau, extends its geographic distribution to higher latitudes, at least to the Antarctic Peninsula area.