台湾海峡西部海域底质柱状样中有孔虫特征及其环境意义

本文通过对台湾海峡西部海域7个柱状样计79块样品中的有孔虫分析,阐述了海峡柱样中有孔虫组合及其特征,并由此讨论台湾海峡西部海域晚更新世以来的沉积环境。     

Cretaceous foraminifera from the Turonian succession at Beer, southeastern Devon, England

During Winter 2000/2001 a major cliff fall occurred at the back of the bay in Beer, southeastern Devon. In the subsequent remedial works the cliff was cleared of loose material prior to stabilisation works. This process provided a suite of samples from previously inaccessible parts of the cliff succession. By adding these samples to earlier suites of samples collected over the last 30 years it has been possible to improve our knowledge of the foraminifera of Turonian age in southwestern England.The planktic foraminifera are, perhaps, the most significant component of the assemblages as many of the taxa recorded in Devon are of southern aspect and are relatively rare in others parts of the U.K. The planktic zonation recognised in this section is, therefore, almost identical with that recorded in Tethyan areas and a precise correlation can be generated. There are relatively large numbers of important taxa such as Helvetoglobotruncana helvetica, Dicarinella imbricata, Marginotruncana sigali, M. pseudolinneiana, M. coronata and M. schneegansi. The benthic foraminifera, by comparison, are relatively rare and are represented by a low diversity assemblage. This is typical of northwestern European chalk successions of Turonian age and is coincident with the highest sea levels of the Cretaceous. In the middle to late Turonian there is a dramatic shallowing event that is recorded world-wide at this level. The assemblage changes towards the top of the accessible succession at Beer record this significant, world-wide event.     

Nouvelles Données sur le Crétacé Supérieur de la Sardaigne Orientale

The stratigraphic distribution of the principal Upper Cretaceous facies in Sardinia ispresented, with special reference to the eastern part of the Island. Included are remarks on the mid-Cretaceous tectonic activity, which marks the base of the Upper Cretaceous depositional cycle. The presence of Upper Santonian and Lower Maastrichtian (the latter represented by marls with sparse turbidite interbeds) in the Lanaitto syncline (Oliena) is documented. Both contain outer-shelf assemblages rich in planktic Foraminifera. Recognition of rare detrital glaucophane in the Maastrichtian sandstones suggests a source area affected by high-pressure metamorphism, possibly corresponding to the southward extension of alpine Corsica.The Tertiary conglomerates exposed near Oliena include pebbles of facies (Campanienand Upper Maastrichtian rudistid limestones with larger Foraminifera) unknown in outcrop. A preliminary study of the rudists suggests a faunal exchange between different palaeobio-geographical provinces belonging, respectively, to the West European and Adriatic Plates.A palaeontological appendix contains remarks on some representatives of the family Heterohelicidae and on one species of Gunnarites found in the Lower Maastrichtian.     

塔里木盆地北缘早石炭世有孔虫

塔里木盆地北缘早石炭世干草湖组和野云沟组产有丰富的有孔虫及(竹蜓)科化石,共计32个属,近100个种,其中7个新种.自下而上建立了四个化石组合即:1.Tournayella discoi-dea-Tuberendothyra tuberculata magna;2.Dainella wushiensis-Endothyra Parain-flata;3.Eostaffella hohsiensis-Archaediscus moelleri;4.Eostaffellinella Prot-vae-Climacammiana ferra.第一组合的时代为杜内(岩关)期,其余三个组合属维宪(大塘)期.     

The use of deep-water agglutinated Foraminifera in correlating Lower Cretaceous pelagic and flysch sequences: current status and prospects for the future

Deep-water agglutinated Foraminifera (DWAF) display potential for correlating pelagic (calcareous and non-calcareous) and flysch environments. This is illustrated by an example from Sites 765 and 261 on the Argo Abyssal Plain. A working zonation based on DWAF has been developed for Lower Cretaceous flysch sequences of the Polish Carpathians, but this zonal scheme has not been tested in other areas of the Tethys. No zonation has yet been developed for abyssal oceanic DWAF. The challenge for the future, under the auspices of Project 262, is to test the existing zonation in other regions and develop a widely applicable biochronology for integration into a general Tethyan biochronological correlation scheme.     

Multivariate analysis of environmentally controlled variation in Lagena: Late Maastrichtian,Sweden

Costate forms of Lagena (benthonic foraminifer) have been studied in an uppermost Maastrichtian bore-hole core sequence (28 levels) from southern Sweden. Analysis of a large sample shows that consistent assignment to previously described “species” of costate Lagena is not possible. This observation is supported by multivariate analysis of five morphologic variables which indicates that there are no distinct clusters of specimens along principal component axes associated with general size, number of costae, and relationships between roundness of test/length and number of costae. Specimens with a basal ring differ from specimens with an apical spine and those with no basal structure with regard to average number of costae. They also differ from specimens with no basal structure with regard to relationships between roundness of test/length and number of costae. These characters grade into each other thus preventing them from being used as taxonomic criteria.Mean ratios of benthonic foraminifers to total benthonic and planktonic formaminifers determined individually for each level are inversely related to mean relative frequencies of costate Lagena and directly related to mean general sizes of costate Lagena. The benthonic/planktonic ratio has been suggested by other workers to represent a paleobathymetric index across a continental slope and shelf when open marine conditions prevailed. If this were so in the Danish basin at the end of the Cretaceous, costate Lagena would have been relatively less frequent and larger at shallower depths.As a result of the study, the analyzed specimens are considered as representing a single morphospecies of the costate species Lagena sulcata. Between-level variation is regarded as ecophenotypic, and within-level variation as natural biologic variation of no taxonomic significance. A total of about 1000 species of Lagena has been described in the literature which is probably many orders of magnitude too great for a genus with such a simple morphology as Lagena. A revision of the taxonomy of Lagena is, therefore, probably necessary on a wide scale.     

The biotic crisis across the Oceanic Anoxic Event 2: Palaeoenvironmental inferences based on foraminifera and geochemical proxies from the South Iberian Palaeomargin

Open marine sediments deposited during the Cenomanian–Turonian transition are well exposed in the Spanish Baños de la Hedionda section (Betic Cordillera, South Iberian Palaeomargin). Analysis of foraminiferal assemblages and geochemical proxies allow inferences on the impact of the Oceanic Anoxic Event 2 (OAE2) in this area of the western Tethys. Three main intervals have been identified corresponding to different lithological units and biozones. (1) The top of the Capas Blancas Member (Rotalipora cushmani Biozone) represents the pre-extinction phase with diverse foraminiferal assemblages and well developed water-column tiering, well-oxygenated, oligotrophic deep-waters and oxygenated to poorly oxygenated, mesotrophic surface-waters. Foraminiferal opportunist species point to a minor event with dysoxic conditions preceding the OAE2. (2) The black radiolaritic shales (Whiteinella archaeocretacea Biozone) consist of a foraminiferal-barren interval, except for the lowermost centimetres where planktic surface-dweller opportunists are common. Redox sensitive elements (Cr/Al, V/Al, U/Th, Mo_EF, Mo_aut, U_EF and U_aut) and increased TOC values reflect oxygen depleted conditions related to the OAE2. The increase in P/Ti values at the base of this stratigraphic interval indicates an abrupt increase in productivity. High concentrations of radiolarians are congruent with high surface productivity probably related to changes in oceanic circulation and enhanced upwelling currents, as well as subsequent shallowing of the oxygen-minimum zone. The increase in Mo_EF and Mo_aut towards the top of the black radiolaritic shales indicates temporal euxinic conditions. (3) A slow, bottom-up recovery of foraminiferal assemblages is inferred at the base of the Boquerón Member (Helvetoglobotruncana helvetica Biozone), with seafloor recolonization by benthic foraminifera being recorded previous to the water column colonization by planktic forms, mainly by intermediate-dwellers typical of mesotrophic waters. The subsequent proliferation of surface-dweller opportunists and deep-dweller opportunists adapted to mesotrophic to eutrophic conditions, and the decrease in planktic foraminiferal diversity, may indicate the persistence of poorly oxygenated conditions in the water column towards the lower-middle part of the H. helvetica Biozone.     

Pseudorhapydionina bilottei sp. nov., an endemic foraminifera from the post-Cenomanian/Turonian boundary (Pyrenees,NE Spain)

A new species of the foraminiferal genus Pseudorhapydionina is reported from the Santonian shallow-water carbonate and mixed deposits of La Cova Unit, in the Montsec and Pedraforca thrust sheets (Southern Pyrenees, NE Spain). Pseudorhapydionina bilottei sp. nov. differs from the Cenomanian species of the genus in its larger test size and the number of chambers in its early planispiral-involute stage. The discovery of P. bilottei sp. nov in the Santonian indicates that the genus Pseudorhapydionina escaped extinction during the Cenomanian-Turonian boundary (CTB) event in the Pyrenean bioprovince. A new subfamily Pseudorhapydionininae is described.     

Lagoon subsidence and tsunami on the West Coast of New Zealand

Sediment core and trench data from a coastal lagoon on the West Coast of the South Island, New Zealand are used to investigate evidence for co-seismic subsidence and associated tsunami inundation. Physical data are used to document a salt marsh soil buried  80 cm below the modern sediment surface that is locally covered by a gravelly sand bed. The sediment record also contains geochemical and biological (diatom and foram) evidence for abrupt changes in salinity of lagoon waters that link to subsidence, tsunami flooding and to the open versus closed state of the lagoon tidal entrance. At the local scale, these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon. We also propose a conceptual connection between these local changes and regional drivers of landscape development, most notably major earthquakes and resultant pulses in sediment supply to the coast.