Showing papers on "Foraminifera published in 1978"

Vital effect on stable-isotope composition seen in foraminifera and coral skeletons

Abstract: Stable-isotope composition of carbonate precipitated by hermatypic corals and associated benthonic foraminifera is strongly influenced by photosynthesis of symbiotic algae. In situ 14C and 45Ca uptake experiments show that when photosynthesis increases, more light metabolic CO2 is incorporated in the skeleton. This mechanism explains the non-equilibrium isotopic compositions previously reported for these organisms (as well as for planktonic foraminifera), and have important implications for palaeoenvironmental determinations based on stable-isotope analysis.

Planktonic foraminiferal and oxygen isotopic stratigraphy and paleoclimatology of Norwegian Sea deep‐sea cores

Abstract: BOREAS Kellogg, T. B., Duplessy, J. C. & Shackleton, N. J. 1978 03 01: Planktonic foraminiferal and oxygen isotopic stratigraphy and paleoclimatology of Norwegian Sea deep-sea cores. Boreas. Vol. 7, pp. 61–73. Oslo. ISSN 0300–9483. Three Norwegian Sea deep-sea cores, which penetrate to sediments at least 200,000 years old, were analyzed for oxygen isotope content, total calcium carbonate, and planktonic foraminifera. The oxygen isotopic stratigraphy was used to refine the time control for paleoclimatic and paleo-oceanographic events previously described for the region. Two pulses of relatively warm subpolar water entered the region between 124,000 B.P. and 115,000 B.P. (the last interglacial), and since about 13,000 B.P. The remaining portion of the last 150,000 years was characterized by extensive ice cover. The magnitude of the change in isotopic composition between peak glacial and peak interglacial conditions is larger than can be explained by the changing isotopic content of the oceans alone suggesting that large temperature and salinity effects are recorded in isotope curves from Norwegian Sea isotope curves. The magnitude of the isotopic change from substage 5e to 5d (greater than 1%) is attributed to a combination of changing oceanic isotopic composition combined with a large temperature effect due to a sudden sea-surface temperature decrease of about 6oC. The persistence of heavy isotope values throughout substages 5d through 5a may be related to the sea-ice cover which prevented dilution of the isotopically heavy waters by isotopically light run-off. Sedimentation rates calculated for each of the isotope stages show large changes from one stage to another with some tendency for odd numbered stages to have higher rates.

Spatial dispersion of benthic Foraminifera in the abyssal central North Pacific 1

Abstract: Five 0.25-m2 box cores (four open cores and one vegematic core subdivided in situ into 25 contiguous lo- x lo-cm subcores) reveal that populations of benthic agglutinated Foraminifera in the central North Pacific are extremely abundant and diverse. As many as 120 species and 10,310 total fragments occur in a single open core, and the Foraminifera outnumber all metazoan taxa combined by at least an order of magnitude. Significant patchiness occurs on both the between-core scale of kilometers and the within-core scale of centimeters. Few species occurred in all cores and those that did were not abundant. Hierarchical classification an d multiple discriminant analysis on the resultant subcore groups in the vegematic core suggest potential interactions between certain species of Foraminifera and such external variables as surface deposit feeders, subsurface deposit feeders, carnivores, filter feeders, biogenic surface structure, and manganese nodules. Multiple regressions of foraminiferan species against all the external variables substantiate the existence of patterns of association. Foraminifera are important components of the benthic fauna, acting, among other things, as predators and disturbance agents. It may well be that they have a more significant effect on the structure and dynamics of deep-sea benthic communities than have any of the metazoan macrofaunal taxa that are the usual objects of deep-sea studies.

Periodic Freshwater Flooding and Stagnation of the Eastern Mediterranean Sea During the Late Quaternary

Abstract: Major negative oxygen isotopic anomalies in planktonic foraminifera are associated with deep-sea anoxic mud layers (sapropels) deposited 9000 and 80,000 years ago in the eastern Mediterranean. The isotopic depletion in surface-dwelling foraminifera is significantly greater than in mesopelagic foraminifera. This difference in isotopic response suggests that surface-water salinities were drastically reduced during times of sapropel formation, possibly as the result of meltwater runoff from the Fennoscandian ice sheet into the eastern Mediterranean by way of the Black and Aegean seas.

Early deglaciation of the labrador shelf.

Abstract: Two marine sediment cores from a basin on the southeastern Labrador Shelf penetrate a mud sequence extending back to 21,000 carbon-14 years before the present (B.P.). The benthic foraminifera are dominated by subartic nearshore species indicative of ice-free summer waters. The pollen record indicates the presence of a sedge-shrub tundra in eastern Labrador as early as 21,000 years B.P. Both sources of evidence suggest less extensive continental ice than has previously been reported for this subarctic region.

Silica oxygen isotopes in diatoms: a 20,000 yr record in deep-sea sediments

Abstract: PALAEOTEMPERATURE determinations based on oxygen isotope composition of planktonic foraminifera are well established for Quaternary and Tertiary deep-sea sediments1–4. Wide areas of the ocean floor, however, are lacking suitable calcareous fossils due to dissolution or unfavourable ecological conditions. Here we show that isotopic analyses of diatom frustules can adequately substitute for the analyses of calcareous micro-fossils. To test the efficiency of diatoms as an isotopic palaeothermometer5,6, we compare the oxygen isotope records of diatoms and of planktonic foraminifera in a box-core from the eastern equatorial Pacific (PLDS 72, latitude 01°08′N; longitude 109°15′6″W; water depth 3,626 m). This core was among other box-cores raised during the S.I.O. Pleiades expedition between May and September 1976, in an effort to obtain undisturbed samples of the uppermost deposits in this fertile area of pelagic sedimentation.

Quantitative forminiferal analysis and environmental interpretation of the Pliocene and topmost Miocene on the south coast of Sicily

Abstract: Benthonic and planktonic foraminiferal faunas have been investigated quantitatively from sediments of the Pliocene and topmost Miocene on the south coast of Sicily. Environmental and bathymetrical reconstructions have been established on the basis of the lithological and foraminiferal data. Two sections are studied in detail: the Lower Pliocene Trubi formation at Capo Rossello and the Middle and Upper Pliocene Monte Narbone formation at Punta Piccola. In both sections relations between benthonic and planktonic foraminiferal assemblages and lithology can be clearly established. Continuous marine sedimentation occurred across the ill-defined Miocene- Pliocene boundary, initially at depths of 50-100 m, but gradually the depth increased to 500-800 m for the middle part of the Trubi. At the onset of more clayey sedimentation at the base of the Narbone formation, depth of deposition decreased to some 100-400 m. For the relatively short biostratigraphic interval of the lower part of the G. puncticulata Interval-Zone the paleobathymetry was estimated at three localities revealing different depositional depths of the same type of Trubi sediment. A multi-depressional paleogeography for the entire Mediterranean during at least Late Messinian and Early Pliocene times is proposed to explain the seemingly conflicting implications of both the "desiccated, deep basin model" and the "shallow water, shallow basin model". This alternative model involves syn- and post-Messinian subsidence and may easily account for the presence of Trubi in deep basinal settings and elevated land-sections. The sections on the south coast of Sicily seem to have been located in an intermediate paleogeographical realm, i.e. on the slope from shoals to deeps. Periods of upwelling are thought to be responsible for increased quantities of planktonic foraminifera, diatoms and radiolarians in some laminated intervals within the Trubi formation. Oxygen depletion at the bottom may explain the low diversity and dwarfing of the benthonic foraminiferal associations in these laminated sediments. Precipitation of ferromanganese oxides during deposition of the Narbone formation determined the composition of foraminiferal assemblages. Oligotypical buliminidjbolivinid assemblages characterize the darker coloured, ferromanganese-rich intervals, whereas Globorotalia bononiensis dominates the planktonic associations in some of these horizons. Deposition of the Monte Narbone formation progressed in a shallowing environment. Superimposed on this process decreasing water temperatures are recorded in the Upper Pliocene Globorotalia inflata Assemblage Zone.

Micropaleontology and ocean surface climate.

Abstract: The interpretation of micropaleontological data based on the fossil remains of planktonic organisms requires an appropriate reference frame. The environmental changes that the plankton experience are a combination of geographic and seasonal factors, correlated by the average drift trajectories. Appropriate methods have been developed to study two drifts in the North Atlantic, one form the west-central Sargasso Sea to the Norwegian Sea and another around the subtropical Sargasso Gyre. The data on planktonic foraminifera from core tops can be used to relate the relative species distribution to the characteristics of the present sea surface. At any one location, the fossil assembly results from a superposition of plankton that have had varied time-temperature histories. To interpret the climatic and geologic history from downcore data will require an iterative technique. One assumes a surface climatology, determines the fossil record this would produce, and then compares this inference with available core data. The climatological assumptions are then modified until a satisfactory agreement is reached.

Recent Foraminifera of an Estuarine Environment in Broken Bay, New South Wales

Abstract: The foraminiferal fauna of Broken Bay, a complex estuary along the east coast of Australia, has been analysed. All the species found (181) have been identified and the individuals counted. From these data biotopes have been determined and their geographical extent briefly analysed in relation to the sediment distribution and the hydrological parameters. A large and varied benthonic population exists predominantly in the section of the estuary not subject to large salinity changes. Taxonomic notes on 56 species, out of 168 forming the benthonic population, are also included; two species, Haplophragmoides australensis and Cribrononion sydneyensis, are described as new taxa. An additional five species and one subspecies are recorded for the first time from Australian waters.

Biostratigraphy, palaeoecology and palaeogeography of the mainly marine Ager Formation (Upper Paleocene — Lower Eocene) in the Tremp Basin, Central-South Pyrenees, Spain

Abstract: During the greater part of the Palaeogene the Tremp Basin was an area which underwent rapid subsidence as compared with the axial zone of the Pyrenees to the north, and the Ebro Massif to the south. As a result the sea occupied this area for a long time and deposition of the Ager Formation took place during the Late Paleocene and Early Eocene in a bay forming an appendix of the Atlantic Ocean. At the maximum of the transgression probably a connection with the Tethys existed. During this entire development the Tremp Basin was tectonically separated from the more southerly Ager Basin by the Montsech High which underwent much less subsidence. The southern side of the Tremp Basin, under the influence of this high, subsided less rapidly than the central part. This resulted in a considerably thinner succession along the southern side, consisting mainly of limestones, and a much thicker pile in the central part mainly built up of marls. Sediments deposited along the northern side of the basin for a greater part have been eroded. Where they have been preserved, they are less limy than those along the southern side. The northern margin moved in the course of time in northern or southern direction, in contrast to the stable Montsech High which formed a stationary southern margin. The correlations within the formation are based on alveolinids and on lithostratigraphical characteristics. Hottinger’s alveolinid biozonation undergoes one modification which has important consequences for the chronostratigraphy of the Mediterranean Palaeogene. The .Fasciolites oblongus Zone namely does not appear to be a higher zone than the F. trempinus Zone, for F. oblongus lived contemporaneously with F. corbaricus and F. trempinus; F. oblongus lived in deeper water than the latter two, which explains that they are rarely found together in one sample. The occurrence of F. oblongus in the Ager Formation proves that the Ilerdian coincides for a large part with the Ypresian (Cuisian). Consequently the usually accepted Paleocene-Eocene boundary comes to lie within the Ilerdian, so that this stage cannot be maintained. Data from all alveolinid species together have resulted in a better comprehension of the evolution of this group. The number of species and lineages proves to be smaller than has been thought. From the palaeoecology of the alveolinids it can be deduced that three possibilities were realized by the successive species of a lineage: (1) they remain restricted to some specific, shallow marine environment during their entire evolution, (2) they adapt themselves to many different, but mainly shallow marine environments and remain so during their further evolution, or (3) they migrate from shallow to deeper marine environments. Fifteen facies types and 51 subfacies types are distinguished on palaeontological and/or sedimentological characteristics. Larger foraminifera, other microfossils and various groups of macrofossils are used for this, together with sedimentary structures and lithology. A large variety of facies types from fluvial and swamp deposits to marls of the deeper shelf occurs. Important facies types to be mentioned are lagoonal and tidal deposits, coral and algal reefs and related facies and various open marine facies. Apart from some minor fluctuations the sea gradually extended over a progressively larger area during the deposition of the lower half of the Ager Formation becoming deeper at the same time. The relief of the sea bottom simultaneously became steeper. Half-way through the formation the transgression reached its maximum, after which the sea again became shallower and the area occupied by it smaller. The relief of the sea bottom then again was reduced. The maximum reef development occurred in the lower part of the F. corbaricus Zone, and was most extensive along the southern side of the basin. In the upper half of the same biozone reef growth was more and more hampered due to important influxes of clastic material. In the lower half of the formation the occurrence of sand and silt is always local, whereas it is found nearly everywhere in the upper half. Most of this material came from NE, E and SE directions. The fauna and the flora point to a tropical climate. The Tremp Basin was situated at the northern margin of the tropics (zone of marginal reef growth). The maximum depth of the sea in the area studied was between 100 and 150 m. An important aid to the determination of the sea depth of various facies is the occurrence of glauconite which cannot have been formed above ca. 50 m depth in the Tremp Basin.

The Ultrastructure and Taxonomic Identity of the Symbiotic Algae of Heterostegina Depressa (Foraminifera: Nummulitidae) *

Abstract: There are numerous examples of symbiotic associations between Foraminifera and unicellular algae. Most of these Foraminifera are larger Foraminifera which occur in the shallow, oligotrophic waters of tropical seas (Table 1). Some of the symbiotic algae have been studied by light microscopy (Table 1, nos. 1–6). Dietz-Elbrachter (1971) suggested that the symbionts of Heterostegina depressa might be diatoms. She was, however, unable to prove this statement satisfactorily. Hottinger & Dreher (1974) published electron micrographs of the symbionts of H. depressa and Operculina ammonoides . From these micrographs identification of the symbionts was not possible. To date, only the symbionts of the following Foraminifera have been classified by electron microscopy: Archaias angulatus, Sorites marginalis, Globigerinoides ruber, Hastigerina pelagica and Globigerinoides sacculifer (Table 1, nos. 7,10,12,13,14).

Biological results of the Snellius expedition XXX : the foraminifera collected in 1929 and 1930 in the eastern part of the Indonesian Archipelago

Abstract: INTRODUCTION Of the bottom material collected by the Snellius-Expedition 78 samples contained Foraminifera. Many of these samples were extremely small, since they were gathered by means of piston core samplers; some were larger, as they were collected by means of a dredge; others were samples in shallow water at beaches or reefs. A l l samples were fixed in formaldehyde, so that after the 40 years they remained in store before they were studied, rests of protoplasma were seldom preserved. The numerous plankton samples, preserved in formaldehyde or in alcohol, did note contain planktonic Foraminifera; obviously the small amount of CaC03 in the samples caused the dissolution of the tests. The planktonic Foraminifera are not described here, as planktonic forms of the Pacific Ocean were already studied by Parker (1962) and by Todd (1965). Planktonic specimens from several of the localities are preserved in cardboard slides, but, as they do not belong to the bottom fauna, they were not considered ecologically. Several slides are preserved containing the planktonic fauna of a sample as a whole.

Maastrichtian-paleocene foraminifera from NW Nigeria and their paleogeography

Abstract: Maastrichtian and Paleocene beds of southeastern Iullemmeden basin contain rich but poorly preserved foraminiferal'microfaunas. Twelve species are described, none of which is new. Although foraminiferal species were noted in these sediments by other workers, no previous attempt has been made to figure and describe them. The Paleocene benthic foraminifera assemblage of the Saharan epicontinental sea that flooded the Iullemmeden Basin has many taxa in common with the European Boreal and Meridional epicontinental faunas. The ancient Tethys Sea served as a corridor for this faunal exchange. However, the benthic foraminiferal microfaunas of the Iullemmeden Basin are very distinct from those of the Southern Nigerian Sedimentary Basin. This suggests that the two basins were not directly connected during the Paleocene.