Showing papers on "Foraminifera published in 1971"

Seasonal distribution of planktonic foraminifera in the western North Atlantic

Abstract: Distinct and predictable patterns for 17 species, frequency distribution depends on phytoplankton, three major faunal assemblages (subarctic, transitional, subtropical)

Late Quaternary foraminifera from Vendsyssel, Denmark and Sandnes, Norway

Abstract: Rolf W. Feyling-Hanssen: Weichselian interstadial Foraminifera from the Sandnes-Jæren area. Five shallow borings in the town of Sandnes, south of Stavanger, revealed clay deposits with marine fossils under a cover of sandy till with large blocks of Archaen rocks. This clay is called the Sandnes Clay. It is stiff and pre-consolidated, and disturbed only in the uppermost part. Four foraminiferal zones were distinguished, 1) the labradoricum-norcrossi assemblage, 2) the upper zone with scattered specimens, 3) the asklundi-bartletti assemblage, 4) the lower zone with scattered specimens. The assemblages are usually dominated by Elphidium clavatum and Cassidulina crassa, and turn out to be of Middle Weichselian (Middle Wisconsin) interstadial age. Deposits of corresponding age were found in the district of Jæren and on the island of Karmøy.

Cenozoic paleoglacial history of Antarctica recorded in Subantarctic deep-sea cores

Abstract: Planktonic foraminifera species diversity and ice-rafted sand grains, indication of glaciation during most of Cenozoic, middle Miocene warming trend

Depth habitats of growth stages of pelagic foraminifera.

Abstract: Oxygen isotopic analysis of different size groups of shells of pelagic foraminiferal species shows that some species deposit their shells at constant depths while others deposit them at increasing or decreasing depths. These patterns show regional variations. Globigerinoides rubra and Globigerinoides sacculifera remain the most convenient species for oxygen isotopic determination of the past surface temperatures of the ocean.

Sedimentology of Fine-Grained Deep-Water Carbonate Turbidites, Monte Antola Flysch (Upper Cretaceous), Northern Apennines, Italy

Abstract: The Monte Antola Flysch consists of alternating calcareous turbidites and subordinate non-carbonate "background" sediment. Graded units as much as 28 m thick (but averaging less than 1 m) were deposited by "single events," and one-half to three-fourths of this material is finer than medium silt. Most of the calcareous sediment is shown to be a reworked and sorted pelagic ooze containing abundant coccoliths, planktonic Foraminifera, sponge spicules, and echinoderm fragments. Chert occurs as cement and replacement; calcite is the major cement and replaces sponge spicules. Evidence for turbidity current emplacement includes repeated graded bedding, microscopic shape sorting, sole markings, Bouma intervals, reworking of Foraminifera, and burrowing from the upper surfaces of beds. All criteria indicate a very distal environment of deposition, and these units clearly show that much of the fine-grained material associated with flysch deposits may be introduced by turbidity currents and not as hemipelagic material. Reworking of contemporaneous deep-water carbonate oozes into a distal environment of deposition, with sediment ponding yielding theobserved thicknesses, and coupled with the absence of carbonate material in the background sediment, are indicative of abyssal-plain sedimentation, probably at depths below the CaCO3 compensation level (4500 to 5000 m in modern oceans). The presence of an oceanic basin in the northern Appennines during the Late Cretaceous has considerable significance for hypotheses on the evolution of the Mediterranean region.

Arctic Ocean Ice Cover and Its Late Cenozoic History

Abstract: Foraminifera abundance patterns and accompanying sediment analysis from Arctic Ocean sediment cores are useful tools in paleoecologic interpretations. In the Brunhes interval, there are at least two abundance peaks of Foraminifera; one, representing present conditions, in the top part of all cores, and the other near the Brunhes-Matuyama boundary (700,000 yrs B.P.). In addition, many cores show a continual fluctuating abundance pattern throughout the Brunhes interval. Cores with older age sediment have two additional Foraminifera abundance peaks, both in the Maruyama. The younger is in the middle part of the Maruyama and the older is near the time of the Olduvai Event in the early part of the Matuyama. Study of the oldest age sediment available (middle Pliocene) confirms that Foraminifera never have been more abundant in the Arctic Ocean than they are today. Therefore, the ice-covered conditions of the present are taken to represent the warmest conditions necessary to explain other older abundance peaks in the cores. If carbonate solution is eliminated as an explanation, the intervals of few or no Foraminifera must represent conditions quite different from those represented by the abundance peaks and the present. The equilibrium ice conditions of the modern Arctic Ocean could be altered by minor atmospheric variations. Thicker ice could form rather quickly and rather simply and this could upset plankton productivity. Thicker ice could also prevent a free accumulation of coarse detritus and erratics such as accumulate in the Arctic Basin today. These sediment types generally are most abundant during times of abundant Foraminifera deposition and are rare in the intervals during which few or no Foraminifera were deposited. These factors considered together lead to the theory that the Arctic Ocean has been frozen since at least the middle Pliocene and that the most significant change in the Arctic ice has been in its thickness. Thicker ice restricted photosynthesis and Foraminifera productivity. Times of thinner ice with conditions more like those of the present are represented by abundance peaks of Foraminifera and concentrations of glacially rafted material. None of the patterns of Foraminifera abundance or glacially rafted material show good correlation with the classical continental glacial stages. Continental glaciers advanced and retreated in the northern hemisphere while the Arctic ice-cover remained relatively stable. There would be important ecologic, economic, and political problems if the Arctic Ocean were to become ice-free. The historical evidence does not support the idea that a renewed pattern of Pleistocene glaciation would be one of the problems, however.

Evolution of planktonic foraminifera and paleotemperatures

Abstract: The evolution of planktonic Foraminifera since the Jurassic is characterized by an alternation of periods of extinction and radiation. Such a pattern can be closely correlated to the isotopic paleotemperature curves for the last 150 m.y., which are also cyclic in nature. Warm intervals on the paleotemperature curve have been characterized by radiations and the cold intervals, such as that of today, have been characterized by extinctions of genera of planktonic Foraminifera.

New Zealand late Cretaceous (Haumurian) Foraminifera and stratigraphy: A summary

Abstract: One hundred and five genera and subgenera and 201 species (65 siliceous and agglutinated species, 121 calcareous benthonic species, and 15 planktonic species) have been recorded in New Zealand Late Cretaceous (Haumurian) marine sediments. Micro-faunas obtained from Dunedin, North Otago, North Canterbury, Marlborough, southern Hawke's Bay, Raukumara Peninsula—East Coast, and Northland are incorporated in the present study. Three assemblage zones are recognised. The Trocham-mina globigeriniformis Zone contains only agglutinated taxa which are believed to be strongly facies-controlled and thus of limited use in correlation. The Rzehakina epigona Zone contains an entirely siliceous and agglutinated fauna which is closely comparable with Senonian-Eocene flysch microfaunas of the West European Alps and Polish Carpathians. The Globotruncana circumnodifer Zone contains rich assemblages of siliceous, agglutinated, and calcareous taxa. Certain elements present in this latter zone (= uppermost Haumurian) al...

Isotopic Analysis of Planktonic Foraminifera from the Cenozoic of the Northwest Pacific, Leg 6

Abstract: Isotopic determinations for oxygen and carbon are reported here for formainifera from forty-two core samples from three sites drilled during Leg 6 (Figure 1). The sites are: Site 44 (Hole 44.0) on the Horizon Ridge, latitude 19° 18.5'N, longitude 169° 00'W; Site 47 (Hole 47.2) on the Shatsky Rise, latitude 32° 26.9'N, longitude 157° 42.7'E; Site 55 (Hole 55.0) on the Caroline Ridge, latitude 19°18.l'N, longitude 142° 32.9'E. Cores from Site 47 contain material from the Pleistocene to Upper Miocene and the Middle Eocene to Upper Maestrichtian; the Oligocene and portions of the adjacent epochs are missing in this hole. At Site 55 a nearly complete Neogene section with the exception of the top of Miocene was recovered. The Lower Oligocene and the Upper Eocene were cored at Site 44. When combined, the three sites offer a nearly complete sequence from the latest Cretaceous through the Tertiary. The basic lithology at the three sites is a calcareous ooze, predominantly a nannofossil-foraminifera chalk ooze.

Stratigraphy and foraminifera of the neogene of the Eastern Guadalquivir basin (Southern Spain)

Abstract: The Neogene succession of the eastern part of the Guadalquivir basin was found to consist from bottom to top of turbidites, fine marly and clayey sedi,- ments and again turbidites. Five formations and one member could be distinguished. In the southern part of the basin sediments appear to be allochthonous; their area of deposition must have been farther south. In the North there is possibly a gradual change in upward direction into autochthonous sediments of the Upper Miocene. In studying the planktonic foraminifera attention has been paid to their horizontal and vertical variation. It appeared necessary to extend the concept of some species, like that of Globigerina pseudobesa and Globigerinoides bulloideus. Several new forms have been described; partly they may be considered as local variants of known species, like Globorotalia d. mayeri, Globigerina aff. pachy.,. derma, Globigerina sp., Globigerinoides d. conglobatus. Other {orms seem to be less close to known species, like Globorotalia sp., Globigerino£des afL Tuber and sphaeroidinellopsis sp. As their stratigraphical occurrence was not studied outside the field area and phylogenetic relationships to other species remained undear,;it seemed not justified to erect them as new species. Study of pre-adult stages was done by removing the final chambers of adult specimens. It proved to be a help in disentangling homeomorphic species. Investigation on several members of the Globigerinoides trilobus - Orbulina universa lineage, indicates that together with a change in relative size and shape of the final chamber also oachange in the earlier stage has taken place. In sections considered to be Middle Tortonian representatives of the Globigerinoides bulloideus group occur in great abundance and with an extremely wide variation. In these strata transition between the genera Globigerina and Globigerinoides is constantly present. For most variants the stratigraphic range is very short, however. For the Globorotalia menardii group a general trend from unkeeled to keeled was found throughout the stratigraphic column. The outline of the chambers in spiral view also underwent a gradual change. As these trends seem to be of local importance only, no names were given to the distinctive forms. Coiling direction of this group changes from left to right in strata which are considered to be Middle Tortonian. On the basis of their content of planktonic foraminifera separate sections could be arranged in biostratigraphic order. Moreover in most cases correlation with the biozonation of BLOW (1969) appeared to be possible, indicating that the sediments range from zone N. 4 toN.-16/N. 17. According to the current literature this should be from Aquitanian to Upper Tortonian/Messinian (?). Miogypsinids found in the oldest sections suggest a Chattian to Aquitanian Age. Uvigerinids belonging to the U. cretensis lineage are present in the younger formations. They allow correlation with the upper part of the Tortonian stratotype, which is in fairly good agreement with the planktonic foraminifera. Some speculations have been made about the factors affecting the deposition of the laminated and non-laminated siliceous marl (moronitas) in the southern part of areas with and without burrowing activities, which might explained by an tion might have been caused by a combination of high and fairly constant production of phytoplankton and zooplankton (as a result of upwelling water) together with a seasonal peak in the influx of terrigenous material from rivers. Absence of burrowing organisms as a consequence of a zone of low concentration of dissolved oxygen might account for the fact that lamination remained preserved. The cooccurrence of laminated and non-laminated sediments of the same age is in favor of areas with and without burrowing activities, which might be explained by an irregular bottom topography. Northward moving slipped masses might account for such sea floor relief. The presence of turbidites as topmost sediment indicates a still rather deep basin at that time. Unless later sediments have been completely eroded away, it suggests that the eastern part of the Guadalquivir basin rather suddenly emerged at the end of the Miocene. In the western part of the basin (Carmona area) sedimentation lingered on, but of a more shallow character. The larger part of the section at Carmona does not seem to have equivalents in time in the eastern part of the basin.

Planktonic foraminifera; sediment production in an oceanic front

Abstract: Faunal composition and phenotypic variation of four assemblages, productivity of planktonic foraminiferal sediments controlled by water movement, food supply, reproduction, predation, Pacific Ocean off Baja California, Mexico

On the temperature relationships of planktonic foraminifera

Abstract: No fixed relationship between temperature and species frequency, certain aspects of distribution not primarily controlled by temperature, reevaluation necessary for application to paleoclimatic interpretations

Ecology of the planktonic Foraminifera living in the surface layer of Drake Passage

Abstract: The planktonic foraminiferal fauna was studied in 104 surface plankton samples collected by the author during the crossing in both directions of Drake Passage between Tierra del Fuego and Elephant Island off the Palmer Peninsula, Antarctica, during the months of January and February, 1969. Samples were gathered by means of a fire pump. This method is discussed and recommended for planktonic foraminiferal collection. Eight species were determined, and their horizontal distribution was established. The percentage abundance of each species, as well as the number of specimens per cubic meter of filtered water, were calculated for every station. Distribution patterns of foraminifers were compared with those obtained by previous authors and were related to the surface hydrology. Some discrepancies were found and discussed. The most simple means of separating Globigerina pachyderma from G. quinqueloba is proposed and the most simple means of locating the Antarctic Convergence by the use of foraminifers is discussed. Abnormal spinosity of foraminiferal tests is considered. Ecology of the planktonic foraminifera living in the surface layer of Drake Passage

Planktonic foraminifera in Gulf of Guinea sediments

Abstract: Taxonomy, four bathymetric biofacies, tropical fauna, some temperate or cold-water species, comparison with living fauna, eastern Atlantic off Africa

Upper Cretaceous foraminifera from the upper Mancos Formation, the Mesaverde Group, and the basal Lewis Formation, northwestern Colorado

Abstract: Systematic descriptions, five new species, Ammobaculites masteri, A. pagodensis, Cyclammina haydeni, Scutuloris batteni, Eoeponidella yampensis, three faunal assemblages (lagoonal, estuarine, near-shore marine)