Showing papers on "Foraminifera published in 1980"

Foraminifera and chlorophyll maximum: vertical distribution, seasonal succession, and paleoceanographic significance.

Abstract: Many planktonic foraminiferal species deposit their shells at the chlorophyll maximum zone, and it is the temperature range here that is relevant to oceanographic models which use ratios of oxygen-18 to oxygen-16 in fossil foraminifera and foraminiferal fossil assemblages to ascertain past climates. During periods of stratification of the upper water column, the temperature at the chlorophyll maximum may differ from the sea surface temperature by 10°C in the western North Atlantic.

Vertical Distribution and Isotopic Composition of Living Planktonic Foraminifera in the Western North Atlantic

Abstract: Thirteen species of planktonic foraminifera collected with vertically stratified zooplankton tows in the slope water, Gulf Stream cold core ring, and northern Sargasso Sea show significant differences in their vertical distributions in the upper 200 meters of these different hydrographic regimes. Gulf Stream cold core rings may be responsible for a southern displacement of the faunal boundary associated with the Gulf Stream when reconstructed from the deep-sea sediment record. Oxygen isotope analyses of seven species reveal that nonspinose species (algal symbiont-barren) apparently calcify in oxygen isotope equilibrium, whereas spinose species usually calcify out of oxygen isotope equilibrium by approximately –0.3 to –0.4 per mil in δ18O values. The isotope data indicate that foraminifera shells calcify in depth zones that are significantly narrower than the overall vertical distribution of a species would imply.

Introduction to marine micropaleontology

Abstract: Marine micropaleontology: an introduction (W.A. Berggren). Calcareous Microfossils. Foraminifera (A. Boersma). Calcareous nannoplankton (B.U. Haq). Ostracodes (V. Pokomy). Pteropods (Y. Herman). Calpionellids (J. Remane). Calcareous algae (J.L. Wray). Bryozoa (K. Brood). Siliceous Microfossils. Radiolaria (S.A. Kling). Marine diatoms (L.H. Burckle). Silicoflagellates and ebridians (B.U. Haq). Phosphatic Microfossils. Conodonts and other phosphatic microfossils (K.J. Muller). Organic-Walled Microfossils. Dinoflagellates, acritarchs and tasmanitids (G.L. Williams). Spores and pollen in the marine realm (L. Heusser). Chitinozoa (A. Jansonius, W.A.M. Jenkins).

Atlas of benthic shelf foraminifera of the southwest Atlantic

Abstract: Area of Study.- Water masses.- Cape Horn current.- Malvin current.- Coastal Argentine waters.- Area influenced by the Rio de la Plata.- Coastal waters of Uruguay and Southern Brazil.- Benthic foraminifera provinces.- North Patagonian subprovince.- South Patagonian subprovince.- Malvin subprovince.- Summary of Benthic Foraminiferal Investigations in the Area.- Principal Factors Influencing the Benthic Foraminiferal Distribution.- Salinity.- Euhaline foraminifera.- Hypohaline foraminifera.- Fresh water foraminifera.- Salt marsh foraminifera.- Temperature.- Depth.- Water mass.- Systematics and Distribution.- Euhaline species.- Hypohaline and fresh water species.- References.- Plates.- Maps.

Palaeoceanographic change in the Pacific at the Eocene-Oligocene boundary

Abstract: Oxygen isotopic studies both of benthic formanifera1–5 and shallow-marine carbonates6–8 have provided a useful monitor of marine palaeotemperatures. The Deep Sea Drilling Project (DSDP) has provided cores from many ocean basins to conduct detailed stable isotopic and palaeoceanographic studies of the Cenozoic and late Mesozoic. DSDP Sites 277 and 292, separated by ∼60° latitude in Palaeogene times, each record an 18O enrichment in benthic foraminifera of nearly 1‰ beginning at the Eocene–Oligocene boundary. Planktonic foraminiferal trends are similar to benthic trends in the high latitude southwest Pacific Ocean, but tropical planktonics show only a minor (∼0.3‰) increase which may reflect a change in seawater composition. These results suggest a sudden cooling of Pacific deep waters and high latitude surface waters forms a useful stratigraphic marker for the Eocene–Oligocene boundary. This boundary is particularly important because of its association with several worldwide palaeo-oceanographic and biogeographic changes. These include a sudden drop in the calcite compensation depth of 1–2 km (refs 9, 10); a decrease in planktonic microfossil diversity11–13; a change in planktonic biogeographic patterns12–14; and increased erosion of deep-sea sediments over wide areas15,16.

Middle and Late Cretaceous planktonic foraminifera of the Western Mediterranean area

Abstract: Planktonic foraminifera from sections in predominantly pelagic and hemipelagic sediments of Late Albian to Late Maastrichtian age in southern Spain, central Tunisia and northern Italy were studied. Their vertical distribution allows for the recognition of 21 zones. They are correlated with the calcareous nannofossil zonation of Verbeek (1977), which was essentially based on the same material. Recent data from stratotypes allow for a rather detailed correlation with the chronostratigraphic scale. An improved calibration of the planktonic biozonations and the Middle and Late Cretaceous magnetostratigraphic scale is proposed. Late Aptian, Late Albian and Cenomanian reversals are documented with micropaleontological evidence from the actual cores. The systematics and phylogeny of several groups of Cretaceous planktonic foraminifera are discussed. The subdivision of post-Cenomanian globotruncanids into genera, as now widely accepted, is shown to be unrealistic from an evolutionary point of view. The genus Globotruncana Cushman is shown to be polyphyletic. Turonian and younger globotruncanids can be subdivided into a number of natural groups by means of conservative diagnostic features, which remain constant throughout the ranges of the groups. Generic features appear to be progressive and develop analogously in each of the groups. The evolution of Middle and Late Cretaceous planktonic foraminifera appears to be closely related to the occurrence of two major crises in the oxygenation of the World's ocean waters. Entirely new associations of keeled forms appear immediately after these anoxic events, which occurred during most of the Aptian and Albian and at the Cenomanian-Turonian boundary. A third event, close to the Santonian-Campanian boundary, is thought to be due to fundamental changes in the oceanic circulation pattern in relation with the opening history of the Atlantic Ocean. The Cretaceous-Tertiary boundary extinction is briefly discussed. Its explanation must be essentially different from that of the other three major events. Taxonomic notes are made on the most important species. New generic names for apparently natural groups have not been introduced and incorrect names for important zonal markers have not been altered as this would hamper the comparison between the zonal scheme as proposed here and previous ones.

Distribution of Recent benthic foraminifera off the North American Atlantic coast

Abstract: Culver, Stephen, J., and Martin A. Buzas. Distribution of Recent Benthic Foraminifera off the North American Atlantic Coast. Smithsonian Contributions to the Marine Sciences, number 6, 512 pages, 150 figures, 2 tables, 1980.—A computer file of all available distributional data on the recent benthic foraminifera off the North American Atlantic Coast was constructed from 142 papers published over the last 130 years. Manipulation of this file produced 5 catalogs and 150 maps. Catalog 1 lists alphabetically species names with publication and locality information as recorded in the literature (i.e. unsynonomized). Catalog 2 lists alphabetically synonomized species names with publication and locality information. Catalogs 3 and 4 list alphabetically all unsynonomized and synonomized species names, respectively. Catalog 5 lists synonomized species names by increasing latitude and longitude. During the last 130 years, 1303 names have been used to record benthic foraminifera off the North American Atlantic Coast. Through synonomization this number was reduced to 876 of which 149 occur at 20 or more of the 542 sample sites. Computer-generated maps were drawn for these 149 most commonly recorded species. Species were grouped by depth and geographic distribution through examination of the maps. Seven species are coastal in their distribution, 71 occur mainly at depths of less than 200 m, 41 at depths of greater than 200 m, and 30 are ubiquitous. Thirteen species alter their depth distribution with latitude. Geographically, the species group into 6 categories. Thirty-one species occur from Florida to Cape Hatteras, 26 from Cape Hatteras to Cape Cod, 4 from Cape Cod to Newfoundland, 22 from Florida to Cape Cod, 40 from Cape Hatteras to Newfoundland, and 26 are ubiquitous. Because of the overlapping distribution of the species, no simple boundaries can be drawn for faunal provinces. We recognize two major overlapping faunal provinces: a northern province from Newfoundland to Cape Hatteras and a southern province from Florida to Cape Cod. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institutions's annual report, Smithsonian Year. SERIES COVER DESIGN: Seascape along the Atlantic coast of eastern North America. Library of Congress Cataloging in Publication Data Culver, Stephen J Distribution of recent benthic foraminifera off the North American Atlantic coast. (Smithsonian contributions to the marine sciences ; no. 6) Bibliography: p. Includes index. 1. Foraminifera—Atlantic coast (North America—Geographical distribution. 2. Protozoa— Geographical distribution. 3. Protozoa—Atlantic coast (North America)—Geographical distribution. I. Buzas, Martin A., joint author. II. Title. III. Series: Smithsonian Institution. Smithsonian contributions to the marine sciences ; no. 6. QL368.F6C62 593.1'2'097 79-607122

Facies Succession of Pliocene-Pleistocene Carbonates, Northwestern Great Bahama Bank

Abstract: Preliminary study of nine core borings from the northwestern Great Bahama Bank has yielded the first regional information on depositional facies and stratigraphy of pre-Holocene carbonates to depths of 75 m below sea level. The cross section of borings extends 120 km from Tongue of the Ocean across Andros Island and the shallow bank to Orange Cay on the western bank margin facing the Straits of Florida. The depositional facies present an atoll-like cross section with thick marginal accumulations of coral-coralline algal limestones at least 5 km wide both on the windward (east) and the leeward (west) margins. The discovery of these reef rims confirms earlier inferences that the Bahama Banks are Tertiary-Quaternary atolls. Although both margins have reef rims, there is a distinct asymmetry of facies within the bank: grainstones are more abundant on the windward margin and wackestone-mudstones are widespread over the interior and leeward part of the bank. The succession in borings from the interior of the bank can be subdivided into three intervals: the upper two intervals whose aggregate thickness averages 43 m are irregularly cemented, unstratified packstones and wackestones in which peloids and ooids are the predominant grains. The third, lowermost interval is predominantly stratified skeletal packstone with subordinate amounts of skeletal wackestone; it has an abundant fauna of bivalves, Foraminifera, and, commonly, branches of the finger-sized coral Stylophora spp. As the change from nonskeletal to skeletal limestones is relatively rapid and traceable for 40 km, it is used to define the base of a new formation, the Lucayan Limestone. The upper boundary of this formation is the limestone surface exposed on the Bahama Islands or cov red by soft Holocene sediments on the submerged banks. The Lucayan Limestone is dated as late Pliocene-Pleistocene on the basis of the disappearance of Stylophora spp. The known uppermost range of Stylophora spp. in the western Atlantic is through the upper Pliocene. Additional support for this dating comes from the distribution of discontinuity surfaces that are considered to be the record of subaerial exposure of the marine deposits. In the Lucayan Limestone, the frequency of discontinuity surfaces per meter of core is twice that of the pre-Lucayan unit; this increased frequency of subaerial exposure is consistent with the assignment of the Lucayan Limestone to the late Pliocene and Pleistocene. The major change in facies from stratified, skeletal, pre-Lucayan limestones to the unstratified, nonskeletal Lucayan Limestone is interpreted as the result of apparent shallowing of the bank triggered by the more frequent fluctuations of sea level and possibly by changes in the elevation of high stands; both began in the late Pliocene and continued throughout the Pleistocene.

Sediments of the Mississippi, Alabama, and Florida (MAFLA) Continental Shelf

Abstract: The eastern Gulf (MAFLA) continental margin may be conveniently divided into two parts of opposing history and character. West of Cape San Blas lies the eastern limb of the Gulf Coast Geosyncline whose surface expression is a clastic sand body, called the MAFLA Sand Sheet, grading westward into the muds of the Mississippi pro-delta. These sediments have a clay mineral suite dominated by smectite. East of Cape San Bias lies the West Florida Margin, a sequence of carbonate and evaporitic rocks which has been cut off from a major clastic source since Jurassic time. The surface expression of this sequence is the West Florida Sand Sheet, predominantly a patchy veneer of shell hash and foraminiferal, algal, and even oolitic sands which is subjected to periodic reworking by frontal system st rms and hurricanes. Kaolinite dominates its clay mineralogy. Seaward of the carbonate sands lies the West Florida Lime Mud facies, slope sediments composed of planktonic foraminifera and coccoliths. Inshore of the carbonate sands and separated from them by a zone of mixed composition lies a mature quartz fine sand, which also makes up the beaches of Southwest Florida. West Florida shelf quartz sands appear to have been deposited at lower sea level stands and to have been transported back and forth with no net drift in a longshore current system which changes seasonally from north to south. Clay mineralogy in portions of the MAFLA region shows distinct changes in composition over a period of a year in the benthos and over periods as short as a few hours in the water column. These changes reflect contribution from two distinct provenances. Benthie variation probably results from occasional intrusion of smectite laden Mississippi River or Loop Current water into the eastern zone. Water column variation may be the result of seiching of the Gulf or the pulsing movement of kaolinite laden eastern shelf water to the west.

Carbonate Sediment Drifts in Northern Straits of Florida

Abstract: High-resolution, air-gun seismic reflection profiles from the northern Straits of Florida (water depths < 800 m) have revealed the presence of large (up to 3,000 sq km) carbonate sediment drifts off the northwest corners of both Little Bahama and Great Bahama Banks. These drifts are hemiconical bodies of carbonate sands up to 600 m thick that have prograded north in response to an intensification of the Florida Current since the middle Miocene. Deposition of the sediment drifts occurred along the Bahama Banks on the lee side of the present oceanic circulation pattern, where there appears to be a convergence of bottom currents having velocities of up to 60 cm/sec. However, depositional rates may have been episodic, with the greatest rates correlating with intensified ci culation patterns during glacial events. Because of widespread submarine cementation, piston coring of these sediment drifts was difficult. Most cores contained less than 1 m of sand and angular rock fragments, suggesting that a thin veneer of sand overlays hardgrounds. In one 5-m-long core, granule-size material constitutes up to 40% of the total sediment (average of 3.9%), sands 50 to 80% (average of 60.4%), silts 5 to 35% (average of 25.0%), and clays 5 to 20% (average of 10.7%). Mean grain size ranges from 0.0 to 3.0 ^phgr (coarse to fine sand) and the sediments are moderately to poorly sorted. The granules are mostly submarine-lithified intraclasts; the fine sands are mostly planktonic Foraminifera; and the coarser sands consist of pteropods and shallow-water material such as Halimeda, peneropolid Foraminifera, fragment of coralline algae, ooids, or micritized mollusk debris. Off-bank sediment transport along the west side of the Bahama Banks and subsequent along-slope transport by the Florida Current appear responsible for the supply of bank-derived sediment to the drifts. Rocks recovered by dredging and in-situ sampling from submersibles are mostly grain-supported biomicrites, biomicrudites, and intramicrudites cemented by submicrocrystalline, amorphous to peloidal high-Mg calcite. Preliminary bulk-rock C14 dates suggest a late Pleistocene or older age. Porosities of up to 40% are common within these rocks, consisting of both primary intergranular and intragranular pores and secondary macroborings and microborings produced by endolithic organisms. In the rock record, sandy sediment drifts formed at relatively shallow depths (< ~ 1 km) by strong bottom currents associated with wind-driven surface currents may be attractive hydrocarbon reservoirs. In contrast, sediment drifts formed at abyssal depths (3 to 5 km) by relatively sluggish thermohaline bottom currents would probably contain too much impermeable muddy sediment to be potential reservoirs.

Labrador Sea bio-, tephro-, oxygen isotopic stratigraphy and Late Quaternary paleoceanographic trends

Abstract: A stratigraphic framework for eastern Labrador Sea cores has been developed for the interval 0–90 000 years BP through analysis of oxygen isotopes, volcanic ash, benthonic foraminifera, and the rad...

Recent, Temperate, Sub-Photic, Carbonate Sedimentation: Rockall Bank, Northeast Atlantic

Abstract: Rockall Bank (56°N to 58°N and 13°W to 16°W) is approximately 20,000 km2 in area and 100 m to 300 m deep, and is effectively removed from present day terrigenous sedimentation by surrounding deep water. Water temperature ranges from 8° C to 12°C. Carbonate sediments presently accumulate on the bank burying Tertiary and older rock outcrops and Pleistocene boulders of glacial origin. Superficial samples were collected by grabbing and dredging and the environments of carbonate production and deposition were observed by underwater television. Component analyses of the sediments indicate a roughly concentric zonation of lithofacies with coarse bryozoan and serpulid remains dominant in the shallow central portion less than 120 m deep. The inner zone is sur ounded by a zone rich in bivalve and echinoderm fragments and benthic foraminifera, which covers most of the bank from depths of about 120 m to 220 m. The peripheral zone below 220 m is dominated by pelagic foraminifera. In water 200 m to 400 m deep, 10 m to 20 m wide patches of I m high living colonies of the branched coral Lophelia pertusa abound and form an annular zone around the bank margin. The bulk of the carbonates are calcitic with some aragonitic remains present in the shallow (molluscan) and deep (coral) zones. Microbial borings are rare in sediments from agitated waters less than 100 m deep but very abundant in sediments (particularly mollusc, echinoderm and coral) from calmer deep waters. The bioerosion of coral framework is probably more rapid than the rate of burial of the upright colonies which will lead to their preservation as irregular bands of broken branches. Below 200 m many pelagic tests are filled with diagenetic glauconite and rarely silica, though conspicuous evidence f inorganic carbonate dissolution or precipitation is absent. The carbonate deposits are not very thick but if accumulation continues to keep pace with the subsidence of the bank, aphotic temperate limestones will ultimately be formed, having a central zone of coarse fragments of benthic organisms rimmed by pelagic deposits containing bands rich in corals.

Stable Isotopes in Benthic Foraminifera: Seasonal Variation in Large Tropical Species

Abstract: The shells of large benthic foraminifera contain a record of seasonal temperature ranges and life history stages. Marginopora vertebralis and Cyclorbiculina compressa show distinct differences in life history, growth rate history, and life-span, as reflected in stable isotope patterns within their shells.

North Atlantic Deep Water formed by the later middle Miocene

Abstract: There is evidence that in Mesozoic and Palaeogene times both north and south subpolar areas had a mild climate1,2. Unlike the present day climatic symmetry, with warm equatorial regions and ice-covered polar regions, a strong planetary asymmetry developed in the middle Miocene, when the Antarctic ice cap was established while the northern high latitudes remained unglaciated3. The symmetry was restored when a Northern Hemisphere continental ice cover was established ∼3 Myr ago in the middle Pliocene4. These changes influenced the formation of deep water in the ocean. At present the cold, dense bottom waters originate in only two high latitude areas—the Weddell Sea producing Antarctic Bottom Water, and the Norwegian Sea, producing Norwegian Sea Overflow Water which after mixing is a major component of the North Atlantic Deep Water. The production of cold deep water in the Southern Ocean started at the Eocene–Oligocene boundary3. We present here new evidence from isotope analyses of benthic Foraminifera from DSDP site 116 indicating that the production of oxygenated deep water in the North Atlantic Ocean started in the late middle-Miocene, ∼12 Myr ago.

Foraminifera: Distribution of Provinces in the Western North Atlantic

Abstract: All published distributional data on recent benthic foraminifera of the North American Atlantic continental margin were archived into computerized catalogs. Cluster analysis of these data delimited seven large, marginally overlapping provinces exhibiting a congruous relationship with western North Atlantic water masses. The single major latitudinal faunal change occurs at Cape Hatteras.