Showing papers on "Foraminifera published in 1970"

Diversity of Planktonic Foraminifera in Deep-Sea Sediments

Abstract: The diversity of a planktonic foraminiferal assemblage on the ocean floor depends on the state of preservation of that assemblage. As dissolution progresses, species diversity (number of species in the assemblage) decreases, but compound diversity (based on relative species abundance) first increases and then decreases; species dominance first decreases and then increases. The reason for these changes is that the species most susceptible to solution deliver moresediment to the ocean floor than do species with solution-resistant shells, possibly because the more soluble tests are produced in surface waters, where growth and production are greatest.

Cenomanian and Turonian foraminifera from the Great Plains, United States

Abstract: Systematic descriptions, new taxa, benthonic and planktonic specimens, depositional environment

Differential Isotopic Fractionation in Benthic Foraminifera and Paleotemperatures Reassessed

Abstract: Different species of benthic Foraminifera taken at the same level in an Atlantic core yielded different oxygen isotopic values. It was therefore impossible to deduce paleotemperature values. In addition, pelagic and benthic species showed the same isotopic variations, an indication that pelagic and benthic species reflect only the variation of oxygen-18 composition of the ocean.

The role of foraminifera in the trophic structure of marine communities

Abstract: Foraminifera are recorded as feeding chiefly upon bacteria, small diatoms, and nannoplankton in a wide variety of marine environments. Thus their food items are usually below 50 μ and commonly below 25 μ in size. Predators upon Foraminifera range from highly specialized microcarnivores that feed largely on Foraminifera to less selective ones that include Foraminifera in a mixed diet and to generalized feeders that ingest Foraminifera along with much other material. Foraminifera thus form part of a key link in marine food chains, assimilating energy available from minute autotrophs and also retrieving energy available during the final stages of degradation of organic debris. In turn, they support a variety of larger organisms and thus contribute to the diversity and secondary productivity of ecosystems.

Biogeography of Jurassic Foraminifera

Abstract: The known Jurassic foraminiferal faunas of the world are classified into five broad types of assemblage rather than into conventional faunal realms, which tend to be geographically exclusive except at the border zones. Each of these broad types retains its general characteristics throughout the Jurassic, although changes occur at species and genus level. Three of the kinds of assemblage are typical of shelf regions, including the western interior region of North America, the northern two-thirds of Europe, and scattered points south of the Tethyan Zone. These three kinds of assemblage often alternate with one another through time. Respectively, they are characterized by simple arenaceous foraminifera including reophacids, simple lituolids, and textulariids; nodosariids, and certain calcareous forms including epistominids, buliminids, or ophthalmidiids. The other two kinds of assemblage are typical of the Tethys seaway and its margins. In these assemblages, either planktonic foraminifera or arenaceous forms including pavonitids, discocyclinids, or others with complex internal structures are characteristic. The planktonic foraminifera invade the shelf region from time to time. In border zones, such as Mexico, Switzerland, and Austria, elements of both shelf and Tethyan assemblages occur. The five broad types of assemblages are considered to be related partly to temperature controls and partly to the broad geotectonic-sedimentary environment. Each group of assemblages contains a number of ecological communities that we cannot define as subunits of the broader pattern until we have more data.

Preservation of Plankton Shells in an Anaerobic Basin off California

Abstract: The sill depth (480 m) in the Santa Barbara Basin, California, separates two strikingly different planktonic sediment assemblages. The anaerobic part of the basin below the sill depth contains abundant aragomtic shells (pteropods and pelecy-pods) and relatively high concentrations of calcitic shells (planktonic foraminifera). In the oxygenated region above sill depth there are no aragonitic shells and concentrations of planktonic foraminifera are much reduced. Percentages of species, size classes, and morphological variants of planktonic foraminifera differ between samples from above and below the sill depth. In contrast, concentrations and faunal composition of siliceous shells (radiolarians and diatoms) apparently are essentially the same above and below the sill. The most important mechanism responsible for the differences between oxygenated and anaerobic calcareous assemblages probably is selective dissolution. Bottom transport may also be important, especially for slowly settling shells that may frequently be returned to suspension by benthomc activity in the aerobic region and consequently settle preferentially in the undisturbed anaerobic region. The accumulation rate of large planktonic fora-minifera in the anaerobic sediment provides an excellent measure of shell output. Comparison with the standing stock of planktonic foraminifera in the productive surface waters yields minimum turnover times of 2 to 3 weeks for the living planktonic foraminifera in the Santa Barbara Basin.

New Evidence for a Pliocene Marine Embayment along the Lower Colorado River Area, California and Arizona

Abstract: Marine foraminiferal, marine to fresh-water molluscan, and brackish- to fresh-water ostracode faunas occur in a thick section of limestone, silt, and clay of the Bouse Formation along the Colorado River from Parker to Yuma in an area now isolated from the sea. Faunas in the Parker-Blythe-Cibola area are limited in number of species but are remarkably persistent through the formation. The presence of marine Foraminifera, including Globigerina sp., is considered evidence that the area was continuously connected with the ocean. Several thousand feet of similar sediments are found in the subsurface near Yuma and contain faunas which at shallow depths are similar to those to the north, but at greater depths contain bathyal assemblages with an abundance of globigerinids, which indicate a post-Miocene age for the section, and oceanic conditions. It is likely that this marine embayment extended into the Imperial Valley, where the Imperial Formation of probable Pliocene age also contains marine faunas. Evidence presented here strongly indicates a large long-lasting Pliocene marine embayment along the lower Colorado River, connected with the Imperial Valley.

Late Maastrichtian nannoplankton provinces.

Abstract: IT has been known for some time that there was a sharp differentiation of late Maastrichtian faunal provinces with respect to planktonic foraminifera. Axelrod1 has presented evidence that this was also the case with some terrestrial megaphyta, for he found a rather abrupt southward shift for the coniferous vegetation of the northern hemisphere during this time. Before this provincialism was discovered, serious problems were encountered in long-range correlation by planktonic foraminifera, because the two late Maastrichtian species, Abathomphalus mayaroensis and Racemiguembelina fructicosa, are both restricted to the tropics (Fig. 1: A. mayaroensis is extremely rare in the two northernmost occurrences (Denmark and Sweden) shown).

Planktonic Foraminifera: Differential Production and Expatriation off Baja CALIFORNIA1

Abstract: The species composition, living : dead ratios, morphology, and size distribution of planktonic foraminifera were studied in 54 depth-controlled tow samples using a 333-p net (O3,000 m) from northwest of Guadalupe Island, Baja California, Paired sampling and replicate tows permitted the determination of confidence limits on concentration and percentage estimates. Average concentrations of living foraminifera range from about l/m’ in shallow water to less than l/1,000 ms at depth, Concentrations of empty shells are between 3 to lO/l,OOO m3 throughout. The depth of equal standing stock for live and empty individuals is between 5,000 and 10,000 m. The minimum replacement time for the living populations corresponds to the settling time through this column and is between 5 and 40 days. The apparent replacement times vary considerably between species and between sizes within species. The living assemblage consists of a mixture of northern, central, and southern species dominated by northern ones. Central water species are relatively abundant immediately below the surface water. The southern element has a maximum at about 1,000-m depth. This distribution is in agreement with physical measurements, suggesting shallow entrainment of central water into the California Current and indicating a countercurrent at depth. It is suggested that the fauna contained in the oxygen-poor intermediate water is expatriated and that its great proportion of specimens with small terminal chambers (“kummerforms”) is due to unfavorable living conditions during submergence. The notion that kummerform development indicates termination or slowing of growth is supported by a trend toward increase of kummerform proportions in living populations in large shell sizes and at subsurface depths and by the relatively high empty shell output of kummcrforms. Oceanic stability of past ages may be recognized in fossil foraminifcral deposits if oceanic mixing enhances kummerform development and if the effects of differential preservation can be accounted for.

Pleistocene climates in the atlantic and pacific oceans: a comparison based on deep-sea sediments.

Abstract: Comparison of Pleistocene climatic records defined by variations in abundance of planktonic Foraminifera in three cores from the southeastern Pacific with similar records in cores from the Atlantic suggests that times of warm surface water in this region of the Pacific were at least partly synchronous with times of cool water in the Altantic. This conclusion opposes the Milankovitch theory of the causation of ice ages, but it harmonizes with a modified form of Simpson's hypothesis.

Sediments and stratigraphy of deep-sea cores from the Tasman Basin

Abstract: Twelve deep-sea cores from the northern Tasman Sea are described and grouped according to sediment characteristics and foraminiferal faunas. Six of the cores from the area between Australia and the Dampier Ridge consist dominantiy of clastics which have been derived from the Australian continental shelf and slope mainly by turbidity currents. Intervening periods when pelagic sedimentation was dominant have occurred. These cores were all taken from depths near the carbonate solution boundary and consequently calcareous foraminiferal tests in the pelagic intervals have been affected by solution. East of Dampier Ridge six cores were taken from the Lord Howe Rise, New Caledonia Basin, and Norfolk Ridge. These consist almost entirely of the calcareous remains of planktonic organisms, mainly foraminifera. Most of the cores are uppermost Pleistocene and Holocene in age, but in one core from the western slope of the Lord Howe Rise Middle to Upper Miocene sediment is unconformably overlain by uppermost Pl...

Studies of Benthonic Foraminifera in the Restigouche Estuary: 1. Faunal Distribution Patterns near Pollution Sources

Abstract: The Restigouche River, flowing into the Bay of Chaleur at its head, forms an estuary about 100 miles long between Gaspe Peninsula, Quebec and northern New Brunswick (Fig. 1). In addition to its many inherent environmental features, the Restigouche estuary is especially well suited for the study of the local effects of industrial and municipal sewage discharges on the physical and chemical characteristics of the nearshore water and sediment, and on the local distribution of benthonic foraminiferal populations. This unique setting has evolved because most large scale industrial and urban development has been confined to the New Brunswick coast. Comparative areas that appear to be relatively unpolluted are available for study along most of the Quebec shore.

Upper Devonian (Frasnian) algae and foraminifera from the Ancient Wall carbonate complex, Jasper National Park, Alberta, Canada

Abstract: Marine algae and foraminifers occur in the Ancient Wall carbonate complex of Upper Devonian (Frasnian) age in Jasper National Park, Alberta, Canada. This microbiota is the most diverse and abundant...

Neogene stratigraphy of the Western Guadalquivir basin (Southern Spain)

Abstract: In the Neogene sediments of the western part of the Guadalquivir Basin eight formations have been distinguished. The planktonic foraminifera in five of these formations have been attributed to seven separate planktonic faunal associations. With these lithostratigraphic and biostratigraphic data the depositional and tectonic history of the basin during the Neogene can be reconstructed. Part of the basin filling appears to be allochthonous. There is ample evidence of a marly sedimentation in the south in a bathyal environment during Late Miocene time; sedimentation may have started in the Early Miocene already. Simultaneously older Tertiary sediment masses slided into this part of the basin from the south. Early Pliocene clayey sediments in the centre and north testify of a much shallower sea depth by their lithology and foraminiferal fauna. The chaotic structure of the bathyal marl and their actual position on top of the younger clay is explained by the assumption of a northward translation of these marls, the gypsiferous Mesozoic sediments that are present below the Tertiary strata facilitating the movement. Middle Pliocene sediments, deposited over both the Late Miocene marl and the Early Pliocene clay testify of a further shallowing of the basin. In search of a section that could be considered a marine equivalent of the Upper Miocene Messinian, PERCONIGproposed the section near Carmona as stratotype for the Andalusian Stage, coeval with the Messinian stratotype and Stage. This is not substantiated by his evidence. A study of the planktonic foraminifera from the Andalusian stratotype indicates that they are homotaxial with those of the stratotypes of the Tabianian and Piacenzian Stages, of Early and Middle Pliocene Age, thus refuting its parallelisation to the Messinian, of Late 1viiocene Age.

Recent foraminifera from off Pentakota, east coast of India

Abstract: A study of the foraminiferal content of samples of the shelf sediments off Pentakota on the east coast of India reveals that the outer shelf sediments at depths greater than 90 meters contain an abundant shallow-water warm-water benthonic fauna. A 70-cm. core taken from a depth of about 1 50 meters in the same area consists of oolitic sediments in the lower 45 cm. and silty clays in the upper 25 cm. The oolitic sediments of the core abound in shallow-water warmwater benthonic fossils. A comparison of the faunas in the core and in the surface sediments of the sea floor is made, and the extent of the relict fauna of the outer shelf sediments is evaluated. After the elimination of the relict elements from population counts, the living population of the sediments of the modern time surface is divided into three depth zones, ranging from 0 to 1 5 meters, from 15 to 40-45 meters, and greater than 40-45 meters. Sediments and fresh water discharged into the Bay of Bengal by the Godavari River to the south of Pentakota and carried northward along the coast and northeastward into deeper waters off Pentakota are found to inhibit the development of populations within the area of their influence. Recent foraminifera from off Pentakota, east coast of India

Jurassic and lower cretaceous stratigraphy of the Rydebäck—Fortuna borings in Southern Sweden: A preliminary report

Abstract: Norling, E.: Jurassic and Lower Cretaceous stratigraphy of the Rydeback— Fortuna borings in southern Sweden. Gcologiska Foreningens i Stockholm For‐handlingar, Vol. 92, pp. 261–287. Stockholm, September 30, 1970. A Mesozoic sequence, ranging in age from Upper Sinemurian (L. Jurassic) to Hauterivian (L. Cretaceous), was penetrated by four shallow borings in the coastal region between Halsingborg and Landskrona in the south of Sweden. Together with the outcropping Lower Lias in this region, the cores seem to comprise the most complete Jurassic sequence ever found in Sweden, including the first finds of marine Upper Bathonian and Callovian to be recorded from this country. The stratigraphical analysis is mainly based on foraminifera closely correlating with the faunas of western Europe. In this report only some few foraminifera of stratigraphic importance are commented on. The micrographs were taken with a Cambridge Stereoscanning Electron Microscope at the Geological Survey of Sweden.

Middle Eocene planktonic Foraminifera from Lakhpat, Cutch, Western India.

Abstract: Systematic descriptions, 36 species, Truncorotaloides haynesi n. sp., association with larger foraminifera, stratigraphic distribution, two assemblage zones

Larger Foraminifera from the Subathus of Beragua-Jangalgali Area, Jammu & Kashmir State

Abstract: A rich assemblage of the larger foraminifera has been recorded for the first time from the Subathus of Beragua-Jangalgali Area, Jammu & Kashmir State. Eleven species of the larger foraminifera belonging to four genera represented by three families, have been studied and described in this paper. This foraminiferal assemblage suggests a Laki (Lower Eocene) age for these formations. The Subathus of the present area have been correlated with the other similar formations occurring in India. The micropalaeontological investigation of the area leads to the conclusion that the Subathus were deposited in neritic environment.

Upper Cretaceous-Cenozoic Paleobathymetric Cycles, Eastern Panama and Northern Colombia: ABSTRACT

Abstract: Analysis of planktonic microfossils and benthic foraminifera indicates one deep-water depositional cycle in the Upper Cretaceous of northern Colombia and two major deep-water sequences in the Cenozoic of both northern Colombia and eastern Panama. Only slight evidence of an Upper Cretaceous deep-water cycle was found in eastern Panama. The Upper Cretaceous deep-water cycle in the radiolarian-rich Campanian sequence of northern Colombia is characterized by a Dictyomitra multicostata radiolarian assemblage. Deep-water or abyssal depths of the next younger cycle (Upper Paleocene-Lower Eocene) are suggested by a Pleurostomella-Nuttallides fauna in combination with a rich radiolarian assemblage. A third abyssal sequence or cycle, in Middle Oligocene-to-Lower Miocene strata, is indicated by a Melonis pompilioides fauna together with a rich radiolarian assemblage. The shallowest-water facies, separating the deep-water cycles, represent mostly neritic or upper-bathyal depths. These are characteristic of the basal Paleocene, the Upper Eocene-Lower Oligocene, and the Upper Miocene through Quaternary sequences of eastern Panama and northern Colombia. Locally, unconformities and/or nonmarine beds may represent these geologic ages. In contrast to the deep-water cycles of eastern Panama, the sections of the Gatun Lake area, to the west of the Rio Limon fault, show relatively shallow-water marine facies (neritic to upper-bathyal depths at the most). These shallow marine facies occur in the Eocene, in the Upper Oligocene, and in the Upper Miocene-Pliocene sections. They are separated by either paralic beds or unconformities. Faults such as the Rio Limon fault separate tectonic blocks that have contrasting stratigraphic and depositional records throughout most of the Cenozic. In eastern Panama and northern Colombia, the shallowest-water horizons of each paleobathymetric cycle may represent times conducive to the migration of land faunas. These times are: latest Cretaceous-earliest Paleocene; late Eocene-early Oligocene; Pliocene and Quaternary.

Calcium carbonate budget of the Southern California Continental Borderland

Abstract: "Calcium carbonate sedimentation of the Southern California Continental Borderland can be examined by means of a budget. Carbonate transfer is the change in amount of calcium carbonate in the Borderland with time. Transfer can be divided into deposition, mechanical transfer other than deposition, biological transfer, and chemical transfer. Most Borderland carbonate deposition occurs on basin floors and basin slopes. Carbonate deposition in the Borderland is 125 x 10e10 g/yr. Aragonite and Mg-calcite percentage decrease with depth; dolomite percentage is a function of geographic coordinate (a response to source area). Total carbonate content of the sediment is independent of depth and geography. Potentially important forms of mechanical transfer include river influx, aerial transfer, and ocean current transfer. Of these, only river influx is an important Borderland carbonate transfer process (16 x 10e10 g/yr). Aerial transfer cycles material produced in the Borderland without removing or adding significant amounts. Ocean currents may be important to intra-system transportation but not to transfer. River input is low-Mg-calcite, with minor amounts of dolomite. Discussion of biological transfer includes only input. Biological input categories are shallow (<30 meters) rocky macrobenthos production, slope macrobenthos production, basin macrobenthos production, foraminifera production, and other production. Shallow rocky macrobenthos production is evaluated from estimates by divers of standing crop and from various estimates of turnover. This production amounts to 40 x 10e10 g/yr. Sandy shelf, slope, and basin macrobenthos production is 34 x 10e10 g/yr. Foraminifera production is 247 x 10e10 g/yr, and other production is assumed to be 25 x 10e10 g/yr. Production by shallow rocky macrobenthos is particularly interesting, because this second-largest of the biological production processes occurs over only 1 percent of the Borderland area. The total production is dominated by low Mg-calcite, with minor amounts of high Mg-calcite and aragonite. Chemical transfer involves solution on the basin floor, where waters are enriched with solution products of 400 x 10e10 g CaCO3. Deep water flushing has been estimated by other workers to be biennial, so 200 x 10e10 g/yr is dissolved. Dolomite is not dissolved; the other carbonate minerals are dissolved to varying extent. Aragonite solution is diminished because only minor amounts of fine-grained aragonite are moved to deep water. Dissolved calcium input rate to the Borderland by rivers can account for 30 per cent of the annual calcium carbonate sedimentation. The remainder of the calcium must be extracted from ocean water flowing through the Borderland. Calcium carbonate production rate in temperate-water shallow rocky bottom areas is comparable to tropical, non-reef production (about 500 g/m2)/yr). Coral reef production is about 10,000 (g/m2)/yr. Pelagic production is about 50 (g/m2)/yr. Pelagic production rates over the world's oceans are capable of exceeding dissolved calcium supply rate of the world's rivers by an order of magnitude. The other two environments may also be able to match river supply of calcium. Excess calcium carbonate is re-dissolved. Tertiary limestones of the Pacific coast of North America are generally either dominated by recognizable debris from one or two phyla or are fine-grained, impure limestones. Both characteristics might be expected of limestones forming in an area similar to the present Borderland. This investigation has demonstrated that considering the budget of carbonate input to and output from an area is an adequate method of enumerating processes controlling carbonate content of marine sediment."

Miocene foraminiferal biotopes in New Zealand: Waitemata Group, Kaipara, Northland

Abstract: Census data for benthic Foraminifera (200-specimen samples, 24 localities) from the Waitemata Group, Kaipara Harbour, are analysed by a hierachical classificatory technique, and by principal components. The classification of localities in terms of species abundances is interpreted as a classification of fossil biotopes. Five biotopes are recognised at the lowest classificatory level. The most distinctive, with an assemblage dominated by Amphislegina, is interpreted as a “near-shoal” locus. It is migratory with respect to the lithostratigraphy and occurs in Pakaurangi and Puketi Formations. Three of the remaining biotopes represent “fore-shoal” and “back-shoal” environments. These occur in the lower and uppermost members of the Pakaurangi Formation. Sandwiched between them is a unit associated with abundant planktonic Foraminifera which may represent an “outer shelf” environment.

Larger foraminifera of late Eocene age from Eua, Tonga

Abstract: Eight species of larger Foraminifera characteristic of the Tertiary b (upper Eocene) stage of the Indo-Pacific region were recovered from a sample collected at an elevation of 400 feet about one-quarter mile north of Vaingana, Eua, Tonga. The most abundant specimens in this fauna are Pellatispira. Heterostegina and Asterocyclina were found in moderate numbers, but Camerina and Spiroclypeus were uncommon. This fauna developed in warm, shallow waters (about 200 feet in depth) in a protected ecologic niche. The genus Biplanispira Umbgrove, 1938, is demonstrated to be a synonym of Pellatispira Boussac, 1906. Specimens previously identified as Pellatispira fulgeria Whipple (synonym: Biplanispira absurda Umbgrove) are considered to be aberrant forms of Pellatispira madaraszi (Hantken).

Circulation of Surface Waters in Parts of the Canadian Arctic Archipelago Based on Foraminiferal Evidence

Abstract: The distribution of planktonic foraminifera, collected 27 May-15 July 1968 from sea ice in McClure Strait, indicates a slow net eastward movement of water from the Arctic Ocean through the strait in the past with increased rates at present. The bottom topography, regional climatology and oceanography of the area are discussed.