Foraminiferal Analysis Research Articles

Foraminiferal stratigraphy of Quaternary deposits in boring no. 51.12 Anholt, Kattegat

Material from a 229 m deep boring on the island of Anholt in the central part of the Kattegat has been stratigraphically analysed on the basis of its foraminiferal content. Due to the lack of casing in the main part of the bore hole, only very few core samples and some samples from the drilling bit were not contaminated. The results of the foraminiferal analyses have, therefore, to be treated with some reservation. The boring did not penetrate the Quaternary. The bottom 143 m of the boring represents deposits of pre-Eemian, possibly Saalian age. This interval seems to contain three marine interstadials, Anholt 1, 2 and 3, of which the upper interstadial is the warmest. Tills and glaciofluvial sediments are found between the marine sequences. The Eemian is represented by 13 m of marine deposits, which can be correlated with Eemian deposits known from other localities in the Vendsyssel-Kattegat region. They correspond to the Lower Turritella terebra Zone of the Skærumhede Series. The Early Weichselian and the lower part of the Middle Weichselian are missing, while the upper part of the Middle Weichselian, 32 m in all, is represented by marine deposits corresponding to foraminiferal zones known from the Vennebjerg Stadial and the Sandnes lnterstadial in the Vendsyssel-Kattegat region. These Middle Weichselian zones correspond to the upper part of the Portlandia arctica Zone of the Skærumhede Series. The non-marine sequence on top of these deposits is considered to be glacial, belonging to the main Weichselian glacial event. Holocene littoral sands and gravels terminate the Quaternary sequence at Anholt.

Laminated sediments from the Vrica section (Calabria, S. Italy): evidence for plio-pleistocene climatic change in the Mediterranean region

Six laminated sedimentary units (laminites) from the Vrica section (Calabria, southern Italy) have been analyzed geochemically and micropaleontologically to assess paleoclimatic conditions in this region during the transition from the Pliocene to the Pleistocene. Two laminites formed during the early Pleistocene and one formed immediately below the Pliocene/Pleistocene boundary; all have a greater organic carbon content relative to the surrounding marls. By contrast, three late Pliocene laminites exhibit no significant increase in organic carbon, which indicates that the conditions associated with the formation of these three units were somewhat different than those associated with the formation of the three younger laminites. Stable isotope analyses of planktonic foraminifera from the laminites indicate that all of these units were formed during periods of decreased salinity concentrations in surface waters. The laminites were formed as a result of basin anoxia brought on by increased surface-water stratification during periods of high runoff. The Vrica planktonic foraminiferal census data indicates that the laminites contain a distinctive fauna which can be partially attributed to increased nutrient concentrations. By contrast, species assemblages within the marls seem to be primarily controlled by surface-water temperatures. Through the use of polytopic vector analysis, the foraminiferal census data can be simplified into five assemblages, each of which reflects temperature, salinity and/or nutrient concentrations. The nutrient-dependent assemblage indicates an intensification in surface water productivity during periods of laminite formation during the later Pliocene and early Pleistocene, while the temperature-dependent assemblages indicate an overall cooling of surface-water temperatures during the same period. The results of the planktonic foraminiferal analyses support the concept of a regional cooling across the Pliocene/Pleistocene boundary in the Mediterranean. In addition, the results of this study indicate that these climatic changes resulted in differences in the nature of the laminites. Cooler climatic conditions during the latest Pliocene and the early Pleistocene favored the formation of laminites slightly richer in organic carbon and nitrogen because of increased organic carbon input or enhanced organic matter preservation. The warmer climatic conditions of the late Pliocene produced laminites relatively poor in organic carbon and nitrogen as a result of either decreased runoff or decreased organic matter preservation.

Foraminifera and Ostracods from the Dinantian Woodbine Shale and Urswick Limestone, South Cumbria, U.K.

Abstract. Macrofaunal and foraminiferal analyses have shown the Woodbine Shale in South Cumbria to be of latest early Asbian age. Ostracods and solid foraminifera from the Woodbine Shale are described and illustrated for the first time. Several ostracods including Rectobairdia cf. dorssenata, Healdia ‘penchfordensis’, Bairdia cf. leguminoides, Pustulobairdia cf. confragosa and Microcheilinella subcorbulinoides, previously only known from late Asbian or younger strata, have now been shown to range into the early Asbian. The numerous bairdiids, heavily ornamented ostracods, trilobites, brachiopods and abundant foraminifera suggest a deep, subtidal, marine environment of deposition for the Woodbine Shale. Foraminifera from the underlying Lower Urswick Limestone suggest an early Asbian age for this formation whilst the overlying Upper Urswick Limestone is shown to be of late Asbian age. The foraminiferal assemblages from these beds can be correlated directly with those in the early Asbian Upper Potts Beck Limestone and the late Asbian Knipe Scar Limestone in the Asbian stratotype section at Little Asby Scar, Cumbria.

Extended Cretaceous/Tertiary boundary extinctions and delayed population change in planktonic foraminifera from Brazos River, Texas

High‐resolution planktonic foraminiferal analysis of three Brazos River sections indicates a nearly continuous Cretaceous/Tertiary [K/T] boundary sedimentary record second only to the world's most complete record at El Kef, Tunisia. Species extinctions occur over an extended period of time and with two major extinction episodes. The first extinction episode with 46% of the species extinct occurs at and just below [10–15 cm] a short hiatus at the base of a sandy shell hash and clay‐sand unit which was interpreted by Bourgeois et al. [1988] to represent a tsunami bed generated by the K/T boundary bolide impact. The top of this tsunami bed is about 17–20 cm below the K/T boundary as defined by the first appearance of Tertiary planktonic foraminifera. The second extinction phase with 45% of the species extinct occurs 25 cm above the K/T boundary [Zone P0/P1a boundary]. Of the remaining seven surviving Cretaceous species, six gradually disappear during planktonic foraminiferal Subzones P1a and basal P1b. No species extinctions or major faunal assemblage changes are directly associated with the K/T boundary. Iridium distribution is ambiguous, with one peak in the upper part of the tsunami bed and a second peak at the micropaleontologically defined K/T boundary. Relative abundances of dominant species are stable through the Late Maastrichtian, and only minor abundance changes coincide with the first extinction episode or the K/T boundary. The first major faunal change in the dominant species group coincides with the second extinction episode and leads to decline and eventual extinction of this group in Subzone P1a. Species disappearing at the two extinction episodes [46% and 45%] constitute only a small percentage [8% and 5%] of the individuals of the total planktonic foraminiferal population. This suggests that weakened species with low numbers of individuals and sensitive to relatively minor environmental changes were primarily affected by these extinction episodes. Magnetostratigraphy indicates that the first extinction phase began about 310,000 years before the K/T boundary, and the second extinction phase occurred 50,000 years after the K/T boundary. This stepped pattern of species extinctions suggests a progressively stressed ecosystem in continental shelf settings which may be related to an observed sea level regression and global cooling. The hypothesis of a global catastrophic mass extinction at the K/T boundary caused by a large extraterrestrial impact is not supported by the Brazos River planktonic foraminiferal data.

Quartz sand grain shape and other criteria used to distinguish glacial and non‐glacial events in a marine core from Frobisher Bay, Baffin Island, N.W.T., Canada

ABSTRACTAnalyses of quartz sand grain shape, sediment influx rates and foraminifera define glacial and non‐glacial episodes in a 9.69 m core from Frobisher Bay, Arctic Canada. Five radiocarbon dates on organic matter provide a preliminary core chronology, with a basal date of 11,910 yr BP. Quartz sand grain morphology is measured for samples at seven core levels using: (1) Fourier shape analysis; (2) percentage of grain surface conchoidally fractured. Samples at 2.0 and 7.5 m are most fractured and have Fourier roughness coefficients similar to particles sampled directly from glacier ice. These two samples probably represent glacial events in the core. Major intervals of non‐carbonate sand influx occur at 9.0–4.5 m and 3.5–1.5 m, separated by several thousand years of slower sedimentation. Detrital carbonate influx rates are relatively high prior to 4.3 m, then decline rapidly indicating a shift in sediment provenance from limestones flooring Frobisher Bay to rafting from far‐travelled icebergs. Bio‐ and lithostratigraphic analysis allows definition of five core units: (1) an environment similar to today below 8.5 m; (2) glacial conditions from 8.5–6.8 m, associated with ice proximal to the core site; (3) ameliorating conditions from 6.8 to 3.2 m; (4) cooler conditions from 3.2 to 0.5 m, probably related to increased iceberg flux rather than neoglacial advances of nearby ice caps; (5) an environment similar to today from 0.5 m. Sand grains sampled at 7.5 and 2.0 m, whose shapes indicate they are derived from glacier ice, lie within the cooler or glacial units defined from foraminiferal analysis. This indicates that quantitative measurement of particle surface morphology can provide useful environmental information in studies of marine cores.

Recent Foraminifera of St. Andrew Bay, Florida: ABSTRACT

Foraminiferal analysis was conducted on 403 bottom samples from St. Andrew Bay, a polyhaline to ultrahaline estuary on the northwest coast of Florida. Intertidal samples (140) and subtidal samples (263) were collected by the National Marine Fisheries Service during November 1974 and April 1975. Water properties samples were collected also at 69 of the subtidal stations. Foraminiferal concentrates were obtained by carbon tetrachloride float from an undisturbed, upper 1 cm (0.4 in.) of tube (intertidal) and grab (subtidal) samples. A census of populations was taken by random, 300-specimen counts. Subspecies were recognized but none are new. Biofacies were based on percentages of populations and geographic patterns of distribution. The genus Ammonia dominates foraminiferal populations at 75% of the statistically valid stations (stations with 300 or more foraminifera) and forms the only major biofacies of the bay. Ammonia parkinsoniana tepida and typica are the dominant Ammonia. The smaller and more fragile A. parkinsoniana tepida is dominant in the central, deeper parts of the St. Andrew Bay, where salinity and temperature are higher; whereas A. parkinsoniana typica is dominant in intertidal areas, where salinity and temperature are lower. The salinity and temperature relationships of the ecophenotypes are the same as reported for San Antonio Bay, Texas, but the bathymetric relationships are reversed. The ecophenotypes define secondary biofacies within the major one. Several species characteristic of the continental shelf occur in widely varying percentages, but with a definite geographic pattern, along the deepest and most central parts of the bay. It is suggested that this secondary biofacies reflects the effect of flood tidal action on meroplanktonic larval stages of the species. The remaining 25% of the stations are dominated by Elphidium, miliolids, Ammobaculites, Nonionella, Miliammina, Rosalina, and Trochammina, which occur erratically in abundance and distribution. Elphidium shows the greatest adaptability to pollution. No biologic relationship is apparent between bottom sediment and foraminifers. End_of_Article - Last_Page 1216------------

Globorotalia truncatulinoides (d'Orbigny) in the Mediterranean Upper Pliocene Geologic Record

Globorotalia truncatulinoides (d'Orbigny) in the Mediterranean Upper Pliocene Geologic Record

ASBIAN AND HOLKERIAN FORAMINIFERA FROM THE BECKERMONDS SCAR BOREHOLE

SUMMARY Foraminiferal analysis of the Beckermonds Scar Borehole to a depth of 200.08 m revealed an abundant faunal assemblage ranging from late Asbian to Holkerian. From rock head to 109 m an Asbian fauna was encountered but from 110 m to the top of the Ashfell Sandstone at 200.08 m a characteristic shallow water Holkerian assemblage occurred containing Rhodesinella avonensis. The foraminifera observed correlated very well with those found in the Asbian stratotype section at Little Asby Scar and with other sections examined from the Askrigg Block.

Coexistence of deep- and shallow-water foraminiferal faunas off Panama City, Florida

Benthic box core sampling along a transect off Panama City, Florida, in the vicinity of the DeSoto Canyon, from 37-m to 200-m depths, were run throughout the Bureau of Land Management's Outer Continental Shelf environmental assessment program for the Mississippi-Alabama-Florida (MAFLA) area from 1974 through 1978. Seasonal samples were taken and analyzed for benthic distribution, abundance, diversity, and faunal affinities. The most striking feature brought out by foraminiferal analyses was the mixture of foraminifera from different depth zones. Species normally found in abundance only at depths of > 100 m in adjacent areas were living at all shallower depths, including 37 m. Coexisting with the deeper assemblage were all of the species normally encountered at the shallow depths. Species diversity, normally showing a progressional increase from inner to outer shelf, either remained constant or decreased due to the decrease of shallow-water species with depth. Along with this mixed assemblage, there was a planktonic foraminiferal content in the shallowest assemblage of as much as 25%. Normally, planktonic percentage of similar water depths is 0%. Seasonality had minor effects on the assemblages. The planktonic content is attributed to Loop Current water providing open-Gulf water to the inner shelf. Because the Loop Current is intermittent, the consistently high percentages of deeper-water species on the inner shelf must be attributed to up-welling currents providing cooler, deeper water to the inner shelf. However, since this deeper water did not restrict survival of shallow-water species, multiple factors must be considered for controlling benthic foraminiferal distribution.

Early to Middle Miocene Planktonic Foraminiferal Datum Levels of the Equatorial and Subtropical Pacific

Early to Middle Miocene Planktonic Foraminiferal Datum Levels of the Equatorial and Subtropical Pacific

Important Stratigraphic Breaks in COST GE-1 Well, Southeast Georgia Embayment: ABSTRACT

A foraminiferal analysis of the recently completed Continental Offshore Stratigraphic Test (COST) GE-1 well reveals that ~1,000 m of Cenozoic, ~700 m of Upper Cretaceous, and ~1,600 m of Lower Cretaceous sedimentary rocks lie above Devonian metamorphic basement in this part of the Southeast Georgia embayment. Seven regional hiatuses interrupt the depositional record and correspond to times of low global sea level. The hiatuses are between Albian and Turonian rocks; upper Maestrichtian and upper Paleocene; upper Paleocene and lower Eocene; upper Eocene and lower Oligocene; middle Oligocene and middle Miocene; middle Miocene and upper Pliocene; and upper Pliocene and lower Pleistocene. The depositional environments represented in the GE-1 well range from terrestrial nonfoss liferous biotopes to ocean depths equivalent to those of a modern continental slope. Most of the Cenozoic and Upper Cretaceous rocks accumulated in continental-shelf biotopes, but the Lower Cretaceous rocks are largely nonmarine and marginal-marine deposits. The sequence of paleo-environments can be correlated with the supercycles of global sea-level change outlined by P. Vail et al. Sediment-accumulation rates were highest (5.0 to 6.4 cm/1,000 years) during the Albian through Santonian interval, the middle and late Eocene, and the middle Miocene. Lowest rates (1.3 to 2.5 cm/1,000 years) prevailed during the Campanian and Maestrichtian, the early and middle Oligocene, and the Pleistocene. Subsidence calculations reveal that Cretaceous subsidence was more rapid than that of the Cenozoic, hat most of the major paleobathymetric changes were caused by eustatic sea-level fluctuations, and that subsidence rate of the embayment was sensitive to sediment loading and unloading. End_of_Article - Last_Page 510------------

The late Quaternary climatostratigraphy of IGS Borehole SLN 75/33 and its application to the palaeoceanography of the north-central North Sea

Synopsis The dinoflagellate cyst and benthonic foraminiferal analysis of the Quaternary sediments of borehole SLN 75/33 in the central-northern North Sea has resulted in the formulation of a climatostratigraphy which is believed to encompass sediments ranging in age from Ipswichian (Eemian) to Recent. Since the areal distribution of the organisms involved is thought to be controlled by water mass, an oceanographic history is attempted for the late Quaternary of the North Sea. This involves the penetration of North Atlantic water and the establishment of a homothermal water mass which allowed high percentages of “species of southern origin” into the area at times of strong climatic amelioration, and the loss of a North Atlantic influence during periods of climatic deterioration. Weaker ameliorations are more difficult to interpret but probably relate to some influence of North Atlantic water and a slight increase of water temperatures in relation to times of climatic deterioration, allowing only low percentages of “southern forms” into the area.

Late pleistocene paleoclimatology: Planktonic foraminiferal analyses of sediment cores from the central North Atlantic

Planktonic foraminiferal analyses of six deep-sea sediment cores from the central North Atlantic east of the Azores Islands between 37°N and 40°N show distinct oscillations in planktonic foramineferal assemblages during the last 300,000 years. A paleoclimatic curve has been constructed using “Total Fauna Analysis” that reveals three glacial and four interglacial episodes. Relatively minor climatic oscillations are superimposed upon the major glacial-interglacial episodes. The paleoclimatic curve is similar to previous paleoclimatic curves from the Atlantic and adjacent areas. Minor paleoclimatic fluctuations are more distinct in paleoclimatic curves from high latitudes of the Atlantic. The faunal assemblages are transitional between subarctic and subtropical assemblages. During portions of the interglacial episodes, the assemblage is dominated by Globorotalia inflata. Neogloboquadrina pachyderma (dextral-coiling) or Globigerina bulloides dominate during the remainder of the interglacial episodes and during the glacial episodes. Glacial episodes are also marked by particularly high frequencies of Globigerina quinqueloba and Globorotalia scitula. Interglacial episodes are also marked by increases in Globorotalia truncatulinoides, Globigerinoides ruber, and Globigerinella aequilateralis. The planktonic foraminiferal faunal oscillations in the cores are complex and cannot be entirely explained by temperature variation. Other parameters such as salinity, nutrients and biological competitin must influence the faunal oscillations. The faunas suggest no major planktonic foraminiferal faunal boundaries migrated across the area between 37°N and 40°N in the central North Atlantic during the last 300,000 years.

Methane in Recent Sediments of the Labrador Shelf

Methane was found in Recent sediments of two basins on the Labrador continental shelf. These basins are carved in what are believed to be Tertiary and Mesozoic strata resting on Precambrian and possibly Paleozoic rocks. Geochemical and foraminiferal analyses of sediments from one piston core indicate that the gas is a product of anaerobic fermentation of organic matter. Mildly anaerobic conditions existed in subsurface sediments, which were deposited under marine conditions shortly after the retreat of the last Pleistocene glaciation.

Biostratigraphic Framework of Grand Banks

Paleontologic and palynologic analyses of samples from wells on the Grand Banks of Newfoundland have established the presence of sedimentary rocks ranging in age from Holocene to Devonian. Several unconformities have been recognized, at least one of which is major in terms of areal extent and temporal magnitude. Upper Cretaceous and Tertiary rocks were deposited in environments ranging from middle shelf to slope. Early Cretaceous and Jurassic environments are interpreted as ranging from nonmarine to outer shelf. A graphic technique of compositing all available biostratigraphic data has permitted detailed correlation of wells located in three different basins. The data utilized were derived from analyses of foraminifers, ostracods, calcareous nanoplankton, dinoflagellates, spores, pollen, and rare megafossils. The foundation for future biostratigraphic work has been established.

Biostratigraphic Framework of Grand Banks: ABSTRACT

Paleontologic and palynologic analyses of samples from wells on the Grand Banks of Newfoundland have established the presence of sedimentary rocks ranging in age from Holocene to Devonian. Several unconformities have been recognized, at least one of which is major in terms of areal extent and temporal magnitude. Upper Cretaceous and Tertiary rocks were deposited in environments ranging from middle shelf to slope. Early Cretaceous and Jurassic environments are interpreted as ranging from nonmarine to outer shelf. A graphic technique of compositing all available biostratigraphic data has permitted detailed correlation of wells located in three different basins. The data utilized were derived from analyses of foraminifers, ostracodes, calcareous nannoplankton, dinoflagellate , spores, pollen, and rare megafossils. The foundation for future biostratigraphic work has been established. End_of_Article - Last_Page 2146------------

SAMPLING AND SPATIAL DISTRIBUTION OF BENTHONIC FORAMINIFERA1

The size, spacing, and number of replicate sediment samples collected for foraminiferal analysis do not, in many cases, adequately represent the living population. In the Gulf of St. Lawrence, the living foraminifera counted in replicate samples show a pronounced patchy geographic distribution in waters less than 24 m deep; species proportions in replicate samples are most variable in waters less than 20 m deep. A significant number of living specimens was encountered to a depth of 9 cm in the bottom sediments.

Foraminiferal Analysis of the Miramichi Estuary

Foraminiferal Analysis of the Miramichi Estuary

Deep-Sea Pleistocene Biostratigraphy

The first detailed paleontological analysis of a deep-sea pistoncore from the Caribbean Sea has been completed. The core, P6304-8, was raised from 3927 meters, east of Beata Ridge at 14 degrees 59'N, 69 degrees 20'W. Formerly, stratigraphic works in this area were based on studies of paleotemperature, measured by the oxygen isotope mass spectrometry method, or on micropaleontological analysis by means of rapid or cursory examinations. For core P6304-8, samples for foraminiferal analysis were taken at 10-centimeter intervals and split into smaller samples containing an average of 710 individuals (smallest sample, 517 individuals); all individuals were then identified and counted. By use of data derived from populations of this size, a statistical reliability was insured within a 5 percent limnit. Temperature oscillations, the best method of portraying Pleistocene stratigraphy, were shown by using ratios of the relative abundances of tropical and subtropical planktonic foraminifera to those found in temperate and cooler waters. These ratios correlate well with existing paleotemperature measurements for the same core, obtained by the oxygen isotope mass spectrometry method.

Cenozoic Planktonic Foraminiferal Zonation and Basinal

Foraminiferal analyses of Cenozoic strata of Central Valley, Luzon, and southern Iloilo, Panay, indicate a general planktonic zonation for the Middle and Later Cenozoic which is similar to that recognized in equivalent marine strata of other tropical areas of the world. There is generally parallel basinal development in Central Valley, Luzon, and Iloilo, Panay, beginning in the Late Oligocene-Early Miocene interval. The cycle commenced with shelf-type conditions and orbitoidal facies giving way upward and with time to increasingly deeper-water facies of the bathyal zone. Maximum water depths of at least 1,000-2,000 meters were attained during the Miocene as indicated by Nonion barleeanus, Nonion pompilioides, Pullenia bulloides, Osangularia bengalensis, Laticarinina pauperata, and others. The parallel history in the two areas stops in the Late Miocene when Central Valley underwent prominent basin-filling and a transition to shallow-water paralic facies. In Iloilo, deep basinal conditions prevailed into the Middle Pliocene before basin-filling occurre . The more complete planktonic sequence is that of Iloilo. Late Oligocene time is suggested by Globigerina concinna ciperoensis in at least one part of the basin. Early Miocene time (Aquitanian) is represented by a lower Globigerina dissimilis zone and an upper Globoquadrina tripartite rohri zone. Middle Miocene time (Burdigalian) is indicated by a lower Globorotalia fohsi fohsi population giving way upsection to first left-coiling populations of Globorotalia menardii praemenardii and then to right-coiling populations of the same species. From bottom to top, Upper Miocene zones include a basal Globoquadrina dehiscens advena zone, a Globoquadrina altispira altispira zone (top of occurrence), a Globigerina nepenthes zone (top of occurrence), and at the top a Globoquadrina altispira globos -Globoquadrina dehiscens dehiscens zone. Lower Pliocene populations are characterized by Sphaeroidinella dehiscens dehiscens and Globigerina eggeri (dextral). Middle Pliocene populations lack these but include an abundance of Globorotalia truncatulinoides and Globorotalia menardii menardii. Pulleniatina obliquiloculata is common to abundant in the Middle and Lower Pliocene sections and rare in the uppermost Miocene. It is dominantly right-coiling in the Middle and most of the Lower Pliocene, left-coiling at the base of the Pliocene, right-coiling and rare in the uppermost Miocene, and mostly left-coiling and very rare below. Upper Pliocene and Pleistocene beds lack definitive planktonic zonation, probably because of the filling of the basins and the advent of paralic facies in the Pleistocene.