Foraminifera In Surface Sediments Research Articles

Distribution pattern of planktonic and benthic foraminifera in surface sediments near the equatorial western Indian Ocean and its indications of paleo-environment and productivity

Distribution pattern of planktonic and benthic foraminifera in surface sediments near the equatorial western Indian Ocean and its indications of paleo-environment and productivity

Distribution of recent planktonic foraminifera in surface sediments of the Basque shelf (S Bay of Biscay): Oceanographic implications

In this work we describe for the first time the distribution of planktonic foraminifera assemblages preserved in recent surface sediments that cover the Basque shelf (southern Bay of Biscay), and their relationship with diverse oceanic currents that affect this area. In the 83 studied samples a total of 18 (morpho)species of planktonic foraminifera have been identified, being the most abundant species: Neogloboquadrina pachyderma dex., Globigerinoides ruber, Globigerina bulloides, Globoconella inflata, Orbulina universa and Turborotalita quinqueloba. These species represent the 92.8% of the total hand-picked specimens. The preferential accumulation of planktonic foraminifera shells in fine sediments deposited in the eastern margin of the Basque shelf, and the random distribution of the dominant species in this area, seem to respond to the general surface current that affect the Basque shelf, which flows eastward during most of the year. Moreover, the input of certain currents and deeper water masses in this area has an important impact on assemblage distribution. Thus, the presence of abundant individuals of Globigerinoides ruber indicates the entrance of the warm and salty Iberian Poleward Current (IPC). Likewise, the dominance of subpolar species Globigerina bulloides, Neogloboquadrina pachyderma dex. and Turborotalita quinqueloba, together with the occurrence, as accessories species, of Neogloboquadrina pachyderma sin., Globorotalia scitula, Globorotalia truncatulinoides and Neogloboquadrina dutertrei, suggest the impact of upwelling processes on the Basque shelf. In conclusion, in this work we have evidenced the useful application of planktonic foraminifera assemblages preserved in surface sediments as indicators of oceanic currents and water masses in shallow continental shelves, such as the Basque shelf.

Environmental inferences based on benthic foraminifera in surface sediments from the Beagle Channel (Argentina): A multiproxy approach

Micropaleontological analysis was performed on 22 samples of recent marine sediments from the Beagle Channel (Tierra del Fuego, Argentina) between 10 and 100 m of depth. The most important foraminifera found in the channel were Cibicidoides dispars (d'Orbigny), Buccella peruviana (d'Orbigny), Cibicides aknerianus (d'Orbigny), Cibicides fletcheri Galloway and Wissler, and Neoeponides bradyi (Le Calvez), which inhabit in clayey–sandy marine sediments. The observed variations in diversity and abundance revealed shallow marine conditions, low-energy, and low to moderate salinity, in the west sector and a deeper environment with normal marine conditions, high-energy, highly‑oxygenated and cold seawater in the east sector of the channel. The study area is a complex scenario with numerous landforms that lead to the formation of micro-environments in which patchy distribution of foraminifera was recognized. This study based on foraminifera and the sedimentological analysis supports the previous palynological information from the channel, which also shows an increase in number and diversity of dinocyst species reflecting the eastward changes of the marine environmental conditions due to the influence of the Atlantic.

Textural characteristics and ecology of near shore benthic foraminifera from Kottaipattinam to Kodiyakarai, Palk Strait, Southeast Coast of India

The present study aims to understand the distribution of benthic foraminifera in surface sediments collected from Kottaipattinam to Kodiyakarai, Palk Strait southeast coast of India. The analysis reveals the presence of 79 species belonging to 42 genera, 24 families, 12 super-families, 19 sub-families, 5 sub-orders and, 5 orders have been reported and illustrated. Out of the total population count of 11,719 specimens, 705 were observed to be Rose Bengal-stained, and are considered to be living at the time of sample collection. Environmental parameters such as water depth, pH, bottom water temperature, dissolved oxygen, salinity, CaCO3, organic matter, sand, silt, and clay contents were determined to adopt standard methodology. Ammonia beccarii (Linnaeus) is the most abundant counterpart in the study area; followed by Asterorotalia trispinosa (Thalmann) and Ammonia tepida (Cushman). Besides that, Spiroloculina corrugata, Spiroloculina angulata, Quinqueloculina bicostata, Quinqueloculina echinata, Pyrgo depressa, Pyrgo laevis, Pseudotriloculina rotunda, Parrina brady, Cancris oblonga, Elphidium hispidulum, Elphidium norvangi, these species were not previously observed in this study site. The textural analysis reveals that the sediments are chiefly composed of sand with less clay and silt. The organic matter content shows a high loading factor in the study site followed by CaCO3. Further, the statistical analysis shows organic matter is major controlling factors in the study site and benthic foraminiferal assemblages are definitely bound to be influenced by the high volume of freshwater influx in the study site.

Distribution and Diversity of Foraminifera in the Northwest of Sarawak Offshore Waters, Malaysia

A study on distribution and diversity of benthic foraminifera in surface sediments was carried out in Northwestern Sarawak waters, Malaysia. The range of water depth at the study site was between 43 m and 71 m. A total of seven sediment samples were taken for this study. As a result, 11 genera were identified from a total of 1,222 individuals of foraminifera. 200 individuals were picked out from each sample. The 11 genera that were identified from the study site included Heterolepa spp., Textularia spp., Quinqueloculina spp., Operculina spp. Pseudorotalia spp., Amphistegina spp., Cylindroclavulina spp., Elphidium spp., Ammobaculites spp., Asterorotalia spp. and Bolivina spp.. The common genera found in the sediments of the study areas were Heterolepa, Textularia, Quincoloculina, Operculina and Pseudorotalia. The highest and lowest values of Fisher alpha and Shannon-Wiener indices were shown at Station C287 and Station B482 respectively. The highest value of Fisher alpha was 3.23 and the lowest value was 1.97. The highest and lowest values of Shannon-Wiener were 2.30 and 1.91. The highest index value of diversity was 3.23 at depth 67.76 m and the lowest value was 1.53 at depth 45.54 m and 68.45 m. From this study, depth is not the main factor that influences the diversity of benthic foraminiferal in northwestern Sarawak waters.

Assessment of the impacts of trace metals on benthic foraminifera in surface sediments from the northwestern Taiwan Strait

The distribution patterns of foraminiferal assemblages in relation to trace metals, sediment grain size, and calcium carbonate were studied in 232 surface sediments collected from the northwestern Taiwan Strait. Multivariate analyses of biotic and abiotic data revealed a separation of near-shore, coastal, and deep-water zones. The modified degree of contamination suggested that the overall contamination was very low to low. Trace metals were enriched in the near-shore and outside bays. Their distribution was likely determined by sediment transport pathways and hydrodynamic conditions. High metal concentrations co-occurred with a low density and diversity of foraminiferal assemblages. Pb, Ba, organic carbon, Ga, Zn, Cu, and Co had a positive correlation with near-shore assemblage, whereas Cr and Ni positively related to the deep-water assemblages. Some calcareous foraminifera were favored by CaCO3, Sr, and sand. This study highlights species’ responses that are specific to environmental variables.

Effect of the Red Sea brine-filled deeps (Shaban and Kebrit) on the composition and abundance of benthic and planktonic foraminifera

Composition and abundance of benthic and planktonic foraminifera in surface sediments of the brine-filled Shaban and Kebrit Deeps and some bathyal-slope environments in the northern Red Sea were examined for correlation with environmental conditions (e.g., bathymetry, sediment grain-size, organic matter, and carbonates) of the brine-filled deeps and normal Red Sea water. About 67 benthic foraminiferal species were recorded in these sediments. The lowest faunal density and diversity were recorded in the Shaban and Kebrit Deeps, whereas the highest density and diversity were recorded in the bathyal-slope sediments. Cluster analysis divided the benthic foraminiferal species into three major faunal assemblages. Buccella granulata–Gyroidinoides soldanii–Bolivina persiensis assemblage dominated the 650–1,300 m depth due to predominance of oligotrophic, highly oxygenated bottom waters. The Melonis novozealandicum–Spirophthalmidium acutimargo assemblage was recorded in the deep and bathyal-slope sediments indicating its tolerance for wider ranges of environmental conditions. The deeps were only dominated by the Brizalina spathulata assemblage indicating existence of un-totally anoxic conditions. The deeps yielded also very low planktonic foraminiferal density that may be attributed to occurrence of the seawater–brine interface which not only minimized the deposition of high buoyancy, large-test species (Globigerinoides sacculifer, Globigerinella siphonifera, and Orbulina universa), but also overestimated the small-test species (Globigerinoides ruber, Globoturborotalita rubescens, and Globigerinita glutinata) in the sediments. These findings should be taken into consideration when reconstructing paleoceanographic conditions of the Red Sea using core sediments from the brine-filled deeps.

Japan Sea planktic foraminifera in surface sediments: geographical distribution and relationships to surface water mass

Modern planktic foraminifera in 51 surface sediments from the Japan Sea, a marginal sea of the western North Pacific, were studied to reveal the relationships between geographical distribution and surface water masses in the Japan Sea. Twenty-four species belonging to 10 genera were identified, of which nine species, namely Neogloboquadrina incompta, Neogloboquadrina pachyderma, Globigerina quinqueloba, Globigerina bulloides, Globigerinoides ruber, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globigerinoides tenellus, and Globigerinita glutinata are predominant. We recognized four geographical distribution patterns of these dominant species that are related to hydrographic conditions in the Japan Sea. The transitional water formed by the mixture between the warm Tsushima Current and cold waters in the Japan Sea is optimal for N. incompta, while the distribution of N. pachyderma is matched with cold water in the northern Japan Sea. Globigerina quinqueloba and G. bulloides appear to be associated with less saline, nutrient-rich river water from the Changjiang (Yangtze River), and G. ruber, N. dutertrei, P. obliquiloculata, G. tenellus, and G. glutinata can be regarded as indicators of Tsushima Current water.

Foraminifera in Surface Sediments of Mandovi River Estuary: Indicators for Mining Pollution and High Sea Stand in Goa, India

NIGAM, R.; PANCHANG, R., and BANERJEE, P., 2005. Foraminifera in surface sediments of Mandovi River estuary: Indicators for mining pollution and high sea stand in Goa, India. Journal of Coastal Research, 21(4), 853‐859. West Palm Beach (Florida). ISSN 0749-0208. Foraminiferal characteristics of 11 surface sediment samples collected from the Mandovi estuary during 2001 have been compared with similar data based on samples collected during 1994. The study reveals drastic fall in total foraminiferal number in the lower reaches of the Mandovi River estuary, from 138/g dry sediment sample in 1994 to 41/g sediment sample in 2001. The decline is also noted in diversity from 22 in 1994 to only 5 species in 2001. The ever-increasing suspended load in Mandovi estuary, probably due to mining activities in the catchment area of the Mandovi River estuary, is suggested as the plausible reason for the decline of fauna. An intriguing finding of the present study is the presence of substantial amount of reworked/older specimens, at the lower reaches of the estuary, that could be indicators of Holocene high sea stand.

A test of different factors influencing the isotopic signal of planktonic foraminifera in surface sediments from the northern South China Sea

The stable isotope composition of planktonic foraminifera is one of the most important proxies in paleoenvironmental research. In this study, three parameters affecting the stable isotope values of Globigerinoides ruber from surface sediment from the northern South China Sea were tested: different cleaning methods, different morphotypes, and different size fractions. Our results show that in the small size fraction, there is a small but significant effect on δ 13C by oxidizing the tests prior to measurement. Our data also confirm a small but significant difference between different morphotypes of G. ruber. However, the variability caused by the seasonal effect stable isotope value is larger than the effect caused by different cleaning protocols or different morphotypes. The large spread of the isotope values (up to 2‰) have some implications to paleoceanographic reconstructions; when measurements are performed on a small number of foraminiferal tests, the isotope value does not necessarily reflect yearly average or a certain season but is a random value of the seasonal variability in that region.

Upwelling and productivity along the Peru–Chile Current derived from faunal and isotopic compositions of planktic foraminifera in surface sediments

We report on the spatial distribution of isotopic compositions of the two planktic foraminifera species Globigerina bulloides and Neogloboquadrina pachyderma (dex.), and the faunal assemblages of planktic foraminifera in 91 surface sediment samples along the Chilean continental slope between 23°S and 44°S. Both δ 13C and δ 18O data of N. pachyderma (dex.) show little variability in the study area. North of 39°S, the isotopic values of N. pachyderma (dex.) are heavier than those of G. bulloides, whereas south of 39°S, this relation inverses. This is indicative for a change from a well-mixed, deep thermocline caused by coastal upwelling north of 39°S to well-stratified water masses in a non-upwelling environment south of 39°S. In addition, the faunal composition of planktic foraminifera marks this change by transition from an upwelling assemblage north of 39°S to a high-nutrient-non-upwelling assemblage south of 39°S, which is characterized by decreased contributions of upwelling indicators such as G. bulloides, N. pachyderma (sin.), and Globigerinita glutinata. In general, we can conclude that food and light rather than temperature are the primary control of the planktic foraminiferal assemblage between 23°S and 44°S off Chile. Our data point to higher marine productivity at upwelling centers north of 25°S and at 30–33°S. South of 39°S, significant supply of nutrients by fluvial input most likely boosts the productivity.

Benthic foraminifera assemblages at Great Meteor Seamount

Foraminiferal assemblages found at Great Meteor Seamount were studied in August 1998. Communities of living foraminifera in surface sediments from the plateau (290–325 m water depth) and from the surrounding base (2,300–4,096 m) were compared in abundances, diversity, and species composition. In this oligotrophic region, densities were very low, but diversity was high. Highest numbers were observed at the deep stations north, south, and east of the seamount and at the shallow station in the north of the plateau. Lowest densities were recorded southwest of the plateau centre and at the lee side of the seamount. We explain this distribution pattern with variable amounts of fresh organic material, caused by local oceanic currents. Generally, plateau stations indicated coarser sediments, lower organic carbon content, and higher temperatures. The foraminiferal fauna showed bathyal to abyssal characteristics and similarities to assemblages previously described from other parts of the North Atlantic and other oceans. Several dominant species extended between the two habitats, on the plateau and in the surrounding deep sediments, but other species were found exclusively at deep stations, at plateau stations, or at the abyssal reference station.

Paleoproductivity in the Equatorial Indian Ocean for the last 260,000 yr: A transfer function based on planktonic foraminifera

A Principal Component Analysis (PCA) of planktonic foraminifera in surface sediment of the Northern Equatorial Indian Ocean defines two major assemblages. The first one dominated by Globigerinoides sacculifer, G. ruber, Globigerinella aequilateralis and Globoquadrina conglomerata characterizes non-upwelling areas. The second dominated by Globigerina bulloides, G. falconensis and Globigerinita glutinata characterizes upwelling areas. The distribution of planktonic foraminiferal species in the area is mainly related to Primary Production (PP). The PCA applied to Core MD 900963 samples defines an alternation of the two assemblages through time, a non-upwelling one similar to that present in the core tops and an upwelling assemblage which contains in addition Neogloboquadrina dutertrei, Globorotalia menardii and G. crassaformis. Equatorial Indian Ocean core-top samples are introduced as additional rows in the PCA calculated on Core MD 900963 samples and a transfer function is constructed correlating factorial coordinates of core tops within the range of changes occurring in Core MD 900963 with estimated PP values. Applied to the last 260,000 yr, the transfer function indicates that the precession is the major orbital forcing on equatorial productivity changes and that annual PP increases by about 85% from interglacial to glacial interstadials. These results are in agreement with an independent productivity index based on coccoliths. Direct impact of insolation on equatorial productivity could be explained by the link between Southern Oscillation and intensity of zonal winds which seem to lead the productivity of surface waters at the location of Core MD 900963.

Lateral variations among populations of stained benthic foraminifera in surface sediments of the North Carolina continental shelf (U.S.A.)

Lateral variations among populations of stained benthic foraminifera in surface sediments of the North Carolina continental shelf (U.S.A.)

Recent calcium carbonate dissolution in the Barents Sea: Paleoceanographic applications

Studies of benthic foraminifera in surface sediments of the Arctic, epicontinental Barents Sea, show several indications of calcium carbonate dissolution. Low values of calcium carbonate correspond to low ratios of calcareous/agglutinating foraminifera, planktic/benthic foraminifera, high ratios of living/dead foraminifera, corroded calcareous foraminifera, and high numbers of exposed organic linings of foraminifera. Dissolution increases eastwards and northwards in the study area. We suggest that the dissolution is caused by the presence of dense, cold, saline and CO2-rich bottom water, which is linked to sea-ice production and the position of the Oceanic Polar Front. We also think calcium carbonate dissolution in this area indicates a sink for atmospheric CO2.

Bathymetric Zonation and Relationship to Sea-Bed Environments of Modern Benthic Foraminiferal Biofacies, Northwestern Gulf of Mexico Slope: ABSTRACT

ABSTRACT The distribution of benthic foraminifera in surface sediments of the northwest Gulf of Mexico slope is studied in 51 piston core-top samples ranging in depth from 141 to 2,134 m (462 to 7,000 ft). Total faunas (living plus dead specimens) are documented as part of a larger study investigating the relationship of living benthic foraminiferal distributions, their relationship to surface sediment and infaunal environments, and taphonomic processes within these environments that produce fossil assemblages. A total of 161 taxa are recognized in the samples, only 23 of which have population abundances greater than 1%. Quantitative analyses of the data include cluster analysis of samples, principal components analysis (PCA), and detrended reciprocal averaging (DRA). Cluster analysis defines four major biotopes that occupy geographically distinct areas and are oriented parallel to depositional strike. Actual depth ranges of the biotopes overlap, pointing to the gradual nature of faunal change with depth on the slope, as recognized by previous studies in this area. Approximate faunal boundaries are present at 500 m (1,640 ft), 1,100 m (3,610 ft), and possibly 1,500 m (4,920 ft). PCA and DRA identify species relationships that characterize the biotopes. The shallowest biotope (141 to 500 m [462 to 1,640 ft]), within the limits of the weak oxygen minimum in this area (ca. 2.6 ml/l), is characterized by Uvigerina peregrina, Bolivina albatrossi, and Bulimina alazanensis. The next deeper biotope (ca. 500 to 1,600 m [1,640 to 5,250 ft]) is distinguished by Epistominella exigua, Pullenia subsphaerica, and Glomospira charoides. This biotope grades downslope (ca. 1,200 to 2,100 m [3,940 to 6,890 ft]) into one delineated by Eponides turgidus, Bulimina aculeata, Osangularia culteri, and Gyroidina orbicularis. The deepest biotope (ca. 1,500 to 2,134 m [4,920 to 7,000 ft]) is characterized by Alabamina decorata, Hoeglundina elegans, Reophax spp., and Hormosina sp. Downslope transport is evident in several samples.

Taphofacies Implications of Infaunal Foraminiferal Assemblages in a Georgia Salt Marsh, Sapelo Island

The occurrence of living infaunal foraminifera and selective preservation significantly alter the composition of assemblages that accumulate in subsurface marsh sediments of Sapelo Island, Georgia. Rose bengal staining and observations on live foraminifers from surface and subsurface marsh sediments identified live infaunal populations of Arenoparrella mexicana (Komfeld 1931) and Haplophragmoides wilberti Andersen 1953 to a depth of 30cm below the marsh surface. Other foraminifera are predominantly surface-dwellers, although some (e.g., Ammonia beccarii (Linne 1758), Miliamminafusca (Brady 1870) and Trochammina inflata (Montagu 1808)) also have shallow infaunal occurrences. INTRODUCTION Salt marsh foraminifera have been widely reported from many localities along U.S. coastlines and selected marshes worldwide (e.g., Murray 1971; Scott and Medioli 1980a; Scott and Leckie 1990). Most previous studies traditionally have emphasized live and/or assemblages present in surface sediments of the marsh. Distributional patterns observed in surface sediments have been correlated to environmental factors such as elevation (Scott and Medioli 1978, 1980a), salinity (Murray 1971, 1973; Scott and Medioli 1980a), pH (Phleger and Bradshaw 1966; Scott and Medioli 1980b) and geographic region (Phleger 1967, 1970; Scott et al. 1990), and constitute the basis for many paleoenvironmental interpretations. Infaunal foraminifera, however, reportedly occur in a variety of marine environments ranging from salt marshes (Akers 1971; Matera and Lee 1972; Steineck and Bergstein 1979; Goldstein 1988) to the deep sea (Corliss 1985; Gooday 1986; Mackensen and Douglas 1989; Corliss and Emerson 1990; Loubere and Gary 1990). In salt marshes, infaunal occurrences may ultimately change the composition of death assemblages that accumulate in subsurface sediments. Foraminifera with infaunal occurrences may become enriched (i.e., have higher relative abundances) with depth in sediments compared to those species that are primarily epifaunal. This process, in addition to selective preservation, may produce subsurface remnant or death assemblages that differ from their counterparts at the marsh surface. Subsurface death assemblages should therefore be evaluated to enhance the accuracy of paleoenvironmental interpretations. This study documents the occurrence of foraminifera living infaunally in selected high, transitional, and low marsh habitats of Sapelo Island, Georgia, and evaluates their effects on death assemblages that accumulate in subsurface sediments, particularly with regard to distributional patterns, diversity and stratification. PREVIOUS WORK Although distributional patterns of salt marsh foraminifera have been widely studied, foraminifera of the extensive salt marshes of the southeastern U.S. have received little attention (Goldstein and Frey 1986; Goldstein 1988). Similarly, few studies on taphonomy, infaunal occurrences and comparisons between surface and subsurface assemblages have been conducted. In an earlier report on foraminiferal taphonomy in salt marshes, Scott and Medioli (1980b) studied the long-term accumulation of foraminiferal assemblages in surface sediments and concluded that (live + dead) counts of foraminifera in surface sediments better reflect distributional patterns with regard to paleoenvironmental studies than those of their live or dead counterparts alone. The composition of total assemblages diminishes seasonal effects. However, Jonasson and Patterson (1992) reported that selective preservation in subsurface salt marsh sediments reduces the number of biofacies or assemblages that can be recognized compared to those present at the marsh surface. Several previous studies on infaunal salt marsh foraminifera (Akers 1971; Matera and Lee 1972; Steineck and Bergstein 1979; Goldstein 1988) found that representatives of some species live infaunally. Furthermore, live surface and subsurface assemblages may differ in density and species composition (Steineck and Bergstein 1979). Akers (1971) reported rose bengal-stained specimens of several agglutinated species to a depth of 30-35cm in salt marshes near Beaufort, North Carolina. In studies on foraminifera of selected marshes and adjacent habitats of Long Island, New York, Matera and Lee (1972) also reported rose bengal-stained foraminifera in subsurface sediments. Abundances of Trochammina inflata (Montagu 1808), in particular, increased with depth (to about 8cm) below the marsh surface, and stratification of foraminifera over shallow sediment depths was noted. Steineck and Bergstein (1979), applying cluster analysis to data on living (rose bengal-stained) surface and subsurface foraminifera, identified two biotopes: a surface assemblage and an impoverished subsurface assemblage. Total (live + dead) assemblages and taphonomy, however, were not evaluated. ENVIRONMENTAL SETTING Sapelo Island, one of several Pleistocene barrier islands of the central coast of Georgia, lies approximately seven kilometers micropaleontology, vol. 39, no. 1, pp. 53-62, text-figures 1-6, tables, 1-2, 1993 53 This content downloaded from 157.55.39.211 on Mon, 08 Aug 2016 06:24:55 UTC All use subject to http://about.jstor.org/terms S. T Goldstein and E. B. Harben: Taphofacies implications of infaunalforaminiferal assemblages in a Georgia salt marsh, Sapelo Island TABLE 1 Classification of salt marsh habitats and subenvironments HABITAT

Multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and Late Quaternary shelf sediments, northern Canada

Benthic foraminifera in surface sediments from northeastern Canada and the Beaufort Shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth, temperature and salinity. Factor analysis shows that 7 factor assemblages account for 92% of the variance between samples. Multiple linear regression shows that different factors are significantly related to water depth, August bottom water temperature or salinity. Multiple correlation coefficients for depth, temperature and salinity are 0.94, 0.72 and 0.92, respectively. Labrador fjords contain arenaceous faunas dominated by either Saccammina atlantica and Reophax fusiformis or by Eggerella advena. Regression analysis shows that the Saccammina-Reophax factor is most strongly related to salinity. The Eggerella factor is related to depth and temperature. A fauna dominated by Trochammina nana and Buliminella elegantissima is correlated with warm, deep water in Davis Strait. Calcareous assemblages dominated by Elphidium excavatum or Cassidulina reniforme are found in Arctic bays and shelf areas. These factor assemblages are strongly related to temperature and depth; Cassidulina is also related to salinity. An Islandiella helenae fauna on the inner Labrador Shelf is strongly correlated with depth and salinity. A Nonionellina labradorica fauna in deep shelf basins is closely related to salinity. The multiple regression model for the sea-bed data estimates water depth, August bottom water temperature and salinity within confidence limits of ± 67 m, 1.3°C and 1.0‰. Paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the Labrador Shelf. Paleo-depth estimates obtained from the core data produce relative sea-level curves which are similar in shape to theoretical curves for this region. Paleo-salinity and -temperature estimates for offshore Core 12 show that the change from a postglacial Nonionellina fauna to a late glacial E. excavatum fauna is accompanied by a decrease of about 2‰ in salinity and 4°C in temperature. Paleoecological estimates for fjord Core 111 show that the change from a modern Saccammina-Reophax fauna to a mid-Holocene I. helenae fauna corresponds to a salinity increase of 3–5‰ and temperature increase of 1–2°C.

Faunal and solution patterns of planktonic foraminifera in surface sediments of the North Pacific

Planktonic foraminifera in the sediments on the North Pacific sea floor follow the distribution patterns of their living counterparts. Left- and right-coiling N. pachyderma, G. bulloides, G. quinqueloba, G. ruber, and G. inflata are important in identifying four major faunal assemblages. These taxa dominate the faunas in various samples. Their distribution is closely related to either temperature or nutrient patterns of surface waters, or both. Multivariate statistical techniques, cluster, factor, and discriminant analysis, group samples from less than 3300 m into a variety of spatial patterns. The group separations generated by a discriminant analysis are readily interpreted in terms of the environment because samples were coded according to their respective zooplankton province, and because those provinces correspond to the major water masses of the North Pacific Ocean. Factor analysis created seven assemblages that map in overlapping patterns. Three of the seven assemblages show little relationship with surface water temperature. Dissolution obscures the record of faunal provinciality in core top samples from depths greater than 3300 m. The degree of dissolution affects percent similarity of samples measured relative to centroids, mean assemblages, for each faunal province. Plotted against depth, values of similarity indices follow trends much like those of percent carbonate. Groupings determined from sample to sample similarity matrices correspond to trends recorded by dissolution indices based on susceptibility rankings. Both measures illustrate a step-like response of foraminiferal assemblages to increasing dissolution. Dissolution can introduce systematic bias into temperature estimates derived from paleoecological transfer functions. The direction of the bias varies according to the temperature aspect of an assemblage. Temperature estimates based on dissolved samples are generally too low for central and equatorial regions and too high for transitional regions (winter conditions).

Distribution of Planktonic Foraminifera in Surface Sediments of the Gulf of Mexico

Frequency distributions of planktonic foraminifera from 140 trigger core-tops in the Gulf of Mexico generally reflect major oceanographic features. The distribution of Globigerinoides sacculifer outlines the Loop Current in the eastern Gulf and Globigerinoides ruber maxima marks salinity extremes, whereas the distributions of Pulleniatina obliquiloculata, Globorotalia truncatulinoides and Globigerinita glutinata parallel winter isotherms in the Gulf. Q-mode factor analysis was used to extract 5 assemblages from 23 species and compare their distributions in the Gulf to those of the well-studied Atlantic Ocean. The 5 assemblages are interpreted as: 1) subtropical, dominated by G. ruber; 2) temperate, composed of Globorotalia inflata, Globigerina falconensis, Globorotalia truncatulinoides, Globigerina buloides and Neogloboguadrina dutertrei; 3) dissolution-resistant, consisting of Globorotalia menardii, Pulleniatina obliquiloculata and N. dutertrei; 4) equatorial, composed of G. sacculifer and P. obliquiloculata; and 5) subpolar, consisting of N. dutertrei, G. inflata, Neogloboguadrina pachyderma and G. bulloides. The modern distributions of these assemblages have been used to develop 4 transfer functions from which the winter and summer temperatures and salinities for the Late Quaternary have been estimated. Distribution of planktonic foraminifera in surface sediments of the Gulf of Mexico