Shallow-water Foraminifera Research Articles

Unparallel resilience of shallow-water tropical calcifiers (foraminifera and scleractinian reef corals) during the early Paleogene global warming intervals

Investigating the fossil record to provide evidence about the response of shallow-water tropical calcifiers to past warming events is crucial considering that they are severely threatened by current global warming. We thus focused our attention on scleractinian reef corals (SRC) and shallow-water foraminifera (SWF), both mainly symbiont-bearing organisms, analysing and comparing their diversity patterns during the Paleocene and Eocene from datasets of the Neothetyan circum-Mediterranean region. In particular, at both genus and species level, we analysed changes in diversity, together with origination and extinction rates.Despite some biases related to biostratigraphic resolution of SRC and SWF data, our results show that they reacted differently to the major warming events of the Early Paleogene. The K/Pg mass extinction caused the disappearance of almost all SWF, whereas several corals passed this crisis and persisted up to the end of Paleocene, when the Paleocene-Eocene Thermal Maximum (PETM) caused a relatively small decrease of coral diversity together with a global collapse of coral reefs. On the other hand, a rapid radiation of nummulitids and alveolinids occurred at species level. The impact of the Early Eocene Climatic Optimum (EECO) was apparently more severe for SWF than for SRC. After the Middle Eocene Climatic Optimum (MECO), the general cooling trend led to the fading of Eocene SWF genera and species, whereas SRC began their rapid diversification from Bartonian to Priabonian and culminating in the Chattian.Our results suggest that rapid warming events favoured speciation in SWF, whereas the slow cooling trend (e.g., after the MECO) favoured diversification of SRC. Our data also underline that SWF reacted differently to warming events as compared to deep-sea smaller benthic foraminifera and that the same events in the planktonic realm are not strictly coeval with those occurring in shallow-water environments.On a wider perspective, we observe that shallow-water calcifiers demonstrate a good degree of resilience to global temperature increases, even if undergoing to more or less marked reduction of biodiversity. We provide evidences for the recovery of past ecosystems from both short and long stressors.

Shallow water foraminifera from Niue and Beveridge Reef (South Pacific): insights into ecological significance and ecosystem integrity.

Niue represents one of many important steppingstones facilitating the dispersal of marine organisms across the tropical Pacific Ocean. This study is part of a collaborative expedition involving National Geographic Pristine Seas, the government of Niue, Oceans 5, and the Pacific Community. We present the first survey documenting the species richness of foraminiferal communities in Niue and nearby Beveridge Reef and explore their significance for ecosystem integrity. A substantial portion (59%) of Niue's foraminiferal assemblages is Large Benthic Foraminifera (LBF), a symbiont-bearing group known as ecosystem engineers and indicators of coral reef regime shifts. LBF species reported here reflect the gradual decrease of tropical diversity from the Coral Triangle towards the central Pacific Ocean. Calcarinidae, an LBF family represented in this study by two species, is the easternmost ever recorded in published literature, and the biogeographical dispersal of this temperature-controlled group is of great importance to future global warming related studies. Foraminifera are an important component of beach development in Niue, with a close relationship between source and depositional zones. These essential ecological-sedimentary linkages highlight the importance of habitat conservation not only as a means to safeguard biodiversity, but also for its role in the island's physical framework.

Recent shallow water foraminifera from the Selvagens Islands (Northeast Atlantic) – Assemblage composition and biogeographic significance

We report the first survey of shallow-water foraminifera from the Selvagens Islands, an isolated archipelago located in the subtropical Northeast Atlantic. In our samples, we identified 63 species of foraminifera belonging to 43 genera in the >63 μm fraction, including eight species of symbiont-bearing Larger Benthic Foraminifera (LBFs). The assemblages consist mostly of epiphytic species and species associated with coarse grain and hard substrate habitats. Analysis of dead assemblages revealed two main clusters that mostly correspond with the two island groups within the archipelago and relates to their environmental characteristics. Our results provide illustrated baseline information for this remote and relatively pristine habitat, wherein foraminifer community assemblages show a higher degree of similarity to those of the Canary Islands, Cape Verde, and Bermuda as compared to those of Mauritania, Northwest Africa. Hence, this study suggests that geographic proximity and oceanic barriers plays a lesser role than environmental parameters when determining foraminiferal biogeography. In addition, given that all LBF species reported in Selvagens are also present across the Atlantic Ocean, our results suggest that the previously defined ‘Caribbean’ LBF realm should be extended to the subtropical North Atlantic, taking into account local conditions, particularly minimal temperatures, controlling specific LBF assemblages.

The impact of the submarine volcano Kick ‘em Jenny on benthic foraminifera

Nothing is known about the impact on marine meiofauna of submarine volcanic eruptions in the Grenada Basin. The benthic foraminiferal fauna is here examined in piston cores taken within ∼8 – 38 km of the crater of Kick ‘em Jenny (KeJ), decadal eruptions of which disseminate ash to the NW via the Caribbean Current. Piston core Gs29, taken ∼8 km W of the crater, consists of clay-rich material from the Globorotalia menardii Zone U, ∼500 ka old, probably exposed by slumping. The remaining cores (from proximal to distal: GC59, GC90, GC99 and GC100), taken between 1000 – 3000 m water depth, comprise volcanic ash and are of presumed Holocene age. Recovery from GC59, GC90 and GC99, the last taken 27.3 km NW of the crater, was poor and apparently reflects volcanic ash impact. Recovery from GC100, 38 km NW of the crater and from the basin floor, was rich. Thus, KeJ disrupts seafloor colonization by foraminifera up to 32 – 38 km from the crater. Bolivina spp., indicative of low dissolved oxygen concentrations, dominated the assemblage in proximal core Gs29. Cassidulina spp. dominated the distal core GC100 assemblage, indicating somewhat higher dissolved oxygen concentrations. This might reflect a long-term change in productivity in the area, or a nutrient-rich surface eddy to the lee of Grenada. Allochthonous, shallow-water foraminifera, recovered throughout cores Gs29 and GC100, were more abundant in the latter. This might indicate that Grenada protects nearshore foraminifera from disruptive hurricanes.

Palaeozoic carbonates and fossils of the Mendeleev Rise (eastern Arctic): A study of dredged seafloor material

Fossiliferous carbonate rocks dredged during the “Arctic-2012” cruise on the Mendeleev Rise (eastern Arctic) provide proof of the presence of Upper Silurian(?)–Middle Devonian, Famennian–Tournaisian, Bashkirian–Kasimovian, Gshelian–lower Asselian(?) and Kungurian–Kazanian carbonate deposits. The wide spectrum of facies includes deposits of both photic zone (with fusulinids, algae, relicts of microbial and coral reefs) and deeper dysphotic areas (with trilobites, deep-water tentaculitids and ostracods). The results obtained suggest that there were at least three periods of carbonate platform sedimentation during the latest Silurian(?) to Permian.The Late Silurian?–Devonian biota do not show biogeographical differentiation, but rather are distributed globally. Shallow-water foraminifera and some algae of early Pennsylvanian–basal Cisuralian age belong to the warm-water province. These forms are unknown in the Moscovian–Permian of the Boreal Realm (Taimyr, New Siberian Islands, Verkhoyanie, Omolon Massif) but are typical for Alaska and Arctic Canada, Wrangel Island, Chukotka, Polar Urals and Svalbard. The disappearance of warm-water biota during late Artinskian-Kungurian times led to a subsequent predominance of smaller foraminifera: this assemblage with Protonodosaria is widely distributed in Permian deposits of Novaya Zemlya, Urals, Barents Sea and the eastern Arctic.The warm-water Bashkirian-Asselian biota suggests that the Mendeleev-Chukotka-Wrangel block was a low-latitude shallow basin with predominant carbonate sedimentation, being part of the Arctida supercontinent, connected temporarily with the eastern margin of Laurasia (Chukcha-Alaska block).

Shallow-water nearshore benthic foraminifera assemblages from Gabon

The Gulf of Guinea is a hotspot of marine diversity, with unique biotas. We provide the first survey of shallow-water foraminifera from nearshore coastal waters of Gabon, an area from which modern benthic foraminifera are virtually unknown. We document the composition of benthic assemblages and assess their biogeographic relation to adjacent faunal provinces. Our analysis survey documents that shallow-water sediments harbor abundant and relatively diverse assemblages of symbiont-bearing and other smaller foraminifera. The 39 species recorded from nearshore coastal waters off Gabon contrast with lower diversity assemblages previously documented from offshore hydrocarbon drilling waste disposal sites. The assemblages of benthic foraminifera recovered suggest a deeply-rooted species diversity, where the true number of foraminiferal taxa present in Gabonese’s pristine waters remains yet to be discovered. The composition of foraminiferal biotas found off Gabon shows them to be distinct from faunas recorded from off Namibia and South Africa, indicating the presence of a marine biogeographic barrier.

ECOSTRATIGAPHIC REGIME SHIFT DURING LATE QUATERNARY MARINE ISOTOPE STAGES 8-9 IN SANTAREN CHANNEL, WESTERN TROPICAL ATLANTIC OCEAN: BENTHONIC FORAMINIFERAL EVIDENCE FROM ODP HOLE 1006A

The Late Quaternary, presumed bathyal foraminiferal fauna in ODP Hole 1006A (Santaren Channel, west of the Bahama Platform) does not show marked glacial-interglacial contrasts. Instead, a major regime shift occurred during Marine Isotope Stages (MIS) 8–9 from one steady community structure to another. ODP Hole 1006A was drilled through the Santaren Drift, a contourite containing an admixture of foraminifera of a) reefal and inner-neritic (0–20 m) and b) deeper-water aspect. The deeper-water assemblage, which includes species with habitats that encompass outer-neritic (100–200 m)–abyssal depths, is for statistical purposes here treated as being in situ. Of the benthonic foraminifera collected from 66 Late Quaternary (MIS 1–17) samples in this study, 60.9% comprise the presumed bathyal assemblage. Percentages of presumed bathyal specimens/sample are unrelated to most marine isotope stages, but are low in MIS 8–9. Sedimentology indicates that the fluctuations were not caused by turbidites and debris flows delivering shallow-water foraminifera from the Bahama Platform and Cay Sal Bank to the site, but possibly from a source off northern Cuba or Hispaniola. Some species abundance counts (e.g., Cassidulina laevigata , Lenticulina rotulata ) may have been augmented by downslope transport. Others (e.g., Globocassidulina subglobosa , Sigmoilopsis schlumbergeri ) are predominantly in situ. Only three species each ( Globocassidulina subglobosa , Planulina ariminensis , Cibicidoides pachyderma ) formed >5% of the total recovery of the presumed bathyal foraminiferal assemblage, but Cibicidoides spp. collectively formed 18.9%, while Uvigerina spp., Brizalina spp., and Bulimina spp. collectively formed 12.8%, indicating a low flux of organic carbon. The mean information function was higher in the subsection below MIS 9 (H = 3.56) than above MIS 8 (H = 3.40), but the mean percentages of Uvigerina spp., Brizalina spp., and Bulimina spp. did not differ, which suggests that there was little change in the organic flux. Instead, the regime shift may have been related to a change in the flux of shallow-water foraminifera, which was greater after MIS 8 than before MIS 9, or to long-term circulation changes. The subsections across the regime shift were separated by a Type-1β boundary, but a complementarity of 76.5 indicates that the interval MIS 8–9 did not act as a barrier to species continuance.

Shallow-water foraminifera of Matsushima Bay: fauna recovery from the 2011 Tohoku-oki tsunami damage

Shallow-water foraminifera of Matsushima Bay: fauna recovery from the 2011 Tohoku-oki tsunami damage

Population dynamics of benthic shallow-water foraminifera: effects of a simulated marine snow event

In this microcosm experiment, we determined the population dynamics of benthic foraminifera from the northern Adriatic Sea (from 32 m water depth) and how they were affected by an artificial marine snow event (AMS). The study focussed on the performance of individuals in 2 dif- ferent size fractions: one commonly used in micropaleontological studies (with foraminifera >63 µm) and 1 with smaller individuals (38-63 µm). Microcosms were incubated for 2 or 4 wk, and under AMS or control conditions. For each, the numbers of live (Rose Bengal-stained) individuals of different spe- cies in both size fractions were counted. From this, demographic parameters (fecundity, survival, growth) of specimens in different size classes were assessed. With these data, population projection matrices were constructed for the 4 most abundant taxa (Bolivina spp., Stainforthia fusiformis, Non- ionella turgida and Hopkinsina pacifica) and all foraminifera together. From the limit properties of these matrices, asymptotic population growth rates (λ) were derived. The results indicate that num- bers of larger benthic foraminifera decline more strongly because of AMS than those of the smaller individuals, and that growth is seriously inhibited. AMS, however, enhanced fecundity. Under AMS conditions (i.e. temporary anoxia and, concomitantly, extra food), the foraminifera seem to shift to an alternative life-history pathway of rapid reproduction and limited growth. After the first 2 wk, values of demographic parameters increase under AMS conditions, resulting in quickly recovering popula- tions. In our view, these demographic characteristics are beneficial for the observed species in peri- odically stressful and disturbed ecosystems, and could explain the increasing success of these species in the progressively eutrophicated northern Adriatic Sea.

Laboratory observations of rates and patterns of movement of continental margin benthic foraminifera

Living calcareous and agglutinated benthic foraminifera were collected from a water depth of 220 m on the Charleston Bump east of Charleston, South Carolina and maintained in aquaria at ambient bottom water temperatures of 12 °C and 1 atm in the laboratory. The rates and patterns of movement of two species, Cibicidoides pachyderma (Rzehak, 1886) (a calcareous foraminifer) and Ammodiscus anguillae Höglund (1947) (an agglutinated foraminifer), are described and compared with published rates of movement for shallow- and deep-water taxa. Cibicidoides pachyderma and A. anguillae move laterally on a thin veneer of sediment in meandering patterns and both vertically and horizontally in thicker sediments with predominantly straighter patterns in the vertical plane. The recorded rates of movement at the substrate surface of C. pachyderma and A. anguillae vary from 1.0 to 23 and 1.0 to 20 mm/day, respectively. Within the sediment (~ 0.5 cm) A. anguillae moved with a rate varying between 1.0 and 10 mm/day. These rates are similar to rates for deep-sea foraminifera and to the slowest rates of shallow-water foraminifera. In the laboratory and in the absence of bioturbating organisms, both species moved in and out of sediments, suggesting that in nature they may be epifaunal and/or shallow infaunal taxa.

Taxonomic Notes on Some Tiny, Shallow Water Foraminifera from the Northern Gulf of Elat (Red Sea)

Taxonomic Notes on Some Tiny, Shallow Water Foraminifera from the Northern Gulf of Elat (Red Sea)

Morphology, water characteristics and sedimentation in the silled Sulu Sea, southeast Asia

During 1977 RV “Valdivia” recovered 46 cores, occupied two hydrographic stations, and ran eleven bathymetric profiles in the roughly rectangular Sulu Sea, which trends northeast and covers about 250,000 km 2. The Sulu Sea Deep in the southeast is separated from the shallower Palawan Depression in the northwest by the northeast-trending Cagayan Ridge. The maximum sill depth between the sea and the open ocean is about 400 m, and the water column is layered, cutting off the deep water, which is homogeneous, warm (10° C), and oxygen deficient (< 1.6 ml/ml O 2), from normal oceanic water. The shelves are generally broad and covered with calcareous sand and gravel, except in the east and southeast, where they are narrow and covered with muddy sand and gravel. The shelf carbonates give way to bathyal oozes, and the muddy sands grade into varied silts dominated by volcanic and sedimentary debris. The smooth abyssal plain of the Sulu Sea Deep is at a depth of 4800–5000 m, and northwest of it is an plain at 4000–4200 m. Turbidites characterize both plains. The aragonite and calcite compensation depths are at about 1400 m and 4500 m, respectively. The turbidite beds average 5–10 cm thick, with all Bouma's divisions recognizable, apart from “a”. The southern turbidites (station 14224) are of two types: calcareous and terrigenous. The calcareous turbidites, characterized by shell debris including shallow-water foraminifera, were derived from the upper slopes flanking the broad shelves. The terrigenous turbidites, characterized by sedimentary and volcanic rock fragments, apparently originated from the slopes off Mindanao. The eastern turbidites (station 14233) are finer grained, characterized by sedimentary rock fragments, and came from the narrow muddy shelves further east, off Panay, Negros and Mindanao. Radiocarbon dating suggests that depositional rates for the turbidite sequences (ca. 100 cm/1000 yr.) are an order of magnitude greater than the rates for bathyal oozes. Organic carbon contents in the surface sediments are highest between 500 m and 1200 m water depth, exceeding 2% off Mindanao (station 14226), and reaching 1.82% on the Palawan slope (station 14206). The lowest contents are at the Palawan Shelf edge (0.11% at station 14204) where the proportion of carbonate sand is very high, and in the bathyal oozes of the central Sulu Sea (< 1%) where sedimentation rates are low and mineralisation of organic matter is effective. Contents average 1% below 4500 m in the Sulu Sea Deep. The colour of the surface sediment appears to be related to the organic carbon content: olive colours above 1200 m and below 4500 m, and brown colours between. The surficial sediments are characterized by living shelly faunas and intense bioturbation above 150 m, and by intense bioturbation and absence of a shelly fauna down to 3000 m. Bioturbation decreases below 3000 m, and in the Sulu Sea Deep is confined to a few Zoophycos, Granulites and Cosmorhaphe burrows. The faunal changes are apparently related to bottom water oxygen concentrations.

Shallow-Water Limestones from Slope off Grand Cayman Island

Limestones of Oligocene age obtained from a submersible at two sites about 3,000 m deep on the Oriente Slope and from two shallow drill holes on nearby Grand Cayman Island were deposited in shallow marine waters. All samples contain calcareous algae and shallow-water foraminifera, but no deep-water remains were found. The limestone on the slope was lithified in fresh water, according to its petrography and stable isotopes. A third dive encountered massive beds presumed to be outcrops of limestone that dip southward down the slope. We conclude that the region began to subside along a hinge line parallel to the Oriente Slope during Oligocene time and soon became too deep to generate a shallow-water carbonate deposit. This subsidence was associated with plate movements along the Cayman Trough.

Paleoecologic Implications of Foraminiferal Distributional Patterns Off Big Pine Key, Florida: ABSTRACT

Foraminifera are important both as biotic elements and as skeletal constituents of sediments in carbonate depositional provinces such as south Florida. A better understanding of distribution, habitats, and ecology of shallow-water Foraminifera can lead to more accurate paleoenvironmental interpretations based on the fossil record. In shallow-water carbonate environments plants are an important foraminiferal habitat, and the plant-dwelling biocoenosis in an area may not be reflected accurately by the thanatocoenosis among the associated bottom sediments. Bottom sediments and vegetation were collected from lagoonal, tidal channel, patch reef, and outer reef environments in the vicinity of Big Pine Key. Living and dead individuals were distinguished for the 106 foram species identified. Sanders' similarity index indicated that the biocoenoses on different kinds of plants within any one environment were similar, whereas the biocoenosis from each major environment was unique. The Shannon-Wiener information function showed a correlation between species diversity and evenness as related to degree of environmental variability. Additionally, biocoenoses from vegetation were dissimilar to thanatocoenoses among sediments. Larger, more robust tests were predominant among sediments, particularly in less sheltered environments. Postmortem processe , such as sorting and differential destruction of tests, affect the character of species diversity and evenness indigenous to living populations. In making paleoecologic and paleoenvironmental analyses of fossil foraminiferal assemblages, it is necessary to discriminate between ecologic factors that influence the distribution of living populations and environmental factors that determine the final character of the dead assemblage. End_of_Article - Last_Page 548------------

Ashes, turbidites, and rates of sedimentation on the continental slope off Hawkes Bay

Abstract Sediments sampled by piston and gravity corers from the continental slope off Hawkes Bay Land District, New Zealand, consist of mud with ash and turbidite layers. The ash layers can be correlated by mineralogical and geochemical methods with dated ash layers on the adjacent land. The 3400-year-old Waimihia ash is identified in all cores. In some cores a band of pumice in mud above the Waimihia ash is considered to represent the Taupo eruption of 1800 years ago, and deeply buried ashes are correlated with Oruanui Ash, Mangaone* Lapilli Formation member (c), and Rotoehu Ash, which were erupted about 20 500, 30 000 and 43 000 years ago respectively. Rates of sedimentation during the last 3400 years are estimated (from the thickness of sediment overlying the Waimihia ash) to range from 0 to 0·36m per thousand years. In synclinal depressions that are downslope from submarine channels, the sediment above and below the Waimihia ash consists of thick layers of mud separated by thin sandy layers, some of which contain shallow water foraminifera. The sandy layers are considered to have been deposited by turbidity currents, and a maximum of nine of them overlie the Waimihia ash.

Submerged Reefs of the Eastern Grenadines Shelf Margin

A seismic and bathymetric survey was made over a segment of the submerged edge reef of the eastern margin of the Grenadines Shelf, which rises to a depth of no more than 30 m above the Lesser Antilles Ridge. This ancient reef is poorly developed and is segmented longitudinally by normal faults; it was once built up to a thickness of about 25 to 35 m above the original shelf surface. Although the reef is now extinct, abundant deposition by calcareous algae is presently occurring. The shelf ends abruptly in a steep scarp of more than 30° above the slope of the Tobago Trough. Thick accumulations of material derived from the shelf by normal deposition, slumping, or turbidity currents are found at the foot of the scarp and on the upper slope. Blocks of cemented calcarenite made up of coral debris and containing shallow-water Foraminifera were dredged up in two places along the upper part of the scarp. C 14 dates of 9,750 and 12,900 yr B.P. obtained on this material indicate the approximate time at which the reef was built, as a consequence of the postglacial rise in sea level. These relations provide additional data about the postglacial history of the southern Lesser Antilles Ridge and also information about the age and development of similar shallow submerged reefs in the Caribbean.

Physiography and Sedimentary Processes of La Jolla Submarine Fan and Fan-Valley, California

The depositional environments of La Jolla canyon, fan-valley, and fan are well known from closely spaced sounding lines, deep-diving vehicle observations, numerous undisturbed box cores, and continuous reflection profiles. The narrow rock-walled canyon changes seaward at 300 fm (549 m) to a wider valley cut into the compacted clayey sediments of a fan, and bordered by discontinuous leveelike embankments. The fan-valley merges gradually into the relatively flat floor of San Diego trough. Numerous dives into the fan-valley have shown precipitous walls along the outside of the bends of the winding channel. Slumping is taking place actively from these walls and large slump blocks of clay are common on the floor. Small scour depressions around isolated erratics suggest the ero ive effect of relatively weak currents in some places but, for the most part, the muddy floor seems to have been little disturbed in recent years. Diagonal tension cracks cut the floor locally. Box cores show that most of the sediment deposited on the valley floor in the past few thousand years consists of poorly sorted clayey silt, underlain by discontinuous layers of well-sorted fine-grained sand with a few coarse sand grains, gravel, and mud balls. Sand layers occur in 94 percent of the valley axis cores, of which 26 percent are graded; 59 percent have parallel laminations; and 41 percent have current-ripple cross-laminations. Sand layers are less common in the cores from levees and from the small discontinuous terraces along the sides of the fan-valley. Cores from the open fan have less and finer grained sand. In all these environments the sand shows no consistent or systematic grain-size variation with increasing water depths. Some of the coarsest sediments, including g avel and mud balls, are found in sand farthest from shore and at the greatest depths. The character of the sand and the finding of shallow-water Foraminifera indicate the probability that sand has been carried from the coastal area along the valley axes and spilled over the levees onto the open fan. However, there is little evidence of recent high-velocity, high-density turbidity currents, because, in general, the covering mud layer is distinctly separated from the underlying sand deposits, and therefore does not suggest deposition at the terminus of a turbidity current. Also, the discontinuous character of the sands and series of laminae with heavy mineral concentrations indicate introduction by a traction type of pulsating current, such as has been seen during vehicle dives, and also has been measured in the few available current-meter records. The locally precipitou fan-valley walls and outcrops of gravel, and the sand layers on the levees and open fan, may be the product of stronger currents that moved down the valley during earlier more pluvial periods, when greater quantities of sediment entered the canyon heads. Possible confirmation of this idea comes from the available C-14 dates in plant layers, which suggest that deposition in the past few thousand years may have been considerably slower than that indicated for the Pleistocene. The finer sediments may be largely the result of slow downslope movement of slightly higher density muddy waters coming from the coastal areas. Continuous reflection profiles have shown that the inner La Jolla fan has only a thin cover of unconsolidated sediments overlying the folded and faulted Miocene-Pliocene rocks. The outer fan and adjacent San Diego trough contain a thick section (more than 1,000 m) of Quaternary sediments with probable buried older channels and possible thick lenses of sand sediments.

Intertidal and Shallow-Water Foraminifera of Tropical Pacific Ocean: ABSTRACT

Intertidal and shallow-water sediment samples from the tropical Pacific Ocean were studied and a quantitative analysis made of their constituents. The foraminiferal components exhibit both eurytopic and stenotopic distribution patterns. Seven methods of dispersal are listed and analyzed to help explain the eurytopic patterns. Hypotheses based on dispersal methods and fluctuations in populations are advanced to explain the stenotopic and sporadic fossil and recent occurrences of two important foraminiferal genera, Tinoporus (Calcarina) and Baculogypsina. An examination of the beach sands shows that although calcite, igneous, and metamorphic grains are the principal components in the majority of the samples, foraminiferal tests commonly comprise over 30 per cent of the sand The remaining constituents are usually less than 1 per cent of the total. The analysis of the shallow-water Foraminifera from Johnson Island indicates that certain species have high numerical values in restricted areas. These occurrences are similar to those of the same species in the shallow waters of other islands. End_of_Article - Last_Page 1763------------

Reconnaissance survey of the abyssal plain south of Newfoundland

This paper presents a new chart of the abyssal plain south of Newfoundland, contoured in 5-fathom intervals, based on a survey with a newly developed precision depth recorder. The area is of interest in connection with the 1929 Grand Banks earthquake. The abyssal plains are flat, nearly level areas which occupy the deepest portions of many of the ocean basins. The development of a precision depth recorder with an accuracy better than ± 1 fathom was required before an effective study of the abyssal plains could be made. In 1953 a reconaissance survey was run with such a recorder on the abyssal plain south of Newfoundland. The gradient of the plain decreases from 1:1,000 at its northern margin near 41°N to 1:5,000 near latitude 32°N. South of 32°N the gradient probably flattens still more before the southern margin of the plain is reached. The plains have been interpreted by various writers as: (1) atectonic areas; (2) subaerial erosion surfaces; (3) lava plains; (4) areas of long continued sedimentation; (5) surfaces produced by the spreading of extremely fine sediments by bottom currents; (6) areas in which the original relief has been buried by the deposit of turbidity currents. Every core obtained from the abyssal plains to date contains evidence of turbidity currents either in the form of graded bedding, shallow water foraminifera or excessively high calcium carbonate content. The plains slope away from areas adjacent to sediment sources. The present writers consider it likely that all abyssal plains represent areas in which most of the original relief is buried beneath the deposits of turbidity currents. Only the partly buried isolated hills and seamounts which rise from the abyssal plain remain of the original topography. Continued turbidity current transport of material into the basins continually extends the abyssal plains.

North Atlantic Core Foraminifera Collected by Swedish Deep-Sea Expedition: ABSTRACT

Foraminifera have been studied from 39 long deep-sea cores and from 53 undisturbed surface sediment samples collected from the North Atlantic. Mid-latitude and low-latitude planktonic assemblages can be differentiated, with at least five different distribution types. The long cores contain faunas normal for their latitude alternating with faunas typical of higher latitudes. These are suggested as representing alternating cold and warm epochs, mostly Pleistocene; correlation of these epochs appears possible in a mid-latitude series of cores. Several cores contain shallow-water Foraminifera which have been displaced from shallow water. It is suggested that much of the mud in the deep ocean may be the finer fraction of sediments displaced from shallow water. Four cores contain planktonic Foraminifera of Miocene age. There is abundant evidence of solution of calcium carbonate; it is suggested that most of this solution occurred at the sediment surface and is related to the rate of production of Foraminifera. A mixed high and low latitude planktonic fauna occurring off Africa between 15° and 20° N. Lat. is attributed to mixing at the convergence of the Equatorial Counter Current and the Canaries Current. Mixed planktonic faunas occur in lower sections of cores off Africa between 0° and 7° N. Lat.; this suggests that the convergence area was displaced southward during the past. End_of_Article - Last_Page 188------------