Showing papers on "Foraminifera published in 1973"

Production of Benthic Foraminifera in Three East Pacific Oxygen Minima

Abstract: Large standing stocks found, characterized by high dominance, low diversity, small thin-shelled specimens, oxygen not limiting ecological factor

Stable Isotope and Magnesium Geochemistry of Recent Planktonic Foraminifera from the South Pacific

Abstract: O 18 /O 16 , C 13 /C 12 , and magnesium analyses were performed on a large number of Recent planktonic Foraminifera from South Pacific Ocean sediments. Results show that oxygen isotopic temperatures of Foraminifera tests may be used to locate ocean currents and to define the orientation of large crustal plates relative to the earth9s rotational poles. Selective solution effects may cause isotopic temperatures of some species to become progressively colder with increasing water depth of the sediments from which they are taken. Where this is not taken into account, erroneous conclusions may result from the comparison of isotopic temperatures of samples from different locations. Depths at which Foraminifera secrete their tests appear to be determined by density and ultimately by osmotic equilibration with surrounding sea water. Susceptibility of Foraminifera tests to selective solution after death increases with magnesium content. Carbon isotope ratios correlate crudely with both temperature and salinity. The C 13 /C 12 ratio of dissolved or particulate carbon in the oceans is probably the most important factor in determining the C 13 /C 12 ratio of the test.

Growth and Submarine Fossilization of Algal Cup Reefs, Bermuda

Abstract: Small charges of explosives were used to section cup-shaped reefs that occur on the margins of the Bermuda Platform. Study of these artificial outcrops, up to 10 m high, and the samples collected from them show how the reef-building community is rapidly converted to well-lithified reef rock in the marine development. The reefs, known locally as boilers and breakers, occur along the wave-swept south shore of the Bermuda Islands and around the northeast and northwest margins of the Platform. They are cup-shaped, up to 30 m in long dimensions, and rise up to the sea surface as much as 12 m above the surrounding sea floor. The reefs are built by an intergrowth of encrusting organisms, principally crustose coralline algae, an encrusting hydrozoan, Millepora sp., and an attached gastropod, Dendropoma irregulare. The growth framework of these algal cup reefs has extensive voids: large and intermediate-sized growth framework and shelter pores; borings of bivalves and sponges; and both intra- and inter-particle pores. A variety of vagile and sessile organisms (coelobites) inhabit these pores: an encrusting Foraminifera, Homotrema rubrum, is the most abundant attached coelobite; the tests of a variety of benthic Foraminifera and ostracods are common: branched coralline algae, barnacles, bivalves, ahermatypic corals, bryozoans, and burrowing crustaceans occur in varying abundance. Beginning millimetres below the living surface, internal sediments accumulate in the extensive voids. Coarse-grained skeletal sand derived from the surface of the reefs is characteristic of the larger voids; lime mud with the tests of planktonic Foraminifera and planktonic algae occurs generally in the smaller voids. Most specimens from the interior of the reefs show multiple generations of internal sediment that vary in grain size, composition, and colour. The sand-sized sediments are pumped into the voids by the frequent and intense wave action; the lime mud settles out in the smaller, less agitated pores. Cementation of internal sediments and surrounding growth frame begins centimetres below the living surface; it is so pervasive that marble-hard reef rock is developed within 1/2 m or less. The cement is principally high-magnesium calcite of micrite size, and subordinately acicular aragonite, but there are locally wide variations in crystal size and morphology. The occurrence of the cement within the reefs well below sea level, the isotope ratios of the cement crystals, the mineralogy, and the age inferred from radiocarbon age determinations of the growth frame all indicate that the cement is submarine and deposited from water of oceanic composition. The algal cup reefs of Bermuda demonstrate the reef-building ability of a community of encrusting organisms that form only crusts in the intertidal zone of the Mediterranean and Northern Brazil. The cup reefs of the northern margins of the Bermuda Platform are true reefs, not merely veneers covering eroded blocks of Pleistocene limestone. In their composition, location, and early diagenesis, the cup reefs closely resemble the algal or lithothamnion ridge of Pacific atolls. Synsedimentary cementation of internal sediments and growth frame makes a major contribution to the rigidity of these ocean-facing reefs and atoll rims. The assemblage of features that characterize the submarine fossilization of the cup reefs is widespread elsewhere in the modern seas: the floors of the Persian Gulf and parts of the Mediterranean; the margins of Pacific atolls; and the reefs off the north coast of Jamaica. This fossilization is characterized by reiterated generations of coelobites, internal sediments, and synsedimentary cements that can in time replace a major part of the original growth framework. Major variations in the sequence of these generations from pore to pore is the signature of this kind of fossilization. The same features of fossilization are described from reefs in the Devonian, Permian, and Triassic.

Species Diversity: Patterns in Modern and Miocene Foraminifera of the Eastern Margin of North America

Abstract: Patterns of foraminiferal species diversity were examined along the eastern margin of North America by utilizing the number of species, S, the information function, H(S), and species equitability, E. The 350 modern samples we studied extended from the Arctic to the Gulf of Mexico at depths ranging from a few meters to more than 5,000 m. In addition, 29 samples from Miocene strata of the Atlantic Coastal Plain and continental shelf were studied. Modern species diversity as measured by S and H(S) generally increases as depth increases and latitude decreases. Some notable exceptions occur, however, which are difficult to explain. For example, species diversity in the Arctic depth interval of 0 to 100 m is as high or higher than that found immediately south of Nova Scotia, in the Gulf of Maine, on Browns and Georges Banks, and even off the Gulf of Mexico deltas. At the moderate depth interval of 100 to 1,000 m, however, the entire margin north of Browns and Georges Banks has lower diversities than that to the south. The highest diversity by far in this depth interval occurs in the northeastern Gulf of Mexico. At the depth interval greater than 1,000 m, the more southern areas studied generally have a higher species diversity than the more northern Cape Cod to Maryland area. An exception to this is the northwestern Gulf of Mexico; this area is also an exception in that species diversity is significantly lower in the deeper waters than in the shallower waters in the same area. The measure of species equitability, E, showed no clear pattern with depth or latitude. This may be so because no simple pattern of species proportions exists or because the sampling was inadequate to measure it. Samples from the Miocene strata show a striking resemblance in species diversity to modern samples at similar depths and latitudes. Our observations indicate that species diversity and equitability have not increased during the last 15 × 106 yrs. The fossil and modern data indicate that each environment has its own carrying capacity and that this capacity is reached rather quickly. Although time and environmental stability are undoubtedly important in determining species diversity, as presently defined they are inadequate to explain all observed patterns. Long-term observations in various environments will be required to determine the relative importance of variables that affect species diversity.

Late Cretaceous to Eocene Planktonic Foraminifera and Stratigraphy of the Leg 15 Sites in the Caribbean Sea

Abstract: The major aims of Leg 15 of DSDP — to drill down to acoustic basement in as many sites as possible and to attempt to recover a complete sedimentary succession — were both successfully fulfilled. The present report covers the older part of the sedimentary succession recovered during this leg, with special reference to its foraminiferal content. Only the six sites where the Late Eocene to latest Turonian sediments were recovered have been considered in this report (see Figure 1). The cores recovered from Sites 146 and 149 together form a more or less complete succession of Late Turonian to Late Eocene. Problems concerning the Cretaceous-Tertiary boundary, selective solution at depths, and the variations in the sedimentation rates are dealt with. The shipboard work on foraminifera of Sites 146 to 154 was carried out jointly by both authors irrespective of the age of penetrated strata. For the preparation of this initial report, however, the part of Cretaceous to Late Eocene was studied and written largely by Premoli Silva, that on Oligocene to Recent by Bolli. The foraminiferal specimens figured on Plates 4 to 10 are deposited at the Natural History Museum, Basel, under the numbers C-29458 to C-29498.

Biogenic Sediments of the Panama Basin

Abstract: The Panama Basin is a miniature ocean basin in which the effect of variable rates of supply, dilution, dissolution, and lateral transport of biogenous sediments can be studied in detail. The rate of input inferred from rates of biologic productivity in surface waters does not resemble the distribution of either carbonate (foraminifera and calcareous nannofossils) or opal (diatoms and radiolaria) in sediments at the sea floor. The distribution of carbonate is primarily controlled by dissolution ; at any depth, the rate is highest adjacent to the continent and decreases offshore in the more pelagic areas. The rate of dissolution increases rapidly with depth at about 1,500 m. Winnowing and lateral transport from ridges into the basin is the second most important factor controlling the distribution of carbonate and the dominant factor governing the distribution of opal. In pelagic sediments of the western basin, about half the carbonate fraction appears to be derived from the surrounding ridges. Dilution by t...

Oligocene to Recent Planktonic Foraminifera and Stratigraphy of the Leg 15 Sites in the Caribbean Sea

Abstract: All nine sites of Leg 15 are in the Caribbean Sea, where three sites were drilled previously during Leg 4 (Figure 1). While none of the Leg 4 sites reached Cretaceous or acoustic basement, this goal was reached in five sites of Leg 15 by improved drilling methods and successful reentry. In the four other sites, Cretaceous or acoustic basement was either not the objective or was out of reach because of excessive sediment thickness. The shipboard work on foraminifera of Sites 146 through 154 was carried out jointly by both authors irrespective of the age of penetrated strata. For the preparation of initial reports, however, it was found to be advantageous to divide the stratigraphic section into two parts. The part on Cretaceous to Late Eocene was written largely by Premoli Silva and that on Oligocene to Recent by Bolli. Compared with the Caribbean Leg 4 sites, no essential differences were recorded in the Oligocene to Recent faunas. The taxonomic treatment of the planktonic foraminifera is therefore much the same as in Leg 4 (Bolli, 1970). However, the zonation of the Pliocene to Recent can now be refined by recognizing a number of new subzones. With this finer subdivision in the Late Pleistocene/Holocene it is now believed possible to detect missing parts of this interval, which are often lost by disturbances in the drilling process. Such a refined zonation of the late Quaternary became possible largely through the much expanded Late Pleistocene-Holocene sequence in Site 147, drilled in the Cariaco Basin (Trench) and the Vema 26-119 piston core taken in the central Venezuela Basin in the neighborhood of Sites 29 and 149. A comparison of the Oligocene to Recent in the continuously cored Site 29 of Leg 4 and Site 149 of Leg 15 shows some improvement in the recovery of the penetrated zones. But the opinion expressed in the Leg 4 Initial Report (Bolli 1970), that the central Venezuela Basin is not the ideal place for obtaining a continuous and well-preserved section, has been confirmed again by the Site 149 results. Though most Oligocene to Recent planktonic foraminiferal zones have been recognized in the two sites combined, the faunal preservation is often strongly affected by CaC03 dissolution. Site 147, drilled in the Cariaco Trench off the Venezuelan north coast, is an outstanding section as far as the Pleistocene-Holocene is concerned. Before drilling had to be suspended because of high gas pressure, 162 meters of mostly euxinic sediments were continuously cored. They represent the Holocene and Late Pleistocene to about 300,000 years ago. The rich and well-preserved planktonic foraminiferal fauna was found well suited for biostratigraphic, as well as climatological and variability investigations., which are dealt with in a separate chapter of this volume (Rögl and Bolli).

Foraminifera from the nearshore turbulent zone, western North America

Abstract: 240 living species recognized, five new species described, three faunal provinces related to coastal water masses, Pacific Ocean, Baja California (Mexico) to Strait of Juan de Fuca (Washington)

Neogene foraminifera from the northeastern pacific ocean, leg 18, deep sea drilling project.

Abstract: Introduction General Methods and procedures Site 172 Geologic and stratigraphic setting Planktonic foraminifera and age Benthonic foraminifera Origin of lower Oligocene carbonate ooze Site 173 Geologic and stratigraphic setting Abundance and preservation of foraminifera Planktonic foraminifera Age, biostratigraphy, and paleo-oceanography Benthonic foraminifera and paleobathymetry Site 174 Geologic and stratigraphic setting Abundance and preservation of foraminifera Planktonic foraminifera, age, and paleo-oceanography Benthonic foraminifera and paleobathymetry Site 175 Geologic and stratigraphic setting Abundance and preservation of foraminifera Planktonic foraminifera, age, and paleo-oceanography Benthonic foraminifera aad paleobathymetry Site 176 Geologic and stratigraphic setting Abundance and preservation of foraminifera Planktonic foraminifera, age, and paleo-oceanography Benthonic foraminifera and paleobathymetry Site 177 Geologic and stratigraphic setting Abundance and preservation of foraminifera CONTENTS

Holocene to Pleistocene Planktonic Foraminifera of Leg 15, Site 147 (Cariaco Basin [Trench], Caribbean Sea) and Their Climatic Interpretation

Abstract: The Pleistocene to Holocene planktonic foraminifera of Site 147 in the Cariaco Basin, off the north coast of eastern Venezuela, were investigated for their ecologic significance. Characteristic species and their frequency, are plotted and the results compared with curves by Emiliani (1966) and Ericson and Wollin (1968). Several warmand cold-water intervals are distinguished. Site 147 falls into the upper part of the Globorotalia truncatulinoides truncatulinoides Zone (approximately 320,000 years to Recent) and comprises from bottom to top the Pleistocene Globorotalia hessi (part only), Globigerina calida calida, Globigerina bermudezi and the Holocene Globorotalia fimbriata subzones. This compares with zones V to Z of Ericson and Wollin (1968). Fifty-nine planktonic foraminiferal species and subspecies were distinguished, of which four are described as new. They are Globigerina clarkei n. sp., Globigerina megastoma cariacoensis n. ssp., Hastigerinella riedeli n. sp., and Globorotalia bermudezi n. sp. Neogloboquadrina blowi is introduced as a new name for Globigerina subcretacea Chapman. Variability and details of wall structures of the well-preserved planktonic foraminifera are illustrated by scanning electron micrographs. Abstract Introduction Hydrological Setting Paleoecological Investigations Working Method Ecology of characteristic planktonic foraminifera Observations on Site 147 Paleoclimatic Interpretation of Site 147 Climatic Zonation and Correlation Climatologic Zonation of Site 147 CONTENTSIntroduction Hydrological Setting Paleoecological Investigations Working Method Ecology of characteristic planktonic foraminifera Observations on Site 147 Paleoclimatic Interpretation of Site 147 Climatic Zonation and Correlation Climatologic Zonation of Site 147 CONTENTS 553 553 554 554 554 555 560 560 560 561 Biostratigraphic Zonation of Site 147 Systematics Globigerinidae Globigerininae Hastigerininae Globorotaliidae Remarks on other faunal and floral components in Site 147 residues Acknowledgments References 561

Cretaceous Benthonic Foraminifera, Leg 20, Deep Sea Drilling Project

Abstract: Lower Cretaceous deposits consist of white, gray, yellow, and greenish chalk; siliceous porcelaneous limestones; marls with intercalations of radio larian clay stones; and red, brown, pinkish, black, and gray cherts (Holes 195, 195A, 195B, 196). Nannofossils and radiolarians are the predominant microfossils in these sediments. Identifiable representatives of calcareous nannofossils constitute at least 10 to 15% of the sediment and indicate an assignment to the lowermost part of the Neocomian (Valanginian, early Hauterivian) (see Nannofossil Biostratigraphy, Hekel, this volume). The radiolarians are usually preserved and suggest an early Cretaceous age for these sediments (see Foreman, this volume). Benthonic foraminifera occur much less frequently than nannoplankton and Radiolaria and were found only in the limestones of Hole 195B (Core 3). Included are both calcareous and agglutinated species; they are characteristically small and not abundant. The most common species in the assemblages are: Lenticulina kugleri Bart., Bett., and Bolli; L. muensteri (Roem.); L. crassa (Roem.);/,. subulata (Reuss); Frondicularia hastata Roem.; Lingulina praelonga ten Dam; Spirillina neocomiana Moull.; Dorothia praeoxycona Moull.; D. zedlerae Moull.; D. ouachensis (Sig.); and D. aff. hauteriviana (Moull.). They are accompanied by rare specimens of a number of other species of Lenticulina, Dentalina, Lagena, Nodosaria, Ramulina, Lingulina, Frondicularia, and Pseudonodosaria. Minute, poorly preserved planktonic foraminifera (Gubkinella sp.) were found together with the benthonic species. The above assemblage of benthonic foraminifera from Hole 195B has much in common with the associations at Sites 49 and 50 of Leg 6 on the western slope of Shatsky Rise. The age of the Site 49 and 50 deposits with Lenticulina kugleri, L. ouachensis, Frondicularia hastata, Dorothia praeoxycona, etc., was originally interpreted as Late Jurassic (Tithonian)-Early Cretaceous (Neocomian) (Fisher et al., 1970). Subsequent study of the benthonic foraminifera of Holes 49 and 50 by Douglas and Moullade (1972) led to the conclusion that they are somewhat younger—late Hauterivian-early Barremian. There is also a discrepancy in defining the age of deposits based on benthonic foraminifera on the one hand (upper Hauterivian-lower Barremian) and nannoplankton on the other (Valanginian-early Haute rivian). However, it should be kept in mind that the zonal scale of the Neocomian based on nannoplankton, and the stratigraphic subdivision of the Neocomian of the northwestern part of the Pacific area based on benthonic foraminifera, have not been sufficiently perfected. This seems to be the cause of the contradiction in age of thesç deposits, though the discrepancy is not large. Thus, limestones, marls, and radiolarian claystones with interbeds of variegated flints of Neocomian age are developed over a considerable area of the extreme northwestern Pacific. They have been penetrated by holes, not only on the western slope of the Shatsky Rise, but also on the abyssal plain towards the west and southwest. At present, the depth of the ocean exceeds 6000 meters here (Holes 195B, 196). Calcareous sediments with flinty interlayers seem to occur on basaltic basement (Hole 197) and underlie pelagic red clays. The deposition of carbonate was naturally proceeding above the level of carbonate compensation; thus, water depth in the Neocomian must have been considerably less than at present. Douglas and Moullade (1972) believe, on the basis that benthonic foraminifera from the Neocomian deposits of the Shatsky Rise display a great similarity with the shallow-water microfauna of the Neocomian of Europe, that the depths of the Neocomian Pacific Ocean were measured in hundreds rather than thousands of meters. However, the composition, morphological peculiarities and preservation of microfossils from the limestones and flints of Hole 195B testify to an abyssal origin for these rocks. Among foraminifera, representatives of the Lagenidae are numerically predominant; the tests of calcareous and agglutinated foraminifera are thin-walled and small; and the walls of agglutinated foraminifera are fine-grained. On this basis, water depth should be estimated to have been on the order of at least 1-1.5 km. The limestones, marls, and variegated flints of the Neocomian of "the northwestern part of the Pacific ocean resembles, in lithological and micropaleontological character, abyssal limestones, radiolarites, and flints of the Mesozoic (Triassic, Jurassic, Lower Cretaceous) of the Alpine belt. As it is known, many workers regard these deposits as oceanic, formed on basaltic crust of an oceanic type.

Association of foraminifera with hydroids on the deep shelf

Abstract: Below 100 m, epifauna with hydroids provide attachment surface for foraminifera (about 70 species recognized), Irish Sea, Malin Sea

Planktonic Foraminifera in Hemipelagic Sediments: Shell Preservation off Portugal and Morocco

Abstract: The preservation of planktonic foraminiferal shell assemblages in sediments can be characterized by their degree of fragmentation. The amount of carbonate removed from the shells can easily be estimated and it is therefore possible to calculate their total loss of CaCO 3 . Arctic deep water today reaches the abyssal plains off Portugal, resulting in high carbonate solution rates and therefore intensive shell fragmentation, while shells from similar depths off Morocco are nearly unfragmented. Late Pleistocene sediments in both areas yield well-preserved planktonic Foraminifera. This is important for the reconstruction of Pleistocene North Atlantic deep-water hydrography. In both areas continental-slope assemblages are better preserved with decreasing water depth, with the exception of its uppermost part where the rate of carbonate solution increases.

Foraminifera, Leg 19 Deep Sea Drilling Project

Abstract: Significant numbers of indigenous foraminifera were found at seven of the eleven sites drilled on Leg 19. Six of these, Sites 184, 185, 188, 189, 190, and 191, are in the Bering Sea. The seventh, Site 192, is at the top of Meiji Guyot in the northwest Pacific Ocean south of the Aleutian Islands. The foraminifera found at each of these sites is discussed in the preceding site reports. This section synthesizes foraminiferal biostratigraphy at Leg 19 sites and explores some of the paleoclimatic implications of the foraminiferal assemblages. It was necessary to apply several methods to disaggregate the sediment samples. Unconsolidated samples from the upper parts of the holes usually disaggregated readily when boiled in a 15% solution of hydrogen peroxide. However, deeper in the holes the samples become sèmiconsolidated and resist this treatment. Boiling in the strong detergent, Quaternary-O, was tried for these latter samples without noticeable success. In order to disaggregate them sufficiently for study, it was usually necessary to use mechanical methods, either breaking lumps apart with fingers or brushing them against the screen. Highly indurated sediment of lithologic Units B and C was disaggregated by placing thoroughly dried samples into varsol or kerosene for several hours and then boiling them in water. All samples were washed on a 63μ mesh sieve, but studies were carried out only on the fraction retained on a 125μ mesh sieve. Checks of the fraction passing through the 125μ sieve showed it to contain up to approximately 30% of Globorotalia (Turborotalia) pachyderma populations. Species of planktonic foraminifera so small that most would be lost through a 125μ sieve (for example, Globigerina quinqueloba and Globigerinita uvula) were never found to be common in checks of the finer fraction. Tables 1 to 7 show estimates of abundance for planktonic species and for total planktonic foraminifera and hyaline, porcelaneous, and arenaceous benthic foraminifera. Indigenous foraminifera are extremely rare at the four deepest sites: Sites 183 (4718 m), 186 (4522 m), 187 (4577 m), and 193 (4811 m). A few examples of displaced assemblages at Sites 183 and 186 are discussed in Chapters 2 and 5. At other sites there are usually a few arenaceous tests throughout, but occurrences of calcareous tests are sporadic. The Quaternary is characterized by sharp fluctuations in abundance from common or abundant to zero, often within the same section of a core. In contrast, the Pliocene and upper Miocene is exceptionally poor in

The Late Pliocene marine formation at St Erth, Cornwall

Abstract: New excavations were made in the long-abandoned sand and clay pits at St Erth, Cornwall, from which rich collections of marine mollusca and foraminifera have come in the past The sediments and stratigraphy revealed are described, and the results of detailed studies of the fossils (mollusca, foraminifera, ostracoda, and plants) in the marine clay are given The sand member is well sorted, and in places contains two fine-sand populations, one of beach and the other of dune origin The clay member was probably deposited not far below low-water mark in a sea whose water temperature was higher than that of Cornwall today, at the time that the final Boytonian beds of the Pliocene Coralline Crag were being deposited in East Anglia, and the Pliocene marnes a Nassa were being deposited at Bosq d'Aubigny in Normandy Sea level appears to have been lowered by about 45 m to its present level since the marine clay was deposited The possibility of crustal movement in Cornwall is referred to

Pliocene planktonic foraminifera, southern North Island, New Zealand

Abstract: Twenty-five taxa (Turborotalia quinqueloba lingulata n. ssp.) described, taxonomic revisions, "Globigerina" pachyderma referred to Neogloboquadrina, Turborotalia name restricted, correlation of New Zealand stages with global biostratigraphic zones

Late Cretaceous, Paleogene and Neogene Planktonic Foraminifera

Abstract: Late Cretaceous, Paleogene, and Neogene calcareous deposits containing planktonic foraminifera were recovered in Holes 199, 200, 200A, and 202 near the margin of the Caroline Abyssal Plain. Stratigraphic sections of these holes supplement one another to form a discontinuous composite stratigraphic succession of Cretaceous and Cenozoic deposits. The deposits of the Maastrichtian, late Paleocene, certain zones of the early and middle Eocene, and almost the whole Neogene beginning from the Burdigalian Stage were sampled. Despite stratigraphic incompleteness, these sections are of interest, since the planktonic foraminiferal biostratigraphy of the Late Cretaceous, Paleogene, and Neogene of the tropical area of the Pacific Ocean has been insufficiently studied. Foraminiferal assemblages of Sites 200 and 202 are listed in Tables 1 and 2, and their distribution in the Miocene through Pleistocene at Site 200 is shown in Table 3.

Living planktonic foraminifera from the Gulf of California

Abstract: Vertical, horizontal and surface plankton tows, distribution and depth concentration discussed

Foraminiferal ecology in the Ria de Arosa, Galicia, Spain

Abstract: SUMMARY The Ria de Arosa is a large inlet of the Atlantic in western Galicia, NW Spain. It is little influenced by river discharge, the salinity is therefore the normal one for sea water, 33-36°/oo. According to Cadee (1968) the rocks exposed on the coast are for for the greater part granites; the rest, especially on the northwestern and northern coast, being gneisses and micaschists. Seven foraminiferal facies could be made. The L/D ratio is extremely low. It varies from zero to 18.5; the medium ratio is 2.3. Transport of shells from the continental shelf into the bay is rather high and more or less confined to the outer bayzone. The Recent foraminiferal fauna of the Arosa Bay has a fairly large number of species in common with the littoral Pliocene and the oldest littoral Pleistocene of the North Sea Basin. On the other hand the Recent and Holocene faunae of the North Sea Basin show hardly any resemblance with that of the Ria de Arosa, nor with that of the Mediterranean. 193 species of Foraminifera were found, of which 3 were new. The areal distribution of 15 species has been plotted on maps. INTRODUCTION The present study forms part of a biological, oceanographical and sedimentological investigation carried out in the Ria de Arosa, northwestern Spain, 1962-1964. The present paper deals with the Foraminifera collected during these investigations. A representative collection of all species of Foraminifera obtained in the Arosa Bay is kept in the Rijksmuseum van Natuurlijke Historie, Leiden, Netherlands and in the Rijks Geologische Dienst, Haarlem, Netherlands.