Benthic Foraminiferal Associations Research Articles

Benthic foraminifera as bioindicators for the heavy metals in the severely polluted Hurghada Bay, Red Sea coast, Egypt

Twenty-nine sediment samples were collected from the Hurghada Bay, a heavily polluted bay on the Red Sea of Egypt, to inspect the environmental quality status and anthropogenic consequences on benthic foraminifera. Some foraminiferal species showed deformations in their apertures and coiling directions as a response to environmental stresses. In addition, the FoRAM index, an index used for evaluating the growth of coral reefs, indicated a hazard in the proximity of nearshore stations. To elucidate the relationships between the biological response and chemistry of sediments, eight heavy metals concentrations (Cu, Cd, Zn, Pb, As, Cr, Ni, and Mn) were analyzed using inductively coupled plasma–atomic emission spectrometers (ICP-AES). Interestingly, two groups of benthic foraminiferal associations were illustrated using multivariate statistical analyses. Group I have extremely high heavy metal concentrations, an enriched total organic matter (TOM)%, high deformation percentages, and mud content. Moreover, it is dominated by Ammonia tepida which is regarded as an opportunistic species. Group II includes low to moderately polluted stations, highly enriched living foraminiferal assemblages, and is dominated by the sensitive rotaliids Neorotalia calcar and Amphistegina lobifera. Alternatively, four geochemical indices, EF, CF, Igeo, and PLI, are used to assess the contamination level that shown ominous spots for the nearshore stations of the Hurghada Bay. The pollution indices (HQ and HI) were also conducted to evaluate the risks of carcinogenic heavy metals on human health. Our findings demonstrated that ingestion and dermal exposure have greater carcinogenic hazards for adults and children than inhalation. The lifetime carcinogenic risk (LCR) is significantly higher than the permissible limit and follows this order: Pb > As > Cr > Cd > Ni. To that end, developing strategies to lessen the negative impact of pollution on human health and/or the Red Sea’s biodiversity is an inevitable issue in the present day and future.

Paleoenvironmental significance of benthic foraminiferal associations of the Hauterivian to Barremian marine beds of the Neuquén Basin, Patagonia, Argentina

The upper Hauterivian-lower Barremian sedimentary sequences of the Agua de la Mula Member of the Agrio Formation (Neuquén Basin, Argentina) represent shallow marine environments characterized by mixed siliciclastic‑carbonate deposition. Ten benthic foraminiferal associations based on species composition were defined and evaluated in relation to explanatory variables such as facies, sequence stratigraphy, location and age. Variations in sedimentation rates, food and oxygen availability related to relative sea-level changes largely control distribution of the benthic foraminiferal associations. Four associations (Guttulina sp., Polymorphinids, Spiroplectammina sp.2-Haplophragmoides sp.1, and Planularia madagascariensis) are mostly composed by shallow infaunal, bacterial and detritivorous foraminiferal scavengers that largely occur in sandy facies within 3rd-order regressive systems tracts. These associations are thought to be indicative of well oxygenated and organic matter-rich sediments below the sediment-water interface. The remaining six associations consist of epifaunal, mainly opportunistic foraminifera with active herbivorous and detritivorous trophic strategies. Among them, Epistomina hechti - Epistomina australis and Reinholdella hofkeri associations occur in fine-grained, dark shales throughout 3rd-order transgressive systems tracts, and are considered related to oxygen and food stressed environment. An integrated approach, using benthic foraminifera (alpha diversity analysis, epifaunal/infaunal ratio) and multivariate statistical methods (cluster analysis, RDA, partial-RDA, PERMANOVA, PCoA), allowed to evaluate the paleosynecological significance of benthic associations, and to relate certain paleoenvironmental settings to relative sea-level changes recorded in the Agua de la Mula Member. The application of foraminiferal associations analysis in the paleoenvironmental interpretations led to recognize the influence of major relative sea-level changes in shaping higher-frequency sequences for this sector of the Neuquén Basin. Such approach can also be applied to other sectors of the basin and to high-frequency sedimentary sequences of comparable shallow marine settings.

New biostratigraphy and microfacies analysis of Eocene Jahrum Formation (Shahrekord region, High Zagros, West Iran). A carbonate platform within the Neo-Tethys oceanic realm

The Eocene Jahrum Formation in High Zagros was studied in Kuh-e- Soukhteh and North Gahrou sections (southwest of Shahrekord region, Chahar-mahal Bakhtiari Province). This formation, composed of limestone, marl, and dolomitic limestone (dolostone), accumulated on a marine platform within the Neo-Tethys ocean realm. It yields a rich foraminiferal fauna, in which three larger benthic foraminiferal assemblage zones were identified. Two assemblage zones in the North Gahrou section were correlated to the Ypresian and Bartonian, and one assemblage zone is represented in the Kuh-e- Soukhteh section and assigned to the Bartonian. In addition, three other groups of benthic foraminiferal associations have been identified based on test wall type (porcellaneous, agglutinate, hyaline) and paleogeographical significance. A discontinuity marked by a hiatus from Cuisian to Lutetian in the North Gahrou section was most probably due to a concealed fault. According to microscopic textures and distribution of benthic foraminifera and other components (peloids, intraclasts, etc.), a gentle depth gradient from the inner ramp to the proximal outer ramp may be reconstructed.

Benthic foraminifera as proxy for fossil seagrass from the Lower Pleistocene deposits of the Stirone River (Emilia-Romagna, Italy)

This paper analyses and describes the benthic foraminiferal associations within the Pleistocene deposits of the Stirone River (Emilia-Romagna, Italy), with the purpose of testing foraminifera as Indirect Palaeo-Seagrass Indicators (IPSIs). Our analyses focused on two different biofacies: a Thalassinoides biofacies, characterised by an oligotypic biotic assemblage and a Pinna biofacies representing an infralittoral soft bottom colonised by marine phanerogams and characterized by high biodiversity. To strengthen the analyses, we have compared the Stirone foraminiferal association with the one of Fauglia (Tuscany, Italy), in which a well-preserved, early Pleistocene, fossil Posidonia meadow, is present. The aim of this work is to provide qualitative and quantitative parameters that can be used to recognize past vegetated environments, where fossil seagrass are no longer present. Considering the influence of ecological constraints and diagenetic processes on the foraminiferal assemblages, several indexes such as the IndexEP, the modified FORAM index (FI’), the “long vs. short life-span index” (ILS), and the K/REXT (keeled/rounded morphotypes) have been calculated and a morphotype-based analysis has been provided. Among the tested indexes, the latter proved to be the most reliable IPSI, in association with the presence of morphotype A*, permanently attached, encrusting foraminifera and the abundance of Rosalinidae.

Living and dead foraminiferal assemblage from the supratidal sand Japsand, North Frisian Wadden Sea: distributional patterns and controlling factors

Supratidal sands are vitally important for coastal defence in the German Wadden Sea. They are less affected by human activities than other areas as they are located far off the mainland shore, touristical and commercial activities are generally prohibited. Therefore, supratidal sands are of high ecological interest. Nevertheless, the faunal inventory and distribution pattern of microorganisms on these sands were studied very little. The composition of living and dead foraminiferal assemblages was therefore investigated along a transect from the supratidal sand Japsand up to Hallig Hooge. Both assemblages were dominated by calcareous foraminifera of which Ammonia batava was the most abundant species. Elphidium selseyense and Elphidium williamsoni were also common in the living assemblage, but Elphidium williamsoni was comparably rare in the dead assemblage. The high proportions of Ammonia batava and Elphidium selseyense in the living assemblage arose from the reproduction season that differed between species. While Ammonia batava and Elphidium selseyense just finished their reproductive cycles, Elphidium williamsoni was just about to start. This was also confirmed by the size distribution patterns of the different species. The dead assemblage revealed 20 species that were not found in the living assemblage of which some were reworked from older sediments (e.g., Bucella frigida) and some were transported via tidal currents from other areas in the North Sea (e.g., Jadammina macrescens). The living foraminiferal faunas depicted close linkages between the open North Sea and the mainland. Key species revealing exchange between distant populations were Haynesina germanica, Ammonia batava and different Elphidium species. All these species share an opportunistic behaviour and are able to inhabit a variety of different environments; hence, they well may cope with changing environmental conditions. The benthic foraminiferal association from Japsand revealed that transport mechanisms via tides and currents play a major ecological role and strongly influence the faunal composition at this site.

Living (stained) calcareous benthic foraminiferal assemblages ([formula omitted]) in a coastal upwelling zone of the Humboldt Current System, Northern Chile ([formula omitted]S)

In coastal upwelling ecosystems, understanding of environmental factors regulating the structure of benthic foraminiferal communities is fundamental to enhance our knowledge of their ecology and to validate their use in palaeoceanographic studies. In this study, we assess the influence of organic matter (quantity/quality) and subsurface oxygenation on living (stained) calcareous benthic foraminifera inhabiting a coastal upwelling ecosystem influenced by Oxygen Minimum Zone (OMZ) off Inglesa Bay, Northern Chile. Benthic foraminifera and their environment (i.e. biochemical/elemental sediment composition and subsurface water column oxygenation) were sampled along a transect perpendicular to the coastline consisting of three stations (30, 70 and 120 m) and covering two seasons (winter and summer). The geochemical composition of surface sediments and subsurface oxygenation reveal a typical pattern of marine ecosystems associated with coastal upwelling centers influenced by OMZ. Forty-seven species of living calcareous benthic foraminifera were identified, in which Bolivinella seminuda, Buliminella elegantissima, Bulimina marginata, and Nonionella miocenica were found as the most abundant species. Total abundance increases remarkably with depth while taxonomic richness and evenness decrease. Multivariate analyses show three benthic foraminiferal associations strongly linked to nutritive organic matter and subsurface oxygenation, regardless of the sampling period. Assemblages “A” (22 species, 4 dominant) and “C” (5 species, 1 dominant) are associated with the shallow (30 m) and deep (120 m) station, and present contrasting subsurface oxygenation and organic matter content. Assemblage “B” (19 species, 3 dominant) is associated with the intermediate station (70 m) characterized by mixed subsurface oxygenation and organic matter content. Our results suggest that local environment conditions (i.e. OMZ intensity, organic matter quality/quantity) govern the structure and composition of the living calcareous benthic foraminiferal assemblages of Inglesa Bay. Such assemblages have similarities and differences with other benthic foraminifera assemblages found in other coastal upwelling ecosystems impinged by an OMZ.

Benthic Foraminifera from the Saïda clay formation (Djebel Brame, northwestern Algeria) biostratigraphy and paleoecology

The analysis of benthic foraminiferal assemblages was performed in the Oxfordian deposits of the “Argile de Saida” in northwestern Algeria. This formation consists mainly of clay and sandstone alternations of the Upper Jurassic. It is located in the western part of the Tlemcenian domain. The first results of the micropaleontological study of Djebel Brame indicated that the microfauna of Foraminifera was quite original and widely abundant during that period. In addition, their biostratigraphic distribution exhibited three microfaunal associations, largely dominated by Nodosariidae. These results also revealed the renewal of the assemblage composition and allowed identifying several species of biostratigraphic divisions which were found consistent with those established for the ammonites. In addition, the palaeoenvironmental interpretations were based on the spatio-temporal distribution of benthic foraminiferal associations with hyaline and agglutinated tests. Besides, the geochemical analyses (calcimetry) reflected the basin infill during the Late Oxfordian.

Coralline algae as depth indicators in the Miocene carbonates of the Eratosthenes Seamount (ODP Leg 160, Hole 966F)

The abundance of the major coralline algal groups has been investigated and quantified in the coralline-rich facies of the Miocene shallow-water carbonates of the Eratosthenes Seamount (eastern Mediterranean, off-shore Cyprus). The analysis is based on the quantification of the most easily-recognizable groups of coralline algae in order to provide a user-friendly approach for palaeobathymetric reconstructions. Coralline algal distribution through the core suggests water depth estimates generally similar to those based on the composition of the skeletal assemblage and the benthic foraminiferal association in particular. The only noticeable difference occurs in the rhodolith and coral facies, where algal distribution suggests deeper waters than those indicated by benthic foraminifera. The distribution pattern of the major groups suggests that the ratio between Hapalidiales and Corallinales is the most reliable indicator of water-depth. The comparison with other models available in literature highlights a general zonation useful for the study of tropical, middle to late Miocene oligotrophic carbonates. Very shallow settings (0–20m) are overwhelmingly dominated by Corallinales; in slightly deeper settings (20–40m) Hapalidiales are more abundant, especially if the sea-floor is shaded (for example by a macrophyte canopy). Between 40 and 60m, Hapalidiales dominate but Corallinales are still common, while below 60m Corallinales are very rare. In non-oligotrophic environments this zonation is not reliable and, due to the reduced water clarity related to the high primary productivity, Hapalidiales clearly dominate even in very shallow settings.

The lower Rupelian cluster reefs of Majella platform, the shallow water record of Eocene to Oligocene transition

The Eocene-Oligocene Transition is a key interval in the evolution of the modern climate, representing the last greenhouse-icehouse transition faced by the Earth. Shallow-water carbonate systems hold essential information of the global changes related to the E-O Transition. In this work, we focus on the Majella Mountain carbonate ramp to identify the shallow-water sedimentary expression of the oceanographic and sea-level changes related to the E-O Transition, and to compare it with the deep-marine records and the coeval shallow-water successions. Field observations, coupled with the study of thin sections to identify textural characters, and of the larger benthic foraminiferal associations for biostratigraphic purposes, allowed reconstructing the depositional model and the stratigraphic distribution of the examined ramp. The lower Rupelian ramp outcropping in the Majella Mountain is characterized by seagrass meadows in the euphotic inner ramp. Corals developed in the middle ramp, building mounded cluster reefs in the mesophotic zone, below wave base, in high hydrodynamic conditions produced by rip-currents induced by storm events or by the breaker zone of internal-waves. The outer ramp consists of alternating bioturbated wackestone rich in planktonic foraminifera, bioclastic packstone and skeletal rudstone to floatstone. The depositional model of the Oligocene ramps is the result of the major changes that occurred during the greenhouse-icehouse transition. In the Majella platform, the E-O Transition corresponds to an unconformity developed on the Priabonian substrate, where the cluster reefs grew and expanded. The unconformity results from the sea level drop of tens of meters, recorded also in the outer ramp, related to the Oi-1 event. The cluster reefs started to develop when the Priabonian ramp was flooded and continued to grow during the following highstands, forming an extensive coral unit that prograded basinwards, interfingering with the outer ramp deposits.

Benthic foraminiferal assemblages of the Middle and Upper Jurassic sediments from the northeastern Alborz and western Koppeh Dagh, Iran: Systematic palaeontology and palaeoecology

This research is focused on a poorly studied Jurassic sequence in the eastern part of Alborz and Western Koppeh Dagh basins. The foraminifera are reported from Callovian (Middle Jurassic) to Tithonian (Upper Jurassic) sediments of the Farsian and Chaman Bid formations. The benthic foraminiferal associations belong to the families Ammodiscidae, Epistominidae, Hauerinidae, Hormosinidae, Ichthyolariidae, Lagenidae, Nodosariidae, Nubeculariidae, Ophthalmidiidae, Polymorphinidae, Rhabdamminidae, Saccamminidae, Spirillinidae, Spirocyclinidae, Textulariidae, Trocholinidae, and Vaginulinidae. In the studied area, the foraminifera are dominated by the families Nodosariidae, Vaginulinidae and Epistominidae. Palaeoecological analysis of the foraminiferal assemblages from the Farsian Formation indicates that these sediments were deposited on the inner to mid shelf environment, with normal salinity (euhaline), and relatively well oxygenated waters, with eutrophic conditions in the Goznawwi area and oligotrophic conditions in the Chaman Bid area. The foraminiferal assemblages in this study are the first record from Jurassic sediments of the eastern part of the Alborz and Koppeh Dagh basins in northern Iran.

Berriasian–early Valanginian calcareous shallow-water facies from the Arperos Basin: A proposal from the foraminiferal assemblage of the clasts of the Guanajuato Conglomerate, central Mexico

The Eocene Guanajuato Conglomerate is composed of clasts derived from igneous and metasedimentary sources that can be related to the Upper Jurassic–Lower Cretaceous arc and back-arc assemblages of the El Paxtle and Arperos Basin. Limestone clasts contain a shallow-water platform fauna that includes bivalves, brachiopods, gastropods, echinoderms and foraminifers. Foraminiferal studies were carried out on these limestone clasts. The benthic foraminiferal association is composed of Pseudocyclammina lituus (Yokoyama, 1890); Everticyclammina virguliana (Koechlin, 1942); Montsalevia salevensis (Charollais, Bronnimann and Zaninetti, 1987); Neotrocholina valdensis (Reichel, 1955); Andersolina cherchiae (Arnaud-Vanneau, Boisseau and Darsac, 1988); Neotrocholina molesta (Gorbatchik, 1959); Pfenderina neocomiensis (Pfender, 1938); Nautiloculina bronnimanni Arnaud-Vanneau and Peybernes, 1978; Hechtina praeantiqua Bartenstein and Brand, 1949; Protopeneroplis cf. P. banatica Bucur, 1993; Istriloculina sp., Moesiloculina sp., Protomarsonella sp., Ammovertellina sp. and Glomospira sp. The Tethysian foraminiferal assemblage observed in the limestone clasts indicate the age of the calcareous source as Berriasian– early Valanginian, which is the age of the deposition within the Arperos Basin. The occurrence of these shallow-water limestone clasts suggests the existence of a shallow-water platform deposit located in the Arperos Basin. This is significant considering that all previous work focused on the deep-water sedimentary rocks (siliciclastic and calcareous). Thus, these clasts are a key to reconstructing the depositional history and architecture of this basin.

Deep-sea benthic foraminiferal turnovers in the early Eocene: The role of the PETM and ETM2

PETM, taxonomy Throughout the Cenozoic, deep-sea benthic foraminiferal communities have faced many periods of environmental turmoil. Three major, yet relatively gradual faunal turnovers occurred during the Eocene-Oligocene, middle Miocene and middle Pleistocene - all periods of pronounced cooling and increases in polar ice volume. In contrast, the PaleoceneEocene Thermal Maximum (PETM; ~56 Ma) – a transient global warming event or hyperthermal - is characterized by a rapid extinction of 30-50% of all deep-sea benthic foraminiferal species (Thomas, 1998; 2007). So far, the exact cause(s) of this severe extinction event that devastated bathyal and abyssal faunas is not known. It is likely that a change in food-web structure, affected by high temperatures, a decrease in the oxygenation state of the oceans, calcite undersaturation, primary productivity or ocean current circulation changes played an important role in the benthic foraminiferal extinction (BFE) and in the establishment of the opportunistic fauna that characterizes the PETM itself (Thomas, 1998, 2007). Historically, the earliest Eocene benthic foraminiferal associations were considered as a transitional fauna, recovering from the BFE and gradually recolonizing vacant niches and habitats. This transition from a Cretaceous-Paleocene Velascotype fauna into a typical Eocene Barbados-type fauna appeared to be characterized by the gradual appearance of new taxa (Tjalsma & Lohmann, 1983; Berggren & Miller, 1989). With the discovery of several Eocene hyperthermals similar to the PETM (e.g. Eocene Thermal Maximum 2; ETM2; ~53.7 Ma), the question arises of what role these events played in the development of early Eocene benthic communities. For instance, how did the impoverished benthic fauna cope with the environmental perturbations associated with these successive and smaller Eocene hyperthermals on short time scales? Did it become more or less sensitive to climatic and oceanographic changes? One can also wonder what the effects were on longer time scales. Did early Eocene hyperthermals hamper or stimulate recolonization of the benthic realm, and if so, in what way?

ANTHROPOGENIC IMPACT ON BENTHIC FORAMINIFERA, ABU-QIR BAY, ALEXANDRIA, EGYPT

The present study examines the foraminiferal distribution in recent bottom sediments of Abu-Qir Bay located along the Mediterranean coast of Alexandria, Egypt. Abu-Qir Bay receives substantial amounts of heavy metals from the surrounding industrial area, as well as agricultural and domestic effluents, which makes it one of the most polluted areas along the Mediterranean coast. Information provided by the benthic foraminiferal associations was integrated with geochemical, sedimentological, and water data to characterize the environments. The benthic foraminifera are recognized as potential indicators of pollution in coastal marine environments. Surface sediment samples were collected in two seasons (May and November) from nine sites. Cluster analysis and Canonical Correspondances Analysis reveal a distinct boundary that separates two areas; the more-polluted stations nearshore, and the less-polluted stations offshore The first area is characterized by sediment with high silt and clay content and rich in total organic carbon, and bottom water with relatively high temperatures, but low in dissolved oxygen, salinity, transparency, and pH. Its foraminiferal fauna is dominated by Ammonia tepida, Quinqueloculina lata , and Porosononion spp., which are species considered as pollution opportunists. The second area is characterized by coarser sediment overlain by bottom waters high in dissolved oxygen, and transparent, saline, cold water, and is dominated mainly by Quinqueloculina vulgaris, Elphidium spp., Asterigerinata mamilla, Rosalina macropora, Ammonia beccarii, Triloculina trigonula, Peneroplis pertusus , and Quinqueloculina spp. Heavy-metal pollutants have a deleterious effect on benthic foraminifera that results in reduced population diversity, increased dominance, and deformed tests.

Reconstruction of deep-water conditions in the North Atlantic during MIS 9 based on benthic foraminiferal assemblages

Marine isotope stage (MIS) 9 is one of the least investigated Pleistocene interglaciations. The present study describes reconstructions of deep-water conditions during this time interval based on benthic foraminiferal assemblages from sediment core M23414 (Rockall Plateau, North Atlantic). The results of faunal analysis were supported by planktic δ18O, sea surface temperature reconstructions based on planktic foraminiferal assemblages and content of ice rafted debris. Statistical data processing using principal component analysis revealed five climate-related benthic foraminiferal associations that changed in response to alterations of deep-water circulation.

Upper Barremian-Lower Aptian Urgonian limestone's in the Rakova bara section (Carpatho-balkanides, NE Serbia): Analysis and comparison with adjacent areas

The Upper Barremian-Lower Aptian succession is recorded from a limestone sequence that crops out in the surrounding of Rakova Bara in the Carpatho-Balkanides range in northeastern Serbia. The micropalaeontological and sedimentological studies lead to recognition of the two types of microfacies. The benthic foraminiferal association consists of Vercorsella laurentii, Rumanoloculina robusta, Praechrysalidina infracretaceae, Dictyoconus gr. arabicus, Debarina hahounerensis, Charentia cuvilieri and Pseudocyclammina lituus that confirm the stratigraphical and palaeoenvironmental connection of the microfossil assemblages with the classical Urgonian-type, shallow-water carbonate sedimentation. The association documented for the first time in the study area is considered typical of the Tethyan Realm. The stratigraphical position of the benthic foraminifera species within the Upper Barremian-Lower Aptian interval is discussed. The Urgonian Limestone's of the studied section are comparable with adjacent areas of eastern Serbia and Romanian South Carpathians. .

The ecology and distribution of benthic foraminifera at the Håkon Mosby mud volcano (SW Barents Sea slope)

To investigate a possible influence of submarine methane seepage on benthic foraminiferal communities, Rose Bengal stained (“live”) and empty tests of benthic foraminifera were studied from the sediment surface down to 15 cm sub-bottom depth of 12 sites at the Håkon Mosby mud volcano (HMMV). In addition, one reference site well away from the seep sites, but from similar water depths and the same general hydrographic setting was occupied for comparison. The HMMV is located at 1265 m water depth on the SW Barents Sea continental slope. Distinct living foraminiferal associations at the HMMV are linked to specific sedimentary, microbial, and macrofaunal habitats. In the center of the crater, and in crater areas completely covered by bacterial mats, Cassidulina reniforme is the only, albeit rare, living species. Below the top few millimeters, sediments are anoxic and devoid of living specimens. At the rim of the mud volcano, at sites densely populated by pogonophoran tube worms, three benthic foraminiferal associations are found; (i) a Fontbotia wuellerstorfi–Lobatula lobatula association living attached to the upper parts of pogonophoran tubes, which protrude into oxic water, (ii) a diverse Cassidulina neoteretis association populating dysoxic sediments of the surface centimeter, and (iii) a species-poor Bolivina pseudopunctata association colonizing the subsurface sediments down to four centimeters. Generally, we did not find endemic or seep indicative species or associations at the HMMV. However, the HMMV live faunas dominated by B. pseudopunctata are not found at the reference site nor are they described from comparable water depths and environments without gas seepages from the Norwegian-Greenland Seas. In the center and outer rim of the mud volcano, a C. neoteretis–Reophax guttifer dead association, similar to the one at the reference site, characterizes an assemblage of strongly corroded and partly displaced tests. At bacterial mat sites, a C. reniforme dead association corresponds to the living one. Thus both the living and the dead associations are indicative of a specific bacterial mat environment at the HMMV.

Foraminifera from the Tepetate Formation (Heim) at Las Pocitas, Baja California Sur, Mexico

In order to constrain the age and depositional paleoenvironment of the Tepetate Formation, benthic and planktonic foraminifera were analyzed in samples recovered from an exploration well located at Las Pocitas, Baja California Sur, Mexico. The planktonic taxa identified allowed recognition of Zone P9 (Planorotalites palmerae-Acarinina pentacamerata), equivalent to a late early Eocene age of 50.4–49 Ma. The benthic foraminiferal association suggests that the sediments were deposited in a continental slope environment at an upper bathyal water depth of ca. 500 m. Composition and diversity of planktonic foraminifera indicate the presence of warm-temperate surface water masses. Micropaleontological evidence presented here and from previous reports indicates that the samples studied represent only a portion of the Tepetate Formation.

ECOLOGICAL DISTRIBUTION OF BENTHIC FORAMINIFERA, OFFSHORE NORTHEAST NEW ZEALAND

Northeast of New Zealand, nine benthic foraminiferal associations are recognized and mapped (50–3800 m depth) based on cluster analysis of faunal census data (>63 μm, 235 species, 56 samples). Similar associations are identified using cluster analysis based on the presence or absence of species. Canonical correspondence analysis shows that the associations correlate most strongly with factors related to water depth, especially decreasing food supply (organic carbon flux) with increasing depth. The depth-stratified distribution of lower bathyal to abyssal (>1000 m) associations accords well with the deep water masses, and is attributed in part to lower oxygen concentrations in the bottom waters. The two deepest associations, dominated by Alabaminella weddellensis , Epistominella exigua , Bulimina marginata f. aculeata , Globocassidulina subglobosa , and Oridorsalis umbonatus , underlie the oxygen minimum zone of Circumpolar Deep Water. A mid-lower bathyal association dominated by Cassidulina carinata , Alabaminella weddellensis , Abditodentrix pseudothalmanni , and Trifarina occidentalis , underlies Antarctic Intermediate Water. In addition to their bathymetric stratification, mid shelf to upper bathyal (50–600 m) associations also show latitudinal variation that may reflect differences in terrigenous mud (abundant Eilohedra vitrea ), bottom current strength, food supply (more abundant Cassidulina carinata ) and nutrient remineralization on the seafloor. At depths of 50 m depth) is similar off northeast (235 species) and eastern (246 species) New Zealand and higher than off the west coast (150 species).

BORINGS IN LARGER BENTHIC FORAMINIFERS FROM TURKEY AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE

Cretaceous/Paleogene outcrops of Turkey provide important areas for the study of trace fossils on larger benthic foraminiferal tests such as Orbitoides and Loftusia from the Maastrichtian, and Nummulites, Assilina and Discocyclina from the Eocene. The current investigation synthesizes previous and new records of borings on Upper Cretaceous and Paleogene foraminifers with information on faunal associations, stratigraphical correlation and paleoenvironmental conditions. The types of borings were distributed according to their shallow-water paleoenvironments. Orbitoides tests in siliciclastic sandstones and calcarenites from northwestern and eastern Turkey contain four forms of borings: semicircular tubes, circular cavities, subspherical cavities and undulating tubes. Benthic foraminiferal associations confirm the Maastrichtian age of the borings. Towards the end of the Cretaceous, a regression took place during the Maastrichtian in the Osmaneli area, resulting in a shallower, bivalve-dominated facies. During initial phases of the regression, semicircular tubes and circular cavities were formed, while later phases of the regression led to the formation of undulating tubes. The Loftusia tests from southeastern and eastern Turkey contain cylindrical holes, paraboloid pits and subspherical cavities formed as predational and dwelling borings. Borings occur on the Eocene larger foraminifera Nummulites , Assilina and Discocyclina from the Ypresian to Bartonian carbonates and siliciclastic sediments in southwestern Turkey. These Eocene sediments comprise back-reef, nummulite-bank, fore-reef and open-sea facies. The benthic foraminifers may contain borings such as cylindrical holes, paraboloid pits, subspherical cavities and spiral tubes. The Eocene foraminiferal tests less commonly contain borings and endobiontic foraminifers than those from the Maastrichtian. The Eocene borings were formed in a shallower carbonate setting.

Benthic foraminiferal associations from Upper Quaternary deposits of southeastern Po Plain, Italy

Research Article| January 01, 2004 Benthic foraminiferal associations from Upper Quaternary deposits of southeastern Po Plain, Italy Flavia Fiorini Flavia Fiorini Dipartimento di Scienze della Terra e Geoloico-Ambientali, Università di Bologna, Via Zamboni 67, 40127 Bologna, Italy email: fiorini@geomin.unibo.it Search for other works by this author on: GSW Google Scholar Micropaleontology (2004) 50 (1): 45–58. https://doi.org/10.2113/50.1.45 Article history received: 05 Apr 2003 accepted: 30 Oct 2003 first online: 06 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Flavia Fiorini; Benthic foraminiferal associations from Upper Quaternary deposits of southeastern Po Plain, Italy. Micropaleontology 2004;; 50 (1): 45–58. doi: https://doi.org/10.2113/50.1.45 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyMicropaleontology Search Advanced Search Abstract Quantitative analysis of benthic foraminifers from three continuously-cored boreholes (130m deep) at different distances from the Adriatic coast and focused within two marine intervals (0–30m and 100–120m depth) that on the basis of AMS 14C dating and pollen data are assigned to oxygen isotope Stage 1 and Substage 5e, respectively, has revealed seven foraminiferal associations. Associations Me (Textularia spp. and Miliolidae) and Md (Miliolidae, Elphidium spp. and Cribroelphidium spp.) are characteristic of infralittoral environments. Associations Mb (Ammonia tepida, A. parkinsoniana and Cribroelphidium spp.) and Ma (Ammonia tepida and A. parkinsoniana) are indicative of shallow-marine environments influenced by freshwater. Reworked and transported microfaunal association Rm corresponds to supralittoral environments (beach-ridge deposits). Associations Bd-b (Ammonia tepida, A. parkinsoniana and brackish ostracods) and Ba (Trochammina inflata) are characteristic of bay, lagoon and estuary environments.Comparison of benthic foraminiferal associations from coeval deposits provides information on the relative distance of cores from the Holocene and Tyrrhenian paleo-shorelines. Core 205-S10 is characterised by deeper marine associations than core 223-S12. Core 240-S13 contains exclusively associations characteristic of lagoonal and brackish marsh environments.Vertical variation in microfaunal associations within each marine deposit reveal in both intervals a transgressive trend, followed upwards by a regressive trend. Benthic foraminiferal associations from cores 205-S10 and 223-S12 show that the Tyrrhenian maximum flooding surface corresponds to a deeper marine environment than peak transgression in the Holocene. This is also shown by core 240-S13, where an open lagoonal microfauna characterizes Tyrrhenian deposits and a brackish marsh association marks the Holocene sediments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.