Shallow-water Benthic Foraminifera Research Articles

Recent shallow-water benthic foraminifera from a tropical estuary, SW Nigeria

This paper presents a comprehensive survey of benthic foraminifera from shallow waters of the Apapa-Badagry Creek estuary in southwestern Nigeria. Sediments of the Apapa-Badagry Creek, an important estuary surrounded by sprawling estates and industrial parks, yielded diverse assemblages of benthic foraminifera with a total of eighty-eight species. They include hyaline-perforate taxa which dominated the inner western sites around the Lagos Harbor in the Apapa Creek with Ammonia aoteana, A. tepida, A. convexa, Ammonia sp. 1, Ammonia sp. 2. Agglutinated taxa are well established in the westernmost areas in the Badagry Creek, where there is seamless fresh-water mixing, with high populations of Ammotium salsum and few occurrences of Milliamina fusca and Ammobaculites species. The miliolids, represented mainly by species of Quinqueloculina, occupy sample stations in the Commodore Channel which flourish under conditions of marine and tidal influences. Cribroelphidium mirum, Pararotalia sarmientoi, Bolivina striatula and Rosalina species are also found within the Commodore Channel sediments. Our study widely extends and completes previous studies from the tropical eastern Atlantic, especially within the Gulf of Guinea and provides new information on the distribution, diversity, and species richness of shallow-water benthic foraminifera fringing the Atlantic coast of Africa.

The Benthic Foraminiferal Assemblages in the Seagrass Bed of Tanjung Berakit Waters, Bintan Island

Seagrass is the most common ecosystem in Tanjung Berakit waters. Therefore, Tanjung Berakit waters have a very important role as a benthic foraminiferal habitat. This study was conducted to describe the distribution of benthic foraminifera relating to the environmental condition of the waters. The samples were collected from eight stations by handling garb in November 2017. This study collected 18 species of shallow water benthic foraminifera dominated by Amphistegina and Heterostegina. This study recorded a correlation between the sediment texture and foraminiferal assemblages. The most common foraminifera were inhabiting fine-textured sediments, especially very fine sand and silt. Only a few foraminifers are collected from extremely fine sediments such as clay sediments, or extremely coarse including pebbles.

50,000 yr of recurrent volcaniclastic megabed deposition in the Marsili Basin, Tyrrhenian Sea

Abstract Megabeds are exceptionally large submarine deposits interpreted to originate from single catastrophic events. Megabeds are significant components of deep-water basins and are critical for understanding geohazards. We discovered a succession of four megabeds within the upper 70 m of the western Marsili Basin, Tyrrhenian Sea, deposited within the past 50 k.y. The megabeds were imaged as distinctive acoustically transparent units with ponded geometries, 10–25 m thick, separated by parallel-bedded strata. Cores from Site 650 of Ocean Drilling Program Leg 107 revealed that three of the four megabeds are made of alternating volcaniclastic sand and mud, and one is a volcaniclastic debris flow. Abundant shallow-water benthic foraminifera within the megabeds suggest that they were not sourced locally from the active Marsili Seamount, but most likely originated from the Campanian volcanic province to the north. The time interval during which the megabeds were deposited includes the 39.8 ka Campanian ignimbrite supereruption of the Campi Flegrei caldera, Italy, which is among the largest known eruptions on Earth, and the 14.9 ka Neapolitan Yellow Tuff supereruption. Volume (minimum) estimates range from 1.3 to 13.3 km3. However, similar megabeds observed in the neighboring Vavilov Basin to the west suggest that the megabeds in both basins may be correlative, and thus volumes could be much larger. The newly discovered megabeds of the Marsili Basin reveal significant geohazard events for the circum–Tyrrhenian Sea coastlines with a recurrence interval on the order of ~10–15 k.y.

Kleptoplast distribution, photosynthetic efficiency and sequestration mechanisms in intertidal benthic foraminifera

Foraminifera are ubiquitously distributed in marine habitats, playing a major role in marine sediment carbon sequestration and the nitrogen cycle. They exhibit a wide diversity of feeding and behavioural strategies (heterotrophy, autotrophy and mixotrophy), including species with the ability of sequestering intact functional chloroplasts from their microalgal food source (kleptoplastidy), resulting in a mixotrophic lifestyle. The mechanisms by which kleptoplasts are integrated and kept functional inside foraminiferal cytosol are poorly known. In our study, we investigated relationships between feeding strategies, kleptoplast spatial distribution and photosynthetic functionality in two shallow-water benthic foraminifera (Haynesina germanica and Elphidium williamsoni), both species feeding on benthic diatoms. We used a combination of observations of foraminiferal feeding behaviour, test morphology, cytological TEM-based observations and HPLC pigment analysis, with non-destructive, single-cell level imaging of kleptoplast spatial distribution and PSII quantum efficiency. The two species showed different feeding strategies, with H. germanica removing diatom content at the foraminifer’s apertural region and E. williamsoni on the dorsal site. All E. williamsoni parameters showed that this species has higher autotrophic capacity albeit both feeding on benthic diatoms. This might represent two different stages in the evolutionary process of establishing a permanent symbiotic relationship, or may reflect different trophic strategies.

Stratigraphic distribution of shallow-water benthic foraminifera from the Lower Cretaceous Taft formation, Central Iran (Yazd Block), with evidence for the importance of hiatuses

In this contribution, two stratigraphic sections are described through the Lower Cretaceous shallow-water platform sediments (Taft formation) from the northern Tethys, which are located in the Yazd Block, Central Iran. Benthic foraminifera are used to propose a biostratigraphy for these successions. They are grouped around several assemblage zones, and several genera and species are reported from the Yazd Block basin for the first time (e.g., Arenobulimina cochleata, A. meltae, Belorusiella sp., Bolivinopsis cf. labeosa, Decussoloculina barbui, Martinotiella jucunda, Myncinabulgarica, Novalesiacornucopia, Sabaudiabriacensis,Simplorbitolina manasi). Their presence can provide a better understanding for the paleogeographic reconstruction of the Tethyan seaways. Furthermore, they represent candidates as potential index fossils in the Lower Cretaceous stratigraphy of the Yazd Block. The new biostratigraphic data allow to date the Lower Cretaceous successions between the probable Valanginian and the late Aptian. Based on the absence of early Barremian indicators and also late Aptian markers, two hiatuses are recognized through the Taft formation. This formation also displays a diachrony in ages at its base and top, which suggests the effect of long-term subsidence in the Yazd Block during the Early Cretaceous, following the Cimmerian phase of orogeny.

Integrated stratigraphy and paleontology of the lower Miocene Monte León Formation, southeastern Patagonia, Argentina: Unraveling paleoenvironmental changes and factors controlling sedimentation

Marine sedimentary rocks of the lower Miocene Monte León Formation of southeastern Patagonia (Austral Basin), Argentina are important geological archives for better understanding regional tectonics, paleoenvironments, oceanography, and climate. In this paper, we describe assemblages of invertebrates, palynomorphs, foraminifera, ostracods and calcareous nannofossils in a stratigraphical and sedimentological framework, which suggest deposition during a transgressive-regressive cycle. From base to top, the lowermost outcropping deposits of the Punta Entrada Member represent an inner shelf environment, formed during a transgressive phase. The zone of maximum flooding is marked by a high diversity of protoperidiniaceans (heterotrophic) and offshore dinoflagellate cysts, an increase in the percentage and size of planktonic foraminifera, and a decrease in shallow water benthic foraminifera. Regressive deposits in the upper part of the Punta Entrada Member exhibit a progradational stratal stacking pattern and are characterized by an upward decrease in bioturbation and in the content of marine invertebrates; the dinoflagellate cyst assemblages point toward shallower and more restricted marine conditions than in underlying deposits. The cycle ends with the Monte Observación Member, which contains an impoverished and mostly reworked fauna of invertebrates. The presence of monospecific reefs of Crassostrea orbignyi, the decrease in dinoflagellate cysts and calcareous microfossils diversity, and the increase of continental palynomorphs suggest progressively shallower conditions and increasing influence of freshwater discharge. Although eustatic controls could have contributed to the sedimentary evolution of the Monte León Formation, the upward regressive trend is interpreted as the result of tectonism linked to the Andean orogeny, which led to the uplift, exhumation, and erosion of the highlands in the west. This is supported by the abundance of pyroclastic material, together with reworked specimens of Upper Cretaceous forams and Upper Cretaceous and middle Eocene dinoflagellate cysts in the upper part of the Punta Entrada Member and in the Monte Observación Member.

Global bioevents and the Cretaceous/Paleogene boundary in Texas and Alabama: Stratigraphy, correlation and ocean acidification

Abstract With increasing levels of atmospheric pCO2 the oceans are becoming progressively more acidic, with the impact of a lowered pH beginning to affect the calcification of numerous invertebrate groups, including foraminifers, pteropods, heteropods and calcareous nannoplankton. Research on the ecology of foraminifera in the Mediterranean Sea, Gulf of California, Caribbean Sea and elsewhere has shown how modern assemblages are responding to acidification. Experimental work in mesocosms and laboratory cultures are also adding to our knowledge of the response to pH changes. Near Ischia (Italy), natural CO2 vents amongst sea grass meadows are creating low pH environments in which it is possible to observe the response of benthic foraminifera. At a pH of 7.8 the foraminiferal assemblages are already becoming less diverse and below pH 7.6 there are often no calcite-secreting benthic foraminifera. In the Gulf of California, in a deeper-water setting, natural CO2 (and methane) vents are also lowering sea floor pH. The foraminifera show the impact of this change, although the relatively high carbonate saturation ensures that calcite-secreting foraminifers are able to live and reproduce in these relatively low pH environments, only becoming impacted by dissolution effects once dead. Using data from the Cretaceous–Paleogene boundary in Texas, Alabama and north-west Europe it is clear that the plankton was severely impacted by surface water acidification while the relatively shallow water benthic foraminifera show little change and no visible signs of post-mortem dissolution due to ocean acidification.

How will Benthic Foraminifera Respond to Warming and Changes in Productivity?: A Laboratory Culture Study on Cymbaloporetta plana

ABSTRACTAnthropogenic activities are likely to cause global warming. Global warming will affect marine productivity and thus food availability for marine organisms. Both the seawater temperature and food availability affect benthic foraminifera, the most abundant marine calcareous microorganisms. Therefore, a laboratory culture experiment was conducted on Cymbaloporetta plana to understand the coupled effect of temperature (25°C, 27°C, 30°C) and food (102±5, 203±9, 305±14, 407±18, 508±23 diatom cells). At all temperatures, growth increased with increase in food. The specimens subjected to 27°C temperature attained the maximum growth and those subjected to 25°C were the smallest. All specimens fed with 508±23 cells reproduced, 0irrespective of temperature. Of all the specimens without food, 40% at 27°C and 20% at 25°C reproduced, whereas specimens subjected to 30°C did not reproduce. The 100% rate of reproduction at 27°C suggests that it is the optimum temperature for growth and reproduction. All the specimens at 30°C and without additional food, died, whereas at 25°C and 27°C, the mortality rate was 80% and 60%, respectively. The limited growth and reproduction with decreasing food clearly indicates that food availability also controls the growth and reproduction of shallow water benthic foraminifer C. plana. Therefore, warming coupled with decreasing productivity is likely to severely affect the growth and abundance of shallow water benthic foraminifera.

Shallow-water Benthic Foraminifera of the Galápagos Archipelago: Ecologically Sensitive Carbonate Producers in an Atypical Tropical Oceanographic Setting

Shallow-water Benthic Foraminifera of the Galápagos Archipelago: Ecologically Sensitive Carbonate Producers in an Atypical Tropical Oceanographic Setting

Effect of seawater temperature, pH, and nutrients on the distribution and character of low abundance shallow water benthic foraminifera in the Galápagos.

In order to help predict the effects of anthropogenic stressors on shallow water carbonate environments, it is important to focus research on regions containing natural oceanographic gradients, particularly with respect to interactions between oceanography and ecologically sensitive carbonate producers. The Galápagos Archipelago, an island chain in the eastern equatorial Pacific, spans a natural nutrient, pH, and temperature gradient due to the interaction of several major ocean currents. Further, the region is heavily impacted by the El Niño—Southern Oscillation (ENSO) and the Galápagos exhibited widespread coral bleaching and degradation following the strong ENSO events of 1982–1983 and 1997–1998. These findings are coupled with reports of unusually low abundances of time-averaged benthic foraminiferal assemblages throughout the region. Foraminifera, shelled single-celled protists, are sensitive to environmental change and rapidly respond to alterations to their surrounding environment, making them ideal indicator species for the study of reef water quality and health. Here, statistical models and analyses were used to compare modern shallow water benthic foraminiferal assemblages from 19 samples spanning the Galápagos Archipelago to predominant oceanographic parameters at each collection site. Fisher α diversity indices, Ternary diagrams, Canonical Correspondence Analysis, regression tree analysis and FORAM-Index (FI; a single metric index for evaluating water quality associated with reef development) implied a combined impact from ENSO and upwelling from Equatorial Undercurrent (EUC) waters to primarily impact foraminiferal abundances and drive assemblage patterns throughout the archipelago. For instance, repeated ENSO temperature anomalies might be responsible for low foraminiferal density, while chronically high nutrients and low aragonite saturation and low pH—induced by EUC upwelling and La Niña anomalies—likely inhibited post-ENSO recovery, and caused foraminiferal assemblages to exhibit a heterotrophic dominance in the southern archipelago. What resulted are low FI values in the southern collection sites, indicating environments not conducive to endosymbiont development and/or recovery.

Biostratigraphy and depositional environment of the Miocene limestone bed of Baripada, Mayurbhanj district, Odisha: Foraminiferal, sedimentological and bulk organic geochemical evidences

Baripada Marine Beds (BMB) have been studied extensively in terms of its mega fossil content. However, not much has been discussed about the foraminiferal content and the organic matter assemblage in these beds. The fossiliferous sequence of BMB consists of sandstone, shale and limestone units. The present study is persued on the limestone unit of BMB. Foraminiferal, thin section and rock-eval pyrolysis studies were performed on the 33 surface samples collected from five sections of Jamdapal and Mukurmatia region along the Budhabalang river bank. Foraminifera are less abundant in the samples of Jamdapal, whereas Mukurmatia is comparatively rich. First appearance datum of Globorotalia menardii [ranges since middle Miocene (12.6 Ma); FAD at planktic foraminiferal zone N12] and last appearance datum of Neogloboquadrina continuosa [ranges between early Miocene (23.2 Ma) to late Miocene (8.3 Ma); FAD at planktic foraminiferal zone N4B and LAD at N16] together suggest that the limestone unit was deposited in between 12.6 to 8.3 Ma within the upper Miocene. Also, the association of shallow water benthic foraminifera (Species of Ammonia, Asterorotalia, Bolivina, Buliminella, Cibicides, Challengerella, Criboelphidium, Cribononion, Elphidium, Hanzawaia, Nonionella ) and planktic foraminifera ( Globigerina falcoensis, Globigerina woodi, Globorotalia menardii, Neogloboquadrina continuosa ) together with oyster bank and shark teeth suggest deposition of limestone within well oxygenated, tropical, shallow water, open marine condition (within 40m water depth). Lithological and thin section studies together with global sea level fluctuation history advocate that upper Miocene marine transgression promoted the formation of this unit. Bulk organic geochemical data obtained by the rock-eval pyrolysis studies on selected samples indicate a low total organic carbon (TOC), with low hydrogen index (HI), high oxygen index (OI). The organic facies is characterised by type-IV kerogen with major contribution from near shore terrestrial plants. This also suggests deposition in shallow, oxygenated environments that did not promote significant accumulation and preservation of organic content in sediments.

Taxonomy and Distribution of Recent Benthic Foraminifera from Bir Ali Beach, Shabwah Governorate, Arabian Sea, Yemen

One hundred and eleven benthic foraminiferal species belonging to 36 genera, 25 families, 16 superfamilies and 4 suborders were identified from twenty samples collected from Bir Ali beach on the Yemeni Arabian Sea coastline. The benthic foraminifera assemblages were dominated by species belonging to Miliolina suborder with 71 species and 17 genera, followed by Rotaliina with 29 species and 14 genera, Textulariina 9 species and 3 genera and Lagenina 2 species and 2 genera. The distribution of recent shallow-water benthic foraminifera in surface sediment samples is in varians from sample to another. Higher abundance of genus Quinqueloculina is recorded in almost all the samples of the study area. The recorded assemblages show a high similarity to the foraminiferal assemblages of the IndoPacific region, East African coast and Red Sea.

Selective transport of palynomorphs in marine turbiditic deposits: An example from the Ascension-Monterey Canyon system offshore central California

The pollen assemblage of a deep-sea core (15G) collected at lower bathyal depths (3491 m) on a levee of Monterey Canyon off central California was investigated to gain insights into the delivery processes of terrigenous material to submarine fans and the effect this transport has on the palynological record. Thirty-two samples were obtained down the length of the core, 19 from hemipelagic and mixed mud deposits considered to be the background record, and 13 others from displaced flow deposits. The pollen record obtained from the background samples documents variations in the terrestrial flora as it adapted to changing climatic conditions over the last 19,000 cal yrs BP. A Q-mode cluster analysis defined three pollen zones: a Glacial Pollen Zone (ca. 20,000–17,000 cal yr BP), an overlying Transitional Pollen Zone (ca. 17,000–11,500 cal yr BP), and an Interglacial Pollen Zone (ca. 11,500 cal yr BP to present). Another Q-mode cluster analysis, of both the background mud and flow deposits, also defined these three pollen zones, but four of the 13 turbiditic deposits were assigned to pollen zones older than expected by their stratigraphic position. This was due to these samples containing statistically significant fewer palynomorphs than the background muds as well as being enriched (∼10–35% in some cases) in hydraulically-efficient Pinus pollen. A selective bias in the pollen assemblage, such as demonstrated here, may result in incorrect interpretations (e.g., climatic shifts or environmental perturbations) based on the floral record, indicating turbiditic deposits should be avoided in marine palynological studies. Particularly in the case of fine-grained flow deposits that may not be visually distinct, granulometry and grain size frequency distribution curves may not be enough to identify these biased deposits. Determining the relative abundance and source of displaced shallow-water benthic foraminifera entrained in these sediments serves as an excellent additional tool to do so.

Functional xanthophyll cycle and pigment content of a kleptoplastic benthic foraminifer: Haynesina germanica.

Some shallow water benthic foraminifera are able to retain functional chloroplasts (kleptoplasts) from their food source, i.e. diatoms. Here we assessed the functionality of the kleptoplast xanthophyll cycle (XC, i.e. the main diatom short-term photo-regulation mechanism) and we surveyed Haynesina germanica kleptoplast pigment composition over time and at different light regimes. Six common diatom lipophilic pigments were detected, two chlorophylls (Chl a, Chl c) and four carotenoids (fucoxanthin and by-products, diadinoxanthin, diatoxanthin and β-carotene), the same pigment profile as the diatom species frequently isolated at the sampling site. The xanthophyll cycle (XC) was functional with kleptoplast diatoxanthin (DT) content increase with concomitant diadinoxanthin (DD) decrease after short term light exposure. DT/(DT+DD) and DT/DD ratios increased significantly in specimens exposed to low light and high light in comparison to specimens maintained in the dark. Specimens placed in very low light after the light treatments reverted to values close to the initial ones, suggesting that H. germanica XC is functional. A functional XC is an indication of H. germanica kleptoplasts capacity for short-term photo-protection from photo-oxidative damages caused by excess of light. Furthermore, the pigment survey suggests that H. germanica preserved some chloroplasts over a longer time than others and that pigment content is influenced by previous light history. Finally, the current study highlighted seasonal differences, with higher pigment contents in winter specimens (27.35 ± 1.30 ng cell-1) and lower in summer specimens (6.08 ± 1.21 ng cell-1), a quantitative and qualitative composition suggesting light acclimation to low or high light availability, according to the season.

Sr partitioning in the benthic foraminifera Ammonia aomoriensis and Amphistegina lessonii

The shallow water benthic foraminifera Ammonia aomoriensis and Amphistegina lessonii were grown at different seawater Sr/Ca and the test Sr/Ca ratio was determined by Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry. A. aomoriensis test Sr/Ca is positively correlated with seawater Sr/Ca. The linear regression has a slope of 0.17, representing the overall Sr partitioning coefficient KDSr. The slope remains unchanged, if seawater Ca concentration is changed in order to change the seawater Sr/Ca. In the case of A. lessonii, the slopes of the linear regressions representing KDSr differ from one another i.e., 0.16 if the Sr concentration is changed and 0.32 if the Ca level is changed. This difference in KDSr can be explained by the, relative to A. aomoriensis, high Mg content of A. lessonii (ca. 40mmol/mol), distorting the calcite lattice and weakening the discrimination against Sr. The Mg content of A. aomoriensis is too low (ca. 4mmol/mol) to observe the influence on Sr partitioning. All data are compatible with a recently developed model for minor element partitioning in foraminifera (Nehrke et al., 2013; Mewes et al., 2015a). On the whole, our data confirm the model (applicability of the model to Sr and dependence of the calcite Sr/Ca on seawater Sr/Ca, as opposed to seawater Sr concentration), and improve our understanding of the model (influence of calcite Mg/Ca on Sr partitioning).

Estuarine Lago Mare fauna from the Tertiary Piedmont Basin indicates episodic Atlantic/Mediterranean exchange during the final stage of the Mediterranean Salinity Crisis

The geochemical signature of fossils from Lago Mare deposits at Moncucco Torinese (NW Italy) indicates a temporary marine ingression into the Tertiary Piedmont Basin just before the Miocene/Pliocene boundary. Isotope (δ18O, δ13C, 87Sr/86Sr) and trace element (Sr/Ca, Ba/Ca) data from mollusk shells of multiple species and croaker otoliths indicate an upper estuarine environment with considerable seasonal variability in evaporation and freshwater input. Reconstructed salinities<10psu and low 87Sr/86Sr values indicate the close proximity of a watershed draining off of Mesozoic ophiolites and carbonates of the Alps and/or Apennines. Communication with an open marine environment is supported by otoliths of fully marine fishes such as lanternfishes, codlets, and slimeheads found in the same assemblage that carry a euhaline signature close to open ocean values. A thorough taphonomic evaluation renders reworking of the otoliths from pre-evaporitic deposits unlikely; instead we explain their presence in the Lago Mare assemblage as related to large predatory marine fish that periodically migrated into marginal marine and estuarine environments.The presence of a paralic paleobiotope with thalassogenic water in the Tertiary Piedmont Basin contradicts ideas of the Mediterranean as a brackish lake fed by the Paratethys during the latest stage of the Mediterranean Salinity Crisis. Instead, our data support previous notions of temporary Atlantic/Mediterranean exchange during sea-level highstands preceding the permanent re-connection at the Miocene/Pliocene transition. The establishment of short-lived and disjunct estuarine and lagoonal environments such as in the Tertiary Piedmont Basin during marine ingressions also puts highly variable 87Sr/86Sr values and occurrences of shallow water benthic foraminifera in Lago Mare deposits of other Mediterranean basins into a new perspective.

Variation in the nitrogen isotopic composition of amino acids in benthic foraminifera: Implications for their adaptation to oxygen‐depleted environments

AbstractWe evaluated nitrate utilization by benthic foraminifera at the redox boundary around the sediment‐water interface by examining the stable nitrogen isotopic composition (δ15N, ‰ vs. AIR) of amino acids. Five foraminiferal species collected from bathyal Sagami Bay (water depth, 1430 m) in three different sampling seasons were analyzed by determining the δ15N values of amino acids from whole cells and those in test (shell) proteins remaining after H2O2 treatment. The δ15N values of phenylalanine fell within a narrow range (typically 1–3‰) in the test proteins of all five species, but the whole‐cell δ15N values of phenylalanine were substantially different from those of the test proteins in two species, Globobulimina affinis (by 6.3‰) and Uvigerina akitaensis (by 4.5‰). These differences in the δ15N values of amino acids suggest that these species utilize nitrate in their cells probably for nitrate respiration (i.e., denitrification) to adapt to oxygen‐depleted environments, as was previously observed in the shallow water benthic foraminifera Ammonia sp. Apparent trophic positions determined using the δ15N values of amino acids also differed between whole cells and tests in G. affinis, U. akitaensis, and Ammonia sp., perhaps because they have different microbial associations, as observed by cellular ultrastructural analysis. These differences in nitrate utilization and microbial associations among benthic foraminifera suggest that foraminifera adapt in diverse ways to conditions in dysoxic to anoxic sediments.

Potential Cretaceous-Paleogene boundary tsunami deposit in the intra-Tethyan Adriatic carbonate platform section of Hvar (Croatia)

An exceptional 47-m-thick succession of Maastrichtian to Paleocene inner-platform carbonates is exposed on the Dalmatian island of Hvar (Adriatic Sea, Croatia) in a seaside locality called Majerovica. The middle part of this succession is an ~5-m-thick intraformational massive deposit, which is underlain by well-bedded peritidal inner-platform limestones containing latest Maastrichtian rudists and shallow-water benthic foraminifera. This deposit includes a polygenic, matrix-supported carbonate breccia characterized by ripped-up platform limestone lithoclasts, up to boulder sized, and polygenic microbreccia in a muddy matrix. The microbreccia contains rare small intraclasts of pelagic mudstone containing terminal Maastrichtian planktonic foraminifera. The deposit is overlain in turn by mudstone containing a planktonic foraminiferal association belonging to the P0 and Pα zones of the basal Paleogene, and by shallow-water muddy limestones containing planktonic foraminifera belonging to the P1 zone. While facies suggest that the deposit was emplaced over the inner platform by a single large tsunami, the biostratigraphic assessment of this section and the presence of enhanced concentrations of platinum group elements, such as iridium, in the topmost part of the massive deposit lend support to the hypothesis that this tsunamite is related to the Chicxulub impact in Yucatan. This is potentially the first case of a tropical carbonate platform sedimentary succession recording the Cretaceous-Paleogene boundary event, which provides a new constraint for modeling both the western Tethyan paleogeography and the catastrophic aftermaths of the Chicxulub impact at the end of the Mesozoic Era.

Shallow water benthic foraminifera from the Polonez Cove Formation (lower Oligocene) of King George Island, West Antarctica

We present the first description of benthic foraminifera from the lower Oligocene of the Antarctic Peninsula sector (South Shetlands) of West Antarctica. The single assemblage was collected at several sites and has no modern Antarctic analogue. It is dominated by robust calcareous species and represents a fan-delta front system. The assemblage includes a group of the most morphologically conservative Antarctic foraminifera known from other Cenozoic neritic sites around Antarctica, indicating their presence since at least the Eocene. Despite including some characteristic taxa, e.g., Ammoelphidiella sp., it is difficult to correlate this assemblage with any particular interval of the Ross Sea record, mainly because of a strong taxonomic imprint of a shallow water environment.

Identification and Abundance of Benthic Foraminifera in Sediments of Southern Caspian Sea from Bahnamir to Babolsar, Iran

Shallow-water benthic foraminifera were identified from sediments of the southern part of the Caspian Sea (from Babolsar to Bahnamir). The samples were collected from 12 stations in the spring, of 2011. Sediment samples were gathered from depths up to 20 meters (5, 10, 15 and 20 m) by a Van Vein grab (0.1m 2 ); the environmental factors (dissolved oxygen, temperature, pH) were measured by an electrical multimeter. Total organic matter, calcium carbonate concentration, and grain size were calculated in the laboratory. A total of 5 species of benthic foraminifera obtained from the sediments were distinguished; four species identified respectively as Ammonia beccarii caspica Stschedrina , Elphidium littorale caspicus (Shokhina), Miliammina fusca (Brady), and Ammotium sp.; and one unidentified species. Ammonia beccarii caspica was dominant at all stations and Elphidium littorale caspicus was also observed at all stations. Structural abnormality in the tests of foraminifera (near all stations) pointed to a relatively polluted environment in the area studied.