Benthic Foraminifers Research Articles

Boreal (Eemian) Transgression in the Northeastern White Sea Region: Multiproxy Evidence from Bychye-2 Section

Reconstructing interglacial marine environments helps us understand the climate change mechanisms of the past. To contribute to this body of knowledge, we studied a high-resolution 455 cm-thick sediment sequence of the Boreal (Eemian) marine beds directly overlying Moscovian (Saalian) moraine in the Bychye-2 section on the Pyoza River. We analyzed lithological and microfossil (foraminifers, ostracods, pollen, aquatic palynomorphs) variations at the studied site. Stratigraphical zonation is based on the local and well-established regional pollen zones, correlated with the western European pollen zones. The studied marine beds accumulated from the end of the Moscovian glacial (>131 ka) until ca. 119.5 ka. We distinguished three successive phases: a seasonally sea-ice-covered, relatively deep, freshened basin in the initial rapid flooding stage (>131–130.5 ka); a deep basin in the maximum flooding phase with less extensive sea ice cover (130.5–130.25 ka); and a shallow basin with reduced sea ice cover (130.25–119.5 ka). According to a pollen zone comparison with other sites, the regional glacioisostatic rebound started ca. 130 ka. The diverse warm-water assemblages of benthic foraminifers and ostracods containing typical Baltic Sea species occurred during the regression, mainly 128–124 ka, thus giving evidence for a relatively long-lasting connection between the White and Baltic Seas.

Berriasian–Valanginian calpionellid biostratigraphy and associated microfossils from the upper Pimienta and lower Tamaulipas formations (Hidalgo state, Mexico): paleoenvironmental and paleobiogeographic significance

A section measured from the upper part of the Pimienta Formation and the lowest part of the Tamaulipas Formation located in the central-eastern part of the state of Hidalgo, NE Mexico was studied. The lower part of the succession consists of an argillaceous and laminated dark gray limestone, black shale, black calcareous shale, siltstone and bentonite; the Pimienta–Lower Tamaulipas transition is marked by the sporadic appearance of light-colored limestone in the upper part of the Pimienta and the shift to a succession dominated by thicker beds of yellowish and bioturbated limestone. The microfossil assemblage consists of calpionellids, radiolarians, and planktonic and benthic foraminifers. The biostratigraphic study of the calpionellids enabled three zones to be identified: Calpionella, Calpionellopsis and Calpionellites as well as five subzones, Elliptica, Oblonga, Murgeanui, Darderi and Major, ranging from early late Berriasian to early Valanginian. This allows a chronostratigraphic correlation to be drawn between the Tethys and the Southeastern Pacific provinces. In addition, we report the occurrence of abundant radiolarians and planktonic and benthic foraminifers. The paleoenvironmental inferences in the studied section are documented from the predominant wackestone texture and microfossil association, indicating a pelagic basin environment. The abundant occurrence of radiolarians mostly in the Elliptica and Oblonga subzones could suggest an increase in the input of nutrients.

Chronology and Paleoenvironment of the Tunga Formation, a new lowermost Miocene sequence in the East Pisco Basin of southern Peru

The East Pisco Basin, occupying the coastal plain of Peru between 13°S and 16°S, is widely known for its extensive Eocene to Quaternary biosiliceous deposits and excellent preservation of fossil marine vertebrates. Biochronologic studies published over the past 35 years record a hiatus of about 13 million years (*32–19 Ma) separating the youngest Paleogene deposits (Otuma Formation) from the oldest Neogene deposits (Chilcatay Formation). We describe a newly identified Lower Miocene depositional sequence that lies below documented Chilcatay strata, rich in diatoms and benthic foraminifers, which we name the Tunga Formation. A low-latitude diatom assemblage from the Tunga Formation indicates an age of 21.6 to 20.5 Ma age, whereas an ash within basal Tunga strata yields an 206Pb/238U weighted mean age of 20.58 ± 0.13 Ma. Benthic foraminifer paleodepth analysis and the diatom assemblage of the Tunga Formation indicate deposition took place along the continental margin at upper bathyal depths under hypoxic conditions beneath highly productive waters, a scenario also supported by the presence of abundant clupeoid fish scales and dolomitized horizons. The Tunga Formation is characterized by a profound scarcity of cetacean fossils, unlike the cetacean-rich neritic sediments of the overlying Chilcatay Formation.

Biostratigraphy and Depositional Environment of the Upper Disang Formation, Indo-Myanmar Ranges, Northeast India

This paper presents the results of Eocene molluscan fauna and benthic foraminifera from the Upper Disang Formation of Indo-Myanmar Ranges (IMR) and discussed here the biostratigraphic zone and depositional environment. These fauna and foraminifera are composed of Bivalvia viz. Noetia magnifica, Pitar (Calpitaria) carteri, Corbula (Bicorbula) rakhiensis, Gastropoda viz. Turritella sp., Turbinella premekranica, Lyria samanaensis and foraminifera Nummulites sp. On the basis of molluscan fauna Noetia magnifica, the biostratigraphic zone (Zone-I) is established and assigned middle-late Eocene age to Upper Disang Formation of IMR, Nagaland. The presence of invertebrate fossils and benthic foraminifers indicate a warm tropical-subtropical climate and shallow marine (neritic) depositional environment during the sedimentation of the Upper Disang Formation. Keywords: IMR, Inner Paleogene Fold Belt, Molluscan Fauna, Nummulites, Phesama, Upper Disang Formation

Paleoclimatic analysis of Quaternary sediments associated with the floodplain depositsof a tropical estuary along the southwestern coast of India

The coastal regions of southwest India which falls in the tropical regime, have witnessed many transgression-regression events and climatic extremes in the Quaternary Period. A core, 15 m long, was recovered from the floodplains associated with a typical backwater body (lake) in the southwestern coast of India. The granulometric analysis proved dominance of sand and silt fractions and extremely high energy conditions over the entire core. The TOC/TN ratio indicated a domination of the C4-type over the C3-type plants in the lower half of the core, suggesting a warm climate. The C3-type plants prevail in the upper part of the core, thus reflecting cool and wet environments. Extremely low values of TOC/TN ratio (0.33% to 10%) of the core indicate short periods of very high rainfall events and the rapid influx of nutrients to the basin and the eutrophication of the basin. The presence of slightly brackish, brackish/marine and marine benthic foraminifers at 12.5–9 m depth indicates episodes of transgression and regression. The derived AMS radiocarbon dates suggest the Marine Isotope Stage 3 for the lower part of the core.

Changes of bottom water oxygenation during the last half millennium in the Gulf of Tehuantepec (Eastern Tropical North Pacific): A multiproxy approach

The Gulf of Tehuantepec (GoT), in the Eastern Tropical North Pacific Ocean, is home to one of the largest and more intense Oxygen Minimum Zones (OMZ). To identify the OMZ variability during the last five hundred years in the GoT, we analyzed the temporal variations of benthic foraminiferal (BF) assemblages, enrichment of redox-sensitive elements (Mo, V, Cd, U, and Re) and δ15Nsed, on a laminated sediment core. During the Little Ice Age (LIA; ∼1500 to ∼1860 CE), the BF assemblages showed high dominance, and the most abundant BF species in the sediments were Epistominella sandiegoensis, Takayanagia delicata, and Buliminella tenuata. This assemblage can withstand the lowest dissolved oxygen conditions, indicating an intensified OMZ consistent with the enrichment of Mo, Re, Cd, U, and enhanced denitrification. During the Current Warm Period (CWP; ∼1860 CE to present), the BF assemblages were more diverse, and the most abundant species were Bolivina seminuda, Epistominella sp.1, Gyroidina nitidula, and Suggrunda eckisi, an assemblage less tolerant to low dissolved oxygen conditions, together with lower concentrations of redox-sensitive elements and δ15Nsed, suggest weakening of the reducing conditions within the OMZ. Additionally, our BF data showed evidence of the influence of the Pacific Decadal Oscillation on bottom-water oxygenation. Bottom-water oxygenation changes appear to respond to increased solar forcing caused by Intertropical Convergence Zone migration and strengthened Pacific Walker Circulation, which in turn modulated productivity, organic matter flux to the seabed, and oxygen consumption in the bottom water. Our findings agree with previous studies further north from the study site, indicating these changes' regional scale.

Bioerosion Structures on Benthic Foraminiferal Tests from the Upper Cretaceous and Paleogene of Western Siberia

Bioerosion Structures on Benthic Foraminiferal Tests from the Upper Cretaceous and Paleogene of Western Siberia

Paleogene carbonate ramp development in the Kohat Basin of northwestern Pakistan

A series of well-exposed Paleogene sedimentary successions in the Kohat Basin of northwestern Pakistan (western Himalayas), are used to document the development of Paleogene sedimentary sequence deposited in a clastic–carbonate–evaporate distally steepened to a homoclinal ramp setting. Larger benthic foraminifer stratigraphy, sedimentology and microfacies were used to reconstruct the depth of deposition of the sediments and to aid in reconstructing the subsidence history of the sedimentary basin through the Paleogene. Based on the timing of the cessation of marine sedimentation and the subsidence analysis of the Paleogene rocks of the Kohat Basin, we conclude that a proto-closure of the basin occurred in the early Eocene (Ypresian) at ca 50–49.5 Ma, followed by return of marine sediments, with full closure of the Tethys seaway in the middle Eocene ca 40–41.2 Ma (Lutetian), potentially resulting in diachroneity of emergence of basins along strike of the orogen.

Outcrop-to-subsurface correlation and sequence stratigraphy of a mixed carbonate–siliciclastic ramp using element geochemistry and well logging; Upper Cretaceous Kometan Formation, Zagros Foreland, NE Iraq

Surface analogues are suitable tools to link reservoir models to real facies but they require a robust outcrop-to-subsurface stratigraphic correlation. In this study, we correlate gamma-ray (GR), and porosity logs from nine wells drilled in the Cretaceous Kometan Formation, a prolific carbonate reservoir of northern Iraq, with geochemical logs from three sections representing surface analogues. The sections were sampled for microfacies, X-ray diffraction mineralogy, and element geochemistry using X-ray fluorescence spectrometry calibrated by ICP-MS data. Six microfacies composed of mudstones to packstones with planktonic, and benthic foraminifers were identified in outcrop, and interpreted as middle ramp, outer ramp, and basin deposits. The microfacies show increasing Al and K, and decreasing Ca concentration trends from the middle ramp to the basin settings. Their subsurface analogues are carbonates, marls and shales with benthic foraminifers, deposited in proximal, inner to middle ramp parts of the Kometan mixed carbonate–siliciclastic ramp system. The K + Al logs are correlated for 33 km, and the subsurface GR logs for over 100 km distance, but both reflect detrital admixture in biogenic carbonate. However, the outcrop- and subsurface log patterns show opposite vertical trends. The subsurface, inner ramp GR maxima in the middle Kometan, correlate with the outcrop K + Al minima jointly reflecting landwards and seawards shifts of the middle ramp carbonate factory during transgressions and regressions, respectively. The maxima and minima are interpreted as maximum regression (mrs) and maximum flooding surfaces (mfs) in the T–R sequence-stratigraphic model. Neutron-density and sonic logs indicate that the best reservoir quality is achieved in fractured pure carbonates, which are controlled by these T–R cycles. The results highlight the importance of elemental geochemistry in stratigraphic correlation of lithologically uniform sequences, and suggest that outcrop geochemistry can be correlated with well logs.

Biostratigraphy of Hartha Formation from Selected Wells in Nasiriyah Oil Field, Southern Iraq

The Hartha Formation has been investigated from a biostratigraphic view in three subsurface sections in the Nasiriyah Oil field, wells Ns1, Ns3, and Ns4, South of Iraq. Hartha Formation is composed of limestone and has various areas of intense dolomitization alternating with marly limestone. The formation ranges in thickness from 126 to 182 meters. Thirteen large and small benthic foraminifer species and genera are identified from Hartha Formation. Based on the large benthic foraminifer's assemblage, one distinct biozone was recognized after an examination of the paleontological datum in the investigated area showed that the studied wells contained a diversity of foraminiferal species, the larger foraminifers biozone was proposed: Orbitoides medius- Orbitoides tissoti - Orbitoides gensacicus -Orbitoides apiculatus - Omphalocyclus macroporus assemblage zone (Late Campanian- Early Maastrichtian), this biozone divided in two range subzone: Orbitoides medius Partial Range Zone (Late Campanian) and Omphalocyclus macroporus Range Zone (Early Maastrichtian). This biozone indicated that the Hartha Formation deposited through (Late Campanian- Early Maastrichtian).

PARURGONINA VALANGINIANA N. SP. FROM THE VALANGINIAN OF SW IRAN (ZAGROS ZONE): THE FIRST CRETACEOUS RECORD OF THE GENUS

The new larger benthic foraminifer Parurgonina valanginiana is described from the Valanginian deposits of the Fahliyan Formation of southwestern Iran (Zagros Zone). It is separated from the uppermost Oxfordian-lowermost Tithonian generotype P. caelinensis (Cuvillier et al.) by a distinct time gap. The Lower Cretaceous specimens exhibit a larger embryonic chamber whereas the internal structural and other biometric data are generally in conformity with the Upper Jurassic morphotypes. Besides the Middle Jurassic P. primaeva Kamoun & Peybernès and the Upper Jurassic P. caelinensis, P. valanginiana sp. nov. represents the third species of the genus described and possibly a Valanginian marker endemic for the Arabian Plate. In the Fahliyan Formation, P. valanginiana sp. nov. occurs in wackestones associated with Pseudocyclammina lituus (Yokoyama). Additional data for the micropalaeontological assemblages (benthic foraminifera, calcareous algae) of the shallow-water carbonates of the Fahliyan Formation are provided. As it is also the case in the United Arab Emirates (Granier, 2008), it is proposed that the Tithonian/Berriasian boundary does not, as generally indicated in the literature, coincide with the boundary of the Hith Formation and the Fahliyan Formation, but instead occurs within the latter. The new finds provide further evidence that the Tithonian/Berriasian boundary did not represent a major rupture or extinction for larger benthic foraminifera. On the contrary, the Berriasian/Valanginian boundary corresponds to a natural discontinuity (both sedimentological and biological) possibly enhanced by a hiatus of the upper Berriasian strata. The foraminiferal diversity remains quite high during early Valanginian times then falls drastically, which suggests that the Berriasian/Valanginian crisis is a double barelled crisis (first base Valanginian, second intra-Valanginian).

Revisiting Oxygen‐18 and Clumped Isotopes in Planktic and Benthic Foraminifera

AbstractForaminiferal isotopes are widely used to study past oceans, with different species recording conditions at different depths. Their δ18O values record both seawater oxygen‐18 and temperature according to species‐specific fractionation factors, while their Δ47 signatures likely depend only on temperature. We describe an open‐source framework to collect/combine data relevant to foraminiferal isotopes, by constraining species‐specific oxygen‐18 fractionation factors (18α) based on culture experiments, stratified plankton tows or core‐top sediments; compiling stratified plankton tow constraints on living depths for planktic species; extracting seawater temperature, δ18O, and chemistry from existing databases for any latitude, longitude, and depth‐range; inferring calcification temperatures based on the above data. We find that although 18α differs between species, its temperature sensitivity remains indistinguishable from inorganic calcite. Based on > 2,600 observations we show that, although most planktic δ18O values are consistent with seawater temperature and δ18O over their expected living depths, a sizable minority (12%–24%) have heavier‐than‐predicted δ18O, best explained by calcification in deeper waters. We use this framework to revisit three recent Δ47 calibration studies of planktic/benthic foraminifera, confirming that planktic Δ47 varies systematically with oxygen‐18‐derived temperature estimates, even for samples whose δ18O disagrees with assumed climatological conditions, and demonstrating excellent agreement between planktic foraminifera and modern, largely inorganic Δ47 calibrations. Benthic foraminifera remain ambiguous: modern benthic Δ47 values appear offset from planktic ones, yet applying equilibrium Δ47 calibration to the Cenozoic benthic foraminifer record of Meckler et al. (2022, https://doi.org/10.1126/science.abk0604) largely reconciles it with δ18O‐derived temperatures, with discrete Δ47/δ18O discrepancies persisting in the Late Paleocene/Eocene/Plio‐Pleistocene.

On the occurrence of Neoplanorbulinella Matsumaru, 1976 (Foraminifera) from the late Oligocene of Central Iran (Qom Formation): Palaeobiogeographic implications

The shallow marine carbonates of the upper Oligocene Qom Formation yielded several occurrences of the foraminiferan genus Neoplanorbulinella Matsumaru. Neoplanorbulinella saipanensis Matsumaru has so far been recorded from the late Eocene–early Miocene of Japan and late Oligocene of NE Italy whereas N. malatyaensis Gedik is only reported from the Oligocene from its type locality in the Malatya Basin, eastern Turkey. The new records reported here from the Qom Formation indicate that both species occur in the Dobaradar section, ca. 10 km south of the city of Qom in North–Central Iran. The palaeogeographic distribution of these two species therefore has to be extended as far as the palaeolongitude of current Central Iran. The accompanying larger benthic foraminifers, including Miogypsinoides complanatus (Schlumberger), M. formosensis Yabe and Hanzawa, Spiroclypeus margaritatus (Schlumberger), Operculina complanata (Defrance), and Risananeiza pustulosa Boukhary et al., indicate the upper Chattian SBZ 23 Zone. The co-existence of the N. saipanensis and N. malatyaensis points to suitable palaeobiogeographic conditions of Central Iran to host Western and Eastern Tethyan taxa.

OLENA SEMENIVNA LYPNYK (to 100th anniversary from the birth)

Olena Semenivna Lypnyk is a well-known specialist micropaleontologist of Ukrainian paleontological science, a student of the Doctor of Geological and Mineralogical Sciences, Professor O.K. Kaptarenko-Chernousova, senior researcher of the Department of Stratigraphy and Paleontology of Mesozoic deposits of the Institute of Geological Sciences of the National Academy of Sciences of Ukraine, Candidate of Geological and Mineralogical Sciences. The article presents the biography and scientific achievements of O.S. Lypnyk, who was engaged in the biostratigraphy of the Upper Cretaceous deposits of the platform Ukraine by foraminifers, in particular, the Upper Cretaceous sediments of the Dnieper-Donetsk depression and the outskirts of Donbas. O.S. Lypnyk is the developer and co-author of the zonal dissection of the Upper Cretaceous deposits of the East European Platform by benthic foraminifers, the developer and author of the zonal scale of the Upper Cretaceous sediments of the Dnieper-Donetsk depression by benthic foraminifers, the author of the division of the Upper Cretaceous stratum of the Dnieper-Donetsk depression into sutes, one of the authors of the regional stratigraphic scheme of the Upper Cretaceous deposits of the Dnieper-Donetsk depression, as well as the outskirts of Donbas. The assessment of the scientific heritage of Olena Semenivna Lypnyk is given. The research was based on the personal file and autobiography of O.S. Lypnyk; photos from the archives of the Institute of Geological Sciences of the National Academy of Sciences of Ukraine and the Doctor of Geological and Mineralogical Sciences, Professor D.E. Makarenko; and memories of employees of the institute.

STRATIGRAPHY OF THE UPPER CRETACEOUS SEDIMENTS WITH OCEANIC RED BEDS (CORBs), UKRAINIAN CARPATHIANS

Cretaceous deposits containing pelagic red beds (CORBs – Cretaceous Oceanic Red Beds) are developed in the Ukrainian Carpathians. CORBs have a global distribution, they are sharply depleted in organic matter and their formation is associated with periods of cooling and intensive circulation of cold, oxygen-enriched deep-sea currents that oxidize organic carbon. CORBs in the Ukrainian Carpathians are common in the Upper Cretaceous, while the Lower Cretaceous sediments, especially in the Outer (Flysch) Carpathians, are often enriched in organic matter (in particular the black shales of the Shypot and Spas formations). Such change in sediments enriched and depleted in organic matter may be associated with regular climate changes. In the Inner Carpathians, in the both the Peniny Klippen Belt and the Marmarosh Klippen Zone, CORBs are represented by thick (100-200 m) mostly red-colored marls and shales that make up the Turonian – Maastrichtian Puchov Formation. A fragment of the Puchov Formation of the Turonian age is presented in the Marmarosh Massif. Stratigraphically, the lowest CORBs represented by layers of pink marls are noted in the upper part (Middle-Upper Cenomanian) of the Tysalo Formation in the Peniny Klippen Belt. Deposits containing CORBs in the Peniny Klippen Belt are intensively deformed, in some places they are transformed into thin shale rocks or friction mud and are part of the tectonic mélange, while in the Marmarosh Klippen Zone they lie monoclinally and are weakly deformed. In the Outer Carpathians, CORBs are represented by: Turonian–Paleocene variegated shales and marls of the Holyatyn Beds (Subsilesian Nappe); Turonian–Coniacian red-colored and variegated shales belonging to the lower member of the Yalovets Formation (Dukla, Chornohora, Svydovets, and Krasnoshora nappes); and pack of Turonian variegated marls included in the Sukhiv Formation (Burkut nappe). CORBs represented by red-brown interlayers, occur both in the uppermust Albian– lower Cenomanian (Eiffellithus turriseiffeli Zone) of the Sukhiv Formation, and in the Santonian upper member of the Yalovets Formation. CORBs in the Outer Carpathians are deformed to a greater or lesser extent, plastic marls of the Sukhiv Formation are especially strongly deformed, which makes it much more difficult to establish their stratigraphic sequence. The age of the deposits of the Ukrainian Carpathians, which contain CORBs, has been clarified. The studied sediments are correlated with the Geologic Time Scale (2020) on the basis of nannoplankton and planktonic foraminifera. The biozonal scale based on nannoplankton of A.M. Romaniv is compared in the range BC27/UC0 (upper Albian – lower Cenomanian) – UC20 (upper Maastrichtian) according to the first appearance of zonal species according to the scale of J. Barnett (1998). Accordantly, the Eiffellithus turriseiffeli Zone (uppermost Albian–Lower Senomanian); Gartnerago obliquum Zone (Middle Senomanian–lowermost Turonian); Eiffellithus eximius-Marthasterites furcatus Zone (Lower Turonian–lowermost Upper Coniacian); Micula staurophora-Tetralithus obscurus-Broinsonia parca Zone (Upper Coniacian- lowermost Middle Campanian); Tetralithus aculeus Zone (Middle Campanian); Tetralithus? trifidus (Middle Campanian– lowermost Upper Campanian); Nephrolithus frequens (Upper Campanian–Upper Maastrichtian) are distinguished. The biozonal division of the Upper Cretaceous of the Carpathians according to planktonic foraminifera after N.I. Maslakova was modified and compared with the biochronozones of a typical section of the Tethys region (Coccioni, Premoli Silva, 2015). In the studied sediments, the following zones are distinguished: Thalmanninella reicheli (middle part of the Lower Cenomanian), Rotalipora cushmani (middle part of the Lower Cenomanian–Upper Cenomanian), Helvetoglobotruncana helvetica (lower part of Turonian), Dicarinella concavata (top of Turonian–lowermost Santonian), Contusotruncana fornicata (most of Santonian), Globotruncanita elevata (lower part of the Campanian), Contusotruncana morozovae (middle part of the Campanian), Globotruncanita stuarti (top of the Campanian–lower part of the Maastrichtian), Abathomphalus mayaroensis (upper part of the Maastrichtian); beds with Thalmanninella globotruncanoides (lower part of the Lower Cenomanian), assemblage with Marginotruncana schneegansi, Marginotruncana sigali, Marginotruncana renzi (upper part of Turonian). Benthic foraminifera Uvigerinammina jankoi Zone (Turonian); Spiroplectinella costata Zone (Coniacian–Lower Santonian); Caudammina gigantea Zone (Upper Santonian–Lower Campanian); Rzehakina inclusa Zone (Upper Campanian– Maastrichtian); Rzehakina fissistomata Zone (Paleocene) were identified accordantly to zonal schemes of L.D. Ponomaryova and B. Olszewska. The lower boundary of the CORBs in the Ukrainian Carpathians is correlated with the Senomanian-Turonian boundary on the basis of appearance of planktonic foraminifers of Helvetoglobotruncana helvetica Zone and benthic foraminifers of Uvigerinammina jankoi Zone in the base of both Puchov Formation (Pieniny Klippen Belt) and Holyatun Beds (Subsilesian Nappe), as well as in the lowermost part of the Yalovets Formation (Dukla, Chornohora, Svydovets and Krasnoshora nappes).

A new pseudolepidinid foraminifer, Hanovolepidina browni gen. nov. sp. nov., from the middle Eocene (mid-Lutetian) of Jamaica and its significance

The new larger benthic foraminifer, Hanovolepidina browni gen. nov. sp. nov., is described from the Chapelton Formation (mid-Lutetian, middle Eocene, ABZ7) of Jamaica. The genus shows the characteristic transition from a single to double equatorial layer about mid-way across the radius as seen in axial sections that characterises the family Pseudolepidinidae. Equatorial sections show the embryo followed by 4 or 5 spiral rotaliid chambers with the last chamber giving rise to a primary spiral and secondary (counter-) spiral of equatorial chambers. The presence of a long rotaliid stage suggests a more primitive form that Pseudolepidina, and Hanovolepidina gen. nov. differs also from the latter in lacking the extra principal accessory chamber seen in axial section. Hanovolepidina gen. nov. is provisionally suggested as an ancestor of the late Eocene Triplalepidina. The new discovery demonstrates a greater diversity of the family Pseudolpeidinidae in the Caribbean that previously recorded, although occurrences of this family are very restricted stratigraphically suggesting that it may appear in the region due to migration events.

Rhodolith-forming coralline red algae in the CaCO3 biofactory — A case study from the Serravallian of tropical northeastern Indian Ocean

Rhodolith-forming non-geniculate coralline red algae have been recorded from the Long Formation, exposed in four different outcrops at Little Andaman Island (Hut Bay) in the northeastern Indian Ocean. The non-geniculate corallines are represented by species of Sporolithon Heydrich, 1897, Mesophyllum Lemoine, 1928, Lithothamnion Heydrich, 1897, Phymatolithon Foslie, 1898, Lithoporella (Foslie) Foslie, 1909, Spongites Kützing, 1841, Neogoniolithon Setchell & Mason, 1943 and Lithophyllum Philippi, 1837. The algal assemblages also include geniculate corallines belonging to the genera Amphiroa Lamouroux, 1812 and Corallina Linnaeus, 1758. In addition, larger benthic foraminifers and few planktonic foraminifers also have been identified in thin section analysis. Based on the earlier study carried out on planktonic foraminifers, the Long Formation has been dated as Serravallian (late middle Miocene) and chronostratigraphically, the Long Formation has been included in the Ongeian Regional Stage. In the rhodolith-forming non-geniculate corallines, various growth forms and taphonomic features have been recognized. Diagenesis affected the studied material by micritization, cementation and compaction. The four outcrops are dominated by bioclastic wackestone and packstone composed of coralline red algae, benthic and planktonic foraminifers, echinoid spines and unidentified coral fragments. The rhodolith-forming coralline red algae, the growth forms and taphonomic features in non-geniculate corallines and the characteristic benthic foraminifers are indicative of a moderate energy depositional environment. This study indicates that the carbonate production was considerably high during the Serravallian of the tropical northeastern Indian Ocean.

Foraminifera and Paleogene Stratigraphy of the Submarine Lomonosov Ridge, Arctic Ocean

Materials on the Paleogene biostratigraphy of the Lomonosov Ridge in the Arctic Ocean are presented, including new data on foraminifers from the M0004A borehole section (interval 390–391 m) in its polar part. The studied benthic foraminifers are united into the complex with Reticulophragmium coksuvorovae of the upper Zelandian–the lower Thanetian stages, which includes some characteristic species of the North Atlantic and West Siberian basins. It also contains information about the connection of these Arctic seas in the Paleocene time.

Evaluation of radioactive properties and microfaunal evidence in the Bosphorus and the Dardanelles straits and Golden Horn sediments

The aim of this study is to investigate radioactive pollutants from pollution loads transported from the Black Sea to the Aegean Sea by the Turkish Straits System and their effects on microfauna (benthic foraminifer and ostracod) assemblages. In the study, the effects of gross alpha and beta activity on the species number, species diversity, dominant species and species richness of benthic foraminiferal and ostracod assemblages were investigated in 16 bottom sediments taken from different depths in the Golden Horn, Bosphorus and Dardanelles straits. In the studied sediment samples examined 61 genera and 64 species of benthic foraminifera, 23 genera and 26 species of ostracoda were identified. In addition two migratory foraminifera species were observed as Spiroloculina antillarum of Atlantic-Pacific origin and Peneroplis pertusus of Indo-Pacific origin. A relationship between the abundance of microfauna and high gross alpha and beta values was found in the Dardanelles samples, but not in the Bosphorus and Golden Horn samples. In this study, the highest radioactivity value was observed in the deepest bottom sediment samples. Consequently, the gross alpha and beta values were seen to be close to each other in the Dardanelles Strait and Golden Horn samples, and they had a broad-spectrum in the Bosphorus samples.

Reconciling biogeochemical redox proxies: Tracking variable bottom water oxygenation during OAE-2 using vanadium isotopes

Oceanic Anoxic Event-2 (OAE-2, ∼94 Ma ago) is marked by a significant perturbation to the carbon and nutrient cycles. Despite the general idea of widespread expansion of the oceanic anoxia during OAE-2, various localities likely experienced heterogeneous redox fluctuations throughout the roughly 500-thousand-year-long event. In certain localities, redox-sensitive elements imply persistent anoxic-to-euxinic conditions, notwithstanding paleontological data that indicate short-term hypoxic-to-anoxic oscillations in bottom waters. Such discrepancies likely result from sampling resolution, local proxy sensitivity, and/or time-integration of signals, particularly for severe hypoxic conditions. We applied vanadium (V) isotopes to three well-studied OAE-2 localities in the proto-North Atlantic Basin. Under the relatively stable anoxic-to-euxinic conditions throughout OAE-2 at Well S75 and Site 367, the sedimentary δ51V values present consistent variations analogous to modern anoxic-to-euxinic environments. However, at Site 1258, the sedimentary δ51V values present greater perturbations toward more negative values that are indicative of short-term oxygenation in bottom waters. These negative perturbations of δ51V values covary with the abundances of the low-oxygen-tolerant benthic foraminifers. Together, these data refine the heterogeneous redox fluctuations in individual localities, revealing occasional short-term weak oxygenation under the generally anoxic conditions throughout OAE-2. This study documents the unique utility of V isotopes to track bottom water redox fluctuations, particularly short-term variations from anoxic to mildly oxic conditions that are hard to track with other methods.