Modern planktic foraminifera

Planktic foraminifers are marine protozoans with calcareous Shells and chambered tests. They first appeared in the mid-Jurassic and spread since the mid-Cretaceous over all the world’s oceans. Modern planktic foraminifers evolved since the early Tertiary, when the first spinose species occurred. Most species live in the surface to sub-thermocline layer of the open ocean, and in marginal seas like the Mediterranean, Caribbean, South China Sea, and Red Sea. Planktic foraminifers are absent in shallow marginal seas, for example, the North Sea. Planktic foraminifers respond to food, temperature and chemistry of the ambient seawater. Species abundance varies according to seasons, water masses, and water depths. Symbiont-bearing species depend on light and are restricted to the euphotic zone. Planktic foraminifers constitute a minor portion of total Zooplankton, but are major producers of marine calcareous particles (shells) deposited on the ocean floor where they form the so-called foraminiferal ooze. Planktic foraminifers contribute substantially to the fossil record of marine Sediments and are of high ecologic, paleoceanographic, and stratigraphic significance since the mid-Cretaceous. Radiocarbon (¹⁴C) gives an absolute age of shell formation within late Pleistocene and Holocene Sediments. Factors that determine the modern faunal composition are applied to Interpretation of the fossil assemblages, for example, by multiple regression techniques (transfer functions) to yield an estimate on ancient environmental parameters. The chemical composition of the calcareous shell (stable isotopes and trace elements) holds clues to the chemical and physical State of the ambient seawater and is useful in the reconstruction of temperature, chemical State, and biological productivity of the ancient marine environment.      

Temperature sensitivity of planktic foraminifera and its influence on the oxygen isotope record

We used oxygen isotope measurements from Holocene surface sediments to infer optimum temperature and temperature sensitivity of the planktic foraminiferal species Globigerinoides ruber (pink) and Globigerinoides sacculifer. The (isotopic) optimum temperature of G. ruber (pink) is close to 27°C. G. sacculifer seems to have optimum vital conditions around 22°C and is less temperature sensitive than G. ruber (pink). Our estimations of optimum temperature and temperature sensitivity are in good accordance with laboratory and field investigations. Two simple experiments show that the temperature sensitivity of planktic foraminifera, determined from oxygen isotopes, can influence phase and amplitude of oxygen isotope records, if the temperature distribution at the sea surface changes through time. To use this distortion for paleoceanography, we suggest to derive an ‘isotopic transfer function’ which allows the calculation of average temperature, temperature variability and the isotopic composition of seawater if the oxygen-isotope differences between at least three species are known.     

New biostratigraphic data from Cretaceous planktic foraminifera in Sahlabad province, eastern Iran

The foraminiferal content of two stratigraphic sections, located in eastern Iran within the Sahlabad province, between the Lut and Afghan blocks and ranging in age from Turonian to Campanian is investigated. Previous studies were general and only indicated the presence of planktonic foraminifera in this province. This paper presents a detailed study of planktonic foraminifera of the Shirshotor unit and establishes for the first time a local biostratigraphy consisting of five biozones. Biozones from the upper Turonian to lower Campanian are recognized, but the upper lower Campanian to lower upper Campanian strata are missing, as demonstrated by the lack of the Globotruncana ventricosa biozone. Tectonic activity in this region during the late early Campanian and mid-Campanian resulted in the presence of an unconformity together with debrites (debris flow deposits) in the lower upper Campanian. About twenty-five planktonic foraminiferal species are reported and illustrated. The largest faunal diversity is encountered in the upper Santonian. The planktonic foraminiferal biozones are precisely defined in selected stratigraphic sections and allow age determinations for the deepest marine sediments (pelagic limestones and bedded cherts) before the collision of the Lut and Afghan blocks.     

Size-related isotopic trends in some Maastrichtian planktic foraminifera: methodological comparisons, intraspecific variability, and evidence for photosymbiosis

The serial test dissection and sieve fraction methods for determining the pattern of size-related change in oxygen and carbon isotopic ratios are compared using four Late Cretaceous planktic foraminifer species (Racemiguembelina fructicosa, Planoglobulina acervulinoides, Planoglobulina multicamerata, and Pseudoguembelina palpebra) from a subtropical site in the North Atlantic (DSDP Hole 390A). Despite the extra labor required, we identify several clear advantages of the dissection method, including: (1) it provides a means of obtaining size-dependent changes in isotopic signatures that are unequivocally ontogenetic, whereas isotopic variation observed from sieve-separated size fractions could be ontogenetic or ecotypic; (2) the taxonomic identity of smaller sized specimens using the dissection method is unequivocal, whereas species identification is increasingly ambiguous in smaller size fractions using the sieve method; (3) it reveals a greater total range and a greater complexity in the pattern of ontogenetic change in stable isotopic values, whereas the sieve method averages the isotopic signal across the entire ontogenetic range preserved within the whole tests that are used. Our results from serial dissections demonstrate that among the species analyzed, R. fructicosa and P. acervulinoides yield relatively negative adult δ¹⁸O values, a large size-related change in δ¹³C values (1.32 and 2.05‰, respectively), and virtually no correlation between size-related δ¹³C and δ¹⁸O values. On this basis we suggest that these were photosymbiotic species that inhabited relatively shallow surface waters. Evidence for photosymbiosis is not as compelling for P. palpebra, as this species yields a 1.06‰ shift in δ¹³C and relatively negative δ¹⁸O values in adult chambers, but much stronger correlation between size-related δ¹³C and δ¹⁸O values (r²=0.40) than in R. fructicosa and P. acervulinoides. Planoglobulina multicamerata yields the most positive adult δ¹⁸O values of the species studied, a strong covariance between size-related δ¹³C and δ¹⁸O values (r²=0.77), and a 0.97‰ shift in δ¹³C composition during ontogeny. We conclude that this species lacked photosymbionts and migrated to a deeper surface water paleohabitat as it increased in size. Single specimen analyses of tightly constrained size fractions reveal a high degree of intraspecific variation. δ¹³C and δ¹⁸O values vary by up to 0.70 and 0.28‰ in R. fructicosa, 1.41 and 0.80‰ in P. acervulinoides, 0.66 and 0.82‰ in P. palpebra, and 0.18 and 0.33‰ in P. multicamerata, respectively. Such a range of isotopic variation has been observed in modern day planktic foraminifer assemblages, and likely results from growth of individuals during different phases of the seasonal cycle and/or the kinetic effect of intraspecific variation in shell calcification rates. As suggested by other investigators, large sample sizes should be analyzed to provide the most reliable correlation of stable isotopic stratigraphic records.     

Cyclic changes in Turonian to Coniacian planktic foraminiferal assemblages from the tropical Atlantic Ocean

Abundance patterns of planktic and benthic foraminifera from a tropical Atlantic drill site (Ocean Drilling Program Site 1259, Demerara Rise, Suriname margin) display a pronounced 400 kyr cyclicity, uninterrupted throughout our  87.8–92 Ma record, between two clearly distinguishable assemblages: (1) a pelagic foraminifer fauna, which represents a deep oxygen minimum zone, and (2) another assemblage representing a shallow oxygen minimum zone where the foraminifer fauna is dominated by a higher diversity population of mostly small clavate and biserial species common in epicontinental seas. The cyclic changes in the long eccentricity band (400 kyr) between these two assemblages are proposed to reflect changes in the mean latitudinal position of the Intertropical Convergence Zone (ITCZ). Associated fluctuations in precipitation and trade wind strength may have influenced the upwelling regime at Demerara Rise leading to the observed cyclicity of planktic foraminiferal assemblages. The severe Turonian to Coniacian paleoclimatic and paleoceanographic changes in the Atlantic Ocean (e.g., gateway opening, cooling, and glaciation), however, seem to have no influence on the composition of tropical planktic foraminiferal faunas. There is no apparent relationship between foraminifer abundances and a major deflection in the stable isotope record interpreted elsewhere as a sign of the growth and decay of a large polar ice sheet.     

Paleoceanographic implications of smaller benthic and planktonic foraminifera from the Eocene Pazin Basin (Coastal Dinarides,Croatia)

Summary Smaller benthic and planktonic foraminifera from the clastic sediments of the Pazin Basin (Istria, Croatia) were studied in order to obtain more data about paleoceanographic conditions that existed in the Middle Eocene Dinaric foreland basin. The succession investigated corresponds to the Middle Eocene planktonic foraminiferal zones Globigerapsis kugleri/Morozovella aragonensis (P11), Morozovella lehneri (P12), and Globigerapsis beckmanni (P13). Benthic foraminiferal assemblages from the clastic succession are dominated by epifaunal trochospiral genera suggesting oligotrophic to mesotrophic conditions and moderately oxygenated bottom waters. Planktonic foraminiferal assemblages indicate mesotrophic to eutrophic conditions of the surface waters, with increased eutrophication in the upper part of the section. Water depth, based on the ratio between planktonic and epifaunal benthic foraminifera and on the recognized species of cosmopolitan benthic foraminifera, was estimated to have been between about 900 and 1200 m. The basin was elongated and open to marine currents on both sides allowing good circulation and ventilation of the bottom water.     

A new type of test wall in the Late Cretaceous (Late Santonian-Campanian) heterohelicid planktic foraminifera

The first Cretaceous serial planktic foraminifer (family Heterohelicidae Cushman, 1927) with simple-ridged test wall is reported from the uppermost Santonian-lower Campanian sediments of the Deep Sea Drilling Project Site 463 (Mid-Pacific Mountains, equatorial Central Pacific). Hendersonites pacificus n. sp. is characterized by the reduced ornamentation over the last pairs of chambers and strong peripheral costae lining the periphery with test wall flexure. This species evolved from H. carinata (Cushman, 1938) of the upper Santonian-Campanian, a frequently reported species from the Atlantic Ocean, Gulf of Mexico and Western Tethyan Realm.     

Oncoid-dwelling foraminifera from Late Jurassic shallow-water carbonates of the Northern Calcareous Alps (Austria and Germany)

Oncoidal limestones with different oncoid types are ubiquitous in back-reef open-lagoonal and, to a minor amount, in closed-lagoonal facies of the Late Jurassic Plassen Carbonate Platform of the Northern Calcareous Alps. A common feature of the oncoids from moderately to well-agitated open-lagoonal habitats are incorporated small trochospiral benthic foraminifers, tentatively assigned to trochamminids, switched between individual micritic layers. Their life style is discussed concluding a specialized feeding on cyanophytes on the outer side of the oncoids and later becoming biomurated by successive sheet formations due to oncoid growing.     

First radiation of Cretaceous planktonic foraminifera with radially elongate chambers at Angles (Southeastern France) and biostratigraphic implications

The study of planktonic foraminifera from the Lower Cretaceous succession at Angles (Southeastern France) directly correlated with ammonites, confirms that the origin of morphotypes with radially elongated chambers occur earlier than previously recorded. In particular, the species Hedbergella semielongata and Hedbergella roblesae bearing subclavate to clavate chambers first appear in the upper Hauterivian, just predating the onset of the oceanic anoxic Faraoni event. Based on these observations, a new zonation is proposed.     

Late Neogene planktonic foraminifera of the Cibao Valley (northern Dominican Republic): Biostratigraphy and paleoceanography

An assemblage of planktonic foraminifera is described from 125 samples taken from the Cercado, Gurabo, and Mao Formations in the Cibao Valley, northern Dominican Republic. The primary objectives of this study are to establish a biochronologic model for the late Neogene of the Dominican Republic and to examine sea surface conditions within the Cibao Basin during this interval. The Cercado Formation is loosely confined to Zones N17 and N18 ( 7.0–5.9 Ma). The Gurabo Formation spans Zones N18 and N19 ( 5.9–4.5 Ma). The Mao Formation is placed in Zone N19 ( 4.5–3.6 Ma). Changes in the relative abundances of indicator species are used to reconstruct sea surface conditions within the basin. Increasing relative abundances of Globigerinoides sacculifer and Globigerinoides ruber, in conjunction with a decreasing relative abundance of Globigerina bulloides, suggests the onset of increasing sea surface temperature and salinity in conjunction with diminishing primary productivity at 6.0 Ma. Abrupt increases in the relative abundances of G. sacculifer and G. ruber at 4.8 Ma suggest a major increase in sea surface temperature and salinity in the early Pliocene. The most likely mechanism for these changes is isolation of the Caribbean Ocean through progressive restriction of Pacific–Caribbean transfer via the Central American Seaway. Periods of high productivity associated with upwelling events are recorded in the upper Cercado Formation ( 6.1 Ma) and in the middle Mao Formation ( 4.2 Ma) by spikes in G. bulloides and Neogloboquadrina spp. respectively. The timing of major increases in sea surface salinity and temperature as well as decreasing productivity ( 4.8 Ma) and periods of upwelling ( 6.1and 4.2 Ma) in the Cibao Basin generally corroborate previously suggested Caribbean oceanographic changes related to the uplift of Panama. Changes in sea surface conditions depicted by paleobiogeographic distributions in the Cibao Basin suggest that shoaling along the Isthmus of Panama had implications in a shallow Caribbean basin as early as 6.0 Ma. Major paleobiologic changes between 4.8 and 4.2 Ma likely represent the period of final closure of the CAS and a nearly complete disconnection between Pacific and Caribbean water masses. This study illustrates the use of planktonic foraminifera in establishing some paleoceanographic conditions (salinity, temperature, productivity, and upwelling) within a shallow water basin, outlining the connection between regional and localized oceanographic changes.     

Palaeoenvironments of deposition of Neogene laminated diatom mat deposits from the eastern equatorial Pacific from studies of benthic foraminifera (sites 844, 849, 851)

Massive sedimentation of mats of the diatom Thalassiothrix longissima forming laminated diatom mat deposits (LDM) occurred intermittently in the equatorial Pacific throughout the Neogene from at least 15 to 4.8 m.y. ago. The background deposition was otherwise calcareous nannofossil diatom ooze (NO). Benthic foraminifera have been used to reconstruct the benthic environment of deposition and the role of both surface waters (as a source of food) and bottom waters (including their corrosivity) during LDM deposition. Three LDM events were studied: Site 844 (11.4 Ma, early Tortonian), Site 849 (4.8 Ma, early Zanclian and 6.6–6.8 Ma, early Messinian). A control section of NO spanning the 4.8 Ma event was studied from Site 851. In addition, the carbonate high NO immediately preceding the 4.8 Ma event was examined in Site 849. From the foraminiferal evidence it can be shown that the LDM was deposited under conditions of normal oxygenation because infaunal taxa are present throughout and there was an increase in epifaunal taxa such as Cibicides spp. However, there was a reduction in test size probably because only those smaller than 250 μm were able to move through the restricted sediment pore spaces caused by the diatom mat meshwork. The rate of accumulation of tests is highest in LDM interval and may reflect reduced predation from macrofaunal endobenthos. Among the epifaunal taxa, Nuttallides spp. show a decrease in abundance in the LDM and even immediately preceding it. This may be linked to a greater influence of corrosive AABW. Species known to feed opportunistically on phytodetritus (Epistominella exigua and Alabaminella weddellensis) are common in both NO and LDM. The increased relative abundance of A. weddellensis in the LDM may be due to this species being smaller than E. exigua and better able to exploit the food resource within the restrictive mat meshwork. The foraminiferal results corroborate the previous interpretation that preservation of lamination in the LDM is due to the physical exclusion of macro endobenthos rather than oxygen depletion of the bottom waters.     

Sedimentary response to basin inversion: Mid cretaceous-early tertiary pre- to syndeformational deposition at the Areif El Naqa anticline (Sinai, Egypt)

Summary The Areif El Naqa domal anticline in northeastern Sinai is part of the ‘Syrian Arc’ which represents an intraplate orogen that has been formed since the late Cretaceous by inversion of an older half-gaben system as a consequence of the collision of the African and Eurasian plates. The here studied pre- and syn-deformational Upper Albian to Lower Eocene sedimentary succession in the anticline was formed under shallow marine to hemipelagic conditions resulting in predominantly carbonate lithologies with only subordinate siliciclastic intercalations. The depositional history at Areif El Naqa has been reconstructed in terms of sequence stratigraphy on the basis of detailed sedimentological, biostratigraphical, and paleoecological investigations of ten sections including comparisons with age-equivalent successions further north and south as well as published data. Following a late Triassic-early Cretaceous extensional period, tectonically rather quiet conditions prevailed during deposition of the Albian-Turonian successions. Inversion started around the Coniacian. Three main phases of uplift have been determined for the Areif El Naqa anticline on the basis of evidence from lateral facies and thickness changes, local development of pronounced hiatuses, and in comparison to the sequence stratigraphic development in the tectonically quiet region of central east Sinai. The first major compressional phase is interpreted to have taken place in Coniacian-early Santonian times. It is characterized by pronounced facies and thickness changes which were documented in an earlier study byBartov et al. (1980). Nevertheless, inter-regional sea level changes still controlled deposition at Areif El Naqa during this period. The second pulse of tectonic uplift is indicated for the late Campanian-early Maastrichtian. This is based on siliciclastic deposits which are interpreted as having been reworked from older siliciclastic rocks uplifted in the anticlinal core. The third compressional pulse is inferred to be of middle Paleocene to early Eocene age as evidenced by a major hiatus in sections on the northern anticlinal flank. The uplift history at Areif El Naqa has been compared with the tectonic development in other parts of the Syrian Arc and in general seems to reflect major movements which occurred throughout the anticlines of the fold belt.     

On the types of mesozoic archostematan beetles (Insecta, Coleoptera, Archostemata) in the Natural History Museum, London

About 40 type specimens of archostematan beetles from the Jurassic, Lower Cretaceous, and Paleogene of England, named by P. Brodie, J.O. Westwood, C. Giebel, A. Handlirsch, F. Zeuner, P. Whalley, and R. Crowson and stored in the Paleontological Department of the Natural History Museum (London) are redescribed. Nine genera and 11 species are recognized, three genera are assigned to Archostemata for the first time. One new species, Tersus crowsoni (Schizophoridae), is described.     

Bioerosional structures and pseudoborings from Late Jurassic and Late Cretaceous-Paleocene shallow-water carbonates (Northern Calcareous Alps, Austria and SE France) with special reference to cryptobiotic foraminifera

Examples of bioerosional processes (boring patterns) are described from shallow-water limestones of the Late Jurassic Plassen Carbonate Platform (PCP) and the Late Cretaceous to Paleocene Gosau Group of the Northern Calcareous Alps, Austria. Some micro-/macro-borings can be related to distinct ichnotaxa, others are classified in open nomenclature. In the Alpine Late Jurassic, bioerosional structures recorded from clasts in mass-flows allow palaeogeographical conclusions concerning the source areas. In particular, these are borings of the Trypanites-ichnofacies detected from clasts (Barmstein limestones) of the PCP or special type of bored ooids of unknown source areas or restricted autochthonous occurrences. In the Lower Gosau Subgroup, Gastrochaenolites macroborings occur in mobile carbonate clast substrates of shore zone deposits (“Untersberg Marmor”). Different types of borings are recorded from rudist shells and coral skeleton, some of which are referable to the ichnotaxon Entobia produced by endolithic sponges. In the present study, special attention is paid to the occurrences of the cryptobiotic foraminifera Troglotella incrustans Wernli and Fookes in the Late Jurassic and Tauchella endolithica Cherchi and Schroeder in the Late Cretaceous. The latter is so far only known to be from the Early Cenomanian of France and is reported here for the first time from the Late Turonian-Early Coniacian stratigraphic interval where it was found in turbulent carbonate deposits within borings penetrating bivalve shells or coralline algae. The records of cryptobiotic foraminifera from the Northern Calcareous Alps are supplemented by a single finding from the Middle Cenomanian of SE France. A palaeoenvironmental interpretation of the occurrences of the cryptobiotic foraminifera is provided.     

Paleogene terrigenous (flysch) sequences in Etoloakarnania region (W. Greece). Plankton stratigraphy and paleoenvironmental implications

Based on calcareous nannofossils and planktonic foraminifera1 biostratigraphic data from flysch sequences, we give evidence for the paleoenvironmental evolution of Gavrovo and Ionian foreland basins (External Hellenides, Etoloakarnania region). Our data suggest that the onset of clastic sedimentation in both foreland basins in the study area is chronostratigraphically placed at Late Eocene (from 36.2-34.4 Ma; nannofossil biozones NP19-20, planktonic foraminifera biozones P16-17). During the earliest Oligocene (NP21-22 nannofossil biozones/34.4-32.45 Ma), both basins represent restricted accumulation of sediments, mainly composed of clays and silts. The presence of thick flysch deposits, accumulated during Early Oligocene (33.4-30 Ma, nannofossil zone NP23), indicates an increasing rate of sediment supply. The flysch sequences in the Ionian basin are associated with a distal depositional environment, while in the same time the sedimentation in the external part of Gavrovo basin is related to a more proximal environment that is gradually deepening. On the contrary, the internal part of Gavrovo basin is characterised by deep-water facies, deposited in the Early Oligocene. At the end of Early Oligocene and the onset of Late Oligocene (nannofossil zone NP24/30-27.2 Ma, planktonic foraminifera zone P21), the deposition of coarse grained sediments in both basins indicates a shift to shallower depositional environment. The accumulation of fine-grained sediments during Late Oligocene (27.2-23.2 Ma, NP25 nannofossil biozone) in the Ionian basin marks the youngest flysch sediments in the Etoloakarnania region and specifies the time of the Gavrovo nappe emplacement on the Ionian zone. Moreover the emplacement of Pindos nappe on the Gavrovo zone is estimated between 30-27.2 Ma (NP24 biozone) as supported by the nannofossil analysis of samples in front of Pindos thrust.     

Living foraminifera and total populations in salt marsh peat cores: Kelsey Marsh (Clinton, CT) and the Great Marshes (Barnstable, MA)

Common species of intertidal agglutinated benthic foraminifera in salt marshes in Massachusetts and Connecticut live predominantly at the marsh surface and in the topmost sediment (0–2.5 cm), but a considerable part of the fauna lives at depths of 2.5–15 cm. Few specimens are alive at depths of 15–25 cm, with rare individuals alive between 25–50 cm in the sediments. Specimens living between the sediment surface and 25 cm deep occur in all marsh settings, whereas specimens living deeper than 25 cm are restricted to cores from the lower and middle marsh, and have an irregular distribution-with-depth. Lower and middle marsh areas are bioturbated by metazoa, suggesting that living specimens reach these depths at least in part by bioturbation. High-marsh sediments in New England consist of very dense mats of Spartina patents or Distichlis spicata roots and are not bioturbated by metazoa. In this marsh region bioturbation by plant roots and vertical fluid motion may play a role in moving the foraminifera into the sediment. The depth-distribution of living specimens varies with species: living specimens of Trochammina inflata consistently occur at the deepest levels. This suggests that species have differential rates of survival in the sediment, possibly because of differential adaptation to severe dysoxia to anoxia, or because of differing food preferences. There is no simple correlation between depth-in-core and faunal diversity, absolute abundance, and species composition of the assemblages. It is therefore possible to derive a signal of faunal changes and thus the environmental changes that may have caused them from the complex faunal signal of fossil assemblages.     

Larger foraminifera as a substratum for encrusting bryozoans (Late Oligocene,Tethyan Seaway,Iran)

Considering the diversity and abundance of larger foraminifera examined from a wide range of Late Oligocene to Early Miocene palaeoenvironments in the Tethyan Seaway, encrusting bryozoans make extremely little use of their tests as substratum. Significant encrustations by bryozoans were exclusively found on large (ø c. 6 cm), undulating tests of Lepidocyclina spp., on which, however, a remarkable 34 taxa of encrusting bryozoans were recorded. This shallow-water fauna of Chattian age was analyzed in respect of the bryozoan taxa present, colony growth type, and mode of budding, colony size, as well as onset of reproduction. Taxic and morphological similarities between the fossil assemblage and modern faunas encrusting mobile substrata indicate a long history of bryozoans as part of the interstitial habitat, while the tests of certain larger foraminifera may have played a significant role in the evolution of shallow-water bryozoans by providing substrata for encrusting species in otherwise unfavorable environments.     

Applications of nummulitids and other larger benthic foraminifera in depositional environment and sequence stratigraphy: an example from the Eocene deposits in Zagros Basin,SW Iran

The Tale-Zang Formation in Zagros Mountains (south-west Iran) is a Lower to Middle Eocene carbonate sequence. Carbonate sequences of the Tale-Zang Formation consist mainly of large benthic foraminifera (e.g. Nummulites and Alveolina), along with other skeletal and non-skeletal components. Water depth during deposition of the formation was determined based on the variation and types of benthic foraminifera, and other components in different facies. Microfacies analysis led to the recognition of ten microfacies that are related to four facies belts such as tidal flat, lagoon, shoal and open marine. An absence of turbidite deposits, reefal facies, gradual facies changes and widespread tidal flat deposits indicate that the Tale-Zang Formation was deposited in a carbonate ramp environment. Due to the great diversity and abundance of larger benthic foraminifera, this carbonate ramp is referred to as a “foraminifera-dominated carbonate ramp system”. Based on the field observations, microfacies analysis and sequence stratigraphic studies, three third-order sequences in the Langar type section and one third-order sequence in the Kialo section were identified. These depositional sequences have been separated by both type-1 and type-2 sequence boundaries. The transgressive systems tracts of sequences show a gradual upward increase in perforate foraminifera, whereas the highstand systems tracts of sequences contain predominantly imperforate foraminifera.     

A new Late Cretaceous (Maastrichtian) serial planktic foraminifer (Family Heterohelicidae) with early planispiral coil and revision of Spiroplecta Ehrenberg, 1844

A new planktic foraminifer, Hartella harti nov. gen., nov. sp. is described from the Maastrichtian sediments of the Atlantic Ocean. H. harti likely evolved from Fleisherites glabrans (Cushman). Spiroplecta Ehrenberg is reviewed and considered monospecific. The only species assigned to this genus is Spiroplecta americana Ehrenberg, which evolved from Heterohelix globulosa (Ehrenberg). It is demonstrated that the early planispiral coil developed in at least three separate lineages of serial planktic foraminifera in the Late Cretaceous (late Campanian-early Maastrichtian).