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

Impacts of storms on Recent planktic foraminiferal test production and CaCO3 flux in the North Atlantic at 47 °N, 20 °W (JGOFS)

Planktic foraminiferal assemblages are well known to vary in accordance with seasonal fluctuations in ocean properties, periodic reproduction cycles, and variations between water masses. Here we report that storms also can significantly influence foraminiferal assemblages. During the RV Meteor cruise 21 to the Northeast Atlantic Ocean (biotrans area), from March to May 1992, planktic foraminifera were sampled using a multiple opening-closing net. While sampling, two storms with wind forces up to 12 Beaufort caused intensified surface layer mixing with shifts in the depth of the upper ocean mixed-layer from 20–40 m to 170–240 m. Subsequently, planktic foraminiferal growth rates increased, resulting in an elevated quantity of small (100–150 μm) tests (Phase 1). When the wind strength increased a second time, the mixed-layer deepened to a depth below the former position of the pycnocline, and again the abundance of small tests increased (Phase 2). During Phase 2, the weight of calcite in specimens of the productive zone reached its maximum. In the export zone, an associated increase in empty tests occurred with a lag time depending on the test sinking velocity. In the upper export zone, down to 700 m water depth, CaCO3 flux increased from 9.3 to 49.8 mg CaCO3 m−2 d−1 after the first storm and from 8.9 to 19.9 mg CaCO3 m−2d−1 after the second storm. In the 700 to 2500 m depth interval, the flux increased from 5.1 mg CaCO3 m−2 d−1 to about 9.2 mg CaCO, m−2 d−1. Thus, the standing stock of living foraminifera and export of empty tests from the productive zone increased after the storms, leading to pulses of CaCO3 exported from the surface to deep water

Taxonomy, biostratigraphy, and phylogeny of Oligocene Ciperoella n. gen.

Ciperoella Olsson and Hemleben n. gen. is erected for Oligocene spinose species that have a neogloboquadrinid-type wall texture and 4½-5 similarly sized chambers in the final whorl. Four species are recognized as distinct, namely Ciperoella anguliofficinalis (Blow), Ciperoella angulisuturalis (Bolli), Ciperoella ciperoensis (Bolli), and Ciperoella fariasi (Bermúdez). Their taxonomy, phylogeny, and biostratigraphy is discussed

Taxonomy, biostratigraphy, and phylogeny of Oligocene and lower Miocene Globoturborotalita

The taxonomy, phylogeny and biostratigraphy of Oligocene and lower Miocene Globoturborotalita is reviewed. Globoturborotalita is a long-ranging genus appearing in the basal Eocene and still present in modern oceans with one living representative G. rubescens. Species attributed to this genus are generally common and cosmopolitan. The following species are recognized as valid: Globoturborotalita barbula Pearson and Wade, Globoturborotalita bassriverensis Olsson and Hemleben, Globoturborotalita brazieri (Jenkins), Globoturborotalita cancellata (Pessagno), Globoturborotalita connecta (Jenkins), Globoturborotalita eolabiacrassata Spezzaferri and Coxall n. sp., Globoturborotalita euapertura (Jenkins), Globoturborotalita gnaucki (Blow and Banner), Globoturborotalita labiacrassata (Jenkins), Globoturborotalita martini (Blow and Banner), Globoturborotalita occlusa (Blow and Banner), Globoturborotalita ouachitaensis (Howe and Wallace), Globoturborotalita paracancellata Olsson and Hemleben n. sp., Globoturborotalita pseudopraebulloides Olsson and Hemleben n. sp., and Globoturborotalita woodi (Jenkins)

Taxonomy, biostratigraphy, and phylogeny of Oligocene and lower Miocene Dentoglobigerina and Globoquadrina

The taxonomy, phylogeny, and biostratigraphy of Oligocene and lower Miocene Dentoglobigerina and Globoquadrina are reviewed. Because of the discovery of spine holes in various species assigned to these genera, the entire group is now considered to have been fully or sparsely spinose in life and hence part of Family Globigerinidae. One new species, Dentoglobigerina eotripartita Pearson, Wade, and Olsson n. sp., is named. Dentoglobigerina includes forms with and without umbilical teeth and species for which the presence or absence of a tooth is a variable feature. A significant finding has been the triple synonymy of Globigerina tripartita Koch, Globigerina rohri Bolli, and Globoquadrina dehiscens praedehiscens Blow, which greatly simplifies part of the taxonomy. The genus Globoquadrina is restricted to its type species, Globigerina dehiscens Chapman and others. The following species from the time interval of interest are regarded as valid: Dentoglobigerina altispira (Cushman and Jarvis), Dentoglobigerina baroemoenensis (LeRoy), Dentoglobigerina binaiensis (Koch), Dentoglobigerina eotripartita Pearson, Wade, and Olsson n. sp., Dentoglobigerina galavisi (Bermúdez), Dentoglobigerina globosa (Bolli), Dentoglobigerina globularis (Bermúdez), Dentoglobigerina juxtabinaiensis Fox and Wade, Dentoglobigerina larmeui (Akers), Dentoglobigerina prasaepis (Blow), Dentoglobigerina pseudovenezuelana (Blow and Banner), Dentoglobigerina sellii (Borsetti), Dentoglobigerina taci Pearson and Wade, Dentoglobigerina tapuriensis (Blow and Banner), Dentoglobigerina tripartita (Koch), Dentoglobigerina venezuelana (Hedberg), and Globoquadrina dehiscens (Chapman, Parr, and Collins). The genus Dentoglobigerina also comprises other Neogene/Quaternary species not listed, including the living species Dentoglobigerina cf. conglomerata (Schwager)

The δ44Ca-temperature calibration on fossil and cultured Globigerinoides sacculifer: New tool for reconstruction of past sea surface temperatures

We report direct δ44Ca-temperature calibration on cultured and fossil calcite foraminifera, showing that Ca isotopes are potentially a new proxy for past sea surface temperatures (SST). Samples have been analyzed using a 43Ca-48Ca double spike and thermal ionization mass spectrometry (TIMS). In order to avoid species-dependent isotope fractionation we focused our investigations on a single foraminifera species (Globigerinoides sacculifer), which is known to inhabit shallow euphotic waters in tropical and subtropical oceans. Ca isotope measurements were performed on cultured G. sacculifer that grew in seawater kept at temperatures of 19.5°, 26.5°, and 29.5°C. A δ44Ca change of 0.24 ± 0.02 per 1°C is defined by the weighted linear regression through reproduced δ44Ca data of the three temperatures (95% confidence level). Application of this new method to fossil G. sacculifer of an Equatorial East Atlantic sediment core (GeoB1112; 5°46.7′S, 10°45.0′W, 3125 m) indicates that the δ44Ca difference between marine isotope stage 1 (MIS-1) and MIS-2 is 0.71 ± 0.24. According to the current δ44Ca-temperature calibration this value corresponds to a temperature difference between MIS-1 and MIS-2 of ∼3.0 ± 1.0°C

The Red Sea, Coastal Landscapes, and Hominin Dispersals

This chapter provides a critical assessment of environment, landscape and resources in the Red Sea region over the past five million years in relation to archaeological evidence of hominin settlement, and of current hypotheses about the role of the region as a pathway or obstacle to population dispersals between Africa and Asia and the possible significance of coastal colonization. The discussion assesses the impact of factors such as topography and the distribution of resources on land and on the seacoast, taking account of geographical variation and changes in geology, sea levels and palaeoclimate. The merits of northern and southern routes of movement at either end of the Red Sea are compared. All the evidence indicates that there has been no land connection at the southern end since the beginning of the Pliocene period, but that short sea crossings would have been possible at lowest sea-level stands with little or no technical aids. More important than the possibilities of crossing the southern channel is the nature of the resources available in the adjacent coastal zones. There were many climatic episodes wetter than today, and during these periods water draining from the Arabian escarpment provided productive conditions for large mammals and human populations in coastal regions and eastwards into the desert. During drier episodes the coastal region would have provided important refugia both in upland areas and on the emerged shelves exposed by lowered sea level, especially in the southern sector and on both sides of the Red Sea. Marine resources may have offered an added advantage in coastal areas, but evidence for their exploitation is very limited, and their role has been over-exaggerated in hypotheses of coastal colonization

Quantitative estimate of the paleo-Agulhas leakage

The Indian-Atlantic water exchange south of Africa (Agulhas leakage) is a key component of the global ocean circulation. No quantitative estimation of the paleo-Agulhas leakage exists. We quantify the variability in interocean exchange over the past 640,000 years, using planktic foraminiferal assemblage data from two marine sediment records to define an Agulhas leakage efficiency index. We confirm the validity of our new approach with a numerical ocean model that realistically simulates the modern Agulhas leakage changes. Our results suggest that, during the past several glacial-interglacial cycles, the Agulhas leakage varied by ~10 sverdrup and more during major climatic transitions. This lends strong credence to the hypothesis that modifications in the leakage played a key role in changing the overturning circulation to full strength mode. Our results are instrumental for validating and quantifying the contribution of the Indian-Atlantic water leakage to the global climate changes