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A new phaeodarian species, characterized by the presence of long developed side branches recurved proximally and distally on the surface of its radial tube, was described as Auloscena pleuroclada. This new species was only collected from the layers below the 250 m depth in the Sea of Japan. They have never been found in the shallower layers (above 250 m) of this sea or in other investigated areas. The distribution of the present new species is presumably restricted within the deep water of this area, and this species could be a specific phaeodarian adapted to the deep-sea environment. [ABSTRACT FROM AUTHOR]

The paper ‘The chemical basis of morphogenesis’ [ Phil. Trans. R. Soc. Lond. B 237 , 37–72 (1952)] by Alan Turing remains hugely influential in the development of mathematical biology as a field of research and was his only published work in the area. In this paper I discuss the later development of his ideas as revealed by lesser-known archive material, in particular the draft notes for a paper with the title ‘Outline of development of the Daisy’. These notes show that, in his mathematical work on pattern formation, Turing developed substantial insights that go far beyond Turing (1952) . The model differential equations discussed in his notes are substantially different from those that are the subject of Turing (1952) and present a much more complex mathematical challenge. In taking on this challenge, Turing's work anticipates (i) the description of patterns in terms of modes in Fourier space and their nonlinear interactions, (ii) the construction of the well-known model equation usually ascribed to Swift and Hohenberg, published 23 years after Turing's death, and (iii) the use of symmetry to organise computations of the stability of symmetrical equilibria corresponding to spatial patterns. This paper focuses on Turing's mathematics rather than his intended applications of his theories to phyllotaxis, gastrulation, or the unicellular marine organisms Radiolaria . The paper argues that this archive material shows that Turing encountered and wrestled with many issues that became key mathematical research questions in subsequent decades, showing a level of technical skill that was clearly both ahead of contemporary work, and also independent of it. His legacy in recognising that the formation of patterns can be understood through mathematical models, and that this mathematics could have wide application, could have been far greater than just the single paper of 1952. A revised and substantially extended draft of ‘Outline of development of the Daisy’ is included in the Supplementary material . [ABSTRACT FROM AUTHOR]

The symbiotic dinoflagellate Gymnoxanthella radiolariae T. Yuasa et T. Horiguchi gen. et sp. nov. isolated from polycystine radiolarians is described herein based on light, scanning and transmission electron microscopy as well as molecular phylogenetic analyses of SSU and LSU rDNA sequences. Motile cells of G. radiolariae were obtained in culture, and appeared to be unarmored. The cells were 9.1-11.4 μm long and 5.7-9.4 μm wide, and oval to elongate oval in the ventral view. They possessed an counterclockwise horseshoe-shaped apical groove, a nuclear envelope with vesicular chambers, cingulum displacement with one cingulum width, and the nuclear fibrous connective; all of these are characteristics of Gymnodinium sensu stricto ( Gymnodinium s.s.). Molecular phylogenetic analyses also indicated that G. radiolariae belongs to the clade of Gymnodinium s.s. However, in our molecular phylogenetic trees, G. radiolariae was distantly related to Gymnodinium fuscum, the type species of Gymnodinium. Based on the consistent morphological, genetic, and ecological divergence of our species with the other genera and species of Gymnodinium s.s., we considered it justified to erect a new, separate genus and species G. radiolariae gen. et sp. nov. As for the peridinioid symbiont of radiolarians, Brandtodinium has been erected as a new genus instead of Zooxanthella, but the name Zooxanthella is still valid. Brandtodinium is a junior synonym of Zooxanthella. Our results suggest that at least two dinoflagellate symbiont species, peridinioid Zooxanthella nutricula and gymnodinioid G. radiolariae, exist in radiolarians, and that they may have been mixed and reported as ' Z. nutricula' since the 19th century. [ABSTRACT FROM AUTHOR]

Anatolia's high-pressure metamorphic belts are characterized in part by a Neotethyan stratigraphic succession that includes a mid-Cretaceous hemi-pelagic marble sequence. This unit contains, towards its stratigraphic top, dm-to-m-long radiating calcitic rods forming rosette-like textures. Here, we refer to these features as 'Rosetta Marble'. The remarkable textural similarity of non-metamorphic selenite crystals and radiating calcite rods in the Rosetta Marble strongly suggests that these textures represent pseudomorphs after selenites. Metamorphosed hemi-pelagic limestones, dominated by Rosetta selenite pseudomorphs, are alternating with siliceous meta-sediments containing relictic radiolaria tests. This stratigraphic pattern is indicative of transient phases characterized by evaporites precipitated from basinal brines alternating with non-evaporative hemi-pelagic deposition from normal-marine seawater. The regional distribution of Rosetta Marble exposures over 600 km is indicative of basin-scale evaporitic intervals. High-pressure, low-temperature metamorphism of these rocks is witnessed by Sr-rich (up to 3500 ppm), fibrous calcite pseudomorphs after aragonite and isolated aragonite inclusions in quartz. Peak metamorphic conditions of 1.2 GPa and 300-350 °C are attested by high-Si white mica thermobarometry. The Rosetta Marble case example examines the potential to unravel the complete history from deposition to diagenesis and metamorphism of meta-sedimentary rocks. [ABSTRACT FROM AUTHOR]

The Amasia ophiolite, situated at the northernmost corner of Armenia, is part of the Sevan-Hakari suture zone which links with the Izmir-Ankara-Erzinçan suture zone in northern Turkey. Three new radiolarian assemblages have been extracted from siliceous sedimentary rocks that accumulated on the Amasia ophiolite in an oceanic setting. Two of these assemblages were extracted from red-brownish bedded cherts overlying basaltic lavas; one of these is likely to be middle Oxfordian to early Kimmeridgian in age, while the second correlates with the Berriasian. Similar time-equivalent lava-chert sequences have been dated recently using radiolarians from the Stepanavan, Vedi and Sevan ophiolite units, where they are considered to relate to submarine volcanic activity in the back-arc marginal basin in which the Armenian ophiolites were formed. The third radiolarian assemblage, of late Barremian age, was extracted from a more than 15-m-thick volcaniclastic-chert sequence. The related volcanic activity is likely to have been subaerial and probably relates to the formation of an oceanic volcanic plateau; no Cretaceous subaerial volcanism has been previously recorded in the Lesser Caucasus area. [ABSTRACT FROM AUTHOR]

Data on the distribution of radiolarians and planktonic and benthic foraminifers are obtained for the first time from the Alan-Kyr Section (Coniacian-Campanian), in the central regions of the Crimean Mountains. Radiolarian biostrata, previously established from Ak-Kaya Mountain (central regions of the Crimean Mountains) were traced: Alievium praegallowayi-Crucella plana (upper Coniacian-lower Santonian), Alievium gallowayi-Crucella espartoensis (upper Santonian without the topmost part), and Dictyocephalus (Dictyocryphalus) (?) legumen-Spongosaturninus parvulus (upper part of the upper Santonian). Radiolarians from the Santonian-Campanian boundary beds of the Crimean Mountains are studied for the first time, and Prunobrachium sp. ex gr. crassum-Diacanthocapsa acanthica Beds (uppermost Santonian-lower Campanian) are recognized. Bolivinoides strigillatus Beds (upper Santonian) and Stensioeina pommerana-Anomalinoides (?) insignis Beds (upper part of the upper Santonian-lower part of the lower Campanian) are recognized. Eouvigerina aspera denticulocarinata Beds (middle and upper parts of the lower Campanian) and Angulogavelinella gracilis Beds (upper part of the upper Campanian are recognized on the basis of benthic foraminifers. These beds correspond to the synchronous biostrata of the East European Platform and Mangyshlak. Marginotruncana coronata- Concavatotruncana concavata Beds (Coniacian-upper Santonian), Globotruncanita elevata Beds (terminal Santonian), and Globotruncana arca Beds (lower Campanian) are recognized on the basis of planktonic foraminifers. Radiolarian and planktonic and benthic foraminiferal data agree with one another. The position of the Santonian-Campanian boundary in the Alan-Kyr Section, which is located stratigraphically above the levels of the latest occurrence of Concavatotruncana concavata and representatives of the genus Marginotruncana, is refined, i.e., at the level of the first appearance of Globotruncana arca. A gap in the Middle Campanian-lower part of the upper Campanian is established on the basis of planktonic and benthic foraminifers. The Santonian-Campanian beds of the Alan-Kyr Section, on the basis of planktonic foraminifers and radiolarians, positively correlate with synchronous beds of the Crimean-Caucasian region, and beyond. Benthic foraminifers suggest a connection with the basins of the East European Platform. [ABSTRACT FROM AUTHOR]

A new species, Milax vitukhini sp. nov., from the newly recognized Kimmeridgian-Tithonian radiolarian association from volcanogenic-siliceous-terrigenous rocks of the Borozda Creek Basin (Ust'-Belsky Mountains, Koryak Upland) is described. [ABSTRACT FROM AUTHOR]

The study of total radiolarian content (TRC) and species richness (SR) for radiolarian assemblage as well as absolute and relative abundance of Cycladophora davisiana and abundance of other dominant taxa in the sediment core from the central Okhotsk Sea (OS) over last 90 kyr with previously established age model, position of millennial cycles of climatic changes and records of variations of various productivity proxies and activity of sea ices was carried out. The trends of TRC and SR in the radiolarian assemblage change synchronously on the orbital scale and are mainly determined by variations of paleoproductivity and input organic matter into the water column. In turn, the productivity of the OS depends, to a great extent, on conditions of the sea ice formation and distribution and increases during the warmer MIS 5a, 3 and 1 with a shorter seasonal sea ice cover. Among various productivity proxies considered by us, only Ba-bio reflects, to the fullest extent, the variations of TRC and SR of radiolarians, probably, due to the fact that the accumulation of insoluble barite in sediment depends on degree of organic matter decomposition immediately within the water column and provision of more favorable for radiolarian food. Variations of TRC of radiolarians and their SR on the millennial scale are also controlled by variations of productivity in the photic layer. The millennial productivity minima associated with the cold Greenland/China stadials (GS/CS) resulted in considerable sharp falls in TRC and SR of radiolarians while subsequent increases in productivity during GI/CI caused the smoother growth in TRC and SR of radiolarians. Such a pattern of changes in the species richness and quantity of radiolarians in time is more similar to variations in δ 18 O of stalagmite carbonates from the China caves than δ 18 O of Greenland ice core and, probably, is determined predominantly by variability of the winter monsoons in the East Asia affecting the environment and ice cover of the OS. Changes in absolute abundance (AA) of C. davisiana on the orbital and millennial scales are closer related to changes in TRC of radiolarians determined mainly by variations of the sea productivity. Changes in relative abundance (RA) of C. davisiana in time are slightly different from variations in their absolute abundance as depend also on changes in percentage of other species in the assemblage. [ABSTRACT FROM AUTHOR]

This paper presents first comprehensive record of Pliocene Radiolaria from Leg 119, Site 745 of the Antarctic region. Twenty five samples were taken from two sections, viz. 14H and 15H, from Kerguelen Plateau in the Southern Ocean region. Thirty well preserved species were determined. Diversification and distribution of radiolarians in the sections were examined. On the basis of appearance and disappearance of taxa, one zone, i.e. Upsilon, is recognized, which is equivalent to the earlier established NR5 zone. [ABSTRACT FROM AUTHOR]

We analyzed the genetic structure of the radiolarian morphospecies Larcopyle buetschlii from the surface to deep waters (up to 2000 m) in the Japan Sea using the internal transcribed spacer (ITS) regions of ribosomal RNA genes. Each individual had several ITS variants, but these polymorphisms show no vertical phylogeographic structure, suggesting a single biological species. Its rapid clonal reproduction suggested by high ITS variation likely plays a pivotal role in maintaining its wide vertical distribution. [ABSTRACT FROM AUTHOR]

Phaeodarians are a group of widely distributed marine cercozoans. These plankton organisms can exhibit a large biomass in the environment and are supposed to play an important role in marine ecosystems and in material cycles in the ocean. Accurate knowledge of phaeodarian classification is thus necessary to better understand marine biology, however, phylogenetic information on Phaeodaria is limited. The present study analyzed 18S rDNA sequences encompassing all existing phaeodarian orders, to clarify their phylogenetic relationships and improve their taxonomic classification. The monophyly of Phaeodaria was confirmed and strongly supported by phylogenetic analysis with a larger data set than in previous studies. The phaeodarian clade contained 11 subclades which generally did not correspond to the families and orders of the current classification system. Two families (Challengeriidae and Aulosphaeridae) and two orders (Phaeogromida and Phaeocalpida) are possibly polyphyletic or paraphyletic, and consequently the classification needs to be revised at both the family and order levels by integrative taxonomy approaches. Two morphological criteria, 1) the scleracoma type and 2) its surface structure, could be useful markers at the family level. [ABSTRACT FROM AUTHOR]

Collodaria are ubiquitous and abundant marine radiolarian (Rhizaria) protists. They occur as either large colonies or solitary specimens, and, unlike most radiolarians, some taxa lack silicified structures. Collodarians are known to play an important role in oceanic food webs as both active predators and hosts of symbiotic microalgae, yet very little is known about their diversity and evolution. Taxonomic delineation of collodarians is challenging and only a few species have been genetically characterized. Here we investigated collodarian diversity using phylogenetic analyses of both nuclear small (18S) and large (28S) subunits of the ribosomal DNA, including 124 new sequences from 75 collodarians sampled worldwide. The resulting molecular phylogeny was compared to morphology-based classification. Our analyses distinguished the monophyletic clade of skeleton-less and spicule-bearing Sphaerozoidae from the sister clades Collosphaeridae (skeleton-bearing) and Collophidiidae (skeleton-less), while the Thalassicollidae was not retrieved as a monophyletic clade. Detailed morphological examination with electron microscopy combined with molecular analyses revealed many discrepancies, such as a mix between solitary and colonial species, co-existence of skeleton-less and skeleton-bearing specimens within the Collosphaeridae, as well as complex intraspecific variability in silicified structures. Such observations challenge a morphology-based classification and highlight the pertinence of an integrative taxonomic approach to study collodarian diversity. [ABSTRACT FROM AUTHOR]

During the mid-Pleistocene Transition (MPT), spanning from 0.8 to 1.2 Ma, the prevailing 41 kyr glacial cycles were replaced by longer cycles with a period of ca. 100 kyr. This event was also accompanied by important climate changes, such as the expansion of the Northern Hemisphere Ice Sheet. The impact of the MPT on the Kuroshio Current off southern Japan remains unknown, however, in the absence of a long core covering the period of the MPT. In this area, preservation of calcareous microfossils is poor, but polycystine radiolarians are abundant and well preserved. Therefore, they are an excellent alternative proxy for reconstructing past climate change. Indeed, because numerous studies have examined the geographic distribution of modern radiolarian species, the relationships between several radiolarian assemblage groups (e.g., equatorial to sub-arctic assemblage groups) and climatic conditions are well understood. We examined the impact of the MPT on the Kuroshio Current off the Kii Peninsula, southern Japan, by investigating radiolarian assemblages in deep-sea cores collected during Integrated Ocean Drilling Program Expedition 314/315. We studied the radiolarian assemblages in 293 samples from cores obtained at Site C0001 Holes E and F and Site C0002 Hole D. The age models for these cores, which are based on biostratigraphy and chemostratigraphy, showed that sediments from the period between Marine Isotope Stage (MIS) 15 and MIS 8, which includes the Mid-Brunhes Event, are missing from these cores. However, continuous data are available between MIS 63 (1.82 Ma) and MIS 15 (0.5 Ma). Therefore, using the ecological properties of 11 key radiolarian species, we reconstructed regional paleoceanographic changes between 1.82 and 0.5 Ma. Radiolarian fauna revealed that the relative abundance of Kuroshio and the Central Pacific water taxa (e.g., Didymocyrtis tetrathalamus and the Polysolenia spinosa/lappacea group, respectively) increased drastically during the MPT, possibly indicating a northward shift of the Kuroshio at that time. The relative abundance of Rhizosphaera mediana , an Oyashio/Kuroshio mixed-water species, also increased during this interval. Thus, a southward shift of the Oyashio Current may have occurred synchronously with a northward shift of the Kuroshio during the MPT. [ABSTRACT FROM AUTHOR]

Radiolarian species relative abundances have been estimated for a suite of 88 surface sediment samples obtained from a broad area of the southwest Pacific/Southern Ocean bounded by 10°S to 65°S in latitude, and 145°E to 170°W in longitude. This allowed the documentation of a long environmental gradient (28.8 to − 1.4 °C for mean annual sea-surface temperature, SST), and covered the most important surface oceanographic features in the area, including the Subtropical (STF), Subantarctic (SAF) and Antarctic Polar (APF) Fronts. The most abundant species in the dataset show strong relationships to surface hydrography, examples are: Antarctissa spp. (5% abundance isoline is a good indicator for the average position of the SAF), Colonials (5% isoline approximates the average location of the Tasman Front, between New Zealand and Australia), Dictyocoryne profunda and Tetrapyle octacantha (essentially absent in subantarctic/antarctic waters, and documenting warm-water connections to higher latitudes, being present in the Tasmanian retroflection region and/or on the Campbell Plateau). The Factor Analysis model, with a calibration error of ± 1.3 °C, was based on 93 taxa (of the 243 taxa recognised in this study) and 7 factors/assemblages, which explained 87.4% of the total information contained in the dataset. The first five assemblages are readily interpreted in terms of water masses, oceanographic fronts and regions: Subtropical Water/Tasman Front (Factor 1), Circumpolar Surface Water (Factor 2), Equatorial Pacific (Factor 3), Subantarctic Water/Campbell Plateau (Factor 4), and as a subfactor for Subtropical Water (Factor 5). A canonical correspondence analysis identified sea surface temperature as the main environmental explanatory variable for samples with SST 7 °C–28 °C. Due to the elevated nitrate concentrations in high southern latitude surface waters, nitrate concentration is the main explanatory variable when all samples are considered. In a companion paper, this modern analogue dataset has been applied to relative abundance data from sediment core Y9, in order to reconstruct the SST changes over the last 160 ka at the easternmost boundary of the Campbell Plateau, east of New Zealand. [ABSTRACT FROM AUTHOR]

A fine clastics–siliceous succession exposed at Laem Krabang Phet, approximately 20 km southwest of Klaeng, Rayong area, southeastern Thailand was examined based on lithology, radiolarian biostratigraphy, and geological correlation. In the study section, thinly bedded chert layers are intercalated with black carbonaceous shale, light-colored tuffaceous shale, brown glassy tuff, and quartz-rich sandstone layers. A horizon of the chert in the section yielded poorly preserved radiolarians, however, several forms including Palaeoscenidium cladophorum Deflandre, Stigmosphaerostylus cf. pusilla (Hinde), and Entactiniidae gen. et spp. indet. were identified. This fauna is probably referable to the Middle–Late Devonian. The study section had been assigned to various stratigraphic units, such as Silurian–Devonian or Carboniferous–Permian, due to a poor fossil occurrence. However, the occurrence of the Devonian radiolarians in this study provides concrete evidence for the sedimentary age of the succession, and supports assignment to the Silurian–Devonian. Although the study succession exposed at Laem Krabang Phet is coeval with the Devonian part of the Fang chert, northern Thailand, the lithological assemblage is dissimilar, and the post-Devonian radiolarian chert is absent. These lithological, chronological, and stratigraphic results indicate that the depositional environment of the study section was close to the continental margin, such as a continental slope or rise. [ABSTRACT FROM AUTHOR]

Stratigraphic sections (Kizilca and Kizilca North) in the Tavas nappe, western Taurides, Turkey records the event of carbonate platform drowning in the western Tethyan realm. Our detailed biostratigraphic study of radiolarians and other microfossils places the important temporal constraints on this event and indicates that drowning occured in the geochronological interval from Early Jurassic (Hettangian–Sinemurian) through to Middle Jurassic (early Bathonian). The basal part of the Kizilca section is represented by platform carbonates with abundant benthic foraminifera and algae of Hettangian–Sinemurian to Pliensbachian age. Toward the upper part of the section, the occurrence of brecciated limestones with some ammonites and belemnites reveals that the drowning event began in the Pliensbachian. The first radiolarian assemblages of early–middle to late Aalenian age were obtained from the overlying units characterized by pelagic limestones and chert alternation. Just after the subsidence of the platform, ribbon chert sedimentation began in the late Aalenian, as indicated by the radiolarians. Successively, early–late Bajocian and latest Bajocian–early Bathonian radiolarian assemblages were obtained from overlying chert with mudstone–silicified mudstones. Similar to that observed in the Kizilca section, the Kizilca North section include successively pelagic limestones, pelagic limestone–chert alternation and chert–mudstone alternation of late Aalenian to early–middle Bajocian age according to radiolarian biostratigraphy. All of these observations indicate that a continuous stratigraphy recorded the drowning event without a large gap from Hettangian–Sinemurian to early Bathonian in the Tavas nappe. This drowning event has close similarities with coeval events in other Tethyan realms in terms of mechanism, facies characteristics and fossil assemblages. Therefore, this study can aid correlation studies of the Tavas nappe with the Jurassic paleogeography worldwide. [ABSTRACT FROM AUTHOR]

Sea-surface temperatures (SSTs) based on radiolarian assemblage changes are estimated for the last 160 kyr, from a sediment core (Y9) recovered from Pukaki Saddle, northeast of Campbell Plateau. Site Y9 lies beneath Subantarctic Surface Water (SAW) immediately to the north of the Subantarctic Front (SAF), which in this region is bathymetrically constrained by the edges of Campbell Plateau and defines the northern boundary of the Antarctic Circumpolar Current (ACC). Radiolarian assemblages are characterised by an exceptionally high abundance of the Antarctic to subantarctic species Antarctissa spp. (up to 68%), especially during glacial intervals. SST estimates are derived using Factor Analysis and the Modern Analog Technique. Both methods capture the glacial-interglacial (G-I) pattern. The SST reconstructions show the changing relative influence of distinct water masses during the past G-I cycle, with major temperature variations of the order of 7–9 °C at glacial Terminations. Glacials (marine isotope stages (MIS) 6 and 2) are associated with particularly cool SSTs that are indicative of a more vigorous SAF/ACC and an enhancement of the inflow through Pukaki Saddle and/or frequent development of cold-core eddies at the SAF. By contrast, the influence of warmer waters and relaxation of the ACC during interglacials can be inferred from temperatures slightly warmer (e.g., mid-Holocene) and/or comparable to present day (e.g., MIS 5e). During these intervals, relatively warmer temperatures most likely indicate a higher warm-core eddy activity due to a strengthened Subtropical Front and/or a weakened inflow of cool water through Pukaki Saddle and/or an increased stratification in the Campbell Plateau region. Furthermore, the SST record is characterised by an abrupt warming at ca. 10 kyr (i.e., Termination I), the occurrence of a reversal at Termination I, and a warming event at the end of MIS 4, coinciding with the A4 event in the Byrd ice core. These characteristics, together with the pronounced G-I cycle shown by the SST estimates, suggest that Site Y9 is influenced by major oceanographic changes in the SW Pacific and responds to thermal changes at high southern latitudes. [ABSTRACT FROM AUTHOR]

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Copyright of Revue de Micropaleontologie is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The vertical distribution of radiolarians was investigated using a vertical multiple plankton sampler (100- 0, 250-100, 500-250, and 1000-500m water depths, 62 µm mesh size) at the Northwind Abyssal Plain and southwestern Canada Basin in September 2013. To investigate seasonal variations in the flux of radiolarians in relation to sea ice and water masses, a time-series sediment trap system was moored at Station NAP (75°00' N, 16°200'W; bottom depth 1975 m) in the western Arctic Ocean during October 2010- September 2012. The radiolarian flux was comparable to that in the North Pacific Ocean. Amphimelissa setosa was dominant during the season with open water as well as at the beginning and end of the seasons with sea-ice cover. During the sea-ice-cover season, however, oligotrophic and cold-watertolerant actinommids were dominant, productivity of Radiolaria was lower, and species diversity was greater. These suggest that the dynamics of sea ice are a major factor affecting the productivity, distribution, and composition of the radiolarian fauna. [ABSTRACT FROM AUTHOR]

A comparison of micropaleontological data on the distribution of the Cycladophora davisiana radiolarian species in the surface sediment layer and the Late Quaternary sediments from the Subarctic Pacific and Far East marginal seas allowed conclusions concerning the possible conditions and occurrence of intermediate waters during the last glacial maximum. We used the modern data on the C. davisiana species, which is a micro-paleontological indicator of the cold oxygen-rich upper intermediate water mass, which is now forming only in the Sea of Okhotsk. The high amount of C. davisiana in sediments of the last glacial maximum may point to the possible formation and expansion of the ventilated intermediate water in the most part of the Subarctic paleo-Pacific: the Bering Sea, the Sea of Okhotsk, within the NW Gyre, and in the Gulf of Alaska. [ABSTRACT FROM AUTHOR]

The Hellenides fold-and-thrust range comprises two subparallel ophiolite belts of Triassic to Jurassic age – the external ophiolite belt (e.g., Mirdita, Pindos, Argolis) in the west, and the internal ophiolite belt in the east – broadly separated by the continental crust units of the Korabi–Pelagonian Zone. It is still a matter of debate whether these ophiolites derived from a single ocean (Meliata–Maliac–Vardar) or mark the suture of two distinct oceanic seaways (Pindos and Meliata–Maliac–Vardar). We contribute to the resolution of this controversy by studying the Migdalitsa Ophiolitic Complex in Argolis (Greece), which contains Triassic oceanic basalts and pertains to the external (western) ophiolite belt. Three key areas were mapped and several sites were targeted for structural, biostratigraphic, and paleomagnetic analyses. Radiolarian cherts in primary or tectonic contact with oceanic basalts were dated to the Late Triassic (Carnian–Norian) using radiolarians, and provided paleomagnetic directions of primary origin carried by magnetite and hematite. The derived mean direction was corrected for sedimentary inclination shallowing and yielded a paleolatitude of ~ 22°N that was placed in a broader paleogeographic context by reconstructing Pangea at ~ 225 ± 5 Ma using a recent apparent polar wander path corrected for sedimentary inclination shallowing. The Late Triassic paleogeography of the Tethys Ocean was constrained using additional paleolatitude estimates from the literature, which we checked and corrected (when possible) for sedimentary inclination shallowing. According to our reconstruction, the Meliata–Maliac–Vardar Ocean between Adria – the promontory of Africa – and Europe represents the locus of origin of the Late Triassic Argolis ophiolitic rocks of the external ophiolite belt, presently resting in tectonic contact on the Pindos–Subpelagonian zones, which represent a deep-water trough with no substantial evidence of in situ oceanization in the Triassic. [ABSTRACT FROM AUTHOR]

The reinvestigation of upper Albian and Cenomanian radiolarians from the Albian-Late Cretaceous Kelevudag section of northeastern Azerbaijan described in classical works by Kh.Sh. Aliev revealed the presence of upper Turonian-?lower Coniacian species among their assemblages. The identified radiolarian taxons form several successive assemblages: Dorypyle? anisa-Crolanium triangulare (upper Albian), Patellula spica-Trisyringium echitonicum (Cenomanian), Orbiculiforma quadrata-Pseudodictyomitra pseudomacro-cephala (upper Turonian-?lower Coniacian). It is established that the species Dictyomitra sagitafera Aliev belongs to the genus Pseudodictyomitra. [ABSTRACT FROM AUTHOR]

Copyright of Revue de Micropaleontologie is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revue de Micropaleontologie is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revue de Micropaleontologie is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The diagnosis of the genus Prunobrachium Kozlova (family Prunobrachidae Pessagno) is emended; descriptions of the type species Prunobrachium crassum (Lipman), zonal species P. articulatum (Lipman), and other prunoid radiolarians figured in the studies of R.Kh. Lipman are supplemented. The generic assignment of Prunobrachium ( Spongoprunum) angustum (Lipman, 1952), P. (S.) articulatum (Lipman, 1952), P. (S.) crassum (Lipman, 1952), Prunobrachium ( Amphymenium) sibiricum (Lipman, 1960), Spongurus ( Amphibrachium) concentricus (Lipman 1960), Pseudobrachium ( Amphibrachium) mucronatum (Lipman, 1960), P. ( A.) ornatum (Lipman 1960), and Spongurus ( Amphibrachium) spongiosus (Lipman 1960) is revised. [ABSTRACT FROM AUTHOR]

Biomineralization of radiolarian skeletons is considered. The development of any skeleton is controlled by the previously formed organic matrix, which serves as a cast or mold of the shell to be formed and provides its development as a whole structure through interaction of the organic and mineral skeletal components. Theoretical and experimental investigation of the organic and mineral components of extant foraminiferal and radiolarian skeletons provide a basis for the development of a hypothetical model for skeletal biomineralization. It begins from the formation of small primary calcitic crystallites in the foraminiferal test or appearance of dense primary opal globules in the developing radiolarian skeleton. These particles are then deposited in the organic matrix enclosed in the living cytoplasmic envelope (cytokalymma). These primary biomineral particles are progressively grouped in the hierarchically interrelating ultrastructural skeletal units E, D, C, B, and A. The interaction of the mineral and biogenic factors occurs at five levels: molecular, nano-, ultra-, micro-, and macrolevels. [ABSTRACT FROM AUTHOR]

Questions of radiolarian skeleton fossilization are analyzed. Complete disruption of the primary organic matrix of the skeleton and different lithogenetic conditions, on the one hand, cause disintegration of skeletons into fragments and, on the other hand, facilitate the fusion of adjacent mineral units and realization of the trend of silica towards structural improvement in the successive series of globular opal A → opal CT → low-temperature tridymite → low-temperature quartz. Transformation of opal A into opal CT and quartz is under control of temperature and time. Thus, modifications of SiO in radiolarian skeletons possibly show a response to respective stages of lithogenesis: sedimentogenesis → diagenesis → early catagenesis → late catagenesis. Great attention is paid to pyritization of skeletons under conditions of hydrosulphuric contamination. It is shown that, in the radiolarian skeleton, silica was secondarily replaced by other minerals. [ABSTRACT FROM AUTHOR]

The history of radiolarian evolution from the Early Cambrian to Recent is the history of the development of diverse skeletons, varying in geometry and tending to classical symmetry, including spheres, spheroids, cones, cylinders, and many other intricate shapes, but with indispensable elements of mixed symmetry. Skeletons with mixed symmetry appeared early in the evolution of radiolarians and permanently dominated. However, from the point of view of classical symmetry, these figures are asymmetrical, lacking distinct orderliness. At the same time, they are harmonious in structure rather than shapeless. Classical symmetry is not precisely realized in biological or crystalline objects. Living organisms and minerals are complex in composition and structurally perfect hierarchically organized natural systems. Therefore, radiolarian skeletons should not be likened to crystalline bodies with perfect symmetry. [ABSTRACT FROM AUTHOR]

Radiolarian assemblages of Late Cretaceous age were studied in a carbonate-clastic section from the Cretaceous sedimentary cover that unconformably overlies Triassic sediments of the Jadar Block. According to the identified radiolarian associations, the studied limestone is of Santonian age. Considering the fact that these sediments belong to a broadly defined Turonian-Senonian geologic map unit, the obtained data are important for further more detailed biostratigraphic assignment of Late Cretaceous rocks in Western Serbia. Moreover, the obtained data are very important for interregional correlations. [ABSTRACT FROM AUTHOR]

Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor. [ABSTRACT FROM AUTHOR]

The red-bed deposits in northern Iraq are situated in an active foreland basin adjacent to the Zagros Orogenic Belt, bound to the north by the Iranian plate thrust over the edge of the Arabian plate. The red-bed successions are composed of alternating red and brown silty mudstones, purplish red calcareous siltstone, fine- to coarse-grained pebbly sandstone and conglomerate. The red beds in the current study can be divided into four parts showing a trend of upward coarsening with fine-grained deposits at the top. A detailed petrographic study was carried out on the sandstone units. The clastic rocks consist mainly of calcite cemented litharenite with rock fragments (volcanic, metamorphic and sedimentary), quartz and minor feldspar. The petrographic components reflect the tectonic system in the source area, laterally ranging from a mixed orogenic and magmatic arc in Mawat–Chwarta area to recycled orogenic material rich in sedimentary rock fragments in the Qandel area. The Cretaceous–Palaeogene foreland basin of northern Iraq formed to the southwest of the Zagros Suture Zone and the Sanandaj–Sirjan Zone of western Iran. During Palaeogene time deposition of the red beds was caused by renewed shortening in the thrust sheets overlying the Arabian margin with uplift of radiolarites (Qulqula Formation), resulting in an influx of radiolarian debris in addition to continuing ophiolitic detritus. Mixed sources, including metamorphic, volcanic and sedimentary terranes, were present during deposition of the upper part of the red beds. [ABSTRACT FROM AUTHOR]