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Four isolated cervical vertebrae from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Abingdon, Oxfordshire, England are identified as from a pliosaurid plesiosaurian sauropterygian on account of their shortness relative to width and height, their near platycoelous nature and the location of tall rib facets on the centrum body. They are noteworthy for their size, with a maximum width of 269 mm, maximum height of 222 mm and maximum length of 103 mm. Simple scaling and comparisons with cervical vertebrae of Mid Jurassic pliosaurs Peloneustes and Liopleurodon , and the Early Cretaceous Stenorhynchosaurus and Sachicasaurus suggest a total body length of between ~ 9.8 m and 14.4 m for the Abingdon Kimmeridge Clay pliosaur. Likely the true length was towards the higher end of this range. A genus and species cannot be confidently determined on the basis of the described material, but they likely belong to Pliosaurus sp. or a similar animal, for which a precise neck length is not known. We estimate a neck length of 0.77 m for Pliosaurus ? brachyspondylus based on the average cervical lengths provided for specimen CAMSM J.35991. [ABSTRACT FROM AUTHOR]

Shallow-platform settings with marked differences in paleoplatform bottom physiography influence the degree of connection with oceanic waters and overall circulation patterns, even when sharing the same palaeoclimatic conditions. Two Kimmeridgian shallow-marine settings have been explored to test the sensitivity and reliability of carbonate chemostratigraphy to detect such differences. An integrated overview of the obtained elemental trends depicted four major facies, shared along specific stratigraphic intervals of both depositional records. Diagenesis obliterated original geochemical signals only throughout the siliciclastics-rich interval, corresponding to the most landward setting. For the remaining facies, elemental features could be attributed to the differential action of forcing mechanisms operating along the south-Iberian paleomargin during Kimmeridgian times. The highest degree of continental influence can be recognized by a strong relationship between Fe and Mn for the most proximal setting, which fades out along the mixed carbonate-fine siliciclastic rhythmic deposition in more open settings. A characteristic geochemical signature of progressively more positive δ 13C values and significantly higher Sr content is identified for the interval dominated by biogenic sponge buildups. Such a local response is related to local forcing by upwelling in the surroundings of a coral fringe. The geochemical signature of a hydrothermal origin can be clearly differentiated from the influence of mere terrigenous pulses. Accordingly, the decoupling of Fe and Mn along marginal settings is the clue to detecting major events of palaeogeographic restructuring. Observed temporal variations in Mg content along both studied sections are attributed to tectonic activity influencing nearshore/coastal water masses. By integrating chemostratigraphic information and complementary evidence, the palaeoenvironmental mechanisms promoting differentiated sedimentary records along ancient subtropical, shallow, coastal settings can be disentangled. Image 1 • Early Kimmeridgian shallow-marine carbonate deposits along southern Iberia. • Contrasting epicontinental settings are tested. • Diagenesis and palaeoenvironmental significance are evaluated. [ABSTRACT FROM AUTHOR]

The laminated marine mudstones of the Late Jurassic of Kimmeridge, southern England, yield two exceptionally well-preserved partial skeletons of a previously unrecognised species of early batoid. These are described as a new genus and species, Kimmerobatis etchesi gen. et sp. nov. which has a general "guitarfish" bauplan as in all other batoids known from the Jurassic. This species possesses a combination of primitive characters such as centra present within the majority of the synarcual and antorbital cartilages that fail to reach the pectoral skeleton along with more derived characters, such as the lack of fin spines. Until now, little study has been carried out on the affinities of Jurassic batoids, despite their key role in understanding batoid evolution. Results from parsimony and likelihood phylogenetic reconstruction indicates that the whole-bodied Jurassic batoids Spathobatis , Belemnobatis , and Kimmerobatis gen. nov. form their own clade, Spathobatidae, and do not lend support to a monophyletic "Rhinobatidae". Among Jurassic batoids, Kimmerobatis gen. nov. is most derived, but with derived characters being independently acquired compared to modern batoids (e.g. presence of a postpelvic process). The inclusion of whole bodied Jurassic fossils have generated a more resolved hypothesis of batoid evolution throughout the Cretaceous and into the Cenozoic. [ABSTRACT FROM AUTHOR]

Abstract Sediments of Kimmeridgian and Tithonian age are well exposed on the Boulonnais coast of northern France between Equihen and Cap Gris Nez and on the south coast of England at and adjacent to Kimmeridge Bay. Both successions were deposited on a marine shelf and lie within the Subboreal faunal province which enables detailed correlations to be made between them based on ammonite assemblages. They are, however, lithologically markedly different due to their environmental settings: close to a land area in the case of the Boulonnais and within a depositional basin in the case of Kimmeridge. The succession adjacent to the Kimmeridgian-Tithonian boundary exposed in the Boulonnais is highly condensed and laterally variable with more attenuated successions occurring close to the former Anglo-Brabant Massif land area. The boundary occurs at the end of a succession of up to six regressive-transgressive events that onlap the land area. This is in contrast to that at outcrop at Kimmeridge, where the Kimmeridgian-Tithonian boundary is marked by a correlative conformity in an unbroken basinal succession. The cliff and foreshore exposures in the Kimmeridge area provide the only unbroken succession in the Subboreal faunal province of the beds adjacent to the Kimmeridgian-Tithonian boundary. [ABSTRACT FROM AUTHOR]

Investigation of the Upper Callovian to Lower Kimmeridgian microfossils from the Makar’yev reference section (Unzha River, East European Platform) has been carried out. The section is characterized by ammonite debris and abundant associations of benthic and planktic foraminifers. It is a perfect object for stratigraphic and paleoecological researches. The biostratigraphic distribution of foraminifers from the Makar’yev section allows one to identify standard foraminifera zones of the East European Platform, as well as to upgrade some of them. The analysis of vertical and lateral ammonites and foraminiferal distribution, completed with litho stratigraphy, has precised the stratigraphic volume and position of boundaries of several lithological units. An improved stratigraphic scheme for the Kostroma area of the Moscow Depression is proposed. Analysis of the composition, structure, and dynamic changes of the foraminiferal assemblages has been performed. The morphofunctional analysis of foraminiferal genera has for the first time identified how foraminiferal morphogroups differing in their life style and feeding strategy varied with short-term paleoenvironmental changes. These morphogroup changes allow establishing four ecostratigraphic levels. These paleoecological data have been calibrated along with geochemical factors. They have shown a crisis of foraminiferal association during the Late Oxfordian and Early Kimmeridgian. A similar crisis has also been discovered in the north of Siberia, which may be an argument for its global distribution. The analysis of the taxonomic composition and the density of foraminiferal associations, in parallel with the structure of the association, has revealed a succession of transgressive and regressive events during the Late Callovian-Early Kimmeridgian. It allows the typification of each assemblage in relation with each event and underlines the occurrence of second-order sea-level fluctuations (middle part of the Middle Oxfordian and the earliest Kimmeridgian). [ABSTRACT FROM AUTHOR]

The former Blue Circle Cement quarry at Westbury, Wiltshire exposed extensive sections in the lower part of the Kimmeridge Clay Formation, and a continuously cored borehole proved the lowest part of the formation and the underlying succession down to the top of the Oxford Clay Formation. The succession exposed in the quarry between 1979 and 2001 ranged from the Cymodoce to Eudoxus zones, and that in the borehole from the Baylei to Mutabilis zones. Taken together, the quarry and borehole proved the most complete section through the Kimmeridge Clay in a region where much of the formation has never been exposed. The lithological and palaeontological successions proved at Westbury are closely similar to those proved in continuously cored boreholes throughout the English outcrop and subcrop of the formation and can be matched in detail with that exposed in the type area on the Dorset coast. When the quarry was in work the sections yielded a profuse ammonite fauna that enabled the Cymodoce–Mutabilis and Mutabilis–Eudoxus zonal boundaries to be studied in detail. They also yielded a diverse bivalve and vertebrate fauna. [ABSTRACT FROM AUTHOR]

The study explored the taxonomic composition of foraminiferal assemblages from cores sampled in the Sil’ga and Yamal-Tyumen’ facies regions—the southern and southwestern West Siberian sedimentary basin. A complete sequence of biostratons was established for the Callovian-Kimmeridgian sediments of the southwestern West Siberian Lowland and was correlated with the units of the General Stratigraphic Scale. A number of biostratons have been revealed for the south of West Siberia. The biofacies analysis of the foraminiferal assemblages revealed that the Yamal-Tyumen’ facies region belonged to a relatively deep marine environment, far away from the Jurassic Sea littoral zone, in the Callovian through the Kimmeridgian and that the Sil’ga facies region was a relatively shallow marine environment in the Oxfordian through the Middle Volgian. [ABSTRACT FROM AUTHOR]

The Late Jurassic evolution of Boreal and Arctic basins is reflected in the widespread deposition of organic-rich black shales (source rocks). In this connection, the priority should be placed on the development and refinement of zonal schemes for the Upper Jurassic of the Laptev Sea coast based on ammonites, foraminifers, ostracods, dinocysts, and spores and pollen from reference sections as the basis for stratigraphic, paleogeographic, and facies studies. The Upper Jurassic and Lower Cretaceous reference section of interest is located on the left side of the Anabar Bay of the Laptev Sea (Nordvik Peninsula, Urdyuk-Khaya Cape). An uninterrupted and continuous section from Upper Oxfordian to Lower Valanginian is exposed in coastal cliffs and consists mainly of silty clay deposits with abundant macro- and microfossils. A reliable biostratigraphic subdivision of the Upper Jurassic interval of this section was taken as the basis for the assessment of the correlation potential of different fossil groups and subsequent interregional correlations, facies analysis, and detailed paleogeographic reconstructions of the study area. The analysis of variations in the composition of macrobenthic communities and microphytoplankton and terrestrial palynomorph assemblages and the biofacies analysis allowed the reconstruction of the evolution of marine paleoenvironmental settings in the western part of the Anabar–Lena sea and in the terrestrial settings in the adjacent land area of Siberia. [ABSTRACT FROM AUTHOR]

The results of biostratigraphic analysis of foraminiferal assemblages were used to identify a nearly complete succesion of biostratigraphic units in the Callovian-Upper Jurassic section of the Shaim region. The finds of the ammonites from different parts of the Callovian-Volgian sections helped to correlate the identified foraminiferal biostratigraphic units to the General Stratigraphic Scale. Analysis of variations in the taxonomic composition and structure of foraminiferal assemblages allowed refinement of paleontological characteristics of the foraminiferal biostratigraphic units for different facies conditions in the southwest of the West Siberian Basin. [ABSTRACT FROM AUTHOR]

Jurassic strata are widespread through Arctic Siberia and host oil and gas fields. However, in most cases, the geology of such vast areas still remains unexplored, and study of the Jurassic stratigraphy and reconstructions of geologic history are possible only through analysis of sediment cores. In this connection, there is a clear need for detailed studies of microfaunas (foraminifera, ostracods) and palynomorphs (dinocysts, spores, and pollen). The studied reference section of the Upper Jurassic and Lower Cretaceous is located on the left side of Anabar Bay of the Laptev Sea (Nordvik Peninsula, Cape Urdyuk-Khaya). An uninterrupted and continuous section from the Upper Oxfordian to the Lower Valanginian is exposed in coastal cliffs and consists mainly of silty clay deposits with abundant macro- and microfossils. Integrated field studies (biostratigraphy, lithostratigraphy, sedimentology) allow a more detailed characterization of the regional geologic framework. A detailed subdivision of the section is based on the systematic composition of ammonites from Upper Oxfordian and Kimmeridgian deposits. Several foraminiferal zones of the Upper Oxfordian and Lower Volgian are defined, and some of them are denfined for the first time. The distribution of ostracods in the section is analyzed for the first time. The section is also studied using palynological analysis, that results in its detailed subdivision on palynological data and recognition of two sequences of palynostratigraphic units. The integrated stratigraphy is used to establish the precise position of stage and substage boundaries. The continuity of the section is defined based on micropaleontological and palynological data. [ABSTRACT FROM AUTHOR]

Abstract: The Middle Oxfordian to lowermost Upper Kimmeridgian ammonite faunas from northern Central Siberia (Nordvik, Chernokhrebetnaya, and Levaya Boyarka sections) are discussed, giving the basis for distinguishing the ammonite zones based on cardioceratid ammonites of the genus Amoeboceras (Boreal zonation), and, within the Kimmeridgian Stage, faunas–for distinguishing zones based on the aulacostephanid ammonites (Subboreal zonation). The succession of Boreal ammonites is essentially the same as in other areas of the Arctic and NW Europe, but the Subboreal ammonites differ somewhat from those known from NW Europe and Greenland. The Siberian aulacostephanid zones—the Involuta Zone and the Evoluta Zone—are correlated with the Baylei Zone (without its lowermost portion), and the Cymodoce Zone/lowermost part of the Mutabilis Zone (the Askepta Subzone) from NW Europe. The uniform character of the Boreal ammonite faunas in the Arctic makes possible a discussion on their phylogeny during the Late Oxfordian and Kimmeridgian: the succession of particular groups of Amoeboceras species referred to successive subgenera is revealed by the occurrence of well differentiated assemblages of typical normal-sized macro and microconchs, intermittently marked by the occurrence of assemblages of paedomorphic “small-sized microconchs” appearing at some levels preceeding marked evolutionary modifications. Some comments on the paleontology of separate groups of ammonites are also given. These include a discussion on the occurrence of Middle Oxfordian ammonites of the genus Cardioceras in the Nordvik section in relation to the critical review of the paper of Rogov and Wierzbowski (2009) by Nikitenko et al. (2011). The discussion shows that the oldest deposits in the section belong to the Middle Oxfordian, which results in the necessity for some changes in the foraminiferal zonal scheme of Nikitenko et al. (2011). The ammonites of the Pictonia involuta group are distinguished as the new subgenus Mesezhnikovia Wierzbowski and Rogov. [Copyright &y& Elsevier]

Abstract: The Oxfordian–Lower Hauterivian section of the Nordvik Peninsula (northern Central Siberia) is a reference for developing zonal scales for various fossil groups and improving the Boreal zonal standard. In the middle 1950s–late 1980s, it was studied extensively by geologists, stratigraphers, lithologists, and experts on various fossil groups. These studies yielded rich fossil and microfossil collections and a set of parallel zonal scales for various faunal groups. Recently, a new detailed ammonite zonation of the Oxfordian and Kimmeridgian units of this section has been proposed. These results contradict the previous biostratigraphic data on ammonites, foraminifers, and palynomorphs. In the present paper, all the biostratigraphic data on the Oxfordian and Kimmeridgian units of the Nordvik Peninsula (Cape Urdyuk-Khaya) and northern Central Siberia undergo a comprehensive analysis and comparison with those on the Boreal Realm. The ammonite-constrained stratigraphic position of the lower Upper Jurassic in the Cape Urdyuk-Khaya section is interpreted as Upper Oxfordian or Middle Oxfordian. In our view, this difference in the understanding is due to the misidentification of some Oxfordian ammonite forms. The zones based on other fossil groups (foraminifers, dinocysts) which were distinguished in the Upper Oxfordian and Kimmeridgian sections of the Nordvik Peninsula are well traceable circumarctically. Their stratigraphic position in various regions of the Northern Hemisphere is constrained by ammonites and bivalves. However, if we use the last alternative ammonite zonation of this section part, hardly explicable contradictions will appear in interregional foraminiferal and dinocyst correlations. [Copyright &y& Elsevier]

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Abstract: The Kimmeridgian Quebrada del Sapo Formation in the southernmost Neuquén Basin in Argentina represents a succession up to 40 m thick of coarse- to fine-grained fluvial deposits overlain by aeolian deposits. These fluvial–aeolian deposits reflect a significant palaeogeographic change in the basin and are related to a major, tectonically enhanced, relative sea-level fall. The fluvial section is dominated by braided-channel, fine-grained ephemeral, and sheetflood deposits. Aeolian facies are dominated by dune deposits, with minor sandsheet and interdune units. Changes in the nature of both fluvial and aeolian sedimentation within the studied area suggest a regional variability of accommodation/sediment supply conditions. The regional changes of the aeolian succession likely reflect different relative positions within a major erg. In the upwind margin of the erg, a shallow water table promoted water-lain sedimentation in interdune areas, whereas in the central parts of the erg, dry sediment accumulation took place above the regional water-table level. The vertical transition observed in the Quebrada del Sapo Formation, from fluvial to aeolian deposits, may be the result of a local climatic change to drier conditions due to the development of a climatic barrier imposed by growth of a magmatic arc to the west. Alternatively, the vertical transition could be related to a lowering of the water table associated with the compartmentalization of the basin during a period of low sea level. [Copyright &y& Elsevier]

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 Upper Jurassic Lopsiya River sections (Nether-Polar Urals) represent the most complete stratigraphical marine sequence throughout Russia. It is characterized by a continuous succession of Kimmeridgian to Lower Volgian deposits and is defined by rich faunal associations including ammonites, belemnites, and bivalves. The Lopsiya River sections were previously studied in detail with palaeontological, lithological, and litho-geochemical purposes. Furthermore, assemblages rich in palynomorphs and foraminifers were found in the currently studied successions of the Lopsiya River sections. It results the establishment of the uppermost Oxfordian to Lower Volgian foraminiferal zones, as well as the Kimmeridgian dinoflagellate cyst zones and palynological assemblage. Then, the Upper Jurassic dinoflagellate cyst and foraminiferal biostratigraphical zonations have been calibrated against the ammonite zones. Finally, current results on the Lopsiya River sections have been compared with biostratigraphic data of the Kimmeridgian dinoflagellate cyst assemblages from northwestern Europe, Russian Platform, and Arctic Siberia. The studied foraminiferal and dinoflagellate cyst assemblages of the Upper Jurassic successions of the Lopsiya River sections hold high potential of correlations, especially for the Kimmeridgian strata. [ABSTRACT FROM AUTHOR]