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Protandrous sex change (sex change from male to female) is one of the diverse sexual expressions exhibited by bivalves, but its expression in the shell is quite rare. Previous studies on living and fossil astartids suggest a relationship between protandrous sex change and the formation of crenulations on the ventral shell margin at later ontogenetic stages. Here we report the formation of such crenulations in the Early Jurassic astartid Nicaniella rakoveci (Kuhn, 1935) from the Amaltheenton Formation at Buttenheim, Franconia. This is the earliest known record of protandrous hermaphroditism in fossil bivalves, predating previous reports by at least 13 Myr. A principal component analysis of linear size measurements and Fourier shape analysis of the shell outlines revealed that the outline of Nicaniella rakoveci specimens varies from subquadrate to subcircular, but this variation is independent of the presence or absence of crenulations and therefore not associated with sex. Crenulated specimens exhibit a lower height/inflation ratio than non-crenulated ones, suggesting that the protandrous females have more inflated valves than the males. The formation of crenulations was probably related to allocation of resources for reproduction. The most likely function of the crenulations was to increase the internal shell volume in the female stage to accommodate more eggs rather than being an adaptation against predation as often assumed for other bivalves. The formation of crenulations is part of the protandrous life history and probably is controlled by a genetic mechanism that is also responsible for sex change.

Previous stable oxygen isotope records of calcitic fossils (δ18Oshell) from Europe have been interpreted to reflect strong climatic perturbations throughout the Jurassic, but it is unknown whether they reflect global trends because data from other regions are sparse. Here, we use bivalve and brachiopod shells from western Asia and northern Africa to examine seawater temperatures at low latitudes as well as latitudinal temperature gradients in the Middle Jurassic. Our results include the first absolute temperature estimates for most of the study areas and this time interval. Furthermore, we acknowledge a latitudinal gradient in δ18O values of seawater (δ18Osea) that leads to more realistic temperature reconstructions of tropical water temperatures, which were underestimated by earlier methods. Following this approach, δ18Oshell values translate into average equatorial water temperatures during the Middle Jurassic several degrees higher than today (as high as 34–35 °C). Such high temperatures cause environmental stress, probably explaining previously documented low diversities of low-latitudinal ecosystems (e.g., coral reefs) during this time interval. A comparison with literature data raises doubts over whether previously published European temperature curves are truly representative of global patterns. Instead, they might reflect the complex paleogeography of European basins influenced by regional and/or short-term changes in δ18Osea values.

Stable isotope (δ18O, δ13C) analyses were performed on well preserved belemnites, oysters, and rhynchonellid brachiopods from the Middle to Upper Jurassic of the Morondava Basin in southern Madagascar. Both brachiopods and oysters indicate similar average temperatures of 18.7 to 19.3 °C in the Early Callovian, followed by a temperature decrease towards the Middle Oxfordian (13.9 °C) and a minimum in the Early Kimmeridgian (12.3 °C). In contrast, belemnites from the Oxfordian show lower average temperatures of 10.0 °C, which is likely caused by specific conditions for these organisms (e.g., different fractionation or life habits). Additionally, three oysters from the Upper Oxfordian and Lower Kimmeridgian were used for high-resolution stable isotope analyses. The data show seasonal fluctuations of >6 °C around averages between 14.4 and 14.7 °C. Latitudinal temperature gradients for the Callovian and Kimmeridgian are similar to today at the examined low latitudes of the southern hemisphere. The observed cooling of around 5 °C from the Callovian to the Oxfordian/Kimmeridgian can be attributed to a concurrent southward drift of Madagascar during the break-up of Gondwana. Thus, the study underlines the importance of considering palaeogeography in interpreting stable isotope data as well as the potential of detecting and timing palaeogeographic events by using stable isotope analyses.

The Aptian Crato Konservat-Lagerstätte is renowned for its exceptionally preserved fossils in lacustrine laminated limestones. Although previous works on this site include numerous taxonomic studies, its taphonomy remains a subject of debate. Herein, we present new data on the taphonomy of decapod crustaceans preserved in wrinkle laminites, highlighting the role of microbial mats in enhancing fossil preservation. Our results suggest that benthic microorganisms may have promoted protection and organic mineralization of some of the allochthonous to parautochthonous organic remains within the microbial laminites of the Crato lake. Overall, this work provides the first empirical evidence that the preservational pathways of the fossils in the Crato Konservat-Lagerstätte involved microbial mats.

Made available in DSpace on 2019-10-04T12:40:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Petrobras Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The Aptian Romualdo Formation is a siliciclastic-dominated sedimentary unit recording the last marine ingression within the Cretaceous interior basins of northeastern Brazil. At the western margin of the Araripe Basin, rocks of the Romualdo Formation are mainly represented by carbonates resting abruptly over the Proterozoic crystalline basement. Detailed mapping and stratigraphic analysis revealed two stromatolite fields that were described and discussed for the first time. Several bioherms, biostromes and isolated stromatolites characterized by distinct microbialite morphologies associated with echinoid-rich strata have been identified, suggesting that hypersalinity, water depth and hydraulic conditions were the main factors controlling stromatolite morphogenesis. A cm-thick amalgamated bivalve rudstone, resting directly on the basement and representing a shell concentration formed above the fair-weather wave base was also recorded. Based on the regional distribution of the stromatolite types and associated sedimentary fades, we interpret the depositional environment as a local low gradient carbonate ramp deepening to the east. Our data robustly indicated that the western rocky shorelines of the Araripe Basin during the Aptian were populated by microbial mats and stromatolites in a condition analogous to the modern world-famous Hamelin Pool, Shark Bay, Western Australia. Finally, the development of stromatolites and echinoid-bearing microbialites at the western margin of the basin may be correlated with the formation of bakevelliid- and cassiopid-rich shell beds in the upper part of the Romualdo Formation at the eastern margin. (C) 2019 Elsevier B.V. All rights reserved. Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Dept Geol Aplicada, Ave 24A,1515, BR-12506900 Rio Claro, Brazil Friedrich Alexander Univ Erlangen Nurnberg, FG Palaoumwelt, GeoZentrum Nordbayern, Loewenichstr 28, D-91054 Erlangen, Germany Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP, Brazil Univ Reg Cariri, Dept Ciencias Biol, Campus Pimenta 1161, BR-63100000 Crato, Brazil Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Dept Geol Aplicada, Ave 24A,1515, BR-12506900 Rio Claro, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP, Brazil FAPESP: 2016/13214-7 FAPESP: 2017/20803-1 FAPESP: 18/01750-7 Petrobras: 2014/00519-9 CNPq: 444070/2013-1 CNPq: 401039/2013-5 CNPq: 1082 30017/2015-3 CNPq: 152385/2016-9 CNPq: 301294/2018-6

The density of vertebrate fossils on bedding planes is generally very low in the Upper Jurassic plattenkalks forming the Solnhofen fossil Lagerstatte. There are, however, a few bedding planes where large concentrations of the small fis Leptolepides sprattiformis (BLAINVILLE, 1818) occur. The aim of this paper is to analyse and interpret these f sh concentrations from a taphonomic point of view. For this purpose, the taphonomic features of L. sprattiformis concentrations on three large slabs were semi-quantitatively analysed. The concentrations of individuals on bedding planes are explained as recording local mass mortality events caused by tropical storms that, for short intervals, disrupted the pycnocline which separated hypersaline, oxygen-poor to anoxic bottom waters from normal marine surface waters in the Plattenkalk basins. Mass mortality is supported by tetany features such as gaping jaws, hyperextended branchiostegal rays, and splayed f ns, which occur in the majority of the specimens. The generally excellent preservation of the f sh resulted from lack of postmortem f oatation, rapid burial and/or overgrowth by microbial f lms, and quick re-establishment of the pycnocline with inhospitable conditions on the basin floo. The post-mortem concave-arching of the backbones and various displacements of the vertebral column were most likely caused by varying decay resistance of soft tissues and the pressure of decay gases in the body cavities, respectively. The taphonomic analysis of f sh concentrations can provide very detailed palaeoenvironmental information and serves as an independent line of evidence for palaeoenvironmental reconstructions that complements geochemical and sedimentary data.

Fil: Caratelli, Martina. Universidad Nacional de Río Negro, Instituto de Investigación en Paleobiología y Geología. Río Negro; Argentina. Fil: Archuby, Fernando Miguel. Universidad Nacional de Río Negro, Instituto de Investigación en Paleobiología y Geología. Río Negro; Argentina. Fil: Fürsich, Franz. Fachgruppe Paläoumwelt, GeoZentrum Nordbayern der Universität Erlangen-Nürnberg, Loewenichstrasse 28, 91054, Erlangen, Germany Fil: Pignatti, Johannes. Dipartimento di Scienze della Terra, Università di Roma “La Sapienza”, Piazzale Aldo Moro 5, 00185, Roma, Italy Macroids, cm-sized biogenically coated grains made of associations of metazoans or protozoans, accumulate in some high-frequency sedimentary sequences of the upper Hauterivian to lower Barremian Agua de la Mula Member of the Agrio Formation in the Neuquén Basin (northern Patagonia, Argentina). The macroids studied are sub-spheroidal and sub-discoidal in shape, 2e3 cm in diameter and 1-2 cm in height. Each macroid is characterised by a rough, weakly bored surface, encrusted by oysters, serpulids, and small, dome-shaped bryozoan colonies. The growth arrangement consists of locally concentric, agglutinated encrusting foraminifers growing above and around skeletal nuclei. The accumulations of macroids on top of some starvation hemi-sequences during the latest Hauterivian 3rd-order transgressive systems tract help in understanding the palaeoenvironmental conditions at the onset of high-frequency regressions, characterised by low but persistent sedimentation rates and a generally low energy environment. Mineralisation of sand-sized glauconite and apatite grains suggests ephemeral periods of reduced sedimentation or non-deposition. Pyrite framboid size-distribution indicates the upper dysoxic zone with oxygen restrictions. The re-establishment of terrigenous sediment input following transgression promoted eutrophication of the water column. Under such palaeoenvironmental conditions, benthic life was represented mainly by species able to thrive with eutrophicated, oxygen poor waters at the sediment-water interface. This setting excludes activity of borers during the formation of macroids. Macroids result pivotal in understanding palaeoecology of inherent benthic communities and in refining the interpretation of palaeoenvironmental parameters in mixed siliciclastic carbonate ramp systems. Los macróides, gránulos revestidos biogénicamente del tamaño de un centímetro formados por asociaciones de metazoos o protozoos, se acumulan en algunas secuencias sedimentarias de alta frecuencia del Hauteriviano superior al Barremiano inferior del Miembro Agua de la Mula de la Formación Agrio en la Cuenca Neuquina (norte de la Patagonia, Argentina). Los macróides estudiados tienen forma subesferoidal y subdiscoide, de 2 a 3 cm de diámetro y 1-2 cm de altura. Cada macroide se caracteriza por una superficie rugosa, débilmente perforada, incrustada por ostras, serpúlidos y pequeñas colonias de briozoos en forma de cúpula. La disposición de crecimiento consiste en foraminíferos incrustantes aglutinados, localmente concéntricos, que crecen por encima y alrededor de los núcleos esqueléticos. Las acumulaciones de macróides encima de algunas hemi-secuencias de inanición durante el último tracto de sistemas transgresivos de tercer orden del Hauteriviano ayudan a comprender las condiciones paleoambientales al inicio de las regresiones de alta frecuencia, caracterizadas por tasas de sedimentación bajas pero persistentes y un entorno de baja energía en general. La mineralización de granos de glauconita y apatita del tamaño de arena sugiere períodos efímeros de sedimentación reducida o no deposición. La distribución de tamaño framboide de pirita indica la zona disóxica superior con restricciones de oxígeno. El restablecimiento de la entrada de sedimentos terrígenos después de la transgresión promovió la eutrofización de la columna de agua. Bajo tales condiciones paleoambientales, la vida bentónica estuvo representada principalmente por especies capaces de prosperar en aguas eutrofizadas y pobres en oxígeno en la interfase agua-sedimento. Esta configuración excluye la actividad de los barrenadores durante la formación de macroides. Los macroides resultan fundamentales para comprender la paleoecología de las comunidades bénticas inherentes y para refinar la interpretación de los parámetros paleoambientales en sistemas mixtos carbonáticos-siliciclásticos de rampa.

Drill holes provide valuable information about palaeoecological interactions in fossil ecosystems, but the Jurassic drill-hole record is scarce. We report circular drill holes in the infaunal bivalve Eothyasira antiqua(Münster in Goldfuss) from the Pliensbachian grey shales of the Amaltheenton Formation of Franconia, southern Germany. The outcrop of the Amaltheenton Formation at Buttenheim yields a rich bivalve fauna (57 species), which represents a typical soft-bottom community. Eothyasira antiqua, the yet oldest known member of the family Thyasiridae, represents only 1% of the total bivalve specimens from Buttenheim, but shows an exceptionally high frequency of drill holes. With a drilling rate of 81% of the well-preserved articulated specimens, this occurence is unique compared with other drilled bivalve records from the Mesozoic and even from Recent assemblages. The drill holes resemble those of modern naticids with a larger outer opening and are assigned to the ichnospecies Oichnus paraboloides Bromley. Statistical methods show a non-random distribution of the drill holes over the shell surface with a concentration on the central flank. The drill-hole producer was highly efficient in drilling and exhibited a remarkable prey and site-selective behaviour. The drill holes on the moderately deep infaunal Eothyasira suggest that the predator was also infaunal for at least parts of its life and could cope with poorly oxygenated substrate conditions occurring temporarily in the Amaltheenton environment. Drill-hole characteristics point to a gastropod as producer. None of the about 50 gastropod taxa of the Amaltheenton Formation can be associated with the drill holes with certainty, but Hayamia reticulata (Münster) seems to be the most likely candidate. The results of this study support the opinion that drill holes are generally a scarce phenomenon in the Early Jurassic generated by rare, probably highly specialised predators. Preservational biases are considered to have been less important.

The Jurassic Bazeh-Howz Formation is a succession of braided river siliciclastics deposited in an intramontane basin. Three major types of facies, conglomerate, sandstone and shale, have been identified. Conglomerates are mainly monomict and polymict orthoconglomerates. The sandstones are quartzarenites, sublitharenites, feldspathic litharenites and phyllarenites. Fine-grained deposits represent more than 65% of the strata, and commonly alternate rhythmically with siltstone and very fine-grained sandstone. Bulk rock geochemistry suggests felsic, mafic and ophiolite rocks as well as Proterozoic recycled sandstones as the source of the Bazeh-Howz sediments. According to petrographic data, the main tectonic origins of the studied sediments are a recycled orogen, passive margin, magmatic arc basin, rifted continental margin and even a subduction zone. Trace element ratios such as Th-Sc-Zr/10 indicate that the sediments of the Bazeh-Howz Formation are mainly derived from a continental island arc. Also, the La-Th-Sc trace element ratio indicates a continental island-arc origin of the sandstones and shales. The rocks formed in the context of the Early Cimmerian collision in northeastern Iran became part of the rising Cimmerian mountain belt.

The palaeoecology of Spinicaudata, the dominant group of benthic invertebrates in many pre-Cenozoic freshwater environments, remains poorly understood. In analogy with extant taxa, it has been oversimplified and often reduced to shallow, temporary environments characterized by few trophic levels, implying ecological stasis from the Devonian to the Recent. We excavated 43 horizons of the Lower Cretaceous Yixian Formation (Anjiagou and Hengdaozi beds) to evaluate whether spinicaudatan ecology can be simplified to such an extent. Sedimentological evidence suggests general perennial conditions during the excavated lake interval. Based on 33226 specimen counts, we identified three arthropod-dominated macrobenthic associations and two assemblages. Response curves indicate that the spinicaudatan Eosestheria middendorfii was exceptionally tolerant to environmental gradients, followed, in decreasing order, by mayfly larvae, water boatmen and oligochaetes. Many spinicaudatan-yielding layers represent death after reproductive senescence rather than mass-mortality events. Spinicaudatan size varies significantly according to faunal association. A forward stepwise regression model suggests that growth responded to population density and diversity: lower densities and higher diversities triggered fast growth, and vice versa. The proposed strong density effect on carapace size has been corroborated by rearing experiments: as for E.middendorfii, natural log regression provided the best fit for the two extant species Eulimnadia texana and Eocyzicus argillaquus. Hence, E.middendorfii was a tolerant and morphologically variable species adapted to perennial waters and the frequent presence of higher trophic levels. Although there are rare records of extant taxa co-occurring with fish, the described Early Cretaceous environment is commonly not inhabited by extant Spinicaudata.

Made available in DSpace on 2020-12-12T01:44:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Petrobras Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The fossil-rich carbonate deposits of the Aptian Crato Formation, Araripe Basin (Brazil) are one of the main Cretaceous Konservat-Lagerstätten of Gondwana, and have come to fame globally. However, information on fossils from deposits other than the famous laminites of the basal part of the unit is scarce. Herein, we describe the first bivalves of the suborder Silesunionidina Skawina and Dzik, 2011 in the order Unionida Gray, 1854 from South America. The specimens were collected from a 0.3–1-m-thick grey to yellow mudstone interval located 0.3 m above the laminated limestones of the lower part of the Crato Formation at Nova Olinda, State of Ceará. They comprise exquisite composite, internal and external moulds, preserving key anatomical characters. Based on the analysis of muscle scars, hinge and ornamentation, these bivalves are here assigned to a new genus and species, Cratonaia novaolindensis gen. et sp. nov. The presence of a series of small pedal elevator scars linearly arranged on the external wall of the umbonal cavity indicates that this is a member of the suborder Silesunionidina. The new form is the by far youngest representative of this group. Closely related bivalves were previously reported from Triassic deposits of Australia, Africa, Europe and potentially India. Detailed stratigraphic, sedimentological and taphonomic observations indicate that the new taxon thrived in a freshwater lake. The occurrence of Silesunionoidea in the Lower Cretaceous of South America indicates that the condition of the musculature in Mesozoic freshwater mussels needs to be established to assign them confidently at family level. Departamento de Geologia Aplicada Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista/UNESP, Avenida 24-A, Bela Vista, 178 Departamento de Zoologia Instituto de Biociências Universidade Estadual Paulista/UNESP, Distrito de Rubião Junior S/n, 510 GeoZentrum Nordbayern FG Paläoumwelt Friedrich-Alexander-Universität Erlangen-Nürnberg, Loewenichstr 28 Department of Animal Physiology Faculty of Biology University of Warsaw, Ilii Miecznikowa 1 CASP, West Building, Madingley Rise, Madingley Road Departamento de Geologia Aplicada Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista/UNESP, Avenida 24-A, Bela Vista, 178 Departamento de Zoologia Instituto de Biociências Universidade Estadual Paulista/UNESP, Distrito de Rubião Junior S/n, 510 FAPESP: 16/13214-7 FAPESP: 17/20803-1 FAPESP: 17/22036-8 Petrobras: 2014/00519-9 CNPq: 304800/2017-1 CNPq: 401039/2014-5

Thirty Kimmeridgian (Upper Jurassic) ammonite specimens of the genera Torquatisphinctes, Pachysphinctes, Katroliceras, and Indodichotomoceras collected from two horizons in the eastern part of the Kachchh Basin were phenetically classified. First, 23 morphological characters were selected for the analysis. The difference matrix was generated by treating the characters as a binary system (0 or 1) and giving scores between 0 and 2. The dendrogram, prepared using the R program, shows perfect groupings of the different taxa identified earlier through a traditional taxonomic approach. The percentage of shared characters has helped choosing significant characters to be used in distinguishing three major groups and one subgroup, which also validates the visual identification of the ammonite taxa. Categorization of the ammonites was also subjected to a Mann-Whitney U test to verify the results. Overall, the dendrogram depicted three distinct clusters, the Torquatisphinctes, Pachysphinctes, and Katroliceras groups. The specimens of Indodichotomoceras (designated the Indodichotomoceras subgroup) were clustered within the Torquatisphinctes group potentially because of their biplicate ornamentation and presence of constrictions. However, the Indodichotomoceras subgroup maintained its identity because of the thickness of the primary and secondary ribs.

A total of 93 surface sediment samples were collected to analyze the environmental factors constraining the foraminiferal distribution pattern in the southern South China Sea (SCS). Species distributions and stable isotopic compositions were combined to reveal the controlling factors, such as depth, salinity, substrate, runoff, currents, and cold seep activities. Water depth is the dominant factor controlling both assemblage composition and δ18O of benthic foraminiferal tests. The 1000 m isobath separates the sites into two clusters (Cluster A and B), which are dominated by deep-water species and shallow-water species, respectively. The sites in the deep-water zone (Cluster A) are characterized by lower absolute abundances, species richness and Shannon Index values (a measure of diversity), and higher proportions of planktonic foraminifers compared with the sites in the shallow-water zone (Cluster B). Increasing proportions of agglutinated tests with depth and rapidly decreasing proportions of planktonic foraminifera in the Nansha Trough Basin provide evidence of calcium dissolution occurring at a depth corresponding with previous reports. Oxygen stable isotopes (δ18OB) of benthic foraminifera become more positive with depth only up to 1000 m and remain constant beyond. Differences in the proportion of agglutinated and porcelaneous tests in the shallow-water zone suggest that terrestrial runoff from nearby river systems (Mekong River and northern Borneo rivers) and seasonal surface currents (SCS Southern Cyclonic Gyre and SCS Southern Anticyclonic Gyre) jointly influence the distribution patterns of foraminifera in the study area. Enrichment of planktonic δ18O is a response to cold waters brought by the SCS southern cyclonic gyre during winter. An upwelling current (Winter Natuna Off-Shelf Current) containing higher amounts of organic matter/nutrients contributes to the depleted δ13C of planktonic foraminifera and to the abnormal abundance of foraminifera at the sites within its area of influence. The dominance of the foraminifer Melonis barleeanus at sites belonging to Subcluster A1 and the stable isotope compositions of benthic foraminifera (δ18O > 0, δ13C

Nineteen late Albian ammonite taxa and one nautiloid species belonging to eight genera and four families are systematically described from reddish coarse-grained bioclastic packstones to rudstones of the Grab well section (Kosmaj Mountain), Vardar Zone of central Serbia. Among the identified taxa, the nautiloid Eutrephoceras cf. clementianum (d’Orbigny, 1840) and seven ammonite taxa, Tetragonites rectangularis Wiedmann, 1962, Puzosia provincialis (Parona and Bonarelli, 1897), Bhimaites cf. pinguis (Crick, 1907), Beudanticeras (Beudanticeras) cf. beudanti (Brongniart, 1822), Hysteroceras cf. pseudocornutum Spath, 1934, Mortoniceras (Subschloenbachia) rostratum (J. Sowerby, 1817), and M. (S.) cf. perinflatum (Spath, 1922) are recorded for the first time from Serbia. The identified taxa are typical representatives of the Tethyan faunal province. Ammonite taxa provide the first reliable biostratigraphic dating of the Grab well section of central Serbia. The reddish coarse-grained bioclastic packstones to rudstones (a 0.5-m-thick lens) belong to the upper Albian, which is proven by ammonites of the uppermost Albian Mortoniceras rostratum and M. perinflatum zones and the early late Albian brancoceratines Hysteroceras orbignyi (Spath, 1922), H. choffati Spath, 1925, and H. varicosum (J. de C. Sowerby, 1824), which are equivalent to the M. pricei, M. inflatum, and M. fallax zones. The overlying 3.5 m of sandy packstones are assigned to the earliest Cenomanian based on the brachiopods Capillithyris capillata (d’Archiac, 1847) and Terebrirostra lyra (J. Sowerby, 1816), which characterize the lowermost Cenomanian Mantelliceras mantelli Zone. The upper part of the Grab well section (20 m in bedded silty marlstones and marly siltstones) is assigned to lower middle Cenomanian based on the presence of the Turrilites costatus Subzone.

The Lower Jurassic Ab-Haji Formation consists of siliciclastic strata which are widespread and superbly exposed across the Tabas and Lut blocks of east-central Iran. The formation records the geodynamic history of central Iran during the Early Jurassic in the aftermath of the main Cimmerian event (near the Triassic–Jurassic boundary) through its sedimentary facies and stratigraphic architecture and allows palaeogeographic and palaeoenvironmental reconstructions. We measured and studied three well-exposed outcrop sections and identified lithofacies and facies associations (fluvial plain, delta plain, delta front, prodelta, and shallow-marine siliciclastic shelf). The integration of all geological, stratigraphic, and sedimentological data shows a west-to-east continental-to-marine gradient within the Ab-Haji Formation. Based on thickness variations, lateral facies changes, palaeocurrent patterns, and changes in the nature of the basal contact of the Ab-Haji Formation on the Tabas and Lut blocks, we locate the fault-bounded Yazd Block in the west and the Shotori Swell at the eastern edge of the Tabas Block as provenance regions. The pattern of thickness variations, rapid east–west facies changes, and provenance is best explained by a tectonic model invoking large tilted fault blocks in an extensional basin. The basal unit shows distinct increase in grain size at the base of the Ab-Haji Formation, similar to the Shemshak Group of the Alborz Mountains (the base of the Alasht Formation) and the non-marine time-equivalent succession of the Binalud Mountains of northeastern Iran. This grain size pattern may have been caused by rapid source area uplift due to slab break-off of the subducted Iran plate in the course of the Cimmerian collision in east-central Iran.

Made available in DSpace on 2018-12-11T17:13:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-08-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Petrobras Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Geologic events related to the opening of the South Atlantic Ocean deeply influenced the sedimentary record of the Araripe Basin. As consequence, upper stratigraphic units of the basin record a marine ingression in northeastern Brazil during the late Aptian. The timing and stratigraphic architecture of these units are crucial to understand the paleogeography of Gondwana and how the proto-Atlantic Ocean reached interior NE Brazil during the early Cretaceous. This marine ingression is recorded in the Araripe Basin as the Romualdo Formation, characterized by a transgressive-regressive cycle bounded by two regional unconformities. In the eastern part of the basin, the Romualdo depositional sequence comprises coastal alluvial and tide-dominated deposits followed by marine transgressive facies characterized by two fossil-rich intervals: a lower interval of black shales with fossil-rich carbonate concretions (Konservat-Lagerstätten) and an upper level with mollusk-dominated shell beds and shelly limestones. Following the marine ingression, an incomplete regressive succession of marginal-marine facies records the return of continental environments to the basin. The stratigraphic framework based on the correlation of several sections defines a transgressive-regressive cycle with depositional dip towards southeast, decreasing in thickness towards northwest, and with source areas located at the northern side of the basin. The facies-cycle wedge-geometry, together with paleocurrent data, indicates a coastal onlap towards NNW. Therefore, contrary to several paleogeographic scenarios previously proposed, the marine ingression would have reached the western parts of the Araripe Basin from the SSE. Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista - Unesp, Avenida 24A, 1515 Curso de Geologia Instituto de Geografia Universidade Federal de Uberlândia, Rodovia LMG 746, Km 1 Departamento de Zoologia Instituto de Biociências Universidade Estadual Paulista - Unesp Distrito de Rubião Júnior GeoZentrum Nordbayern FG Paläoumwelt Friedrich-Alexander-Universität Erlangen-Nürnberg, Loewenichstr 28 Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista - Unesp, Avenida 24A, 1515 Departamento de Zoologia Instituto de Biociências Universidade Estadual Paulista - Unesp Distrito de Rubião Júnior FAPESP: 2004/15786-0 Petrobras: 2014/00519-9 FAPESP: 2014/27337-8 CNPq: 401039/2014-5

The Jurassic succession of Gangta Bet in the Kachchh basin of western India comprises around 130 m of mostly siliciclastic rocks. The strata belong to the Gangta Member of the Gadhada Formation and are herein sub-divided into four units: the Gangta sandstone beds, the lower silty sandstone beds, the upper silty sandstone beds, and the Gangta ammonite beds. These units can be separated by three marker horizons: the Brachiopod bed, the Gangta Conglomerate Bed, and the Gervillella Bed. Ammonites indicate an Oxfordian age for the upper half of the succession, but the scarcity of identifiable fossils in its basal part so far prevented precise biostratigraphic assignments. The shallow-water sediments can be interpreted as parasequences as a result of minor sea-level changes. Deposition took place close to the palaeo-coastline at water depths around the fair-weather wave-base.

The nuculanid bivalveCostinuculana magharensisnew genus new species is described from the middle to upper Bathonian Kehailia Formation of Gebel Maghara, North Sinai, Egypt.Costinuculanadiffers from other genera of the family Nuculanidae by the presence of opisthocline ribs along the rostrum. These ribs are variable in shape and size, straight to folded posteriorly, bifurcate ventrally and occasionally postero-dorsally, and cover an area~45% of the total valve length from the posterior end. The life position ofC.magharensisn. gen. n. sp. is reconstructed on the basis of a functional interpretation of its morphology and by comparison with closely related Recent forms. The asymmetrical commarginal ribs facilitated the burrowing process. The posterior oblique ribs are asymmetrical in cross-section with a steeply concave side in the burrowing direction and slightly convex side in the opposite direction. They probably kept the bivalve in a stable position once the desired depth had been reached. The thick oblique ribs probably also increased the strength of the rostrum and offered resistance against durophagous predators, being presumably partly exposed above the sediment-water interface. Based on the associated fauna,Costinuculanan. gen. lived in a low-energy environment characterized by a fine-grained, soft substrate.

Stable isotope (δ 18 O, δ 13 C) analyses of brachiopod and oyster shells from the Gebel Maghara, Egypt, were used to reconstruct the first detailed dataset on peri-equatorial water temperatures during the Middle to Late Jurassic. Throughout this time interval, temperatures remained relatively constant around an average of 25.7 °C. Slightly warmer conditions existed in the Early Bathonian (~ 27.0 °C), while the Kimmeridgian shows the lowest temperatures (~ 24.3 °C). As expected for a tropical palaeolatitude, the seasonality was very low ( 18 O value of seawater).

Made available in DSpace on 2020-12-12T02:17:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Petrobras Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Two new taxa of freshwater mussels (Bivalvia: Unionida) from the Aptian Crato Formation of the Araripe Basin, NE Brazil, are described. The fossil bivalves are confined to 30- to 130-cm-thick bioturbated mudstones overlying the fossil-rich laminated limestones of the Crato Formation Konservat-Lagerstätte. Individuals are often preserved with closed or splayed articulated valves, some of them potentially in life position, forming an autochthonous to parautochthonous assemblage. Monginellopsis bellaradiata nov. gen., nov. sp. shares key characters with the Trigonioidoidea: (i) the anterior pedal retractor muscle scar is clearly separated from the anterior adductor muscle scar; (ii) the shell has fold-like radial ribs on the posterior half; (iii) a right valve anterior tooth has a striated facet. Araripenaia elliptica nov. gen., nov. sp. is the most abundant and widely distributed unionid of the Crato Formation. Its ornament of anterior inverted V-shaped riblets, and central and posterior radial and sub-radial riblets resembles modern and fossil Hyriidae from the Americas, but also Trigonioidoidea from Eurasia. Its dentition of two smooth anterior pseudocardinals and two smooth posterior laterals in each valve provides no further clues for systematic assignment; muscle scars are not preserved. Assignment to the Hyriidae would make Araripenaia the oldest member of this family known from South America. Moreover, this bivalve assemblage of trigonioidoidids, hyriids, and previously reported silesunionoids suggests palaeobiogeographic links to other areas in both Gondwana and Laurasia. Departamento de Geologia Aplicada Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista/UNESP, Avenida 24-A 1515 Instituto de Biociências Universidade Estadual Paulista/UNESP, Distrito de Rubião Junior s/n, 510 Instituto Lamir Universidade Federal do Paraná Setor de Ciências da Terra Centro Politécnico, Av. Cel. Francisco H. dos Santos, 100, Jardim das Américas GeoZentrum Nordbayern FG Paläoumwelt Friedrich-Alexander-Universität Erlangen-Nürnberg, Loewenichstr 28 Department of Animal Physiology Faculty of Biology University of Warsaw, Ilii Miecznikowa 1 CASP West Building, Madingley Rise, Madingley Road Departamento de Geologia Aplicada Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista/UNESP, Avenida 24-A 1515 Instituto de Biociências Universidade Estadual Paulista/UNESP, Distrito de Rubião Junior s/n, 510 FAPESP: 16/13214-7 FAPESP: 17/20803-1 FAPESP: 17/22036-8 FAPESP: 18/01750-7 Petrobras: 2014/00519-9 CNPq: 304800/2017-1 CNPq: 401039/2014-5

The stable isotope (δ13C, δ18O) composition of a collection of Lower Jurassic brachiopods and oysters from the Andean Basin of northern Chile was analyzed. The results allow the first reconstruction of absolute water temperatures for several ammonite zones in the Lower Jurassic of South America. The temperature record starts with comparatively high values in the Late Sinemurian (average: 27.0 °C; Raricostatum Zone). Just before the Sinemurian–Pliensbachian transition, temperatures dropped to an average of 24.3 °C. The lowest temperature value in the dataset was recorded for a brachiopod shell of the latest Pliensbachian Spinatum Zone (19.6 °C). No data are available for the Early Toarcian, but results for the late Toarcian show again comparatively warm conditions (average: 24.4 °C; Thouarsense–Levesquei zones). Even though more material and analyses are necessary to corroborate the recorded temperatures, the present dataset seems to indicate the global nature of the Late Pliensbachian Cooling Event. In contrast, the global warming during the Toarcian Oceanic Anoxic Event has not been recorded due to a lack of Early Toarcian material. The δ13C record of brachiopods and oysters documents a gradual increase in values representing background conditions. Oyster shells were used for high-resolution stable isotope analyses and show seasonal temperature fluctuations over a period of around 3 years in the life time of the bivalves. If explained only by temperatures, the δ18O values point to a minimum estimate for the seasonality in the late Toarcian of slightly more than 3 °C.

Made available in DSpace on 2019-10-06T16:10:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-01 Petrobras Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The Cretaceous (upper Aptian) Romualdo Formation of the Araripe Basin, northeastern Brazil, is a marine-influenced, predominantly fine-grained siliciclastic unit. In the eastern part of the basin, it corresponds to a depositional sequence composed of two transgressive-regressive cycles. Low-diversity benthic macrofaunas document high-stress conditions. Their palaeoecological and taphonomic analysis allows for the detailed reconstruction of the palaeoenvironments and of the temporal changes in the palaeoecosystem. The transgressive part of the lower cycle is a black shale with calcareous concretions that contain excellently preserved fishes and other vertebrates (the famous “Santana fossils”), but apart from abundant ostracods and rare decapod crustaceans, benthic faunal elements are very rare due to anoxic to dysoxic conditions. A low-diversity parautochthonous molluscan fauna of small bivalves and gastropods records fluctuating dysoxic conditions during early regression. Towards the top of the measured sections (late regression), thin gastropod shell beds become conspicuous. At the top of the sections decimetre-thick shell concentrations show signs of reworking and a greater marine influence (transgressive part of the upper cycle). The distribution pattern of three benthic associations and two assemblages is almost equally shaped by three environmental parameters: The low overall species diversity, small size of the fauna, and the lack of stenohaline elements suggest lowered and fluctuating salinity conditions. Fluctuating redox conditions with anoxia to dysoxia, identified especially in the lower parts of the succession, and substrate were the other two factors shaping the faunal distribution. The late Aptian sedimentary and faunal history of the eastern part of the basin indicates restricted marine influence, coupled with increasing freshwater input during phases of sea-level lowstand, and low-energy conditions offshore, which led to widespread anoxia, especially in the lower part of the formation. Thus, palaeoecological analyses are an excellent tool to disentangle the various environmental parameters that shaped the palaeoenvironments of the basin, to understand more closely its Fossil-Lagerstätten, and to corroborate and fine-tune the sequence stratigraphic framework. GeoZentrum Nordbayern FG Paläoumwelt Friedrich-Alexander-Universität Erlangen-Nürnberg, Loewenichstr 28 Universidade Federal do Amazonas ICE - Instituto de Ciências Exatas Avenida Rodrigo Otávio, Japiim Instituto de Biociências Departamento de Zoologia Universidade Estadual Paulista/UNESP, Distrito de Rubião Junior s/n, 510 Institut für Geologische Wissenschaften Fachrichtung Paläontologie Freie Universität Berlin, Malteserstraße 74-100 Curso de Geologia Instituto de Geografia Universidade Federal de Uberlândia, Rodovia LMG 746, Km 1 Instituto de Geociências e Ciências Exatas Departamento de Geologia Aplicada Universidade Estadual Paulista/UNESP, Avenida 24-A, Bela Vista, 178 Instituto de Biociências Departamento de Zoologia Universidade Estadual Paulista/UNESP, Distrito de Rubião Junior s/n, 510 Instituto de Geociências e Ciências Exatas Departamento de Geologia Aplicada Universidade Estadual Paulista/UNESP, Avenida 24-A, Bela Vista, 178 Petrobras: 0050.0023165.06.6 CNPq: 152385/2016-9 FAPESP: 2014/27337-8 FAPESP: 2017/20803-1 CNPq: 30017/2015-3 CNPq: 401039/2014-5 CNPq: 444070/2014-1

The 2-m-thick Wood-Log Bed is a highly ferruginous Middle Oxfordian rock unit exposed in the dry bed of the river Tramau in the Wagad Uplift of the eastern Kachchh Basin, western India, and composed of several layers. The bed contains, at several levels, permineralised conifer wood logs, seeds (Carpolites), cones (Araucarites), leaves (Brachyphyllum, Podozamites), possible bennettitalean flowers (?Williamsonia), and abundant wood debris in a poorly sorted muddy sandstone with scattered coarse quartz grains. The wood concentration is interpreted as the result of episodic flash floods in the hinterland situated in the east. Associated with the wood fossils are abundant ammonites which, together with the ferruginous nature of the sediment, point to offshore sediment starvation. Decay of the plant material might have led to widespread anoxia at the sea floor which restricted the benthic macrofauna for much of the time. Thus, the Wood-Log Bed is the product of two processes, episodic flash floods and sediment starvation. Signs of these processes can be seen in age-equivalent sediments throughout the Kachchh Basin.

Clam shrimps have been recognized as a key group for the study of reproductive system evolution, owing to the diversity of sexual systems in extant members. However, there are comparatively little data on fossil taxa. In this study, we reveal the sexual system of the Early Cretaceous clam shrimp Eosestheria middendorfii (Yixian Formation, China). This is the first study that restricts the analysis to a single cohort, minimizing the otherwise considerable impact of ecophenotypic variation within this species. In addition, the presence of egg clutches, which identifies some individuals as either female or hermaphroditic, serves as an independent indicator for sex prior to the statistical treatment of the data. Obligate sexuality (‘dioecy’) is the inferred reproductive system for E. middendorfii and sexual dimorphism accounts for about 10% of the adult shape variation. Carapace shape variation resulting from malformation and deformation is more pronounced than the underlying sexual dimorphism. Subtle sexual dimorphism, smaller and slightly more elongate females, lateral egg clutches, and egg diameters of about 140 μm indicate that E. middendorfii is closely allied with the extant family Cyzicidae.

A 44 cm long trackway from the Kimmeridgian-Tithonian of the western Kachchh Basin represents the first evidence of the occurrence of members of the order Xiphosura in the Jurassic of India. The track consists of the imprints of the legs and the tail spine of a 36–44 cm long limulid and can be assigned to the ichnogenus Kouphichnium Nopsca, 1923. It was formed in a soft, silty to fine sandy substrate below the storm wave-base and preserved as a hyporelief at the base of a thin sandstone bed deposited by storm-induced currents. Eight different types of xiphosuran behaviour are known to be preserved as trace fossils: “swimming”, running, walking, crawling, mating, dying, ploughing, and resting. The present trackway from the Jurassic of India represents crawling, i.e., comparatively slow locomotion (Repichnia).

Bivalves are comparatively rare elements of the benthic faunas of Jurassic and Early Cretaceous lakes of northeastern China. In the past, Arguniella and Sphaerium have been regarded as belonging to the communities that populated the offshore areas of lake Sihetun, represented by the Lower Cretaceous Yixian Formation of western Liaoning. A detailed biostratinomic analysis of these bivalves suggests, however, that they were introduced from marginal lake habitats where they were reworked by storms and occasionally were transported in suspension offshore. Some of these bivalves were dead and settled on the lake floor as single valves or articulated but opened valves (butterfly position). Others were transported alive but died on their arrival at the bottom due to inimical conditions caused by reduced oxygen levels. A similar interpretation is given for articulated valves of Ferganoconcha in thinly bedded siltstones of the Jurassic Daohugou Fossil Beds of Inner Mongolia, which were also carried alive by hyperpycnal flows to their burial site where they died due to lack of oxygen.

The Campanian-Maastrichtian Duwi Formation in the Eastern Desert of Egypt is an economic-rich part of the Middle East phosphorite belt, which has been formed during an extensive high-productivity and anoxic episode in the southern Tethys. To understand the consequences of these environmental conditions on the paleo-ecosystems, the sediments and the benthic macrofauna was analyzed. Although the macrobenthic elements are poorly represented throughout the studied sections, four monospecific biostromes were recognized. They included two Ambigostrea oyster biostromes, which have developed under high-energy and fully aerated environments above the storm wave-base. In contrast, the heterodont bivalves Integricardium and Aphrodina biostromes were deposited under mesotrophic, low-energy, and dysoxic regimes. Shell orientation, shell size-frequency, and multivariate analysis of other taphonomic features indicated that one of two Ambigostra biostromes were partially generated by waves and/or storms (i.e. parabiostromes), while the other one is mostly in situ (i.e. autoparabiostromes). In contrast, the heterodont biostromes are intrinsic autochthonous concentrations (autobiostromes). The link between occurrences of biostromes and cyclicity of deposits suggests a clear association to sea-level fluctuations. The autobiostromes dominating the maximum-flooding and early highstand intervals and were differentiated from the parabiostromes, which formed by physical instead of biologic agents during initial transgressions or late highstand. The palaeo-ecosystem was reconstructed and the environmental factors behind the biostromes were identified; the monospecific nature of the biostromes is interpreted to be a consequence of high-stress environment (e.g., high productivity and associated anoxia). The global climate during the Campanian-Maastrichtian, sea level fluctuations, and physiography influenced salinity and oxygen levels and played the pivotal role in the formation of the monospecific biostromes of the Duwi Formation.

Biostratigraphy of ammonite, inoceramid and orbitolinid foraminifer faunas from the mid-Cretaceous (Aptian–Turonian) succession at the eastern border of the Anarak Metamorphic Complex, a basement uplift in the north-western part of Central Iran, helped to understand complex lithostratigraphic patterns, to trace tectonic unconformities and to reconstruct the geodynamic significance of the succession. The basal continental Noqreh Formation can only be dated by stratigraphic superposition as pre-late early Aptian. An orbitolinid assemblage in the overlying shallow-marine Shah-Kuh Formation indicates a latest early Aptian age. The lower member of the overlying Bazyab Formation documents a considerable deepening in the early late Aptian (Epicheloniceras subnodosocostatum Zone). The boundary to the middle member of the Bazyab Formation is a conspicuous sedimentary unconformity, separating marly offshore strata below from shallow-marine, bioclastic sandstone above. The upper part of the middle member yielded ammonites of the upper lower Albian Douvilleiceras mammillatum Zone. In the upper member of the Bazyab Formation, ammonites of the upper Albian Mortoniceras rostratum Zone have been found. The base of the overlying Debarsu Formation is of earliest Cenomanian age (Mantelliceras mantelli Zone, Neostlingoceras carcitanense Subzone) and lower Cenomanian shallow-marine limestones range up to an intra-formational unconformity below the upper marl member of the formation, yielding early Turonian inoceramid bivalves and ammonites in the lower part. The Debarsu Formation is truncated along a major regional unconformity at the base of the Haftoman Formation. The erosional episode is correlated to a Coniacian tectonic event but further studies are needed to fully understand its geodynamic significance.

A set of two to three prominent hardgrounds can be traced for more than 40 km from east to west within the Jurassic succession of the Jaisalmer Basin at the western margin of the Indian Craton. The hardgrounds started to form under subtidal conditions in a mixed carbonate–siliciclastic setting during the last phase of a transgressive systems tract, i.e. the maximum flooding zone. The age difference between the hardgrounds is very small, but they differ lithologically. Typically, the stratigraphically oldest hardground occurs at the top of a 1-m-thick calcareous sandstone. It is characterized by a spectacular megaripple surface encrusted with oysters and subsequently occasionally bored by bivalves. The hardground is overlain by 10–25 cm of biowackestone to biopackstone, at the top of which another hardground is developed. This second hardground is characterized by abundant bivalve (Gastrochaenolites isp.) and “worm” borings (Trypanites and Meandropolydora isp.) and occasional oyster encrustations. The third hardground can be found within the overlying 60-cm-thick, bioturbated, fossiliferous silty marly packstone. It shows common to abundant oyster encrustations and occasional borings together with reworked concretions. The individual hardground can be well recognized throughout the basin based on lithology and biotic components. The second hardground (biowackestone to biopackstone) with abundant bivalve and worm borings is most prominent and widespread. Lithostratigraphically, these three hardground surfaces belong to the uppermost part of the Bada Bag Member of the Jaisalmer Formation. Based on ammonites, such as Perisphinctes congener (Waagen), brachiopods, and corals, this interval of the Bada Bag Member has been assigned a late Bathonian age. The entire succession above the first hardground is bioturbated up to the overlying marly silt of the Kuldhar Member of the Jaisalmer Formation, which is already Callovian in age. The characteristic hardground lithologies, together with the ammonite record, allow long-distance correlations within the basin emphasizing their importance as valuable marker horizons. The biotic components associated with the hardgrounds and alternating sediments represent high diversity community relicts developed in shallow-water, open-marine environments.

29 pages; International audience; Sedimentological investigations have been carried out in the southwestern part of the Gissar Range (Uzbekistan) in order to document the stratigraphic evolution of a vast Middle–Upper Jurassic carbonate platform developed on the northern margin of the Amu Darya Basin. Two major sequences are distinguished, based on their contrasting facies pattern, platform configuration and carbon isotope signature: (1) a Callovian Sequence and (2) an Upper Jurassic Sequence, potentially Oxfordian to Kimmeridgian in age. A carbonate ramp with a double proximal-distal polarity developed during the Callovian Sequence. Oo-bioclastic grainstones were produced in two permanently agitated shallow water areas developing to the north and to the south. Patch and pinnacle reefs mainly built up close to the storm-wave base, passing distally to pellet- and foraminiferal-oncoid-rich mid-to outer-ramp deposits. The top of the Callovian Sequence is a regional discontinuity that could have formed by subaerial exposure of the platform. This probable hiatus could record a major climatic change associated to the Middle‒Late Jurassic transition. The Upper Jurassic Sequence consists of metre-thick alternations of pellet/algal-pack- to grainstones, microbial oncoid floatstones, ooid grainstones, and mudstones, which have likely accumulated in a vast lagoon protected by a large-scale barrier reef observed south of the study area. Gypsum and anhydrite content gradually increased towards the top of the Upper Jurassic Sequence, ending up with a thick chicken-wire gypsum accumulation recording the progradation of a large-scale sabkha over the lagoon. This phenomenon is related to a progressive aridification and restriction of the Amu Darya Basin that could have begun during the Middle/Late Oxfordian and reached its climax during the Tithonian with massive halite deposition. Comparable events occurred in Jurassic platforms located along the Tethyan margins, pointing to regional and global controls on sedimentation.

The Upper Albian–Turonian Debarsu Formation in its type area around Haftoman, south of Khur (Central Iran) has been investigated using an integrated approach of high-resolution logging, bio- and sequence stratigraphic dating, and facies analysis based on field observations and detailed microfacies studies. The up to 500-m-thick Debarsu Formation consists of stacked, several 10- to ~ 100-m-thick, essentially asymmetric shallowing-upward cycles from grey offshore marl via skeletal and intraclastic limestone with large-scale clinoformed foresets to thick-bedded bioclastic, locally rudist-bearing shallow-marine topset strata capped by palaeokarst surfaces. The diverse (micro)facies inventory (29 facies types) is dominated by skeletal carbonates (bioclastic pack-, grain-, float- and rudstone) that reflect deposition on a carbonate ramp with a lagoonal shoreline that was attached to an elevated area in the west and southwest. The outer ramp facies association of the Debarsu ramp contains predominantly microbioclastic marl with open-marine microfossils (planktic foraminifera) and fine-grained bioturbated packstone. The transition into the mid-ramp facies association, dominated by bioclastic pack- and grainstone (foreset strata), is commonly gradational. The inner-ramp facies association is very diverse, mainly consisting of high-energy (well-washed and cross-bedded) grainstone as well as back-ramp or inter-shoal bioclastic float- and rudist bafflestone. The Debarsu Formation occurs in an area of more than 2500 km2 to the west, southwest, and south of Khur but had its depocenter with maximum thicknesses and thick offshore marl intervals in the type area. The large-scale shallowing-upward cycles correspond to third-order depositional sequences. The chronostratigraphic positions of the sequence-bounding unconformities in the Upper Albian to Lower Cenomanian match equivalent surfaces known from other Cretaceous basins on different tectonic plates. However, a large-scale intraformational stratigraphic gap (Middle Cenomanian to lowermost Turonian) at a major palaeokarstic surface in the upper part of the formation must be related to tectonic uplift. The Debarsu Formation shows similarities in (sequence) stratigraphic stacking patterns to hydrocarbon-bearing formations of the southern Tethyan margin (Arabian Plate).

An integrated study of the litho-, bio-, and microfacies of several sections has greatly improved the knowledge on the stratigraphy and depositional setting of the Coniacian to Campanian Haftoman Formation in the Khur area of the northern Yazd Block, Central Iran. Generally, the Haftoman Formation rests on a major tectonic unconformity and commences with a basal conglomerate followed by up to 900 m of shallow-water carbonates with local red sandstone intercalations. Five different depositional environments (from distal to proximal) characterize the facies associations (FA) of the Haftoman Formation: silty, spiculitic wackestone (proximal basin, FA I), bio-/intraclastic wacke-, pack-, and grainstone (marginal shoals, FA II), bioclastic rud-/float-/boundstone (outer platform, FA III), silty mud-/wackestone (lagoonal inner platform, FA IV), and sandstone/sandy limestone (areas close to the mouth of ephemeral streams, FA V). The litho-, micro-, and biofacies of the Haftoman Formation are typical for an epeiric carbonate platform characterized by an arid climate and lagoonal circulation, resulting in nutrient-poor waters, warm temperatures, and high salinities. The Haftoman Platform was attached to an emergent arid hinterland formed by the Anarak Metamorphic Complex to the west and southwest of the study area. Unconformity-bounded depositional units indicate sea-level changes that may correspond to 400-kyr high-frequency sequences but further studies are needed to fully exploit the potential of sequence stratigraphy for regional and inter-regional correlation of the Haftoman Formation.

International audience; Based on 11 sections, the palaeoenvironments and depositional history of the NW Afghan–Tajik Basin in southern Uzbekistan have been reconstructed for the time interval of the Early Jurassic–Early Callovian. The earliest sediments, resting on Palaeozoic basement rocks, date from the Early Jurassic Period. Up to the end of the Early Bajocian time, more than 500 m of non-marine sediments accumulated as a result of extensional tectonics inducing active subsidence. In the Late Bajocian time interval, transgression led to the establishment of siliciclastic ramps that were influenced by storm processes. After a condensed unit in the Middle Bathonian, sedimentation resumed in an outer carbonate ramp–basinal setting as the subsidence rate outpaced the diminished siliciclastic sediment supply. The change from siliciclastic to carbonate sedimentation in the Middle Jurassic Period is thought to be multifactorial, reflecting levelling of relief in the hinterland, the subsidence moving to a thermally more quiet stage and a change from humid to arid climatic conditions. These features are also observed in the area of present-day Iran. Similarly, the timing of the transgression coincides with that in eastern and northern Iran, stressing the regional significance of this event.

Twenty-two species of the bivalve order Pholadomyida, belonging to six genera and seven subgenera of the families Pholadomyidae, Pleuromyidae and Poromyidae are described from the Cenomanian–Coniacian Cotinguiba Formation of the Sergipe Basin, north-eastern Brazil. Eleven species, Pholadomya (Ph.) cf. agrioensis Weaver, Ph. (Ph.) kasimiri Pusch, Ph. (Ph.) nodulifera Munster, Ph. (Ph.) occidentalis Morton, Ph. (Procardia) vignesi Lartet, Pleuromya ligeriensis (d’Orbigny), Pl. servesensis Choffat, Liopistha (L.) aequivalvis (Goldfuss), L. (Psilomya) elongata Stanton, L. (P.) globulosa (Forbes) and L. (Sergipemya) gigantea (J. Sowerby) are recorded from the Sergipe Basin for the fi rst time. The new subgenus Sergipemya of the genus Liopistha, family Poromyidae, is erected on the basis of morphological characters such as numerous commarginal ribs, large and highly infl ated valves, a well-developed rounded umbonal anterior ridge bordering a deep depression on the anterior part, and the presence of two unequal cardinal teeth with a cardinal tear-shaped socket in the left valve. The pholadomyid fauna of Sergipe closely resembles that of other Tethyan regions in western and southern Europe, northern and western Africa and the Middle East. The distribution patterns of the taxa were probably influenced by east–west-directed currents. Southern Tethyan pholadomyids reached western Africa and north-eastern South America via the Trans-Saharan Seaway.

An articulated and partially preserved skeleton of an ichthyosaur was found in the Upper Jurassic (Upper Kimmeridgian) Katrol Formation exposed at a site south of the village Lodai in Kachchh district, Gujarat (western India). Here we present a detailed description and inferred taxonomic relationship of the specimen. The present study revealed that the articulated skeleton belongs to the family Ophthalmosauridae. The new discovery from India further improves the depauperate fossil record of ichthyosaurs from the former Gondwanan continents. Based on the preserved length of the axial skeleton and anterior part of the snout and taking into account the missing parts of the skull and postflexural region, it is suggested that the specimen may represent an adult possibly reaching a length of 5.0–5.5 m. The widespread occurrence of ophthalmosaurids in the Upper Jurassic deposits of western Tethys, Madagascar, South America and India points to possible faunal exchanges between the western Tethys and Gondwanan continents through a southern seaway.

Sixteen early and middle Albian bivalve species, belonging to fourteen genera, eleven families and seven orders, and one brachiopod species are systematically described from the Mitrovcic section near Topola (Oplenac Hill), Vardar Zone of central Serbia. Four bivalve species: Acesta subrigida (Roemer, 1836), Acesta cf. dorbignyana (Matheron, 1843), Neithea (Neithea) sexcostata (S. Woodward, 1833), “Cardium” cottaldinum d'Orbigny, 1844, and one terebratulide species, Praelongithyris rogeri Gaspard, 1974 are recorded from the lower and middle Albian rocks of central Serbia for the first time. The section comprises reddish ferruginous calcareous sandstones that are assigned to the lower Albian as indicated by the presence of the ammonite Douvilleiceras mammillatum (Schlotheim), while yellowish sandy wackestones/packstones located below the late Albian Mortoniceras (M.) inflatum (J. Sowerby), are middle Albian in age. Most of the identified bivalve taxa have a Tethyan affinity and seem to be closest to faunas from western and eastern Europe. This indicates that these regions were close to Serbia during the early–middle Albian. The occurrences of some of these Tethyan bivalves at the northern and western Pacific coast of South America and southern coast of North America is explained by dispersal through the opening of the North Atlantic Ocean during the Albian (Proto-North Atlantic Ocean). Meanwhile, the occurrence of some other Albian taxa along the eastern coast of South America (South Atlantic) was probably a result of the opening of the equatorial Atlantic gateway during that time. The faunas are not endemic, indicating that the larvae were long-lived and possessed a high dispersal potential, facilitated by seaways during the Albian.

Made available in DSpace on 2018-11-26T17:13:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Petrobras Sao Paulo State University-UNESP, Brazil The origin of the Cretaceous laminites of the Crato Formation, Araripe Basin, northeastern Brazil, has been intensely debated since the beginning of the last century. The monotonous, up to 10-m-thick succession composed of very fine fossiliferous laminites in the middle of the unit lacked diagnostic features for assigning a chemically or biologically induced origin for this facies. The presence of a highly diverse and very well preserved alloch-thonous to parautochthonous fossil assemblage, associated with scattered halite pseudomorphs throughout the succession, led many authors to believe that these limestones were chemically deposited in a highly stressful, evaporitic shallow-water environment, such as a hypersaline lake close to marine environments. Recently, a micro-and ultrastructural analysis of the laminites yielded structures undoubtedly associated with a biological origin. Several examples of lithified in situ preserved coccoid and filamentous cells and extracellular polymeric substances suggest that the deposition of the laminated limestones was, at some levels, strongly influenced by microbial activity. Here, we record various examples of stromatolite microbialites (mounds, domes, and pseudo-columns) found at distinct stratigraphic levels in the middle part of the Crato Formation. Macro-, meso-, and microscopic features confirm the biologically induced mineralization and the existence of metabolic activity of microbes during the formation of the laminites. Biomat growth may also have played a major role in the excellent preservation of fossils in this famous Cretaceous Konservat-Lagerstatte from Brazil. Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Ave 24A,1515, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP, Brazil Friedrich Alexander Univ Erlangen Nurnberg, FG Palaoumwelt, GeoZentrum Nordbayern, Loewenichstr 28, D-91054 Erlangen, Germany UNLP Conicet, Ctr Invest Geol, Diagonal 113 275,Esq 64, RA-1900 La Plata, Buenos Aires, Argentina Petroleo Brasileiromatriz Ctr, Ave Republ Chile 65, BR-20031912 Rio De Janeiro, Brazil Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Ave 24A,1515, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP, Brazil CNPq: 444070/2014-1 CNPq: 401039/2014-5 CNPq: 30017/2015-3 FAPESP: 2014/27337-8 FAPESP: 2004/15786-0 Petrobras: 0050.0023165.06.4

Made available in DSpace on 2018-11-26T17:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-08-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) This is the first record of a Permian seep deposit and an associated, morphologically bizarre, bivalve-dominated fauna from the Passa Dois Group, Parana Basin, Brazil. Shales of the outer-shelf facies of the Serra Alta Formation preserve a low-diversity but high-abundant, large-sized bivalve fauna with unusual morphologies inside discoidal carbonate concretions. The bivalves are about ten times larger than tiny bivalves found scattered in laterally equivalent mudstones of the same unit. Intercalated between two concretion-bearing horizons, a cm-thick, sheet-like, disrupted, brecciated, partially silicified carbonate layer with microbially-induced lamination is recorded. In some areas, the carbonate layer shows vertical structures formed by injections of mud mixed with white limestone clasts and microbial linings. Immediately above this, silicified mudstones preserve small domal structures (= mounds) with a slightly depressed center. Monospecific concentrations of closed articulated shells of Tambaquyra camargoi occur at the base of these domes. Carbon-isotope (delta C-13) values from the shells, brecciated carbonates, and fossil-rich concretions are all depleted (negative values similar to -6.1 to -7.6 parts per thousand). Combined taphonomic, sedimentological, petrographic, geochemical and paleontological data suggest that the disrupted, brecciated carbonate and associated fauna and domes may have formed by an exudation system. Indeed, this interval of the Serra Alta Formation is similar to 8.7 m above the contact with the underlying, oil-rich Irati Formation. This unit has very high total organic carbon (up to 23%) values and high sulphur contents, supporting the interpretation of the lithological and paleontological features as result of seepage of organic compounds at the seafloor. Where the gases and hydrocarbons escaped, the seabed was colonized by, at least facultatively, chemosymbiotic bivalves. The species above belong to a highly endemic group of pachydomids that were shallow infaunal bivalves (SIB). Hence, they are not related to classical bivalves with extant representatives, which are chemosymbionts. This may reflect an extreme adaptive radiation and repopulation of anoxic-dysoxic bottoms of the Parana Basin by SIB species. (C) 2017 Elsevier Ltd. All rights reserved. Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618970 Botucatu, SP, Brazil Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo, Brazil Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Dept Geol Aplicada, Campus Rio Claro, BR-13506900 Rio Claro, SP, Brazil Friedrich August Univ Erlangen Nurnberg, FG Palaoumwelt, GeoZentrum Nordbayern, Loewenichstr, D-91054 Erlangen, Germany Univ Sao Paulo, Inst Energia & Ambiente, Sao Paulo, SP, Brazil Univ Sao Paulo, Inst Geociencias, Sao Paulo, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618970 Botucatu, SP, Brazil Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Dept Geol Aplicada, Campus Rio Claro, BR-13506900 Rio Claro, SP, Brazil FAPESP: 96/09708-9 FAPESP: 12/12508-6 CNPq: 302903/12-3 CNPq: 401039/2014-5

Phanerozoic trends in shell and life habit traits linked to postmortem durability were evaluated for the most common fossil brachiopod, gastropod, and bivalve genera in order to test for changes in taphonomic bias. Using the Paleobiology Database, we tabulated occurrence frequencies of genera for 48 intervals of ∼11 Myr duration. The most frequently occurring genera, cumulatively representing 40% of occurrences in each time bin, were scored for intrinsic durability on the basis of shell size, reinforcement (ribs, folds, and spines), life habit, and mineralogy.Shell durability is positively correlated with the number of genera in a time bin, but durability traits exhibit different temporal patterns across higher taxa, with notable offsets in the timing of changes in these traits. We find no evidence for temporal decreases in durability that would indicate taphonomic bias at the Phanerozoic scale among commonly occurring genera. Also, all three groups show a remarkable stability in mean shell size through the Phanerozoic, an unlikely pattern if strong size-filtering taphonomic megabiases were affecting the fossil record of shelly faunas. Moreover, small shell sizes are attained in the early Paleozoic in brachiopods and in the latest Paleozoic in gastropods but are steady in bivalves; unreinforced shells are common to all groups across the entire Phanerozoic; organophosphatic and aragonitic shells dominate only the oldest and youngest time bins; and microstructures having high organic content are most common in the oldest time bins.In most cases, the timing of changes in durability-related traits is inconsistent with a late Mesozoic Marine Revolution. The post-Paleozoic increase in mean gastropod reinforcement occurs in the early Triassic, suggesting either an earlier appearance and expansion of durophagous predators or other drivers. Increases in shell durability hypothesized to be the result of increased predation in the late Mesozoic are not evident in the common genera examined here. Infaunal life habit does increase in the late Mesozoic, but it does not become more common than levels already attained during the Paleozoic, and only among bivalves does the elevated late Mesozoic level persist through the Holocene.These temporal patterns suggest control on the occurrence of durability-related traits by individual evolutionary histories rather than taphonomic megabiases. Our findings do not mean taphonomic biases are absent from the fossil record, but rather that their effects apparently have had littleneteffect on the relative occurrence of shell traits generally thought to confer higher preservation potential over long time scales.

The Callovian–Lower Kimmeridgian Kamar-e-Mehdi Formation of the western Tabas Block, part of the Central-East Iranian Microcontinent, represents the fill of an extensive carbonate shelf lagoon situated between a barrier carbonate platform in the east and the uplifted Yazd Block in the west. In the course of its development, the shelf lagoon experienced increasing isolation which, together with a climatic change to more arid conditions, led to deposition of evaporites and severe restriction of the benthic fauna. Sedimentation in the predominantly low-energy lagoon was controlled by an influx of fine-grained carbonate from the neighboring platform, biogenic carbonate production within the lagoon and episodic influx of siliciclastic material by high-density currents from the uplifted western margin. Much of the succession is composed of meter-scale asymmetric cycles that record decreasing terrigenous input as well as increasing shelliness and substrate firmness due to a decreasing sedimentation rate. They are interpreted as small-scale climatic cycles recording changes in humidity. Larger-scale cycles, comprising 250–400 m in thickness, document changes in terrigenous influx and may also be climate-controlled, although a tectonic origin cannot be excluded. The shelf lagoon was populated by several level-bottom communities and small patch reefs. The latter are of low diversity, composed of calcareous sponges, corals, or oysters, and are usually associated with thick microbial crusts. The level-bottom assemblages are dominated by bivalves, and rarely also by gastropods or brachiopods. Fossils occur scattered or concentrated in pavements and beds. Shell concentrations are autochthonous to allochthonous, most commonly parautochthonous. Concentrating agents were storm-induced flows and low sedimentation rates, less commonly also storm-waves. Within the small-scale cycles, infaunal assemblages prevail but are replaced by epifaunal assemblages at their top. The latter are commonly dominated by the bivalves Pseudopecten tipperi and Camptonectes (Grandinectes) teres, the two most characteristic faunal elements of the shelf lagoon. Diversity values of the benthic fauna were low to moderate. Environmental stress was mainly produced by elevated salinity values, at times possibly intensified by lowered oxygen values and soft substrate conditions. Paleobiogeographically, the benthic macrofauna exhibits a close relationship to that of European shelf seas but contains some immigrants from the southern shores of the Tethys and the northwestern Pacific. The degree of endemism was low (two taxa).

Biological veracity of the sharp diversity increase observed in many analyses of the post-Paleozoic marine fossil record has been debated vigorously in recent years. To assess this question for sample-level (“alpha”) diversity, we used bulk samples of shelly invertebrates, representing three major fossil groups (brachiopods, bivalves, and gastropods), to compare the Jurassic and late Cenozoic sample-level diversity of marine benthos. After restricting the data set to single-bed, whole-fauna, bulk samples (n≥ 30 specimens) from comparable open marine siliciclastic facies, we were able to retain 427 samples (255 Jurassic and 172 late Cenozoic), with most of those samples originating from our own empirical work.Regardless of the diversity metric applied, the initial results suggest that standardized sample-level species (or genus) diversity, driven by evenness and/or richness of the most common taxa, increased between the Jurassic and late Cenozoic by at least a factor of 1.6. When the data are partitioned into the three dominant higher taxa, it becomes clear that (1) the bivalves, which dominated the samples for both time intervals, increased in sample-level diversity between the Jurassic and the late Cenozoic by a much smaller factor than the total fauna; (2) the removal of brachiopods, which were a noticeable component of the Jurassic samples, did not significantly affect standardized sample-level diversity estimates; and (3) the gastropods, which were rare in the Jurassic but common in many late Cenozoic samples, contributed notably to the increase in sample-level diversity observed between the two time intervals. Parallel to these changes, the samples revealed secular trends in ecological structure, including Jurassic to late Cenozoic increases in proportion of (1) infauna, (2) mobile forms, and (3) non-suspension-feeding organisms. These trends mostly persist when data are restricted to bivalves.Supplementary analyses indicate that these patterns cannot be attributed to sampling heterogeneities in paleolatitudinal range, lithology, or paleoenvironment of deposition. Likewise, when data are restricted to samples dominated by species with originally aragonitic shells, the observed temporal changes persist at a comparable magnitude, suggesting that the pervasive loss of aragonite in the older fossil record is unlikely to have been the primary cause of the observed patterns. The comparable ratio of identified to unidentified species and genera, observed when comparing the Jurassic and late Cenozoic samples, indicates that the relatively poorer (mold/cast) preservation of Jurassic aragonite species also is unlikely to have been responsible for the observed patterns. However, the diagenesis-related taphonomic and methodological artifacts cannot be ruled out as an at least partial contributor to the observed post-Paleozoic changes in diversity, taxonomic composition, and ecology (the outcomes of the three tests of the diagenetic bias available to us are incongruent).The study demonstrates that the post-Paleozoic trends in the sample-level diversity, ecology, and taxonomic structure of common taxa can be replicated across multiple studies. However, the diversity increase estimated here is much less prominent than suggested by many previous analyses. The results also narrow the list of causative explanations down to two testable hypotheses. The first isdiagenetic bias—a spurious trend driven by either (a) increasing taphonomic loss of small specimens in the older fossil record or (b) a shift in sampling procedures between predominantly lithified rocks of the Mesozoic and predominately unlithified, and therefore sievable, sediments of the late Cenozoic. The second hypothesis isgenuine biological changes—macroevolutionary trends in the structure of marine benthic associations through time, consistent with predictions of several related models such as evolutionary escalation, increased ecospace utilization, and the Mesozoic marine revolution. Future studies should focus on testing these two rival models, a key remaining challenge for identifying the primary causative mechanism for the long-term changes in sample-level diversity, ecology, and taxonomic structure observed in the Phanerozoic marine fossil record.

Resume Les facies purbeckiens de la marge septentrionale du Bassin aquitain affleurent sur une epaisseur de 30 m environ dans la carriere de gypse de Champblanc, commune de Cherves-de-Cognac situee a une dizaine de kilometres au nord-est de Cognac (Charente, SW France). Deux unites lithologiques ont ete identifiees. L'unite basale (U1) representee par une alternance de gypse et de marnes noires finement litees presente occasionnellement un aspect stromatolithique. L'unite superieure (U2) est une alternance marno-calcaire plus ou moins fossilifere. Dans la partie superieure de cette unite, un niveau d'environ 1 m d'epaisseur a livre une riche faune de vertebres. Une analyse micropaleontologique de ces niveaux, jusqu'a present consideres comme d'âge Jurassique terminal, a livre de riches associations d'ostracodes lagunaires et limniques et de charophytes permettant de leur attribuer un âge Berriasien et de proposer une correlation avec la partie inferieure du Middle Purbeck du Sud de l'Angleterre. Pour citer cet article : J.-P. Colin et al., C. R. Palevol 3 (2003).

The evidence for macroscopic life during the Palaeoproterozoic era (2.5-1.6 Gyr ago) is controversial(1-5). Except for the nearly 2-Gyr-old coil-shaped fossil Grypania spiralis(6,7), which may have been eukaryotic, evidence for morphological and taxonomic bio-diversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6-1.0 Gyr)(8). Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization(9). The Gabon fossils, occurring after the 2.45-2.32-Gyr increase in atmospheric oxygen concentration(10), may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion. The evidence for macroscopic life during the Palaeoproterozoic era (2.5–1.6 Gyr ago) is controversial1,2,3,4,5. Except for the nearly 2-Gyr–old coil-shaped fossil Grypania spiralis6,7, which may have been eukaryotic, evidence for morphological and taxonomic biodiversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6–1.0 Gyr)8. Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization9. The Gabon fossils, occurring after the 2.45–2.32-Gyr increase in atmospheric oxygen concentration10, may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.

With a thickness of 3900 m, the Tazareh section is one of the thickest developments of the Shemshak Formation in the Alborz range. It overlies with sharp and disconformable contact the limestones and dolomites of the Lower–Middle Triassic Elikah Formation and is topped, again with a disconformable contact, by the marls and limestones of the Middle Jurassic Dalichai Formation. The nearly exclusively siliciclastic succession represents a range of environments, from fluvial channels, flood plains, swamps and lake systems to storm-dominated shelf, and a comparatively deep marine and partly dysoxic basin. The segment of the section between 2300 and 3500 m is exclusively marine and contains a moderately diverse ammonite fauna, ranging from the Middle Toarcian to the Upper Aalenian. The ammonite fauna comprises 21 taxa, among them the new genus Shahrudites with two new species, Shahrudites asseretoi and S. stoecklini from the Middle Aalenian Bradfordensis Zone. The other ammonites from the Shemshak Formation at Tazareh (as elsewhere in North and Central Iran) are exclusively Tethyan in character and closely related to faunas from western and central Europe. An ammonite-based correlation of Toarcian–Aalenian successions of the eastern Alborz with time-equivalent strata of the Lut Block, part of the Central-East Iranian Microcontinent (ca. 500 km to the south), suggests a strong influence of synsedimentary tectonics during the deposition of the upper Shemshak Formation.

Some minerals are considered to be representative of specific natural environments. Among them glauconite is considered to be formed in marine deep platform conditions. However, the term glauconitic is misused to designate green minerals formed in marine outer-shelf environments. X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analyses of individual green materials were carried out leading to the identification of glauconite in the Purbeckian facies. Green glauconite grains predominantly occur as burrow fills and occasionally as faecal pellet replacements. Two depositional environments have been identified from bottom to top of the succession: (1) an argillaceous dolomitic lagoonal sediment formed in saline, shallow water; (2) a marl-limestone alternation deposited in a brackish water estuary. The crystallochemical properties of the glauconites change abruptly. These findings show that glauconite may form in coastal environments and not only in mid-shelf to upper deep water platform environments as classically assumed. Moreover, the glauconite composition changes with the chemical conditions imposed by the local environment.

The San Salvador Patlanoaya section (Puebla State of Mexico) has been subdivided into seven informal members labeled A–F. Members C–F have been dated as Missourian to Leonardian (equivalent to Kasimovian to Kungurian, i.e. lower Upper Pennsylvanian to upper Lower Permian). Members C–E display a shallowing-upward trend as does member F. The biodiversity of these carbonate deposits outcropping in the San Salvador Patlanoaya section is relatively low, although multiple microfossils (algae, small foraminifera, fusulinids and fish remains) are represented. Member C consists of calcarenitic limestone interpreted as distal tempestites interbedded with shaly limestone facies. These storm beds are composed mainly of silt, sand-sized quartz grains and bioclasts. Member D corresponds to coarse bioclastic limestones represented by calcareous tempestites and channel beds with erosional bases. Member E is composed of green shales and cross-bedded sandstones and gravelly conglomerates. Member F corresponds to a condensed package of limestones and interbedded siliciclastics and is Cisuralian (Early Permian) in age. Member G consists of condensed black shales and limestone nodules. The results of the study have significant implications for recognition of climatic and/or sea-level fluctuations in bioclastic–siliciclastic facies during the Late Pennsylvanian–Early Permian. The skeletal limestones and channel sandstones, common throughout the Pennsylvanian–Permian section, provide a constraint on palaeobathymetry, with the water depth fluctuating frequently around a position below, but near, the storm wave base.

The Purbeckian facies of the northern margin of the Aquitaine Basin is exposed in the Cherves-de-Cognac section (SW France), considered as basal Cretaceous in age. Two lithological units have been identified. The basal unit (U1) is composed of an alternation of gypsum and finely bedded black dolomitic marlstone, occasionally stromatolitic in nature. It represents mostly hypersaline, dolomitic tidal flat, lagoonal, and sabkha-type environments. The upper unit (U2) consists of variably fossiliferous limestone-marl alternations that contain a diverse fauna and flora. In the upper part of this unit, a 4-m-thick level has yielded a rich vertebrate fauna. The preservational quality of the vertebrate fossils varies within the section. On the basis of faunal, floral, sedimentological and mineralogical information the vertebrate remains accumulated in brackish water environments in which the influence of freshwater has progressively increased towards the top of the section. The close association of environments representing varying degrees of marine and continental influence suggest an estuarine setting.