Late Hauterivian Research Articles

Early Cretaceous palynoflora from palaeotropics of NE Africa (correlation and significance): an example from the Shushan Basin, Egypt

We re-assessed and re-evaluated the diverse spores and pollen associations, presently recovered from clastics of the Shushan Basin. Eight (informal) Early Cretaceous (Valanginian to middle Cenomanian) spores/pollen zones are suggested, dated and correlated with regional/interregional records. Palynological dating offered bases for borehole stratigraphic resolution and basin correlation. It permitted revision of the homogeneous Early Cretaceous sediments of the borehole. Intrabasinal correlation, based on closely-spaced palynologically- productive samples, revealed the existence of an undetected sediment hiatus east of the basin, manifested by the wedging/missing of the Aptian Dahab clastics from west to east. The Shushan palynoflora exhibits great similarity with their counterparts in other provinces of the Northern Gondwana continent. But, however, A fern-dominated hygrophilous spores, along with Classopollis pollen, validated previous assumptions that humid conditions were responsible for the delayed appearance and scarcity of Dicheiropollis pollen in NE Africa (Egypt, Libya and Sudan), by the late Hauterivian. This humidity is thought to have triggered the production of Afropollis in the regional North African records, which reached an acme. Three main peaks of this pollen are inferred from the late Aptian, early Albian and early-middle Cenomanian intervals of the Shushan-1X well. Chronologically, these peaks can be of great stratigraphic value in NE Africa or other areas in Northern Gondwana that witnessed wet palaeoclimates during the Early Cretaceous.

Lower Cretaceous ammonoids from the Neuquén Basin, Argentina: The late Hauterivian Paraspiticeras and associated faunas

The Paraspiticeras groeberi Zone (upper Hauterivian) is one of the five ammonoid biozones previously recognized in the Agua de la Mula Member of the Agrio Formation in the Neuquén Basin of west-central Argentina. However, the ammonoid faunas of this zone and the beds immediately below, corresponding to the upper levels of the current Crioceratites diamantensis Zone, remain poorly known. Extensive collections now allow us to recognize a diverse endemic ammonoid fauna. After an exhaustive taxonomic and stratigraphic review, the Paraemericiceras argentinense and Paraspiticeras bituberculatum Zones are proposed to replace the P. groeberi Zone and the original index species is now placed in Vutacuracrioceras gen. nov. Vutacuracrioceras groeberi first appears with the earliest Paraemericiceras argentinense gen. et sp. nov. and extends through both zones. It is joined in the Paraspiticeras bituberculatum Zone by the index species and Paraspiticeras sp. aff. P. precrassispinum, Australopseudothurmannia flexuosa gen. et sp. nov. and Hamulinites sp. Based on this new biostratigraphic scheme, the upper Hauterivian in the Neuquén Basin is represented now by six ammonoids zones that can be correlated provisionally with the European standard of the West Mediterranean Province of the Tethyan Realm.

Bottom water redox dynamics during the Early Cretaceous Weissert Event in ODP Hole 692B (Weddell Sea, Antarctica) reconstructed from the benthic foraminiferal assemblages

Benthic foraminifera at Ocean Drilling Program (ODP) Hole 692B were studied to understand variations in oxygen and organic-matter fluxes in bottom waters during the Early Cretaceous. The upper Berriasian to lower Barremian black shales, characterized by high concentrations of total organic carbon (TOC) ranging between 1.3 and 18%, were deposited in an outer neritic-upper bathyal environment (~200–500 m) according to benthic foraminifera assemblages. A new high-resolution record of benthic foraminiferal assemblages of high-latitude, dominated by infaunal taxa ( Citharina , Eoguttulina , Laevidentalina , Lagena , Lenticulina , Marginulina , N odosaria, Planularia , Saracenaria , and Vaginulinopsis ), is described in depleted‑oxygen and high organic‑carbon flux conditions. Extremely dysoxic conditions are recorded at the onset of the carbon isotope excursion (CIE) marking the Weissert Event (late Valanginian), followed by a period of anoxic conditions in bottom waters. A repopulation event of benthic foraminifera, linked to an increase in oxygen concentrations, coincided with the global cooling episode that characterized the late part of the Weissert Event. Subsequently, there were short periods in the late Valanginian and the late early Hauterivian when the bottom waters experienced increased oxygen concentrations. Possibly, bottom currents related to the influx of Southern Ocean waters favored short-term pulses of ventilation under constant increased organic‑carbon flux during the late Valanginian and late Hauterivian. • New Lower Cretaceous micropaleontological data from the southern high latitudes • Benthic foraminifera indicate an outer neritic-upper bathyal setting. • Alternated anoxic and dysoxic conditions during the Weissert Event in bottom-waters • Benthic foraminiferal repopulation through the Weissert Event • ODP 692B was influenced by the interplay of short-term pulses of ventilation.

Weathering events recorded in uppermost Hauterivian\u2013lower Barremian clay-dominated continental successions from the NW Iberian Range: climatic vs. tectonic controls

The facies and clay mineral study of clay/marl-rich levels from the Torrelapaja Formation (latest Hauterivian–early Barremian, NW Iberian Range, NE Spain) allowed to establish the palaeoclimatic and palaeoenvironmental conditions under they were generated. The muddy levels and pisoids contained therein of two logs were sampled and studied by X-ray diffraction and optical and electron microscopy. A similar mineralogical upwards trend is recorded in both logs, with a decrease in calcite coupled with an increase in quartz and orthoclase content and constant proportions in goethite, hematite, diaspore, anatase, rutile, ilmenite, and clay mineral content. The lower muddy levels have higher kaolinite content than the upper levels, where illitic phases are the dominant clay minerals. Smectite and intergrowths of illitic phases and kaolinite are also detected upwards. The kaolinite and smectite textures indicate an authigenic origin, whereas the illitic phases are former phases acting as a substrate for kaolinite crystallization. Pisoids mineralogy and texture show an in-situ origin, but some are fractured, indicating reworking processes. The mineral association found in the muddy levels is characteristic of oxisols formed under warm and humid conditions. The upward decrease in kaolinite content is coeval with an increase in the illitic phases and quartz content, related to siliciclastic input, but is also coeval with the presence of authigenic smectite. This indicates a decrease in chemical weathering, not fully registered due to the siliciclastic contribution, which was possibly associated with a change to colder, drier conditions during the latest Hauterivian–early Barremian in the studied area.

Osmium Isotopic Evidence for Eccentricity‐Paced Increases in Continental Weathering During the Latest Hauterivian, Early Cretaceous

AbstractThe 405‐kyr eccentricity cycle is a consistent orbital parameter throughout the Phanerozoic that is associated with long‐term variations in global continental weathering. However, a lack of reliable geological evidence has hampered the understanding of the relation between the 405‐kyr eccentricity cycle and continental weathering during the Cretaceous. Os isotopic ratios (187Os/188Os) of the sedimentary record reflect the balance between radiogenic Os derived from continental weathering and Os derived from unradiogenic sources (e.g., hydrothermal activity, weathering of mafic rocks, and extraterrestrial sources). This ratio is therefore considered as a good proxy for the evaluation of short‐term changes in continental weathering patterns. To trace orbital‐paced continental weathering, this study reconstructs the marine Os isotopic records in upper Hauterivian to lower Barremian (Lower Cretaceous) carbonate rocks in central Italy, where previous studies have reported that variations in clay mineral composition are paced by the 405‐kyr cycle. Our new Os isotopic record documents periodic oscillations of187Os/188Os between 0.7 and 0.9 that correspond to the 405‐kyr Earth's eccentricity cycle. Because the sedimentary interval with radiogenic187Os/188Os values (∼0.9) corresponds to a time interval characterized by a humid climate in areas surrounding the Tethys, variations in the187Os/188O values likely reflect cyclic changes in continental weathering caused by eccentricity‐paced intensification of monsoonal activity at low latitudes. This variation could have been further amplified by increased input of radiogenic Os from Paleozoic shale and Precambrian crust at higher latitudes that resulted from a latitudinal shift of the intertropical convergence zone.

Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

AbstractDespite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

Biostratigraphy of Baghamshah Formation based on calcareous nannofossils in the Southwest Tabas, Iran

The Tabas Block is part of the Central Iran microcontinent, located between the Lut Block in the East and the Yazd Block in the West. The Baghamshah Formation is the second lithostratigraphic unit from the sedimentary cycle of the Magu Group and the Baghamshah Subgroup in the Jurassic of Tabas Block. This formation is conformably underlaid with the grey pisoidal limestones of the Parvadeh Formation and overlaid with the Pectinid limestones of the Kamar-e-Mehdi Formation (Esfandiar Subgroup). In this research, the biostratigraphy of the Baghamshah Formation in the Rizu and Kamar-e-Mehdi sections, based on calcareous nannofossils, is examined. The thickness of the Baghamshah Formation in the Rizu section is 270 m (mostly including marl and green shales with intercalation of limestones and calcareous sandstones), and in the Kamar-e- Mehdi section is 236 m (composed of gypsiferous marly shales, marl, marly shales and alternation of marl-shale with limestones and calcareous sandstones). According to the taxonomic studies in the Rizu section, 52 species belong to 24 genera, and in the Kamar-e-Mehdi section, 45 species belong to 23 genera of calcareous nannofossils. Based on index calcareous nannofossils, the CC1, CC2, CC3, and CC4 biozones established by Sissinghh in both sections were determined. It is mentioned that CC5 biozone only occur in Kamar-e-Mehdi section. According to the identified biozones, the suggested age of the Baghamshah Formation is early Berriasian–early Hauterivian in the Rizu section, and early Berriasian–late Hauterivian in the Kamar-e-Mehdi section. Keywords: biostratigraphy, Baghamshah, calcareous nannofossils,Tabas, Iran.

The late Berriasian early evolutionary burst of the Orbitolinidae: New insights into taxonomy, origin, diversification and phylogeny of the family based on data from eastern Serbia

New data from the Carpatho-Balkanides of eastern Serbia evidence the more or less near-simultaneous "explosive" first appearances of several genera of the Orbitolinidae in the late Berriasian. Most of the observed taxa were previously recorded from strata not older than the Late Hauterivian (= classical Urgonian of southeastern France), evidence that these ages refer to local first appearance data. The diversified assemblage from Serbia includes representatives of the subfamilies Dictyoconinae: genera Cribellopsis ARNAUD-VANNEAU, Montseciella CHERCHI & SCHROEDER, Orbitolinopsis HENSON, Urgonina FOURY & MOULLADE, Valserina SCHROEDER & CONRAD, Vanneauina SCHLAGINTWEIT, and Dictyorbitolininae: genus Paracoskinolina MOULLADE. Representatives of the Orbitolininae (with complex embryo) have not been observed. They appeared later in the fossil record seemingly during the Late Hauterivian-early Barremian. All together 17 taxa are reported, of which three in open nomenclature. A new species is described as Cribellopsis sudari n. sp. The majority of the observed species display medium- to high-conical tests and a rather simple exoskeleton lacking horizontal partitions (rafters). The new data contradict a phylogenetic evolution of distinct genera displaying different internal test structures one after the other in time (= ancestor-descendant relationships) as postulated by some authors. The explosive radiation ("early burst") of the Orbitolinidae in the late Berriasian is accompanied by the first appearance date of several other large benthic foraminifera including mostly agglutinating (e.g., Ammocycloloculina, Choffatella, Drevennia, Eclusia, Moulladella, Pfenderina, Pseudotextulariella) but also complex porcelaneous taxa (Pavlovcevina) providing evidence for a bioevent in this time period that exceeds the number of taxa originating in the previous (Tithonian) and the following stage (Valanginian). The early evolutionary history of the Orbitolinidae can be considered a classical example of adaptive radiation within the clade's history.

Lithostratigraphic revision and biostratigraphy of Upper Hauterivian–Barremian strata from the Kugmallit Trough, Mackenzie Delta, Northwest Territories

Abstract The Kipnik Formation, named herein, is defined from the Late Hauterivian to Barremian Kugmallit Trough in the Mackenzie Delta, Arctic Canada. The trough was formed by extensional tectonics associated with the opening of the Canada Basin and was infilled by kilometre-thick accumulations of clastic sediments. Samples from the Kugmallit Trough are known only from two exploration wells – Shell Kipnik O-20 and Gulf Mobil Ogruknang M-31. Examination of palynomorphs, foraminifera, and ostracods from cuttings of these wells, integrated with regional subsurface and outcrop correlations, indicated that the existing subsurface stratigraphic interpretations [Upper Jurassic to Barremian] of the Kugmallit Trough were in need of revision. The revised Upper Hauterivian–Barremian succession thus consists of the Siku, Kipnik (new), and Mount Goodenough formations. The Siku and Kipnik formations are known only from the subsurface, but the Mt. Goodenough Formation is widespread and was deposited over a regional unconformity. The Siku to Kipnik deposition is a large-scale transgressive-regressive succession that represents deposition during a period of initial subsidence (transgression) followed by uplift and erosion (regression). The shale dominant Siku Formation contains a distinctive unnamed foraminiferal assemblage that consists of agglutinated species typical of offshore or deeper water. Ostracods of the Siku Formation are contained in the informal Galliaecytheridea postsinuata zone, which is confined to the Siku Formation. Ostracods of the G. postsinuata zone suggest shelf environments. The Kipnik Formation is sand-dominant with thin beds of shale, siltstone and coal. Agglutinated foraminifera occur sparsely because of coarse, rapid sedimentation. Inner shelf environments are suggested by the foraminifera. The lower half of the Mount Goodenough Formation is shale-dominant and the upper half consists of intercalated shale and sandstone. Foraminifera and ostracods occur abundantly in the Mt. Goodenough subsurface and outcrops of the Richardson Mountains. The foraminiferal Convallina mcneili Zone of Barremian age occurs in the Mt. -Goodenough Formation and its composition of agglutinated and calcareous benthic foraminifera suggests outer shelf or deeper environments. Ostracods of the Mt. Goodenough Formation in subsurface and outcrop are assigned to the informal Clithrocytheridea spp. zone. Ostracods suggest an outer shelf or deeper-water environment. Palynomorphs indicate that the Siku Formation is Late Hauterivian, the Kipnik Formation is probably latest Hauterivian to Early Barremian, and the Mount Goodenough Formation is Barremian.

Paleoclimate and ecology of Cretaceous continental ecosystems of Japan inferred from the stable oxygen and carbon isotope compositions of vertebrate bioapatite

Abstract We investigated the environmental conditions that prevailed in continental ecosystems recorded in sedimentary deposits of Japan during the Cretaceous through the analysis of oxygen and carbon isotope compositions of phosphate (δ18Op) and apatite-bound carbonate (δ18Oc and δ13Cc) of vertebrate teeth and bones. Local surface water δ18Ow values were calculated using known phosphate-water isotope fractionation equations. Anomalously low δ18Ow values of local waters strongly suggest a significant contribution of high-altitude precipitation from nearby mountains to local surface waters. Mean air temperatures were estimated using a global meteoric water δ18Omw value – Mean Annual Air Temperature relationship, and compared to surface water temperatures estimated from fish apatite δ18Op values. Local mean annual precipitations (MAP) were estimated using the known relationship existing between MAP and C3 plant δ13Cp value, the latter being calculated using apatite-diet 13C-enrichment applied to plant-eating sauropod and ornithopod dinosaur δ13Cc values. Reconstructed environmental conditions suggest that climate changed from cool temperate to warm temperate, being relatively cold and dry during the Late Hauterivian and Barremian to warmer and seasonally more humid during the Aptian and Albian, and even warmer during the Cenomanian-Coniacian. Proposed thermal evolution during the Early Cretaceous is compatible with the absence of thermophilic taxa such as crocodylomorphs before the Aptian in the fossil record of Japan.

Palaeoenvironmental conditions for the preservation of organic matter during the late Hauterivian in the Neuquén Basin (Western Argentina)

The Agua de la Mula Member of the Agrio Formation, comprises marine deposits accumulated in a mixed carbonate-siliciclastic outer ramp during the late Hauterivian. An innovative multi-proxy study that includes sedimentological, geochemical and paleobiological data from the El Portón section were combined in order to constrain the environmental context.Two major sedimentary cycles have been recognised (TST-HST) reflecting the position of both distal and proximal sediments within the depositional system. The distal outer ramp deposits (FA1) are predominantly characterised by carbonate-bearing mudstones, with TOC content up to 4.43 wt% TOC (average 1.62 wt%) and Type II marine-derived amorphous organic matter. The high TOC could be reflecting enhanced bioproductivity during periods of decreased salinity as mirrored by peaks of Micrantholithus, and reduced dilution by siliciclastic material in a distal setting. Conversely, the proximal outer ramp succession (FA2) shows a higher siliciclastic pattern, along with the terrestrial organic matter signal (Type II-III kerogen) and TOC content around 1 wt% (average 1.05 wt%). In this interval primary production is associated with more stable conditions and stratified water, as reflected in peaks of Nannoconus. These conditions allowed a greater diversity and high abundances of calcareous nannofossil assemblages.

Exploring the reservoir potential of Lower Cretaceous Clinoforms in the Fingerdjupet Subbasin, Norwegian Barents Sea

AbstractSandy clinothems are of interest as hydrocarbon reservoirs but there is no proven, economic, clinothem reservoir in the Norwegian Barents Sea. We used high‐resolution, 2D and 3D seismic, including proprietary data, to identify a previously untested, Barremian, clinoform wedge in the Fingerdjupet Subbasin (FSB). Data from recent well 7322/7‐1 plus seismic have been used to characterize this wedge and older Lower Cretaceous clinoforms in the FSB. In the latest Hauterivian – early Barremian, during post‐rift tectonic quiescence, shelf‐edge clinoforms (foreset height > 150 m) prograded into an under‐filled basin. Increased sediment input was related to regional uplift of the hinterland (northern Barents Shelf). Early Barremian erosion in the north‐western FSB and mass wasting towards the SE were followed by deposition of delta‐scale (<80 m high), high‐angle (c. 8°) clinoform sets seaward of older shelf‐edge clinoforms. This may be the local expression of a regional, early Barremian, regressive event. By the close of the Barremian, clinoforms had prograded, within a narrow, elongate basin, across the FSB and towards the uplifted Loppa High. A seismic wedge of high‐angle (10–12°), low‐relief, delta‐scale (25–80 m) clinoform sets occurs between shelf‐edge clinoforms to the NW and the uplifted area to the SE. Well 7322/7‐1, positioned on a direct hydrocarbon indicator, <1 km NNW of the high‐angle, low‐relief, delta‐scale clinoforms, found upward coarsening siltstone‐cycles linked to relative sea‐level fluctuations on a marine shelf. Sand may have accumulated, offshore from the well, in high‐angle, low‐relief foresets of the delta‐scale clinothems (which are typical geometries elsewhere interpreted as ‘delta‐scale, sand‐prone subaqueous clinoforms’). Deposition was controlled by the paleosurface, storms and longshore currents on an otherwise mud‐dominated shelf. The study highlights challenges associated with exploration for sandstone reservoirs in seismic wedges on an outer shelf.

Glaucoceras gen. nov., a small uncoiled ammonoid from the Tethyan late Hauterivian (Early Cretaceous): evolutionary implications at the dawn of the diversification of heteromorphic lineages

The poorly-known species Baculites Renevieri Ooster, 1860 is revised using the type material from Switzerland and new conspecific specimens collected in deposits from Mallorca and the Betic Cordillera (Western Mediterranean), listing all the previous mentions of the species. The uniqueness of its ornamentation pattern and shell shape compared to other coeval ammonoid faunas demands for the description of Glaucoceras gen. nov. to contain this species. In addition, a thorough comparison of Glaucoceras renevieri to other morphologically reminiscent genera or species is provided. This new set of data allows to improve the knowledge of one of the many phylogenetic lines of heteromorphic ammonites that diversified over the latest Hauterivian in the Mediterranean Province, also providing hints about the timing of those radiation events. This aspect is preliminary explored using data on other coeval heteromorphic ammonoid groups from the literature and new finds, concluding that there occurred two main radiation events of heteromorphic ammonites at the latest Hauterivian, most likely related to environmentally stressful episodes, specifically, transgressive events.

Lower and upper Cretaceous paleosols in the western Sichuan Basin, China: Implications for regional paleoclimate

Pedogenic features of paleosols preserved in the lower and upper Cretaceous sedimentary strata of the western Sichuan Basin, China, were described and examined in terms of their macromorphology and micromorphology, mineralogy, and geochemistry. These Cretaceous paleosols (entisols, inceptisols, and aridisols) are analogous to modern soil orders based on soil taxonomy (Soil Survey Staff, 2014). A quantitative reconstruction of paleoclimates inferred from the geochemical composition of paleosol horizons, depth to carbonate nodules, and the stable oxygen isotopic composition of pedogenic carbonates in paleosols indicates that a cool‐arid climate associated with short‐term subhumid fluctuations prevailed in the early Cretaceous (Hauterivian) and a cool‐arid climate regime existed in the late Cretaceous (Maastrichtian) of the Sichuan Basin. Atmospheric CO2 concentrations estimated from the paleosol barometer indicated values between 156 ± 138 and 753 ± 339 ppmv for the Hauterivian and between 110 ± 71 and 235 ± 77 ppmv for the middle–late Maastrichtian. An overall coupling between atmospheric pCO2 and paleotemperature occurred in the Sichuan Basin, while the covariations are likely linked to global cooling events in the Maastrichtian and/or are likely associated with the Faraoni oceanic anoxic event (F‐OAE) during the late Hauterivian. Paleoclimate variations in the Sichuan Basin were controlled by regional paleogeography, the prevalence of subtropical high‐pressure systems, monsoonal circulation, and the atmospheric CO2 level in the early and late Cretaceous.

Shell Microstructure of Kabanoviella obliterata Lahusen (Brachiopoda, Rhynchonellidae) from the Upper Hauterivian of Ulyanovsk Region

The shell microstructure of Kabanoviella obliterata from the Late Hauterivian of the Boreal Basin of Russian Platform was studied. The most part of its primary finely crystalline layer is composed of curved plates. The plate walls are joined to form a net composed of rhombic, rarely loop-shaped meshes. The upper part of secondary fibrous layer is capillate. The fibrous layer contains several prismatic sublayers.

Mercury anomalies, volcanic pulses, and drowning episodes along the northern Tethyan margin during the latest Hauterivian-earliest Aptian

The latest Hauterivian-earliest Aptian time interval includes three episodes of significant environmental change (Faraoni, late early-Barremian, and Taxy Episodes). This time interval appears to partially overlap with large-scale volcanic activity related to the Tristan da Cunha plume along the Rio Grande Rise, High Arctic large igneous province volcanism, and the early phase in the formation of the greater Ontong Java LIP in the Pacific. The establishment of exact temporal relationships between volcanic activity and environmental change remains, however, a major challenge, due to the scarcity of numerical ages for the Early Cretaceous. We report mercury (Hg) contents in uppermost Hauterivian-lowermost Aptian marl/limestone alternations from seven sections along a NS transect in the Western Tethys. The Hg contents in marl samples display rather scattered records, which are generally well correlated with the total organic carbon (TOC) records. In associated limestone beds, five distinct spikes in Hg concentrations occur in three intervals (latest Hauterivian, early Barremian, and latest Barremian). The small amounts of organic matter (<0.2 wt%) in the limestones suggest that organic matter only played a limited role in Hg sequestration. Three Hg peaks in the middle of the Balearites balearis Zone, in the Faraoni level, and in the early Barremian occur only in one of the seven studied sections, which indicate a regionally variable distribution of Hg during these episodes. However, two distinct enrichments in Hg concentrations at the top of the B. balearis Zone (below the Faraoni level) and the M. sarasini Zone (below the Taxy level) appear comparable and correlatable between the sections. These data indicate that important volcanic activity antedating the Faraoni and the Taxy episodes may have contributed to the onset of associated environmental and ecological perturbations during the latest Hauterivian and latest Barremian, such as carbonate platform drowning phases.

The Faraoni event (latest Hauterivian) in ichnological record: The Río Argos section of southern Spain

The Early Cretaceous (latest Hauterivian) Faraoni Oceanic Anoxic Event (F-OAE) in the Río Argos section (Caravaca region, southern Spain), the candidate for the Global Boundary Stratotype Section and Point (GSSP) of the Hauterivian–Barremian transition, has been studied. Its ichnological bed-by-bed analysis allows for interpretation of oxygenation changes through the Faraoni Level interval and improvement upon previous characterization of oxygen conditions prior, during and after the F-OAE. The trace fossil assemblage belongs to the Zoophycos ichnofacies and it includes Chondrites intricatus, Chondrites targionii, Halimedides isp., Palaeophycus isp., ?Patagonichnus isp., Planolites isp., Rhizocorallium isp., Taenidium isp., Thalassinoides isp., Trichichnus linearis, Zavitokichnus fusiformis, and Zoophycos isp. Their diversity in particular beds fluctuates. Beds with four to six ichnotaxa reflect a multi-tiered macrobenthic trace maker assemblage living in good oxic and trophic conditions. In one bed below and one bed above the Faraoni Level (both marls without primary lamination), there are only two or three, mostly opportunistic ichnotaxa (Trichichnus, Chondrites, Planolites). They record dysoxic conditions. At the base of the Faraoni Level, one thicker and two thinner beds of marly mudstones (21.2 and 3.5 cm thick, respectively) are characterized by primary lamination. At the top and in the basal part of the thicker bed and in the thinner beds some trace fossils are present. These beds were deposited under anoxic conditions and later colonized by trace makers either from overlying beds deposited under oxic conditions or from the level of a greenish lamina in the lower part of the thicker bed, recording short episodes of dysoxic conditions. The thinner anoxic beds are separated by marls deposited under dysoxic conditions.

Pseudothurmanniid ammonites from quarries near Lietavská Lúčka and their stratigraphical significance (Late Hauterivian, Central Western Carpathians, Slovakia)

Pseudothurmanniid ammonites within Upper Hauterivian calcareous deposits are present in quarries on Polomec Hill near the village of Lietavska Lucka, Slovakia. These deposits belong to the Mraznica Formation of the Križna Nappe that is a part of the Fatricum Unit in the Central Western Carpathians. Nine ammonite species are described in detail, one of which, Binelliceras michaliki , is new. The species identified indicate the Upper Hauterivian Balearis and Ohmi ammonite zones. The zone of the uppermost Hauterivian, Catulloi Zone, is not documented as far as pseudothurmanniid ammonites are concerned. The lack of developmentally younger representatives of the pseudothurmanniid ammonites neither in the studied locality, nor in other Slovak localities, is explained by marked changes in the northern Tethyan margin in Europe during the latest Hauterivian.

Leptolepid otoliths from the Hauterivian (Lower Cretaceous) Lower Weald Clay (southern England)

Teleostean saccular otoliths from the upper part of the late Hauterivian Lower Weald Clay Formation of the Wealden Supergroup exposed at Langhurstwood Quarry, West Sussex, UK, and Clockhouse Brickworks, Surrey, UK are described for the first time. Two new species of the genus Leptolepis, Leptolepis wealdensis and Leptolepis toyei are described. Many of the specimens are densely packed on individual bedding planes and they are interpreted as coprocoenotic accumulations. Additional mechanisms of deposition and concentration are discussed, in particular wave action. Ontogenetic series show isometric growth of the otoliths, and some specimens show growth rings on two orders of magnitude.

Diversity dynamics of Early Cretaceous brachiopods in the tectonic units of Serbia: regional versus global patterns

The Danubian, Getic, and Vardar tectonic units of Serbia (northern Neo-Tethys) provide a rich palaeontological record permitting quantitative assessment of the Early Cretaceous brachiopod diversity dynamics. The compilation and the subsequent revision of the available information permit to document the stratigraphical ranges of 44 species, 26 genera, 15 families, and 11 superfamilies. Three diversity peaks (Late Valanginian, Early Barremian, and Early Albian) are established, as well as the Late Barremian–Late Aptian long-term diversity decline. Brachiopods were absent in the Berriasian–Early Valanginian, Late Hauterivian, and the Middle–Late Albian. It is established that the post-Early Barremian diversity decline occurred chiefly because of rare taxa appearances. The vulnerability of representatives of the superfamilies Terebratuloidea and Hemithiridoidea to external influences shaped the regional diversity dynamics of brachiopods. The amplitude of changes of the assemblage composition through the epoch was high. There were both similarities and dissimilarities between the regional and global diversity dynamics of brachiopods, and weak correspondence between the patterns is an evidence of heterogeneity of the Early Cretaceous brachiopod diversity changes in the global space. For instance, the Barremian radiation did not occur on the planetary scale. The interplay of the global factors (global diversity dynamics, eustatic changes, and oceanic anoxic events) and the regional factors (e.g., changing depositional environment) is proposed to explain the observed diversity patterns.