Submediterranean Province Research Articles

Ammonite biozonation and chronostratigraphy of the Upper Bajocian–Upper Oxfordian of the Dalichai Formation at the Kuh-e-Varvari section (North of Damghan, Alborz and North Iran)

ABSTRACT The Middle–Upper Jurassic strata in the eastern part of the Alborz, North of Iran (Dalichai Formation) were studied based on ammonite fauna to correlate with zonation of other West Tethyan areas (Sub-Mediterranean province). In this section, like other studied sections in North and northeast of Iran, the ammonite assemblages such as Parkinsoniidae, Morphoceratidae, Sphaeroceratidae, Macrocephalitidae and Reineckeiidae mainly show the characteristics of etyan groups. Abundant ammonite fauna in some levels has enabled an accurate chronostratigraphy. The presence of this ammonite fauna that is seen in the epicontinental seas, bordering the northern margins of the western Thetys, led to the identification of some zones in accordance with the standard of Sub-Mediterranean province zonation. The Garantiana and Parkinsoni Zones of the Late Bajocian, the Zigzag and Aurigerus Zones of the Early Bathonian, the Retrocostatum and Discus Zones of the Late Bathonian, the Bullatus and Gracilis Zones of the Early Callovian, the Anceps and Coronatum Zones of the Middle Callovian and the Athleta and Lamberti Zones of the Late Callovian have been recognised and characterised. These assemblages show a relation between these regions with the Sub-Mediterranean province during the Jurassic. Low percentage of Phylloceratidae in this section is an indicative of Sub-Mediterranean affinity. Based on the ammonite fauna, the Dalichai Formation is Late Bajocian-Late Oxfordian in age.

Kimmeridgian and early Tithonian cephalopods from the Kisújbánya Limestone Formation, Zengővárkony (Mecsek Mountains, southern Hungary), their faunal composition, palaeobiogeographic affinities, and taphonomic character

A new collection at Zengővárkony (Mecsek Mountains, Hungary) provided a rich and diverse but poorly preserved cephalopod-dominated fossil assemblage representing the Kimmeridgian and the lower Tithonian. The material came from mixed scree, soil, and amongst roots affected by weathering processes having been exposed to the elements for a long time. The nautiloid Pseudaganides strambergensis is the first record from the Mecsek Mountains. Due to the weathering, the ammonite fauna consists of mainly fragmentary and dissolved individuals that comprises 528 specimens belonging to 34 species and 30 genera out of which 20 species and 15 genera are reported for the first time from the Mecsek Mountains. The fauna includes specimens of known taxa. No new taxa are introduced. Based on the comparison with other faunas, this assemblage most closely resembles the fauna of the Venetian Alps (Italy). Additional faunal elements include aptychi (Laevaptychus latus, Lamellaptychus murocostatus), belemnites (Hibolithes semisulcatus), and an indetermined brachiopod. The first record of Spiraserpula spirolinites, an encrusting fossil polychaete preserved on the internal mould of a Taramelliceras shell fragment indicates favourable bottom conditions for the epifauna. The presence of Aspidoceras caletanum, Gravesia aff. gigas, and Pseudowaagenia inerme indicates faunal connections with the Submediterranean Province of the Tethys, which is in line with the tectonic and palaeogeographical position of the Mecsek Zone during the Late Jurassic. The ammonite assemblage represents elements of five Tethysian ammonite zones of the Kimmeridgian and Tithonian. The lower Kimmeridgian Herbichi Zone is indicated by Streblites tenuilobatus and Praesimoceras herbichi. The upper Kimmeridgian Acanthicum Zone is indicated by Aspidoceras acanthicum, and the Cavouri Zone by Mesosimoceras cavouri and Aspidoceras caletanum. The upper Kimmeridgian Beckeri Zone is suggested by Hybonoticeras pressulum and Pseudowaagenia inerme. Whereas Gravesia aff. gigas, Lithacoceras aff. siliceum, and Malagasites? denseplicatus are faunal elements characterising the Early Tithonian Hybonotum Zone. Phylloceratid and lytoceratid specimens account only for 12% of the fauna, while the majority of the specimens belong to the Oppeliidae and Ataxioceratidae (60%).

Nejdia (Hildoceratidae, Ammonoidea) in the Toarcian (Lower Jurassic) of the Iberian Peninsula. Systematics, phylogenetic affinities and palaeobiogeography

ABSTRACT The genus Nejdia Arkell, 1952 has rarely been cited outside the Arabo-Malgach Province and, few specimens have been recorded outside this province. On the Iberian Peninsula it has been identified in three sites, two of these in the southwest of the Iberian Basin and one in the Lusitanian Basin. Three species are described: N. cf. bramkampi, N. pseudogruneri and N. duartei sp. nov., Following the indications of the journal the new species was recorded in the ZooBank recorded in the interval between the upper part of the Serpentinum Chronozone, where they are associated with Harpoceras falciferum and Orthildaites douvillei and the lower part of the Bifrons Chronozone containing Hildoceras sublevisoni. In all the Iberian outcrops having a record of Nejdia, the fossils constitute ademic or parademic taphonic entities, as there is no evidence to indicate that the known populations inhabited an area close to the southwest sector of the Iberian Range, or the northern part of the Lusitanian Basin, where were recorded. With the specimens obtained in Portugal, the known geographic distribution of the genus Nejdia is extended, currently comprising, apart from the Arabo-Malgach Province, the Iberian Range and the Lusitanian Basin in the Submediterranean Province, and the Middle Atlas and the Apennines in the Mediterranean Province. url:lsid:zoobank.org:pub:BEE9F42E-92FE-483E-9CC1-B4B8FB927E82

A summary of the Jurassic System in North and East-Central Iran

The rocks of the Jurassic System in North and Central Iran are represented by very thick sedimentary successions reflecting the deposition during two tectono-stratigraphic megacycles, bounded by three important unconformities. The older (Early to early Middle Jurassic) cycle starts, after the Late Triassic closure of the Palaeotethys and the collision of the Iran Plate with the southern margin of Eurasia (Turan Plate), with an abrupt uplift of the Cimmerian Mountains around the Triassic–Jurassic boundary (Main-Cimmerian Event) and is terminated by the Mid-Cimmerian Tectonic Event in the mid-Bajocian. The predominantly siliciclastic sediments of this tectono-stratigraphic cycle are accommodated in the Ab-e-Haji Subgroup of the (upper) Shemshak Group. The Ab-e-Haji Subgroup consists of thick and widespread, partly coal-bearing siliciclastic strata and also records some important marine ingressions, especially in the Toarcian and Aalenian. The younger tectono-stratigraphic cycle starts with an extensive marine transgression in the Late Bajocian and ends around the Jurassic-Cretaceous boundary with the Late Cimmerian Tectonic Event. In the aftermath of the Mid-Cimmerian Tectonic Event, the Iran Plate was dissected into several structural units, the geological histories of which differed and so did their facies patterns. Thus, in North Iran two main sedimentary areas developed, namely the Alborz and Koppeh Dagh basins, which show moderate diffe-rences in lithology and thicknesses. However, the differentiation is much more pronounced on the Central-East Iranian Microcontinent, which comprises three N–S-oriented and independent structural units, i.e., from east to west the Lut, Tabas and Yazd blocks. During the Jurassic Period, the sea mostly covered the Tabas and Lut blocks, whereas the Yazd Block remained largely emergent. The lithologically diverse and numerous formations of the area are combined in the Magu and Bidou groups. Early to Early Middle Jurassic ammonite fau-nas of North and Central Iran are palaeobiogeographically closely related to Northwest European (Subboreal) ammonite faunas, allowing a similar biozonation. Concurrent with the Late Bajocian transgression, there is an abrupt change in faunal composition and the Middle and Late Jurassic ammonite faunas of North and Central Iran are much more similar to those of epicontinental seas bordering the nort-hern margin of the western Tethys and occupy an intermediate position between the Mediterranean and the Submediterranean Province. The results of the studies on ammonoid palaeobiogeography are in line with Early Jurassic palaeogeographic reconstructions that place the Iran Plate at fairly high palaeo-latitudes of about 45°N, followed by a rapid southward shift throughout the Middle and Late Jurassic to a position of about 30°N.

Pacing of late Pliensbachian and early Toarcian carbon cycle perturbations and environmental change in the westernmost Tethys (La Cerradura Section, Subbetic zone of the Betic Cordillera, Spain)

Abstract Detailed assessment of high-resolution elemental and isotopic geochemical datasets collected from the marl–limestone alternations cropping out at La Cerradura (Subbetic domain of the Betic Cordillera, Spain) and chrono- and chemostratigraphic correlation with the reference Mochras borehole (Cardigan Bay Basin, UK) unveiled valuable new insights into understanding of late Pliensbachian–early Toarcian palaeoenvironmental dynamics in a key geographical area between the northern European seaway and the Tethys Ocean. This study shows that deposition in the study area took place under dominantly oxic water column conditions, indicated, for example, by the generalized lack of enrichment in organic matter and redox metals typically associated with anoxia and euxinia. Carbon isotope stratigraphy (δ 13 C TOC ) allowed recognition of the spinatum (= emaciatum in the Submediterranean Province), Pliensbachian–Toarcian, and early Toarcian Oceanic Anoxic Event negative carbon isotopic excursions and the late Pliensbachian positive carbon isotopic excursion. It is here suggested that the observed periodic changes in lithology and sedimentary geochemistry occur at orbital frequencies (i.e. long and short eccentricity and, tentatively, precession), hinting at an astronomical control of the local–regional climate and environment during the Pliensbachian and Toarcian in the mid- to low-latitude South Iberian palaeomargin area.

Sr-isotope stratigraphy (87Sr/86Sr) of the lowermost Toarcian of Peniche, Portugal, and its relation to ammonite zonations

At Peniche, Portugal, the GSSP for the base of the Toarcian and in a Submediterranean province, a value of 0.707 073 ± 0.000 002 (2s.e., n = 13) is determined for 87Sr/86Sr at the base of the Toarcian. In Yorkshire, UK, a Subboreal province, the base of the Toarcian has an 87Sr/86Sr value of0.707 072 ± 0.000 002 (2s.e., n = 23). The similarity of the values shows that, within analytical uncertainty, these levels are exactly equivalent in time. At Peniche, the base of the Serpentinum (Falciferum/Levisoni) Chronozone has an 87Sr/86Sr value of 0.707 096 ± 0.000 003 (2.s.e). The value for this boundary in Yorkshire is 0.707 094 ± 0.000 002 (2s.e., n = 27). The similarity of the values shows that, within analytical uncertainty, these levels are exactly equivalent in time. The same ammonite successions occur through the lowermost Toarcian successions at Peniche and in Yorkshire. Between Peniche and Yorkshire, there is therefore an exact coincidence, within measurement uncertainty, between the Lower Toarcian, Tethyan Realm, Tenuicostatum (Polymorphum) [ammonite] Chronozone of Peniche and the Lower Toarcian, Boreal Realm, Tenuicostatum [ammonite] Chronozone of Yorkshire. The 87Sr/86Sr profile through the Tenuicostatum Subchronozone at Peniche reveals large variations in sedimentation rate, with lowest rates in a condensed basal 3 m of the zone, highest rates in mid-zone, with rates decreasing upward through the upper half of the zone. Apportioning time in proportion to 87Sr/86Sr shows that around half of Tenuicostatum time is condensed into the basal 3 m of the section.

Lower Toarcian ammonite and foraminifera assemblages in the San Miguel de Aguayo Section (Basque-Cantabrian Basin, Spain)

We present the biostratigraphical events, ammonites and foraminifera from the Pliensbachian (Spinatum Chronozone) to the Toarcian (Bifrons Chronozone) in San Miguel de Aguayo. We sampled the profile layer by layer for ammonites (400 specimens in 86 successive levels), and we extracted 19 samples for foraminifera (4858 picked specimens). In the Spinatum Chronozone, the Amaltheidae Family dominated, with little presence of the Arieticeratinae or Harpoceratinae. The Tenuicostatum Chronozone presents a good record of Dactylioceratinae, with successive species, from Dactylioceras (Eodactylites) simplex to Dactylioceras (Orthodactylites) semicelatum. The Serpentinum Chronozone is characterised by Harpoceratinae (Eleganticeras, Cleviceras, Harpoceras), Hildoceratinae (Hildaites, Orthildaites) and by the persistence of Dactylioceras (Orthodactylites). The Bifrons Chronozone presents a good succession of Hildoceras. The foraminifera are benthic and autochthonous, and the calcareous hyaline taxa of the Lagenina Suborder, Vaginulinidae Family, are dominant. The most diverse genera are Nodosaria and Lenticulina. The most abundant species is Lenticulina toarcense, which constitutes 55.37% of the total number of specimens. Also represented, albeit as a minority, are the Textulariina, Miliolina, Spirillinina and Robertinina Suborders. The ammonites are typical of the Submediterranean Province and common to the Subboreal Province; the species of the Mediterranean Province are scarce and their record is sporadic in the Pliensbachian–Toarcian transition. The foraminifera are typical of the Atlantic Boreal Domain; two main biotic events were recognised: step-wise extinction of species between the Hawskerense and Semicelatum subchronozones, with a maximum extinction rate in the Semicelatum Subchronozone, and faunal turnover principally in the Elegantulum Subchronozone (Serpentinum Chronozone).

Comments on the identification of Ammonites planula Hehl in Zieten, 1830 (Upper Jurassic, SW Germany)

Ammonites planula Hehl in Zieten, 1830 is the type species of the Late Jurassic ammonite genus Subnebrodites Spath, 1925 and the index species of the well-established Planula Zone of the Submediterranean Province. Recently, Enay and Howarth (2017) classified this stratigraphically important ammonite species as a ʻnomen dubiumʼ and considered it to be the possible macroconch counterpart of Idoceras balderum (Oppel, 1863). These authors claimed “Subnebrodites planula Spath, 1925” instead of Ammonites planula (Hehl in Zieten, 1830) to be the type species of Subnebrodites. However, their nomenclatorial acts are based on erroneous assumptions. For future taxonomic stability we here propose a neotype for Ammonites planula (Hehl in Zieten, 1830) and a lectotype for Ammonites planula gigas Quenstedt, 1888. In addition, dimorphism within the stratigraphically much younger Idoceras balderum (Oppel) is demonstrated showing that there is no morphological resemblance and no closer relationship with Ammonites planula (Hehl in Zieten, 1830).

The Upper Oxfordian and Lower Kimmeridgian ammonite genera Idoceras Burckhardt, 1906, and Subnebrodites Spath, 1925

ABSTRACT The type species of the genera Idoceras Burckhardt and Subnebrodites Spath are clarified in order to preserve the current universal usage of the Planula Zone in the Upper Oxfordian and the Balderus Zone in the Lower Kimmeridgian of the Submediterranean Province. To protect both zones, the identification of Ammonites planula Hehl in Zieten, 1830 in 1830–1833, is investigated and found to be a nomen nudum.

Pseudoteloceras, a new stephanoceratid genus (Ammonitida) of the lower Humphriesianum Zone (lower Bajocian, Middle Jurassic) from western Tethys

The new dimorphic genus Pseudoteloceras (type-species: P. crosillense gen. et sp. nov.) is defined within the subfamily Stephanoceratinae. It constitutes the terminal step of an early Bajocian phyletic trend that produces Teloceras-like morphologies throughout the lower Humphriesianum Zone of the western Mediterranean-Caucasian Subrealm, at an older chronological interval and with morpho-structural features that stand apart from those of the best known genus Teloceras of the uppermost Humphriesianum and lower Niortense zones at the early/late Bajocian transition. Three new species are described: P. croisillense, P. maerteni and P. boursicoti. Their biochronostratigraphical ranges are confirmed by the distribution in expanded sections of the Subalpine Basin in Submediterranean Province (Digne area) and the taphonomic analysis of fossil assemblages from the condensed sections of the “Oolithe ferrugineuse de Bayeux” Formation in Calvados, North West European Province. The biochronostratigraphical range of Pseudoteloceras gen. nov. is limited to the Romani Subzone, lower Humphriesianum Zone. P. crosillense gen. et sp. nov. marks a well-defined biohorizon of the upper Romani Subzone in the Digne stratigraphical successions. The extreme degree of the cadiconic morphology in the inner whorls of P. boursicoti gen. et sp. nov., and the biostratigraphical gap separating the first appearance of the genus Teloceras in the upper Humphriesianum Zone, support its erection as a new taxon Pseudoteloceras gen. nov. A fourth species, Pseudoteloceras geometricum (Maubeuge), is interpreted as the earliest species of this phyletic lineage, derived from Stemmatoceras and widely distributed through western Tethys in the lower Humphriesianum Zone.

The Early Tithonian (Late Jurassic) ammonite genus Virgatosimoceras Spath (Ammonoidea: Simoceratidae) revision and value for correlation

New findings of the Early Tithonian genus Virgatosimoceras SPATH (Simoceratidae) from Hungary confirm the existence of a new chronospecies (Virgatosimoceras dunaii n. sp.) which fills the gap between V. albertinum and V. rothpletzi. The successive chronospecies demonstrate a well defined lineage through the Early Tithonian Darwini, Semiforme and Fallauxi zones, opening the possibility of enhancement of the time-correlation of the Submediterranean Province with adjacent regions. All figured records of Virgatosimoceras are revised. Micro- and macroconchs are tentatively distinguished for the first time. The similarities between Virgatosimoceras and some homoeomorphic perisphinctids are discussed. Based on the known records, is concluded that the genus was restricted to the western Tethys.

Oxfordian magnetostratigraphy of Poland and its correlation to Sub-Mediterranean ammonite zones and marine magnetic anomalies

A nearly continuous magnetostratigraphic polarity pattern was compiled from several ammonite-zoned carbonate successions of southern Poland and from a composite magnetostratigraphy from the Iberian Range of Spain. The array of sections spans the middle two-thirds of the Oxfordian within the Sub-Mediterranean Province (Cordatum through Bifurcatus ammonite zones). The average paleopole calculated from eight of these Polish sections is at 78.5°N, 184.9°E ( δp = 2.6°, δm = 3.5°). The Sub-Mediterranean polarity pattern is consistent with an independent polarity pattern derived from the Boreal-realm sections of the British Isles, and improves the inter-correlation between these faunal realms. Cycle stratigraphy published for these ammonite subzones from southern France enabled temporal scaling of the polarity pattern, thereby facilitating correlation to marine magnetic anomalies M28 through M33 as modeled from deep-tow magnetometer surveys in the Western Pacific. The bases of the Middle and Upper Oxfordian substages as defined in the Sub-Mediterranean zonation in Poland correspond approximately to chrons M33 and M29 of that Pacific M-sequence model.

Ammonite succession at the Bajocian/Bathonian boundary in the Cabo Mondego region (Portugal)

The Cabo Mondego outcrops exposed along the cliffs, on the western margin of the Iberian Plate, show an expanded stratigraphic section of Lower Bathonian deposits containing abundant ammonoids. Upper Bajocian deposits correspond to similar facies, of muddy limestones alternating with marlstones, although ammonoids are scarce. A detailed succession of ammonites across the Bajocian/Bathonian boundary has been recognized at Cabo Mondego, which can form a useful bio- and chronostratigraphic standard for the Lusitanian Basin. The revision of previous collections from the classical section and new field samplings of two other separate sections allow the recognition through up to twenty metres of thickness, the highest zone of Bajocian (Parkinsoni Zone) and the lowest zone of Bathonian (Zigzag Zone). The Parkinsoni and the Zigzag zones established for NW European areas and belonging to the Northwest European Province, can be identified in the Lusitanian Basin, although the ammonite fossil assemblages are composed of Submediterranean taxa. However, a subdivision of the Parkinsoni Zone is not possible, due to the scarcity of well preserved ammonoids. The Zigzag Zone can be recognized and characterized as composed of two subunits (Parvum and Macrescens subzones) as represented in diverse European basins of the Submediterranean Province. Ammonite fossil assemblages of the Parvum Subzone may be grouped into two successive horizons, which are biochronostratigraphically equivalent to the subdivisions of the Convergens Subzone distinguished in the Digne-Barreme area (SE France). New biochronostratigraphic data on the Bigotitinae, youngest members of Leptosphinctinae and oldest members of Zigzagiceratinae are relevant in understanding the evolution and faunal turnover of the West Tethyan Perisphinctidae during earliest Bathonian. The ammonite succession at the Bajocian/Bathonian boundary in the Cabo Mondego region (Portugal) represents one of the most complete biostratigraphic records so far recognized on the Iberian Plate.

The Sub-Boreal/Boreal ammonite succession at the Oxfordian/Kimmeridgian boundary at Flodigarry, Staffin Bay (Isle of Skye), Scotland

ABSTRACTThis paper describes extensive new collections of ammonites made bed-by-bed across the Oxfordian/Kimmeridgian boundary sequence in the Flodigarry sections at Staffin Bay on the Isle of Skye. The ammonites belong to the Sub-Boreal family Aulacostephanidae and the Boreal family Cardioceratidae, enabling recognition of both the current standard Sub-Boreal and Boreal ammonite zonations. In consequence, it is possible to make a close correlation of these two zonal schemes through the interval studied in Skye. The research has provided new palaeontological data at levels of precision that justify the proposal of the section at Staffin as the site of a potential Global Boundary Stratotype Section and Point (GSSP) for the Oxfordian/Kimmeridgian boundary.The traditional Oxfordian/Kimmeridgian boundary placed at the Pseudocordata/Baylei zonal boundary of the Sub-Boreal zonal scheme corresponds precisely to the Rosenkrantzi/Bauhini zonal boundary of the Boreal zonal scheme. This level is characterised by the appearance of the first Pictonia (Pictonia flodigarriensis sp. nov.) together with first Prorasenia, replacing an older assemblage of Ringsteadia–Microbiplices (Sub-Boreal). It is also characterised by the first occurrence of small-sized Amoeboceras (Plasmatites) spp., as well as large Amoeboceras schulginae Mesezhnikov (Boreal). An alternative level that may be considered as a potential GSSP is the boundary between the Bauhini Zone and the Kitchini Zone of the Boreal zonal scheme, characterised by first occurrence of Amoeboceras (Amoebites) of the A. bayi group. This level corresponds to the Planula/Galar subzonal boundary of the Sub-Mediterranean zonal scheme, and lies close to the currently accepted Oxfordian/Kimmeridgian boundary in the Sub-Mediterranean Province.

THE STRATIGRAPHY OF THE UPPER BATHONIAN TO MIDDLE OXFORDIAN SUCESSION OF THE ARAGONESE BRANCH OF THE CORDILLERA IBÉRICA (SPAIN) AND ITS EUROPEAN CONTEXT

The Upper Bathonian-Middle Oxfordian succession of the Aragonese branch of the Cordillera Iberica is one of the most completely developed in Europe and includes localities of international importance for Jurassic bio- and chronostratigraphy. Of particular importance are a potential stratotype for the Upper Bathonian of North West Europe and reference sections for a number of Submediterranean Province Middle Oxfordian biostratigraphic units. The intervening Callovian sequence, albeit locally strongly condensed, also includes faunas of key stratigraphical importance. The sequence of stratigraphically important ammonite faunas for this interval is here reviewed and placed in its European context.

OXFORDIAN BIOSTRATIGRAPHY AND AMMONITE ASSOCIATIONS FROM WEST SICILY: BIOSTRATIGRAPHIC SUCCESSION OF GENUS GREGORYCERAS AND CORRELATION WITH TETHYAN PERISPHINCTID SCALE

Middle to lower upper Oxfordian ammonite successions from northwest Sicily, are mainly composed of groups showing a typical Mediterranean character. These include common representatives of suborder Phylloceratina. Among Ammonitina, the bulk of recorded associations is formed by representatives of Mediterranean subfamilies Passendorferiinae, Euaspidoceratinae and Peltoceratinae, with a minor representation of family Oppeliidae. The studied ammonite associations include over two hundred specimens, from which, a whole of one hundred and fifty have been identified and described. They have been collected from three sections located on the southern side of Mount Erice, southwest from the town of Erice (Trapani province). Taphonomic features displayed by the recorded ammonites indicate, on one hand, sedimentation conditions on an open hemipelagic platform under low turbulence conditions and low sedimentation rate values. On the other hand, Perisphinctid (Passendorferiinae) and Aspidoceratidae assemblages appear dominated by juvenile or pre-adult specimens, indicating palaeobiological entities probably colonizing the area and spreading to epicontinental areas farther North from the southern slope of Tethys. From the biostratigraphic point of view, stratigraphic succession of representatives of genus Gregoryceras has allowed recognising a biostratigraphic succession in the Mediterranean Province, which can closely correlate with the one established with representatives of Passendorferia and Perisphinctes for the Submediterranean Province.

Carbon and oxygen isotope composition of Oxfordian–Early Kimmeridgian belemnite rostra: palaeoenvironmental implications for Late Jurassic seas

Stable isotope analyses have been undertaken on Oxfordian–Early Kimmeridgian belemnite rostra derived from three palaeogeographic provinces of Europe: (1) the Boreal–Subboreal Province (Isle of Skye in Scotland); (2) the Submediterranean Province (central Poland and southern Germany); and (3) the Mediterranean Province (Pieniny Klippen Belt in the Western Carpathians). The samples have been screened for possible diagenetic alteration by using cathodoluminescence and trace element analyses and have been found to be largely well-preserved. Calculated palaeotemperatures (10–15°C) and analyses of belemnite habitats suggest that the Boreal–Subboreal belemnites were living in a relatively shallow sea (not deeper than 100–150 m) while the other belemnites possibly inhabited deeper neritic environments. Despite the influence of a vital effect, the δ 13C values of belemnite rostra are interpreted to reflect primary variations in the oceanic carbon isotope signal. The fairly uniform Submediterranean δ 13C values indicate a similar isotope composition of dissolved inorganic carbon (DIC) in the area of sedimentation of sponge megafacies in the deep Tethyan shelves. The slightly lowered δ 13C values of some Mediterranean belemnites might occur due to upwelling providing 12C enriched bottom waters onto the area of the Czorsztyn Ridge in the Oxfordian. The discernibly more positive (1–2.5‰) δ 13C values of Boreal–Subboreal belemnites are related to a high biologic productivity and a high organic matter burial in the partly isolated Boreal Sea. The stated differentiation in carbonate δ 13C values distinctly exceeds present-day differences in isotope composition of seawater DIC.

The Middle Jurassic of western and northern Europe: its subdivisions, geochronology and correlations

The palaeogeographic settings of Denmark and East Greenland during the Middle Jurassic are outlined. They lay in the widespread epicontinental seas that covered much of Europe in the post-Triassic transgression. It was a period of continuing eustatic sea-level rise, with only distant connections to world oceans: to the Pacific, via the narrow Viking Straits between Greenland and Norway and hence the arctic Boreal Sea to the north; and to the subtropical Tethys, via some 1200 km of shelf-seas to the south. The sedimentary history of the region was strongly influenced by two factors: tectonism and climate. Two modes of tectonic movement governed basinal evolution: crustal extension leading to subsidence through rifting, such as in the Viking and Central Grabens of the North Sea; and subcrustal thermal upwelling, leading to domal uplift and the partition of marine basins through emergent physical barriers, as exemplified by the Central North Sea Dome with its associated volcanics. The climatic gradient across the 30º of temperate latitude spanned by the European seas governed biotic diversity and biogeography, finding expression in rock-forming biogenic carbonates that dominate sediments in the south and give way to largely siliciclastic sediments in the north. Geochronology of unrivalled finesse is provided by standard chronostratigraphy based on the biostratigraphy of ammonites. The Middle Jurassic saw the onset of considerable bioprovincial endemisms in these guide-fossils, making it necessary to construct parallel standard zonations for Boreal, Subboreal or NW European and Submediterranean Provinces, of which the NW European zonation provides the primary international standard. The current versions of these zonations are presented and reviewed.

Sea-level changes and ammonite faunal turnover during the Lias/Dogger transition in the western Tethys

Abstract The aim of this paper was to investigate the possible connections between ammonite faunal turnover and the eustatic events recorded in Tethyan sequences during the middle Toarcian/early Bajocian time interval. For this we have analysed the biostratigraphic ranges, at the subzone level, of approximately 600 ammonite species belonging to 160 genera from several selected sections of the western Tethys (Mediterranean and Submediterranean provinces). The analysis of taxon ranges enabled us to plot curves for ammonite faunal turnovers, inter-subzonal distance, and diversity. Comparing the mentioned curves with Tethyan sequences [Hardenbol et al., 1998], we find that sea-level changes correlate well with origination and extinction events and faunal diversity. Most of the faunal turnovers correlate with stratigraphic events. Extinction events with their corresponding decrease in diversity correlate with regressive intervals and with major or minor sequence boundaries. Origination events and their corresponding increase in diversity were clearly connected with transgressions in Tethyan sequences. In several cases, the major sequence boundary and the subsequent transgressive phase correlate with major ammonite faunal turnover, whereas minor or medium sequence boundaries generally gave rise to minor or medium turnovers.

Réinterprétation de Peltoceratoides athletoides (Lahusen), 1883 (Ammonitina, Aspidoceratidae). Conséquences sur la biozonation du Callovien supérieur et de l'Oxfordien inférieur

Peltoceratoides athletoides (Lahusen) is currently used in the Tethyan domain (Submediterranean province) as an index-species for two separate biochronological units: one a horizon near the top of the Callovian, the other a zone at the base of the Oxfordian. Paleontological revision of the species, from specimens collected in situ in South East France and in Normandy shows that species is strictly localized in the lowermost Oxfordian. Consequently, the Callovian horizon, originally defined in Anjou, should be renamed the Schroederi horizon. The usefulness of Peltoceratoides athletoides as an indicator of the first Oxfordian zone in the Tethyan domain, the counterpart of the Mariae zone, is confirmed. In addition, strict localization of the species makes it is possible to define a subzone and a horizon for the base of the Oxfordian, which are the boreal equivalents of the Scarburgense subzone and Scarburgense horizon. These new data contribute to build a standard West Tethyan scale entirely independant of the boreal zonation for the Upper Callovian and Lower Oxfordian.