The Early Jurassic palynostratigraphy of the Lusitanian Basin,western Portugal

A comprehensive investigation of the Early Jurassic stratigraphical palynology of the Lusitanian Basin in western Portugal was undertaken, with most emphasis placed on dinoflagellate cysts. A total of 214 samples from an upper Sinemurian to upper Toarcian composite section based on six successions were examined. The Sinemurian material examined was barren of dinoflagellate cysts; however, the Pliensbachian and Toarcian successions are characterised by relatively low diversities where Luehndea spinosa, Mancodinium semitabulatum, Mendicodinium microscabratum, Nannoceratopsis gracilis, Nannoceratopsis senex, and Scriniocassis priscus are relatively common and biostratigraphically significant. Luehndea spinosa dominates the lowermost Toarcian (Dactylioceras polymorphum ammonite Biozone), and is an index species. At the base of the Hildaites levisoni ammonite Biozone, the effects of the Toarcian Oceanic Anoxic Event (T-OAE) caused Luehndea spinosa to become extinct. At the same time, dinoflagellate cyst abundance and diversity markedly decreased. After the T-OAE, during the middle and late Toarcian, phytoplankton recovery was prolonged and slow in the Lusitanian Basin. The Luehndea spinosa and Mendicodinium microscabratum dinoflagellate cyst biozones are defined, both of which are subdivided into two dinoflagellate cyst subbiozones.     

Global radiolarian zonation for the Pliensbachian, Toarcian and Aalenian

Jurassic radiolarians from 220 samples in Queen Charlotte Islands, B.C., Williston Lake, B.C., east-central Oregon, Baja California Sur, southern Spain, Austria, Slovenia, Turkey, Oman, Japan and Argentina were studied in order to construct global zonation for the Pliensbachian, Toarcian and Aalenian stages. Well-preserved faunas from continuous stratigraphic sections in Queen Charlotte Islands provide the most detailed record for this time interval, and all collections are tied to North American ammonite zones or assemblages. Collections from nearly all other areas lack independent dating except for early Toarcian carbon-isotope dating in Slovenia and late Aalenian ammonites in Spain.A database of 197 widely distributed updated taxonomic species was used to construct a Unitary Association (UA) zonation for the interval. A global sequence of 41 UAs was obtained for the top of the Sinemurian to the base of the Bajocian. The first and the last UAs represent the Late Sinemurian and the Early Bajocian respectively. The remaining 39 UAs were merged into nine zones (four Early Pliensbachian, one Late Pliensbachian, one Early Toarcian, one Middle-Late Toarcian, and two Aalenian) according to prominent radiolarian faunal breaks and ammonite data. The new zones are the Canutus tipperi - Katroma clara Zone (latest Sinemurian/earliest Pliensbachian); Zartus mostleri - Pseudoristola megaglobosa, Hsuum mulleri - Trillus elkhornensis and Gigi fustis - Lantus sixi zones (Early Pliensbachian); Eucyrtidiellum nagaiae - Praeparvicingula tlellensis Zone (Late Pliensbachian); Napora relica - Eucyrtidiellum disparile Zone (Early Toarcian); Elodium pessagnoi - Hexasaturnalis hexagonus Zone (Middle and Late Toarcian); Higumastra transversa - Napora nipponica Zone (early Aalenian); and Mirifusus proavus - Transhsuum hisuikyoense Zone (late Aalenian). These zones can be correlated worldwide and link previously established UA zonations for the Hettangian-Sinemurian and the Middle to Upper Jurassic. The new zonation allows high-resolution dating in the studied interval and provides a solid basis for analyzing faunal turnovers and the paleobiogeography of Jurassic radiolarians.     

New constraints on the last aragonite–calcite sea transition from early Jurassic ooids

Calcite and aragonite seas are commonly distinguished based on the prevailing primary mineralogy of ooids and carbonate cements over time. Secular oscillations of these seas are usually attributed to changes in ocean chemistry and paleoclimate. While the veracity of such oscillations has been verified by independent data and modeling approaches, the timing of the transition from one ocean state to the other remains poorly resolved. Here, the timing of the last aragonite–calcite sea transition is estimated by assessing the preservation of Early Jurassic ooids from the Trento Platform in northern Italy. Point counting of ooid-bearing limestones from four distinct stratigraphic levels provides a contrasting pattern: Hettangian and Sinemurian ooids are all poorly preserved and were probably predominantly originally aragonitic, whereas Pliensbachian and Toarcian ooids are excellently preserved, suggesting a primary calcitic mineralogy. Although calcitic ooids may have already been common in the Late Triassic, it is proposed that the last aragonite–calcite sea transition occurred in the Early Jurassic between the Sinemurian and Pliensbachian, at least in this subtropical region. Therefore, the selective extinction of aragonite-secreting organisms at the end-Triassic mass extinction cannot be attributed to secular changes in ocean chemistry.     

Biostratigraphie des brachiopodes et âge carixien (Pliensbachien inférieur) des calcaires à grands bivalves en Algérie occidentale

Recent researches on the Lower Jurassic of Western Algeria allow to establish a lithostratigraphic standard correlating the different members and formations developed in the Ouarsenis and Tlemcen Mountains, the Oran High Plains, the Nador and Ksour Mountains. The position of the large bivalve limestones (= Lithiotis limestones) is well established in the different lithologic successions. This facies is widespread in Western Algeria where it is interbedded with brachiopod marker beds, indicating short periods of maximum flooding. The large number of collected brachiopods are distributed into four “faunas” (assemblages) ranging from the Late Sinemurian (= Lotharingian) to the Early Pliensbachian (= Carixian). These faunas have been dated by the age of the species that they have in common with the NW european and western tethyan provinces. These chronological data are confirmed by rare ammonites. All these results evidence the age of the large bivalve facies in Western Algeria. They are contained in the Middle to Late Carixian (Demonense and Dilectum Zones). This datation is in conformity with that known from the Eastern High-Atlas (Bou Dahar). Consequently, the large bivalves cannot be considered as “markers for the unique Domerian” as it has been too often asserted. The palaeontological part of our study shows that the multicostate Zeilleriids (several Tauromenia species from the Late Sinemurian to the Early Carixian) are older than the multicostate Terebratulids (Hesperithyris species from the Middle to Late Carixian).     

Upper Sinemurian and Lower Pliensbachian ammonite faunas from Herford-Diebrock area (NW Germany)

At Herford-Diebrock a section from the Upper Sinemurian (Raricostatum to Aplanatum Subzone) to the Lower Pliensbachian (Polymorphus Subzone) is studied in respect of its ammonite faunas. Precise correlations in terms of faunal horizons are carried out between Yorkshire and SW Germany through Hessische Straße. Special emphasis is given to the taxonomical position ofEoderoceras armatum (Sowerby).Eoderoceras miles (Simpson) is now placed in synonymy withSowerby’s species. The section does not fulfill the requirements for the GSSP of the Sinemurian/Pliensbachian boundary.     

First evidence of brachiopod diversification after the end-Triassic extinction from the pre-Pliensbachian Internal Subbetic platform (South-Iberian Paleomargin)

Lower Jurassic brachiopods are widely known in the External Betic Zone. Their occurrence was so far virtually restricted to the easternmost Subbetic Zone where they underwent a diversity burst and radiation event during the late Sinemurian–early Pliensbachian interval, leading to a bloom in brachiopod diversity from the early Pliensbachian onwards. Taxonomical and paleobiogeographical analyses performed in a newly recorded assemblage from the most offshore areas of the Subbetic Basin (Granada province, Spain) reveals that this diversification event occurred earlier than expected hitherto, probably in the Turneri–Obtusum chronozones, as similarly observed in the most intra-Tethyan basins such as the Northern Calcareous Alps and Transdanubian Ranges, illustrating the recovery of the background conditions for the establishment of diversified brachiopod communities after the end-Triassic extinction event. A new rhynchonellide species, Alebusirhynchia vorosi nov. sp., is formally described among the ten different taxa recorded for the first time in this area. The Mediterranean paleobiogeographical affinities revealed by the brachiopod assemblage emphasizes that the onset of the Mediterranean/Euro-Boreal bioprovinciality and the initial brachiopod diversification in the pre-Pliensbachian Internal Subbetic platform took place earlier in the Sinemurian as well, following the Euro-Boreal monotypic record previously reported in this region.     

Facies of Liassic sponge mounds, central High Atlas, Morocco

Summary Liassic sponge mounds of the central High Atlas (Rich area, northern Morocco) have a stratigraphic range from the Lower/Upper Sinemurian boundary interval up to the lower parts of the Lower Pliensbachian (Carixian). The base of Liassic sponge mounds consists of a transgressive discontinuity, i.e., a condensed section of microbioclastic wackestones with firm- and hardgrounds, ferruginous stromatolites, sponge spicules and ammonites. The top of Liassic sponge mounds is an irregular palaeorelief covered by cherty marl-limestone rhythmites, namely hemipelagic spicular wackestones with radiolaria. In the Rich area, section Foum Tillicht, the sponge mound succession has a total thickness of about 250 meters. Within this succession we distinguished between three mound intervals. The lower mound interval shows only small, meter-scale sponge mounds consisting of boundstones with lyssakine sponges, commensalicTerebella and the problematicumRadiomura. This interval forms a shallowing-upward sequence culminating in a bedded facies withTubiphytes, calcareous algae (Palaeodasycladus), sponge lithoclasts, coated grains, and thin rims of marine cement. The middle mound interval is aggradational with decametric mounds and distinct thrombolitic textures and reefal cavities. The mound assemblage here consists of hexactinellid sponges, lithistid demosponges, non-rigid demosponges,Radiomura, Serpula (Dorsoserpula), Terebella, encrusting bryozoa, and minor contributions by calcareous sponges, and excavating sponges (typeAka). Thrombolites are dendrolitic and may reach sizes of several tens of centimeters, similar to the maximum size of siliceous sponges. The upper mound interval appears retrogradational and geometries change upsection from mound shapes to flat lenses and level-bottom, biostromal sponge banks. The biotic assemblage is similar to that of the middle mound interval and there is no difference between mound and bank communities. The demise of sponge mounds is successive from regional spread in the Sinemurian to more localised spots in the Lower Pliensbachian. This reduction correlates with an increasing influence of pelagic conditions. At Foum Tillicht, sponge mounds lack any photic contribution and there is virtually no differentiation into subcommunities between mound surface and cavity dwelling organisms. There is some evidence that the heterotrophic food web of mound communities was sourced by oxygen minimum zone edge effects, namely microbial recycling of essential elements such as N and P. Basin geometry suggests a waterdepth of several 100's of meters, well below the photic zone and possibly only controlled by the depth range of the oxygen minimum zone. Palaeoceanographic conditions of well-stratified deeper water masses diminished gradually during widespread transgression across the Sinemurian to Pliensbachian boundary culminating in the Lower Pliensbachianibex ammonite zone.     

Jurassic reef events in the Moroccan Atlas: A review

In the Moroccan Atlas, sedimentary deposits provide important data on reef events that characterize the Jurassic period. Recent work allows us to enhance knowledge of the Jurassic reefs in the Atlas, in particular their age, character and palaeogeographic distribution. Numerous localities with sponge-microbial mud mounds, coral reefs, and lithiotid bioherms are recorded from the Middle and High Atlas regions. These different biogenic constructions occupy different palaeogeographic settings: on the top of tilted blocks within the basin center; in slightly deeper positions, at the basin platform junction; and on adjacent platforms in the middle of the coastal area. The main episodes of reef building span nearly 30 million years, as follows: (1) Sinemurian, (2) early Pliensbachian, (3) late Toarcian, (4) Aalenian–early Bajocian (pars), and (5) late Bajocian. These five distinct reef events can be linked with general fluctuations of sea level and tectonism, and have palaeoclimatic implications.     

Brachiopod faunal exchange through an epioceanic-epicontinental transitional area from the Early Jurassic South Iberian platform system

The La Mola region (eastern External Betic Zone) can be regarded as one of the easternmost complete Jurassic successions of the Betic Cordillera in the Iberian Peninsula, but the paleogeographical setting of their outcrops remains widely discussed. Analysis of brachiopod assemblages from the Lower Jurassic improves the accuracy of previous paleogeographical data, enabling identification of a mainly epioceanic transitional area in which influences of epicontinental habitats are also detected. Assemblage 1, mainly with a Mediterranean affinity but also sharing several constituents with the African and Northeastern Iberian basins, typifies the Sinemurian–Pliensbachian transition. Assemblage 2, as a whole, shows a transitional character between epioceanic and epicontinental habitats; it is subdivided into two successive and interrelated sub-assemblages: Ass. 2a (Demonense–Tenuicostatum Zones) reveals a free connection with the epioceanic Subbetic area, whereas Ass. 2b (Uppermost Pliensbachian–Lower Toarcian) shows a closer relationship with epicontinental environments. Assemblage 3 (Uppermost Spinatum–basal Serpentinum Zones) is commonly recorded in the peri-Iberian epicontinental platform system integrated within the NW-European bioprovince, but it can also be regarded as a marginal assemblage that is widespread in the westernmost Tethyan margin prior to the Early Toarcian extinction event. Assemblage 2 constitutes a suitable index for assessing the paleobiogeographical affinity of the La Mola region, as Ass. 2a is progressively replaced by Ass. 2b, thus triggering the arrival of epicontinental taxa to the more intra-epioceanic Subbetic environments, inferring a possible connection through the La Mola transitional slope. Consequently, this region enabled a faunal mixing and exchange between both environments, and La Mola likely remained as an area that would facilitate migration and an effective dispersal seaway or, at least, did not constitute an ecological filter-barrier for brachiopods. Biostratigraphical data from brachiopods and ammonites are correlated for the first time in La Mola, refining and calibrating biochronostratigraphical gaps in the pre-Domerian deposits where biochronological markers are usually scarce, and around the Pliensbachian–Toarcian boundary, a crucial timespan in which the Early Toarcian extinction event took place.     

A new Pliensbachian ichthyosaur from Dorset, England

The first ichthyosaur to be recorded from the Pliensbachian Stage of the English Lower Liassic is described as Leptonectes moorei sp. nov., extending the geological range of Leptonectes to the Pliensbachian. According to criteria for assessing the maturity of ichthyosaurs, it is concluded that L. moorei is an immature individual of a relatively small, slender and short snouted species close to the earlier long-snouted L. tenuirostris (Conybeare) which ranges from the Rhaetian to the Sinemurian. The presence of a short-snouted leptonectid in the Pliensbachian suggests two contrasting patterns of rostral morphology within the clade Leptonectidae in the latest Early Jurassic, rostral reduction within the genus Leptonectes and rostral elongation in Excalibosaurus Eurhinosaurus .     

Microscopic evidence of serpulid affinities of the problematic fossil tube ‘Serpula’ etalensis from the Lower Jurassic of Germany

Tube structure, ultrastructure and mineralogy support serpulid affinities of the problematic worm fossil ‘Serpula’etalensis from the Lower Jurassic of Germany. The original tube mineralogy of ‘Serpula’etalensis is purely aragonitic and is preserved in Upper Pliensbachian specimens from eastern Germany. ‘Serpula’etalensis represent the earliest record of aragonitic mineralogy for serpulids. The tube is formed of irregularly oriented prismatic crystals that are 3–6 µm in length and 0.5–1.0 µm in diameter. Calcitic specimens of ‘Serpula’etalensis from Upper Sinemurian of southwestern Germany were recrystallized during the diagenesis and lack the original tube ultrastructure.     

Hiatal shell concentrations, sequence analysis, and sealevel history of a Pleistocene coastal alluvial fan, Punta Chueca, Sonora

Richly fossiliferous marine sediments exposed along the Sonoran coastline of the Gulf of California near Punta Chueca provide an excellent setting in which to test (a) the strength of the association of skeletal concentrations with sedimentary hiatuses, (b) the utility of taphonomic evidence for reconstructing detailed histories of those non-depositional episodes, and thus (c) the largely unexploited potential of skeletal concentrations in the identification and interpretation of lithologically obscure unconformities and condensed sequences in shallow marine deposits. Sequence analysis based on discontinuity surfaces is possible in the complex, alluvial fan-to-shallow marine transition at Punta Chueca despite rapid facies changes. Progradation of depositional sequences that contain cobbles reworked from older terrace deposits indicates accumulation during a fall in eustatic sea level. The supratidal to subtidal conglomerates and sands contain a variety of predominantly molluscan shell concentrations that, on the basis of postmortem histories of shells, formed during periods of low net sedimentation (i.e. depositional hiatuses); the majority of these shell beds lie along discontinuity surfaces identified by independent physical stratigraphic evidence. Although not all discontinuity surfaces in the terrace are paved by shell material. and not all relative concentrations of shells indicate distinct discontinuities, the strength of the association between skeletal concentrations and stratigraphic hiatuses reveals the high degree of control on fossil occurrence by sedimentation rates, and indicates that skeletal concentrations can provide good clues to stratigraphically significant surfaces. Moreover, the detailed dynamics of non-depositional episodes are reliably revealed by taphonomic analysis of the associated fossil assemblages, improving interpretations of non-depositional episodes in local sedimentary history.     

Quantification of high-frequency sea-level fluctuations in shallow-water carbonates: an example from the Berriasian–Valanginian (French Jura)

When quantifying sedimentary processes on shallow carbonate platforms, it is important to know the high-frequency accommodation changes through time. Accommodation changes in cyclic successions are often analysed by simply converting cycle thickness to Fischer plots. This approach is not satisfactory, because it does not account for differential compaction, possible erosion, sea-level fall below the depositional surface, or subtidal cycles. An attempt is made here to reconstruct a realistic, high-frequency accommodation and sea-level curve based on a detailed facies and cyclostratigraphical analysis of Middle Berriasian to Lower Valanginian sections in the French Jura Mountains. The general depositional environment was a shallow-marine carbonate platform on a passive margin. Our approach includes the following steps: (1) facies interpretation; (2) cyclostratigraphical analysis and identification of Milankovitch parameters in a well-constrained chronostratigraphic framework; (3) differential decompaction according to facies; (4) estimation of depth ranges of erosion and vadose zone; (5) estimation of water-depth ranges at sequence boundaries and maximum flooding intervals; (6) estimation of mean subsidence rate; (7) classification of depositional sequences according to types of facies evolution: ‘catch-up’, ‘catch-down’, ‘give-up’, or ‘keep-up’; (8) classification of depositional sequences according to long-term sea-level evolution: ‘rising’, ‘stable’, ‘falling’; (9) calculation of ‘eustatic’ sea-level change for each depositional sequence using the parameters inferred from these scenarios, assuming that sea-level cycles were essentially symmetrical (which is probable in Early Cretaceous greenhouse conditions); (10) calculation of a sea-level curve for each studied section; (11) comparison of these curves among each other to filter out differential subsidence; (12) construction of a ‘composite eustatic’ sea-level curve for the entire studied platform; (13) spectral analysis of the calculated sea-level curves. Limitations of the method are those common to every stratigraphic analysis. However, the method has the potential to improve the original cyclostratigraphical interpretations and to better constrain the high-frequency sea-level changes that control carbonate production and sediment fluxes.     

A review of the chronostratigraphical ages of Middle Triassic to Late Jurassic dinoflagellate cyst biozones of the North West Shelf of Australia

The chronostratigraphical ages of the 20 dinoflagellate cyst zones and one dinoflagellate cyst assemblage for the Middle Triassic (Ladinian) to the Jurassic-Cretaceous transition of the North West Shelf of Australia are comprehensively reviewed. Evidence from macro- and micropalaeontology, palynology and strontium isotopes made available after the establishment of these biozones in the 1980s has been used to reassess the ages of this important zonal scheme and to calibrate it to the international stratigraphical stages. The Shublikodinium Superzone is renamed herein as the Rhaetogonyaulax Superzone, and based on conodont evidence is determined to span the Ladinian to Early Sinemurian. This is significantly shorter in duration than was originally envisaged (Late Anisian to Late Pliensbachian). The Luehndea Assemblage is a low diversity dinoflagellate cyst association which marks a eustatic rise; it is subdivided into two subzones. It is of latest Pliensbachian to Early Toarcian age, based largely on palynological evidence. The Bajocian to earliest Oxfordian Pareodinia ceratophora Superzone represents the inception of a continuous Mesozoic-Cenozoic dinoflagellate cyst record in Australia. It comprises seven zones, which are considered to be slightly older than originally interpreted. The overlying Pyxidiella Superzone is characterised by diverse dinoflagellate cyst associations. It is Early Oxfordian to Kimmeridgian in age, and comprises three zones. The bases of the Wanaea spectabilis and Wanaea clathrata zones are reinterpreted as being slightly older than originally proposed. The superjacent Fromea cylindrica Superzone is Tithonian to earliest Valanginian and modified ages are indicated for four of the nine zones. This unit is dominated by endemic dinoflagellate cysts, reflecting a global trend towards provincialism at this time due to a regressive eustatic regime.     

Ammoniten aus dem tiefen unter jura von nord-peru

From the Hettangian and Lower Sinemurian of the Utcubamba Valley in Northern Peru 10 ammonite species belonging to the families Psiloceratidae, Schlotheimiidae, and Arietitidae are described. They are compared with European forms. In South America the use of European zone successions is practicable without difficulties.     

Development of rudist lithosomes in the Coniacian–Lower Campanian carbonate shelves of central-southern Italy: high-energy vs low-energy settings

The Late Cretaceous shallow-water depositional areas of southern Tethys were complexes of unprotected shelves occupied by foramol assemblages that produced loose, diagenetically stable bioclastic debris not involved in significant in situ cementation processes. Both storm- and wind-induced currents and waves exercised a strong control on the distribution of the shifting biogenic sediments which covered the open sea-floor, constituting large coalescing sheets of winnowed fine to coarse skeletal sands. Rudists spread over all shelf sectors, from more open and external areas to more internal ones, occupying different substrata and furnishing the bulk of the skeletal component by means of bioerosion processes. They colonised mobile sediments giving rise to complex bodies with peculiar characteristics related to environmental parameters of the different sectors of the shelf. On the basis of detailed sedimentological, taphonomic and palaeontological data, we recognised two main rudist-rich depositional settings (‘end members’) in the southern Italy Senonian rudist-bearing successions. In successions pertaining to hypothesised marginal shelf sectors, characterised by high-energy regime deposits, rudist lithosomes are metric in thickness and lateral extent and lens-like in morphology, rich in bioerosion-derived skeletal sand and silt. Rudists are highly diversified. Large elongated cylindro-conical hippuritids (mostly pertaining to the genera Hippurites and Vaccinites), thick-shelled radiolitids and plagioptychids largely dominate. Rudists clustered in life position are subordinate; they often form small bouquets. More commonly these organisms appear fallen but only barely reworked. The rudist-rich bodies laterally pass into clean bioclastic grainstone in which sedimentary structures, related to current and/or storm erosional action, are common. No evidence of significant original relief of the rudist bodies in respect of the neighbouring sediment can be recognised. The submarine erosion and/or the high-energy processes operating presumably inhibited the aggradation of the tidal sediments above the marginal ones. As a consequence the vertical facies organisation shows widespread subtidal cycles, as commonly recognised in open shelves with ramp-like morphologies. In successions pertaining to more internal and/or low-energy sectors, rudist-rich beds rhythmically alternate with finer-grained foraminiferal limestones. Small elevator radiolitids with oligospecific diversity are dominant, mostly concentrated in clumps. Rudists in growth position are abundant, although a large quantity of shells appear toppled with little reworking. They may form laterally continuous biostromal shell beds. Sedimentary structures such as cross-lamination and gradation are only occasionally present. The resulting facies are commonly arranged in peritidal/shallow subtidal cycles in which evidence of subaerial (up to pedogenic modifications on a large and small scale) and, less frequently, submarine exposure is common. Intermediate successions have been recognised, characterised by deposits of silty-sand plains, which present intercalations of graded, bioclastic, storm-related beds. Sedimentological characteristics seem to document more open conditions in which submarine erosion was intermittently prevalent. In these successions rudist species that are commonly found both in high-energy and low-energy assemblages coexist.     

Influence of the Late Ordovician glaciation on basin configuration of the Yangtze Platform in China

The Late Ordovician paleogeographic changes in the Yangtze Platform indicate a widespread regression and consequent subaerial exposure probably caused by the 'locking up' of substantial amounts of marine waters during the Late Ordovician glaciation. The subsequent rapid paleogeographic changes on the Yangtze Platform during the earliest Silurian suggest a rapid melting of the ice. The relatively cool waters in the partially closed Yangtze basin during the latest Ordovician were replaced by open and warm waters during the earliest Silurian. Sedimentation rates and composition of faunal assemblages underwent marked changes during latest Ordovician and Early Silurian. Glaciation, Ordovician, Silurian, Paleogeography, sedimentary rate, faunal change.     

Early jurassic (Upper Pliensbachian) gastropods from the Herforder Liasmulde (Bielefeld, Northwest Germany)

An Early Jurassic (Upper Pliensbachian) gastropod fauna from the Herforder Liasmulde (Herford Lias Syncline) near Bielefeld, Northwest Germany is described. This is one of the first detailed and illustrated reports of Pliensbachian gastropods from this area. Sixteen species are reported. Surface collecting yielded relatively large vetigastropods (pleurotomarioids amd trochomorphs). Bulk samples yielded abundant small caenogastropods (especiallyLevipleura blainvillei andKalchreuthia frankei) and cylindrobullinid opisthobranchs (e.g.Cylindrobullina dornend). These small species are also abundant in the Pliensbachian of South Germany (N Bavaria, Franconia). Therefore, this characteristic Pliensbachian microgastropod assemblage was widespread in Germany and probably also in other comparable marine deposits of Central Europe (e.g. the Paris Basin).      

Effects of Temperature on Electron Transport in Arum maculatum Mitochondria

The effects of temperature upon the respiratory pathways of Arum maculatum mitochondria have been studied. The alternate oxidase sustained a greater proportion of the total respiration at low temperatures than at higher temperatures. Arrhenius plots of respiratory activities show two discontinuities, one at 14°C and one at 21°C. The lower temperature discontinuity was associated with electron transport from succinate dehydrogenase to the alternative oxidase, enzymes that face the inner side of the membrane while the higher temperature discontinuity was associated with electron transport from the external NADH dehydrogenase to cytochrome c oxidase, which face the outer side of the membrane. Both discontinuities resulted in a decrease in the activation energy for electron transport on one side of the membrane. Arrhenius plots of transmembrane electron transport showed discontinuities at both 14° and 21°C but the upper discontinuity resulted in an increase in the activation energy. Activation energies determined for the respiratory activities show that above 21°C the exogenous NADH-cytochrome pathway and the succinate-alternative oxidase pathway were lower than those for the NADH-alternative pathway or the succinate cytochrome pathway.     

Les faunes d’ammonites du Pliensbachien inférieur des séries dauphinoises de la Durance (Jurassique inférieur, Barrage de Serre-Ponçon, Hautes-Alpes, France)

The Liassic ammonite faunas and especially those of the Early Pliensbachian are of major importance for the understanding of the stratigraphic framework of the “Dauphiné” zone of the southern subalpine ranges (“dôme de Remollon”). Until now, only listed by the authors, these faunas are, for the first time, described and illustrated in the present paper. With about twenty species, these faunas cover the whole of the Early Pliensbachian. There are poorly diversified and of clearly Euroboreal affinities. Nearly all of the species are abundant and common in most of the NW European fossiliferous localities. Despite of a paleogeographical location fairly close to the Alpine zones (Southern Alps and Austroalpine units) with rather diversified faunas of mainly Mediterranean affinities, none Mediterranean taxa are present in the studied area. Unfortunately, the current stratigraphic and paleogeographic knowledge do not allow to ascertain if this reflects a separation due to paleoenvironmental or true paleogeographic barriers. In this latter case, the general geologic implications would be remarkable.