Article

Palaeoecology of the Triassic black shale bivalve Daonella - New insights into an old controversy

February 2005
Palaeogeography Palaeoclimatology Palaeoecology

February 2005

DOI:10.1016/j.palaeo.2004.11.002

Authors:

Zurich Law School

Several modes of life have been proposed for bivalves of the genus Daonella. Taphonomic studies revealed that most taphocoenoses containing lumachellas (shellbeds) and butterflied preserved specimens are allochthonous. Articulated specimens with closed valves and well-orientated sagittal planes are interpreted to be in situ. Autochthonous assemblages show a population structure dominated by subadults and adults. Monospecific and paucispecific taphocoenoses with daonellids are not due to preservational biases but reflect the former biocoenoses. Most species show a dependence on facies. Some are restricted to dysoxic milieus, others are only known from normoxic facies, but all preferred soft, soupy sediments. Morphological examination does not support the presence of byssus gland in adult stages of daonellids, which suggests that they could not be attached to floats. Proposed life habits such as semi-infaunal mud-stickers, epibenthic chemosymbionts, holonekton, holoplankton or byssal attached pseudoplankton conflict with taphonomical constraints, distribution and morphology. Daonellids are herein interpreted as epibethic, pleurothetic bivalves, showing adaptive features to dysoxic milieus like subcircular, flat, thin shelled valves. Daonellids were well adapted to soft, soupy substrates. The use of lighter calcite in place of aragonite, the thin shell and the general form of the shell qualified them to float on soft sediments (snow-shoe strategists).

Middle Triassic Nautilida from the Besano Formation of Monte San Giorgio, Switzerland

Article

Full-text available

Dec 2022

Vittorio Pieroni

For the first time, nautilids from the Besano Formation (Anisian/Ladinian boundary) are documented. The extremely rare material was collected from two different outcrops at Monte San Giorgio (Southern Alps, Ticino, Switzerland). This material is represented by only five specimens described here. The three best specimens belong to the taxa Enoploceras rieberi sp. nov., Germanonautilus aff. ellipticus and Syringonautilus sp. indet., documenting the presence of the families Tainoceratidae and Syringonautilidae in the middle Besano Formation. Another nautilid specimen is described in open nomenclature, representing an additional taxon. The new species Enoploceras rieberi n. sp. is currently the only occurrence of the genus Enoploceras in the Middle Triassic. Nautilida are poorly known from the Middle Triassic Tethyan region, mostly from sediments deposited in pelagic environments. This is the first record of these nautilids from an usually anoxic depositional paleoenvironment of an intra-platform basin, where the sediments of the Besano Formation were laid down.

Unravelling the paleoecology of flat clams: New insights from an Upper Triassic halobiid bivalve

Article

Apr 2020
GLOBAL PLANET CHANGE

Flat clams are ubiquitous in marine Triassic and Jurassic deep-water environments, where they are often recovered as mono- or pauci-specific assemblages. Their abundance in deep-water facies deposited under oxygen-depleted conditions suggests a potentially unique, but nevertheless debated, paleoecology. The distribution of Halobia cordillerana in an Upper Triassic hemipelagic succession outcropping at Tsiko Lake, Vancouver Island, Canada, serves as a revealing case study. There, deep-water deposits were investigated using a multi-disciplinary approach including facies description (mineralogical, fossil and organic content), taphonomy, morphometry, microscopy (cathodoluminescence, scanning-electron microscope) and independent paleo-redox proxy constraints (framboidal pyrite distributions, Fe speciation). Overall, halobiids' taphonomy at Tsiko Lake is indicative of in situ accumulations with little or no reworking. Among the hemipelagic deposits, three major litho-biofacies (BFC 1, 2, 3) were identified; paleo-redox proxies indicate that these litho-biofacies were deposited under different oxygen conditions ranging from extreme dysoxic (BFC 1) to dominantly euxinic (BFC 3). The distribution of H. cordillerana is shown to be directly influenced by bottom water oxygenation with this organism peaking both in abundance and dimensions under extreme dysoxic to anoxic conditions (i.e. BFC 1 & 2). Conversely, under prevailing euxinic conditions (i.e. BFC 3), the population of H. cordillerana is dominated by forms at larval or post-larval stage which were presumably killed by water-column euxinia. Thus, although the species is here shown to have lived most likely as an epibenthic recliner, an early (larval) planktonic/nektonic stage is needed to explain its mode of occurrence during dominantly euxinic conditions (i.e. BFC 3), and its wide distribution and rapid expansion. Finally, this study highlights the colonizing capacity of halobiids in case of restored oxygen conditions, stressing the potential significance of flat clams for paleoenvironmental reconstruction.

Sedimentology, taphonomy, and palaeoecology of a laminated plattenkalk from the Kimmeridgian of the northern Franconian Alb (southern Germany)

Article

Jan 2007
PALAEOGEOGR PALAEOCL

At Wattendorf in the northern Franconian Alb, southern Germany, centimetre- to decimetre-thick packages of finely laminated limestones (plattenkalk) occur intercalated between well bedded graded grainstones and rudstones that blanket a relief produced by now dolomitized microbialite-sponge reefs. These beds reach their greatest thickness in depressions between topographic highs and thin towards, and finally disappear on, the crests. The early Late Kimmeridgian graded packstone–bindstone alternations represent the earliest plattenkalk occurrence in southern Germany. The undisturbed lamination of the sediment strongly points to oxygen-free conditions on the seafloor and within the sediment, inimical to higher forms of life. The plattenkalk contains a diverse biota of benthic and nektonic organisms. Excavation of a 13 cm thick plattenkalk unit across an area of 80 m2 produced 3500 fossils, which, with the exception of the bivalve Aulacomyella, exhibit a random stratigraphic distribution. Two-thirds of the individuals had a benthic mode of life attached to hard substrate. This seems to contradict the evidence of oxygen-free conditions on the sea floor, such as undisturbed lamination, presence of articulated skeletons, and preservation of soft parts. However, palaeoecological and taphonomic analyses indicate that the benthic faunal elements are allochthonous having settled out of suspension and thus must have been derived from hard substrate areas of neighbouring topographic highs. Solely the bivalve Aulacomyella, which occurs concentrated on a single bedding plane, may have colonised the plattenkalk depression during brief periods of oxygenation. Alternatively, a pseudoplanktonic mode of life, attached to floating sea weed, is envisaged for the bivalve. The formation of the plattenkalk is related to local and global factors: a drop in relative sea level caused the death of the microbialite-sponge reefs. Restricted circulation in depressions between the crests of the former reefs led to anoxic conditions and the formation of finely laminated sediments stabilised by microbial mats. The small depressions received sediment and skeletal elements of benthic organisms that were swept off neighbouring topographic highs by storms and that entered the depressions partly as turbidity currents, partly as suspension clouds. A rise in the relative sea level finally terminated the restricted circulation in the depressions and closed the taphonomic window that led to the preservation of the plattenkalk biota.

Late Visean-Early Namurian Bivalves From the Zonguldak Coal Basin, Northwestern Turkey

Article

Full-text available

Jan 2007

Izzet Hoşgör

Marine bivalves Septimyalina sublamellosa (Etheridge 1878), Septimyalina lamellosa (de Koninck 1842), Septimyalina minor (Brown 1841) and Posidonia becheri Bronn, 1828 are described from the Visean Namurian transition of Zonguldak coal basin, Northwestern Turkey. Macroinvertebrate fossils are rare in the Lower Carboniferous of the Zonguldak coal basin and only a few shallow marine forms of Myalinidae and Posidoniidae families are present. Their palaeobiogeographic distribution delineates a seaway from Britain to the Black Sea coast during the Carboniferous.

Patterns of bivalve biodiversity from Early to Middle Triassic in the Southern Alps (Italy): Regional vs. global events

Article

Apr 2008
PALAEOGEOGR PALAEOCL

Renato Posenato

The Triassic records the severe effects of the end-Permian mass extinction and the beginning of the Mesozoic/modern adaptive radiation of marine invertebrates. As far as bivalves are concerned, a group which was relatively unaffected by the extinction, diversification started in the Middle Triassic, more particularly during the Anisian. Thus, the interval between the basal Triassic (Induan) and Anisian is crucial in analysing the biodiversity changes and diversification patterns of these molluscs. This analysis is discussed at genus level and based on the regional records of the Southern Alps. Biodiversity changes are examined in connection with palaeogeographic evolution, the conquest of vacated ecologic niches, and climatic changes.

The Triassic of Timor: Lithostratigraphy, chronostratigraphy and palaeogeography

Article

Full-text available

Oct 2009
J ASIAN EARTH SCI

The palaeontologically rich and lithologically diverse Triassic successions of Timor provide a key stratigraphic and palaeontological link between northwestern Australia and other terranes of former eastern Gondwana (present-day Southeast Asia). Timor is now located in the zone of collision between the northern margin of the Australian continent and island arc terranes bordering the Eurasian plate, with the Triassic successions exposed in a fold-and-thrust belt and an extensive mélange complex. Three formal lithostratigraphic units have been defined previously within the main Triassic succession in Timor (Niof, Aitutu and Babulu formations), with a fourth, the Wai Luli Formation, primarily Jurassic in age but extending down into the Triassic. The Niof Formation (Anisian to Ladinian, possibly also Early Triassic) is a fine-grained deepwater succession, succeeded conformably by the Aitutu and Babulu formations (Ladinian to Norian/Rhaetian), which were deposited contemporaneously, with the Aitutu Formation continuing locally into the Lower Jurassic. The Aitutu Formation consists of deep shelf limestones interbedded with shales and marls, while the Babulu Formation is a deltaic to turbiditic siliciclastic succession. The Late Triassic to Jurassic Wai Luli Formation is characterised by marine shales and marls.

Paléobiologie ReVUe De VolUMe 39 (2 ) -2020 Une institution Ville de Genève

Article

Full-text available

Jun 2023

For the first time gastropods from the Meride Limestone (Ladinian) are documented. The material was collected from the outcrop Valle di Sceltrich at Monte San Giorgio (Southern Alps, Ticino, Switzerland) in the newly discovered Sceltrich beds. The taxa include Cryptonerita? sp., Coelostylina stotteriand Omphaloptychacf. marianii. The findings represent the first identifiable Ladinian gastropods so far described from this UNESCO Fossillagerstätte and document the occurrence of several taxa of the clades Neritimorpha and Caenogastropoda from the Meride Limestone.

Multi‐elemental chemostratigraphy of Triassic mudstones in eastern Svalbard: Implications for source rock formation in front of the World’s largest delta plain

Article

Full-text available

Mar 2022

The Triassic Boreal Ocean was a shallow epicontinental basin and the sink of the World's largest delta plain known to date. Nutrient and freshwater supply from this delta have been regarded as important causes for high productivity and water mass stratification, forming Middle Triassic oil‐prone source rocks. Recent studies attribute upwelling and a productivity‐induced oxygen minimum zone as important factors. A multi‐elemental chemostratigraphic study of a Spathian–Carnian mudstone succession exposed in eastern Svalbard was performed to investigate their formation. This includes 89 samples from three localities, from which 34 elements were acquired using combustion and X‐ray fluorescence analyses. The goal is to provide a correlation framework and infer the role of productivity, redox and water mass restriction on organic matter accumulation and source rock formation. These processes had major impact on the source potential. The Spathian Vendomdalen Member suggests deposition during intermittent benthic euxinia and low productivity, corresponding with a reported deep thermocline that obstructed upwelling. The lower Anisian lower–middle Muen Member shows negligible enrichment in redox‐sensitive elements but in situ phosphate nodules, consistent with developing upwelling and moderate productivity. The middle Anisian upper Muen Member formed during high productivity and phosphogenesis and is linked with basin‐wide upwelling. Productivity, phosphate and redox proxies are all strongly enriched in the upper Anisian–Ladinian Blanknuten Member. In the south‐western Barents Sea, the pro‐deltaic environment of the emerging Triassic Boreal Ocean delta system had terminated these conditions. The upper Ladinian upper Blanknuten Member formed within intermittent euxinic bottom waters due to the shallowing sea level. The Carnian Tschermakfjellet Formation marks the dominance of the prograding delta system and the end of Triassic oil‐prone source rock formation in Svalbard.

Sedimentological study of bivalve fossils site locality in Hong Hoi Formation, Lampang, Thailand

Conference Paper

Full-text available

Nov 2019

Hong Hoi Formation is a Middle Triassic deep marine succession presented in outcrops throughout the Lampang Basin of northern Thailand. The primary goal of this research is to diagnose the paleoenvironment, petrographic compositions, and sedimentary sources of the Hong Hoi Formation in Ban Huat, Ngao District. The Triassic Hong Hoi Formation is chosen because the outcrops are continuous and fossils are greatly exposed and abundant. Depositional environment is reconstructed through sedimentological studies along with facies analysis. The Hong Hoi Formation is petrographically divided into two major facies, they are: sandstones with mudstone interbeds, and mudstones or shale with sandstone interbeds. Sandstone beds are lithic arenite and lithic greywacke, volcanic lithic fragments are dominated. Sedimentary structures, paleocurrent data and lithofacies arrangement indicate that the formation deposited in a part of deep marine abyssal plain environment. The sedimentological and petrographic features suggest that during the deposition the Hong Hoi Formation received sediment supply from nearby volcanic arc. This suggested that the intensive volcanic activity within the Sukhothai Arc during the Middle Triassic is the main sediment source.

Middle Triassic gastropods from the Besano Formation of Monte San Giorgio, Switzerland

Article

Full-text available

Dec 2020

For the first time gastropods from the Besano Formation (Anisian/Ladinian boundary) are documented. The material was collected from three different outcrops at Monte San Giorgio (Southern Alps, Ticino, Switzerland). The taxa here described are Worthenia (Humiliworthenia)? aff. microstriata, Frederikella cf. cancellata, ?Trachynerita sp., ?Omphaloptycha sp. 1 and ?Omphaloptycha sp. 2. They represent the best preserved specimens of a larger collection and document the presence in this formation of the clades Vetigastropoda, Neritimorpha and Caenogastropoda that were widespread on the Alpine Triassic carbonate platforms. True benthic molluscs are very rarely documented in the Besano Formation, which is interpreted as intra-platform basin sediments deposited in usually anoxic condition. Small and juvenile gastropods could have been lived as pseudoplankton attached to floating algae or as free-swimming veliger planktotrophic larval stages. Accumulations of larval specimens suggest unfavorable living conditions with prevailing disturbance in the planktic realm or mass mortality events. However, larger gastropods more probably were washed in with sediments disturbed by slumping and turbidite currents along the basin edge or storm activity across the platform of the time equivalent Middle San Salvatore Dolomite.

A Griesbachian (Early Triassic) Mollusc Fauna from the Sidazhai Section, Southwest China, with Paleoecological Insights on the Proliferation of Genus Claraia (Bivalvia)

Article

Full-text available

Aug 2018

After the end-Permian mass extinction, genus Claraia (Bivalvia) was the most abundant and most noticeable fossil during the survival and recovery stage. However, the reasons for the proliferation of Claraia are still debated. This paper describes a new Griesbachian (Early Triassic) mollusc fauna from deep-water settings in South China in the aftermath of end-Permian mass extinction. This fauna yielded five bivalve species in two genera (Claraia griesbachi, C. wangi, C. stachei, C. radialis, and Promyalina putiatinensis) and two ammonoid species (Ophiceras sp. and Ussuridiscus sp.) and could be assigned to the Claraia wangi-C. griesbachi assemblage zone, indicating a Middle-Late Griesbachian Age. The bivalves were dominated by Claraia griesbachi and were featured by articulated Claraia fossils. As Claraia was epibyssate, it was an excellent autochthonous fauna. While the shallow and deep marine water became dysoxic to anoxic globally, as indicated by recent studies of the early Early Triassic, we suggest the genus Claraia could tolerate dysoxic and/or anoxic conditions and its proliferation could be attributed to its physiological features which were adapted to the stressed environment. The wide distribution of Claraia was probably related to its planktonic larval stage. Where the larva of Claraia could have been transported by ocean flow and increased its potential for long-distance dispersal. In addition, Claraia was a significant disaster and opportunistic taxon during the Early Triassic based on observations in South China.

An enigmatic marine reptile—the actual first record of Omphalosaurus in the Muschelkalk of the Germanic basin

Article

Dec 2017

Omphalosaurus is an enigmatic marine reptile of probable ichthyosaurian affinities known from Early and Middle Triassic marine deposits of the Northern Hemisphere. Based on its unique crushing dentition combined with elongate jaws, Omphalosaurus appears to have been a specialized ammonoid feeder. Here we describe a jaw fragment from the Lower Muschelkalk of Silesia, Poland (Karchowice Formation, Anisian, Pelsonian/early Illyrian), and assign it to Omphalosaurus sp. based on tooth morphology, tooth replacement pattern, enamel surface morphology, and enamel microstructure. This is the first record of Omphalosaurus from shallow marine carbonates and from the Muschelkalk facies, a classical source of Middle Triassic marine reptiles. The discovery is unexpected because all other records of Omphalosaurus are from open-water deposits rich in ichthyosaurs and ammonoids. We reidentify an earlier putative record of Omphalosaurus from the Lower Muschelkalk of Rüdersdorf near Berlin, Germany, as the left maxilla of the common Muschelkalk placodont Placodus. This reidentification is based on shared characters of osteology, dentition, mode of tooth replacement, and tooth enamel microstructure. Data on both specimens were collected using visual inspection, micro-computed tomography (µCT), and scanning electron microscopy. Citation for this article: Wintrich, T., H. Hagdorn, and P. M. Sander. 2017. An enigmatic marine reptile—the actual first record of Omphalosaurus in the Muschelkalk of the Germanic Basin. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1384739.

Permian endemic bivalves of the “Irati anoxic event”, Paraná Basin, Brazil: Taphonomical, paleogeographical and evolutionary implications

Article

Dec 2016
PALAEOGEOGR PALAEOCL

Evidence of a preservational gradient in the skeletal taphonomy of Ichthyopterygia (Reptilia) from Europe

Article

Dec 2015
PALAEOGEOGR PALAEOCL

Studies of preservation have allowed environmental conditions at numerous localities in space and time to be inferred. However, in the search for sufficient vertebrate specimens to provide a large dataset, details of specimen taxonomy, geographic origin and stratigraphic level are often ignored or not collected. Any preservational variation identified as a result is therefore from a broad range rather than a specific group, locality or time. The effect of this limitation, mainly regarding the loss of crucial information on environmental processes in ancient settings and the biology of long extinct organisms, is demonstrated using specimens of Ichthyopterygia (Reptilia). Taphonomic analysis of a dataset of 173 specimens infers a consistent reduction of skeletal condition from peripheral to medial within a carcass and a taphonomic pathway involving minimal floating and prolonged residence on the sediment surface. The same dataset divided into three sub-datasets, from the Middle Triassic Besano Formation, Lower Jurassic Blue Lias Formation and Lower Jurassic Posidonia Shale Formation, highlight preservational variation, in the extent of loss of articulation and completeness that follows an environmental gradient related to proximity to major landmasses.

Bivalves and brachiopods in the Carboniferous - Early Permian of Argentine Precordillera: Diversification and faunal turnover in Southwestern Gondwana

Article

Full-text available

Dec 2010
GEOL ACTA

Diversification patterns and faunistic turnovers of bivalves and brachiopods through the Carboniferous - Early Permian interval in the central western Argentinian basins are analyzed and compared with the global events proposed in former studies. This study reveals a generalized increase of bivalves, at familiar and generic levels, through three time intervals, i.e., Early carboniferous (Tournaisian-Visean), Late Carboniferous (Bashkirian-Kasimovian) and Early Permian (Asselian-Sakmarian), while the brachiopod diversity seems to remain stable from the Late Carboniferous to the Early Permian. The trends recognized in the faunistic diversity appear to be closely related to the palaeoclimatic, palaeogeographic and palaeotectonic evolution at the Southwestern Gondwana margin. Highly stressing environmental changes in the Early Carboniferous, resulting fundamentally from the development of glacial conditions, may account for the lowest faunistic diversity recorded. Particular stress conditions, such as the nutrient availability, temperature and oxygen level, would have mainly affected the brachiopod faunas that evidence the lowest diversity recognized in the interval studied. At the Visean-Serpukovian boundary, the Late Palaeozoic marine record of the Precordillera shows a major break linked to a globally recognized glacial maximum, whereas an important faunistic turnover is mainly identified in the brachiopod faunas at the beginning of the Late Carboniferous. The more stable, less stressing environmental situation developed during the Late Carboniferous-Early Permian postorogenic sedimentation is also reflected by the different faunal assemblages studied. The Late Carboniferous was characterized by postglacial transgressions. During this time local rebound, a continuous increase of the diversity and an important faunal turnover, which mainly affected the brachiopod faunas, were recorded. These faunal trends may be related to the Early Permian climatic amelioration that affected the central western Argentinian basins. The subsequent Permian transgressive events, which produced new areas of potential spreading for the benthic fauna, allowed its increase and diversification, much better reflected by the bivalve assemblages.

Carbonate lithologies of the Mississippian Barnett Shale

Article

Full-text available

Jan 2012

The architecture of oceanic plateaus revealed by the volcanic stratigraphy of the accreted Wrangelia oceanic plateau

Article

Feb 2010
GEOSPHERE

The accreted Wrangellia flood basalts and associated sedimentary rocks that compose the prevolcanic and postvolcanic stratigraphy provide an unparalleled view of the architecture, eruptive environment, and accumulation and subsidence history of an oceanic plateau. This Triassic large igneous province extends for ~2300 km in the Pacific Northwest of North America, from central Alaska and western Yukon (Nikolai Formation) to Vancouver Island (Karmutsen Formation), and contains exposures of submarine and subaerial volcanic rocks representing composite stratigraphic thicknesses of 3.5-6 km. Here we provide a model for the construction of the Wrangellia oceanic plateau using the following information and visualization tools: (1) stratigraphic summaries for different areas of Wrangellia; (2) new 40Ar/39Ar geochronology results; (3) compilation and assessment of geochronology and biostratigraphy for Wrangellia; (4) compiled digital geologic maps; (5) an online photographic archive of field relationships; and (6) a Google Earth file showing the mapped extent of Wrangellia flood basalts and linked field photographs. Based on combined radiometric (U-Pb, 40Ar/39Ar, K-Ar), paleontological, and magnetostratigraphic age constraints, the Wrangellia flood basalts were emplaced during a single phase of tholeiitic volcanism ca. 230-225 Ma, and possibly within as few as 2 Myr, onto preexisting submerged arc crust. There are distinct differences in volcanic stratigraphy and basement composition between Northern and Southern Wrangellia. On Vancouver Island, ~6 km of high-Ti basalts, with minor amounts of picrites, record an emergent sequence of pillow basalt, pillow breccia and hyaloclastite, and subaerial flows that overlie Devonian-Mississippian (ca. 380-355 Ma) island arc rocks and Mississippian-Permian marine sedimentary strata. In contrast, Alaska and Yukon contain 1-3.5-km-thick sequences of mostly subaerial high-Ti basalt flows, with low-Ti basalt and submarine pillow basalts in the lowest parts of the stratigraphy, that overlie Pennsylvanian-Permian (312-280 Ma) volcanic and sedimentary rocks. Subsidence of the entire plateau occurred during and after volcanism, based on late-stage interflow sedimentary lenses in the upper stratigraphic levels and the presence of hundreds of meters to >1000 m of overlying marine sedimentary rocks, predominantly limestone. The main factors that controlled the resulting volcanic architecture of the Wrangellia oceanic plateau include high effusion rates and the formation of extensive compound flow fields from low-viscosity, high-temperature tholeiitic basalts, sill-dominated feeder systems, limited repose time between flows (absence of weathering, erosion, sedimentation), submarine versus subaerial emplacement, and relative water depth (e.g., pillow basalt-volcaniclastic transition).

Local versus global effects on changes of fossil diversity: Paleoenvironmental interpretation of Triassic faunas of the Balaton Highland (Hungary)

Article

Full-text available

Sep 2009

Attila Vörös

The formations of the Balaton Highland provide a high-resolution record of various fossil groups (ammonoids, bivalves, brachiopods) from the Early Triassic to the Carnian, with remarkable changes in taxonomic diversity. The local data differ considerably from the gradually increasing global diversity trends of the respective fossil groups. Ammonoids are rare in the Early Triassic; during the Anisian they reach a diversity maximum and remain rather diverse until the Carnian. This is connected to the considerable deepening of the sedimentary basin in the Middle Triassic. The benthic fossil groups show almost inverse local trends. In the Early Triassic, the proliferation of bivalves largely follows the transgressive pulses in the shallow marine setting; brachiopods are represented solely by Lingula specimens. Both the bivalve and the brachiopod diversity culminate in the middle Anisian what is interpreted in terms of extensional tectonic movements: the rocky escarpments of the disintegrated carbonate platforms provided favorable biotopes for sessile benthic organisms. The benthic diversities decreased significantly in the rest of Middle Triassic, which is due to the significant deepening of the local basin floor. The benthic groups reached maximum diversity in the Carnian. This is attributed partly to the filling up and shallowing of the local basin, partly to redeposition in the course of platform progradations, carrying rich fossil shell material from the neighboring shallow marine environments to the basin. Simultaneously, the sudden increase of the humidity ("Carnian pluvial event") created extensive river systems in the European continent; the increasing supply of organic matter was favorable for the benthos in the marine environments.

"Levipustula Fauna" in central-western Argentina and its relationships with the Carboniferous glacial event in the southwestern Gondwanan margin

Article

Full-text available

Jan 2010

The Levipustula Fauna (included in the Levipustula levis Zone) is a relatively diversified fossil assemblage composed of brachiopods, bivalves, bryozoans, gastropods, and crinoids. This fauna usually is associated with glaciomarine sequences related to the Carboniferous glacial event that affected the southwestern Gondwanan margin. The Levipustula Fauna has been identified in different units (e.g., Hoyada Verde, La Capilla, Leoncito, and Yalguaraz Formations) exposed in the Calingasta-Uspallata Basin. The Hoyada Verde Formation, herein proposed as a key section, contains the most complete record of the Levipustula Fauna. A detailed compositional, taphonomic, and paleoecological study of this section allows us to propose two associations within the so-called Levipustula Zone: the "Intraglacial Levipustula Fauna," present in the diamictite-dominated lower part, and the "Postglacial Levipustula Fauna," dominant in the upper part of section. The fossils of the "Intraglacial Levipustula Fauna" are scarce and poorly diversified. These two features suggest environmentally stressed conditions, probably related to low temperatures in areas close to glaciers. In comparison, the "Postglacial Levipustula Fauna," relatively more abundant and diverse, exhibits compositional variations that could be explained by paleoenvironmental changes associated with fluctuations in substratum and food supply, such as those identified in modern ecosystems. The identification of the "Intraglacial Levipustula Fauna" and the "Postglacial Levipustula Fauna" may constitute a new tool for understanding the particular relationship between faunal assemblages and climatic variations linked to the Gondwanan glaciation in the Calingasta-Uspallata Basin. Also, the new "Intraglacial Levipustula Fauna" identified in the Hoyada Verde Formation would have biostratigraphical and paleogeographical implications in intra-and interbasinal correlations.

Death, decay and disarticulation: Modelling the skeletal taphonomy of marine reptiles demonstrated using Serpianosaurus (Reptilia; Sauropterygia)

Article

Jun 2012
PALAEOGEOGR PALAEOCL

Taphonomic models for fossil vertebrates are designed to reconstruct processes that affected carcasses during the transition from biosphere to geosphere, in particular in the interval between death and burial. To circumvent various limitations in existing methodologies, a new taphonomic method, assessing vertebrate skeletons as nine anatomical units (the head, neck, dorsal, tail, ribs and four limbs) scored independently for two characters (articulation and completeness), was developed. The potential of the method is demonstrated using the Triassic marine reptile Serpianosaurus from Monte San Giorgio, Switzerland. Specimens are preserved in alternations of black shale and dolomite, representing normal background sediment and event beds respectively, deposited into a shallow, intra-platform basin. All specimens exhibit disarticulation of skeletal elements though loss of completeness varies considerably. Minor loss of fidelity occurred during the ‘floating phase’, but individuals reached the sediment-water interface relatively soon after death, and largely intact, where they decayed during the ‘residence phase’. Carcasses allowed to reach extensive states of decay became prone to the effects of weak bottom currents, resulting in removal of elements. The episodic deposition of event beds rapidly buried individuals at various stages of decay, inhibiting further disarticulation and loss of completeness.

Preservation of larval bivalve shells in a radiolarian chert in the Late Triassic (Early Norian) interval of the Malampaya Sound Group, Calamian Island, western Philippines

Article

Full-text available

Apr 2011
Mar Micropaleontol

Silicified thin larval bivalve shells occur in Upper Triassic radiolarian chert (Early Norian) in the Liminangcong Formation of the Malampaya Sound Group, part of a Late Jurassic to Early Cretaceous subduction-related accretionary complex in the North Palawan Block, western Philippines. The bivalve-bearing radiolarian chert, which we term “bivalve chert,” is considered to be a deep-sea sediment that accumulated in an open-ocean realm of the Panthalassa Ocean. Radiolarian and conodont biostratigraphies indicate an early Norian deposition of the thin-shelled bivalves. The bivalve morphology, thin shells (less than 30μm thick), smooth ornamentation, and small size (less than 1.3mm long), suggests they represent larval shells. Although their taxonomic identity cannot be established with certainty, halobiid bivalves that lived in Norian times apparently had such a planktonic larval mode of life.

Paleoecology of Inoceramus amakusensis Nagao et Matsumoto, 1940 (Bivalvia) in a Late Cretaceous shallow clastic sea: The Himenoura Group, Kyushu, Japan

Article

Full-text available

Dec 2011

The taphonomic features and paleoecology of this species were investigated focused on vertically embedded individuals of articulated Inoceramus amakusensis Nagao et Matsumoto. In the Hinoshima Formation, Himenoura Group of Kyushu, Japan, this Santonian (Late Cretaceous) inoceramid bivalve characteristically occurs in incised-valley fill siliciclastic marine deposits. Modes of I. amakusensis occurrence and preservation, from in situ (= occurrence in life position) to allochthonous shell fragments, are strongly affected by its paleoecology and depositional environments. Several I. amakusensis (up to 25 cm in shell height) were recovered from bioturbated sandstones associated with storm-influenced deposits. Their commissural planes are almost perpendicular to the bedding plane, with the anterior face oriented downward and the posteroventral portion extending upward. Furthermore, I. amakusensis is morphologically comparable to endobyssate mytilid bivalves today. These results suggest that this Cretaceous species was an orthothetic sand sticker at least during mid-ontogeny that preferentially inhabited a well-oxygenated, nearshore seafloor. I. amakusensis was distributed in various depositional environments and has been regarded as a recliner in offshore muddy substrate. However, the present discovery suggests that it was also well adapted, with an upright life position, to high-energy shallow clastic environments characterized by high sediment supply.

Depositional response to the Late Triassic ascent of calcareous plankton in pelagic mid-oceanic plate deposits of Japan

Article

Full-text available

Mar 2010
J ASIAN EARTH SCI

Calcareous nannofossils occur in Upper Carnian to Middle Norian siliceous micrites of the Sambosan accretionary complex, the origin of which is the Panthalassan Ocean. The siliceous micrite consists of presumably calcareous nannofossil derived lime–mud and locally yields abundant radiolarians and filaments (thin-shelled bivalves). This type of accumulation of siliceous micrite represents a significant change in oceanic sedimentation since Late Triassic times, which appears as a depositional response to the simultaneous Late Triassic rise of calcareous nannoplankton in the world-ocean.

Palaeoecology of the pseudoplanktonic Triassic crinoid Traumatocrinus from Southwest China

Article

Apr 2007
PALAEOGEOGR PALAEOCL

Colonies of Traumatocrinus (Echinodermata, Crinoidea, Encrinida) attached to driftwood from the Late Triassic (Carnian) Xiaowa Formation of the Guanling area (Guizhou, Southwest China) give evidence for a pseudoplanktonic lifestyle of this specialized offshoot of the otherwise benthic Middle Triassic family Encrinidae. The stem of Traumatocrinus individuals may exceed 11 m in length. Colonies attached by root cirri to logs of driftwood may consist of more than 150 individuals. After the end-Carnian extinction of Traumatocrinus, its ecological niche was taken over in Norian times by Seirocrinus and Pentacrinites with convergent morphological modifications. Seirocrinus and Pentacrinites were derived from the Middle Triassic benthic articulate crinoid family Holocrinidae. After the Toarcian (Lower Jurassic), the niche occupied by Pentacrinitidae disappeared, possibly because of the emergence of wood-boring bivalves and their destructive impact. Due to a larval and adult planktonic and pseudoplanktonic lifestyle, the pelagic Traumatocrinidae were dispersed over the Triassic seas. While genus Traumatocrinus was a Palaeo-Tethys faunal element, its sister genus Vostocovacrinus inhabited the Boreal realm.

Permian non-marine bivalves of the Falkland Islands and their paleoenviromental significance

Article

Full-text available

Dec 2012

Simões, M.G., Quaglio, F., Warren, L., Anelli, L.E., Stone, P., Riccomini, C., Grohmann, C.H. & Chamani, M.A.C. iFirst article. Permian non-marine bivalves of the Falkland Islands and their palaeoenvironmental significance. Alcheringa, 1–13. ISSN 0311-5518.We describe the occurrence of non-marine bivalves in exposures of the Middle Permian (Capitanian) Brenton Loch Formation on the southern shore of Choiseul Sound, East Falklands. The bivalves are associated with ichnofossils and were collected from a bed in the upper part of the formation, within a 25 cm thick interval of dark siltstones and mudstones with planar lamination, overlain by massive sandstones. The shells are articulated, with the valves either splayed open or closed. At the top of the succession, mudstone beds nearly 1.5 m above the bivalve-bearing layers yielded well-preserved Glossopteris sp. cf. G. communis leaf fossils. The closed articulated condition of some shells indicates preservation under high sedimentation rates with low residence time of bioclasts at the sediment/water interface. However, the presence of specimens with splayed shells is usually correlated to the slow decay of the shell ligament in oxygen-deficient bottom waters. The presence of complete carbonized leaves of Glossopteris associated with the bivalve-bearing levels also suggests a possibly dysoxic-anoxic bottom environment. Overall, our data suggest that the bivalves were preserved by abrupt burial, possibly by distal sediment flows into a Brenton Loch lake, and may represent autochthonous to parautochthonous fossil accumulations. The shells resemble those of anthracosiids and are herein assigned to Palaeanodonta sp. aff. P. dubia, a species also found in the Permian succession of the Karoo Basin, South Africa. Our results confirm that (a) the true distributions in space and time of all Permian non-marine (freshwater) bivalves are not yet well known, and (b) there is no evidence for marine conditions in the upper part of the Brenton Loch Formation.

Late Triassic (Carnian-Norian) mixed carbonate-volcaniclastic facies of the Olds Ferry terrane, eastern Oregon and western Idaho

Article

Jan 2008

Todd A. LaMaskin

The Late Triassic (Carnian-Norian) time interval is well represented by strata in the Wallowa and Baker terranes and in the Izee-Suplee area of central Oregon. Strata of the Olds Ferry terrane, by contrast, have received little attention beyond fi eld mapping and reconnaissance-level efforts. This paper describes the sedimentol-ogy of Carnian-Norian deposits in the Olds Ferry terrane and describes a model for arc-fl anking mixed carbonate-volcaniclastic sedimentation. A distinctive thin-bedded limestone unit in the lower Huntington Formation is underlain and overlain by volca-nic and shallow intrusive rocks. Ammonite and bivalve age assignments indicate that the limestone unit spans the late Carnian to early Norian; portions of the section may, more specifi cally, represent the welleri or dilleri ammonite zones. Four lithofacies— Graded Skeletal Packstone and Mudstone, Tuffaceous Peloidal Grainstone, Skeletal Peloidal Packstone, and Lapilli-Tuff Breccia—record episodic sedimentation infl u-enced by earthquakes, storms, and volcanic eruptions on an oxygen-poor carbonate slope apron. The limestone unit represents an echinoderm-and mollusk-dominated heterozoan faunal assemblage characterized by abundant delivery of unlithifi ed car-bonate sediment to deeper water.

Biochronology of Triassic bivalves

Article

Full-text available

Jun 2010

Christopher A McRoberts

Substantial advances by numerous researchers over the past 20 years have made it possible to develop a composite biochronological scheme for the Triassic based on the bivalves Claraia , Peribositria , Enteropleura , Daonella , Halobia , Eomonotis and Monotis . These bivalves exhibit temporal durations nearly equal to ammonoids and conodonts. Widely distributed across the Tethys, Panthalassa and Boreal regions, these bivalves occur in a wide variety of marine facies and water depths, but are most notable for their thick shell accumulation in deeper-water oxygen deficient environments. They were most likely resting or reclining benthos, may have housed chemosymbionts, and were part of episodic opportunistic palaeocommunities in or near oxygen deficient settings. A new biochronological zonation for bivalves is presented that encompasses the entire Triassic and is integrated with standard ammonoid schemes. The Lower Triassic is characterized by 2–3 zones of Claraia , most notably from the eastern Tethys representing the entire Induan and lower portion of the Olenekian. Later in the Olenekian, and most notably from the Boreal realm, species of Peribositria (included by some workers within Bositra ) provide useful zonal indexes. The Middle Triassic is well represented by Enteropleura (Middle Anisian) and Daonella (Upper Anisian through Ladinian) in the Tethys and North America with significant occurrences throughout the circum-Pacific and Boreal realms. The Upper Triassic can be subdivided into 8–13 bivalve zones based on the succession of Halobia , Eomonotis and Monotis sensu lato species with best representation in the Tethys, Boreal and eastern Panthalassa regions.

The end Triassic mass extinction record of Williston Lake, British Columbia

Article

Sep 2007
PALAEOGEOGR PALAEOCL

Triassic–Jurassic boundary sections on the shore of Lake Williston, British Columbia record a spectrum of depositional environments from the western Canadian continental margin. A primarily deep-water, anoxic record of deposition, indicated by V/V + Ni, V/Cr, Th/U indices and pyrite framboid and facies data, is seen throughout the Late Triassic–Early Jurassic (Norian-Hettangian) interval in a section at Black Bear Ridge. Abundant Monotis bivalve populations in Norian strata are interpreted to have lived on the seabed during transient oxygenation events that punctuated the background anoxic conditions. Monotis went extinct around the Norian/Rhaetian boundary and the deep-water assemblages are subsequently dominated by thin-shelled pectinids. An intra-Rhaetian sea-level fall generated a major hiatus in the proximal Black Bear Ridge section whilst distinctive lowstand strata were developed in the more distal and more complete Ne Parle Pas Point and Pardonet Creek sections. These consist of shallow-water, phosphatic ooid sand facies that contain diverse bivalves. The majority of the infaunal bivalves (but not the epifaunal ones) disappeared at the acme of the regression. This is the end-Triassic mass extinction event and it occurred shortly before a terminal Triassic flooding event. This transgressive event is associated with a rapid negative shift of δ13Corg values interpreted to be the Initial Isotope Excursion of Hesselbo et al. [Hesselbo, S.P., Robinson, S.A., Surlyk, F., Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle perturbation: a link to initiation of massive volcanism? Geology 30, 251–254]. The Rhaetian record of Williston Lake thus records an extinction of shallow-water infaunal bivalves during a lowstand prior to the development of a transgressive record that is associated with a major, negative C isotope.

Decoding the drivers of deep-time wetland biodiversity: insights from an early Permian tropical lake ecosystem

Article

Full-text available

Jun 2023
Palaeontology

Wetlands are important to continental evolution, providing both arenas and refugia for emerging and declining biotas. This significance and the high preservation potential make the resulting fossiliferous deposits essential for our understanding of past and future biodiversity. We reconstruct the trophic structure and age of the early Permian Manebach Lake ecosystem, Germany, a thriving wetland at a time when the tropical biosphere faced profound upheaval in the peaking Late Palaeozoic Icehouse. Nine excavations, high-resolution spatiotemporal documentation of fossils and strata, and U-Pb radioisotopic dating of tuffs allow us to distinguish autogenic and allogenic factors shaping the limnic biocoenosis. The Manebach Lake was an exorheic, oxygen-stratified, perennial water body on the 10¹–10² km² scale, integrated into the catchment draining much of the European Variscides. Lake formation paralleled an Asselian regional wet climatic interval and benefited from rising base level due to post-Variscan half-graben tectonics. Stromatolite-forming cyanobacteria, bivalves, several crustaceans , amblypterids and xenacanthid sharks formed a differentiated biocoenosis in the lake. Fossil stomach remains and teeth prove the rare presence of acanthodians, branchiosaurs and large amphibians. The results indicate woody-debris-bearing lake littorals devoid of semi-aquatic and aquatic plants as places suitable for stromatolites to grow, underpin the model of declining freshwater-shark diversity in most Permian Variscan basins, demonstrate fish/amphibian ratios in limnic assemblages to measure lake perenniality and reveal taphonomic biases in lake taphocoenoses. Our outcomes call for more knowledge about the diversity, ecology and fossilization pathways of past limnic biotas, particularly microorganisms and actinopterygian fishes, to reconstruct deep-time continental ecosystems.

Linking facies variations, organic carbon richness and bulk bitumen content – A case study of the organic-rich Middle Triassic shales from eastern Svalbard

Article

Full-text available

Jun 2021
MAR PETROL GEOL

The organic-rich shales of the Middle Triassic Botneheia Formation in Svalbard and its correlative units offshore are considered important source rock intervals for oil and gas generation in the Norwegian Barents Shelf region. Detailed investigation of these intervals is essential to better understand the intra source rock variations and thus to improve exploration models. As source rocks are rarely cored during exploration campaigns, outcrop studies of analogue source rocks onshore Svalbard are of great importance for gaining a comprehensive understanding of the Triassic petroleum system offshore. This integrated sedimentological and geochemical study of the Botneheia Formation investigates the intricate relationship between mudstone facies, total sulfur, total organic/inorganic carbon, and the absolute and relative abundance of bulk bitumen content. Both the Muen Member (Anisian) and the overlying Blanknuten Member (mostly Ladinian) of the Botneheia Formation were densely sampled and analyzed from three outcrop localities on Edgeøya, eastern Svalbard. The results show that total sulfur, total organic carbon, bitumen richness, and relative and absolute aromatic hydrocarbon content increase from bioturbated, gray-colored shales in the lower to middle Muen Member upwards into non-bioturbated, phosphogenic black shales in the middle part of the Blanknuten Member. From here, organic carbon and bulk bitumen richness subsequently decrease upwards in concert with the occurrence of bioturbated, calcareous mudstones and impure limestones towards the top of the Blanknuten Member. Optical vitrinite reflectance variations do not suggest significant maturity variations with depth in the sample profiles, highlighting that the total organic carbon and bulk bitumen content are dominantly coupled with the developing source facies. These facies and chemostratigraphic trends mirror the implied marine vs terrigenous organic matter sedimentation and benthic preservation potential, which were at a maximum in the middle Blanknuten Member. These processes appear to be closely related to the supply of nutritious upwelled waters that are further linked with an evolving pan-Arctic 2nd order Middle Triassic transgressive–regressive sequence. Facies and multivariate analyses of the geochemical data show that the lower to middle Muen Member are comparable to the pro-delta mudstones of the younger Tschermakfjellet Formation (Carnian), and that both units are clearly distinct from the increased source rock potential and richness in the upper part of the Muen Member and the entire Blanknuten Member. This provides evidence of genetically different paleo-depositional environments and source rock properties that are confined to the lower and upper parts of the Middle Triassic Botneheia Formation, and may have wide application for Triassic source rock assessment in the offshore Norwegian Barents Sea.

First report of myalinid bivalves in the Lower Carboniferous of the Hakkari Basin, SE Turkey: Paleoecologic and Paleogeographic implications

Article

Full-text available

Feb 2021

Izzet Hoşgör

Knowledge of the Late Paleozoic sedimentary history of the northern Gondwana shelf is advanced by new data from the Şort Dere section (Hakkari Basin). Early Carboniferous myalinid bivalves from the Middle East are reported here for the first time. The pre-Permian basement of the Hakkari Basin consists of a Lower Carboniferous sedimentary sequence including the Köprülü and Belek formations. The Köprülü Formation has yielded rich assemblages of vertebrates and invertebrates. Hitherto myalinid bivalves were unknown from this formation; this paper reports the discovery of small and poorly calcified myaliniform shells from two thin beds in the middle part of the Köprülü Formation of the Şort Dere section in the Zap Valley. The morphological characteristics of the specimens, especially the umbonal region with the numerous rounded wrinkles, suggest that it probably belongs to an undescribed species of Selenimyalina Newell, 1942. Based on this record, the state of the art of warm-water myalinid taxa in the Paleotethyan Realm is shortly discussed with a focus on the pteriomorph bivalve faunas within a global scenario for both paleobiogeography and patterns of Gondwana-Laurussia faunal exchange. The new occurrence is one of the most important pteriomorph bivalve records ever made in Southeast Turkey, helping to assist paleogeographic reconstructions of the Paleotethyan paleocontinents.

Chapter 3 Lithostratigraphy and depositional characteristics, age dating and sequence stratigraphy

Article

Nov 2020

A. O. Wilson

This chapter reviews the lithostratigraphy, biostratigraphy, age dating and sequence stratigraphy of the Arabian Intrashelf Basin to document the basic data used in the interpretations in this Memoir. The factors important to understanding these topics are discussed, including the typical facies, general depositional models, the effects of dolomitization, well log characteristics and the problems with obtaining precise age dates. Comments are included to show the interpretations preferred in this Memoir.

Southern Hemisphere Palaeobiogeography of Triassic-Jurassic Marine Bivalves. Chapter 1. Introduction

Chapter

Full-text available

Jan 2013

Bivalves have proven to have a great potential for paleobiogeographic analyses due to their relatively complete fossil record, especially for Mesozoic and Cenozoic times. Being mostly benthonic, they have a large variety of life habits which should be taken into account, particularly in detailed paleobiogeographic studies. We will analyze marine bivalve distribution in the Southern Hemisphere during several successive time slices within the Triassic and Jurassic, an epoch marked by critical geologic and biotic events. This period covers both the biotic recovery after the harshest diversity crisis ever (the Permian/Triassic extinction event), and later also the biotic reaction to another severe crisis at the Triassic/Jurassic boundary. This allows the opportunity to evaluate the response of paleobiogeographic patterns to such events. The Earth’s configuration drastically changed from a concentration of land masses in a unique supercontinent (Pangea) and two oceans (Tethys and Panthalassa), to a fragmented series of continental land masses. These began to disperse, opening sea corridors which largely affected not only the global distribution of biotas but also paleoclimate and sea paleocurrents as well. This dynamic paleogeography adds an interesting ingredient to the study of past distributions of benthic organisms making it possible to frame them into a physically and biologically changing scenario.

Southern Hemisphere Palaeobiogeography of Triassic-Jurassic Marine Bivalves. Chapter 3. A Bivalve Perspective

Chapter

Jan 2013

Mesozoic bivalves have been the subject of many paleobiogeographic studies, either with the aim of recognizing units, to argue about the proposal of opening of seaways and exotic terranes movements, or even to relate biogeography with extinction and evolution. With a few notable exceptions, Northern Hemisphere data were used and frequently conclusions extrapolated worldwide. In the analysis of bivalve geographic distribution, some special issues should be taken into account, such as larval type, mode of life, and tolerance to certain environmental factors, which are here briefly discussed for Southern Hemisphere bivalves. Special attention is paid to the proposed pseudoplanktonic habit as an aid to dispersal, to reef-building bivalves, and to those with special low-oxygen tolerance. For some of the various analyses performed, Triassic-Jurassic bivalve genera were classified according to their paleobiogeographic affinities in truly cosmopolitan, low-latitude (Tethyan), high-latitude (austral or bipolar), trans-temperate (Pacific), and endemic.

Facies and palaeoecology of the late Viséan Actinopteria Black Shale Event in the Rhenish Mountains (Germany, Mississippian)

Article

Full-text available

Mar 2015
Z DTSCH GES GEOWISS

The isochronous, mid-Brigantian (latest Viséan) Actinopteria Black Shale is intercalated in between upper Viséan calciturbidites within the northern part of the Rhenish Mountains (Germany). It shows characteristic mass-occurrences of the eponymous bivalve Ptychopteria (Actinopteria) lepida (Goldfuss). The case study of a classical, exceptionally well preserved outcrop in the Lüdenscheid Syncline documents the facies and palaeoecology of this event horizon. Hitherto, sediments had been regarded as deep-marine anoxic deposits, resulting from pelagic rain. Now, microfacies analysis of the mostly silicified mudstones revealed a heterogeneous sedimentary facies, showing ample evidence of current-driven microevent deposits regarded as mud turbidites. Various but simple ichnofabrics indicate mostly dysoxic conditions of the soupy sediment. Discussion of palaeobiological constraints proves the earlier assumed pseudoplanktic mode of life for Ptychopteria (Actinopteria) lepida and contradicts epibenthic colonisation by that bivalve. “Mass-occurrence” might be a compaction artefact, but occurrence on few distinct bedding planes in an interval several centimetres thick is related to an extraordinary complete sedimentary record that protected the “paper pectens” from erosion. This variant of a taphonomic epibole is termed “maximum completeness epibole”. In the case of the Actinopteria Shale, in sequence stratigraphic terms a transgressive systems tract, this bioevent is postulated to represent the maximum flooding surface with minimum sedimentary input and reworking.

Postmortem encrustation of the alien bivalve ensis americanus (binney) by the barnacle balanus crenatus brugire in the North Sea

Article

Nov 2011

Stephen K. Donovan

The alien razor shell Ensis americanus (Binney) is a common bioclast on Dutch beaches. It is uncommonly encrusted by the balanid Balanus crenatus Brugière on both the interior and exterior surfaces of both valves. This occurs postmortem, but before the ligament breaks. A well-preserved specimen from Zandvoort is described which confirms that this pattern of skeletozoan infestation is initiated in dead shells still in the burrow, but protruding above the sediment surface. After exhumation, the recumbent shell can be further infested by subsequent balanid spatfalls. Such a pattern of encrustation is only likely in burrowing bivalves with a permanent and prominent gape to the shell.

Southern Hemisphere Palaeobiogeography of Triassic-Jurassic Marine Bivalves

Book

Jan 2013

Preface The study of global biodiversity changes is a strong issue these days, as we become aware of the fragility of the Earth system and the urgent need to understand it better to keep it working. One of the key aspects of biodiversity is the distribution of organisms, and biogeography is the discipline which tries to recognize and characterize the causes of that distribution. It is closely linked to ecology, since the distribution of organisms is related to ecologic factors, but it cannot ignore other matters, such as species origin, dispersal, and extinction, and thus it becomes a historic science. Introducing the important time dimension, scientists are turning their interest to the past distribution of organisms, and paleobiogeography is now a complex subject which processes information provided by both Biology and Earth Sciences. It is conceptually and philosophically equivalent to neobiogeography. Nevertheless, its methods are somewhat different, since it is seriously limited by the incompleteness of the fossil record. On the other hand, it has direct access to the time involved, a key ingredient of organic evolution. This book is a synthesis of many years of research on Mesozoic bivalve mollusks from South America. The task of updating and processing all the information was triggered by a Symposium on ‘‘Seaways and landbridges: Southern Hemisphere biogeographic connections through time’’, organized by Dr. Silvio Casadío (CONICET and Universidad Nacional de Río Negro) and Dr. Miguel Griffin (CONICET and Universidad Nacional de La Plata), held at the Universidad Nacional de Río Negro, General Roca, Río Negro Province, Argentina, April 26–May 1, 2011, and who kindly encouraged us to complete this contribution. After that memorable meeting we put together our knowledge and skills to produce this book together, and present a picture of present-day knowledge on Triassic and Jurassic bivalve distribution in the Southern Hemisphere. Benthonic bivalves have been widely used in biogeography and paleobiogeography, but data from the Southern Hemisphere Mesozoic are still few and scattered. We trust this book will encourage future research on this subject to build better databases and allow the application of more sophisticated methodology. Through the book we analyze the subject from several viewpoints. From a merely descriptive perspective, bivalve distribution shows latitudinal gradients and distributional patterns, both at regional and global scales, which are the basis for the recognition of biochoremas (i.e., paleobiogeographic units of different ranks). Moving forward toward a causal paleobiogeography, these organisms also provide interesting insight into particular biogeographic questions, such as bipolarity and its origin. The evolution in time of the recognized biochoremas can be discussed in relation to paleoclimates and paleogeography. Finally, some of the results obtained from the analysis of the distribution of past bivalve biotas were even used to propose and discuss the development of marine corridors and argue about the distribution of continents in the past.

The Late Triassic Black Shales of the Guanling Area, Guizhou Province, South-West China: a unique marine Reptile and pelagic Crinoid fossil Lagerstätte

Article

Jan 2008
Palaeontology

: Black shales of the lower member of the Carnian Xiaowa Formation (previously known as the Wayao Member of the Falang Formation or as the Wayao Formation) in the Guanling area, Guizhou Province, south-west China, are yielding a rich marine reptile fauna and exceptional remains of pelagic crinoids. The black shales represent deposition on the drowned southern margin of the Yangtze Platform during a Maximum Flooding Interval. The relatively reduced sedimentation rates led to the formation of the Lagerstätte through the accumulation of fossils in the anoxic bottom sediments over a prolonged period of time. Invertebrate fossils represent almost exclusively pelagic forms, such as a diverse ammonite fauna and halobiid bivalves. The spectacular finds of colonies of large (stem lengths > 11 m) crinoids of the genus Traumatocrinus attached to driftwood prove that this crinoid was the first to evolve a pseudoplanktonic life style. The other crinoid is the planktonic roveacrinid Osteocrinus. The marine reptile fauna, represented by probably hundreds of skeletons, is numerically dominated by three species of ichthyosaurs and four species of thalattosaurs. The thalattosaurs fill a palaeobiogeographic gap between the Alpine thalattosaur faunas and those from western North America. Two species of placodonts are rare finds. As for the thalattosaurs, the placodont occurrences greatly expand the geographic range of the group because placodonts have been known previously only from the Mediterranean region, the Alps and the Muschelkalk Basin. The unique abundance of thalattosaurs contrasts with a scarcity of fishes. Although we suggest that the fauna is authochthonous and inhabited surface waters, it must have represented an unusual ecosystem. However, the possibility remains that both the marine reptiles and the Traumatocrinus colonies were concentrated in the region by currents and do not reflect the biocoenosis.

Anatomy And Sequence Architecture of the Early Post-Rift In the Neuquen Basin (Argentina): A Response To Physiography and Relative Sea-Level Changes

Article

Full-text available

Aug 2013

A detailed architectural and sequence stratigraphic analysis was carried out in the early-post-rift succession of central Neuquén Basin (Middle Jurassic Cuyo Group), integrating outcrop and subsurface information from a 3,000 km2 area. Sedimentary facies analysis allowed the definition of six marine facies associations, which are grouped in two main depositional systems. During the late Toarcian to early Bathonian a storm- and wave-dominated shoreface to offshore system was developed. This is overlain by a late Bathonian–early Callovian fluvio-deltaic depositional system. The sequence stratigraphic analysis of this succession identified parasequences limited by marine flooding surfaces with little evidence of erosion. Parasequences could be grouped into four parasequence sets that show the evolution of the depositional systems and can be interpreted in terms of shoreline trajectories. In this sense, a log-term transgressive event defined by a complicated retrogradational stacking pattern and spanning for almost 10 My is identified for the older deposits. This succession is eventually replaced by a progradational unit that represents highstand conditions. The Cuyo succession identified in this part of the basin is completed by the development of a regressive surface and the onset of a deltaic depositional system with no parasequence development but indicating an abrupt basinward facies shift. The long-term transgression that dominates the early post-rift succession in this part of the basin is interpreted to represent a period of sustained accommodation creation produced by the combination of thermal subsidence, differential compaction of syn-rift deposits, and eustatic rise under a relatively low sediment supply. Changes in the stacking pattern of retrogradational parasequence sets are thought to be produced by changes in the bathymetry of the topography being flooded, which is a relic of a complex array of footwalls and shoulders generated during the syn-rift stage. Regional changes in thickness and timing for the early post-rift succession could be therefore the result of the relatively passive infill of an inherited topography of the syn-rift, suggesting that most of the accommodation was already created before the onset of the long-term transgressive trend that characterizes the post-rift succession in this part of the basin. The Cuyo Group succession reported here reflects the complexity in terms of depositional styles, sequence stratigraphic patterns, and controls that can be expected during the early-post rift infill of syn-rift structural depressions. Therefore, the results of this study can provide useful lessons for post-rift systems having prolific hydrocarbon production worldwide (e.g., in the Northern North Sea, Norwegian Sea, Thailand, and Argentina and Chile).

Deposition and taphonomy of the Hound Island Late Triassic vertebrate fauna: Fossil preservation within subaqueous gravity flows

Article

Aug 2009

Thomas L Adams

Late Triassic marine vertebrates occur in the Hound Island Volcanics exposed on the eastern shore of Hound Island, southeastern Alaska. This fossil assemblage derived from slope deposits within an intra-are basin of a volcanic island are complex. It is associated with the allochthonous Alexander Terrane prior to its northern translation from tropical latitudes to its current latitude. Fossils occur within a 13-m-thick succession of interbedded calcareous shale and volcaniclastic-rich bioclastic limestone. The limestone layers are skeletal (vertebrate and invertebrate) packstones to wackestones and are interpreted as episodic thin-bedded turbidite and debris flow deposits that resulted from redeposition of slope sediments. Forty-seven vertebrate fossils were collected that consist of complete and fragmented cranial and postcranial elements belonging to Eosauropterygia, Thalattosauria, and Ichthyosauria, including the genus Shonisaurus. Bones are frequently disassociated and show predepositional abrasion and breakage. Another less common taphonomic mode is observed, characterized by several large associated elements, representing a single individual, found parallel to bedding and draped by shale. Rare Osteichthyes and Chondrichthyes teeth are also present. Bivalve and conodont fossils indicate a middle Norian age for the assemblage.

A new daonella from the ladinian platform of the ESINO limestone (Southern Alps, Italy)

Article

Full-text available

Apr 2006

The bivalve Daonella Mojsisovics, 1874 is very common in the Middle Triassic pelagic facies, whereas the record of this genus from shallow water limestones is rare. In the present paper a new species of Daonella, named D. pseudograbensis, is described from the Esino Limestone, a Ladinian (Middle Triassic) carbonate platform in the central Southern Alps. The species is described from Brembana Valley, where the Esino Limestone is rather rich in bioclastic lenses yielding faunas with bivalves, cephalopods, gastropods, brachiopods, corals and calcareous algae. Daonella pseudograbensis n. sp. is based on very well preserved specimens, which are often articulated and closed, all coming from the same locality. The new species shows a narrow range of intraspecific and ontogenetic morphologic variations. It is easy distinguishable from the other species of the genus for the outline and ornamentation; it therefore differs from D. grabensis Kittl, 1912, the most similar species, for the longer anterior dorsal margin.

Facies, depositional environment, and palaeoecology of the Middle Triassic Cassina beds (Meride Limestone, Monte San Giorgio, Switzerland)

Article

Full-text available

Jul 2010

Rudolf Stockar

The Ladinian Cassina beds belong to the fossiliferous levels of the world-famous Middle Triassic Monte San Giorgio Lagerstätte (UNESCO World Heritage List, Canton Ticino, Southern Alps). Although they are a rich archive for the depositional environment of an important thanatocoenosis, previous excavations focused on vertebrates and particularly on marine reptiles. In 2006, the Museo Cantonale di Storia Naturale (Lugano) started a new research project focusing for the first time on microfacies, micropalaeontological, palaeoecological and taphonomic analyses. So far, the upper third of the sequence has been excavated on a surface of around 40m2, and these new data complete those derived from new vertebrate finds (mainly fishes belonging to Saurichthys, Archaeosemionotus, Eosemionotus and Peltopleurus), allowing a better characterization of the basin. Background sedimentation on an anoxic to episodically suboxic seafloor resulted in a finely laminated succession of black shales and limestones, bearing a quasi-anaerobic biofacies, which is characterized by a monotypic benthic foraminiferal meiofauna and has been documented for the first time from the whole Monte San Giorgio sequence. Event deposition, testified by turbidites and volcaniclastic layers, is related to sediment input from basin margins and to distant volcanic eruptions, respectively. Fossil nekton points to an environment with only limited connection to the open sea. Terrestrial macroflora remains document the presence of emerged areas covered with vegetation and probably located relatively far away. Proliferation of benthic microbial mats is inferred on the basis of microfabrics, ecological considerations and taphonomic (both biostratinomic and diagenetic) features of the new vertebrate finds, whose excellent preservation is ascribed to sealing by biofilms. The occurrence of allochthonous elements allows an insight into the shallow-waters of the adjoining time-equivalent Salvatore platform. Finally, the available biostratigraphic data are critically reviewed.

Thin-shelled bivalves from the Jurassic Rosso Ammonitico and Calcari a Posidonia Formations of the Umbrian-Marchean Apennine (Central Italy)

Article

Full-text available

Jan 1992

An anoxic intraplatform basin in the Middle Triassic of Lombardy (southern Alps, Italy): anatomy of a hydrocarbon source

Article

Full-text available

Jan 1991

The Ladinian rocks of Central Lombardy consist of carbonate platforms subdivided by intraplatform troughs represented either by dark, well bedded limestones, marls and dolomites of poorly oxic to anoxic environment or by grey nodular cherty limestones. Subsidence and deposition rates were high (>100 m/MA), both on the carbonate platform and in the anoxic intraplatform troughs. Sedimentological study of the anoxic intraplatform rocks in the Grigne Mountains has identified 12 main lithofacies with mudstone/ wackstones, both massive and laminated, forming more than 2/3 of the total thickness. The Grigne Mountains are presently arranged in three main tectonically stacked sheets. Vitrinite reflectance, illite crystallinity index, and conodont alteration index, all suggest an increase of temperature within the sheets, from south to north. -from Authors

Assessment of degree of pollution on the basis of macrozoobenthos in marine and brackish-water environments

Article

Full-text available

Sep 1975

Erkki Leppäkoski

Soft-bottom macrofauna were sampled in Saltkällefjord (west coast of Sweden), polluted by sulphite pulp and paper mill wastes, and in certain SW-Finland coastal inlets into which both domestic and industrial wastes are discharged The parameters studied were: species composition, abundance, wet weight biomass, distribution of species, size class distribution, faunal affinity, and diversity. Changes in these over a period of 35 years in Saltkällefjord and 13 years in the Finnish waters are discussed. The benthic fauna were divided into progressive, regressive and indifferent groups on the basis of their reaction to organic pollution and the applicability of both species-level and community-level benthic parameters as indicators of pollution are discussed. The Northern Macoma baltica community was divided into five variants characteristic of different degrees of impoverishment. Benthic recolonization, subsequent to pollution abatement, could be studied in both marine and brackish-water conditions. A benthic pollution index (BPI) was calculated on the basis of primary and secondary maxima and minima of animal densities distinguished in the studied waters, The terminology concerning the zones of benthic pollution in marine and brackish water all over the world is reviewed and the zones redefined on the basis of approx. 180 original papers referred to. Index words: macrobenthos, bottom communities, indicator organisms, pollution, Baltic Sea, Skagerack

Pseudoplankton

Article

Full-text available

Jan 1990

All attached epifaunal species have the potential to colonize floating substrates. Such pseudoplankton are preserved in a much wider range of facies than their benthic relatives. However, they are never as abundant as benthos due to the rarity of attachment sites. Pseudoplanktonic species utilize five attachment strategies: cemented, adpressed, pendent, boring and clinging. Most reported examples of pseudoplankton, particularly those from black shale facies, are too abundant to be attributed to this group and, in the majority of cases, a benthic mode of life is more plausible. The fossil record of pseudoplankton is thought to be considerably poorer than has hitherto been suggested. -from Authors

Factors affecting oxygen consumption in the coot clam Mulinia lateralis (Say)

Article

Full-text available

Dec 1983

Sandra E Shumway

The effects of intrinsic (body size, gill surface area and activity patterns) and extrinsic (temperature, salinity and oxygen concentration and food) factors on oxygen consumption were measured in the mactrid clam Mulinia lateralis. Both acclimated and acute rates of VO2 were measured under 9 salinity-temperature combinations and a model is presented which indicates that: 1) body size is the over-riding factor determining VO2, 2) acclimation temperature alone has no significant effect on either fed or starved animals 3) the interaction of acclimation temperature and salinity and exposure salinity is the strongest factor influencing VO2 after body size, 4) exposure conditions are more likely to determine energy levels of expenditure than acclimation conditions. Small individuals have a greater gill surface area per body weight than larger individuals. The degree of oxygen independence is dependent on both body size and on acclimation temperature and shows a slight increase after exposure to anoxic conditions.

Microfacies, geochemistry and palaeoecology of the Middle Triassic Grenzbitumenzone from Monte San Giorgio (Canton Ticino, Switzerland)

Article

Full-text available

Jan 2001

The Middle Triassic Grenzbitumenzone from Monte San Giorgio (Ticino, Switzerland) has been investigated in detail to reconstruct the palaeoecological environment. Euxinic and anoxic conditions were interrupted by oxygenated (dysaerobic) periods with benthic faunal colonization of monospecific to paucispecific assemblages. Physicochemical conditions changed trough time and were strongly related to water depth. Sediments of the lower and upper Grenzbitumenzone were deposited in a shallow restricted carbonate platform environment. By contrast, in the middle part a slightly deeper intraplatform basin prevailed. Diversity, composition and size of vertebrate fossils also reflect the bathymetric trend. Microfacies development, corresponding changes in total organic carbon and sulphur contents as well as taphonomic observations reveal that the sediments were not deposited under permanently anoxic conditions. The results show that the sedimentation during the Anisian/Ladinian-transition in the Monte San Giorgio area was highly dynamic, reflecting a long-term bathymetric trend overprinted by a short-term cyclicity.

Geographic variation in the macrofaunal associates of pelagic Sargassum and some biogeographic implications

Article

Full-text available

Jan 1984

Oxygen Consumption in the American Oyster Crassostrea virginica

Article

Full-text available

Jan 1982

Functional anatomy, chemosymbiosis and evolution of the Lucinidae

Article

Full-text available

Dec 2000

All Lucinidae species studied so far possess sulphide-oxidizing. chemosymbiotic bacteria housed in bacteriocytes of gill filaments. The ecology, functional anatomy and evolution of the Lucinidae must be considered in relation to this symbiosis. The ctenidia have been extensively studied but other anatomical structures peculiar to lucinids have received much less attention. Reviewed are the morphological diversity of living lucinids, highlighting features of their anatomy including ctenidia, pallial apertures, anterior adductor muscle, pallial blood vessel and mantle gills. The latter are much more complex than previously understood and are here redescribed, They comprise Folded structures located near the anterior adductor muscle in Codakia, Phacoides and Lucina, and on the septum of Anodontin. These are interpreted as secondary respiratory surfaces, their location enabling the separation of the anterior inflow of oxygenated water from sulphide-containing water. The latter is released from the sediment by the probing activities of the highly extensible foot and is pumped over the gill through the pedal gape and perhaps also via the exhalant tube. The shell Features of Ilionia from the Silurian Period suggests that the lucinid chemosymbiosis is an ancient association.

Floating articulated bivalves, Texel, North Sea

Article

Full-text available

Jul 2002
PALAEOGEOGR PALAEOCL

Gerhard Cornelis Cadee

Articulated, closed, empty bivalves were collected from a modern beach on the island of Texel, The Netherlands. They included many 2-year-old Spisula subtruncata (average length 25.5 mm). Experiments indicated that they could float. Normally, dead but still articulated bivalves on the beach gape; because the adductor muscles no longer pull the valves together, the ligament opens the two valves. These bivalves most probably had arrived alive on the beach after being dislodged during a storm. The animal inside desiccated on the beach, the remains of the animal glued the valves together, air was trapped inside and the next high tide brought the Spisula floating to a higher drift line on the beach. Such closed, empty bivalves may float for days and cover considerable distances as exemplified by a freshwater Dreissena polymorpha also found on the beach of Texel as a closed, floating bivalve, 20 km from the nearest place where it occurs alive. For the palaeoecologist this indicates that closed, articulated bivalves do not necessarily indicate an absence of transport.

The case of the missing community: Low-oxygen adapted Paleozoic and Mesozoic bivalves ("flat clams") and bacterial symbioses in typical Phanerozoic seas

Article

Jan 1988

E.G. Kauffman

Relation of shell form to life habits of the Bivalvia (Mollusca)

Article

S.M. Stanley

Elementi per una revisione stratigrafico-paleontologica del Trias medio superiore della regione compresa tra il Lario e il Ceresio

Article

Jan 1988

The taphonomy of soft‐bodied animals.

Article

Jan 1991

Macrobenthic succession in relation to organic enrichment and pollution of the marine environment

Article

Jan 1978

The Formation of the Bituminous Layers of the Middle Triassic of Ticino (Switzerland) (Abstract)

Chapter

Jan 1982

Helene Tryti Rieber

The black shales of the Middle Triassic of the Limestone Alps of Ticino are famous for their perfectly preserved marine vertebrates, reptiles and fishes. They are also well-known for their high content of organic matter (up to about 50%). The so-called Grenzbitumenzone is the most famous bituminous member within the Middle Triassic of the Ticino. It is situated at the boundary Anisian/Ladinian and well exposed near Serpiano at the Monte San Giorgio and at Besano (Italy). It consists of finely laminated, highly bituminous claystones, more or less laminated bituminous dolomites and some thin layers of argillaceous tuffites.

Review of oxygen depletion and associated mass mortalities of shellfish in the Middle Atlantic Bight in 1976

Article

Jan 1978

Les pétrifications d'Esion, ou déscription des fossiles appartenant au depôt supérieur des environs d'Esino en Lombardie

Article

A. Stoppani

Revision der untergattung Daonella (Pichlerella) (Bivalvia, Ladin)

Article

Jan 2001

Wolfgang Schatz

The bivalve genus Daonella MOJSISOVICS 1874 has an excellent biostratigraphic potential for the Middle Triassic. However, for a supraregional biostratigraphic application, a new coherent systematic is indispensable. This paper presents the results of a systematic revision of the subgenus Daonella (Pichlerella) TURCULET 1972. Many names like D. obliqua MOJSISOVICS 1874, D. reticulata MOJSISOVICS 1874, D. nodigulera BITTNER 1895 and D. pauli KITTL 1912 are deemed as younger synonyms of D. pichleri MOJSISOVICS 1874. D. descata SCHAFHÄUTL 1863 is assigned to the subgenus D. (Arzelella) TURCULET 1972. The stratigraphic distribution of D. pichleri MOJSISOVICS 1874 is limited to the upper gredleri-Zone/lower archelaus-Zone. The geographic occurrence ranges from the Northern Calcareous Alps, Southern Alps (Dolomites) up to Southeastern Asia.

Zur Entstehung der Grenzbitumenzone der Mittleren Trias der Tessiner Kalkalpen

Article

Jan 1968

Helene Tryti Rieber

The case of the missing community; Low-oxygen adapted Paleozoic and Mesozoic bivalves ("flat clams") and bacterial symbioses in typical Phanerozoic seas

Article

Jan 1988

E.G. Kauffman

Materialien zu einer Monographie der Halobiidae und Monotidae der Trias

Article

E. Kittl

Neue Ergebnisse auf dem Gebiete der kologie, Stratigraphie, und Phylogenie der halobien (Bivalvia)

Article

Jan 1976

B. Gruber

Geochemical and microbial controls on dolomite formation in anoxic environments: A case study from the Middle Triassic (Ticino, Switzerland)

Article

Jan 1994

Stefano Bernasconi

The palaeobiology of the bivalve families Pectinidae and Propeamussiidae in the Jurassic of Europe

Article

Jan 1984

Andrew L. A. Johnson

Organic Geochemistry and Depositional Environment of a Hydrocarbon Source Rock: The Middle Triassic Grenzbitumenzone Formation, Southern Alps, Italy/Switzerland

Chapter

Jan 1993

The Middle Triassic Grenzbitumenzone Formation is a 16-m-thick sequence of finely laminated, organic-rich dolomites and black shales. TOC contents reach 10% in the dolomites and 40% in the shales. Sedimentological and geochemical data suggest deposition in a shallow marine basin under permanently anoxic conditions. The organic matter is of type II. Based on geochemical parameters the Grenzbitumenzone can be divided into two sections. In the lower part, hopanes are present in very high concentrations (up to one order of magnitude higher than steranes) and the δ13C of the TOC varies between -30.0 and -31.8‰ (PDB). Above 13 m from the base hopanes are scarce and the δ13C of the TOC becomes less negative. Sedimentological and geochemical data suggest that a planktonic “bacterial plate” developed at the oxic-anoxic boundary in the water column and that bacteria were a significant contributor to the primary organic matter production in the basin. Variations in the maturity-dependent Ts/Tm ratio and 20S/20R C29 sterane isomerization ratio occur over thicknesses of a few metres. Their correlation with the carbon isotope composition of the extracts suggests that the scatter may be related to changes in organic matter input and/or bacterial activity during early diagenesis and not differences in maturity.

Ammonite shells as habitats in the Posidonia Shales of Holzmaden - Floats or benthic islands?

Article

Feb 1982
Neues Jahrbuch Geol Palaontol Monatsh

A. Seilacher

Epizoans as a key to ammonoid ecology

Article

Jan 1960

A. Seilacher

Uber die Umgebungeu von Esino in der Lombardei

Article

E.W. Benecke

The decline of macrofauna in the deeper parts of the Baltic proper and the Gulf of Finland

Article

Jan 1978

The mode of life of two Jurassic species of "Posidonia" (Bivalvia)

Article

Jan 1965

Adaptive pathways of benthic organisms in marine oxygen-controlled environments

Article

Jun 1994
Neues Jahrbuch Geol Palaontol Abhand

Wolfgang Oschmann

Notes on Mesozoic "planktonic" bivalves

Article

Jan 1969

Itaru HAYAMI

Anaerobic metabolism in bivalve molluscs

Article

Jan 1977
OCEANOGR MAR BIOL

A. De Zwaan

Black Shales

Article

Feb 1995

Taphonomy of a Modern Shrimp: Implications for the Arthropod Fossil Record

Article

Jun 1986

Roy Elliot Plotnick

This paper examines some of the taphonomic variables that may bias the arthropod fossil record. The short-term preservation potential of the modern carid shrimp, Pandalus danae, was studied in a variety of laboratory and field settings. Destruction by scavengers (crabs?) was the probably primary cause of carcass destruction in the field. Further breakdown was caused by bacterial decomposition and disturbance by burrowing infauna. Shrimp remains were placed in a series of glass jars in the laboratory. Decomposition destroyed nearly all soft tissues within a period of two weeks. The cuticle became extremely soft, resulting in loss of physical integrity of the remains. Differences between oxic and anoxic decomposition were minor. These results suggest that disturbance by scavengers or burrowing infauna is a major factor in the destruction of buried arthropod remains. The absence or inhibition of bioturbation may be a necessary condition for arthropod preservation. The preservation potential of arthropods, and of other soft-bodied forms, may have declined since the Paleozoic.-from Author

Palaeoecology of a bituminous shale-the Lower Oxford Clay of Central England

Article

Jan 1975
Palaeontology

Keith Duff

Reproductive Ecology and Biogeography of Indo-West Pacific Angelfishes (Pisces: Pomacanthidae)

Article

Jul 1985

Analysis of the relationships between duration of the pelagic larval stage (as indicated by otolith microstructure), adult size, and the extent of geographic distribution for Indo-West Pacific angelfishes (Pomacanthidae) indicates that neither adult size nor larval duration significantly predicts extent of distribution, either individually or jointly in a multiple regression. These results are robust for both the family as a whole and the genus best represented in our data (Centropyge). If larval duration and adult size do have an effect, it is only jointly and at the genus level. However, larval duration and adult size do correlate significantly and negatively with one another. The operational factor seems to be egg size, which correlates positively with adult size, and negatively with duration of the pelagic larval stage. Similar correlations are evident in both marine invertebrates and at least some other coral-reef fishes, suggesting they are of widespread significance. The limited ability of either reproductive parameter to predict extent of species distribution indicates, first, that even in a group as morphologically conservative as the Indo-West Pacific pomacanthids, neither a two-fold difference between species in larval duration nor a two order of magnitude difference in female fecundity markedly affects extant distributions; and secondly, that either undescribed biological factors or historical constraints are of paramount importance. Available evidence suggests that dispersal abilities of most coral reef fishes, in fact, may be limited, despite the nearly universal occurrence of a pelagic stage in development.

Metazoan Life Without Oxygen

Article

Oct 1991

Many multicellular animals do not require oxygen to live, but respire anaerobically. This volume lays out summaries of the strategies for anaero- or anoxy-biosis employed by each major group of metazoan animals. It begins with a description of the physical chemistry of oxygen, followed by a dissertation on the perils - and opportunities - created for life by oxygen derived free radicals. It moves on to examine the geochronology of the accumulation of oxygen in the environmment and to analyse the first explosive adaptive radiation of the Metazoa in the Ediacarian and early Cambrian. It then explores the biochemistry of sulphide-dependent organisms and follows with a detailed account of the evolution of fumarate reductase, the enzyme system that makes anaerobiosis possible in many invertebrate phyla. After the survey of invertebrate phyla, there is a chapter concerned with the strategies adopted by various vertebrates for anoxybiotic survival, and one on the dependence of many vertebrates on anaerobic processes. -from Publisher

The Callovian-Oxfordian boundary in Oxfordshire and Wiltshire based on two new temporary sections

Article

Dec 1992
P GEOLOGIST ASSOC

New temporary exposures of the Lower, Middle and Upper Oxford Clay (Callovian-Oxfordian) provide palaeoecological data that record the changing marine depositional conditions during the Callovian to Oxfordian in southern England. The faunally impoverished Lower Oxford Clay indicates oxygen restricted depositional conditions. The succeeding late Callovian Spinosum Clay in Oxforshire contains a moderate diversity benthic macrofauna in pale mudstones. These grade upwards into the Lamberti Limestone which yields a distinctive gastropod and echinoid fauna. The Limestone thins to the south-west of Oxford and is represented in Wiltshire by a Gryphaea-Oxytoma shell bed. Benthic faunas in the dark mudstones of the Upper Oxford Clay (Mariae Clay) are of low diversity and dominated by deposit feeders although moderately diverse epibionts occur on the occasional Gryphaea. Very soft substrates are inferred. Ammonites from the Upper Oxford Clay are commonly preserved as small pyritic nuclei but in Wiltshire they retain their original aragonitic shells.

Demographic Analysis of Bivalve Populations

Chapter

Jan 1980

Robert Cerrato

The influence of multiple environmental stressors on susceptibility to parasites: An experimental determination with oysters

Article

May 1999

A large-scale field experiment was used to test whether exposure to a suite of potential environmental factors (flow speed, temperature, salinity, and low dissolved oxygen) influences the level of parasitic infection of the oyster Crassostrea virginica. The parasite was the protozoan Perkinsus marinus, which has decimated populations of oysters in estuaries of North America. The environmental factors were considered stressors because they influence the physiological condition of either the host or parasite. Between December 1994 and July 1995, flow speed, temperature, salinity, dissolved oxygen concentration (DO), Perkinsus infection, and mortality of oysters were monitored across 24 experimental oyster reefs in the Neuse River estuary, North Carolina. Eight reef treatments were created consisting of an orthogonal combination of three factors: water depth (3 m vs. 6 m deep), reef height (2 m vs. 1 m tall), and position on reef (base vs. crest). Principal component analysis revealed that there was clear separation of environmental factors among reefs and that a majority of the variation (96.2%) among treatments could be explained by two principal component axes (PCs): one (24.3% of variation explained) was formed by flow and the other (71.9% of variation explained) by temperature, salinity, and DO. Oysters with the highest proportion of individuals infected (prevalence), highest intensity of infection, and highest mortality were located at the base of reefs, where flow speeds and food quality were lowest and sedimentation rates highest. However, there was no significant effect of hydrographic conditions on Perkinsus infection or mortality of oysters, despite large differences in mean salinity, DO, and exposure to hypoxia-anoxia. Temperature did not vary among treatments. Correlation of disease responses (infection prevalence and intensity, and mortality) with the first two PCs showed that these response variables were significantly (and negatively) correlated with flow only. Oysters in low flow were hypothesized to have the greatest susceptibility to Perkinsus infection because of their poor physiological condition. The restoration of oyster reefs increases reef height and thus flow speeds (by elevating oysters higher above the boundary and by actively influencing flow), thereby reducing the negative effects of disease by restoring reef morphology to its natural size.

Chemoautotrophic metabolism of intracellular gill bacteria in the marine bivalve Spisula subtruncata (da Costa)

Article

Feb 1989
Neth J Sea Res

Spisula substruncata, a mactrid bivalve living in well-oxygenated sublittoral sandy bottoms, contains two types of intracellular bacteria in its gills. Chemoautotrophic metabolism of these bacteria was tested in different ways. Homogenates of gill tissues showed a slight ribulose — 1.5 — bisphosphate carboxylase activity. Fixation of 14C-labelled bicarbonate in S. subtruncata was higher than in Venus gallina, a clam without bacteria living in the same environment. Other experiments were performed with and without two reduced compounds (sodium thiosulphate and ammonium chloride) at different incubation times (45 to 300 min). With the two compounds, the levels of fixed carbon per g of gill tissue increased significantly after 60 min incubation. A possible ammonia utilization by gill bacteria is demonstrated and may be explained by the fact that the most abundant dissolved reduced compound available for chemoautotrophs is ammonia. The values obtained in this association were lower than those recorded for other bivalves with bacterial cells in their gills. These low values may be explained by the relatively small number of the two types of bacteria observed in the gills of S. subtruncata.

Floating and Algal Rafting as Potential Dispersal Mechanisms in Brooding Invertebrates

Article

Jan 1985

Raymond C. Highsmith

Carbonate Sediment Production by Sargassum Epibionts

Article

Jan 1985

Harold Pestana

Sargassum and associated calcareous epibionts were collected at sea and on a Bermuda beach. The weight percent of calcium carbonate produced by epibionts averaged 9.4% for samples collected at sea and 5.3% for beached samples. This indicates that Sargassum epibionts are a major potential source of carbonate sediment. Beached Sargassum adds between 8213 g/m2/yr and 3431 g/m2/yr to the sampled beach and is a significant actual source of carbonate sediment.-Author

A biofacies analysis of the Gastrioceras cumbriense Marine Band (Namurian) of the central Pennines

Article

Jun 1987

Paul B Wignall

The Gastrioceras cumbriense Marine Band (G 1b ) is the highest marine horizon in the Namurian Series of the central Pennines and does not generally exceed 60cm in thickness. In the present paper local variations are examined at six sections along a 60km distance from west Yorkshire to south Lancashire. The initial onset of marine conditions is recorded by Lingula -bearing grey shales in the central Pennines, but by the productoid facies (Calver 1968) to the west in south Lancashire. This is interpreted as reflecting a slight shallowing of the sea towards the west, a palaeotopography that persisted throughout the marine phase. The deepest water conditions, which occurred at the acme of the incursion, produced a marked change in cephalopod and bivalve species ratios and an associated change to a black shale lithology. Euxinic conditions appear to have occurred only temporarily. Over the whole of northern England the basal marine shales record a series of distinct faunal profiles, with fully marine faunas recorded to the west of the area. The regression appears to have been more rapid than the advance, and retreat faunal facies are more sporadically developed.

Palaeoecology and sedimentology across a Jurassic fault scarp, NE Scotland

Article

Apr 1993

A detailed palaeoecological and sedimentological analysis of the Kimmeridgian coastal outcrops around Helmsdale (northeast Scotland) has been related, for the first time, to a detailed biostratigraphical scheme allowing the depositional history of this important area (adjacent to some North Sea oilfields) to be elucidated. A broad, shallow marine, sub-tropical, shelf was disrupted by the onset of normal faulting along the Helmsdale fault in earliest Kimmeridgian times. Initially, water depths remained shallow on the hanging wall, reflected by a normal benthic fauna, but a rapidly steepening southeast-directed palaeoslope produced frequent sediment sliding. Shoreface sands developed immediately to the west of the fault and were transferred to the hanging wall via a fault-transfer zone where they now constitute the Allt na Cuile Formation. Continued rapid subsidence during the remainder of the Kimmeridgian and the Portlandian produced deep, poorly oxygenated to anoxic benthic conditions on the hanging wall in which a combination of rock slide/debris flow/turbidity current deposition alternated with hemipelagite deposition to produce the Helmsdale Boulder Bed Formation. The Eathie locality (Cromarty), previously regarded as a deeper, more distal setting than Helmsdale, contains a slightly more diverse benthic fauna implying shallower water. The deepest waters were immediately adjacent to the fault scarp as predicted by the standard half-graben depositional model.

Sedimentation and climatic patterns in the Santa Barbara Basin during the 19th and 20th centuries

Article

Jan 1977

The thickness of annual sediment laminations in the Santa Barbara Basin is compared to southern California drought-resistant tree growth and to regional indices of rainfall and temperature. The rate of sedimentation was found to be independent of temperature, but it is highly correlated with rainfall and tree growth. We suggest that sedimentation, like tree growth, is a function of the amount of rainfall in the prior seasons as well as the current season. The natural filter displayed by the sedimentation and tree-growth records can be described by a simple mathematical model which, in the case of sedimentation, can be related to upstream aggradation or to distributional processes on the shelf. The pair of laminae that constitute a single year's sediment accumulation are directly related. This suggests that the process of detrital sediment delay and redistribution operates primarily in the marine environment. The density difference that distinguishes " winter" laminae and " summer" laminae is ascribed to the interaction of the seasonal rate of deposition and the growth of a mat-forming organism endemic to the surface sediment of the Santa Barbara Basin.

Taxonomic survey of fossil isocrinids with a list of the species found in the USSR

Article

Dec 1982
Geobios

Vladimir G. Klikushin

The taxonomic scheme of the two families of the order Isocrinida (Isocrinidae and Pentacrinidae) is given. The first family is divided at five subfamilies: Balanocrininae, Isocrininae, Metacrininae, Diplocrininae and Isselicrininae. Six genera are included in subfamily Balanocrininae: Balanocrinus (four species found in USSR), Laevigatocrinus (USSR: 3 species), Margocrinus (USSR: 4 species), Percevalicrinus (USSR: 5 species), Singularocrinus nov. gen. (monotypic) and Terocrinus nov. gen. (USSR: 1 species). Five fossil genera are included in subfamily Isocrininae: Chariocrinus (USSR: 1 species), Chladocrinus (USSR: 4 species), Isocrinus (USSR: 6 species), Raymondicrinus nov. gen. (Oligocene of USA : 2 species) and Tyrolecrinus nov. gen. (6 triassic species). Fossil representatives of three genera, namely, Metacrinus (Miocene-Recent), Nielsenicrinus (USSR: 4 species) and Cainocrinus (USSR: 1 species) are noted in subfamily Metacrininae. Five genera are included in subfamily Isselicrininae: Austinocrinus (USSR: 5 species), Buchicrinus (USSR: 5 species), Doreckicrinus (USSR: 1 species?), Isselicrinus (USSR: 4 species) and Praeisselicrinus (USSR: 1 species). Two genera are included in family Pentacrinidae: Pentacrinus (USSR: 1 species) and Seirocrinus (USSR: 4 species). Besides, the localities of 24 isocrinid species, systematic position of which is unknown, are listed (from Triassic upon Cretaceous). Three erroneous attributions to Isocrinida in USSR are pointed out. In the conclusion an outline of the phylogeny of the Isocrinida is discussed. For a majority of the wide-spread species in USSR figures are given.

Pelagic Sargassum and its presence among the deep-sea benthos

Article

Oct 1970
Deep Sea Res Oceanogr Abstr

Palaeoecology of the Triassic black shale bivalve Daonella - New insights into an old controversy

Abstract

No full-text available

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