bluuebunny/crossref_metadata_2025_split huggingface dataset:
Marine bivalves of the Florida Keys: discovered biodiversity
Authors: Mikkelsen Paula M. , Bieler Rüdiger 
Published: April 2008

Abstract
A survey of marine bivalve biodiversity in the Florida Keys, an island archipelago off southern Florida, was compiled from original collecting, museum specimens and the literature. Assembly of over 6000 records resulted in 325 species, 47% of which can be considered common to abundant in the Keys. This represents a 100% increase over the previously known fauna, largely attributable to critical review of museum specimens. Capture of species occurrences from the literature, especially when non-traditional sources (newsletters, agency reports) are excluded, is shown to be least effective, producing only 44% of the total. Bivalve distributions within the Keys show that the fauna is tropical. One-third of the species are wide ranging along the island chain; however, a latitudinal cline in faunal similarity exists from the Upper Keys southwestwards to Dry Tortugas. The fauna of Florida Bay is the most divergent within the study region and also compared to other, ecologically complex, western Atlantic tropical-subtropical regions. Limited historical records indicate little species turnover in the Keys, although population reductions along the main highway and habitat shifts (from natural to artificial substrata) are evident. These results have implications for biodiversity survey methods and, more locally, for management of the Florida Keys National Marine Sanctuary.
Genetic relationships of
Mytilus galloprovincialis
Lamarck populations worldwide: evidence from nuclear-DNA markers
Authors: Daguin Claire , Borsa Philippe 
Published: April 2008

Abstract

Allozyme surveys of genetic variation in
Mytilus galloprovincialis
Lamarck throughout the world have identified three groups within this species: a northeastern (NE) Atlantic group that also includes the
M. galloprovincialis
population of South Africa, a Mediterranean group that also includes the
M. galloprovincialis
populations from the eastern and the western coasts of the North Pacific, and an Australasian group. Hypotheses that have been proposed to account for the genetic differentiation patterns and disjunct, worldwide distribution of
M. galloprovincialis
include the recent introduction of this species into the southern hemisphere and the North Pacific through human agency, and an alternative hypothesis that each of the three groups is endemic. In this study, two nuclear-DNA markers (the polyphenolic adhesive protein gene
Glu-5′
and the first intron of the actin gene
mac-1
) were used to investigate in more depth the genetic relationships among
M. galloprovincialis
populations. Samples were taken between 1996 and 1999 from California, the NE Atlantic, the Mediterranean Sea, South Africa, Korea, Western Australia, Tasmania and New Zealand. NE Atlantic
M. edulis
L. were used as an outgroup. While all
M. galloprovincialis
samples were fixed, or nearly so, for the diagnostic
G
allele at locus
Glu-5′
, correspondence analysis of
mac-1
allele frequency data highlighted the genetic distinctness of Australasian mussels relative to other
M. galloprovincialis
populations. The latter consisted of two differentiated groups (NE Atlantic and Mediterranean) as formerly reported at allozyme loci. Another sample, from Chile, was nearly identical to Mediterranean
M. galloprovincialis
. Nuclear-DNA data thus enforce the idea that
M. galloprovincialis
have probably been introduced from the Mediterranean to the North Pacific (and now Chile), and from the NE Atlantic to South Africa. It is argued in this study that Australasian mussels derive from a proto-
M. galloprovincialis
population introgressed by
M. edulis
-like genes, and should be considered as a regional subspecies of
M. galloprovincialis
.
Herring gulls feeding on a recent invader in the Wadden Sea,
Ensis directus
Authors: Cadée Gerhard C. 
Published: April 2008

Abstract

The American razor clam
Ensis directus
has been a successful non-indigenous invader in the Wadden Sea since the late 1970s. It often shows poorly understood mass mortalities in the winter half-year, which are also known from its native area. During such mass mortalities
Ensis directus
partly leaves its burrow and, as it is unable to re-burrow, is an easy prey for herring gulls during low tide. During a mass mortality in March 1999,
Ensis
consumption by herring gulls was studied. Shell fragmentation was achieved by shaking the shell vigorously, not by hammering. This caused characteristic shell fragmentation ranging from small fragments broken from one or both valves near the middle, to both valves broken near the middle, but still connected by the ligament. About one-quarter of the shells remained undamaged. No other predators are known to produce similar
Ensis
shell fragments. In taphonomic studies the importance of predators in fragmenting shells should be taken into account.
Isolated carbonate platforms of Belize, Central America: sedimentary facies, late Quaternary history and controlling factors
Authors: Gischler Eberhard , Lomando Anthony J. 
Published: April 2008

AbstractThe closely spaced, isolated carbonate platforms of Glovers Reef, Lighthouse Reef and Turneffe Islands (Belize) differ significantly with regard to geomorphology and distribution of sedimentary facies, especially in platform interiors. Glovers Reef has a deep (18 m) lagoon with 860 more or less randomly distributed patch reefs. The interior of Lighthouse Reef is characterized by a linear trend of hundreds of coalescing patch reefs that separate a deeper (8 m) eastern and a shallower (3 m) western lagoon. Within both Glovers and Lighthouse Reefs, non-skeletal (peloidal) wackestone and packstone are found in shallow (<5 m) water depths. Deeper lagoon parts are characterized by mollusc-foram wackestones. Facies belts are circular in Glovers Reef, as opposed to linear in Lighthouse Reef. The Turneffe Islands platform has up to 8 m deep interior lagoons that are surrounded by large land/mangrove areas. These lagoons have restricted circulation, are devoid of coral patch reefs, and are dominated by organic-rich wackestone.These differences are largely a consequence of variations in antecedent topography and in exposure to waves and currents from platform to platform. Differences in elevation and relief of the Pleistocene basement are most likely controlled by differential subsidence and latitudinal variation in karstification. Differences in exposure to waves and currents are created as the Turneffe Islands platform is in a leeward position, protected from the open Caribbean Sea by Lighthouse Reef to the east. Variation in Pleistocene elevation caused the platforms to flood successively at different rates during Holocene sea-level rise. However, all reefs investigated kept pace with the rising Holocene sea level. Sediment is now largely bypassing the margins and filling in platform interior lagoons.These examples indicate how local attributes of antecedent topography and exposure to waves and currents can be at least as important as globally operating factors such as sea-level fluctuations. This observation should be kept in mind when interpreting palaeo-relationships in the geologic record.
Reef episodes, anoxia and sea-level changes in the Frasnian of the southern Timan (NE Russian platform)
Authors: House M. R. , Menner V. V. , Becker R. T. , Klapper G. , Ovnatanova N. S. , Kuz’min V. 
Published: April 2008

Abstract

The development of the Frasnian (Upper Devonian) reef complexes of the southern Timan and Pechora region of northern European Russia is described. Barrier reef complexes progressively prograded eastwards during the Frasnian but the carbonate complexes were interrupted many times by regressive events. Using new conodont and ammonoid biostratigraphical dating, the timing of reef building episodes has been established which enables international correlation with other similar Devonian areas. Basinal anoxic and hypoxic deposits associated with the reef complexes of the Domanik facies provide the major hydrocarbon source rocks of the region and the palaeoenvironmental interpretation of these is discussed. Initial transgressions appear to have been associated with the global Taghanic Onlap of the late Givetian. The new level for the base of the Frasnian and Upper Devonian lies in the Timan Formation, after the deposition of which marine conditions mostly prevailed in the area examined until the late Frasnian when a sharp regression occurred with no evidence of the typical Kellwasser facies of Western Europe and other areas. Transgressive pulses initiated ammonoid biofacies in the Regional Sargaev Stage and the widespread Timan Event was marked by the spread of
Timanites
faunas. A significant deepening event which initiated the Domanik facies correlates approximately with the Middlesex black shale of New York and the main development of the Domanik facies with the Rhinestreet black shale of New York. There are faunal and floral peculiarities of the area, shown by endemic genera and rather different ranges of cosmopolitan species than elsewhere, which complicates precise international correlation. Nevertheless, several of the main sea-level deepening pulses of the Frasnian, documented in North America, Western Europe, North Africa and Australia, are recognizable and these are thought to represent eustatic events.
Sedimentation rates and growth potential of tropical, cool-water and mud-mound carbonate systems
Authors: Schlager Wolfgang 
Published: April 2008

Abstract
Carbonate fixation in the ocean proceeds in three basic modes: abiotically, biotically induced (with organic trigger), and biotically controlled (where organisms determine timing, location and composition of the product). The three modes combine in a variety of ways to produce carbonate sediment. When viewed on the scale of formations and global facies belts, three benthic carbonate production systems, or ‘factories’, emerge: (1) the tropical shallow-water system, dominated by biotically controlled (mainly photoautotrophic) and abiotic precipitates; (2) the cool-water system, dominated by biotically controlled (mainly heterotrophic) precipitates; and (3) the mud-mound system, dominated by abiotic and biotically induced (mainly microbial) precipitates.
The sedimentation rates of all three factories decrease as the time span of observation increases. This scaling trend is not just an artifact of ratio correlation; it is almost certainly related to the episodic, pulsating nature of sedimentation.

The growth potential of the three systems can be estimated by drawing the envelope of the maximum observed rates of aggradation. The tropical system shows the highest rates: 10
4
μm a
−1
at 10
3
years, decreasing to 10
2
μm a
−1
at 10
7
years. The maximum rates of the cool-water system are comparable to those of the tropical carbonates for intervals shorter than 2 × 10
5
years but they amount to only 25% of the tropical standard in the domain of 10
6
–10
8
years. The high short-term rates of cool-water carbonates are probably caused by reworking and local trapping of sediment. The growth rates of the mud-mound system significantly exceed cool-water rates and rival the aggradation rates of tropical shallow-water carbonates. However, the mud-mound system exports less sediment than its tropical counterpart and is, therefore, somewhat less productive.
From Cadomian subduction to Early Palaeozoic rifting: the evolution of Saxo-Thuringia at the margin of Gondwana in the light of single zircon geochronology and basin development (Central European Variscides, Germany)
Authors: Linnemann U. , Gehmlich M. , Tichomirowa M. , Buschmann B. , Nasdala L. , Jonas P. , Lützner H. , Bombach K. 
Published: April 2008

Abstract
Saxo-Thuringia is classified as a tectonostratigraphic terrane belonging to the Armorican Terrane Collage (Cadomia). As a former part of the Avalonian-Cadomian Orogenic Belt, it became (after Cadomian orogenic events, rift-related Cambro-Ordovician geodynamic processes and a northward drift within Late Ordovician to Early Silurian times), during Late Devonian to Early Carboniferous continent-continent collision, a part of the Central European Variscides. By making use of single zircon geochronology, geochemistry and basin analysis, geological processes were reconstructed from latest Neoproterozoic to Ordovician time: (1) 660–540 Ma: subduction, back-arc sedimentation and tectonomagmatic activity in a Cadomian continental island-arc setting marginal to Gondwana; (2) 540 Ma: obduction and deformation of the island arc and marginal basins; (3) 540–530 Ma: widespread plutonism related to the obduction-related Cadomian heating event and crustal extension; (4) 530–500 Ma: transform margin regime connected with strike-slip generated formation of Early to Mid-Cambrian pull-apart basins; (5) 500–490 Ma: Late Cambrian uplift and formation of a chemical weathering crust; (6) 490–470 Ma: Ordovician rift setting with related sedimentation regime and intense igneous activity; (7) 440–435 Ma: division from Gondwana and start of northward drift. The West African and the Amazonian Cratons of Gondwana, as well as parts of Brittany, were singled out by a study of inherited and detrital zircons as potential source areas in the hinterland of Saxo-Thuringia.
Chronological constraints on the pre-Variscan evolution of the northeastern margin of the Bohemian Massif, Czech Republic
Authors: Kröner A. , Štípská P. , Schulmann K. , Jaeckel P. 
Published: April 2008

Abstract
New single zircon ages enable us to provide an evolutionary scenario for the Neoproterozoic to Cambro-Ordovician tectonic history of part of the easternmost Sudetes along the northeastern margin of the Bohemian Massif. The easternmost crustal segment (Brunia) yields Neoproterozoic ages from both autochthonous and allochthonous Variscan units; these ages document a Cadomian (Pan-African) history that may be linked with the northern margin of Gondwana. A Cambro-Ordovician magmatic-thermal event in Brunia is represented by granitic to pegmatitic dykes intruding Neoproterozoic crust and by localized partial anatexis. Farther west a narrow zone of Cambro-Ordovician rifting is identified (Staré Městro belt), marked by gabbroic magmatism, bimodal volcanism and medium-pressure granulite facies metamorphism. The westernmost crustal domain (Orlica-Sniezník dome) is represented by Neoproterozoic crust intruded by Cambro-Ordovician plutons consisting of calk-alkaline granitoid rocks and affected by widespread Cambro-Ordovician anatexis. The geodynamic setting of the Neoproterozoic and Cambro-Ordovician domains is similar to that of the Western Sudetes, where both Cambro-Ordovician rifting and calc-alkaline magmatism were identified. We discuss the rifting mechanics in terms of sequential crustal thinning along the northern margin of Gondwana. The calc-alkaline magmatism, in conjunction with crustal rifting, is related to a back-arc geometry in front of a retreating south-dipping subduction zone during progressive closure of the Tornquist Ocean southeast of Avalonia.
Heat flow evolution, subsidence and erosion in the Rheno-Hercynian orogenic wedge of central Europe
Authors: Littke R. , Büker C. , Hertle M. , Karg H. , Stroetmann-Heinen V. , Oncken O. 
Published: April 2008

Abstract

Numerical, thermal and rheological modelling techniques are applied to unravel the basin-forming processes and the heat flow and burial history of the Rheno-Hercynian fold belt (Rhenish Massif), the adjacent Subvariscan foreland (Ruhr Basin), and the intramontane Saar-Nahe Basin. Thermal history and crustal architecture in the study areas were affected mainly by the Variscan Orogeny during late Palaeozoic times. Calibration of the simulated thermal histories is primarily based on vitrinite reflectance and fission-track data. Mechanical modelling reveals average
β
values of 1.7, reaching a maximum of 2.4 in the central basin (Mosel Graben) and at the transition to the Giessen Ocean to the south during Early Devonian rifting. This stage was associated with tholeitic magmatism and an elevated heat flow of up to 110 mW m
−2
, preserved in weakly overprinted syn-rift sediments. Average basal heat flow during maximum burial at the end of the Carboniferous period (i.e. the end of crustal shortening) was between 50 and 70 mW m
−2
with a slight decrease from the Subvarian foreland basins towards the Rheno-Hercynian in the south. The values suggest average crustal thicknesses of between 32 and 36 km during late Carboniferous time. For the Saar-Nahe Basin, values between 50 and 75 mW/m
2
represent the thermal regime in the upper crust during the late Stephanian and early Permian time. Estimated eroded thicknesses of Palaeozoic sediments vary between 2500 m in the northern and central Ruhr Basin and more than 6000 m in the Osteifel and the Siegen Anticline within the Rheno-Hercynian, and between 1800 and 3600 m in the Saar-Nahe Basin. Fission-track data provide evidence for significant reheating during the Mesozoic era within the entire study area. This phase of heating, probably linked to North Atlantic rifting, coincides with post-Variscan ore formation and with major tectono-magmatic events in central Europe.
White mica
40
Ar/
39
Ar ages of Erzgebirge metamorphic rocks: simulating the chronological results by a model of Variscan crustal imbrication
Authors: Werner Olaf , Lippolt Hans J. 
Published: April 2008

Abstract

In the Erzgebirge, which is part of the Saxo-Thuringian Mid-European Variscides, an
40
Ar/
39
Ar study was performed on white mica and hornblende separates from 68 metamorphic rocks of varying lithologies. Two groups of late Early Carboniferous cooling ages of 340 ± 2 Ma and 329.7 ± 1.5 Ma are distinguished by evaluating spectra shapes. A third group of rocks yielded intermediate argon ages, presumably related either to thermal rejuvenation or to neoformation of white mica during a reheating process 330 Ma ago. A model that explains rejuvenation is proposed. The observed age patterns and the shape of the age spectra cannot be simply explained by assuming a single uplift and exhumation process set in motion by extensive forces. Chronological and structural arguments favour the idea that Variscan crustal imbrication took place during the mineral cooling phase. A tectonic process that intercalated, at about 20 km depth, a unit of cool rocks into a much hotter environment suitably models the chronological results. This is shown by a simulation of the age record. Temperature profiles are calculated for both intercalation and subsequent uplift models. Rocks in these profiles, which preserved their 340 Ma signature, are distinguished from those heated 330 Ma ago by contact with adjacent hotter rocks and reset isotopically to varying degrees. The agreement between analytical results and modelled ages favours the crustal imbrication hypothesis as explanation for the age distribution throughout all lithologies.
Exhumation of high-grade rocks in the Saxo-Thuringian Belt: geological constraints and geodynamic concepts
Authors: Franke W. , Stein E. 
Published: April 2008

Abstract

The Saxo-Thuringian Belt on the northern flank of the European Variscides resulted from SE-ward subduction of a Cambro-Ordovician rift basin under the Teplá-Barrandian (Bohemian) margin. It contains ultra-high-pressure (UHP) metamorphic rocks, which are now exposed in different tectonic settings, and were exhumed in different modes, under different thermal regimes. Eclogites of the upper allochthon (tectonic klippen of Münchberg, Wildenfels and Frankenberg) originated from early Devonian (
c.
400 Ma) subduction. Cooling ages in the klippen, combined with clast spectra and ages of detrital minerals in the foreland flysch record exhumation in Famennian time. The high-pressure (HP) rocks rose in a narrow corridor along the suture zone, were retrogressed under amphibolite facies conditions, and rapidly recycled into the foreland flysch. Rocks of the lower allochthon are exposed in dome structures emerging from under the relative autochthon. The HP Saxonian Granulites were formed at
c.
20 kbar/1050 °C, and the Erzgebirge contains diamond-bearing quartzo-feldspathic rocks, associated with eclogites. Peak temperatures of the lower allochthon were attained at
c.
340 Ma. Immediately afterwards, these rocks were emplaced under the floor of the relative autochthon, which, at this time, was a foreland basin receiving clastic sediments from the orogen adjacent to the SE. Emplacement of the lower allochthon is most clearly documented in the Saxonian Granulite Dome, in which HP granulites are juxtaposed against low-pressure-high-temperature (LP-HT) rocks of the hanging wall. The interface is a zone of HT shear, which cuts out ⩾ 60 km of crustal thickness. In more internal parts of the belt (Erzgebirge), the newly emplaced lower allochthon was subsequently reworked by thrusting and polyphase refolding. Emplacement of the hot, low-viscosity lower allochthon was probably driven by buoyancy and the hydraulic gradient between the crustal root to the SE and the lower crust of the foreland. Unlike the earlier HP rocks exposed in the upper allochthon, the 340 Ma HP rocks of the lower allochthon were thermally softened, and, instead of piercing their cover, intruded into the foreland. Therefore, the 340 Ma rocks do not appear in the clastic record of the flysch. The two contrasting mechanisms of exhumation observed in the upper and lower allochthon are apparently due to different thermal regimes.
The fundamental Variscan problem: high-temperature metamorphism at different depths and high-pressure metamorphism at different temperatures
Authors: O’Brien Patrick J. 
Published: April 2008

Abstract

The evolution of the crystalline internal zone of the European Variscides (i.e. Moldanubian and Saxo-Thuringian) is best understood within a framework of two distinct subduction stages. An early, pre-Late Devonian (older than 380 Ma), subduction stage is recorded in medium-temperature eclogites and blueschists derived from low-pressure basaltic and gabbroic protoliths now found as minor relics in amphibolite facies meta-ophiolite or gneiss-metabasite nappe complexes. A second subduction and exhumation event produced further nappe complexes containing different types of mantle peridotites, along with their enclosed pyroxenites and high-temperature eclogites, associated with large volumes of high-
T
-high-
P
(900–1000°C, 15–20 kbar) felsic granulites. Abundant geochronological evidence points to a Carboniferous age (
c.
340 Ma) for the high-
P
-high-
T
metamorphism as well as an extremely rapid exhumation because the fault-bounded, granulite-peridotite-bearing tectonic units are also cut by late Variscan granitic plutons (315–325 Ma). The massive heat energy for the characteristic, and most widespread feature of the Variscan event, the low-
P
-high-
T
metamorphism (750–800°C, 4–6 kbar) and voluminous granitoid magmatism (325–305 Ma), comes from three sources. An internal heat component comes from imbrication of crust with upper-crustal radiogenic heat production potential in the region parallel to the subduction zone; an external mantle heat component is undoubtedly contributing to the transformation of crust taken to mantle depths (i.e. the granulites); and a heat component advected to the middle and lower crust seems inescapable if the hot granulite-peridotite complexes were exhumed and cooled as rapidly as petrological and geochronological evidence seems to suggest. Major mantle delamination and asthenospheric upwelling as a cause of heating in Early Carboniferous times is not supported by geochemical, geophysical or petrological-geochronological studies, although slab break-off probably did occur.