Facies of a Lower Ordovician carbonate shelf (Mungok Formation: Taebaeksan Basin,Korea)

Summary The lithologic associations within the Lower Ordovician Mungok Formation in Korea define four depositional facies that formed across a continental margin fringing the Sino-Korean block: these facies represent lagoonal/restricted marine, shoal, inner shelf, and outer shelf environments. The stacking pattern of these facies reveals two systems tracts composed of five depositional sequences. The lower highstand systems tract consists of the lagoonal/restricted marine and shoal facies, whereas the upper lowstand systems tract comprises, in ascending order, inner shelf, outer shelf, and inner shelf facies. Three trilobite biofacies are recognized in the Mungok Formation: i.e.,Yosimuraspis, Kainella, andShumardia biofacies in ascending order. TheYosimuraspis Biofacies is dominated byYosimuraspis but also containsJujuyaspis andElkanaspis. The predominance of the endemic eponymous taxon suggests a lagoonal/restricted marine environment. The nearly monotaxicKainella Biofacies, which comprises pandemic genera such asKainella and occasionallyLeiostegium, may represent a less restricted environment than theYosimuraspis Biofacies. TheShumardia Biofacies occurs in the marlstone/shale lithofacies through relatively thick stratigraphic interval and is dominated by cosmopolitan trilobite taxa with some endemic species. The lithofacies and cosmopolitan trilobite assemblage of theShumardia Biofacies indicate that it occupied an outer shelf environment. The vertical succession of lithofacies and trilobite biofacies in the Mungok Formation records in general a shift from a restricted, shallow water environment to deeper-water environment.     

Sedimentary facies from the modern coral reefs,Jordan Gulf of Aqaba,Red Sea

Summary Sixty-three sediment samples collected from the modern fringing reefs off the Jordan coast (Gulf of Aqaba, Red Sea) have been analysed in order to determine variations of composition and texture by using correspondence factor analysis. From the shore seawards, the following physiographic zones are recognized: beach; shallower backreef zone; reef flat zone; forereef zone including sandy or coral-built slopes. Eight sediment facies and subfacies can be recognized on the basis of total component composition and foraminiferal assemblages and four sediment facies can be recognized using grain-size data. Wellsorted, fine to medium, quartzofeldspathic sands (terrigenous facies) occur on beaches and outer sandy slopes close to wadi mouths. Backreef areas exhibit relatively well-sorted fine sands of terrigenous-coral and Miliolidae-Soritidae facies. Poorly sorted, coarse sands of coral-coral-line algal and Homotremid facies characterize reef flats and the upper parts of coral-built forereef areas, which respecitively display an Amphistegina-Spirolina subfacies and an Acervulina one. Poorly sorted, medium sands of coralmolluscan-foraminiferal (Amphistegina-Acervulina) facies are restricted to the lower parts of the forereef zone. Latcral limits of the various biofacies coincide with the distribution of the related organic communities.     

Microfacies and cycle stacking pattern in Liassic peritidal carbonate platform strata, Gavrovo-Tripolitza platform, Peloponnesus, Greece

Platform carbonate sediments of Liassic age cropping out in the area of the Pigadi-Fokianos Gulf (SE of Leonidion, Peloponnesus) have been investigated in order to determine their depositional environment. Facies analysis allowed the recognition of several microfacies types and their cyclic stacking pattern. The carbonates were deposited in a restricted inner platform environment (lagoon-peritidal domain) and are arranged into small-scale shallowing-upward cycles. Palaeosol horizons containing typical pedogenic features are developed on the top of the peritidal facies or are directly superimposed on subtidal deposits, forming diagenetic caps. This implies repeated sea-level fluctuations and periodic emersion episodes. The presence of orbitally forced cyclicity though is mostly probable, cannot be clearly documented by the available data. The studied carbonates are comparable with other coeval analogous peritidal cycles of the same age along the southern margin of the Tethys.     

Palynofacies and sedimentology-based high-resolution sequence stratigraphy of the lignite-bearing muddy coastal deposits (early Eocene) in the Vastan Lignite Mine, Gulf of Cambay, India

Geological records of early Paleogene warming are rare in low latitudinal regions. The Indian subcontinent preserves records of this global event on western and eastern margins. We attempt to decipher paleoenvironmental setup and facies architecture of the paleo-equatorial early Eocene succession at the Vastan Lignite Mine, Gulf of Cambay, western India. The Vastan lignite succession was deposited in a low-energy coastal marsh-bay complex receiving only fine-grained muddy sediments from the weathered Deccan Traps. The lower part of the Vastan lignite deposit, designated as “Vastan Succession A”, comprises four depositional facies representing distinct environments (open bay, restricted bay, creek and channel, and coastal marsh) and one diagenetic facies. Palynofacies analysis, backed by precise sedimentological framework, records changes in terrestrial supply and fluctuating marine characters of bay and marshes. Eleven Palyno-Units are identified in distinct lithofacies sequences stacked in shallowing-upward cycles representing five parasequences that constitute a Transgressive Systems Tract (TST) deposit. Each parasequence starts with a transgressive sheet deposit, followed by shallowing-upward bay fill-marsh deposits. In the vertical succession, each parasequence acquires increasing marine character, culminating in a maximum flooding surface (shell carbonate) that represents large-scale coastal onlap during early Ypresian time. The TST is followed by a Highstand Systems Tract deposit, which shows an erosional surface at the top of the upper lignite indicating Lowstand Systems Tract and a sequence boundary at ~52 Ma. The Vastan Succession A represents TST (3rd-order cycle) deposits with parasequences and hemicycles representing 4th- and 5th-order cycles. The study demonstrates sea level rise along the Indian western coastal margin in response to early Eocene warming between ~55 and ~52 Ma with maximum transgression at 53.7 Ma.     

Reconstructing atoll-like mounds from the Frasnian of Belgium

A succession of Frasnian mounds on the southern border of the Dinant Synclinorium (Belgium) was investigated for their facies architecture, sedimentary dynamics and palaeogeographic evolution. Seven mound facies were defined from the Arche (A) and Lion (L) members, each characterized by a specific range of textures and association of organisms (A2/L2: red or pink limestone with stromatactis, corals and crinoids; A3/L3: grey, pink or green limestone with stromatactis, corals and stromatoporoids; A4/L4: grey limestone with corals, peloids and dasycladaceens; A5/L5: grey microbial limestone; A6/L6: grey limestone with dendroid stromatoporoids; A7/L7: grey laminated limestone with fenestrae; and A8/L8: grey bioturbated limestone). Laterally equivalent sediments include substantial reworked material from the buildups and background sedimentation. Textures and fossils suggest that A2/L2 and A3/L3 facies developed close to storm wave base, in a subphotic environment. Facies A4/L4, occurring near fair weather wave base in the euphotic zone, includes lenses of A5/L5 with stromatolitic coatings and thrombolithes. A6/L6 corresponds to a slightly restricted environment and shows a progressive transition to fenestral limestone of A7/L7. This facies was deposited in a moderately restricted intertidal area. A8/L8 developed in a quiet lagoonal subtidal environment. The mounds started with A2/L2 or A3/L3 in which microbial lenses and algal facies A4/L4 became progressively more abundant upwards. Following 20 m of laterally undifferentiated facies, more restricted facies occur in the central part of the buildups. This geometry suggests the initiation of restricted sedimentation, sheltered by bindstone or floatstone facies. The facies interpretation shows that after construction of the lower part of the mounds during a transgression and a sea-level highstand, a lowstand forced reef growth to the margin of the buildups, initiating the development of atoll-like crowns during the subsequent transgressive stage. The persistence of restricted facies results from the balance between sea-level rise and reef growth.     

Facies mosaic in the inner areas of a shallow carbonate ramp (Upper Jurassic,Higueruelas Fm,NE Spain)

The internal facies and sedimentary architecture of an Upper Jurassic inner carbonate ramp were reconstructed after the analysis and correlation of 14 logs in a 1 × 2 km outcrop area around the Mezalocha locality (south of Zaragoza, NE Spain). The studied interval is 10–16 m thick and belongs to the upper part of the uppermost Kimmeridgian–lower Tithonian Higueruelas Fm. On the basis of texture and relative proportion of the main skeletal and non-skeletal components, 6 facies and 12 subfacies were differentiated, which record subtidal (backshoal/washover, sheltered lagoon and pond/restricted lagoon) to intertidal subenvironments. The backshoal/washover subenvironment is characterized by peloidal wackestone–packstone and grainstone. The lagoon subenvironment includes oncolitic, stromatoporoid, and oncolitic-stromatoporoid (wackestone and packstone) facies. The intertidal subenvironment is represented by peloidal mudstone and packstone–grainstone with fenestral porosity. Gastropod-oncolitic (wackestone–packstone and grainstone) facies with intercalated marl may reflect local ponds in the intertidal or restricted lagoon subenvironments. Detailed facies mapping allowed us to document 7 sedimentary units within a general shallowing-upward trend, which reflect a mosaic distribution, especially for stromatoporoid and fenestral facies, with facies patches locally more than 500 m in lateral extent. External and internal factors controlled this heterogeneity, including resedimentation, topographic relief and substrate stability, combined with variations in sea-level. This mosaic facies distribution provides useful tools for more precise reconstructions of depositional heterogeneities, and this variability must be taken into account in order to obtain a solid sedimentary framework at the kilometer scale.     

Facies architecture and depositional development of Middle Miocene carbonate strata at Siwa Oasis, Northwestern Egypt

Based on microfacies analyses and sedimentological data, 17 facies are identified within the Middle Miocene carbonates at Siwa Oasis in the northern Western Desert of Egypt. These facies are attributed to five main facies belts. Within these facies and facies belts, five foraminiferal assemblages are recognized. A depositional model relates the reported facies and biofacies to a down-dip depositional profile of an inner to middle carbonate ramp. The facies of the peritidal to restricted lagoon (facies belt 1) and the less-restricted lagoon (facies belt 2) were deposited in the inner ramp behind the barrier/beach shoal facies belt 3. Basinward, lime mudstone of facies belts 4 and 5 accumulated in a proximal to distal middle ramp, respectively. The depositional evolution involved three stages, which are strongly controlled by tectonics and eustatic sea-level changes. The first stage comprises the transgressive Lower Miocene clastic-dominated fluvial facies of the Moghra Formation. The second stage heralds the deposition of the Langhian inner-ramp carbonate and shale facies of the basal Oasis Member of the Marmarica Formation under a relatively high stand of sea level, constrained clastic influx and climate warming. The final stage is represented by Langhian to Serravallian mid-ramp carbonate-dominated facies of the Siwa Escarpment and El Diffa Plateau members under fluctuating sea level, and a westward restriction in clastic supply and water turbidity.     

Upper ordovician turbidites in western Asturias: A facies analysis with particular reference to vertical and lateral variations

Ab Upper Ordovician sandstone—shale sequence in Asturias, Northwest Spain, is analysed with particular regard to lithology, sedimentary structures and trace fossils. It is deduced that deposition of the sandstones was from axially flowing turbidity currents in a deep-water trough. Trace fossils are rare but there is a predominance of deep-water turbidite-facies types including Helminthopsis, Spirophycus, Cosmorhaphe, and Protopaleodictyon. Arenicolites, normally regarded as typical of shallow water, is, however, also recorded. The low abundance and diversity of trace fossils in this succession is in marked contrast to the situation in many younger turbidite sequences.The initiation of turbidite deposition followed a long period of quiet-water mud sedimentation. Recognition of this abrupt facies change in two sections separated by a down-current distance of 40 km, provides a reference level from which vertical and lateral facies changes are quantitatively documented. In each section, deposition starts with a fining and thinning-upwards cycle and continues with several similar cycles. The onset of turbidite deposition, abrupt facies transition, and repetition of the cycles, are probably largely the result of fault block uplift at source, while initial development of the deep-water trough may have resulted from associated downthrow. The lateral facies variations, which include downcurrent reduction in sandstone/shales ratio and the Walker ABC index, probably result from a combination of factors, including reduced flow velocity and decreased sediment load.     

Autochthonous facies and allochthonous debris flows compared: Early oligocene carbonate facies patterns of the Lower Inn Valley (Tyrol, Austria)

Summary This study presents a microfacies analysis and palaco-environmental interpretations of Early Oligocene carbon ates from the Lower Inn Valley Tertiary (“Unterinntal-Terti?r”) of Austria. The well preserved biogenic components allow detailed investigations of component relationships and controlling ecological parameters. The carbonates are dominated by coralline algae, corals, small and large benthic foraminifers, bryozoans and lithoclasts. Bivalves, gastropods, echinoderms, brachiopods and serpulids are subordinate. The limestones are present as A) autochthonous carbonates transgressing directly above the Triassic basement and B) allochthonous debris flows within deeper-water marls. These carbonates are found within the Paisslberg Formation. The Werlberg Member within this formation, pertains to the autochthonous carbonates and larger debris flows. Five facies types are separated following fabric analysis and statistical treatment (correlation, cluster analysis, principal components analysis) of semi-quantitative data consisting of component frequencies of thin sections. Facies distribution patterns are principally controlled by variations in substrate characteristics, turbulence and light along a depth gradient. Reconstruction of facies pattern distribution reveal both lateral and proximal-distal facies trends: coral-coralline algal facies, coralline algal facies as well as foraminiferal facies were situated in shallower environments, laterally adjacent to each other. These grade distally into coralline algal-bryozoan facies, bryozoan facies and finally into mollusc rich marls. Debris flows consisting of reworked material from all of the known facies (bioclastic packstone facies) is restricted to the debris flow and possible represents transport induced differentiation of components and grain size within distal debris flows.     

Sedimentary facies and paleoenvironmental interpretation of the Oligocene larger-benthic-foraminifera-dominated Qom Formation in the northeastern margin of the Tethyan Seaway

The well-exposed outcrops of the Bujan, northern Abadeh, and Varkan stratigraphic sections of the Qom Formation in the Iranian part of the “northeastern margin” of the Tethyan Seaway were characterized by abundant biogenic components dominated by foraminifers, coralline red algae, and corals. The Qom Formation is Rupelian–Chattian in age in the study areas. Based on the field investigations, depositional textures, and dominant biogenic components, fifteen (carbonate and terrigenous) facies were identified. These facies can be grouped into four depositional environments: open marine, open lagoon, restricted lagoon, and continental braided streams. The marine facies were deposited on a ramp-type platform. The euphotic inner ramp was characterized mainly by imperforate foraminifera, with co-occurrence of some perforate taxa. These facies passed basinward into a mesophotic (middle) ramp with Neorotalia packstone (F5), coral, coralline algae, perforate foraminiferal packstone (F4), and coral patch reefs (F7). The deeper, oligophotic ramp facies were marly packstones with planktonic and hyaline benthic foraminifera, including large lepidocyclinids and nummulitids. The abundance of perforate foraminifera and the absence of facies indicating restricted lagoonal or intertidal settings suggest that the Varkan section was deposited mainly in open marine settings with normal salinity. The prevalence of larger benthic foraminiferal and red algal assemblages, together with the coral facies, indicates that carbonate production took place in tropical–subtropical waters.     

环渤海湾苹果产区老果园与连作果园土壤线虫群落特征

应用类群多样性、类群丰富度、个体密度和功能类群指数等群落参数,于2009年5-10月分3次对环渤海湾苹果栽植区老果园不同位置和连作果园取样研究了土壤线虫群落特征。结果表明:苹果连作对果园土壤生物环境具有明显的恶化作用,连作果园土壤环境条件恶劣;对功能类群指数的统计表明,苹果连作明显改变了果园土壤中植物寄生性线虫r-选择和k-选择的比例,与自由生活线虫比较,连作对植物寄生线虫影响更明显;连作提高了果园的土壤线虫PPI/MI,说明连作对果园土壤健康的扰动最大;土壤不同食性线虫数量统计结果显示,环渤海湾苹果栽植区植食性线虫数量未达线虫伤害阈值,线虫不是引起环渤海湾地区苹果连作障碍的主要原因。     

Late Quaternary marginal marine palaeoenvironments of northern Australia as inferred from cluster analysis of coccolith assemblages

Cluster analyses (R- and Q-mode) were applied to upper Quaternary coccolith assemblages in a sediment core (MD972132) collected in the Gulf of Carpentaria, northern Australia. This shallow gulf is influenced by the Australian monsoon, is tectonally stable and represents an important link between marine and terrestrial palaeoenvironments. The Gulf of Carpentaria is linked to the Pacific Ocean to the east by Torres Strait (12 m water depth) and to the Indian Ocean to the west by the Arafura Sill (53 m water depth), and therefore has been separated from both oceans during sea-level low-stands, resulting in the formation of Lake Carpentaria. Coccolith assemblages in the gulf are similar to modern assemblages in the region, and correspond to typical assemblages in marginal seas. The cluster analysis defines six species assemblages (R-mode), and six groups of samples (i.e., defined by depth in core depth; Q-mode), some with sub-groups, which were deposited under similar environmental conditions. We thus recognised, four major environmental facies over the past 125 ka, corresponding to closed Lake Carpentaria stages, the transitional periods while active channels sporadically connected Lake Carpentaria to the Indian Ocean, and the opening of the Gulf of Carpentaria to the ocean over either one, or both of the sills. Lake Carpentaria was isolated from both oceans through Marine Isotope Stages (MIS) 5d, MIS 4 and MIS 2, and the Gulf of Carpentaria was connected to both oceans during MIS 5c and MIS 1. Torres Strait was emergent during MIS 5b, was flooded again during MIS 5a and persisted as land bridge from MIS 4 to MIS 1. The Arafura Sill was opened from MIS 5c to MIS 5a and episodically connected the Gulf to the Indian Ocean during MIS 3.     

Facies models for middle to late devonian Shallow-Marine carbonates,with comparisons to modern reefs: a guide for facies analysis

Summary Shallow marine tropical Devonian carbonates commonly were deposited in two major geologic settings, i.e., shallow shelf with shelf margin reef, and gently sloping ramp that grades into peritidal to supratidal, in places evaporitic facies. The facies types within these two settings can be grouped into a few distinct zones on the basis of water, energy, texture, amount of micrite, porosity, fossil assemblages, and indicaton fossils. These zones have been integrated into a composite facies model for shallow marine, tropical Devonian carbonates. The facies zones are easily recognizable in hand specimen and core, and can be used for fast and accurate facies analysis. Some facies recognizable in hand specimen or core do not easily fit into the integrated model and represent facies of short-lived depositional events, such as hurricanes or slump deposits, or spatially restricted areas, such as channel fills. Such facies have to be interpreted on a case-by-case basis by comparison to the surrounding facies and depositional framework through time. Comparisons with Cenozoic reefs reveal a number of similarities. In particular, large metazoans in both Devonian and Cenozoic reefs display a range of growth forms that is not species-specific. Furthermore, several metazoans display comparable growth forms in equivalent facies zones. For example, dendroid stromatoporoids, such asStachyodes, and branching coral, such asPorites porites, occur in equivalent facies zones.     

Late Quaternary marginal marine palaeoenvironments of northern Australia as inferred from cluster analysis of coccolith assemblages

Cluster analyses (R- and Q-mode) were applied to upper Quaternary coccolith assemblages in a sediment core (MD972132) collected in the Gulf of Carpentaria, northern Australia. This shallow gulf is influenced by the Australian monsoon, is tectonally stable and represents an important link between marine and terrestrial palaeoenvironments. The Gulf of Carpentaria is linked to the Pacific Ocean to the east by Torres Strait (12 m water depth) and to the Indian Ocean to the west by the Arafura Sill (53 m water depth), and therefore has been separated from both oceans during sea-level low-stands, resulting in the formation of Lake Carpentaria. Coccolith assemblages in the gulf are similar to modern assemblages in the region, and correspond to typical assemblages in marginal seas. The cluster analysis defines six species assemblages (R-mode), and six groups of samples (i.e., defined by depth in core depth; Q-mode), some with sub-groups, which were deposited under similar environmental conditions. We thus recognised, four major environmental facies over the past 125 ka, corresponding to closed Lake Carpentaria stages, the transitional periods while active channels sporadically connected Lake Carpentaria to the Indian Ocean, and the opening of the Gulf of Carpentaria to the ocean over either one, or both of the sills. Lake Carpentaria was isolated from both oceans through Marine Isotope Stages (MIS) 5d, MIS 4 and MIS 2, and the Gulf of Carpentaria was connected to both oceans during MIS 5c and MIS 1. Torres Strait was emergent during MIS 5b, was flooded again during MIS 5a and persisted as land bridge from MIS 4 to MIS 1. The Arafura Sill was opened from MIS 5c to MIS 5a and episodically connected the Gulf to the Indian Ocean during MIS 3.     

Upper Ordovician sequences of western Estonia

The Upper Ordovician (uppermost Caradoc-Ashgill) section of western Estonia consists of a series of seven open-shelf carbonate sequences. Depositional facies grade laterally through a series of shelf-to-basin facies belts: grain-supported facies (shallow shelf), mixed facies (middle shelf), mud-supported facies (deep shelf and slope) and black shale facies (basin). Locally, a stromatactis mud mound occurs in a middle-to-deep shelf position. Shallow-to-deep shelf facies occur widely across the Estonian Shelf and grade laterally through a transitional (slope) belt into the basinal deposits of the Livonian Basin.

Each sequence consists of a shallowing-upward, prograding facies succession. Sequences 1 (Upper Nabala Stage) and 2 (Vormsi Stage) record step-wise drowning of underlying shelf units (lower Nabala) that culminated in the deposition of the most basinal facies (Fjäcka Shale) in the Livonian Basin. Sequences 3–6 comprise the overlying Pirgu Stage and record the gradual expansion of shallow and middle-shelf facies across the Estonian Shelf. The Porkuni Stage (sequence 7) is bracketed by erosional surfaces and contains the shallowest-water facies of the preserved strata. The uppermost part of the section (Normalograptus persculptus biozone) is restricted to the Livonian Basin, and includes redeposited carbonate and siliciclastic grains; it is the lowstand systems tract of the lowest Silurian sequence 8. Sequence 7 and the overlying basinal redeposited material (i.e., the lowstand of sequence 8) correspond to the latest Ordovician (Hirnantian) glacial interval, and the bracketing unconformities are interpreted as the widely recognized early and late Hirnantian glacial maximums.

The sequences appear correlative to Upper Ordovician sequences in Laurentia. Graptolite biozones indicated that the Estonian sequences are equivalent to carbonate ramp sequences in the western United States (Great Basin) and mixed carbonate-siliciclastic sequences in the eastern United States (Appalachian Basin–Cincinnati Arch region). These correlations indicate a strong eustatic control over sequence development despite the contrasting tectonic settings of these basins.     

THE GENUS PLATOMA (GIGARTINALES,RHODOPHYTA) WITH A DESCRIPTION OF P. ABBOTTIANA SP. NOV.1

Platoma abbottiana (Gymnophlaeaceae; Gigartinales), a new species of benthic red algae, is described from Isla Mejía and is the second member of this genus reported from the Gulf of California, Mexico. Vegetative anatomy and reproductive details of the carpogonial and auxiliary cell branches of the new species are described and illustrated. Geographical distributions of the seven previously described Platoma species are given. Their distinguishing morphological characteristics are compared to those of the new species. The correct time and place of valid publication of the generic name, Platoma, and some of its binomials are discussed.     

Offshore sedimentary facies of a modern carbonate ramp, Kuwait, northwestern Arabian-Persian Gulf

The Kuwait example studied here may serve as a model for ancient carbonate ramp systems just as the classical—but markedly different—southern Arabian-Persian Gulf ramp of the Trucial Coast (United Arab Emirates). Five sedimentary facies may be distinguished on the modern southern Kuwait carbonate ramp based on quantitative sedimentological, mineralogical, and geochemical analyses of 130 surface sediment samples and by using multivariate statistics. These facies include (1) inner ramp ooid-skeletal grainstone with common aggregate grains, peloids, and molluscs, (2) limited occurrences of nearshore quartz-ooid sand, (3) mid ramp mollusk packstone to grainstone, (4) outer ramp mollusk-marl wackestone with abundant siliciclastic fines, and (5) coralgal grainstone that is found on small nearshore patch reefs and outer ramp pinnacle and platform reefs. In addition to facies (1), an aggregate grain packstone to grainstone sub-facies is mapped out where abundances of this grain type exceed 20%. Ooid-skeletal grainstone, mollusk packstone to grainstone, and coralgal grainstone are predominantly aragonitic with 5–10% insoluble residue on average. Mollusk-marl wackestone has 55% insoluble residue on average with aragonite and low-magnesium calcite predominating in the carbonate fraction. Dolomite in this facies is interpreted to be of eolian origin derived from the upwind deserts of Syria and Iraq. Facies distribution is correlated with water depth, and hence controlled by depositional energy, primarily wavebase. This correlation is seen in the results of statistical analyses and in the fact that facies boundaries are more or less parallel to depth contours. Ooid-skeletal grainstones are found in depths from 0 to <10 m. The boundary between the mollusk packstone to grainstone and the mollusk-marl wackestone, which also marks the transition from grain-supported to mud-supported textures, is situated between 15–20 m depth and is much sharper than the boundary between the ooid-skeletal and the mollusk packstone to grainstone facies. Carbonate-dominated facies may also be distinguished geochemically as indicated by significantly different carbon and oxygen isotope compositions. The latter should be kept in mind when using bulk isotope values for chemostratigraphy or for paleo-environmental reconstructions in fossil carbonate ramps and platforms.An erratum to this article can be found at .     

Bats of the Gulf of Guinea islands: faunal composition and origins

The present study compares the bat faunas of the islands of the Gulf of Guinea. Species composition. endemism and hypothetical origins are discussed. All families present in the mainland region are found in Bioko, a typical landbridge island. Foliage gleaning guild species (Nycteridae) show limited colonization abilities. This is also true of the family Rhinolophidae, but not for the closely related family Hipposideridae. The majority of the oceanic island species are African bats which show a widespread distribution and, therefore, have a high ecological plasticity. The continental relatives of the two endemic species Myonycteris brachycephala and Chaerephon tomensis are restricted to relatively small forested areas. Bioko's bat fauna is the result of the recent isolation from a formerly land-connected community. The oceanic bat faunas originated from the establishment of incomers from other areas. Nevertheless, extinction appears in both vicariant and dispersal processes, as an important factor in modelling the current bat communities of the Gulf of Guinea islands.     

Taxonomy and biogeography of the fiddler crabs (Ocypodidae: Genus Uca) of the Atlantic and Gulf coasts of eastern North America

Fifteen species of fiddler crabs are reported for eastern North America between Massachusetts and Quintana Roo, Mexico. Thirteen occur in the United States and 11 in Mexico, with eight in common to the two countries. Of 13 species in the Gulf of Mexico, five are endemic and a sixth is restricted largely to the peninsulas of Florida and Yucatan. The status of U. rapax in the northern Gulf remains to be resolved. Range limits of most species approximate one or the other of two sets of intersecting thermal and geological boundaries that subdivide the Gulf of Mexico along north-south and east-west axes. Species belonging to subgenus Minuca tend to replace one another at the thermally-controlled Carolinian-Caribbean marine biotic boundary across the Florida peninsula and northern Gulf. However, only U. minax of all the North American fiddler crabs exhibits the classical disjunct Carolinian distribution, and this appears basically to reflect the discontinuous distribution of temperate salt marshes that are the habitat of the species. Distributions of species belonging to subgenus Celuca adhere for the most part to the subdivision of the Gulf into western terrigenous and eastern carbonate sedimentary provinces. The northern transition occurs in the vicinity of Apalachee Bay and the southern at Laguna de Terminos. A third distributional pattern is shown by U. subcylindrica , a specialized endemic species of the hypersaline Laguna Madre system of the western Gulf. The level of endemism in the fiddler crabs is relatively high in comparison with that of other marine groups within the Gulf of Mexico. This may be a consequence of the adaptations of fiddler crabs as specialized deposit feeders to regional differences in climatic and edaphic characteristics of a marginally marine upper shore habitat. The distributional patterns of the endemics could prove useful in reconstructing palaeoecological events of evolutionary significance within the Gulf of Mexico.