Triassic/Jurassic carbonates from the Hochfelln Mountain (Northern Calcareous Alps)—its facies, silicified fauna and implications for the end-Triassic biotic crisis

A suite of Early Mesozoic (Late Triassic, Norian to Early Jurassic) calcareous beds was studied from the Hochfelln Mountain in the Northern Calcareous Alps (NCA, South Germany). The Hauptdolomit Group consists of thick peritidal deposits and is overlain by basin deposits of the Rhaetian Kössen Formation and Rhaetian reefoidal limestone with corals. Unlike many other sections in the Tethys realm, coral growth seems to continue into the Jurassic or starts again relatively early within the Early Jurassic. Silicified corals and other marine invertebrates are present in the calcareous, micritic Hochfelln Beds. A re-examination of previously collected ammonite material indicates the presence of Coroniceras sp. which suggests an Early Sinemurian age for the Hochfelln Beds. Abundant sponge spicules (spiculites) suggest that sponges were the source for the silicification. The site produced one of the most diverse Early Jurassic (Sinemurian) gastropod faunas of the NCA (25–30 species, some undescribed). The relatively diverse Early Sinemurian gastropod fauna and coral growth indicate rapid recovery from the end-Triassic biotic crisis.     

Taphonomy of the middle Cambrian (Drumian) Ravens Throat River Lagerstätte,Rockslide Formation,Mackenzie Mountains,Northwest Territories,Canada

The Middle Cambrian (series 3, Drumian, Bolaspidella Biozone) Ravens Throat River Lagerstätte in the Rockslide Formation of the Mackenzie Mountains, northwestern Canada, contains a Burgess Shale‐type biota of similar age to the Wheeler and Marjum formations of Utah. The Rockslide Formation is a unit of deep‐water, mixed carbonate and siliciclastic facies deposited in a slope setting on the present‐day northwestern margin of Laurentia. At the fossil‐bearing locality, the unit is about 175 m thick and the lower part onlaps a fault scarp cutting lower Cambrian sandstones. It consists of a succession of shale, laminated to thin‐bedded lime mudstone, debris‐flow breccias, minor calcareous sandstone, greenish‐coloured calcareous mudstone and dolomitic siltstone, overlain by shallow‐water dolostones of the Broken Skull Formation, which indicates an overall progradational sequence. Two ~1‐m‐thick units of greenish calcareous mudstone in the upper part exhibit soft‐bodied preservation, yielding a biota dominated by bivalved arthropods and macrophytic algae, along with hyoliths and trilobites. It represents a low‐diversity in situ community. Most of the fossils occur in the lower unit, and only the more robust components are preserved. Branching burrows are present under the carapaces of some arthropods, and common millimetre‐sized disruptions of laminae are interpreted as bioturbation. The fossiliferous planar‐laminated calcareous mudstone consists of chlorite, illite, quartz silt, calcite and dolomite and is an anomalous facies in the succession. It was deposited via hemipelagic fallout of a mixture of platform‐derived and terrestrial mud. Geochemical analysis and trace‐element proxies indicate oxic bottom waters that only occasionally might have become dysoxic. Productivity in the water column was dominated by cyanobacteria. Fragments of microbial mats are common as carbonaceous seams. Complete decay of soft tissues was interrupted due to the specific sediment composition, providing support for the role of clay minerals, possibly chlorite, in the taphonomic process.     

An integrated reconstruction of the early Pleistocene palaeoenvironment of Homo erectus in the Denizli Basin (SW Turkey)

The early Pleistocene travertines from Kocabaş in the Denizli Basin (SW Turkey), from which the only known Homo erectus from Anatolia derives, are covered by a succession of lake deposits. So far, the taphonomic history of the site has precluded a detailed palaeoecological analysis. This paper details the sedimentary succession and palaeoenvironmental conditions by analysing the micro- and macropalaeontological species compositions. These data provide direct evidence of the opportunities and limiting factors of the environment inhabited by hominins during the early Pleistocene. Four distinctive lithostratigraphic units are recognized in the Quaternary succession, consisting of: Lower Travertine, Lower Conglomerates, Upper Travertine, and Upper Conglomerates. These units correspond to an alternation of lacustrine limestone, fluvial-lacustrine siliciclastic deposits and subaerially precipitated travertine accumulations. The age of the succession is constrained by cosmogenic nuclide concentration, palaeomagnetic measurements and large mammal biostratigraphy which suggest deposition occurred between ∼1.6 and 1.2 Ma. The travertine succession contains a moderately diverse macromammal fauna, including Homo erectus, decapod crustaceans and leaf imprints. The herbivore association likely dwelled in a mixed landscape during temperate and humid climatic conditions, supported by negative δ¹⁸O values from analysed gastropod and bivalve shells. The presence of an anomalohaline lake is indicated by an abundant and well-preserved ostracod community, consisting of alkaline tolerant taxa and freshwater genera further supported by the presence of cardiid bivalves.     

The Cambrian of Malaysia

The Cambrian of Malaysia is best represented by the quartzose Machinchang Formation in Langkawi, Kedah, northwest Peninsular Malaysia. It is divisible into three members. The oldest Hulor Member (>1260 m thick) is a coarsening upward succession of rhythmically interlayered graded siltstone, mudstone and clayey sandstone deposited as a prograded prodelta deposit. The middle Chinchin Member (>1575 m thick) is a fining upward succession of quartzose conglomerate and sandstone subdivisible into three beds. The lowest Anak Datai Bed (575 m thick) is made up of graded bedded, cross-bedded pebbly sandstone and conglomerate of estuarine channel-fills and thin to thick beds of low angle, planar cross-bedded sandstone with heavy mineral concentrations deposited as upper shoreface to beach deposits. The Temurun Bed (340 m thick) is of upper estuarine deposits of wavy-bedded sandstone and pebbly sandstone, fine tuffs and thin argillites. The upper Tengkorak Bed (>200 m thick) spans the Cambro-Ordovician boundary and consists of thick tabular bedded upper shoreface to beach fine sandstone with interbeds of fine rippled sandstone, acid tuff beds and mudstone belonging to a series of barrier beach complexes. The youngest Jemurok Member (>420 m thick) is a fining upward succession of siltstone, mudstone and hummocky cross-bedded sandstone and thin limestone deposited in storm influenced shoreface to back barrier lagoon with tidal channel environments. It has fragmentary trilobites, brachiopods, abundant trace fossils and the Kinneyian wrinkle marks.The overall sequence belongs to a highly destructive, wave-influenced delta deposit with a series of preserved beach-ridge complexes. Clastic sedimentation was reduced by peneplation of the source area as shown by the finer and thinner beds that grade into limestone of the overlying Ordovician Setul Formation.     

新疆吐鲁番盆地桃树园晚二叠世非海相腹足类

提要新疆吐鲁番盆地桃树园地区晚二叠世地层称作下仓房沟群,自下而上分为泉子街组、梧桐沟组和锅底坑组,为河–湖相碎屑沉积,剖面连续,层序清楚,动、植物化石丰富。文中研究的腹足类标本产于桃东沟剖面梧桐沟组下部和中部的介壳灰岩层和灰岩透镜体中,见有2层,计有2科4属6种:Xinjiangospira rotundata Yu et Zhu,Xinjiangospira habita sp.nov.、Hydrobia turpanensis Wei、Hydrobia orientalis sp.nov.、Pseudamnicola taodonggouensis sp.nov.和Valvata complanusa sp.nov.;与腹足类共生的有双壳类、叶肢介、介形类,以及植物和脊椎动物化石等,其中双壳类主要是Palaeanodonta,Palaeomutela和Anthraconauta等属。该腹足动物群由Hydrobiidae和Valvatidae的属种组成,标本数量多,壳体小,保存完好,是迄今已知属种最丰富的古生代淡水腹足类动物群。当前梧桐沟组腹足动物群面貌与准噶尔盆地大龙口剖面小龙口组...     

Late Triassic (Late Norian) gastropods from the Wallowa Terrane (Idaho,USA)

A diverse Late Triassic (Late Norian) gastropod fauna is described from the Mission Creek Limestone of the Wallowa terrane (Idaho, USA). Sample standardization by rarefaction analysis indicates that the fauna is even more diverse than the Late Triassic gastropod fauna from the Pucara Formation (Peru) which represents the most diverse gastropod fauna from South America. The gastropod fauna consists of 66 species; several genera are reported for the first time from North America. A high percentage of the species are highly ornamented and several have distinct siphonal canals. This suggests that the appearance of truly Mesozoic elements among the gastropods began before the Mesozoic Marine Revolution in other clades. The fauna is dominated by high-spired strongly ornamented procerithiids, a group more characteristic for the Jurassic. Comparison of the present fauna and the Iranian Nayband Formation gastropod fauna show that the procerithiids underwent a first global radiation in the Late Triassic. The high number of new species in this fauna suggests that sampling of Late Triassic gastropod faunas is still incomplete and hinders palaeobiogeographic considerations. Previous suggesions that gastropod faunas from the Wallowa and Wrangellia terranes resemble each other and are distinct from those of Alexander, Chulitna, and Farewell terranes are basically corroborated. The gastropod fauna of the Mission Creek Limestone differs considerably from that of the western and central Tethys but shares several taxa with the Late Triassic gastropod fauna of the Pucara Formation in Peru. Thus, the Hispanic corridor was probably not present in the Norian but opened only in the Early Jurassic. The subfamily Andangulariinae is introduced and placed in the Zygopleuridae. The generaSpiniomphalus, Nodoconus, Gudrunella, Blodgettella, Idahospira, andSiphonilda and the subgenusCryptaulax (Wallowax) are introduced. 27 species are erected. A lectotype is designated forCryptaulax rhabdocolpoides Haas, 1953.      

Planktonic foraminiferal succession in late Cretaceous to early Palaeocene strata in Meghalaya, India

A roughly 10.5-m-thick succession within the Langpar Formation of the Um Sohryngkew River section, Meghalaya, India, constrained by the last occurrence of Globotruncanita stuarti and the first occurrence of Parasubbotina pseudobulloides , spans the K/T (Cretaceous–Tertiary) transition. The unit is divisible into three parts with the lower consisting of shaly limestone, weakly calcareous shale and silty shale with coal streaks. The middle part is dominated by calcareous shale with mud flakes, coprolites, burrows and pyrite nodules, followed by alternating limestone and marlite at the top. Planktonic foraminifera are rare to frequent within the unit. Based on the distribution of zonal indices, seven successive planktonic foraminiferal zones are recognized from across the K/T boundary. From base to top, these are CF4, CF3, CF2 and CF1 in the upper Maastrichtian part and Zone P0, Zone Pα and Subzone P1a in the lower Danian part. The biozones indicate that the section is biostratigraphically continuous across the K/T boundary. A similar foraminiferal succession and K/T transition is observed in the Langpar of the Cherrapunji-Mahadeo road section at a distance of over 5km. These K/T outcrops from Meghalaya provide the first record of a continuous K/T sequence in the Indian subcontinent with respect to planktonic foraminifera.     

Habitat associations of epigeal spiders in upland calcareous grassland landscapes: the importance for conservation

Upland calcareous grassland landscapes are typically comprised of a matrix of calcareous grassland, acid grassland and limestone heath plant communities. This matrix of habitats is produced by a combination of underlying geology, climate and management. These landscapes are typically managed through grazing, with management targeted to maintain particular plant communities in the calcareous grassland habitat, whilst patches of acid grassland and limestone heath are not targeted by conservation management. The biodiversity value of acid grassland and limestone heath patches within the calcareous grassland matrix are unknown. This study provides the first assessment of their biodiversity value by examining aspects of epigeal spider diversity supported by these non-target habitat patches in comparison to calcareous grassland. Spiders were sampled in each habitat from April to August 2014 using pitfall traps across three upland regions in Great Britain. Spider species assemblages were distinct between limestone heath and both grassland types. Distinction in species assemblages are likely due to differences in vegetation structure and microclimate, e.g., humidity, degree of shade. Each habitat type supported several rare species (e.g., Jacksonella falconeri, Agyneta subtilis) revealing the contribution to spider fauna. The distinct spider species assemblage and presence of rare species in limestone heath patches demonstrate their importance in the upland calcareous grassland matrix. This study highlights the value of monitoring biodiversity in non-target habitats within a habitat matrix alongside those that are actively targeted by management.     

Trace-fossils and minor discontinuities in a marl limestone rhythmite, Lower-Middle Kimmeridgian, southern Spain

In a fine-grained Lower to Middle Kimmeridgian marly limestone rhythmite succession, with scarce benthos, fluctuations in ecological and depositional conditions that affected the substrate are detected by analysing trace-fossil assemblages. The dominant grey mudstones with Chondrites and Planolites superimposed on lumpy matrix sediments indicate both late colonisation of dysaerobic mixed layers and the completeness of the stratigraphic record. Major disruptions in rhythmic deposition and substrate colonisation are recorded at the base of thick intercalations of marls in sedimentary packages that were related to tectonic instability. Minor disruptions affected only the deposition of the overlying limestone beds. The trace-fossils reveal changes in the ecological and depositional conditions affecting the substrate during deposition of monotonous marly limestone rhythmites at levels of resolution higher than biostratigraphic, ecostratigraphic and taphonomic resolution. This research demonstrates the application of trace-fossil analysis to approach stratigraphic completeness (maturation) in homogeneous marly limestone rhythmites     

Late Silurian brachiopods from Darhan Mumingan Joint Banner, Inner Mongolia

Seven brachiopod species (including three new species) and three undetermined forms are described and figured here from an unnamed stratigraphic unit which mainly consists of argillaceous and bioclastic limestone near the stratotype of the Late Silurian Xibiehe Formation of the Xibiehe section in the Darhan Mumingan Joint Banner, north of the Bateaobao area, Inner Mongolia. Three new species, Eoschizophoria minuta, Navispira navicula and Howellella asiatica are established with transverse serial sections for their interiors. All brachiopod taxa described here show that this unnamed stratigraphic unit is higher than the Late Silurian Xibiehe Formation in the Xibiehe section and is possibly transitional between the Late Silurian and the Early Devonian. Authors temporarily regard this unit as the upper part of the Xibiehe Formation in this paper.     

Middle Eocene Ostracods from southeast Fayoum area,Egypt: Systematics,paleobathymetry and paleobiogeography

This study deals with the Middle Eocene ostracods from southeast Fayoum area, Egypt. To carry out this investigation, three outcrops are examined, Gebel Elwe El Breig, Gebel Sath El Hadid and Gebel Munqar El-Shinnara. This study is based on the Midawara Formation that consists mainly of fossiliferous limestone, marly limestone and clay. The studied ostracod assemblage includes thirty-one species and subspecies, belonging to twenty-three genera and seventeen families. The ostracod group belonging to Cytheroidea Baird, 1850 represents the most abundant group that reaches 81.99% in Munqar El-Shinnara section, 81.88% in Sath El Hadid section, and 61.12% in Elwe El Breig section. The structure of the investigated assemblages (abundance of ostracods, number of taxa, Fisher's alpha, Shannon index, and equitability) indicates deposition in an environment belonging to the neritic zone. Moreover, this study tries to use the multivariate analyses to distinguish the paleobiogeographic provinces in Tethyan region during the Middle Eocene. These analyses are applied on a matrix consists of some nominated Middle Eocene species from 13 countries. The results point to two distinctive provinces, Southern Tethys Province (Algeria, Tunisia, Libya, Egypt and Jordan) and the Northern Tethys Province (England, Germany, Spain, France, Belgium, Ukraine, Hungary and Turkey). The reasonable similarities between these provinces may reflect a possible connection between both sides of the Tethys during the Middle Eocene age.     

The Cenomanian–Turonian boundary in the northwestern part of the Adriatic Carbonate Platform (Ćićarija Mtn., Istria,Croatia): characteristics and implications

The Cenomanian–Turonian boundary (CTB) in the ?i?arija Mountain region (northern Istria, Croatia) is characterized by calcisphere limestone successions with a firmground and glauconite horizon, bioturbated intervals, tempestites, and slumped structures as well as microbially laminated and organic-rich interbeds deposited in the northwestern part of the intra-Tethyan Adriatic Carbonate Platform (AdCP). Compilation of the results from three studied sections (Vodice–Jelovica, Martinjak and Planik) of litho-, bio-, and microfacies analyses, X-ray diffraction, SEM, EDS, and stable isotope analyses allowed reconstruction of marine paleoenvironmental conditions during this time period. Shallow-marine carbonate deposits of the Milna Formation underlie a drowned-platform succession of the Sveti (Sv.) Duh Formation. The contact between these two formations is sharp and commonly marked by slumped deposits. The Sv. Duh Formation consists of about 100 m of calcisphere wackestone enriched in organic matter. The results of preliminary δ¹³C and δ¹⁸O stable isotope analyses indicate the influence of the global Oceanic Anoxic Event (OAE2) on the deposition of this carbonate succession. Anoxic and hypoxic conditions in the water column lead to major changes in the shallow-marine carbonate system of the AdCP. Numerous benthic foraminifera declined during that time, but planktonic foraminifera and calcareous dinoflagellates diversified and expanded greatly. The results of this research provide new insights into the character of the CTB interval in this part of the Tethyan realm. Local and regional synsedimentary tectonics combined with global upper Cretaceous sea-level dynamics allows the correlation of the investigated deeper-marine lithostratigraphic units with OAE2.     

The persistence of calcareous grassland species in the soil seed bank under developing and established scrub

The relationships between the composition of the soil seed bank, the field layer vegetation, and the scrub canopy were investigated along a 69 m transect, grading from incipient woodland, through scrub, into intensively rabbit-grazed calcareous grassland. The results are used to assess the persistence of species associated with open calcareous grassland in the seed bank under developing scrub. Scrub age, composition and density, changed along the transect from the woodland to open grassland. A total of 35 forb and grass species were found in the field layer. The pattern evident in the scrub layer was also reflected in the herbaceous vegetation. The field layer in the most closed portion of the transect, where the scrub was oldest, was dominated by shade-tolerant species normally associated with woodland habitats. The abundance of these species decreased along the transect as the scrub age declined, and the field layer became increasingly dominated by species typical of open grassland. A total of 47 species germinated from the seed bank. Few species were recorded in the seed bank along the entire length of the transect. Overall, the seed bank was dominated by Hypericum perforatum and Centaurium erythraea, which accounted for 38.2% and 28.6% of emerging seedlings respectively. As with a number of similar studies, the composition of the seed bank had a low correspondence with the composition of the field layer vegetation. The results also emphasise that the composition of the seed bank can be viewed as an ecological palimpsest, with germinable seed of species from each stage of the old-field succession occurring in the soil. The seed bank is an important component in the re-vegetation of an area after disturbance such as scrub removal. This study supports the findings of previous research in showing that relatively few characteristic calcareous grassland species form persistent seed banks. The soil seed bank would therefore appear to be of limited value in the restoration of such grassland following scrub removal.     

Nitrogen deposition and soil carbon content affect nitrogen mineralization during primary succession in acid inland drift sand vegetation

Background and aims

Two inland dunes in the Netherlands receiving low (24) and high (41 kg N ha^?1 yr^?1) nitrogen (N) deposition were compared for N dynamics and microbial activity to investigate the potential effect of N on succession rate of the vegetation and loss of pioneer habitats.

Methods

Primary succession stages were sampled, including bare sand, and vegetation dominated by Polytrichum piliferum, Campylopus introflexus, lichens and grasses respectively, representing a series of vegetation types in undisturbed drift sand sites with succession starting on bare sand containing virtually no organic matter. Microbial characteristics and potential N mineralization were analysed in a laboratory experiment.

Results

Organic matter accumulated during succession, resulting in a lower pH and in higher microbial biomass (bacteria and fungi), respiration and net N mineralization. The increase in respiration and N mineralization was largely due to the development of an ectorganic layer in the middle stages of succession. The observed effects of N deposition were (1) decrease of microbial biomass, (2) higher net N mineralization per m², (3) higher levels of free nitrogen in the soil, and (4) a higher microbial N:P ratio.

Conclusions

Elevated N deposition leads to higher N availability which may cause accelerated succession.     

Late Famennian gastropoda from south-west England

The gastropod fauna of the Upper Devonian Baggy and Pilton formations in south‐west England is revised and includes some 30 taxa. The topmost part of the Upper Famennian succession in Devon is represented by clastic near‐shore and shallow shelf sediments, indicating a short‐term transgressive phase (‘Strunian Transgression’). The sequence yields a highly diverse fauna dominated by brachiopods and ostracodes, locally supplemented by crinoids, bryozoans, trilobites and molluscs. The taxa ‘Patellostium’britannicum sp. nov., Angyomphalus (Angyomphalus) junius sp. nov. and Dictyotomaria eurocapillaria sp. nov. are erected; a junior homonym is replaced by Macrochilina? piltonensis nom. nov. The gastropod fauna displays an independent character, where latest Devonian faunal elements overlap with Late Palaeozoic taxa expressing a transition similar to that of the bivalves, brachiopods, echinoderms and corals, without a sharp faunal break at the Devonian/Carboniferous boundary. Apart from the Caenogastropoda, all subclasses of gastropods are represented. Members of the bellerophontoids, pleurotomarioids and loxonematoids are most abundant, followed by murchisonioids, naticimorphs, euomphalomorphs and platyceratoids. The various gastropod groups represent different ecological demands and trophic categories, and together with the accompanying fauna indicate that nearly all habitats and niches were occupied in the shallow South Laurussian Shelf.     

Rare, threatened and alien species in the gastropod communities in the clay pit ponds in relation to the environmental factors (The Ciechanowska Upland, Central Poland)

The objectives of the present survey were to formulate a zoocenological analysis of the gastropod communities in clay pit ponds, as well as to determine the relationships between the gastropods and their environments, and to evaluate the water habitats in terms of their ecological-conservation value. The physical and chemical parameters of water, gastropod species and macrophytes occurring in the ponds indicate mesotrophic conditions. Principal Component Analysis (PCA) reveals a correlation between gastropod density and nitrates, a correlation between gastropod density and alkalinity, and additionally shows a correlation between gastropod density and chlorides. The pond surface area, nitrates, chlorides concentrate, alkalinity, and substratum have all affected these gastropod communities. The occurrence of the first permanent population of Ferrissia clessiniana (Jickeli, 1882) was recorded in Poland. Valvata naticina Menke 1845 has become a critically rare species (CR) due to the pollution of water environments. Five other species, e.g. Anisus vorticulus (Troschel, 1834) and Planorbis carinatus O.F. Müller, 1774 are recorded on the Polish Red List of Species. The clay pit ponds of the Ciechanowska Upland, because of their distinctive environmental features, provide a refuge where a number of rare, threatened and alien gastropod species live.     

Structure of shells from eggs of kinosternid turtles

Shells from eggs of five species of kinosternid turtle (Sternotherus minor, Kinosternon flavescens, K. baurii, K. Hirtipes, and K. alamosae) were examined with light and scanning electron microscopy. Except for possible differences among species in thickness of eggshells, structure of shells from all eggs was similiar. In general, kinosternid turtles lay eggs having a rigid calcareous layer composed of calcium carbonate in the form of aragonite. The calcareous layer is organized into individual shell units with needlelike crystallites radiating from a common center. Most of the thickness of the eggshell is attributable to the calcareous layer, with the fibrous shell membrane comprising only a small fraction of shell thickness. Pores are found in the calcareous layer, but they are not numereous. The outer surface of the eggshells is sculptured and may have a thick, organic layer in places. The outer surface of the shell membrane of decalcified eggshells is studded with spherical cores which presumably nucleate growth of shell units during shell formation. The shell membrane detaches from eggs incubated to hatching, carrying with it remnants of the calcareous layer. Such changes in shell structure presumably reflect withdrawal of calcium from the eggshell by developing embryos.     

Storm-induced coral rubble deposition: Pleistocene records of natural reef disturbance and community response.

Shallow-water Pleistocene coral reef facies in Barbados (dominated by Acropora palmata rubble) record evidence of deposition under contrasting non-catastrophic - (fair-weather?) and storm-induced conditions. Depositional styles are interpreted on the basis of coral rubble fabrics and calcareous encruster successions. Terrace exposures on the west of the island comprise uniform (3-4 m thick) depositional sequences. Individual coral samples exhibit similarities in encruster community composition and thickness, and a transition from photophilic to sciaphilic encrusting forms. These are indicative of colonization during gradual burial in an accumulating rubble pile. By contrast, NE coast sites comprise repetitive sequences of discrete (0.4-1 m thick) depositional units. Rubble colonization within each unit is characterized by a vertical succession from thin (1-2 mm), sciaphilic encruster-dominated sequences at the base, to progressively thicker (up to 20 mm), photophilic encruster-dominated sequences at the top. These are interpreted as multiple storm deposits, with upper surfaces colonized by opportunist coral species (primarily Agaricia agaricites). In contrast to many modern hurricane-impacted reef systems, however, there is no evidence of long-term shifts in coral community composition following physical disturbance. Colony sizes of opportunist corals at the tops of storm units are consistent with growth over timescales of <10 years. These are overlain on each occasion by a new A. palmata rubble pile, indicating successful recovery over successive physical disturbance cycles.     

Paleoenvironmental model and sequence stratigraphy of the Asmari Formation in southwest Iran

The Asmari Formation is a thick carbonate succession of the Oligo-Miocene in southwest Iran (Zagros Basin). The Zagros Basin was a continental margin attached to the eastern edge of Africa throughout the Phanerozoic. The foraminiferal limestone from the Asmari Formation has been studied to determine its microfacies, paleoenvironments and sedimentary sequences. Based on analysis of larger benthic foraminiferal assemblages and microfacies features three major depositional environments are identified. These include open marine, barrier and lagoon-lower intertidal. These three are represented by eleven microfacies. A carbonate ramp platform is suggested for the depositional environment of the Asmari Formation. The inner ramp facies are characterized by wackestone-packstone, dominated by various taxa of imperforate foraminifera. The middle ramp facies represented by packstone-grainstone to floatstone with a diverse assemblage of larger hyaline foraminifera. The outer ramp is dominated by argillaceous wackestone, characterized by planktonic foraminifera and larger hyaline foraminifera. Two third-order sequences are identified based on deepening and shallowing patterns in microfacies, staking patterns and the distribution of Oligocene-Miocene foraminifers.     

Calcareous nannofossil biostratigraphy and paleoclimatology of the Paleocene succession,Tenida area,Western Desert,Egypt

This study is a preliminary quantitative analysis of Paleocene calcareous nannofossil assemblages of the Tenida area (Egypt) in order to establish a detailed biostratigraphic framework as well as to reconstruct the paleoclimatic trends. A total of 48 samples with an average sample spacing of 1.5 m allowed the identification of 63 calcareous nannofossil species belonging to 19 different genera. The preservation of the studied samples varies from poor to moderate and is characterized by the frequent presence of small frangible placoliths, and nannoliths. This study recognizes three calcareous nannofossil biozones in the Danian-Thanetian time interval; Chiasmolithus danicus (NP3) Zone, Ellipsolithus macellus (NP4) Zone, and Heliolithus kleinpellii (NP6) Zone. Moreover, the multivariate statistical analysis of the calcareous nannofossil communities reveals a relationship between the distribution of these nannofossil assemblages and variations in paleoclimatic trends. Accordingly, the relative abundances of Coccolithus pelagicus in addition to nine calcareous nannofossil genera along with the diversity and preservation indices of calcareous nannofossil elements have been used to elucidate changes in paleoclimatic trends. Based on the cyclic change from cold to warm climates, it was possible to subdivide the Paleocene Period recorded in the Tenida section into four paleoclimatic intervals. The oldest is a global cooling trend spanning 2.01 Myr long, starting in the early Paleocene (Danian) during the deposition of the lower part of the Kharga Shale Member. This cooling trend is followed by a ～ 0.56 Myr warming trend during deposition of the middle part of the Kharga Shale Member that was followed by a return to a cooling mode, with an estimated duration of roughly 1.67 Myr. The last interval includes a 0.39 Myr long period at the Selandian/Thanetian boundary interval, which is dominated by a global warming trend during deposition of the upper part of the Upper Kharga Shale Member.