An unusual brachiopod assemblage in a Late Jurassic (Kimmeridgian) stromatactis mud-mound of the Eastern Carpathians (Hăghimaş Mountains), Romania

An unusual fossil assemblage dominated by superabundant rhynchonellid brachiopods in a stromatactis mud-mound is recorded from the Hăghimaş Mountains (Eastern Carpathians), Romania. The mound mainly consists of bioclastic wackestones to packstones with a very rich macrofauna including crinoids, sponges, juvenile ammonites, and echinoids. The brachiopods represent a low-diversity but high-abundance association, dominated by the rhynchonellids Lacunosella and Septaliphoria. The taphonomical features of the fossil assemblage indicate an autochthonous fauna, with successive generations of brachiopods in life position and complete well-preserved individuals in different growth stage alongside an accessory population of crinoids and sponges. Brachiopod-brachiopod endosymbiotic life strategy is documented for the first time from a post-Paleozoic brachiopod assemblage. The mound reveals abundant stromatactis, filled by radiaxial fibrous or drusy calcite cement and internal polymud sediments. This is the first Late Jurassic (Kimmeridgian) stromatactis mud-mound identified in the Eastern Carpathians.     

Biologic response to environmental stress in tropical reefs: Lessons from modern Polynesian coralgal atolls and Middle Permian sponge and Shamovella-microbe reefs (Capitan Limestone USA)

Despite prejudices that comparisons of paleoecological patterns in modern and fossil reef communities are of doubtful validity, we compare the biologic response of living coralgal reefs in French Polynesia to environmental stress with an exceptionally well exposed Middle Permian sponge reef and Shamovella-microbial reef of the Capitan Limestone in New Mexico. In the western Tuamotu Archipelago, reef margins are characterized by depth-related changes of biodiversity. The subtidal basic reefbuilding community contains the highest diversity (23 coral and 6 calcareous algal species). With decreasing water depth and increasing environmental stress, diversity reaches a minimum of five taxa on the reef flat. The Capitan consists of two reef stages. Reefbuilders of the lowermost exposed part of Stage 1 formed a cement-rich sponge reef with 42 taxa (28 sponge species). Decreasing water depth along the reef face is accompanied by loss of five taxa, variations in the gross morphology of sponges and changes in framework architecture. Stage 2, dominated by Shamovella obscura, one bryozoan species and microbes, is sandwiched between two unconformities suggesting much shallower water and higher environmental stress. Despite differences in shelf profile and taxonomy, both the modern and Permian reefbuilders respond to increasing environmental stress with diversity impoverishment and dominance of binders.     

Strengths abd weaknesses of the reef guild concepts and quantitative data: Application to the upper Capitan-massive community (Permian), Guadalupe Mountains, New Mexico-Texas

Summary Analyses of large acatate sheet tracings, close-up photos and 105 sub-horizontal quadrat surfaces at four localities near the base of the Guadalupe Mountains Escarpment indicate that the biotic framework of the upper Capitan reef was built by about 35 species: one codiacean (Eugonophyllum sp.), 17 calcisponges, 9 bryozoans, one richthofenid brachipod, some crinoid (known only from columns), 4 Problematica and microbes. This widespread fossil community included members of the Constructor, Baffler and Binder Guilds. A re-evaluation of the Guild Concept (Fagerstrom, 1987, 1991) highlights the validity of the functional roles of the Constructor and Binder Guilds for reef construction. Members of the Baffler Guild, however, need to be revised and an interpretation of microbial micrite and cryptic biota remains controversial. Open surface phylloid algal and cryptic sponge-bryozoan dominated sub-communities were of only local importance. The upper Capitanmassive differs from its Permian conterparts in the low diversity and areal cover of the frame-building biota, low micrite content and abundant micro-frameworks, i.e, intergrown small sponges, Problematica and syndepositional cements (botryoidal and isopachous, fibrous calcite). Quantitative areal cover data were assessed at various scales. Large acetate sheets generally have low coverage of macro-biota (5.4%). By contrast, analysis of small areas of local high areal cover (selected acetate sheet quadrats, subvertical photographs, and quadrat samples: 15–21%) provide detailed insights into clustered patches forming the inital reef framework. Both data sets provide useful clues for an integrated approach to framework assessment. Mean acetate sheet data are limited by their somewhat generalized pattern, while small investigation areas may overemphasize local variation. Erect and pendant sponges with solitary, sub-cylindrical and multi-branche/clonal forms, were the predominant initial frame-builders in both open surface and cryptic habitats. Selective larval recruitment of erects sponges to firm substrates produced continous upward accretion of the initial framework. On open surfaces and in pores formed by tabular sponges and fenestrate bryozoans, erect and pendant sponges were supported in their hydrodynamically unstable growth position by encrusters, chieflyArchaeolithoporelle hidensis, Shamovella obscura, an unnamed tubular organism, and microbes. Subsequent growth ofArchaeolithoporella hidensis, microbial crusts and syndepositional cements on the outer walls of live sponges would have impeded ambient water circulation and may have led to ‘creeping sponge death by suffocation’ or complete encrustation after death. Filling of pores in the initial and encrusted reef framework by internal sediment (packstone-grainstone; derived from the framework and the back-reef shelf/platform) and voluminous syndepositional marine-phreatic cements completed the framebuilding process.     

Bioerosion in the Miocene Reefs of the northwest Red Sea,Egypt

Macroborings provide detailed information on the bioerosion, accretion and palaeoenvironment of both modern and fossil reefs. Dolomitized reefal carbonates in the Um Mahara Formation exhibit an outstanding example of spatially distributed, well‐preserved bioerosion structures in tropical to subtropical syn‐rift Miocene reefs. Ten ichnospecies belonging to five ichnogenera are identified; three belonging to the bivalve‐boring ichnogenus Gastrochaenolites, three attributed to the sponge‐boring ichnogenus Entobia, and four ichnospecies assigned to three worm‐boring ichnogenera Trypanites, Maeandropolydora and Caulostrepsis. The distribution of the reported borings is strongly linked to the palaeo‐reef zones. Two distinctive ichnological boring assemblages are recognized. The Gastrochaenolites‐dominated assemblage reflects shallower‐marine conditions, under water depths of a few metres, mostly in back‐reef to patch‐reef zones of a back‐reef lagoon. The Entobia‐dominated assemblage signifies relatively deeper marine conditions, mostly in reef core of the fringing Miocene reefs. These ichnological assemblages are attributed herein to the Entobia sub‐ichnofacies of the Trypanites ichnofacies. This ichnofacies indicates boring in hard carbonate substrates (such as corals, rhodoliths, carbonate cements and hardgrounds) during periods of non‐sedimentation or reduced sediment input.     

Ichnology of Lower Jurassic beach deposits in the Shemshak Formation at Shahmirzad,southeastern Alborz Mountains,Iran

A 19 m thick package of well-sorted lowermost Jurassic (Hettangian-Lower Sinemurian?) sandstones within the Shemshak Formation of the southeastern Alborz Mountains displays features characteristic of foreshore to upper shoreface environments such as tabular bedding, low-angle lamination, trough cross-stratification, parting lineation, and oscillation ripples. In contrast to most other beach successions recorded in the literature the sandstones contain a trace fossil assemblage characterised by low abundance but comparatively high diversity. The assemblage, comprising 14 ichnotaxa, is dominated by Palaeophycus heberti, Rhizocorallium irregulare, Gyrochorte comosa, and Parahaentzschelinia surlyki. Contrary to predictions, which assume a dominance of suspension-feeders in such high-energy environments, the trace fossil assemblage represents a variety of ethological groups ranging from suspension-feeders to deposit-feeders, detritus-feeders, scavengers, and a possible trap constructor (Ctenopholeus), whereby deposit-feeders predominate. This anomaly is explained by a high amount of organic detritus in the sediment, indicated by abundant plant material, and a position of the beach in the vicinity of a river mouth.     

Coral assemblages, biofacies, and ecological zones in the mid-Holocene reef deDosits of the Enriquillo Valley, Dominican Republic

Stemann, T. A. & Johnson, K. G. 1992 07 15: Coral assemblages, biofacies. and ecological zones in the mid-Holocene reef deposits of the Enriquillo Valley, Dominican Republic. A large, subaerially exposed mid-Holocene reef in the Enriquillo Valley (southwest Dominican Republic) provides an excellent opportunity to examine the relationship between reefal ecology and reefal deposits. Coral species richness and diversity in the Enriquillo reef are comparable to that found in the recent of the Caribbean, and ecological zonation comprised of a shallow-water branching coral zone and a deeper water mixed-coral zone is apparent. Similar zonation and diversity patterns have been recognized on living Caribbcan reefs with moderate wave exposure. Three statistically discrete biopdcies can be discriminated in the Enriquillo deposits using quadrat point-counting techniques commonly used to census modern reefs. They include a facies dominated by Acropora cervicornis, a low diversity assemblage with abundant, large colonies of Siderastrea siderea and Stephanocoenia intersepta, and a higher diversity assembbdge composed of various taxa including Montastraea spp., Colpophyllia spp., and Agaricia spp. Each facies can be recognized at scales of 1–3 m², though in some cases they extend for more than 20 m². In general, the A. cervicornis facies is spatially segregated from the other two biofacies. although neither the shallow nor the deep-water ecological zone is comprised of a single reef biofacies. Rather, the biofacies described here appear to represent distinct micro-environments resulting from ecological variation at a subzonal scale. Micro-environments of similar scale are most likely preserved in other reef deposits. Recognition of these subzonal biofacies may have important consequences for the stratigraphical and paleoccological interpretation of fossil reefs. Corals, biofacies, reef zonation, coral communities, fossil reefs.     

Late Paleozoic reef mounds of the Carnic Alps (Austria/Italy)

The Late Paleozoic (early Kasimovian-late Artinskian) sedimentary sequence of the Carnic Alps (Austria/Italy) is composed of cyclic, shallow-marine, mixed siliciclastic-carbonate sedimentary rocks. It contains different types of skeletal mounds in different stratigraphic levels. The oldest mounds occur at the base of the Auernig Group, within a transgressive sequence of the basal Meledis Formation. These mounds are small and built by auloporid corals. Algal mounds are developed in the Auernig Formation of the Auernig Group, forming biostromes, and Lower Pseudoschwagerina Limestone of the Rattendorf Group forming biostromes and bioherms. The dominant mound-forming organism of these mounds is the dasycladacean alga Anthracoporella spectabilis. In mounds of the Auernig Formation subordinately the ancestral corallinacean alga Archaeolithophyllum missouriense is present, whereas in mounds of the Lower Pseudoschwagerina Limestone a few calcisponges and phylloid algae occur locally at the base and on top of some Anthracoporella mounds. Mounds of the Auernig Formation formed during relative sea level highstands whereas mounds of the Lower Pseudoschwagerina Limestone formed during transgression. The depositional environment was in the shallow marine, low-turbulence photic zone, just below the active wave base and lacking siliciclastic influx. The algal mounds of the Carnic Alps differ significantly from all other algal mounds in composition, structure, zonation and diagenesis; the formation of the mounds cannot be explained by the model proposed by Wilson (1975). The largest mounds occur in the Trogkofel Limestone, they are composed of Tubiphytes/Archaeolithoporella boundstone, which shows some similarities to the “Tubiphytes thickets” of stage 2 of the massive Capitan reef complex of the Guadalupe Mountains of New Mexico/West Texas.     

Facies and palaeoecology of Upper Jurassic (Middle Oxfordian) coral reefs in England

Summary This study documents the facies and fauna of Late Jurassic (Middle Oxfordian) coral reefs in England. Sedimentological and palaeoecological analysis of these reefs distinguishes three generic reef types: (1) small reef patches and thickets associated with siliciclastic deposits; (2) small reef patches and thickets associated with siliciclastic-free bioclastic grainstones and packstones; and (3) biostromal units associated with deep water facies. The depositional environments of these reef types are discussed. Two coral assemblages are identified: (1) the microsolenid assemblage; and (2) theThamnasteria, Isastraea, Fungiastraea andThecosmilia assemblage (Thamnasteria assemblage). TheThamnasteria assemblage developed in all shallow water environments in the study area, regardless of local environmental conditions. The fauna is very eurytopic,r-selected and can tolerate significant environmental fluctuations on short temporal scales (sub-seasonal). The main control on the development of the microsolenid assemblage was low light intensity, low background sedimentation rates and low hydrodynamic energy levels.     

Growth forms and palaeoenvironmental interpretation of stromatoporoids in a Middle Devonian reef, southern Morocco (west Sahara)

Growth forms of well-preserved stromatoporoids, including genera Actinostroma, Stachyodes, and Stromatopora, are described for the first time from the Devonian Sabkhat Lafayrina reef complex of southern Morocco (west Sahara), one of the best exposed Middle-Devonian stromatoporoid-dominated fossil reefs. Three facies types representing the well illuminated fore-reef, reef-core and transition to back-reef facies display the distribution and growth of stromatoporoids in a high latitude setting at 40–50° south of the palaeoequator. Stromatoporoids are largely in growth position and reflect the well-preserved reef architecture. Although outcrops are low topography, the reef's prominent profile is indicated by presence of spur and groove form and a clearly defined reef margin. Stromatoporoids are mostly laminar and domical forms, with little evidence of ragged margins, and indicate normal turbulence shallow waters, with low sediment deposition.     

塔里木板块塔中区上奥陶统良里塔格组的生物礁类型

塔里木板块塔中Ⅰ号坡折带附近上奥陶统良里塔格组取芯井段中可识别多种生物礁灰岩类型,包括珊瑚骨架/障积岩、海绵骨架/绑结岩、苔藓虫绑结岩、钙藻障积岩、钙质菌藻障积/绑结岩等礁灰岩类,藉此可归纳出珊瑚礁、珊瑚-钙藻礁、层孔虫礁、层孔虫-钙藻礁、珊瑚-层孔虫-钙藻礁、苔藓虫礁丘、钙藻礁丘、灰泥丘和微生物礁等生物建造单元。这些礁体的时空分布模式与古环境分异相关联,纵向上具有灰泥丘向珊瑚-层孔虫-钙藻礁至苔藓虫礁丘和钙藻礁的群落结构更替趋势;空间分布则向台地北缘,即I号坡折带延伸显示由低能带灰泥丘向高能带珊瑚-层孔虫-钙藻礁的相变,而且高能带珊瑚-层孔虫-钙藻主体礁和环其周缘相对低能带的钙藻礁丘、灰泥丘等在一定范围内构成造礁群落结构分异。     

THE EVIDENCE OF REPRODUCTIVE MECHANISMS IN FOSSIL DASYCLADS (ALGAE: CHLOROPHYTA)

Dasyclads (members of Order Dasycladales: Algae, Chlorophyta) are reviewed for evidence of reproductive structures in the fossil state, and then compared with what is known of the reproductive processes in living examples. The effects of poor preservation in most of the fossils are shown to result in many uncertainties, and the resulting degree of interpretation required is emphasized. Selected genera of fossil dasyclads considered relevant to this problem are briefly analysed and discussed: Archaeobatophora (Ordovician), Kulikia (Carboniferous), Imperiella (Permian), Stichoporella (Jurassic) and Cympolia (Cretaceous to Recent). The pioneer views of J. Pia on dasyclad reproduction through geological time are seen to need much modification in the light of later work. The fundamental dasyclad nucleus-fragmentation-reproduction mechanism is believed to have operated within the great morphological variety of known dasyclads, giving rise to modification in genera where basic evolution was structural. In this way the variety of dasyclads can be seen to be the result of varied morphological evolution, often modified by the consistently simple basic reproductive mechanism.     

Polymorphism of the Noncoding Region of the Mitochondrial Genome in Three Kazakh Populations Inhabiting Different Areas of Kazakhstan and in DNA Samples from Ancient Populations of the Kazakhstani Altai

The polymorphism of the major noncoding region of mitochondrial DNA (mtDNA D loop, 528 bp) has been studied in samples from three modern Kazakh populations (from Almaty, the Semipalatinsk Region, and the Altai Mountains) and in DNA samples of ancient human populations of the Kazakhstani Altai. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis for 13 restriction sites, including BamHI, EcoRV, Sau3AI (one site each), KpnI (two sites), HaeIII (three sites), and RsaI (five sites) were used. The frequency distributions of all sites have been determined. The gene diversity (h) and the genetic distances between different Kazakh populations and other populations of the world have been calculated. The RFLP analysis of the mtDNA control region of fossil samples has been performed similarly to the analysis of modern mtDNA samples. Two fossil mtDNA samples from burial mound 11 are monomorphic with respect to all restriction sites analyzed.     

Anthracoporella mounds in the Late Carboniferous Auernig Group,Carnic Alps (Austria)

Summary A heretofore undocumented example of skeletal mounds formed by the dasycladacean algaAnthracoporella spectabilis is described from mixed carbonate-clastic cycles (Auernig cyclothems) of the Late Carboniferous (Gzhelian) Auernig Group of the central Carnic Alps in southern Austria. The massive mound facies forms biostromal reef mounds that are up to several m thick and extend laterally over more than 100 m. The mound facies is developed in the middle of bedded limestones, which are up to 16 m thick. These limestones formed during relative sea-level highstands when clastic influx was near zero. The mound facies is characterized by well developed baffler and binder guilds and does not show any horizontal or vertical zonation. Within the massive mound faciesAnthracoporella is frequently found in growth position forming bafflestones and wackestones composed of abundantAnthracoporella skeletons which toppled in situ or drifted slightly.Anthracoporella grew in such profusion that it dominated the available sea bottom living space, forming ‘algal meadows’ which acted as efficient sediment producers and bafflers. BecauseAnthracoporella could not provide a substantial reef framework, and could not withstand high water turbulence, the biostromal skeletal mounds accumulated in shallow, quiet water below the active wave base in water depths less than 30 m. The massive mound facies is under- and overlain by, and laterally grades into bedded, fossiliferous limestones of the intermound facies, composed mainly of different types of wackestones and packstones. Individual beds containAnthracoporella andArchaeolithophyllum missouriense in growth position, forming “micromounds’. Two stages of mound formation are recognized: (1) the stabilization stage when bioclastic wackestones accumulated, and (2) the skeletal mound stage when the sea-bottom was colonized byAnthracoporella and other members of the baffler and binder guilds, formingAnthracoporella bafflestones and wackestones of the mound facies. A slight drop in sea-level led to the termination of the mound growth and accumulation of organic debris, particularly calcareous algae, fusulinids, crinoids and bryozoans, forming well bedded limestones, which overlie the mound facies     

Paleobotanical remains from the Paleocene–lower Eocene Vagadkhol Formation, western India and their paleoclimatic and phytogeographic implications

A small assemblage of macro- and micro floral remains comprising fossil leaf impressions, silicified wood, spores, and pollen grains is reported from the Paleocene–lower Eocene Vagadkhol Formation (=Olpad Formation) exposed around Vagadkhol village in the Bharuch District of Gujarat, western India. The fossil leaves are represented by five genera and six species, namely, Polyalthia palaeosimiarum (Annonaceae), Acronychia siwalica (Rutaceae), Terminalia palaeocatapa and T. panandhroensis (Combretaceae), Lagerstroemia patelii (Lythraceae), and a new species, Gardenia vagadkholia (Rubiaceae). The lone fossil wood has been attributed to a new species, Schleicheroxylon bharuchense (Sapindaceae). The palynological assemblage, consisting of pollen grains and spores, comprises eleven taxa with more or less equal representation of pteridophytes, gymnosperms, and angiosperms. Angiospermous pollen grains include a new species Palmidites magnus. Spores are mostly pteridophytic but some fungal spores were also recovered. All the fossil species have been identified in the extant genera. The present day distribution of modern taxa comparable to the fossil assemblage recorded from the Vagadkhol area mostly indicate terrestrial lowland environment. Low frequency of pollen of two highland temperate taxa (Pinaceae) in the assemblage suggests that they may have been transported from a distant source. The wood and leaf taxa in the fossil assemblage are suggestive of tropical moist or wet forest with some deciduousness during the Paleocene–early Eocene. The presence of many fungal taxa further suggests the prevalence of enough humidity at the time of sedimentation.     

THE SYSTEMATIC POSITION OF EOGINKGOITES

Eoginkgoites is a fan-shaped, imparipinnate leaf with a short rachis and long petiole. It was first described from the Upper Triassic Newark Group of Pennsylvania by Bock who assigned the fossil to the Ginkgoales. The fossil has also been found in the Upper Triassic Chinle Formation in Utah and Arizona and in the Newark Group in North Carolina. Investigation of the well-preserved specimens found in the Chinle Formation shows that the leaf has anastomosing venation, a marginal vein and paracytic (syndetocheilic) stomata. These characters indicate that the leaf is bennettitalean and Eoginkgoites is reassigned to the Bennettitales although its shape is perplexing. Eoginkgoites may be an important index fossil to the lower Upper Triassic (middle Carnian) rocks of North America.     

Two waves of colonization straddling the K–Pg boundary formed the modern reef fish fauna

Living reef fishes are one of the most diverse vertebrate assemblages on Earth. Despite its prominence and ecological importance, the origins and assembly of the reef fish fauna is poorly described. A patchy fossil record suggests that the major colonization of reef habitats must have occurred in the Late Cretaceous and early Palaeogene, with the earliest known modern fossil coral reef fish assemblage dated to 50 Ma. Using a phylogenetic approach, we analysed the early evolutionary dynamics of modern reef fishes. We find that reef lineages successively colonized reef habitats throughout the Late Cretaceous and early Palaeogene. Two waves of invasion were accompanied by increasing morphological convergence: one in the Late Cretaceous from 90 to 72 Ma and the other immediately following the end-Cretaceous mass extinction. The surge in reef invasions after the Cretaceous–Palaeogene boundary continued for 10 Myr, after which the pace of transitions to reef habitats slowed. Combined, these patterns match a classic niche-filling scenario: early transitions to reefs were made rapidly by morphologically distinct lineages and were followed by a decrease in the rate of invasions and eventual saturation of morphospace. Major alterations in reef composition, distribution and abundance, along with shifts in climate and oceanic currents, occurred during the Late Cretaceous and early Palaeogene interval. A causal mechanism between these changes and concurrent episodes of reef invasion remains obscure, but what is clear is that the broad framework of the modern reef fish fauna was in place within 10 Myr of the end-Cretaceous extinction.     

A new aglaspidid arthropod from the Upper Cambrian of Tasmania

Abstract: The aglaspidid arthropod, Australaglaspis stonyensis gen. et sp. nov., is described from the Idamean (Upper Cambrian) of Stony Point, Montagu, north‐western Tasmania. The dorsal exoskeleton comprises a semicircular cephalon with a well‐defined marginal rim, acute genal angles, oval eyes, subtriangular glabella area and a subtrapezoidal hypostome. The trunk bears eleven somites with well‐developed pleural spines that progressively curve backwards. Paired postventral plates cover the last trunk tergites and the base of the tailspine, which is long and characterized by a medial cleft. Bilobed ventral impressions indicate the presence of homopodous appendages, forming a food groove along the trunk. The fossil assemblage and its mode of preservation suggest that Australaglaspis originally possessed a phosphatic cuticle, but chemical traces of it have been lost because of regional metamorphism and weathering. Australaglaspis appears to be closely related to the North American aglaspidid Chraspedops modesta Raasch, 1939, based on its medially cleft tailspine.     

新疆巴楚中奥陶统上部一间房组瓶筐石礁丘的演化意义

从建造时代和群落组成的角度,专论新疆巴楚地区一间房组瓶筐石礁丘的演化定位。瓶筐石作为群落的主体造礁始于早奥陶世早期,繁盛于早奥陶世晚期,中奥陶世开始趋于衰落。一间房组发育中小型点礁丘,除礁灰岩中常见的藻屑外,主要由瓶筐石并伴生少量石海绵共同形成礁格架岩。在群落组成上,一间房组的瓶筐礁丘与世界其它地区的瓶筐礁类似,但在建造时间上却显得极为特殊:中奥陶世晚期。这时,一个全新的群落——珊瑚—层孔海绵礁群落开始在世界其它地区起源,却全然不见于一间房组。一间房组的礁丘在时间上完全不吻合于早奥陶世的瓶筐石造礁事件,而是晚于此类礁繁盛期并滞后了约10Ma,是目前所发现这类礁群落在全球范围内的孓遗孤例,是承先而不启后的礁群落。