Fossiliferous Interval Research Articles

New rhynchonellid and spire-bearing brachiopods from the Carboniferous of Mexico. Paleogeographical significance of the Oaxacan brachiopod fauna through the Serpukhovian–Moscovian

AbstractThis work describes a rhynchonellid and spire-bearing brachiopod fauna from the Ixtaltepec Formation of Oaxaca, Mexico.Leiorhynchoidea perrilliatae,Allorhynchus scientiana, andAnthracospirifer oaxacaensisare new species. The specific determination, along with information of previously described taxa, allowed the establishment of precise relative ages of the different fossiliferous intervals (API-1 to API-8) of the formation. The occurrence of Serpukhovian taxa in API-1 to API-3 allowed assignment of the strata to the Upper Mississippian. The presence of Bashkirian species allowed the assignment of the rocks of API-5 and API-6 to the Lower Pennsylvanian. Likewise, Middle Pennsylvanian brachiopods in API-7 and API-8 enabled correlation of the strata with the Moscovian stage. This study shows that the Ixtaltepec Formation is represented by a succession of well-delimited Serpukhovian, Bashkirian, and Moscovian rocks. Regarding paleogeography, the brachiopod fauna displays clear taxonomic variations that concur with global geological changes that occurred between the Serpukhovian to Moscovian. In the Serpukhovian intervals, we recorded numerous cosmopolitan taxa of tropical waters, coinciding with the migration pathway of the Rheic Ocean. For the Bashkirian, we observed a North American provincialism; however, because of the presence of Australian and South American species, it is proposed that the Austropanthalassic-Rheic corridor had a close connection with Oaxaca. The main provincialism was observed in the Moscovian association because most of those taxa have been reported from different localities in the United States. This study supports that the main resemblance between Oaxacan and North American faunas continued until the Pennsylvanian and not the Mississippian, as was previously proposed.UUID:http://zoobank.org/181e49cf-a08a-4e99-8200-65f4a90dafcd

Evidence for microbially mediated silver enrichment in a middle Cambrian Burgess Shale-type deposit, Mackenzie Mountains, northwestern Canada

The Selwyn basin and Mackenzie platform of northwestern Canada house an array of mineral deposits and prospects that are rich in silver, including Neoproterozoic red-bed or Kupferschiefer-type Cu and lower Paleozoic sedimentary exhalative (SEDEX) and Zn–Pb deposits. Within this overall metallogenic setting, the middle Cambrian (Drumian) Rockslide Formation was deposited under a largely oxic water column on the platform-to-basin slope along the eastern side of the Selwyn basin. The formation includes an interval termed the Ravens Throat River Lagerstätte, which is a localized Burgess Shale-type calcareous mudstone about 2 m thick that preserves soft-bodied fossils. The mudstone contains comparatively large amounts of organic carbon preserved as thin carbonaceous laminae and discontinuous seams, representing benthic microbial mats, the remains of cyanobacteria and algae that were living in the water column, fecal pellets, large coprolites, and degraded animal tissues. The upper part of the Rockslide Formation, including the fossiliferous interval, contains elevated concentrations of Ag, up to 0.47 ppm. Some of the Ag in the mudstone occurs as aggregates of elemental particles ∼10 µm in size, preferentially on the carbonaceous material comprising the coprolites. This localized enrichment suggests bioaccumulation of Ag nanoparticles or Ag+ from the water column by microorganisms on the coprolites or degrading organic matter in them. The source of the Ag may have been from penecontemporaneous SEDEX metallogeny or from broadly related subsurface fluids in the Selwyn Basin that enriched the overlying seawater.

The macrofauna of the Vale House Flints Member (Burnham Chalk Formation, Upper Turonian, Late Cretaceous) of Lincolnshire and a palaeoenvironmental reconstruction

The Burnham Chalk Formation (Upper Cretaceous) in Lincolnshire is particularly well exposed at the large disused quarry at North Ormsby and, in north Lincolnshire, at the Ulceby Vale quarry. Biostratigraphical collecting by the author over a period of more than twenty years, in particular at North Ormsby, has yielded a large and varied fauna from the relatively fossiliferous interval between the Wootton Marls and the Ulceby Marl. This fauna is described herein, and is placed within the context of a reconstructed palaeoenvironmental setting.

RECORD OF KHURMALA FORMATION (LATE PALEOCENE – EARLY EOCENE) IN THE SULAIMANIAH GOVERNORATE, KURDISTAN REGION, NORTHEAST IRAQ

The present study focuses on the field, petrography and stratigraphic analyses of a thick and sparsely fossiliferous dolomitic limestone succession in the west, north, and northwest of Darbandikhan town from Sulaimaniah governorate. The succession thins toward northwest and east and located in the stratigraphic position of and Khurmala (or Sinjar) Formation (Late Paleocene – Early Eocene) between Kolosh and Gercus formations at the base and top respectively. The Khurmala Formation is a lagoonal crystallized limestone, dolomite with interbeds of different clastic rocks. It also contains an occasional occurrence of gypsum and rare gastropods, miliolids, and algae in some beds. Previous studies found the formation and described in Duhok, Kirkuk and Erbil Governorates while in Sulaimani area it not proved until now. The present article studied four different sections of succession (previously and indicated as Sinjar Formation) and correlated them stratigraphically with each other and with Khurmala Formation in its type section in the well K-114. The study showed that these sections belong to Khurmala Formation. The sections reveal many evidences and signs of the occurrence of Khurmala Formation in between Kolosh and Gercus formations. These signs are the occurrence of 160 m of dolomitic limestone (80%) with beds of sparsely fossiliferous limestone (18%) and conglomeratic limestone (2%) in Zawali section on Shameran Mountain. The fossiliferous intervals contain lagoonal sparse and small miliolids, gastropods, pelecypods green and red algae. The formation laterally changes to Kolosh (in Mirade section) or partly to Sinjar Formation (in Dara Rash section). In the Mirade section, neither Sinjar nor Khurmala Formation is deposited and yellow marly limestone, sandstone and few beds of conglomerate occupy their stratigraphic position.

New biostratigraphic and chemostratigraphic data from the Ediacaran Doushantuo Formation in intra-shelf and upper slope facies of the Yangtze platform: Implications for biozonation of acanthomorphic acritarchs in South China

Carbon isotopic and microfossil records of the Doushantuo Formation in South China provide a valuable window onto major perturbations of the Ediacaran carbon cycle and the evolution of morphologically complex acanthomorphic acritarchs. Both records exhibit significant geographic heterogeneity related to environmental, taphonomic, and diagenetic variations. Absolute δ13Ccarb values vary by as much as 10‰ between sections of the Doushantuo Formation. The geographic and stratigraphic distribution of microfossils in the Doushantuo Formation is controlled by the occurrence of early diagenetic cherts and phosphorites that preserve microfossils. Early diagenetic cherts of the Doushantuo Formation have been investigated extensively at intra-shelf sections around the Huangling anticline but have been poorly documented elsewhere in South China. Here we present new petrographic and micropaleontological data from three Doushantuo sections to the south of the Huangling anticline, including the Wangzishi and Huangjiaping sections representing intra-shelf settings, as well as the Siduping section representing an upper slope setting. We also present δ13Ccarb data from Wangzishi. Petrographic observations indicate that some chert nodules at Siduping were formed in situ, whereas others were reworked and probably transported from the outer shelf along with olistostromes. Integrated lithostratigraphic and chemostratigraphic correlations suggest that the fossiliferous intervals at the three studied sections belong to the lower Doushantuo Formation. The new micropaleontological data extend the geographic range of Ediacaran acanthomorphs and suggest that elements of the Tanarium conoideum–Hocosphaeridium scaberfacium–Hocosphaeridium anozos biozone recognized in the upper Doushantuo Formation around the Huangling anticline, specifically Hocosphaeridium anozos and Urasphaera nupta, are also present in the lower Doushantuo Formation at the Siduping section. The data suggest that the first appearance of Hocosphaeridium anozos may be in the δ13Ccarb chemostratigraphic feature EP1 and it is necessary to revise the acritarch biozonation developed in the Yangtze Gorges area. This study highlights the importance of integrating δ13Ccarb chemostratigraphic and acritarch biostratigraphic data from multiple facies to develop Ediacaran acanthomorph biozonation in South China and beyond.

Carboniferous postglacial faunas in the late Serpukhovian–Bashkirian interval of central-western Argentina

Cisterna, G.A., Sterren, A.F., López Gamundí, O. & Vergel, M.M., March 2017. Carboniferous postglacial faunas in the late Serpukhovian–Bashkirian interval of central-western Argentina. Alcheringa, ISSN 0311-5518.Typical glacial–postglacial sequences associated with the Late Palaeozoic Ice Age (LPIA) are recognized in the Calingasta-Uspallata Basin, central-western Argentina, particularly in the Hoyada Verde and El Paso formations (late Serpukhovian–Bashkirian) at Barreal Hill (San Juan province). Brachiopods and bivalves accompanied by gastropods, conulariids, nautiloids, corals and ostracods constitute the marine assemblages of the El Paso Formation. They are assigned to the Aseptella–Tuberculatella/Rhipidomella–Micraphelia (AT/RM) fauna, characterized by two fossil assemblages: Aseptella–Tuberculatella, identified in the lower fossiliferous interval, and Rhipidomella–Micraphelia in the upper. The development of the different invertebrate assemblages within the El Paso Formation, and their relationship with coeval suite in the Hoyada Verde Formation, can be explained by a complex array of abiotic factors (substrate stability, turbidity, nutrient availability, variation in oxygen levels, poor circulation and salinity variations in the water column) that were directly related to glacial retreat dynamics and coastal configuration. A restricted palaeofjord setting is proposed for the depositional environment of the El Paso Formation in contrast to an exposed open marine coast with a gently sloping shelf for the Hoyada Verde Formation. The study of the postglacial fauna of the El Paso Formation and its relationship with the Levipustula fauna in the Calingasta-Uspallata Basin, help determine the main controls on the distribution of the postglacial faunas in other late Palaeozoic South American basins, such as the Tepuel Genoa Basin in Patagonia and the Tarija Basin in Bolivia.Gabriela A. Cisterna [gabrielacisterna@conicet.gov.ar], CONICET-UNLAR, Av. Dr. Luis M. de la Fuente s/n, La Rioja, 5300, Argentina; Andrea F. Sterren [asterren@unc.edu.ar], CICTERRA (CONICET – Universidad Nacional de Córdoba), Av. Vélez Sarsfield 1611, X5016GCA, Córdoba, Argentina; Oscar López Gamundí [orlg2003@yahoo.com], P1C Consultants 1121 Banks Street, Houston, TX 77006, USA; María del Milagro Vergel [vergelmar@tucbbs.com.ar], CONICET – INSUGEO – Facultad de Ciencias Naturales e Instituo Miguel Lillo (UNT), Miguel Lillo 205, 4000, San Miguel de Tucumán, Argentina.

Paleoecology and paleoenvironment of the Middle–Upper Jurassic sedimentary succession, central Saudi Arabia

Four Middle–Upper Jurassic sections from central Saudi Arabia have been investigated to evaluate microfacies types and macro-invertebrate paleocommunities and to interpret their paleoecology and paleoenvironments. The studied Jurassic successions are part of the Middle–Upper Callovian Tuwaiq Mountain Limestone and the Middle–Upper Oxfordian Hanifa Formation. Three main facies were recorded, including mud-supported microfacies, grain-supported microfacies and boundstones. A data matrix comprising 48 macrobenthic species in 35 samples collected from four sections were grouped into fifteen assemblages and one poorly fossiliferous interval by means of a Q-mode cluster analysis. The recorded macrofaunal assemblages have been subdivided into low-stress and high-stress on the basis of hydrodynamic conditions, substrate type, nutrient supply and hypoxia. The low-stress assemblages occur in (a) high-energy paleoenvironments with firm substrates; (b) high-energy shoals with unstable substrates of low cohesion and in (c) low-energy open marine environments with soft-substrates. The moderate- to high-stress assemblages occur in (a) oligotrophic environments with reduced terrigenous input in shelf lagoonal or in restricted inner ramp settings; (b) low-energy, soft substrate environments with hypoxia below the sediment–water interface; and, in (c) high-energy shoals and shelf lagoonal environments. The temporal distribution patterns of epifaunal and infaunal bivalve taxa are controlled by variations in water energy, substrate characteristics and productivity level. The reported litho- and biofacies confirmed that the Callovian Tuwaiq Mountain Limestone and the Oxfordian Hanifa Formation were deposited across wide spectrum of depositional environments, ranging from restricted lagoon to moderately deeper open marine basin, and providing the perfect conditions for macrofossils.

A genetic link between Konzentrat- and Konservat-Lagerstätten in the Fezouata Shale (Lower Ordovician, Morocco)

In the central Anti-Atlas (Morocco; Zagora region), the Fezouata Shale has yielded an extraordinary fossil Lagerstätte documenting the initial stages of the Great Ordovician Biodiversification Event. This Lagerstätte contains abundant and exceptionally well-preserved fossils (EPF) exhibiting soft-bodied preservation as well as “hard”, mineralized parts of extinct organisms. While soft-bodied preservation in the Fezouata Shale is confined to a few stratigraphic intervals, other fossiliferous intervals contain only shelly fossils in sandstone lenses (SL).Placed in the context of a previously established depositional model, EPF are interpreted as autochthonous assemblages buried by storm deposits, close to storm wave-base. There, the current component of storms is reduced compared to proximal settings and weak oscillation is dominant resulting in the record of oscillation ripples. In contrast, bioclastic accumulations were generated upslope in shallower, more proximal lower shoreface environments. There, the current component of storms was significant, as suggested by the disarticulation of skeletal remains. Bioclastic materials are localized in SL, which are lenses a few tens of centimeters in thickness and a few meters in width and length. These lenses commonly display erosive bases and convex tops, resulting in a lobate or a channel-lobe morphology. A large amount of sediment was thus rapidly deposited, resulting in the rapid burial of allochthonous material across a strongly localized surface of the sea floor.Integrating both sedimentological and paleontological evidence, intervals yielding EPF are considered as Konservat-Lagerstätten (KsL), in contrast with bioclastic accumulations defined as Konzentrat-Lagerstätten (KzL). Thus, KsL assemblages are interpreted to approximate biocenoses, in which organisms experienced rapid burial by distal tempestites, while KzL assemblages more likely correspond to thanatocenoses, locally deposited by storm back-currents. Here, a genetic link between KsL and KzL is suggested within the Fezouata Shale. Both types of Lagerstätten were related to storm activity, but at different depths.

Rugose corals at the Devonian-Carboniferous Boundary in NW Turkey

An uppermost Famennian (Strunian) coral assemblage has been recovered in the middle part of the Yilanli Formation of the Istanbul Zone (Zonguldak and Bartin areas, NW Turkey). In the Bartin area, the studied fossiliferous interval corresponds to a c. 30 m-thick unit of bioclastic to peloidal wackestone to packstone grading to grainstone and including two stromatoporoid biostromes. In the Zonguldak area, 60 km westward, the bioclastic facies is dominant. The rugose corals are mainly solitary taxa belonging to the genera Campophyllum, Bounophyllum, Amplexocarinia, and ?Metriophyllum, and only one colonial genus occurs: Pseudoendophyllum. This fauna is similar to that documented in Europe. The campophyllids and dibunophyllids are the main component of the uppermost Famennian assemblages in S Belgium, N France, W Germany, NW and S Poland. The endophyllids occur in S Poland, Novaya Zemlya, and in the Ural Mountains. The Istanbul Zone is supposed to be situated in the central part of the Palaeotethys Ocean, alo...

ANNULATA EVENT Z PROFILU V JÁMOVÉM LŮMKU U OCHOZI U BRNA – POZNÁMKY KE KONODONTOVÉ BIOSTRATIGRAFII (FAMEN, MORAVSKÝ KRAS)

About two meters thick section of the Famennian Křtiny Limestones (Líšeň Formation) was studied in a small pit-quarry near the road leading from Brno-Líšeň to Ochoz u Brna. Conodont samples were taken from seven diff erent stratigraphical levels. A richly fossiliferous interval (about 40 cm thick) can be distinguished in the higher part of the section. This interval is characterized by abundant occurence of clymenids, bivalves, orthocone nautiloids, trilobites and other groups. Black limestone lenses (maximal thickness about 10 cm) are developed in the lowermost part of the richly fossiliferous interval. A presence of Palmatolepis glabra lepta (late morphotype), Palmatolepis minuta minuta and Palmatolepis rugosa trachytera suggests these black limestones probably represent the Lower Annulata event (Upper Palmatolepis rugosa trachytera zone). Polygnathus styriacus indicating the base of the Palmatolepis perlobata postera zone enters within about 10 centimeters thick interval of dark grey biodetritic limestones which occur closely above the black limestone lenses. The Upper Annulata event and equivalents of „Wagnerbank“ or „Annulata limestone“ were not distinguished in the studied section. This might be caused by condensed sedimentation. Grey limestones and marly limestones belonging to the higher part of the richly fossiliferous interval are placed above the base of the Palmatolepis perlobata postera zone. The studied locality might correspond to the original fossil site described by Rzehak in 1910.

Biostratigraphy and depositional environment of the sediments in Borno Basin, North Eastern Nigeria

A biostratigraphic study was carried out on 83 drill cutting samples retrieved from Kemar-1 well, Borno Basin, northeastern Nigeria. They were subjected to palynological and foraminiferal analyses to determine their biozonation, age and depositional paleoenvironments. The studied intervals ranged between 600 and 1745 metres and were sampled at 30- and 20-metre intervals for the palynological and foraminiferal analyses respectively. Lithologically, the drill cutting samples are made up mainly of predominantly grey to dark grey shale, sandy mudstone and silty mudstone. An igneous rock with argillaceous sandstone and argillaceous siltstone intercalations was also observed. Three major palynological assemblage zones were recognised in the study area. They are Cretacaeiporites scabratus/mulleri Assemblage Zone, which correlates with the basal sequence, Droseridites senonicus Assemblage Zone, and Proteacidites dehaani/Dinogymnium euclaense Assemblage Zone of the well section’s upper part. Also, two foraminiferal biosequences were established for the studied interval. The environment of deposition of the well was generally shallow. It ranges from Coastal Deltaic in the upper part through Fluviomarine to Shallow Inner Neritic in the lower part of the Fika ‘Shale’ Formation. The age of the fossiliferous interval of the studied section of the well ranges from Early Turonian at the base to Early Campanian at the top. Three unconformities were observed and mapped within the studied section of the well at 790m, 1300m and 1700m. The unconformities were marked by noticeable faunal discontinuities, associated with reduction in paleowater depth and abrupt shift in the environment of deposition. Biostratigraphy is a valuable tool in oil and gas exploration when it is integrated with other geological and geophysical data sets, such as outcrops, seismic lines or well logs. This paper constitutes a significant contribution to the understanding of the biostratigraphy of Borno Basin, which is currently the focus of intensive hydrocarbon exploration activities. Keywords: Biostratigraphy, Depositional environments, Bornu Basin, Fika “Shale” Formation, Turonian

Biostratigraphy and Depositional Environment of the Sediments in Borno Basin, North Eastern Nigeria

A biostratigraphic study was carried out on 83 drill cutting samples retrieved from Kemar-1 well, Borno Basin, northeastern Nigeria. They were subjected to palynological and foraminiferal analyses to determine their biozonation, age and depositional paleoenvironments. The studied intervals ranged between 600 and 1745 metres and were sampled at 30- and 20-metre intervals for the palynological and foraminiferal analyses respectively. Lithologically, the drill cutting samples are made up mainly of predominantly grey to dark grey shale, sandy mudstone and silty mudstone. An igneous rock with argillaceous sandstone and argillaceous siltstone intercalations was also observed. Three major palynological assemblage zones were recognised in the study area. They are Cretacaeiporites scabratus/mulleri Assemblage Zone, which correlates with the basal sequence, Droseridites senonicus Assemblage Zone, and Proteacidites dehaani/Dinogymnium euclaense Assemblage Zone of the well section's upper part. Also, two foraminiferal biosequences were established for the studied interval. The environment of deposition of the well was generally shallow. It ranges from Coastal Deltaic in the upper part through Fluviomarine to Shallow Inner Neritic in the lower part of the Fika 'Shale' Formation. The age of the fossiliferous interval of the studied section of the well ranges from Early Turonian at the base to Early Campanian at the top. Three unconformities were observed and mapped within the studied section of the well at 790m, 1300m and 1700m. The unconformities were marked by noticeable faunal discontinuities, associated with reduction in paleowater depth and abrupt shift in the environment of deposition. Biostratigraphy is a valuable tool in oil and gas exploration when it is integrated with other geological and geophysical data sets, such as outcrops, seismic lines or well logs. This paper constitutes a significant contribution to the understanding of the biostratigraphy of Borno Basin, which is currently the focus of intensive hydrocarbon exploration activities.

Palynological, palynofacies, paleoenvironmental and organic geochemical studies on the Upper Cretaceous succession of the GPTSW-7 well, North Western Desert, Egypt

The present study of the Abu Roash and Bahariya formations in well GPTSW-7 refines our understanding of the subsurface Cretaceous of the north Western Desert of Egypt. Our investigations are based on the palynological analyses of 71 cuttings samples, of which 24 have also been analyzed for geochemistry, in addition to 3 sidewall cores analyzed for vitrinite reflectance ( R o). Four palynological zones and three subzones in addition to a poorly fossiliferous interval ranging in age from Coniacian–Santonian to early Cenomanian are proposed. These include a poorly fossiliferous interval (Coniacian–Santonian), Dinogymnium vozzhennikovae Interval Zone (late to middle Turonian), Ephedripites ambiguus– Ephedripites multicostatus– Foveotricolpites giganteus– Foveotricolpites gigantoreticultus Assemblage Zone (early Turonian), Classopollis brasiliensis Interval Zone (late to middle Cenomanian), and Afropollis jardinus Interval Zone (early Cenomanian). The succeeding subzones are; Afropollis kahramanensis Interval Subzone, Elaterosporites klaszii Interval Subzone and Cretacaeiporites densimurus Interval Subzone, all of early Cenomanian age. Total organic carbon (TOC) and Rock–Eval pyrolysis and palynofacies analyses indicate that the Bahariya Formation and the Abu Roash G Member are primarily of kerogen III type and hence gas prone, suggesting a strong influence of hydrogen-enriched organic matter. The Abu Roash A, C–E Members may also be gas prone (type III kerogen) and appear to contain highly oxidized terrestrial organic matter. In contrast, the Abu Roash F Member has very high TOC and HI values and contains a very high proportion of amorphous organic matter (AOM) indicating a highly oil-prone facies. While this finding is not unexpected for anoxic black shale, it contrasts with earlier studies that suggest a gas prone nature. R o measurements show that the Bahariya Formation represents an immature-early genesis dry gas phase. This is also true for all investigated samples from the Abu Roash and Bahariya formations, based on their low thermal alteration index (TAI). Quantitative and qualitative analyses of both the palynoflora and palynofacies show that the Abu Roash A and C Members (B is missing), both of Coniacian–Santonian age, represent oxic proximal and distal shelf environment. The Abu Roash D and E Members, dated as Turonian, represent oxic (proximal) shelf, whereas the Cenomanian Abu Roash F Member was deposited in a distal suboxic–anoxic basin. The Cenomanian Abu Roash G Member and the Bahariya Formation were deposited in a shallow marine and shallow marine to fluvio-deltaic setting, respectively. The Senonian Palmae Province is recognized in the palynoflora by the presence of Proteacidites, Auriculiidites reticulatus, Ariadnaesporites, Gabonisporis vigourouxii. On the other hand the Albian–Cenomanian Elaterates Province is characterized by the presence of Steevesipollenites, Gnetaceaepollenites, Elaterocolpites, Elaterosporites, Elateroplicites, Senegalosporites, Sofrepites, Afropollis and Cretacaeiporites.

Reinterpretation of ‘Middle’ Cambrian stratigraphy of the rifted western Laurentian margin: Burgess Shale Formation and contiguous units (Sauk II megasequence), Rocky Mountains, Canada

Until recently, research on the renowned fossil animals of the Burgess Shale has advanced to a greater degree than an understanding of the rocks in which they are found. Studies addressing lithostratigraphy and hydrothermal petrography of the so-called ‘inner carbonate belt’ and adjacent Chancellor Group, however, have begun to re-evaluate long-standing hypotheses on the Middle Cambrian of Western Canada. Tectonic activity along the Kicking Horse Rim (buried remnants of Neoproterozoic rifting) during the Cambrian Period had more influence on local sedimentation than previously thought. Notably, large-scale collapse of the Cathedral carbonate platform margin at ∼ 509 Ma BP is evidence of reactivated basement faults. These failures produced listric Megatruncation Surfaces, having near vertical escarpments (> 150 m in height) where they terminate against the platform. The majority of what have been interpreted as shed olistoliths from the Cathedral platform margin is herein shown instead to be carbonate mud mounds. These grew in situ along the face of the Cathedral Escarpment, and are associated with fossiliferous intervals in overlying basinal mudstones at three distinct stratigraphic horizons (two within the Burgess Shale) during the Delamaran and Marjuman stages. The mounds nucleated where deep-seated normal faults intersected the seafloor, building primarily during periods of relative sea level transgression. Mound growth is associated with syndepositional exhalative activity, inferred from stratigraphic relations, sedimentology, and geochemistry. The new name Monarch Formation is proposed for the initial post-collapse beds and mounds deposited against the Cathedral Escarpment (early Glossopleura Zone); the variably-defined term ‘Takakkaw Tongue’ is thereby confined to pre-collapse slope deposits coeval to and correlative with the Cathedral Formation.

Epeirogenic transgression near a triple junction: the oldest (latest early–middle Cambrian) marine onlap of cratonic New York and Quebec

AbstractThe discovery of a fossiliferous interval (Altona Formation, new unit) under the Potsdam Formation requires a new geological synthesis of a large part of the northeast Laurentian craton. Potsdam sandstones can no longer be regarded as the oldest sedimentary unit on the middle Proterozoic Grenville orogen in northern New York and adjacent Quebec and Ontario. The thickest Potsdam sections (to 750 m) in the east Ottawa–Bonnechere aulocogen have been explained by deposition with normal faulting possibly associated with Ediacaran rifting (c. 570 Ma) that led to formation of the Iapetus Ocean. However, sparse trilobite faunas show a terminal early Cambrian–middle middle Cambrian age of the Altona, and indicate much later marine transgression (c. 510 Ma) of the northeast Laurentian craton. Altona deposition was followed by rapid accumulation of lower Potsdam (Ausable Member) sandstone in the middle–late middle Cambrian. The Altona–Ausable succession is probably conformable. The Altona is a lower transgressive systems tract unit deposited on the inner shelf (sandstone, reddish mudstone, and carbonates) followed by aggradation and the deposition of highstand systems tract, current cross-bedded, in part terrestrial(?), feldspathic Ausable sandstone. Unexpectedly late Altona transgression and rapid Ausable deposition may reflect renewed subsidence in the Ottawa–Bonnechere aulocogen with coeval (terminal early Cambrian) faulting that formed the anoxic Franklin Basin on the Vermont platform. Thus, the oldest cover units on the northeast New York–Quebec craton record late stages in a cooling history near an Ediacaran triple junction defined by the Quebec Reentrant and New York Promontory and the Ottawa–Bonnechere aulocogen.

Palynology of late Palaeozoic sediments (Tupe Formation) at La Herradura Creek, San Juan province, Argentina

Vergel, M., December, 2008. Palynology of late Palaeozoic sediments (Tupe Formation) at La Herradura Creek, San Juan province, Argentina. Alcheringa 32, 339–352. ISSN 0311-5518. Palynomorph assemblages recovered from the Tupe Formation at La Herradura Creek, San Juan province, Argentina, are analysed. The middle section of the sequence includes a marine fossiliferous interval belonging to the Tivertonia jachalensis–Streptorhynchus inaequiornatus (T–S) Faunal Biozone, recently ascribed an Early Permian age. The section below the marine fossiliferous unit yielded palynofloras typical of previously described ‘Tupense’ assemblages. The palynoflora recovered from beds above the marine horizon is diverse, relatively well preserved and includes species never recorded from the Tupe Formation. This latter palynoassemblage includes species diagnostic of Early Permian palynofloras such as Converrucosisporites confluens (Archangelsky & Gamerro) Playford & Dino, Pseudoreticulatispora pseudoreticulata (Balme & Hennelly) Bharadwaj & Srivastava, Horriditriletes ramosus (Balme & Hennelly) Bharadwaj & Salujha, Anapiculatisporites tereteangulatus (Balme & Hennelly) Playford & Dino, Laevigatosporites colliensis (Balme & Hennelly) Venkatachala & Kar, Marsupipollenites triradiatus Balme & Hennelly, Protohaploxypinus sewardii (Virkki) Hart and Pakhapites fusus (Bose & Kar) Menéndez. Correlations with assemblages from western Argentina and other Gondwanan regions suggest an Early Permian age (not older than Asselian–Sakmarian) for the upper part of the sequence, supporting the age attributed to the T–S Biozone.

Discussion on palaeoecology of the Late Triassic extinction event in the SW UK Journal , Vol. 165, 2008, pp. 319–332

Jonathan Radley writes: The Penarth Group (of Late Triassic and possibly ranging to Early Jurassic age) of the southern UK marks a marine transgression and the establishment of a shallow epicontinental seaway (Hallam & El Shaarawy 1982; Warrington & Ivimey-Cook 1992), influenced by regressive–transgressive pulses and characterized by rapid facies changes (Hallam & Wignall 2004; Hesselbo et al . 2004). A well-documented invertebrate macrofauna includes corals, brachiopods, molluscs and echinoderms (Swift & Martill 1999). Facies developments range from storm-influenced, shallow-marine mudrocks (Westbury Formation) upwards into calcareous mudstones, siltstones and essentially fine-grained carbonates (Lilstock Formation) demonstrating extremely shallow-water conditions: wave ripples, storm beds, desiccation and omission surfaces (Swift 1999 a ; Wignall 2001; Hallam & Wignall 2004). The low-diversity macrofauna of the Lilstock Formation has frequently been attributed to salinities deviating from that of normal seawater within shallow-water, partly landlocked settings, isolated from the open sea (Hallam & El Shaarawy 1982; Swift 1995; Allison & Wright 2005). However, widespread occurrences of stenohaline marine macrofossils such as corals and echinoderms (Swift & Martill 1999) suggest that salinity fluctuations were at most slight (Wignall 2001). Mander et al . (2008) have presented high-resolution benthic macrofaunal data, principally from molluscan macrofossils, for significant palaeoecological change within the Penarth Group of two key sections in the SW UK. Their detailed results demonstrate loss of taxonomic richness within the uppermost Westbury Formation–lower Lilstock Formation (Cotham Member) interval (latest Rhaetian), followed by a poorly fossiliferous interval represented by the latest Rhaetian or early Hettangian upper Lilstock Formation (upper Cotham Member–lower Langport Member). They attributed this pattern to an extinction event followed by a post-extinction ‘Dead Zone’; the latter coinciding with the onset of a negative organic carbon-isotope excursion, and an extinction event recorded in the terrestrial palynoflora. The relatively diverse shelly …

Late Vendian Miaohe-type ecological assemblage of the east European platform

Upper Vendian rocks of the East European Platform (EEP) are characterized by the presence of the White Sea fossil biota, which colonized the region from the southeastern White Sea area to the Central Urals [1]. The White Sea biota includes ecological assemblages of the Avalon (Newfoundland), Ediacara (South Australia), and Nama (Namibia) types, each related to certain environmental conditions [2]. In 2006, we found a previously unknown and morphologically diverse assemblage of carbonaceous macroscopic fossils in the fine-grained aluminosiliciclastic rocks of the Perevalok Formation (Sylvitsa Group) in the Central Urals. Together with the organic-walled macrofossils from the rocks of the Lyamtsa Formation (Valdai Group) in the southeastern White Sea area, the carbonaceous fossils from the Perevalok Formation represent a new (fourth) ecological assemblage of the White Sea fossil biota. The ecological assemblage is older than 557‐558 Ma [3, 4] and includes macroscopic microbial colonies, multicellular and coenocytic eukaryotic macroalgae. In the Late Vendian history of the EEP, this assemblage predated the appearance of the world’s most diverse soft-bodied assemblage, which was found in the overlying rocks of the White Sea area (Verkhovka and Erga formations) and Central Urals (Chernokamen Formation) [1, 2, 5]. The carbonaceous fossils are confined to a thick (200‐400 m) transgressive sequence at the base of the Upper Vendian succession in the southeastern White Sea area and Central Urals (Fig. 1). The lower part of the sequence (laminated mudstones with layers of volcanic tuffs) is gradually replaced upsection by thinly interbedded siltstones and mudstones with rare layers of wave-bedded sandstones. The sequence was formed by the advance and periodic retreat of storm-dominated coastal depositional setting into subaqueous muddy planes with relatively quiet sedimentation in the course of oscillating wane in transgression. Fossiliferous intervals contain thin laminae of phosphorites and organic matter and mark the peak of shallow-water transgression over the platform. In the southeastern White Sea area, this sequence correlates with the Lyamtsa Formation and lower part of the Verkhovka Formation; in the Central Urals, with the upper part of the Staropechny and Perevalok formations [6, 7] (Fig. 1).

The problem with the Paleozoic

Unfossiliferous marine sedimentary rocks of Phanerozoic age are known to all field-oriented paleontologists. These troublesome units are often encountered in the field, perhaps cursed roundly for a moment or two, and usually shrugged off in pursuit of the next fossiliferous interval. Paleontologists tend not to discuss barren units, and they rarely publish on the absence of a fauna from what appears to be unaltered marine rock. But aren't barren marine sediments revealing something important about their paleoenvironment and possibly about the paleoenvironments of conformably adjacent fossil-bearing units? Shouldn't paleontologists be just as interested in knowing the locations and ages of unfossiliferous sediments as they are fossiliferous strata?

Paleoenvironment of an Early Devonian Land-Sea Transition: a Case Study from the Southern Margin of the Old Red Continent (Mosel Valley, Germany)

An interdisciplinary approach was used to investigate the facies and paleogeography of the Lower Devonian sedimentary sequence of the Alken quarry, Mosel Valley, Germany. This 87-m-thick sequence consists of stratified sandstones and sandy shales of the Nellenkopfchen Formation (uppermost Lower Emsian). Previous interpretations of the depositional environment include terrestrial, deltaic, and shallow-marine settings. Two distinct fossiliferous units contain abundant terrestrial plant remains and a diverse mixed terrestrial to marine fauna. Physical sedimentary structures are common throughout, whereas bioturbation is restricted mostly to the fossiliferous intervals. Erosional surfaces frequently separate the beds. Aside from ripple cross-stratification and parallel bedding, longitudinal inclined stratification is most common. Channel-fill structures are less frequent. Scour-and-fill structures exhibit marked disconformities of irregular shape on a smaller scale (dm). Mud-pebble lags at the base of laterally prograding cross-bedded layers, scour-and-fill structures, and drainage rills characterize the upper part of the section. Desiccation cracks, wind-induced striation, and water-level marks occur more sporadically in the exposure. The sedimentary structures and the paleontological information indicate a marine to brackish depositional environment that frequently was emergent. The presence of conspicuous channel-related structures reflects intertidal conditions along the coastal region of a presumed Hunsruck Island/Archipelago. Lagoons and estuaries were bordered by extended tidal flats, in which migrating channels frequently occurred. Terrestrial plant remains, however, indicate a position at the land/sea interface, which was characterized by a complex configuration of different environments. The accumulation of concentrated plant material may have been related to distinct meteorological events such as hurricanes.