Turbidite Deposits Research Articles

Turbidite lobe deposits in a canyon-fill system

Geological feature: Turbidite lobe deposits in a canyon-fill system Seismic appearance: Isolated and irregularly shaped sandstone pods Alternative interpretations: Mid-channel bars in a braided channel system Features with similar appearance: Alluvial fans Formation: Lower Wilcox Group Age: Late Paleocene to Early Eocene Location: Shelf edge at the Central Gulf Coast Region of Texas Seismic data: Donated by a petroleum exploration company in Houston, Texas Analysis tools: Seismic attributes such as instantaneous phase, root-mean-square amplitude, and spectral decomposition

Challenges in the Petrophysical and Dynamic Characterization of Deepwater Turbidite Deposits of the Colombian Caribbean Offshore–A Case Study

The Colombian Caribbean region has become an important exploratory target, and recent discoveries confirm its potential as a gas province to overcome the expected near-future gas deficit. A petrophysical and dynamic characterization workflow was implemented for this challenging deepwater play, where the depositional environment is the result of turbidity current processes. The reservoirs consist mostly of thin to very thin sand layers, corresponding mainly to the Ta, Tb, and Tc divisions of the Bouma sequence as observed in the cored intervals. Bouma divisions Td and Te are related with the lowest rock quality and represent the nonreservoir intervals. The greatest challenge in the characterization of this particular reservoir is the vertical resolution, given the very low thickness of the layers, which becomes very difficult to detect using standard resolution logs. Thus, tomography images, resultant CT-scan curves, and their integration with routine and special core analyses were used to reveal the true nature of this complex reservoir. The proposed methodology focuses on the integration of routine and special core analysis for the petrophysical and dynamic characterization of the reservoir, where the pore-throat-radius distribution from high-pressure mercury injection becomes the basis of the differentiation between what is considered reservoir and what is not. Pore-throat radius estimated from high-pressure mercury injection (R35) correlates extremely well with textural features and clay content in the rock; therefore, this parameter (R35) was used to define the different classes for rock typing. The approach taken was to develop a multilinear regression model of R35 as a function of very high-resolution tomography outputs in the cored zones and then see how it may be extrapolated to the uncored zones using available high-resolution logs. Special petrophysical analyses, such as NMR low field, porous-plate capillary pressure, electrical properties, and relative permeability curves (steady state), showed correlation with the defined rock types and, in turn, allowed for a determination of the gas accumulation potential of the area. Finally, rock and fluid (dry-gas) properties have been used to build a single-well radial model to design initial well tests (DST) and predict production performance from each interval (selective tests). The simulation model represents the lateral and vertical heterogeneity related to the geological environment (turbidites). The final results have defined the flow and shut-in times during tests to optimize the budget.

Structural styles, deformation, and uplift of the Olympic Mountains, Washington: Implications for accretionary wedge deformation

Abstract The Olympic subduction complex is the exposed subaerial Cascadia accretionary wedge in the Olympic Mountains of Washington State. Uplift of the mountains has been attributed to two competing models: margin-normal deformation from frontal accretion and underplating, and margin-parallel deformation from the clockwise rotation and northward movement of the Oregon Coast Range block compressing the Olympic Mountains block against the Canadian Coast Range. East-northeast–oriented folds and Quaternary thrust faults and paleostress analysis of faults in the Coastal Olympic subduction complex, west of the subduction complex massif, provide new evidence for north-south shortening in the Coastal Olympic subduction complex that fills a large spatial gap in the north-south shortening documented in prior studies, substantially strengthening the block rotation model. These new data, together with previous studies that document north-south shortening in the subduction complex and at numerous locations in the Coast Range terrane peripheral to the complex, indicate that margin-parallel deformation of the Cascadia forearc has contributed significantly to uplift of the Olympic Mountains. Coastal Olympic subduction complex shallow-level fold structural style and deformation mechanisms provide a template for analyzing folding processes in other accretionary wedges. Similar-shaped folds in shallow-level Miocene turbidite sediments of the Coastal Olympic subduction complex formed in two shortening phases not previously recognized in accretionary wedges. Folds began forming by bed-parallel flow of sediment into developing hinges. When the strata could no longer accommodate shortening by flexural flow, further shortening was taken up by flexural slip. Similar-shaped folds in the deeper accretionary wedge rocks of the subduction complex massif have a well-developed axial-surface cleavage that facilitated shear folding with sediment moving parallel to the axial surface into the hinges, a structural style that is common to accretionary wedges. The pressure-temperature conditions and depth at which the formation of similar folds transitions from bed-parallel to axial-surface–parallel deformation are bracketed.

Oblique plate collision and orogenic translation of the Southern Apennines revealed by post-Messinian interregional unconformities in the Bradano Basin (Ionian Sea - Central Mediterranean)

The Bradano Basin is a foreland basin along the Africa/Eurasia plate boundary. Due to its location and physiography, between Southern Apennines (SA) and Calabrian Arc (CA), it represents a natural recorder of Plio-Pleistocene tectonic processes. Integrated analysis of seismic reflection data, exploration well logs and seafloor bathymetry allowed us to unravel the basin architecture and the interplay between tectonics and sedimentation, providing stratigraphic and structural evidences on deep processes and shallow morpho-structural development. It results, that the post-Messinian tectonic evolution on this area is marked by two major tectonic events, whose effects are recorded in four sedimentary sequences bounded by interregional unconformities. During Pliocene times, an obliquely convergent margin led to collision between SA and CA, associated with shelf to deep marine turbiditic deposits. Around the Pliocene-Pleistocene boundary (2.58 Ma), a sudden and widespread rearrangement took place. The SA front, along with portions of the earlier obliquely collisional margin, started to move toward the NE, along progressively deeper detachments involving the lower Apulia plate. During this phase, a fast (3.8–8.3 cm/yr) ~50 km translation of the orogenic wedge was followed by uplift and slow-rate shortening (1.9 mm/year), associated with seafloor folding. This second phase is marked by deep marine deposits in the central part of the basin, and clinoforms in shallower western and northern sectors. Our data suggest that no oceanic crust is presently subducting below the Bradano Basin, although we cannot exclude that a narrow sliver of oceanic lithosphere was subducted before and/or during Pliocene times. The complex deformation pattern observed, represents the response to the interaction of (small-) plates, which is still active and important to be considered in neotectonics and paleoseismological reconstructions.

Calibrating the marine turbidite palaeoseismometer using the 2016 Kaikōura earthquake

Turbidite palaeoseismology has produced arguably the most comprehensive multimillennial scale records of subduction-zone earthquakes but is underpinned by techniques that are vigorously debated in earthquake science. Resolving this argument requires new direct observations that test the approach’s essential assumptions. Here we present measurements from turbidites triggered by the 2016 Mw 7.8 Kaikōura earthquake in New Zealand, one of the most well-instrumented earthquakes in history. This natural experiment provides an ideal test for turbidite palaeoseismology because fault source, ground motions and turbidite deposition in discrete canyons are well-resolved by analysis of sediment cores combined with physics-based ground-motion modelling. We find that the Kaikōura earthquake triggered flows in ten consecutive canyon–distributary systems along a 200 km segment of the Hikurangi subduction margin where long-period (>2 s) peak ground velocities exceeded turbidity-current-triggering thresholds between 16–25 cm s−1. Comparison between ground motions and turbidite deposition confirm that there is a predictable relationship between earthquake source, ground motions and deposition of coseismic turbidites. We demonstrate that the patterns of triggering and resultant turbidite character may preserve evidence of fault-rupture direction along with the radiating patterns and amplification of earthquake ground motions. Marine turbidite deposition is confirmed to relate to earthquake ground motions by an analysis of turbidite deposits and simulations of ground motions from the 2016 Kaikōura earthquake.

Active fault segments along the North Anatolian Fault system in the Sea of Marmara: implication for seismic hazard

A new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara region to formulate reliable seismic hazard scenarios.

Significance of biozone correlation in understanding the Cretaceous–Paleogene transition and its associated turbidite deposits in the Northern Delta, Niger Delta Basin

Significance of biozone correlation in understanding the Cretaceous–Paleogene transition and its associated turbidite deposits in the Northern Delta, Niger Delta Basin

Dinoflagellate cyst biostratigraphy of Upper Cretaceous turbiditic deposits from a part of the Bąkowiec section in the Skole Nappe (Outer Carpathians, southern Poland)

Dinoflagellate cysts from turbiditic deposits of the Ropianka Formation in an interval of the Bąkowiec section (Skole Nappe, Outer Carpathians, southern Poland) have been analyzed. This interval, previously attributed to the Cretaceous–Paleogene boundary transition based on planktic and benthic foraminifera, contains organic-walled dinoflagellate cysts (dinocysts) of a latest Campanian age. The difference in age, revealed here between foraminifera and dinocyst findings, is considered as an unresolved dilemma, which is pending some explanations, probably on the basis of further multidisciplinary studies envisaged in the same outcrop. The palynological content is well preserved and rich in dinocyst cyst taxa, including 37 upper Campanian index species among 92 species in total. The dinocyst assemblages observed in this interval are similar to those previously recognized in biostratigraphically well-calibrated sections of Western Europe. The dinocyst marker events enabled a correlation of the studied interval with the Samlandia mayi dinocyst Zone of Slimani (2001a), which is an equivalent to the Belemnitella minor Zone in the northwestern Europe. These dinocyst events include the first occurrences (FOs) of Kleithriasphaeridium truncatum, Nematosphaeropsi philippotii, Samlandia carnarvonensis, Samlandia mayi and last occurrences (LOs) of Corradinisphaeridium horridum, Raetiadinium truncigerum, Odontochitina operculata and Xenascus ceratioides subsp. ceratioides. The palynological content shows significant reworking of Campanian dinocyst taxa and a richness in palynodebris of continental origin, which are likely related to deposition by turbiditic currents.

The Late Miocene Rifian corridor as a natural laboratory to explore a case of ichnofacies distribution in ancient gateways

Oceanic gateways have modulated ocean circulation and have influenced climatic variations throughout the Earth´s history. During the late Miocene (7.8–7.35 Ma), the Atlantic Ocean and the Mediterranean Sea were connected through the Rifian Corridor (Morocco). This gateway is one of the few examples of deep ancient seaways with a semi-continuous sedimentary record. Deposits comprise turbidites intercalated between deep-sea mudstone (i.e., hemipelagites and drift deposits), channelized sandstone contourite facies, and shallow marine sandstone. Herein an ichnological analysis was conducted in these upper Miocene sediments to improve characterisation of palaeoenvironmental conditions. In addition, ichnofacies were analysed to elucidate how bottom currents control ichnofacies distribution and can modify their attributes. Turbidite deposits are typified by vertical trace fossils (i.e., Ophiomorpha), conforming the Ophiomorpha rudis ichnosubfacies. Contouritic sandstone exhibits high density and low diversity trace-fossil assemblage, with predominant Macaronichnus and Scolicia, resembling a proximal expression of the Cruziana ichnofacies. Shallow marine environments are dominated by vertical trace fossils (e.g., Conichnus, Ophiomorpha, Skolithos), allowing an assignation to the Skolithos ichnofacies. This study reveals for the first time a variability in ichnofacies attributes and distribution at the Rifian Corridor, associated with turbidites, contourite and shallow marine sediments. Hydrodynamic energy reveals as the major factor controlling trace maker communities in the studied seaway. Highly energetic conditions typical of shallower settings are present in deeper-water environments (i.e., slope), contributing to ichnodiversity impoverishment in ichnofacies.

A New Approach to Constrain the Seismic Origin for Prehistoric Turbidites as Applied to the Dead Sea Basin

AbstractThe seismic origin of turbidites is verified either by correlating such layers to historic earthquakes, or by demonstrating their synchronous deposition in widely spaced, isolated depocenters. A historic correlation could thus constrain the seismic intensity required for triggering turbidites. However, historic calibration is not applicable to prehistoric turbidites. In addition, the synchronous deposition of turbidites is difficult to test if only one deep core is drilled in a depocenter. Here, we propose a new approach that involves analyzing the underlying in situ deformations of prehistoric turbidites, as recorded in a 457 m‐long core from the Dead Sea center, to establish their seismic origin. These in situ deformations have been verified as seismites and could thus authenticate the trigger for each overlying turbidite. Moreover, our high‐resolution chemical and sedimentological data validate a previous hypothesis that soft‐sediment deformation in the Dead Sea formed at the sediment‐water interface.

A tuffaceous volcaniclastic turbidite bed of Early Miocene age in the Temburong Formation of Labuan, North‐West Borneo and its implications for the Proto‐South China Sea subduction in the Burdigalian

AbstractA 2 m thick bed of smectite‐rich clay within a sequence of distal deep water turbidites and marine mudstones of the Temburong Formation on the island of Labuan, Sabah, North‐West Borneo, is an altered, re‐sedimented pyroclastic tuff which is geochemically of rhyolite‐dacite composition. The tuff bed was deposited in deep water, although probably <1,000 m, by traction currents and retains relic siliceous shards, feldspar phenocrysts and biotite crystals but was dominated by ash‐grade material. The tuff is interpreted as a turbidite deposit and most probably records long distance sub‐marine transport down the depositional slope from an active volcanic system in the hinterland. It has a zircon U–Pb weighted mean age of 19.6 ± 0.1 Ma whilst combined forminiferal and nannofossil ages from the enclosing marine mudstones range from 21.5 to 19.4 Ma; together these indicate an early Miocene age for the Temburong Formation. The tuff is the result of a very short‐lived volcanic arc magmatic episode and was either related to similar aged volcanics of the Sintang Suite in central Borneo or a product of the Proto‐South China Sea subduction beneath the Cagayan arc north‐east of Borneo. The age indicates that deep water sedimentation in North‐West Borneo continued into the Burdigalian suggesting the subduction trench of the Proto‐South China Sea was active into the early Miocene, beneath the depocentre of the Temburong turbidite fan. By contrast, sandstones representative of the typical marine Temburong Formation yield abundant zircons which are dominately Cretaceous in age indicating an important switch in source provenance during the Early Miocene from the Crocker Formation that is dominated by Permian‐Triassic zircons. This difference in zircon populations likely reflects an important tectonic event in the early Miocene that resulted in uplift of central Borneo to supply sediment to the Sabah Trough whilst the input of material derived from the western terrains diminished. The Temburong Formation was sourced by reworking of uplifted Rajang Group, Sapulut or Trusmadi formations.

Fingerprinting sand from Asian rivers to the deep central South China Sea since the Late Miocene

Abstract The complex sedimentary processes from source to sink lead to a substantial fractionation of sediment size and composition. Relatively coarse-grained, continent-derived detritus is rarely transported and deposited in the deep ocean, and the terminus of this sediment routing system is poorly understood. Sandy turbidite deposits within the Upper Miocene–Pleistocene strata drilled in the deep central South China Sea during the International Ocean Discovery Program (IODP) Expedition 349 provide valuable samples for evaluating the evolution of sediment contributions from different Asian landmasses. This study reconstructs this ancient source-to-sink system based on an integration of heavy mineral and detrital zircon analyses (including U-Pb age, trace element, grain size and shape), obtained from IODP sites U1431 and U1432, as well as a zircon age-based mixture modeling of well-defined provenance end-members. The results show several provenance shifts that correspond to more complex and dynamic source-to-sink scenarios than previously envisaged. Certain source areas, like East Vietnam, present a different provenance signature than that of today. Multiple provenances have been mixed and diluted during sediment transport, exhibiting a large regional variability. We interpret that siliciclastic turbidite deposits in the central South China Sea were mainly derived from East Vietnam during the early Late Miocene and Pliocene, and the Pearl River Basin during the late Late Miocene and Pleistocene. Additional, but less significant, contributions from the Red and Mekong river basins and coastal Southeast China are also observed.

Sedimentology and stratigraphy of syn-subduction Miocene fine-grained turbidites deposited in first stages of trench-slope basin development: Whakataki Formation, North Island, New Zealand

This study provides a detailed sedimentological, stratigraphic and depositional model for the lower Whakataki Formation. The fine-grained nature of the turbidite successions and common Tbcde successions suggests deposition associated with medial to distal submarine fan deposits. However, the textural and compositional immaturity, combined with a high carbonaceous and carbonate content of the clastic sediments indicates a proximal detrital input. In the examined section of the lower Whakataki Formation the sedimentology and facies associations identified that the turbidite successions were deposited as dilute low-density turbidity currents that transported sediment down-slope, overflowing or bypassing upper- and mid-trench-slope basins into a structurally confined lower trench-slope basin. Flows entering the structurally confined basin were deflected to the north-northeast, producing palaeo-flow along the axis of the basin and represent deposition in the early stages of trench-slope basin development. Here, we provide a depositional model for a lower (immature) trench-slope basin and highlight that the application of the ‘classical’ submarine-fan model to all fine-grained turbidite deposits is not always appropriate.

Introduction to the cartographic and sedimentological study of the coverage of the TAHANAOUT BASIN (HIGH ATLAS, MOROCCO)

This study is carried out on the northern edge of the High Atlas of the MARRAKECH basin. The TAHNAOUT DOUAR SOUR basin belongs to the Atlasic domain which is structured by the Hercynian orogeny, taken up and elevated by the Alpine orogeny, our main goal in this studying is to map the TAHNAOUT DOUAR SOUR basin and to characterize all these geological formations, For this purpose we analysed sedimentary tectonic structures ,made lithostratigraphic sections with description and draw a geological map at scale 1/25000 on a topographic background by used MapInfo platform. As final results, our studying of the TAHANOUT basin consists of two main lithological units: the basement formed by conglomeratic and turbidite deposits (alternating sandstone and pelites), and the lithological unit that forms the cover of the TAHNAOUT basin formed by a red detrital material and, carbonate deposits in some cases depending on the deposition environment, The TAHNAOUT basin is also affected by tectonic activity at the basement and Meso-Cenozoic cover levels [1-2]. Magmatic activity is absent and no trace has been recorded.

Lithofacies and ichnofacies of turbidite deposits, West Java, Indonesia

This study focuses on the analysis of sedimentary facies and ichnogenus variations to determine the palaeogeographic setting of turbidite deposits that are clearly exposed in the surroundings of Majalengka area, West Java, Indonesia. Lithofacies variation in turbidite deposits, identified from detailed stratigraphic sections, were visually presented as a composite log and indicated a thickening and coarsening pattern due to a regressive event. Trace fossils exposed in all stratigraphic levels consist of Thalassinoides, Chondrites, Cruziana and Planolites. They are commonly found in a series of thin to medium bedded fine grained turbiditic sandstones intercalated with shales. Hereinafter, the integration analysis in between sedimentology and ichnology data, the sediment shed into the basin in the submarine channelized related to slope system. Such findings cast no doubt as to whether integrated sedimentary facies and ichnofacies analysis can be viewed as precise methods for sedimentary basin interpretation, in which external parameter, for example magmatic processes, also are considered to play a role.

Review of the syn-rift to early post-rift depositional systems of the Cretaceous Mauléon rift: sedimentary record of continental crust hyperextension and mantle denudation (Western Pyrenees)

The Mauléon Basin, in the northwestern Pyrenean Belt, is related to Early Cretaceous rifting and mantle denudation. Here we review the evolution of depositional systems in the Mauléon Rift Basin during Albian and Cenomanian time. This review includes the lithostratigraphy, regional distribution, boundaries, age and facies sedimentology of the basin’s syn-rift formations and their members. We construct paleogeographic maps to elucidate (1) the 3D distribution of sedimentary facies and depositional systems during the Albian and Cenomanian from the Iberian proximal margin to the hyperextended domain and (2) the link between major extensional structures and sedimentation during rifting and mantle denudation. The Mauléon Rift was supplied during most of the Albian by sediments from the Iberian proximal margin. The southern margin had a steep and abrupt topographic boundary related to a northward crustal rollover along the south-dipping Saint-Palais detachment. This feature controlled the deposition of coarse-grained turbidites at the base of the margin that abruptly gave way to low-density turbidites, then deep-basin deposits in the hyperextended domain. During uppermost Albian to Early Cenomanian time, mantle denudation occurred in the eastern Mauléon Basin and the vergence of the detachment systems reversed. Minor debris-flow deposits formed at the foot of fault scarps associated with the newly formed north-dipping detachments. Elsewhere, sediment from deltaic systems to the west in the Saint-Jean-de-Luz area deposited low-density turbidites in the hyperextended domain. During the post-rift stage, the flux of coarse sediment from the detachment footwall gradually declined as deformation waned, and low-density turbidites expanded onto the hyperextended domain from the European Upper Cretaceous carbonate platform. These paleogeographic reconstructions, in addition to offering a synthetic view of the evolution of sedimentary environments during rifting, offer new insight into the post-rifting exhumation of the lower crust and mantle.

Тектоно-седиментаційна еволюція передової частини насувної споруди Українських Карпат

For the first time in the Ukrainian Carpathians, the depths and tectono-sedimentation processes in the north-eastern part of the Outer Carpathian Basin (Skyba and Boryslav-Pokuttya units) have been restored on the base of sedimentological and microfaunistic studies. It was established that in the Cretaceous-Eocene time, the deep-water (near Calcite Compensation Depth) turbidite and similar sedimentation (turbidites with Bouma textures, grainites, debris-flow deposits), which periodically alternated with (hemi)pelagic sedimentation (red, green and black shales) was dominant here. Sedimentation took place on the continental margin of the the Carpathian branch of the Tethys, where deep-water fans were formed. Cretaceous-Eocene background red and green shales are enriched in buried in situ benthic foraminifera which are similar in taxonomic composition and morphological features to the microfauna of the Carpathian-Alpine and Atlantic regions (deep-water agglutinated foraminifera), which indicate lower bathyal – abyssal depths of flysch sedimentation. Latest Eocene Globigerina Marl horizon contains the foraminiferal assemblage with plankton dominance, which indicates a general shallowing of the Outer Carpathian Basin (middle-upper bathyal conditions above a calcite compensation depth). Oligocene – lowermost Miocene Menilite-Krosno and Polyanytsia formations were accumulated in the Skyba and Boryslav-Pokuttya sub-basins. In the Miocene, shallow-water molasses were accumulated here. Probably, the tectonic uproot of flysch deposits from its substrate and their synsedymentary thrusting towards the platform caused a significant shallowing of the Skyba and Boryslav-Pokuttya sub-basins starting from the latest Eocene. These processes reflected the growth of the Carpathian frontal nappes at the final orogen formation stage.

СТРАТИГРАФІЯ ТА УМОВИ НАКОПИЧЕННЯ ЧОРНОСЛАНЦЕВИХ ТОВЩ УКРАЇНСЬКИХ КАРПАТ

Узагальнено та доповнено матеріали зі стратиграфії відкладів Українських Карпат, які містять чорносланцеві потенційно нафтогенеруючі товщі, вперше виконано їх зіставлення з сучасною Шкалою геологічного часу, доповнено та уточнено реконструкції умов осадконакопичення за аналізом дрібних форамініфер та седиментологічними даними. В нижній крейді чорносланцеві утворення представлені спаською та шипотською світами (Бориславсько-Покутський, Скибовий, Сілезький, Дуклянський, Чорногорський, Свидовецький та Красношорський покриви), а також нижньою частиною тисальської світи (Пенінська зона), у верхній – березнянською світою (Дуклянський покрив), в еоцені – сойменською світою (Сілезький покрив), в олігоцені-міоцені – менілітовою світою та її аналогами, поширеними в більшості тектонічних елементів Карпат. Більша частина відкладів, які містять чорні сланці, накопичена турбідитними та іншими гравітаційними потоками. (Гемі) пелагічна седиментація була фоновою, за недостачі кисню глинисті осади збагачувались органічною речовиною, надаючи седиментам чорний колір, а за покращення аерації накопичувались світліші осади із залишками бентосу. Відповідно до вивчення мікрофауни і седиментологічних ознак, глибини частин Карпатського басейну, де осаджувались збагачені органікою майбутні чорносланцеві утворення, змінювались від батіальних вище CCD в баремі (нижні частини спаської і шипотської світ) до батіально-абісальних переважно нижче CCD в апті (верхні частини шипотської і спаської світ). Глибоководна турбідитна седиментація продовжувалась і в пізній крейді (березнянська світа) та еоцені (сойменська світа). В кінці еоцену відбулась зміна глибини басейну від батіально-абісальної до верхньобатіально-субліторальної (горизонт “глобігерінових мергелів” межі еоцену-олігоцену та олігоценова менілітова світа). Чорні сланці приурочені або до певних стратиграфічних рівнів (нижня крейда, олігоцен), або до окремих тектонічних елементів (верхня крейда Дуклянського покриву, чорний еоцен Сілезького покриву). Відповідно, їх накопичення пов’язано, або з домінуючим впливом глобальних (аноксичні події ранньої крейди), регіональних (ізоляція Карпатського басейну внаслідок колізійних процесів у районі майбутніх Альп і утворення Паратетису в олігоцені), або ж місцевих (наявнісю внутрішньоба-сейнових піднять, які затруднювали циркуляцію придонних, збагачених киснем, течій в пізній крейді та еоцені) факторів.

Late Ordovician (Katian) Graptolites and Shelly Fauna from the Phu Ngu Formation, North-East Vietnam

Two new graptolite assemblages are identified from discrete intervals within the Phu Ngu Formation, Na Ri District, Bac Kan Province, north-east Vietnam. The graptolites occur in laminated mud/siltstones thought to be distal turbidite deposits. A low-diversity diplograptid sensu lato assemblage occurs in mud-rich layers that are interlaminated with silty and sandy horizons containing the dendroid graptolite Dictyonema sp. This level also contains orthoconic nautiloids and conulariids. A few metres stratigraphically above, a second more diverse graptolite assemblage comprises a single Dicellograptus, tentatively identified as D. flexuosus, together with Climacograptus dorotheus and Orthograptus truncatus pauperatus in mud and silt laminae that also yield brachiopods, orthoconic nautiloids, conulariids, fragmentary trilobites, and ostracods. The ostracods include the first East Asian occurrence of the typically Baltic genus Kinnekullea, and we describe the new species Kinnekullea gaia. The graptolites suggest a Late Ordovician Katian age, most probably in the Dicranograptus clingani Biozone, this being older than previous biostratigraphical constraints on the Phu Ngu Formation.

Stratigraphic and sedimentological aspects of the worldwide distribution of Apectodinium in Paleocene/Eocene Thermal Maximum deposits

Abstract The Paleocene/Eocene Thermal Maximum (PETM) is characterized by pronounced global warming and associated environmental changes. In the more-or-less two decades since prior regional syntheses of Apectodinium distribution at the PETM, extensive biological and geochemical datasets have elucidated the effect of rising world temperatures on climate and the biome. A Carbon Isotope Excursion (CIE) that marks the Paleocene/Eocene Boundary is associated with an acme of marine dinocysts of the genus Apectodinium in many locations. Distinctive foraminiferal and calcareous nannofossil populations may also be present. For this updated, dinocyst-oriented view of the PETM, data from worldwide locations have been evaluated with an emphasis on stratigraphic and sedimentological context. What has emerged is that a change in lithology is common, often to a distinctive siltstone or claystone unit, which contrasts with underlying and overlying lithotypes. This change, present in shallow marine/coastal settings and in deep-water turbidite deposits, is attributed to radical modifications of precipitation and erosional processes. An abrupt boundary carries the implication that some time (of unknowable duration) is potentially missing, which then requires caution in the interpretation of the pacing of events in relation to that boundary. In most instances an ‘abrupt’ or ‘rapid’ CIE onset can be attributed to a data gap at a hiatus, particularly in shallow shelf settings where transgression resulted from sea-level rise associated with the PETM. Truly gradational lower boundaries of the PETM interval are quite unusual and, if present, are poorly known so far. Gradational upper boundaries are more common, but erosional upper boundaries have been reported. Taxonomic changes have been made to clarify identification issues that have adversely impacted some biostratigraphic interpretations. Apectodinium hyperacanthum has been retained in Wetzeliella , its original genus. The majority of specimens previously assigned to Apectodinium hyperacanthum or Wetzeliella ( Apectodinium ) hyperacanthum have been reassigned to an informal species, Apectodinium sp. 1. Dracodinium astra has been retained in its original genus as Wetzeliella astra and is emended.