Facies Changes Research Articles

The glass ramp of Wrangellia: Late Triassic to Early Jurassic outer ramp environments of the McCarthy Formation, Alaska, U.S.A.

Abstract The marine record of the Triassic–Jurassic boundary interval has been studied extensively in shallow-marine successions deposited along the margins of Pangea, particularly its Tethyan margins. Several of these successions show a facies change from carbonate-rich to carbonate-poor strata attributed to the consequences of igneous activity in the Central Atlantic Magmatic Province (CAMP), which included a biocalcification crisis and the end-Triassic mass extinction. Evidence for a decline in calcareous and an increase in biosiliceous sedimentation across the Triassic–Jurassic boundary interval is currently limited to the continental margins of Pangea with no data from the open Panthalassan Ocean, the largest ocean basin. Here, we present a facies analysis of the McCarthy Formation (Grotto Creek, southcentral Alaska), which represents Norian to Hettangian deepwater sedimentation on Wrangellia, then an isolated oceanic plateau in the tropical eastern Panthalassan Ocean. The facies associations defined in this study represent changes in the composition and rate of biogenic sediment shedding from shallow water to the outer ramp. The uppermost Norian to lowermost Hettangian represent an ∼ 8.9-Myr-long interval of sediment starvation dominated by pelagic sedimentation. Sedimentation rates during the Rhaetian were anomalously low compared to sedimentation rates in a similar lowermost Hettangian facies. Thus, we infer the likelihood of several short hiatuses in the Rhaetian, a result of reduced input of biogenic sediment. In the Hettangian, the boundary between the lower and upper members of the McCarthy Formation represents a change in the composition of shallow-water skeletal grains shed to the outer ramp from calcareous to biosiliceous. This change also coincides with an order-of-magnitude increase in sedimentation rates and represents the transition from a siliceous carbonate-ramp to a glass ramp ∼ 400 kyr after the Triassic–Jurassic boundary. Sets of large-scale low-angle cross-stratification in the Hettangian are interpreted as a bottom current–induced sediment drift (contouritic sedimentation). The biosiliceous composition of densites (turbidites) and contourites in the Hettangian upper member reflects the Early Jurassic dominance of siliceous sponges over Late Triassic shallow-water carbonate environments. This dominance was brought about by the end-Triassic mass extinction and the collapse of the carbonate factory, as well as increased silica flux to the ocean as a response to the weathering of CAMP basalts. The presence of a glass ramp on Wrangellia supports the hypothesis that global increases in oceanic silica concentrations promoted widespread biosiliceous sedimentation on ramps across the Triassic to Jurassic transition.

Decadal and seasonal changes in landcover at Padre Island: Implications for the role of the back‐barrier in signaling island state change

AbstractLong‐term and seasonal geomorphological changes at Padre Island, Texas are identified and linked with potential external drivers. Aerial and satellite images from 1950 to 2018, monthly images from 2019 to 2020, and a 2018 LiDAR data set are used to assess long‐term and seasonal geomorphological changes within a 50 km2 area of Padre Island near Port Mansfield, Texas. Trends in landcover are evaluated by mapping and comparing the relative areal coverage of each facies. Vegetated dunes, absent initially, emerged in the fore‐island and expanded into the back‐barrier to cover 14% of the study area. The active vegetation‐free back‐barrier dune field steadily decreased in areal extent from 12% to 6% as vegetation spread. Nebkha dune coverage fluctuated between 4% and 7%. Expansive microbial mats colonized the wind tidal and deflation flats surrounding the vegetated dunes and back‐barrier dune field giving rise to a remarkably different landscape over the 50‐year period studied. An assessment of external forcing factors identifies increased rates of relative sea level rise and decreased sediment influx as the most likely primary factors driving the geomorphological changes. These changes have induced a widespread shift toward stabilization of island sediments by vegetation and microbial mats, which in turn has starved the back‐barrier of sediments resulting in low rates of accretion and increased flooding. These findings highlight the sensitivity of the back‐barrier and, in particular, the dune facies to changes in sea level and sediment supply, and show that microbial mats are effective at stabilizing island sediments and may be harbingers to barrier island response to rising sea level. As shown in this study, long‐term monitoring of geomorphic facies changes and topography can detect important shifts in the island state that can be used to inform decision making for these sensitive coastal landscapes.

Invertebrate trace fossils from Paleogene fluvial strata in Western Washington, USA

Fluvial strata in the Paleogene Chuckanut Formation contain a wealth of trace fossils that include both vertebrate and invertebrate ichnofossils. Vertebrate traces have received careful scrutiny, but invertebrate traces have not previously been described. Trace fossils occur in two sediment types. Mudstones deposited in subaqueous environments include highly bioturbated layers that are dominated by horizontal meniscate burrows. Siltstone and fine-grained sandstone beds primarily contain vermiform trails on bedding surfaces, with sparse vertical traces. Some of these sandy beds also contain vertebrate tracks. Chuckanut Formation beds commonly show rapid facies changes in sediments that were deposited along a meandering river during a time of semitropical climate. Transitions from subaqueous to subaerial conditions may have been related to changing water levels caused by variations in seasonal precipitation or episodic flood events. Other possible factors include ponds created by abandonment of channels, overbank sediment s deposited by floods, and breaching of levees to form crevasse splay deposits. Trace fossil assemblages show local variations in the diverse depositional environments of the Chuckanut Formation. Many of the ichnofossil suites clearly represent Scoyenia Ichnofacies, but some occurrences may involve overprinting of Scoyenia and Mermia ichnofacies.

KARGI-İSKİLİP EOSEN YAŞLI DENİZALTI YELPAZE SİSTEMLERİNİN DEPOLANMA ÖZELLİKLERİ VE TEKTONO-SEDİMANTER GELİŞİMİ (ÇORUM, K-TÜRKİYE)

The Kargı-İskilip Eocene deposits located in southern part of the North Anatolian Fault are very well exposed between Kargı and Çorum settlements in N-Turkey. These Eocene deposits are observed as submarine fan and fan delta systems. Submarine fan system is characterized by clastic sediments such as conglomerate, sandstones, siltstones, greyish coloured shale and mudstone alternations. Fan delta system is represented by pebbly sandstones, siltstones and coal seams in some parts. In this study, Kargı-İskilip Eocene sediments involved in İskilip Group were examined in detail (Hacıhalil, Yoncalı and Karabalçık formations). Thus, the sedimentary facies indicating depositional environments and processes were revealed. For this research, six measured sedimentary sections (MSS) have been taken systematically and eight sedimentary facies are described and interpreted. The facies changes in vertically and laterally indicate that Kargı-İskilip Eocene deposits present as regressive character from south to north. Well outcropped sections in the studied area show that the Kargı-İskilip deposits particularly represent as flysch character (Lower Eocene) and progressively passed to the fan delta (Middle Eocene) which characterized by coarse grained clastics alternating with fine grained sediments with coal-bearing. besides, volcanic rocks outcropped as syn-sedimentary deposition with Lower Eocene marine sediments is observed commonly. In the investigated area, which formed as a piggy-back basin, syn-sedimentary growth faults also play an active role for the deepening of the basin infill.

Hybrid event bed characteristics and its role in high-frequency facies change of the Upper Triassic submarine fan in the West Qinling area of NE Tibetan Plateau

Hybrid event beds (HEBs) record disequilibrium in submarine fan evolution attributed to mud-forced dampening turbulence, which could be caused by allogenic and autogenic forcings in either the proximal or distal segment of a lobe-dominated submarine fan on several timescales. Detailed field investigation combined with petrographic and mineralogical analysis of selected outcrop samples indicate that the Upper Triassic submarine fan succession mainly comprises turbidites, HEBs, and debrites in the West Qinling (WQ) area of NE Tibetan Plateau. Five types of HEBs are recognized based on the thickness, sedimentary structure, and texture. Bed-by-bed description and measurement reveal that these HEBs show a distinct distribution pattern throughout the submarine fan succession, including dominance of HEB-1 and HEB-2 beds (∼71.50%) in distributary channel to lobe off-axis (FA1–FA3) and significant portion of HEB-3 to HEB-5 beds (∼54.22%) in lobe fringe to lobe distal fringe environments (FA4–FA5). Textural and petrographic characteristics of mudclasts suggest disaggregation of heterolithic, homogenous and less cohesive mudclasts (MC-1 to MC-4 type) within H1b and H3 interval of HEBs, which could play different roles in the longitudinal mud-driven flow transformation between turbulent and laminar flow behavior patterns. The vertical distributions of the HEB-prone succession are characterized by four types of depositional scenarios, which yields significant allogenic and autogenic signatures combined with the recognition of the dominant HEB types and thickening- or thinning-upward trend of the vertically stacked submarine lobes. This study can enhance our understandings of flow transformation of sediment gravity flows (SGF) along the eastern margin of the Paleo-Tethys Ocean based on the anatomy of several undiscovered deep-water outcrops, which were reflected by the initiation, gradual switching, and avulsion of the high-frequency submarine fan evolution during the Late Triassic.

The Ediacaran−Cambrian transition in the southern Great Basin, United States

The Ediacaran−Cambrian boundary strata in the Great Basin of the southwestern United States record biological, geochemical, and tectonic change during the transformative interval of Earth history in which metazoans diversified. Here, we integrate new and compiled chemostratigraphic, paleontological, sedimentological, and stratigraphic data sets from the Death Valley region, the White-Inyo Ranges, and Esmeralda County in Nevada and California and evaluate these data within a regional geologic framework. A large negative carbon isotope (δ13C) excursion—also known as the Basal Cambrian Excursion, or BACE—is regionally reproducible, despite lateral changes in sedimentary facies and dolomitization across ∼250 km, consistent with a primary marine origin for this perturbation. Across the southern Great Basin, Ediacaran body fossils are preserved in a variety of taphonomic modes, including cast and mold preservation, two-dimensional compressional preservation, two-dimensional and three-dimensional pyritization, and calcification. The stratigraphic framework of these occurrences is used to consider the relationships among taphonomic modes for fossil preservation and paleoenvironmental settings within this basin. In this region, Ediacaran-type fossils occur below the nadir of the BACE, while Cambrian-type trace fossils occur above. Sedimentological features that include giant ooids, stromatolites, and textured organic surfaces are widespread and abundant within the interval that records biotic turnover and coincide with basaltic volcanism and the BACE. We hypothesize that the prevalence of these sedimentological features, the BACE, and the disappearance of some Ediacaran clades were caused by environmental perturbation at the Ediacaran-Cambrian boundary.

The Cretaceous/Tertiary boundary event in Tibet

The Cretaceous/Tertiary boundary in the Gamba and Tingri regions of Tibet occurs between the Zongshan and Jidula Formations. Arenaceous facies similar to those of the Jidula Formation are widespread in Tibet and Pakistan; collectively, these represent the diachronous deposits of the Latest Cretaceous-Early Tertiary regression. Major faunal changes took place in Tibet during the Late Cretaceous. Ali of the Cretaceous ammonoids, planktonic and benthonic foraminifera, rudistid and inoceramid bivalves became extinct over the Campanian Maastrichtian interval in a stepwise pattern, with abrupt Late Campanian and Late Maastrichtian extinction events (Tabs. 3, 4). A large number of new taxa appeared during the Danian (Tabs. 3, 4). These faunal changes in the shallow-water marine facies of Tibet demonstrate that this region was not isolated from major global faunal changes taking place in the Cretaceous/Tertiary boundary mass extinction interval.

The control of Pleistocene palaeogeography on the distribution of sandy patches in a silty Holocene lagoon (central Netherlands)

The brackish lagoon in the central part of The Netherlands was closed by a dike in 1932 and gradually changed into a lake. Parts of this lake were reclaimed and the surficial sediments of one of the polders (Noordoostpolder), reclaimed in 1942, has been investigated in detail by mapping of the walls of some 1500 km of drainage ditches approx. 1.4 m deep. It appeared that the sediments consist of an uncommonly large amount of silt, to different degrees mixed with reworked peat that had developed during the Holocene transgression. Some sandy deposits occur locally, at places that are at first sight distributed in a haphazard way. The various sandy patches have different characteristics (grain-size distribution, rounding of the grains, mineral composition). These sands cannot have been introduced from the sea, nor can they have been supplied by the rivers that discharged into the lagoon, so they must have a local origin. It is found that several types of Pleistocene sandy or diamictic deposits below the Holocene peat and lagoonal sediments had an irregular topography and became eroded during the Holocene by wave activity. This resulted in sandy deposits around these Pleistocene highs, which consisted of glacial tills (boulder clays), river dunes (formed by aeolian activity along rivers under dry permafrost conditions) and coversand ridges, formed by aeolian activity in a belt between the ice margin and the more distal loess belt. This finding implies that palaegeographical interpretations of local grain-size anomalies in a specific deposit should not only consider facies changes due to changes in the sediment supply, but should also consider local erosion leading to the exposure of previously deposited material with a divergent composition.

3D forward stratigraphic modeling of the Albian succession in a part of the northeastern margin of the Arabian Plate and its implications for exploration of subtle traps

During the Albian age, siliciclastic input in the Arabian carbonate-dominated shelf formed important petroleum system elements. Hence, the Albian Burgan-Kazhdumi succession hosts world-class sandstone reservoirs in some Middle East oil fields. Moreover, stratigraphic traps are possible due to changes in facies and structural dips. Accordingly, we used process-based forward stratigraphy modeling as a powerful tool to predict Burgan-Kazhdumi units and de-risking new exploration prospects. A 3D stratigraphic model was constructed in this study for the first time by integrating multi-disciplines and multi-scales of seismic and well data from several countries. The model (324 km × 264 km, 4 km × 4 km grid size) encompasses NW of the Persian Gulf, Kuwait, south Iraq and SW of Iran and is vertically divided into three units based on Albian regional third-order sequences.Results indicated that the lower unit, unit-1, contains onlapping aggradational-retrogradational stacking compounds, high sand bodies thickness and distribution as well as good reservoir quality. This unit was deposited on a tide-dominated delta system. Gradually, with rising sea level, progradational fine-grain marine sedimentation dominated in units 2 and 3. Hence, intra-formational seal facies formed in the proximal and organic-rich facies in the distal intra-shelf areas. The gentle topography of the basin floor seems responsible for the lack of turbidity lobes. The sand bodies of up-dip arches such as Khafji-Norooz and Kharg-Mish highs and pinched out in fine-grained facies provide a significant potential for stratigraphic traps.The model sensitivity analysis showed eustasy, and water-driven diffusion coefficient (Kw) has the most critical impact on the clastic sedimentation of unit-1 and unit-3. Furthermore, tectonic events have the most significant sedimentation effect in unit-2 sedimentation.The findings of this study can help for better understanding of a more precise regional sequence stratigraphic and stratigraphic architecture of the Albian succession of the study area. This study also helps identify elements of petroleum plays as well as stratigraphic trap potential between mixed siliciclastic-carbonate depositional systems.

Orbital-scale climate changes detected in Lower and Middle Ordovician cyclic limestones using oxygen isotopes of conodont apatite

Recent studies using δ18O trends from conodont apatite suggest that the Ordovician greenhouse-to-icehouse climate transition was characterized by repeated Myr to multi-Myr-scale sea surface temperature (SST) oscillations throughout the Ordovician making it difficult to pinpoint the temporal onset of cooling and glaciation. This study utilizes high-resolution δ18Oapatite trends from Lower and Middle Ordovician meter-scale carbonate cycles to evaluate orbital-scale (~104–105 yr) climate changes superimposed on the Myr-scale oscillations. Detailed facies analysis and δ18Oapatite variations from 14 cycles deposited along the western Laurentian margin (Nevada and Utah) show trends indicating glacio- and/or thermo-eustatic sea-level changes along with associated wetter versus drier climate shifts controlled meter-scale cycle formation and δ18O signals. Using the range of magnitudes of intracycle isotopic shifts (0.45–1.4‰) and reasonable isotopic proportionalities, ~25–45 m glacio-eustatic changes with ~2–6 °C SST variations are estimated. However, observed cyclostratigraphic facies changes do not support the higher end of estimated eustatic changes suggesting that the apparent overestimation is due to local δ18O shifts related to variations in paleotropical surface ocean evaporation and/or dilution by freshwater runoff during orbital-scale wetter versus drier climatic changes. These new δ18Oapatite results indicate that orbital-scale climatic oscillations, including glaciation, were superimposed upon Myr-scale and ~107 yr-scale Ordovician SST variations as early as the late Early Ordovician and that the greenhouse-to-icehouse climatic transition was more complex and protracted than previously thought.

Late Holocene Tephrostratigraphy at Chokai Volcano, Northern Japan, and Contribution to Hazard Assessment

History and pattern of explosive eruptions at Chokai volcano, Japan, in the last 2500 years were investigated from tephra survey and accelerator mass spectrometry (AMS) radiocarbon dating. The tephrostratigraphy was established based on observations at eight hand-dug trenches and three outcrops. The well-correlated tephra layers were dated at c. 2.5 ka, 2.1–1.9 ka, 1.8 ka, and 1.6 ka, indicating major eruptions occurred at these ages. The tephra from the documented 871 CE eruption was also identified. Componentry analysis of ash was carried out for these five eruption deposits. The changes in tephra facies and ash components within an unbroken series of tephra layers indicate a shift from hydrothermal-dominant phreatic or phreatomagmatic eruption to magma-dominant eruptions in a single episode. Common eruption sequences were identified based on the combination of tephra facies variation and records of witnessed eruptions. Every volcanic activity begins with precursory activity of seismicity, fumaroles, and snow melting for weeks to months, then onset hydrothermal-dominant eruption happens. Then, the eruption evolves to a magma-dominant eruption, or alternatively, the hydrothermal-dominant eruption persistently continues until cessation. The eruption sizes are VEI 2 or more minor. Lahar can occur at any stage of the eruption, resulting in damage to the residential area at the base of the volcano. The eruption patterns and the extent of hazard risks elucidated by this study will be utilized to hazard mitigation plans.

Refined conodont stratigraphy at Martenberg (Rhenish Massif, Germany) as base for a formal middle/upper Frasnian substage boundary

The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical Frasnian goniatite and conodont zonations, has been restudied in order to document the microfacies development and to refine the conodont stratigraphy around the global semichatovae Event/Transgression, the proposed level to define a future upper Frasnian substage. More than 8.000 platform elements were identified and include new taxa. Palmatolepis jamieae is subdivided into the subspecies Pa. jamieae jamieae, Pa. jamieae savagei n. ssp., Pa. jamieae rosa n. ssp., and Pa. jamieae ssp. δ. Another new species, Pa. adorfensis n. sp., was previously partly identified as Pa. jamieae, while Pa. descendens n. sp. has previously been described in open nomenclature from Inner Mongolia. Morphotypes are defined in Icriodus symmetricus, Pa. ljaschenkoae, and Pa. proversa. A global literature survey shows that the eustatic semichatovae Event can be recognised in more than 20 regions of all continents with (sub)tropical Upper Devonian outcrops. At Martenberg, the transgression is preceded by a thin but distinctive interval with unconformities, microbial mats, sheet cracks, and currents that brought in the regionally youngest volcaniclastics. The new conodont data confirm that no typical Pa. jamieae (sensu the holotype) occur in the two beds originally supposed to represent the jamieae Zone in its reference section. We fully support the conclusion of Ovnatanova and Kononova (2020) that the jamieae Zone should be abandoned. Early Pa. jamieae subspecies and the related new taxa enter at Martenberg and in a few other regions in the globally easily recognisable Frasnian Zone 10 (= plana Zone). Frasnian Zone 11 (feisti Zone) is subdivided into subzones FZ 11a (= feisti Subzone) and FZ 11b (= nasuta Subzone). The base of the latter coincides with the semichatovae Transgression, the semichatovae Subzone of more shallow shelf settings, and is proposed to define in future the upper Frasnian substage base. On a global scale, the Martenberg section is currently the best bed-by-bed documented section for facies changes, conodont and goniatite biostratigraphy at the middle/upper Frasnian transition. Therefore, it is a prime candidate for a future GSSP selection. A global literature survey identified more than 20 other pelagic conodont successions that have the potential for precise correlation and a better understanding of the environmental changes associated with the semichatovae Event.

Aptian−Albian extension in Tethyan rifted continental passive margin of Tunisia inferred from sequential restorations of balanced cross-sections and expansion index

This article presents an overview of regional extensional deformation across the north-facing southern Tethyan continental passive margin of Tunisia during the Aptian and Albian syn-rift stages. Because of the Late Eocene, Late Miocene and Pleistocene orogenic overprinting, the earlier extensional history of the Tunisian Atlassic province had to be reconstructed from balanced and sequentially restored transects across four key fault systems active at the time. These were used to (i) estimate the amount and timing of extension and (ii) calculate the expansion index (EI) for each fault system. The analysis demonstrates the region experienced a very significant amount of mid-Cretaceous extension, representing the last of several Permian-Mesozoic rift events. Two closely linked styles of deformation were recognised: thick-skinned basement involved faulting and shallow listric faulting detached on decollement surfaces within late Triassic evaporites. Both styles of faulting triggered salt diapirism.Sequential pre-orogenic restorations of a transect across the Tebaga Kebili and Orbata faults in the southern part of this province suggest both experienced a large amount of extensional displacement during the Aptian and Albian (Aptian-Albian extension = 2.6 km), recorded by footwall erosion, growth strata, rollover structures and changes in sedimentary facies. A similar restoration across the Labaiedh (M'rhila-Cherichira) fault system further north, identified both thick and thin-skinned extensional movement associated with diapiric growth and salt extrusion reaching a maximum during the Aptian (Aptian-Albian extension = 0.55 km). A pre-Tertiary restoration of the Teboursouk fault system in the northern part of the province, demonstrated thick-skinned extension peaking during the Albian (Aptian-Albian extension = 0.4 km). This accommodated a thick sequence of basinal shales to the north, deformed by active diapirism with sea-floor salt extrusion, triggered by deep basement faulting and enhanced by the plastic incompetent character of the thick shale dominant overburden.Regional extension across the Tunisian Atlassic province during the Aptian-Albian was contemporaneous with a significant change in intra-plate stress across northern Africa, the opening of the South Atlantic and structural reorganization along the East African continental margin. This synchroneity across such a wide region may reflect some still poorly understood deep crustal processes, ultimately responsible for reactivating older rift faults and regional tilting across the province. The associated gravity salt gliding and diapirism bear comparison with the post-rift deformational style of the South Atlantic passive margin. However intra-evaporite decollement surfaces were more local, limited by active thick-skinned faulting with diapirism typically soft linked to deeper fault movement.

Sedimentology and New Paleo-geographic Data of the Upper Cretaceous-Lower Paleocene Haria Formation in the Gafsa Basin (Tunisia) Southern Tethyan Margin

Abstract Facies associations and environmental evolution of the late Cretaceous–lower Paleocene shallow platform of the Haria Formation (upper Maastrichtian–Danian–Selandian) have been studied from the Gafsa basin, located in southern Tunisia. Four main lithostratigraphic units have been identified. Unit 0, deposited on a restricted platform, is organized into aggradational and shallowing-upward sequences. Unit 1 is composed of shallowingand deepening-upward sequences that are deposited in externally restricted platform environments. Unit 2 is a peritidal shallowing-upward sequences deposited in shallow restricted environments ranging from the intertidal to supratidal environments. Unit 3,is composed of shallowing-upward sequences corresponding to the “muddy” type in the lower part, deposited in the proximal part of the shallow restricted external platform, and the “grainy” type in the upper part, representing wave-dominated bioclastic shoals and channel deposits. The proximal-distal transition of depositional environments gradually ranges from lagoon to offshore environments. Lateral variation of thickness and facies is generated by the reactivation of NW-SE extensive and/or transtensive faults, acting since the late Cretaceous during the intermediate closing phase of the Neotethys. These tectonic features were also expressed by changes in facies. The Haria Formation’s mixed carbonate-marls successions are classified into seven major facies associations, with carbonates considered a new facies represented by channel deposits and lumachellic limestones. This study establishes for the first time a clear and detailed regional stratigraphic correlation and paleogeographic maps based on the new litho- and biostratigraphic data.

The Role of Inertinite Characteristics and Coal Porosity of Seam A-1 of Muara Enim Formation in West Merapi, Lahat, South Sumatera, Indonesia

Coal contains a complex network of nano-, meso-, and a macro-pore can store fluids and allow fluids to flow through it. Nanoporosity in coal is primarily a result of molecules that have aromatic molecular structures and have been preserved in coal. Most adsorbate compounds, including gases, are stored here. The study area is located in South Sumatera, West Merapi Area, Lahat Regency. Geologically, the area in South Sumatra Basin belongs to the Middle-Late Miocene Muara Enim Formation. Using the ply-by-ply method, coal samples were taken directly from Seam-A in the coal mine walls outcrop, based on macroscopically determinable lithotype information. During laboratory analyses, coal is microscopically analyzed to determine the amount of porosity, permeability, and vitrinite reflectance. The purpose of this study is to investigate the change in composition and characteristics of inertinite macerals when the porosity value is varied.. Vitrinite content is between 91.00-92.80 %; liptinite 0.90-3.40%; inertinite 3.70-4.80%; mineral matter 0.7%-1.8%. Withh a vitrinite reflectance average of 0.34-0.36%, the variation in composition is an indication of changes in plant communities or coal facies. It is generally classified as sub-bituminous coal (ASTM). Porosity value of seam A upper is 1.9% and seam A lower 1.51%, permeability value seam A upper is 70.1 mD and seam A lower 27.1%. Composition of mineral matter in seam A upper is 0.8% and seam A lower 1.7%. The increasing number of inertinite pore is followed by lower porosity value. The inertinite maceral is predominantly aromatic with a high level of cross-linking, and exhibits a high level of aromatization and condensation. They have the highest carbon and the lowest oxygen hydrogen content. A coal maceral's porosity is composed of void spaces, such as open cell lumens preserved in semifusinite and sclerotinite. The porosity of cleats is the percentage of volume in relation to volume of coal, and the porosity of permeability. In coal, semifusinite has extensive interconnected pores that can form significant conduits for fluid flow.

Pliocene-Pleistocene evolution of the lower Yellow River in eastern North China: Constraints on the age of the Sanmen Gorge connection

The Yellow River, the second longest river in China, originates in the northeastern Tibetan Plateau, flows in a contorted square-bend-shaped path through the Loess Plateau, then enters the Fenwei Graben before discharging through the Sanmen Gorge onto the North China Plain. Prior to its connection through the Sanmen Gorge, which cuts through the drainage divide of the Hua and Taihang mountain belt, the Yellow River had been partly impounded as a large lake filling the Fenwei Graben. To help decipher the Pliocene-Pleistocene history of the development of the lower reaches of the Yellow River, we analyzed the sedimentary histories of the Fenhe sub-basin in the northeast part of the Fenwei Graben and of fluvial-lacustrine sediments in the Huangdigou (HDG) section, which is now exposed at the upstream entrance to the current Sanmen Gorge. The Fenhe sub-basin changed from lacustrine/peat deposition to fluvial gravels at ~2.5 Ma. We suggest that this sedimentary facies change indicates the establishment of a significant outflow of the former Fenwei Graben Lake through the deepening Sanmen Gorge. The continuing lowering of base-level in the Fenwei Graben, which culminated in the direct flow of the Yellow River through the Sanmen Gorge and/or fluvial inland regressive erosion, also led to headward erosion of a new paleo-Fenhe River that cut through the Fenhe sub-basin. Tectonic activity and climate shifts may have contributed to the change to the modern path of the Yellow River. • The Fenhe sub-basin changed from lacustrine/peat deposits to fluvial gravels at ~2.5 Ma. • The detrital material deposited in the Sanmenxia isthmus was mainly from local sources at ~2.5 Ma. • Tectonic activity and climate shifts may have contributed to the change to the modern path of the Yellow River.

IS ABERRANCY A RELIABLE INDICATOR FOR MAJOR PALEOCLIMATIC DISTURBANCE?

ABSTRACT Aberrant forms of many different spore and pollen taxa (sporomorphs) are often used to assess timings and extent of environmental stress at major extinction/climate events. However, little is known about the normal level of malformations in these taxa. Malformation can manifest in several different ways, including significant size differences (± from the accepted range for the species), retention of pollen/spores within tetrads, and unusual and inconsistent morphological aberrations. This study analyses one commonly used pollen genus, Classopollis, and its aberrant forms, from the Bajocian of Argentina. Tetrads, including those incorporating malformed/aborted pollen grains, are found to be common, showing that tetrads of Classopollis are not a reliable signal of major environmental disturbance. The results and discussion presented here emphasize why palynological data must be interpreted in context of the depositional dynamics, facies changes and how they affect the assemblages in conjunction with understanding variations in the strategies of individual flora.

Mercury evidence of intense submarine volcanism and hydrothermal activity during a mid-Tournaisian anoxic event in the Carnic Alps

The mid-Tournaisian Event, or Lower Alum Shale Event (LASE), is linked to severe facies changes including pelagic carbonates and widespread black siliceous shales and radiolarites in many parts of the world. For the first time, high-resolution inorganic geochemistry and framboidal pyrite analyses were applied to decipher depositional condition changes during the mid-Tournaisian event in the Carnic Alps. The predominance of tiny pyrite framboids, high Corg/P, U/Th, and V/Cr ratios, generally higher enrichments of redox-sensitive metals such as Mo, U, V, and depletion in Mn suggest anoxic/euxinic conditions at the sea bottom. Moreover, we found very large anomalous Hg spikes (with maximum values reaching 3650 ppb) for the first time in the mid-Tournaisian deep-water marine succession of the Carnic Alps. Our results suggest intense volcanism during the LASE, which triggered the mid-Tournaisian anoxic event. The most likely candidate for the observed Hg anomalous contents is submarine arc volcanism and hydrothermal activity connected with the collision of the peri-Gondwanan terranes Paleo-Adria and probably Armorican Terrane Assemblage (ATA) and/or Noric terrane during the first phase of the Variscan orogeny.

Sedimentology and stratigraphy of the Cenomanian Buda Limestone in central Texas, U.S.A.: Implications on regional and global depositional controls

The Cenomanian Buda Limestone is a distinctive rock formation widely distributed in Texas and its neighboring regions. The extensive character and regional significance of this unit make the Buda Limestone a key stratigraphic datum in the Texas Gulf Coast Basin. Detailed sedimentologic and stratigraphic studies of this formation were mostly focused on the west Texas exposures. In central Texas, on the contrary, very few studies have been performed. Thus, the sedimentary environments and depositional dynamics in this region are still poorly understood. Moreover, the regional correlation between the central and west Texas lithostratigraphic members of this formation remains unknown. Here, based on a detailed sedimentologic and stratigraphic study of central Texas sections (Austin-Kingsbury-San Antonio transect), the Buda Limestone is interpreted as a shallow-subtidal, semi-restricted to nearly open marine (lagoonal) shelf deposit. This unit is subdivided into two members (comprising 4th-order sequences S1 and S2) laterally variable in the study area. Vertical and lateral facies changes in the Buda Limestone are interpreted to be a function of the dynamic interaction of an irregular topography with fluctuating sea levels, under possible eustatic control. The informal (central Texas) “lower Buda” member is laterally correlated with the Lechuguilla Member (lower Buda) and Red Light Member (middle Buda) of western Texas. The informal (central Texas) “upper Buda” member, on the other hand, corresponds to the Love Station Member (upper Buda) from west Texas.

Differentiate allogenic and autogenic controls on the formation of parasequences and depositional sequences of a tide‐ and wave‐dominated carbonate platform (Lower Cretaceous, Kopet‐Dagh Basin, Iran)

The carbonate‐dominated successions of the Tirgan Formation (Latest Barremian‐Early Aptian) in the Kopet‐Dagh Basin (Iran) were studied to decipher the tectonic and eustatic sea‐level effects, as well as the autogenic influence on lateral and vertical facies changes, depositional environment, and sequence stratigraphy of the tide‐wave‐dominated sediments at the northern margin of the Neo‐Tethys Ocean. Fourteen facies were identified in the studied sequences, here grouped into five facies associations according to the depositional setting: tidal flat (A), lagoon (B), shoal (C), shallow open‐marine (D), and deep‐open marine (E). A third‐order depositional sequence, including a transgressive system tract (TST) and a highstand system tract (HST) was also identified, along with several medium‐ and small‐scale, thickening‐ and shallowing‐upward cycles (parasequences). The development of the depositional sequence and parasequences of the studied successions of the Tirgan Formation were controlled by interactions between allogenic (tectonic and eustasy) and autogenic factors (wave and tidal hydrodynamic regimes). The allogenic factors mainly affected the stacking pattern and parasequence development of the TST deposits in the lower part of the Tirgan Formation, characterized mainly by the deep‐open marine association. Autogenic factors display a main influence on the stacking pattern and formation of the HST deposits and related parasequences, characterized by shallow open‐marine‐lagoon–shoal associations developed in the upper part of the Tirgan Formation. The tectono‐sedimentary model for the evolution of the tide‐wave‐dominated carbonate platform represented by the Tirgan Formation may be useful for further studies on sedimentary basin evolution or palaeogeographic reconstructions of the Neo‐Tethys margin.