Fining-upward Succession Research Articles

Sedimentary characteristics and geophysical architecture of the Cretaceous Bambalo claystone formation (Mayo Oulo-Lere Basin, North Cameroon)

• Depth and spatial development of Bambalo sedimentary sequences during the Cretaceous. • The Bambalo Formation described in terms of lithostratigraphy, VES and ERT. • Fluvio-lacustrine deposits including claystone, siltstone and limestone. • Sequences dominated by retrogradational sequences in a lacustrine environment. The Mayo-Oulo-Lere Basin, with an overall surface area of 122 km 2 is located in northern Cameroon between the western extension of the Doba Basin and the eastern edge of the Benue Trough. This study maps the depth and spatial development of Bambalo sedimentary sequences in the Mayo Oulo-Lere Basin that were deposited during the Cretaceous. The depositional sequences present an exposure of crocodile fossils and plants evidenced by superficial alteration. The Bambalo Formation is described in terms of lithostratigraphy, vertical electrical sounding (VES) and electrical resistivity tomography (ERT) to provide a better understanding of stratigraphic evolution and setting conditions during sedimentation. Sedimentary deposits in the Mayo Oulo-Lere Basin are mainly fluvio-lacustrine deposits consisting of alternating claystone, siltstone and limestone. The lithostratigraphic log of Bambalo for the subsurface geology up to 25 m presents three main depositional sequences named S1, S2 and S3. S1 presents ripples marks and desiccation cracks that are directly observed on the surface outcrop. The separation between S1-S2 and S2-S3 is marked by unconformity surfaces. The sedimentary sequences are dominated by retrogradational depositional trends that describe short sequences of fining-upwards successions. The ERT image results obtained from geophysical analysis using Res2Dinv display local features associated with folding in the aforementioned sedimentary thickness of approximately 30 m. Additionally, the VES analyses using ipi2win software show that the upper 78 m part of the Bambalo formations is composed of four layers (L1, L2, L3 and L4) distinct by resistivity. L4 Layer correlated with the top of lithostratigraphic log S3, while L3 is a semiresistive set of 78 Ω·m layering S1 and S2 lithostratigraphy sequences. Layer L2 corresponds to a conductive set with resistivity of approximately 27 Ω·m above the lower layer L1, a resistive sequence with resistivity greater than 1000 Ω·m. The combination between the major rifting faults (N70°, N110° and N130°E), syntectonic sedimentation and Barremian-Aptian age attributed to sediments of Bambalo demonstrate clearly that the sediments were deposited during or few time after the rifting phases. The sediments are resulting from a rapid filling of the basin characterised with retrogradational sequences that are controlled by the evolution between accommodation space created after each tectonic phase and the base water level rise within the basin. The rapid elevation of water and sedimentation might be one of the reasons of the massive death of crocodilians. The results of this study demonstrate that the combination of ERT and lithostratigraphic analysis is a powerful tool for a better understanding of the Bambalo sedimentary process and basin evolution. The lateral and vertical evolution of the layers being proven, a future deep excavation will certainly make it possible to bring to light new types of fossils from these deposits and in the neighbouring basins.

Integration of well logs and seismic data for facies analysis and modelling of the El-Wastani Formation in the Sequoia Gas Field, offshore Nile Delta, Egypt

Reservoir rock facies modelling helps in determining the degree of reservoir variability for enhanced management of the heterologous facies’ reservoirs, both at borehole scale and more regionally at seismic scale. The Pliocene Offshore Sequoia Gas Field is located near the boundary between the Rosetta Concession and the West Delta Deep Marine Concession (WDDM) on the western side of the Nile Delta. It is characterised by canyon systems of complex turbidite channel-levee deposits that are multi-stacked. In order to create various depositional facies that are compatible with a deep marine environment, an advanced facies model was built from the combination of the seismic, core, and formation micro imager (FMI). Sandstones (laminated and massive), shale (laminated and massive mud-rock), silt, and thin sandstone beds were identified as four major facies. In the Sequoia field area, the El-Wastani Formation is known as a heterogeneous sequence of sandstones and mudstones arranged into a broad upward-fining succession. High-quality, blocky sands exist at the base, while the upper portion is characterised primarily by isolated sand bodies intercalated with mudstones in the presence of some thin-bedded sands (their thickness less than 1 m).

Badenian (middle Miocene) continental paleoenvironment in the Novohrad–Nógrád Basin (Central Paratethys): a volcano-sedimentary record from the Páris-patak Valley in Hungary

Two levels of volcaniclastics, comprising conglomerates, sandstones and mudstones, are interbedded with upper middle Miocene (upper Badenian) andesite pyroclastics near the Hungarian-Slovakian border in the distal region of the Central Slovakian Neogene Volcanic Field. Based on the field sedimentological investigations, the facies of the volcaniclastics (e.g., lateral and vertical grain size changes, sedimentary structures, textures, clast composition), their geometry and field relationships are documented herein with the aim of reconstructing the depositional environment. The silica-cemented volcaniclastics are mostly andesite clasts with only ~ 5% being granitoid, quarzitic, and tuff clasts as well as charred fossil wood fragments. The coarse-grained facies association includes crudely stratified, tabular or lenticular, clast-supported pebble-cobble conglomerates with erosive basal surfaces, b-axis imbrication, alternating with sets of cross-bedding. The fine-grained facies association comprises cross-bedded pebbly to medium-grained sandstone and lenses of tuffaceous clayey siltstone with rare horizontal lamination and water-escape structures. Rip-up mudstone clasts, with diametre up to 1 m, are present in both facies associations, revealing the co-existence of abandoned silty palaeo-channel plugs. Facies associations are arranged in several 0.5-4-m-thick, fining-upwards successions that likely formed in shallow channels as downstream- to laterally accreting longitudinal bars, extensive gravel sheets and bars that migrated in peak flow during floods. Palaeocurrent indicators (i.e., clast imbrication, direction of planar cross-bedding, orientation of petrified wood logs) show bedload transport by traction currents, initially towards ~S, and later towards ~W. Intermittently debris flows also occurred. Cross-bedded sandstones formed as in-channel transverse bars during medium/low discharge. Variation of grain size shows frequent discharge fluctuations during permanently wet conditions in the late Badenian. The 4-5-m-deep, low-sinuosity channels were part of a high-energy, gravel-bed braided-river system on the south-eastern foothills of the Lysec palaeo-volcano. Here, pyroclastics were reworked and redeposited as volcaniclastics during inter-eruption, high-discharge episodes.

A Review of the Lithostratigraphy of the Early Cretaceous Sao Khua Formation, Khorat Group in Northeastern Thailand

Non-marine Cretaceous rocks are widespread in northeastern Thailand and is well known as “the red bed” Khorat Group. The Sao Khua Formation is in the upper half of the Khorat Group which is comprised of six formations. This formation was named and defined at the type section for the rocks between the restricted PhraWihan Formation and the Phu Phan Formation in the drainage area of the Huai Sao Khua, an intermittent stream that flows westward parallel to the highway between Nong Bua Lamphu and UdonThani Provinces. It contains richest and most diverse vertebrate and invertebrate Mesozoic fossils in Thailand. The Sao Khua Formation is characterized by the sequence of the fining-upward successions of at least 4-5 megacycles throughout the formation with the total thickness ranging between 400-700 meters. Each cycle starts with a channel lag conglomerate which the clasts consist totally of re-worked calcrete nodules. The conglomerates were overlain by fine-to medium-grained sandstones of point bar deposit. Finally, the top part of each cycle was covered by a succession of fine-grained floodplain deposit that makes up 60%-70% of the formation. Paleosols are commonly found in the Sao Khua Formation within the floodplain sequence and their geochemistry indicates a semi-arid paleoclimate. Based on lithostratigraphy, the Sao Khua Formation is interpreted to have been deposited by a meandering river system under a semi-arid climate condition. The age of the formation is assigned as the Hauterivian-Late Barremian based on vertebrate and bivalves fossils.

The late Paleozoic Ice Age along the southwestern margin of Gondwana: Facies models, age constraints, correlation and sequence stratigraphic framework

The southwestern margin of South America offers a complete record of the Late Paleozoic Ice Age (LPIA) that affected the Gondwana supercontinent. The tripartite division of LPIA glacial episodes has been refined with the help of new radiometric dates and biostratigraphic (flora and fauna) zonations in recent years to five shorter-lived discrete events: 1. Latest Devonian-earliest Tournaisian, 2. Tournaisian, 3. Visean, 4. Serpukhovian-Early Bashkirian, 5. late Pennsylvanian-earliest Permian. These glacial events are capped by postglacial transgressive deposits with marine fauna. The unbalanced preservation potential of the glacial deposits, skewed toward the glaciomarine sediments, provides an uneven stratigraphic record with few cases of continental glacial sedimentation, confined to the Serpukhovian-Early Bashkirian event, and numerous examples of glacial sedimentation in marine environments. Glacial sedimentation in marine settings has been grouped in two main facies associations: a valley-glacier-retreat (fjord) facies association and a submarine-retreat (glaciomarine apron) facies association in open-marine areas.Transitional facies, correspondent to those formed by the flooding of valleys during postglacial transgressions, are widely distributed along the Protoprecordillera in western Argentina, where paleofjord successions are well exposed particularly in western Paganzo Basin, and mapped in subsurface in the Tarija basin. A general paleofjord model includes (from base to top) the following stages: (i) Incision of paleovalley and deposition of subglacial diamictites in ice contact deltas, (ii) Early Transgressive stage characterized by resedimentation of subglacial material by subaqueous sediment gravity flows and slumps in proglacial settings, (iii) Maximum flooding (late transgressive stage) dominated by black shales or laminated mudstones related to a marine incursion that flooded valleys; normal marine or brackish conditions may dominate this stage and (iv) Highstand: progradation of a fluvial-deltaic system including in some cases Gilbert-type deltas. In glaciomarine apron environments, the basal facies includes massive clast-supported conglomerates, with few striated and polished clasts, followed by fining-upward successions including thinly bedded diamictites with ice-rafted debris (IRD) and locally contorted sandstone masses in diamictite beds, indicative of mass-emplacement mechanisms. The presence of inter- and intratill pavements suggests glacial advance/retreat fluctuations along the basin margins.Deglaciation sequences, reflecting deposition mainly during the retreat of ice sheets, ice caps and alpine glaciers and successive deglaciation, can be used as operational tools for the analysis of glacial successions in southwestern Gondwana. They are characterized as rather simple upward-fining successions in open marine settings as exemplified in most of the Calingasta-Uspallata Basin,Claromecó Basin (and adjacent Ventana foldbelt, VFB) and central portions of the Paraná and Karoo basins. In more proximal areas (i.e., paleofjords) this vertical trend is commonly punctuated with deltaic wedges fed by nearby provenance areas.The late Paleozoic glacial-related successions of southwestern Gondwana exhibit a common tripartite motif, equivalent to second-order sequences with estimated durations of 10–80 Myr. The lower section corresponds to glacial and glacially-influenced diamictites; the middle interval is initiated with postglacial transgressions. The lower and middle intervals correspond to the deglaciation sequence as described and identified in several basins of Gondwana. Finally, the upper term includes coastal progradation, followed in some places by continentalization, accompanied in many sectors by increasing aridization. Examples of second-order sequences can be identified in the thick late Paleozoic successions of the Paraná and Karoo basins and in the VFB. Thinner second order sequences can be identified in the Calingasta-Uspallata, Rio Blanco, Paganzo and San Rafael basins. In the Paganzo and San Rafael basins the middle interval is also punctuated by short lived marine ingressions. The basal sequence boundary is commonly an abrasion surface (glacial erosion surface, GES) developed on bedrock. Deglaciation sequences are assigned to third order sequences made up, when present, of a thin lowstand system tract (LST) of subglacial deposits followed upward by thick glaciomarine and glacially influenced sediments. These facies are part of a thick transgressive systems tract (TST) that culminates with marine shales that reflect interglacial or postglacial conditions during ice retreat. Thus, the deglaciation sequences are proposed to be third order sequences made up of LST-TST or exclusively TST.

Re-evaluation of depositional models for the lower Permian Patchawarra Formation, Cooper Basin, South Australia: implications for petroleum exploration

The Late Carboniferous–Triassic Cooper Basin is Australia’s most prolific onshore petroleum province. The lower Permian Patchawarra Formation, which is up to 680 m thick and consists of up to 10% coal, is a major exploration target in the basin. Eighteen cores through the formation have been logged to re-evaluate the existing fluviolacustrine depositional model. The siliciclastics form fining- and coarsening-upward sequences that are 1–10 m thick. They are predominately fine-grained with abundant lenticular bedding, wavy bedding and thinly interlaminated siltstones and clays resembling varves. Granules and pebbles, interpreted as dropstones, are present throughout the formation. Coal beds are up to 60 m thick and rich in inertinite. Other than the coal beds, there is little evidence of the establishment of terrestrial conditions: roots are rare and there are no siliciclastic palaeosols. The siliciclastics are interpreted as the deposits of a large glaciolacustrine system, with the fining-upward successions deposited in subaqueous channels cut by hyperpycnal flows and the coarsening-upward successions deposited as overbank splays between those channels. Hyperpycnal flows may have resulted from sediment-laden cold water emanating from glacially-fed rivers, similar to those seen in many large glacial lakes in high latitudes and altitudes today. Much of the coal is interpreted as the accumulation of peats from floating mires that covered large parts of the glaciolacustrine system at certain time intervals. The high inertinite content of many coals is interpreted as the decay of organic matter within the floating mire. These new interpretations have the potential to enhance reservoir characterisation within the basin.

Shallow marine basaltic volcanism of the Machadodorp Member (Silverton Formation, Pretoria Group), Transvaal Basin, South Africa — An example of Paleoproterozoic explosive intraplate volcanic activity in an epeiric embayment

The early Paleoproterozoic Machadodorp Member of the Silverton Formation (Pretoria Group, Transvaal Supergroup), South Africa, is an example of ancient submarine explosive volcanism in an intra-cratonic setting under incipient rifting conditions. The Silverton Formation consists of three different members, which include, in ascending order, the Boven Member, the Machadodorp Member and the Lydenburg Member. The formation is primarily characterized by the muddy sediments of the Boven and Lydenburg members, which formed in a relatively shallow submarine environment, predominantly as sub-storm wave-base pelagic deposits, within an epeiric embayment on the Kaapvaal Craton. The subaqueous Machadodorp Member volcanic activity is mostly distributed in the eastern part of the basin. So far, the volcanism of the Machadodorp Member has not been studied in detail. Therefore, a detailed facies analysis of its volcanism was initiated, allowing constraints on its volcanic evolution.The Machadodorp Member consists of a basal unit of basaltic sheet lava, followed by a fining-upward succession of volcaniclastic rocks, ranging from breccias, tuff-breccias and tuffs, rich in fluidal-shaped clasts, to laminated tuffs that are related to subaqueous mass flows, and a final sheet lava that characterized the end of volcanic activity in the section studied.The Machadodorp Member rocks are tholeiitic basalts in composition, with all samples plotting in the low-TiO2 suite. Fractional crystallization of clinopyroxene, olivine and plagioclase was the predominant evolutionary process as illustrated by mineral chemistry and major element geochemical modeling. AFC (Assimilation and Fractional Crystallization) processes could not account for all the trace element variations, nor for the arc-like signatures observed on the primitive mantle normalized plots. Variable ancient mantle enrichment beneath this area is a more plausible cause for the trace elements variations observed in the Machadodorp rocks. Trace element modeling indicates that the parental composition of these rocks was a variably enriched spinel lherzolite source. Such enrichment must have occurred before 3 Ga during episodes of arc collision and subduction.

Stratigraphic charactertistic and tectonic control on the paleogene sedimentary evolution of the Baxian Half-graben, Bohai Bay Basin, east China

The depositional and structural development of a deltaic dominated succession, interpreted from seismic data, cores, well curves and lab data, is discussed. The case is from a comprehensive analysis of stratigraphy and the depositional process of a deltaic to continental succession in the early to late Paleogene in the Baxian Half-graben, Bohai Bay Basin, East China. The evolution of three genetic successions with a total thickness of 1000–7000 m, comprising three facies associations, including fan delta, braided-river to shallow water delta and lacustrine deposit, records: a, initial rift stage, b, late rift stage, and c, post-rift stage. (1) The initial rift stage is made up of several fining-upward successions, mainly stacked in retrogradation style that pass from the fan delta plain, through the fan delta front to pro-delta in a deep lacustrine environment. This stage is characterized by high intensity rifting and the deposition was keeping up with subsidence. (2) The late rift stage is made up of several successions stacked in both progradation and retrogradation styles. The succession is defined by braided-river deltas, distributary channels, subaqueous channels, swamp, levees, and fluvial-dominated mouth bar, which are mainly identified using core data. This stage is characterized by a decrease in the intensity of rifting and finer-grained deposits. (3) The post-rift stage is made up of several successions stacked mainly in an aggradation style. Shallow water delta developed in the early phase, and lacustrine deposits developed in the late phase. The transition from initial-rift to late-rift phase is represented by a seismically identifiable regional angular unconformity and an overall upward decrease in the quantity of syn-depositional faults. The late-rift to post-rift evolution is represented by an overall decrease in grain size, decrease in fluvial influence and increase in wave influence. The research process can be a reference for the study of stratigraphic architecture and sedimentary process in other lacustrine basins where tectonic movements are well developed. The achievements of this article can be an important basis for the further exploration in the half-graben.

Tectonically controlled evolution of the Yellow River drainage system in the Weihe region, North China: Constraints from sedimentation, mineralogy and geochemistry

This study investigated the evolution of the middle reach of the Yellow River by examining the latest Cenozoic (∼5.0–0.15 Ma) sedimentary history of the Weihe and Sanmenxia basins in the Weihe region of North China. Although the development of the two basins and the evolution of the Yellow River have long been related to the rapid uplift of the Tibetan Plateau, the relationship between the landform evolution and regional tectonics is still poorly understood. Here, we report the results of a detailed study on sedimentation and provenance of the two basins and their spatial and temporal relationships to regional fault development. The results show that the two basins were possibly originally isolated from each other, between ∼5 Ma and ∼2.8–2.6 Ma, but later connected by the Yellow River at ∼2.8–2.6 Ma. This process is recorded in the coarsening-upward sequence of the Weihe Basin strata and the coeval fining-upward succession of the Sanmenxia Basin strata. At ∼1.0 Ma, the Sanmenxia Basin strata developed a coarsening-upward trend, which we interpret as an indication of the formation of the Yellow River in the region. In addition, changes in the drainage system at ∼2.8–2.6 Ma and at ∼1.0 Ma have been recorded as dramatic provenance changes in the sediments of the Sanmenxia Basin.

Late Pleistocene-Holocene sedimentary facies and evolution of the Jeju Strait shelf, southwest Korea

The depositional environments of the Jeju Strait shelf since the last interglacial period are analyzed using sedimentary structures, grain size textures, sediment color, and optically-stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) ages of vibro-cores. The shelf deposits can be divided into 12 sedimentary facies grouped into four depositional units: 1) shelf sand, 2) estuarine sand/mud, 3) fluvial sand/mud, and 4) shelf sand/mud. Each unit is separated by a sharp and unconformable erosion boundary. Unit 1 shows massive to slightly bedded sandy shells with oyster fragments, representing a shelf environment during sea-level highstand. The OSL date of the base of the unit is 124.4 ± 10.0 ka. Unit 2 is characterized by thin periodic parallel laminated mud, suggesting tidal signatures in tidal flats. Sediments are typically moderate brownish, suggesting extreme weathering after deposition. The OSL dates of this unit range from 81.1 ± 5.3 to 74.2 ± 4.7. Unit 3 consists of lower cross-bedded sand and laminated mud with fining-upward successions. It is interpreted as the product of channel deposits in a fluvial environment during a sea-level falling. The OSL ages of Unit 3 range from 50.6 ± 2.9 to 26.1 ± 1.6 ka, belonging to the Weichselian glacial period. The uppermost unit (Unit 4) is composed of homogeneous mud and massive sand with molluscan shell fragments in the modern shelf environment during sea-level highstand. OSL and 14C-AMS ages range from 0.32 ± 0.02 to 11.2 ± 0.1 ka. Consequently, the late Pleistocene-Holocene sedimentary facies in this area consist of marine and non-marine environments, which mainly correspond to sea-level changes.

Three-dimensional characterisation of sedimentary heterogeneity and its impact on subsurface flow behaviour through the braided-to-meandering fluvial deposits of the Castissent Formation (late Ypresian, Tremp-Graus Basin, Spain)

Abstract Fluvial deposits of the Castissent Formation (late Ypresian) form part of the Eocene infill of the Tremp-Graus piggyback basin. The Castissent Formation has been subdivided into three complexes (A, B, and C). This project focuses on the proximal fluvial-sandstones of Complex A in the Mas de Faro outcrop (NE Iberian Peninsula). There, three amalgamated channel belts are exposed in a 15–24 m thick succession that passes upwards from sandy braided-river deposits (A1-A2) to coarse-grained meandering-river deposits (A3). Sedimentary heterogeneities within these deposits are characterised and their impact on oil recovery in a reservoir analogue are estimated using field descriptions, virtual outcrop interpretation, a 3D geocellular facies model and fluid-flow simulations. Petrophysical values of different facies types were derived from well data through analogous fluvial deposits of the Eiriksson Formation, in the Norwegian North Sea. Facies analysis show a waning succession of gravel channel lags, unit-bar and dune deposits in A1; a basal mud-clast channel lag, unit-bars and dune deposits in A2, and a coarse-grained point-bar succession in A3. Flow simulation shows: a) fingering of the waterfront related to the gravel channel lag and unit-bars of A1 and A2, and the gravel bars, scour-and-fill deposits and dunes of A3, which act as thief zones hindering efficient sweeping of the intervals immediately above; b) segregation of the injected fluids towards the base of the channel belts due to the fining-upwards successions; and c) vertical compartmentalization due to a relatively impermeable barrier at mud-clast channel lag beds. Permeability contrasts trapped 35% of the original oil in place after 0.5–0.6 pore volumes were injected.

Sequence stratigraphic analysis of the Lower Jurassic Precipice Sandstone and Evergreen Formation in the Surat Basin, Australia: Implications for the architecture of reservoirs and seals for CO2 storage

Abstract The Lower Jurassic Precipice Sandstone and Evergreen Formation in the Surat Basin, Australia are a highly prospective interval for carbon capture and storage (CCS). However, their stratigraphic nomenclature is inconsistently applied, and a basin-wide stratigraphic framework that is ubiquitously agreed upon remains elusive. In particular, a sandy transitional sandstone interval that occurs above the main Precipice Sandstone reservoir unit has caused confusion about how the two units should be subdivided. To address this issue, we integrate core observations with seismic interpretation and wireline log correlation to construct a sequence stratigraphic framework for the Lower Jurassic System that goes beyond lithostratigraphy. The main findings of our work include: (1) the identification of three 3rd-order sequences, SQ1-SQ3, from base to top. Two main sandstone intervals, the Precipice Sandstone and the Boxvale Sandstone Member (Evergreen Formation), represent the lowstand systems tracts (LSTs) of SQ1 and SQ3, respectively. The Westgrove Ironstone Member in the upper Evergreen Formation – a distinctive oolitic ironstone unit – represents the transgressive system tract (TST) of SQ3; (2) the transitional interval above the main Precipice Sandstone reservoir corresponds to the lower TST in SQ1 (lower Evergreen Formation). It is manifest as an upward-fining succession with a retrogradational facies stacking pattern, and is significantly different from the main Precipice Sandstone reservoir which shows an aggradational stacking pattern; (3) the Precipice Sandstone and lower Evergreen Formation progressively onlap the western and the eastern margins of the Surat Basin, and this confines the Precipice Sandstone to the central portion of the basin; (4) the three sequences (SQ1-SQ3) approximately coincide with global sea-level cycles documented from the early Jurassic. Two episodes of accelerated tectonic subsidence were responsible for the thinning and onlap of SQ1 and SQ3 onto the basin margins. In contrast, weaker tectonic subsidence was responsible for the overall finer grained sediment, the uniformity in thickness, and widespread distribution of SQ2. The results of our stratigraphic analysis indicate that the architecture of the reservoir and seal significantly differs from previous thinking, such that: (1) the Precipice Sandstone, the main reservoir unit, has a distribution that is limited to the basin centre; (2) the transitional interval above the main Precipice Sandstone reservoir forms poorly-connected, localized reservoirs that onlap and backstep towards the basin margins; and, (3) SQ2 and SQ3 are sealing units because they are very widespread and mud-dominated. Viewing the Precipice Sandstone and Evergreen Formation from a sequence stratigraphic standpoint provides important information about how to subdivide them and helps clarify the stratal relationships that were previously unclear from a mixture of terminology. Furthermore, this study gives insights into the spatial-temporal evolution of this reservoir and sealing interval that is an important CCS target in Australia.

An unusual association of hadrosaur and therizinosaur tracks within Late Cretaceous rocks of Denali National Park, Alaska

We report details of a unique association of hadrosaur and therizinosaur tracks found in the Late Cretaceous lower Cantwell Formation, Denali National Park, central Alaska Range, Alaska. This rock unit is now well-documented as a source of thousands of fossil footprints of vertebrates such as fishes, pterosaurs, and avialan and non-avialan dinosaurs. The lower Cantwell Formation in this area consists of numerous fining-upward successions of conglomerates and pebbly sandstones, cross-stratified and massive sandstones, interbedded sandstones and siltstones, organic-rich siltstones and shales, and rare, thin, bentonites, typically bounded by thin coal seams, and it contains a diverse fossil flora. We report the first North American co-occurrence of tracks attributable to hadrosaurs and therizinosaurs in the lower Cantwell Formation. Although previously un-reported in North America, this association of hadrosaur and therizinosaur tracks is more characteristic of the correlative Nemegt Formation in central Asia, perhaps suggesting that parameters defining the continental ecosystem of central Asia were also present in this part of Alaska during the Latest Cretaceous.

Infilling of the Canche Estuary (eastern English Channel, France): Insight from benthic foraminifera and historical pictures

Abstract A multiproxy approach based on benthic foraminifera, sediment grain-size, total organic carbon content, major and trace element concentrations, and radionuclide activities was used to investigate the recent landscape evolution of the Canche Estuary (eastern English Channel, France). In the present study the radiometric dating based on 210Pb and 137Cs activities could only establish that the sediments were deposited recently. As an alternative method, aerial historical pictures were used for the first time to date core sediments as well as to enhance the palaeoenvironmental interpretations. In approximately one hundred years, an initial naked tidal flat has been gradually replaced by a vegetated salt marsh. In the bottom part of the core, foraminiferal assemblages are dominated by Cribroelphium excavatum and Elphidium margaritaceum. Haynesina germanica is the most abundant taxon in the middle part of the core while Entzia macrescens is dominant in the upper part. The sediment core represents a typical fining-upward succession in a low-impacted tide-dominated estuary filled by progradation. Our outcomes highlight how a multidisciplinary approach based on abiotic and biotic parameters is essential for understanding complex transitional areas like estuaries. When dating is not provided by classic radiometric methods, historical pictures (

Uniqueness Deposit of Sediment on Floodplain Resulting From Lateral Accretion on Tropical Area

Kampar rivers has a length of 413 km with average depth of 7.7 m and width of 143 m. Sixty percent of this rivers are meandering fluvial system which transport and deposit a mixture of suspended and bed-load (mixed load) along low energy. River channel that moving sideways by erosion is undergoing lateral migration and the top of the point bar becomes the edge of the floodplain and the fining-upward succession of the point bar will be capped by overbank deposits of Kampar River. Along the Kampar Rivers, there are more than 60% of floodplain sediments and almost all of the floodplain formed by bend migration on the suspended-load channels of Kampar watershed. This formation consist of succession of fine to medium sand and silt/mud, with root traces, that form as drapes on the prograding bank. These beds dip mostly channel wards and quickly wedge out as they grade up and onto the floodplain. The depositional model is presented showing how lateral accretion can make a significant contribution to the preservation of fine-grained within channel deposits in contemporary floodplains. The examples presented here demonstrate that analogues to ancient point-bar deposits containing alternating sandstone and shale sequences are common in the low-energy fluvial environments of Riau rivers especially Kampar rivers.

Erosion and deposition by supercritical density flows during channel avulsion and backfilling: Field examples from coarse-grained deepwater channel-levée complexes (Sandino Forearc Basin, southern Central America)

Erosion and deposition by supercritical density flows can strongly impact the facies distribution and architecture of submarine fans. Field examples from coarse-grained channel-levée complexes from the Sandino Forearc Basin (southern Central America) show that cyclic-step and antidune deposits represent common sedimentary facies of these depositional systems and relate to the different stages of avulsion, bypass, levée construction and channel backfilling. During channel avulsion, large-scale scour-fill complexes (18 to 29m deep, 18 to 25m wide, 60 to >120m long) were incised by supercritical density flows. The multi-storey infill of the large-scale scour-fill complexes comprises amalgamated massive, normally coarse-tail graded or widely spaced subhorizontally stratified conglomerates and pebbly sandstones, interpreted as deposits of the hydraulic-jump zone of cyclic steps. The large-scale scour-fill complexes can be distinguished from small-scale channel fills based on the preservation of a steep upper margin and a coarse-grained infill comprising mainly amalgamated hydraulic-jump zone deposits. Channel fills include repeated successions deposited by cyclic steps with superimposed antidunes. The deposits of the hydraulic-jump zone of cyclic steps comprise regularly spaced scours (0.2 to 2.6m deep, 0.8 to 23m long) infilled by intraclast-rich conglomerates or pebbly sandstones, displaying normal coarse-tail grading or backsets. These deposits are laterally and vertically associated with subhorizontally stratified, low-angle cross-stratified or sinusoidally stratified sandstones and pebbly sandstones, which were deposited by antidunes on the stoss side of the cyclic steps during flow re-acceleration. The field examples indicate that so-called spaced stratified deposits may commonly represent antidune deposits with varying stratification styles controlled by the aggradation rate, grain-size distribution and amalgamation. The deposits of small-scale cyclic steps with superimposed antidunes form fining-upwards successions with decreasing antidune wavelengths, indicating waning flows. Such cyclic step-antidune successions form the characteristic basal infill of mid-fan channels, and are inferred to be related to successive supercritical high-density turbidity flows triggered by retrogressive slope failures.

Depositional architecture and peculiar sedimentary features of late Cretaceous Utrillas Formation at Tamajón (Guadalajara, Spain)

The Utrillas Formation represents clastic wedges that accumulated in relation to continental-coastal areas of Iberian Basin during the worldwide late Cretaceous sea-level rise. At the Tamajon outcrop the late Cenomanian Utrillas wedges are composed of four facies associations (FA1 to FA4), which unconformable overlay Triassic deposits. Basal sediments (FA1) are interpreted as high energy, braided fluvial deposits, characterized by coarse-grained (conglomerate–sandstone) facies; which grade upwards to tide-influenced, estuarine sedimentation (sandstones and mudstones with inclined heterolithic stratification, FA2), and then to high-energy, coastal sheet and channelled sandstones with different tidal features (FA3); and finally, to fine-grained (mudstones and minor burrowed sandstones) of an offshore marine associations (FA4). The depositional architecture based in the presence and hierarchy of several ranks of bounding surfaces and the overall upward-fining succession show the long term retrogradational trend of these facies associations. Peculiar sedimentary features of these sediments are 1) the presence of large-scale, single sets of cross beds infilling large erosive channels, which are tidal (not aeolian) in origin. 2) The size and length of the cross-bedding defined by couplets of different grain size; here interpreted as originated by flow unsteadiness in relation to changing tides. And 3) an unusual association of ironstones, wrinkle structures and vertebrate tracks with microbial mats and penecontemporaneous iron encrusting allowing track preservation in the sedimentary record.

Sedimentary characteristics of shallow-water braided delta of the Jurassic, Junggar basin, Western China

The shallow-water braided deltas are hot topic in global sedimentology. In China, this depositional environment forms an important reservoir and exploration target within the basins. Therefore, geological and sedimentologic settings of the Jurassic shallow-water braided deltas in the Junggar basin of western China have attracted much attention in recent years based on the comprehensive analysis of geological and geophysical data acquired. These braided deltas deposited in the shallow Junggar lacustrine basins with gentle slope gradients and prograded towards to the central basin from northeast to southwest (more than 10km). This kind of Jurassic delta was characterized by coarse grain-size (sand to pebble), large cross-beddings, discontinuous fining-upward successions vertically, high percentage of sandstone ratios (up to 70%), very unique distributary channels with few distributary mouth bars, and seismic facies of shingled with a progradational reflections. Based on the detailed research on basin evolution and sedimentary characteristics of deltaic sub-facies, this paper presents the relationship between the shallow-water braided deltaic deposition and lithologic traps predicted to be the favorable and explorable lithological traps in the Junggar Basin.

Detrital zircon geochronology (U–Pb SHRIMP and LA-ICPMS) from the Ampani Basin, Central India: Implication for provenance and Mesoproterozoic tectonics at East Indian cratonic margin

The present study aims at tracking sediment provenance for a Mesoproterozoic craton-margin basin in eastern India, i.e. the Ampani Basin. Occurring on the eastern flank of the Archean Bastar Craton, the basin occupies a very strategic geographic position coinciding with the boundary between Archean craton and a Proterozoic orogenic belt with spatially varied tectonothermal history. The studied basin succession includes unmetamorphosed siliciclastic sediments deposited under three different environmental set-up viz. fluvial, shoreface and shelf. The basin sediment package defines a fining-upward succession with fluvial products at its base, shoreface deposits in the middle and shelf sandstone–siltstone–shale sediments at the top. In this study sandstone–siltstone and shale units encompassing the entire basin succession are analyzed geochemically and with U–Pb detrital zircon geochronology in order to characterize the sediment source/s. The basin was fed mainly by the Paleoarchean to late Paleoproterozoic granitoid source with minor contribution from mafic source particularly at the closing part of its depositional history. Except for relative enrichment, REE and trace element patterns of the three arenaceous units, viz. fluvial, shoreface, shelf sandstone are quite similar. U–Pb analysis of detrital zircon grains from the three units indicate that in the initial phase of basin deposition, sediments were sourced from Paleo- to Neoarchean and Palaeoproterozoic (with an age spread from ca. 3700 to 2400Ma) provenance. From the middle shoreface part upwards, the Paleo- to Neoarchean sources fade away and a new Mesoproterozoic source (ca. 2000–1700Ma) was added with the continued Paleoproterozoic source/s. The youngest zircon populations of the three analyzed units yield an upper age limit of sedimentation at 2079±44Ma (lower being close to 1446±21Ma, as evident from the age of tuffaceous rocks on the middle shoreface part of the basin). The change in detrital zircon age spectra from the middle part of the stratigraphy might be due to some basin-adjacent tectonic activities.

The discovery and significance of a sedimentary hiatus within the Carboniferous Taiyuan Formation, northeastern Ordos Basin, China: Discussion

The paper by Jiang et al. (2012) documented a hiatus and overlying incised-valley fill between the Lower Pennsylvanian Taiyuan Formation (Ct1) and the Upper Pennsylvanian Taiyuan Formation (Ct2). Herein, we provide credible evidence suggesting that the incised-valley fill mentioned by Jiang et al. (2012) is a barrier island. Our work also indicates that the contact between Ct1 and Ct2 is continuous and without hiatus. The Paleozoic Ordos Basin has two stages of sedimentary environments: the early Paleozoic marine carbonate deposition and the Late Paleozoic (Carboniferous to Permian) transformation from paralic to terrestrial. Most scholars believe that the Carboniferous Taiyuan Formation is a barrier–lagoon–tidal flat system (Zhao and Liu, 1990; Hao et al., 2007; Luo et al., 2011) that formed during the relatively large-scale transgression at the North China block. The predominant sedimentary environment of the Taiyuan Formation is the barrier shoreline and has been documented as a barrier island, lagoon, and swamp (Chen et al., 2001; Yang et al., 2005; Hao et al., 2007; Luo et al., 2011). In particular, Jiang et al. (2012) confirmed the facies of Ct1 as a barrier–tidal system and interpreted the interval of Ct2 as a northeast–southwest-trending incised-valley fill and further claimed a hiatus between the Ct1 and Ct2 units. Well D23 locates in the incised-valley fill, as mentioned in figure 14 of Jiang et al. (2012). Its core of the lower Ct2 (above the bottom coal of D23; Figure 1) suggests that it is tidal in origin based on the following sedimentary structures: lens (starved ripples), ripples, and flaser beddings; herringbone bedding; and tidal bundles (couplet) (Figure 1). The fining-upward succession with erosive-based structures of tidal origin is a tidal inlet (Figure 1C, H). The coarsening-upward succession with parallel …