Miocene Sediments Research Articles

Cenozoic reorganization of fluvial systems in eastern China: Sedimentary provenance of detrital K-feldspar in Taiwan

Cenozoic passive margin sediments in Taiwan provide an important natural archive to reconstruct drainage reorganization in eastern China. In this study, we used Pb isotope compositions of detrital K-feldspar to investigate the sedimentary provenance of Cenozoic strata in Taiwan and to constrain fluvial system evolution in eastern China. Eocene to lower Oligocene sandstones in Taiwan are characterized by radiogenic K-feldspar grains (206Pb/204Pb>18.4), indicating that the eastern Cathaysia Block served as the dominant sediment contributor. In contrast, a late Oligocene sample has a Pb isotopic character indistinguishable from that of the Gan River, a major tributary of the Yangtze River. This provenance change is interpreted as the result of headward (westward) migration of the paleo-Min River to the Wuyishan (Wuyi Mountains) during the late Oligocene. Miocene deposits are enriched in relatively unradiogenic K-feldspar (206Pb/204Pb<17.0) which can be reliably traced back to the Dabie and Sulu orogenic belts. Since the early Miocene, the paleo-Yangtze River, mainly draining the Yangtze Craton and the Dabie orogenic belt, delivered a large volume of detritus to the East China Sea Shelf Basin and also to the proto-Taiwan region.

Quantifying the relative contributions of Miocene rivers to the deep Gulf of Mexico using detrital zircon geochronology: Implications for the evolution of Gulf Basin circulation and regional drainage

AbstractSediment routing from hinterland to the deep sea is complicated because it involves evolution of river drainage from source areas to coastal plains and sediment mixing on the shelf and slope by marine currents. Previous regional paleogeographic mapping in the Gulf of Mexico (GOM) has observed a &gt;150 km offset between the middle Miocene paleo‐Tennessee fluvial axis and the associated deep‐sea fan depositional axis, indicating a complicated sediment pathway. We integrate new and published detrital zircon (DZ) U‐Pb age data from fluvial, shelf and deep‐sea deposits to examine the complex Miocene sediment routing system in the northern GOM. These data suggest an increase in sediment load derived from western North America (increased Western Cordillera terranes; &lt;300 Ma zircon age component) from the early to middle Miocene in the deep‐water Green Canyon protraction area. The early Miocene Green Canyon area received sediments mainly from fluvial axes located directly updip: the paleo‐Mississippi River (44%–56%; characterized by Yavapai‐Mazatzal, Mid‐Continent and Western Cordillera sourced 1800–1600 Ma, 1500–1300 Ma and &lt;300 Ma, respectively, and Grenville‐Appalachian sourced 1300–950 Ma and 500–300 Ma age components) and smaller rivers and tributaries draining the Appalachian Mountains (e.g. paleo‐Tennessee River, 18%–43%; mainly Grenville‐Appalachian sourced 1300–9500 Ma and 500–300 Ma age components). In contrast, the middle Miocene Green Canyon deep‐sea fan shows a strong DZ signal from the paleo‐Red River (38%; increased &lt;300 Ma zircon age component), which requires input of additional sediment sources from west of the paleo‐Mississippi system. In addition, the paleo‐Tennessee River, which was a major middle‐Miocene sediment source for the central‐eastern GOM due to uplift and increased erosion of the Appalachian Mountains, is underrepresented (34%; decreased 1300–950 Ma zircon age component) in the middle Miocene Green Canyon fan. We suggest that two mechanisms combined to produce the increased middle Miocene input from western sediment sources and restriction of locally up‐dip Tennessee River sources: (1) regional drainage changes involving middle Miocene capture of the paleo‐Red River and its tributaries by the paleo‐Mississippi River, which at the same time lost some of its eastern tributaries owing to expansion of the paleo‐Tennessee and (2) eastward (clockwise) marine transport of western‐sourced sediment along the shelf or slope, which deflected the paleo‐Tennessee signal &gt;150 km eastward to feed the deep‐sea fan further east, perhaps reflecting intensification of a precursor to the GOM Loop Current.

Palaeoecologic and Palaeoclimatic Inferences from Calcareous Nannofossils in Western Lobe Offshore, Niger Delta

In support of the ongoing temporal palaeoenvironment and palaeoclimatic reconstructions of the Neogene sediments, this study attempts to detail the paleo-proxies recovered from DEL-1 Well, western offshore Niger Delta. The standard smear slide method enabled the recovery of well-preserved calcareous nannofossils that depict early to mid–Miocene (NN4–NN5) sediments. The up-hole relationships between the nannofossil accumulation rate (NAR), the relative abundance of Discoaster and coccolith size of Reticulofenestra show step by step collapse of sea surface stability from early to middle Miocene. The lower horizons (8000–9460 ft) exhibit a low NAR, relatively high Discoaster abundance and relatively large Reticulofenestra size to suggest a deep thermocline and nutricline that characterise oligotrophic conditions in less warm-water induced climate. Conversely, upper horizons (5225–6550 ft) exhibit a high NAR, relatively low Discoaster abundance and relatively small Reticulofenestra size to suggest a shallow thermocline and nutricline that characterise eutrophic conditions in warm-water induced climate. The relative abundance of Helicosphaera carteri within the mid-NN5 suggests mesotrophic conditions within a stressed environment, with the possible occurrence of carbonate crash events. The combined parameters indicate gradual eutrophication and collapse of sea surface stability favouring nutrients and influx of terrestrial sediments in the ocean water as it progressed from early to middle Miocene. The abundance of the palaeo-proxies assemblages suggests hyposaline waters in a neritic environment that prevailed during the warm climatic condition.

Middle and Upper Miocene Deposits and Facies of Northern Ustyurt (Western Kazakhstan)

Abstract —We present data on the most complete Neogene sections and wells of northern Ustyurt and the Cis-Aral area. Miocene deposits in the northern chinks and the North Ustyurt depression are composed of sediments of the Tarkhanian, Chokrakian, Karaganian, Konkian, and Sarmatian regional stages of the Eastern Paratethys, which are overlapped by lower Pontian beds. The distribution of thickness and facies shows that the North Ustyurt depression remained the main synclinal structure of the region, along which the waters of all Miocene transgressions were spread. Sandy material was brought by the rivers from the north: A sandy lens of Chokrakian age is traced along the Shomishtykol Sor almost to the axial part of the depression. Transgressions were pulsating, and the lower and middle Sarmatian deposits were most widespread. These data are presented as a geological profile near Beineu Village and as schematic maps of facies for the middle Miocene regional stages.

The Norwegian mountains: the result of multiple episodes of uplift and subsidence

The elevation of the mountains in Norway is geologically young. Much of the present‐day land surface was buried below a thick cover of relatively young sediments in the early Miocene, 23 Ma, when Scandinavia started to be uplifted. Big river systems eroded deeply into the rising landscape and transported sand and gravel from Norway and Sweden to Denmark where the detritus was deposited in a large delta. In Norway, the erosion formed an extensive plain near sea level that included the present‐day mountain plateau of Hardangervidda and extended across a thick pile of sediments that covered the present‐day coastal areas of Norway. Hardangervidda was uplifted to its present elevation of about 1200 m after a second phase of uplift that began about 5 Ma, in the early Pliocene. The hard bedrock of Hardangervidda has preserved this part of the plain as an elevated plateau, but the part of the plain that extended across the sediments has been eroded away, exposing the underlying basement rocks. That re‐exposed basement surface was shaped in the Jurassic when the climate was warm and humid. The basement rocks were weathered where rainwater seeped into fracture zones. Erosion of the weathered rocks has left a terrain of fracture valleys and hilly relief that contrasts with the sub‐horizontal plain of Hardangervidda. This weathered landscape is today exposed on the slope between the west coast and Hardangervidda. While the elevation of the mountains is young, today's landscape has a long history.

E&amp;P Notes (January 2022)

E&amp;P Notes (January 2022)

Sandstone reservoir quality in light of depositional and diagenetic processes of the Messinian Qawasim Formation, onshore Nile Delta, Egypt

• Sandstone in the upper part of the Qawasim Formation is the main reservoir in the El Tamad field. • Primarily, the sandstone is arenite in composition, well sorted with sub-rounded to rounded grains. • Diagenesis enhanced the reservoir quality of the sandstone with low-cement content, poor compaction and weak fracturing. • Clastic rocks of the Qawasim Formation were deposited in a shelf environment as stacked barrier-island bars. • Carbonate rocks of the Qawasim Formation were deposited in a shelf lagoon with open circulation. The Nile Delta region is the main gas-producing province in Egypt. Late Miocene sediments are the target of drilling in the onshore Nile Delta where it has the potentiality to store and produce hydrocarbons. Five wells of the Messinian Qawasim Formation at El Tamad Field were selected for the present study. Detailed petrographic investigations were carried out to reveal the depositional and diagenetic features of the Qawasim Formation rock units. Two main facies were distinguished in the studied formation: clastic and carbonate facies. The clastic rocks include conglomerate, sandstone and shale, while the carbonate rocks include limestone and dolostone. Depositional, diagenetic and petrophysical parameters of the sandstones of the Qawasim Formation reflect that this rock unit an excellent reservoir for hydrocarbon. These microfacies display depositional features such as well sorting, open packing and poor cementation in both coarse and fine-grained microfacies. The porosity of sandstone was enhanced by diagenetic processes such as dolomitization of calcite cement and low compaction that resulted in grain cracking, while the dissolution of feldspars had a subordinate impact on increasing porosity due to their low abundance and the resultant authigenic clay minerals.

Application of seismic attribute analysis in Lower Miocene reservoir characterization, northeast Bach Ho field, Vietnam

The Cuu Long basin is an Early Tertiary rift basin of southern Vietnam, and the most potential basin in the country with high productive for oil and gas. Special interest in the Lower Miocene reservoir in the Cuu Long basin is caused by the gradual depletion of unique oil-bearing in the fractured basement and the possibility of transferring production wells to overlying deposits in the terrigenous rocks of the sedimentary cover and entering new deposits into development. In recent years, seismic attributes analysis has emerged as an effective tool to predict ancient riverbeds where sand bodies may exist in nonstructural traps. Understanding the distribution of these sand bodies will be of great significance in the orientation of oil and gas exploration activities. The paper applied seismic attribute analysis method combined with artificial neural network (ANN) and well data to predict the distribution of sandstones reservoirs of Lower Miocene sediments in the Northeastern Bach Ho oil field. Seismic attributes selected as input for ANN training including Relative Acoustic Impedance, Root Mean Square, Sweetness. The attributes provide the most obvious opportunity to display geological features with varying seismic amplitude characteristics as well as predict lithofacies, petrology and the distribution of sand bodies. The research results have identified the potential reservoirs in the Northeastern area of Bach Ho field, which are deposited in the fluvial, marginal lacustrine and deltaic environments.

Mineralogická charakteristika sekundárních změn miocenních vulkanoklastických hornin z jižní a střední Moravy (Česká republika)

Bentonite is a significant industrial raw material which deposits deserve protection. The initiative for elaborating this study was the decision from November 2019 of the current owner (the town of Ivančice) to remediate the entire area of the deposit Ivančice-Réna. Lower Miocene volcaniclastic rocks from the Ivančice-Réna (Ivančice) and Middle Miocene sediments in surrounding area of Lipník nad Bečvou are relatively rich in clay minerals (smectites). The mineralogical characteristics of the volcaniclastic rocks were examined using several methods: polarized-light microscopy, X-ray powder diffractometry (XRD), electron microprobe (SEM–WDX), and whole-rocks chemical analysis (ICP-MS). Acid ash-fall tuff and/or very fine-grained tuffite form layers with variable thickness (several cm to m). Grains larger than clay fraction are formed by K-feldspars, plagioclase, biotite, muscovite and quartz crystals accompanied by fragments of pumice and glass shards. The whole-rocks chemical composition of the investigated volcaniclastic rocks indicates similar magmatic sources for both examined samples (Y = 28 and 29 ppm, Yb = 2.8 and 3.2 ppm, Nb = 12 and 14 ppm, Ta = 1.1 and 1.2 ppm, Zr/Ti = 0.16 and 0.17 and Nb/Y = 0.4 and 0.5). The formation of smectite from alteration of rhyolite volcanic glass is accompanied by an increased loss on ignition (LOI: 9.4 and 20.2 wt. %) together with a decrease in K2O (0.7 and 2.1 wt. %) and Na2O (0.6 and 2.1 wt. %). The absence of a negative Ce anomaly suggests that secondary alterations took place under suboxic or anoxic conditions. Smectite and minor opal partially replace volcanic glass and pumice shards. Plagioclase (Ab59–60) and K-feldspar (Or62–78 Ab21–33 An0–1) crystals are relatively fresh (weak sericitic alteration). Biotite is partly to wholly oxidized and chloritized (4.9–6.2 wt. % K2O). Iron oxyhydroxides are present only as minor components. Variation of intensity of secondary alteration (bentonitization) within the studied volcanoclastic layer from the Ivančice-Réna suggests sedimentation in lacustrine environment. In contrast to the case of the sample from Lipník nad Bečvou, the smectite was formed authigenetically from volcanic glass in interaction with seawater or during an early diagenetic process.

First pod record of Mucuna (Papilionoideae, Fabaceae) from the late Miocene of the Yen Bai Basin, northern Vietnam

The genus Mucuna Adans. (Papilionoideae, Fabaceae) contains approximately 105 extant species. It is widely distributed in pantropical areas, with its center of diversity located in Asia. Recent molecular phylogenetic analyses investigated the historical biogeography of the genus; however, a lack of fossil evidence has limited a fuller understanding of the genus. Here, we present the first macrofossil record of Mucuna in the form of pod, collected from late Miocene sediments of the Yen Bai Basin, northern Vietnam. This fossil specimen is characterized by linear-oblong, compressed, torulose, slightly curved pods containing at least three to five seeds, a pair of thickened marginal wings, and an apex with a cone-shaped beak. Detailed morphological observation indicates that these fossil pods belong to Mucuna, and are provisionally assigned to M. cf. birdwoodiana Tutcher. Our discovery supports the hypothesis that Mucuna originated in Asia; moreover, it implies that the genus has been present and has adapted to the humid tropical climate in northern Vietnam since at least the late Miocene.

Forward Modelling for Structural Stratigraphic Analysis, Offshore Sureste Basin, Mexico

The stratal architecture of deep-water minibasins is dominantly controlled by the interplay of two factors, structure growth and sediment supply. In this paper we explore the utility of a reduced-complexity, fast computational method (Onlapse-2D) to simulate stratal geometry, using a process of iteration to match the model output to available subsurface control (well logs and 3D seismic data). This approach was used to model the Miocene sediments in two intersecting lines of section in a complex mini-basin in the deep-water Campeche Basin, offshore Mexico. A good first-pass match between model output and geological observations was obtained, allowing us to identify and separate the effects of two distinct phases of compressional folding and a longer-lasting episode of salt withdrawal/diapirism, and to determine the timing of these events. This modelling provides an indication of the relative contribution of background sedimentation (pelagic and hemipelagic) vs. sediment-gravity-flow deposition (e.g. turbidites) within each layer of the model. The inferred timing of the compressional events derived from the model is consistent with other geological observations within the basin. The process of iteration towards a best-fit model leaves significant but local residual mismatches at several levels in the stratigraphy; these correspond to surfaces with anomalous negative (erosional) or positive (constructive depositional) palaeotopography. We label these mismatch surfaces “informative discrepancies” because the magnitude of the mismatch allows us to estimate the geometry and magnitude of the local seafloor topography. Reduced-complexity simulation is shown to be a useful and effective approach, which, when combined with an existing seismic interpretation, provides insight into the geometry and timing of controlling processes, indicates the nature of the sediments (background vs. sediment-gravity-flow) and aids in the identification of key erosional or constructional surfaces within the stratigraphy.

First report of a bothremydid turtle, Sindhochelys ragei n. gen., n. sp., from the early Paleocene of Pakistan, systematic and palaeobiogeographic implications

We report the discovery of remains of a large chelonian from the base of the early Paleocene Khadro Formation exposed in the Ranikot Fort area (Ranikot Group, Sindh Province, Southern Pakistan). This formation already yielded the snake Gigantophis Andrews, 1901, studied by our friend Jean-Claude Rage. The chelonian specimens consist of a large carapace and a shell fragment of Bothremydidae, a family of Gondwanan origin. A new genus and species, Sindhochelys ragei n. gen., n. sp. is identified from the first specimen and named in honor of Jean-Claude Rage. It is the first report of a Bothremydidae in Southern Pakistan. Its affinities with Cretaceous and Paleocene representatives of the family are discussed. The association of characters such as the shape of the shell, anterior plastral scute pattern and strongly marked decoration characterize the taxon and, despite some similarities, allows excluding close phylogenetic affinities with Taphrosphyini and Carteremys group; other well-documented bothremydids are also excluded. The shell fragment, also strongly decorated, is left undetermined. The discovery of two new littoral bothremydid specimens in the early Paleocene of Pakistan fills a geographic and stratigraphic gap in our knowledge of the family, which is known since the continental early Cretaceous of Africa, diversifying in the world up to the Miocene deposits of the Neotethys. A particular diversification during the Maastrichtian-Paleocene is recognized along the neotethyan coasts, and occasional dispersals across this ocean were possible. Sindhochelys ragei n. gen., n. sp. may have colonized the Indian subcontinent by this time, or may represent an older diversification before the Gondwana breakup.

Structural features in the Miocene sediments of the Pécs-Danitzpuszta sand pit (SW Hungary)

The Pécs-Danitzpuszta sand pit in southern Hungary exposes middle and upper Miocene (Badenian to Pannonian/Langhian to Tortonian) sediments along the mountain front fault zone of the Mecsek Mts and preserves an essential record of tectonic events during and after the early late Miocene, which are not exposed elsewhere in the region. In this paper we present structural observations recorded over 20 years of work, date the deformation events with mollusk biostratigraphy and make inferences on the structural evolution of the area. At the beginning of the time interval between 10.2–10.0 Ma, NNW–SSE (to NW–SE) extension created normal faults and negative flower structures. These show that extension-related fault activity lasted here up to the late Miocene. Shortly thereafter, still in the early part of the time interval between 10.2–10.0 Ma, N–S to NNW–SSE compression ensued and dominated the area ever since. Deformations under this stress field included reverse faulting in the Pannonian marls and sands, folding of the whole succession, with bedding-plane slip and shearingelated block rotation in the already deposited middle and upper Miocene marl layers and continuously changing bedding dips and southward thickening layers in the Pannonian sands. Lake level changes of Lake Pannon must have played a role in the formation of an angular unconformity within the sands besides compression. The compressional event can be explained by the Africa (Adria) – Europe convergence, but cannot be correlated regionally; it pre-dates basin inversion-related events reported from the region so far.

A diverse Miocene fish assemblage (Chondrichthyes and Osteichthyes) from the Pécs-Danitzpuszta sand pit (Mecsek Mts, Hungary)

Chondrichthyans and osteichthyans are widely reported from marine sediments of the Central Paratethys, not only by sporadic occurrences, but also by complex, diverse fish assemblages. Here we present a rich fish fauna from the upper Miocene (Pannonian, Tortonian) lacustrine sediments exposed in the Pécs-Danitzpuszta sand pit, in the SW Pannonian Basin. Altogether 22 227 specimens were investigated, and they could be classified into 17 chondrichthyan and 16 osteichthyan taxa. Among the chondrichthyans Odontaspididae (55.51%) and Myliobatidae (14.4%) are the most abundant, while the bony fishes are dominated by the Sparidae (77.07%). The limonitic, yellow, coarse-grained, gravelly sands yielded an extremely large amount of isolated fish fossils. A considerable part of the vertebrate material of the sands is likely reworked from older, middle Miocene (Badenian and Sarmatian, i.e. Langhian and Serravallian) sediments. The late Miocene calcareous marls underlying the sands also yielded a variety of fish remains. From these remains, associated and articulated latid bones are coeval with the sediment and suggest freshwater and brackish conditions in the area, in accord with other biotic data. Other, isolated fossils, namely teeth, otoliths, cycloid scales and jaw elements of Gadidae, Gobiidae, Sparidae and Latidae could be reworked and thus have a very limited paleoecological significance. Based on habitat preferences of extant relatives, all chondrichthyans and most osteichthyan taxa found in the sands must be of Badenian origin. The abundant remains allow for some conclusions on the environmental conditions during the Badenian. They refer to a shallow, coastal environment with tropical-subtropical climate with connection to more open water habitats. Remains of some osteichthyan taxa were found in coprolites, showing that these taxa were part of the food chain as prey items. Sirenian ribs and odontocete limb bones bearing tooth marks refer to trophic relations between marine mammals and large sized macropredatory sharks. The Pécs-Danitzpuszta record of shark-attributed bite marks on bones of marine mammals is the second of the Badenian of the Central Paratethys. Acipenserids and latids of the sands, linked to brackish and/or freshwater environments, could originate from any Miocene stratigraphic units.

An exceptional surface occurrence: the middle to upper Miocene succession of Pécs-Danitzpuszta (SW Hungary)

The Pécs-Danitzpuszta sand pit is the most important outcrop of the oldest Pannonian (upper Miocene, Tortonian) deposits in southern Hungary. A trench excavated in 2018 exposed Lake Pannon deposits and underlying Paratethys strata down to the upper Badenian (Serravallian), and together with the sand pit they make up a continuous sedimentary succession with a true thickness of ~220 metres. Due to tectonic deformation, middle Miocene deposits and carbonates in the lowermost Pannonian are overturned. Layers become vertical close to the marl-sand boundary, then the dip changes to normal, with continuously decreasing dip angles. The exposed succession starts with 5 m of upper Badenian (13.8-12.6 Ma old) calcareous marls and sandy limestones with sublittoral, then littoral molluscs, which were deposited in the normal salinity seawaters of the Central Paratethys. The overlying 8 m of sand, silt, sandy breccia and conglomerate are fossil-free,; only the lowermost silt layer contains reworked Badenian microfauna. This unit probably accumulated from gravity-driven flows in a fan-like, probably terrestrial depositional setting. The next 7.5 m of frequently alternating thin-bedded limestones, marls and clays with sublittoral biota represent rapid transgression. Foraminifers, ostracods, molluscs and calcareous nannoplankton indicate late Sarmatian, then Pannonian age for this interval. However, the locations of the boundaries indicated by the various groups are not are not consistent, making the position of the Sarmatian/Pannonian boundary uncertain. The Sarmatian beds with marine fossils still accumulated in the Paratethys, between ~12.1–11.6 Ma, under varying salinities due among others to temporary freshwater input. The Pannonian strata already represent sediments of the brackish Lake Pannon. Above these beds, uniform calcareous marl becomes dominant with some clay layers and graded or structureless conglomerate to sandstone interbeds. The deposition of the overall 64- m- thick Pannonian calcareous marl section took place in the open, probably few -hundred -metres -deep water of the lake between ~11.62 and 10.5–10.2 Ma. It may represent a rare, well-exposed surface occurrence of the Endrőd Formation which is known from thousands of wells in the Pannonian Basin. Above this section, a 6-7 -m- thick transitional interval of silty marls and sands is followed by ~140 m of limonitic, pebbly sands. They have poor to moderate sorting and rounding, metre -thick beds with transitional boundaries and abundant fossils and clasts reworked from older Miocene units. Their accumulation took place between 10.2-10.5 and 9.6 Ma by gravity flows connected to deep-water portions of fan deltas.

Temperature Estimates of Lower Miocene (Burdigalian) Coastal Water of Southern India Using a Revised Otolith “Clumped” Isotope Paleothermometer

AbstractCarbonate clumped isotope thermometry is based on the ordering of 13C and 18O in the carbonate lattice and is based on the relative abundance of 13C18O16O in CO2 produced through acid digestion of carbonate minerals. The major advantage of this technique is its non‐dependency on the δ18O value of water from which the carbonate precipitated. Ghosh et al. (2007, https://doi.org/10.1016/j.gca.2007.03.015) previously published calibration data for fish otoliths referenced to heated gases and used the Gonfiantini 17O parameter set in their data evaluation. Herein, we present a new clumped isotope (Δ47) calibration for aragonitic fish otoliths in the absolute reference frame using the International Union of Pure and Applied Chemistry 17O correction. Our revised calibration equation for otolith is: . To test the accuracy of this calibration, we apply it to otoliths of modern Lutjanus lutjanus from the Bay of Bengal. The estimated average temperature (22.3°C ± 4.2°C) for the Bay of Bengal and δ18OV‐SMOW composition of waters of −1.7‰ (±0.5) are consistent with the onsite observations. We also apply the new calibration to well‐preserved otoliths of “genus Ambassidarum” sp. and “genus Gobiidarum” sp. from lower Miocene (Burdigalian) sediments of the Quilon Formation, India to quantify coastal water conditions. Estimated average environmental water temperatures in their habitats were 12.9°C ± 1.7°C, and the average δ18OV‐SMOW of ambient waters calculated yielded a value between −3.5‰ and −2.6‰ (V‐SMOW) (mean: −2.9‰ ± 0.4) and −4.4‰, respectively. These results indicate δ18O values reflect the kinetic effects impacting the δ18O of fish otoliths independently of Δ47, although we cannot fully preclude diagenesis.

Provenance Shifts During Neogene Brahmaputra Delta Progradation Tied to Coupled Climate and Tectonic Change in the Eastern Himalaya

AbstractThe Bengal Basin preserves the erosional signals of coupled tectonic‐climatic change during late Cenozoic development of the Himalayan orogen, yet regional correlation and interpretation of these signals remains incomplete. We present a new geologic map of fluvial‐deltaic deposits of the Indo‐Burman Ranges (IBR), five detrital zircon fission track analyses, and twelve high‐n detrital zircon U‐Pb age distributions (dzUPb) from the Barail (late Eocene–early Miocene), Surma (early–late Miocene), and Tipam (late Miocene–Pliocene) Groups of the ancestral Brahmaputra delta. We use dzUPb statistical tests to correlate the IBR units with equivalent age strata throughout the Bengal Basin. An influx of trans‐Himalayan sediment and the first appearance of ∼50 Ma grains of the Gangdese batholith in the lower Surma Group (∼18–15 Ma) records the early Miocene arrival of the ancestral Brahmaputra delta to the Bengal Basin. Contributions from Himalayan sources systematically decrease up section through the late Miocene as the contribution of Trans‐Himalayan Arc sources increases. The Miocene (∼18–8 Ma) deposition of the Surma Group records upstream expansion of the ancestral Brahmaputra River into southeastern Tibet. Late Miocene (&lt;8 Ma) progradation of the fluvial part of the delta (Tipam Group) routed trans‐Himalayan sediment over the shelf edge to the Nicobar Fan. We propose that Miocene progradation of the ancestral Brahmaputra delta reflects increasing rates of erosion and sea level fall during intensification of the South Asian Monsoon after the Miocene Climate Optimum, contemporaneous with a pulse of tectonic uplift of the Himalayan hinterland and Tibet.

Paleodepositional Environment and Sequence Stratigraphy of Miocene Sediments in Well TN-1, Coastal Swamp Depobelt, Niger Delta Basin, Nigeria

This research focused on the interpretation of paleodepositional environment and development of a sequence stratigraphic framework for the well TN-1 section, located in the coastal swamp depositional belt of the Niger Delta Basin. Integration of interpreted litho- and biofacies data sets that facilitated the interpretation of the paleodepositional environment enabled the erection of a sequence-stratigraphic framework. Three lithotypes (sand, clay, and shale) distributed within fourteen facies variants were integrated with palynomorph components to delineate five paleodepositional cycles ranging from distal delta plain to bathyal. Eight systems tracts (closely related to depositional cycles, but transcended depositional boundaries in some intervals) that hosted three maximum flooding surfaces (MFS), three sequence boundaries (SBs), distributed within four third-order and three second-order sequences, were defined. Age-significant palynomorphs recovered indicated an Aquitanian to Messinian age range (with non-deposition or erosion of Burdigalian, Langhian, Serravallian Stages sediments), distributed within five pollen zones (P628–P840) that correlated with published global cycles. This study demonstrates the significance of integrated studies to erect a sequence-stratigraphic framework applicable for field and basin-scale exploration and exploitation purposes.&#x0D; Keywords: Sequence stratigraphy, paleodepositional cycles, systems tract, cyclic sedimentation,lithofacies analysis, integrated studies.

Petrographic and filtration-volume features of Miocene deposits of the western flank of the South Caspian basin

Petrographic and filtration-volume features of Miocene deposits of the western flank of the South Caspian basin

Možnosti hodnocení zatížení říčních sedimentů stopovými prvky na příkladu řeky Svratky a jejích přítoků

Most methods of evaluating river system contamination use an enrichment factor, but there is no consensus concerning the specific values of the natural geochemical background to be. This is critical for evaluation of the anthropogenic loading. Taking into account that the final evaluation is strongly dependent on the choice of this parameter, the aim of the paper is to show the importance of the choice of the natural background in assessing the pollution degree of river sediments. Element concentrations of the surrounding rocks are considered to be the natural geochemical background. The Svratka River springs in the Žárské vrchy Highlands. It flows through crystalline rocks in upstream, and further then through metamorphic volcanic rocks, sediments of the Boskovice furrow and plutonic rocks of the Brno Massif. Further on, it flows through a straight watercourse over the plain of the Dyje-Svratka deep valley, and the downstream flows through Miocene sediments of the Carpathian foredeep and flysch units of the Western Carpathians (Fig. 1). 24 samples of river sediments were taken from the Svratka River and its tributaries (Fig. 1). The samples were decomposed in a solution of 1 ml HF (40%) and 3 ml HNO3 (65%). The Al, Ti and As contents were determined by AAS, the Pb, Zr contents were determined by FAAS, and Cr and Ni element contents were determined by ICP-MS (Table 2). The Enrichment Factor (EF) was calculated for each sample using Al, Ti and Zr as reference elements and recommended concentration of the natural background values in Table 1. The resulting EF values are very different (Fig. 2a, b). The results of the statistical processing for lead, arsenic, nickel and chromium (Fig. 3a–d) using the reference elements titanium, aluminium and zirconium demonstrated that the choice of the reference element is not the main factor that significantly influences the final evaluation. The choice of the appropriate natural geochemical background value is absolutely crucial for the evaluation of the anthropogenic loading