Delta Plain Research Articles

Late Pleistocene - Holocene Sedimentary Evolution of Nam Bo Plain and Correlation from the Ca Mau Peninsula to the Mekong River Delta in Midle-Late Holocene

Located in southern Vietnam, the Southern plain is one of the largest in Asia. Within the coastal area, this study has indicated that there are two plains forming by different hydrodynamic mechanisms: the river dominated Mekong Delta plain and the tidal dominated plain of the Ca Mau peninsula. Studying lithofacies based on: (i) sedimentary parameters indicating environment of 29 boreholes in tidal flat and coastal plains, hundreds of surveyed surface sediment stations; (ii) stratigraphy seismic characteristics of the 21 seismic sections; and (iii) absolute age data, evolutionary history of late Pleistocene - Holocene sediments in the Southern plain and the relationship between the Mekong Delta and the tidal plain of the Ca Mau peninsula in the middle Holocene - late be clarified. Both plains are characterized by 3 lithofacies complexes corresponding to 3 phases of sea-level change: (i) lowstand alluvial facies complex (arLST Q13b); (ii) coastal facies complex (amtTST Q21-2) and shallow marine-lagoon greenish-gray clay facies (mtTST Q21-2); (iii) the phase of the middle-late Holocene (Q22-3 HST) has a differentiation between the two plains. The Me Kong delta is characterized by three deltaic facies complexes: (1) the late middle-late Holocene buried submarine deltaic facies complex (amh1Q22-3); (2) late Holocene deltaic plain facies complex (amh2Q23) and modern submarine deltaic facies complex (amh3Q23). The tidal plain of Ca Mau peninsula is characterized by a complex of sandy bars, tidal plains and tidal channels. In the regressive process, four periods of relative sea-level stopped, creating three ancient shoreline (5ka BP, 2.5ka BP; and 1 ka BP). The delta plain is marked by deltaic lobes turning to the southeast sea, while the Ca Mau plain characterized by the sand bars that tend to change direction from the east (2.5 ka BP) to the southeast (0.5ka BP and 0.2ka BP).
 

Palaeoenvironment and organic matter of the Triassic Chang 9 lacustrine shales, Ordos Basin, China

The Ordos Basin, a large mainly non‐marine basin, is an important petroliferous basin in northern China. The Triassic Chang 9 shales, including the delta plain shale (DPS), delta front shale (DFS), and deep lake shale (DLS), are proven to be the main source rocks in the lower Yanchang Formation (LYF). This study investigates the source rock potential, palaeoenvironment, and organic matter (OM) source. According to the OM thermal maturity, abundance, and type, the shales have excellent source rock potential. The DLS has the highest quality with average TOC of 7.08%, S1 + S2 of 14.41 mg HC/g rock, and Type II1–II2. According to correlations of Rb/Sr versus Sr/Cu, the shales were mainly deposited in arid conditions. Based on the major element (S), trace elements (V, Ni, Co, Cr, U, and Th), rare earth element (Ce) concentrations, and biomarkers (Pr, Ph, dibenzofuran, fluorene, and dibenzothiophene), redox conditions for the DPS, DFS, and DLS were oxidizing, sub‐oxidizing to sub‐reducing, and reducing, respectively. The palaeosalinity was fresh‐ to brackish‐water, ascertained by the trace elements (Sr and Ba) and biomarkers (gammacerane). The water stratification was controlled by the temperature changes and the palaeosalinity differences, and the maximum water depth was ~100 m during the Chang 9 deposition. Aquatic microorganisms (e.g., algae, bacteria, and phytoplankton) were the main organic matter sources for the shales, mixed together with terrigenous plants in DPS and DFS. The DLS has the most aquatic microorganisms and has the least higher plant fragments, supported by the higher TOC (up to 14%), lowest vitrinite contents (Avg. = 14.1%), and highest liptinite contents (Avg. = 59.5%). Laterally, the DPS, DFS, and DLS were distributed successively from the lake margin to the depocentre. Vertically, the DLS, DFS, and DPS were developed successively from the bottom lake to the upper lake. The DLS was mainly formed in an environment of high‐level sapropelinite and favourable preservation conditions, and the DPS was mainly formed in an environment of high‐level terrigenous inputs and poor preservation conditions, while the DFS was mainly formed in an environment of medium‐level of sapropelinite productivity and terrigenous inputs and fair preservation conditions. The DPS and DFS were formed during both the early stage (shallow lake) and the late stage (deep lake) of the Chang 9 deposition, while the DLS was only developed in the deep lake during the late Chang 9 deposition. The high‐level sapropelinite production and favourable preservation controlled the formation of the organic‐rich shales, especially for the organic‐rich DLS.

Surface elevation and sedimentation dynamics in the Ganges-Brahmaputra tidal delta plain, Bangladesh: Evidence for mangrove adaptation to human-induced tidal amplification

In the Ganges-Brahmaputra (G-B) delta, periodic flooding of the land surface during the tidal cycle coupled with enormous sediment delivery during the monsoon promotes sediment accretion and surface elevation gain through time. However, over the past several decades, widespread embankment (“polder”) construction in the G-B tidal delta plain has led to numerous environmental disturbances, including channel siltation and tide range amplification. While previous research indicates that rates of sediment accretion are relatively high in the G-B tidal delta plain, it remains unclear if and how surface elevation is maintaining pace with relative sea-level rise (RSLR) in this region. In this study, we utilize an array of surface elevation tables, sediment traps, and groundwater piezometers to provide longitudinal trends of sedimentation and elevation dynamics with respect to local platform elevation and associated hydroperiod. Two hydro-geomorphic settings of the Sundarbans mangrove forest are compared: higher elevation stream-bank and lower elevation interior. Seasonal measurements over a time span of 5 years reveal that elevation gain is occurring in all settings, with the highest rates observed at elevated stream-bank zones. Elevation gain occurs primarily in response to sediment accretion, with possible minor contributions from pore-water storage and swelling of clay minerals during the monsoon season (i.e., belowground biomass and organic contribution is minimal). As a result, elevation loss and shallow subsidence in the G-B delta is unlikely to be caused by compaction of organic-rich soils, but rather appears to be controlled by seasonal lowering of the groundwater table and compaction of clay minerals. Rates of surface elevation gain in the Sundarbans greatly exceed rates of RSLR and more closely follow rates of RSLR augmented from tide range amplification, indicating that this landscape is adapting to human-induced environmental change. The proceedings of this study underscore the adaptability of the natural G-B tidal delta plain to local environmental disturbances, with the caveat that these defenses may be lost to future upstream reductions in sediment supply.

Linking Holocene vegetation dynamics, palaeoclimate variability and depositional patterns in coastal successions: Insights from the Po Delta plain of northern Italy

Mediterranean deltaic-coastal plains represent relatively underexplored depositional archives that record the Holocene response of vegetation and depositional systems to high-frequency climate changes. In this study, we examine a 25 m-thick succession of Holocene age (core EM2) recovered in the innermost portion of the Po delta plain of northern Italy, applying an integrated palyno-stratigraphic approach. The existence of a paludal, freshwater setting inland of the line of maximum marine transgression favoured a low degree of pollen transportation. Application of cluster analysis to this palynological record leads to the identification of pollen-derived biomes and seven (auto)ecological groups of taxa that discriminate environmental signal (depositional facies) and regional climate conditions within a well-dated coastal record. Percentage variations of hygrophytes, aquatics and pasture-meadow herbs reveal local environmental dynamics, enabling the detailed facies characterisation of the cored succession, especially in terms of water table conditions. Framed into a chronologically constrained, high-resolution facies context, the proportion of montane taxa (climate degradation indicator) relative to Mediterranean taxa and Quercus + other deciduous trees (climate optimum indicators) highlight a vegetation-climate variability in the plain that fits with Bond events, especially for the early-mid Holocene (i.e., Preboreal and Boreal Oscillation, 8.2 ka event), supporting a strong Mediterranean–North Atlantic climate connection. For the first time, pollen from a continental succession of the Adriatic area clearly depicts the effects of the 8.2 ka cooling event on vegetation patterns (progressive degradation in high altitude communities) and depositional dynamics (increased fluvial activity), assessing the major role played by climate changes in shaping coastal landscapes in addition to glacio-eustatic variations.

Glomalin‐related soil protein distributions in the wetlands of the Liaohe Delta, Northeast China: Implications for carbon sequestration and mineral weathering of coastal wetlands

AbstractArbuscular mycorrhizal fungi (AMF) is presumably to be associated with carbon sequestration and nutrient acquisition through mineral weathering in wetland ecosystems. However, information on AMF‐carbon‐weathering interactions is limited. Grain size, concentrations of nutrients, and the major components of 304 surface sediment samples and glomalin‐related soil protein (GRSP) in 133 surface sediment samples were analyzed in various environments, including the upper delta plain wetlands (UDPW) and its adjacent shallow sea wetlands (SSW), to evaluate the relationship among the GRSP, carbon content, nutrients, and chemical index of alteration (CIA) in the wetlands of the Liaohe Delta (LHD). The concentrations of GRSP in surface sediments ranged between ~ 0.11 and 11.31 mg g−1, with an average of 2.30 ± 0.17 mg g−1, and were significantly affected by the vegetation types. The ratios of organic carbon in GRSP (GRSP‐C) to soil organic carbon (SOC) varied from 0.71% to 25.34%, with an average of 10.34% ± 0.52%, indicating that the GRSP was an important carbon pool in sediments, and the carbon dynamics in these wetlands were closely related to human activities. Moreover, the CIA values ranged from ~ 18.97 to 68.75, and were significantly higher in the UDPW than in the SSW (p < 0.05), and were significantly correlated with the concentrations of GRSP (r2 = 0.22 [r = 0.43], p < 0.01). Meanwhile, both the CIA and GRSP were significantly correlated with SOC, Total Nitrogen, and Fe (r2 > 0.17 [r > 0.41], p < 0.01). The results indicate that AMF excursions in wetland ecosystems enhance carbon sequestration and mineral weathering, and in turn they alter retention of at least some nutrients.

PALEOPHYTOSOCIOLOGICAL ASPECT OF SUBSTANTIATION OF INTERREGIONAL CORRELATION OF THE UPPER CARBONIFEROUS DEPOSITS OF THE DONETS BASIN

The paper presents the results of a paleophytosociological substantiation of the interregional correlation of the Kasimovian and Gzhelian deposits of the Donets Basin in connection with consideration of the question of a difference in stratigraphic volumes of the Sphenopteris mathetii (= Alethopteris zeilleri) and Sphenophyllum angustifolium Zones in the Donets Basin and the Sabero Coalfield of Spain due to a diachronicity of the lower boundary of the Sphenophyllum angustifolium Zone. Paleophytosociological data about a composition and spatio-temporal dynamic of ancient plant communities give an understanding of the process of a flora development, which is recorded in the phytostratigraphic scale, and make it possible to carry out the substantiation of the correlation of phytozonal units taking into account ecological-cenotic features of vegetation cover. Based on the analysis of the literary paleoclimate and lithological-facial data and own paleophytosociological studies, it was concluded that during the early Gzhelian time, corresponding to more or less stable glacio-climatic conditions of the middle part of the interglacial interval of the Late Paleozoic glacial period, the diachronicity of the floristic changes in the basins with different types of tectonical and sedimentation processes within a single paleophytochoria may be due to the differences in ecological-landscape conditions that determined the composition and spatial differentiation of vegetation cover. The paleophytosociological studies have shown that the marking taxa of the Sphenophyllum angustifolium Zone, defining its lower boundary by the limestone O5 at the base of the Gzhelian Stage in the Donets Basin, are the diagnostic species of the paleophytocenoses, which dominated in the vegetation cover of the Donets Basin during the early Gzhelian time. The base of the Sphenophyllum angustifolium Zone in the Donets Basin corresponds to the temporal level of an appearance of these new paleophytocenoses, which were spread within coastal lowlands and delta plains. At the beginning of the Gzhelian time, these dominant plant communities of lowlands in the Donets Basin occupied less humid and waterlogged environments than the existing environments at the same time in the Sabero Coalfield of Spain where the marking fern and pteridosperm species of the Alethopteris zeilleri Zone continued to grow. The lower boundary of the Sphenophyllum angustifolium Zone in the Sabero Coalfield, which according to radiometric dating corresponds to the level located close to the limestone Р2 in the Donets Basin, is consistent with the base of the upper Odontopteris schlotheimii Subzone of the Sphenophyllum angustifolium Zone. The lower boundary of the Odontopteris schlotheimii Subzone in the Donets Basin records the temporal level reflecting а change of distribution areas of the paleophytocenosis, i.e. а change of the dominant paleophytocenosis, namely, a reduction of the plant communities on coastal lowlands and a wider distribution of the plant communities within delta plains.

Sedimentary characteristics and internal architecture of a river-dominated delta controlled by autogenic process: implications from a flume tank experiment

Autogenic processes are widely found in various sedimentary systems and they play an important role in the depositional evolution and corresponding sedimentary architecture. However, autogenic processes are often affected by changing allogenic factors and are difficult to be identified and analyzed from modern and ancient records. Through the flume tank experiment under constant boundary conditions, the depositional process, evolution principles, and the sedimentary architecture of a river-dominated delta was presented, and a corresponding sedimentary architecture model was constructed. The evolution of river-dominated delta controlled only by autogenic process is obviously periodic, and each autogenic cycle can be divided into an initial progradational stage, a middle retrogratational stage, and a late aggradational–progradational stage. In the initial progradational stage, one feeder channel incised into the delta plain, mouth bar(s) was formed in front of the channel mouth, and small-scale crevasse splays were formed on the delta plain. In the middle retrogradational stage, the feeder channel was blocked by the mouth bar(s) which grew out of water at the end of the initial stage, and a set of large-scale distributary splay complexes were formed on the delta plain. These distributary splay complexes were retrogradationally overlapped due to the continuous migration of the bifurcation point of the feeder channel. In the late aggradational–progradational stage, the feeder channel branched into several radial distributary channels, overlapped distributary channels were formed on the delta plain, and terminal lobe complexes were formed at the end of distributary channels. The three sedimentary layers formed in the three stages constituted an autogenic succession. The experimental delta consisted of six autogenic depositional successions. Dynamic allocation of accommodation space and the following adaptive sediments filling were the two main driving factors of the autogenic evolution of deltas.

The grade index model as a rationale for autogenic nonequilibrium responses of deltaic clinoform to relative sea‐level rise

AbstractGrade index (Gindex) is a dimensionless number given as the volume‐in‐unit‐time ratio of subaerial allocation to both subaerial and subaqueous allocations of sediment supplied to a delta from upstream. It was originally proposed for understanding the effect of basin water depth on the morphodynamics of delta distributary channels under stationary relative sea level. We here examine how rising relative sea level modulates the Gindex, using geometrical reasoning and numerical simulations. We find that the grade index model can account for autoretreat of the deltaic shoreline, autodrowning of the whole system, and autobreak of the deltaic sedimentation, all of which are the consequences of autogenic nonequilibrium responses to steadily rising relative sea level. The regressive‐to‐transgressive threshold (i.e. the onset of autoretreat) is crossed when the delta plain's dimensionless basal area (At*) encounters a critical value that is expressed in terms of Gindex: regression and transgression are sustained when At* is below and above the threshold, respectively. The mode of transgression depends on the slope conditions. If the hinterland slope (γ) is steeper than the foreset slope (β), both At* and Gindex decrease as the relative sea‐level rises. Eventually, the depositional system experiences autodrowning when At* = Gindex = 0. If γ < β; on the other hand, both At* and Gindex increase. This latter slope condition eventually causes autobreak of the deltaic sedimentation, afterward of which At* = Gindex = 1. The grade index model is useful for interpreting and predicting the stratigraphic responses of natural deltaic clinoforms in conditions of rising relative sea level.

Multi-proxy approach on the hydrocarbon generation perspective of Barjora Basin, India

Abstract Barjora Basin in India is a small basin characterized by a high organic richness of early mature nature. The present study aims to find the source of organic matter (OM) and hydrocarbon generation potential of Barjora Basin. Systematically collected coal and shale samples from R-II seam of the basin were used for proximate and ultimate analyses, Rock Eval pyrolysis along with total organic carbon (TOC) content, organo-micropetrographic framework, thermal maturity, carbon isotopic signature, biomarker composition, functional group studies and estimation of relative aliphaticity and aromaticity through Fourier Transform infrared spectroscopy (FTIR). The novelty of the present work lies in the application of multiple proxies such as stable isotope ratio of organic carbon (δ13C), biomarker signatures, thermal maturity parameters, organo-micropetrography and estimation and quantification of functional groups for palaeoenvironmental reconstruction and to assess the hydrocarbon productivity of the basin. A dominant terrestrial OM input in Barjora Basin is indicated by the TOC to total nitrogen ratio (C/N), δ13C and biomarker compositions. High gelification index (GI), tissue preservation index (TPI), and carbon preference index (CPI) values indicate that coals are deposited in wet swamp forest regime under high rainwater conditions and shales are formed in upper delta plain regime under high groundwater activity. In addition, large liptinite content, TPI and GI designate short transportation of the OM before burial leading to organic richness of the Barjora Basin. Moreover, high liptinite content, type II-III admixed kerogen input, S2/S3 ratio, TPI and index for hydrocarbon generation (IHG) signify higher potential of the basin for hydrocarbon generation.

Dinosaur ichnology and sedimentology of the Chignik Formation (Upper Cretaceous), Aniakchak National Monument, southwestern Alaska; Further insights on habitat preferences of high-latitude hadrosaurs.

While there are now numerous records of dinosaurs from Cretaceous rocks around the state of Alaska, very few fossil records of terrestrial vertebrates are known from the Mesozoic rocks of the southwestern part of the state. Here we report the new discovery of extensive occurrences of dinosaur tracks from Aniakchak National Monument of the Alaska Peninsula. These tracks are in the Late Cretaceous (Maastrichtian) Chignik Formation, a cyclic sequence of rocks, approximately 500–600 m thick, representing shallow marine to nearshore marine environments in the lower part and continental alluvial coastal plain environments in the upper part of the section. These rocks are part of the Peninsular Terrane and paleomagnetic reconstructions based on the volcanic rocks of this terrane suggest that the Chignik Formation was deposited at approximately its current latitude which is almost 57° N. Recent field work in Aniakchak National Monument has revealed over 75 new track sites, dramatically increasing the dinosaur record from the Alaska Peninsula. Most of the combined record of tracks can be attributed to hadrosaurs, the plant-eating duck-billed dinosaurs. Tracks range in size from those made by full-grown adults to juveniles. Other tracks can be attributed to armored dinosaurs, meat-eating dinosaurs, and two kinds of fossil birds. The track size of the predatory dinosaur suggests a body approximately 6–7 m long, about the estimated size of the North Slope tyrannosaurid Nanuqsaurus. The larger bird tracks resemble Magnoavipes denaliensis previously described from Denali National Park, while the smaller bird tracks were made by a bird about the size of a modern Willet. Previous interdisciplinary sedimentologic and paleontologic work in the correlative and well-known dinosaur bonebeds of the Prince Creek Formation 1400km-1500km further north in Alaska suggested that high-latitude hadrosaurs preferred distal coastal plain or lower delta plain habitats. The ichnological record being uncovered in the Chignik Formation of southwestern Alaska is showing that the hadrosaur tracks here were also made in distal coastal and delta plain conditions. This similarity may corroborate the habitat preference model for Cretaceous high-latitude dinosaurs proposed for the data gathered from the Prince Creek Formation, and may indicate that at least Beringian hadrosaurids had similar habitat preferences regardless of latitude.

“Grain-size bookkeeping,” a new aid for siliciclastic systems with examples from paralic environments

ABSTRACTSedimentary logs form the foundation of many studies of ancient and modern sedimentary successions. In siliciclastic settings in particular, vertical grain-size trends are important records of past depositional processes and environments, so that they are recorded with care and are often central to final interpretations. It is rare for the actual grain size to play a similar role. Yet there is significant value in (i) digitizing sedimentary logs to produce statistical grain-size data and (ii) the deliberate study of grain size, a process described here as “grain-size bookkeeping.” To illustrate this, over 5.9 km of sedimentary logs have been digitized from the Miocene to Pliocene paleo–Orinoco delta, the Cretaceous Ferron Last Chance and Notom deltas, and the Jurassic Ravenscar Group. The digital data reveal how grain size partitions into distinct sedimentary facies, proximal-to-distal changes, changes related to stratigraphy and base level, and the overall grain size of paralic systems. It emerges that fluvio-distributary channels are the coarsest-grained sediment bodies in each of the studied systems. The coarsest material does not reach the shoreline, though the grain sizes of fluvio-distributary channels and shoreline sand bodies overlap, in accordance with the concept that the former feeds the later. By contrast, overbank sediments are relatively fine-grained, suggesting that, with the exception of channel belts, coarse sediment can largely bypass the delta plain. Grain-size changes occur across some key stratigraphic surfaces, but not consistently so. Channels in valleys are, on average, coarser than similar channels in unconfined systems, but, in the presented datasets, valleys do not contain the coarsest channels. The data have also allowed the analysis of down-system fining rates in ancient, sandy fluvio-distributary systems, with grain size being measured to decrease at rates ranging from 0.7 to 7.7 μm/km—values that compare favorably with modern rivers. Such large-scale trends are ornamented by, and link to, smaller-scale spatial changes associated with, for example, channel bars, crevasses, and mouth bars, and an initial dataset of associated fining rates has been collected. In general, very large systems (rivers) have low fining rates because of their great size, whereas the converse is true for small systems, especially if the grain size range is large. Consideration of downstream fining rates has led to the insight that avulsion initiates an unequal race to the shoreline. Suspended very fine sand and silt is likely to reach the shoreline with the avulsion flood waters, but bedload will advance far more slowly, perhaps too slowly to reach the shoreline before the river avulses again. Some avulsions may lead to notable temporal variations in the caliber of sediment supplied to shorelines. As expected, the largest system, the paleo-Orinoco, is the finest grained. The Ferron deltas have catchment areas 12 and 22 times smaller than the Orinoco, and are the coarsest grained. Remarkably, though their catchment areas differ by a factor of two, they have almost identical sand grain-size distributions. The data have also proved powerful in refining paleogeographic reconstructions, in particular suggesting “missing” depositional elements needed to complete local sediment routing systems. Careful tracking of grain size is also beneficial in that it is a key control on permeability, the description of which is crucial to the prediction of subsurface fluid flow.

An enigmatic Arthropoda from the Upper Triassic (Carnian) southwestern Gondwana (Argentina)

AbstractThe presence of a new taxon,Duraznovis gallegoinew genus new species is reported and described from an early Late Triassic (Carnian) deposit in Argentina. Two specimens, recovered from the Quebrada del Durazno locality, uppermost levels of the Potrerillos Formation, Cuyana Basin (Mendoza), are represented by the molds of their shield and imprints of soft parts. The identity of these specimens appears enigmatic but closely resembles in the possession of a generalized arthropod morphology and a distinctive combination of characters, to living and fossil representatives of xiphosurans (Chelicerata) and notostracans (Branchiopoda). The new fossils are associated with a rich biota comprising abundant insects, spinicaudatans, plants, and scarce fish remains living in semipermanent swamps and/or ponds within a delta plain environment with intermittent episodes of flooding, in a warm temperate and humid megamonsoonal climate during Triassic times. In this context, we analyze the taphonomic and ecological implications of their presence. Lastly, these unique specimens at the Quebrada del Durazno locality adds to the diversity of the biota, revealing the importance of this site as an exceptional paleontological Triassic deposit.UUID:http://zoobank.org/8d1194c2-170c-4b7a-b0c6-5c08b0974d95

Radiocarbon age offsets of Plants and Bioclasts in the Holocene Sediments from the Miyazaki Plain, Southeast Coast of Kyushu, Southwest Japan

AbstractTo investigate the relationship between paleoenvironmental changes and marine reservoir effects, the radiocarbon ages of marine bioclasts and terrestrial plants from the same horizons of a sediment core in the Holocene Epoch were measured. This core, with a length of approximately 9 m, was obtained from the southern part of the Miyazaki Plain southeast of Kyushu Island, which faces the Kuroshio warm current. This drilling site is located in an uplift area associated with the subduction of the Philippine Sea Plate. Based on analyses of lithology, molluscan and foraminifera assemblages, and radiocarbon dating, we interpreted four sedimentary units in order of age: tidal flat, inner bay, Kikai-Akahoya volcanic ash, and delta plain. These paleoenvironmental changes were mainly associated with the sea-level rise during the deglacial period. The reservoir ages of nine pairs from the tidal flat to inner bay facies were found to be from the time span of 7300–8200 cal BP. The chronological changes in the reservoir effect are correlated with those seen in Holocene sediments of the other coastal area in East Asia.

Investigation into Groundwater Resources in Southern Part of the Red River’s Delta Plain, Vietnam by the Use of Isotopic Techniques

Groundwater in the Red River’s delta plain, North Vietnam, was found in Holocene, Pleistocene, Neogene and Triassic aquifers in fresh, brackish and saline types with a total dissolved solids (TDS) content ranging from less than 1 g L−1 to higher than 3 g L−1. Saline water exists inHolocene aquifer, but fresh and brackish water exist in Pleistocene, Neogene and Triassic aquifers. This study aims at the investigation into genesis and processes controlling quality of water resources in the region. For this isotopic, combined with geochemical techniques were applied. The techniques include: (i) measurement of water’s isotopic compositions (δ2H, δ18O) in water; (ii) determination of water’s age by the 3H- and 14C-dating method, and (iii) chemical analyses for main cations and anions in water. Results obtained revealed that saline water in Holocene aquifer was affected by seawater intrusion, fresh water in deeper aquifers originated from meteoric water but with old ages, up to 10,000–14,000 yr. The recharge area of fresh water is from the northwest highland at an altitude of 140–160m above sea level. The recharge water flows northwesterly towards southeasterly to the seacoast at a rate of 2.5m y−1. Chemistry of water resources in the study region is controlled by ferric, sulfate and nitrate reduction with organic matters as well as dissolution of inorganic carbonate minerals present in the sediment deposits. Results of isotopic signatures in water from Neogene, Triassic and Pleistocene aquifers suggested the three aquifers are connected to each other due to the existence of faults and fissures in Mesozoic basement across the delta region in combination with high rate of groundwater mining. Moreover, the high rate of freshwater abstraction from Pleistocene aquifer currently causes sea water to flow backwards to production well field located in the center of the region.

Towards a high-resolution chronostratigraphy and geochronology for the Pannonian Stage: Significance of the Paks cores (Central Pannonian Basin)

A new stratigraphic standard for the open lacustrine to deltaic Pannonian Stage is emerging from the combined sedimentological, lithostratigraphical, sequence stratigraphical, biostratigraphical, seismic stratigraphical, geochronological, and magnetostratigraphical investigations of 6 long drill cores. These were drilled by Paks II Nuclear Power Plant Plc. as a preparatory step for the construction of a new power plant near the city of Paks, Central Pannonian Basin, between 2015 and 2016. The boreholes are in a distance of 8-12 km from each other, and five of them fully penetrated the local Pannonian sequence in a thickness of 390 to 662 m. Each core includes offshore clay marl deposited far from sediment entry points (Endrőd Fm), heterolithic, sandy siltstones of a <200 m high shelf-margin slope (Algyő Fm), and several stacked deltaic deposits from prodelta silts to sandy mouth bars, heterolithics, lignite and sandy channel-fills of the delta plain (Újfalu Fm). Magnetostratigraphic investigations from two cores and authigenic 10Be/9Be dating from two others were combined by means of seismic correlation between the boreholes, and thus they provide a solid geochronological and chronostratigraphic basis for the interpretation of the sedimentologial and paleontological records of the cores. The continuous representation of the earliest Pannonian (11.6–9.1 Ma) in the cores needs further investigation, as neither magnetostratigraphy nor authigenic 10Be/9Be dating gave reliable age data from the basal, condensed calcareous marls. The 9.1 to 6.5 Ma interval, however, is represented in the cores by various lithologies and abundant and sometimes excellently preserved fossils. In the deltaic succession, 8 sedimentary sequences were correlated between the cores; as their duration is not more than 400 kyr each, they can be regarded as 4th-order sequences. The paleontological record of the cores shows a very good agreement with the formerly established biochronostratigraphical system. The cores provide an insight into the evolution of the sedimentary environment and the biota of Lake Pannon between 9.1 and 6.5 Ma with a so far unprecedented temporal and spatial resolution.

Application of Mesofacies Analysis Technology in Lithologic Reservoir Prediction

As an effective technique for exploration and development of lithologic reservoirs, curves and logging facies of several exploration wells and development wells in the facies analysis area were analyzed and sedimentary interpretation was carried out. Based on the analysis of well logs in the study area, this paper concluded that the main sedimentary facies in the study area are delta plain and fore-delta. It is concluded that the study area has experienced the sedimentary evolution process and sedimentary law of delta front, delta plain and delta front. It is pointed out that sedimentary micro-facies are the main oil and gas reservoir. Finally, the distribution and regularity of oil and gas enrichment areas are studied.

Seismic geomorphology and sedimentology of a fluvial-dominated delta: Implications for the Neogene reservoirs, offshore Bohai Bay Basin, China

Fluvial-dominated deltas are common along modern and ancient coasts and act as important hydrocarbon reservoirs. In this paper, an integration of high-resolution three-dimensional seismic, well log, and core data are employed to investigate the seismic geomorphology, depositional facies, reservoir types, and controlling factors of fluvial-dominated delta deposition in the lower segment of the Minghuazheng Formation (N1mL), Bohai Bay Basin, China. Three typical seismic facies and seismic geomorphologic units are identified. Seismic facies 1 displays discrete high-amplitude reflection and a distinct U-shape incision. In plan form, this seismic facies shows a linear, dendritic, and sinuous morphology with high root-mean-square amplitudes. Seismic facies 2 occurs interspersed with seismic facies 1 and shows low-frequency and low-amplitude reflection. Seismic facies 3 shows a continuous high-amplitude reflection and uniform sheet-like morphology covering more than 10 km2 (>3.86 mi2). The N1mL was primarily deposited in the upper delta plain, lower delta plain, and delta front environments and is dominated by three major facies types: (1) distributary channel (seismic facies 1), (2) interdistributary bay (seismic facies 2), and (3) sheet sand (seismic facies 3). Among them, the distributary channel sandstones and sheet sandstones are the major reservoirs in the N1mL. Fluvial processes and lake level cycles were important factors in the development and distribution of reservoirs and traps in fluvial-dominated delta systems. Integration of the seismic geomorphology and a modern geomorphology investigation provide an effective way to predict the sandstone reservoirs and traps in fluvial-dominated delta systems.

Depositional characteristics and evolution of the shallow water deltaic channel sand bodies in Fuyu oil layer of central downwarp zone of Songliao Basin, NE China

Relatively few subsurface studies have been conducted on shallow water deltaic channel characteristics and evolution in Songliao Basin’s Fuyu oil layer. Using data from 2000-m cores and 60 wells, the shallow water deltaic channels sand bodies in the Fuyu oil layer are reconstructed. The main controlling factors over depositional system evolution are identified. Twelve lithofacies and four main facies associations are summarized. Four facies associations are identified, including (1) a simple distributary channel association, (2) type A point bar distributary channel association, (3) type B point bar distributary channel association, and (4) an underwater distributary channel association. The depositional evolution of the channels is derived from a lacustrine regressive–transgressive cycle that is driven by climate variability and tectonics, and linked to changes in relative lake-level. During periods of rapid drops in relative lake-level or rises in the semi-arid lower shallow water delta plain, channel, sand bodies are type B point bar distributary channel of laterally aggregational deposits. When relative lake level reaches to its lowest value, it results in a large-scale erosive bounding surface juxtaposed with type A point bar distributary channel sand bodies that are infilled with thick bedding in the upper shallow water delta plain. When high relative lake levels generate regional high accommodation/sediment supply ratios, the thin-bedding underwater distributary channel sand bodies are deposited in the humid shallow water deltaic front. Shallow water delta fills are capped by laterally extensive and continuous deep lacustrine dark mudstone and oil shale elements as the relative lake level rises to its highest value.

Mitigating the Effects of Sea-Level Rise on Estuaries of the Mississippi Delta Plain Using River Diversions

Using the Mississippi River as a tool for restoration has been a key element of restoration planning in Louisiana for decades. The results of allowing river water and sediment back into the coastal system are manifested in a number of places in present day Louisiana, with additional plans for large scale sediment and water diversions from the Mississippi River. Many previous numerical modeling studies have focused on sediment delivery to Louisiana estuaries. This study examines the effects of river diversions on salinity gradients in receiving estuarine basins. The Integrated Compartment Model, a planning-level model that simulates multi-decadal change in estuarine hydrodynamics and wetland systems under assumed sea-level rise scenarios, was used to assess the estuarine salinity gradient under potential management regimes. The simulations for current conditions are compared to a future 50-year simulation with additional diversions, as well as cases with a variety of diversion options. This modeling analysis shows that without additional action, 50-years of sea-level rise could result in substantial increases in salinity throughout the Mississippi Delta Plain estuaries. This can be largely offset with additional large river diversions which can maintain variable salinity gradients throughout the estuary basins.

Arsenic mitigation in rice grain loading via alternative irrigation by proposed water management practices

Over the past three decades, the occurrence of high concentrations of arsenic (As) in drinking-water and its subsequent poisoning in rice has been recognized as a major public-health concern globally, especially in Ganga Delta Plain with more than 80 million peoples in serious As exposure far beyond than its allowable limit. An extensive field study was conducted for consecutive four years viz. 2013 to 2016, introducing a process of intermittent irrigation pattern comparing to the conventional practice of rice cultivation in India. The practice provides a combination of aerobic and anaerobic irrigation resulting better rice productivity with lesser arsenic mobility and accumulation in rice grains. This present research finding clearly points out to the marked reduction of arsenic load from average 1.6 mg/kg to 0.5 mg/kg in rice grain, much closer to FAO/WHO prescribed safe limit and in the continuous practice of proposed agricultural strategy resulting in a gradual decrease of 15% bioavailable arsenic in each year. Total productivity (in kg/hectare) also increased by 540 kg/year in boro and 340 kg/year in amon subsequently achieving the prescribed safe limit of As in grain.