Mud Deposits Research Articles

Sedimentological and ichnological variations in fluvio‐tidal translating point bars, McMurray Formation, Alberta, Canada

ABSTRACTSedimentological and ichnological descriptions of fluvio‐tidal translating point bars are rare, and complex physico‐chemical processes make highly detailed but concise facies descriptions challenging. Herein, mesofacies are defined to describe and interpret three ancient translating point bars from the Lower Cretaceous McMurray Formation, Alberta, Canada. Twenty‐three mesofacies are defined, based on their recurring sedimentological and ichnological characteristics. These mesofacies form the building blocks of beds and bedsets that make up three depositional facies. Facies 1 reflects sand dune migration at the channel base, which grades into inclined heterolithic stratification of Facies 2 and 3. Facies 2 occurs in the centre and seaward portions of the translating point bars and records tide‐dominated deposition of sand and muddy sand during periods of reduced river discharge. Ichnological suites and bioturbation intensities in these beds reflect persistent but variable brackish‐water conditions, fluctuating deposition rates and the deposition of mud. Mud beds are derived from flows with high suspended‐sediment concentrations. Tidally derived mud beds are typically bioturbated with trace fossil suites indicative of slow deposition rates and brackish‐water conditions. Mud deposited during elevated river discharge is burrowed after the dewatering of the bed. Facies 3 occurs at the landward apex of the translating point bar and is marked by sand‐rich and mud‐rich dune deposits with abundant soft‐sediment deformation, indicative of elevated flow velocities and deposition rates. Bioturbation is rare and sporadically distributed owing to unstable substrates. The distribution of the facies reflect the hydrodynamic variations that occurred vertically and laterally across the bar in response to temporal variations in fluvial and tidal flow interaction, as recorded by their mesofacies. The detailed facies analysis strongly suggests that deposition of the three McMurray Formation translating point bars occurred in proximity to the turbidity maximum zone of a fluvio‐tidal channel system.

Groundwater Quality Analysis for Domestic Needs in the Lampulo Coastal Region of Banda Aceh

Morphology Gampong Lampulo is a coastal region with alluvial plains. The groundwater potential on the alluvial plains is quite significant. Alluvial plains are formed by deposits of sand, mud, and grass carried by rivers and deposited for a long time. The research aims to analyze the quality of groundwater for domestic needs in the area of Lampulo City, Banda Aceh. To achieve this goal, a descriptive method and cross-sectional approach are used by measuring physical parameters (taste, color, smell), DHL, and pH directly in the field using a water checker device at 50 sampling points based on a grid of samplings to obtain representative information about a particular characteristic or variable in the broader area or region. This method involves the creation of a network or grid consisting of sampling points regularly scattered throughout the area to be studied. The results of the field survey were an analysis of the quality of fresh groundwater for domestic needs in some parts of the region of Lampulo based on several parameters, such as the physical parameters 80% clear, 100% odorless, and 80% non-sense (sensitive). In contrast, for the DHL parameters, 88% are freshwater, and the last is for the dominant pH parameters. 68% of groundwater reacts base because the soil water is affected by carbonates, bicarbonates, and hydroxides, resulting in groundwater loss in the study area. According to the results of interviews with the citizens of Lampulo, the ground is used only for household needs. The land altitude in the Lampulo region ranges from 1.42 to 6.78 meters, with a stream of land flowing from the south, an alluvial plain region, to the north, a coastal region.

Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments of the East China marginal seas: Significance of the terrestrial input and shelf mud deposition

To investigate the distribution, sources, influencing factors, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in East China Marginal Seas (ECMSs) sediments, we measured the concentrations of 16 PAHs in 104 surface sediment samples collected from the ECMSs in 2014 and 2016. Total PAH concentration (∑PAHs) ranged from 4.49 to 163.66 ng/g dry weight (dry w), with 65.98 ± 33.00 (mean ± SD) ng/g dry w. The highest PAH concentrations and total organic carbon were observed in areas with fine-grained sediments in the Bohai Sea (BS), Yellow Sea (YS), and coastal East China Sea (ECS), indicating the prominent influence of regional hydrodynamics and sediment properties. The dominant PAH congener in BS and YS was BbF, whereas coastal ECS was Phe. The heterogeneity of PAH sources implies that terrestrial PAH input and shelf mud deposition have crucial roles in the source–sink processes of PAHs in a strongly human-influenced marginal sea.

Reconstruction of the sedimentary environment of Nayband Bay during the last 1600 years; implications for relative sea level and climate change in Northern Persian Gulf

This paper reconstructs the relative sea level (RSL) and palaeoclimate of the northern coasts of the Persian Gulf (PG) during the last 16 centuries using physiochemical and ecological proxies from a radiocarbon-dated sediment core from the Nayband Bay (NB) estuary. The results show that between 1600 and 1150 cal yr BP, the NB was a marine lagoon with high river discharge, indicated by low organic matter content sandy silt sediments, high foraminiferal abundance (7900 tests per 10 cm3), and balanced agglutinated and hyaline taxa. During the Medieval Warm Period, the NB became a shallow lagoon, and consequently, a playa with high eolian input and low river discharge formed in the studied site that extended until 500 cal. yr BP. This condition is indicated by sediment finning trend, elevated magnetic susceptibility in sandy mud sediments, and low foraminiferal frequency dominated by hyaline taxa (mainly opportunist Ammonia beccarii). During the stillstand condition corresponding to 500–250 cal yr BP, the evolution of tidal channels in the area provided a platform for developing the upcoming mangrove habitat. In the last 250 years, RSL in the north of NB dropped enough to create a low-energy intertidal flat sheltered by a sandbar, which allowed mangrove growth. We conclude that the ecological and sedimentological evolution of the shallow marginal NB is mainly driven by eustatic RSL decline superimposed by local uplift. We suggest that the current orbitally-induced increasing insolation trend, enhanced by human-induced global warming, could increase aridity in the PG and the southern Zagros.

Natural and anthropogenic forcing on the fate of sedimentary organic matter in the South Yellow Sea during the Holocene

Long-term organic matter (OM) burial in the ocean is essential to the global carbon cycle. Mud deposits, such as South Yellow Sea mud deposit (SYSMD) located in the central South Yellow Sea (SYS), are ideal for the study of long-term OM burial. A sediment core YS-A from the SYSMD was analyzed for lignin phenols and bulk OM properties to reveal the driving forces of sedimentary OM (SOM) fate during the Holocene. SOM burial was found to be dominantly influenced by sea level rise and increased East Asian summer monsoon during 11.0–7.0 ka BP. During 7.0–1.0 ka BP, the fate of SOM was controlled by El Niño Southern Oscillation on the millennial time scale, and correlated with East Asian winter monsoon variability on the centennial time scale. Remarkably, anthropogenic perturbation has gradually overwhelmed long-term climate control on the fate of SOM since 1.0 ka BP, and this phenomenon became more evident after 0.4 ka BP.

Geochemical proxies of the gryphon breccia of mud volcanoes in East Azerbaijan: regularities in the distribution of chemical elements and spatial characteristics of sedimentation

The paper is devoted to the study of the patterns of distribution of major oxides and trace elements in the gryphon breccia of 12 active mud volcanoes located in various oil and gas regions (Absheron, Gobustan and Lower Kura) of Azerbaijan. Interpretations of the chemical elements found in gryphon breccia samples have allowed the composition of their source rocks, sedimentation conditions, and sedimentation areas to be determined. Purpose. The main goal of the study is to conduct geochemical studies of gryphon breccias belonging to various oil and gas regions, determine spatial patterns, achieve their explanation, and at the same time determine the conditions for the deposition of mud sediments. Methods. The chemical composition of mud volcanic breccia samples was analyzed using an “S8 TIGER Series 2” spectrometer and an “Agilent 7700 Series ICP-MS” mass spectrometer. Based on the results obtained, in addition to identifying patterns in the areas, modern approaches based on geochemical interpretation were used to explain them. The results on the genesis of breccias are consistent with the results of the published literature on the development of geodynamic and paleobasin conditions in the region. Results. Samples with the lowest Si content are characteristic of the Lower Kura mud volcanoes, where the youngest (Quaternary) deposits are recorded. In samples from these mud volcanoes, relatively high contents of Mg and P are also noticeable. High contents of Ca are characteristic of volcanoes located near the Caspian Sea. These mud volcanoes are also rich in trace elements such as Li, Ga, Rb, Zr, Mo, Cs, Pr, Tl, Pb, Th, U and others, but depleted in Ni, Sr, Ba and etc. Conclusions. Plagioclase-rich source rocks and oxygen-dominated paleobasin environments played a key role in the formation of breccia deposits belonging to the mud volcanoes of Azerbaijan. Geochemical proxies make it possible to link the paleobasin conditions of the formation of the gryphon breccia of the most mud volcanoes of South and Central Gobustan with the continental setting, especially in comparison with some volcanoes of the Lower Kura, as well as Gobustan and Absheron, located on the shores of the Caspian Sea and relatively close to it. The breccias of mud volcanoes located at a relatively large distance from the modern sea boundary and in the steepest northern part of the Lower Kura are associated with marine conditions, as are breccias of mud volcanoes located in the south of this tectonic zone (subjected to intense subsidence) and at a short distance from the Caspian Sea, may be due to geological factors.

Mass movement hazard & global climate change: Physical-deterministic modelling study of the rest and be thankful pass, Scotland UK

Mass movements frequently affect infrastructure corridors, particularly so in mountainous areas. The A83 at the Rest and be Thankful pass (Scotland, UK) is a prime example of a road experiencing frequent closure due to precipitation-triggered landslides and debris flows. The closures result in long (>90 km) diversions and severe economic losses (>£60 million). To ensure persistence of transport services, future engineered interventions and maintenance schedules must anticipate the potential consequences of climate change that affects the frequency and magnitude threshold precipitation events that are capable of triggering mass movement. In turn this requires a better understanding of the hydrological implications of climate change on precipitation-triggered landslides and debris flows. The area is prone to mass movements due to steep topography, the glacial history, reworked deposits of mud and siltstone, and landslide-triggering precipitation. The objective here is to assess the severity of future events, i.e. the coming decades, was assessed by means of an event-based runout model for selected events that were identified using a present-day precipitation threshold applied to hydro-meteorological forecasts for this part of the UK. A convex hull method was applied to these forecasts to create a comprehensive selection of modelled events and a much reduced computational load. This selection is considered to be representative for the largest variation within the forecasts.Results show that 61 mm of daily precipitation will likely trigger mass movement. This threshold reduces by 0.15 mm for every millimetre accounted for in an antecedent precipitation index calculated based on 8 antecedent days. On the basis of the hydro-meteorological forecasts it can be concluded that the frequency of these trigger conditions gradually declines, as seven out of the eleven RCM (Regional Climate Model) configurations show longer recurrence intervals. This corresponds with the decline in the modelled future precipitation. However, it is observed that, for scenarios with lower average daily precipitation and antecedent precipitation indices, event severity is likely to increase as intense daily precipitation follows drier antecedent conditions. For scenarios with higher average daily precipitation and antecedent precipitation indices, persistent wetting appears to expand source areas and increases material entrainment. The simulations show that the main source areas, situated between 300 and 500 metre elevation, extend upslope when the antecedent precipitation regime has peak precipitation values in the latter stages of the 8 antecedent days.

Sulfurovum mangrovi sp. nov., an obligately chemolithoautotrophic, hydrogen-oxidizing bacterium isolated from coastal marine sediments.

A novel mesophilic, chemolithoautotrophic, hydrogen-oxidizing bacterium, designated strain ST1-3T, was isolated from mud sediment samples collected from mangroves in Jiulong River estuary. The cells were Gram-stain-negative, non-motile and rod-shaped. The temperature, pH and salinity ranges for growth of strain ST1-3T were 4-45 °C (optimum, 35 °C), pH 5.0-8.5 (optimum, pH 7.0) and 0-8.0 % (w/v) NaCl (optimum, 4.0 %). The isolate was an obligate chemolithoautotroph capable of growth using hydrogen as the only energy source, and molecular oxygen, thiosulphate and elemental sulphur as electron acceptors. The major cellular fatty acids of strain ST1-3T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c). The major polar lipids were phosphatidylethanolamine, phosphatidyldimethyl ethanolamine and phosphatidylglycerol. The respiratory quinone was menaquinone-6. The genomic DNA G+C content was 43.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and core genes showed that the novel isolate belonged to the genus Sulfurovum and was most closely related to Sulfurovum lithotrophicum 42BKTT (94.7 % sequence identity). The average nucleotide identity and digital DNA-DNA hybridization values between ST1-3T and S. lithotrophicum 42BKTT were 74.6 and 16.3 %, respectively. On the basis of the phenotypic, phylogenetic and genomic data presented here, strain ST1-3T represents a novel species of the genus Sulfurovum, for which the name Sulfurovum mangrovi sp. nov. is proposed, with the type strain ST1-3T (=MCCC M25234T=KCTC 25639T).

Current Status of Zoobenthic Communities Associated with Deep Circalittoral Habitats from the Romanian Continental Shelf

The European environmental policies related to marine water management require periodic environmental status assessments. Particularly, the Marine Strategy Framework Directive 2008/56/EC, clearly specifies that assessment must take into consideration benthic habitat types, including their associated biological communities. The aim of this study is to present the results from the ecological analysis of macrobenthic fauna from deep circalittoral habitats with mixed and mud sediments dominated by Modiolula phaseolina and Terebellides stroemii and to provide new information on the current structure and distribution of communities. The analyzed data covers the period 2021-2022 based on the processing of 56 samples on depths ranging between 60 m to 130 m. A total of 70 macrozoobenthic species were found in the assemblages, of which Polychaeta group had the highest number of species and individuals, mostly T. stroemii and Aonides paucibranchiata. For data interpretation, a synecological analysis was performed allowing the identification of the species with the most significant contribution to the ecosystem in terms of function, energy exchanges with the environment, the species characteristic of a biotope or those that have an accidental presence in the studied area. Also, the present ecological status of deep circalittoral habitats was assessed using the M-AMBI*(n) index, which was proposed as one of the indicators for assessing the good environmental status of marine habitats in Romanian marine waters.

Pleistocene glaciomarine laminated muds in the Central Basin of the northwestern Ross Sea and their palaeoceanographic records

AbstractGlaciomarine laminated muds around the Antarctic continental margin are important in the marine geological record related to ice sheet dynamics. Microscopic observation and backscattered electron imagery of Pleistocene laminated muds in the Central Basin (Ross Sea) reveal that the light laminae comprise terrigenous angular to subangular silt‐sized particles, scattered diatom fragments, and eroded sand‐sized lumps of fossil‐bearing mud. In contrast, the dark laminae are clayey and biogenic with very tiny pieces of fossils. These laminated muds are interpreted to have been deposited by subglacial meltwater plumes underneath the advancing glaciers that torn off the earlier‐deposited and semi‐consolidated diatom‐rich sediments. Thus, most biogenic components of these laminated muds were recycled from older deposits, indicating that they are not related to enhanced biological production during the mud deposition. Our study suggests that the recycling of biogenic particles should be considered when interpreting the palaeoclimatic and palaeoceanographic implications of Antarctic environmental system.

Sediment distributions and transport patterns in the Pearl River Estuary and its adjacent coastal ocean

Coastal sediment is important for the development of river deltas and for carrying both nutrients and pollutants into estuaries and coasts. Totally 265 surficial sediments collected from the Pearl River Estuary and its adjacent coastal ocean were analyzed by using Gao-Collins method to study the sediment transport path and deposition center. The Pearl River Estuary was an area of sandy mud sediment and showed some muddy patches. There were 5 distinguishable sediment convergence centers, which represent 3 types of sediment transport patterns and hydrodynamic environments. The net sediment transport pathways in the estuary and shelf sea were mainly in the offshore and landward direction, respectively. The analyzed results indicated that the main part of muddy sediment was confined to the mouth of the estuary due to the combined effects of the expansion and salinity intrusion.

Low temperature and high pressure dramatically thicken the gas hydrate stability zone in rapidly formed sedimentary basins

Rapid sedimentation reduces the temperature and raises the pore pressure in sedimentary basins. During rapid sedimentation (>0.5 mm yr−1), cold sediment is buried fast and there is insufficient heat flow to keep the sediment at its steady state conductive equilibrium temperature. In addition, rapid deposition of low permeability mud results in overpressure due to the inability of the pore fluid to drain. It dramatically expands the thickness of the zone where hydrates are stable (the gas hydrate stability zone or GHSZ). We explore this effect with one-dimensional models. We then simulate the two-dimensional evolution of temperature and pressure of the Terrebonne Basin in the Gulf of Mexico. We use seismic, well data, and salt restoration to provide the initial and boundary conditions. We show that rapid burial reduces the geothermal gradient from ∼30 °C/km, which would be expected under equilibrium pressure and temperature, to as low as ∼10 °C/km; we also show that 25 MPa of overpressure is developed. This deepens the thickness of the GHSZ from ∼600 mbsf (its equilibrium depth) at the basin margin, to as much as 2000 mbsf basin-ward, in response to the increasing sedimentation rates. The model successfully simulates the deepening of the base of GHSZ that is interpreted from a bottom simulating reflection in the seismic data. The model and the observations suggest that the thickness of the GHSZ may be much thicker than commonly presumed and as a result the volume of carbon stored may be underestimated. Furthermore, the thickness of the hydrate stability will change significantly with time as sedimentation rate waxes and wanes implying that the hydrate stability zone is a dynamic component of the carbon cycle.

Textural characteristics and sediment transport dynamics of the sandstones of the Nkporo group, Southern Anambra Basin (Nigeria): evidence for the upper cretaceous sea-level lowstand

The Anambra sedimentary basin is one of the major inland basins in Nigeria. It covers an area of approximately 30,000 square kilometres and is named after the Anambra River, which traverses the basin. The geology of the basin is characterized by a complex sequence of sedimentary rocks that record a long history of deposition and tectonic activity. Detailed and systematic field investigation of its rock sequences exposed at Leru junction and adjoining localities revealed five dominant lithologic units consisting of massive sandstone facies, argillaceous sandstone facies, fissile black shale and mudstone facies, planar and ripple laminated sandstone facies, and massive and pebbly sandstone facies. The area is dominated by transgressive facies characterized by alternating sequences of thinly and parallel laminated fissile black shales, mudstones, and argillaceous sandstones overlain by regressive deposits dominated by massive and partly pebbly sandstones. The transgressive sequences perhaps represented shelf mud sedimentation that was probably interrupted by episodic influxes of sands rich in argillaceous materials transported down the shelf probably by shoreface waves or gravity-driven flows, while the regressive facies may have probably been emplaced by liquefied sand flows of the frontal slope of an advancing mouth bar. The erosion of the shelf deposits by the pebbly sandstones possibly reflected seaward migration of shallow distributary channels during sea-level low stand. Thus, facies transition from argillaceous sandstones to massive and pebbly sandstones within the continental shelf perhaps signified a fall in the relative sea level possibly triggered by the erosion of the shelf or perhaps a high rate of sediment supply.

Equilibrium configurations of sandy-muddy transitional beaches on South China coasts: Role of waves in formation of sand-mud transition boundary

Sandy-muddy transitional beaches (SMT-Beaches) consisting of the upper sandy beach and lower mudflat can be found on coasts with weak wave conditions and sufficient sediment supply. Currently, such SMT-Beaches receive limited attention, and their morphological characteristics as well as the mechanisms of the formation of sand-mud transition (SMT) boundary are still not clear. Based on field surveys on SMT-Beaches at South China Coasts, traditional equilibrium functions are assessed on SMT-Beaches, and an equilibrium profile function for SMT-Beaches is parameterized with only inputs of the offshore distance of the SMT boundary, tidal ranges and offshore wave heights. The present function exhibits good performance on both mesotidal and macrotidal SMT-Beaches. It improves the accuracy of profile curvature of the upper beachface compared with the traditional power function and reduces uncertainties in determining coefficients. Sediment characteristics differ between both sides of the SMT boundary. Shoreward of the SMT boundary, the probability distribution of grain size is generally unimodal with a peak located at sand grains and turns to be bimodal or trimodal with a significant increase at clay-to-silt grains seaward of the SMT boundary. Based on the exceeded Shields parameter, the critical position for the deposition of mud generally corresponds well with the SMT boundary, indicating that wave-related oscillatory motions play a dominant role in the formation of the SMT boundary.

Numerical study of the dam-break flood over natural rivers with macroscopic rocks on movable beds

This paper presents a three-dimensional model of dam break flows over fixed and movable beds. As the consequences of a dam break, the model considers the transport of solid particles and deposition due to the momentum of the flow. The movement of the free surface of water and mud is performed by Newtonian and non-Newtonian fluid models, and the solid macroscopic particles movement is carried out by the discrete phase model (DPM) and macroscopic particle model (MPM) models. It has been detected that the model was reliable and well balanced, and could accurately capture the dam break flow movement in complex terrain. Moreover, using the proposed model, a partial dam break of the Mynzhylky Dam was simulated. Even more in the calculation, the presence of mud sediment and solid particles were taken into account, which is very close to the real dam break problem.

Can Mud Deposits Indicate Inundation Extent of Paleotsunamis? Insights From Sediment‐Transport Simulations for Sand and Mud

AbstractField surveys following the 2011 Tohoku‐oki tsunami showed that mud tsunami deposits reached close to the tsunami inundation limit. However, the factors controlling the distribution of mud tsunami deposits remained unclear. We investigated these influencing factors by numerically simulating sand and mud transport after validating the tsunami inundation and distributions of sand and mud deposits during the 2011 Tohoku‐oki tsunami based on our sensitivity analysis of parameters used in the mud and sand sediment simulations. We have revealed that when the source of mud sediments is only on the seafloor (i.e., no terrestrial source), mud is deposited along less than 10% of the inundation distance. In contrast, if a terrestrial source of mud is present, mud deposits can cover 100% of the inundation distance. We have also revealed that mud sediments are not formed when topographic slopes are steep (1/20–1/500), irrespective of a terrestrial mud source, because flow stagnation does not occur. Therefore, to reproduce past inundation ranges of tsunamis from the distribution of mud deposits, two conditions are required: (a) regions with onshore mud sediments and (b) a gentle topographic slope (around 1/1,000) to allow for long‐time (more than 100 min) flow stagnation.

Developing sediment provenance discrimination tracers using major elements in East China Sea mud deposits

Discriminating shelf sediment provenances using sediment trace metal and rare earth element (REE) concentration and isotope ratios and clay mineral contents has several unavoidable hurdles, such as the effect of sediment grain size on metal concentrations, ubiquitous inclusion of REE-rich heavy minerals in sediments, and meager and inconsistent compositional differences. Furthermore, to date, no study has analyzed and determined a convincing tracer that can differentiate between Huanghe (HH) and Changjiang (CJ) sediment provenances, especially quantitatively. In this study, we quantitatively discriminated the provenances of the southwestern Cheju Island mud deposit (SWCIM) in the northern East China Sea (ECS) shelf, using seven major elements (Si, Al, Fe, K, Na, Ca, and Mg), and further determined the spatial variations of the contributions from the HH and CJ rivers to the northern ECS sediments. The results indicate that the SiO2/Al2O3 and Fe2O3/Al2O3 ratios of the HH, CJ, and Korean (KR) river sediments can be considered as reliable tracers for differentiation of the northern ECS shelf sediment provenance. Furthermore, the quantitative contributions of HH, CJ, and KR to the northern ECS sediment budget were approximately 80, 20, and 0%, respectively. The systematic spatial variations of the HH and CJ river contributions to the sediment provenances in the study area, such as the significant contributions of the HH river in the northwestern part of the SWCIM and the CJ river in the southwestern part, support the availability and applicability of the Fe2O3/Al2O3 ratio as a sediment provenance discrimination tracer. We propose that these major element concentration ratios can be applied to distinguish other siliciclastic shelf sediment provenances.

The role of waves in the resuspension and transport of fine sediment and mine tailings from the Fundão Dam failure, Doce River, Brazil

In one of the world's worst mining disasters, after flowing 670 km down the Doce River, about 20 million m3 of tailings reached the coast of Brazil in November 2015. The occurrence of persistent northerly winds favored the detachment of the river plume from the coastline and its displacement southward. However, observations of the sediment plume along the coast during the year following the breach, using aerial photographs, indicated that the plume is more extensive and persistent in a northerly direction. Previous studies have shown that although the most persistent winds are from the northern sector (70%), there is a greater incidence of waves from the southern sector (62%), especially with greater heights and periods. In this research, the effect of gravity waves on the transport of sediments is investigated, and, therefore, tailings from the Doce River and deposited on the adjacent inner continental shelf, mixed with the fluvial mud deposit also are investigated. Two mechanisms were investigated: 1) the effect of waves on sediment resuspension and their combination with tidal and wind forcings, using a two-dimensions in the horizontal directions (2DH) numerical model within the DELFT3D software, and 2) the capture of the fluvial plume by littoral drift, calculated by means of analytical models using data from wave propagation modeling. Both mechanisms were studied for 2019, also considering two major meteorological events in the region. Both effects were relevant for the northward dispersion of fine sediment, highlighting the effect of waves on the potential for northward transport of tailings towards the Abrolhos Bank.

Macaronichnus ‘co-occurrence’ in offshore transition settings: Discussing the role of tidal versus fluid muds influence

Macaronichnus is a key trace fossil in palaeoceanographic, palaeoclimatic, and petroleum exploration research. Small ichnosubspecies such as Macaronichnus segregatis segregatis, M. s. lineiformins, M. s. maeandriformis and M. s. spiriformis, typically occur in wave-dominated foreshore sands where large M. s. degiberti was never found. The latter shows a wide environmental distribution, occurring in sandy deposits of tidal channels, tidal bar sand sandridges, tidal-flat sand sheets, shorefaces, bioturbated sandy shelf, shelf storm-sheets, shelf sand ridges, and upper slopes. Small M. segregatis and large M. s. degiberti have not been observed to date due the ecological segregation of the tracemakers. An abundant record of large M. s. degiberti in a Tortonian (Late Miocene) mixed carbonate-siliciclastic unit from the Betic Cordillera (southern Spain) has been studied. Occurrence of M. s. degiberti is the result of the interaction of tidal and waves, storm influenced environment determining high-energy conditions and associated palaeoenvironmental parameters as shifting substrates, organic matter availability, and oxygenated pore and bottom-waters. Locally, associated to M. s. degiberti appear small, sinuous traces infilled by light material that were originally assigned to M. s. maeandriformis, and very rare M. s. spiriformis. However, the absence of the typical rim of Macaronichnus avoid a conclusive assignment. The coexistence of both small traces (?M. s. maeandriformis) and large M. s. degiberti is identified in the deposits underlying mudstone layers, revealing the importance of mud deposition during tidal slack water intervals or linked to fluid mud events favouring the co-occurrence of the trace makers of both Macaronichnus ichnosubespecies. This fact would have significant palaeobiological and palaeoecological implications, and could be the first record of both ichnosubspecies in the same intervals.

Classification and Control Factors of Reservoir Types in Hybrid Sedimentary Rocks: A Case Study on Lucaogou Formation in the Jimusaer Sag, Junggar Basin.

Hybrid sedimentary rocks (HSR) represent a significant reservoir type in fine-grained sediments. However, the classification and understanding of HSR reservoirs, including their storage mechanisms and identification of optimal "sweet spots," have been limited due to the lack of clarity regarding the multiple sources of components and their mixing processes. This study focuses on the Lucaogou formation of Jimusaer Sag and aims to highlight the reservoir classification principles, controlling factors, and evolutionary patterns associated with the components of HSR, beginning with examining the microscopic pore structure. The analysis of the microscopic pore structure characteristics reveals the presence of five distinct reservoir types within the HSR. The quality of these reservoirs is governed by various factors, including the composition and support mode of particles, diagenesis, provenance, and sedimentary microfacies. In regions near a provenance with strong hydrodynamic conditions, the HSR predominantly exhibits type I and type II reservoirs, characterized by numerous coarse-grained components and a granular-support mode. As the distance from the provenance increases, transitioning into medium hydrodynamic conditions, the HSR shifts to an interbedded-support mode, primarily developing type III reservoirs. In areas far from the provenance with weak hydrodynamic conditions, HSR reservoir types primarily consist of type IV and type V. Additionally, diagenetic effects such as compaction and calcite cementation further deteriorate intergranular and dissolution pores, consequently diminishing reservoir quality. Notably, during the mixing deposition processes of sand and dolomite, the developmental mode of HSR shifts from type I to type II and type III. Likewise, in the mixing deposition of mud and sand, the HSR transitions from type II to type III and type IV. Similarly, the mixing deposition of dolomite and mud leads to a change in the developmental mode of HSR from type III to type IV and type V. Moreover, this study effectively predicts the occurrence of "sweet spots" using reservoir classification, which reveals their continuous distribution. These findings provide a geological foundation for evaluating "sweet spots" and testing the oil production in HSR reservoirs.