Central Basin Research Articles

Differential evolution of pore fluid pressure in the Sinian carbonate reservoirs of the central and eastern Sichuan Basin, China: Implication for gas preservation and destruction

Trillions of cubic meters of gas reserve have been found in the Sinian Dengying carbonate reservoirs with normal pressure in the central Sichuan Basin, while no industrial gas reservoir have been detected in the Sinian Dengying reservoir with normal pressure in the eastern Sichuan Basin. The pore fluid pressure of gas reservoir is usually closely related to total gas content. To investigate the pore fluid pressure evolution and its implication for gas reserve preservation in the Sinian Dengying reservoir of the central and eastern Sichuan Basin, we conducted a comprehensive analysis including fluid inclusion petrography, microthermometry and Raman spectroscopy. The timings of gas inclusions captured in the central and eastern Sichuan Basin occurred from 175 to 92 Ma and 191 to 183 Ma, respectively. The presence of two‐phase vapour‐solid bitumen inclusions with similar phase proportions in a single fluid inclusion assemblage of fluorite provides direct evidence of in situ oil cracking to gas. The widespread solid bitumen from the Sinian Dengying reservoir in the central Sichuan Basin indicates the existence of massive oil cracking, which results in the formation of overpressure in the reservoir. Pore fluid pressure evolution of the Sinian Dengying reservoir of the central Sichuan Basin experiences normal pressure stage (200–155 Ma), overpressure development stage (155–90 Ma) and overpressure release stage (90–0 Ma). The maximum pore fluid pressure and its corresponding pressure coefficient of the Sinian Dengying reservoir of the central Sichuan Basin are approximately 141.4 MPa and 1.95, respectively. The overpressure development stage reflects the processes of oil cracking and gas accumulation, and the overpressure release stage reflects the dissipation of some natural gas in the Sinian Dengying reservoir of the central Sichuan Basin. The pore fluid pressure of the Sinian Dengying reservoir in the eastern Sichuan Basin has maintained at normal pressure since 200 Ma, indicating that the gas reservoir was small during the oil cracking stage and natural gas completely leaked due to tectonic uplift.

Innovative graph neural network approach for predicting soil heavy metal pollution in the Pearl River Basin, China

Predicting soil heavy metal (HM) content is crucial for monitoring soil quality and ensuring ecological health. However, existing methods often neglect the spatial dependency of data. To address this gap, our study introduces a novel graph neural network (GNN) model, Multi-Scale Attention-based Graph Neural Network for Heavy Metal Prediction (MSA-GNN-HMP). The model integrates multi-scale graph convolutional network (MS-GCN) and attention-based GNN (AGNN) to capture spatial relationships. Using surface soil samples from the Pearl River Basin, we evaluate the MSA-GNN-HMP model against four other models. The experimental results show that the MSA-GNN-HMP model has the best predictive performance for Cd and Pb, with a coefficient of determination (R2) of 0.841 for Cd and 0.886 for Pb, and the lowest mean absolute error (MAE) of 0.403 mg kg−1 for Cd and 0.670 mg kg−1 for Pb, as well as the lowest root mean square error (RMSE) of 0.563 mg kg−1for Cd and 0.898 mg kg−1 for Pb. In feature importance analysis, latitude and longitude emerged as key factors influencing the heavy metal content. The spatial distribution prediction trend of heavy metal elements by different prediction methods is basically consistent, with the high-value areas of Cd and Pb respectively distributed in the northwest and northeast of the basin center. However, the MSA-GNN-HMP model demonstrates superior detail representation in spatial prediction. MSA-GNN-HMP model has excellent spatial information representation capabilities and can more accurately predict heavy metal content and spatial distribution, providing a new theoretical basis for monitoring, assessing, and managing soil pollution.

Feeding Habits and Prey Composition of Six Mesopelagic Fish Species from an Isolated Central Mediterranean Basin

Mesopelagic fishes hold an important position in marine food webs, serving as a link between lower trophic levels and top predators and transferring energy from their deep mesopelagic habitat to shallower oceanic layers. Despite their ecological importance, research on mesopelagic fishes’ diet and feeding habits in the Mediterranean Sea is far from thorough. The present work attempts to assess the preying patterns and diet composition of four myctophid (Benthosema glaciale, Ceratoscopelus maderensis, Myctophum punctatum, Notoscopelus elongatus) and two sternoptychid (Argyropelecus hemigymnus, Maurolicus muelleri) species from the Corinthian Gulf (Ionian Sea, Greece), sampled during pelagic trawl surveys in 2018 and 2019. Stomach vacuity was high for myctophids caught during daytime, a pattern which sternoptychids did not follow. Estimated trophic indices revealed high dietary diversity (Shannon’s H’ index) for most investigated species, but a narrow trophic niche breadth (Levins’ normalized Bn index). Copepods and various marine crustaceans were dominant in all diets, classifying them under the zooplanktivorous trophic guild, while A. hemigymnus exhibited high concentrations of particulate organic matter in their stomachs and N. elongatus exhibited consumption of fish. Diet overlap was significant among most studied mesopelagic species, as indicated by Shoener’s S index and confirmed by both the multidimensional scaling ordination and a hierarchical cluster analysis. Information on mesopelagic fishes’ diet composition in this poorly studied part of the Mediterranean is useful in further assessing and parameterizing marine food webs and midwater trophic interactions, as well as in quantifying the ensued energy transfer to top predators of commercial interest or conservation concerns.

Shifts in elevational distributions of montane birds in an arid ecosystem

Montane species are generally predicted to respond to climate change via upslope movement. Elevational range shifts of birds rarely have been examined in arid regions. Here, we examine shifts in the elevational distributions of breeding birds from two regions of the Great Basin, a desert in the western USA, over 10 to 20 years. We collected data annually from 2001 to 2020, a relatively long and consistent time series that is uncommon in research on distributional shifts. We used single‐species occupancy models of 32 bird species to examine shifts along the full elevational gradient (1650–3200 m a.s.l.) and within the lowest and highest edges (25%) of the gradient. We then conducted simulations to test whether population stochasticity could confound inferences about shifts. We examined whether temperature, precipitation, and primary productivity (normalized difference vegetation index) were associated with occupancy and shifts. The elevational distributions of 23 species shifted, and simulations indicated that shifts in the distributions of 18 species were unlikely to be stochastic. The majority of shifts in the western Great Basin were downslope, whereas those in the central Great Basin were upslope. More shifts occurred at the edges of the elevational gradient than along the full gradient. Elevational shifts lacked a consistent climate‐response signal, but those of some species appeared to follow changes in primary productivity. We found regional differences in elevational shifts and climate associations, and our work suggests that these desert bird populations may be relatively resilient to climate change.

Patterns and controls of topographic change within the deflation basins of a trough and bowl coastal blowout

AbstractIn North‐West Europe and throughout the world, dune systems are increasingly stabilised by vegetation, due to both human intervention and changes in climate. Blowouts are erosional hollows produced by wind erosion in vegetated or semi‐vegetated dune systems. Where active blowouts are present in vegetated dunes, they provide a source of dynamism and sediment in an otherwise fixed environment. The transition from a fixed vegetated dune to an active blowout is poorly understood, however, and anthropogenic attempts to reactivate areas of bare sand in dunes are often unsuccessful. In this study, we measured topographic change at a monthly resolution in the deflation basins of one bowl and one trough blowout over a 23‐month period in Ainsdale Sand Dunes National Nature Reserve, North‐West England. Our results show that monthly surface change in the blowouts did not correlate strongly with the transport capacity of winds measured at a meteorological station 10 km south of the site. Precipitation was found to have a moderate negative correlation with all indices of surface change, that is, the more it rained the less the surface changed. Inter‐annual (23 months) patterns of topographic change in the bowl and trough blowouts were distinctly different. In the deflation basin of the bowl blowout erosion predominantly took place on the erosional walls facing into the prevailing winds, while minimal change occurred on the erosional walls facing away from the prevailing wind direction. This produced a moderate negative correlation between surface change and slope, that is, the steeper the slope, the more erosion occurred. In the trough blowout, erosion took place in the centre of the deflation basin and minimal change was measured on the easternmost erosional wall, which faced the prevailing winds. Patterns of monthly topographic change were highly variable and demonstrated that changes in the direction of above‐threshold winds can cause blowout walls and floors to ‘flip’ from erosional to depositional surfaces. These findings highlight the variability and complexity of surface change in blowouts and demonstrate that patterns vary because of landform morphology and climatic conditions.

Spatiotemporal variation of sterols in sediment as markers of primary production and ocean sewage dumping in the southwestern East Sea (Japan Sea)

The sedimentation of organic carbon in the Ulleung Basin, in the southwestern East Sea (Japan Sea) was investigated using radiocarbon and sterols. The accumulation rates of organic carbon and the contents of brassicasterol and dinosterol were higher on the slope than in the central basin, reflecting the surface water productivity, whereas cholesterol showed similar or higher contents in the central basin. The coprostanol concentration in surface sediments reflected the dispersion of sewage dumped in this region. The vertical distribution showed that the coprostanol concentration was the highest in the top 5-cm layer near the Korea Strait, close to one of the two dumping sites. A high coprostanol concentration was also found near the coast further north, where the content peaked at ∼10 cm depth. The vertical distribution of coprostanol helped to estimate the sediment accumulation rate at sites where radiocarbon gradient was too small or the values were too variable.

4D fault evolution revealed by footwall exhumation modelling: A natural experiment in the Malawi rift

The evolution of normal fault arrays during rift extension reflects paleo-plate boundary conditions and lithospheric rheology, while controlling seismic hazard and the distribution of basin-hosted resources. Yet, constraining their spatiotemporal development is challenging, particularly where geophysical and subsurface data are absent. Here, we test footwall exhumation modelling using thermochronology as a means of elucidating 4D normal fault array evolution, using the Miocene Central Basin of the Malawi Rift as a natural laboratory. Along-strike trends in exhumational cooling recorded by vertical transects of apatite fission-track and (U–Th)/He data from the basin-bounding Usisya fault scarp reveal a diachronous footwall uplift history that closely reflects 4D trends in hangingwall subsidence recorded by previously published seismic and well data. Initially, pronounced footwall exhumation is restricted to the centres of a series of four isolated normal faults, mirroring the distribution of early syn-rift depocentres. The later onset of footwall exhumation in the intervening areas marks subsequent fault segment propagation and linkage as they formed the through-going Usisya fault system. Elsewhere, cumulative exhumation recorded in the Usisya footwall remains low, coinciding with more significant intra-basinal faulting. This study shows that footwall exhumation modelling constrained by thermochronologic data can reveal the spatiotemporal evolution and strain partitioning within normal fault arrays.

Paleostress constraints on the tectonic evolution of the Central High Atlas orogen

The Central High Atlas is distinguished by map-scale, sigmoid, and narrow magmatic-cored ridges, which separate wide and open synclines. The origin of these structures has been debated for years. This study addresses this issue from a paleostress perspective, using mesostructural analysis in the Imilchil region and incorporating insights from previous research.Our analysis reveals that the Central High Atlas ridges developed through two main structural stages from the Jurassic to the Cenozoic. The first stage involved an extensional event characterized by NW-SE-oriented σ3, coeval with the Early Jurassic Tethyan extension. This was followed by wrench tectonics driven by oblique left-lateral motion of Africa with respect to Europe. This events is marked within the Central High Atlas by ENE-WSW-oriented σ1 and NNW-SSE-oriented σ3. The basin-scale left-lateral motion likely drove the formation of sigmoid stepovers, facilitating the emplacement of magmatic bodies from the Middle Jurassic to the Early Cretaceous. The second deformation stage is likely associated with the convergence between Africa and Europe and the consecutive Alpine orogeny. In the study area, this stage consists of three events: a pre-folding strike-slip event with NNE-SSW to N–S-oriented σ1, and a pre-folding strike-slip event with NW-SE-oriented σ1. Near the diapirs, the analyzed mesostructures display syn-to post-folding patterns in some locations, indicating pre-Alpine layer tilting driven by salt tectonics. The final event is marked by significant post-folding NW-SE compression, associated with the Central High Atlas basin inversion and the compaction of pre-existing magmatic-cored salt diapirs.This study highlights the complex deformation history that has influenced the evolution of the Central High Atlas ridges and provides evidence of the significant role of strike-slip tectonics during the post-rift period and magmatic emplacement, as well as in the early phases of basin inversion.

Sequence Stratigraphy and Depositional Environment of the ‘Perahu’ Sand, Bekasap Formation, ‘DAP’ Field, Central Sumatera Basin

Abstract The ‘DAP’ Field is one of the oil and gas fields within the Central Sumatera Basin that is proven to have hydrocarbon reserves. One of the proven reservoirs in the ‘DAP’ Field is the ‘Perahu’ Sand, Bekasap Formation. This study aims to determine the depositional environment and facies distribution focusing on the ‘Perahu’ Sand, Bekasap Formation through a sequence stratigraphic approach. The research was based on an integrated analysis of sedimentary facies from one core data and a key well log to interpret the facies association. Then the key well is correlated to eight other well logs with the help of sequence stratigraphic concept to determine the depositional facies distribution and succession at the study interval. Lithofacies that are identified from core data were interpreted as floodplain, tidal channel, mud flat, mix flat, and sand flat, hence the depositional environment of ‘Perahu’ Sand was interpreted to be a tide-dominated estuarine. The parasequence set level of Bekasap Formation was interpreted to be in a transgressive system tract, with the ‘Perahu’ Sand divided into three flooding surfaces that is FS3, FS4, and FS5. The FS3 distribution consists of tidal-fluvial channel, crevasse splay and floodplain facies. The FS4 distribution consists of two tidal channels and one sand flat facies. The FS5 distribution consists of one sand flat facies. The depositional trend of the ‘Perahu’ Sand shows a northeast to southwest trend, with basinward toward southwest.

Mid- to Late-Miocene hypogene speleogenesis tied to the tectonic history of the central Basin and Range province, USA

Twenty-five caves displaying evidence of hypogene speleogenesis in White Pine County, Nevada, were studied between May 2022 and October 2023. Results demonstrate that the central Basin and Range Province is a major hypogenic cave region with speleogenesis dating back to the Middle Miocene. The U-Pb radiometric dates of cave mammillaries obtained so far cover a wide span of time, ranging between 14 Ma to 2 Ma. Tectonic shearing along the Snake Range Décollement up to about 22 Ma probably brackets the maximum age of speleogenesis. Thus, speleogenesis began between 22-14 Ma, which predates most of the Basin and Range extensional tectonism of the Late Miocene. Robust dates for the common mammillaries in the region have been hard to obtain mostly due to Pb contamination. There are elevated levels of Pb throughout the area, likely due to mineralized fluids associated with the décollement. While 11 mammillary samples (from 10 caves) have been assessed for U-Pb dating viability, five contained too much Pb for analysis. Hypogenic features in these caves include mammillaries, tilted folia, bubble trails, cupolas, ceiling vents/tubes, floor vents, acid lake basins, pseudoscallops (cusps), and boneyard (megacusps). A common and newly identified feature of these caves is extensive secondary deposits of a complex mixture with silt-sized calcite and quartz grains. Some quartz grains have calcite overgrowths, suggesting authigenic growth. We named these lithified, and very porous, deposits “calc-siltite”. Sulfuric acid speleogenesis (SAS) has been clearly demonstrated in only one cave, Lehman Caves, but is strongly suspected in at least four other study sites (Old Mans, Cathedral, #041709-NS-012, and #LC01 caves). However, the great antiquity of these hypogenic caves means that they have probably experienced climatic and surface geomorphologic changes resulting in extensive alterations by epigenic groundwater. The evidence specific to demonstrating SAS processes may have been removed or covered by later epigenic activities.

Dispersal of Late Triassic clam shrimps across Pangea linking northwestern Gondwana and central Pangea rift basins

Clam shrimps are a group of freshwater crustaceans who prospered during the Late Triassic. They were abundant in lacustrine sedimentary records of continental basins distributed throughout Pangea during this time. However, they show significant taxonomic differences between the clamp shrimp faunas from the rift basins of central Pangea and the southern Gondwanan basins. In this contribution, we show new fossil clam shrimp assemblages from the lacustrine sedimentary successions of the Eastern Cordillera of Colombia (the Bocas and Montebel formations), providing information on the Late Triassic species that inhabited the northwestern Gondwana basins. This study demonstrates that the basins of northwestern Gondwana shared Norian clamp shrimp species with rift basins of central Pangea and differed in their faunas with the basins of the southern portion of Gondwana. In addition, the Late Triassic clam shrimps paleobiogeographic distribution reflects the dispersal of this fauna throughout fluvial-lacustrine environments established in the rift valleys along the central Pangea. Therefore, the rift valleys produced during the early fragmentation of central Pangea could have acted as corridors for dispersion. Simultaneously, rift valleys also provided paleobiogeographic barriers that isolated the central Pangea clam shrimp faunas from southern Gondwana.

Thermal evolution differences of reservoir bitumen and their implications: A case study of the Moxi area in the central Sichuan basin

Temperature and time were generally considered as the two key influences on the thermal evolution of both source organic matters and secondary hydrocarbon products (i.e., oil, gas, bitumen and solid bitumen). And for the hydrocarbons, other factors such as the types of source organic matters, the alteration reactions and fluid pressure evolution can also influence their degree of thermal maturation. As a consolidated product of bitumen, the traditional view is that the solid bitumen originated from the same source would exhibit similar maturity after experiencing identical paleo-temperature. However, things need to be more thoughts, such as the impact of system open or not on the solid bitumen thermal evolution and maturation degree. In this regard, we compared the solid bitumens within both reservoir pores and inclusions in deep carbonate reservoirs of lower Cambrian Longwangmiao Formation (Є1l) and the fourth member of the Sinian Dengying Formation (Z2dn4) in the Moxi area in the central Sichuan Basin. And by analyses of the Raman spectroscopy and bitumen reflectance, our results show a significant difference of maturities for these homologous solid bitumens after experienced the same highest geological temperature. Specifically, based on petrological observations, three types of solid bitumen occurrences (Bit. A, Bit. B, and Bit. C) were identified. Bit. A fills the early fine-grained dolomite dissolution pores with small and dispersed morphology, which eRo-Raman (equivalent vitrinite reflectance obtained by Raman) values show a narrow range from 2.60% to 2.80%. Bit. B with larger, blocky morphology, distributes within pores between the early recrystallized dolomites or the subsequent euhedral dolomites, including the bitumen filling in the fracture as stylolite. Their eRo-Raman values mainly concentrate in the range of 1.80%–1.90%. Bit. C refers to the bitumen inclusions hosted in various diagenetic minerals, with eRo-Raman values range from 2.70% to 2.87%. Since these solid bitumens originated from the same source rocks and have experienced the same highest geological temperature, their heterogeneous eRo-Raman values, therefore, suggest that whether the system open or not matters the thermal evolution of solid bitumen. Our results suggest that caution should be applied when using maturity to study the thermal evolution history in an open system, and hydrocarbons trapped in a closed system (e.g., fluid inclusion) can serve as a more credible recorder of thermal evolution.

Paleoenvironment and vegetational history of a Middle Pennsylvanian intramontane peat swamp: an example from the Lower Radnice Coal, Kladno coalfield (Czech Republic)

AbstractThe depositional environment, hydrology and vegetational history of the Lower Radnice Coal (Duckmantian) in the Kladno coalfield was studied using sedimentary geology, coal petrology and paleobotanical/palynological methods. The peat accumulating wetland of the coal formed in a fluvial paleovalley approximately 15 km long and 2–5 km wide, bordered by basement paleohighs and landlocked in the interior of the central European Variscides. The peat swamp evolved on top of mud-dominated floodplain successions pedogenically modified to a vertic gleyed Protosol. Probably climatically controlled rising ground water table resulted in paludification that from downstream part gradually spread upstream. Most clastic load was deposited in the upper part of the valley, whereas only mud suspension was dispersed downstream throughout the vegetated swamp. The best conditions for peat accumulation were situated in the eastern part of the paleovalley, where up to 1.5 m thick coal with thin bands of impure coal and carbonaceous mudstone formed in an occasionally inundated rheotrophic system with peat accretion controlled by regional ground water table. The peat swamp was vegetated mainly by lepidodendrid lycopsids with Lepidodendron and Paralycopodites being dominant genera. Shrubby to ground cover vegetation was represented by medulosallean pteridosperms, small shrubby lycopsids, sphenopsids, and herbaceous ferns. Tree ferns were locally abundant, especially in mineral-rich substrates. The rheotrophic character of the peat swamp may indicate higher seasonality of the Variscan interior, compared to coastal areas in the North Variscan foreland with contemporaneous ombrotrophic peats. Modern equivalents of the Lower Radnice Coal swamp are inland planar tropical peat swamps in tributary paleovalleys of the Tasek Bera in peninsular Malaysia and central Congo basins. Graphical abstract Lower Radnice Coal peat swamp.

Implications to basin evolution from the interpretation of superficial and buried geological features from remote sensing and magnetic data sets, Lower and Middle Benue Trough, Nigeria

The Lower and Middle Benue Trough is an intra-continental rifted basin with most rocks concealed by thick sediments and vegetation. Geological field mapping is very difficult resulting in high uncertainties. Remote sensing and geophysical techniques can assist in refining lithological boundaries and detecting buried geological features such as intrusive bodies, which can be very useful in interpreting the structural history of a basin. The main aim of our study is to re-process and interpret aeromagnetic and multispectral satellite datasets to understand the evolution of the Benue Trough. We used high-resolution aeromagnetic data and, Landsat 8 and ASTER data sets to interpret surface and near-surface lithologies, particularly igneous bodies, within the Benue Trough, Nigeria, with the aim of better constraining the basin evolution in time and space. A matched bandpass filter was applied to the aeromagnetic data to separate shallow/near-surface (residual) anomalies from deep (regional) anomalies. The result of the residual anomaly was further filtered by derivative-based filters to delineate surface/near-surface igneous bodies. The satellite remote sensing datasets were processed and enhanced, and diagnostic mineral spectral signatures related to geology were interpreted. A spectral angle mapping (SAM) supervised classification was used to map various lithologies and their boundaries. The delineated igneous bodies (volcanic rocks, plugs, dykes, bosses, and sills) are concentrated along the SE margin of the Trough where they intruded along a major NE-SW trend; but changes in the intrusion style are interpreted to relate to specific stages in the basin history. We suggest that the initial magma emplacement was controlled by structures mostly along the SE margin of an asymmetric basin, but the rifting locus later migrated towards the centre of the present basin.

Particle size shapes prokaryotic communities and vertical connectivity in the water columns of the slope and central basin of the South China Sea

Sinking of organic matter represents an essential mechanism for sequestration of carbon that is exported from the ocean surface to deeper depths. While recent studies have highlighted the important role of microorganisms in the biological pump, the impact of sinking particles on the vertical connectivity of microbial communities has received limited attention. In this study, we present the microbial profile of sinking particles in the northern slope and the central basin of the marginal South China Sea (SCS) using an in-line size-fractionated water filtration and Illumina high-throughput 16S rRNA amplicon sequencing. We investigate the microbial community composition within organic particles of different size fractions (30, 5, 3, 0.22 μm), and we reveal significant differences in the microbial community structure between these two distinct areas of SCS. The vertical connectivity of microbial communities in the slope and the central basin of SCS shows distinct patterns of microbial dispersal along the water column that occurs via the sinking of organic particles. We find that the microbial communities have different abundances on the different examined particle size fractions and which highlights the role of sinking particles in shaping microbial lifestyles along the water column. Our study underscores the influence of environmental variations on the vertical connectivity of microorganisms and provides additional insights into the marine biological pump under different environmental conditions.

Preliminary analysis of the indicators and accumulation models of gas hydrates in the central Zhongjiannan Basin, western South China sea

The Zhongjiannan Basin is located in the western continental margin of the South China Sea (SCS). It was recently reported that there are geophysical indicators of gas hydrates in the northern Zhongjiannan Basin. However, due to the lack of in-depth studies, it remains unknown whether geophysical indicators of gas hydrates are also available in the central and southern Zhongjiannan Basin. Based on the latest geophysical data, we have identified the seismic anomaly features of gas hydrates and observed an obvious bottom simulating reflector (BSR) in the seismic section in the central Zhongjiannan Basin. Based on a comprehensive analysis of seismic characteristics, geological structures (e.g., faults, diapirs and pockmarks) and regional sedimentary conditions, we propose three accumulation models of gas hydrates in the central Zhongjiannan Basin. The first model is that gas develops in deep depression areas, migrates upwards from deep source rocks along vertical faults and forms reservoirs in shallow formations. The second model is that gas also forms in deep depression areas and rises along mud diapirs or gas chimneys from source rocks to shallow formations, with reservoirs formed above diapirs and/or mud volcanoes. The third model is that gas is mainly generated in slope areas where strata are relatively thin and fault structures are well developed; gas migrates upwards from source rocks along vertical faults, and reservoirs are formed beneath pockmarks. The geophysical indicators of gas hydrates are found for the first time in the central Zhongjiannan Basin of the SCS, yielding an important reference for further exploration and development.

Evaluation of the sensitivity of meteorological drought in the Mediterranean region to different data record lengths.

The division and evaluation of data series used in monitoring drought into different time intervals is a practical approach to detecting the spatial and temporal extent of drought spread. This study aimed to determine meteorological drought's spatial and temporal distribution using overlapping and consecutive periods and cycles of the standardized precipitation index (SPI) time series in the Mediterranean region, Turkey. In the scope of the research, SPI values for the SPI12, SPI6 (1), and SPI6 (2) seasons were calculated for consecutive and overlapping hydrological years (1978-1998/21years, 1978-2008/31years, and 1978-2018/41years) at 28 meteorological stations. Autocorrelation, Mann-Kendall, and Sen slope trend tests were applied at a 5% significance level for each season (SPI12, SPI6 (1), and SPI6 (2)) and different time scales (21, 31, and 41years). For each season and period, maps of the SPI drought class, average formation of drought class, Mann-Kendall (MK) trend, and Sen's slope (SS) trend test statistics for the Mediterranean region were obtained, and the spatial distribution rate of trends was determined by drawing hypsometric curves. Changes in drought occurrence at different time scales were thoroughly evaluated with the changing length of data recording.Consequently, it was determined that the mild wet (MIW) and mild drought (MID) classes dominate the study area in the Mediterranean region. Significant and nonstationary changes detected in extreme wet and drought occurrences (extreme wet, EW; severe wet, SW; extreme drought, ED; severe drought, SD) were found to pose a risk in the study area. It was observed that there were spatially and temporally insignificant decreasing drought trends in the Mediterranean basin, considering that the time scales of these trends slowed down. Despite a nonsignificant trend from the MID drought class to the MIW drought class, it is predicted that the MIW and MID classes will maintain their dominance in the Mediterranean region. The central part of the study area (central Mediterranean basin) is the region with the highest drought risk.

Evidence of theropod dinosaurs in the upper hauterivian–lower barremian of Jebel Kebar (central Tunisia): Paleobiogeographic implications

The fossil record of Mesozoic dinosaurs in Tunisia has long been thought to be restricted exclusively to the southern part of the country. Although tidal and continental environments have been recognized within Cretaceous formations in central Tunisia based on sedimentological analyses, no skeletal remains ascribable to dinosaurs have been found in these deposits. The hypothesis of a possible land connection between central and southern Tunisia during the Early Cretaceous has not been previously explored due to notable lateral variations in facies, marked by the recurrent occurrence of shallow marine deposits separating these domains. The vertebrate ichnological record in the Central Tunisian Atlas was limited to isolated tridactyl footprints exclusively observed in the Albian Kebar Formation. Here, we report the first dinosaur tracks from the pre-Albian Cretaceous (upper Hauterivian–lower Barremian) of central Tunisia. These tracks consist of large tridactyl footprints left behind by medium to large-sized non-avian theropods. They occur within an extensively fractured dolostone bed and exhibit poor morphological preservation. Besides their dimensions, some tracks show morphological features, including broad digit impressions with some terminating in sharp claw traces, low to moderate mesaxony, and a wide divarication angle of the outer digits, reminiscent of the ichnogenus Megalosauripus. However, due to their poor state of preservation and limited number, we refrain from assigning these tracks to the ichnogeneric level and refer to them as indeterminate eubrontid footprints. The occurrence of theropod tracks in the Lower Cretaceous of central Tunisia confirms the sedimentology-based hypotheses about a temporal emergence of parts of this area, which was probably related to tectonic events. We compile previous biostratigraphic, sedimentological, and paleoichnological data to suggest possible periodic connections between the mainland in the south and the tidal flat environments within the central basins. Additionally, two possible scenarios regarding the biogeographic implications of the Jebel Kebar tracks are discussed. The first scenario suggests that a Gondwanan theropod fauna would have been exploring and residing in newly emerged regions of higher latitudes, whereas the alternative scenario posits the existence of a paleogeographic link between the northern margin of Gondwana and Adria, which would have allowed an interchange of theropod faunas between the two landmasses at least in the early Barremian.

Evaluation of carbon dioxide storage potential in wells of the Bredasdorp Basin offshore South Africa

This study focuses on determining how carbon dioxide (CO2) storage can be stored in the central Bredasdorp basin offshore South Africa. Logs, seismic lines, and reports of three exploration wells were used to build a 3D static model, and the compressibility method was used to estimate the CO2 static storage capacity of the reservoir. The wells displayed fair to good porosity and moderate permeability. The zone of interest had little to no faulting, and there is evidence of differential deposition of marine sandstones that overlie fluvial shales. The sandstones have good reservoir characteristics and are overlain by thick shales that serve as seals. The reservoir displayed thinning in the eastern direction and over structural highs. A static storage assessment of the reservoir showed 0.64 Mt of CO2, and the effect of changing pore volume and water saturation on overall CO2 storage volume was observed. The results revealed that an increase in pore volume would also increase the amount of CO2 stored in the reservoir. Conversely, increased water saturation leads to decreased CO2 that can be stored in the reservoir. This study has shown that the pre-existing reservoir fluid has an impact on CO2 storage volume; the greater the volume of water in the reservoir, the less the volume of CO2 that can be stored in the reservoir; this is because water is less compressible than rock, oil or gas.

Geochemical constraints on ridge-plume interaction in the West Philippine Basin

The West Philippine Basin is not only a back-arc basin resulting from the subduction of the paleo-plates, but it has also undergone modification due to intraplate processes. However, the interaction between intraplate processes and back-arc spreading processes remains unclear. In this study, we present geochemical compositions of basaltic lavas from various tectonic sites in the West Philippine Basin. Lavas from the Benham Rise and its adjacent seamount, as well as basement crust samples from the West Philippine Basin, are similar to oceanic island basalts and mid-oceanic ridge basalts, respectively. The lavas from the Central Basin Fault lie between the two aforementioned types. Based on the mixing modeling of geochemical data, morphological structure of the West Philippine Basin, and age data for lavas, we developed a conceptual model for the three-stage tectonic evolution, with the simultaneous influence of back-arc spreading and mantle plume processes.