Tectonic Movements Research Articles

Quasi-coseismic variations and geosphere coupling associated with the strong 2023 Turkey earthquakes

On 6 February 2023, two massive shallow earthquakes of Mw 7.8 and Mw 7.5 occurred successively in Turkey. Unlike earlier studies on pre-seismic anomalous signals, here we focus on the co-seismic changes in ocean, land, and atmospheric parameters associated with these two earthquakes. The quasi-coseismic variations have been clearly observed in ocean, atmosphere, and snow parameters from satellite and reanalysis datasets. Our results show a decline in the seawater temperature and salinity, and enhancement in the chlorophyll-a concentration in the eastern Mediterranean Sea associated with the earthquakes. Over the epicentral region, the total ozone column and snowfall have been observed to increase with the occurrence of earthquakes. After a detailed analysis of the hourly parameters (atmospheric pressure, air temperature, relative humidity, and wind speed), we found the atmospheric pressure variation caused by the ground motion of seismic waves is the possible reason for the co-seismic changes. Based on the results discussed in this paper, a model of multi-geosphere co-seismic response associated with the 2023 Turkey events is proposed. Additionally, our results show that the crustal motion in the high mountain region within the earthquake preparation zone could be more sensitive prior to the earthquake due to the enhancement of electric field as suggested by the theory of positive holes.

Unraveling the Complexities of Groundwater Salinization in Coastal Environments: Insights from Laizhou Bay’s Eastern Coast, China

Coastal areas have made substantial contributions to global economic development but are plagued by challenges such as groundwater salinization. Groundwater serves as the primary source for drinking, industrial, and domestic purposes in these coastal areas. Therefore, understanding the causes and processes of groundwater salinization holds paramount significance for effective groundwater management. The coastal area of Laizhou Bay in northern China serves as a quintessential example of such a scenario. With substantial groundwater extraction and severe groundwater salinization issues, it exacerbates the disparity between water-resource supply and demand. Currently, our understanding of the processes and influencing factors related to groundwater salinization in this region remains limited. In this study, employing hydrochemical and stable chlorine isotope analyses on 35 groundwater and seawater samples, an in-depth investigation into the complex mechanisms underlying groundwater salinization in the Quaternary aquifers of the eastern coastal plain of Laizhou Bay was conducted. The test results of the samples indicate that brine and saline groundwater are primarily of the Na-Cl type, exhibiting a hydrochemical composition similar to that of seawater. Brackish groundwater exhibits a diverse hydrochemical composition. The hydrogen and oxygen isotope characteristics of brackish and fresh groundwater resemble atmospheric precipitation, while brine, seawater, and saline groundwater show hydrogen and oxygen isotope depletion. Compared to seawater, brine exhibits significant δ37Cl depletion. The analysis of the test results reveals that the formation of brine aquifers results from a complex interplay of climate change, tectonic movements, and sea–land evolution, involving lagoon development during seawater regression, salt concentration through evaporation, and subsequent water–rock interactions. The genesis of saline groundwater involves a complex interplay of brine–seawater mixing, significant evaporation, and potential input of fresh groundwater from atmospheric precipitation and river sources. The formation of brackish groundwater is predominantly influenced by atmospheric precipitation, and agricultural activities, with significant variations in NO3− concentrations attributed to varying intensities of fertilizer application in the northern plain area. These insights contribute to a deeper understanding of the origins of groundwater and can inform the development of policies for groundwater protection in this area.

Large gravitational collapse structure on a rocky coast (Kvarner, NE Adriatic Sea)

The studied rock collapse structure is located on the Liburnian coast (Rijeka Bay, channel zone of the NE Adriatic). The relief of the southern part of this coast, with a length of 6.5 km, is a large escarpment with very steep to vertical slopes reaching heights of 100 m above sea level, as a result of tectonic movements along the Kvarner fault zone. These events probably led to a sudden relaxation of the highly fractured rock mass. The progressive expansion occurred at locations where previously favourably oriented faults and fissures had formed a polygonal rock collapse resembling a rock-slide which is the focus of this study. Another aim of this study is to reconstruct and explain the complex morphological evolution of the studied landslide, from the pre-failure deformations, through the failure itself, to post-failure displacements, as well as possible future instabilities. Recent techniques to survey the instability, location and to analyse the evolution of the rupture surface and its dimensions were combined (Unmanned Aerial Vehicle, Side Scan Sonar and Remotely Operated Vehicles). The estimated total volume of displaced rock mass is 950,000 m3. The lower part of the instability phenomenon was submerged during the Holocene sea level rise. Since then, a large part of the displaced rock mass has been in a stable position, with sporadic rock falls. However, given unfavourable orientation and discontinuity characteristics, as well as unfavourable environmental influences, possible instabilities might also be expected in the future.

Emmanuel de Martonne's glacial geomorphology research in Parâng Massif (the Southern Carpathians)

We are publishing this article in 2023, the year when the 150th anniversary of the birth of the French geographer is celebrated, the article being a tribute to Emmanuel de Martonne's work in Romania, especially for his contribution to the research of the Transylvanian Alps (the Southern Carpathians). Of the two doctoral theses that the French geographer elaborated on the territory of Romania, the last one, defended in 1905 and published in 1907 at the Sorbonne University in Paris, was dedicated to the geomorphological evolution of the Transylvanian Alps (the Southern Carpathians). Of the 14 field campaigns that Emmanuel de Martonne carried out in Romania, eight were carried out in the Southern Carpathians (Banat Massif, Transylvanian Massif) and in the neighboring regions closely related in their paleogeographical evolution to the Transylvanian Alps (the Subcarpathian area of Oltenia, the Subcarpathian area of Muntenia, and Mehedinți Plateau). For the French geographer, the transverse valleys of the Southern Carpathians were examples indicating the extensive tectonic movements that affected the territory of Romania in the Paleogene and Neogene. Glacial influences and relief forms in the high part of the Southern Carpathians became the main concern of the French geographer for at least a decade of research in Romania. More obviously, in some parts of the Southern Carpathians, the action of glaciation cut out specific shapes within the platform of the high peaks (Borăscu planation platform). In the research in Parâng Mountains, Emmanuel de Martonne aimed to identify some key evidence of glaciation: glacial cirques, lakes, valleys, thresholds, glacial grooves, glaciated knobs, and moraines. Above all, the French geographer believed that the general topography of the valleys and cirques is the fundamental element that certifies glaciation and the presence of lateral cirques justifies the succession of glacial periods.

Holocene Evolution of the Pearl River Delta: Mapping Integral Isobaths and Delta Progradation

The Pearl River Delta (PRD, China) has undergone complex geological development within a multi-island faulted basin, shaped by the interplay of regional tectonic movements, Quaternary sea-level fluctuations, and fluvial-marine interactions. Despite a great number of studies on the Holocene sedimentary sequences and spatial differences of lithofacies and environments, scant attention has been paid to the overarching human influence on deltaic evolution and coastline modifications since the Neolithic epoch. To further elucidate the spatial variation in Holocene sedimentation and its underlying basement topography shaped during the Last Glacial Maximum (LGM), we compiled a comprehensive dataset incorporating borehole data from over 2800 cores (the maximum depth can reach 92.5 m) within the PRD. Subsequently, high-resolution isobath maps of Quaternary deltaic deposits were generated, offering unprecedented insights into sediment distribution. This dataset facilitated a nuanced reconstruction of pre-Holocene topography, revealing a zone characterized by elongated, deep-incised valleys governed by NW-SE fault orientations. Further, we delineated coastline shifts since the period of maximum Holocene transgression (~7000 years BP), contributing to an enhanced understanding of the formation and evolutionary patterns of the delta and river network oscillations. Our findings illuminate an increasing anthropogenic impact on the rate of fluvial sedimentation and land growth, particularly accentuated over the last two millennia, favoring deltaic accretion.

Reduction of Satellite Signature Effect in High-Accuracy Satellite Laser Ranging to Etalon

Etalon is considered to be one of the most promising satellites for studying crustal motions, Earth rotation, and other scientific applications. Unfortunately, its outsized shape and signature result in a measurement range bias of several millimeters. On the basis of simulations of the echo signals, we analyze the center of mass corrections (CoM) for Etalon due to variations in satellite signature effect at different incidence angles. To minimize range bias caused by satellite signature effects, a center of mass corrections filter has been proposed for the processing of standard SLR data. According to the relationship between RMS of CoM and the upper limits of the rejection criteria, the measurements with the lowest variability of CoM are selected for normal points. Statistics indicate that the center of mass corrections filter can improve the stability of the collected data by 79%, and reduce the mean RMS of normal points from 163.7 × 41.8 ps to 118.2 × 8.94 ps. Additionally, the new algorithm is applicable to Etalon-2. In particular, this paper enriches and provides a useful reference for minimizing the effects of satellite signatures on the production of SLR data by providing a theoretical model that incorporates systematic errors in SLR.

Morphology and Depositional Processes of a Carbonate-Filled Canyon in the Carboniferous KT-II Formation of the Eastern Precaspian Basin, Kazakhstan: Insight from 3D Seismic Data

Canyons in carbonate depositional settings, as important elements of the source-to-sink system, remain poorly studied compared to those in siliciclastic depositional environments. The latest high-resolution three-dimensional seismic data, well logs, and core data at the eastern edge of the Precaspian Basin are used to investigate the geomorphology, infillings, and depositional process of a unique carbonate-filled canyon in the Carboniferous KT-II formation parallel to the carbonate platform, which is distinct from other slope-perpendicular canyons. The canyon has a total length of more than 52.3 km with a nearly N-S orientation and an S-shaped geometry, and the whole canyon can be divided into three segments by two knickpoints. The slope-parallel orientation of the canyon is mainly controlled by the palaeogeomorphology and reverse faults. Due to the collision of the Kazakh and European plates in the early-middle Visean (early Carboniferous), the canyon was formed in a northern tilted, elongated, and restricted palaeotopographic feature between uplifts. The development of reverse faults related to tectonic movement controlled the variations in the width of the canyon and the positions of the knickpoints. Tectonics controlled the orientation and formation of the canyon, while sedimentary processes contributed to its infilling. The well-seismic tie analysis indicated two distinct periods of the canyon fillings, Ss1 and Ss2, which were separated by a second-order sequence boundary. The lower part contained sediments supplied by both sides of the canyon through channels or gullies, and the upper part was dominated by a carbonate platform that prograded from the eastern side of the canyon. The evolution of the canyon can be subdivided into three stages. The increasing stage was mainly characterized by significant upslope erosion through headward retrogressive mass failures in the slope-parallel confined negative relief to form the canyon during the lowstand system tract of Ss1. Subsequently, in the early filling stage, the carbonate factory was productive during the highstand, and massive excess carbonate sediments were transported into the adjacent canyon by channels or gullies on both sides and deposited. The canyon was basically filled, and the morphology became much gentler. During the subsequent late filling stage, the carbonate platform was flooded again during the highstand, and the production rates of the carbonate factory greatly increased. The lateral progradation of carbonate platforms accelerated on the canyon of the early filling stage and further into the inner sag.

Micropaleontological Evidence of A Submarine Fan in the Lower Coaledo Formation, Southwestern Oregon, USA

Abstract The middle Eocene lower Coaledo Formation was interpreted as ten shoaling upward delta-margin cycles based on sediments and macrofauna. The strata, however, contains deep-water foraminifers. Explanations to resolve this anomaly included reworking, bathymetric range extension, or upward migration of water masses. Paleoecology analysis of foraminifers indicates that the few shelf species are poorly preserved whereas the well-preserved lower bathyal species dominate, and planktic organisms are present. Evidence for reworking, bathymetric range extension, or upward migration of water masses was not found in any of the cycles. The paleoecologic utility of hummocky cross-bedded sandstones is questioned as these features are controversial. In addition, there is no evidence of sea-level changes or tectonic activity to accommodate the bathymetric changes needed. Deposition of the lower Coaledo Formation on a submarine fan at lower bathyal depths eliminates the need to explain bathymetric anomalies or lack of tectonic movement.

Tectonic features, genetic mechanisms and basin evolution of the eastern Doseo Basin, Chad

The features of the unconformity, fault and tectonic inversion in the eastern Doseo Basin, Chad, were analyzed, and the genetic mechanisms and basin evolution were discussed using seismic and drilling data. The following results are obtained. First, four stratigraphic unconformities, i.e. basement (Tg), Mangara Group (T10), lower Upper Cretaceous (T5) and Cretaceous (T4), four faulting stages, i.e. Barremian extensional faults, Aptian–Coniacian strike-slip faults, Campanian strike-slip faults, and Eocene strike-slip faults, and two tectonic inversions, i.e. Santonian and end of Cretaceous, were developed in the Doseo Basin. Second, the Doseo Basin was an early failed intracontinental passive rift basin transformed by the strike-slip movement and tectonic inversion. The initial rifting between the African and South American plates induced the nearly N-S stretching of the Doseo Basin, giving rise to the formation of the embryonic Doseo rift basin. The nearly E-W strike-slip movement of Borogop (F1) in the western section of the Central African Shear Zone resulted in the gradual cease of the near north-south rifting and long-term strike-slip transformation, forming a dextral transtension fault system with inherited activity but gradually weakened in intensity (interrupted by two tectonic inversions). This fault system was composed of the main shear (F1), R-type shear (F2-F3) and P-type shear (F4-F5) faults, with the strike-slip associated faults as branches. The strike-slip movements of F1 in Cretaceous and Eocene were controlled by the dextral shear opening of the equatorial south Atlantic and rapid expanding of the Indian Ocean, respectively. The combined function of the strike-slip movement of F1 and the convergence between Africa and Eurasia made the Doseo Basin underwent the Santonian dextral transpressional inversion characterized by intensive folding deformation leading to the echelon NE-SW and NNE-SSW nose-shaped uplifts and unconformity (T5) on high parts of the uplifts. The convergence between Africa and Eurasia caused the intensive tectonic inversion of Doseo Basin at the end of Cretaceous manifesting as intensive uplift, denudation and folding deformation, forming the regional unconformity (T4) and superposing a nearly E-W structural configuration on the Santonian structures. Third, the Doseo Basin experienced four evolutional stages with the features of short rifting and long depression, i.e. Barremian rifting, Aptian rifting–depression transition, Albian–Late Cretaceous depression, and Cenozoic extinction, under the control of the tectonic movements between Africa and its peripheral plates.

Tectonic Control on Shale Pore Structure and Gas Content from the Longmaxi Formation Shale in Southern Sichuan Basin, China: Insights from Fractal Analysis and Low-Pressure Gas Adsorption

Tectonic deformation of different intensities significantly controls shale pore structure, seepage channels, and gas content. The Longmaxi Formation shales in the southern Sichuan Basin have experienced multi-stage tectonic movements, resulting in a diverse fracture system and tectonic deformation. This study focuses on three representative tectonic morphologies: deeply buried strongly deformed (DBSD), deeply buried weakly deformed (DBWD) and shallowly buried weakly deformed (LBWD). We investigated the pore structure characteristics and heterogeneity of these shales under various tectonic conditions using total organic carbon (TOC) content, X-ray diffraction (XRD), scanning electron microscopy (SEM), a low-pressure N2/CO2 adsorption experiment (LP-N2/CO2 GA), and multi-scale fractal theory. The results reveal that strong tectonic compression and deformation conditions lead to the compression and flattening of organic pores by brittle minerals, resulting in long, oriented OM pores. Fracturing of brittle pore creates multiple internal fracture systems linked to dissolution pores, forming a complex micro-fracture–pore network. With intense tectonic deformation, mesopores tend to be compressed, increasing micropore pore volume (PV) and surface area (SA). The DBSD shale exhibits the highest micropore heterogeneity, while the LBWD shale shows the lowest heterogeneity. Fractal analysis indicates a significant decrease in micropore fractal dimension (Df) with increasing burial depth. In contrast, the surface and matrix fractal dimensions (Ds and Dm) of low-buried shale micropores and meso-macropores align vertically. Shale reservoirs in tectonically stable regions exhibit more favourable gas-bearing characteristics than strongly tectonically deformed areas. The LBWD has stable tectonic conditions that are favourable for shale gas preservation. Conversely, slip faults under deep burial conditions lead to extrusion and deformation of shale pore space, ultimately compromising the original reservoir capacity and hindering shale gas enrichment. These findings contribute significantly to our understanding of pore structure and heterogeneity in tectonically deformed shale reservoirs, providing invaluable guidance for the exploration, development, and prediction of shale gas resources.

LAND SUBSIDENCE DYNAMICS IN MALAYSIA BASED ON TIME-SERIES VERTICAL DEFORMATION USING MODIFIED D-INSAR SENTINEL-1

Land subsidence in urban areas is geohazard that can be caused by tectonic movements, changes in aquifer networks, or anthropogenic activities such as excessive groundwater extraction, mining, tunnelling, and plantations. The degree of land subsidence can be monitored using time-series vertical deformation data extracted from Sentinel-1 satellite imagery using the modified D-InSAR method. This study aims to determine the land subsidence dynamics of 16 cities in Malaysia based on time-series vertical deformation data, including Kota Bahru, Kuala Terengganu, George Town and Butterworth, Alor Setar, Kangar, Ipoh, Seremban, Malacca, Kuala Lumpur, Putra Jaya, Shah Alam, Kuantan, Johor Bahru, Kinabalu, Bandar Labuan (Victoria), and Kuching. The time-series vertical deformation data used in this study were extracted between 2014-2022. Negative values of vertical deformation indicate that land subsidence is occurring, while positive values of vertical deformation are indicative of regional uplift. The overall rate of land subsidence in Malaysia is between -0.5 cm to -6.0 cm, while the average uplift rate is between +0.5 cm to +4.5 cm. An analysis of the data extracted reveals that the city that is most vulnerable to land subsidence is Johor Bahru, followed by Kuala Terengganu, Seremban, Kuala Lumpur, Shah Alam, Malacca, and Kuantan, while the city that has the lowest risk of land subsidence is Kangar. In contrast, cities that are vulnerable to regional uplift are Kinabalu and Bandar Labuan (Victoria). The results of this study can be used to guide urban planning initiatives, allowing them to consider any threats that might be posed by land subsidence.

The boundary between the Middle and Upper Cambrian strata in the Tarim Basin, NW China: Regional to global SPICE event correlation

The subdivision and correlation of the Cambrian System have long been controversial globally with multiple schemes. This is especially the case for the Tarim Basin, western China where regional and global correlations of the Middle-Upper Cambrian boundary are hampered by incomplete biostratigraphy. The Middle-Upper Cambrian boundary (T81) in the Tarim Basin is characterized by an abrupt switch of lithological and sedimentary facies, a sudden change of wireline log responses, and the contrasting seismic features, structural styles and carbonate platform architectures. The T81 boundary manifests in various forms and styles including syn-sedimentary unconformity, overlapping unconformity, tectonic unconformity, multi-stage superimposed unconformity, parallel unconformity and conformity. Each manifestation type of the T81 boundary was influenced by at least one of the factors including paleo-geomorphology, tectonic movement, eustacy, and climatic change. Based on the correlation between carbon isotopes and sedimentary characteristics in different regions globally, we suggest that the δ13C weak negative shift that follows the strongly positive shift of the Late Cambrian SPICE event can serve as a reliable isotope stratigraphic marker for identifying the T81 boundary of the western Tarim Platform. The top of the Awatag Formation (the top of the Middle Cambrian) in the western Tarim Platform should thus be correlated to the top of the Mohershan Formation in the eastern Tarim Basin, corresponding to the top of the Miaolingian Stage. The absence of the SPICE event in the western part of the Tarim Basin may have been caused by a regional depositional hiatus associated with the T81 boundary.

Detrital zircon U–Pb analysis indicate a provenance shift on the Neogene Barreiras formation, atlantic coast of Brazil

The Neogene Barreiras Formation is composed of continental to shallow marine sedimentary rocks that fringe the Brazilian Atlantic coast. Due to the large outcropping extent, various open questions about the evolution of this unit are still under debate. We present new U–Pb detrital zircon age spectra of four samples from the southern Espírito Santo state (Marataízes section) and two samples from the southern Bahia state (Arraial section). In both of the studied outcrops, a basal succession composed of coarse-grained cross-bedded sandstone, conglomerate and arkose with mudstone and claystone intercalations is superposed by an upper succession composed of massive sandstone, conglomerate and wacke. The U–Pb detrital zircon age spectra of all samples are dominated by Cambrian and Neoproterozoic grains. However, while the lower portion of both sections is dominated by Ediacaran-Cambrian grains, their upper portions also present significant Cryogenian-Tonian and sparse Paleoproterozoic (mainly Rhyacian and Statherian) and Neoarchean grains. This marks an important provenance shift within the Barreiras Formation, with a simple, local provenance sourced from the G1 to G5 granite supersuites of the Brasiliano Araçuaí Orogen for the basal layers contrasting with exposure of older basement rocks and Neoproterozoic anorogenic suites during deposition of the superior layers. We interpret the lower coarse sandstone and arkose-rich succession as deposited in an alluvial setting, with mud/claystones related to local flooding plains. Tectonic movements related to the evolution of the Atlantic passive margin, as described in previous works, caused a renewed uplift of the basement areas, exposing and denuding older rocks. Then, the upper layers deposited through debris flows covering the first succession. Further geochronological data is needed to test if the erosional event responsible for exposure of older basement rocks and sourcing of the upper layers would correspond to the Tortonian Sea level fall, related to growth of the Antarctic ice sheet to its present size. In this case, deposition of the lower succession would have occurred during the early Miocene, and the upper succession during the Pliocene. Our results shed light in the complex evolution of the sedimentary rocks generally grouped under the Barreiras Formation, and suggest important tectonic and climatic shifts during the Neogene evolution of the Brazilian Atlantic coast.

Analysis of structural-tectonic and petrophysical features of productive horizons of Mishovdag fold


 
 
 The article analyzes the geological structure, lithofascial, tectonic, and morpho- logical features of the Mishovdag oil field, which is a productive area in terms of oil content. Morphologically, it represents a brachianticlinal fold located in the north-west and south-east directions. The Mishovdag fold is located on the Kalamaddin-Bandovan anticline zone between the Kichik Harami (in the northeast) and Galmaz (in the northwest) structures. The Mishovdag-Galmaz part of the anticlinal zone extends in the sub-southern direction. The structures included in the zone are represented on the surface mainly by Aghjagil, Absheron, and ancient Khazar sediments. Productive layer sediments come to the surface in few areas. The tectonic movements and activity of mud volcanoes (active or buried) have left characteristic traces in the geological structure of the research area. Brachianticlinal and other types of structures were formed here. Under the strong influence of tectonic movements, the layers forming them were deformed and broken into blocks by regional tectonic faults. The anticlinal structures of the zone are complicated by longitudinal and latitudinal faults. The Mishovdag fold is represented by a brachianticline, 20-25 km long and 4-6 km wide. Brachianticline has a sharply asymmet- rical structure. The southwestern limb is steep, and inclined at an angle of 25-450, while the northeastern limb is flat and characterized by an inclination angle of 7-250. As a result of the analysis of the cross-sections of deep wells drilled in the field, it was determined that Mesozoic, Paleogene-Miocene, and Pliocene-Anthropogenic sediments are developed in the section of the fold. Sediments repre- senting the cross-section are characterized by high reservoir properties. Geological-geophysical works are carried out in the field. Core materials were taken from wells. The lithological-petrophysical characteristics – carbonate, porosity, and permeability of reservoir rocks have been determined according to core samples taken from exploration wells drilled in the field. The lithological-petrophysical characteristic regularities of change were investigated depending on depth.
 
 

Paleo-lake evolution influenced by tectonic processes and climate changes in the Hetao Basin during the late Quaternary

Exploration of paleo-lake evolution is crucial for the understanding of climatic and tectonic roles in earth surface. Previous studies mainly focused on the climatic effect on river-lake transitions and lake evolutions through lacustrine deposits, but with limited consideration of tectonic drivers, especially for the tectonic rift lakes in the Hetao area.Based on the analyses of lacustrine and fluvial piedmont terraces and a 400-m core from the northern Hetao Basin, along with the optically stimulated luminescence and detrital zircon U-Pb dating, we adopted an integrated “tectonics-climate-surface processes” approach to explore the climatic and tectonic effects on the lake evolution of the Hetao rift basin. Results show that lacustrine deposition on the piedmont terrace T1 (60–47 ka), underlying the T3 fluvial (80–60 ka), has an erosion contact with pluvial deposits at 55 ka, implying the paleo-lake formation at ∼ 80–60 ka and shrinkage at ∼ 55–47 ka. Lake formation was forced by basin depression under the tensile stress of tectonic movement, and was recharged by the Yellow River due to obstruction of the outlet at Tuoketuo caused by uplift.Lake shrinkage was due to the combined effect of basin lifting and warm-wet climate conditions that promoted outflow. A substantial decrease in the erosion base level and rapid water drainage induced by river cutting caused erosion of lacustrine deposits in the basin. The limited sedimentary space of the lake basin in early MIS 2 should be considered a factor in lake disappearance in addition to the dry climate. This study highlights that tectonic effects may be more important than climatic effects in the evolution of rift lakes near the young fold mountain belts.

Mineralogical and geochemical compositions of the early permian coal in the Huixiang Mine, Dengfeng Coalfield, Henan, China: Occurrence modes and origins of NH4-illite

In this study, we investigated the mineralogy and geochemistry of the Pennsylvanian No. 21 coal seam at the Huixiang Mine in the Dengfeng Coalfield, North China by employing a range of analytical techniques, including electron probe micro-analysis, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, and X-ray powder diffraction. The No. 21 coal in Huixiang Mine is classified as semi-anthracite and is characterized by a low total sulfur and ash contents. The predominant minerals identified in the Huixiang coal are NH4-illite, kaolinite, calcite, and chlorite, alongside trace amounts of Al-hydroxide minerals, zircon, and pyrite. Coalification in the Huixiang Mine has been primarily influenced by the heat generated by gravity-gliding tectonic movements since the Yanshan period, and the presence of hydrothermal fluids. During the coalification process, organic nitrogen undergoes thermal ammoniation, releasing NH4+ ions that subsequently react with kaolinite, leading to the formation of NH4-illite. Concurrently, when kaolinite is converted into NH4-illite, the released Si and excess Al may provided the necessary material for the formation of Al-hydroxide minerals and chamosite. The coal in the Huixiang Mine is slightly enriched with Li, Zr, Nb, Ta, and Th, rendering it a promising candidate for potential industrial recovery. The strong correlation of these elements with ash content suggested that their presence was largely influenced by terrestrial material input, attributable to the source materials originating in the North Qinling Orogenic Belt.

Depositional model of clastic and carbonate rocks in a continental rift basin: a case study of the Paleogene Shahejie Formation in the Cangdong Depression, Bohai Bay Basin

The study of a clastic and carbonate rock depositional model in a continental rift basin is helpful to better understand the sedimentary processes active in continental rift basins. However, the spatiotemporal evolution characteristics and controlling factors of clastic and carbonate rocks in continental rift basins are still unclear. Therefore, the sedimentary characteristics of the clastic and carbonate rocks in the Paleogene Eocene Shahejie Formation (Es) are analysed via seismic, well log, core, thin section, and geochemistry data. Then, the impacts of tectonic movement, sediment supply and hydrologic conditions on sedimentary characteristics are discussed, and a depositional model is finally established. Five 3rd-order sequences, named SQ1–SQ5 from bottom to top, are identified in the Es. Fan delta, braided delta, meandering river delta, and lake sedimentary systems are identified in the Es; clastic rock sedimentary systems are identified in SQ1–SQ4, while concurrent clastic and carbonate rock sedimentary systems are identified in SQ5. During the SQ1–SQ4 period, the palaeogeomorphology formed by differential faulting activity or fault interactions and the inherited palaeogeomorphology resulted in different distributions of the sedimentary systems. The changes in accommodation space and sediment supply caused by tectonic movement led the delta to prograde or disappear. During the SQ5 period, the clastic rock sedimentary systems underwent a transition into clastic rock and carbonate rock sedimentary systems as a result of rift weakening, broad crustal thermal subsidence, sediment supply reduction and high-salinity lake water. This study provides a typical case for the evolution characteristics of the clastic rock and carbonate rock systems in continental rift basins, identifies changes in the tectonic, sediment supply, and hydrologic characteristics during their mutual transformations, and provides an important reference for hydrocarbon reservoir prediction.

Biogeographic influences on the evolution and historical dispersal of the Australo‐Pacific Dacini fruit flies (Tephritidae: Dacinae)

AbstractFruit flies (Tephritidae: Dacini) are a frugivorous insect group that exhibit high endemic diversity in the rainforests of Australia and the western Pacific. In this region, biogeography has been influenced by tectonic plate movements and cycles of isolation and re‐connection of landmasses and rainforest habitats during glacial periods. However, how such factors have influenced the speciation and historical dispersal of the regional Dacini is largely unknown. To address this, we use a dated phylogeny to reconstruct the biogeographical history of the tribe. We found the Dacini radiated eastward into the Pacific islands largely from sources in New Guinea. We also found evidence for historical dispersal from both Australia and New Guinea into New Caledonia, a pathway unique to this island compared with neighbouring islands. There was also evidence for multiple, bidirectional dispersal events between Papua New Guinea and Australia, likely facilitated by the cyclically exposed Torres Strait land bridge. Cape York in far northern Australia was likely the only entry point for species dispersing into Australia; there was no evidence for entry of flies into Australia directly from West Papua or Wallacea. Several lineages radiated after entering Australia, such as members of the Bactrocera dorsalis species group. Within Australia, speciation was not associated with the biogeographic barriers known to have impacted other rainforest fauna in eastern Australia. Overall, we demonstrate that isolation between islands and large landmasses is important in the evolution of the Australo‐Pacific Dacini, but the reason for their extensive radiation within Australia and Papua New Guinea remains unclear.

Numerical Study on the Influence of Fault Structure on the Geostress Field

A geostress field continuously evolves with long-term tectonic activity. A fault, as a general product of tectonic movements, has a great influence on the geostress field in the vicinity. To analyze the geostress field characteristics and influencing factors near the fault fracture zone in high-altitude areas, this study takes the Dianda-Piru fault on the Qinghai–Tibet Plateau as its research object. Based on the geological conditions and in situ stress measurement data in the study area, a refined numerical model was established using numerical simulation to invert the geostress field in the vicinity of the fault fracture zone, and a quantitative analysis of the factors influencing the geostress distribution was carried out. The results show that the overall relationship between large horizontal principal stress σH, vertical stress σv, and small horizontal principal stress σh is σH > σv > σh, and the surrounding rock stress is dominated by horizontal stress. Geostress is released within the fault fracture zone to a certain extent, and there is a certain degree of stress concentration within the intact rock mass on the upper plate of the fault. The elastic modulus has a greater influence on the geostress field near the fracture structure area than Poisson’s ratio, and the range of the stress-weakening zone increases with the decrease in the elastic modulus. The maximum principal stress inside the fault increases with the increase in the angle between the fault strike and regional principal stress, while the deflection angle of the surrounding principal stress direction decreases with the increase in this angle. The study of the distribution law of geostress fields with developed fracture structures can provide theoretical guidance for the sustainable development of engineering construction in tectonically active areas.

Paleoenvironmental characteristics and organic matter enrichment mechanisms of the upper Ordovician-lower Silurian organic-rich black shales in the Yangtze foreland basin, South China

The Wufeng Formation-Longmaxi Formation (O3w-S1l1) black shales within the Yangtze foreland basin (South China) hold significant potential as unconventional oil and gas resources. However, several challenges, including sluggish sedimentation rates, thin sedimentary layers, and notable homogeneity, hinder a comprehensive grasp of the organic matter enrichment (OME) mechanism within these shales. These challenges impede the exploration of unconventional oil and gas resources. This study aims to identify the O3w-S1l1 black shales in the Weiyuan area through a combined approach of organic and inorganic geochemical analyses. By doing so, it delves into the controlling mechanism behind OME in the black shales of the Yangtze foreland basin. The findings of this research reveal that the O3w-S1l1 black shales primarily consist of sapropelic kerogen and exhibit signs of over-maturation, with TOC content ranging from 0.43% to 8.21%. These shales are classified as organic-rich, mainly composed mixed and siliceous lithofacies. The presence of silica in the shales originates mainly from biogenic sources, and the highest TOC content coincides with a Sixs contribution of around 30% to the total silica content. During the late Katian, a global sea level drop led to an oxic paleoenvironment, transitioning into a euxinic paleoenvironment as sea levels rose in the early Rhuddanian. Notably, TOC content exhibited a significant correlation with paleoceanographic conditions (e.g., V/Cr, Ni/Co) and paleoproductivity levels (e.g., P/Al, Babio), while displaying a negative correlation with paleoclimate conditions (e.g., CIA, C-value), terrigenous detrital input intensity (e.g., Sixs, Ti/Al), and sedimentation rate ((La/Yb)N). Specifically, favourable conditions for OME encompass robust reducing seawater conditions, high paleoproductivity, a humid climate, reduced influx of terrigenous debris, and relatively elevated sedimentation rates. Regional tectonic movements (Guangxi movement) and fluctuations in relative sea levels exert influence over the deposition of O3w-S1l1 black shales. This study provides a valuable case study for exploring and developing shale gas resources within the Yangtze foreland basin.