Uplift Processes Research Articles

Structural Characteristics and its Significances on Hydrocarbon Accumulation in the Yunkai Low Uplift, Pearl River Mouth Basin

AbstractThe Yunkai low uplift with low exploration degree is close to the Baiyun sag, and has hydrocarbon exploration potential in the deepwater area of the Pearl River Mouth Basin. Based on seismic and drilling data, balanced profiles and growth strata, this paper mainly discusses geological structures and formation processes of the Yunkai low uplift, and also analyzes the characteristics of fault system and their influence on hydrocarbon migration and accumulation. The EW‐trending basement faults divide the Yunkai low uplift into two parts, i.e. the southern sector and the northern sector. The northern sector is a relatively wide and gentle uplift, while the southern sector is composed of two secondary half‐grabens with faulting in the south and overlapping in the north. The Yunkai low uplift experienced three major formation stages, including the rapid uplifting stage during the deposition period of the Eocene Wenchang Formation, the slow uplifting stage during the deposition period of the Late Eocene‐Middle Miocene Enping‐Hanjiang formations, and the whole burial stage from the Middle Miocene to present. The extensional faults in the Yunkai low uplift and its adjacent areas strike mainly along the NW, NWW and near‐EW directions. Also, the strikes of faults present a clockwise rotation from the deep to the shallow strata. According to effects of faults on hydrocarbon accumulation, the faults in the Yunkai low uplift and its adjacent areas can be divided into trap‐controlled faults and source‐controlled faults. The trap‐controlled faults control trap development and can effectively seal oil and gas. The source‐controlled faults connect directly source rocks and reservoirs, which are highly active during the rifting stage and weakly active since the Miocene. This activity features of the source‐controlled faults is beneficial to migration of the early crude oil from the Baiyun sag to the high part of the Yunkai low uplift, but is not good for migration of the late natural gas. In the Yunkai low uplift and its adjacent areas, the traps in the deep Zhuhai and Enping formations that are close to source rocks in the Baiyun sag should be the favorable exploration objectives.

Study on the Shale Gas Reservoir-Forming Characteristics of the Taiyuan Formation in the Eastern Qinshui Basin, China.

Shales are widely developed in the strata of the Carboniferous-Permian coal measures in the Qinshui Basin, and these shales have great potential for shale gas exploration. In this paper, the shales of the Taiyuan Formation in the eastern Qinshui Basin are studied. The shales of the Taiyuan Formation in the study area are investigated through field investigation, organic geochemical testing, X-ray diffraction, scanning electron microscopy, high pressure mercury injection, low temperature liquid nitrogen adsorption and PetroMod simulation and through other tests to study the reservoir characteristics, such as organic geochemistry, mineralogy, petrology, pore permeability, and gas burial history. The results show that the shales of the Taiyuan Formation are well developed over the whole area with a thickness of more than 60 m. The average organic matter content is 2.95%, and the kerogen type is type III. The shale maturity (average value is 2.45%) corresponds to the stage of high maturity evolution, indicating that a large amount of shale gas has been generated in this area. A high content of quartz and clay minerals indicates a high fracturability. The nanopores in the shale reservoir are well developed at pore sizes between 2˜10 nm and greater than 1000 nm; however, the pores at the other pore sizes are poorly developed, resulting in weak pore connectivity in the reservoir. According to the results of the PetroMod simulation, the shale of the Taiyuan Formation has undergone two subsidence and two uplift processes. The Yanshanian magmatic intrusion is the key factor for the rapid increase in gas production. In addition, the geological structure of the area is relatively simple, and the burial history and caprock thickness are also the main controlling factors of gas generation and preservation. The shale-sandstone-shale combination and shale-coal-shale combination are the main models of shale gas preservation. This comprehensive study suggests that the shale gas of the Taiyuan Formation in the eastern Qinshui Bain has good potential for exploration and development.

Exhumation and preservation conditions of Suyunhe porphyry molybdenum deposit in the West Junggar, Xinjiang (NW China): Constraints from the fission track and (U-Th)/He thermochronology

斑岩型矿床多形成于汇聚型板块边界。由于其较浅的就位深度，大部分古老的斑岩型矿床很容易受到后期的剥蚀而消失殆尽。研究斑岩型矿床成矿后的埋藏和去顶过程对于深入理解矿床的保存条件和区域找矿前景至关重要。新疆西准噶尔西部的苏云河斑岩型钼矿床形成于晚石炭世，是一处保存良好的斑岩型矿床，为我们研究前中生代斑岩成矿系统的保存条件提供了天然的实验室。本文首次针对该矿床开展了锆石和磷灰石裂变径迹与锆石（U-Th）/He低温热年代学分析，结合热历史反演模拟以及前人的年代学数据显示，苏云河斑岩钼矿的蚀变过程至少持续了55Myr。在早二叠世到中三叠世，矿区接受5.2~8.1km厚的沉积物覆盖。中三叠世至早白垩世（240~120Ma），矿床经历了快速剥露作用，剥露速率为49.0~56.7m/Myr，去顶量为7.4~9.2km。早白垩世（120Ma）至今为缓慢剥露阶段，剥露速率为6.7~21.7m/Myr，去顶量为0.8~2.6km。中三叠世至早白垩世的快速冷却事件可能并不是特定构造事件（比如：南部羌塘和昆仑-柴达木碰撞或者羌塘和拉萨碰撞）远程效应的产物，而与区域内走滑断层的活化密切相关。而矿床早期沉积的巨厚盖层以及早白垩世以来干旱气候和缓慢剥露，为石炭-二叠纪斑岩型钼矿得以保存提供了条件。;Porphyry deposit is a kind of epithermal deposit, which is mostly formed in the convergent plate boundary. However, ancient porphyry deposit was often destroyed and disappeared due to later tectonic or exhumation. Therefore, it is vital to reveal the exhumation and uplift process after mineralization for further understanding the preservation conditions and regional prospecting prospects of the deposits. Suyunhe porphyry molybdenum deposit in the west part of the West Junggar, Xinjiang was formed in Late Carboniferous. It is a well-preserved porphyry deposit, which provides a natural laboratory for us to study the preservation conditions of ancient porphyry metallogenic system. In this paper, we present new zircon and apatite fission track (ZFT and AFT) and zircon (U-Th)/He (ZHe) data for the Suyunhe porphyry molybdenum deposit. Combined with thermal modeling inversion, we suggest that the hydrothermal alteration process of the Suyunhe porphyry molybdenum deposit lasted at least 55Myr. It underwent a thick burial (5.2~8.1km) sediments from Early Permian to Middle Triassic. The deposit experienced a rapid exhumation stage from Middle Triassic to Early Cretaceous (240~120Ma). The exhumation rate was 49.0~56.7m/Myr, and the corresponding denudation amount was 7.4~9.2km. After the Cretaceous (120Ma), it entered a slow exhumation stage with an exhumation rate of 6.7~21.7m/Myr and exhumation amount of 0.8~2.6km. Among them, the Middle Triassic to Early Cretaceous rapid exhumation was not the product of far-field effects (e.g., the collision between Qiangtang and Kunlun-Qaidam or the collision between Qiangtang and Lhasa), but related to the activation of strike slip faults in the region. Therefore, early thick burial and later dry climate and slow exhumation provided key conditions for the preservation of the Carboniferous Suyunhe porphyry molybdenum deposit.

ІНТРУЗИВНО-МАГМАТИЧНІ УТВОРЕННЯ АРХІПЕЛАГУ ВІЛЬГЕЛЬМА ЗАХІДНОЇ АНТАРКТИКИ (ЧАСТИНА 1 – ІНТРУЗИВИ ГАБРОЇДІВ, ДІОРИТІВ ТА ГРАНІТОЇДІВ)

The Wilhelm Archipelago and the adjacent coast of Graham Land are typical areas of calc-alkaline magmatism associated with the protracted evolution of the Antarctic Peninsula igneous belt. The authors studied intrusive complexes of the Wilhelm Archipelago (WA) in order to characterize their geographical distribution, geological occurrence and age, mineralogical and petrographical features. Geological surveys revealed that gabbro, diorite, and granitoid intrusions are widespread on the WA. Due to the processes of tectonic uplift and exhumation, both apical and bottom parts of individual intrusive bodies can be exposed on the modern erosion level. Recent geological observations have shown that plutons of different ages intersect each other in a complex sequence. This made it possible to determine their relative geological age and reconstruct the general direction of the deep magmatic development from the Early Cretaceous to the Early Paleogene, inclusive. It has been proved that the oldest massifs of gabbroids are parts of much larger intrusive bodies. They were formed in the period between the Jurassic and the Early Cretaceous periods. Crystallization differentiation of basaltic magmas gave them various scale layering. In the bottom parts of gabroid intrusions there were conditions for the formation of Fe-Ti-V and Cu-Ni-EPG mineralization. Diorite and granitoid intrusions occupy much larger areas compared to gabbroids. The formation of diorite intrusions took place in the period between the Early Cretaceous and the Paleocene. Although the oldest gabbroids were formed much earlier than diorites, the phenomena of magmatic mingling in the latter indicate that magmas of basic and intermediate composition could also synchronously intrude in common magmatic chambers. Granitoid magmatism on the WA covers the Late Cretaceous and the Paleogene periods. Most granitoid intrusions formed in the Paleocene after the main phase of tectonic deformations. Cu-Mo mineralization may be associated with these intrusions.

Construction of plastic deformation areas in a homogeneous base of strip foundation

The article discusses two approaches to the question of plastic deformations constructing areas in a homogeneous baseof a strip foundation: a trivial approach based on the use of the Coulomb plasticity condition, and the approach proposed by the authors based on the approximate analytical solution of the theory of elasticity and the theory of soil plasticity mixed problem. It has been established that the “Coulomb” regions, which originally generated under the edges of the strip load, close under the basement as it increases and form a single crescent-shaped plastic area. Plastic areas built on the basis of a mixed solution develop inward and outward from the foundation. Their closure under the foundation occurs at the beginning of the soil uplift process under the foundation, which is accompanied by the appearance of deep heaving zones (Fig. 8; 9). All other things being equal, the “Coulomb” regions are much larger in size and extend to a greater depth than the regions constructed on the basis of a mixed solution of the theory of elasticity and the theory of soil plasticity problem. The elastic soil core, enveloped by “Coulomb” plastic areas, has a shape close to the shape of a half ellipse or a curved trapezoid, and, alternatively, has the shape of an isosceles triangle with concave lateral sides. If we construct the regions of plastic deformations at the base of a strip foundation using the Coulomb plasticity condition, or apply a solution to a mixed problem, then, all other things being equal, the sizes of the “Coulomb” regions, the “rate” of their development and sensitivity to changes in the value of the lateral pressure coefficient of the soil will always be more than in the alternative case. If the value of the ultimate load is taken as its value corresponding to the closure of the plastic areas under the foundation, then the mixed solution of the theory of elasticity and the theory of plasticity of soils problem gives higher (≥500%) the values of the latter. When finding the value of the bearing capacity of the strip foundation base, it is recommended to apply the solutions of the corresponding problems in the elastoplastic (mixed) formulation, since their results, and this has been shown in the work, are in satisfactory agreement with the experimental data.

Geochemical discrimination of the altered volcanic tuff from sediments in the Lunpola Basin, central Tibetan Plateau

AbstractVolcanic tuffs are important in determining the stratigraphic age of sedimentary sequences, which is closely related to the tectonic, sedimentological, geomorphological, palaeoclimatic, and palaeo-ecological evolution of the sequences. However, it may be difficult practically to identify tuffs in stratigraphic sections, especially when they are altered after deposition. In this study, a series of petrographic, mineralogical, and geochemical analyses was deployed in the tuff layers cropping out in the Lunpola Basin of the central Tibetan Plateau, which is a crucial site for studying the dynamics and processes of the Cenozoic uplift of the Tibetan Plateau and its environmental impacts. In these pyroclastic layers, authigenic analcime is the main volcanic glass alteration product. The analcime-bearing samples are Na-enriched, in contrast to the K-abundant magmatic rocks in the central Tibetan Plateau. The distribution patterns of the rare earth elements (REEs) of the bulk analcime-bearing samples are similar to those of the magmatic rocks but different from those of the analcime-poor sediments and analogues of well-mixed upper continental material (e.g. the upper continental crust and post-Archaean Australian average shales). The distinct distributions of Na and REEs among analcime-bearing samples, analcime-poor sediments, and volcanic rocks reveal that analcime formed both from alteration of volcanic material and from mixing processes with non-volcanic sediments. It is proposed, therefore, that the discrimination plot of Na2O/Al2O3-(La/Yb)Nmay be used to distinguish the analcime-related pyroclastic rocks from the basin sedimentary sequence, and thus it may provide a means of discriminating between various volcanic material and of supporting age dating by tephrochronology in the central Tibetan Plateau.

Tectonic evolution in the Early to Middle Pleistocene off the east coast of the Boso Peninsula, Japan

Abstract The Kanto Basin developed, starting c. 3 Ma, influenced by the subduction of the Philippine Sea plate and the Pacific plate. Sediments in this basin have influenced the geomorphology of the Kanto region. In the Boso Peninsula, located at the eastern edge of the Kanto Basin, uplift continues in what is called the Kashima–Boso uplift zone. Although the development of this uplift after the Late Pleistocene is well understood, there are few data from the Early to Middle Pleistocene. In this study, we investigated the offshore shelf area east of the Boso Peninsula using a high-resolution seismic reflection survey, and report new information on the geological structure and uplift processes in the area from the Early to Middle Pleistocene. We identified the Kujukuri-oki anticline and the Kujukuri-oki normal fault zone. The Kujukuri-oki anticline, more than 47 km long, is north–south striking and deforms the Kujukuri-oki Group. There are numerous normal faults with displacements of less than tens of metres spread widely in the survey area (Kujukuri-oki normal fault zone). These findings reveal that the Kujukuri-oki anticline uplifted during the end of the Early Pleistocene and attenuated during the Middle Pleistocene. This anticline comprised the axis of the Kashima–Boso uplift zone at the Boso Peninsula from the Early to Middle Pleistocene and the Boso Peninsula is located at the western limb of this anticline.

Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans–North China orogen

AbstractIn worldwide orogenic belts, crustal-scale ductile shear zones are important tectonic channels along which the orogenic root (i.e., high-grade metamorphic lower-crustal rocks) commonly experienced a relatively quick exhumation or uplift process. However, their tectonic nature and geodynamic processes are poorly constrained. In the Trans–North China orogen, the crustal-scale Zhujiafang ductile shear zone represents a major tectonic boundary separating the upper and lower crusts of the orogen. Its tectonic nature, structural features, and timing provide vital information into understanding this issue. Detailed field observations showed that the Zhujiafang ductile shear zone experienced polyphase deformation. Variable macro- and microscopic kinematic indicators are extensively preserved in the highly sheared tonalite-trondhjemite-granodiorite (TTG) and supracrustal rock assemblages and indicate an obvious dextral strike-slip and dip-slip sense of shear. Electron backscattered diffraction (EBSD) was utilized to further determine the crystallographic preferred orientation (CPO) of typical rock-forming minerals, including hornblende, quartz, and feldspar. EBSD results indicate that the hornblendes are characterized by (100) <001> and (110) <001> slip systems, whereas quartz grains are dominated by prism <a> and prism <c> slip systems, suggesting an approximate shear condition of 650–700 °C. This result is consistent with traditional thermobarometry pressure-temperature calculations implemented on the same mineral assemblages. Combined with previously reported metamorphic data in the Trans–North China orogen, we suggest that the Zhujiafang supracrustal rocks were initially buried down to ∼30 km depth, where high differential stress triggered the large-scale ductile shear between the upper and lower crusts. The high-grade lower-crustal rocks were consequently exhumed upwards along the shear zone, synchronous with extensive isothermal decompression metamorphism. The timing of peak collision-related crustal thickening was further constrained by the ca. 1930 Ma metamorphic zircon ages, whereas a subsequent exhumation event was manifested by ca. 1860 Ma syntectonic granitic veins and the available Ar-Ar ages of the region. The Zhujiafang ductile shear zone thus essentially record an integrated geodynamic process of initial collision, crustal thickening, and exhumation involved in formation of the Trans–North China orogen at 1.9–1.8 Ga.

Chasing the 400 kyr pacing of deep-marine sandy submarine fans: Middle Eocene Aínsa Basin, Spanish Pyrenees

In an attempt to understand the relative importance of climate and tectonics in modulating coarse-grained sediment flux to a tectonically active basin during what many researchers believe to be a greenhouse period, we have studied the Middle Eocene deep-marine Aínsa Basin, Spanish Pyrenees. We use orbital tuning of many spectral gamma-ray-logged fine-grained siliciclastic sections, already shown to contain Milankovitch frequencies, in conjunction with a new high-resolution palaeomagnetic study through the basin sediments, to identify polarity reversals in the basin as anchor points to allow the conversion of a depth-stratigraphy to a chronostratigraphy. We use these data, in conjunction with a new age model incorporating new biostratigraphic data, to pace the development of the deep-marine sandy submarine fans over c . 8 million years. Timing for the sandy submarine fans shows that, unlike for the fine-grained interfan sediments, coarse-grained delivery to the basin was more complex. Approximately 72% of the sandy fans are potentially coincident with the long-eccentricity (400 kyr) minima and, therefore, potentially recording changing climate. The stratigraphic position of some sandy fans is at variance with this, specifically those that likely coincide with a period of known increased tectonic activity within the Aínsa Basin, which we propose represents the time when the basin was converted into a thrust-top basin (Gavarnie thrust sheet), presumably associated with rapid uplift and redeposition of coarse clastics into deep-marine environments. We also identify sub-Milankovitch climate signals such as the c . 41.5 Ma Late Lutetian Thermal Maximum. This study demonstrates the complex nature of drivers on deep-marine sandy fans in a tectonically active basin over c . 8 Myr. Findings of this study suggest that, even during greenhouse periods, sandy submarine fans are more likely linked with times of eccentricity minima and climate change, broadly consistent with the concept of lowstand fans. However, hysteresis effects in orogenic processes of mountain uplift, erosion and delivery of coarse siliciclastics via fluvial systems to coastal (deltaic) and shallow-marine environments likely contributed to the complex signals that we recognize, including the 2–3 Myr time gap between the onset of deep-marine fine-grained sediments in the early development of the Aínsa Basin and the arrival of the first sandy fans. Supplementary Materials : Filtered records for each of the analysed gamma-ray logged sections. Anchor points, SARs tables and graphs and alternative tuning sections are available at: https://doi.org/10.6084/m9.figshare.c.5132975

Biogeography, phylogenetic relationships and morphological analyses of the South American genus Mutisia L.f. (Asteraceae) shows early connections of two disjunct biodiversity hotspots

The Andes is recognized as one of the most biodiverse places on Earth, promoting in its uplift process a series of recent rapid diversification events in different biotic groups like birds, mammals, insects and vascular plants. The uplift of the Andes during the Cenozoic acted as a barrier for many biotic groups, as a scenario for radiation processes due to occupancy of different niches and as a corridor for others. Connections between the Andes and the Atlantic Forest showed intermittent phases along the Cenozoic, affecting the distribution patterns and diversification of different biotic groups. Nowadays, the Andes and the Atlantic Forest are both considered globally relevant biodiversity hotspots. Floristic groups thriving in both hotspots are crucial for a better understanding of their biogeographic history, as well as for informing future conservation actions. Mutisia (Asteraceae), a genus comprising 63 perennial shrubs and vines endemic to South America, shows a marked West-East disjunction: Most species occupy almost the whole Andean chain from Colombia to Patagonia, while a second group encompasses four species distributed in eastern Brazil and the surrounding areas of Paraguay, Uruguay and Argentina. We reconstructed the phylogeny of the genus to assess its possible biogeographic history. We analysed three DNA regions, i.e. the chloroplast trnL-trnF intergenic spacer and the nuclear ribosomal internal and external transcribed spacers, ITS and ETS. Using maximum likelihood and Bayesian inference, gene trees were reconstructed, and a concatenated phylogenetic tree was inferred. Divergence times were estimated by means of BEAST, and the ancestral areas were inferred using BioGeoBEARS. An ancestral reconstruction of morphological traits was also performed, as well as maps representing current richness hotspots within the genus. Phylogenetic analyses strongly support the monophyly of Mutisia, with two well-supported main clades: clade A, with presence of Atlantic-central-northern Andes species, and clade B, with central/southern Andes species. Dating analyses suggest that a main clade separation occurred at the early Miocene, followed by the separation of the Atlantic clade A2 by the late Miocene, and more recent radiations occurred in the central, northern and southern Andes during the Pliocene. Results are in tune with other angiosperm taxa that also underwent rapid radiations, possibly related to environmental and pollinator changes. The biogeographic history of Mutisia is related to morphological adaptations, history and geographic factors acting since the Miocene along the Andes and adjacent areas. Threat assessments and conservation actions for the genus shall include the whole distribution range, including low-range northern and southern Andes species, as well as the distinctive Atlantic Forest clade.

Crustal structure underneath central China across the Tibetan Plateau, the North China Craton, the South China Block and the Qinling-Dabie Orogen constrained by multifrequency receiver function and surface wave data

Abstract Investigating the crustal structure at the juncture region of the Tibetan Plateau, the North China Craton, the South China Block and the Qinling-Dabie Orogen is important to understand processes of uplift of the Tibetan Plateau and the craton destruction and preservation. In this study, we dropped the H-k stacking of receiver functions (RFs), RF nonlinear inversion, and joint inversion of RF and surface wave dispersion with multiple Gaussian factors successively to invert the crustal thickness (H), average Vp/Vs ratio (k) and S-wave velocity in the juncture region. The imaging results and the synthetic tests of multifrequency H-k stacking were further used to study the crustal structure and related tectonic evolution. Our results show that the H and k values generally increase and decrease, respectively, as the Gaussian factor increases in the study region, which is consistent with synthetic tests of H-k stacking. The cores of the Ordos Block and the Sichuan Basin exhibit a typical cratonic crust, whereas the Zhongtiao Mountains and adjacent Qinling-Dabie Orogen to the south may have undergone delamination of the lower crust. Local low-velocity anomalies in the middle-lower crust were observed in the Western Qinling Orogen and Qilian Orogen, whereas high S-wave velocities in the middle-lower crust were observed at the juncture region between the Western Qinling Orogen and the Qinling-Dabie Orogen. Our results suggest that the lower crustal flow is probably restricted to the central area in the Western Qinling Orogen and does not flow into the Qilian Orogen or the Qinling-Dabie Orogen.

Shear-wave splitting beneath Fennoscandia — evidence for dipping structures and laterally varying multilayer anisotropy

SUMMARYThe geodynamic evolution of Fennoscandia in northern Europe (Finland, Sweden and Norway) is coined by ca. 3 Ga history of tectonic processes including continental growth in its central and eastern parts and Neogene uplift processes of the Scandinavian mountains (Scandes) located along its western edge. Many details are still under debate and we contribute with new findings from studying deep-seated seismic anisotropy. Using teleseismic waveforms of more than 260 recording stations (long-running permanent networks, previous temporary experiments and newly installed temporary stations) in the framework of the ScanArray experiment, we present the most comprehensive study to date on seismic anisotropy across Fennoscandia. The results are based on single and multi-event shear-wave splitting analysis of core refracted shear waves (SKS, SKKS, PKS and sSKS). The splitting measurements indicate partly complex, laterally varying multilayer anisotropy for individual areas. Consistent measurements at permanent and temporary recording stations over several years and for seismic events of specific source regions allow us to robustly constrain dipping anisotropic structures by adding systematic forward modelling. Although the data coverage is partly limited to only few source regions, our findings support concepts of continental growth due to individual episodes of (paleo-) subduction, each affecting a plunging of the anisotropic fast axis direction due to collisional deformation. Along the northern Scandes the fast axis direction (ϕ) is parallel to the mountain range (NE-SW), whereas an NNW-SSE trend dominates across the southern Scandes. In the south, across the Sorgenfrei–Tornquist Zone, a NW-SE trend of ϕ dominates which is parallel to this suture zone. The Oslo Graben is characterized by an NNE-SSW trend of ϕ. In northern Norway and Sweden (mainly Paleoproterozoic lithosphere), a dipping anisotropy with ϕ towards NE prevails. This stands in contrast to the Archean domain in the NE of our study region where ϕ is consistently oriented NNE-SSW. In the Finnish part of the Svecofennian domain, a complex two-layer anisotropy pattern is found which may be due to lateral variations around the seismic stations and which requires a higher data density than ours for a unique model building. Based on these findings our study demonstrates the importance of long recording periods (in the best case > 10 yr) to obtain a sufficient data coverage at seismic stations, especially to perform meaningful structural modelling based on shear-wave splitting observations.

Quantitative assessment of ground deformation risks, controlling factors and movement trends for onshore petroleum and gas industry using satellite Radar remote sensing and spatial statistics

ABSTRACT A number of productive oil and gas fields are located in the Absheron Peninsula of Azerbaijan. The primary goal of the presented study was to quantitatively assess the ground deformation (subsidence and uplift) rates of oil and gas fields, determine natural and man-made influencing factors and predict deformation trends. Persistent Scatterer Interferometric Synthetic Aperture Radar technique was used for the present studies to detect ground deformation rates and velocities in the Absheron oil and gas fields. The existence of ground deformation processes was observed for the period of 2015–2017 with three hotspots of highest subsidence rates and three hotspots of highest uplift rates in oil and gas fields. The determined maximum displacement rates of subsidence and uplift processes were −26 mm/y and +23 mm/y, respectively. However spatial density analysis of deformation velocity presented the natural patterns of uplift and subsidence tectonic processes. This allowed to determine that two oil and gas fields hold a higher probability of being affected by man-made oil and gas exploration activities, whereas the one oil field is affected by both natural and man-made processes. Geographically Weighted Regression analysis revealed that well concentration and elevation factors provided 32% of explanation to subsidence processes.

The impact of earthquakes on orogen-scale exhumation

Abstract. Individual, large thrusting earthquakes can cause hundreds to thousands of years of exhumation in a geologically instantaneous moment through landslide generation. The bedrock landslides generated are important weathering agents through the conversion of bedrock into mobile regolith. Despite this, orogen-scale records of surface uplift and exhumation, whether sedimentary or geochemical, contain little to no evidence of individual large earthquakes. We examine how earthquakes and landslides influence exhumation and surface uplift rates with a zero-dimensional numerical model, supported by observations from the 2008 Mw 7.9 Wenchuan earthquake. We also simulate the concentration of cosmogenic radionuclides within the model domain, so we can examine the timescales over which earthquake-driven changes in exhumation can be measured. Our model uses empirically constrained relationships between seismic energy release, weathering, and landsliding volumes to show that large earthquakes generate the most surface uplift, despite causing lowering of the bedrock surface. Our model suggests that when earthquakes are the dominant rock uplift process in an orogen, rapid surface uplift can occur when regolith, which limits bedrock weathering, is preserved on the mountain range. After a large earthquake, there is a lowering in concentrations of 10Be in regolith leaving the orogen, but the concentrations return to the long-term average within 103 years. The timescale of the seismically induced cosmogenic nuclide concentration signal is shorter than the averaging time of most thermochronometers (>103 years). However, our model suggests that the short-term stochastic feedbacks between weathering and exhumation produce measurable increases in cosmogenically measured exhumation rates which can be linked to earthquakes.

Natural fractures in carbonate-rich tight oil reservoirs from the Permian Lucaogou Formation, southern Junggar Basin, NW China: Insights from fluid inclusion microthermometry and isotopic geochemistry

Natural fractures within tight reservoirs form preferred pathways for hydrocarbon charge and provide space for hydrocarbon preservation. However, the mechanism that controls the formation of natural fractures in tight reservoirs remains controversial. This study investigates natural fractures within carbonate-rich tight oil reservoirs from the Permian Lucaogou Formation in the Jimsar Sag, southern Junggar Basin. Drill core and image log observations show that fractures in the Lucaogou Formation can be categorized into two types: bedding-parallel fractures and inclined fractures. The carbon and oxygen isotopic compositions of calcite cements in the bedding-parallel fractures range from 0.6‰ to 6.0‰ (δ13CPDB), and from −15.5‰ to −8.9‰ (δ18OPDB), respectively, which are similar to those of the organic-rich host rock. This suggests that the bedding-parallel fractures likely formed in a closed fluid system. Fluid inclusion analyses of the aqueous inclusions in calcite cements from the bedding-parallel fractures record homogenization temperatures of 91.5 °C–130.4 °C, indicating that they formed at the Cretaceous to Cenozoic, during when the Lucaogou Formation reached peak oil generation stage. Therefore, the bedding-parallel fractures were most likely generated by hydrocarbon generation overpressure. The presence of hydrocarbon inclusions in bedding-parallel fracture cements supports natural fracturing by high pore-fluid pressure. The δ13CPDB and δ18OPDB of calcite cements within the inclined fractures vary from 3.6‰ to 9.6‰, and from −11.0‰ to −2.9‰, respectively, which are close to those of the carbonate-rich parent rock. This also supports a closed fluid system scenario. The relatively lower fluid inclusion trapping temperatures (70.5 °C–109.7 °C) suggest that they were likely generated by decrease of confining stress during uplift processes. Therefore, both an increase in pore-fluid pressure and a decrease in confining stress contribute to the formation of natural fractures in the Lucaogou Formation tight oil reservoirs.

Using SBAS-InSAR to Detect Surface Movement above Old Mining Areas after Mine Closure

The impact of underground coal mining on the surface is not only manifested in the period of coal mining, but also after the coal mining stops and after the coal mine closes down, there will still be residual settlement, or the opposite movement - surface uplift. With the continuous development of microwave earth observation technology, time series InSAR technology has become one of the important means of surface deformation observation in mining areas. In this paper, SBAS-InSAR technology is applied to study the surface deformation movement in Lingzi coal mine, Shandong Province. The time series observations of Sentinel-1A/B data acquired from March 2015 to August 2019 were analyzed, it is found that the seasonal variation of atmosphere is more obvious under the short revisit period and long time series of satellite data, especially in mountainous areas. Considering this effect, the polynomial method is used to fit the observed results. The results show that the surface deformation in Lingzi coal mine is diverse. Some areas continue to uplift, with the maximum uplift of 69mm. Others first subsidence and then uplift, with the maximum subsidence of - 80mm. The process of subsidence and uplift is based on different mechanisms. The subsidence is the residual subsidence of underground caving caused by coal mining, and the process of uplift is related to the recharge of groundwater.

Lake and mire isolation data set for the estimation of post-glacial land uplift in Fennoscandia

Abstract. Postglacial land uplift is a complex process related to the continental ice retreat that took place about 10 000 years ago and thus started the viscoelastic response of the Earth's crust to rebound back to its equilibrium state. To empirically model the land uplift process based on past behaviour of shoreline displacement, data points of known spatial location, elevation and dating are needed. Such data can be obtained by studying the isolation of lakes and mires from the sea. Archaeological data on human settlements (i.e. human remains, fireplaces etc.) are also very useful as the settlements were indeed situated on dry land and were often located close to the coast. This information can be used to validate and update the postglacial land uplift model. In this paper, a collection of data underlying empirical land uplift modelling in Fennoscandia is presented. The data set is available at https://doi.org/10.1594/PANGAEA.905352 (Pohjola et al., 2019).

Seismic reflection imaging of crustal deformation within the eastern Yarlung-Zangbo suture zone

Various models have been proposed to explain formational mechanisms for the Himalayan orogeny but uncertainties remain concerning uplift processes and deeper crustal structure of the orogen. Imaging of the orogen's deep structure can help resolve these uncertainties. This paper describes one migrated deep seismic reflection profile across the eastern Yarlung-zangbo suture (YZS) at 92° E, which provides a high resolution image of crustal structure that reveals (1) Yarlhashampo dome is divided into upper, middle and lower tectonic units by two detachments from rim, mantle to the core of dome, (2) one blind north-dipping reverse fault that offsets the South Tibet detachment (STD) developed along the northern flank of the Yarlhashampo dome, (3) a shift of the Main Himalayan thrust (MHT) dip angle from 18° into relatively gentle dips (6°) in the central part of the profile (18–20 s, t.w.t). Meantime, further inferring that (4) North-south compression event happened after ca.10 Ma in North Himalayas, (5) multi-stage duplexing as the primary mechanism for crustal thickening in the eastern YZS based on interpreted structures.

Interaction between sediment transport rate and tectonic activity: the case of Kızılırmak Basin on the tectonically active NAFZ, Turkey

The degree of interaction between sediment transport rate and tectonic activity is a major issue that draws the attention of researchers. Because of the complexity in the modeling process of uplift and subsidence rate, it is quite difficult to determine the rate of interaction between erosion and tectonic activity. In this study, the sediment transport rate of Kizilirmak Basin, which is located on the tectonically active North Anatolian Fault Zone (NAFZ), was investigated to determine the effect of tectonic activity on sediment transport rate. The sediment transport rate of the basin was evaluated by using the drainage channel width, the topographic wetness index (TWI), and the revised universal soil equation (RUSLE) model. The Aster Global Digital Elevation Model (GDEM), Landsat 8 Operational Land Imager (OLI) scenes, a 1:800,000 scale soil map, and 30 years of rainfall records at 41 stations were used for the analysis. The drainage channel width, the TWI, and derivation and grid-based integration of the RUSLE parameters were performed by using GIS (terrain analysis, spatial data analysis) and remote sensing image processing techniques. The relationship among the derived parameters and tectonic activity was evaluated by Getis–Ord $$ {G}_i^{\ast } $$ statistics. The results show that at the 99 and 95% confidence intervals, statistically significant cold spot values of the channel widths, hot spot values of the mean annual soil loss values, and cold spots of the TWI values are more intensely clustered around fault lines. These clustering areas not only indicate the areas where the rate of sediment transport is high, but also the areas where the tectonic activity of the NAFZ is more vigorous.

Hydrogeochemical and isotopic characteristics of surface water and groundwater in the Qinghai Lake catchment (China)

Qinghai Lake plays an important role in the study of climate change in the western China and Qinghai-Tibet Plateau uplift processes and environmental effects. This study focused on the hydrogeochemistry of different waters (river, lake, groundwater, and precipitation) around and within Qinghai Lake. We analyzed major chemical elements and stable isotopes to examine water-rock interactions and the hydrogeochemical evolution of lake. The geochemical characteristics of river, groundwater, and precipitation have direct effects on the chemical composition of lake. The hydrochemical type of the river was HCO3-Ca·Na or HCO3-Na·Ca; groundwater was HCO3-Na·Ca, Cl·HCO3-Na·Ca, or HCO3-Ca·Na; and lake was Cl-Na, which was different from Erhai (Cl·HCO3-Na). The different geological settings and amount of river and groundwater input between the Buha and Shaliu subcatchments led to fluctuation in the major chemical ions present in the Buha River. The supply to river and groundwater is different in the various areas and manifests as overlap in the ion concentrations in river and groundwater. The relationship of major ions showed that sulfate reduction, ion exchange, carbonate and silicate rock weathering, dissolution, and evaporation occurred in the evolution of the groundwater, river, and lake in the Qinghai Lake catchment. The evolution of Qinghai Lake may be towards poor calcium and potassium enrichment as well as the removal of carbonate and increasing chloride. The salinity of Qinghai Lake is likely to become much higher if the amount of river and groundwater input decreases or the climate continues to dry in the future.