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Global Geology
2023 Vol.26 Issue.4
Published 2023-11-25
199
Exploring the first occurrence of Scincomorpha lizard from Nenjiang Formation (lower Campanian) of Jilin, Northeast China: a follow-up study
MUHAMMAD Hassan, WU Wenhao and YANG Jinyue
In a region where lizard fossils are rare, this study explores a groundbreaking discovery of squamate lizard materials from the upper part of Nenjiang Formation (early Campanian) in Jilin Province, Northeast China. Despite the fragmentary nature of the dentaries, they exhibit distinct tooth morphological characteristics of squamate lizards, suggesting insectivorous and omnivorous diets for these small reptiles. This finding not only represents a significant addition to the squamate lizard fossil records from the Late Cretaceous in Northeast China but also contributes to our understanding of the paleogeographic distribution of squamate lizards. Furthermore, it sheds new light on the terrestrial vertebrate fauna of the Cretaceous Songliao Basin.
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2023 Vol. 26 (4): 199-210 [
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211
Characteristics and identification of weathering crust of Pennsylvanian volcanic rocks in Shixi area, Junggar Basin
HAN Junwei,SHAN Xuanlong,YIMING Ablimiti,BIAN Baoli,LIU Hailei,LI Ang and YI Jian
Based on drill core and thin section observation, major geochemical element analysis and conventional well log analysis, this study summarizes the characteristics and thickness of weathering crust of Pennsylvanian volcanic rocks (Carboniferous) in Shixi area, Junggar Basin. The weathering crust is identified and divided into three types according to the petrological characteristics and well log interpretations in Shixi area, and the isopach of weathering crust is mapped. The results show that: (1) With the increase of depth, the weathering weakens, and the rocks become less fractured with decreased porosity; (2) the weathering crust of the Upper Carboniferous volcanic rocks can be divided into strongly weathered and mildly weathered layers in Shixi area; (3) the weathering crust is relatively thicker in Dinan uplift and Shixi uplift. This study provides research basis for further evaluation of Upper Carboniferous volcanic reservoir, and will benefit for well location deployment and potential oilfield development in the Shixi area.
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2023 Vol. 26 (4): 211-221 [
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222
Geochemical characteristics of temperature and pressure of Paleozoic reservoir fluid inclusions in Xuanjing region, Lower Yangtze area
DONG Min, LIANG Minliang, DONG Hui, FENG Xingqiang, ZHANG Linyan and WANG Zongxiu
In order to understand the geochemical characteristics of Paleozoic reservoir fluids in Xuanjing region, Lower Yangtze area, drilling core samples from Y and D wells were tested and analyzed to study the fluid inclusion types and composition. Pressure correction was undertaken to determine the temperature and pressure environment for inclusion formation, and the influence of fluid characteristics of the Upper Permian and Lower Triassic reservoirs on the preservation of shale gas was investigated. According to petrographic observations, fluid inclusions are mainly brine and bitumen inclusions. Bitumen inclusions are mainly distributed in holes and fractures, and with smaller individuals. No visible fluorescence was observed, and the vitrinite reflectance is 3.39%–3.92%. This indicates that there had been oil and gas accumulation in the early stage of diagenesis in the study area, but due to the influence of magmatic hydrothermal solution, oil and gas underwent thermal metamorphism in the early stage, making liquid petroleum into solid bitumen. At present, oil and gas in the reservoir were largely formed in the late stage. During the continuous process in which shale was buried, light oil and gas were generated. Light oil and gas underwent magmatic and tectonic hydrothermal processes in some areas, resulting in high-temperature metamorphic cracking that formed dry gas. Moreover, nitrogen inclusions are found in fluid inclusions, forming metamorphic fluids caused by magmatic hydrothermal activities. The study shows that Paleozoic reservoirs in Xuanjing area are characterized by self-generation and self-storage. Furthermore, the mechanism of shale gas accumulation is not only related to the buried hydrocarbon generation process of shale itself, but is also related to later magmatic activity and tectonic hydrothermal transformation. Therefore, preservation conditions are generally key factors of shale gas accumulation in this area.
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2023 Vol. 26 (4): 222-236 [
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237
Least-squares reverse time migration in visco-acoustic media based on symplectic stereo-modeling method
LI Jingshuang,ZHANG Xiangjia,HE Xijun and ZHOU Yanjie
The authors proposed a symplectic stereo-modeling method (SSM) in the Birkhoffian dynamics and apply it to the visco-acoustic least-squares reverse time migration (LSRTM). The SSM adopts stereo-modeling operator in space and symplectic Runge-Kutta scheme in time, resulting in great ability in suppressing numerical dispersion and long-time computing. These advantages are further confirmed by numerical dispersion analysis, long-time computation test and computational efficiency comparison. After these theoretical analyses and experiments, acoustic and visco-acoustic LSRTM are tested and compared between SSM method and the conventional symplectic method (CSM) using the fault and marmousi models. Meanwhile, dynamic source encoding and exponential decay moving average gradients method are adopted to reduce the computation cost and improve the convergence rate. The imaging results show that LSRTM based on visco-acoustic wave equations effectively takes into account the influence of viscosity can therefore compensate for the amplitude attenuation. Besides, SSM method not only has high numerical accuracy and computational efficiency, but also performs effectively in LSRTM.
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2023 Vol. 26 (4): 237-250 [
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Change of cultivated land area and effect on ecosystem service in black soil region in Northeast China: a case study of Lishu County, Jilin Province
WANG Ruiqi, LI Hong and SHANG Yi
It is of great significance to study the influence of spatial pattern change of cultivated land on ecosystem service, including the sustainable utilization and ecological protection in black soil region in Northeast China. Taking Lishu County of Jilin Province as the study area, we quantitatively evaluated soil conservation, habitat quality, carbon storage and grain production service, and analyzed the change of cultivated land and ecosystem service pattern in Lishu County from 1990 to 2020 by using Pearson correlation analysis on the correlation between cultivated land change and ecosystem service. The results show that: (1) The cultivated land area of Lishu County was reduced by 19.67 km2 , the characteristics of cultivated land change are significant; (2) the overall change rate of carbon storage, habitat quality, soil conservation and grain production service in the study area was 10.82%, −0.09%, 4.07% and 1.80%, respectively. They all had significant spatial differentiation features; (3) the change of habitat quality, grain production service showed a significant positive correlation with the change of cultivated land area. The change in soil conservation and carbon storage were negatively related to cultivated land area. In order to promote the rational development and utilization of cultivated land in the research area, it is suggested to scientifically carry out the comprehensive utilization of cultivated land reserve resources such as saline-alkali land, strengthen the management and protection of newly added cultivated land at the same time. The results can provide scientific reference for formulating comprehensive land use planning under ecological security conditions.
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2023 Vol. 26 (4): 251-263 [
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Optimization design of conical reaction teeth of shear wave vibroseis vibration plate
WANG Hongxiang,DU Lizhi1 and SUN Zhen
The vibrator plate is the link between the vibroseis vehicle and the earth, as well as the core component of the vibrator vehicle. In this paper, the coupling effect between the vibrator plate and the earth is analyzed from two aspects of reaction tooth arrangement and reaction tooth conical angle, and three groups of experimental models are optimized and designed. The model construction and numerical analysis of the shear wave vibroseis vibrator plate are carried out with ANSYS software.The motion law between the vibration plate and the earth at work was studied, the strain energy of the three experimental models in operation, the maximum displacement of particle at the same position and other reference indices were compared and analyzed, with 28 conical reaction teeth were arranged on both sides. The coupling effect between the vibration plate and the earth was best when the tooth angle was 60°. Compared with the toothless vibration plate, the energy efficiency is improved by about 20%, and the coupling effect between the vibrator plate and the earth is effectively enhanced. It is found that the coupling effect is enhanced through increasing the number of reaction teeth of the vibration plate by increasing the coupling area between the vibration plate and the earth.
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2023 Vol. 26 (4): 264-272 [
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