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Original Articles
The response between glacier evolution and eco-geological environment on the Qinghai-Tibet Plateau
Xi-yong Sun, Rui-jiang Zhang, Wei Huang, Ang Sun, Liang-jun Lin, Hong-gen Xu, De-cai Jiang
2019, 2(1): 1-7. doi: 10.31035/cg2018078
[Abstract](317) [FullText HTML] (350) [PDF 18007KB](27)
Based on the remote sensing survey and monitoring results of snow lines on the Qinghai-Tibet Plateau, the authors analyzed the following eco-geological factors such as water resources, permafrost, desertification, wetlands, lake, geological disasters, sea-level rising, earthquake, etc., affected by the change of snow lines over the past 40 years, and discuss the response between glacier evolution and the eco-geological environment preliminarily.
Characteristics of clay minerals in sediments of Hemudu area, Zhejiang, China in Holocene and their environmental significance
Rui Liu, Xi Mei, Jin Zhang, De-bo Zhao
2019, 2(1): 8-15. doi: 10.31035/cg2018069
[Abstract](629) [FullText HTML] (443) [PDF 18111KB](15)
The Ningshao Plain experienced sea-level fluctuation and climate change in the Holocene and gave birth to a Neolithic Civilization, the Hemudu Culture (about 5000 BC). Using XRD method, this paper studied the clay mineralogy of sediments in core HMD-1301 from Hemudu Site area in Ningshao Plain. Results show that the clay mineral assemblages in all samples are quite consistent. They are dominated by illite (about 57%) and smectite (about 26%), and a small amount of kaolinite (about 6%) and chlorite (about 9%). In addition, illite, chlorite, and kaolinite are originated mainly from eolian loesses. Smectite is resulted mainly from chemical weathering of local volcanic rocks outcropped. Illite crystallinity indicates the climatic characteristics of the source region, and illite chemistry index reflects the climate nature of the sedimentary area. It is our understanding that water medium properties in a sedimentary environment affect clay mineral assemblage and the distribution, based on which were cognized the Holocene transgression-regression events in the Hemudu Site area. These mineral indices are well comparable with geochemical indicators in identifying the transgression-regression events. We believe that these events affected the ancient civilization of the ancient residential communities at the time.
Sediment distribution and provenance since Late Pleistocene in Laizhou Bay, Bohai Sea, China
Mao-sheng Gao, Fei Guo, Xue-yong Huang, Guo-hua Hou
2019, 2(1): 16-25. doi: 10.31035/cg2018062
[Abstract](687) [FullText HTML] (468) [PDF 18169KB](15)
There are three transgression-regression events and evolutions of the sedimentary environment by sea level changes since the Pleistocene in the southern section of the Bohai Sea, China. It is obvious that a multi-source fluvial delta sedimentary system may be more dominant in a sedimentary environment. Based on previous research and survey or historical data, we carried out studies on the division of sedimentary units, sedimentary facies analysis and strata division and comparison, which aim to establish the sedimentary stratigraph of Laizhou Bay. We focus on the sedimentary procession of the Laizhou Bay since the early Late Pleistocene. It can be divided into two glacial periods and three interglacial periods, corresponding to two regression and three transgression events in Laizhou Bay since Late Pleistocene. In 124.6−72.0 ka BP, 60.0−24.4 ka BP and 10.2−4.0 ka BP, three times warm-wet periods occurred, respectively corresponding to the Cangzhou transgression, Xianxian transgression, and Huanghua transgression. In 72.0−60.0 ka BP and 24.4−10.2 ka BP, two dry and cold periods, it was the continental sedimentary environment, corresponding to Wurm early glacier and Wurm late glacier. The results show: (1) Sediments have the characteristics of phase and stage under the terrestrial input of the Yellow River and middle-small rivers in the southern section of the Bohai Sea. (2) PI moved towards coastal in Cangzhou transgression strata in early Late Pleistocene. PI moved northward from land in Xianxian transgression strata in the late Pleistocene. PI moved further north in the Huanghua transgression strata in Holocene. (3) During the regressive period, the land source input increased and the estuarine or lagoon sedimentation developed, which manifested as progradational superposition. (4) During the transgressive period, it mainly developed shallow coastal sediment and transitionally formed regressive deposition to the south in delta/tidal flat deposition.
The impact of sea-level rise on the coast of Tianjin-Hebei, China
Fu Wang, Jian-fen Li, Pei-xin Shi, Zhi-wen Shang, Yong Li, Hong Wang
2019, 2(1): 26-39. doi: 10.31035/cg2018061
[Abstract](678) [FullText HTML] (470) [PDF 24918KB](15)
Bulletins of China’s National Sea Level show that the average rising rate of sea-levels in China is 3.3 mm/a over the past 40 years, with an obviously accelerated rising trend in the last decade. The rate of relative sea-level rise of the Yangtze River Delta reached >10 mm/a after considering the land subsidence, and Bohai Bay is even greater than 25 mm/a. The impact of the sea level rise to the coastal area will be greater in the coming years, so carrying out an assessment of this rising trend is urgent. This paper, taking the coastal area of Tianjin and Hebei as examples, comprehensively evaluates the impact of sea-level rise through multitemporal remote sensing shoreline interpretation, ground survey verification, elevation measurements for both seawall and coastal lowlands. The results show that the average elevation of the measured coastal areas of Tianjin and Hebei is about +4 m, and the total area of >100 km2 is already below the present mean sea level. More than 270 km, ca. 31% of the total length of the seawall, cannot withstand a 1-in-100-year storm surge. Numerical simulations of the storm flooding on the west coast of Bohai Bay, for 1-in-50-years, 1-in-100-years, 1-in-200-years and 1-in-500-years, show that if there were no coastal dykes, the maximum flooding area would exceed 3000 km2, 4000 km2, 5300 km2 and 7200 km2, respectively. The rising sea has a direct and potential impact on the coastal lowlands of Tianjin and Hebei. Based on the latest development in international sea-level rise prediction research, this paper proposes 0.5 m, 1.0 m and 1.5 m as low, middle and high sea level rise scenarios by 2100 for the study area, and combines the land subsidence and other factors to the elevation of the existing seawall. Comprehensive evaluation results indicate that even in the case of a low scenario, the existing seawall will not be able to withstand a 1-in-100-years storm surge in 2030, and the potential flooding areas predicted by the model will become a reality in the near future. Therefore, the seawall design in the coastal areas of Tianjin and Hebei must consider the combined effects of land subsidence, sea level rise and the extreme storm surges caused by it.
Distribution of potential geological hazards and control factors in Qingdao offshore, China
Ze Ning, Man-man Lin, Yong Zhang, Xiao-bo Zhang, Xiang-huai Kong
2019, 2(1): 40-48. doi: 10.31035/cg2018074
[Abstract](581) [FullText HTML] (432) [PDF 18626KB](7)
Engineering construction actively occurs in coastal zones, and these areas have numerous potential geological hazard factors. Since 2009, the development of geological surveys in sea areas has promoted extensive geophysical surveys in Qingdao offshore. In the present study, the types and distribution of potential geological hazard factors were systematically revealed using sub-bottom profile data, side-scan sonar data, and single-channel seismic data, among others. Based on previous research findings, the potential geological hazard factors are classified, and control factors in Qingdao offshore are discussed. The research results show that the primary potential geological hazards include active faults, buried paleo channels, shallow gas, irregular bedrock, eroded gullies, estuary deltas, tidal sand ridges, and seawater intrusion. In addition, neotectonic movement, sea level changes and sedimentary dynamic processes were the main factors that affected the distribution of geological hazards in Qingdao offshore.
Numerical studies of gas hydrate evolution time in Shenhu area in the northern South China Sea
Yun-xin Fang, Jing-an Lu, Jin-qiang Liang, Zeng-gui Kuang, Yun-cheng Cao, Duo-fu Chen
2019, 2(1): 49-55. doi: 10.31035/cg2018054
[Abstract](574) [FullText HTML] (463) [PDF 18062KB](8)
Although the Shenhu sea area has been a topic and focus of intense research for the exploration and study of marine gas hydrate in China, the mechanism of gas hydrate accumulation in this region remains controversial. The formation rate and evolution time of gas hydrate are the critical basis for studying the gas hydrate formation of the Shenhu sea area. In this paper, based on the positive anomaly characteristics of chloride concentration that measured in the GMGS3-W19 drilling site is higher than the seawater value, we numerically simulated the gas hydrate formation time of GMGS3-W19 site. The simulation results show that the gas hydrate formation rate positively correlates with the chloride concentration when the hydrate reaches the measured saturation. The formation time of gas hydrate in the GMGS3-W19 site is approximately 30 ka. Moreover, the measured chloride concentration is consistent with the in-situ chloride concentration, indicating that the formation rate of gas hydrate at the GMGS3-W19 site is very fast with a relatively short evolution time.
Characteristics and potential analysis of Madagascar hydrocarbon-bearing basins
Da-tian Wu, Johanne Iomimalala Ramaniraka, Feng-ming Xu, Jian-bo Shao, Yong-heng Zhou, Yuan-dong Zhao, Bruno Ralison
2019, 2(1): 56-66. doi: 10.31035/cg2018076
[Abstract](332) [FullText HTML] (322) [PDF 21239KB](5)
Madagascar becomes a large isolated island after its dislocation from East Africa at its western part during the opening of the Mozambique Channel and its separation from India at its eastern part during the opening of the basin of the Mascarene. From a stratigraphic point of view, Karroo of Madagascar shares substantial similarities with the stratigraphic strata of East Africa.While oil companies have taken a liking to the basins of East Africa, they also turn to the basins in the western part of Madagascar especially after the discovery of large oil fields at Tsimiroro and Bemolanga. According to the study of their geological history, the basins of Madagascar contain huge hydrocarbon potential. The western basins, which is more developed than the east coast of the island, have been the subject of many in-depth studies by numerous researchers. The cross-referencing of bibliographic data with geological studies, and knowledge of hydrocarbon formation and maturation stages, carried out in this study served to determine the nature of source rocks, reservoir rocks, bedrock and eventual trapping system of hydrocarbons in Madagascar. This study identified the properties of Madagascar source rocks, reservoir rocks, bedrock and the final oil and gas trap system by cross-referencing the literature and geological research, oil and gas formation and maturity stages, and shows that Madagascar has considerable hydrocarbon potential.
Review Articles
Prospective prediction and exploration situation of marine Mesozoic-Paleozoic oil and gas in the South Yellow Sea
Jian-wen Chen, Ming Xu, Bao-hua Lei, Jie Liang, Yin-guo Zhang, Shu-yu Wu, Jian Shi, Yong Yuan, Jian-qiang Wang, Yu-xi Zhang, Gang Li, Wen-juan Wang
2019, 2(1): 67-84. doi: 10.31035/cg2018072
[Abstract](328) [FullText HTML] (326) [PDF 19030KB](8)
The South Yellow Sea Basin is a large sedimentary basin superimposed by the Mesozoic-Paleozoic marine sedimentary basin and the Mesozoic-Cenozoic terrestrial sedimentary basin, where no oil and gas fields have been discovered after exploration for 58 years. After the failure of oil and gas exploration in terrestrial basins, the exploration target of the South Yellow Sea Basin turned to the marine Mesozoic-Paleozoic strata. After more than ten years' investigation and research, a lot of achievements have been obtained. The latest exploration obtained effective seismic reflection data of deep marine facies by the application of seismic exploration technology characterized by high coverage, abundant low-frequency components and strong energy source for the deep South Yellow Sea Basin. In addition, some wells drilled the Middle-Upper Paleozoic strata, with obvious oil and gas shows discovered in some horizons. The recent petroleum geological research on the South Yellow Sea Basin shows that the structure zoning of the marine residual basin has been redetermined, the basin structure has been defined, and 3 seismic reflection marker layers are traceable and correlatable in the residual thick Middle-Paleozoic strata below the continental Meso-Cenozoic strata in the South Yellow Sea Basin. Based on these, the seismic sequence of the marine sedimentary strata was established. According to the avaliable oil and gas exploration and research, the marine Mesozoic-Paleozoic oil and gas prospects of the South Yellow Sea were predicted as follows. (1) The South Yellow Sea Basin has the same sedimentary formation and evolution history during the sedimentary period of the Middle-Paleozoic marine basin with the Sichuan Basin. (2) There are 3 regional high-quality source rocks. (3) The carbonate and clastic reservoirs are developed in the Mesozoic-Paleozoic strata. (4) The three source-reservoir-cap assemblages are relatively intact. (5) The Laoshan Uplift is a prospect area for the Lower Paleozoic oil and gas, and the Wunansha Uplift is one for the marine Upper Paleozoic oil and gas. (6) The Gaoshi stable zone in the Laoshan Uplift is a favorable zone. (7) The marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin has the geological conditions required to form large oil and gas fields, with remarkable oil and gas resources prospect. An urgent problem to be addressed now within the South Yellow Sea Basin is to drill parametric wells for the Lower Paleozoic strata as the target, to establish the complete stratigraphic sequence since the Paleozoic period, to obtain resource evaluation parameters, and to realize the strategic discovery and achieve breakthrough in oil and gas exploration understanding.
Types, characteristics and implication for hydrocarbon exploration of the Middle Miocene deep-water sediments in Beikang Basin, southern South China Sea
Zhen-yu Lei, Li Zhang, Ming Su, Shuai-bing Luo, Xing Qian, Bo-da Zhang
2019, 2(1): 85-93. doi: 10.31035/cg2018094
[Abstract](316) [FullText HTML] (333) [PDF 19174KB](8)
The internal seismic architectures of the Middle Miocene in Beikang Basin, southern South China Sea, were investigated and described using regional 2D seismic data from Guangzhou Marine Geology Survey. In particular, five typical seismic facies were identified based on an integrated analysis of the amplitude, continuity, contact relationship, and morphologies of seismic reflections. Bathyal-abyssal fine-grained sediments, deltaic front sandy bodies, turbidites, and small-scale turbidite channels were developed in the Middle Miocene according to the tectonic-sedimentary evolution of the sedimentary basins in the southern South China Sea. The findings of this study suggest that deltaic front sandy bodies and turbidites can be considered as the two major types of deep-water clastic reservoirs for the depression stage of Beikang Basin. A well-developed source-reservoir-cap assemblage was composed by deep rift-stage source rocks, deep-water clastic reservoirs of the Middle Miocene, and bathyal-abyssal deep-water fine-grained sediments after the Middle Miocene, implying a good potential for hydrocarbon exploration.
Characteristics of boundary fault systems and its hydrocarbon controlling on hydrocarbon accumulation in Awati Sag, Tarim Basin, China
Zhong-kai Bai, Xiu-xiang Lü, Zong-xu Song, Hai-jun Qiu, Xin-gui Zhou, Yong-jin Gao, Ying-min Qi, Li-chun Zhu, Xiao-tao Fu, Yuan-yuan Zhou
2019, 2(1): 94-107. doi: 10.31035/cg2018095
[Abstract](303) [FullText HTML] (327) [PDF 19141KB](9)
Based on the interpretation of two-dimensional seismic data, this paper analyzes the characteristics of three boundary fault systems including the Shajingzi fault, the Aqia fault and the Tumuxiuke fault around the Awati sag of the Tarim Basin, and studies its controlling on hydrocarbon accumulation. Neotectonic movement is ubiquitous in oil and gas bearing basins in China, such as Neogene intense activities of large boundary thrusting faults of the Awati sag: Shajingzi fault, Aqia fault and Tumuxiuke fault. Based on a large number of seismic data, it is showed that they have section wise characteristics in the direction of fault strike, and active periods and associated structures formed of different sections are different. Usually, large anticlinal structures are formed in the upper wall, and faulted anticline controlled by companion faults are formed in the bottom wall. Large faults cut the strata from Cambrian up to Neogene. For the anticline in the upper wall, fault activities caused by neotectonic movement played a destructive role in hydrocarbon accumulation, thus the preservation condition is critical for reservoir formation. In this sense, attention should be paid to formations in the upper walls of Aqia fault and Tumuxiuke fault under the Cambrian salt bed, whose plastic deformation could help to heal faults. Companion faults in the bottom wall cut down to the Cambrian and up to the Triassic serving as the pathway for hydrocarbon migration, and associated structures in the bottom wall are noteworthy exploration targets.
Research Advances
Sedimentary environment of organic-rich shale in the Upper Permian Longtan Formation in Qinglong area, western Guizhou, China
Rong Chen, Kun Yuan, Zi-ya Zhang, Qiu-feng Xu
2019, 2(1): 108-109. doi: 10.31035/cg2018086
[Abstract](299) [FullText HTML] (291) [PDF 17793KB](17)
New evidence of Silurian hydrocarbon accumulation is discovered by fluid inclusion analysis in the South Yellow Sea Basin
Jie Liang, Jian-wen Chen, Yin-guo Zhang, Guang-xi Ou, Peng-hui Zhang, Yong Yuan
2019, 2(1): 110-111. doi: 10.31035/cg2018077
[Abstract](457) [FullText HTML] (395) [PDF 17663KB](15)
A new design of measuring marine primary productivity to support eco-geological survey
Shao-feng Pei, Ya-xuan Zhu, Si-yuan Ye, Hong-ming Yuan, Ruo-shun Guo, Li-xin Pei, Edward A. Laws
2019, 2(1): 112-113. doi: 10.31035/cg2018080
[Abstract](486) [FullText HTML] (365) [PDF 17803KB](15)
News and Highlights
Ten major progress of geological science and technology of China Geological Survey(CGS) and Chinese Academy of Geological Sciences (CAGS) in 2018
2019, 2(1): 114-115. doi: 10.31035/cg2018093
[Abstract](435) [FullText HTML] (424) [PDF 17612KB](106)
Introduction to GeoCloud, national geological information service platform of China
2019, 2(1): 116-118. doi: 10.31035/cg2018084
[Abstract](361) [FullText HTML] (336) [PDF 17643KB](4)
Editorial Committee of China Geology
2019, 2(1): 119-120.
[Abstract](52) [PDF 114KB](20)