西秦岭甘南地区上二叠统毛毛隆组古环境演变:基于遗迹网络分析          下载免费PDF全文

党志英  张立军 《古地理学报》2020,22(6):1171-1180

西秦岭地区是二叠系—三叠系之交深水相保存较为连续的地区,西秦岭甘南地区上二叠统毛毛隆组发育丰富的遗迹化石(12属17种)。遗迹网络分析作为新兴的研究方法,侧重于用相互连接的遗迹分类群来重建遗迹群落系统,这为研究遗迹群落的行为学和生态学提供了丰富的手段。笔者以西秦岭甘南地区上二叠统毛毛隆组发现的遗迹化石为数据源,运用遗迹网络分析方法,揭示出毛毛隆组遗迹群落具结构化特征,遗迹群落体现出环境驱动的遗迹组合面貌特征: Palaeophycus-Lockeia-Arenicolites-Dictyodora-Planolites-Protovirgularia-Chondrites组合(C1,近源浊流区),Palaeophycus-Lockeia-Arenicolites-Dictyodora-Protovirgularia-Phycodes-Chondrites-Helminthopsis组合(C2,浊流过渡区—浊流远源区),和Palaeophycus-Nereites-Scolicia-Protovirgularia-Helminthopsis组合(C3,远源浊流区)。该遗迹群落由C1演变至C3的过程,揭示了古环境从近源浊流区至远源浊流区的演变历程。  相似文献   

Carbon pools and fluxes in the China Seas and adjacent oceans     

Nianzhi Jiao  Yantao Liang  Yongyu Zhang  Jihua Liu  Yao Zhang  Rui Zhang  Meixun Zhao  Minhan Dai  Weidong Zhai  Kunshan Gao  Jinming Song  Dongliang Yuan  Chao Li  Guanghui Lin  Xiaoping Huang  Hongqiang Yan  Limin Hu  Zenghu Zhang  Long Wang  Chunjie Cao  Yawei Luo  Tingwei Luo  Nannan Wang  Hongyue Dang  Dongxiao Wang  Si Zhang 《中国科学:地球科学(英文版)》2018,61(11):1535-1563

The China Seas include the South China Sea, East China Sea, Yellow Sea, and Bohai Sea. Located off the Northwestern Pacific margin, covering 4700000 km~2 from tropical to northern temperate zones, and including a variety of continental margins/basins and depths, the China Seas provide typical cases for carbon budget studies. The South China Sea being a deep basin and part of the Western Pacific Warm Pool is characterized by oceanic features; the East China Sea with a wide continental shelf, enormous terrestrial discharges and open margins to the West Pacific, is featured by strong cross-shelf materials transport; the Yellow Sea is featured by the confluence of cold and warm waters; and the Bohai Sea is a shallow semiclosed gulf with strong impacts of human activities. Three large rivers, the Yangtze River, Yellow River, and Pearl River, flow into the East China Sea, the Bohai Sea, and the South China Sea, respectively. The Kuroshio Current at the outer margin of the Chinese continental shelf is one of the two major western boundary currents of the world oceans and its strength and position directly affect the regional climate of China. These characteristics make the China Seas a typical case of marginal seas to study carbon storage and fluxes. This paper systematically analyzes the literature data on the carbon pools and fluxes of the Bohai Sea,Yellow Sea, East China Sea, and South China Sea, including different interfaces(land-sea, sea-air, sediment-water, and marginal sea-open ocean) and different ecosystems(mangroves, wetland, seagrass beds, macroalgae mariculture, coral reefs, euphotic zones, and water column). Among the four seas, the Bohai Sea and South China Sea are acting as CO_2 sources, releasing about0.22 and 13.86–33.60 Tg C yr~(-1) into the atmosphere, respectively, whereas the Yellow Sea and East China Sea are acting as carbon sinks, absorbing about 1.15 and 6.92–23.30 Tg C yr~(-1) of atmospheric CO_2, respectively. Overall, if only the CO_2 exchange at the sea-air interface is considered, the Chinese marginal seas appear to be a source of atmospheric CO_2, with a net release of 6.01–9.33 Tg C yr~(-1), mainly from the inputs of rivers and adjacent oceans. The riverine dissolved inorganic carbon (DIC) input into the Bohai Sea and Yellow Sea, East China Sea, and South China Sea are 5.04, 14.60, and 40.14 Tg C yr~(-1),respectively. The DIC input from adjacent oceans is as high as 144.81 Tg C yr~(-1), significantly exceeding the carbon released from the seas to the atmosphere. In terms of output, the depositional fluxes of organic carbon in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea are 2.00, 3.60, 7.40, and 5.92 Tg C yr~(-1), respectively. The fluxes of organic carbon from the East China Sea and South China Sea to the adjacent oceans are 15.25–36.70 and 43.93 Tg C yr~(-1), respectively. The annual carbon storage of mangroves, wetlands, and seagrass in Chinese coastal waters is 0.36–1.75 Tg C yr~(-1), with a dissolved organic carbon(DOC) output from seagrass beds of up to 0.59 Tg C yr~(-1). Removable organic carbon flux by Chinese macroalgae mariculture account for 0.68 Tg C yr~(-1) and the associated POC depositional and DOC releasing fluxes are 0.14 and 0.82 Tg C yr~(-1), respectively. Thus, in total, the annual output of organic carbon, which is mainly DOC, in the China Seas is 81.72–104.56 Tg C yr~(-1). The DOC efflux from the East China Sea to the adjacent oceans is 15.00–35.00 Tg C yr~(-1). The DOC efflux from the South China Sea is 31.39 Tg C yr~(-1). Although the marginal China Seas seem to be a source of atmospheric CO_2 based on the CO_2 flux at the sea-air interface, the combined effects of the riverine input in the area, oceanic input, depositional export,and microbial carbon pump(DOC conversion and output) indicate that the China Seas represent an important carbon storage area.  相似文献   

Instantaneous Shorelines as an Intermediate for Island Shoreline Mapping based on Aerial/Satellite Stereo Images     

Yamin Dang  Xinghua Zhou  Jun Xu  Shuqiang Xue 《Marine Geodesy》2018,41(3):219-229

Island shoreline mapping based on field measurements by collecting visually discernible features is costly and even unrealistic to be implemented in practice because of the nonuniqueness, fuzziness, and ambiguity of shoreline features. The MHHW (the mean higher high water) shoreline, i.e., the intersection of the coastal profile with the MHHW, is recommended to be chosen as a significant shoreline indicator of an island. An approach for mapping the MHHW shoreline using the aerial/satellite stereo images is proposed. In the proposed procedure, first, the height difference between the instantaneous shoreline and the MHHW shoreline is calculated by the ocean tide model; then the orthometric/normal height of the instantaneous shoreline is determined from the stereo images; last, the instantaneous shoreline is used as an intermediate for determination of the height of the MHHW shoreline. The proposed procedure is applied to the MiaoZiHu Island located in the East China Sea. Preliminary experimental result shows that in ideal cases, the horizontal positional accuracy of the extracted shoreline can reach 0.2 m from aerial images of 0.1 m resolution.  相似文献   

Correction to: Hydro-geochemical characteristics of the groundwater resources in the southern part of the Red River’s Delta plain,Vietnam     

Hoan V. Hoang  Lam V. Nguyen  Nhan D. Dang  Frank Wagner  Nhan Q. Pham 《Environmental Earth Sciences》2018,77(20):714

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The influence of the Three Gorges Reservoir regulation on a typical tributary heat budget     

Yao Cheng  Yuchun Wang  Huaidong Zhou  Chenghua Dang 《Environmental Earth Sciences》2018,77(22):764

Reservoir regulation and local climate both affect the heat budget of tributary bay. It is difficult for traditional methods to identify the influence of different factors on heat budget quantitatively. In this paper, for analysis of the control mechanisms of the heat budget of a large reservoir tributary, the water temperature distribution, and heat budget processes of the Meixi River, a typical tributary to the Three Gorges Reservoir was measured, and a new method was used to calculate the heat content composition of the tributary bay and identify the key factor of the heat balance. The result shows significant variation in the spatial and temporal distributions of water temperatures in the Meixi River, ranging from 12.4 to 28.9 °C on the surface and 12.0 to 24.4 °C at the bottom. The total heat exchange across the air–water interface that ranges from 0.1 to 6% of the budget is not the primary control factor of the annual tributary heat budget. Rather, the change in water depth produced by regulation of the Three Gorges Reservoir is the primary control factor of the tributary heat budget in the whole year, which ranges from 72 to 99% of the budget. The water temperature difference between the main stream and tributary is the not key factor of the heat budget, which ranges from 0.1 to 28% of the heat budget.  相似文献   

The dominant driving force for supercontinent breakup: Plume push or subduction retreat?     

Nan Zhang  Zhuo Dang  Chuan Huang  Zheng-Xiang Li 《地学前缘(英文版)》2018,9(4):997-1007

Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth's geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered: the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling(superplume) systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that:(1) at the center half of the supercontinent, plume push stress is ～3 times larger than the stress induced by subduction retreat;(2) an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;(3) the extensional stress induced by subduction retreat concentrates on a ～600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.  相似文献   

Investigation of gas content of organic-rich shale:A case study from Lower Permian shale in southern North China Basin,central China     

Wei Dang  Jin-Chuan Zhang  Xuan Tang  Xiao-Liang Wei  Zhong-Ming Li  Cheng-Hu Wang  Qian Chen  Chong Liu 《地学前缘(英文版)》2018,9(2):559-575

Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus to determine their gas contents. Due to the air contamination that is introduced into the desorption canister, a mathematical method was devised to correct the gas quantity and quality.Compared to the chemical compositions of desorbed gas, the chemical compositions of residual gas are somewhat different. In residual gas, carbon dioxide and nitrogen record a slight increase, and propane is first observed. This phenomenon may be related to the exposure time during the transportation of shale samples from the drilling site to the laboratory, as well as the differences in the mass, size and adsorptivity of different gas molecules. In addition to a series of conventional methods, including the USBM direct method and the Amoco Curve Fit(ACF) method, which were used here for lost gas content estimation, a Modified Curve Fit(MCF) method, based on the 'bidisperse' diffusion model, was established to estimate lost gas content. By fitting the ACF and MCF models to gas desorption data, we determined that the MCF method could reasonably describe the gas desorption data over the entire time period, whereas the ACF method failed. The failure of the ACF method to describe the gas desorption process may be related to its restrictive assumption of a single pore size within shale samples. In comparison to the indirect method, this study demonstrates that none of the three methods studied in this investigation(USBM, ACF and MCF) could individually estimate the lost gas contents of all shale samples and that the proportion of free gas relative to total gas has a significant effect on the estimation accuracy of the selected method. When the ratio of free gas to total gas is lower than 45%, the USBM method is the best for estimating the lost gas content, whereas when the ratio ranges from 45% to 75% or is more than 75%, the ACF and MCF methods, are the best options respectively.  相似文献   

Geochemistry of organic matter and elements of black shale during weathering in Northern Guizhou,Southwestern China: Their mobilization and inter-connection     

Xuan Tang  Jinchuan Zhang  Yang Liu  Chao Yang  Qian Chen  Wei Dang  Panwang Zhao 《Chemie der Erde / Geochemistry》2018,78(1):140-151

Different from previous studies on effect of weathering upon geochemical variation along a single weathered profile, this paper provides a new methodology validated by comparing a weathered outcrop samples and their stratigraphic counterpart un-weathered core samples in a nearby shallow borehole. This outcrop and borehole penetrated the Ordovician-Silurian Wufeng–Longmaxi shales, located in the same anticline structure in the northern part of Guizhou Province, Southern China. The mineral composition, major, trace and rare earth elements (REEs) composition and Rock-Eval parameters of outcrop and core samples were analyzed and compared. Organic matter (OM) was observed in the microscope and extracted for elements analysis. The results show that short-term weathering still has significant influence on OM, mineral and elemental composition of black shales. The elements composition shows the outcrop profile was moderately weathered. The REEs compositions do not alter much during weathering process and the REEs composition and their relative ratios still are valid for rock origin determination. The OM, mainly composed by graptolite and bitumen, even entering the highly-over thermal maturity, is still sensitive to the weathering with a systematic loss 30–50% of TOC along the outcrop profile, which suggests that the OM consumption is predominantly controlled by weathering duration and the distance from the weathering surface. In turn, OM has significant influence on the trace elements transportation behavior during weathering. Some trace elements associated with the OM such as V, Cr, Th, U, Ni and Co, change significantly in their absolute concentration during weathering, but their relative ratios do not necessarily change too much and might be still reliable proxies for paleo-environmental determination. The mobility of shale minerals during weathering is in the following order: plagioclase?>?potassium feldspar and dolomite >pyrite and OM. Short-term weathering can also result in considerable transportation of elements and significant variation of minerals content in black shale, which may pose potentially high environmental and engineering risk in the regions rich in black shale.  相似文献   

Simplified formulae for designing coastal forest against tsunami run-up: one-dimensional approach   总被引：2，自引：0，他引：2  

Nguyen Ba Thuy  N. A. K. Nandasena  Vu Hai Dang  Norio Tanaka 《Natural Hazards》2018,92(1):327-346

In the present study, laboratory experiments were conducted to validate the applicability of a numerical model based on one-dimensional nonlinear long-wave equations. The model includes drag and inertia resistance of trees to tsunami flow and porosity between trees and a simplified forest in a wave channel. It was confirmed that the water surface elevation and flow velocity by the numerical simulations agree well with the experimental results for various forest conditions of width and tree density. Further, the numerical model was applied to prototype conditions of a coastal forest of Pandanus odoratissimus to investigate the effects of forest conditions (width and tree density) and incident tsunami conditions (period and height) on run-up height and potential tsunami force. The modeling results were represented in curve-fit equations with the aim of providing simplified formulae for designing coastal forest against tsunamis. The run-up height and potential tsunami forces calculated by the curve-fit formulae and the numerical model agreed within ± 10% error.  相似文献   

基于FY2G卫星的宁夏空中云水资源特征研究     

常倬林  党张利  孙艳桥  林彤 《气象研究与应用》2022,43(1):47-52

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