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Late Holocene brGDGTs-based quantitative paleotemperature reconstruction from lacustrine sediments on the western Tibetan Plateau 基于全新世晚期青藏高原湖沼沉积物的古温度定量重建研究
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2024-01-12 DOI: 10.1007/s11707-022-1082-2
Xiumei Li, Sutao Liu, Juzhi Hou, Zhe Sun, Mingda Wang, Xiaohuan Hou, Minghua Liu, Junhui Yan, Lifang Zhang

We present a quantitative mean annual air temperature (MAAT) record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from a sediment core from Xiada Co, an alpine lake on the western Tibetan Plateau (TP). The record indicates a relatively stable and warm MAAT until 2200 cal yr BP; subsequently, the MAAT decreased by ∼4.4°C at ∼2100 cal yr BP and maintained a cooling trend until the present day, with centennial-scale oscillations centered at ∼800 cal yr BP, ∼600 cal yr BP, and ∼190–170 cal yr BP. MAAT decreased abruptly at ∼500–300 cal yr BP and reached its minimum for the past 4700 years. We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past ∼5000 years. The results show divergent temperature variations, including a gradual cooling trend, a warming trend, and no clear trend. We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies, the length of the freezing season of the lakes, the choice of proxy-temperature calibrations, and chronological errors. Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance, clear seasonality, site-specific calibration, and robust dating, to better understand the processes, trends, and mechanisms of Holocene temperature changes on the TP.

我们基于对青藏高原西部高山湖泊霞大湖沉积岩芯中支链甘油二烷基甘油四醚(brGDGTs)的分析,提供了跨越过去4700年的年平均气温(MAAT)定量记录。该记录表明,在公元前2200年之前,青藏高原最高气温相对稳定且偏高;随后,在公元前2100年时,青藏高原最高气温下降了4.4°C,并一直保持降温趋势,直到今天,其中以公元前800年、公元前600年和公元前190-170年为中心出现了百年尺度的震荡。MAAT在公元前500-300年骤然下降,并在过去的4700年达到最低值。我们将我们的记录与 15 个已发表的横跨过去 5000 年的 TP 古温度记录进行了比较,以评估其代表性。结果显示了不同的温度变化,包括逐渐变冷的趋势、变暖的趋势以及无明显趋势。我们认为,这些差异可能是由温度代用指标的季节性、湖泊冰冻季节的长度、代用指标-温度校准的选择以及年代学误差等因素造成的。我们的研究结果突出表明,需要更多具有明确气候意义、清晰季节性、特定地点校准和可靠年代测定的高质量古温度重建,以更好地理解全新世大洋洲温度变化的过程、趋势和机制。
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引用次数: 0
Deformation characteristics and analog modeling of transtensional structures in the Dongying Sag, Bohai Bay Basin 渤海湾盆地东营下陷横断构造的变形特征与模拟模型
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-29 DOI: 10.1007/s11707-022-1062-6
Dawei Dong, Li Zhao, Weizhong Zhang, Jiyan Li, Ruixiang Zhang, Jianlei Yang, Guangzeng Wang

Hydrocarbon exploration in the Dongying Sag is constrained by the development of many Cenozoic transtensional structures with complex patterns and dynamic mechanisms. This study uses seismic interpretation and analog modeling to investigate these transtensional structures. Significant results include dividing these transtensional structures into boundary fault, oblique rifting, and deep strike-slip fault controlled structures, according to the relationships between main and secondary faults. They developed in the steep slope zone, the central sag zone, and the slope zone, respectively. In profile, the transtensional structures formed appear to be semi-flower-like, step-like, or negative-flower-like. In plan-view, they appear to be broom-like, soft-linked, or en-echelon structures. Further, these transtensional structures are controlled by the oblique normal slip of boundary faults, by the oblique extension of sub-sags, and by the later extension of deep strike-slip faults. The geometric deformation of these transtensional structures is controlled by the angles between the regional extension direction and the strike of boundary faults, deep faults, or sub-sags, where a larger angle corresponds to less developed transtensional structures. Further, the transtensional structures in the Dongying Sag were created by multiphase and multi-directional extensions in the Cenozoic— which is also controlled by pre-existing structures. The strike of newborn secondary faults was determined by the regional extension direction and pre-existing structures.

东营下陷的油气勘探受制于新生代许多具有复杂形态和动态机制的转折构造的发育。本研究利用地震解释和模拟建模来研究这些横断构造。重要成果包括:根据主次断层之间的关系,将这些横断构造分为边界断层、斜断裂和深层走向滑动断层控制构造。它们分别发育在陡坡带、中央凹陷带和斜坡带。从剖面上看,形成的转折构造呈半花状、台阶状或负花状。从平面图上看,它们似乎是扫帚状、软连接或内螺纹结构。此外,这些转折构造受边界断层的斜向法向滑动、副鞍状断层的斜向延伸以及深走向滑动断层的后期延伸的控制。这些转折构造的几何变形受区域延伸方向与边界断层、深层断层或次级塌陷走向之间夹角的控制,夹角越大,转折构造越不发达。此外,东营下陷的横断构造是新生代多期、多向延伸形成的,这也受原有构造的控制。新生次生断层的走向是由区域延伸方向和原有构造决定的。
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引用次数: 0
Detecting the spatial-temporal pattern of moisture evolution on the Tibetan Plateau during the Holocene by model-proxy comparison 通过模式-实证对比探测全新世青藏高原水汽演变的时空格局
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-28 DOI: 10.1007/s11707-022-1049-3
Zeyu Zheng, Liya Jin, Jinjian Li, Xiaojian Zhang, Jie Chen

The Tibetan Plateau (TP) is a key region for environmental and climatic research due to its significant linkages with large-scale atmospheric circulation. Understanding the long-term moisture evolution pattern and its forcing mechanisms on the TP during the Holocene may provide insights into the interaction between low-latitude climate systems and midlatitude westerlies. Here, we synthesized 27 paleoclimate proxy records covering the past 9500 years. The results of the rotated empirical orthogonal function analysis of the moisture variation revealed spatial-temporal heterogeneity, which was classified into 5 subregions. Proxy records were then compared with the results from the Kiel Climate Model and other paleorecords. The results showed that moisture evolution on the western-southern-central TP was controlled by the Indian summer monsoon (ISM). On the south-eastern TP, moisture change was affected by the interplay between the East Asian summer monsoon (EASM) and the westerlies, as well as the ISM. With diverse patterns of circulation system precipitation, moisture changes recorded in the paleorecords showed spatial-temporal discrepancies, especially during the early to middle Holocene. Moreover, given the anti-phase pattern of summer precipitation in the EASM area under El Niño/Southern Oscillation (ENSO) conditions and the unstable relationship between the ISM and ENSO, it is reasonable to conclude that relatively strong ENSO variability during the late Holocene has contributed to these discrepancies as Asian summer monsoon precipitation has declined.

青藏高原与大尺度大气环流有着重要的联系,是环境和气候研究的关键地区。了解全新世青藏高原的长期水汽演变模式及其强迫机制,有助于深入了解低纬度气候系统与中纬度西风之间的相互作用。在此,我们综合了过去 9500 年的 27 条古气候代用记录。水汽变化的旋转经验正交函数分析结果显示了时空异质性,并将其划分为 5 个亚区域。然后将代理记录与基尔气候模型和其他古记录的结果进行了比较。结果表明,中西部-南部热带潮湿带的水汽演变受印度夏季季风(ISM)控制。在东南大陆架,水汽变化受到东亚夏季季候风和西风以及印度夏季季候风之间相互作用的影响。由于环流系统降水模式的多样性,古记录中记录的水汽变化呈现出时空差异,尤其是在全新世早中期。此外,考虑到在厄尔尼诺/南方涛动(ENSO)条件下 EASM 地区夏季降水的反相模式以及 ISM 与 ENSO 之间的不稳定关系,可以合理地得出结论:随着亚洲夏季季风降水量的减少,全新世晚期相对较强的 ENSO 变异是造成这些差异的原因之一。
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引用次数: 0
The important role of Turbidity Maximum Zone in sedimentary dynamic of estuarine mangrove swamp 最大浊度区在河口红树林沼泽沉积动力学中的重要作用
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-28 DOI: 10.1007/s11707-022-1083-1
Tao Liu, Ying Liu, Baoqing Hu

Sedimentation is a key process affecting wetland sustainability and carbon burial flux. In context of sea level rise, climate change and human activities, further understanding about the sedimentary dynamic in wetland is critical in predicting the landscape evolution or the change in carbon burial flux. In this study, based on the field hydrological observation in a mangrove system in the Nanliu River estuary, we found the net flux of suspended sediment to mangrove is 39–72 kg/m in tidal cycles with Turbidity Maximum Zone (TMZ) forming in surface layer and only is 9–18 kg/m in tidal cycles without TMZ. The higher net flux of suspended sediment to mangrove in tidal cycles with TMZ forming in surface layer is attributed to high SSC in rising tide and intense flocculation in mangrove. The significant discrepancy in sedimentation rate in the mangrove patches also can be explained by the probability of TMZ forming in the surface layer of estuary. In future, rapid sea level rising may lead to the change of TMZ pattern in estuary, which will result in non-negligible variation in sedimentation rate in wetlands. According to the present data of sedimentation rate in wetlands, the fragility of wetlands in river estuary may be miscalculated.

沉积是影响湿地可持续性和碳埋藏通量的一个关键过程。在海平面上升、气候变化和人类活动的背景下,进一步了解湿地沉积动态对于预测景观演变或碳埋藏通量的变化至关重要。本研究基于对南流江河口红树林系统的实地水文观测,发现在表层形成浊度最大区(TMZ)的潮汐周期中,红树林的悬浮泥沙净通量为 39-72 kg/m,而在没有形成浊度最大区的潮汐周期中,红树林的悬浮泥沙净通量仅为 9-18 kg/m。在表层形成浊度最高区的潮汐周期中,红树林的悬浮沉积物净通量较高,这是因为涨潮时 SSC 高,红树林中的絮凝作用强烈。红树林斑块沉积速率的巨大差异也可以用河口表层形成沼泽化带的概率来解释。未来,海平面的快速上升可能会导致河口 TMZ 模式的改变,从而导致湿地沉积速率出现不可忽略的变化。根据目前的湿地沉积速率数据,河口湿地的脆弱性可能被误判。
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引用次数: 0
Alternating influences of the Westerlies and Indian Summer Monsoon on the hydroclimate of the source region of the Yarlung Tsangpo over past 4000 yr 过去 4000 年西风和印度夏季季风对雅鲁藏布江源地区水文气候的交替影响
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-28 DOI: 10.1007/s11707-022-1055-5
Zhe Sun, Zirui Huang, Kejia Ji, Mingda Wang, Juzhi Hou

The Yarlung Tsangpo, the longest river in the southern Tibetan Plateau (TP), has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the context of ongoing climate change. However, partly due to the complex regional climatic background, no consistent conclusions have been reached, especially for its upper reaches. Paleohydrological reconstructions of the source region of the Yarlung Tsangpo can potentially improve our understanding of the history of humidity and its response to climatic variability. In this study, we used a 97 cm gravity core from Gongzhu Co to reconstruct the hydrology change during the late Holocene. The core was dated using AMS 14C and Pb/Cs methods, and we used measurements of element contents (determined by high-resolution XRF scanning), grain size, IC/TOC, and magnetic susceptibility to reconstruct hydroclimatic changes in the source of the Yarlung Tsangpo watershed since ∼4000 yr ago. Combined with a modern meteorological data set, we found that PC1 of the XRF data, the Ca/(Fe + Ti) ratio, and EM1 of the grain size data were indicative of changes in humidity. Our records demonstrate a wet interval during ∼4−1.7 ka BP (ka = 1000 yr, BP represents years before 1950 AD), followed by a dry period during since ∼1 ka BP. Comparison with independent regional paleoclimatic records revealed shifts in the dominant factors controlling humidity. The wet interval during ∼4−1.7 ka BP was coeval with a strengthened Westerlies, implying a dominant moisture supply from northern high latitudes. However, the extremely low values of Ca/(Fe + Ti) ratio during ∼4−2.5 ka BP indicate potential glacial freshwater source, which is corroborated by the concurrent high magnetic susceptibility values and increased grain size. The rapid drying trend during ∼1.7−1 ka BP suggests a switch in moisture supply from the Westerlies to the Indian Summer Monsoon (ISM). We attribute the drought conditions after ∼1 ka BP to a weakened ISM, although a Westerlies influence and the potential effect of high temperatures on evaporation cannot be excluded. We suggest that future hydroclimatic research in this region should attempt to distinguish the individual moisture contributions of the ISM and the Westerlies during the last millennium.

雅鲁藏布江是青藏高原南部(TP)最长的河流,其现代水文和未来可能的排水量的控制因素在当前气候变化的背景下吸引了大量研究人员的关注。然而,部分由于复杂的区域气候背景,尚未得出一致的结论,尤其是对其上游而言。对雅鲁藏布江源头地区进行古水文重建,有可能加深我们对湿度历史及其对气候变异反应的理解。在本研究中,我们使用了来自公珠公司的 97 厘米重力岩芯来重建全新世晚期的水文变化。利用 AMS 14C 和 Pb/Cs 方法对岩心进行了年代测定,并通过测量元素含量(通过高分辨率 XRF 扫描确定)、粒度、IC/TOC 和磁感应强度,重建了雅鲁藏布江流域源头自 4000 年前以来的水文气候变迁。结合现代气象数据集,我们发现 XRF 数据的 PC1、Ca/(Fe + Ti)比值和粒度数据的 EM1 都表明了湿度的变化。我们的记录表明,在公元前 4-1.7 ka(ka = 1000 年,BP 代表公元 1950 年之前的年份)期间是一个湿润时期,而自公元前 1 ka 起则是一个干燥时期。通过与独立的区域古气候记录进行比较,发现控制湿度的主要因素发生了变化。公元前 4-1.7 ka年间的湿润期与西风增强同时出现,这意味着湿气主要来自北部高纬度地区。然而,公元前 4-2.5 ka年间的钙/(铁+钛)比值极低,表明可能有冰川淡水来源,同时出现的高磁感值和粒径增大也证实了这一点。1.7-1 ka BP期间的快速干燥趋势表明,水汽供应已从西风转向印度夏季季风(ISM)。我们将公元前 1 ka 年之后的干旱状况归因于 ISM 的减弱,尽管不能排除西风的影响以及高温对蒸发的潜在影响。我们建议,该地区未来的水文气候研究应尝试区分 ISM 和西风在上一个千年期间对水汽的贡献。
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引用次数: 0
The determination of sedimentary environment and associated energy in deep-buried marine carbonates: insights from natural gamma ray spectrometry log 确定深埋海洋碳酸盐中的沉积环境和相关能量:天然伽马射线光谱记录的启示
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-28 DOI: 10.1007/s11707-022-1053-7
Jingyan Liu, Qian Chang, Junlong Zhang, Hui Chai, Feng He, Yizan Yang, Shiqiang Xia

It has always been challenging to determine the ancient sedimentary environment and associated energy in deep-buried marine carbonates. The energy represents the hydrodynamic conditions that existed when the carbonates were deposited. The energy includes light and chemical energies in compounds and kinetic energy in currents and mass flow. Deep-buried marine carbonates deposited during the Ordovician depositional period in the eastern Tarim Basin result from a complex interplay of tectonics, sedimentation, and diagenesis. As a result, determining the ancient sedimentary environment and associated energy is complex. The natural gamma-ray spectrometry (GRS) log (from 12 wells) is used in this paper to conduct studies on the sedimentary environment and associated energy in deep-buried marine carbonates. The findings show that the values of thorium (Th), uranium (U), potassium (K), and gamma-ray without uranium (KTh) in a natural GRS log can reveal lithological associations, mineral composition, diagenetic environment, stratigraphic water activity, and ancient climatic change. During the Ordovician, quantitative analysis and determination of sedimentary environment energy are carried out using a comprehensive calculation of natural GRS log parameters in typical wells (penetrating through the Ordovician with cores and thin sections) of well GC4, well GC6, well GC7, and well GC8. The results show that GRS log can determine different lithology associations in typical wells than a sieve residue log. Furthermore, cores and thin sections can be used to validate the determination of lithology associations. Based on the determination of lithology associations, the lithology associations that reflect the sedimentary environment and associated energy can be analyzed in a new approach. Furthermore, the sedimentary environment energy curve derived from a natural GRS log can reveal hydrodynamic fluctuations during depositional periods, which will aid in the discovery of carbonate reservoirs, establishing sequence stratigraphic frameworks, and the reconstruction of sea-level changes in the future.

确定深埋海相碳酸盐岩的古沉积环境和相关能量一直是一项挑战。能量代表碳酸盐沉积时的水动力条件。能量包括化合物中的光能和化学能,以及水流和质量流中的动能。塔里木盆地东部奥陶纪沉积时期沉积的深埋海相碳酸盐是构造、沉积和成岩作用复杂相互作用的结果。因此,确定古代沉积环境和相关能量是非常复杂的。本文利用天然伽马射线光谱仪(GRS)测井记录(来自 12 口井)对深埋海相碳酸盐岩的沉积环境和相关能量进行了研究。研究结果表明,天然伽马能谱测井中的钍(Th)、铀(U)、钾(K)和不含铀的伽马射线(KTh)值可以揭示岩性关联、矿物组成、成岩环境、地层水活动和古气候变化。在奥陶纪期间,利用 GC4 井、GC6 井、GC7 井和 GC8 井典型井(用岩心和薄片穿透奥陶纪)的天然 GRS 测井参数的综合计算,对沉积环境能量进行了定量分析和测定。结果表明,与筛余物测井相比,GRS 测井能确定典型油井中不同的岩性关联。此外,岩心和薄片也可用于验证岩性关联的确定。在确定岩性关联的基础上,可采用新方法分析反映沉积环境和相关能量的岩性关联。此外,从天然 GRS 测井中得出的沉积环境能量曲线可以揭示沉积时期的水动力波动,这将有助于发现碳酸盐岩储层、建立层序地层框架以及重建未来的海平面变化。
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引用次数: 0
Holocene temperature variation recorded by branched glycerol dialkyl glycerol tetraethers in a loess-paleosol sequence from the north-eastern Tibetan Plateau 青藏高原东北部黄土-页岩序列中支链甘油二烷基甘油四醚记录的全新世温度变化
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-28 DOI: 10.1007/s11707-023-1094-6
Tianxiao Wang, Duo Wu, Tao Wang, Lin Chen, Shilong Guo, Youmo Li, Chenbin Zhang

Reconstructing Holocene temperature evolution is important for understanding present temperature variations and for predicting future climate change, in the context of global warming. The evolution of Holocene global temperature remains disputed, due to differences between proxy reconstructions and model simulations, a discrepancy known as the ‘Holocene temperature conundrum’. More reliable and quantitative terrestrial temperature records are needed to resolve the spatial heterogeneity of existing records. In this study, based on the analysis of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from a loess-paleosol sequence from the Ganjia Basin in the north-eastern Tibetan Plateau (NETP), we quantitatively reconstructed the mean annual air temperature (MAAT) over the past 12 ka. The MAAT reconstruction shows that the temperature remained low during the early Holocene (12–8 ka), followed by a rapid warming at around 8 ka. From 8 to 4 ka, the MAAT record reached its highest level, followed by a cooling trend from the late Holocene (4–0 ka). The variability of the reconstructed MAAT is consistent with trends of annual temperature records from the Tibetan Plateau (TP) during the Holocene. We attribute the relatively low temperatures during the early Holocene to the existence of ice sheets at high-latitude regions in the Northern Hemisphere and the weaker annual mean insolation at 35°N. During the mid to late Holocene, the long-term cooling trend in the annual temperature record was primarily driven by declining summer insolation. This study provides key geological evidence for clarifying Holocene temperature change in the TP.

在全球变暖的背景下,重建全新世的气温演变对于了解目前的气温变化和预测未来的气候变化非常重要。由于代用资料重建与模型模拟之间的差异,全新世全球气温的演变仍存在争议,这一差异被称为 "全新世气温难题"。要解决现有记录的空间异质性问题,需要更可靠和定量的陆地温度记录。本研究基于对青藏高原东北部甘家盆地黄土-页岩序列中支链甘油二烷基甘油四醚(brGDGTs)的分析,定量重建了过去12 ka年的年平均气温(MAAT)。年平均气温重建结果表明,全新世早期(12-8 ka)气温较低,8 ka左右气温迅速升高。从 8 ka 到 4 ka,MAAT 记录达到最高水平,随后从全新世晚期(4-0 ka)开始出现降温趋势。重建的 MAAT 的变化与全新世青藏高原(TP)的年温度记录趋势一致。我们将全新世早期相对较低的温度归因于北半球高纬度地区冰盖的存在以及北纬35°地区较弱的年平均日照。在全新世中期至晚期,年气温记录中的长期降温趋势主要是由夏季日照减少造成的。这项研究为澄清全新世大洋洲的气温变化提供了关键的地质证据。
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引用次数: 0
Characteristics of microscopic pore heterogeneity and development model of Wufeng–Longmaxi Shales in the Pengshui area of south-east Chongqing 重庆东南部彭水地区五峰-龙马溪页岩的微观孔隙异质性特征及发育模式
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-28 DOI: 10.1007/s11707-023-1087-5
Lu Sun, Zhigang Wen, Guisong He, Peixian Zhang, Chenjun Wu, Liwen Zhang, Yingyang Xi, Bo Li

Normal-pressure shale gas reservoirs are widely distributed in south-eastern Chongqing and show good potential for resource exploration. This paper reports the organic matter (OM), physical, and pore characteristics, mineral composition, and gas content of representative shale samples from the Upper Ordovician Wufeng Formation and Member 1 of the Lower Silurian Longmaxi Formation (Long 1 Member). Microscopic pores within different shale layers of the Long 1 Member were classified, quantitatively evaluated, and their development mechanisms were systematically studied. We found that OM characteristics, mineral composition, and pore type were the main factors affecting the enrichment and preservation of shale gas. The characteristics of the Long 1 Member are mainly controlled by changes in the sedimentary environment. There are evident differences in total organic carbon content and mineral composition vertically, leading to a variable distribution of pores across different layers. Organic matter abundance controls the degree of OM pore development, while clay minerals abundance control the development of clay mineral-related pores. Total organic carbon content generally controls the porosity of the Long 1 Member, but clay minerals also play a role in OM-poor layers. Pore connectivity and permeability are influenced by the development of pores associated with brittle minerals. We propose a microscopic pore development model for the different layers. Combining geochemical data and this pore development model, layers 1–4 are considered to be excellent shale gas preservation and enrichment reservoirs. Poor preservation conditions in layers 5–7 result in high levels of shale gas escape. Layers 8–9 possess a better sealing condition compared with layers 5`-7 and are conducive to the enrichment and preservation of shale gas, and can thus be used as future potential target strata. This research provides a theoretical basis for exploring and evaluating shale gas potential in the studied region or other complex normal-pressure shale blocks.

常压页岩气藏广泛分布于重庆东南部地区,具有良好的资源勘探潜力。本文研究了上奥陶统五峰组和下志留统龙马溪组 1 号层(龙 1 组)代表性页岩样品的有机质、物性、孔隙特征、矿物组成和含气量。对龙一系不同页岩层中的微观孔隙进行了分类和定量评价,并对其发育机制进行了系统研究。研究发现,OM 特征、矿物组成和孔隙类型是影响页岩气富集和保存的主要因素。长 1 号成员的特征主要受沉积环境变化的控制。总有机碳含量和矿物成分在垂直方向上存在明显差异,导致孔隙在不同地层的分布各不相同。有机质丰度控制着有机质孔隙的发育程度,而粘土矿物丰度则控制着与粘土矿物有关的孔隙的发育。总有机碳含量通常控制着长 1 号成员的孔隙度,但粘土矿物在有机碳贫乏的地层中也发挥着作用。孔隙连通性和渗透性受到与脆性矿物相关的孔隙发育的影响。我们为不同地层提出了一个微观孔隙发育模型。结合地球化学数据和孔隙发育模型,1-4层被认为是极佳的页岩气保存和富集储层。5-7 层的保存条件较差,导致页岩气逸散程度较高。8-9 层与 5-7 层相比具有更好的密封条件,有利于页岩气的富集和保存,因此可作为未来潜在的目标地层。该研究为勘探和评价研究区域或其他复杂常压页岩区块的页岩气潜力提供了理论依据。
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引用次数: 0
Spatial distribution of charcoal in topsoil and its potential determinants on the Tibetan Plateau 青藏高原表层土壤炭的空间分布及其潜在影响因素
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-05 DOI: 10.1007/s11707-023-1095-5
Yixuan Wang, Chaoqun Cao, Yanrong Zhang, Lina Liu, Nannan Wang, Wenjia Li, Xianyong Cao

As an important proxy for investigating past fire activities, charcoal is often used to explore the characteristics of fire distribution and its relationships with vegetation, climate, and human activities. Research into the spatial distribution and environmental determinants for charcoal, however, is still limited. In this study, we identified and counted charcoal from topsoil samples covering the Tibetan Plateau using the pollen methodology, and investigated its relationships with vegetation net primary production (NPP), elevation, climate (precipitation, mean temperature of the coldest month and warmest month) and human population by boosted regression trees (BRT). Results reveal that the concentration of microscopic charcoal, macroscopic charcoal, and total charcoal all increase from south-west to north-east, which is consistent with the trend that the population density on the Tibetan Plateau is high in the east and low in the west, suggesting that an increase in human activity is likely to promote the occurrence of fire. The BRT modeling reveals that NPP, elevation, and mean temperature of the coldest month are important factors for total charcoal concentration on the Tibetan Plateau, and the frequency and intensity of fires further increase with increasing vegetation biomass, decreasing elevation, and decreasing mean temperature of the coldest month. The spatial variation characteristics of charcoal from topsoil on the Tibetan Plateau not only reflect well the spatial fire situation in the region, but also have a good indicative significance for vegetation, climate, and human activities.

作为研究过去火灾活动的重要指标,木炭常被用于研究火灾分布特征及其与植被、气候和人类活动的关系。然而,对木炭的空间分布和环境决定因素的研究仍然有限。本研究采用花粉法对青藏高原表层土壤样品中的木炭进行了鉴定和计数,并利用增强回归树(BRT)研究了其与植被净初级生产量(NPP)、海拔、气候(降水、最冷月和最暖月平均温度)和人口的关系。结果表明,微观炭浓度、宏观炭浓度和总炭浓度均由西南向东北增加,这与青藏高原人口密度东高西低的趋势一致,表明人类活动的增加可能促进火灾的发生。BRT模型表明,NPP、海拔高度和最冷月平均温度是影响青藏高原总炭浓度的重要因素,随着植被生物量的增加、海拔高度的降低和最冷月平均温度的降低,火灾发生的频率和强度进一步增加。青藏高原表层土壤炭的空间变化特征不仅能很好地反映该地区的空间火情,而且对植被、气候和人类活动都有很好的指示意义。
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引用次数: 0
A re-evaluation of the average chain length of lacustrine sedimentary n-alkanes as a paleoproxy on the Qinghai-Tibet Plateau 青藏高原湖相沉积正构烷烃平均链长作为古代用物的再评价
IF 2 4区 地球科学 Q2 Earth and Planetary Sciences Pub Date : 2023-12-05 DOI: 10.1007/s11707-022-1084-0
Mingda Wang, Qin Li, Jaime Toney, David Henderson, Juzhi Hou

Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives. nalkanes are relatively resistant to degradation and thus they can provide high-fidelity records of past vegetation and climate changes. Nevertheless, previous studies have shown that the interpretation of n-alkane proxies, such as the average chain length (ACL), is often ambiguous since this proxy depends on more than one variable. Both vegetation and climate could exert controls on the n-alkane ACL, and hence its interpretation requires careful consideration, especially in regions like the Qinghai-Tibet Plateau (QTP) where topography, biome type and moisture source are highly variable. To further evaluate the influences of vegetation and climate on the ACL in highelevation lakes, we examined the n-alkane distributions of the surface sediments of 55 lakes across the QTP. Our results show that the ACL across a climatic gradient is significantly affected by precipitation, rather than by temperature. The positive correlation between ACL and precipitation may be because of the effect of microbial degradation during deposition. Finally, we suggest that more caution is needed in the interpretation of ACL data in different regions.

长链正构烷烃是陆生植物中最常见的有机化合物之一,在各种地质档案中保存完好。烷烃相对不易退化,因此它们可以提供过去植被和气候变化的高保真记录。然而,先前的研究表明,正构烷烃的代理解释,如平均链长(ACL),往往是模棱两可的,因为这个代理取决于多个变量。植被和气候都可能对正构烷烃ACL产生控制作用,因此对正构烷烃ACL的解释需要慎重考虑,特别是在青藏高原等地形、生物群系类型和水分来源变化很大的地区。为进一步评价植被和气候对高海拔湖泊地表沉积物正构烷烃分布的影响,研究了青藏高原55个湖泊地表沉积物正构烷烃分布特征。我们的研究结果表明,在气候梯度上,ACL受降水的影响显著,而不是受温度的影响。ACL与降水呈正相关关系可能是由于沉积过程中微生物降解的影响。最后,我们建议在解释不同地区的ACL数据时需要更加谨慎。
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引用次数: 0
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Frontiers of Earth Science
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