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.
{"title":"Late Holocene brGDGTs-based quantitative paleotemperature reconstruction from lacustrine sediments on the western Tibetan Plateau","authors":"Xiumei Li, Sutao Liu, Juzhi Hou, Zhe Sun, Mingda Wang, Xiaohuan Hou, Minghua Liu, Junhui Yan, Lifang Zhang","doi":"10.1007/s11707-022-1082-2","DOIUrl":"https://doi.org/10.1007/s11707-022-1082-2","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139462050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 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.
{"title":"Deformation characteristics and analog modeling of transtensional structures in the Dongying Sag, Bohai Bay Basin","authors":"Dawei Dong, Li Zhao, Weizhong Zhang, Jiyan Li, Ruixiang Zhang, Jianlei Yang, Guangzeng Wang","doi":"10.1007/s11707-022-1062-6","DOIUrl":"https://doi.org/10.1007/s11707-022-1062-6","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139068547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-28DOI: 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.
{"title":"Detecting the spatial-temporal pattern of moisture evolution on the Tibetan Plateau during the Holocene by model-proxy comparison","authors":"Zeyu Zheng, Liya Jin, Jinjian Li, Xiaojian Zhang, Jie Chen","doi":"10.1007/s11707-022-1049-3","DOIUrl":"https://doi.org/10.1007/s11707-022-1049-3","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139063609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-28DOI: 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.
{"title":"The important role of Turbidity Maximum Zone in sedimentary dynamic of estuarine mangrove swamp","authors":"Tao Liu, Ying Liu, Baoqing Hu","doi":"10.1007/s11707-022-1083-1","DOIUrl":"https://doi.org/10.1007/s11707-022-1083-1","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139063606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-28DOI: 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。
{"title":"Alternating influences of the Westerlies and Indian Summer Monsoon on the hydroclimate of the source region of the Yarlung Tsangpo over past 4000 yr","authors":"Zhe Sun, Zirui Huang, Kejia Ji, Mingda Wang, Juzhi Hou","doi":"10.1007/s11707-022-1055-5","DOIUrl":"https://doi.org/10.1007/s11707-022-1055-5","url":null,"abstract":"<p>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 <sup>14</sup>C 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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139071885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"The determination of sedimentary environment and associated energy in deep-buried marine carbonates: insights from natural gamma ray spectrometry log","authors":"Jingyan Liu, Qian Chang, Junlong Zhang, Hui Chai, Feng He, Yizan Yang, Shiqiang Xia","doi":"10.1007/s11707-022-1053-7","DOIUrl":"https://doi.org/10.1007/s11707-022-1053-7","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139063332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-28DOI: 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。
{"title":"Holocene temperature variation recorded by branched glycerol dialkyl glycerol tetraethers in a loess-paleosol sequence from the north-eastern Tibetan Plateau","authors":"Tianxiao Wang, Duo Wu, Tao Wang, Lin Chen, Shilong Guo, Youmo Li, Chenbin Zhang","doi":"10.1007/s11707-023-1094-6","DOIUrl":"https://doi.org/10.1007/s11707-023-1094-6","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139063608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-28DOI: 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.
{"title":"Characteristics of microscopic pore heterogeneity and development model of Wufeng–Longmaxi Shales in the Pengshui area of south-east Chongqing","authors":"Lu Sun, Zhigang Wen, Guisong He, Peixian Zhang, Chenjun Wu, Liwen Zhang, Yingyang Xi, Bo Li","doi":"10.1007/s11707-023-1087-5","DOIUrl":"https://doi.org/10.1007/s11707-023-1087-5","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139063672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Spatial distribution of charcoal in topsoil and its potential determinants on the Tibetan Plateau","authors":"Yixuan Wang, Chaoqun Cao, Yanrong Zhang, Lina Liu, Nannan Wang, Wenjia Li, Xianyong Cao","doi":"10.1007/s11707-023-1095-5","DOIUrl":"https://doi.org/10.1007/s11707-023-1095-5","url":null,"abstract":"<p>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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138525094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-05DOI: 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.
{"title":"A re-evaluation of the average chain length of lacustrine sedimentary n-alkanes as a paleoproxy on the Qinghai-Tibet Plateau","authors":"Mingda Wang, Qin Li, Jaime Toney, David Henderson, Juzhi Hou","doi":"10.1007/s11707-022-1084-0","DOIUrl":"https://doi.org/10.1007/s11707-022-1084-0","url":null,"abstract":"<p>Long-chain <i>n</i>-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 <i>n</i>-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 <i>n</i>-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 <i>n</i>-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.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138525066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}