Organic-walled microfossils from the Tonian Tongjiazhuang Formation of the Tumen Group in western Shandong,North China Craton and their biostratigraphic significance     

《Gondwana Research》2019

Neoproterozoic successions in western Shandong of North China Craton contain fine-grained siliciclastic rocks which offer a unique opportunity to explore the Neoproterozoic biosphere. In this study, we have revealed a well-preserved and diversified microfossil assemblage from the Tongjiazhuang Formation, Tumen Group in western Shandong, North China Craton, which is characterized by abundant smooth-walled sphaeromorphic acritarchs and cyanobacterium-like filamentous forms and relatively low abundance of more complex acritarchs. A total of 40 microfossil taxa belonging to 20 morphological genera have been identified, most of which are described for the first time from the Tongjiazhuang Formation of the Tumen Group in western Shandong, including Simia sp., Trachyhystrichosphaera aimika, T. botula, Germinosphaera bispinosa, Unnamed sp. A, Jacutianema solubila, and Pololeptus rugosus. The Tongjiazhuang assemblage revealed in this study is much more diverse than previously reported and well comparable to the Tonian Liulaobei and Gouhou assemblages in the Xuhuai region. Particularly, the occurrence of T. aimika, T. botula, G. bispinosa, J. solubila, and P. rugosus indicates a late Mesoproterozoic to Tonian age for the Tongjiazhuang Formation. In addition, the occurrences of macroscopic carbonaceous compressions, including Chuaria-Tawuia assemblage from the Tongjiazhuang Formation and Tawuia and Sinosabellidites from the Shiwangzhuang Formation, are consistent with geochronological data, suggesting a Tonian age for the Tongjiazhuang, Fulaishan, and Shiwangzhuang formations of the middle and upper Tumen Group, while the Heishanguan and Erqingshan formations of the lower Tumen Group are likely late Mesoproterozoic to Tonian in age. Thus, available biostratigraphic data, lithostratigraphic correlation, and geochronological data suggest that the whole Tumen Group is late Mesoproterozoic to Tonian in age, rather than Cryogenian or Ediacaran. This study significantly improves our knowledge about the diversity of the Tonian biosphere and implies a ∼200–300 million years unconformity (the ‘Great Unconformity’) between the late Mesoprotoerozoic to Tonian Tumen Group and the early Cambrian Liguan Formation in western Shandong.  相似文献   

Early Paleozoic magmatism and metallogeny related to Proto-Tethys subduction: Insights from volcanic rocks in the northeastern Altyn Mountains,NW China     

《Gondwana Research》2019

Remnants of the Proto-Tethys are mainly preserved in the region between south of the North China-Tarim Block and north of Qiangtang-Sibumasu/Baoshan Blocks. Magmatic-metallogenic events related to the Proto-Tethyan subductions were rarely reported, and the subduction history and polarity of the Proto-Tethyan are still under debate. Here, we presented new data of zircon UPb ages, whole-rock Sr–Nd–Pb isotopes, major and trace elements and zircon Hf isotopes for the volcanic rocks in the northeastern Altyn Mountains. Information of over 14 volcanic-hosted deposits/prospects in the region has been compiled. These volcanic ore hosts consist mainly of basaltic andesite, andesite, dacite and rhyolite rocks. The andesite and rhyolite rocks are newly zircon UPb dated to be Late Cambrian-Early Ordovician (andesite: 490.5 ± 5.2 Ma; rhyolite: 492.6 ± 2.9 Ma and 491.6 ± 5.6 Ma), representing the timing of volcanism and VMS (Volcanogenic Massive Sulfide) mineralization. All the volcanic rocks belong to the high-K calc-alkaline and shoshonite series: the andesite rocks from the Kaladawan area in north of the region display arc geochemical affinities and contain (⁸⁷Sr/⁸⁶Sr)_i (0.7082–0.7083) and ε_Nd(t) (−9.7 to −7.6), indicating that they were likely formed by partial melting of the mantle wedge with subducted sediment inputs. The rhyolite rocks from the Kaladaban area in south of the region are characterized by high SiO₂ (64.46–78.55 wt%), low alkali (Na₂O + K₂O, 3.46–7.17 wt%), and contain (⁸⁷Sr/⁸⁶Sr)_i (0.7063–0.7095), ε_Nd(t) (−6.6 to −1.5), and zircon ε_Hf(t) (−5.5 to 5.4), indicating that they were likely derived from partial melting of the lower crust with depleted mantle inputs. Rock assemblage and geochemistry suggest that volcanic rocks in the northeastern Altyn Mountains may have formed in a continental arc setting. Their spatial distributions with respect to the ophiolites in the region suggest that the subduction was likely south-dipping. This subduction-related arc magmatism may have formed the many important VMS and porphyry–skarn deposits in the region.  相似文献   

硒化物在文蛤响应镉胁迫过程中作用的转录组学分析     

郑年昊  孙铭  姚琳琳  荆圆圆  张天文  胡凡光  王兴强  刘广斌 《海洋科学》2024,48(1):25-35

研究两种硒化物在文蛤富集、排出镉过程中的作用,对文蛤进行转录组测序,并进行生物信息学分析,以探讨硒化物对Cd2+代谢相关机制。硒化卡拉胶组和亚硒酸钠组共产出587 855条高质量reads。基因本体分析功能注释到15 380条unigenes, KEGG通路注释到18 866条unigenes。差异基因主要富集到肌球蛋白复合物(myosin complex)、离子通道抑制(ion channel suppression)等基因本体分析功能中。差异基因KEGG通路富集显示,在嘌呤代谢(purinemetabolism)、ECM受体相互作用(extracellularmatrix receptor interaction)、硒化合物代谢(metabolism of selenium compounds)等通路显著富集。从结果分析Cd2+可以使文蛤体内蛋白转录修饰出现异常;有机硒可以通过调控金属离子通道活性来排出细胞内的Cd2+;无机硒主要作用于文蛤细胞表面,增强其表面活性抵御Cd2+进入细胞;差异基因KEGG注释结果表明有机硒与无机硒在文蛤重金属代谢中作用机制以及途径不相同。  相似文献   

Lunar cycles and seasonal variations in deposition fluxes of planktic foraminiferal shell carbonate to the deep South Atlantic (central Walvis Ridge)     

《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(7):1178-1188

Several authors have argued that lunar reproductive cycling controls the shell fluxes of planktic foraminifera, one of the major carbonate-producing groups in the global pelagic ocean. A time-series sediment trap at 2700 m depth on the central Walvis Ridge below the South Atlantic central gyre demonstrate for the first time that shell deposition fluxes of Hastigerina pelagica are synchronous with lunar periodicity. Spectral analysis of the 6-month time-series with 8-day resolution showed a strong 30-day cyclicity in the flux maxima of H. pelagica arriving at the ocean floor on average 12.5 days after each full moon. Given a shell settling velocity of about 400 m day⁻¹, which implies about 7 days for settling, this coincides with the pronounced endogenous reproduction rhythm of 5±2 days after full moon as originally observed in laboratory-cultured isolates from off Bermuda in the North Atlantic. By contrast, no endogenous or exogenous lunar periodicity was observed in the deposition flux or size distribution of any of the 27 other shell species from austral winter (August 2000) to austral summer (February 2001). Instead, the deposition fluxes of shell species, the bulk carbonate and the total mass were dominated by a seasonal maximum during austral spring, without any periodicity in the 16–90-day domain of this study. Since H. pelagica exhibits low fluxes with a low burial efficiency, and continuous (re)production is shown by the deposition fluxes of other species, lunar reproductive cycling appears not to affect pelagic carbonate productivity and deep ocean sedimentation fluxes.  相似文献   

Biogeochemical studies of metallophytes from four copper-enriched sites along the Yangtze River, China   总被引：1，自引：0，他引：1  

M. Ye  J. T. Li  S. N. Tian  M. Hu  S. Yi  B. Liao 《Environmental Geology》2009,56(7):1313-1322

The area along middle and lower reaches of the Yangtze River is one of the biggest Cu belts in China. In the present study, the metallophytes growing in four copper (Cu)-enriched sites along the Yangtze River were surveyed to get detailed information about vegetation composition and their Cu uptake characteristics. In all sampling sites, Cu concentrations of soils were high; whereas the organic matter, acidity and salinity of most soils were on normal levels. Totally 82 plant species belonging to 45 families were recorded. All the species recorded in the present study exhibited high tolerances for Cu although they differed greatly in their abilities to accumulate Cu. Except for Rumex acetosa and Phytolacca acinosa, most species were Cu-excluders and no Cu hyperaccumulator was found. The Cu translocation factors (TFs) and bioconcentration factors (BCFs) of the 12 dominant species were fairly low, indicating low concentrations of Cu were translocated to the shoots of these species. On this basis, the potential utilization of these metallophytes for phytoremediation was discussed.  相似文献   

低温对厚皮甜瓜幼苗光合特性的影响   总被引：2，自引：0，他引：2  

陈年来  王兴虎  安黎哲  王刚 《冰川冻土》2009,31(5):986-991

在人工控制条件下研究了低温对厚皮甜瓜幼苗光合特性的影响.结果表明:低温(昼15℃/夜5℃)胁迫导致甜瓜幼苗的光合色素含量和叶片光能捕捉下降,可利用光强范围变窄,对CO2的利用效率降低,光合作用的瞬时水分利用效率显著降低.在亚适宜温度(昼20℃/夜10℃)下,制约甜瓜光合作用的主导因素为气孔限制,在胁迫低温下则以非气孔因素为主.气孔限制在降低植物碳同化速率的同时,也提高了水分利用效率.低温条件下,伊丽莎白较黄河蜜具有更高的光合色素含量、更大的光能和CO2利用效率、更强的弱光和低浓度CO2利用能力.甜瓜温室型品种伊丽莎白对低温的适应性优于露地品种黄河蜜.  相似文献   

应用多光谱遥感信息反演干旱区浅水湖泊水深   总被引：3，自引：0，他引：3       下载免费PDF全文

于瑞宏  许有鹏  刘廷玺  李畅游 《水科学进展》2009,20(1):111-117

选取位于中国北方干旱区的湖泊乌梁素海为研究区,基于2002-2004年的LandsatTM数据以及同期实测水深数据,根据水深遥感原理,通过1次,2次,3次实测水深数据与遥感影像反射率及其组合之间的相关关系,选取五变量,三变量,二变量及一变量的非对数及对数模型进行湖泊水深估值,继而通过误差分析及模型对比,最终确定出3次实测数据五变量非对数模型作为乌梁素海的最优估值模型。该模型利用多光谱组合确定水深的估值模式,克服了单光谱信息难以综合反映沉水植物、芦苇、水色及底质空间变化的困难,符合干旱区浅水湖泊的特性,结果可为干旱区其它浅水湖泊水深反演提供新的思路和参考。  相似文献   

Effects of hydrodynamic dispersion on plume lengths for instantaneous bimolecular reactions     

《Advances in water resources》2004,27(8):803-813

  相似文献   

Holocene thermal maximum in the western Arctic (0–180°W)     

《Quaternary Science Reviews》2004,23(5-6):529-560

The spatio-temporal pattern of peak Holocene warmth (Holocene thermal maximum, HTM) is traced over 140 sites across the Western Hemisphere of the Arctic (0–180°W; north of ∼60°N). Paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer-than-present conditions at 120 of these sites. At the 16 terrestrial sites where quantitative estimates have been obtained, local HTM temperatures (primarily summer estimates) were on average 1.6±0.8°C higher than present (approximate average of the 20th century), but the warming was time-transgressive across the western Arctic. As the precession-driven summer insolation anomaly peaked 12–10 ka (thousands of calendar years ago), warming was concentrated in northwest North America, while cool conditions lingered in the northeast. Alaska and northwest Canada experienced the HTM between ca 11 and 9 ka, about 4000 yr prior to the HTM in northeast Canada. The delayed warming in Quebec and Labrador was linked to the residual Laurentide Ice Sheet, which chilled the region through its impact on surface energy balance and ocean circulation. The lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change. The spatial asymmetry of warming during the HTM resembles the pattern of warming observed in the Arctic over the last several decades. Although the two warmings are described at different temporal scales, and the HTM was additionally affected by the residual Laurentide ice, the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing. Unlike the HTM, however, future warming will not be counterbalanced by the cooling effect of a residual North American ice sheet.  相似文献   

Geochemistry and geochronology of quartz diorite host rocks of the Liudaowaizi skarn copper deposit in Jilin Province,NE China     

《Chemie der Erde / Geochemistry》2019,79(1):153-161

The Liudaowaizi Cu deposit is located in the east of Jilin Province and represents one of the few known Early Jurassic skarn Cu deposits in NE China. Here, we present new whole-rock major and trace element, zircon U–Pb and Hf isotopic data of quartz diorite exposed in the Liudaowaizi skarn Cu deposit. The quartz diorite belongs to the calc-alkaline series, is enriched in some of the large-ion lithophile elements (LILE; e.g., Rb, Ba, Th, and K) and is depleted in high-field-strength elements (HFSE; e.g., Ta, Nb, and Ti). LA-ICP-MS dating of zircons from the quartz diorite in the deposit yielded ages of 196 ± 1 Ma that are interpreted to be the emplacement age of this intrusion. Positive εHf values (6.6–11.6) and young T_DM2 (490–813 Ma) of the quartz diorite indicate that the parent magma was derived from the partial melting of a juvenile lower crust, and magmatism and Cu mineralization were possibly related to the subduction of the Paleo-Pacific Plate.  相似文献