柴达木盆地鱼卡地区中侏罗统石门沟组砂岩碎屑组分特征及其物源构造环境分析

利用砂岩碎屑骨架成分统计和碎屑颗粒结构特征分析,研究柴达木盆地北缘鱼卡地区中侏罗统石门沟组碎屑岩的源岩类型及其构造环境。石门沟组砂岩成分成熟度中等、结构成熟度较低,具有近源物源的特点。砂岩碎屑骨架成分统计结果表明石门沟组的物源区构造背景属于再旋回造山带。结合柴达木盆地北缘中侏罗统古地理特征,确认鱼卡地区石门沟组物源区为祁连山造山带。砂岩碎屑组分可能来自于南祁连山上石炭世宗务隆山群火山岩和达肯达坂山群变质岩。     

祁连山区多年冻土空间分布模拟

祁连山区位于青藏高原东北边缘,是亚洲水塔重要的组成部分,多年冻土的变化对生态系统和水资源平衡有着重要影响。基于青藏高原第二次综合科学考察、道路勘察钻孔点以及前人所获得的多年冻土下界资料,回归得出祁连山区多年冻土下界统计模型,借助ArcGIS平台在DEM数据的支持下,模拟出祁连山区多年冻土空间分布图。结果表明：祁连山区多年冻土分布的下界具有良好的地带性规律,表现为随经纬度增加而降低的规律;祁连山区多年冻土在空间分布上呈现出以哈拉湖为中心向四周扩散的分布格局;祁连山区总面积约为16.90×10⁴ km²,其中多年冻土面积约为8.03×10⁴ km²,占总面积约47.51%。多年冻土区与季节冻土区之间存在着有不连续多年冻土分布的过渡区,过渡区面积约1.43×10⁴ km²,占总面积约8.46%。     

基于遥感的大兴安岭小扬气镇用地类型变化及生态环境状况评价

大兴安岭小扬气镇位于大兴安岭南部,属大小兴安岭森林生态功能区,森林覆盖率高,湿地资源丰富,曾是木材生产基地。为掌握小扬气镇用地类型现状及其变化,开展生态状况评价,利用多源卫星遥感数据,通过多尺度图像分割、决策树及目视解译等方法分别对该区1985年、1998年、2008年和2018年土地利用类型进行提取,计算生态环境状况指数(I_E),评价生态环境状况。结果表明: 小扬气镇土地利用类型以林地、沼泽、水域为主,三者占研究区总面积的97%以上; 沼泽草地主要由阔叶林转化而来,耕地主要由阔叶林、沼泽草地转化而来,草地主要转化为阔叶林、沼泽草地,阔叶林与沼泽草地之间的相互转化最为剧烈; 新增工矿仓储用地主要占用了原有阔叶林土地,新增住宅用地主要占用了原有的沼泽草地、阔叶林、森林沼泽等。总体来看,区内生态环境状况良好,在维护生态安全、促进当地绿色经济发展中起到了重要作用。     

Role of the Nocturnal Low-level Jet in the Formation of the Morning Precipitation Peak over the Dabie Mountains

The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is verified against surface rain-gauge observations. The observed morning precipitation peak on the windward(relative to the prevailing synoptic-scale wind) side of the DBM is reproduced with good spatial and temporal accuracy. The interaction between the DBM and a nocturnal boundary layer low-level jet(BLJ) due to the inertial oscillation mechanism is shown to be responsible for this precipitation peak. The BLJ is aligned with the lower-level southwesterly synoptic-scale flow that carries abundant moisture.The BLJ core is established at around 0200 LST upwind of the mountains. It moves towards the DBM and reaches maximum intensity at about 70 km ahead of the mountains. When the BLJ impinges upon the windward side of the DBM in the early morning, mechanical lifting of moist air leads to condensation and subsequent precipitation.     

The Valley and Ridge Province of eastern Pennsylvania—stratigraphic and sedimentologic contributions and problems

Many contributions that have led to a better understanding of Appalachian geology have resulted directly from work in the folded Appalachian Mountain and Great Valley sections of the Valley and Ridge physiographic province of eastern Pennsylvania. Disagreements have been common since H.D. Rogers first described the geology of the area in 1858. Many differing opinions still exist regarding the stratigraphy, structural geology, geomorphology, and glacial geology. The rocks in the area, which range from Middle Ordovician to Late Devonian in age, are more than 25000 feet (7620 m) thick. This diversified group of sedimentary rocks was deposited in many different environments, ranging from deep sea, through neritic and tidal, to alluvial. In general, the Middle Ordovician through Lower Devonian strata are a sedimentary cycle related to the waxing and waning of Taconic tectonism. The sequence began with a greywacke-argillite suite (Martinsburg Formation) representing synorogenic basin deepening. This was followed by basin filling and pro-gradation of a sandstone-shale clastic wedge (Shawangunk Formation and Bloomsburg Red Beds) derived from the erosion of the mountains that were uplifted during the Taconic orogeny. The sequence ended with deposition of many thin units of carbonate, sandstone, and shale on a shelf marginal to a land area of low relief. Another tectonic-sedimentary cycle, related to the Acadian orogeny, began with deposition of Middle Devonian rocks. Deep-water shales (Marcellus Shale) preceded shoaling (Mahantango Formation) and turbidite sedimentation (Trimmers Rock Formation) followed by another molasse (Catskill Formation).     

西南天山阔克萨彦岭巴雷公镁铁质岩石的地球化学特征、LA-ICP-MS U-Pb年龄及其大地构造意义

巴雷公镁铁—超镁铁质岩套出露于南天山阔克萨彦岭地区,本文对其中的镁铁质岩石进行了详细的地球化学和锆石U-Pb年代学研究。岩石学和地球化学特征表明：巴雷公镁铁质岩石主要为洋岛拉斑岩石系列,P2O5 (0.33%~0.75%)、TiO2 (2.49%~370%)、TFe2O3 (12.69%~15.63%)含量高,富集轻稀土,LREE/HREE分异明显,(La /Yb)N介于3.66~6.54之间。 Cr (28.93×10-6~123.99×10-6)、Co (44.04×10-6~52.40×10-6)和Ni (25.61×10-6~63.04×10-6)含量低,且Ni、Cr与MgO呈正相关关系指示其母岩浆在岩浆房中或上升途中经受了橄榄石和尖晶石分离结晶作用。Zr/Nb(7.06~7.99) 和Zr/Hf (35.98~37.53) 比值低,推测其可能来自于含石榴子石的富集地幔的深部熔融。Zr/Y—Nb/Y和Nb/Th—Zr/Nb图解显示,其源区具有EM1—EM2型地幔端元组分混入,可能主要有再循环的发生了交代熔融作用的深部大洋岩石圈的参与。锆石LA-ICPMS U-Pb定年结果表明,巴雷公洋岛火山岩的结晶年龄为450±2Ma。结合新获得的该岩套夹层灰岩中的牙行刺化石资料,指示该岩体在早石炭世以后成为蛇绿混杂岩的一部分。综合区域年代学和地球化学研究资料,推测南天山古洋盆在晚奥陶世—早志留世期间已演化成为成熟的多岛洋盆。     

用树木年轮重建伊犁南天山北坡西部的降水量序列

根据采自伊犁地区南天山北坡11个采点的树木年轮样本,建立了每个采点的3种年表。通过单相关普查发现,标准化树轮年表序列与当年1~5月的降水显著相关。分析表明该时段降水与树木年轮生长呈正相关具有明确的树木生理学意义。利用新源上限(XNAUt)、昭苏上限(ZUt、ZUt 2)和特克斯下限(TLt)4个标准化树轮年表序列可较好地重建该区域在该时段的降水量。经交叉检验,所得重建方程是稳定可靠的,重建的降水序列是可信的。通过分析发现:伊犁地区南天山北坡300年以来1~5月的降水大致经历了6个偏湿阶段和6个偏干阶段;有2.0~2.8年、24.8年、28.3年、33年、99年的变化准周期;在1909年发生由多向少的突变;1740年、1870年发生由少向多的突变,其中又以1870年前后的突变最为明显。     

天山南麓山前平原土壤盐分空间异质性对植物群落组成及结构的影响

将轮台天山南麓山前平原中下部自北至南分为4个地貌带:洪水剥蚀带、溢出带、三角洲带及两河交汇区带。并以土壤电导作为积盐程度的指标,分析了天山南麓山前平原4个地貌带土壤盐的分布特征:溢出带和三角洲带土壤盐分含量高,两端洪水剥蚀带和两河交汇区带盐分含量低。物种多样性及物种组成分析结果表明,自北至南物种多样性及物种数量都在下降,洪水剥蚀带主要为柽柳群落、琵琶柴群落,溢出带主要为柽柳群落、盐节木群落、盐角草群落,三角洲带及两河交汇区均为柽柳群落。通过相关性分析,土壤盐分与群落物种多样性相关性不显著。但是,土壤盐渍化的变化明显影响到植物群落物种组成的变化、群落类型的空间分布和演替。     

Late quaternary seismic stratigraphy and active faults of the Gulf of İzmit (NE Marmara Sea)

The Upper Quaternary seismic stratigraphy and active faults of the Gulf of İzmit were investigated by means of high-resolution shallow seismic profiling data in the source region of 1999 İzmit earthquake. High-resolution seismic reflection data correlated with borehole data indicate that the stratigraphy of İzmit Bay consists of three distinct depositional sequences formed in response to middle Pleistocene-Holocene sea-level changes. Reflector R, separating the pre-Holocene sequences (1 and 2) from the Holocene sequence (3), represents an erosional unconformity produced by the subaerial fluvial erosion of the continental shelves at the time of the last glacial maximum. Occasional, anomalous reflections (acoustic turbidity) observed within the Holocene sequence are interpreted as gas accumulations. The maximum thickness of the Holocene sediments is found to be about 25 m. The isopach map of Holocene sediment implies that the thickness of the Holocene decreases from the east towards the central and western basins of İzmit Bay. Two distinct fault systems are interpreted in İzmit Bay. The main fault system extending roughly in an E-W direction along the Gulf of İzmit is an active right lateral strike slip fault with a normal component. The secondary faults are normal faults striking in different directions and these are identified as being both active and inactive. In addition, prominent compressive features are identified in the seismic cross-sections of some profiles acquired to the east of Hersek Peninsula where the focal mechanisms of the aftershocks of the 1999 İzmit earthquake also reveal predominantly reverse faulting mechanisms, as identified by a local dense seismic network.     

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