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1.
The Kachchh Basin and the Jaisalmer Basin are two neighboring Mesozoic sedimentary basins at the western margin of the Indian craton. The Jurassic succession of the Kachchh Basin is more complete and more fossiliferous than that of the Jaisalmer Basin. Consequently, intrabasinal correlation of the sedimentary units has been possible in the Kachchh Basin, but not in the Jaisalmer Basin. However, some marker beds existing in the Kachchh Basin can be recognized also in the Jaisalmer Basin. Ammonite evidence shows that they are time-equivalent. The following four units form marker intervals in both basins: (1) the pebbly rudstone unit with Isastrea bernardiana and Leptosphinctes of the Kaladongar Formation (Kachchh Basin) and the Isastrea bernardiana-bearing rudstone of the Jaisalmer Formation (Jaisalmer Basin) both represent transgressive systems tract deposits dated as Late Bajocian; (2) bioturbated micrites with anomalodesmatan bivalves within the Goradongar Yellow Flagstone Member (Kachchh Basin) and bioturbated units in the Fort Member (Jaisalmer Basin) represent maximum flooding zone deposits of the Middle to Late Bathonian; (3) trough-crossbedded, sandy pack- to grainstones of the Raimalro Limestone Member (Kachchh Basin) and the basal limestone-sandstone unit of the Kuldhar section of the Jaisalmer Formation (Jaisalmer Basin) correspond to Late Bathonain transgressive systems tract deposits; and (4) ferruginous ooid-bearing carbonates with hardgrounds of the Dhosa Oolite member (Kachchh Basin) and the middle part of the Jajiya Member (Jaisalmer Basin) are Oxfordian transgressive systems tract deposits. The fact that in both basins similar biofacies prevailed during certain time intervals demonstrates a common control of their depositional history. As the two basins represent different tectonic settings, the most likely controlling factors were the relative sea-level changes produced by eustatic processes, a common subsidence history of the northwestern margin of the Indian craton, and the paleoclimate.  相似文献   

2.
为了解河流大型底栖动物对环境压力的响应关系,以人类干扰程度不同的太湖流域和巢湖流域为研究区,系统调查区域内河流大型底栖动物,结合水体、沉积物理化数据及生境质量状况,运用空间分析和多元统计分析等方法,探讨了大型底栖动物多样性及典型物种对关键环境因素的响应规律.结果表明,太湖流域和巢湖流域的环境质量和大型底栖动物群落结构均差异较大,巢湖流域的生境质量优于太湖流域,巢湖流域平原区部分点位的水体营养盐(特别是氮浓度)高于太湖流域平原区.巢湖流域丘陵区的敏感型物种(主要为水生昆虫)密度远高于太湖流域丘陵区,太湖流域丘陵区的耐污型物种(寡毛纲)平均密度稍高于巢湖流域丘陵区,而巢湖流域平原区的寡毛纲霍甫水丝蚓(Limnodrilus hoffmeisteri)和苏氏尾鳃蚓(Branchiura sowerbyi)平均密度远高于太湖流域平原区.广义加性模型建立的响应关系曲线表明,栖境多样性和总氮浓度可以作为生物多样性的指示因子.铜锈环棱螺(Bellamya aeruginosa)、椭圆萝卜螺(Radix swinhoei)、河蚬(Corbicula fluminea)、霍甫水丝蚓、苏氏尾鳃蚓、黄色羽摇蚊(Chironomus flaviplumus)等特征物种与特定环境因子的响应关系显著,这些物种也可以作为环境监测的指示物种.底栖动物环境梯度的响应曲线能够定量地描述底栖动物群落对环境因子的响应关系,有利于深入了解水体水质、营养状态及生境质量与大型底栖动物群落结构的相关关系,进而预测不同人为干扰下大型底栖动物群落结构的变化趋势和演替过程.  相似文献   

3.
Cenozoic basin-forming processes in northwestern Kyushu were studied on the basis of geological and geophysical data. Gravity anomaly analysis delineated four sedimentary basins in the study area: Goto-nada, Nishisonogi, Amakusa-nada, and Shimabara. Borehole stratigraphy and reflection seismic interpretation suggest that the Goto-nada Basin was subdivided into the Paleogene and Plio-Pleistocene depocenters (Goto-nada 1 and 2). In the Paleogene, Amakusa-nada Basin was rapidly subsiding together with the Shimabara Basin as part of a large graben. Goto-nada 1 and Nishisonogi basins belonged to another depositional area. After stagnant subsidence stage in the early Miocene, the study area became a site of basaltic activity (since 10 Ma) and vigorous subsidence in the Plio-Pleistocene. Goto-nada 2 Basin is accompanied with numerous east–west active faults, and separated from the Amakusa-nada Basin by a northeast– southwest basement high, Nomo Ridge. Plio-Pleistocene subsidence of the Amakusa-nada Basin is related with low-angle normal faulting on the eastern flank of the Nomo Ridge. Shimabara Basin is a composite volcano-tectonic depression which is studded by east–west faults. Focal mechanism on active faults suggests transtensional stress regime in the study area.  相似文献   

4.
新疆天山地区壳幔S波速度结构特征及变形分析   总被引：1，自引：0，他引：1       下载免费PDF全文
天山地区地质构造复杂，地震活动频繁，其壳幔变形和深部结构一直受到学者们的高度关注.然而，由于天山地区地震台站资料较少，致使壳幔变形研究结果与解释存在诸多争议.本研究利用在天山地区（40°N-46°N，78°E-92°E）新布设的11个流动宽频带地震台站和该地区39个固定台站的观测资料，采用接收函数与面波联合反演方法，获得了研究区地壳厚度及壳幔S波速度结构.反演结果显示天山地区（41.5°N-44°N，78°E-88°E）平均地壳厚度为56 km，塔里木盆地（40°N-41.5°N，79°E-90°E）、准噶尔盆地（44°N-46°N，82°E-90°E）和吐鲁番盆地（42°N-43°N，88°E-90°E）具有较厚的沉积层，地壳平均厚度为43 km、53 km和46 km，整体表现为天山厚、盆地相对较薄的特征；在研究区南天山的最高峰（42°N，80.5°E）及北天山的最高峰（43.5°N，86°E）附近，中下地壳存在较厚的低速层，我们认为在强烈挤压作用下低速、低强度的中下地壳强烈变形可能是导致该区域快速隆升的主要原因.在研究区中部，位于塔里木盆地与准噶尔盆地之间的天山地区，中下地壳及上地幔均存在低速层，且盆地莫霍面向天山倾斜明显.结合前人的研究成果推测，在南北向构造挤压应力作用下，塔里木盆地与准噶尔盆地发生了向天山造山带方向的双向壳幔层间插入俯冲.在研究区东部，塔里木盆地东北缘与天山东部接触带的地壳内没有明显的低速层，推测应处在早期挤压变形状态，该区域的壳幔边界为缓变的速度梯度带，可能与上地幔热物质侵入或渗透有关.  相似文献   

5.
江淮流域是我国暴雨频发的地区之一，而乌拉尔山阻塞高压和西太平洋副热带高压是北半球两个主要的大气环流系统.本文统计分析了1971~2003年期间乌山阻塞高压和西太平洋副高的逐日强度变化特征，研究了乌山阻塞高压和西太平洋副高对江淮流域强暴雨过程的响应关系.结果表明，江淮流域多数强暴雨过程发生在乌山阻高的减弱期，在乌山阻高的建立和加强期较少有持续性暴雨发生.乌山阻高的突然减弱是江淮流域强暴雨过程发生的强信号之一.同时，西太平洋副热带高压的加强西伸登陆是江淮流域强暴雨过程发生的必要条件之一.  相似文献   

6.
Abstract   The Kurile Basin in the Okhotsk Sea, northwestern Pacific, is a back-arc basin located behind the Kurile Island Arc. It is underlain by oceanic crust and its origin has been attributed to back-arc spreading. Two models for the opening of the Kurile Basin exist, for which the spreading axis is oriented northeast–southwest and northwest–southeast, respectively. New data are presented here on the morphostructure of the slope of the northern Kurile Basin and of the central Kurile Basin which support a strike of the spreading axis in the latter direction. Bathymetric as well as single-channel and multichannel seismic reflection data demonstrate the existence of dominant northwest-striking normal faults on the northern slope of the Kurile Basin. In the central Kurile Basin a basement rise striking north-northwest–south-southeast (here named the Sakura Rise) was mapped. The rise morphology has the distinct imprint of a rift structure with symmetrical volcanic edifices on the rise axis and faulted blocks that tilt in opposite directions on the flanks. These data suggest that the Kurile Basin opened in a northeast–southwest direction. In the generally accepted plate tectonic reconstructions, northwest–southeast spreading associated with dextral strike–slip along the north–south-striking shear zone of Sakhalin and Hokkaido islands has been assumed. In the present model, spreading in the Kurile Basin was presumably connected with dextral displacement along a northeast-striking shear zone on the southern segment of the Okhotsk Sea.  相似文献   

7.
无定河流域位于黄土高原与毛乌素沙地过渡带,水土流失严重,生态环境具有脆弱性和波动性。于2021年春季(4月)和秋季(10月)对无定河流域上、中、下游及其6条支流和流域内的3个淤地坝开展水生态系统调查,旨在厘清无定河流域底栖动物群落特征,构建底栖动物生物完整性指数并开展健康评价。无定河流域春季共采集到底栖动物105种,平均密度为181 ind./m2,平均生物量为0.760 g/m2,秋季共采集到底栖动物67种,平均密度为94 ind./m2,平均生物量为0.454 g/m2。通过对两季度研究区域内底栖动物27个生物参数开展分布范围检验、判别能力分析和相关性分析,构建无定河流域底栖动物生物完整性指数,对全流域40个样点(6个参照点和34个受损点)进行B-IBI健康评价。评价结果表明,总体上无定河流域底栖动物生物完整性较好,40个样点中春季有19个处于健康或亚健康状态,秋季有23个处于健康或亚健康状态,其中无定河上、中游干支流大都以健康和亚健康为主,无定河下游干支流以及3个淤地坝水体健康状况较差。在不同水土流失类型区域,底栖动物群落特征和生物完整性评价具有显著性差异。本研究结果可为无定河流域河流健康评估提供科学依据。  相似文献   

8.
Kaftar Lake is a high‐altitude fresh water lake located in High Zagros, south of Iran. Despite the high annual evaporation to precipitation ratio in the area, lake water electrical conductivity is usually lower than 1000 µS/cm, this may be due to high seepage from the floor of the lake. Therefore, the hypothesis of possible underground connections between Namdan Basin, where the lake is located, and the surrounding basins with lower elevation (Aspas and Dehbid Basins) was investigated. Hydrogeology, hydrochemistry, and stable isotopes data of the lake and surrounding basins along with the lake water balance study were applied to test the hypothesis. Results indicate that Kaftar Lake has no connection with Aspas Basin in south, but it is hydraulically connected to Dehbid Basin. In Dehbid Basin, “Ghasr_e_Yaghoob spring” (average discharge ?1200 L/s) emerges from a small outcrop (about 0.8 km2) of Daryan limestone Formation, where this outcrop is much smaller than the required recharge area for such average discharge rate. The study shows that this spring is recharged by Kaftar Lake and Namdan Basin aquifer, through Daryan Formation of Gandboee Syncline located to the northern part of the lake.  相似文献   

9.
Heat-flow and coal-maturation data suggest that the thermal history of the San Juan Basin has been influenced by magmatic and volcanic activity in the San Juan Mountains-San Juan volcanic field located to the north of the Basin. Time-dependent isothermal step models indicate that the observed heat flow may be modelled by a (near) steadystate isothermal step extending from 30–98 km depth whose edge underlies the northern San Juan Basin. The observed maturation levels of the Fruitland formation coals in the northern and central Basin, however, require more heat than can be associated with conduction from a deep thermal source (steady-state step) and from the shallow crustal batholith which underlies the San Juan volcanic field. Magmatic activity within the Basin does not appear to be a reasonable source of additional heat. Increased burial depths of the coals may explain some of the elevated maturation levels observed in the central and northern Basin, but it seems likely that an additional source of heat is still required. Heat advection by groundwater movement may have influenced the coal maturation levels in the Basin as well. Both magmatic activity associated with the emplacement of the San Juan batholith and elevated geothermal gradients associated with the steady-state thermal source at depth may have contributed to heating of the groundwater. An appreciation of heat advection by groundwater flow may therefore be most important to understanding regional patterns of heat flow and hydrocarbon maturation.  相似文献   

10.
Nine heat flow values from Baja California and Sonora represent the first determinations of heat flux from Mexico and, in general, justify southerly extensions of the Basin and Range and Southern California thermal provinces of the southwestern United States. Heat flow in northern Baja California is low (0.84 hfu), consistent with known values from the Sierra Nevada Batholith, but a value of 1.23 hfu was recorded in the central area of the peninsula. Seven measurements from Sonora, averaging 2.5 hfu, are similar to Basin and Range values.Reduced heat flow values (q*) have been calculated for Sonora and are interpreted as indicative of a separate Basin and Range thermal subprovince in Mexico. A tectonic model developed for northwestern Mexico attributes the high heat flow of the Basin and Range to behind arc extension associated with the termination of Cenozoic subduction. Opening of the Gulf of California and sea-floor spreading therein has provided a vent for the release of heat accumulated under northwestern Mexico. Thus, the southern portion of the Basin and Range province (in Mexico) appears to be cooling and narrowing and a subprovince of high reduced heat flow is defined east and perhaps southwest of the Gulf of California.  相似文献   

11.
基于2009—2014年渭河盆地及邻区GPS资料,利用Shen提出的连续形变场与应变场计算方法,获得渭河盆地及邻区的水平形变场及应变率场,结合构造地质、地震目录等资料对渭河盆地及邻区的现今地壳形变及构造特征进行研究,并得到如下结论:(1)鄂尔多斯地块南缘西段和东段GPS形变场变化差异明显,六盘山—陇县—宝鸡断裂带形变场以挤压变形为主,渭河盆地中部西安—咸阳地区的形变场呈现EW向挤压、SN向拉张特征;(2)主应变率、剪应变率、面应变率变化明显的区域位于鄂尔多斯地块西南缘的六盘山—陇县—宝鸡断裂带、渭河盆地中部的长安—临潼断裂与渭南塬前断裂以及韩城断裂与双泉—临猗断裂附近;(3)未来需要警惕六盘山—陇县—宝鸡断裂带、长安—临潼断裂与渭南塬前断裂以及韩城断裂与双泉—临猗断裂附近的地震危险性。  相似文献   

12.
Hyesu  Yun  Songsuk  Yi  Jinyong  Oh  Hyunsook  Byun  Kooksun  Shin 《Island Arc》2007,16(2):262-275
Abstract   The Ulleung Basin is located in the southwestern part of the East Sea (Japan Sea) and contains thick Neogene sediment. Detailed examination of the stratigraphic distribution of dinoflagellates was carried out on samples from the onshore Pohang Basin (E well) and two wells (Gorae I and Dolgorae VII) in the southwestern Ulleung Basin, to investigate the early evolution of the basin. The results show that thick syn-rift sediments mainly consist of terrestrial deposits and are widespread over the basin. This supports an extensional tectonic origin for the basin. The initiation of the deposits dates back to 17–16.4 Ma. Furthermore, well-preserved Eocene to Oligocene dinoflagellate taxa found in Miocene deposits of wells implies that the age of initial rifting might be Oligocene or earlier. Our results provide constraints for understanding the opening process of the East Sea.  相似文献   

13.
近20年来巢湖流域景观生态风险评估与时空演化机制   总被引：3，自引：0，他引：3  
黄木易  何翔 《湖泊科学》2016,28(4):785-793
基于1995、2005、2013年3期Landsat TM/ETM+遥感影像及DEM,应用GIS方法开展巢湖流域景观格局特征分析及生态风险网格化定量评估.研究表明:(1)近20年来,巢湖流域景观格局特征变化明显,表现为建设用地景观破碎度、分离度均呈先下降后上升趋势;农地、林地与水体景观破碎度、分离度均呈上升趋势.(2)生态风险时序分析表明,19952013年,巢湖流域低、较低和中等级生态风险区域面积在逐渐缩小,而较高和高等级生态风险区域范围在不断蔓延.近20年来,巢湖流域生态风险主要由低级向高级转化,面积达6025 km2,是由高级向低级转化面积的2.30倍.(3)生态风险时空演化机制分析表明,巢湖流域生态风险变化区域主要集中在北、西南和东南部,具有明显的阶段性和区域性.近20年来,巢湖流域经历了快速的城市化、工业化以及受到行政区划调整的政策影响,高强度土地利用模式及县域经济活力的释放叠加于本身脆弱的流域生态条件,对景观生态系统造成的强烈干扰促进流域生态风险整体有恶化趋势,需重点加强中级以上生态风险区域的生态保护与建设工作.因此,生态风险演化趋势体现了该流域自然特点和区域社会经济发展对景观生态系统干扰的压力响应.  相似文献   

14.
Asymmetry of the Weihe Basin is discussed in the paper,and also the master control fault,secondary control fault of asymmetric basin is proposed in the paper.The asymmetry of the Weihe Basin is expressed as follows:(1) its shape of the cross sections is asymmetrical;(2) the tectonic activity of the southern margin fault and the northern margin one is apparently different;(3) its deep tectonics is asymmetrical.Finally,we use the Weihe Basin as an example to establish a "cantilever-beam" model for calculations.The results show that:(1) flexure leads to stress accumulation and forming extensional fractures;(2) fractures slope steeply towards the free end;(3) when the length of beam becomes longer,it is possible that new extensional fractures will occur in the fixed end.  相似文献   

15.
Regional estimates of aquifer recharge are needed in data-scarce regions such as the Basin of Mexico, where nearly 20 million people are located and where the Basin’s aquifer system represents the main water source. In order to develop the spatio-temporal estimates of aquifer recharge and to analyze to what extent urban growth has affected aquifer recharge, this work presents a daily soil water balance which uses different vegetation and soil types as well as the effect of topography on climatological variables and evapotranspiration. The soil water balance was applied on a daily time step in the Basin of Mexico for the period 1975–1986, obtaining an annually-lumped potential recharge flow of 10.9–23.8 m3/s (35.9–78.1 mm) in the entire Basin, while the monthly values for the year with the largest lumped recharge value (1981 = 78.1 mm) range from 1 m3/s (0.3 mm) in December to 87.9 m3/s (23.7 mm) in June. As aquifer recharge in the Basin mainly occurs by subsurface flow from its enclosing mountains as Mountain Block Recharge, urban growth has had a minimal impact on aquifer recharge, although it has diminished recharge in the alluvial plain.  相似文献   

16.
库木库里盆地位于青藏高原北缘,与柴达木盆地一山之隔,是二者的过渡地带,也是高原主体部分向NE扩展的前缘地区;现今构造表现为被3条大型活动构造带(走滑的阿尔金断裂带、东昆仑断裂带和逆冲的祁漫塔格褶皱逆冲系)所夹持。因此,该盆地对于研究青藏高原北缘的构造活动性、活动历史,探讨高原的扩展模式具有十分重要的意义。虽然库木库里盆地南、北两侧均发育活动性很强的大型走滑断裂,但是在盆地中央发育1条大型背斜,走向NWW-SEE,与祁漫塔格褶皱逆冲系和柴达木盆地内的褶皱构造走向一致,说明盆地目前遭受NNE向的挤压。通过对盆地地形横、纵剖面和阶地展布形态的分析,得出背斜有自西向东扩展变形的特征;野外调查和测年结果显示,背斜东段冰川融水形成了大型冰水扇,形成年龄为(87.09±2.31)~(102.4±3.7)ka,进而获得背斜东段自晚更新世以来平均隆升速率的最大值为(2.78±0.28)~(3.28±0.28)mm/a。库木库里盆地整体的活动性很强,在构造上与其北边的柴达木盆地类似,都受控于阿尔金断裂南侧的NNE向的区域挤压作用。  相似文献   

17.
New major and trace element and Sr–Nd isotope data are presented for basaltic glasses from active spreading centers (Central Lau Spreading Center (CLSC), Relay Zone (RZ) and Eastern Lau Spreading Center (ELSC)) in the Central Lau Basin, SW Pacific. Basaltic lavas from the Central Lau Basin are mainly tholeiitic and are broadly similar in composition to mid-ocean ridge basalts (MORB). Their generally high 87Sr/86Sr ratios, combined with relatively low 143Nd/144Nd ratios are more akin to MORB from the Indian rather than Pacific Ocean. In detail, the CLSC, RZ and ELSC lavas are generally more enriched in large ion lithophile elements (Rb, Ba, Sr, and K) than average normal-MORB, which suggests that the mantle beneath the Central Lau Basin was modified by subducted slab-derived components. Fluid mobile/immobile trace element and Sr – Nd isotope ratios suggest that the subduction components were essentially transferred into the mantle via hydrous fluids derived from the subducted oceanic crust; contributions coming from the subducted sediments are minor. Compared to CLSC lavas, ELSC and RZ lavas show greater enrichment in fluid mobile elements and depletion in high field strength elements, especially Nb. Thus, with increasing distance away from the arc, the influence of subduction components in the mantle source of Lau Basin lavas diminishes. The amount of hydrous fluids also influences the degree of partial melting of the mantle beneath the Central Lau Basin, and hence the degree of melting also decreases with increasing distance from the arc.  相似文献   

18.
New paleomagnetic investigation was carried out on the late Neogene fluviolacustrine sequence of the Yuanmou Basin, located near the southeastern margin of the Tibetan Plateau. Magnetostratigraphic results indicate nine reverse magnetozones (R1 to R9) and eight normal magnetozones (N1 to N8) in the sedimentary profile, which can be correlated to the geomagnetic polarity timescale from C3n.3r to C1r.1r. The age of the sedimentary sequence of the Yuanmou Basin can thus be paleomagnetically constrained to an interval from early Pliocene to Pleistocene, with sedimentation rates varying from 12.5 to 55 cm/kyr. In addition to its highly resolved magnetostratigraphic sequence, the Yuanmou Basin provides a record of Plio-Pleistocene tectono- and climato-sedimentary processes. The mean declinations of the seventeen polarity units (excluding samples with transitional directions) can be grouped into three distinct directional intervals, Group I (2.58–1.37 Ma), Group II (4.29–2.58 Ma) and Group III (4.91–4.29 Ma). These directions indicate that the Yuanmou Basin has probably experienced vertical-axis clockwise rotation of about 12° from 1.4 Ma to 4.9 Ma, which may be related to slip activity of the Red River fault to the southwest and the Xianshuihe–Xiaojiang fault to the east.  相似文献   

19.
The concentrations of222Rn and226Ra in the water column and in the sediments of Santa Barbara and San Nicolas Basins have been measured semi-annually over the last four years. Approximately one-third of excess radon profiles obtained in the water column in these basins can be adequately fit with a one-dimensional eddy diffusion-decay model. Exponential profiles in the center of San Nicolas Basin yield a vertical eddy diffusivity of 26±16 cm2/s and 3.4±1.0 cm2/s for Santa Barbara Basin. The application of a two-dimensional eddy diffusion-decay model to profiles obtained in the center and on the margins of San Nicolas Basin produces a better fit than is found using a one-dimensional vertical eddy diffusivity. The two-dimensional model for San Nicolas Basin predicts a vertical eddy diffusivity of 17 cm2/s and a horizontal eddy diffusivity of 105 cm2/s. These values are in reasonable agreement with those predicted from the vertical buoyancy gradient and the horizontal length scale.The vertically integrated radon excess (standing crop) in the water column of Santa Barbara Basin averages 53±23 atoms/m2 s. This is in good agreement with the flux across the sediment-water interface of 60±15 atoms/m2 s, calculated by measuring radon emanation in the sediments as a function of depth and applying a molecular diffusion-reaction model. Hence, one-dimensional molecular diffusion accurately predicts the flux of radon from the laminated Santa Barbara Basin sediments. In San Nicolas Basin the integrated radon excess in the water column is 376±143 atoms/m2 s, but the diffusive randon flux from San Nicolas Basin sediments averages only 190±53 atoms/m2 s. This descrepancy indicates that a non-diffusive process, probably macrofaunal irrigation, supplies much of the flux of radon from San Nicolas Basin sediments.  相似文献   

20.

The Xunhua, Guide and Tongren Basins are linked with the Laji Mountain and the northern West Qinling thrust belts in the Xunhua-Guide district. Basin depositional stratigraphy consists of the Oligocene Xining Group, the uppermost Oligocene-Pliocene Guide Group and the Lower Pleistocene. They are divided into three basin phases by unconformities. Basin phase 1 is composed of the Xining Group, and Basin phase 2 of the Zharang, Xiadongshan, Herjia and Ganjia Conglomerate Formations in the Guide Group, and Basin phase 3 of the Gonghe Formation and the Lower Pleistocene. Three basin phases all develop lacustrine deposits at their lower parts, and alluvial-braided channel plain depositional systems at upper parts, which constitute a coarsening-upward and progradational sequence. Basin deposition, paleocurrent and provenance analyses represent that large lacustrine basin across the Laji Mountain was developed and sourced from the West Qinling thrust belt during the stage of the Xining Group (Basin phase 1), and point-dispersed alluvial fan-braided channel plain deposition systems were developed beside the thrust and uplifted Laji Mountain and sourced from it, as thrusting migrated northwards during the stage of the Guide Group (Basin phase 2). Evolution of basin-mountain system in the study area significantly indicates the growth process of the distal Tibetan Plateau. The result shows that the Tibetan Plateau expanded to the northern West-Qinling at Oligocene (29–21.4 Ma) by means of northward folded-and-thrust thickening and uplifting and frontal foreland basin filling, and across the study area to North Qilian and Liupan Mountain at the Miocene-Pliocene (20.8–2.6 Ma) by means of two-sided basement-involved-thrust thickening and uplifting and broken foreland basin filling, and the distant end of Tibetan Plateau behaved as regional erosion and intermontane basin aggradational filling during the Pliocene and early Pleistocene (2.6–1.7 Ma).

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