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1.
黄骅坳陷王徐庄油田古近系沙河街组一段下部厚40-50m，由碳酸盐岩与泥页岩互层组成，为湖泊中的碎屑岩-碳酸盐岩混积台地沉积。碳酸盐岩主要为石灰岩，其中包括亮晶颗粒石灰岩、泥晶颗粒石灰岩和泥晶石灰岩。颗粒主要为腹足类，也有鲕粒和内碎屑。根据沉积特征，混积台地可进一步划分为亮晶颗粒石灰岩滩、泥晶颗粒石灰岩滩和滩间等三种相。亮晶颗粒石灰岩滩为高能持续动荡环境，水深在正常浪基面之上，以亮晶颗粒石灰岩沉积为主；泥晶颗粒石灰岩滩为间歇动荡环境，水深在正常浪基面附近，以泥晶颗粒石灰岩沉积为主；滩间为安静低能环境，水深在正常浪基面之下，以泥晶石灰岩和页岩沉积为主。滩主要分布在台地边缘。同生断层的活动控制了台地的形成及滩的展布。亮晶颗粒滩是最好的储集相带，泥晶颗粒滩次之，滩间最差。油气分布主要受沉积相控制，高产井并不是位于构造高部位的滩间，而是位于低部位的亮晶颗粒石灰岩滩。 相似文献
2.
ABSTRACT The world's modern warm-water carbonate platforms are large-scale topographic features. This paper shows that the distribution of platform depths is systematic. The depths to the seafloor of most isolated banks and continent-attached platforms, and the depths to the lagoon floors of most atolls, are all less than 70 m below present sea-level, so that there is a 0–70 m 'depth window'. The depth distribution reflects the platforms' evolution and its controls. The relation of this distribution to Quaternary sea-level fluctuations and sedimentary dynamics sheds light on these controls. 相似文献
3.
塔中地区良里塔格组台缘颗粒滩沉积特征及分布规律 总被引：1，自引：0，他引：1
塔中地区良里塔格组礁滩复合体蕴含着丰富的油气资源。通过钻井、录井、岩芯、薄片及测井等大量资料的综合分析,结合前人研究结果,对塔中I号坡折带上奥陶统颗粒滩类型和特征进行了系统研究。塔中地区良里塔格组台缘颗粒滩包括内碎屑滩、生屑滩、核形石滩、鲕粒滩等类型,具有类型多、发育旋回多以及厚度大的特点。颗粒滩在纵横向上并非是孤立存在的,通常与生物礁伴生,形成纵向叠置,横向指状交叉的礁滩复合体,属油气储集的有利相带。台缘颗粒滩亚相沿塔中I号坡折带呈带状展布,自西向东分布范围逐渐变窄,表现出以（藻）砂屑滩为背景,其他类型颗粒滩呈条带状、块状、点状分布于其间的规律。 相似文献
4.
Ben De Mol Max Kozachenko Andy Wheeler Hugo Alvares Jean-Pierre Henriet Karine Olu-Le Roy 《International Journal of Earth Sciences》2007,96(1):103-120
High-resolution seismic profiles, swath bathymetry, side-scan sonar data and video imageries are analysed in this detailed
study of five carbonate mounds from the Belgica mound province with special emphasis on the well-surveyed Thérèse Mound. The
selected mounds are located in the deepest part of the Belgica mound province at water depths of 950 m. Seismic data illustrate
that the underlying geology is characterised by drift sedimentation in a general northerly flowing current regime. Sigmoidal
sediment bodies create local slope breaks on the most recent local erosional surface, which act as the mound base. No preferential
mound substratum is observed, neither is there any indication for deep geological controls on coral bank development. Seismic
evidence suggests that the start-up of the coral bank development was shortly after a major erosional event of Late Pliocene–Quaternary
age. The coral bank geometry has been clearly affected by the local topography of this erosional base and the prevailing current
regime. The summits of the coral banks are relatively flat and the flanks are steepest on their upper slopes. Deposition of
the encased drift sequence has been influenced by the coral bank topography. Sediment waves are formed besides the coral banks
and are the most pronounced bedforms. These seabed structures are probably induced by bottom current up to 1 m/s. Large sediment
waves are colonised by living corals and might represent the initial phase of coral bank development. The biological facies
distribution of the coral banks illustrate a living coral cap on the summit and upper slope and a decline of living coral
populations toward the lower flanks. The data suggest that the development of the coral banks in this area is clearly an interaction
between biological growth processes and drift deposition both influenced by the local topography and current regime. 相似文献
5.
基于前人研究成果, 综合四川盆地龙王庙组野外露头、钻测井、岩心及薄片等资料, 对龙王庙组的岩石类型、沉积亚相和岩石物性进行了详细的分析, 探讨了龙王庙组颗粒滩沉积组合的特征、分布规律及其对储集层发育的控制作用。结果表明： （1）四川盆地龙王庙组可以识别出4种主要的岩石类型, 垂向上主要发育3种与颗粒滩相关的水体向上变浅的沉积组合： 多期颗粒滩垂向叠置、颗粒滩—台坪（混积潮坪）、滩间海—颗粒滩（—台坪）;（2）颗粒滩沉积组合分布受控于古地貌和海平面升降;平面分布主要受控于古地貌, 多期颗粒滩垂向叠置组合主要发育在川中地区, 颗粒滩—台坪（混积潮坪）组合主要发育在川北、川西南地区, 滩间海—颗粒滩（—台坪）组合主要发育在川东、川东南地区;垂向分布主要受控于海平面升降, 与所处层序地层的位置有密切关系, 滩间海—颗粒滩组合多发育于层序中下部, 颗粒滩—台坪（混积潮坪）, 多期颗粒滩垂向叠置组合发育于层序中上部;（3）多期颗粒滩垂向叠置组合最有利于储集层发育, 其次是颗粒滩—台坪（混积潮坪）组合, 滩间海—颗粒滩（—台坪）组合储集层物性较差。 相似文献
6.
Depositional combination of carbonate grain banks of the Lower Cambrian Longwangmiao Formation in Sichuan Basin and its control on reservoirs 
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下载免费PDF全文 Yang Wei-Qiang Liu Zheng Chen Hao-Ru Lan Cai-Jun Xu Zhe-Hang Lu Chao-Jin Zou Hua-Yao 《古地理学报》1999,22(2):251-265
Rock types, sedimentary subfacies and grain bank properties of the Longwangmiao Formation are studied in detail by outcrop, drilling and logging data, core, thin section and physical property of the Longwangmiao Formation in the Sichuan Basin. The characteristics, development and distribution of grain bank depositional combinations of the Longwangmiao Formation in Sichuan Basin and their control on reservoir development are discussed. The results show that: （1）four main rock types can be identified in the Longwangmiao Formation in Sichuan Basin. Vertically, three upward shallowing depositional combinations associated with carbonate grain bank can be identified: multi-stage vertical overlapping of grain banks, grain bank-tidal flat（mixed tidal flat）, interbank-grain bank（-tidal flat）; (2）the distribution of depositional combinations of grain banks is controlled by paleogeomorphy and sea level fluctuation;and the horizontal distribution is mainly controlled by paleogeomorphy, the vertical overlapping of multi-stage grain banks is mainly developed in the central Sichuan Basin, grain bank-tidal flat（mixed tidal flat）mainly develop in northern and southwestern Sichuan Basin, and interbank-grain bank（-tidal flat）mainly develop in the eastern and southeastern Sichuan Basin;vertically, they are mainly controlled by sea level changes, and have close relationship with their locations in the sequence stratigraphy, and interbank-grain bank（-tidal flat）mostly develop in the middle and lower parts of the sequence, multi-stage vertical overlapping of grain banks and grain bank-tidal flat（mixed tidal flat）develop in the upper part of the sequence; (3）multi-stage vertical overlapping of grain banks is the most favorable for reservoir development, followed by grain bank-tidal flat（mixed tidal flat）combination, and interbank-grain bank（-tidal flat）combination has the poor reservoir physical properties. 相似文献
7.
干旱区土壤种子库的研究进展 总被引：24，自引：0，他引：24
土壤种子库在连接过去、现在和将来的植物种群和群落的结构和动态中起着重要的生态和进化作用,对保护和恢复干旱区植被起着重要的作用。从土壤种子库的研究方法、数量特征、分布格局、时空动态、与地上植被关系、年龄结构及影响因素等方面论述了干旱区土壤种子库研究的若干进展,展望了干旱区土壤种子库的研究趋势。 相似文献
8.
碳酸盐岩颗粒滩是一种十分重要的油气储集体。综合野外露头剖面、岩心、测井、录井及薄片资料,对鄂尔多斯盆地南部地区中寒武统张夏组颗粒滩沉积特征、分布规律及控制因素进行分析。结果表明:研究区张夏组碳酸盐岩颗粒滩沉积广泛发育,以鲕粒滩为典型代表的颗粒滩沉积占绝对优势;颗粒滩岩性主要为颗粒石灰岩、颗粒白云岩和晶粒白云岩3种,颗粒类型主要有鲕粒、生屑、砾屑和砂屑等;颗粒滩纵向上通常表现为下细上粗的反旋回序列,多期旋回垂向叠置,形成相当厚度规模的颗粒滩沉积。结合鄂尔多斯盆地寒武纪岩相古地理特征,认为研究区颗粒滩发育特征及平面展布规律受海平面相对变化、基底古地貌及构造活动综合控制,尤其是鄂尔多斯盆地南部寒武纪近北东向裂陷槽的发育,对张夏组台地边缘带鲕粒滩发育及分布的控制作用更为显著。 相似文献
9.
The contact zone at the base of the Waulsortian (Upper Tournaisian) carbonate mud‐bank complex in western Ireland has been investigated at four localities spaced over a distance of 120 km. At all localities, a transition facies up to 3 m thick, characterized by several types of grumous (clotted and/or peloidal) carbonate muds, immediately underlies the Waulsortian facies. These muds show a developmental sequence provisionally interpreted as a necessary precursor to the formation of Waulsortian polymuds. Such pre‐bank precursors produced thin (a few decimetres) units of transition facies. The same mud types also persisted as an aureole around growing banks (mud‐mounds). Migration of the aureole during bank progradation produced thicker units of transition facies. The distribution of skeletal grain types in the Waulsortian banks, the transition facies and the ‘background’ argillaceous bioclastic limestones show two trends: one regional and one local. The regional trend is expressed by progressive north–south attenuation and, in some cases (for example, plurilocular foraminifera), the disappearance of organism groups. It parallels changes in Waulsortian Phases (defined by skeletal grain‐type assemblages) and is thought to indicate a southerly increase in water depth. The local trend, which occurs only in the two southern localities (deeper water), expresses differences between the skeletal grain content of the various lithofacies. These differences result partly from increased sensitivity to substrate texture by organism groups suffering southward attenuation (notably gastropods, hyalosteliid sponges, aoujgaliids, Earlandia and kirkbyacean ostracods) and partly from selective colonization, particularly of the transition facies, by tabulate corals and stick/ramose bryozoans. However, the developmental sequence of precursor carbonate muds is the same at all localities, indicating that the mud‐making process (probably microbial) was independent of water depth. 相似文献
10.
礁、礁丘、丘同属碳酸盐建隆,礁、滩是重要勘探目的层。但各自在沉积组分、组构、环境和时空分布,以及油气地质条件上迥然不同,因而无论从理论还是勘探实践上,都有必要将其各成体系划分开来。礁滩自身为好储集岩,当建设性成岩作用叠加后可形成好的储层。碳酸盐岩优质储层形成,主要受沉积微相与建设性成岩作用两大因素控制。前者是基础,并以高能的礁滩相带为最好;后者主要包括破裂、白云石化和溶蚀三大类,并以白云石化或溶蚀为最优,其中的溶蚀分布最广泛、影响最深刻而对优质储层形成起决定性作用。礁滩储层中的古岩溶类型最为丰富多彩,包括同生期、准同生期、表生期和埋藏期热流体岩溶的所有类型,白云岩化礁滩体也不例外。其中,同生-准同生期岩溶的形成机制与礁滩沉积时高频层序旋回向上变浅序列的短暂暴露淋溶有关,表生期岩溶则受控于礁滩沉积后三级层序旋回Ⅰ型界面的暴露淋溶。由此,导致礁滩储层中除了可以也是(碳酸盐岩中)唯一保存原生孔隙外,还发育了次生溶蚀孔洞缝和大型溶洞。礁丘、灰泥丘尤其是丘间洼地中发育高有机质丰度烃源岩;它们自身没有有效的原生孔隙,但岩溶作用可以形成次生孔隙。 相似文献
11.
鄂尔多斯盆地中部马家沟组地层蕴含丰富的油气资源,以马五7亚段为主要储集层位的盐下碳酸盐岩油气勘探近期取得了重要突破。基于钻井、测录井、岩芯及薄片等资料,对盆地中部马五7亚段颗粒滩沉积特征、纵横向展布规律进行综合分析,进而探讨了研究区沉积古地理格局及其颗粒滩发育控制因素。结果表明:研究区马五7亚段主要由晶粒白云岩及各类型颗粒白云岩构成,纵向上发育潟湖-颗粒滩-灰泥丘-台坪、潟湖-颗粒滩-滩间海-颗粒滩、潟湖-颗粒滩-灰泥丘三种沉积相序,颗粒滩位于向上变浅旋回的中上部,且常与微生物丘构成丘滩复合体建造,具有良好的储集意义。横向上,马五7亚段发育两套较大规模的颗粒滩,层位稳定且连续性较好,整体表现为中西部厚而东部较薄的特征,平面上则呈南北向发育并沿东部凹陷环带状分布。研究区沉积规律表明马五7亚段相对缺乏潮坪相沉积特征,推测其沉积环境更符合局限-蒸发台地。沉积期海平面的频繁变化控制了滩体发育规模及其垂向叠置样式,区内西高东底的古构造格局及其内部的微地貌起伏则决定了马五7颗粒滩平面分布的差异性。 相似文献
12.
三峡水库峡谷区矗立着大量岩溶不稳定库岸,危及长江黄金水道安全。采用野外勘查和力学分析,对三峡库区碳酸盐岩区岩溶作用与斜坡破坏关系进行深入研究。野外勘查发现,三峡库区碳酸盐岩库岸存在许多与溶洞、溶隙、溶蚀带、溶槽、溶沟等表层岩溶作用有关的斜坡不稳定现象。巫峡段库岸内共发育岩溶地质灾害及隐患点186处,其中滑坡隐患点37处,大型以上危岩体6个。岩体力学分析表明:强降雨、蓄水和岩体劣化会因为有效应力减少、强度下降而造成破裂的节理/裂隙逐渐扩大。同时,水位变动带岩体劣化的裂缝扩展速率比三峡的平均溶蚀率高出约1 300倍,极大地加快了已经进入屈服状态的不稳定岩体的演化进程。溶蚀作用是岩溶岸坡中最基本的作用,库水长期波动加快了岩溶岸坡演化。本次研究将为三峡库区峡谷段不稳定库岸识别和防灾减灾提供技术支撑。 相似文献
13.
川西北中二叠统栖霞组发育厚层白云岩储层,成为近年来四川盆地油气勘探开发的重点领域,但栖霞组有利相带分布和储层发育的主控因素并不明朗,制约了该地区油气勘探进展。根据野外露头、岩心、薄片、测井和地震资料,结合区域地质演化,对川西北栖霞组沉积特征、沉积格局以及古地貌进行研究发现:川西北栖霞组主要为碳酸盐岩台地沉积,自西北向东南方向依次发育盆地—斜坡相、台地边缘相和开阔台地相,并发育台缘滩或台内滩等若干亚相类型。其中栖一期沉积水体较深,为弱镶边碳酸盐岩台地形成期,台缘滩厚度薄,展布范围有限;栖二期为栖霞组主要成滩期,滩体厚度大,展布范围广,具典型镶边碳酸盐岩台地特征。栖霞组白云岩主要为台地边缘高能滩相沉积背景,栖霞组沉积期,研究区具西北高、东南低,西南高、东北低的古地貌格局,其不仅控制着台地边缘高能滩相的沉积分布,并进一步为该区白云岩储层发育奠定了基础,白云岩具有西北向东南、西南向东北逐渐减薄的特点。结合沉积演化和古地貌分析结果,认为古地貌为栖霞组白云岩发育的主要控制因素,西北及西南方向等古地貌高地为研究区栖霞组白云岩储层发育的有利沉积相带。 相似文献
14.
川东北下三叠统飞仙关组白云岩的地球化学特征 总被引：8，自引：1，他引：7
四川盆地川东北部下三叠统飞仙关组是我国重要的天然气储集层,白云石化的鲕粒滩为主要的油气储集层,鲕粒滩主要发育在川东北碳酸盐台地的边缘,台地内主要为泥晶碳酸盐岩夹蒸发岩。鲕粒滩在不同程度上发生白云石化并形成鲕粒白云岩,一些研究者把它们看成近地表混合水白云岩,但飞仙关组鲕粒白云岩的微量元素铁和锰、白云石的阴极发光、白云岩的稳定同位素C和O值、87Sr/86Sr比值等特征表明这些白云岩具有埋藏成因的证据。下三叠统飞仙关组白云岩具有暗红色阴极发光,微量元素Fe为600×10-6~1000×10-6,Mn为14×10-6~78×10-6,稳定同位素氧组分为-6.73~-3.65‰（PDB）,（平均值为-4.89‰PDB）,稳定同位素锶（87Sr/86Sr）为0.707 35~0.708 00。薄片下可以看到白云石沿着裂缝交代,上述的特征表明白云岩在埋藏条件下形成的。 相似文献
15.
准确建立四川盆地龙王庙组沉积模式和精细刻画颗粒滩时空分布规律,是提高天然气勘探成功率的关键。依据野外露头、钻井、测井和地震等资料,综合分析四川盆地及周缘下寒武统龙王庙组沉积相类型及特征;以四级层序为单元,精细刻画等时地层格架内沉积相时空展布特征,建立沉积模式,揭示颗粒滩发育规律,指出下一步天然气勘探方向。结果表明: (1)四川盆地及周缘龙王庙组发育典型浅水碳酸盐岩镶边台地沉积体系,自盆地西缘向东依次发育混积潮坪、局限台地(颗粒滩、云坪和咸化潟湖等微相类型)、开阔台地(颗粒滩、灰坪等微相类型)、台地边缘和斜坡—盆地等沉积相类型;(2)建立了“一凹两隆,双滩成带”的沉积模式,颗粒滩的发育主要受控于古地貌和相对海平面升降,具体表现为垂向上主要发育于四级层序海退时期,平面上沿台地边缘带和围绕咸化潟湖的相对隆起区呈带状分布。由于颗粒滩是优质储集层发育的有利相带,因此该结果可为四川盆地寒武系龙王庙组下一步天然气勘探提供沉积地质基础。 相似文献
16.
Sedimentary facies and model of shallow water carbonates platform of the Lower Cambrian Longwangmiao Formation in Sichuan Basin 下载免费PDF全文
下载免费PDF全文 Liu Zi-Liang Deng Kun Shi Ze-Jin Tian Ya-Ming Wang Yong Shen Fang Tan Qian Gong Xiao-Xing 《古地理学报》1999,22(3):504-522
Building the sedimentary model accurately and delineating the spatial-temporal distribution of grain bank are the keys to increase the rate of success in natural gas exploration. Thus,the types and characteristics of sedimentary facies of the Longwangmiao Formation in the Sichuan Basin were studied based on field outcrops,drilling,logging and seismic data. Taking a fourth-order sequence systems tract as a unit,the spatial-temporal distribution characteristics of sedimentary facies within the chronostratigraphic framework were precisely described,and the depositional model of the Longwangmiao Formation was established to reveal the development mechanisms of grain bank and point out the future natural gas exploration. The results showed that: (1)The typical shallow carbonate platform depositional system was developed in the Longwangmiao Formation of the Sichuan Basin and its surrounding areas. Mixed tidal flat,restricted platform(microfacies types including grain bank,dolomitic tidal flat,lagoon,and gypsum lagoon),open platform(microfacies types including grain bank,lime tidal flat),platform margin,and slope-basin were developed from the edge to the interior of the basin;(2)A sedimentary model was established,which was characterized by “one depression,two uplifts,and two grain banks in the form of belts”. The development of grain banks was mainly controlled by palaeo-topography and relative sea-level fluctuation. It was mainly developed in the highstand systems tract of a fourth-order sequence vertically,and distributed as a belt along the platform margin and around the lagoon area horizontally. Our paper pointed out the grain shoal deposits are the material basis for the development of high-quality reservoirs,the results thus provide a sedimentary geological basis for future natural gas exploration of the Cambrian Longwangmiao Formation in the Sichuan Basin. 相似文献
17.
This investigation used two approaches to examine the flux of bank-derived carbonate particles and determine the potential influence of benthic carbonate particle dissolution on the carbon chemistry of the waters around the Hawaiian Archipelago. First, the particle flux near several representative carbonate banks in the Hawaiian Archipelago was measured and compared with the flux at a distal site (ALOHA) approximately 100 km north of Oahu, Hawaii. The results of four sediment trap deployments on three carbonate banks in the Hawaiian Archipelago demonstrate that the flux of bank-derived carbonate particles are consistently one to two orders of magnitude higher than the fluxes at the distal station. Furthermore, the mineralogy of the carbonate flux near the banks, which includes very soluble bank-derived aragonite and magnesian calcite particles, is distinctly different from that of the distal fluxes. Second, the chemistry of the waters at each bank station along the archipelago was characterized and compared with the chemistry of the distal waters to determine if differences in the particle flux were reflected in the carbon chemistry. Higher alkalinity and carbonate ion concentrations were observed around all of the banks studied. The saturation state of these waters suggests that the dissolution of some magnesian calcite and aragonite phases could explain the higher alkalinity values. Calculations suggest that the dissolution of benthically-derived aragonite and magnesian calcite may be an important component of the North Pacific alkalinity budget and a potential sink for anthropogenic CO2. 相似文献
18.
Combination Patterns and Depositional Characteristics of Ordovician Carbonate Banks in the Western Tarim Basin,China 总被引：2，自引：0，他引：2
HU Xiaolan FAN Tailiang GAO Zhiqian YU Bingsong CHEN Xiaozhi WANG Hongyu WANG Jianping LI Rangbin DING Meng and LI Yifan 《《地质学报》英文版》2012,86(4):894-911
The combination patterns and depositional characteristics of the carbonate banks are investigated based on outcrop sections, thin sections, and carbon isotopes of Ordovician in the western Tarim Basin, China. Four carbonate bank combination patterns are deposited in the Ordovician, western Tarim Basin, including: Reef-Bank Complex (RBC), Algae-Reef-Bank Interbed (ARBI), Thick-Layer Cake Aggradation Bank (TLCAB), and Thin-Layer Cake Retrogradation Bank (TLCRB). All combination patterns show clear periods vertically. The RBC is mainly composed of reefs and bioclastic banks, and the dimension of the RBC depends on the scale of the reefs. Bioclastic banks deposits surround the reefs. The range of the ARBI is determined by the scale of algae-reefs, algae peloid dolomite microfacies and algal dolomite microfacies deposit alternating vertically. TLCAB and TLCRB are deposited as layer-cakes stacking in cycles and extending widely with cross bedding developed. The grains of TLCAB and TLCRB are diverse and multi-source. With the impacting of relative sea level change, biological development and geomorphology, the ARBI, TLCAB or TLCRB, RBC are successively developed from the Lower Ordovician Penglaiba Formation to the Middle Ordovician Yijianfang Formation. The depositional environment analysis of Ordovician indicates that the RBC and ARBI can form effective oil and gas reservoirs, and the TLCAB and TLCRB have the potential to form the huge scale oil and gas reservoirs and to be the crucial targets of exploration for the Ordovician carbonate banks in the future. 相似文献
19.
塔中I号坡折带上奥陶统台缘礁滩复合体建造模式 总被引：3，自引：0，他引：3
塔中Ⅰ号坡折带的台缘高能区发育上奥陶统良里塔格组礁滩体,主要包括生物礁丘、灰泥丘、粒屑滩、滩间海等沉积类型,纵向上表现为粒屑滩、灰泥丘、礁丘的多旋回组合。单个礁滩复合体下部发育粒屑滩,上部为灰泥丘和(或)礁丘,之上为下一旋回的粒屑滩亚相所覆盖。横穿宽3～10km的区域,特别是台地边缘向陡坡转折的高地为礁生长相对集中区,而向内侧则更多出现滩相。不同沉积期礁滩单元分布范围不同,从良三段到良一段沉积期间内呈现逐步向塔中Ⅰ号坡折带迁移的缩减趋势。经后期多次成岩作用和构造破裂的改造,形成沿台缘分布且具有非均质性变化的礁滩型储层。 相似文献
20.
Erosional marks, including grooves, current crescents and flutes, are present on banks and slump blocks of the Rupen River on the semi-arid plains of north-west India. The channel has a width:depth ratio of 6, and is incised up to 8 m through well consolidated, fine-grained aeolian sediment dated at ～ 20–60 ka. Pedogenic carbonate nodules embedded in the channel walls have localized scour, and reworked carbonate particles probably promoted corrasion during strong seasonal flow. Similar erosional marks are apparently scarce on modern river banks, and a distinctive combination of conditions, including a consolidated substrate and strong flow in a confined channel, is probably required for their generation and preservation on channel walls and on slump blocks. 相似文献