风成沉积物中不同粒径石英颗粒表面机械结构的变化特征

按搬运方式将风成石英颗粒分级,逐级测量并统计表面机械结构的类型、数量和大小,并计算其面积。发现悬移为主的颗粒表面结构的类型、数量最少,仅见少量不规则坑、V形坑,在颗粒表面分布面积最小;跃移搬运为主的颗粒表面结构类型最丰富,不规则坑、蝶形坑、V形坑、新月形坑、贝壳状断口大而深,在颗粒表面的分布面积最大;滚动搬运为主的颗粒表面结构数量最多,以小而浅的不规则坑为主,伴有Ⅴ形坑、贝壳状断口等,在颗粒表面的分布面积大小适中。不同搬运方式在石英颗粒表面形成的结构不同,撞击频率、颗粒大小、搬运速度共同影响表面结构的发育,高撞击频率、大粒径可以形成并承载更多的表面结构,大动能撞击可形成多种类且大尺寸的表面结构。在借助石英颗粒表面结构进行成因判别时需根据粒径大小选择相应粒级的石英颗粒表面结构特征组合,以及结构的数量、大小特征等进行综合判别。     

Fate and identification of oil-brine contamination in different hydrogeologic settings

Past disposal of oil-field brine at the surface has caused substantial contamination of water resources in Kansas. Natural saline water occurs in and discharges from Permian bedrock in parts of the state, and other anthropogenic sources of saline water exist, requiring clear identification of different sources. Time-series analysis of Cl⁻ concentration and streamflow relative to pre-contamination contents, and end-member mixing plots, especially for Br⁻ and Cl⁻, are practical methods for source differentiation and quantification. Although regulations preventing escape of saltwater from oil wells were first passed in Kansas in 1935, much oil and gas brine was disposed on the surface through the 1940s. Hydrogeologic characteristics of the areas with past surface disposal of oil brine differ appreciably and result in large differences in the ratio of saltwater transported in streams or ground water. Much of the brine disposed during the 1910s to 1940s in an area of silty clay soils overlying shale and limestone bedrock in south-central Kansas soon ran off or was flushed from the surface by rain into streams. Chloride concentration in the rivers draining this area often exceeded 1000 mg/L after the start of oil production up to the 1950s. Chloride content in the rivers then generally declined to about 100 mg/L or less in recent low flows. Oil brine was also disposed in surface ponds overlying the unconsolidated High Plains aquifer in south-central Kansas from the latter 1920s into the 1940s. Most of the surface-disposed brine infiltrated to the underlying aquifer. Where the High Plains aquifer is thin, saltwater has migrated along the top of clay layers or the underlying shaly bedrock and either discharged into small streams or flowed into thicker parts of the aquifer. Where the aquifer is thick, surface-disposed oil brine moved downward until reaching clay lenses, migrated latterly to the edge of the clay, and again moved downward if still dense enough. Water-level declines from pumping have increased the lateral migration rate of the saltwater contamination in the aquifer towards water-supply wells. The period of flushing most of the surface-disposed saltwater from the area of shale and limestone bedrock is on the order of many decades but is at least many centuries for the deeper parts of the High Plains aquifer.     

湖南衡阳盆地东缘白垩系风成沉积的发现及其古环境意义

首次报道了湘中南衡阳盆地东缘上白垩统红花套组中的风成沉积,重新认识了该地区晚白垩世时期的古地理环境。研究区红花套组主要出露一套紫红色块状中-细粒长石石英砂岩、岩屑石英砂岩,普遍见指示风成沙漠环境的巨型板状、楔状交错层理、双向交错层理、平行层理以及典型的风棱石;镜下不含泥质、云母等悬移组分,电镜下可见碟形坑、新月形撞击坑、上翻（平坦）节理片等,综合分析后确认该套砂岩为风成沉积。该套风成砂岩具有重要的古环境意义:风成砂岩的发现,指示该时期为干热气候,沙漠化、盐湖化明显,食物的短缺可能导致衡阳盆地一带恐龙的迁徙;依据沙丘前积纹层倾向特征,恢复了湘中南乃至湖南地区的地表风带特征,为佐证衡阳盆地与其周缘红盆相连通提供一种新的依据。该发现为湖南省的风成沉积领域提供了宝贵的研究材料。     

Weathered bedrock as a source of sand and gravel aggregate in north-eastern New South Wales, Australia

 The most commonly recognized sources of sand and gravel aggregate are the deposits of coastal, fluvial and glacial sedimentary processes. It is not commonly recognized that weathered bedrock is also an important source of sand and gravel aggregate. In the case of weathered sedimentary bedrock the product may be indistinguishable from modern sedimentary materials and deposits may be misidentified. Batson's quarry is a major sand and gravel aggregate resource for the rapidly developing region of north-eastern New South Wales. The deposit has previously been assumed to be a young sedimentary deposit, but detailed field examination and comparison with surrounding rock types indicates that it has formed from weathered Mesozoic sandstone bedrock. The extraction of weathered bedrock aggregate deposits has distinctive environmental implications because, unlike sedimentary aggregates, they are not restricted by the geometry of sedimentary environments and do not necessarily interfere with surface drainage systems. This study shows that the recognition of the geological origin of a resource is essential in order to determine its potential geographical extent, and thereby maximize its utilization and minimize land use conflict. Received: 3 January 1996 / Accepted: 1 November 1996     

Glacial deposits at Wylfa Head,Anglesey, North Wales: Evidence for Late Devensian deposition in a non-marine environment

The nature and origin of glacial sediments at Wylfa Head are described, and their significance with regard to sedimentary environments during Late Devensian deglaciation of the Irish Sea Basin is discussed. Recent models of deglaciation under glaciomarine conditions are challenged. The Quaternary sequence at Wylfa consists of eroded and glaciotectonically deformed bedrock, locally derived lodgement till, calcareous silt-rich lodgement till containing northern erratics, discontinuous units of orange-brown silty sand of possible aeolian origin, and grey laminated freshwater silts filling a small kettle hole. The till units thicken to the south where the surface is drumlinised. It is concluded that the landforms and deposits result from a warm-based Irish Sea glacier, which moved towards the southwest. Spatial variation in basal water pressure resulted from localised drainage through zones of more heavily jointed bedrock. Rapid glacial erosion occurred in areas where subglacial water pressure was relatively high, while deposition of the resulting basal sediment took place where water pressures were reduced. The glacier also carried basal calcareous silty till onshore, which was deposited by lodgement processes. None of the deposits at Wylfa are interpreted as glaciomarine in origin, and there is no evidence at this site for an isostatically induced marine transgression prior to deglaciation.     

薄基岩浅埋煤层覆岩破坏移动演化规律研究

以榆阳煤矿为研究基地,进行了地下水动力学参数、覆岩力学组合结构特征与基岩风化带的阻隔水特性试验。结果表明,风积沙层底部为强含水层;主采煤层上覆覆岩泥岩强度高于砂岩;砂岩孔隙率高,含水率大,抗压、抗拉强度比值高;泥岩和砂岩的黏土矿物含量低、具有典型的脆性易裂、抗扰动能力差和再生隔水能力弱等新的破坏移动特性,并通过多因素拟合,确立了薄基岩浅埋煤层覆岩采动破坏“两带”高度的动态变化特征,提出了长壁工作面开采防止突水溃砂的调控技术,成功应用于榆阳煤矿并实现绿色保水开采,为陕北榆神大煤田薄基岩浅埋煤层进一步推广高效开采技术和保护生态环境实现绿色保水开采奠定了基础。     

克里雅河沿线沙丘沉积物石英砂表面特征分析

对沙漠内部典型河流沿线沙丘石英颗粒表面微形态特征的系统研究尚少。沿塔里木盆地南缘克里雅河下游丹丹乌里克、喀拉墩、圆沙古城、北方墓地及其北部塔里木河一带的沙丘顶部采到5件表沙样品。扫描电镜观察172颗经能谱挑选的石英颗粒表面微形态,筛析法测定5件样品的粒度。结果表明:1）丹丹乌里克样品以极细沙为主,其余均以细沙为主,各样品几乎不含黏土;2）样品磨圆度特征以次棱和次圆状为主,圆状很少,未见棱状特征,次棱状与次圆状特征之间消长关系显著,沙漠南北边缘样品的次棱状特征出现频率较腹地高;3）颗粒中V形坑频率呈现出沙漠边缘较高腹地低的特征,而沙漠边缘的化学作用结构特征低于腹地。石英砂表面特征结构以机械作用为主,同时伴生化学环境作用特征,可认为克里雅河下游沙物质包括了河流、冰川与戈壁成因及风输送而来的颗粒;颗粒表面特征总体新鲜,沙丘应较年轻。纵穿塔克拉玛干沙漠沉积物样品的表面微形态观察与粒度测定,为该地区沉积环境分析与沙丘砂溯源研究增添了新数据。     

中国海岸带晚更新世风成沉积分区、序列特征及其气候—环境意义

本文提出海岸风沙沉积和海岸风尘沉积是晚更新世期间,由东北季风风系控制的风沙流活动所成。每一期风沙流活动的时限不恒定,其盛行风向前缘随着风力衰减而产生风尘沉积,形成海岸风沙—海岸风尘沉积匹配带。中国海岸带自北而南可划分出四个海岸风沙—海岸风尘沉积匹配区。海岸风沙－海岸风尘沉积均具有多发、高频变化特征,与其中交互更叠的土壤层、冲－洪积层、侵蚀间断面等一起,可成为晚更新世期间气候－环境判别的标志。     

黄河源区玛多县沙漠化成因与发展过程

通过分析黄河源区玛多县沙漠化的成因和过程,结果表明,玛多县沙漠化成因类型有三种,分别为固定沙丘/古沙丘活化、滑塌陡坎及风蚀斑块,其形成都与多年冻土退化相关.在固定沙丘或古沙丘分布区,冻土退化导致热融沉陷,形成沉陷坑,沉陷坑边缘形成拉裂缝或陡坎,使下伏松散沙露出.在斜坡上,冻土退化形成滑塌陡坎,使底层土壤从侧面暴露.在平坦的冲积平原,差异性冻胀和融沉导致草皮拉裂,形成积水坑洼,冻土退化导致土壤变干,土壤的底层暴露.下伏风成沉积物暴露后,遭受风蚀,形成侧向凹槽,致使上部土体坍塌,使更多的风成沉积物暴露,这些过程的不断重复,使风蚀坑、陡坎、风蚀斑块扩大相连,最终形成流动沙丘、风蚀劣地、戈壁等地貌.     

内蒙古赤峰召庙花岗岩表面的冰川壶穴、泄水槽、盐风化穴和剥离面理

在内蒙古赤峰市巴林左旗林东镇以南约20 km的召庙, 出露一片面积约20 km2的花岗岩, 称为召庙花岗岩体。该岩体被至少2组垂直节理及与地面起伏一致的剥离面理切割成大小不等的弧形岩块, 构成高于周围地表300~400 m的花岗岩山区。在多条花岗岩山脊上保存有大小不等的壶穴, 山脊两侧则发育从上到下紧密排列的泄水槽, 而泄水槽则被剥离面理横向切割, 沿剥离面理的露头线发育大小不等的风化穴。通过详细的野外调查, 认为花岗岩山脊上的壶穴不是风蚀和风化所致, 而是晚更新世冰盖上的冰川融水下泄冲刷形成的; 山脊两侧的泄水槽也是冰川融水下泄冲刷的结果; 剥离面理是第四纪冰川发育导致地表之下岩石温度变化的热变应力所致, 可用于恢复第四纪冰川作用时期的基岩古地貌; 盐风化穴是第四纪冰川退缩后本区重要的物理风化类型, 优先沿着剥离面理发育。本区3种微型地貌景观和大型的剥离面理共生组合记录了更新世以来召庙花岗岩山区的地貌演化史。     

Synchronism of Holocene East Asian monsoon variations and North Atlantic drift-ice tracers

Eighteen radiocarbon-dated eolian and paleosol profiles within a 1500-km-long belt along the arid to semi-arid transition zone of north-central China record variations in the extent and strength of the East Asian summer monsoon during the Holocene. Dated paleosols and peat layers represent intervals when the zone was dominated by a mild, moist summer monsoon climate that favored pedogenesis and peat accumulation. Brief intervals of enhanced eolian activity that resulted in the deposition of loess and eolian sand were times when strengthened winter monsoon conditions produced a colder, drier climate. The monsoon variations correlate closely with variations in North Atlantic drift-ice tracers that represent episodic advection of drift ice and cold polar surface water southward and eastward into warmer subpolar water. The correspondence of these records over the full span of Holocene time implies a close relationship between North Atlantic climate and the monsoon climate of central China.     

Wind erosion of the wind-deposited Navajo Sandstone, USA

Outcrops of the Early Jurassic Navajo Sandstone in southern Utah and northern Arizona, south-western USA are being actively eroded by sand-laden, south-westerly winds. Small-scale stepped topography with risers facing into the wind develops even on steep canyon walls when wind-swept grains strike the rock at a low angle. Photosynthetic, endolithic microbes directly underlie most outcrop surfaces; the crusts formed by these organisms are essential to formation of the small-scale steps. Wind erosion of highlands also forms troughs and pits that are tens of metres across. The pits have deeply scalloped, overhanging walls, and contain central domes surrounded by 'moats' filled with dune sand. Wind erosion of aeolian sandstone is favoured by a positive feedback mechanism in which grains that are liberated from outcrops by impacting particles become a fresh supply of pre-sorted abrasive particles for further attack.     

江西信江盆地晚白垩世风成沙丘的发现及其古风向

长期以来,江西信江盆地晚白垩世圭峰群塘边组(K2t)均定为水成沉积,本文的研究结果则认为属风成沉积.沉积结构、构造和石英沙颗粒表面特征研究结果表明,该组的主体岩性为紫红色中-细粒净砂岩,基本不含泥质和云母等悬移质,大型高角度平板状交错层理发育,层系厚度巨大,风成沙丘前积层特征明显,石英沙磨圆度好,在电子显微镜下普遍可见风成沙特有的碟形撞击坑、新月形撞击坑和毛玻璃化表面特征,属于风成沙丘沉积.古流向恢复表明,信江盆地以西风为主,东北风为次,同时见有少量东南风与西北风.根据当时的古地理格局及地表风带模式判断,研究区位于当时的北半球西风带和东北信风带之中,同时可能存在东南向和西北向的古季风.     

西宁黄土碎屑锆石年龄特征及其 对黄土高原黄土物源的指示意义

物源研究是理解黄土高原风成沉积物中古环境记录的关键一环。众多证据表明,黄土高原西北部的阿拉善高原及其周边广袤干旱地区是黄土高原黄土的主要风尘源区。但是,基于锆石U-Pb同位素地质年代学的证据对此提出了质疑。黄土高原黄土与青藏高原北部物质中的锆石具有相似的年龄分布,预示黄土高原风尘主要以西风搬运的方式来自青藏高原北部,特别是柴达木盆地。本研究通过分析西宁黄土的锆石年龄特征验证此假说。西宁处于在从青藏高原北部到黄土高原的假想搬运路线上。西宁黄土主要来自青藏高原北部的干旱区。西宁黄土中锆石的主要年龄分布与黄土高原黄土相似,反映青藏高原北部确实为黄土高原黄土的主要物质来源。但是,与黄土高原黄土相比,西宁黄土缺少年龄在360Ma左右和年龄小于100Ma的锆石。这两组年龄的锆石可能来自其他地区,例如处于中亚造山带。由于阿拉善干旱区也通过河流搬运接收来自青藏高原北部的物质,锆石 U-Pb年龄证据并不能排除阿拉善干旱区作为主要风尘物源的可能。相反,阿拉善干旱区还接受来自其北部中亚造山带和其本身华北克拉通的物质,来自阿拉善干旱区的风尘可能更好地解释黄土高原黄土中的锆石年龄特征。     

鄂尔多斯盆地志靖安塞地区长9油层组沉积相及其沉积演化特征

志靖安塞地区位于鄂尔多斯盆地陕北斜坡中部。以钻井取心观察为基础,结合砂岩厚度、砂地比、自生绿泥石分布、古生物化石分布等因素,对长9油层组2个层段沉积相空间展布特征及沉积演化规律进行研究。结果表明,长9油层组发育一套三角洲-湖泊沉积,北部主要发育三角洲前缘沉积,在南部发育浅湖沉积。长92沉积期,湖盆范围较小,长91沉积期湖盆初始扩张,湖岸线向北推进,湖域面积增大。从长92沉积期到长91沉积期,研究区经历了沉积水体由浅变深的过程,并在长91顶部发育一套具有生烃潜力的高阻泥岩。三角洲前缘水下分流河道砂体是较有利的储集砂体。     

浅水三角洲沉积体系与储层岩石学特征

浅水三角洲已经成为当前沉积学研究和油气勘探的重点领域,浅水三角洲常规和非常规砂岩储层中发现了丰富的油气资源。鄂尔多斯盆地中—古生界发育大型浅水三角洲沉积,结合岩芯、测井、分析化验等资料,对盆地西部地区山1—盒8段浅水三角洲的母岩特征、沉积充填、砂体展布与储层岩石学特征进行研究,为研究区常规砂岩储层和致密砂岩油气勘探提供地质依据。分析表明,研究区南部和北部砂岩重矿物组合相似,以锆石和白钛矿为主。综合La/Yb-REE与Dickinson三角图解、稀土元素配分模式和碎屑锆石定年分析认为,北部物源主要来自盆地西北部阿拉善古陆太古界和元古界花岗岩、片麻岩、石英砂岩,向南影响到陇东地区北部;南部物源主要来自盆地南部北秦岭地区太古界、元古界花岗岩、片麻岩和片岩,向北影响陇东地区中南部。山1段发育曲流河三角洲,盒8段发育辫状河三角洲,孤立型与垂向叠置型水下分支河道砂体是主要的砂体类型。盒8段沉积时期,古湖泊可能萎缩;南北物源形成的三角洲在研究区中部环县东南一带交汇混合。砂岩类型主要为岩屑质石英砂岩、石英砂岩和岩屑砂岩,结构成熟度中等—较差。砂岩成岩改造强烈,水—岩反应复杂,压实作用是储层致密化的主因,多期胶结作用使砂岩的孔喉结构变得十分复杂。孔隙类型以微米—纳米级的岩屑溶蚀孔、剩余粒间孔和高岭石晶间孔为主,整体上属于非常规致密砂岩储层。砂体分布与“甜点”预测是研究区致密油气勘探的关键。     

沙粒不能“远走高飞”———有关“尘暴”的一条根本原理

沙与尘虽然都是岩石物理风化的产物, 但在风力作用下, 习性截然不同。拜格诺用严格的物理实验证明, 尘粒能随风远走高飞, 而沙粒却只能在地面附近跳跃前进。从北方侵袭华北平原的所谓沙尘暴, 实质上都是尘暴。对历次重大天气事件沉积物的分析, 也完全证明了这一点。因此, 尘暴物质的源头不是来自有沙, 而是有尘的地方; 从而可以使人们采取正确的治理方法。      

库车前陆盆地古－新近系铜矿化特征及铜的来源、富集分布初探

库车盆地铜成矿作用发生在新近纪,主要有砂岩型、泥岩型、灰岩型、含石英脉硫化物型铜矿化。矿化主要分布在盆地南部的秋里塔格构造带和北部的克拉苏构造带,基本位于背斜核部偏两翼部位,沿近东西向的断裂带呈带状分布,发育在盐丘附近。主要的地表铜矿物是氯铜矿,为干旱气候条件下含盐盆地的产物。盆地古近系蒸发岩电镜分析、石膏铜含量化学分析及新近系碎屑岩中铜含量变化分析结果表明：盐岩、膏岩,褐红色碎屑岩（粉砂岩、泥质粉砂岩、泥岩）为铜的矿源层,灰绿色粉砂岩、泥岩、灰白色（含砾）中粗砂岩为铜的含矿层。铜离子的运移载体为源自大气降水溶解蒸发岩所形成的卤水,卤水淋滤褐红色碎屑岩中的铜并下渗到地下,在以构造挤压为主及盐构造卸负作用产生流体上涌的驱动力下沿断裂向地表运移,随着卤水温度压力降低,在干旱气候条件下,在地表碎屑岩节理面、部分层理面上盐、膏、铜矿物析出,形成地表砂岩型、泥岩型、灰岩型铜矿化。如果含铜卤水经过被方解石交代的硬石膏带时,遇到由于TSR反应形成的还原硫、氧化－还原化学障,铜会发生富集,可能形成地下铜矿体。     

松辽盆地西斜坡水动力场与油气的聚集成藏

本文以松辽盆地西斜坡大量水化学分析数据和钻井、地球化学等资料为基础,利用对水动力场的计算,通过平面和纵向上的研究认为,西斜坡高台子油层和萨尔图油层地层水化学性质和分布特征较为相似,表明两者间应该存在允许地下流体(包括油气)相互连通的窗口,从而导致高台子油层的规模弱于萨尔图油层;研究区内地层水以压实流和渗入流两种为主,由四周向中心交汇,在水动力方面,泥岩层以向上下排出为主,砂岩层则是顺层向上倾方面流动;寻找有利勘探区应以压实流和渗入流的交汇区为主,在其中以高矿化度的浓缩亚区为主要目标,即高台子油层应富裕构造带以南至泰康隆起带中部,萨尔图油层应以齐齐哈尔至平洋地区为下一步的重点考虑对象.     

Groundwater geochemistry in shallow aquifers above longwall mines in Illinois, USA

 Aquifers above high-extraction underground coal mines are not affected by mine drainage, but they may still exhibit changes in groundwater chemistry due to alterations in groundwater flow induced by mine subsidence. At two active longwall mine sites in Illinois, USA, glacial-drift aquifers were largely unaffected by mining, but the geochemistry of the bedrock aquifers changed during the post-mining water-level recovery. At the Jefferson site, brackish, high-sulfate water present in the upper bedrock shale briefly had lower values of total dissolved solids (TDS) after mining due to increased recharge from the overlying drift, whereas TDS and sulfate increased in the sodium-bicarbonate water present in the underlying sandstone due to downward leakage from the shale and lateral inflow of water through the sandstone. At the Saline site, sandstones contained water ranging from brackish sodium-chloride to fresh sodium-bicarbonate type. Post-mining recovery of the potentiometric levels was minimal, and the water had minor quality changes. Longwall mining affects geochemistry due to subsidence-related fracturing, which increases downward leakage from overlying units, and due to the temporary potentiometric depression and subsequent recovery, whereby water from surrounding areas of the aquifer recharges the affected zone above and adjacent to the mine. Received, December 1998 / Revised, August 1999 / Accepted, August 1999