早白垩世义县盆地义县组顶部金刚山层沉积相及其古环境意义

辽西义县盆地内近东西走向的马神庙-刀把地-三百垄-金刚山一带为义县组标准地层剖面出露地,义县组建阶标准地层剖面枣茨山金刚山层为一套古湖盆相沉积组合。野外详细的沉积学和地层学研究将金刚山层自下而上划分为湖缘碎屑浊流相、浅水湖坪相和半深湖相3个沉积亚相。金刚山层下部湖缘碎屑浊流相包括3个粗-细粒序递变沉积韵律。粗粒岩石单元为灰绿色含长石岩屑凝灰质砂砾岩、杂色砾岩、灰白色含砾凝灰岩;细粒岩石单元由灰白色含砾凝灰岩、灰绿色致密凝灰岩、质纯膨润土组成。韵律沉积底部粗粒岩石单元为浊流头部沉积产物,其中常形成弥散式正粒序递变层理,细粒岩石单元为浊流体部、尾部逐渐稀释的沉积结果,其中常发育水平层理。中部浅水湖坪相沉积由5个膨润土化粉砂岩（质纯膨润土或页岩）-泥灰岩（含方解石细脉灰岩）沉积韵律构成。每一湖坪相的碳酸盐岩与下伏火山灰质沉积厚度之比值变化范围为:0.11~0.47,指示湖盆围缘经历了多期次湖坪沉积时间间隔相等的地质规律。金刚山层上部半深湖相沉积为灰白色纸片状页岩-粉砂质页岩组合。金刚山层下部湖缘火山碎屑浊流沉积指示火山喷发物质近源性、火山喷发多期作用的地质演化规律。中部湖坪相的5个膨润土化粉砂岩（质纯膨润土或页岩）-泥灰岩（含方解石细脉灰岩）沉积韵律指示古湖盆水体至少经历了5期变浅过程,在区域性干旱气候影响下,形成湖坪相泥灰岩沉积。湖盆中心相对深水沉积区接受大量细粒悬浮质沉积,形成静水半深湖相沉积。     

The peterson limestone — early cretaceous lacustrine carbonate deposition in western wyoming and southeastern idaho

The lacustrine Peterson Limestone of western Wyoming and southeastern Idaho comprises six lithofacies throughout its 20,000 km² aerial extent. These are: (1) calcareous sandstone and shale, (2) red nodular limestone, (3) pink sandy micrite, (4) biomicrite, (5) graded silty micrite, and (6) limestone conglomerate. The first two represent floodplain deposition and paleosols, whereas the remaining are shallow nearshore and deeper lacustrine sediments.This sequence was developed in a large fresh, hardwater lake surrounded by fluvial systems and associated flood plains in a warm temperate climate. Well-oxidized sandy terrigenous rocks, together with calcareous paleosol nodules, indicate that flood-plain deposition both preceded and was concurrent with lacustrine carbonate deposition. Micrite and biomicrite formed in deeper parts of the basin while sandy and silty carbonate accumulated in shallower lake-margin areas. Less-calcareous shale units which are interbedded with deeper-water carbonate were deposited either during rapid basin subsidence and deepening of the lake center or during periods of slower carbonate precipitation. Turbidity currents and subaqueous debris flows generated along steeper lake margins, resulted in the deposition of rhythmic layers of graded silty micrite and diamictic limestone conglomerate in the deepest part of the basin. The carbonate-rich sediments comprising these two lithofacies were originally deposited on shallow lake-margin benches and subsequently were transported downslope toward the lake center.Comparison with other carbonate-precipitating lacustrine systems indicates that this lake was not like modern playas. Although no known modern lacustrine system is precisely like Lake Peterson, the flora, fauna, composition, and distribution of facies within modern temperate-region lakes most closely resemble those of the Peterson Limestone.     

Peat-marl deposition in a Holocene paludal-lacustrine basin—Sucker Lake, Michigan

Exceptionally thick (over 15 m) deposits of peat which fill the northern end of Sucker Lake basin in northcentral Michigan document the volumetric importance of allochthonous organic material in a modern coal-forming environment. Organic debris that originates in, and is derived from, a highly vegetated floodplain immediately upstream is deposited as a lakeward-prograding lobe that exhibits features typical of most lacustrine Gilbert deltas, but is composed almost entirely of organic material. This system overlies an additional 7 m of nearly pure, brecciated lacustrine carbonate, deposited as shallow lake-margin benches and emplaced into the deep basin centre by gravity sliding prior to deltaic progradation. In the southern end of the basin, bottomset beds of fine silt-size organic phytoclasts onlap distal facies of progradational bench carbonates, which originate (in shallow water) through calcite encrustation about stems of the dominant macrophyte Chara. With continued sedimentation, a stratigraphic succession in which allochthonous organics will overlie pure, allochthonous lacustrine carbonates and in part be overlain by autochthonous carbonates will characterize the northern end of this Holocene system. In the southern end around the basin margins, however, autochthonous carbonates will entirely underlie allochthonous organics. Numerous continuous cores (up to 22 m) through these units document: (1) the importance of sources of allochthonous organic debris in modern coal-forming complexes, (2) the genetic relationship between nearly pure calcareous and nearly pure carbonaceous facies within these paludal-lacustrine settings, and (3) the complexity of interrelationships between the several component facies within such continental sedimentary systems.     

Sedimentology and isotope geochemistry of lacustrine carbonates of the Oligocene Campins Basin, north-east Spain

The non-marine Campins Basin developed in the Oligocene, during a period of early rifting of the Catalan Coastal Ranges. Lacustrine deposits, interbedded between two alluvial units, comprise shallow and deep lacustrine facies. The lower, shallow lacustrine facies are made up of microbialite buildups and thin limestone beds. In the studied area, these facies are overlain by deep lacustrine facies which consist of alternations of several, metre-thick carbonate- and mudstone-dominated intervals. In addition to calcite, which is characteristic of the shallow lacustrine facies, aragonite and abundant dolomite are present in the deep lacustrine facies. This mineralogical change in the sequence reflects an overall increase in the Mg/Ca ratio of the lake waters. The deep lacustrine sequences are interpreted as having formed in a hydrologically closed basin that was subject to changes in the Mg/Ca ratio of the water, probably related to variations in the evaporation/precipitation rate. The sedimentological, mineralogical and isotopic characteristics of the Campins Basin dolomites suggest that, in general, they are primary in origin. The stable isotope data show an approximate covariance between δ¹³C and δ¹⁸O in the lower shallow lacustrine carbonates (calcite) which suggests that they formed during the onset of closure of the lake. The δ¹³C and δ¹⁸O values of the deep lacustrine carbonates display three different clusters that are roughly related to the carbonate mineralogy. Normalisation with respect to calcite of the isotopic compositions of dolomite and aragonite from the deep lacustrine carbonates allows the integration of all these isotope values into one covariant trend. The sequential appearance of different carbonate minerals and the isotopic covariant trend may indicate an overall evaporative concentration of the lake waters. The change in slope of the covariant trend for the isotope values between the shallow and the deep lacustrine carbonates might reflect the change in the waterbody morphology recorded in the basin fill sequence.     

湖南地区晚奥陶世桑比期—凯迪期早期沉积特征及沉积模式*

湖南地区地处扬子陆块和华夏陆块之间,根据沉积地层的岩石学特征、古生物特征及其他沉积特征变化,将湖南地区晚奥陶世桑比期—凯迪期早期的沉积相,划分为开阔台地相、浅海陆棚相、深水盆地相和陆架边缘—斜坡相。开阔台地相以沉积“龟裂纹”灰岩和瘤状灰岩为特征,浅海陆棚相转为沉积砂质板岩,板岩并夹有粉砂岩及泥灰岩透镜体。深水滞流盆地发育黑色碳质页岩及含放射虫硅质页岩,沉积厚度很小,代表了一个相对缺氧还原的欠补偿深水环境;陆架边缘—斜坡相则为岩屑石英粉—细砂岩,长石石英粉—细砂岩及砂质板岩、板岩的韵律互层,沉积厚度超过1000m,具浊流沉积特征。晚奥陶世桑比期—凯迪期早期,湖南地区总体表现为由西北和东南方向往中部逐渐变深,湘中南一带为水体最深地区。     

广西百色盆地东部古近系那读组湖相灰岩

百色盆地东部田东坳陷那坤地区古近系那读组三段下部发育一套数米至数十米厚的湖相灰岩,岩石以浅灰色-灰色、含大量的螺蚌化石和具核形石结构为特征,间夹有薄层的泥岩、钙质泥质粉砂岩。本文在实测地表剖面和详细观察岩心的基础上,仔细研究了此套灰岩的岩石学特征。依据丰富的原生沉积构造、古生物化石标志以及沉积地球化学、测井相特征将湖相灰岩的沉积相划分为滨湖、颗粒滩、浅湖三个亚相以及灰泥坪、沼泽、颗粒坪、滩缘、滩核、滩间水道、灰泥浅湖、泥质浅湖等八个微相,并详细地研究了各微相的沉积特征。结合该灰岩的区域分布和沉积相的平面展布格局指出沉积相主体属于浅湖的颗粒滩,并提出了相应的沉积相模式。     

新疆巴里坤湖十五万年来古水文演化序列

通过巴里坤湖钻孔岩芯沉积相分析、年代学测定、粒度分析、碳酸盐及其稳定同位素测定、孢粉分析等综合研究,建立了巴里坤湖沉积岩芯剖面十五万年来的时间序列、湖水位变化的古水文演化序列,分辨出十五万年来经历的高湖面阶段和低湖面阶段。低湖面阶段对应于冰期阶段,在冰期时,降水主要积累于山地,进入湖泊的水量较少,湖水位降低;高湖面阶段对应于间冰期的到来,山地冰川融化,湖水位迅速上升,但很快达到新的平衡,水位保持稳定。     

新疆库车坳陷中、新生界碳酸盐岩及其成因意义?

新疆库车坳陷古近系库姆格列木群为与广海连通不畅的半封闭局限海湾-蒸发潟湖环境沉积，它应是新特提斯洋向北的延伸部分，其中的碳酸盐岩主要为海相蒸发潮坪环境的潮上带膏云坪，潮间带生屑滩、砂屑滩、鲕滩和潮下带泥晶灰岩、泥岩、泥晶云岩等。白垩系巴什基奇克组底部的灰黑色泥灰岩为深湖环境的沉积，分布较局限，仅见于克拉201井；白垩系巴什基奇克组中部的浅灰色透镜状泥灰岩结核是典型干旱陆上暴露环境的产物，仅在库车河剖面见零星分布。侏罗系湖相碳酸盐岩主要分布在恰克马克组，其次是阳霞组和克孜勒努尔组，在卡普沙良河剖面的恰克马克组上部，可见到大量的叠层石灰岩，它们主要形成于能量较强的浅湖环境；深灰色泥晶灰岩常与灰黑色泥岩伴生，是深湖-半深湖环境产物。以上这些不同时期不同沉积环境的碳酸盐岩具有不同规律的微量元素和碳、氧同位素特征，它们对于研究库车坳陷的沉积环境变迁和盆地演化具有重要意义。个别样品地球化学数据的偏差不能代表对整体沉积环境的判别，所以碳酸盐岩沉积环境的判别需要结合共生岩石沉积构造、沉积组合序列、古生物和沉积地球化学等资料进行综合分析。     

华北地台晚寒武世层序地层及其与北美地台海平面变化的对比

华北地台在晚寒武世为一个较为典型的缓坡型台地。在其北部地层中,以发育风暴砾屑灰岩及生物丘灰岩闻名,包括崮山组、长山组和凤山组。在该套地层中,深缓坡相泥岩和泥灰岩与浅缓坡相颗粒灰岩和泥粒灰岩一起构成若干潮下型碳酸盐米级旋回,这些米级旋回本身即为有序的异成因岩相序列而成为基本工作单元。在长周期三级层序中。米级旋回形成有序垂直叠加形式,反映了三级层序本身是一个与三级相对海平面变化相关的、环境加深和变浅过程中所形成的沉积相序列根据这些特征,在华北地台北部晚寒武世地层中可识别出4个三级层序。从北向南,相变为一套白云岩,其中三级层序的高水位体系域则发育较多的潮坪相白云岩以及由其构成的环潮坪型米级旋回。这些层序的典型特征是：层序界面为淹没不整合面,层序的相序序列以“深缓坡相—浅缓坡相”为特征,从而构成特殊的“CS(?) HST”序列;而在华北地台南部,层序界面多为暴露间断面,层序的相序组构多以“缓坡相—潮坪相”为特征。从北向南的变化,形成了一个富有规律性的层序地层格架。从旋回到层序、从岩相序列到沉积相序列的层序地层研究表明：作为基本工作单元,米级旋回实际上是由“间断—加积作用”旋回机制所形成的岩相序列,由米级旋回的有序叠加形式所构成的三级层序则是一个沉积相序列。由各剖面点的古水深变化曲线,可以定性地综合出华北地台晚寒武世的海平面变化曲线。与北美晚寒武世海平面变化曲线相对比,既存在相似性更存在差异性,说明了长周期海平面变化既受全球性海平面变化的控制,同时也受区域因素的影响。     

Palaeoenvironmental reconstruction of a middle Miocene alluvial fan to cyclic shallow lacustrine depositional system in the Calatayud Basin (NE Spain)

ABSTRACT The middle Miocene sedimentary fill of the Calatayud Basin in north‐eastern Spain consists of proximal to distal alluvial fan‐floodplain and shallow lacustrine deposits. Four main facies groups characteristic of different sedimentary environments are recognized: (1) proximal and medial alluvial fan facies that comprise clast‐supported gravel and subordinate sandstone and mudstone, the latter exhibiting incipient pedogenic features; (2) distal alluvial fan facies, formed mainly of massive mudstone, carbonate‐rich palaeosols and local carbonate pond deposits; (3) lake margin facies, which show two distinct lithofacies associations depending on their distribution relative to the alluvial fan system, i.e. front (lithofacies A), comprising massive siliciclastic mudstone and tabular carbonates, or lateral (lithofacies B) showing laminated and/or massive siliciclastic mudstone alternating with tabular and/or laminated carbonate beds; and (4) mudflat–shallow lake facies showing a remarkable cyclical alternation of green‐grey and/or red siliciclastic mudstone units and white dolomitic carbonate beds. The cyclic mudflat–shallow lake succession, as exposed in the Orera composite section (OCS), is dominantly composed of small‐scale mudstone–carbonate/dolomite cycles. The mudstone intervals of the sedimentary cycles are interpreted as a result of sedimentation from suspension by distal sheet floods, the deposits evolving either under subaerial exposure or water‐saturated conditions, depending on their location on the lacustrine mudflat and on climate. The dolomite intervals accumulated during lake‐level highstands with Mg‐rich waters becoming increasingly concentrated. Lowstand to highstand lake‐level changes indicated by the mudstone/dolomite units of the small‐scale cycles reflect a climate control (from dry to wet conditions) on the sedimentation in the area. The spatial distribution of the different lithofacies implies that deposition of the small‐scale cycles took place in a low‐gradient, shallow lake basin located in an interfan zone. The development of the basin was constrained by gradual alluvial fan aggradation. Additional support for the palaeoenvironmental interpretation is derived from the isotopic compositions of carbonates from the various lithofacies that show a wide range of δ¹⁸O and δ¹³C values varying from ?7·9 to 3·0‰ PDB and from ?9·2 to ?1·7‰ PDB respectively. More negative δ¹⁸O and δ¹³C values are from carbonate‐rich palaeosols and lake‐margin carbonates, which extended in front of the alluvial fan systems, whereas more positive values correspond to dolomite beds deposited in the shallow lacustrine environment. The results show a clear trend of δ¹⁸O enrichment in the carbonates from lake margin to the centre of the shallow lake basin, thereby also demonstrating that the lake evolved under hydrologically closed conditions.     

Sedimentology of the Madumabisa Mudstone Formation (Late Permian), Lower Karoo Group,mid-Zambezi Valley Basin,southern Zambia

Sediments of the Upper Carboniferous to Lower Jurassic Karoo Supergroup (∼ 4.5 km thick) were deposited in the mid-Zambezi Valley Basin, southern Zambia. The Upper Palæozoic Lower Karoo Group in this area ends with a Late Permian sedimentary unit called the Madumabisa Mudstone Formation. The formation is 700 m thick and comprises four lithofacies grouped into two facies assemblages, collectively interpreted as lacustrine deposits. Sediments of a massive mudrock facies assemblage were deposited from suspension, probably from sediment-laden rivers entering a lake. Concretionary calcilutite beds probably mark the positions of palæosediment-water interfaces where calcite was precipitated. A laminated mudrock facies assemblage is attributed to lacustrine deposition from inflowing rivers at the lake margins and shallow parts of the lake. Repeated thickening-upward cycles are evidence of upward shallowing, interrupted by events of more abrupt deepening. Sandstone interbeds are interpreted as fluvial deposits laid down during low lake stands, with cross-lamination and asymmetrical ripples indicating current rather than wave deposition. A fossil assemblage of ostracods, bivalves, gastropods, fish scales, the alga Botryococcus sp. and fossil burrows is consistent with a lacustrine origin for the formation.     

吉尔嘎郎图凹陷赛汉塔拉组沉积特征与超厚煤层异地成因分析

吉尔嘎郎图凹陷的赛汉塔拉组沉积于基底减速沉降-充填演化阶段,是凹陷进入湖泊萎缩阶段早-中期的产物,其层序地层单元属于水退体系域。自下而上由浅湖相、三角洲相和曲流河相组成。其中的超厚煤层与大量薄层浊积砂岩共生,形成于该凹陷的次级深断槽中,沉积环境应为浅湖和局部较深湖。传统的煤沉积模式难以解释其超厚煤层的成因。通过对煤层和夹矸的沉积学研究,以及凹陷充填序列分析,建立了一种陆相超厚煤层异地成因新模式--“弱风暴及水下泥质、砂质重力流亚模式”,简称为胜利盆地亚模式。推测成煤物质是由远源河流搬运而来的巨量异地高灰泥炭,可能先沉积于滨湖三角洲,后经滑塌和浊流作用转移至浅湖中,并经再次分异、沉积成为超厚的低灰煤层。     

西藏羌塘盆地中侏罗世布曲期及夏里期岩相古地理与油气远景

在露头剖面地层学及沉积学研究的基础上,采用单因素分析多因素综合作图法,编制了西藏羌塘盆地中侏罗世布曲期和夏里期的单因素图和岩相古地理图。布曲期以碳酸盐岩沉积为主,自北而南依次发育局限台地（潮坪、泻湖）、开阔台地（台盆、浅滩/点礁）、台缘礁/浅滩、台缘斜坡、盆地等沉积（亚）相;夏里期以陆源碎屑沉积为主,发育泻湖、潮坪、滨岸、陆棚等沉积（亚）相。布曲组台盆和泻湖相泥灰岩和泥晶灰岩是良好的烃源岩,台缘礁和浅滩相碳酸盐岩是良好的储集岩,而上覆的夏里组泻湖和潮坪相泥岩和膏盐层是良好的区域性盖层,共同构成良好的生、储、盖组合。该生储盖组合大都被上覆的上侏罗统、白垩系、第三系覆盖。因此,布曲组是盆地内最好的油气勘探目的层,沿中央隆起带两侧以及北羌塘地区的琵琶湖－半岛湖凸起一带应是油气勘探的有利区带。     

The St George Group (Lower Ordovician) of western Newfoundland: tidal flat island model for carbonate sedimentation in shallow epeiric seas

The St George Group consists of peritidal carbonate rocks deposited on the continental shelf of North America bordering the ancient Iapetus Ocean. These Lower Ordovician rocks are similar to other lower Palaeozoic limestones and dolostones that accumulated in epeiric seas and veneer cratonic areas worldwide. A wide variety of facies in the St George is grouped into seven lithotopes, interpreted to represent supratidal, intertidal and shallow, high- and low-energy subtidal environments. Rapid lateral facies changes can be observed in some field exposures, and demonstrated by correlation of closely spaced sections. The stratigraphic array of these lithotopes, although too irregular to be simplified into shallowing-upward cycles, suggests that they were deposited as small tidal flat islands and banks. Shallow subtidal areas around islands generated sediment and permitted tidal exchange. Tidal flat islands were somewhat variable in character at any one time, and evolved with changing regional hydrographic conditions. The St George rocks suggest an alternative theory of carbonate sedimentation in large, shallow epeiric seas, namely as small islands and banks built by processes that operated in a tidal regime. Furthermore, this island model provides a framework for a mechanism of cyclic carbonate sedimentation, by which small-scale, peritidal cycles represent tidal flat islands that accreted vertically and migrated laterally as local sediment supply from neighbouring subtidal areas waxed and waned during relatively constant subsidence.     

渤海海域沙一、二时期碳酸盐岩沉积特征及主控因素分析

渤海海域沙一、二时期湖相碳酸盐岩分布广泛。根据其沉积特征可划分为台地型、斜坡型、水下隆起型和混合沉积型4大类及相应的亚相、微相,其中位于湖平面之下浪基面之上的各类浅水湖泊碎屑滩(生物滩、陆屑滩)储层最为发育。该时期渤海海域为温暖潮湿的北亚热带气候、封闭的微咸水-半咸水的环境。古地貌特征为影响碳酸盐岩发育和富集分布规律的主控因素,周边陆源碎屑供给能力则影响碳酸盐岩的发育程度。     

周口坳陷谭庄-沈丘凹陷早白垩世沉积相类型和层序地层特征

早白垩世周口坳陷谭庄-沈丘凹陷接受了商水期、永丰期和巴村期的一套陆相湖盆沉积,主要沉积相类型有冲积扇相、扇三角洲相、滨浅湖相和较深湖相。这套地层可以划分3个层序,构成一个构造层序。湖平面的升降变化直接控制了层序的形成和发育。层序的演变反映出本区经历了3次湖平面的升降,同时反映出构造对层序变化的控制。     

平邑盆地官庄群湖相碳酸盐岩的古地理意义

[摘 要] 本文旨在以平邑盆地官庄群湖相碳酸盐岩为例,研究湖相碳酸盐岩的古地理指示意义。以沉积学理论为指导,依据野外露头剖面分析了平邑盆地古近纪官庄群的地层及其沉积特点,结合盆地的形成及演化,分析了古生物、古气候、物源、水介质物理化学条件等沉积环境条件,明确了官庄群湖相碳酸盐岩沉积时的古地理格局与特征。研究表明平邑盆地在古近纪官庄群沉积时为温暖的内陆淡水湖泊环境,构造活动相对静止,地形平坦,有利于湖泊相碳酸盐岩沉积,且碳酸盐岩集中发育在浅水、中等偏低能量、低陆源碎屑物质的环境。从而说明湖相碳酸盐岩地层形成的古地理背景为构造活动平静、地形平坦、浅水低能沉积环境。     

下扬子盆地石炭纪的岩石学特征及沉积相

位于扬子板块东部的下扬子盆地，在石炭纪时，为被动大陆边缘的陆表海沉积，陆源碎屑来自于北边的胶南古陆和南边的江南古陆东延部分─—皖浙赣古陆。石炭系分为上、下两统。早石炭世，盆地南部宣城、广德等地主要发育碎屑岩，中部巢县、南京一带以及北部滨海、洪泽一带为碎屑岩和碳酸盐岩沉积。从南往北，金陵期从滨岸碎屑岩相→开阔海台地碳酸盐岩相→潮坪碳酸盐岩和碎屑岩相；高骊山期为滨岸平原沼泽碎屑岩相→浅海陆棚碎屑岩相→海岸萨布哈白云岩、石膏、碎屑岩相；和州期盆地南部隆起，中部到北部为礁及礁后泻湖一潮坪碳酸盐岩相→开阔海台地碳酸盐相。晚石炭世主要是碳酸盐沉积，黄龙期从滨岸石英砾岩相→潮坪白云岩相→开阔海台地碳酸盐岩相；船山期是黄龙期开阔海台地碳酸盐岩相的继续，以发育核形石生物碎屑颗粒岩为特征。整个盆地的岩相带均以ＮＥＥ—ＮＥ方向展布。     

坳陷湖盆浅水三角洲的沉积特征--以松辽盆地南部姚一段为例

坳陷湖盆浅水三角洲的形成古地形背景、水动力学特征、平面形态、微相类型及三角洲内部结构等多个方面与正常三角洲有着极大的差异。姚一段沉积时期,松辽盆地古地形平坦并不具备明显的坡折带,水体浅、面积小并且湖泊能量较弱,湖岸线不稳定并常常发生大范围的迁移,为典型的浅水沉积湖盆。浅水湖盆的沉积充填主要以浅水三角洲和滨浅湖沉积为主,深湖、半深湖相对不发育,浅水三角洲砂体是湖泊砂体的主要类型。根据供源水系的不同,松南的浅水三角洲可以分为浅水型扇三角洲、浅水型辫状河三角洲和浅水曲流河三角洲等。浅水型三角洲主要有以下特点:1.具高建设性河控三角洲的沉积特点,平面上呈鸟足状,前缘相带延伸较远,形成了大规模的湖盆中心砂体;2.浅水三角洲前缘主要以分流河道为主,河口坝极不发育;3.前缘分流河道呈网状展布,河道遭受不同程度的席状砂化,依次划分为弱席状化、中等席状化、强席状化等3种类型;4.不具备典型三角洲的三层式沉积结构及向上变粗的反序列特征。松南姚一段沉积时期,总体表现为基准面上升的湖侵过程,I、II砂组低位和湖侵域的砂体为成藏提供了的有利储集空间,III砂组的湖侵为区域性成藏提供了良好的盖层。     

Geolimnology of Freefight Lake: an unusual hypersaline lake in the northern Great Plains of western Canada*

Freefight Lake, Canada's deepest salt lake, is a meromictic, hypersaline lake located in the most arid part of the northern Great Plains. The lake has a distinctive basin morphology, with a large expanse of seasonally flooded mud flats and sand flats adjacent to a deep, flat bottomed perennial waterbody. The mixolimnion, dominated by magnesium, sodium and sulphate ions, has an average salinity of 110 ppt and overlies a monimolimnion of 180 ppt total dissolved salts. The entire water column is strongly supersaturated with respect to a variety of calcium and magnesium carbonate minerals; the lower water mass is also saturated or supersaturated with respect to a number of very soluble sodium, magnesium and sodium + magnesium salts. The modern sedimentary processes operating in Freefight Lake give rise to six main sedimentary facies: (i) colluvium, (ii) mud flats and sand flats, (iii) algal flats, (iv) delta, (v) slope and debris apron, and (vi) deep basin. The colluvium, mud flats and sand flats, and delta facies are dominated by physical processes and consist mainly of detrital siliciclastic sediment. The algal flats, slope and debris apron, and deep basin facies are dominated by endogenic and authigenic sediments derived mainly by physicochemical and biologically mediated carbonate and evaporite mineral precipitation. As one of very few deep water lakes in the world in which soluble evaporite minerals are forming and being preserved, Freefight Lake occupies an important position within the realm of lacustrine sedimentology. Although many of the sedimentological and geochemical processes taking place in the basin today are unusual, the delineation and evaluation of these processes is essential in order to decipher properly the stratigraphic records of Quaternary lake sediments in this large area of North America, as well as lacustrine sequences from other arid and semi-arid regions of the world.