马依西勘探区含煤地层岩相及沉积环境分析

根据盘南矿区马依西井田大量地质资料分析,认为龙潭组形成于潮坪、三角洲及海湾—泻湖沉积体系,下部为潮坪—潮道沉积组合,主要由潮坪相、潮道相、沼泽及泥炭沼泽相组成,形成的煤层硫分高,连续性差;中部为三角洲沉积组合,主要由前三角洲相、三角洲前缘相及三角洲平原相组成,其煤层硫分低,稳定性好,分叉少;上部为海湾—潟湖相沉积组合,由潟湖相局部海湾相及沙洲砂坝相组成。分流河道的泛滥盆地、支流间湾、废弃河道、潮坪—潮道为本区煤层的形成提供了有利沉积环境。     

Stromatolites in the Late Ordovician Eureka Quartzite: implications for microbial growth and preservation in siliciclastic settings

Well-preserved siliciclastic domal stromatolites, up to 2 m wide and 1·5 m high, are found in a 10 to 15 m thick interval within the Late Ordovician Eureka Quartzite of Southern Nevada and Eastern California, USA. These stromatolites appear as either isolated features or patchy clusters that contain more than 70% by volume quartz grains; their association with planar, trough and herringbone cross-bedding suggests that they were formed in an upper shoreface environment with high hydraulic energy. In this environment, sand bars or dunes may have provided localized shelter for initial microbial mat colonization. Biostabilization and early lithification of microbial mats effectively prevented erosion during tidal flushing and storm surges, and the prevalence of translucent quartz sand grains permitted light penetration into the sediment, leading to thick microbial mat accretion and the formation of domal stromatolites. Decimetre-scale to metre-scale stromatolite domes may have served as localized shelter and nucleation sites for further microbial mat colonization, forming patchy stromatolite clusters. Enrichment of iron minerals, including pyrite and hematite, within dark internal laminae of the stromatolites indicates anaerobic mineralization of microbial mats. The occurrence of stromatolites in the Eureka Quartzite provides an example of microbial growth in highly stressed, siliciclastic sedimentary environments, in which microbial communities may have been able to create microenvironments promoting early cementation/lithification essential for the growth and preservation of siliciclastic stromatolites.     

黄河北煤田潮坪沉积体系及成煤作用

黄河北煤田煤系广泛发育潮坪沉积体系,通过对其沉积特征及沉积模式的研究,认为潮坪沉积体系主要包括潮道（潮沟或潮渠）、泥坪、沙坪、砂泥混合坪及潮坪沼泽和潮坪泥炭沼泽相等沉积相类型,其特征是砂泥比值较高,沉积厚度大,为含煤地层发育提供物质基础;在沉积环境演化方面与整个鲁西南地区沉积特征相似,整体为海水逐渐衰退的过程;在潮坪沼泽和潮坪泥炭沼泽中形成含硫量相对较高的煤层与海平面的变化密不可分,潮坪沉积物中发育的10煤、8煤、7煤、6煤等与潮坪泥炭沼泽沉积在该区分布特点具有一致性,由此可知,潮坪沉积体系的沉积物与煤层形成特点和形成规律有着密切关系,为研究区成煤作用研究提供了理论依据。     

航空激光高程测量在黄河三角洲北部潮滩监测中的应用

调查潮滩的演化对海岸保护和开发非常重要。随着人为活动的增强,即使过去认为稳定的潮滩也在发生着显著变化。利用航空激光测高(LIDAR)数据和实测剖面数据对黄河三角洲北部潮滩的地形特征和变化进行了分析。这段海岸的西段海岸平直,潮滩坡降小于1/1000,不发育潮沟,潮间有人工开挖的沟道。海岸的东段为老黄河刁口流路岸段。老黄河口岸段突出海岸,同时在两侧形成2个小海湾。LIDAR数据揭示了本段潮滩的三维地形和剖面特征。老黄河口突出岸段西北侧潮滩剖面为平直斜坡,坡度1/1000。而其东侧小海湾湾底的剖面呈上凸的形态,该特征与平面的地形分布、潮间茂密的盐地碱蓬一起,指示淤积。再向东在大堤围成的岬湾内,潮滩受波浪作用形成潮间坝。因此,黄河三角洲北部潮滩受局部地形影响大,局部岸段呈侵蚀状态或淤积状态。LIDAR数据还揭示了潮沟的特征。顺着潮沟的走向,沟底的坡度比潮间带的坡度小,近乎水平,说明涨潮时为何潮沟水位会迅速上升。     

A sandy tidal coast in the uppermost Muschelkalk and the origin of the Muschelkalk/Keuper boundary in the southwestern Germanic basin

A tidal coast is documented in mixed siliciclastic and carbonate sands of the uppermost Muschelkalk (Middle Triassic) along the southwestern margin of the Germanic basin in Luxembourg. The coastal sediments are vertically and laterally stacked channel fills, interpreted to have formed in a tidal flat environment. The channel fills overlie carbonates of a shallow subtidal ramp. The strong progradation of the tidal flat indicates deposition during a late stage of sea-level highstand, but before sea-level fall. In their upper part, the channel fills are overprinted by a thick paleosol, which resulted from subaerial exposure around the time of the Muschelkalk/Keuper boundary. The exposure and formation of the paleosol in the subtidal coastal sediments and, in basinward sections, the deposition of dolomicrites above the Muschelkalk/ Keuper boundary in the lowermost Keuper both indicate a sea-level fall.     

Messinian stromatolite-thrombolite associations,Santa Pola,SE Spain: an analogue for the Palaeozoic?

Stromatolite-thrombolite associations are the dominant facies forming large portions of the Santa Pola carbonate platform (SE Spain) during deposition of the Terminal Carbonate Complex (TCC). The TCC, the last period of marine sedimentation in the Western Mediterranean associated with the Messinian Salinity Crisis, comprises a NE-SW trending thrombolite reef with occasionally interlayered stromatolite horizons and a predominantply stromatolite and oolite facies in the back-reef area. The stromatolites are mainly dome shaped, but fine-columnar or wavy-undulose forms can occur. The stromatolites form huge bioherms, extending tens to hundreds of metres. They are finely laminated with alternating layers of dolomicrite and dolomicrospar. The dolomicrite layers appear to be a primary dolomite precipitate, whereas the dolomite crystals in the dolomicrospar layers apparently formed around a meta-stable nuclei which was subsequently dissolved or degraded. The low content of sand-sized particles in the stromatolitic layers indicates formation under low-energy conditions, possibly on a tidal flat. As reported from other areas in the Western Mediterranean, deposition of the TCC at Santa Pola was apparently cyclic, whereby stromatolites generally terminate each depositional cycle. Subtidal Conophyton stromatolites, possibly the only known occurrence younger than Palaeozoic, are, however, found on the reef slope at the base of the first TCC depositional cycle. The dolomitic nature of the unadulterated stromatolitic laminations and the association of stromatolites and thrombolites as platform builders were a common feature in the Early Palaeozoic but are unusual in post-Ordovician carbonate facies. We propose that the conditions during TCC deposition were very restricted, possibly reflecting an environment similar to that of the Early Palaeozoic.     

平沟矿区山西组潮控三角洲—河流沉积及聚煤特点

通过野外和室内研究,提出山西组形成于河流—潮控三角洲环境。河流沉积包括辫状曲流河和高弯度曲流河。潮控三角洲以潮汐沉积发育为标志,潮汐沙坝、潮河道构成其沉积骨架,揭示了沉积期仍受海水内泛影响。煤聚积发生在河道岸后边缘沼泽环境、废弃潮汐沙坝上发育起来的潮坪环境及分流间湾充填变浅形成的泥炭沼泽环境。总结了不同沉积环境的聚煤特点。     

Genesis of large siliceous stromatolites at Frying Pan Lake, Waimangu geothermal field, North Island, New Zealand

Lilypad stromatolites, up to 3 m long and 1·5 m wide, were found to be actively growing in the shallow marginal waters of Frying Pan Lake and its outflow channel. These stromatolites, composed of Phormidium (> 90%), Fischerella, and a variety of other microbes, develop through a series of distinct growth stages. Dark green microbial mats cover the floor of the outflow channel and give rise to columns of various sizes and shapes in the shallower marginal waters. Once the columns reach the water level, the mats spread laterally to form a lilypad stromatolite. The lilypads are characterized by a raised, dark green rim, 4–5 mm high, that encircles a flat interior covered with a distinctive orange-red mat. The microbes forming the columns and lilypad plate are being actively silicified. The stromatolites are formed of: (i) flat-lying Phormidium filaments (P-laminae), (ii) upright filaments of Phormidium that are commonly associated with Fischerella (U-laminae), and (iii) mucus, diatoms and pyrite framboids (M-laminae). P-laminae dominate most of the columns, with tripartite cycles of P-, U-, to M-laminae being found mostly in the upper parts of the stromatolites. The transition from the P- to U-laminae is marked by a change in the growth pattern of the Phormidium and branching of Fischerella, which was probably triggered by a change in environmental conditions. In the Frying Pan Lake outflow channel, this change may be related to fluctuations in water level and flow rates that are caused by periods of heavy rain, seasonal changes, long-term variations in rainfall, and/or the unique 40-day hydrological cycle that exists between Frying Pan Lake and Inferno Crater, which is a nearby hydrothermal crater lake.     

豫西太原组、山西组中潮道沉积的类型和特征

豫西太原组中的潮道为陆表海滨岸潮道类型,其特点为:向上变细的层序,冲刷切割下伏的灰岩层,具大型板状、槽状交错层理和双向交错层理,潮道曲流砂坝发育。山西组下段的潮道为障壁后潮道,位于障壁砂坝后的潮坪区;潮道砂岩泥质杂基较高,正粒序,砂体自海向陆分叉尖灭;潮坪、潮道等亚环境组合影响了其上发育的煤层的厚度变化。山西组上段的潮道为下三角洲平原潮道类型,多位于分流河口,砂岩为正粒序,双(单)粘土层和潮汐周期层序发育。     

湘西渔塘早寒武世生物礁沉积相特征

湘西渔塘早寒武世清虚洞期生物礁为国内外罕见的规模较大的堤状藻礁,发育于川滇黔碳酸盐台地南东边缘。造礁生物为表附藻、尼科尔森藻及葛万藻等,具明显的生长生态及分带性特征。该生物礁的形成及演化受同沉积断裂控制,发育三个造礁旋回,每个旋回由四个依次向上变浅的沉积阶段组成和相对应的礁基、礁核、礁前、礁后及礁顶亚相。礁后藻砂屑灰岩系渔塘铅锌矿极为重要的控矿岩相。     

Middle Ordovician Bioturbation Structures from Southeastern Margin of Ordos Basin and Their Environmentary Interpretation

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近三十年长江口横沙岛潮滩湿地地貌演变对河口工程的响应

由于人类活动的不断加剧和入海泥沙的日益减少,我国部分河口潮滩湿地已面临严重的侵蚀退化风险,给沿岸城市发展带来巨大威胁,实现河口潮滩湿地的科学管理和合理利用极为紧迫。本研究利用1990—2017年多期长江口深水航道北导堤工程与横沙岛成陆-促淤工程前后区域海图地形数据,使用ArcGIS地理配准、等深线数字化、数字高程模型建立和叠加分析等功能分析长江口横沙岛潮滩湿地地貌、等深线形态与地形冲刷-淤积厚度的时空变化过程。研究结果表明,长江口深水航道北导堤工程与横沙岛成陆-促淤工程的实施,改变了横沙岛潮滩湿地周边水域的水文泥沙动力条件,使得地貌冲淤时空特征发生变化：1）深水航道北导堤工程与横沙岛成陆-促淤工程的实施极大地推动了特征等深线的向外延伸,其中0、2和5 m等深线包络面积年均最大增长率（2009—2013年）分别是工程前（1990—1998年）的42.13、280.73和235.65倍,0~1、1~2、2~3、3~4及4~5 m等深线包络体积整体呈现1990—1998年、1998—2009年、2009—2013年增加,2013—2017年较为明显减少,潮滩湿地"长高不长大"的趋势;2）冲刷-淤积频率特征表现为工程前微淤（1990—1998年）、工程后微淤（1998—2009年）、淤积增加明显（2009—2013年）及微冲（2013—2017年）,长江入海泥沙通量的减少对2 m等深线以深区域的潮滩发育可能产生一定影响。     

川南马边黄家坪磷矿下寒武统麦地坪组沉积相特征及磷成矿模式研究

川南马边地区下寒武统麦地坪组是昆阳式磷矿的重要赋矿层位,磷矿的分布受沉积古环境控制。以马边黄家坪地区麦地坪组含磷地层野外剖面实测及钻孔岩芯观察为基础,对麦地坪组沉积相特征、磷块岩特征、磷矿成因模式进行了详细研究。研究表明：黄家坪地区麦地坪组发育碳酸盐岩潮坪相沉积,可识别出潮上坪、潮间坪和潮下坪3个亚相共计6种微相类型：潮上坪包括潮上滩和潮上云坪微相;潮间坪包括潮汐水道、潮间滩、潮间灰坪;潮下坪则仅发育低能潮下坪,垂向上表现出海退-海侵的沉积演化序列。据此建立了麦地坪组海湾潮坪相沉积模式。磷块岩的富集严格受沉积相带控制,潮间坪内高能水动力的潮间滩和潮汐水道是最有利于磷块岩形成的微相环境,砂砾屑磷块岩是马边地区发育较为广泛的磷块岩类型。磷矿床的成矿模式为上升洋流将富磷海水带入到海湾潮坪环境内,受生物-化学作用使磷以胶体-化学的形式发生凝聚富集,形成半固结—弱固结的磷酸盐沉积物,后遭受水流的冲刷、破碎、搬运、簸选再次发生沉淀,经压实、固结即形成高品位的磷块岩。     

Evolution of depositional settings in the Torrey area during the Smithian (Early Triassic,Utah, USA) and their significance for the biotic recovery

This work focuses on well‐exposed Lower Triassic sedimentary rocks in the area of Torrey (south‐central Utah, USA). The studied Smithian 8 deposits record a large‐scale third‐order sea‐level cycle, which permits a detailed reconstruction of the evolution of depositional settings. During the middle Smithian, peritidal microbial limestones associated with a rather low‐diversity benthic fauna were deposited seaward of the tidal flat siliciclastic red beds. Associated with siliceous sponges, microbial limestones formed small m‐scale patch reefs. During the late middle to late Smithian interval, the sedimentary system is characterized by tidal flat dolostones of an interior platform, ooid‐bioclastic deposits of a tide‐dominated shoal complex, and mid‐shelf bioclastic limestones. Microbial deposits, corresponding to sparse stromatolites formed in the interior platform, are contemporaneous with a well‐diversified marine fauna living in a seaward shoal complex and mid‐shelf area. The nature and distribution of these Smithian microbial deposits are not related to any particular deleterious environmental condition, highlighting that observed patterns of biotic recovery after the end‐Permian mass extinction were directly influenced by depositional settings. Facies evolution and stratal stacking patterns allow us to identify large, medium and small‐scale, as well as elementary depositional sequences. Large‐ and medium‐scale sequences are consistent with sea‐level changes, whereas small‐scale and elementary sequences are better explained by autocyclic processes. Copyright © 2015 John Wiley & Sons, Ltd.     

A palaeoenvironmental interpretation of the Early Proterozoic Malmani dolomite from Zwartkops,South Africa

The Malmani Subgroup northwest of Johannesburg consists of dolomite and chert with only minor clastic sediments.A precise upper intertidal to marginal supratidal analogy and the associated relationship of varied structures suggest that much of the succession represents a tidal flat to intertidal complex formed within differing semiprotected to protected conditions. The dolomites from these environments are recrystallized, reflecting a meteoric influence, and the cherts which are commonly developed within them are also related to prevailing lower pH's. This dolomitization is considered to have been enhanced by the influx of meteoric waters which however resulted in the dolomites having undersaturated iron-manganese ratios. Rare colour-banded dolomites containing columnar stromatolites are thought to represent more steeply shelving intertidal conditions than are normally encountered in the epeiric sea. These dolomites contain quartz crystals rather than chert, suggestive of a lower concentration of silica in the original alkaline solutions. The exposure is part of a very widespread carbonate unit, dated at ca. 2.250 m.y.Subtidal conditions in which large elongate stromatolitic domes developed can be related to a marine transgression across a basal clastic beach sand; and secondly to a progradational tidal flat seawards of which a talus breccia developed on a steepened slope leading down to the subtidal regime. These dolomites formed by interaction with marine waters saturated with respect to iron and manganese, while the absence of chert reflects persisting alkaline conditions.A dark chert-free dolomitic facies with high iron and manganese contents of saturated ratios is considered to have developed in an alkaline lagoonal environment behind a subaqueous bar that is now represented by an overlying thick oolitic unit.The succession contains numerous chert breccias with which shales are associated. The breccias represent subaerial exposure phenomena related to regressions which were followed by periods of short-lived terrigenous influx.     

钱塘江河口涌潮河段滩槽演替与沉积层序

通过分析时间序列的卫片资料、4 m高的露头剖面的沉积学和元素地球化学特征, 研究钱塘江涌潮河段的滩槽冲淤变化规律、涌潮沉积特征和沉积层序.涌潮河段河道宽浅, 受径流与潮流相互作用强烈, 冲淤频繁且剧烈, 滩槽演替存在约20 a的周期, 与流域年代际洪、枯期转变有关.在滩槽叠置的垂向层序中, 底部为河槽、低潮滩相的厚层块状砂质沉积, 发育各种变形沉积构造, 为典型的涌潮沉积; 顶部为高潮滩相的潮汐韵律沉积, 发育典型的潮汐成因的双黏土层、大小潮周期; 二者之间的中潮滩相呈渐变过渡.C-M图和概率累计曲线可较好地区分涌潮沉积与潮成砂、泥质沉积.涌潮沉积层Si/Al、Zr/Al、Ti/Al等元素比值较高, 而潮汐韵律层Fe/Al、Mn/Al等元素比值较高, 这与它们的赋存方式和水动力分异有关.Si、Zr和Ti主要见于石英和重矿物中, 因此在强水动力沉积层中富集; 而Fe、Mn易被黏土矿物吸附, 在水动力较弱的中高潮滩富集.      

潮控河口湾岩相类型及沉积模式

潮控河口湾是厄瓜多尔Oriente盆地北部上白垩统Napo组的主力储层,当前对其识别标志、岩相及沉积分布规律认识不清,建立可靠的潮控河口湾的沉积模式,对于预测油气储层有重要意义。通过研究区LU碎屑岩段岩芯、粒度、测井、薄片以及地化资料的综合分析发现:1）综合岩相类型、地化、垂向序列特征认为其发育潮控河口湾和陆棚;2）研究区潮控河口湾主要发育中河口湾亚相及外河口湾亚相,中河口湾亚相发育潮汐河道、潮坪、高流态沙坪等微相,在测井曲线上呈钟形;外河口湾轴部发育潮汐沙坝、高流态沙坪微相,测井曲线上为箱型;外河口湾两侧为泥质潮坪微相,测井曲线上呈指形;浪基面之下发育泥质陆棚沉积和风暴形成的海绿石席状砂;3）研究区倾向西南,中河口湾的潮汐河道边滩沉积发育在东北部;向西南河道逐渐拓宽,外河口湾轴部潮汐沙坝南北向展布,向两翼泥质含量增高,发育泥质潮坪,呈席状展布。     

Morphodynamic evolution and stratal architecture of translating tidal point bars: Inferences from the northern Venice Lagoon (Italy)

The widespread distribution of tidal creeks and channels that undertake meandering behaviour in modern coasts contrasts with their limited documentation in the fossil record, where point‐bar elements arising from the interaction between a mix of both fluvial and tidal currents are mainly documented. The sedimentary products of tidal channel‐bend evolution are relatively poorly known, and few studies have focused previously on specific facies models for tidal point bars present in modern settings. This study improves understanding of tidal channel meander bends through a multi‐disciplinary approach that combines analyses of historical aerial photographs, measurements of in‐channel flow velocity, high‐resolution facies analyses of sedimentary cores and three‐dimensional architectural modelling. The studied channel bend (12 to 15 m wide and 2 to 3 m deep) drains a salt marsh area located in the north‐eastern sector of the microtidal Venice Lagoon, Italy. Historical photographs show that, during the past 77 years, the bend has translated seaward ca 15 m. Results show that the channel bend formed on a non‐vegetated mud flat that was progressively colonized by vegetation. Seaward translation occurred under aggradational conditions, with an overall migration rate of 0·2 to 0·3 m year⁻¹, and was promoted by the occurrence of cohesive, poorly erodible outer bank deposits. Ebb currents are dominant, and translation of the channel bend promotes erosion and deposition along the landward and seaward side of the bar, respectively. Tidal currents show a clear asymmetry in terms of velocity distribution, and their offset pattern provides a peculiar grain‐size distribution within the bar. During the flood stage, sand sedimentation occurs in the upper part of the bar, where the maximum flow velocity occurs. During the ebb stage, the bar experiences the secondary helical flow that accumulates sand at the toe of the bar. Lateral stacking of flood and ebb deposits has caused the formation of localized coarsening‐upward and fining‐upward sedimentary packages, respectively.     

琼东南盆地崖南凹陷海湾扇三角洲体系沉积构成及演化模式

本文以琼东南盆地崖南凹陷陵水组三段扇三角洲体系为例，详细讨论了进积于海湾背景环境下扇三角洲体系的岩性相、成因相及其空间配置关系。研究区海湾扇三角洲体系自下而上潮汐作用越来越强，其垂向演化可划分为三个阶段，早期为以河流作用占优势阶段，中期为河流和潮汐混合作用阶段，晚期为以潮汐作用占优势逐渐过渡为以潮汐作用占优势。