Architecture of an Oligocene fluvial ribbon sandstone in the Ebro Basin,North‐eastern Spain

Fluvial ribbon sandstone bodies are ubiquitous in the Ebro Basin in North‐eastern Spain; their internal organization and the mechanics of deposition are as yet insufficiently known. A quarrying operation in an Oligocene fluvial ribbon sandstone body in the southern Ebro Basin allowed for a three‐dimensional reconstruction of the sedimentary architecture of the deposit. The sandstone is largely a medium‐grained to coarse‐grained, moderately sorted lithic arenite. In cross‐section, the sandstone body is 7 m thick, occupies a 5 m deep incision and wedges out laterally, forming a ‘wing’ that intercalates with horizontal floodplain deposits in the overbank region. Three architectural units were distinguished. The lowest and highest units (Units A and C) mostly consist of medium‐grained to coarse‐grained sandstone with medium‐scale trough cross‐bedding and large‐scale inclined stratasets. Each of Units A and C comprises a fining‐up stratal sequence reflecting deposition during one flood event. The middle unit (Unit B) consists of thinly bedded, fine‐grained sandstone/mudstone couplets and represents a time period when the channel was occupied by low‐discharge flows. The adjoining ‘wing’ consists of fine‐grained sandstone beds, with mudstone interlayers, correlative to strata in Units A and C in the main body of the ribbon sandstone. In plan view, the ribbon sandstone comprises an upstream bend and a downstream straight reach. In the upstream bend, large‐scale inclined stratasets up to 3 m in thickness represent four bank‐attached lateral channel bars, two in each of Units A and C. The lateral bars migrated downflow and did not develop into point bars. In the straight downstream reach, a tabular cross‐set in Unit A represents a mid‐channel transverse bar. In Unit C, a very coarse‐grained, unstratified interval is interpreted as deposited in a riffle zone, and gives way downstream to a large mid‐channel bar. The relatively simple architecture of these bars suggests that they developed as unit bars. Channel margin‐derived slump blocks cover the upper bar. The youngest deposit is fine‐grained sandstone and mudstone that accumulated immediately before avulsion and channel abandonment. Deposition of the studied sandstone body reflects transport‐limited sediment discharges, possibly attaining transient hyperconcentrated conditions.     

秦岭东段卢氏盆地始新世沉积序列与气候环境变迁

始新世是新生代重要的暖期,其气候环境的特征与演化备受学界关注。位于秦岭东段的卢氏盆地保存了>1000 m厚的连续的始新世河湖相沉积物,是揭示古气候和环境变化规律的宝贵沉积记录。在前人工作基础上,本研究利用沉积学、古生物学、碎屑年代学等方法对卢氏盆地始新世地层的沉积特征、年代和环境进行了分析。结果表明：1）碎屑磷灰石裂变径迹与碎屑锆石U-Pb年龄指示沉积序列年代晚于约60 Ma,与前人将张家村组-卢氏组化石组合对比到中始新世的结论基本吻合。2）始新统张家村组沉积相演化表现为冲积扇→河流→洪泛平原或滨湖,反映盆地拉张、初期成湖的过程;卢氏组为滨浅湖→深湖/半深湖→滨浅湖或洪泛平原→浅湖/半深湖,反映湖泊开始稳定出现后的扩张、收缩和复活过程;大峪组为河流→洪泛平原→冲积扇,反映湖泊淤满消亡后河流与冲洪积物相继充填的历史。3）沉积相、化石组合、盐类矿物种类揭示中始新世卢氏盆地古气候为半湿润半干旱,地表景观呈现径流活跃、动物种类多样、树木茂盛、发育淡水至微咸水湖的特征,并可能具有一定的季节性。卢氏盆地沉积序列提供了始新世暖期中国中部气候环境变化的重要证据。

     

Multi‐scale classification of fluvial architecture: An example from the Palaeocene–Eocene Bighorn Basin,Wyoming

Fluvial channel geometry classification schemes are commonly restricted in relation to the scale at which the study took place, often due to outcrop limitations or the need to conduct small‐scale detailed studies. A number of classification schemes are present in the literature; however, there is often limited consistency between them, making application difficult. The aim of this study is to address this key problem by describing channel body geometries across a depositional basin to ensure that a wide range of architectures are documented. This was achieved by studying 28 locations over 4000 m of vertical succession in Palaeocene‐aged and Early Eocene‐aged deposits within the Bighorn Basin, Wyoming, USA. Five different channel body geometries have been defined based on the external geometric form, and internal arrangement and nature of storey contacts. These include the massive channel body geometry, semi‐amalgamated channel body geometry, internally amalgamated channel body geometry and offset stacked channel body geometry, which are considered to be subdivisions of the sheet geometry of many other classifications. An isolated channel body geometry has also been recognized alongside splay channel and sheet sandstone geometries in the floodplain facies associations. Field evidence, including the stacking style of storey surfaces, suggests that the different geometries form a continuum. The nature and degree of amalgamation at the storey scale are important in producing the different geometries and are related to the degree of channel migration. It is speculated that this is the result of differences in sediment supply and available accommodation. In contrast to previous schemes, the classification scheme presented here recognizes the importance of transitional geometries. This geometrical range has been recognized because of the basin‐scale nature of the study.     

抚顺盆地始新统计军屯组油页岩地球化学特征及其沉积环境

沉积物元素地球化学特征是盆地沉积环境变化的响应。本文根据元素Ti、Mn、Li、Cr、Co、Ni、Cu、Zn、Ga、Cd、Ba、Pb、Sr、Rb、V的含量及Sr／Ba、Ni／Co、Ni／V、Cu／Zn、V／（V＋Ni）比值的变化规律，并结合有机地球化学特征，对抚顺盆地始新统计军屯组油页岩的沉积环境进行了分析。以Li、Ti为代表的外源元素，贫矿段的含量高于富矿段；而Sr、Ba等湖盆内化学沉积元素，富矿段的含量高于贫矿。Sr／Ba、V／（V＋Ni）、Ni／Co、Cu／Zn比值从贫矿段到富矿段呈现逐渐增大的趋势。富矿段有机质类型主要为Ⅰ型，而贫矿段主要为Ⅱ1、Ⅱ2。分析表明，本区油页岩富矿段形成于水体盐度较贫矿段高、还原性强的深湖环境，而贫矿段则形成于还原性较弱的半深湖一浅湖环境。     

温室背景下陆相抚顺盆地始新世西露天组古气候演化

古近纪古新世—始新世极热事件和始新世后期变冷的古气候事件是目前沉积学和古气候学研究的热点, 但相关研究在陆相地层中较少涉及。前人对抚顺盆地始新世一系列极热事件进行了识别和成因研究, 但针对始新世后期开始变冷的古气候波动状况尚未进行系统分析。本文采用了古气候参数磁化率和色度对抚顺盆地始新世西露天组(晚始新世)古气候的波动和演化特征进行研究。通过对高精度磁化率和色度数据进行聚类分析和垂向演化规律对比发现, 西露天组沉积记录具有高的频率磁化率(12.58%~39.63%)、中高色度a*值(5.6%左右)和中高色度b*值(9.1%左右), 且这些数值均与古气温具有很好的对应性, 鉴于此, 这两种参数可以作为始新世陆相古气候演化研究的有效手段。抚顺盆地西露天组自底部到顶部, 频率磁化率呈由高值到低值缓慢下降的趋势, 色度a*值和b*值总体呈现先增加后减少的趋势, 这些均显示了抚顺盆地始新世整体温室气候背景下的降温过程。本次对晚始新世古气候变化趋势研究的认识, 联合前人在早始新世古气候演化的研究成果, 可以共同为东亚地区完整的始新世古气候演化研究提供可靠素材。     

Basin‐scale predictive models of alluvial architecture: Constraints from the Palaeocene–Eocene,Bighorn Basin,Wyoming, USA

Basin‐scale models are required to interpret ancient continental sedimentary successions, and reduce uncertainty in assessing geological resources in basins. Recently, modern studies show distributive fluvial systems to comprise a substantial proportion of modern sedimentary basins, but their role in ancient basin fills has yet to be quantitatively documented at the basin scale. This study analysed key fluvial characteristics to construct a detailed basin‐wide model of the Palaeogene Fort Union and Willwood formations (Bighorn Basin, Wyoming), using observations from modern studies, and ancient system scale studies of distributive fluvial systems, to guide interpretations. Mapping showed these formations to be highly heterogeneous with channel‐body proportion (from 12 to 81%) and geometry types (large amalgamated bodies to isolated channels), grain size (silt to conglomerate), average channel‐body thickness (4 to 20 m) and average storey thickness (3 to 10 m) varying significantly across the basin. Distributive fluvial systems in the form of alluvial and fluvial fans in transverse configurations were recognized as well as a wide axial system, with heterogeneity in the formations being closely aligned to these interpretations. Furthermore, numerous individual depositional systems were identified within the formations (Beartooth Absaroka, Washakie, Owl Creek and axial). Predicted downstream distributive fluvial system trends (i.e. downstream decrease in channel proportion, size and grain size) were identified in the Beartooth, Absaroka and Owl Creek systems. However, predicted trends were not identified in the Washakie system where intrabasinal thrusting disturbed the sequence. Importantly, a wide axial fluvial system was identified, where reverse downstream distributive fluvial system trends were present, interpreted to be the result of the input of transverse systems of variable size. This study provides a new level of detail in the application of basin‐scale models, demonstrating their usefulness in trying to understand and predict alluvial architecture distribution and heterogeneity, with important implications for economic resources and palaeogeographic reconstructions.     

四川石渠县沙尔木盆地始新世孢粉的发现

热鲁组因其下部发现孢粉、轮藻等化石,被定为始新世,但其上部地层时代无从定论。笔者等最近在上部地层中发现较多的植物孢粉,并建立了Lycopodiumsporites oligocenicus-Ephedripites(Distachyapites)eocenipites-Peltandripites davissii孢粉组合带,确定热鲁组上部地层的形成时代为始新世。     

衡阳盆地始新世含鱼地层的成因分析

衡阳市郊五马归槽始新世鱼化石保存在黑色湖相纹层中。根据纹层序列的对比,发现该地的鱼化石均为同一层位;根据鱼化石在纹层序列中的具体位置及鱼化石的保存状况,笔者推测鱼群的死亡并非由于季节更替,而是由气候干旱引起的湖水盐度升高所控制;黑白纹层的变化是由大气降雨所致。     

Paralic parasequences associated with Eocene sea-level oscillations in an active margin setting: Trihueco Formation of the Arauco Basin, Chile

The Eocene Trihueco Formation is one of the best exposed successions of the Arauco Basin in Chile. It represents a period of marine regression and transgression of second-order duration, during which barrier island complexes developed on a muddy shelf. The strata are arranged in classical shoaling-upward parasequences of shoreface and beach facies capped by coal-bearing, back-barrier lagoon deposits. These fourth-order cycles are superimposed upon third-order cycles which caused landward and seaward shifts of the coastal facies belts. The final, punctuated rise in sea level is represented by shelf mudrocks with transgressive incised shoreface sandstones. Relative sea-level oscillations as revealed in the stratigraphy of the Trihueco Formation show a reasonable correlation with published Eocene eustatic curves.     

三水盆地古近系(土布)心组黑色页岩中黄铁矿的形成及其控制因素

黄铁矿是富有机质沉积的特征矿物。根据TOC/S、TOC/DOP、S/Fe关系以及S TOC Fe多重线性回归分析结果对三水盆地古近系〖HT5”,6”〗土〖KG-*3〗布〖HT5”SS〗心组红岗段黑色页岩中沉积黄铁矿的形成及其控制因素进行了分析。土布心组红岗段黑色页岩的黄铁矿有成岩黄铁矿和同生黄铁矿两种成因组分。红岗段下部（亚段A）有机碳含量普遍较低,底部水体以弱氧化条件为主,硫酸盐还原作用发生于沉积物/水界面以下,黄铁矿为成岩成因,其形成主要受有机质的限制。红岗段中上部（亚段B和C）的沉积条件变化频繁,其有机碳含量变化幅度大。富有机质（TOC>4%）岩层形成于缺氧的底部水体条件下。水体中可含H2S,碎屑铁矿物在埋藏之前即与之在水体中反应形成同生黄铁矿。这一过程不受有机质的限制,而是受活性铁与H2S接触时间的限制。同时,由于大量淡水输入导致硫酸盐浓度的降低,从而对硫化物形成有一定的限制作用。对于低有机质（TOC<4%）样品,黄铁矿由同生和成岩组分组成。其中以成岩黄铁矿为主,其形成过程主要受有机质限制,而同生黄铁矿受铁矿物与H2S接触时间的限制。     

Sedimentary characteristics of large‐scale lacustrine beach‐bars and their formation in the Eocene Boxing Sag of Bohai Bay Basin,East China

The beach‐bar reservoir play has become an important exploration target within the Bohai Bay Basin, especially in the Boxing Sag within the Dongying Depression, where a large‐scale lacustrine beach‐bar oil pool has been discovered recently. The sedimentary characteristics, distribution patterns and formation mechanisms of beach‐bar sand bodies in the upper fourth member of the Eocene Shahejie Formation (Es4s) in the Boxing Sag were studied in detail based on seismic, well log data and core data. The Es4s in the Boxing Sag is composed of a third‐order sequence consisting of three systems tracts, i.e. a lowstand systems tract, a transgressive systems tract and a highstand systems tract. Beach‐bar sand bodies were deposited widely in the basin during the lowstand systems tract period. The sandy beach‐bars are characterized by siltstones, fine‐grained silty sandstones interbedded with thin mudstone units. The presence of well‐developed sedimentary structures, such as swash bedding, parting lineation, parallel bedding, ellipsoidal mud clasts, ripples, terrestrial plant debris and vertical burrows, suggests that beach‐bars were deposited in a relatively shallow water environment under the influence of strong hydrodynamics. Laterally, the sandy beach facies occurred as a more continuous sheet‐like body around the sandy bar in most parts of the sag. Stratigraphically, beach‐bars were distributed mainly in the lowstand systems tract and they were less well‐developed in the transgressive systems tract and highstand systems tract. Several factors were probably responsible for the occurrence of the large‐scale beach‐bars during the lowstand systems tract period, including: (i) a gentle palaeoslope and relatively weak structural activities; (ii) a shallow‐water condition with a strong hydrodynamic environment; (iii) high‐frequency oscillations of the lake level; and (iv) an abundant terrigenous clastic feeding system with multiple‐point and linear sediment sources.     

A depositional model for deep‐lacustrine,partially confined,turbidite fans: Early Cretaceous,North Falkland Basin

This paper presents a model of facies distribution within a set of early Cretaceous, deep‐lacustrine, partially confined turbidite fans (Sea Lion Fan, Sea Lion North Fan and Otter Fan) in the North Falkland Basin, South Atlantic. As a whole, ancient deep‐lacustrine turbidite systems are under‐represented in the literature when compared with those documented in marine basins. Lacustrine turbidite systems can form extensive, good quality hydrocarbon reservoirs, making the understanding of such systems crucial to exploration within lacustrine basins. An integrated analysis of seismic cross‐sections, seismic amplitude extraction maps and 455 m of core has enabled the identification of a series of turbidite fans. The deposits of these fans have been separated into lobe axis, lobe fringe and lobe distal fringe settings. Seismic architectures, observed in the seismic amplitude extraction maps, are interpreted to represent geologically associated heterogeneities, including: feeder systems, terminal mouth lobes, flow deflection, sinuous lobe axis deposits, flow constriction and stranded lobe fringe areas. When found in combination, these architectures suggest ‘partial confinement’ of a system, something that appears to be a key feature in the lacustrine turbidite setting of the North Falkland Basin. Partial confinement of a system occurs when depositionally generated topography controls the flow‐pathway and deposition of subsequent turbidite fan deposits. The term ‘partial confinement’ provides an expression for categorising a system whose depositional boundaries are unconfined by the margins of the basin, yet exhibit evidence of internal confinement, primarily controlled by depositional topography. Understanding the controls that dictate partial confinement; and the resultant distribution of sand‐prone facies within deep‐lacustrine turbidite fans, is important, particularly considering their recent rise as hydrocarbon reservoirs in rift and failed‐rift settings.     

Recognition and significance of sharp‐based mouth‐bar deposits in the Eocene Green River Formation,Uinta Basin,Utah

Sandstone bodies in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, previously considered as point bars formed in meandering rivers and other types of fluvial bars, are herein interpreted as delta mouth‐bar deposits. The sandstone bodies have been examined in a 2300 m long cliff section along the Argyle and Nine Mile Canyons at the southern margin of the Uinta lake basin. The sandstone bodies occur in three stratigraphic intervals, separated by lacustrine mudstone and limestone. Together these stratigraphic intervals form a regressive‐transgressive sequence. Individual sandstone bodies are texturally sharp‐based towards mudstone substratum. In proximal parts, the mouth‐bar deposits only contain sandstone, whereas in frontal and lateral positions mudstone drapes separate mouth‐bar clinothems. The clinothems pass gradually into greenish‐grey lacustrine mudstone at their toes. Horizontally bedded or laminated lacustrine mudstone onlaps the convex‐upward sandstone bars. The mouth‐bar deposits are connected to terminal distributary channel deposits. Together, these mouth‐bar/channel sandstone bodies accumulated from unidirectional jet flow during three stages of delta advance, separated by lacustrine flooding intervals. Key criteria to distinguish the mouth‐bar deposits from fluvial point bar deposits are: (i) geometry; (ii) bounding contacts; (iii) internal structure; (iv) palaeocurrent orientations; and (v) the genetic association of the deposits with lacustrine mudstone and limestone.     

Controls of faulting on synrift infill patterns in the Eocene PY4 Sag,Pearl River Mouth Basin,South China Sea

Tectono-stratigraphic analysis of the Eocene PY4 Sag, Pearl River Mouth Basin, reveals that the evolution of normal faulting exerted an important control on the basin infill patterns. Seismic, well log and core data jointly indicate the Eocene Wenchang Formation can be subdivided into four third-order sequences that are related to early rift (WSQ1), rift climax (WSQ2–3) and late rift (WSQ4) stages. During the early rift stage, the PY4 Sag was defined by three, small-sized depocentres; it was related to low tectonic subsidence and likely overfilled by footwall-derived fan-delta deposits. The isolated depocentres coalesced and formed a larger and more uniform depocentre during the rift climax stage. Significantly increased tectonic subsidence during the rift climax WSQ2 sub-stage gave rise to prominent deep lake deposition including nearshore subaqueous fans, turbidite fan deposits and good source rocks. Two sediment infill patterns adjacent to boundary fault are developed during the rift climax WSQ3 sub-stage: (i) a more likely sediment balance-filled pattern controlled by the low-angled fault and (ii) a sediment under-filled pattern adjacent to the relatively high-angle boundary fault. The late rift stage was characterised by a waned displacement on the NE-striking fault but an increase in displacement on E-striking rift-related faults; this non-synchronous faulting has led to the sediment overfilled pattern observed in the South Sub-sag but a more sediment balance-fill on the South-western Slope. The variability in the basin infill patterns is suggested to have resulted from the different fault displacement patterns, which are closely linked to the boundary fault angles and possible stress field transitions during the basin evolution. This study may provide potential implications for basin infill evaluations in the Eocene Pearl River Mouth Basin and other similar rift systems.     

塔里木盆地周缘库车组、西域组磁性地层学初步划分

作者用磁性地层方法研究了塔里木盆地周缘库车组西域组地层。结果表明:库车组记录了吉尔伯特（Gilbert）负极性带,年龄为3.40～5.30Ma,其中显示了柯奇蒂（Cochiti）正极性亚带（3.80～3.90）,努尼瓦克（Nunivak）正极性亚带（4.05～4.20Ma）、西杜夫加尔（Sidufjal）正极性亚带（4.32～4.47Ma）及思维拉（Thvera）正极性亚带（4.85～5.00Ma）。下西域组记录了高斯（Gauss）正极性带,所龄为2.48～3.40Ma。其中包括凯纳（Kaena）负极性亚带（2.92～3.01Ma）与马莫斯（Mammoth）负极性亚带（3.05～3.15Ｍａ）。上西域组记录了松山（Matuyama）负极性带下段,年龄为1.50～2.48Ma。其中包括留尼昂（Reunion）正极性亚带（2.12～2.15Ma）与奥尔都维（Olduvai）正极性亚带（1.67～1.87）Ma）。根据上述古地磁资料,作者将库车组划为下上新统（N1 ₂ｋ）,年龄为3.40～5.30Ｍａ。下西域组划为上上新统（N2 ₂ｘ）,年龄为2.48～3.40Ma。上西域组划为下下更新统（Q1 ₁）,年龄为1.50～2.48 Ma 。作者认为由于印度板块向欧亚板块的俯冲造成塔里木盆地周缘山系的迅速抬升 ,形成高大山系的时代为上新世初期 ,大约 5.30 Ma 。     

桦甸盆地始新统桦甸组扇三角洲和水下扇粒度分析与对比

桦甸盆地始新统桦甸组扇三角洲主要划分出泥石流、水上分流河道、水下分流河道、河口坝、席状砂等沉积微相; 水下扇主要划分出辫状沟道和远源浊积岩等沉积微相。扇三角洲沉积物以颗粒支撑为主,自下而上按席状砂、河口坝、水下分流河道、水上分流河道、泥石流的顺序,沉积物粒度和标准偏差递增; 频率曲线尖度递减; 概率累计曲线由高--较高斜度两段式逐渐过渡为中--低斜度两段式、微向上凸的弧线式。反映出上述各微相向上粒度由细变粗的反粒序沉积特征,分选由好变差,杂基含量和水介质能量均逐渐增加。水下扇沉积普遍为杂基支撑,自下而上从远源浊积岩到辫状沟道沉积,粒径和标准偏差增大; 频率曲线尖度减小; 概率累计曲线主要由斜度较高的一段式过渡为斜度不大的一段式或微向上凸的弧线式,说明从远源浊积岩到辫状沟道微相粒度逐渐变粗,分选逐渐变差,杂基含量和水介质能量也逐渐增强。本区扇三角洲CM 图像呈“S”形,主要表现为牵引流沉积特征; 水下扇CM 图像表现为与C = M 线平行的长条带状重力流沉积特征。     

Evolution of an organic‐rich lake basin – stratigraphy,climate and tectonics: Piceance Creek basin,Eocene Green River Formation

The Piceance Creek basin formed as a continental foreland basin ca 53 to 48 Ma in the early to middle Eocene. On a global basis, the basin contains one of the richest oil shale resources known, where the profundal oil shale deposits, kerogen‐rich mudstones (clay and carbonate), exist over most of the basin. Despite its economic importance, the evolution of the Piceance Creek basin is still somewhat unclear. Based on facies association analysis, depositional trends, and gamma ray and Fischer assay data, six evolutionary lake stages are recognized: (i) fresh lake; (ii) transitional lake; (iii) highly fluctuating lake; (iv) rising lake; (v) high lake; and (vi) closing lake. Lake stages are composed of depositional units and characterize large‐scale changes in sedimentological patterns, depositional trends and fluctuations in the oil shale richness related to changes in climate and tectonics. Lake stage evolution is also consistent with the global Eocene climate trend. Stage 1 formed prior to the Eocene climate optimum. At the beginning of the Eocene climate optimum, a saline‐restricted lake formed (Stage 2) and evolved into the highly fluctuating lake (Stage 3) indicating rapid climate changes during the peak of the Eocene climate optimum. This stage was followed by the rising and high lakes (Stages 4 and 5) after the climate optimum and during a change to a more humid climate. The closing of the lake (Stage 6) was caused by increased sand input from the north, indicating the influence of both tectonics and climate. Based on depositional trends and climate evolution, it is suggested that, during the arid climate, laterally heterogeneous highly cyclic depositional units dominate, whereas, during the humid climate, depositional units form laterally continuous sediments that can be traced over long distances.     

Multiepisodic evaporite sedimentation as an indicator of palaeogeographical evolution in foreland basins (South‐eastern Pyrenean basin,Early–Middle Eocene)

Extensive deposition of marine evaporites occurred during the Early–Middle Eocene in the South‐eastern Pyrenean basin (north‐east Spain). This study integrates stratigraphic and geochemical analyses of subsurface data (oil wells, seismic profiles and gravity data) together with field surveys to characterize this sedimentation in the foredeep and adjacent platform. Four major evaporite units were identified. The oldest was the Serrat Evaporites unit, with a platform‐slope‐basin configuration. Thick salina and sabkha sulphates accumulated on the platform, whereas resedimented and gravity‐derived sulphates were deposited on the slope, and salt and sulphates were deposited in the deep basin. In the subsequent unit (Vallfogona evaporites), thin sulphates formed on the platform, whereas very thick siliciclastic turbidites accumulated in the foredeep. However, some clastic gypsum coming from the platform (gypsarenites and gypsum olistoliths) was intercalated in these turbidites. The following unit, the Beuda Gypsum Formation developed in a sulphate platform‐basin configuration, where the topography of the depositional surface had become smooth. The youngest unit, the Besalú Gypsum, formed in a shallow setting. This small unit provides the last evidence of marine influence in a residual basin. Sulphur and oxygen isotope compositions are consistent with a marine origin for all evaporites. However, δ³⁴S and δ¹⁸O values also suggest that, except for the oldest unit (Serrat Evaporites), there was some sulphate recycling from the older into the younger units. The South‐eastern Pyrenean basin constitutes a fine example of a foreland basin that underwent multiepisodic evaporitic sedimentation. In the basin, depositional factors evolved with time under a structural control. Decreasing complexity is observed in the lithofacies, as well as in the depositional models, together with a diminishing thickness of the evaporite units.     

Late Eocene Sporopollen and Paleoclimate, Paleoenvironment of the Yuanqu Basin, Shanxi

1.IntroductionTheYuanquBasinisoneoftheearliestst-UdiedCenozoicinlandbasinsinChina.Duetotheabun-dantmammalfossilsexcavatedfromthePaleogenestrataofthebasin,especiallythecompIeteandsuc-cessivestrataaswellasvariousabundantmammalfossilsofLateEocene,whichprovidesasufficientfoundationforthedeterminationofstratigraphicalage,itisregardedasaremarkablecriterionforcor-relationwithotherbasins.TheYuanquBasinIiesatthesouthemmarginoftheNofthChinaplatform,theFigurel.1ndexmapshowingthelocationoftheYuanqu…