Eocene fauna of Messel Pit Fossil Site, Germany

The paper reports sunthetically the Cocene fauna of the Messel Pit Fossil site of Germany, in detail, including its rich taxanomic composttions, geological and paleogeographic backgroud, and the studying and applying history.     

近岸水下扇扇中厚砂体储层构型及对剩余油控制——以南襄盆地泌阳凹陷古近系核桃园组三段四砂组2小层为例

南襄盆地泌阳凹陷赵凹油田安棚主体区古近系核桃园组三段四砂组2小层(H3_IV2)为厚层近岸水下扇扇中砂体沉积,不同期次沟道砂体相互切割叠置,形成复杂的空间结构样式,极大影响了油田开发。亟需开展厚层砂体内部结构解剖,揭示不同期次沟道砂体分布,明确其结构样式对油水运动影响及剩余油分布控制。本文以储层构型要素分析法为指导,综合利用岩芯、测井、生产动态资料,对近岸水下扇扇中厚砂体构型进行了精细刻画。通过研究明确了研究层段构型界面6级级次划分方案,建立了复合辫状沟道内部单砂体边界的垂向和侧向识别标志,其中垂向边界识别标志有泥质类岩性界面和底冲刷界面2种,侧向边界的识别标志包括不同单砂体的顶面高程差异、厚度差异、测井曲线形态差异等5种;在单砂体识别的基础上开展了目的层厚砂体井间构型分布规律研究,将复合辫状沟道砂体解剖为单一期次辫状沟道砂体,明确了各单期辫状沟道砂体的展布特征,并统计分析了辫状沟道单砂体构型单元的特征参数;通过上述研究总结了研究区单砂体构型单元接触样式,主要包括孤立式、叠加式、叠切式3种垂向接触样式和分离式、对接式、侧切式3种平面接触样式;分析了单砂体对剩余油的控制作用,研究发现4级构型单元内部韵律性以及构型单元之间接触样式对油水运动有重要影响,是造成剩余油富集的两个重要因素。     

Tectono-stratigraphic evolution and hydrocarbon exploration in the Eocene Southern Lufeng Depression,Pearl River Mouth Basin,South China Sea

The structural evolution and stratigraphic architecture of the Southern Lufeng Depression in the Pearl River Mouth Basin, South China Sea show two second-order sequences (SSQ1 and SSQ2) and nine third-order sequences (WSQ1-5 and ESQ1-4) within the Eocene rift-related successions. Based on integrated interpretations of seismic reflections, well logs and core data, five distinct tectono-stratigraphic patterns are identified: (1) the initial synrift-I sequence (WSQ1) of low tectonic subsidence, overfilled by alluvial fan or fan-delta deposits and volcanic deposits, with no clear systems tracts; (2) the climax synrift-I sequences (WSQ2–4) developed in response to rapid tectonic subsidence, generally consisting of a low-stand systems tract (LST), transgressive systems tract (TST) and high-stand systems tract (HST); (3) the late synrift-I sequence (WSQ5) characterised by a decreased tectonic subsidence rate, dominated by braided delta, deep and shallow lacustrine sediments, mainly constructed by TST and HST; (4) the early synrift-II sequences (ESQ1–2) rapidly filled by braided deltaic sandstone and mainly composed of TST and HST with less common LST units; and (5) the late synrift-II sequences (ESQ3–4), which are totally filled by braided deltaic system in a shallow-water lake setting, presenting typical imbricate clinoforms or sub-parallel seismic configurations, consisting of only TST and HST components. During the climax stage of synrift-I development, the depositional setting changed from a prominent shallow lake (WSQ2) to a deep-lucustrine with turbiditic deposits (WSQ3) and finally dominated by mostly braided deltaic-shallow lacustrine deposits (WSQ4); the HST occupies an increasing proportion from early to late. Furthermore, the stratigraphic patterns, especially LST units of the climax synrift-I stage, are significantly influenced by topographic variations and slope-break belt types in the hanging dip-slope. This study reveals that the spatial and temporal evolution of lacustrine depositional and stratigraphic patterns were significantly controlled by the interplay of tectonic subsidence and sediment supply, and provides a fundamental basis for predicting the favourable reservoirs and geometry of source rocks related to the general variability of Eocene rift-related tectonic subsidence in the Southern Lufeng Depression of the Pearl River Mouth Basin. Furthermore, the topographic responses of differential active fault-stepped patterns associated with magma intrusions, highlight the variability of relevant sequence architectures in the hanging dip-slope in lacustrine rift basins.     

Community Structure in the Amber Forest: Study of the Arthropod Syninclusia in the Rovno Amber(Late Eocene of Ukraine)

<正>Arthropodan syninclusions in the Late Eocene Rovno amber were examined using x~2 to reveal correlation of the component groups(some taxa of Diptera,ants,aphids,and mites) supposedly indicative of the biocoenotic relationships in the ancient amber forest.Three tightly correlated groups were identified,representing a putative aerial plankton guild(Chironomidae+Ceratopogonidae) and two tree-trunk guilds,one of which (Dolichopodidae+Germaraphis) is possibly connected to more open or/and more hygrophilous habitats than the other(Sciara zone Diptera +"Acarus"rhombeus).The ants were not linked with any of the above components.     

New Taxa of Chrysomelidae (Insecta:Coleoptera)from Rovno Amber,Late Eocene

<正>Leaf beetles Chrysomelidae of Rovno amber,from the Late Eocene,are recorded and described. Chrysomelidae of Rovno amber are represented by three subfamilies:Galerucinae(Alticini),Chrysomelinae,and Eumolpinae.Two new genera and three new species of Alticini:Manobiomorpha Nadein,gen.nov.(type species Manobiomorpha eocenica Nadein,sp.nov.),Psyllototus Nadein,gen.nov.(type species Psyllototus progenitor Nadein,sp.nov.),and Crepidodera decolorata Nadein et Perkovsky,sp.nov.are described.A new chrysomeline genus and species Paleophaedon minutus Nadein gen.nov.et sp.nov.is described.Probable trophic association of Crepidodera decolorata sp.nov.,the taxonomic positions of Manobiomorpha gen.nov.and Psyllototus gen.nov., and the composition of leaf beetle faunas of Middle and Late Eocene of Europe are discussed.     

A New Species Group in the Genus Tanytarsus van der Wulp(Diptera:Chironomidae)Based on a Fossil Record from Baltic Amber

<正>A new fossil chironomid,Tanytarsus serafini,found in Baltic amber is described and illustrated based on adult males.The new species and similar extant species of the genus Tanytarsus van der Wulp are compared. Due to several distinct characters of wing,legs and hypopygium,a new species group for Tanytarsus serafini is proposed,and its diagnostic features are evaluated.     

Biostratigraphy of a Paleocene-Eocene Foreland Basin boundary in southern Tibet

<正>This study of the Paleocene—Eocene boundary within a foreland basin of southern Tibet, which was dominated by a carbonate ramp depositional environment,documents more complex environmental conditions than can be derived from studies of the deep oceanic environment.Extinction rates for larger foraminiferal species in the Zongpu-1 Section apply to up to 46%of the larger foraminiferal taxa. The extinction rate in southern Tibet is similar to rates elsewhere in the world,but it shows that the Paleocene fauna disappeared stepwise through the Late Paleocene,with Eocene taxa appearing abruptly above the boundary.A foraminifera turnover was identified between Members 3 and 4 of the Zongpu Formation—from the Miscellanea—Daviesina assemblage to an Orbitolites—Alveolina assemblage.The Paleocene and Eocene boundary is between the SBZ 4 and SBZ 5,where it is marked by the extinction of Miscellanea miscella and the first appearance of Alveolina ellipsodalis and a large number of Orbitolites. Chemostratigraphically,theδ~(13)C values from both the Zongpu-1 and Zongpu-2 Sections show three negative excursions in the transitional strata,one in Late Paleocene,one at the boundary,and one in the early Eocene.The second negative excursion ofδ~(13),which is located at the P—E boundary,coincides with larger foraminifera overturn.These faunal changes and the observedδ~(13)C negative excursions provide new evidence on environmental changes across the Paleocene—Eocene boundary in Tibet.     

Magnetic Stratigraphy from Deep Clastic Turbidites: An Example from the Eocene Hecho Group (Southern Pyrenees)

A paleomagnetic study of a 2200-meter thick section of clastic turbidites from the Eocene Hecho group (southcentral Pyrenees, Spain) allows defining its magnetostratigraphic record. Natural remanent magnetization is carried by up to three components: a viscous low-temperature component; a second component unblocked between 300°C and 345°C, likely carried by iron-sulphides; and a third component which demagnetizes at temperatures higher than 345°C and is likely carried by magnetite. The second and third components may display opposite polarities at the same site. The magnetite component delineates different polarity zones and has a more consistent behavior along section if compared with the iron-sulphide component, which displays either a normal or a reverse direction without any stratigraphic consistency along section. The bulk of iron sulphides are interpreted to be secondary in origin and to carry diagenetic overprints acquired at different times after deposition and the magnetite component is taken as the characteristic primary magnetization. As supported by biostratigraphy, the section is correlated from chrons C20r to C18n.2n (Lutetian-Bartonian transition), which indicates a mean sediment accumulation rate of about 52 cm/ky for the studied section. The new chronostratigraphy allows constraining the age of the upper Hecho Group (Banastón and Jaca allogroups) to an unprecedented level and is consistent with previous magnetostratigraphic work in younger sediments from the Jaca Basin. Deep clastic sedimentary systems should not be neglected as a target for magnetostratigraphic studies despite diagenetic growth of secondary minerals may mask the primary signal.     

Organic-walled phytoplankton from Paleogene sections of Kamchatka

Organic-walled phytoplankton assemblages from Eocene and Oligocene reference sections of western Kamchatka are analyzed. They are close in taxonomic composition to coeval assemblages of northern Japan and Sakhalin that is a good opportunity to correlate regional units and verify their age. The euryhaline species Trinovantedinium boreale that is associated with Paralecaniella indentata and Micrhystridium preferring shallow low-salinity waters, on the one hand, and taxa dwelling in normal-salinity open sea environments, on the other, are dominant in most assemblages, which are examined. The suggested variant of bed succession with dinocyst assemblages may be valid for Japan, Sakhalin, Kamchatka, and the Bering Sea.     

Gigantic volcanic eruptions and climatic change in the early Eocene

23 layers of altered volcanic ash (bentonites) originating from the North Atlantic Igneous Province have been recorded in early Eocene deposits of the Austrian Alps, about 1,900 km away from the source area. The Austrian bentonites are distal equivalents of the “main ash-phase” in Denmark and the North Sea basin. We have calculated the total eruption volume of this series as 21,000 km³, which occurred in 600,000 years. The most powerful single eruption of this series took place 54.0 million years ago (Ma) and ejected ca. 1,200 km³ of ash material, which makes it one of the largest basaltic pyroclastic eruptions in geological history. The clustering of eruptions must have significantly affected the incoming solar radiation in the early Eocene by the continuous production of stratospheric dust and aerosol clouds. This hypothesis is corroborated by oxygen isotope values, which indicate a global decrease of sea surface temperatures between 1 and 2°C during this major phase of explosive volcanism.