西藏札达盆地上新统一早更新统河湖相地层多重地层划分与对比

根据札达盆地河湖相地层实测剖面中的接触关系、沉积旋回、沉积体系、岩相、岩性、古生物特征和ESR、古地磁测年结果,笔者对札达盆地上新统一早更新统河湖相地层进行了重新划分和时代确定。结合该套河湖相沉积的岩石地层、生物地层、年代地层、磁性地层、层序地层和地质构造事件,对札达盆地上新统一早更新统河湖相地层进行了多重地层的划分与对比。将札达盆地河湖相地层划分为3个组、4个沉积相、7个沉积亚相、11个岩性段。由新到老划分为：早更新统香孜组（Qp^1-1X）、上新统古格组（N22g）和上新统托林组（N2^1t）。     

Climate‐controlled aggradation and cyclicity of continental loessic siliciclastic sediments in Asselian–Sakmarian cyclothems,Permian, Hugoton embayment,USA

Siliciclastic intervals in Lower Permian carbonate–siliciclastic cyclothems in western Kansas record climate control on facies progression, deposition and preservation. The 26 000 km² study area comprises seven marine‐continental (carbonate–siliciclastic) cyclothems caused by glacioeustasy. Core data and a three‐dimensional geological model provide a detailed view of the sub‐surface on a gently sloping ramp. Siliciclastic intervals in the cyclothems are fine‐grained red beds with extensive pedogenic features, indicating a continental origin. Bed geometry (sheet‐like deposits that thin to the east), lateral grading, grain size (very fine‐grained sand to silt) and grain angularity (sub‐angular to angular) suggest that the sediment is loess sourced from the west, probably the Ancestral Rocky Mountains. There is a repeated record of glacial‐cycle‐scale, climate‐controlled cyclicity within siliciclastic intervals that has not been recognized previously. Aeolian silt grain size coarsens upward towards the middle, then fines upward in each siliciclastic interval. When sea‐level was high (interglacial) and carbonate production flourished, aeolian sedimentation nearly ceased, suggesting increased vegetation and rainfall at the source. As sea‐level fell, fine‐grained siliciclastic sediments were deposited under relatively dry, but seasonally wet conditions on an exposed ramp. Laterally graded coarser grained siliciclastic sediments with diagnostic fabrics indicate drier conditions with seasonal rainfall during a continued relative fall in sea‐level. The coarsest siliciclastic sediments were deposited during the lowest sea‐level and driest conditions, but still with sufficient seasonal moisture to allow vegetative cover and bioturbation. Subsequent upward fining is correlated with sedimentological indications of wetter conditions during relative sea‐level rise. Unlike common sequence stratigraphic models that relate siliciclastic sediment accumulation to base‐level rise, continental deposits were preserved because plants and pedogenesis stabilized aeolian sediment. The aggradational landscape formed by this process had several metres of positive relief that reduced accommodation for overlying marine carbonate strata. Thus, this mechanism for continental siliciclastic aggradation has a significant effect on sequence stratigraphic architecture.     

Small mammals from the early Pleistocene of the Granada Basin, southern Spain

The Pliocene and Pleistocene continental sedimentary records of the western sector of the Granada Basin, southern Spain, consist of alternating fluvial and lacustrine/palustrine sediments. Two Quaternary sections from this sector have been sampled: Huétor Tájar and Tojaire. They have yielded remains of rodents, insectivores and lagomorphs. The presence in the Huétor Tájar and Tojaire sections of Mimomys, Apodemus atavus, Castillomys rivas and two different species of Allophaiomys, indicates an Early Pleistocene age. These deposits, which are related to a fluvio-lacustrine system, can be differentiated from an older (Pliocene) braided fluvial system. Their dating has important repercussions on the paleogeographic reconstruction of the basin. The conditions inferred from the ecological preferences of the small mammal associations are wet and cold. These associations suggest a predominance of open herbaceous habitats, followed by forested habitats; semiaquatic habitats are the least represented.     

Pliocene sedimentation in a shallow, cool-water, estuarine gulf, Murray Basin, South Australia

The Pliocene Norwest Bend Formation is a well‐preserved succession of terrestrial and shallow‐marine deposits in the Murray Basin, South Australia. Sediments in this unit consist of two discrete terrigenous clastic‐rich, decametre‐scale sequences, or informal members, which record episodes of marine incursion during the Early and Late Pliocene respectively. The base of each sequence is a transgressive lag and/or strandline deposit that is transitional upwards into a highstand, subtidal, terrigenous clastic and cool‐water carbonate sediment accumulation. The top of each sequence is incised by fluvial channels that are filled by river deposits which formed as relative sea‐level fell and terrestrial environments prograded basinward. Sedimentological data suggest that gross stratigraphic architecture was primarily determined by glacioeustasy. Differences in sedimentary style between these two sequences, however, reflect a major climatic change that took place in southern Australia during the mid‐Pliocene. The lower quartzose sand member is formed of siliciclastic sediment derived from prolonged, deep, subaerial weathering and contains a bivalve‐dominated, cool‐temperate, open‐marine mollusc assemblage. These sediments accumulated under an equitable, relatively warm, humid climate. The Murray Basin during this time, because of high fluvial discharge, was a salt‐wedge estuary with typical estuarine circulation. In contrast, the upper, oyster‐rich member is typified by large monospecific oyster buildups that grew in restricted coastal environments. Strandline deposits contain a warm‐temperate skeletal assemblage. Contemporaneous aeolian sediments accumulated under warm, semi‐arid climatic conditions. Well‐developed ferricrete, silcrete and calcrete horizons reflect cyclic conditions of rainwater infiltration and evaporation in the seasonally dry climate that typifies southern Australia today. Highly seasonal rainfall produced an estuary that fluctuated annually from being well to partially mixed. These Pliocene sediments support the notion that mollusc‐rich facies are the signature of cool‐water carbonate accumulations in inboard neritic environments. Unlike bryozoans that dominate the outer parts of Cenozoic cool‐water carbonate shelves, molluscs evolved to exploit an array of coastal ecosystems with wide salinity variations and variable sedimentation rates.     

Genesis of deformation structures affecting Plio-Pleistocene sediments in the western Portuguese mainland (West Iberia). Implication on the regional neotectonics

A careful analysis of the morphology, geologic setting, stratigraphic distribution and sedimentological context of deformation features in sediments can give valuable information for the interpretation of their genesis, namely if they are of sedimentary or tectonic origin. This approach was used for the study area, located in the western region of the Portuguese mainland (West Iberian margin), where significant neotectonic and seismic activities occur, contrasting with the stabler interior of Iberia. Notwithstanding the regional neotectonics (intended as upper Pliocene to Recent), part of the deformation features observed in the studied deposits (Pliocene to Pleistocene in age) may be attributed to other phenomena but seismic shaking and/or active faulting. Slump beds and flame structures in coarse sand deposits are probably related to sedimentary overloading in high supply delta plain setting. Part of the deformation observed in the sediments that overlie Jurassic marls and limestones was probably induced by karst sink. This process is plausible even in Plio-Pleistocene sediments that overlie low carbonate content basement rocks, such as marl dominated successions. Thus, the abundance of deformation features affecting the studied Plio-Pleistocene sedimentary cover may lead to an overestimation of the regional active tectonics. The neotectonic activity in this area is reconsidered from the interpretation of the triggering mechanisms responsible for the observed deformation.     

Downslope‐migrating sandwaves and platform‐margin clinoforms in a current‐dominated,distally steepened temperate‐carbonate ramp (Guadix Basin,Southern Spain)

During the Late Tortonian, platform‐margin‐prograding clinoforms developed at the south‐western margin of the Guadix Basin. Large‐scale wedge‐shaped deposits here comprise 26 rhythms of mixed carbonate–siliciclastic bedset packages and marl beds. These sediments were deposited on a shallow‐water, temperate‐carbonate distally steepened ramp. A downslope‐migrating sandwave field developed in this ramp, with sandwaves moving progressively down the ramp to the ramp‐slope, where they destabilized, folded and occasionally collapsed. Downslope sandwave migration was induced by currents flowing basinwards. During the Late Tortonian, the Guadix Basin was open north to the Atlantic Ocean via the Dehesas de Guadix Strait and connected east to the Mediterranean Sea through the Almanzora Corridor. According to the proposed current circulation model for the Guadix Basin for this time, surface marine currents from the Atlantic entered the basin from the northern seaway. These currents moved counter‐clockwise and shifted the sediment on the ramp, forming sandwaves that migrated downslope. The development of platform‐margin prograding clinoforms by the basinward sediment‐transport mechanisms inferred here is known relatively poorly in the ancient sedimentary record. Moreover, these wedge‐shaped geometries are similar to those found in some shelves in the Western Mediterranean Sea and could represent an outcrop analogue to (sub)‐recent, platform‐margin clinoforms revealed by high‐resolution seismic studies.     

混合沉积研究进展与关键问题

近年来,混合沉积研究已逐渐成为沉积学领域颇受关注的重要课题。在前人研究的基础上系统梳理、总结了国内外混合沉积研究所取得的进展,提出了现阶段混合沉积研究面临的主要问题。国内外混合沉积研究可划分为4个阶段:现象描述阶段、基础理论研究阶段、海相混合沉积研究阶段、陆相混合沉积及综合研究阶段。受不同地质条件的约束,混合沉积岩石学分类方案并未形成统一的标准。混合沉积成因类型一般包括间断混合、相混合、原地混合与母源混合。混合沉积现象具有普遍性,可发育于海相、淡水湖盆、咸化湖盆等各类型沉积环境中,具有多样化的沉积类型,其控制因素一般包括碎屑物质供给、气候与水体环境、海（湖）平面变化、古地貌条件、构造作用以及水动力条件等。混合沉积具有重要的油气地质意义,与三角洲伴生的近源混合沉积、水下隆起区的远源混合沉积以及藻混合沉积可形成优质的陆相混积型油气储层。现阶段混合沉积研究中主要存在以下几方面问题:岩石分类方案不统一、缺乏与野外露头剖面和现代沉积的考察对比、层序格架内混合沉积发育模式不清、传统的成因类型在复杂陆相混合沉积研究中的应用存在较大局限性、混积型储层地震响应特征不明确。针对混合沉积进行全面、深入的研究,对古地理环境恢复、沉积动力学分析及相关油气勘探具有重要的意义。     

Review of the chronostratigraphic charts in the Sinú-San Jacinto basin based on new seismic stratigraphic interpretations

Disperse and punctual studies; absence of integration of data ranging from local to regional focus; interpretations based only on lithostratigraphic features; and interpretation of data premised on an allochthonous origin of the Caribbean plate, are some of factors that increase the confusion and uncertainty in understanding the Sinú-San Jacinto Basin. The sedimentary record of Upper Cretaceous to Eocene has been traditionally interpreted as the record of deep-water settings. However, recently these sediments have been related to shallow marine and deltaic settings. Second problematic point is about the deposition environment of the Oligocene to Late Miocene succession. Some studies suggest canyons, turbidites and sediments deposited in deep-water settings. However, recent studies propose deltaic and shallow marine settings. The last stratigraphic problem is related to the controversial fluvial vs. shallow marine interpretations of the Pliocene sediments. Based upon seismic stratigraphic analysis in recent and reprocessed 2D seismic data, integrated with well data, we propose chronostratigraphic charts for the northern, central and southern zones of the Sinú-San Jacinto Basin. Twenty seismic facies based on amplitude, continuity, frequency and geometry of seismic reflectors and twelve seismic sequences were recognized. The seismic stratigraphic analysis in this study suggests that the sediments of Upper Cretaceous to Paleocene/Eocene were associated to continental to shallow marine settings. Lagoons, coastal plain and carbonate platform dominated during this period. The Oligocene to Middle Miocene record was characterized by deep-water deposition, whereas the Late Miocene to recent sedimentation was characterized by falling base level, characterized by deltaic and fluvial deposits. Five syn-rift sequences with wedge-shaped geometry were identified in this study. Three Triassic to Jurassic syn-rift sequences were characterized by seismic facies typical of fluvial to lacustrine and flood plain sedimentation. Two Cretaceous to Paleocene syn-rift sequences were characterized by seismic facies related to lagoons to coastal plain settings. Normal high-angle faults with a northeast-southwest direction related to rifting processes controlled the development of these sequences. The sheet-drape post-rift section was characterized by passive margin settings in the northern part of the Sinú-San Jacinto Basin and by diachronic tectonic inversion of older normal faults during Cenozoic, predominantly in the central and southern zones. The stratigraphic record related to the Mesozoic to Early Cenozoic rifting; the shallow marine sedimentation during Eocene and the tectono-stratigraphic continuity across the northern Colombia and northwestern Venezuela is coherent and well explained by the in situ origin of the Caribbean plate and is not explained by the “allochthonous” model.     

Seismic stratigraphy as indicator of late Pleistocene and Holocene sea level changes on the NE Brazilian continental shelf

The late Pleistocene Holocene stratigraphic architecture on the northeastern Brazilian continental shelf off the Parnaíba Delta has been explored by high-resolution seismic profiles. The seismic surveys reveal the widespread distribution of incised valleys of different size in offshore continuation of the present-day Parnaiba delta. According to morphology two channel types can be distinguished: U-shaped channels in the eastern part and V-shaped channels in the western part. The stratigraphic successions were grouped into four seismic units separated by different seismic boundaries. The characteristics of the seismic boundaries and internal reflectors of the seismic units were used to distinguish between marine and riverine deposits. The incised-valleys architectural elements were used to link sedimentation processes and variations in base level from late Pleistocene channel avulsion and channel infill in the lowermost course of the paleo-Parnaíba River to marine sediments of the present-day inner shelf. The change of the depositional environments in relation to deglacial sea-level rise is compared to incised valley infills of the Mekong River and Red River systems in Southeast Asia.     

济源盆地中侏罗统马凹组上段混合沉积特征及其控制因素

陆源碎屑与碳酸盐混合沉积是一种沉积机理特殊而又有重要意义的沉积现象。目前陆相地层的混合沉积研究相对薄弱。混合沉积在豫西济源盆地中侏罗统马凹组上段较发育,本文综合应用沉积学、沉积地球化学、古生物地层学方法对其特征及控制因素进行了研究。结果表明,研究区马凹组上段发育泥质灰岩、灰质泥岩和含灰泥岩等多种岩性组成的成分混合沉积和由其夹层或互层组成的结构混合沉积,较干燥炎热气候条件及弱氧化-弱还原的半咸水环境有利于混合沉积发育,混合沉积是古构造、古气候和物源供给共同控制的结果。本研究对于充实沉积机理理论有一定的意义,亦为陆相混合沉积研究提供了一个较好的实例。     

西藏札达盆地上新统古格组和托林组的厘定与层序地层划分

根据札达盆地剖面中地层的接触关系、沉积旋回、沉积体系和岩相岩性特征,可将上新统河湖相地层划分为2个组、5个沉积相、8个岩段。古格组(N22g)一岩段为砾岩,属河流相沉积;二、三、五岩段以细碎屑岩为主,属浅湖相沉积;四岩段以含粘土质细碎屑岩为主,属深湖相沉积。托林组(N21t)一、二、三岩段为一套砾岩、含砾中粗粒钙质长石岩屑砂岩和中细粒砂岩的碎屑岩,为典型冲(洪)积扇沉积物。ESR法和古地磁法测年结果表明,古格组形成时代为上新世晚期(4.40～2.47Ma);托林组形成时代为上新世早期(5.44～4.40Ma)。札达盆地为一同生断陷盆地,在上新世时期的构造运动过程中,盆地演化经历了水进体系域—湖泊扩张体系域—湖泊收缩体系域3个发展阶段。     

Sequence stratigraphy of a Mesozoic carbonate platform-to-basin system in western Sicily

Sequence stratigraphic studies of the Triassic through Paleogene carbonate successions of platform, slope and basin in western Sicily (Palermo and Termini Imerese Mountains) have identified a sedimentary cyclicity mostly caused by relative oscillations of sea level. The stratigraphic successions of the Imerese and Panormide palaeogeographic domains of the southern Tethyan continental margin were studied with physical-stratigraphy and facies analysis to reconstruct the sedimentary evolution of this platform-to-basin system. The Imerese Basin is characterized by a carbonate and siliceous-calcareous succession, 1200–1400m thick, Late Triassic to Eocene in age. The strata display a typical example of a carbonate platform margin, characterized by resedimented facies with progradational stacking patterns. The Panormide Carbonate Platform is characterized by a carbonate succession, 1000–1200 m thick, Late Triassic to Late Eocene, mostly consisting of shallow-water facies with periodic subaerial exposure. The cyclic arrangement has been obtained by the study of the stratigraphic signatures (unconformities, facies sequences, erosional surfaces and stratal geometries) found in the slope successions. The recognized pattern has been compared with coeval facies of the shelf. This correlation provided evidence of sedimentary evolution, influenced by progradation and backstepping of the shelf deposits. The stratigraphic architecture of the platform-to-basin system is characterized by four major transgressive/regressive cycles during the late Triassic to late Eocene. These cycles, framed in a chronostratigraphic chart, allows the correlation of the investigated shelf-to-basin system with the geological evolution of the African continental margin during the Mesozoic, showing tectono-eustatic cycles. The first cycle, encompassing the late Triassic to early Jurassic, appears to be related to the late syn-rift stage of the continental margin evolution. The following three cycles, spanning from the Jurassic to Eocene, can be related to the post-rift evolution and to thermal subsidence changes.     

西藏阿里札达盆地下更新统香孜组地层厘定与层序地层划分

根据札达盆地香孜组河湖相地层剖面的接触关系、沉积旋回、沉积体系和岩相岩性特征,可将札达盆地下更新统香孜组河湖相地层划分为2个沉积相、3个岩段。香孜组一、二岩段为一套砾岩夹砂岩的粗碎屑岩,属典型的冲（洪）积扇沉积物;第三岩段为砾岩与砂岩互层,属冰水冰缘相沉积。ESR法和古地磁法测年结果表明,札达盆地香孜组河湖相地层的形成时代为早更新世早期（2．68—1．36Ma）。札达盆地为一同生断陷盆地,在后期重新复活的过程中,盆地只经历了冲积体系域和水进体系域。冲积体系域形成于札达盆地早更新世早期重新复活层序发育的早、中期,水进体系域形成于札达盆地早更新世早期重新复活层序发育的晚期。     

Sedimentological and palynological constraints on the basal Triassic sequence in Central Switzerland

In Central Switzerland, Mesozoic sedimentation began after erosion and peneplainisation of the Hercynian relief and late Paleozoic continental deposition in SW-NE striking pull-apart basins. The first Triassic sedimentary sequence overlaying a weathered crystalline basement consists of a relatively thin (<10 m), lithologically highly variable unit with coarse-grained siliciclastic deposits at the base, grading into a mixed sandstone/shale-dolomite sequence followed by well-bedded dolomites with chert nodules.Sedimentary texture analyses and petrological investigations revealed four different sedimentary units starting at the base with a regolith unit that represents the weathered crystalline basement. It is overlain by terrestrial plain deposits, followed by mixed siliciclastic-carbonaceous sediments and a sequence of dolomites, deposited between the supralittoral and eulittoral zones of a tidal flat (Mels-Formation), and the eulittoral to sublittoral zones of a carbonate tidal flat environment (Röti-Dolomit), respectively.Palynological data from four localities in Central Switzerland indicate a heterochronous early Anisian age (Aegean – Bithynian/Pelsonian) for the supra- to eulittoral mixed siliciclastic-carbonaceous sediments. These new biostratigraphic ages suggest that the first Triassic marine transgression in Central Switzerland is time equivalent with those of the basal Wellendolomit in Northern Switzerland but slightly older than in the Germanic Basin. Consequently, Central Switzerland was located at this time at the northern shoreline of the Tethys and not on the southern limit of the Germanic Basin.     

Quantitative subsidence-uplift analysis of the Bajo Segura Basin (eastern Betic Cordillera, Spain): tectonic control on the stratigraphic architecture

The Bajo Segura Basin is located in the eastern Betic Cordillera, at present connected with the Mediterranean Sea to the east. It has a complete stratigraphic record from the Tortonian to the Quaternary, which has been separated into six units bounded by unconformities. This paper is concerned with the northern edge of the basin, controlled by a major strike–slip fault (the Crevillente Fault Zone, CFZ), where the most complete stratigraphic successions are found. The results obtained (summarised below) are based on an integrated analysis of the sedimentary evolution and the subsidence-uplift movements. Unit I (Early Tortonian) is transgressive on the basin basement and is represented by ramp-type platform facies, organised in a shallowing-upward sequence related to tectonic uplift during the first stages of movement along the CFZ. Unit II (lower Late Tortonian) consists of shallow platform facies at bottom and pelagic basin facies at top, forming a deepening-upward sequence associated with tectonic subsidence due to sinistral motion along the CFZ. Unit III (middle Late Tortonian) is made up of exotic turbiditic facies related to a stage of uplift and erosion of the southern edge of the basin. Unit IV (upper Late Tortonian) consists of pelagic basin facies at bottom and shallow platform facies at top, defining a shallowing-upward sequence related to tectonic uplift during continued sinistral movement on the basin-bounding fault. Units V (latest Tortonian–Messinian) and VI (Pliocene–Pleistocene p.p.) consist of shallowing-upward sequences deposited during folding and uplift of the northern margin of the basin. No definitive evidence of any major eustatic sea-level fall, associated with the ‘Messinian salinity crisis’, has been recorded in the stratigraphic sections studied.     

Platform margins, reef facies, and microbial carbonates; a comparison of Devonian reef complexes in the Canning Basin, Western Australia, and the Guilin region, South China

Devonian reef complexes were well developed in Western Australia and South China, but no detailed direct comparison has been made between reef building in the two regions. The regions differ in several respects, including tectonic, stratigraphic and palaeoceanographic–palaeogeographic settings, and the reef building styles reflect minor differences in reef builders and reef facies. Similarities and differences between the two reef complexes provide insights into the characteristics of platform margins, reef facies and microbial carbonates of both regions. Here we present a comparison of platform margin types from different stratigraphic positions in the Late Devonian reef complex of the Canning Basin, Western Australia and Middle and Late Devonian margin to marginal slope successions in Guilin, South China. Comparisons are integrated into a review of the reefal stratigraphy of both regions. Reef facies, reef complex architecture, temporal reef builder associations, 2nd order stratigraphy and platform cyclicity in the two regions were generally similar where the successions overlap temporally. However, carbonate deposition began earlier in South China. Carbonate complexes were also more widespread in South China and represent a thicker succession overall. Platforms in the Canning Basin grew directly on Precambrian crystalline basement or early Palaeozoic sedimentary rocks, but in South China, carbonate complexes developed conformably on older Devonian siliciclastic strata. Pre-Frasnian reef facies in South China had more abundant skeletal frameworks than in Canning Basin reefs of equivalent age, and Famennian shoaling margins containing various microbial reefs may have been more common and probably more diverse in South China. However, Late Devonian platform margin types have been documented more completely in the Canning Basin. Deep intra-platform troughs (deep depressions containing non-carbonate pelagic sediments — Nandan-type successions) that developed along syndepositional faults characterize Devonian carbonate platforms in South China, but have no equivalent on the Lennard Shelf, Canning Basin where inter-reef areas were more shallow. The South China platform-to-depression pattern was generally continuous from the Lower to Upper Devonian, indicating that many pre-Devonian tectonic features continued to exercise considerable effect through deposition. Localized, fault-controlled subsidence was an important factor in both regions, but similarities in 2nd order aggradation–progradation cycles suggest that eustasy was also an important control on the larger scale stratigraphic development of both regions.     

Large- and small-mammal distribution patterns and chronostratigraphic boundaries from the Late Pliocene to the Middle Pleistocene of the Italian peninsula

Over the last 50 years the studies on terrestrial mammals of the Italian peninsula have provided a large volume of data and a more detailed knowledge of faunal events during the Late Pliocene and Quaternary. Moreover geological, sedimentological, palynological and magnetostratigraphical investigations on the Pliocene–Pleistocene continental sedimentary basins have yielded the possibility of a detailed calibration of the faunal successions. Thus, palaeontologists have been able to reconstruct faunal sequences and to propose biochronological scales based on large and small mammals, respectively. In the present contribution an integration of the two biochronological scales is proposed, and the successions of bioevents are carefully compared. This integrated approach allows the constraint of the sequence of large- and small-mammal events in a more reliable way, and therefore it results in a more detailed and consistent chronological use of mammalian assemblages. Particular attention is paid to the faunal changes that correspond to the Middle–Late Pliocene (2.6 ma), Pliocene–Pleistocene (1.8 ma) and Early–Middle Pleistocene (Gauss–Matuyama transition) chronostratigraphical boundaries.     

西藏阿里札达盆地上新世-早更新世河湖相地层层序地层分析

根据札达盆地河湖相剖面地层岩性、粒度、沉积构造、古生物等反映的沉积岩相,以及不整合面等沉积特征,可将札达盆地上新世—早更新世河湖相地层,初步划分为两个三级层序(Ⅰ、Ⅱ)。层序Ⅰ代表上新统地层层序,并进一步区分出退积准层序组和进积准层序组。对应上新世湖相沉积由低位体系域—湖泊扩张体系域—湖泊收缩体系域的演化,反映湖泊由源区水系冲积亚相—滨湖三角洲亚相—滨浅湖亚相—半深湖亚相—滨浅湖亚相的湖泊,由扩张到萎缩的一个完整的发展演化旋回。层序II代表下更新统地层层序,反映一个盆地受构造和气候(冰期—间冰期)双重控制的夭折型冰湖形成演化的由冰水冲积相到冰湖沉积相的不完整沉积旋回,为青藏高原新近系上新统与第四系的研究与划分提供了重要依据。     

A stratigraphical-geochemical study on the Chaco Paraná continental rift basin—An approach study based on regional sedimentology and drill-hole core analyses, South América

1IntroductionThis paper is focused on the Southamerican geo-logical history of the Chaco Paran偄Basin rift system inthe last75-65Ma,including some Quaternary phe-nomena(Fig.1).The study presents a new interpre-tation to its evolution and stratigraphy.The …