Geological note: Pyro‐intrusive veins in the northeastern Sydney Basin

Stratigraphic and sedimentological investigation of the interglacial succession within the Cryogenian-aged Umberatana Group of the Northern and Central Flinders Ranges reveals a complex array of sedimentary successions lying between the Sturtian and Marinoan glacial deposits. The Sturtian–Marinoan Series boundary was first defined from the Adelaide area at the uppermost contact of the Brighton Limestone. In the Northern Flinders Ranges the Sturtian–Marinoan Series boundary has been positioned at the uppermost contact of the Balcanoona Formation, which is thought to correlate with the Brighton Limestone. In the Northern Flinders Ranges a major unconformity separates the Sturtian and Marinoan-aged sedimentary successions (Nepouie–Upalinna Subgroups). In moderately deep marine depositional settings, this submarine unconformity is located at the base of the Yankaninna Formation where erosion has deeply incised (up to 300 m) into the underlying Tapley Hill Formation. In shallower marine settings the unconformity is found at the base of the Weetootla Dolomite. In very deep water depositional settings this unconformity is not recognised, and the Yankaninna Formation appears to conformably overlie the Tapley Hill Formation suggesting that this erosional feature is restricted to shallow and moderately deep depositional settings. This unconformity presents a regionally persistent chronostratigraphic marker horizon, which reliably marks the Sturtian–Marinoan Series boundary at the base of the Yankaninna Formation from shallow shelfal to deep-water basinal settings throughout the Northern Flinders Ranges. In the Central Flinders Ranges the post-Sturtian glacial stratigraphy records a very similar depositional record to that observed in the Northern Flinders Ranges. In the Central regions the Tapley Hill Formation is overlain by deep-marine carbonates and calcareous shales of the Wockerawirra Dolomite and Sunderland Formations, respectively. The base of the Wockerawirra Dolomite is found to be in erosional contact with the underlying Tapley Hill Formation. This stratigraphic relationship, together with lithological similarities, indicates the Wockerawirra Dolomite and Sunderland Formation of the Central Flinders Ranges are lateral correlatives of the Yankaninna Formation of the Northern Flinders Ranges. The regional nature of the Sturtian–Marinoan unconformity in the Adelaide Geosyncline suggest the possible existence of a glacio-eustatic event that may correlate with glacials/glaciation elsewhere on the Earth during the Cryogenian.     

Discussion: History of coastal dunes at triangle Cliff,Fraser Island,Queensland

The Drummond Basin represents a major, backarc extensional system located at the inboard margin of the northern New England Orogen. Its synrift (cycle 1) infill is distinctively volcanic and volcani‐clastic in character and displays complex facies relationships and considerable variations in thickness controlled by the history and fabric of extensional faulting and the distribution of coeval volcanic centres. Subtle inheritance signatures in the age spectra obtained by SHRIMP (II) Pb‐U dating of zircons from volcanic units have impeded age assignment. New geochronologic data indicate that basinal subsidence was initiated in the north in latest Devonian (Famennian) time but was delayed until the Early Carboniferous (Tournaisian) in the south. Northern successions are dominated by volcaniclastic strata that accumulated distal to the loci of contemporary volcanism, whereas southern successions are dominated by silicic flows and ash‐flow tuffs and associated hypabyssal intrusive suites proximal to, or coincident with, volcanic loci. The Burdekin, Clarke River and Bundock Creek Basins located north of the Drummond Basin are broadly coeval features with comparable Infill. They likewise represent backarc basins developed inboard of the northern New England Orogen which trends offshore at latitude 20°S and appears to be represented in basement cores recovered from the Coral Sea. Calc‐alkaline magmatism of Late Devonian‐Early Carboniferous age extended at least 400 km inboard of the Gondwanan plate margin now represented in Queensland and related to an acute angle of subduction along the active margin at that time.     

Stratigraphy and tectonics of the Early to Middle Proterozoic transition,Katherine‐El Sherana area,Northern Territory

Abstract

Two unconformity‐bound groups of volcanic rocks and associated sediments (El Sherana and Edith River Groups) separate the older Pine Creek Geosyncline metasediments from platform cover of the McArthur Basin. Dominated by intersecting NW and ENE rift systems, the volcanics are genetically related to an extensional tectonic system which was also active during deposition of the Pine Creek Geosyncline sequence. In contrast, the younger platform cover was deposited in a relatively stable environment. The rift valleys were filled with rhyolite flows, ignimbrite and ill‐sorted arenite and rudite, and flyschoid sediments spread onto adjacent lands. Following tight upright folding, granite intrusion and erosion, an extensive ignimbrite sheet (=6000 km²) spread from a centre probably at the intercept of the two rifts. Microgranite at this intersection was possibly emplaced in the evacuated magma chamber. The volcanic sequences were deeply eroded and weathered before platform cover deposition began. The platform sediments, represented in the area by the Kombolgie Formation, were deposited from about 1690 Ma to 1650 Ma, and their base is taken as the closest stratigraphic indicator of the boundary between the Early and Middle Proterozoic.     

苏北断陷湖盆坡折带类型与戴南组隐蔽圈闭分布

对苏北盆地高邮凹陷上白垩统—第三系层序地层及戴南组沉积特征研究表明,断陷湖盆中发育多级多类断裂坡折带,它们控制着层序和沉积体系的发育以及砂体的加厚带.高邮凹陷中真1断层为陡坡盆缘坡折带,控制了盆地的边界并控制着戴南组粗碎屑扇体的发育;真2断层为陡坡盆内坡折带,控制了戴南组粗碎屑扇体的加厚带;汉留断层为缓坡盆内坡折带,控制了戴南组三角洲前缘砂体的加厚带和滑塌浊积扇的分布,同时也控制着低位体系域以及高位体系域三角洲前缘—岸线的分布.坡折带的发育受到盆地幕式构造运动的控制.沿盆内坡折带附近发育各类隐蔽圈闭,是断陷湖盆中油气勘探的重点地区.     

Interactions climat-eustatisme-tectonique. Les enseignements et perspectives du Crétacé supérieur (Cénomanien-Coniacien)

Résumé

Une analyse de séries sédimentaires d’âge Crétacé supérieur dans le Sud-Est de la France a été entreprise et intégrée dans un cadre de stratigraphie séquentielle. Les limites Cénomanien–Turonien et la limite Turonien–Coniacien sont marquées par des variations rapides et de fortes amplitudes du niveau marin relatif. La comparaison effectuée avec d’autres bassins mondiaux nous amène à envisager le problème dans un cadre global. On constate : (1) le synchronisme d’événements à haute fréquence dans des contextes géodynamiques différents. (2) les effets de la superposition de cycles eustatiques hiérarchiquement différents, c’est-à-dire la superposition d’oscillations à haute fréquence sur une composante de 3^e ordre. Ces observations sont confrontées à deux hypothèses : le glacio-eustatisme et la tectonique à haute fréquence. © Elsevier, Paris.     

Sedimentary record of Late Paleozoic rift and break-up in Northern Gondwana: a case history from the Thini Chu Group and Tamba-Kurkur Formation (Dolpo Tethys Himalaya,Nepal)

The Gottero unit of the Northern Apennines, Italy, is representative of the sedimentary cover of the Ligure-Piemontese oceanic lithosphere. This unit consists of a thick sedimentary sequence that includes Valanginian-Santonian pelagic deposits and Campanian-early Paleocene turbiditic deposits. The latter are overlain by early Paleocene trench deposits related to frontal tectonic erosion of the accretionary wedge slope. This sequence is interpreted as recording trenchward motion of the oceanic lithosphere.

The Gottero unit records a pre-Late Oligocene, complex deformation history related to subduction and accretion events. This deformation history has developed through underthrusting (D1a), underplating (D1b and D1c) and later exhumation (D2a and D2b) episodes. The folding phase related to the main underplating sub-phase (D1b) is predated by a sub-phase (D1a) connected to rapid fluid escape and followed by a sub-phase dominated by the development of shear zones (D1c). The D1b sub-phase is characterized by similar folds and a slaty cleavage developed under P/T conditions of 0.4GPa/210°-270 °C. The D1c sub-phase, characterized by west-verging thrusts, is particularly signficative in understanding the dynamics of the Ligure-Piemontese accretionary wedge because it testifies active shortening of the Gottero unit also after its transfer to the prism. In addition, sub-phase D1c represents the transition from the sub-phases connected to accretion and the tectonics dominated by extension, characterized by parallel folds and low-to high-angle normal faults. The gravity driven extension is represented by the D2a and D2b sub-phases and can be interpreted as the result of the thicknening of the Ligure-Piemontese accretionary wedge, produced by continuous underplating at its base but also by shortening of the previously underplated units. These final tectonic events resulted in the exhumation of the Gottero unit to the surface during the Early Oligocene, when this Unit became one of the source areas of the conglomerates deposited in the Tertiary Piedmont basin.

This deformation history suggests the occurrence of a complex sequence of deformations during the transition from accretion to exhumation, even in the intermediate levels of the accretionary wedge.     

鄂尔多斯盆地南部上三叠统延长组层序地层格架内沉积相特征与演化*

应用高分辨率层序地层学和沉积学的原理与方法,综合岩心、钻井以及测井和地震资料,对鄂尔多斯盆地南部上三叠统延长组进行了深入的研究,识别出5个层序界面,划分出4个三级层序和11个四级层序,建立了鄂尔多斯盆地南部上三叠统延长组层序地层格架。在研究区识别出曲流河三角洲、辫状河三角洲、深水重力流和湖泊4种沉积相。分析了层序格架内沉积相时空展布特征,揭示了层序格架内沉积相的时空演化规律,归纳了层序格架内砂体发育与展布的特点。讨论了层序界线划分与以往地层界的区别及其实际意义,探讨了重力流沉积对鄂尔多斯盆地油气勘探的重大意义。     

Constraining the dating of late Quaternary marine sediment records from the Scotia Sea (Southern Ocean)

In Southern Ocean sediments south of the Antarctic Polar Front, the scarcity of calcareous microfossils hampers the development of sediment chronologies based on radiocarbon dating and oxygen isotope stratigraphy established from carbonate. In this study, radiometric dating, magnetic susceptibility (MS), biogenic opal content, diatom abundance fluctuation, and paleomagnetic information were investigated on a north–south transect of central Scotia Sea sediment cores to verify their reliability as stratigraphic tools in the study area. Radiocarbon dating on organic carbon humic acid fraction can be used to establish the stratigraphy of upper core sections, but regional comparison and correlation are needed to verify a possible bias by fossil carbon contamination. For the long-term stratigraphy, MS, which can be correlated to the Antarctic ice core dust/climate signal, represents the most valuable parameter. Fine-grained single domain magnetite, probably of biogenic origin, makes a significant contribution to the interglacial MS signal, while major contributions from detrital material affect the glacial MS record. The core from the southern Scotia Sea contains significant proportions of biogenic magnetite also in glacial sediments, suggesting depositional environments different from those of the northern Scotia Sea. Our data suggest low contributions of high-coercive minerals to the overall magnetic intensity of glacial and interglacial Scotia Sea sediments, which excludes dust as a main source of the magnetic signal. Opal content can be used to distinguish between cold and warm intervals for the past 300 thousand years. Abundance fluctuation patterns of diatom species Fragilariopsis kerguelensis and Eucampia antarctica are useful stratigraphic tools for periods back to Marine Isotope Stage (MIS) 6. The Mono Lake geomagnetic excursion is identified in Scotia Sea sediments for the first time. Possible correlations of ash layers are suggested between Scotia Sea sediments and East Antarctic ice cores. They have potential to serve as additional age markers for further studies in this area.     

苏北盆地TZK9孔磁性地层及重矿物组合特征研究

通过对苏北盆地TZK9孔的磁性地层和重矿物组合分析,探索了该地区晚上新世以来沉积物的物源变化特征。古地磁结果显示,TZK9孔的M/G界线位于250.3 m,B/M界线位于78.5 m,并很好记录了2次正极性亚时（Jaramillo和Olduvai）,分别位于129.0~150.2 m与172.55~192.80 m,通过沉积速率外推获得该钻孔的底界年龄约为3.0 Ma。对TZK9孔重矿物组合、特征指数进行分析,并结合淮河及长江下游的重矿物组合特征,揭示在距今3.0~2.6 Ma其沉积物主要来自于淮河流域。而相比晚上新世,第四纪的磷灰石、锆石、金红石、电气石含量增加,表明该地区开始受到了长江流域的影响,而第四纪以来重矿物特征指数（ZTR）逐渐增大可能主要受控于全球气候变化。