Alternating aeolian,sabkha and shallow-lake deposits from the Middle Triassic Gipsdalen Formation,Scoresby Land,East Greenland

Gypsum-bearing deposits of the Gipsdalen Formation (Anisian ? Ladinian ?) are described and interpreted on the basis of lithology, sedimentary structures and sequential pattern.The basal Kolledalen Member consists in the northwestern part of the area of coarse-grained alluvial-fan deposits overlain by cross-bedded aeolian sandstones and finer-grained sabkha or shallow desert-lake deposits. The overlying Kap Seaforth Member displays wel;-developed cyclic sedimentation. In the southeastern part of the area the ideal cycle consists of, from bottom to top: cross-bedded aeolian sandstone, structureless or wave-rippled sandstone of sabkha flat—marginal desert-lake origin, thin wave-rippled sandstone and irregularly bedded mudstone of marginal desert-lake origin and horizontally laminated mudstone deposited in an expanded desert lake.Foreset dips of the cross-bedded aeolian sandstones suggest alternating periods of north-northeast and south-southeast palaeowinds. It is concluded that the aeolian deposits of the Gipsdalen Formation were deposited at low palaeolatitudes in the northern hemisphere. In the Middle Triassic summer seasons the Intertropical Convergence Zone probably lay north of the Jameson Land Basin, which was reached by south-southeast trade winds. During the rest of the year the zone was situated to the south and the area came under the influence of north-northeast trade winds.     

A Late Triassic lake system in East Greenland: facies, depositional cycles and palaeoclimate

The Upper Triassic Fleming Fjord Formation of the Jameson Land Basin in East Greenland contains a well-exposed succession, 200–300 m thick, of lake deposits. The Malmros Klint Member, 100–130 m thick, is composed of cyclically bedded intraformational conglomerates, red siltstones and fine-grained sandstones and disrupted dolomitic sediments (paleosols). The cyclicity is composite with cycles having mean thicknesses of (25), 5.9 and 1.6 m. The overlying Carlsberg Fjord beds of the Ørsted Dal Member, 80–115 m thick, are composed of structureless red mudstones rhythmically broken by thin greyish siltstones. This unit also has a composite cyclicity with cycles having mean thicknesses of 5.0 and 1.0 m. The uppermost Tait Bjerg Beds of the Ørsted Dal Member, 50–65 m thick, can be divided into two units. A lower unit is composed of cyclically bedded intraformational conglomerates or thin sandstones, red mudstones, greenish mudstones and yellowish marlstones. An upper unit is composed of relatively simple cycles of grey mudstones and yellowish marlstones. Recognized cycles have mean thicknesses of 5.6 and 1.6 m. The lake deposits contain evidence of seasonal, orbital and long-term climatic change. Seasonal change is documented by numerous desiccation surfaces especially in the Malmros Klint Member and Carlsberg Fjord beds, orbital change is suggested by the composite cyclicity, and long-term climatic change is indicated by the systematic upwards change in sedimentary characteristics of the lake deposits. The sedimentary features of the Malmros Klint Member suggest lacustrine deposition in a dry climate that fluctuated between desert and steppe conditions, the Carlsberg Fjord beds probably record lacustrine lake deposition in a rather constant dry (steppe) climate, while the Tait Bjerg Beds record lake sedimentation in a climate that fluctuated between dry (steppe) and warm moist temperate. In the Tait Bjerg Beds the upward change in cycle characteristics indicates a shift towards more humid conditions. Climatic deductions from sedimentary facies are in good agreement with climate maps of Laurasia, as simulated by numerical climate models. Palaeomagnetic data indicate a northward drift of East Greenland of about 10° from ca. 25°N to ca. 35°N in the Middle to Late Triassic. The Fleming Fjord Formation which represents ca. 5 m.y. of the Late Triassic interval was deposited during latitudinal drift of 1–2°. It is possible that the observed long-term upward shift in climatic indicators within the formation can be ascribed to plate drift, but southward shift of climatic belts could also have been of importance.     

Stratigraphic application of Thalassinoides ichnofabric in delineating sequence stratigraphic surfaces (Mid-Cretaceous), Kopet-Dagh Basin,northeastern Iran

This study integrates ichnological and sedimentological data to refine depositional sequences and interpretations of sea-level dynamics for the shallow marine, Albian–Cenomanian Aitamir Formation in northeastern Iran. Three ichnofabrics are present in a succession of glauconitic mudstone and sandstone. This is a sequence that grades upward from a lower glauconitic sandstone unit with trough cross-stratification, hummocky and ripple cross-lamination into a fining-up unit of mudstone with intercalated sandstone beds. The lower unit contains an ichoassemblage of the Ophiomorpha–Palaeophycus ichnofabric (upper shoreface), whereas the upper unit bears ichnoassemblages of the Thalassinoides ichnofabric (in a distinctive level at the top cycle which demarcates the base of the next cycle) (middle shoreface) and the Chondrites–Planolites ichnofabric (lower shoreface). An upper shoreface–lower shoreface trend from the Ophiomorpha–Palaeophycus ichnofabric to the Chondrites–Planolites ichnofabric represents a deepening-upward sequence. An integrated sedimentological and ichnological approach has allowed the recognition of the internal organization of the sequence and the characterization of significant discontinuity surfaces at sequence scales. Thalassinoides ichnofabric reveals colonization of firmgrounds during prolonged times between erosion and deposition related to transgressive surfaces. Transgressive surfaces (sequence boundaries) are generally well-cemented and marked by increased glauconite content, and densely crowded, predominantly vertical or oblique, relatively large, very distinct, unlined, and uncompacted burrows (omission suite) and are associated with rare highly abraded and fragmented shell remains.     

Taphonomy of the middle Cambrian (Drumian) Ravens Throat River Lagerstätte,Rockslide Formation,Mackenzie Mountains,Northwest Territories,Canada

The Middle Cambrian (series 3, Drumian, Bolaspidella Biozone) Ravens Throat River Lagerstätte in the Rockslide Formation of the Mackenzie Mountains, northwestern Canada, contains a Burgess Shale‐type biota of similar age to the Wheeler and Marjum formations of Utah. The Rockslide Formation is a unit of deep‐water, mixed carbonate and siliciclastic facies deposited in a slope setting on the present‐day northwestern margin of Laurentia. At the fossil‐bearing locality, the unit is about 175 m thick and the lower part onlaps a fault scarp cutting lower Cambrian sandstones. It consists of a succession of shale, laminated to thin‐bedded lime mudstone, debris‐flow breccias, minor calcareous sandstone, greenish‐coloured calcareous mudstone and dolomitic siltstone, overlain by shallow‐water dolostones of the Broken Skull Formation, which indicates an overall progradational sequence. Two ~1‐m‐thick units of greenish calcareous mudstone in the upper part exhibit soft‐bodied preservation, yielding a biota dominated by bivalved arthropods and macrophytic algae, along with hyoliths and trilobites. It represents a low‐diversity in situ community. Most of the fossils occur in the lower unit, and only the more robust components are preserved. Branching burrows are present under the carapaces of some arthropods, and common millimetre‐sized disruptions of laminae are interpreted as bioturbation. The fossiliferous planar‐laminated calcareous mudstone consists of chlorite, illite, quartz silt, calcite and dolomite and is an anomalous facies in the succession. It was deposited via hemipelagic fallout of a mixture of platform‐derived and terrestrial mud. Geochemical analysis and trace‐element proxies indicate oxic bottom waters that only occasionally might have become dysoxic. Productivity in the water column was dominated by cyanobacteria. Fragments of microbial mats are common as carbonaceous seams. Complete decay of soft tissues was interrupted due to the specific sediment composition, providing support for the role of clay minerals, possibly chlorite, in the taphonomic process.     

山东北部地区古新统孢粉组合*

统计了黄县地区龙口组和昌潍地区侯镇组孢粉100余个属种,描述6新种、4个新亚种,1个新联合种.在概述孢粉组合的基础上,重点讨论了该组合所代表的地质时代应属古新世.还阐述了这—孢粉植物群所反映的古气候特征.     

东昆仑山西段上石炭统的四射珊瑚

青海柴达木盆地西南缘祁曼塔格山一带的上石炭统分下部缔敖苏组和上部四角羊沟组,该组的珊瑚化石自下而上可分两组合：１）Ｂｒａｄｙｐｈｙｌｌｕｍ ｓｔｅｒｅｏｍａｒｇｉｎａｔｕｍ－Ｃｙｓｔｏｐｈｏｒａｓｔｒａｅａ ｍｏｌｌｉ－Ｓｋｏｌｅｋｏｐｈｙｌｌｕｍ ｂｕｌｌｉｔａｂｕｌａｔｕｍ组合,２）Ａｍｙｇｄａｌｏｐｈｙｌｌｏｉｄｅｓ ｍａｎｇｎａｉｅｎｓｅ－Ｎｅｏｋｏｎｉｎｃｋｏｐｈｙｌｌｕｍ ｐｅｔｉｌｕ     

Revised Lithostratigraphy of the Sonsela Member (Chinle Formation,Upper Triassic) in the Southern Part of Petrified Forest National Park,Arizona

Background

Recent revisions to the Sonsela Member of the Chinle Formation in Petrified Forest National Park have presented a three-part lithostratigraphic model based on unconventional correlations of sandstone beds. As a vertebrate faunal transition is recorded within this stratigraphic interval, these correlations, and the purported existence of a depositional hiatus (the Tr-4 unconformity) at about the same level, must be carefully re-examined.

Methodology/Principal Findings

Our investigations demonstrate the neglected necessity of walking out contacts and mapping when constructing lithostratigraphic models, and providing UTM coordinates and labeled photographs for all measured sections. We correct correlation errors within the Sonsela Member, demonstrate that there are multiple Flattops One sandstones, all of which are higher than the traditional Sonsela sandstone bed, that the Sonsela sandstone bed and Rainbow Forest Bed are equivalent, that the Rainbow Forest Bed is higher than the sandstones at the base of Blue Mesa and Agate Mesa, that strata formerly assigned to the Jim Camp Wash beds occur at two stratigraphic levels, and that there are multiple persistent silcrete horizons within the Sonsela Member.

Conclusions/Significance

We present a revised five-part model for the Sonsela Member. The units from lowest to highest are: the Camp Butte beds, Lot''s Wife beds, Jasper Forest bed (the Sonsela sandstone)/Rainbow Forest Bed, Jim Camp Wash beds, and Martha''s Butte beds (including the Flattops One sandstones). Although there are numerous degradational/aggradational cycles within the Chinle Formation, a single unconformable horizon within or at the base of the Sonsela Member that can be traced across the entire western United States (the “Tr-4 unconformity”) probably does not exist. The shift from relatively humid and poorly-drained to arid and well-drained climatic conditions began during deposition of the Sonsela Member (low in the Jim Camp Wash beds), well after the Carnian-Norian transition.     

Lithostratigraphy, petrography and facies analysis of the Late Cenozoic sediments in the foreland basin of the West Kunlun

The Yecheng profile, lying in the southwest Tarim Basin at the northern foot of the West Kunlun Mountains, comprises 4.5 km of conformable Miocene to Pliocene strata. The lower part of the section, the Wuqia Group, is composed of interbedded red mudstone and pale-coloured fine sandstone with a thickness of 1700 m. The Artux Formation is 800 m thick and composed of mudstone, sandstone with thin gravel and conglomerate beds. The upper part of the section, known as the Xiyu Formation, consists of 2000 m of cobble and boulder conglomerate intercalated with massive siltstone lenses.Compositional study of the sandstones in the Wuqia Group and Artux Formation indicates that they were sourced from low relief areas of the Kunlun region and probably further south from Tibet. The provenance of the conglomerate in the Xiyu Formation is the West Kunlun Mountains. Compositional trends within the conglomerate indicate that Upper Palaeozoic marine, and Mesozoic to Tertiary terrestrial silicic rocks were eroded first, along with the Proterozoic to Lower Palaeozoic Proto-Tethys metasedimentary rocks. Erosion into deeper levels of the Kunlun Mountains provided igneous and high-grade metamorphic sediment, which first appears 640 m above the base of the Xiyu Formation.Lithofacies change from fine-grained mudstone and sandstone to coarse clasts coincides with the onset of aeolian sedimentation, indicating major shift of regional palaeoclimatic regime. Although climatic changes may have played an important role in controlling the sedimentary regime worldwide, our study of the lithostratigraphy and petrography of the Yecheng section suggests that the lithofacies change recorded the progressive unroofing history of the source rocks in the West Kunlun Mountains.     

A fan delta succession rich in water escape structures (Upper Turonian, Brandenberg, Austria): Possible record of paleoseismicity

Summary The Upper Turonian of Brandenberg (Austria) is based by a transgressive fan delta succession rich in water escape structures that, at least in part, may have formed in association with earthquakes. The investigated fan delta is among the oldest deposits of the Lower Gosau Subgroup (Upper Turonian to Lower Campanian), a terrestrial to neritic succession that unconformably overlies older carbonate rocks. In its subaerial part, the fan succession consists mainly of conglomerates deposited from mass flows, interlayered with red claystones to siltstones. Along the fringe of marine transgression, beachface/channel mouth conglomerates and bioturbated siltstones to fine sandstones accumulated. The marine part of the fan delta succession consists mainly of cross-laminated and hummocky cross-laminated arenites deposited in a wave/storm-domainated shoreface. Excellent preservation of sedimentary lamination throughout and near absence of bioturbation indicate (intermittently) rapid sediment accumulation. Intercalated shoreface conglomerates are present as compound channel-fills, and as thin sheets alongside and off channels. Offshore transport of gravels to cobbles into the shoreface may have been driven by river floods (in the most proximal positions) and by storm rip currents (farther seaward). Towards the top of the succession, conglomerate sheets disappear, and the arenites become bioturbated. In the succession of shore zone arenites, abundant water escape structures include distorted/convoluted lamination, short fluidization planes, tabular fissures (some associated with offset of beds), pods and lenses of internal breccias, pillow beds up to more than 1 m thick, and hitherto undescribed, cyclindrical structures (“onion structures”) built by concentrically arranged planes interpreted as water escape routes. The tabular fissures, internal breccias and the pillow beds are closely similar to water escape structures documented from historical earthquakes and from inferred paleo-earthquakes. Storm wave loading or wave-induced microseisms are considered less probable triggers of the larger dewatering structures. Water escape structures represent an hitherto unappreciated, although not strictly diagnostic, indicator of syndepositional tectonism in the Upper Cretaceous of the Eastern Alps.     

粤西云开地区中奥陶世翼形类(双壳类)一新超科——郁南蛤超科 Yunannioidea superfam.nov.

本研究记述粤西云开地区中奥陶统东冲组一种奇异的翼形类(双壳类)化石,建立了郁南蛤超科(新超科)Yunannioidea superfam.nov.,郁南蛤科(新科)Yunanniidae fam.nov.,郁南蛤属(新属)Yunannia gen.nov.及2新种:干坑郁南蛤(新属新种)Yunannia gankeng...     

Integrated sedimentological,ichnological and sequence stratigraphical studies of the Koti Dhaman Formation (Tal Group), Nigali Dhar Syncline,Lesser Himalaya,India: paleoenvironmental,paleoecological, paleogeographic significance

Abstract

Integrated ichnology, sedimentology and sequence stratigraphy of the Lower Quartzite Member to the Arkosic Sandstone Member of the Koti Dhaman Formation (Cambrian Series 2, Stage 4), Tal Group, Nigali Dhar Syncline, Lesser Himalayan lithotectonic zone are presented. Trilobite traces of Gondwanan affinity i.e., Cruziana salomonis, Cruziana fasciculata, Rusophycus dispar and Rusophycus burjensis are recorded along with Arenicolites isp. and Skolithos isp. from the Lower Quartzite Member. A rich and diverse ichnoassemblage attributed to the Cruziana ichnofacies is described for the first time from the Arkosic Sandstone Member of the same formation. Seven ichnofossil assemblages, i.e., Cruziana-Rusophycus, Planolites-Palaeophycus, Cruziana problematica, Diplichnites, Cochlichnus anguineus, Bergaueria perata and Psammichnites gigas have been recognized in the Lower Quartzite to Arkosic Sandstone members of the Koti Dhaman Formation. Seven sedimentary facies i.e., sandstone–shale facies (FT1), cross-bedded (trough and planar) sandstone (FT2), bedded sandstone facies (FT3), shale facies (FT4), shale–sandstone facies (FT5), shale-rippled sandstone facies (FT6) and planar and trough cross-laminated sandstone (FT7) and four facies associations FA1-FA4 are identified in the Koti Dhaman Formation. The formation contains shallowing upward parasequences of a tidal flat complex. Overall, two major events are recognized: i) the break in sedimentation between the Lower Quartzite Member and the overlying Shale Member probably related to forced-regressive event and ii) the facies shift from FT6 to FT7 of the Arkosic Sandstone Member represents an erosive transgressive event; the surface is interpreted as wave ravinement surface, which also serves as a sequence boundary. Integrated ichnology, sedimentology and sequence stratigraphic studies indicate that the Lower Quartzite Member was deposited in a shallow subtidal sand sheet complex and tidal flat complex; the Shale Member was deposited in a mud flat setting of a tidal flat complex, and the Arkosic Sandstone Member in a mixed-flat (tidal flat complex) to sand sheet complex front and margin (subtidal sand sheet complex). Overall, the lower to middle part of the Koti Dhaman Formation represents a tide-dominated shallow subtidal–intertidal to mud-flat subenvironments of the tidal flat complex. A palaeogeographic reconstruction of lower Cambrian (516–514?Ma) is presented based on the distribution of trilobite traces from the Lesser Himalaya and the Bikaner–Nagaur area of Peninsular India (eastern Gondwana), Egypt, Jordan, Turkey (western Gondwana) and Canada (Avalonia).     

The schulterkofel section in the Carnic Alps,Austria: Implications for the carboniferous-permian boundary

Summary The upper part of the LowerPseudoschwagerina Limestone (Rattendorf Group), outcropping on the northwestern flank of Schulterkofel Mountain, Carnic Alps (Austria) is described with special emphasis on fusulinid microfossils and facies. This fusulinid-rich section offers an ideal opportunity for biostratigraphy in defining the Permo-Carboniferous boundary in this region. The LowerPseudoschwagerina Limestone is composed of shallow-marine limestones with intercalated thin siltstone and sandstone beds. Fusulinid limestones are represented by two types of wackestones, both containing large quantities of smaller foraminifers. Fusulinid grainstones are rare. Limestones rich in fusulinids were found only within the bedded limestone facies in beds both below and especially above siliciclastic intercalations. This may indicate that the best living conditions for fusulinids existed immediately before and especially after the climax of a regressive phase (sea-level lowstand). The fusulinid limestones were deposited within a protected, shallow-marine shelf environment with normal salinity. Pseudoschwagerinid fusulinids appear in the upper part of the LowerPseudoschwagerina Limestone, in samples SK 107d (undeterminable species) and SK 108, i.e. between 92 m and 93 m above the base of the section within a bedded limestone immediately above the uppermost clastic intercalation. The fusulinid fauna is represented by about 30 species belonging to only a few genera. Species ofTriticites andRugosofusulina dominate, whereas those ofDaixina, Rugosochusenella andPseudofusulina are rare. A characteristic feature of the fauna is the strong similarity with fusulinid faunas described from Russia as well as from Middle and East Asia. Some of the described fusulinids are new for the Carnic Alps. The first appearance ofPseudoschwagerina andOccidentoschwagerina (Occidentoschwagerina alpina Zone) in the upper part of the LowerPseudoschwagerina Limestone in the Schulterkofel section defines the position of the Carboniferous-Permian boundary.     

Two new dinosaur tracksites from the Lower Cretaceous Jiaguan Formation of Sichuan Basin,China: specific preservation and ichnotaxonomy

Two new dinosaur tracksites are reported from the Lower Cretaceous Jiaguan Formation in the Sichuan Basin, Qijiang District of Chongqing. These are the Gaoqing-Yongsheng and the Huibu tracksites, which represent the 13th and 14th reports from this formation. The Gaoqing-Yongsheng tracksite reveals the trackway of a large biped (ornithopod) in association with isolated sauropod tracks and large indeterminate undertracks with radial cracks. These features are preserved as natural casts with pebble infillings in a coarse, cross bedded and very thick bedded sandstone sequence. The Huibu tracksite reveals isolated theropod tracks and ornithopod tracks, the latter having a quadripartite, Caririchnium-like morphology, preserved in a thin bedded sandstone sequence with intercalated mudstone.     

Sediments of the Middle Cambrian Burgess Shale, Canada

The Phyllopod Bed of the Burgess Shale, in which Walcott found the famous soft bodied fossils, consists of thin graded beds of calcareous siltstone and mud-stone, which are probably turbidites. The Burgess Shale was deposited on a reef front submarine fan, and the preservation of the fossils is probably due to rapid burial.     

Facies architecture and sequence stratigraphy of the Ordovician Bromide Formation (Oklahoma): a new perspective on a mixed carbonate-siliciclastic ramp

The Upper Ordovician (Sandbian; late Whiterockian to Mohawkian) Bromide Formation of south-central Oklahoma was deposited along a distally steepened ramp that descended into the Southern Oklahoma Aulacogen (SOA). It provides an unparalleled opportunity to examine a spectrum of marine facies that extended from back ramp peritidal settings to the center of the basin. The depositional history and environmental context of the unit are reconsidered using lithofacies analysis and the characterization of sequence stratigraphic patterns at a variety of hierarchical scales. Inner-ramp (above fair weather wavebase; FWWB) lithofacies suggest deposition in a range of environments: tidal flat, lagoon, shoreface, semi-restricted shallow subtidal, and bioclastic shoal. Middle-ramp environments between FWWB and storm wavebase (SWB) are thick and faunally diverse, and consist of rhythmically bedded marls, wackestone, packstone, and shales. Outer-ramp environments (below SWB) are represented by either fissile tan-green shale or thin-bedded carbonate mudstone and shale. Ramp stratigraphy, facies associations, and bounding surfaces suggest that three third-order depositional sequences are present in the Bromide. They demonstrate the transition from a clastic-dominated ramp in the late Whiterockian to a carbonate-dominated ramp in the Mohawkian, and show that the deposition of the Bromide was considerably more complex than the simple transgressive–regressive cycle traditionally used to describe accommodation dynamics in the basin. Meter and decameter-scale cycles (high-frequency sequences) are a common motif within the depositional sequences, and the Corbin Ranch Submember records an important peritidal succession prior to a major sequence boundary with the overlying Viola Springs Formation. New correlations based on measured sections, outcrop gamma-ray profiles, and subsurface well-logs document a novel pattern where the middle Bromide depositional sequence 2 (Mountain Lake Member) expanded down-ramp, whereas the succeeding carbonate-dominated sequence 3 (Pooleville Member) was progressively removed down-ramp. This demonstrates the existence of a major, regionally angular unconformity at the base of the Viola Springs Formation that has implications for basin evolution. Other implications include the validation of high-frequency sequences as a model for elementary cycles in mixed carbonate-siliciclastic systems and, more regionally, documentation of a new depositional sequence at the Turinian–Chatfieldian stage boundary.     

Depositional environment and biofacies characterization of the Upper Pennsylvanian–Lower Permian deposits of the San Salvador Patlanoaya section (Puebla, Mexico)

The San Salvador Patlanoaya section (Puebla State of Mexico) has been subdivided into seven informal members labeled A–F. Members C–F have been dated as Missourian to Leonardian (equivalent to Kasimovian to Kungurian, i.e. lower Upper Pennsylvanian to upper Lower Permian). Members C–E display a shallowing-upward trend as does member F. The biodiversity of these carbonate deposits outcropping in the San Salvador Patlanoaya section is relatively low, although multiple microfossils (algae, small foraminifera, fusulinids and fish remains) are represented. Member C consists of calcarenitic limestone interpreted as distal tempestites interbedded with shaly limestone facies. These storm beds are composed mainly of silt, sand-sized quartz grains and bioclasts. Member D corresponds to coarse bioclastic limestones represented by calcareous tempestites and channel beds with erosional bases. Member E is composed of green shales and cross-bedded sandstones and gravelly conglomerates. Member F corresponds to a condensed package of limestones and interbedded siliciclastics and is Cisuralian (Early Permian) in age. Member G consists of condensed black shales and limestone nodules. The results of the study have significant implications for recognition of climatic and/or sea-level fluctuations in bioclastic–siliciclastic facies during the Late Pennsylvanian–Early Permian. The skeletal limestones and channel sandstones, common throughout the Pennsylvanian–Permian section, provide a constraint on palaeobathymetry, with the water depth fluctuating frequently around a position below, but near, the storm wave base.