Investigating human and megafauna co-occurrence in Australian prehistory: Mode and causality in fossil accumulations at Cuddie Springs

Human arrival in Sahul – Pleistocene Australia and New Guinea – has long been argued as the catalyst in the decline and disappearance of a suite of extinct animals referred to as megafauna. The debate concerning causality in Sahul is highly polarised, with climate change often cited as the alternative explanatory model. On continental Australia, there are few datasets available with which to explore the likely processes leading to the extinction events. At the present time, there is one site in New Guinea (Nombe Rockshelter) and one on continental Australia (Cuddie Springs) where the coexistence and temporal overlap of humans and megafauna has been identified. The Cuddie Springs Pleistocene archaeological site in southeastern Australia contains an association of fossil extinct and extant fauna with an archaeological record through two sequential stratigraphic units dating from c. 36 to c. 30 ka ago. A taphonomic study of the fossil fauna has revealed an accumulation of bone in a primary depositional context, consistent with a waterhole death assemblage. Overall the faunal assemblage studied here (n: 8146; NISP: 1355) has yielded little direct evidence of carnivore damage or human activities. Post depositional factors such as physical destruction incurred by trampling, compaction of sediments, and/or the hydrological status of the lake at that time have played important roles. As the only known site on continental Australia where megafauna and humans co-occur, the Cuddie Springs faunal assemblage yields equivocal evidence for a significant human role in the accumulation of the fauna here. At the present time there is no evidential basis to the argument that humans had a primary role in the extinction of the Australian megafauna. The first colonisers are likely to have preyed upon those few species known to have persisted to this time, but their impact may have been restricted to the tail end of a process that had been underway for millennia prior to human arrival.     

新疆克拉玛依油田三叠系克下组冲积扇内部构型*

应用研究区丰富的密井网和邻近露头资料,探讨了新疆克拉玛依油田三叠系克下组冲积扇内部构型单元的层次划分系统,并建立相应的沉积构型模式。在冲积扇的扇根、扇中和扇缘各亚相带,进一步划分了3个级次的构型要素以表达其内的沉积复杂性。扇根亚相主要由主槽、片流带和漫洪带组成,其中,在主槽内主要发育槽流砾石（岩）体（可细分为砾石坝和流沟）与泥石流沉积,在片流带内主要发育片流砂砾体（可细分为砾石坝和流沟）,在漫洪带主要发育漫洪砂体和漫洪细粒沉积,总体构型样式以广泛分布的砾石坝夹含流沟和漫洪沉积的“泛连通体”为特征;扇中亚相主要由辫流带和漫流带组成,其中,辫流带的主体构型要素为辫流水道（可细分为砂坝和沟道）,总体构型样式为复合宽带状辫流水道砂体与漫流细粒沉积侧向相间、垂向互层为特征;扇缘亚相主要由径流带和漫流带组成,其中,径流带的主体构型要素为径流水道,总体构型样式以窄带状径流水道和漫流砂体镶嵌于漫流—湿地泥岩之中为特征。     

Preservation of large titanosaur sauropods in overbank fluvial facies: A case study in the Cretaceous of Argentina

Patagonia exhibits a particularly abundant record of Cretaceous dinosaurs with worldwide relevance. Although paleontological studies are relatively numerous, few include taphonomic information about these faunas. This contribution provides the first detailed sedimentological and taphonomical analyses of a dinosaur bone quarry from northern Neuquén Basin. At Arroyo Seco (Mendoza Province, Argentina), a large parautochthonous/autochthonous accumulation of articulated and disarticulated bones that represent several sauropod individuals has been discovered. The fossil remains, assigned to Mendozasaurus neguyelap González Riga, correspond to a large (18–27-m long) sauropod titanosaur collected in the strata of the Río Neuquén Subgroup (late Turoronian–late Coniacian). A taphonomic viewpoint recognizes a two-fold division into biostratinomic and fossil-diagenetic processes. Biostratinomic processes include (1) subaerial biodegradation of sauropod carcasses on well-drained floodplains, (2) partial or total skeletal disarticulation, (3) reorientation of bones by sporadic overbank flows, and (4) subaerial weathering. Fossil-diagenetic processes include (1) plastic deformation of bones, (2) initial permineralization with hematite, (3) fracturing and brittle deformation due to lithostatic pressure; (4) secondary permineralization with calcite in vascular canals and fractures, and (5) postfossilization bone weathering. This type of bone concentration, also present in Rincón de los Sauces (northern Patagonia), suggests that overbank facies tended to accumulate large titanosaur bones. This taphonomic mode, referred to as “overbank bone assemblages”, outlines the potential of crevasse splay facies as important sources of paleontological data in Cretaceous meandering fluvial systems.     

Dating megafaunal extinction on the Pleistocene Darling Downs,eastern Australia: the promise and pitfalls of dating as a test of extinction hypotheses

A key to understanding Late Pleistocene megafaunal extinction dynamics is knowledge of megafaunal ecological response(s) to long-term environmental perturbations. Strategically, that requires targeting fossil deposits that accumulated during glacial and interglacial intervals both before and after human arrival, with subsequent palaeoecological models underpinned by robust and reliable chronologies. Late Pleistocene vertebrate fossil localities from the Darling Downs, eastern Australia, provide stratigraphically-intact, abundant megafaunal sequences, which allows for testing of anthropogenic versus climate change megafauna extinction hypotheses. Each stratigraphic unit at site QML796, Kings Creek Catchment, was previously shown to have had similar sampling potential, and the basal units contain both small-sized taxa (e.g., land snails, frogs, bandicoots, rodents) and megafauna. Importantly, sequential faunal horizons show stepwise decrease in taxonomic diversity with the loss of some, but not all, megafauna in the geographically-small palaeocatchment. The purpose of this paper is to present the results of our intensive, multidisciplinary dating study of the deposits (>40 dates). Dating by means of accelerator mass spectrometry (AMS) ¹⁴C (targeting bone, freshwater molluscs, and charcoal) and thermal ionisation mass spectrometry U/Th (targeting teeth and freshwater molluscs) do not agree with each other and, in the case of AMS ¹⁴C dating, lack internal consistency. Scanning electron microscopy and rare earth element analyses demonstrate that the dated molluscs are diagenetically altered and contain aragonite cements that incorporated secondary young C, suggesting that such dates should be regarded as minimum ages. AMS ¹⁴C dated charcoals provide ages that occur out of stratigraphic order, and cluster in the upper chronological limits of the technique (～40–48 ka). Again, we suggest that such results should be regarded as suspicious and only minimum ages. Subsequent OSL and U/Th (teeth) dating provide complimentary results and demonstrate that the faunal sequences actually span ～120–83 ka, thus occurring beyond the AMS ¹⁴C dating window. Importantly, the dates suggest that the local decline in biological diversity was initiated ～75,000 years before the colonisation of humans on the continent. Collectively, the data are most parsimoniously consistent with a pre-human climate change model for local habitat change and megafauna extinction, but not with a nearly simultaneous extinction of megafauna as required by the human-induced blitzkrieg extinction hypothesis. This study demonstrates the problems inherent in dating deposits that lie near the chronological limits of the radiocarbon dating technique, and highlights the need to cross-check previously-dated archaeological and megafauna deposits within the timeframe of earliest human colonisation and latest megafaunal survival.     

Ichnofabric characterization of a deep‐marine clastic system: a subsurface study of the Middle Eocene Ainsa System,Spanish Pyrenees

This paper documents a subsurface trace fossil and ichnofabric study of the proximal parts of a structurally confined and channelized sand‐rich, lower slope and proximal basin‐floor deep‐marine system in the Middle Eocene Ainsa basin, Spanish Pyrenees. Five depositional environments are recognized based on sedimentary facies associations, depositional architecture and stratigraphic context (channel axis, channel off‐axis, channel margin, leveé‐overbank and interfan), as well as a channel abandonment phase. Each environment is characterized by distinct and recurring ichnofabrics. Ichnological measurements and observations were recorded from six cores recovered from six wells drilled at a spacing of between 400 m and 500 m at outcrop, and totalling 1213 m in length. From channel axis to levée‐overbank environments, there is a trend of increasing bioturbation intensity and ichnodiversity. Ichnofabrics in channel axis and channel off‐axis environments are characterized by low bioturbation intensity and low ichnodiversity. Thalassinoides‐dominated firmground ichnofabrics associated with erosive sediment gravity flows are common in these environments. In contrast, channel margin and levée‐overbank environments are characterized by ichnofabrics associated with high bioturbation intensity and ichnodiversity. Sediments of the interfan are characterized by the highest bioturbation intensity, associated with burrow mottling and an absence of primary sedimentary structures. This paper demonstrates that in core‐based studies, ichnofabric analysis is an important and valuable tool in discriminating between different environments in channelized deep‐marine siliciclastic systems. The results of this study should find wide applicability in reservoir characterization studies in the petroleum industry, in field‐based analogue ichnofabric studies and other core‐based studies in deep‐water siliciclastic systems worldwide such as the Integrated Ocean Drilling Program.     

The sedimentology,ichnology and invertebrate palaeontology of the late Silurian Downton Bone Bed

The Downton Bone Bed is a Konzentrat-Lagerstätte deposit located in the Welsh Borderlands, United Kingdom. The Downton Bone Bed is late Silurian, considered to be P?ídolí in age, and occurs within the Platyschisma Shale Member of the Downton Castle Sandstone Formation. The bone bed is exposed at Weir Quarry (Herefordshire), which this study proposes should become established as the type locality for this stratigraphic horizon, due to the destruction of other localities and lack of access to other sites. As Weir Quarry is one of the last remaining exposures of this unit, the objective of this study is to qualitatively describe the sedimentology, ichnology, and invertebrate palaeontology of the bone bed, to enhance the regional understanding of the palaeogeography, depositional environments and depositional processes of the Welsh Borderlands during the late Silurian. Parasequence thickness and frequency, and sedimentary structures such as hummocky cross stratification, observed within the Downton Castle Sandstone Formation, have traditionally been explained to have formed by sea-level oscillations. These are interpreted to have formed entirely by nearshore to shoreface, shallow marine autogenic sedimentary processes, such as storm events (tempestites) and tidal scour. It is interpreted that formation of the Downton Bone Bed occurred as a by-product of these autogenic sedimentary processes, through winnowing and erosion during storm-driven scour and reworking. The low diversity ichno- and invertebrate fauna observed within the Downton Bone Bed is consistent with a nearshore depositional environment and is indicative of a stressed ecosystem due to fluctuating salinity and oxygen levels.     

Upward-thickening patterns and lateral continuity of Permian sand-rich turbidite channel fills, Laingsburg Karoo, South Africa

Abstract Analysis of extensive exposures of the Permian Laingsburg Formation, Karoo basin, South Africa, have enabled a detailed reconstruction of the base of slope stratigraphy and palaeoenvironments in a deep-water system characterized by a very narrow grain-size range (fine sandstone). The deposits include an ≈ 4 km wide and 80 m thick channel complex, fringed by sandy sheet deposits that extend laterally for at least 6 km across depositional strike. Within the channel complex, individual channel fills are marked by shallow basal erosion surfaces draped by thin, parallel-stratified beds of very fine sandstone and siltstone, interpreted as flow tails to largely bypassing flows. These thin beds are overlain by 0·4 to 5 m thick beds of structureless, fine-grained sandstone that represent the majority of the channel fills. The basal packages may be partially to completely removed by localized scour in the axial zone of the channel complex but can be mapped laterally into overbank areas where they thicken and are dominated by rippled fine sandstones with intercalated siltstones. Axial confinement resulted from subtle topography on the basin floor, whereby the lower, dense parts of the initially erosive and bypassing flows were partially confined in the lows and the more dilute, slower moving upper parts of the flows deposited sheet-like successions across slightly elevated overbank areas. The narrow grain-size distribution prohibited the formation ofcoarse-grained residual bypass deposits during the initial phases of channel formation. With decreasing magnitude, later flows became more depositional, filling remaining axial depressions with thick-bedded structureless sandstone. The smaller volumes of late-stage sediment were more axially focused, producing local scour-and-fill features and starvation of the overbank areas. Resulting grain-size vertical profiles are complex. The basal flow tail packages and overlying massive deposits form a thickening and slightly coarsening-upward trend in the channel fills. The overbank deposits show a thinning- and fining-upward profile as a result of less bypass plus late-stage starvation of sand. Application of traditional deep-water facies models could therefore potentially lead to erroneous interpretations of the channel complex as a prograding lobe and the overbank sheets as channel-fills.     

Taphonomic analysis,associational integrity,and depositional history of the Fetterman Mammoth,eastern Wyoming,U.S.A.

The Fetterman Mammoth locality, eastern Wyoming, U.S.A., produced the remains of a single subadult mammoth and a small lithic assemblage. This paper employs a fine‐grained taphonomic approach to investigate the events responsible for the deposit's creation. No cultural modifications were noted on any of the specimens. Long axis orientations plotted against a reconstruction of the depositional surface suggest limited postdepositional movement of individual disarticulated elements. Weathering patterns based on in situ upside and downside positioning document two discrete episodes of sedimentation. These results suggest that the mammoth remains and the cultural assemblage may be separated by at least one depositional event and, as such, their association is considered equivocal. © 2002 Wiley Periodicals, Inc.     

黄骅盆地港西开发区新近系明化镇组沉积微相特征

综合利用油田开发区岩心和测井等资料,对黄骅盆地港西开发区一区l断块新近系明化镇组进行沉积微相研究。结果表明,明化镇组为中一高弯度曲流河沉积,沉积微相单元可以细分为主河道、支河道、河间溢岸沉积、废弃河道和泛滥平原等,不同的微相单元在测井曲线上具有较好的电性响应特征。在总结沉积微相发育模式的基础上,认为在高可容纳空间体系阶段,孤立的条带状河道砂体镶嵌在大面积分布的河间及泛滥平原细粒沉积背景当中,河道砂体被泥岩所分隔;而在低可容纳空间体系阶段,多层不同期次的河道砂体发生切割叠置,造成砂体厚度较大,连通性较好。垂向上,河道砂体的不同配置方式体现了A／S比值随时间的旋回性变化的控制作用。     

The Paleoenvironment and Lithic Taphonomy of Shi’Bat Dihya 1, a Middle Paleolithic Site in Wadi Surdud,Yemen

The Shi'bat Dihya 1 site in western Yemen, dated by optically stimulated luminescence to 55 ka, provides insight into the Middle Paleolithic peopling of the Arabian Peninsula. The archaeological layer is interstratified within thick, sandy silt floodplain deposits filling a piedmont basin. Luminescence dates, lack of soil development, and gypsum precipitation indicate a high accretion rate of the floodplain during Marine Isotope Stage 3, in connection with a (semi)‐arid environment. Rapid overbank sedimentation was likely a result of the remobilization of loess material deposited on the Yemeni Great Escarpment at the periphery of the adjacent Tihama coastal sand desert or of other sources. Fabric and size analyses of the lithic artifacts, together with spatial projections, indicate site modifications by floods. Primary modifications include (1) selective accumulation of medium‐sized lithic pieces as a result of hydraulic sorting, (2) bimodal orientation of artifacts, and (3) ripple‐like arrangement of lithics and bone/tooth fragments. The overrepresentation of teeth may also be a consequence of sorting. Although floods have distorted the original site patterning, long‐distance transport of artifacts by water can be excluded, as indicated by relatively high refitting rate, close proximity of artifacts derived from the same block of raw material, and lack of abrasion of the pieces. Therefore, the site is considered “geologically” in situ because its remobilization by water occurred shortly after human abandonment. This study also stresses that the effective preservation of a site cannot be assessed without careful taphonomic study, even in a potentially favorable depositional context such as silty alluvium.     

杏北油田低弯度分流河道储层构型及其控制的剩余油分布模式

低弯度分流河道储层是杏北油田的重要储层类型,深入研究其储层构型特征对于油田调整挖潜意义重大。综合密井网岩心、测井和生产动态等资料,采用“层次分析和模式指导”的方法,分“复合河道和溢岸砂体、单期河道及其相互接触关系”两个主要层次开展储层构型精细解剖,构建了三维储层构型模型。基于密闭取心井、水淹层测井解释资料和生产动态数据分析了不同时期的水淹特征和剩余油分布,并通过基于三维构型模型的油藏数值模拟对剩余油分布模式进行验证,最终总结出不同储层构型控制下的剩余油富集模式。结果表明,在河道内,剩余油在顶部、边部、河道间夹层控制部位以下以及仅与低渗溢岸砂连通造成注采不完善的河道内部富集;在河道外,剩余油在河间物性较差的溢岸砂内、注采不完善的溢岸砂末端和孤立砂体内富集。     

Submarine channel levee shape and sediment waves from physical experiments

Submarine channel levees aggrade through repeated overspill events from the channel axis. The shape of the levees may therefore reflect some characteristic(s) of the overspilling flow. It has been noted that basin floor levees typically have a relatively low-relief and taper exponentially to their termination; in contrast slope channel levees may be much steeper close to the channel. A simple physical experiment was performed where a surge-like sediment-laden current flowed through a curved channel. Significant overspill occurred and generated a deposit flanking the channel on either side. The experiment was repeated 25 times to build up low-relief channel-levees. It was found that in proximal areas, levees were steep and characterised by power-law decays, a transitional zone of logarithmically thinning levee was found a little further down-channel, followed by exponential decays in medial to distal areas. The style of levee decay is a function of spatial variation in overbank sedimentation rates. Where flows rapidly lose momentum and deposit across the grain-size spectrum, i.e., in proximal areas, levees tend to be steep; farther down the channel, the steep levee slope gives way to a more gradually tapering deposit. In more distal parts of the channel, deposition is directly related to sediment settling velocity (rather than the suspended load exceeding flow transport capacity as is the case in proximal areas), the deposit reflects this with relatively simple exponential thickness decays. Additionally, small-scale sediment waves developed under lee wave conditions on the inner-bend overbank. The waves initially migrated slightly towards the channel, but as the style of overspill evolved due to intra-channel deposition, flows moved out of the lee wave window and sedimentation became out of phase with the wavelength of the features and the topography was healed.     

Taphonomic and sedimentological aspects from PICOS II paleontological site,a quaternary pond deposit of Alagoas,Brazil

The Picos II Paleontological Site (PIIPS), located in the city of Piranhas, in Alagoas State, is a fossil deposit with a pond-like geomorphological feature, a kind of peculiar deposit for the Quaternary of Northeast Brazil. A detailed taphonomic study is presented about the PIIPS assemblage, from material collection to the laboratory analysis. The conservation state of the collected fossils in PIIPS is different from that found in other tank deposits, showing a high degree of specimen preservation. Two taxa of pleistocenic mammals have been identified: Eremotherium laurillardi and Notiomastodon platensis, and fragments of an avian bone, whose taxonomic identification was not possible. The taphonomic analysis indicates that the deposited material experienced a short transportation in high-energy event, with a short period of subaerial exposure before the final burial, where at least the final disarticulation occurred in situ, which explains the high conservation level of the material. The sedimentological analysis made in each layer of the deposit corroborates the information related to the transport of the material, which were obtained in taphonomic analysis. Regarding these aspects, PIIPS reflects nearly non-biased biocenotic patterns. The well-preserved material found in PIIPS demonstrates the great potential of deposits with pond-like geomorphological features, with sidelines that are less steep than traditional tanks, providing smoother transport and accommodation for skeletal elements, which is a distinguishing factor in preserving fossils of vertebrates.     

扇三角洲沉积模式探讨:以准噶尔盆地玛北地区下三叠统百口泉组为例*

扇三角洲是一类非常重要的油气聚集场所,准确可靠的扇三角洲沉积模式,对储集层预测具有重要意义。准噶尔盆地玛北地区三叠系百口泉组发育一套扇三角洲沉积体系,虽然前人做了大量的研究,但在沉积模式方面仍存在一些争议。通过现代沉积考察、前人水槽模拟实验、研究区测井、岩心等资料综合分析发现: (1)玛北地区百口泉组扇三角洲平原发育3类微相,即辫状河道微相、砾质漫滩微相、水上朵前泥微相,同时可见泥石流沉积;玛北地区百口泉组扇三角洲前缘发育2种微相,即砾质浅滩微相、砂质浅滩微相,同时可见碎屑流沉积;(2)扇三角洲平原河道与河道间均为砂砾岩,河道砂砾岩的分选性明显好于河道间砂砾岩;(3)扇三角洲前缘不发育水下分流河道,扇三角洲前缘的砂砾岩主体是由扇三角洲平原片流入湖形成的,呈席状。     

Hydrogeological implications of paleo-fluvial architecture for the Paskapoo Formation, SW Alberta, Canada: a stochastic analysis

Fluvial systems tend to deposit sediment in well-defined relational geometries and in vertically and laterally repeating patterns. These sedimentary deposits are preserved to varying degrees depending on how much the fluvial system reworks the deposits. The Paskapoo bedrock aquifer system in southern Alberta, Canada, was deposited in a foreland depositional basin during uplift of the Rocky Mountains, and both the geomorphic model and field evidence indicate that the upper 100 m of the local aquifer system contains well-preserved, highly connected paleo-channels and associated overbank deposits. In order to evaluate the value of different types of data, a simplified stochastic-numerical groundwater flow model was developed to examine the sensitivity of results to model parameters. Parameters examined include: fraction of the formation made up of channel sands; meander and sinuosity factors; width-to-depth ratios of preserved channels; and crevasse splay conductivity. In all cases examined, the system exhibited anisotropic behavior with the along-channel flow direction being the most permeable and the vertical direction being least permeable. In general, the strongest control on the resulting effective anisotropic hydraulic conductivities was channel fraction, but geometric factors that control between-channel connectivity (e.g., channel sinuosity) had an appreciable effect on the across-channel flow direction effective permeability.     

Overbank sediment: a representative sample medium for regional geochemical mapping

In Scandinavia, most fluvial erosion takes place in the Quaternary glacial overburden at a restricted number of small source areas along individual drainage channels. As a consequence, a sample of active stream sediment is representative of only a very limited portion of the drainage area. This restriction makes stream sediment less reliable for regional exploration than generally expected. Overbank (levee or river-plain) sediment produced during large floods is an alternate more representative sampling medium. The sediment suspended during a flood has a much more widespread origin, and when the load is deposited upon the flood plain, nearly horizontal strata are formed and preserved at levels above the ordinary stream channel. A composite sample through a vertical section of such strata represents a great number of sediment sources that have been active at different times and forms an integrated sample of the entire catchment area. Because young sediments overlay older, the uppermost layers will be contaminated by pollutants in industrialized regions, but those at depth may remain pristine and will to a greater extent reflect the natural pre-industrial environment. In regional geochemical mapping, overbank sediment can be sampled at widely spaced sites, keeping costs per unit area low. Examples from Norway (1 sample station per 500 km²) show that overbank sediment produces broad geochemical patterns with high contrasts reflecting the bedrock geochemistry. Some patterns agree with known geological units and metallogenic provinces, but hitherto unknown major structures have also been indicated. A large Mo-deposit missed by a traditional stream survey is readily detected in the overbank sediment. It is concluded that overbank sediment is a promising alternate sample medium that should be tested in other physiographic regions.     

冀中坳陷饶阳凹陷留西地区古近系沙河街组沙三上亚段沉积相与隐蔽油藏

通过岩心观察和单井相分析,结合沉积背景资料,认为留西地区古近系沙河街组沙三上亚段发育辫状河三角洲相和湖泊相,以辫状河三角洲前缘亚相和滨浅湖亚相为主,主要发育辫状分流河道、越岸沉积、水下分流河道、河口坝、席状砂等微相。根据层序地层学基本原理,结合前人研究成果,认为本区沙三上亚段为一完整的三级层序,可划分为低位、湖侵和高位3个体系域,分别对应于沙三上亚段沉积时期的早期、中期和晚期,绘制了每个沉积阶段的沉积相图,在此基础上研究了沉积体系的平面展布特征。沙三上亚段沉积时期形成的北高南低的构造背景与辫状河三角洲近东西向展布的砂体形态相互配置,加之良好的油源供给,为后期成藏创造了条件。沙三上亚段沉积早期发育的辫状河三角洲前缘水下分流河道与河口坝砂体是主要的储集体,与沉积中期发育的烃源岩形成了十分有利的生储盖组合,具有优越的隐蔽油藏发育条件。总结了该区隐蔽油藏成藏的4种模式,确定留西地区中南部沙三上亚段沉积早期发育的辫状河三角洲前缘砂体是下一步隐蔽油藏勘探的有利目标。     

Taphonomic analysis of small mammal bone remains preyed upon by wildcats (Carnivora: Felidae) from the central Monte Desert (Mendoza,Argentina)

The present study analysed the taphonomic characteristics of small mammal bone accumulations produced by small felids in an area from the central Monte Desert (Mendoza, Argentina). In order to provide criteria to identify the role that these predators had in the formation of zooarchaeological assemblages, the anatomical representation, bone breakage patterns and degrees of digestive corrosion were evaluated. The main taphonomic results are: low average values for the relative abundance of skeletal elements; greater representation of mandibles, maxillae, isolated incisors, humeri and femora than the remaining elements; preponderance of cranial elements with high proportion of isolated teeth; elevated frequencies of proximal limb bones compared with distal parts; high degree of breakage in all skeletal elements and digestive corrosion on almost all diagnostic bones (mainly moderate and heavy). The values of the studied taphonomic variables indicate that small felids in this area made severe alterations to the bones of their prey (mainly rodents), attributable to the category of extreme modifier, while preserving enough skeletal elements to allow their taphonomic characterization. Tooth marks or grooves on bone surfaces produced by scratching and chewing were not detected. The low relative abundance of skeletal elements, the high degree of breakage and the elevated frequency of elements with digestion traces represent general taphonomic patterns that fall within those reported for other South American small carnivores.     

Levee morphology and sedimentology along the lower Tuross River, south-eastern Australia

Levees on the lower Tuross River in south-eastern Australia reflect a complex interplay between depositional and erosional processes. Stream power, conditioned primarily by valley width, is the key determinant of levee morphology and sedimentology in this confined valley setting. Three styles of levee are described. The Rewlee levee is functionally linked to a flood channel in narrow valley settings (< 250 m). These levees contain a diverse facies assemblage characterized by various scales of erosion surfaces. Vertical accretion on levees has produced conditions under which stream power values exceed the threshold for catastrophic floodplain stripping. The levee at the Mortfield site is associated with less confined settings (valley width 500–600 m), which present lower flood stage and stream power conditions. This levee hosts a wide range of facies, but erosion surfaces are seldom observed. In the more open valley setting at the Central site (valley width 700–1000 m), levees comprise uniform, fine-grained deposits, which grade to pronounced distal floodplains with backswamps. As levees reflect a combination of within-channel and overbank processes, both depositional and erosional, these geomorphic features influence the character and sedimentology of adjacent landforms and the associated alluvial architecture of the basin.     

鄂尔多斯盆地镇-泾地区中侏罗统延安组沉积体系及聚煤特征

在前人研究的基础上,结合大量新的钻井、测井资料,以鄂尔多斯盆地镇原-泾川地区中侏罗统延安组为例,运用沉积学的方法详细阐述了研究区目的层位的沉积体系,以及重点沉积微相的发育特征。延安组自下而上由河流沉积体系逐渐过渡为三角洲沉积体系。沉积微相主要发育有河流体系的心滩、边滩、河漫滩和岸后沼泽,以及三角洲体系的分流河道、洪泛平原和平原沼泽等。另对研究区延安组的聚煤特征给予了分析,并从构造、环境、气候及古地形等方面讨论了该区的成煤控制因素。