probable benthic macroalgae from the ediacara member south australia abstract the ediacara biota records the rise of morphologically complex macroscopic eukaryotes including animals and other heterotrophs eltonian ecology demands that ediacaran ecosystems must have been supported by primary producers e g cyanobacteria phytoplanktonic eukaryotes benthic macroalgae but the fossil record of ediacaran primary producers has not been fully documented particularly with respect to benthic macroalgae hampering a complete understanding of ediacaran ecosystems here we provide systematic description of probable benthic macroalgal fossils from the ediacara member of the rawnsley quartzite at the national heritage site nilpena in south australia these fossils include flabellophyton stupendum sp nov f typicum liulingitaenia irregularis sp nov and longifuniculum cf dissolutum previously informally referred to as bundles of filaments bof they are characterized by bundled filaments that can be twisted loosened or otherwise deformed although many are fragmented some specimens of flabellophyton stupendum sp nov f typicum and possibly longifuniculum cf dissolutum bear structures that resemble variants of pseudorhizostomites and mop but interpreted here as holdfasts suggesting that in life these were epibenthic organisms attached to the substrate atypical populations of relatively small ediacara type fossils are found on a bedding surface dominated by benthic macroalgae suggesting that together with microbial mats these primary producers were beneficial for juvenile settlement of ediacara type organisms potentially contributing both oxygen and nutrients although debates about animal affinity dominate ediacaran paleontology this study highlights the importance of benthic macroalgae in ediacaran ecosystems

controls on alluvial fan long profiles water and debris flows exiting confined valleys have a tendency to deposit sediment on steep fans on alluvial fans where water transport of gravel predominates channel slopes tend to decrease downfan from 0 10 0 04 to 0 01 across wide ranges of climate and tectonism some have argued that this pattern reflects grain size fining downfan such that higher threshold slopes are required just to entrain coarser particles in the waters of the upper fan whereas lower slopes are required to entrain finer grains downfan threshold hypothesis an older hypothesis is that slope is adjusted to transport the supplied sediment load which decreases downfan as deposition occurs transport hypothesis we have begun to test these hypotheses for alluvial fan long profiles using detailed hydraulic and particle size data in sediment transport models on four alluvial fans in the western u s we find that channel hydraulic radiiare largely 0 5 0 9 m at fan heads decreasing to 0 1 0 2 m at distal margins we find that median gravel diameter does not change systematically along the upper 60 80 of active fan channels as slope declines so downstream gravel fining cannot explain most of the observed channel slope reduction however as slope declines channel bed sand cover increases systematically downfan from areal fractions of 20 above fan heads to distal fan values in excess of 70 as a result entrainment thresholds for bed material might decrease systematically downfan leading to lower slopes however current models of this effect alone tend to underpredict downfan slope changes this is likely due to off channel gravel deposition calculations that match observed fan long profiles require an exponential decline in gravel transport rate so that on some fans approximately half of the load must be deposited off channel every 0 20 1 4 km downfan this leads us to hypothesize that some alluvial fan long profiles are statements about the rate of overbank deposition of coarse particles downfan a process for which there is currently no mechanistic theory

late pleistocene holocene ruptures of the lima reservoir fault sw montana abstract active tectonics within the northern basin and range province provide a natural laboratory for the study of normal fault growth linkage and interaction here we present new geologic mapping and morphologic fault scarp modeling within the centennial valley montana to characterize pleistocene holocene ruptures of the young and active lima reservoir fault geologic relationships and rupture ages indicate middle pleistocene activity on the henry gulch 50 ka and 23 10 ka trail creek 43 ka and 13 ka and reservoir 23 ka segments offset quaternary deposits also record holocene rupture of the reservoir segment 8 ka but unfaulted modern streams show that no segments of the lima reservoir fault have experienced a large earthquake in at least several millennia the clustered pattern of rupture ages on the lima reservoir fault segments suggests a seismogenic linkage though segment length and spacing make a physical connection at depth unlikely trail creek and reservoir segment slip rates were non steady and appear to be increasing the fault helps accommodate differential horizontal surface velocity measured by gps geodesy across the boundary between the northern basin and range province and the snake river plain

environmental interpretation and a sequence stratigraphic framework for the terminal proterozoic ediacara member within the rawnsley quartzite south australia abstract fossils of the ediacara biota are confined to preservational windows in the ediacara member of the rawnsley quartzite pound subgroup from the flinders ranges south australia the base of the ediacara member is a type 1 sequence boundary incised into the partly lithified chace quartzite member of the rawnsley quartzite the ediacara member and the upper half of the rawnsley quartzite comprise the rawnsley depositional sequence bounded above by the early cambrian uratanna depositional sequence the rawnsley sequence developed over an erosional surface cut into the chace quartzite member with some 250 m of relief southeasterly directed palaeovalleys are filled with a sequence of massive sandstone and laminated siltstone passing up into well bedded sandstone at lowstand local channels were filled by massive sand the highstand systems tract consists of several parasequence sets of laminated siltstone and channelized amalgamated massive sandstone overlain by interbedded siltstone and sandstone grading up into well bedded clean sandstone impressions of soft bodied ediacaran organisms are preserved above the valley fill facies on sandstone partings within upward shoaling delta front environments between storm and fairweather wavebase the ediacara member is in places conformably overlain by up to 500 m of sandstone of the same lithofacies as those underlying the member distinctive microbial mat bound sand laminae described as petee structures are characteristic of the rawnsley quartzite above and below the ediacara member during deposition of the ediacara member colonization of the deeper substrates by microbial mat communities enabled preservation of the ediacara biota the erosional surface at the base of the ediacara member is one of at least four incision events recorded in the terminal proterozoic and early cambrian succession of the adelaide geosyncline the similarity of incision filling lithofacies of the rawnsley and uratanna sequences has in condensed sections led to confusion between the depositional sequences characteristic trace and body fossil assemblages provide the only clear distinction between depositional cycles spanning the proterozoic cambrian boundary

a microscopic sedimentary succession of graded sand and microbial mats in modern siliciclastic tidal flats microscopic studies of thin sections from modern siliciclastic tidal flat sediments in the southern north sea demonstrate the significant role of microbial mats in the buildup of sedimentary sequences this is documented by a unit only a few millimetres thick it starts at the base with a fine to medium grained quartz sand often containing secondary pores fenestrae type merging gradually into finer sediments the lower siliciclastic part is superposed by an upper organically dominated layer built by microbial mats within the organic material single quartz grains without any contact to each other are oriented with their long axes parallel to the bedding planes each siliciclastic part in the lower section of the unit indicates the initial deposition of coarser grains in a stronger flow regime followed by gradually decreasing flow velocities each microbial mat in the upper part essentially represents a period of low sedimentation rate during its growth grains still settle down onto the mat and become bound in the organic matrix the orientation of these grains with their long axes parallel to the bedding plane points to an energetically suitable position to gravity achieved by the friction reduction of the soft organic matter repeated depositional events followed by low rate deposition cause the buildup of various units there is no visible reworking of the former surfaces since the microbial mats prevent erosion during periods of increased flow the buildup is characteristic of siliciclastic sediments repeatedly occupied stabilized and fixed by microbial films or mats

deep water facies processes and models a review and classification scheme for modern and ancient sediments abstract a review of previous work on modern and ancient deep water facies processes and models is presented with a new classification scheme involving 40 distinct facies related to 15 conceptually distinct facies groups these facies are fixed points in a spectrum of facies generated in a process continuum from resedimentation processes through semi permanent bottom currents to pelagic settling in essence the scheme is descriptive of the sedimentary attributes of sediments although it is designed to aid interpretation of possible sediment transport deposition processes the classification scheme is three tier with facies classes groups and constituent facies and is hierarchical to allow flexibility in its use there are seven facies classes with classes a e defined largely on the basis of grain size differences class f on the basis of internal organization and class g on composition the facies classes are class a gravels muddy gravels gravelly muds and pebbly sands with 5 gravel grade class b sands with 80 sand grade and 80 mud 40 silt and 0 20 sand class e muds and clays with 95 mud grade for the purpose of large scale mapping or reconnaissance fieldwork either the level of facies classes or groups may be appropriate whereas for more detailed sedimentology the more detailed facies level will be necessary

textured organic surfaces associated with the ediacara biota in south australia abstract the ediacaran period takes its name from the fossils of the ediacara biota which represent the first appearance of large and diverse assemblages of organisms in the fossil record although the global record of these distinctive body fossils is now well known a previously unrecognized megascopic organic record of textured organic surfaces tos occurs in the ediacara biota however tos is also a feature over a wider range of paleoenvironmental settings where body fossils are unknown in ediacaran siliciclastic successions that have been studied in australia namibia and western north america paleoecological analysis of successive bedding planes of strata from the late ediacaran rawnsley quartzite in the flinders ranges of south australia reveals that tos represent the most common organic features in bedding surface assemblages of the ediacara biota the tos consist of preserved patterned assemblages of textured organic mats fibers and simple tubular body fossils complex ediacara body fossils while striking for their distinctive body plans and dominating some of the beds are relatively minor components of combined overall surface area many elements of tos have previously been miss diagnosed as trace fossils which are in practice limited to two or at most three morphotypes that indicate the presence of bilateria although tos represent a simpler grade of organismic construction than discrete and more complex ediacara body fossils they were preserved in a similar manner marked variability in all components of the biota between successive surfaces suggests that ediacara ecologies fluctuated at short intervals despite an apparently consistent sedimentary regime

post glacial range of variability in the conejos river valley southern colorado usa fluvial response to climate change and sediment supply effective river management strategies require an understanding of how fluvial processes vary both spatially and temporally here we examine the natural range of variability in the conejos river valley southern colorado through documentation of terrace morphostratigraphic and sedimentological characteristics as well as through investigation of sediment contributions from headwaters hillslopes and tributary streams additionally soil development and radiocarbon ages together with local and regional paleoclimate reconstructions were used to infer the range of processes acting in this system since de glaciation the conejos river has fluctuated between episodes of bedrock strath formation aggradation and vertical incision morphostratigraphic relationships soil development and radiocarbon ages enable us to propose a chronology for periods of alluvial deposition around 8 9 7 6 ka 5 5 ka and from 3 5 to 1 1 ka separated by intervals of fluvial incision we infer potential forcing mechanisms by utilizing multiple working hypotheses specifically we discuss the potential for increases in sediment supply during periods of 1 para glacial adjustment 2 climatic cooling 3 increased frequency of climate change and 4 increased fire frequency or severity we also consider the effects of changes in stream discharge and extreme storm occurrence we conclude that combinations of these processes operating at different times have contributed to sediment mobilization since de glaciation stream and landform morphology also varies longitudinally due to the influence of remnant glacial topography in particular valley bottom overdeepening at tributary junctions has resulted in incision and strath formation into unlithified glacial deposits i e fill cut terraces rather than bedrock in some reaches overall the conejos fluvial system has varied significantly both temporally and spatially since de glaciation and appears to be sensitive to changes in sediment supply related to holocene scale climate fluctuations this natural range of variability must therefore be a key consideration in any future stream management policies copyright 2012 john wiley sons ltd

a diverse calcified cyanobacteria assemblage in the latest ediacaran abstract a three dimensionally preserved phosphatized cyanobacterial fossil assemblage tentatively identified as a distinct calcified cyanobacterial combination of oscillatorialeans and rivulariacean is recognized in the latest ediacaran in the southern shaanxi province china based on the morphological and preservation modes oscillatorialean cyanobacteria herein contain 3 genera which are girvanella obruchevella and subtifloria with thin walled tubes tangled coiled or aligned a kind of fan shaped fossils composed of filaments with tapered trichomes and pseudo branches cambricodium is clarified as calcified rivulariacean cyanobacteria prosperous calcified cyanobacteria co occurring with the earliest mineralized skeletal tubular fossils cloudina and sinotubulites in addition to contributing new morphological and preservation information the discovery of these cyanobacteria perhaps strengthens the case for prosperity in cyanobacterial calcification in the terminal neoproterozoic

distributed extensional deformation in a zone of right lateral shear implications for geodetic versus geologic rates of deformation in the eastern california shear zone walker lane 1 the eastern california shear zone ecsz walker lane belt represents an important evolving component of the pacific north america plate boundary geodetic data suggest the northern ecsz is accumulating dextral shear at a rate of 9 3 mm a more than double the total measured late pleistocene rate at 37 5 n at this latitude the silver peak lone mountain splm extensional complex plays an important role in accommodating and transferring slip among the strike slip and normal faults of the ecsz and walker lane to better understand the recent geodynamic evolution of this region we determined late pleistocene extension rates for the clayton valley fault zone one of a series of down to the northwest normal faults comprising the splm using geologic mapping differential gps fault scarp surveys and cosmogenic nuclide geochronology extension rates along the clayton valley fault zone are time invariant at 0 1 0 1 to 0 3 0 1 mm a depending on fault dip since 137 ka when combined with other published fault slip rates at this latitude the cumulative late pleistocene geologic slip rate is 3 3 to 5 2 mm a this rate is lower than both the geodetic rate of dextral shear and other long term slip rate budgets in the northern ecsz our results suggest that deformation in clayton valley is spread across a diffuse set of normal faults and that not all of the deformation is recorded in the surficial geology we suggest that the low cumulative geologic slip rate in the northern ecsz may be a result of this distributed extension which can cause long term rates of deformation to be significantly underestimated

organic walled microfossils from the tonian gouhou formation huaibei region north china craton and their biostratigraphic implications abstract the meso and neoproterozoic huaibei group in the huaibei region north china craton ncc is emerging as a target for geobiological and tectonic studies due to its thick unmetamorphosed sediments with well preserved organic walled fossils however the lack of accurate age constraints for this sedimentary sequence dramatically hampers our ability to take full advantage of the rich geological and paleontological history recorded in the huaibei group particularly the depositional age of the uppermost unit of the huaibei group the gouhou formation is a controversial issue although it is widely accepted that there is an unconformity between the gouhou formation and the overlying early cambrian houjiashan formation the magnitude of this unconformity and hence the scale of the underlying tectonic event are unconstrained due to the uncertainty of the sedimentary age for the gouhou formation which has been variously interpreted as cambrian cryogenian ediacaran 720 ma to 541 ma and tonian 1000 ma to 720 ma to improve our knowledge about this sedimentary gap we carried out a biostratigraphic study of the gouhou formation our investigation using a low manipulation maceration technique revealed a diverse organic walled microfossil assemblage a total of 22 taxa have been revealed including a new species dictyosphaera tacita n sp importantly the co occurrence of trachyhystrichosphaera valeria and dictyosphaera in the gouhou formation suggests a likely tonian age the biostratigraphic data indicate an infra cambrian depositional gap of 200 myr between the tonian gouhou formation and cambrian houjiashan formation perhaps driven by a major tectonostratigraphic event

tectonothermal evolution of the neoproterozoic grampian and appin groups southwestern monadhliath mountains scotland metasedimentary rocks of the neoproterozoic grampian and appin groups exposed in the glen roy district monadhliath mountains scotland were strongly folded during an initial progressive tectonothermal event of the caledonian orogeny the attitude and style of the first folds varies from open upright ne trending structures in the west e g the appin synform to recumbent nw facing nappes in the east e g the treig synform these early nappes occur only south of the corrieyairack complex and their amplitude decreases towards the nw ductility contrasts induced sliding such as that locally recorded along the grampian appin group lithostratigraphical boundary subsequently the early structures were deformed by tight upright d2 folds nw thrusting along the eilrig shear zone during d2 is interpreted as occurring in response to a transfer of bulk transport to deeper structural levels relative to d1 prograde metamorphism accompanied deformation with the thermal peak in the glen roy district t 500 600 c p 7 0 8 0 kbar coinciding with d2 folding it is suggested that the regional variation in the style of deformation was controlled at least in part by pre existing major structures most notably fundamental transverse basement lineaments temporal changes in the style of deformation occurred in response to changing crustal architecture during progressive deformation the study demonstrates the diachronous nature of deformation and also illustrates how its is possible to preserve areas with simple deformation histories in the centre of a major orogenic belt

relative sea level changes and the development of a cambrian transgression the lower cambrian in northwest scotland is one example of a lower palaeozoic orthoquartzite carbonate succession deposited on a slowly subsiding peneplained precambrian basement during a period of relative sea level rise this particular setting led to the development of a very wide low gradient shelf which was extremely sensitive to minor sea level changes the basal quartz arenite section lower member pipe rock is a transgressive tide dominated systems tract but lacks a systematic parasequence architecture because of three factors a fluvial sediment flux was insufficient to induce shoreline progradation accommodation space was limited during sea level falls which are commonly expressed by widespread erosional surfaces and sediment yield to the shelf by transgressive reworking was a major contributor towards the preserved stratigraphy the storm dominated fucoid beds represent a condensed section and also show the effects of rapid and widespread facies belt oscillations because of the low shelf gradient an overlying highstand systems tract is also lacking partly due to the absence of a large fluvial sediment yield and also due to lowstand and transgressive reworking an erosively based tidal sandsheet at the top of the fucoid beds interpreted to be a lowstand systems tract therefore rests directly on the condensed section of the underlying sequence this was in turn reworked into linear tidal sandbanks salterella grit during slow sea level rise prior to the next major transgression the limited accommodation space therefore introduced a preservational bias towards deepening upward trends on a parasequence and sequence scale the oscillations in facies belts episodic subareal exposure and the potential to remove substantial portions of systems tracts suggests that lower palaeozoic orthoquartzite successions may exhibit regular and abrupt vertical shifts in depositional environment which given their subtle lithological character may require detailed analysis to identify such successions may also display incomplete development of several components of transgressive regressive sequence architecture

the grampian group a major late proterozoic clastic sequence in the central highlands of scotland a stratigraphic framework is proposed for the late proterozoic grampian group of the scottish highlands the grampian group is divided into three subgroups each defined by distinctive lithofacies associations reflecting different environments of deposition the thin ord ban subgroup which is locally developed at the base of the grampian group on speyside and strath dearn consists of shallow marine shelf sediments in association with concordant amphibolite sheets elsewhere the corrieyairack subgroup which is thickest around loch laggan forms the lower portion of the grampian group and comprises a thick turbiditic clastic sequence laid down in deeper water during rapid basin subsidence the glen spean subgroup comprises the upper part of the grampian group and is thickest in the atholl district it is composed of shallow water tidal and deltaic deposits marking a shallowing of the grampian group basin lateral facies changes and diachronous contacts are indicative of differential subsidence and the grampian group basin apparently developed and filled before the onset of regional subsidence which heralded deposition of the overlying dalradian sediments the possibility that the grampian group was unconformable on the structurally underly ing central highland division and glenshirra succession is currently unresolved

affirming life aquatic for the ediacara biota in china and australia the ediacara biota has been long championed as a snapshot of the marine ecosystem on the eve of the cambrian explosion providing important insights into the early evolution of animals fossiliferous beds in the eponymous ediacara member of south australia have been recently reinterpreted as paleosols and ediacara fossils as lichens or microbial colonies that lived on terrestrial soils this reinterpretation here dubbed the terrestrial ediacara hypothesis would fundamentally change our views of biological evolution just prior to the cambrian explosion we take a comparative paleobiology approach to test this hypothesis the ediacara member shares a number of forms with assemblages in ediacaran marine black shales in south china shales that show no evidence of pedogenesis thus the shared ediacara fossils and by extension other co occurring fossils are unlikely to have been terrestrial organisms a terrestrial interpretation is also inconsistent with functional morphological evidence some of the shared forms are not morphologically adapted to address the most critical challenges for terrestrial life e g mechanical support and desiccation thus the terrestrial ediacara hypothesis can be falsified on comparative paleobiological and functional morphological grounds and we urge paleopedologists to critically reevaluate evidence for pedogenesis in the ediacara member and other ediacaran successions

chronosequence development and soil variability from a variety of sub alpine post glacial landforms and deposits in the southeastern san juan mountains of colorado abstract surficial processes acting on post glacial alpine and sub alpine landscapes vary at small temporal and spatial scales and are thus often difficult to conceptualize in the context of large scale landscape evolution models soils developing in this setting can thus provide valuable information about landform genesis sedimentology and age relatively few post glacial chronosequences have been examined in these settings however particularly for the variety of landforms and parent materials that exist within alpine and sub alpine environments here we examine a chronosequence of relatively young post glacial landforms with varying parent materials and climate histories we dug and described 39 soil pits in the upper conejos river valley of colorado on a variety of deposits and landforms including alluvial fans terraces colluvium glacial till and terminal moraines and compared soil properties with radiocarbon ages from the area our results suggest that some typical chronosequence soil properties e g ph structure color do not correlate with time over short time scales however extractable iron ratios feo fed show a relatively strong correlation with age across late pleistocene and holocene time scales and maximum profile clay content shows a weak but statistically significant relationship with age both of these trends are stronger when examined across a single parent material differences in initial parent material texture and dust inputs seem to be the most significant complicating factors over post glacial time scales soil property development through time is most inconsistent in cumulic alluvial fan soils this observation may indicate that alluvial fans are more responsive to sub basin scale processes as opposed to fluvial terraces that are more likely respond to processes active across the entire basin these differences would explain why stratigraphically similar alluvial fans are mantled by soils with varying development nonetheless horizonation clay content and extractable iron ratios provide a useful tool for correlating young deposits assigning ages and interpreting the geomorphic history of complex post glacial environments

piecing together the puzzle of the ediacara biota excavation and reconstruction at the ediacara national heritage site nilpena south australia abstract patterns of origination and evolution of early complex life on this planet are interpreted largely from the fossils of the precambrian soft bodied ediacara biota excavation and reconstruction of beds of the ediacara member of the rawnsley quartzite at the national heritage ediacara fossil site nilpena in the flinders ranges of south australia has exposed nearly 300 square meters of fossiliferous bedding planes as a result the taphonomy and sedimentology of the succession are well constrained rendering it possible to disentangle ecological from environmental and taphonomic signals the fossil record that is preserved on these beds is a function of a number of factors including 1 sedimentary environment 2 initial colonization 3 nature of textured organic surfaces 4 duration of time between episodes of disturbance and 5 biostratinomic processes the excavation and reconstruction of beds at nilpena yield an exceptional and unique opportunity to examine not only the taxonomic composition of ediacara communities but also their ecological character at various stages of development preserved ecological snapshots of fossil assemblages range from immature communities of small bodied individuals associated with poorly developed organic mats to communities characterized by a high diversity of macrofaunal taxa wide range of body sizes and the presence of dense textured organic surfaces

revised neoproterozoic and terreneuvian stratigraphy of the lena anabar basin and north western slope of the olenek uplift siberian platform abstract the early to mid neoproterozoic pre glacial sedimentary succession of the lena anabar basin northeast siberian platform records protracted faulting and subsidence possibly as part of the widespread continental rifting and the break up of rodinia there is a significant stratigraphic unconformity separating the pre glacial neoproterozoic strata and the overlying upper ediacaran succession in the lena anabar basin with the terreneuvian strata most likely to be deposited in a foreland of the central taimyr accretionary belt the cryogenian sensu strictum i e younger than 720 ma and lower ediacaran deposits are missing in the area in this study we assess the palaeontological content of the precambrian and terreneuvian strata of the lena anabar basin and the adjacent north western slope of the olenek uplift and revise the chronostratigraphy of the region with special emphasis to biostratigraphic index taxa for the pre glacial neoproterozoic section we establish the new tukulan kulady taimylyr formations and redefine the khastakh formation we also refine the ediacaran and terreneuvian stratigraphy by formalising the maastakh khatyspyt and turkut formations of the khorbusuonka group whereas the kessyusa formation is raised to group rank and subdivided into the syhargalakh oppokun mattaia and chuskuna formations the proposed stratigraphic correlation scheme is based upon depositional unity and is consistent both lithologically and biostratigraphically providing a robust framework for future stratigraphic sedimentological and palaeobiological studies

gamma ray spectroscopy in structural correlations an example from the neoproterozoic dalradian succession of donegal nw ireland the caledonian horn head slide is a spectacular ductile shear zone transecting neoproterozoic appin group dalradian metasediments in donegal nw ireland two conflicting stratigraphic interpretations exist for the inverted succession exposed in the hanging wall of the structure these are based on correlation with two quite separate exposed pelite formations elsewhere the two formations are lithologically indistinct and unfossiliferous here we document the novel use of assayed and logged spectral gamma ray measurements in comparing the contentious pelite in the hanging wall of the horn head slide to the two possible correlative pelite formations from a wide area of their unequivocal outcrop the data from the contentious pelite show a clear statistical and stratigraphical affinity with one candidate unit only thus providing the stratigraphical definition necessary for refining previous cross sections a new model based on our spectral gamma ray correlation is proposed to account for the northwestwards directed emplacement of the lower falcarragh pelite formation along the slide this model requires pre caledonian normal faulting as a precursor to the ensuing compressional event in which stratigraphically younger rocks were thrust over older a common instance in fold and thrust belt geometry our work suggests that spectral gamma ray measurements may provide a rapid field based method for differentiating unfossiliferous pelite or mudstone units at outcrop and in geophysical well logs even in structurally complex areas

carbonate hosted avalon type fossils in arctic siberia avalon type fossils are crucial to understanding the origin of phanerozoic ecosystems but their usual occurrence in volcaniclastic and siliciclastic facies greatly limits their paleobiological resolution the unique carbonate hosted assemblage of the khatyspyt formation on the olenek uplift of north central siberia promises a much enhanced anatomical and paleo ecological view of these enigmatic organisms avalon type fossils are preserved by authigenic carbonate cementation in intervals of finely laminated nodular limestones khatyspyt type taphonomic window interbedded silicified calcareous mudstones yield diverse carbonaceous compressions occasionally with taphonomic phantoms of avalon type taxa miaohe type taphonomic window styles of moldic preservation do not appear to be taxon selective and therefore cannot alone be responsible for the morphological distinctiveness of ediacaran macrofossils and the profound disparity in the taxonomic composition between fossil assemblages on the other hand the exclusion of avalon type fossils from carbonaceous compressions miaohe type preservational window is a real taphonomic signal that provides an important constraint on the properties of certain ediacaran tissues

seaweeds through time morphological and ecological analysis of proterozoic and early paleozoic benthic macroalgae abstract benthic marine macroalgae or seaweeds are key ecological players in oceans today and have been since the proterozoic to date however morphological and evolutionary patterns for precambrian macroalgae have been documented only in rather broad terms to refine our understanding in this critical interval we updated a dataset of proterozoic to early paleozoic noncalcified macroalgal fossils preserved as macroscopic carbonaceous compressions the data were analyzed using non parametric multidimensional scaling nmds and functional form group ffg approaches in order to characterize morphological and ecological evolutionary patterns of these macroalgae at the broadest scale the results show progressive increases in thallus size morphospace range and aspects of ecological complexity such as canopy heights surface area volume ratios and functional form groups through time these trends however are not always monotonous in particular significant increases in proterozoic macroalgal morphological diversity and maximum size appear to have occurred in the neoproterozoic tonian and ediacaran periods respectively analysis of ediacaran macroalgal assemblages shows that macroalgae broadly follow the ediacara like fossil assemblages with a significant drop in most studied metrics in the terminal ediacaran stage 550 539 ma the latter event occurs during the kotlinian crisis experienced by ediacara type macro organisms highlighting the possibility that this extinction event during the ediacaran cambrian transition affected both macroalgae and ediacara type macro organisms our analysis also confirms an ordovician increase in the morphological and ecological diversity of macroalgae

trace fossil evidence for ediacaran bilaterian animals with complex behaviors abstract distinguishing ediacaran trace fossils from tubular body fossils can be a challenge and several ediacaran fossils previously interpreted as animal traces have been shown to be tubular body fossils nonetheless true ediacaran trace fossils are present but they are relatively few and morphologically simple dominated by horizontal trails and shallow burrows such simple morphologies have been taken as evidence for a modest behavioral complexity and limited geobiological impact of animal bioturbators before the cambrian explosion here we report three types of trace fossils horizontal tunnels surface tracks trails and vertical traces from the latest ediacaran dengying formation 551 541 ma in the yangtze gorges area of south china cross cutting tunnels and the presence of scratch marks indicate that these traces are unlikely tubular body fossils instead these three types of traces likely represent animal activities related to under mat feeding epibenthic locomotion and temporary dwelling respectively we show that these three types of traces were constructed by the same bilaterian animals that had moderately complex interactions with microbial mats to exploit nutrients and o 2 resources these animals heralded a new age in ecosystem engineering animal sediment interaction and biogeochemical cycling

a sequence stratigraphical approach to the understanding of basin history in orogenic neoproterozoic successions an example from the central highlands of scotland

impact of the magnitude and frequency of debris flow events on the evolution of an alpine alluvial fan during the last two centuries responses to natural and anthropogenic controls the dynamics and the surface evolution of a post lgm debris flow dominated alluvial fan tartano alluvial fan which lies on the floor of an alpine valley valtellina northern italy have been investigated by means of an integrated study comprising geomorphological field work a sedimentological study photointerpretation quantitative geomorphology analysis of ancient to modern cartography and consultation of historical documents and records the fan catchment meteoclimatic geological and geomorphological characteristics result in fast rates of geomorphic reorganization of the fan surface 2 km2 the dynamics of the fan are determined by the alternation of low return period catastrophic alluvial events dominated by non cohesive debris flows triggered by extreme rainstorms which caused aggradation and steepening of the fan and avulsion of its main channel with periods of low to moderate streamflow discharge punctuated by low to intermediate magnitude flood events causing slower but steady topographic reworking the most ancient parts of the fan surface date back at least to the first half of the 19th century but most of the fan surface has been restructured after 1911 mainly during the debris flow dominated events of 1911 and 1987 phases of rapid fan toe incision and fan degradation have been recognized since the 1930s or 1940s the tartano fan has been subjected to a state of deep entrenchment and narrowing of the main trunk channel and distributary area post little ice age climate change and present day surface uplift rates have been considered as possible explanations for the observed geomorphic evolution but tectonic or climatic controls cannot account for the order of magnitude of the erosional pace anthropogenic controls plausibly override the natural ones in particular the building of a dam in the late 1920s about 2 km upstream of the fan seems to have triggered fan dissection having altered the sediment discharge through sediment retention copyright 2011 john wiley sons ltd

organic walled microfossils from the tonian tongjiazhuang formation of the tumen group in western shandong north china craton and their biostratigraphic significance abstract neoproterozoic successions in western shandong of north china craton contain fine grained siliciclastic rocks which offer a unique opportunity to explore the neoproterozoic biosphere in this study we have revealed a well preserved and diversified microfossil assemblage from the tongjiazhuang formation tumen group in western shandong north china craton which is characterized by abundant smooth walled sphaeromorphic acritarchs and cyanobacterium like filamentous forms and relatively low abundance of more complex acritarchs a total of 40 microfossil taxa belonging to 20 morphological genera have been identified most of which are described for the first time from the tongjiazhuang formation of the tumen group in western shandong including simia sp trachyhystrichosphaera aimika t botula germinosphaera bispinosa unnamed sp a jacutianema solubila and pololeptus rugosus the tongjiazhuang assemblage revealed in this study is much more diverse than previously reported and well comparable to the tonian liulaobei and gouhou assemblages in the xuhuai region particularly the occurrence of t aimika t botula g bispinosa j solubila and p rugosus indicates a late mesoproterozoic to tonian age for the tongjiazhuang formation in addition the occurrences of macroscopic carbonaceous compressions including chuaria tawuia assemblage from the tongjiazhuang formation and tawuia and sinosabellidites from the shiwangzhuang formation are consistent with geochronological data suggesting a tonian age for the tongjiazhuang fulaishan and shiwangzhuang formations of the middle and upper tumen group while the heishanguan and erqingshan formations of the lower tumen group are likely late mesoproterozoic to tonian in age thus available biostratigraphic data lithostratigraphic correlation and geochronological data suggest that the whole tumen group is late mesoproterozoic to tonian in age rather than cryogenian or ediacaran this study significantly improves our knowledge about the diversity of the tonian biosphere and implies a 200 300 million years unconformity the great unconformity between the late mesoprotoerozoic to tonian tumen group and the early cambrian liguan formation in western shandong

remarkable preservation of microbial mats in neoproterozoic siliciclastic settings implications for ediacaran taphonomic models abstract it is beyond doubt that the appearance of infaunal bioturbation and metazoan biomineralization across the ediacaran cambrian transition irreversibly affected the nature of marine sediment architecture and biogeochemistry here we review those changes in relation to their likely effect upon the processes of fossil preservation especially within siliciclastic sediments processes of soft tissue preservation in siliciclastic settings from the ediacaran period including microbes and microbial mats as well as ediacaran macrofossils are here reviewed within this context highlighted examples include the exceptional preservation of microbes found in association with wrinkle structures and ediacaran macrofossils in england and newfoundland replicated by silicate minerals and in the white sea region of russia replicated by iron sulphide these occurrences show that soft tissue preservation in siliciclastic settings went well beyond that typical for ediacaran macrofossils alone and also extended to similar modes of preservation in associated microbes using these new observations it can be argued that several existing explanations for ediacaran fossil preservation can be united within a biogeochemical model that involves evolution of the sediment mixed layer across this transition

interactions between ediacaran animals and microbial mats insights from lamonte trevallis a new trace fossil from the dengying formation of south china abstract a new ichnogenus and ichnospecies lamonte trevallis is formally described from the shibantan member limestone of the upper ediacaran dengying formation yangtze gorges area south china it is characterized by horizontal tunnels connected with short vertical burrows and surface trails the horizontal burrows are elliptical or bilobed in transverse cross section preserved in full relief and filled with carbonate intraclasts micrites as well as calcite and silica cements they occur exclusively in silty crinkled and microlaminated layers that are interpreted as amalgamated cyanobacterial microbial mats no burrows have been found in intraclastic layers adjacent to the microlaminated layers the vertical traces are filled with the same material as the burrows but they typically project through the crinkled microlaminae and are exposed on the bedding surface the surface tracks are always preserved in negative epirelief or positive hyporelief and consist of two parallel series of either sharp scratch marks or small knobs the burrow infill has 18ocarb and 13ccarb values distinct from but intermediate between microlaminated and intraclastic layers consistent with petrographic observation that burrow infill consists of a mixture of early carbonate cements intraclasts and micrites bedding plane bioturbation intensity 20 40 measured as percentage of bedding plane area covered by l trevallis traces is comparable to similar measurements in pre trilobite cambrian carbonates the exclusive occurrence of l trevallis within microbial mats may have both taphonomic and ecological significance these mats may have provided firm substrates and localized geochemical conditions that contributed to the structural integrity of the burrows and they may have also facilitated early diagenetic cementation of burrow infill thus facilitating burrow preservation the close association of these burrows with microbial mats implies that the trace producers actively mined cyanobacterial mats to exploit oxygen or nutrient resources the trace makers of l trevallis were better able to utilize the resources around them than many other ediacaran trace makers and provide an ichnological record of a flourishing benthic ecology in late ediacaran oceans at the dawn of the agronomic revolution

high resolution sequence stratigraphy the east coulee delta alberta abstract the fundamental concept on which sequence stratigraphy is based is that stratal architectures develop in response to the interaction between base level change and sediment flux a small lacustrine fan delta at east coulee alberta illustrates these principles and demonstrates that sequence stratigraphic concepts are scale and time independent this fan delta formed in a matter of days in a roadside drainage ditch as water level rose and then fell changes in the subaqueous space available for sediment to fill i e accommodation resulted in the development of a succession of systems tracts analogous to those formed within sedimentary basins over much longer time frames deposition began during lake level rise with progradation of a fan deltaic wedge accelerating lake level rise resulted in a backstepping of the shoreline and deposition of a transgress systems tract subsequent lake level fall resulted in subaerial exposure of the relatively steep delta front and caused incised valley formation and deposition of a lowstand delta this stratigraphic response to base level fall is typical of lowstand systems tract development on basin margins characterized by high relief slopes e g passive margins further lake level fall resulted in minor additional valley incision and development of a second lowstand delta on a surface characterized by lower relief as lowering water level exposed a flatter physiography this development of lowstand deltas and coa tlines during base level fall constitutes a forced regression of posamentier et al 1990 and is typical of lowstand systems tracts on basin margins characterized by gentle slopes in spite of its small size this example clearly illustrates that sequence stratigraphic principles apply to lacustrine as well as marine settings and at all spatial and temporal scales

a neoproterozoic multi phase rift sequence the grampian and appin groups of the southwestern monadhliath mountains of scotland the grampian and appin groups of the southwestern monadhliath mountains form the earliest known syn rift sequences of the scottish central highlands they were likely to have formed in an intracontinental setting and represent deposition of mixed clastic and carbonate shallow and deep marine strata the grampian group of the southern monadhliath mountains was deposited during a period of initial basin rifting nw se extension followed by a phase of thermal subsidence syn rift sediments comprise a 2 5 6 km thick turbidite system thermal subsidence brought about the basinward progradation of shallow marine shelf sediments resulting in the infilling of pre existing basin topography the overlying appin group commenced with deposition of a shallow marine sequence alternating between nearshore tidal sand and offshore mud deposition this formed in response to renewed rifting and concomitant subsidence accelerated rifting resulted in localized footwall uplift and erosion while sedimentation continued in the hanging wall areas resultant subsidence perhaps partly thermally driven caused gradual basin widening and produced an onlapping marine sequence there followed a period of progressive clastic deprivation when carbonates were precipitated and at the onset of anoxic conditions deposition of organic muds the fundamental structural elements responsible for the formation of the grampian and appin group basins were also influential in the orogenic evolution of the basin fill half graben fills were deformed to produce regionally extensive folds such as the stob ban craig a chail synform

quaternary evolution of cedar creek alluvial fan montana abstract cedar creek alluvial fan is a textbook example of an alluvial fan because of its fan shape with smooth concentric contours and excellent symmetry similar planimetric shapes have been used to infer uniform fan deposition however cedar creek alluvial fan is composed of four fan deposits of quaternary age qf1 oldest to qf4 youngest indicating that fan deposition was nonuniform in both time and space field studies indicate that deposition of cedar creek alluvial fan is related to glaciofluvial outwash activity during the pleistocene and upper fan entrenchment and lower fan deposition during the holocene qf1 and qf2 deposits are sub horizontally bedded clast supported sandy gravels uniformly imbricated upfan comparison of soil profiles developed in these deposits to radiogenically dated chronosequences within the region indicates that qf1 and qf2 are correlative with bull lake and pinedale age deposits respectively these relationships are substantiated by physical correlation of qf1 and qf2 with bull lake and pinedale moraines respectively in the cedar creek drainage basin the sedimentology and timing of qf1 and qf2 indicate deposition in high energy proglacial braided streams furthermore the present morphology of cedar creek alluvial fan was established largely during aggradation of qf1 and qf2 when sediment supply to the fan was sufficient to activate 60 to greater than 90 of the total fan area during bull lake glaciation the apex of qf1 deposition formed the apex of cedar creek alluvial fan as qf1 covered more than 90 of the present fan area during pinedale glaciation qf2 deposition shifted downfan qf2 is inset into qf1 above the intersection point but below the intersection point it eroded and or buried qf1 as it activated as much as 60 of the fan area qf3 and qf4 comprising 21 of the fan area are inset into qf2 in the lower fan area soil development in qf3 and qf4 deposits indicate episodic deposition and entrenchment beginning in early holocene and continuing to present a post glacial decrease in sediment supply to cedar creek alluvial fan is indicated by sediment storage within the cedar creek drainage basin decreased sediment supply to the fan resulted in upper fan entrenchment of qf2 and deposition of qf3 and qf4 in the lower fan area

infilling of the younger kathmandu banepa intermontane lake basin during the late quaternary lesser himalaya nepal a sedimentological study the kathmandu and banepa basins central nepal are located in a large syncline of the lesser himalayas the older kathmandu lake evolved during the pliocene and early pleistocene the younger kathmandu lake which is the focus of this study is infilled with late quaternary sediments three formations arranged in stratigraphical order the kalimati gokarna and thoka formations formed during the infilling stage of this lacustrine basin structural and textural sedimentological analyses a chemical survey across the basin and mineralogical investigations of fine grained sediments form the basis of this palaeogeographical study the basin under investigation was covered by a perennial freshwater lake before 30 000 yr bp the lake was infilled with alluvial and fluvial sediments delivered mainly from the mountains north of the basin a fairly low gradient was favourable for the formation of diatomaceous earths carbonaceous mudstones and siltstones which were laid down in the centre of the lake and in small ponds towards the basin edge lacustrine sediments gave way to deltaic deposits spread across the delta plain crevasse splays and anastomosing rivers mainly delivered suspended load for the widespread siltstones and mudstones the proximal parts of the alluvial fluvial sedimentary wedge contain debris flows that interfinger with fine grained floodplain deposits three highstands of the water level 30 000 yr bp 28 000 19 000 yr bp 11 000 4000 yr bp have been recognised in the sedimentary record of the younger kathmandu lake in the late quaternary second order water level fluctuations are assumed to be triggered by local processes damming by tectonically induced landslides first order water level fluctuations are the result of climatic changes copyright 2003 john wiley sons ltd

ediacaran body and trace fossils in miette group windermere supergroup near salient mountain british columbia canadarevision of the paper was carried out by dr guy narbonne following the passing away of both hans hofmann deceased may 19 2010 and eric mountjoy deceased june 18 2010 after manuscript submission siliciclastic beds in the upper part of the miette group in southeastern british columbia have yielded an assemblage of late ediacaran soft bodied macrofossils and trace fossils the macrofossils comprise aspidella bradgatia and miettia salientensis gen et sp nov the ichnofossils include archaeonassa cochlichnus didymaulichnus gordia halopoa helminthoidichnites helminthopsis planolites and a large unnamed crawling trace in addition two types of unidentified problematica are recorded representing either tubular vendotaenia like body fossils or trace fossils the bradgatia constitutes the youngest occurrence of this type of fossil and is the first to be recorded from laurentia having previously been noted only in avalonia with cloudina and namacalathus in associated shallow water platform carbonates the miette biota in the study area contains a combination of namibian type and avalonian type elements

debris flow dominance of alluvial fans masked by runoff reworking and weathering arid alluvial fan aggradation is highly episodic and fans often comprise active and inactive sectors hence the morphology and texture of fan surfaces are partly determined by secondary processes of weathering and erosion in addition to primary processes of aggradation this introduces considerable uncertainty in the identification of formative processes of terrestrial and martian fans from aerial and satellite imagery the objectives of this study are i to develop a model to describe the sedimentological and morphological evolution of inactive fan surfaces in arid settings and ii to assess the relative importance of primary processes of aggradation and secondary processes of weathering and reworking for surface morphology and sedimentology and for the stratigraphic record we studied an alluvial fan characterized by a recently active sector and a long abandoned inactive sector along the coast of the hyperarid atacama desert here rates of primary geomorphic activity are exceptionally low because of extreme aridity while weathering rates are relatively high because of the effects of coastal fogs long term processes of fan aggradation and reworking were determined through sedimentological facies analysis of stratigraphic sections ground surveys for textural and morphological patterns at the fan surface were integrated with remote sensing by an unmanned airborne vehicle uav discharges and sediment transport capacities were calculated to estimate the efficiency of secondary runoff in reshaping the inactive fan sector stratigraphic sections reveal that the fan was dominantly aggraded by debris flows whereas surface morphology is dominated by debris flow signatures in the active sector and by weathering and runoff on the inactive sector on the latter rapid particle breakdown prevents the formation of a coarse desert pavement furthermore relatively frequent local runoff events erode proximal debris flow channels on the inactive sector to form local lag deposits and accumulate fine sediment in low gradient distal channels forming a well developed drainage pattern that would suggest a runoff origin from aerial images nevertheless reworking is very superficial and barely preserved in the stratigraphic record this implies that fans on earth and mars that formed dominantly by sporadic mass flows may be masked by a surface morphology related to other processes

characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data 1 range front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages these distinct landforms are often defined by descriptions of their surface morphology desert varnish accumulation clast rubification desert pavement formation soil development and stratigraphy although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past high resolution airborne laser swath mapping alsm digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail here we use alsm data to calculate surface roughness on two alluvial fans in northern death valley california we define surface roughness as the standard deviation of slope in a 5 m by 5 m moving window comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99 confidence level furthermore there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10be and 36cl surface exposure ages of 70 ka beyond 70 ka alluvial landforms become progressively rougher with age these data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces

a tale of three taphonomic modes the ediacaran fossil flabellophyton preserved in limestone black shale and sandstone abstract ediacaran macrofossils are typically preserved in three taphonomic modes casts molds in siliciclastic rocks casts molds in carbonate rocks and carbonaceous compressions in black shales only a few taxa are known to be preserved in more than one of these taphonomic modes flabellophyton is a genus that has been previously reported from lower ediacaran black shale of the lantian formation 635 551 ma in south china and upper ediacaran sandstone of the ediacara member 560 550 ma in south australia here we report flabellophyton from upper ediacaran limestone of the shibantan member of the dengying formation 551 539 ma in south china making flabellophyton the only genus that occurs in all three taphonomic modes we also provide a systematic description of flabellophyton based on material from the lantian and dengying formations in south china recognizing three morphospecies f lantianense f typicum sp nov and f obesum sp nov flabellophyton is reconstructed as an erect epibenthic marine organism attached to sandy carbonate and muddy substrates its phylogenetic affinity remains ambiguous though it was historically interpreted as an algal fossil the wide environmental and stratigraphic distribution of flabellophyton allow comparative taphonomic and paleoecological analysis taphonomic analysis of flabellophyton indicates that multiple taphonomic pathways can facilitate the preservation of ediacaran macrofossils as a window into ediacaran paleoecology flabellophyton and other ediacaran fossils played a crucial role in the construction of epibenthic communities in ediacaran oceans and helps to understand the ecological migration and evolutionary expansion from deeper to shallower oceans during the ediacaran period

sedimentology and paleogeographic evolution of the intermontane kathmandu basin nepal during the pliocene and quaternary implications for formation of deposits of economic interest abstract the kathmandu valley is an intermontane basin in the center of a large syncline of the lesser himalayas the sedimentary basin fill comprises three units of plio pleistocene to holocene age the study aimed at modeling the paleogeographic evolution of the basin with emphasis on sedimentary series of fossil fuels and non metallic deposits the lithological setting of the basin and the tectonic framework were instrumental to basin subsidence alluvial through lacustrine sedimentation during incipient stages is a direct response to uplift in the hinge zone of the synclinorium axial parallel sediment dispersal gave way to fluviodeltaic sedimentation mainly from the limbs of the synclinorium ongoing compression and renewed uplift in the core zone of the synclinorium drove the uplift of a nw se running divide and a subdivision of the mono lake into two basins this ridge blocked the flow of transverse rivers and the northern subbasin became gradually choked ongoing uplift of the entire basin during the recent geological history caused a reorganization of the drainage pattern and triggered linear erosion in the southern mountain range step by step the remaining lacustrine basins disappeared fan aggradation coincide with cold dry or warm seasons fluvial dissection and discharge increased during warmer and more humid periods high lake levels exist during phases of increased humidity the results of this basin analysis may be used predictively in the exploration for coal natural gas diatomaceous earths and quarrying for sand or clay the gas potential is at its maximum in the lacustrine facies sand and clay for construction purposes may be quarried economically from various fluvial and deltaic deposits diatomaceous earths predominantly accumulated in marginal parts of the lake and some landslide dammed ponds lignitic brown coal can be mined together with combustible shales from poorly drained swamps

dickinsonia liftoff evidence of current derived morphologies abstract dickinsonia an iconic member of the ediacara biota is abundant in the ediacaran deposits found at the nilpena field site south australia despite exquisite fossil preservation at this site many specimens of dickinsonia appear to be incomplete with an apparently missing piece on the periphery orientation measurements from specimens on three fossil beds suggest that these so called missing pieces are aligned irrespective of the axial orientation of dickinsonia the nonrandom orientation of incomplete specimens matches that of other aligned structures found on two of these beds the preferred directionality of this feature suggests the molding of incomplete specimens under the influence of current activity prior to or during burial we propose that this feature originates where part of a dickinsonia was lifted off of the substrate during a storm event and that sand was deposited beneath this lifted portion this model suggests that dickinsonia was easily separated from the sea floor and was not attached to the substrate on which it lived this is consistent with the data from dickinsonia footprints suggesting that dickinsonia was mobile

mapping quaternary alluvial fans in the southwestern united states based on multiparameter surface roughness of lidar topographic data 1 quaternary alluvial fans have diverse surface morphologies related to both depositional and weathering processes numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition but only recently has there been an effort to utilize high resolution topographic data to differentiate alluvial fans by surface age with automated and quantifiable routines we developed a quantitative model for mapping the relative age of alluvial fan surfaces based on multiparameter surface roughness values computed from 1 m resolution lidar topographic data roughness is defined as a function of observational scale and integration of slope curvature and aspect topographic parameters alluvial fan roughness values were computed across multiple observation scales 3 3 m to 150 150 m based on the standard deviation sd of slope curvature tangential and aspect topographic parameters plots of roughness value versus size of observation scale suggest that the sd of each parameter over a 7 7 m observation window best identified the signature of surface roughness elements roughness maps derived from slope curvature and aspect at this scale were integrated using fuzzy logic the integrated roughness map was then classified into five relative morphostratigraphic surface age categories active wash to 400 ka and statistically compared with a similar fivefold surface age map of alluvial fans developed using traditional field surveys and aerial photographic interpretation the model correctly predicted the distribution and relative surface age of 61 of alluvial fan landforms based on traditional mapping techniques

pleistocene geomorphology and geochronology of eastern grand canyon linkages of landscape components during climate changes we report new mapping soils survey and geochronologic luminescence u series and cosmogenic nuclide data from pleistocene deposits in the arid setting of eastern grand canyon the result is a stratigraphic framework of inset fill gravels and associated terraces that provide a record of the responses of hillslopes tributary streams and the colorado river to the last 400 kyr of glacial interglacial climate change the best preserved last 80 kyr of this record indicates a stratigraphic chronologic disconnect between both deposition and incision along the colorado river versus along the trunks of local tributaries for example the colorado river finished aggrading and had already begun incising before the main pulse of aggradation in the trunks of local catchments during marine isotope stage 3 and then tributary incision followed during the millennial scale fluctuations of the last glacial epoch potentially concurrent with mainstem aggradation the mainstem record appears to broadly correlate with regional paleoclimate and upstream geomorphic records and thus may be responding to climatic hydrologic changes in its mountain headwaters with aggradation beginning during full glacial times and continuing into subsequent interglacials the contrasting lag time in responses of the dryland catchments within grand canyon may be largely a function of the weathering limited nature of hillslope sediment supply r 2005 elsevier ltd all rights reserved

the significance of the geal charn ossian steep belt in basin development in the central scottish highlands the geal charn ossian steep belt is a major composite synclinal structure cored by an upward facing appin group succession it is located at the margin of a west facing sedimentary basin where more than 8 km of grampian group sediment was deposited adjacent to an intrabasin structural high the high comprises mainly gneissose metasedimentary rocks the glen banchor succession which acted as the basement to the grampian and appin group rocks major unconformities are recognized at more than one level as the sedimentary basin successions onlapped onto the 9high9 the primary major upright folds and associated slides of the steep belt developed when considerable shortening was focused along the basin margin during the caledonian orogeny

how well do fossil assemblages of the ediacara biota tell time patterns of origination evolution and extinction of early animal life on this planet are largely interpreted from the fossils of the precambrian soft bodied ediacara biota spanning nearly 40 m y of the terminal ediacaran period localities containing these fossils are loosely considered as part of either the avalon white sea or nama associations these associations have been interpreted to have temporal paleobiogeographic preservational and or paleoenvironmental significance surprisingly elements of all three associations occur within the ediacara member of the rawnsley quartzite of south australia an analysis of over 5000 specimens demonstrates that fossil distribution is strongly controlled by facies and taphonomy rather than time or biogeography and that individual taxa vary considerably in their environmental tolerance and taphonomic integrity the recognition that these taxa represent organisms living in various distinct environments both juxtaposed and shared holds strong implications for our interpretation of the record of early animal life on this planet and questions the biostratigraphic utility of the three associations furthermore although in situ soft bodied preservation provides a unique perspective on composition of benthic fossil assemblages the record should not be interpreted as a simple snapshot fossil beds represent a range of preservational modifications varying from current winnowed census samples of benthic communities at different depths and ecological maturity to entirely transported assemblages unless the appropriate environments and taphonomic conditions are present for certain taxa the absence of a particular taxon may or may not indicate its extinction in space or time