archaeocyathan zonation of the yangtze platform implications for regional and global correlation of lower cambrian stages detailed analysis of the distribution of archaeocyaths in five lower cambrian sections in south china has resulted in the erection of four new archaeocyathan zones and one new archaeocyathan bed listed in order of ascending age these are the dailycyathus xiuqiensis zone the dictyocyathus shaanxiensis zone the spirillicyathus duplex range zone the sibirecyathus meitanensis range zone and the archaeocyathus yanjiaoensis beds these new subdivisions permit a correlation of lower cambrian strata both within the area of the yangtze platform south china as well as between this region and siberia australia western europe and north america within the yangtze platform area archaeocyaths of the dailycyathus xiuqiensis and dictyocyathus shaanxiensis zones co occur with trilobites of the middle and upper eoredlichia trilobite zone of the qiongzhusian stage the spirillicyathus duplex and the sibirecyathus meitanensis range zone correspond to the malungia yiliangella yunnanaspis and drepanuroides trilobite zones of the basal and middle canglangpuan stage respectively finally the archaeocyathus yanjiaoensis beds belong to the palaeolenus fengyangensis trilobite zone of the upper canglangpuan stage global correlations based on archaeocyath assemblage zones suggest that 1 the middle upper qiongzhusian of south china correlates with the middle atdabanian stage of the siberian platform the warriootacyathus wilkawillinensis archaeocyath zone in south australia the middle issendalenian stage of morocco and the lower ovetian stage in spain 2 the lowermost canglangpuan stage of south china correlates with the uppermost atdabanian of the siberian platform the spirillicyathus tenuis jugalicyathus tardus archaeocyath zones in south australia the uppermost issendalenian lower banian stages of morocco the middle ovetian stage of spain and the middle montezuman stage of north america 3 the middle canglangpuan stage approximates the lowermost botoman stage of the siberian platform middle banian stage of morocco the uppermost ovetian lowermost marianian stages of spain and the upper montezuman stage of north america 4 the uppermost canglangpuan stage is equivalent of the middle toyonian stage of the siberian platform archaeocyathus abacus beds in australia the middle bilbilian stage in spain and the middle dyeran stage bolbolenellus euryparia trilobite zone in north america

provenance of neoproterozoic and early paleozoic siliciclastic rocks of the tepla barrandian unit bohemian massif evidence from u pb detrital zircon ages abstract new la icp ms u pb detrital zircon ages from ediacaran and paleozoic siliciclastic rocks are used to constrain provenance and paleogeographic affinities of the tepla barrandian unit tbu in the centre of the bohemian massif central europe czech republic the samples taken span the period from 635 ma to 385 ma and permit recognition of provenance changes that reflect changes in geotectonic regime detrital zircon age spectra of two ediacaran one lower cambrian and three upper ordovician samples resemble the ages known from the nw african proportion of gondwana particularly the trans saharan belt while three rocks from higher lower cambrian to lowermost ordovician strata contain detritus that may have been derived exclusively from local sources the age spectrum of the devonian rock is a combination of the nw gondwanan and local features these new findings in combination with a wide range of published data are in agreement with a neoproterozoic subduction related setting at the margin of gondwana followed by a cambrian early ordovician rifting stage and an ordovician passive margin setting furthermore the data are in favour of a position of the tbu at the gondwanan margin throughout pre variscan times

stratigraphic signature of a terminal early cambrian regressive event in the iberian peninsula in the iberian peninsula the uppermost lower cambrian early bilbilian age is represented by the deposition of conglomerates and sandstones except in a northwestern region the cantabrian mountains where carbonate deposition took place these coarse siliciclastic deposits indicate a regressive trend called the daroca regression in its type area the iberian chains northeast spain this regressive episode represents a progradational highstand systems tract which did not result in widespread subaerial exposure of the shelf in addition the absence of important stratigraphical gaps and the good biostratigraphical control based on trilobites and acritarchs in the iberian chains permit a correlation of this regressive trend with other neighboring areas where the top of this trend is represented by a regional unconformity and a hiatus that began in the latest early cambrian and extended through early middle cambrian times

first report of wiwaxia from the cambrian chengjiang lagerstatte research was supported by the chinese academy of sciences kzzd ew 02 2 the national basic research program of china 2013cb835006 the national natural science foundation of china 41472012 the natural science foundation of jiangsu province bk2012893 and clare college cambridge

lower cambrian shelled phosphorites from the northern montagne noire france shelled phosphorites of early cambrian age are common in the avene mendic autochthonous unit marcory formation and the melagues nappe heraultia beds of the lastours formation northern montagne noire france palaeogeographically the concentration of phosphate took place along the shelf edge between a stable inner platform southern montagne noire and an unstable slope to basin sea floor preserved in the northern montagne noire petrography back scattered sem scanning election microscopy and elemental mapping by eds energy dispersive system show that the phosphorites were generated by repeated alternations of low sedimentation rates and condensation forming hardgrounds in situ early diagenetic phosphogenesis winnowing and polyphase reworking of previously phosphatized skeletons and hardground derived clasts the succession of repeated cycles of sedimentation phosphate concentration and reworking led to multi event phosphate deposits rich in allochthonous particles associated accumulations of exhumed and reworked pyrite clasts reflect final deposition in a mainly dysaerobic substrate

a wind tunnel investigation of the influences of fetch length on the flux profile of a sand cloud blowing over a gravel surface wind tunnel tests were conducted to examine the fetch effect of a gravel surface on the ux pro le of the sand cloud blowing over it using typical dune sand the results suggest that the ux pro le of blown sand over a gravel surface differs from that over a sandy surface and is characterized by a peak ux at a height above the surface while that over a sandy surface decreases exponentially with height the ux pro le of a sand cloud over a gravel surface can be expressed by a gaussian peak function q a b exp 0 5 h c d 2 where q is the sand transport rate at height h and a b c and d are regression coef cients the signi cance of the coef cients in the function could be de ned in accordance with the fetch length of the gravel surface and wind velocity coef cient c represents the peak ux height and increases with both wind velocity and fetch length implying that the peak ux height is related to the bounce height of the particles in the blowing sand cloud coef cient d shows a tendency to increase with both wind velocity and fetch length the sum of a and b representing the peak ux increases with wind velocity but decreases with fetch length the average saltation height derived from the cumulative percentage curve shows a tendency to increase with both the fetch length and wind velocity for any fetch length of a gravel surface the sand transport equation is expressed as q c 1 ut u g u3 where q is the sand transport rate u is the wind velocity ut is the threshold velocity measured at the same height as u g is the gravitational acceleration is the air density c is a proportionality coef cient that decreases with the fetch length of the gravel surface at a given wind velocity the sand transport rate over a gravel surface is only 52 68 per cent of that over a sandy surface the ux rate in true creep over a gravel surface increases with wind velocity but decreases with the fetch length whereas the creep proportion the ratio of creep ux to the sand transport rate decreases with both the wind velocity and fetch length two variable including fetch length and wind velocity equations were developed to predict the peak ux height average saltation height and transport rate copyright 2004 john wiley sons ltd

palaeogeographical controls on the cambrian trilobite immigration and evolutionary patterns reported in the western gondwana margin abstract southward drifting of the western gondwanan margin during the cambrian has been demonstrated by means of both palaeomagnetic methods and lithological indicators of climate such as carbonates and evaporites recent improvements in biostratigraphical correlations permit an enhanced understanding of the climatic and palaeobiogeographical constraints that controlled the distribution of cambrian benthic communities palaeogeographical and biogeographical reconstructions based on trilobites are reported in this paper in order to test interaction between migration speciation and extinction rates the variability of the documented biogeographical patterns is directly related to species diversity in which wider distribution coincides with transgressive trends and subsequent connection of neighbouring platforms early cambrian trilobite faunas show a high degree of both substrate control and endemicity although transgressions led to parallel shifts in faunal compositions by contrast mid cambrian trilobite faunas are relatively uniform across western gondwana and latest mid and late cambrian associations document influence of an increased similarity with asian trilobite faunas

siliciclastic carbonate slope apron in an immature tensional margin upper precambrian lower cambrian central iberian zone salamanca spain abstract the middle upper vendian and upper series lower cambrian of the central part of the central iberian zone of the iberian massif comprise for the most part siliciclastic sediments in the upper part of the middle series and at the base of the upper series a siliciclastic carbonate succession is predominant in the middle series the siliciclastic carbonate succession consists of limestone breccias sandstone limestone couplets and sandy limestone facies these were resedimented by debris flows low and high concentration turbidity currents and occasionally tractive flows the facies associations and the lack of well defined sequences in them suggest sedimentation on a mixed slope apron in the upper series the siliciclastic carbonate succession is composed in the east of chaotic facies conglomerates sandstones and shales corresponding to sedimentation by rockfalls slides debris flows and high concentration turbidity currents whereas in the west it is composed of conglomerates sandstones and shales that correspond to sedimentation by traction storms tides and deposition from suspension the facies associations and their sequential arrangement in the west suggest that sedimentation occurred on a prograding shelf with the development of bars and channels whereas in the east sedimentation occurred on a slope the relationship between the proposed depositional model and the previously established tectonic model ortega et al 1988 of a tensional margin suggests that the slopes were formed by faults that led to the development of horsts and grabens the faults were active during deposition of the middle and upper series the general tendency towards rising sea level observed in other parts of the world during late vendian early cambrian times shanmugam and moiola 1982 has been recorded in the study area

micro topographic analysis of shell pavements formed by aeolian transport in a wind tunnel simulation 1 beach surfaces containing shell materials represent one end member of a range of environments in which armoring is the primary control on wind erosion unlike spheres and cylinders which have formed the basis of theoretical model formulation and much of the early work in wind tunnels mollusc shells have complex and non uniform shapes which vary with their orientation identification of shell perimeter height and frontal area relative to the bed area roughness density is therefore a formidable task but nonetheless is essential for modeling sediment entrainment from beach surfaces a methodology is suggested in this paper for capturing and analyzing these geospatial data in the context of a wind tunnel simulation designed to improve understanding of the geophysical processes involved in armoring for deposits where non erodible shells represent half of the volume of the parent material the surface appears to be highly stable to wind erosion from the outset although minor reworking of the intervening erodible sediment does occur in comparison the shell coverage must increase to approximately 30 during wind erosion events in order for any given beach surface to stabilize especially beach deposits with a low concentration of shells by volume with suitable calibration the raupach shear stress partitioning model can be forced to perform well in predicting the threshold conditions for particle entrainment however this approach overlooks the pivotal involvement of particle impact and ricochet in the creation and sculpting of the armored bed as a case in point when the shells are removed from digital elevation models of armored beach surfaces formed in aeolian systems the adjusted topography is not suggestive of the presence of coherent flow structures e g horseshoe vortices and wedge shaped shelter areas as assumed to exist in the stress partitioning approach for isolated flows this would suggest that future work on the armoring of natural surfaces affected by wind erosion must allow for more complexity in the flow perturbation

duration of the early cambrian u pb ages of volcanic ashes from avalon and gondwana volcanic zircons from three ashes give a u pb date of 511 1 ma on trilobite bearing upper lower cambrian upper branchian series strata of southern new brunswick that correlate into the siberian middle botomian toyonian stage interval this very young age on the late but not latest early cambrian of avalon is consistent both with a 519 1 ma age on the older caerfai bay shales of south wales that are tentatively correlated into strata with the oldest avalonian trilobites lower branchian and with a 517 1 5 ma age on the antatlasia gutta pluviae zone trilobites of morocco determination of a 522 2 ma zircon age on the moroccan subtrilobitic lower cambrian lie de vin formation is consistent with an earlier reported 521 7 ma age from the lie de vin but suggests that a 526 4 ma age on australian trilobite bearing lower cambrian rocks may be too old a 33 ma duration of the avalonian early cambrian and an 8 ma length of the avalonian trilobite bearing lower cambrian support proposals that

sedimentary patterns across the lower middle cambrian transition in the esla nappe cantabrian mountains northern spain in the carbonate platforms of the western gondwana margin the extinction recorded at the lower middle cambrian boundary is accompanied by a profound change in the style of carbonate deposition the lancara formation of the esla nappe cantabrian mountains northern spain contains a distinct sedimentary turnover due to a combination of tectonism eustatic fluctuations and immigration and colonization of new benthic communities such as the youngest archaeocyathan assemblage of the entire iberian peninsula during latest early cambrian times a regressive trend is recorded in the lancara formation this regression was recorded on a peritidal dominant homoclinal ramp that is topped by a tectonically induced discontinuity d1 the latter surface marks the beginning of a last prograding regressive tendency recorded on an intra shelf ramp with ooidal bioclastic shoals protecting archaeocyathan microbial patch reefs the overlying discontinuity d2 corresponds to a major erosive unconformity which coincides with the lower middle cambrian boundary in the cantabrian mountains the subsequent long term earliest middle cambrian rise in relative sea level allowed deposition of low relief bioclastic shoals bearing a diverse and cosmopolitan assemblage of benthic fauna finally the previous evolution is bounded by a third discontinuity d3 which marks the beginning of a rhythmic sedimentation indicative of a major phase of tectonic breakdown and drowning of platforms recognised throughout southwestern europe two associations of calcimicrobes occur in the latest early cambrian regressive trend of the lancara formation i proaulopora and subtiflora are identified in peritidal high energy settings lacking self supported structures whereas ii intergrowths of epiphyton renalcis and girvanella encrusted branching colonies and solitary archaeocyaths in protected back shoal patch reefs the latest early cambrian regression is correlated in southwestern europe in both siliciclastic iberian chains and ossa morena and carbonate dominant platforms cantabrian mountains montagne noire and sardinia its tops are recognised as diachronous unconformities ranging in age from early bilbilian to the bilbilian leonian or lower middle cambrian boundary

c o and sr isotope stratigraphy across the lower middle cambrian transition of the cantabrian zone spain and the montagne noire france west gondwana c o and sr isotopes have been analysed for three sections of the cantabrian zone northern spain and the southern montagne noire france that cross the lower middle cambrian transition or bilbilian leonian transition in its iberian sense the base of the leonian middle cambrian is regionally defined by the first appearance of the trilobite acadoparadoxides mureroensis which is well constrained in the cantabrian zone but absent in the montagne noire in the bilbilian parts of the three sections nearshore to peritidal strata are capped by erosive unconformities the succeeding leonian relative sea level rise is recorded in similar fashion in both environments leading to the deposition of aggradational bioclastic limestones and or transgressive limestone shale couplets the so called griotte facies overlain by offshore shales which relate to platform drowning and coastal smothering during the leonian caesaraugustan transition bilbilian leonian carbonates show a long term trend to higher 13c values that was punctuated by a succession of positive excursions in cremenes valdore cantabrian zone and ferrals les montagnes montagne noire two bilbilian 13c shifts an older uncertain peak at 0 1 0 01 and a younger certain shift at 0 6 1 7 and two leonian shifts peaking at 1 1 1 2 and 1 3 respectively are apparent at genestosa cantabrian zone a fifth early middle caesaraugustan shift is identified peaking at 2 1 these positive excursions and increasing trend are similar to published trends from the lower middle cambrian transition in siberia and australia although in those areas only two 13c excursions have been reported so far the marked negative 13c excursion reported from the lower middle cambrian boundary of laurentia and china is not recorded in our dataset oxygen isotope and trace element ca mn and sr data indicate that our 13c trends are unlikely to be diagenetic features while the lack of correlation with relative sea level fluctuations facies changes or benthic community dynamics means that they could be of potential for global stratigraphic correlation sr isotope compositions for the cantabrian zone succession exhibit consistent values upsection which suggests that seawater 87sr 86sr remained around 0 7089 0 7090 our more limited dataset for the montagne noire region confirms this value and both are consistent with published constraints from laurentia for seawater 87sr 86sr across the lower middle cambrian boundary the only other 87sr 86sr study to cover the boundary interval reported significantly lower 87sr 86sr values not vert similar0 7087 0 7088 indicating perhaps that the lower middle cambrian boundary in siberia lies stratigraphically below its equivalent levels in europe and laurentia however we consider it more likely that these siberian samples have been diagenetically altered to less radiogenic values

early palaeozoic palaeobiogeography and palaeoecology of stylophoran echinoderms abstract stylophorans cornutes mitrates represent one of the most diverse classes of cambro ordovician echinoderms they were free living benthic non radiate forms closely related to asterozoans and crinoids taphonomic sedimentological and palaeosynecological data provide useful information on key aspects of stylophoran palaeoecology such a combined approach suggests that the rarity of stylophorans in proximal environments above storm wave base was probably original and does not exclusively result from the possession of a loosely articulated polyplated calcitic test conversely stylophorans were relatively abundant in deeper settings below storm wave base where they frequently occur in low diversity dense beds several tens to hundreds of individuals per square metre such assemblages were either largely dominated by stylophorans only middle cambrian darriwilian or by the association of both stylophorans and ophiuroids latest darriwilian silurian comparison with ecological requirements of similar modern and fossil dense populations of ophiuroids suggests that stylophoran beds occurred in well oxygenated oligotrophic waters with low predatory pressure and that sea temperature played a key role in the palaeobiogeographic distribution of stylophorans seven main stylophoran biofacies are identified and described the associated environments and tropical distribution of primitive heavily plated forms suggest that the initial radiation of the class probably took place in warm to temperate shallow settings earliest middle cambrian late cambrian however from this primitive stock stylophorans radiated several times towards deeper and or colder environments possibly because of the lower predation pressure in such settings cothurnocystid cornutes in the middle cambrian mitrates in the late cambrian hanusiids in the tremadocian as a consequence the fact that most cambro ordovician cornutes and mitrates were psychrospheric i e cold water adapted probably explains their relatively wide palaeobiogeographic distribution in high palaeolatitudes cambro ordovician stylophorans were abundant and diverse in shallow to deep environments but they were generally restricted to deep settings in low palaeolatitudes the great caradocian transgression favoured the extension of stylophorans from circum polar regions e g western margin of gondwana towards external settings at lower palaeolatitudes avalonia baltica and eastern margin of laurentia where one group of mitrates underwent a major radiation anomalocystitids and extended towards shallower and warmer palaeoenvironments in contrast all silurian stylophoran assemblages known so far are rare poorly diversified and restricted to shallow warm to temperate environments in tropical regions this distribution partly results from 1 the probable eradication of psychrospheric forms e g cornutes because of the prolonged anoxia of deep environments in the late hirnantian early silurian of west gondwana 2 the radiation of some mitrates anomalocystitids in shallow tropical settings in the late ordovician and 3 of strong taphonomic and or sampling biases numerous ghost lineages

morphological assessment of the earliest paradoxidid trilobites cambrian series 3 from morocco and spain a cambrian immigration event of paradoxidid trilobites has traditionally marked some regional lower middle cambrian boundaries in the acado baltic subprovince including baltica and the mediterranean and avalonian margins of west gondwana the earliest paradoxidine species in morocco and the iberian peninsula have been used as a chronostratigraphic link to support the definition of a common base for the cambrian series 3 but recent studies have proposed new species without revising previously established ones this paper offers a morphological statistical analysis based on both linear measurement and landmark based geometric morphometric approaches performed on the earliest paradoxinine trilobites sampled in the anti atlas morocco and the iberian chains spain as a result the diagnosis of acadoparadoxides mureroensis is emended and several species recently erected in morocco a cf mureroensis a levisettii a ovatopyge and a pampalius are suggested as synonyms of a mureroensis until 3d statistical analyses are available based on material preserved on carbonate or silica nodules the first appearance of a mureroensis in both areas can be provisionally used for regional correlation until homotaxic tests are checked

guzhangian mid cambrian trilobites from siliceous concretions of the valtorres formation iberian chains ne spain in the carbonate siliciclastic strata of west gondwana e g in the montagne noire france the aftermath of the mid languedocian mid cambrian regression is characterized by a late languedocian major turnover of trilobite families and a furongian early tremadocian radiation related to the stepwise immigration of trilobite invaders from east gondwana under persistent transgressive conditions the scarcity of upper languedocian fossil accumulations in clayey substrates has inspired the sampling of the palaeogeographically most distal parts of the iberian chains spain where diagenetic dissolution of ubiquitous hexactinellid sponge spicules has favoured the formation of siliceous concretions these have yielded the trilobites peronopsis cf insignis oidalagnostus trispinifer proampyx difformis proampyx aculeatus bailiaspis glabrata holocephalina agrauloides by ontogeny holasaphus cf centropyge and a paradoxidid gen et sp indet despite preservation and sampling biases the identification of this taphonomic window in offshore clayey substrates of west gondwana allows the recognition of a strong biogeographical link with baltica and the correlation of the global guzhangian stage and the solenopleura brachymetopa zone of scandinavia with part of the mediterranean upper languedocian substage less

palynological approach in upper quaternary terrestrial carbonates of central italy anything but a mission impossible a palynological survey has been carried out on two late quaternary travertine s l deposits of central italy at serre di rapolano and bagnoli tuscany region the principal aim was to improve the understanding of factors that affect the accumulation and preservation of pollen grains in thermal i e travertine and ambient temperature i e calcareous tufa terrestrial carbonates for this purpose 52 526 pollen grains belonging to 118 pollen taxa from local to extra regional sources were analysed in 200 samples from different travertine and calcareous tufa lithofacies of these 97 samples generally from thermal travertines were barren in palynomorphs by contrast pollen grains in the remaining samples were well preserved and did not show differential preservation features these observations suggest that the ph of the solutions from which travertine or tufa precipitate is not a limiting factor in causing corrosion and or destruction of pollen grains rather the barrenness recorded in many samples appears to reflect a paucity of pollen rather than post depositional destruction results suggest that the depositional energy of the environment during the deposition of travertine plays an important role in controlling pollen concentration as verified in both depressions lower energy to higher pollen concentration and slopes higher energy to lower pollen concentration respectively analysis of pollen data suggests that relatively high depositional temperatures and rates of carbonate deposition are also major limiting factors for efficient accumulation of pollen grains results of this study reveal that understanding pollen taphonomy processes in travertine and calcareous tufa is critical to developing accurate palaeoenvironmental and palaeoclimatic reconstructions

northward intrusions of low and mid latitude storms across the saharo arabian belt during past interglacials the rain regime of the levant during the late quaternary was controlled primarily by mediterranean cyclonic systems associated with north atlantic climate shifts lake levels in the dead sea basin have been robust recorders of the regional hydrology and generally indicate highstand wet conditions throughout glacial intervals and lowstands dry during interglacials however sporadic deposition of travertines and speleothems occurred in the negev desert and arava valley during past interglacials suggesting intrusions of humidity from southern sources probably in association with enhanced activity of mid latitude red sea synoptic troughs and or low latitude tropical plumes the southerly incursions of wetness were superimposed on the long term interglacial levantine arid conditions as refl ected by the current prevailing hyperaridity and could have had an important impact on human migration through the red sea dead sea corridor

microbial crusts as indicators of stratigraphic diastems in the cambrian breche a micmacca atlas mountains of morocco the presence of microbial crusts interrupting high energy clastic sediments in carbonate and mixed carbonate siliciclastic platforms can be considered as distinct indicators of stratigraphic diastems characterized by either very low rates of deposition or non deposition this analysis is based on a microfacies study of the cambrian breche a micmacca atlas mountains morocco which contains some stratigraphically condensed limestones characterized by i disarticulation and fragmentation of skeletons ii abundance of volcanigenic debris iii rarity of muddy fraction iv dominance of a sessile epibenthic shelly fauna dominated by echinoderms chancelloriids and sponge spicules and v a complex diagenetic history due to erosion and reworking of lithified substrates the breche a micmacca limestones are composite event concentration low relief shoal complexes composed of parautochthonous and allochthonous bioclastic assemblages these units can be desribed as hiatal accumulations because of the subdivision of the coquinas by minor discontinuities or hiatal surfaces and the composite multiple event nature of the grainstones packstones the growth of microbial mats can be used as a record of time interrupting background sedimentation patterns characterized by the amalgamation of high energy events the breche a micmacca was deposited in an environment in which some intervals of non deposition or under extremely low sedimentation rates alternated with the succession of sedimentary events the biological response of microbial communities to coat stratigraphic discontinuities can be considered as an integral part of event stratigraphy they enhance the preservation and identification potential of interruption in the background sedimentation on substrates devoid of burrowing activity a distinct event of non deposition is also recognized based on the presence of microbial fabrics at the top of the breche a micmacca its microkarst structures reflect a major fall in the relative sea level of a reduced region of the platform resulting in dissolution and colonization of coelobiontic cavities by microbial mats and branching filaments

the margins of laurussia in central and southeast europe and southwest asia the continuation of the laurussian margin into central and southeast europe and southwest asia is defined by the rheic suture which becomes harder to trace to the southeast because of complex post variscan strike slip displacements and tectonic stacking linked to the cimmerian and alpine cycles the uncertain extent of the neoproterozoic baikalian orogeny fringing baltica ambiguous early paleozoic paleobiogeographic data and strike slip activity complicate the distinction of the tornquist suture from the transeuropean suture zone there is growing evidence for the incorporation of the brunovistulian malopolska and west moesian terranes into the late neoproterozoic cambrian baltican margin the istanbul zonguldak terrane along with the bitesh and east moesia terranes may have been part of the avalonian terrane assemblage although an arabian nubian shield or baltica provenance cannot be excluded the terranes of the armorica terrane assemblage bordering the rheic suture include the outer carpathian tatra getic and balkan terranes in southeast europe and sakarya and the anatolide tauride terrane in turkey further east the rheic suture may be present in the caucasus in all probability between the greater caucasus and the scythian platform or alternatively between the greater caucasus and transcaucasia alborz in northern iran is interpreted as a distal part of transcaucasia the location of the rheic suture in the southeast part of the turan domain of central asia is poorly constrained

palaeomagnetism palaeogeography and the multicomponent analysis of middle and upper cambrian rocks of the barrandian in the bohemian massif abstract with a view to the importance of the barrandian in the bohemian massif for global palaeogeographic reconstructions considerable attention has been devoted to palaeomagnetic stability tests and multicomponent analysis of rocks of the pre variscan formations using substantially improved laboratory techniques this study is devoted to samples of upper cambrian andesite and middle cambrian sediments alternating and thermal fields were used for magnetic cleaning a thermal demagnetizer fitted with a newly developed inductor of high sensitivity the rocoma rotating coil magnetometer with a sensitivity of 0 1 to 0 2 nt was used the whole newly built and fully tested mavacs system magnetic vacuum control system guaranteed a high degree of compensation of the magnetic field in a volume of 5 1 to a value not exceeding 2 nt as numerous laboratory experiments have shown the high magnetic vacuum was necessary to derive the palaeomagnetic directions of rocks of the older formations affected significantly by the variscan orogenic phase the position of the upper cambrian pole 28 6 s 131 2 e should be considered tentative because it was derived using samples from only three andesite outcrops two other andesite outcrops preserved carboniferous or permo carboniferous palaeomagnetic directions the position of the middle cambrian pole 11 3 s 154 0 e was determined using samples of sediments mainly greywackes and shales from ten outcrops some of which represent extensive rock cross sections by combining multicomponent analysis with fold tests the mean direction of the pre variscan magnetization could be derived the very low values of the moduli of the natural remanent magnetization of the middle cambrian sediments and the considerable amount of magnetically soft components required special care to be taken in the laboratory procedures the palaeozoogeographic zones of the barrandian are related to palaeogeographic latitudes of about 40 s derived from palaeomagnetic data cold water is characteristic for the bohemian fauna but arctic conditions can be ruled out due to the amount of primary red sediments mostly of continental origin

the margins of avalonia during cambrian and earliest ordovician times avalonia was an area forming an integral part of the huge gondwanan continent probably along the northern margin of amazonia until in early ordovician late arenig or llanvirn time it split off from gondwana leaving a widening rheic ocean to its south today its southern margin with gondwana extends northeast from east of cape cod massachusetts through nova scotia north of the meguma terrane and thence below sea level to the south of newfoundland on the eastern side of the present atlantic the southern margin may separate southwest portugal from the rest of the iberian peninsula it can be traced eastwards with more certainty from the south cornwall nappes to a line separating the northern phyllite belt on the southern margin of the rhenohercynian terrane and the mid german crystalline high there is no certain evidence of avalonian crust to the northeast of the elbe line the northern margin of avalonia extends westwards from south of denmark to the british isles where it merges with the iapetus ocean suture between scotland and england traced westwards it crosses ireland and reappears in northern newfoundland to the east of new world island where it may follow the trace of the dog bay line and the cape ray fault recent work suggests that the northern margin of avalonia may clip the northern tip of cape breton island in nova scotia and then enter the north american mainland at the bay of chaleur it may then be traced from north and west of the popelogan and bronson hill arcs to long island sound near newhaven connecticut the cambrian to devonian faunas reflect the history of avalonia initially they were purely gondwanan but as ordovician time proceeded more genera crossed firstly the tornquist ocean as it narrowed between avalonia and baltica to close in latest ordovician and early silurian times and secondly the iapetus ocean so that by the early silurian most of the benthic shelly faunas apart from the ostracods were the same round the adjacent margins of all three palaeocontinents

the cadomian unconformity in the saxo thuringian zone germany palaeogeographic affinities of ediacaran terminal neoproterozoic and cambrian strata abstract the most complete ediacaran terminal neoproterozoic to early cambrian record in the saxo thuringian zone is provided by the cadomian deformed ediacaran rothstein formation and the unconformably overlying early cambrian zwethau formation in the torgau doberlug syncline tds conglomerates and greywackes of the marine rothstein formation are of continental magmatic arc provenance and record detrital zircon shrimp ages that indicate a late cryogenian to early ediacaran 700 580 ma age for the arc source and its emplacement into palaeoproterozoic 2000 ma crust tuffaceous intercalations record extrabasinal eruptions of evolved calc alkaline lavas that point to ongoing cadomian continental arc magmatism shrimp zircon ages from a tuffaceous layer date this volcanic activity and the formation s deposition as late ediacaran 566 10 ma close correlation in provenance and age to other ediacaran units of the saxo thuringian zone points to a common palaeogeographic setting in the avalonian cadomian belt detrital and inherited zircon ages and nd isotopic ratios from these ediacaran siliciclastic rocks suggest a position on the active margin of gondwana near the west african craton the early cambrian zwethau formation records the erosion of the underlying ediacaran rocks followed by the successive evolution of i a carbonate dominated subtidal ramp with calcimicrobial archaeocyathan buildups ii a shallow subtidal to intertidal mixed ramp with peritidal sediments and oolite shoal complexes and iii a more siliciclastic depositional environment calcimicrobial archaeocyathan buildups oolite shoals and sulfate nodules in intertidal sediments indicate warm arid to semi arid climatic conditions and a palaeogeographic setting in equatorial to sub equatorial latitudes archaeocyaths the trilobite taxon dolerolichia and the sedimentary facies assemblages compare closely to those of the mediterranean early cambrian constraining the palaeogeographic setting to the european sub equatorial western gondwana shelf realm archaeocyaths record a mid early cambrian middle issendalenian ovetian age making these the oldest cambrian sediments in both the saxo thuringian zone and the bohemian massif the middle cambrian lithological and palaeontological records of the tds closely resemble those of the frankenwald area of the saxo thuringian zone as well as those of other fragments of the western gondwana shelf in spain morocco and bohemia archaeocyaths early cambrian trilobites and correlations with morocco suggest cambrian deposition commenced at ca 520 ma such that the cadomian unconformity represents a time gap of about 35 55 ma latest ediacaran to early lower cambrian this gap which is related to the cadomian orogeny and so common to all areas of the cadomian belt obscures some of palaeobiological palaeogeographic and climatic change that marks the precambrian cambrian transition

skeletal carbonate productivity and phosphogenesis at the lower middle cambrian transition of scania southern sweden the lower middle cambrian transitional interval of scania is largely represented by condensed limestone beds lithostratigraphically grouped in the gislov formation 1 5 7 m thick and the forsemolla and exsulans limestone beds lower part of the alum shale formation up to 4 in thick the strata display a combination of skeletal carbonate productivity episodic nucleation of phosphate hardground nodules and polyphase reworking recorded on a platform bordering the nw corner of baltica the shell accumulations can be subdivided into three deepening upward parasequences separated by distinct erosive unconformities the parasequences correspond biostratigraphically to the holmia kjerulfi ornamentaspis linnarssoni and ptlychagnostus gibbus zones the latter two generally being separated by a stratigraphic gap that includes the middle cambrian acadoparadoxides oelandicus superzone except for the exsulans limestone the carbonates reflect development of a prolific epibenthic biota dominated by filter feeding nonreefal chancelloriid echinoderm sponge meadows rich in trilobites and brachiopods and which were subjected to high energy conditions the absence of microbial mats or veneers encrusting the erosive surfaces of these event concentration low relief shoal complexes may be related to long hiatal episodes resulting in microboring proliferation high levels of nutrient supply resulted in high primary productivity eutrophic conditions glauconite precipitation phosphogenesis in some case microbially mediated and rnicroendolithic infestation an early diagenetic mildly reducing environment is suggested by the presence of authigenic subsequently reworked pyrite which contrasts with the syndepositional normal oxygenated conditions reflected by macroburrowing and the abundance of benthic fossils

carbon chemostratigraphy of the cambrian ordovician transition in a midlatitude mixed platform montagne noire france the cambrian drumian carbon isotope excursion dice and the steptoean positive carbon isotope excursion spice have been so far reported in subtropical platforms the dice event is a large negative excursion in 13ccarb record that nearly coincides with the beginning of the drumian cambrian series 3 whereas the spice event is a large positive shift in 13ccarb identified close to the base of the paibian furongian series the chemostratigraphic excursions have been recognized in carbonate dominated platforms and their application to mid and high latitude siliciclastic dominated platforms has been problematic this paper offers for the first time a high resolution stratigraphic analysis of this time span in a temperate water platform montagne noire france that recorded episodes of carbonate productivity in nearshore environments two sections were analyzed in detail a complete cambrian series 3 tremadocian succession devoid of carbonate interbeds and paleogeographically located in the distal part of the platform pardailhan nappe and a furongian tremadocian succession which has limestone interbeds and represents the proximal part of the platform minervois nappe the lower part of the la gardie formation in the pardailhan nappe displays background 13corg values of 22 punctuated by a large negative middle languedocian regional substage shift peaking at 24 5 this negative excursion is similar to the dice event reported close to the base of the drumian although the latter is exclusively based on 13ccarb values stable isotopes of 13ccarb and 13corg from both sections also indicate a common chemostratigraphic shift at the onset of the furongian in nearshore deposits of the minervois nappe the 13ccarb background values for the interbedded limestone strata of the val d homs formation gradually increase from 3 to 1 and are punctuated by a sharp increase in 13ccarb values to 3 0 by contrast in basinal shales of the la gardie formation in the pardailhan nappe the 13corg background values decrease from 22 to 27 1 this trend is directly controlled by total organic carbon toc contents and is interpreted to have been initiated by changes in the degree of biodegradation of organic matter sulfate reduction and methanogenesis before or soon after burial despite this overprinting and the very low degree of metamorphism reached by the shales the 13corg background trend is also punctuated by a sharp positive shift in 13corg values to 4 0 similar to the spice event in addition the asymmetric shape of the spice excursion in the montagne noire shows evidence for the herb event a late furongian negative carbon isotope excursion not yet accepted as a worldwide chemostratigraphic anomaly the recognition of both chemostratigraphic shifts in mixed and clayey strata opens new possibilities of chemostratigraphic correlation in mid and high latitude platforms where carbonate factories did not widely develop and strata only contain endemic fauna this implication has a major consequence because the global stratotype section and point gssp of the drumian and paibian stages occurs near the base of both excursions

precambrian cambrian boundary global stratotype ratified and a new perspective of cambrian time the precambrian cambrian boundary global stratotype is the base of the phycodes pedum zone at fortune head southeastern newfoundland the initial two stage radiation of the phanerozoic fauna the appearance of phanerozoic aspect trace producers and subsequent origin of diverse skeletalized metazoans was earliest cambrian fossil assemblages with deep complex burrows or originally mineralized skeletal fossils with exception of cloudina are early cambrian or younger correlation into avalon indicates that strata once referred to the proterozoic e g manykaian or nemakit daldynian and rovno stages are lowest cambrian and that the siberian tommotian stage is middle lower cambrian the thick sequence and complex epeirogenic history of the placentian series as compared with the trilobite bearing branchian series suggest that most early cambrian time is represented by the subtrilobitic lower cambrian

an extensive erosion surface of a strongly deformed limestone bed in the gushan and chaomidian formations late middle cambrian to furongian shandong province china sequence stratigraphic implications abstract in order to understand sequence development and sea level fluctuations during the late middle cambrian to early furongian on the north china epeiric platform the present study focuses on a unique subtle erosion surface of an extensive approx 100 km strongly deformed limestone bed in the uppermost part of the gushan formation shandong province china the gushan formation and the overlying chaomidian formation consist mainly of shales and a variety of carbonates that were deposited in subtidal environments e g deep subtidal shallow subtidal shoreface shoal subtidal microbial flat and restricted platform interior three third order depositional sequences s1 3 are identified each of which comprises a thin transgressive systems tract tst and a relatively thick highstand systems tract hst each sequence is bounded by a drowning unconformity sb1 a subaerial unconformity sb2 or a surface of submarine erosion sb3 the upper sequence boundary sb2 of sequence 1 s1 is represented by a subtle erosion surface of an extensive deformed limestone bed with a wide variety of soft sediment deformation structures e g lime mudstone breccias chaotic wacke packstone laminae and fragments homogenized oolites and clastic dykes and is overlain by small sporadic microbial buildups and an extensive bioclastic grainstone bed the deformed limestone was formed during early diagenesis by differential deformation processes brecciation liquefaction fluidization and injection which were most likely induced by pore water overpressure during the period of rapid sea level fall despite the lack of subaerial exposure features e g paleokarst paleosol etc the characteristics of the erosion surface cutting well lithified sediment below the missing of a significant geological record the prochuangia biozone and the worldwide correlatable positive carbon isotope excursion collectively indicate that the erosion surface developed under conditions of subaerial exposure after contemporaneous marine cementation of the deformed sediment the missing of the prochuangia biozone is most likely due to non deposition at a subaerial hiatal surface the erosion surface was submerged as a result of subsequent rise in sea level where sporadic microbial buildups formed under suitable conditions freshly deposited winnowed shell dominated transgressive lag deposits containing chuangia trilobite fragments brachiopod shells and abundant glauconite grains formed with continued rise in sea level which became in turn overlain by shale dominated facies the unique combination of the subtle erosion surface sensu stricto a subaerial unconformity and the underlying deformed limestone bed provides an important criterion for recognizing the subtle changes in relative sea level on shallow epeiric platforms

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

a general framework for modeling sediment supply to coastal dunes including wind angle beach geometry and fetch effects a series of spatially explicit equations are derived that form the foundation of a modeling framework that provides insight into how the interaction of the fetch effect and angle of wind approach leads to tradeoffs that govern the magnitude of aeolian sediment transport across beaches of different geometry the spatial distribution of sediment transport rate per unit width at any point on the beach is shown to vary predictably as a function of wind angle critical fetch and beach geometry and this has evident implications for the total volume and distribution of sediment transport into the dunes behind the beach as well as the proportion of sediment lost from the beach dune system at the downwind margin as the wind field shifts from onshore shore perpendicular to oblique shore parallel approach angle total sediment transport rate across a dune line segment will reflect a tradeoff between transport reduction because of the cosine effect and transport enhancement because of potentially longer fetch distances traversed by the wind prior to encountering the dune line this tradeoff is most evident on long narrow beaches when beach width is less than the critical fetch for such beaches and with onshore winds the total sediment transport rate across the dune line will be less than that predicted for a wide beach because of the constraint imposed by the fetch effect however as the angle of wind approach becomes oblique the available fetch becomes progressively longer transport limitations imposed by the fetch effect are negated and transport enhancement across the dune line is to be expected with very large angles of wind approach the cosine effect dominates the interaction and transport reductions across the dune line occur until the wind is shore parallel and sediment supply to the dunes ceases altogether this sequence of adjustments and tradeoffs were only partially understood prior to this study and yet they form the foundation of coastal dune modeling the framework proposed in this paper serves to place future studies of process form interaction in beach dune systems on a robust theoretical foundation it also facilitates the testing of various alternative hypotheses regarding the uneven spatial and temporal distribution of dune height and growth rate in coastal environments

cambrian ordovician boundary age and duration of the lowest ordovician tremadoc series based on u pb zircon dates from avalonian wales two thin volcaniclastic sandstone beds in the bryn llin fawr road section in north wales overlie an apparent sequence boundary within the uppermost cambrian acerocare zone and are overlain by lowest ordovician lower tremadoc rhabdinopora faunas u pb geochronology of zircons from these sandstones yields a maximum cambrian ordovician boundary age of 489 0 6 ma this age indicates both that the tremadoc series lowest ordovician may be shorter in duration than was previously thought and that the duration of the middle and late cambrian c 22 ma was much less than that of the early cambrian c 33 ma cambrian trilobite zones locally had an average duration as short as 1 ma

palynology of pleistocene travertines from the arava valley israel abstract pollen samples from the arava travertines dated to oxygen isotope stages 5 and 7 show relatively high arboreal pollen levels these spectra are probably a result of an expansion of the mediterranean maquis in transjordan which indicates periods of wetter climatic conditions these periods probably represent humid fluctuations within stages 5 and 7

dead sea pollen provides new insights into the paleoenvironment of the southern levant during mis 6 5 abstract the paleoclimate of the southern levant especially during the last interglacial lig is still under debate reliable paleovegetation information for this period as independent evidence to the paleoenvironment was still missing in this study we present a high resolution pollen record encompassing 147 89 ka from the dead sea deep drilling core 5017 1a the sediment profile is marked by alternations of laminated marl deposits and thick massive halite indicating lake level fluctuations the pollen record suggests that steppe and desert components predominated in the dead sea surroundings during the whole investigated interval the late penultimate glacial 147 3 130 9 ka and early last glacial 115 5 89 1 ka were cool and relatively dry with sub humid conditions confined to the mountains that sustained moderate amounts of deciduous oaks prior to the lig optimum a prevalence of desert components and a concomitant increase in frost sensitive pistachio trees demonstrate the occurrence of an arid initial warming phase 130 9 124 2 ka the lig optimum 124 2 ka 115 5 ka was initiated by an abrupt grass expansion that was followed by a rapid spread of woodlands in the mountains due to increased moisture availability the remarkable sclerophyllous expansion points to a strong seasonal moisture deficit these results contradict previous dead sea lake level investigations that suggested pluvial glacials and a warm dry lig in the southern levant prominent discrepancies between vegetation and dead sea lake stands are also registered at 128 115 ka and the potential causes are discussed in particular while the pollen spectra mirror increased effective moisture during the lig optimum the massive halite deposition is indicative of an extremely low lake level given that the climate amelioration triggered the migration of early modern humans to the southern levant we speculate that the diverse ecosystems in the region provided great potential for their residence across the eastern mediterranean region an analogous vegetation succession pattern is observed

a preliminary note on the dispersal of the cambrian burgess shale type faunas abstract the common or similar elements of faunas shared by the early cambrian chengjiang fauna and the middle cambrian burgess shale fauna are listed in a generic level so as to have a better understanding of the palaeogeographic relationship between the south china block and laurentia the burgess shale type faunas probably had a worldwide distribution during the interval ranging from the late tommotian to atdabanian the geographic and biological contributions to the cosmopolitan geographic distribution of the burgess shale type faunas are discussed however newly developed pelagic larvae in many phyla which probably acquired their first bloom in the cambrian might have promoted the dispersal

the earliest species of burlingia walcott 1908 trilobita from south china biostratigraphical and palaeogeographical significance burlingia balangensis sp nov from the lower cambrian of south china represents the earliest species of this genus and suggests that the genus may have originated in south china a revision of the genus shows that b primitiva and b obscura can be used in order to indentify the base of the cambrian stage 5 when other trilobites are absent because their last appearance datum lad coincides with the first appearance datum fad of oryctocephalus indicus available palaeogeographic and palaeoclimatic models suggest five major palaeocurrents during cambrian times which could control the migration patterns of the burlingia clade from south china to baltica

the effects of artificial pebble concentrations on eolion sand transport on a beach a field experiment to measure the effects of differing concentrations of pebbles on rate of eoliao sediment transport was carried out on a sand beach on the northumberland strait new brunswick sq

cambrian trilobites from brzechow holy cross mountains poland and their significance in stratigraphic correlation and biogeographic reconstructions a revision of the trilobite fauna from brzechow in the holy cross mountains poland shows that the assemblage consists of palaeolenus medius bednarczyk issafeniella orlowinensis samsonowicz kingaspidoides sanctacrucensis czarnocki paradoxides acadoparadoxides oelandicus sjogren p a cf mureroensis sdzuy and p a sp it is earliest middle cambrian in age according to the west gondwana standard of geyer landing 2004 and can be correlated with the cephalopyge notabilis zone of morocco moreover the co occurrence of the ranges of p a oelandicus with p a cf mureroensis might suggest that p a oelandicus appears earlier in the brzechow sandstones than in scandinavia thus the strata exposed here do not find their correlative in the scandinavian succession as a result the banian agdzian boundary lower middle cambrian boundary according to the west gondwana standard probably lies within the kamieniec formation and also below the brzechow sandstones in the upper part of the ocieseki formation close similarity of the discussed assemblage with contemporaneous assemblages from morocco jordan or new brunswick indicates that the fauna is generally of peri gondwanan and gondwanan aspect

early cambrian continental reconstructions climatically related sedimentary facies and faunal distributions have been combined with palaeomagnetic data to make provisional reconstructions of the early cambrian world laurentia baltica and siberia appear to have formed a continental group which rifted apart from each other prior to 600 ma the consolidation of much of gondwana probably occurred in the pan african orogeny well before the cambrian though the assembly of several east asian terranes is still speculative the archaeocyathan reefs of siberia southern europe and morocco with their bigotinid trilobite fauna suggest that these areas were adjacent to each other and at low latitudes avalonia had close faunal links with western gondwana but lacked bigotinids and archaeocyathans and may have been situated off west africa and florida during the early cambrian there was a northward migration of laurentia towards the equator as its separation from baltica and siberia increased and a southward movement of gondwana

geological constraints on the paleozoic tectonic evolution of tectonostratigraphic terranes in the iberian massif abstract the presence of oceanic paleozoic sequences in the iberian variscan fold belt is used to identify and separate suspected exotic terranes from a reference iberian autochthon terrane which constitutes the greater part of it in this paper the relevant data characterizing the pre accretionary evolution of the paleozoic iberian terranes are presented as well as the available evidence concerning the accretionary process itself emphasis is placed on the analysis of the sedimentary igneous and structural expression of the major events which affected the iberian terranes before during and after their amalgamation the main conclusions of such an analysis may be summarized as follows 1 a recognition of rift and passive margin stages in all the iberian massif terranes during the early paleozoic 2 b late paleozoic accretion of the exotic terranes to the iberian autochthon via a long and complex process variscan orogeny which involved initial subduction underneath the latter and eventual obduction followed by oblique collision of a promontory the iberian autochthon northwestern margin with a northwestern continental block this latter process could account for the large scale crustal imbrication shown by the northern branch of the orogen coeval with predominant strike slip faulting in the southern branch as well as with the formation of the typical arcuate shape of this orogenic belt major present uncertainties relate to the palinspastic provenance of continental suspect terranes and their correlation with similar units in other circum atlantic paleozoic orogens a discussion and speculations on this subject are dealt with in the final section of this paper

evidence of past environmental conditions during the evolution of a calcretised wadi system in southern jordan using stable isotopes abstract a stratigraphically and temporally ordered sequence of channel calcretes preserved along the wadi dana southern jordan records the quaternary evolution of the formation and infilling of rock cut channels and their subsequent incision in a tectonically subsiding basin it is currently unknown under what palaeoenvironmental conditions these non pedogenic calcretes formed stable isotope analyses have been used to investigate whether any past topographical hydrological vegetational diagenetic and or temporal signatures can be identified from the channel calcretes the results of this research indicate that channel calcrete development is influenced by altitudinal variation affecting vegetation and hydrology within the landscape as well as location within individual wadi channels which has an affect on diagenetic processes the lack of calcretisation of a terrace that is between 1 and 1 5 m above the modern wadi floor supports the idea that the environment is currently too arid for calcrete to develop thus the presence of older wadi dana channel duricrusts suggests wetter conditions when they formed the 18o data of the calcrete implies cooler conditions than today as there is little evidence of a strong evaporative effect any temporal control is limited and mainly a function of stratigraphic position with some numeric dating

from cadomian subduction to early palaeozoic rifting the evolution of saxo thuringia at the margin of gondwana in the light of single zircon geochronology and basin development central european variscides germany

the great atlasian reef complex an early cambrian subtropical fringing belt that bordered west gondwana abstract the so called great atlasian reef complex developed during early cambrian time throughout the moroccan margin souss basin of west gondwana according to the syndepositional tectonic activity associated with its intracratonic ediacaran cambrian rift the great reef complex can be subdivided into four major archaeocyathan microbial reef episodes i the atdabanian episode is recorded by a sw ne trending 400 km long barrier reef that extended across the western anti atlas it was controlled by large scale reactivation of an inherited rifting branch which resulted in the nucleation and growth of linear reef complexes located along its margin the interplay of block tilting sharp modifications in accommodation space and relative sea level rise led to a composite retrogradational aggradational reef systems tract characterized by archaeocyathan microbial kalyptrate complexes tiout member and amouslek formation that protected stromatolite dominated back barrier environments lower member of the igoudine formation ii the western anti atlas recorded an early botoman reactivation of the same rifting branch that triggered a lateral migration of frame building centres of carbonate productivity as a result the involved grabens and half grabens recorded the development of fringing mound complexes lower issafen formation these occupied some linear intra platform deeper depressions capped by marls and shales whereas laterally equivalent shallower environments recorded the development of patch reefs and bioherms iii the western anti atlas subsequently recorded a late botoman interval of tectonic quiescence superimposed to a local interval of progradational pulses this favoured the nucleation of dispersed archaeocyathan microbial patch reefs and bioherms iv a distinct palaeogeographic area is recognized in the southern high atlas where the entire atdabanian botoman interval recorded small scale synsedimentary block tilting and high rates of volcaniclastic input as a result this sector was characterized by the record of microbial and archaeocyathan microbial patch reefs and bioherms preferentially developed on the uplifted parts of tilted blocks the end of reef development and carbonate productivity in the souss basin is related to the progradation of siliciclastic depositional systems toyonian regression considered to have caused the collapse of reef communities throughout west gondwana

cambrian and ordovician stratigraphy related to structure and seismic profiles in the western part of the english midlands in england the cambrian successions include relatively continuous dominantly argillaceous sequences nuneaton area 900 m thick and arenaceous successions punctuated by hiatuses malvern shropshire the tremadoc lower ordovician succeeds paraconformably it is widespread dominantly argillaceous and locally very thick 2000 m deposition of the lower tremadoc is thought to have been rapid uplift of regional extent occurred in early ordovician post tremadoc times and inversion of the basins such as the tremadoc worcester graben occurred during the variscan orogeny the disposition of the cambrian tremadoc beneath the upper llandovery unconformity is thought to reflect the arrangement of basins and highs at that time evidence from seismic profiles indicates deposition in half grabens in the welsh borderland evidence from outcrops and boreholes suggests that the st david s series middle cambrian is locally thickened against syn depositional faults the thinning and local absence of the st david s series across such faults is attributed to the influence of tilt block highs rifting and tilting allowed thick tremadoc to accumulate e g in a precursor worcester graben but evidence for the direction of thickening is masked by lack of seismic markers and by the effect of pre landovery erosion

desert speleothems reveal climatic window for african exodus of early modern humans one of the fi rst movements of early modern humans out of africa occurred 130 100 thousand years ago ka when they migrated northward to the levant region the climatic conditions that accompanied this migration are still under debate using high precision multicollector inductively coupled plasma mass spectrometry mc icp ms u th methods we dated carbonate cave deposits speleothems from the central and southern negev desert of israel located at the northeastern margin of the saharan arabian desert speleothems grow only when rainwater enters the unsaturated zone and this study reveals that a major cluster of wet episodes the last recorded in the area occurred between 140 and 110 ka this episodic wet period coincided with increased monsoonal precipitation in the southern parts of the saharanarabian desert the disappearance at this time of the desert barrier between central africa and the levant and particularly in the sinai negev land bridge between africa and asia would have created a climatic window for early modern human dispersion to the levant

trilobite diversity patterns in the middle cambrian of southwestern europe a comparative study abstract this paper describes the pattern of trilobite diversity throughout the middle cambrian in two fossiliferous basins of the western gondwana margin the iberian chains northeastern spain and the montagne noire southern france the documented fluctuations of species diversity allow us to recognize 1 a substantial extinction event recorded in latest early cambrian times named valdemiedes event which separates the culmination of a widespread decline of trilobites and the stepwise immigration of cosmopolitan invaders 2 a major trilobite radiation occurring in the earliest leonian and culminating across the caesaraugustian languedocian transition in which a peak in diversity of trilobites and carpoids was close to a major flooding surface 3 a major reduction of trilobite taxa across the early middle languedocian transition related to a well documented regressional trend and 4 a second immigration of trilobite fauna in the late languedocian which coincided with trangressional pulses and the establishment of suitable shaly substrates in addition we summarize the known trilobite occurrences from the middle cambrian of southwestern europe maps of the distribution of some relevant taxa genera and species over the western gondwana margin are documented

the role of abiotic factors in the cambrian substrate revolution a review from the benthic community replacements of west gondwana abstract the cambrian substrate revolution refers to a substantial and rapid change to the nature of marine sedimentary substrates in the early cambrian and is widely interpreted as a biologically driven event a direct response to evolutionary innovations in metazoan burrowing and the development of new shelly faunas however abiotic factors such as tectonic and climatic evolution also had the potential to restructure cambrian substrates and are here shown to be more plausible drivers of change in the benthic faunas of western gondwana the western mediterranean region underwent a southward drift during cambrian times which drove a switch from subtropical carbonates to temperate siliciclastic substrates with short term episodes of temperate carbonate productivity as a result microbial and shelly carbonates disappeared diachronously in a stepwise manner across the lower middle cambrian boundary interval archaeocyathan microbial reefs were replaced by chancelloriid eocrinoid spiculate sponge meadows in which the stepwise immigration of new echinoderm taxa was primarily controlled by extensional tectonic events first recorded in rifting settings and later in passive margin platforms availability of new kinds of substrate was thus the primary factor that controlled where and when evolutionary innovations in benthic strategies arose examples of this include the early cambrian colonization of phosphatic hardgrounds and thrombolite crusts by chancelloriids archaeocyathan and spiculate sponges and the exploitation by benthos to the increasingly widespread availability of shelly grounds and carbonate firmgrounds by early diagenetic cementation a microbial mat epifaunal antagonistic relationship is demonstrated for echinoderm pelmatozoans based on the non overlapping palaeogeographic distributions of microbial reefs and mats versus mud sticker pelmatozoans cambrian benthic communities thus evolved in parallel with substrates in response to abiotic factors rather than being the primary drivers of substrate change

first evidence for cambrian glaciation provided by sections in avalonian new brunswick and ireland additional data for avalon gondwana separation by the earliest palaeozoic abstract the first evidence for cambrian glaciation is provided by two successions on the avalon microcontinent the middle lowest cambrian middle terreneuvian series and fortunian stage stage 2 boundary interval has an incised sequence boundary overlain by a fluvial lowstand facies and higher olive green marine mudstone on hanford brook southern new brunswick this succession in the lower mystery lake member of the chapel island formation may be related to melting of an ice sheet in avalon the evidence for this interpretation is a muddy diamictite with outsized up to 10 cm in diameter proterozoic marble and basalt clasts that penetrated overlying laminae in the marine mudstone that eustatic rise was associated with the mudstone deposition is suggested by an approximately coeval rise that deposited sediments with watsonella crosbyi zone fossils 650 km away in avalonian eastern newfoundland a sea level rise within the watsonella crosbyi chron at ca 535 ma may correspond to a unnamed negative 13 c excursion younger than the basal cambrian excursion bace and the zhuce excursion in stage 2 of the upper terreneuvian series cambrian dropstones are now also recognized on the northern gander margin of avalon in continental slope rise sedimentary rocks in southeast ireland although their age early middle cambrian is poorly constrained dropstones in the booley bay formation provide additional evidence for cambrian glaciation on the avalon microcontinent besides providing the first evidence of cambrian glaciation these dropstone deposits emphasize that avalon was not part of or even latitudinally close to the terminal ediacaran cambrian tropical carbonate platform successions of west gondwana

the first furongian late cambrian echinoderm from the british isles furongian late cambrian echinoderms are extremely rare in the fossil record and only two previous reports have been described from the paibian stage worldwide here the third occurrence of an echinoderm from the paibian and the first ever reported in the furongian of britain is presented it is a primitive pelmatozoan which shows intermediate characteristics between eocrinoids with columnalbearing stems and primitive glyptocystitid rhombiferans the palaeobiogeographic affinities of cambrian echinoderm faunas from britain eastern avalonia are shown to be with gondwana

cambrian evolutionary radiation context correlation and chronostratigraphy overcoming deficiencies of the first appearance datum fad concept abstract use of the first appearance datum fad of a fossil to define a global chronostratigraphic unit s base can lead to intractable correlation and stability problems fads are diachronous they reflect species evolutionary history dispersal biofacies preservation collection and taxonomy the cambrian evolutionary radiation is characterised by diachronous fads biofacies controls and provincialism of taxa and ecological communities that confound a stable lower cambrian chronostratigraphy cambrian series and stage definitions require greater attention to assemblage zone successions and non biostratigraphic particularly carbon isotope correlation techniques such as those that define the ediacaran system base a redefined basal cambrian trichophycus pedum assemblage zone lies above the highest ediacaran type biotas vendobionts putative metazoans and calcareous problematica such as cloudina and the basal asteridium tornatum comasphaeridium velvetum zone acritarchs this definition and the likely close correspondence of evolutionary origin and local fad of t pedum preserves the fortune head newfoundland gssp of the cambrian base and allows the presence of sub cambrian branched ichnofossils the sub tommotian equivalent base of stage 2 a suggested laolinian stage should be defined by the i l4 zhuce 13 c positive peak bracketed by the lower ranges of watsonella crosbyi and aldanella attleborensis molluscs and the skiagia ornata fimbrioglomerella membranacea zone acritarchs the w crosbyi and a attleborensis fads cannot define a stage 2 base as they are diachronous even in the newfoundland type w crosbyi zone the series 2 base cannot be based on a species fad owing to the provincialism of skeletalised metazoans in the terreneuvian series 2 boundary interval and global heterochrony of the oldest trilobites a series 2 and stage 3 a suggested lenaldanian series and zhurinskyan stage new gssp base is proposed at the siberian lower atdabanian 13 c iv peak which correlates into south china avalonia and morocco and assigns the oldest trilobites to the terminal terreneuvian series

a review of the late cambrian furongian palaeogeography in the western mediterranean region nw gondwana abstract the cambrian ordovician transition of the western mediterranean region nw gondwana is characterized by the record of major erosive unconformities with gaps that range from a chronostratigraphic stage to a series the hiatii are diachronous and involved progressively younger strata along the gondwanan margin from sw morocco to ne montagne noire they can be related to development of a multi stage rifting further north currently connected to the opening of the rheic ocean and concomitant erosion on southern rift shoulders the platforms of this margin of gondwana occupied temperate water mid latitudes and were dominated by siliciclastic sedimentation while carbonate factories were only episodically active in the montagne noire platform the upper cambrian is devoid of significant gaps in the southern montagne noire and the iberian chains there the sedimentation took place in a transgressive dominated depositional system with common offshore deposits and clayey substrates and was bracketed by two major regressive trends the late cambrian is also associated with the record of volcanic activity e g in the cantabrian and ossa morena zones and the northern montagne noire and widespread development of a tectonic instability that led to the episodic establishment of palaeotopographies and record of slope related facies associations several immigration events are recognized throughout the latest middle cambrian late cambrian and tremadocian the trilobites show a stepwise replacement of acado baltic type families e g the conocoryphid paradoxidid solenopleurid assemblage characterized by i a late languedocian latest middle cambrian co occurrence of middle cambrian trilobite families with the first anomocarid dorypygid and proasaphiscid invaders ii a late cambrian immigration replacing previous faunas composed of trilobites aphelaspidids catillicephalids ceratopygids damesellids eulomids idahoiids linchakephalids lisariids onchonotinids and pagodiids linguliformean brachiopods acrotretids obolids scaphelasmatids siphonotretids and zhanatellids echinoderms mitrates glyptocystitid cystoids and stromatocystoids and conodonts belonging to the lower peltura zone and iii the subsequent input of new trilobites asaphids calymenids catillicephalids nileids and remopleurids which marks the base of the proteuloma geinitzi zone associated with pelmatozoan holdfasts oryctoconus and a distinct input of late tremadocian conodonts paltodus deltifer zone the biogeographic distribution of latest middle and late cambrian trilobites supports brachiopod data indicating strong affinities between the western mediterranean region east gondwana north china korea south china australia and antarctica and kazakhstania during the late languedocian which became significantly stronger during the late cambrian this major shift may suggest modification in oceanic circulation patterns throughout gondwana across the middle late cambrian transition

the birth of the rheic ocean early palaeozoic subsidence patterns and subsequent tectonic plate scenarios abstract new plate tectonic reconstructions of the gondwana margin suggest that the location of gondwana derived terranes should not only be guided by the models but should also consider the possible detrital input from some asian blocks hunia supposed to have been located along the cambrian gondwana margin and accreted in the silurian to the north chinese block consequently the gondwana margin has to be subdivided into a more western domain where the future avalonian blocks will be separated from gondwana by the opening rheic ocean whereas in its eastern continuation hosting the future basement areas of central europe different periods of crustal extension should be distinguished instead of applying a rather cylindrical model it is supposed that crustal extension follows a much more complex pattern where local back arcs or intra continental rifts are involved guided by the age data of magmatic rocks and the pattern of subsidence curves the following extensional events can be distinguished during the early to middle cambrian a back arc setting guided the evolution at the gondwana margin contemporaneous intra continental rift basins developed at other places related to a general post pan african extensional phase affecting africa upper cambrian formation of oceanic crust is manifested in the chamrousse area and may have lateral cryptic relics preserved in other places this is regarded as the oceanisation of some marginal basins in a context of back arc rifting these basins were closed in a mid ordovician tectonic phase related to the subduction of buoyant material mid ocean ridge since the early ordovician a new phase of extension is observed accompanied by a large scale volcanic activity erosion of the rift shoulders generated detritus armorican quartzite and the rift basins collected detrital zircons from a wide hinterland this phase heralded the opening of palaeotethys but it failed due to the silurian collision eo variscan phase of an intra oceanic arc with the gondwana margin during this time period at the eastern wing of the gondwana margin begins the drift of the future hunia microcontinents through the opening of an eastern prolongation of the already existing rheic ocean the passive margin of the remaining gondwana was composed of the galatian superterranes constituents of the future variscan basement areas remaining under the influence of crustal extension they will start their drift to laurussia since the earliest devonian during the opening of the palaeotethys ocean

paleoclimatic implications of u series dates for lake sediments and travertines in the arava rift valley israel abstract the sayif travertines and lacustrine limestones cropping out in the northern arava valley a region of extreme aridity have been dated by the 230 th 234 u disequilibrium method the consistency between the stratigraphic position and the apparent ages at each of the sampling sites strongly supports the reliability of the ages most of the ages fall within two clusters that are coincident with ages representative of oceanic oxygen isotope stages 5 and 7 the colder intervening stage 6 was not a period of substantial travertine formation during the warmer global episodes of isotopic stages 5 and 7 the arid south of israel apparently was considerably wetter than at present

sediment and pollen evidence for an early to mid holocene humid period in the eastern sahara a major problem in the study of holocene palaeoenvironments of the arid and wind deflated sahara is the low preservation potential of sediments from which a record of past climatic change can be established several indirect and imprecisely dated pieces of evidence have suggested humid episodes in the holocene that may have supported more productive ecosystems and denser human populations than today searches for reliable proxy data on past climates however have failed to yield satisfactory results we report here the discovery of buried lake muds in north west sudan in the hyperarid core of the eastern sahara which yield sedimentological and palynological data clearly interpretable as recording an early to mid holocene humid episode that supported a relatively deep stratified lake surrounded by tropical savanna woodland vegetation

the absence of echinoderms from the lower cambrian chengjiang fauna of china palaeoecological and palaeogeographical implications abstract although deuterostome phylogeny has now achieved a good degree of consensus echinoderm emergence and early evolution remain highly enigmatic different phylogenetic scenarios have emerged based partially on early cambrian enigmatic animals of the chengjiang biota yuanshan formation cambrian series 2 yunnan china interpreted as primitive echinoderms they include cambrofengia yunnanensis hou et al 1999 cotyledion tylodes luo and hu 1999 and two vetulocystids dianchicystis jianshanensis and vetulocystis catenata shu et al 2004 their interpretation as echinoderms is here critically revised and c tylodes based on newly sampled specimens is tentatively re interpreted as a cnidarian polyp as a result it appears that the chengjiang biota one of the most diverse and earliest recorded communities is most probably devoid of echinoderm representatives this is not interpreted as a taphonomic artefact but as a palaeoecological signal of the radiation of echinoderm during the early cambrian on carbonate substrates up to ten exceptional biotas are described from the yangtze platform south china from cambrian stage 2 to early stage 5 in siliciclastic environments varying from shallow platform to basin slope the absence of echinoderms in those burgess shale type deposits from cambrian stages 2 and 3 along with their report from laterally coeval carbonate sediments argue for a proximal radiation of echinoderms during early cambrian times in carbonate environments they would have later colonized siliciclastic proximal and distal environments the same colonization sequence is generally observed at a global scale with the first appearance of echinoderms varying in time according to local palaeogeographical controls

cambroclaves from the cambrian of sardinia italy and germany constraints for the architecture of western gondwana and the palaeogeographical and palaeoecological potential of cambroclaves cambroclaves represent a group of problematic microfossils previously known from strata close to the early middle cambrian boundary of only a few palaeogeographic regions kazakhstan china australia because of their frequent occurrence as disarticulated remains they have hitherto been assumed to be provincially restricted microfossils of unclear palaeobiological affinity discoveries of cambroclaves from the early to early middle cambrian of southern sardinia and central germany europe point to a much wider distribution during their short stratigraphic range and imply closer palaeogeographic relations between the european shelf of western gondwana and the areas from which cambroclaves were previously known these relations are also supported by the common occurrence of other small shelly fossils these facts support the existence of a widespread uniform facies belt shelf around parts of gondwana during the early middle cambrian time interval and contradict the interpretation of the european depositional areas as isolated basins or as distinctly separate cambrian terranes the western gondwana cambroclaves occur in carbonate successions indicative of special palaeoecological conditions the specimens are limited to distinct layers formed during transgressive phases that opened inner and partly restricted platform areas to open marine and more distal deeper subtidal environments possibly accompanied by a transition from a rather arid to more humid climatic conditions because of the short stratigraphic window of occurrence and of distinctive facies characteristics cambroclaves are palaeoecologically and palaeobiogeographically useful and consequently contribute important evidence for both the reconstruction of the perigondwana realm and the relations to other palaeocontinents in the cambrian 7 2003 elsevier science b v all rights reserved

origin of basaltic soils at gusev crater mars by aeolian modification of impact generated sediment 1 textural properties of soils including grain size sorting modality skewness shape quantified as sphericity and qualified as form roundness and grain size distribution have been measured and calculated from microscopic imager mi high resolution images from the mars exploration rover mer spirit in gusev crater soil targets were classified by grain size into five groups fine to medium sand dark soil medium sand to very fine pebble bed form armor and very fine to medium pebble lithic fragments a bimodal mixed soil and an excavated soil trench the abundance of submature very poorly sorted bimodal mixed soils indicates incomplete sorting by soil type probability distributions of excavated subsurface soil match crushed sediment analogs indicating impact comminution while all other soils show no direct evidence of an impact origin if soils were produced primarily by impacts then the evidence from probability distributions angular shapes and agglutinates have been reworked by postimpact surface activity soils in gusev crater are continuously modified reworked and sandblasted textures of surface sediments are disconnected from subsurface textures and only reflect modern surficial aeolian processes models to reconstruct physical and chemical soil formation properties should not assume a static three dimensional structure a three step model initiated by the formation of basaltic crust and its alteration followed by bolide impact and finally modification by aeolian reworking is envisioned for the formation of soils such a scenario accounts for the potential that surface sediments may be compositionally and texturally distinct from the subsurface

facies distribution of the lower cambrian cryptic microbial and epibenthic archaeocyathan microbial communities western anti atlas morocco marine microbial communities recorded in the moroccan anti atlas were unaffected across the neoproterozoic cambrian transition a stromatolite dominated consortium was replaced at the beginning of the atdabanian ca 20 myr after the neoproterozoic cambrian boundary by shelly metazoan and thromboid consortia which contain the oldest biostratigraphically significant fossils of the moroccan cambrian the associated collapse of microbial mat stromatolitic growth appears to coincide with a change from pre atdabanian shallow water restricted conditions into atdabanian deeper open sea conditions it is postulated that this environmental change led to an episode of improved water circulation over carbonate platform interiors promoting shelly metazoan immigration into the region the tiout amouslek lithostratigraphic contact in the early atdabanian marks the end of an episodically unstable seafloor as suggested by the abundance of slumping and sliding structures and synsedimentary microfaults and cracks recorded in the underlying tiout member concurrent with the transition is the occurrence of a network of cryptic fissures and cavities that provided habitats for a coelobiontic chemosynthetic heterotrophic microbial community composed of stromatolitic crusts renalcis epiphyton girvanella intergrowths and kundatia thalli in the overlying amouslek formation archaeocyathan thromboid reefs were constrained by substrate stability water depth and subsidence rate four reef geometries are distinguished i patch reefs surrounded by shales ii bioherms in which flank beds intercalate laterally with carbonate and shale inter reef sediments iii biostromes or low relief structures formed as a result of lateral accretion of patch reefs and iv kalyptrate complexes that nucleated because of a marked tendency for aggregation and in which patch reefs and bioherms occur stacked together bounded by clay marl silt seams

biogeographical significance of cambrian trilobites from the carolina slate belt abundant middle middle cambrian trilobites of the ptychagnostus atavus interval zone are described from the upper asbill pond formation informal name near batesburg south carolina the fauna containing at least nine species has strong affinities with cool water faunas of both armorica and baltica but little affinity with warm water shelf faunas of laurentia this is compatible with previous conclusions that the carolina slate belt is an exotic terrane that was accreted to north america during the early or middle paleozoic further evaluation however introduces an alternative possibility that the fauna could have lived in deep cool water environments along the periphery of laurentia and subsequent displacement need not necessarily have been great combined faunal and stratigraphic components of the carolina slate belt do not precisely match those of any known region but may be closest to those of bohemia although a southpolar location in proximity to armorica baltica and gondwana seems likely a definitive placement in a reconstruction of the cambrian world is not yet possible included in the trilobite fauna are the agnostoids hypagnostus mammillatus h parvifrons peronopsis fallax ptychagnostus sp and tomagnostus fissus the polymeroids include agraulos sp paradoxides cf polonicus paradoxides sp and skreiaspis sp