a debris flow calendar derived from sediments of lake lago di braies n italy abstract in this study lake sediments were used for developing a high resolution calendar of past debris flow events debris flows frequently occur in the high alpine catchment of the lake lago di braies n italy while the coarse grained material accumulates on the debris flow cones the fine grained material is flushed into the lake this material forms characteristic layers in the lake sediments which are different from the typical annual lamination by analysing thin sections of sediment debris flow events of the last 2250 years were reconstructed with an annual resolution since debris flow frequency varies strongly periods with high and low frequencies can be distinguished however neither a debris flow magnitude frequency relationship nor a strong reaction of debris flow activity to past climate changes was identifiable in this study

upper devonian conodont zonation sea level changes and bio events in offshore carbonate facies lali section south china abstract the lali section guangxi province south china is composed of quiet water carbonates containing abundant conodonts which allowed recognition of 12 frasnian and 20 famennian biozones the kellwasser and annulata events are characterized by transgressive black carbonates while the hangenberg event is represented by black shale deposits other transgressive events recognized at lali include the middlesex nehden enkeberg and dasberg as well as the strunian transgression four regressive events were recognized on the basis of lithological and microfacies changes i e the linguiformis regression condroz event velifer regression and the derwer regression these sea level change events were of short duration and globally isochronous based on conodont correlations microfacies analyses and the abundance of palmatolepis indicate that the highest frasnian sea level lies in fz 12 13 upper rhenana zone whereas the highest famennian sea level was in the utahensis zone

sediment dynamics and hydrologic events affecting small lacustrine systems on the southern central tibetan plateau the example of tt lake a sedimentological geochemical micropaleontological and palynological study of a lacustrine sediment record from the small tt lake southern central tibetan plateau shows that the background sedimentation was frequently interrupted by event related deposits these event related deposits are interpreted as the result of hydrologic events that are triggered by above average precipitation events in total 11 events were recorded in the tt lake sequence two types can be differentiated fluvial runoff events caused by precipitation that carried sediment in suspension into the lake and a sediment mass transport caused by torrential precipitation the hydrologic events appear to be decoupled from long term climate and environmental variations but there is evidence that anthropogenic impact in terms of pastoralism might have favored the runoff events the multi proxy approach proved to be valuable and allowed for a detailed study of sedimentary processes within the lake and its watershed in order to asse

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

global events of the late paleozoic early devonian to middle permian a review abstract the late paleozoic early devonian to middle permian was an interval of profound changes in earth surface systems reflected in dynamic interplay among the biosphere hydrosphere atmosphere and geosphere major events transpired including the colonization of landmasses by vascular plants the assembly of the supercontinent pangea two first order mass extinctions the frasnian famennian and devonian carboniferous boundary events and the most severe icehouse climate mode of the phanerozoic the late paleozoic ice age lpia the goals of the present review are 1 to summarize major global developments in climate oceanography and paleobiology during the late paleozoic 2 to examine the roles of land plant evolution global tectonics and large igneous province magmatism in driving these developments and 3 to serve as an introduction to the 23 contributions to this special issue of palaeogeography palaeoclimatology palaeoecology indicating how they advance our knowledge of various scientific issues related to these developments

sea level and environmental changes around the devonian carboniferous boundary in the namur dinant basin s belgium ne france a multi proxy stratigraphic analysis of carbonate ramp archives and its use in regional and interregional correlations abstract the paper focuses on high resolution multidisciplinary research on three devonian carboniferous boundary sections in shallow water carbonate rocks in the namur dinant basin belgium france the aim of the study is to provide palaeo environmental reconstructions and correlations supported by several independent quantitative proxies we describe several correlative horizons and provide their sequence stratigraphic interpretation based on facies analysis spectral gamma ray data element concentrations xrf and 13ccarb with foraminifer biostratigraphy age control the most prominent surface is a basal surface of forced regression which is indicated by a sharp basinwards facies shift and a drop in clay gamma ray values and al concentrations at the base of the hastiere and avesnelles formations in more distal settings in proximal settings this surface merges with a hiatus at the devonian carboniferous boundary inferred from foraminifer biostratigraphy this hiatus can be correlated with the global hangenberg sandstone event which indicates a glacioeustatic sea level fall increasing values of zr al k al sr al and mn al coincide with the proximal facies of the falling stage system tract and lowstand system tract in the hastiere and avesnelles formations as a consequence of the enhanced input of siliciclastics and nutrients during low sea levels the top of the middle hastiere member is interpreted as the maximum regression surface which is overlain by transgressive system tract of the upper hastiere member the patterns of gamma ray 13ccarb th k al and zr al curves are well correlated between the studied sections the 13ccarb excursions are correlated with the unnamed excursion in the upper expansa conodont zone carnic alps and with the global hangenberg event s l excursion in the kockeli conodont zone this sequence stratigraphic framework is used for correlations with deltaic successions from the tafilalt basin morocco the basal surface of the forced regression equivalent to the hangenberg sandstone event which is typical for deeper water settings is easily recognisable and correlatable with gaps in more shallow water settings we suggest that it should be taken into account as a possible candidate for the natural solution of the devonian carboniferous boundary in discussions concerning its redefinition

shift in the paradigm for gssp boundary definition abstract for over 200 years the use of biotic events as the basis for the establishment of chronostratigraphic boundaries has been the only approach successfully utilized for international and national chronostratigraphy the traditional biostratigraphic method provides relatively high resolution averaging 1 ma or sometimes less this biochronological evolutionary approach to the global boundary stratotype section and point gssp utilizes biotic primary markers pm with a few exceptions encompasses the integrated pm and other non pm markers as the general principles for defining gssp boundaries and is a reasonably reliable mechanism for global correlation and a relatively stable international geologic time scale igts the biotic pm s however possessed several serious restrictions the nature of biological taxonomy climatic sedimentary environmental and directly applicable within the tropics subtropics only biotic evolution and radiogenic isotopes are the only systems in geologic time that encompass the direction of time the latter possessed less restrictions than the former the recent tendency to define gssp s utilizing magnetic chrons climatic events and geochemistry may work in the cenozoic but is useless in the mesozoic and older sediments because their cyclic nature repeatedness and the need for a second directional in time index biostratigraphic or radioisotopic to place the pm in the right position within the scale i propose here to utilize volcanic ash beds as the best primary marker in geologic chronostratigraphy the u pb system is one of the most dependable of the geochronologic systems because it relies on a simple and non interpretive radioisotopic decay constant the ash bed gssp as a lithological horizon is universal for the gssp definition and can be correlated as an age in any facies marine lagoon and continental regardless of paleoclimatic zones paleoceanographic geochemical and most other geological factors even moderate level metamorphism 900 does not affect the u pb dating of zircons the gssp at the base of a volcanic ash bed primary marker could be established in a short working time and these ash beds can be integrated with the existing as well as new biostratigraphic geochemical magnetostratigraphic and astronomical data secondary markers to create a robust accurate and highly useable time scale several potential gssp s that could be established with the volcanic ash beds close to the traditional and or historical boundaries serve as examples for this approach and include devonian carboniferous moscovian kasimovian kasimovian gzhelian and sakmarian artinskian boundaries

later pleistocene holocene climate conditions of qinghai xizhang plateau tibet based on carbon and oxygen stable isotopes of zabuye lake sediments abstract we present a time series of carbon and oxygen stable isotope records of the last 30 000 14c years throughout the last glacial postglacial cycle from western qinghai xizhang tibet plateau a 20 m core drilled in the south basin of zabuye salt lake was analyzed for inorganic and organic carbon and total sulfur contents 13c and 18o values of carbonates our results indicate that climatic changes have led to a drastic negative shift of stable isotope ratios at the transition between the last full glacial and the postglacial phase during later pleistocene times 16 2 kyr bp and a rapid positive shift at the transition from pleistocene to holocene 10 6 kyr bp the first shift is marked by the drop of 18ocarb values of about 10 from 2 to 8 and 13ccarb values of about 3 from 5 to 2 the second shift which occurred at the transition from pleistocene to holocene was of similar magnitude but in the opposite direction isotope data combined with total organic and inorganic carbon contents and the lithological composition of the core suggest this lake was an alluvial pre lake environment prior to ca 28 14c kyr bp during ca 28 16 2 14c kyr bp zabuye lake was likely a moderately deep lake with limited outflow the cool and arid glacial climate led the lake level to drop drastically extended residence time overwhelmed the lower temperature and caused a steady increase of 13ccarb and 18ocarb values and total inorganic carbon content in the sediments during ca 16 2 10 6 14c kyr bp this lake probably overflowed and received abundant recharge from melting glaciers when the deglaciation was in its full speed a spike of markedly enhanced 13ccarb and 18ocarb is seen at 11 5 kyr bp probably due to the isotopic effects left behind by the short but severe younger dryas yd event after ca 10 6 14c kyr bp zabuye lake probably closed its surface outflow due to strong desiccation and drastic climate warming the early and middle holocene were characterized by unstable climatic conditions with alternating warmer cooler episodes as indicated by the severe fluctuations of total organic carbon 13c and 18o values a hypersaline salt lake environment was finally formed at zabuye after 5 14c kyr bp when the mirabilite and halite concentrations steadily increased and became the dominant minerals in the sediments severe imbalance of inflow outflow resulted in the drastic increase of total sulfur 13ccarb and 18ocarb values and dominance of halite in the lake since ca 3 8 kyr bp to present

cosmogenic 10be and 26al dating of paleolake shorelines in tibet abstract we have used in situ produced cosmogenic nuclides 10be and 26al to date lacustrine shorelines around eight lakes in tibet two lakes located south of the yarlung tsangpo river discharged at high lake levels one of them drolung co co is a local term meaning lake became closed its water level fell below its outlet channel at 3 8 ka and lowered over 120 m vertically since then this implies a significant change in intensity of precipitation driven by the indian monsoon over southern tibet in the middle late holocene nam co and dajia co located to the north of the yarlung tsangpo river also drained at high lake levels and became closed 53 36 ka and 48 ka respectively of four other lakes developed closely in the qiangtang basin north of the yarlung tsangpo river tangra yum co and siling co located at 31 32 n show exposure ages for high lake shorelines of over 220 ka the oldest lake shorelines reported for tibet while towards the north and west the high lake of zhari nam co appeared after the last glacial maximum lgm the different pattern of lake development to the north of yarlung tsangpo river may reflect regional climate effects

palaeoenvironmental changes at col des tribes montagne noire france a reference section for the famennian of north gondwana related areas we present detailed biostratigraphy based on conodonts and palaeoenvironmental trends deduced from microfacies and conodont abundance through the famennian late devonian at col des tribes montagne noire france the succession is characterized by micritic limestones deposited in settings oscillating between mid to outer ramp facies contain poor fauna widely dominated by nektonic organisms this section is complete and one of the most conodont rich for the famennian of the north gondwana related area the upper kellwasser event frasnian famennian boundary and the hangenberg devonian carboniferous boundary have been lithologically identified they are characterized by decimetre thick black dysoxic to anoxic argillaceous sediments the condroz and annulata events although not materialized by lithological changes have been positioned due to the precise stratigraphy the first event occurred during the deposition of condensed ferruginous facies griotte limestones and the second event during the deposition of micrites barren of benthic fauna the combination of information from both facies and conodont biofacies changes allows a general sea level curve through the entire famennian for north gondwana to be proposed for the first time at col des tribes the general trend is a slight deepening upwards from triangularis to trachytera zones then a pronounced shallowing upwards trend from upper trachytera to praesulcata zones this curve correlates with the well known reference curve from euramerica concerning the late famennian trachytera to praesulcata zones there are some discrepancies in minor cycles which can be explained by tectonical phenomena at the onset of the edification of the variscan belt in europe

late quaternary lacustrine paleo seismic archives in north western alps examples of earthquake origin assessment of sedimentary disturbances abstract the late quaternary sedimentary fills of several lakes of the north western alps are revealed to be possible paleo seismological archives in a moderately active seismo tectonic region the strongest historically reported events can be correlated with specific layers whose textures result from different processes i mass failures of sub aqueous slope deposits especially delta foresets evolving into hyperpycnal currents influenced by seiche effects and or multiple reflections on lake basin slopes ii in situ liquefaction and flowage and iii micro fracturing based on identification of the sedimentary signature of a well documented historical earthquake the paleoseismic interpretation can be extrapolated back to 16 000 yrs bp with a reconstruction of a time series and textural identification of slope failure related turbidites the most frequent earthquake signature the obtained time series are compatible with historical seismicity in terms of recurrence interval

a 450 year record of spring summer flood layers in annually laminated sediments from lake ammersee southern germany 1 a 450 year spring summer flood layer time series at seasonal resolution has been established from the varved sediment record of lake ammersee southern germany applying a novel methodological approach the main results are 1 the attainment of a precise chronology by microscopic varve counting 2 the identification of detrital layers representing flood triggered fluxes of catchment material into the lake and 3 the recognition of the seasonality of these flood layers from their microstratigraphic position within a varve tracing flood layers in a proximal and a distal core and correlating them by application of the precise chronology provided information on the depositional processes comparing the seasonal flood layer record with daily runoff data of the inflowing river ammer for the period from 1926 to 1999 allowed the definition of an approximate threshold in flood magnitude above which the formation of flood layers becomes very likely moreover it was possible for the first time to estimate the completeness of the flood layer time series and to recognize that mainly floods in spring and summer representing the main flood seasons in this region are well preserved in the sediment archive their frequency distribution over the entire 450 year time series is not stationary but reveals maxima for colder periods of the little ice age when solar activity was reduced the observed spring summer flood layer frequency further shows trends similar to those of the occurrence of flood prone weather regimes since a d 1881 probably suggesting a causal link between solar variability and changes in midlatitude atmospheric circulation patterns

10 000 yr record of extreme hydrologic events well dated lacustrine sediments provide a hydrologic record indicating that the frequency and magnitude of runoff events and by inference storms have varied over the past 10 k y in northern new england we used five sediment cores and radiocarbon dating to develop a chronology of holocene hydrologic events for the ritterbush pond basin northern vermont chemical and physical analyses allow us to identify 52 distinct layers of predominately inorganic sediment that represent terrestrially derived material delivered to the pond by runoff events the thickness of some layers suggests hydrologic events at least equal in size to and probably much larger than any storm or flood recorded during nearly 300 yr of written regional history layer thickness and frequency and by analogy storm size and recurrence change through the holocene the largest events occurred 2620 6840 and 9440 calibrated 14c years before present cal 14c yr b p the most frequent hydrologic events occurred in three periods 1750 to 2620 6330 to 6840 and 8600 cal yr b p the recurrence interval of layer deposition during stormy periods averages 130 100 cal yr whereas the recurrence interval during less stormy periods is longer 270 170 cal yr the ritterbush pond event record illustrates the potential of inorganic lacustrine sediment to serve as a proxy record for estimating paleoflood frequency and deciphering climate change

constraining holocene lake level highstands on the tibetan plateau by 10be exposure dating a case study at tangra yumco southern tibet abstract many lakes on the tibetan plateau are surrounded by palaeo shorelines that document former lake level highstands and hence past changes in climate establishing accurate chronologies for these shorelines is crucial to correlate lake level fluctuations with palaeo environmental histories that are commonly inferred from lake sedimentary records here we apply surface exposure dating to constrain the age of two lake level highstands at one of the largest tibetan lakes tangra yumco which has well developed palaeo shorelines located up to 185 m above the current lake for sampling we focussed on wave cut bedrock terraces that vary considerably in width because they were carved into rocks of different erodibility samples from the highest strath terrace 180 185 m above the lake at three different sites yield tightly clustered 10 be ages between 7 39 0 19 ka and 7 87 0 27 ka internal errors which constrain the end of an early holocene lake level highstand at 7 6 0 6 ka external error the consistency of the 10 be ages indicates that bedrock erosion by wave attack reduced the inherited 10 be component to negligible amounts because otherwise samples would show considerable age scatter two bedrock samples from a lower terrace 140 145 m above the lake and one amalgamated clast sample from a beach ridge on the same terrace yield 10 be ages between 4 04 0 14 ka and 4 50 0 15 ka these ages document that the lake level dropped by 40 m between 7 6 ka and 4 3 ka granite boulders from the two investigated terraces yield apparent 10 be ages that are 6 ka and 27 ka older than the ages of the respective terraces indicating that this sample type is not reliable in this setting overall our results demonstrate that exposure dating of bedrock terraces provides a valuable tool to reconstruct lake level histories on the tibetan plateau

conodonts across the devonian carboniferous boundary a review and implication for the redefinition of the boundary and a proposal for an updated conodont zonation this paper is a contribution to the redefinition of the base of carboniferous system at present the criterion for the definition of the devonian carboniferous boundary is the first occurrence of a conodont species in order to evaluate the stratigraphic potential for new criteria for the definition of the devonian carboniferous boundary the distribution of conodont species of bispathodus branmehla palmatolepis polygnathus protognathodus pseudopolygnathus and siphonodella across the boundary is presented and discussed an updated biozonation scheme across the boundary based on the first appearance of bispathodus ac aculeatus bispathodus costatus bispathodus ultimus protognathodus kockeli siphonodella bransoni and siphonodella duplicata is proposed and it is suggested that the new criterion for the definition of the base of the carboniferous system be the first appearance datum of pr kockeli or si bransoni

foraminiferal responses to major pleistocene paleoceanographic changes in the southern south china sea a detailed age model for core 17957 2 of the southern south china sea was developed based on delta 18 o coarse fraction magnetostratigraphy and biostratigraphy for the last 1500 kyr the delta 18 o record has clear similar to 100 kyr cycles after the mid pleistocene revolution mpr at the entrance of marine isotopic stage mis 22 planktonic foraminifera responded to the mpr immediately showing the increased sea surface temperature sst and dissolution after the mpr benthic foraminifera did not respond to it until the brunhes matuyama boundary since the mpr the depth of thermocline gradually became shallower until miss 6 5 this major change within miss 6 5 was also reflected in the decreased ssts and increased productivity and deep water mass thus two major pleistocene paleoceanographic changes were found one was around the mpr the other occurred within miss 6 5 which speculatively might be ascribed to the reorganization of surface and deep circulation possibly induced by tectonic forces

the expression of the hangenberg event latest devonian in a relatively shallow marine succession pomeranian basin poland the results of a multi proxy investigation the uppermost famennian lowermost tournaisian interval has been analysed in detail using biostratigraphy sedimentology magnetic susceptibility and geochemistry in a reference section of the relatively shallow carbonate ramp environment within the pomeranian basin high resolution biostratigraphic study based on miospores allows recognition of the standard western european lepidophyta nitidus ln and verrucosus incohatus vi zones as well as the convolutispora major zone a local pomeranian equivalent of the european standard hibernicus distinctus hd zone the sedimentary succession and specific phenomena recognized close to the devonian carboniferous boundary such as fluctuations in water column euxinia wildfire evidence relative sea level changes and perturbations of the carbon cycle reflected by positive carbon excursions display a pattern partly similar to that observed in many areas in europe during the hangenberg event although the hangenberg black shale horizon is not developed here these important microscale environmental perturbations were observed not only within the famennian ln miospore zone but in a wide interval between the ln and the lowermost local convolutispora major miospore zones lower part of hd standard miospore zone it is still uncertain whether the recognized event s were connected solely with the hangenberg event which was possibly complex and multi phased as is sometimes suggested or whether they represent a succession of regionally limited post hangenberg events this question needs to be further investigated on broader stratigraphic and geographical scales

holocene variations in the asian monsoon inferred from the geochemistry of lake sediments in central tibet we present a record of monsoon variations for the early and middle holocene that is inferred from the geochemistry of sediment cores from ahung co a lake in central tibet the resolution of this record is better than 50 yr and the age model is derived from radiocarbon ages of terrestrial charcoal which eliminates errors associated with the lake hard water effect we made down core geochemical measurements of carbonate organic carbon c n and 13c of bulk organic matter 13c and 18o of carbonate and dolomite proxy calibration and modern water balance reconstruction show that these are proxies for lake depth and the amount of monsoon precipitation we find that lake level and monsoon precipitation have been decreasing at ahung co since the early holocene 7500 cal yr b p superimposed on this trend are rapid declines in monsoon rainfall at 7000 7500 and 4700 cal yr b p and seven century scale wet dry oscillations the cores do not contain sediment from the last 4000 yr surface sediments from the lake accumulated during the 20th century however from this we argue that lake levels have risen again recently following a late holocene dry period

lower sappington formation palynofacies in montana confirm upper famennian black shale paleoenvironments and sequences across western north america abstract for the first time late devonian palynofacies analyses of the lower sappington shale units u1a d was carried out at peak 9559 sacajawea and ainger lake in the bridger range of montana diagnostic spore species apiculiretusispora verrucosa diducites mucronatus and d versabilis allowed the correlation of our u1a d with the european late famennian a verrucosa v hystricosus palynozone the first appearance of gorgonisphaeridium winslowiae in u1 is the oldest record before the inception of retispora lepidophyta four palynofacies correlative with u1a d and new findings of invertebrates and microfossils allow the interpretation of paleoenvironmental changes amorphous organic matter marine phytoplankton and pyrite in black shales of u1a b indicate anoxic bottom conditions occurred in offshore marine environments an erosional fossiliferous phosphatic lag above these units confirms a regional sb u1c black shales composed by aom marine and terrestrial phytoplankton land derived remains and pyrite reveal shallower dysoxic anoxic brackish water environments a thin layer at the base of unit 1d yielded aom and marine phytoplankton and low terrestrial input indicating dysoxic anoxic conditions were maintained the lack of organic matter and the presence of invertebrates and microfossils in a thin green fossiliferous mudstone supports the establishment of normal oxygenated marine conditions maintained in the basal middle sappington member u2 these two thin units are not part of the underlying anoxic black shale u1a b sequence as commonly was over simplified instead they are part of a transgressive interval with the basal middle sappington a correlation of the u1 shale interval is established with the global multiphase dasberg event

a high resolution multiproxy stratigraphic analysis of the devonian carboniferous boundary sections in the moravian karst czech republic and a correlation with the carnic alps austria a multidisciplinary correlation of the devonian carboniferous d c boundary sections from the moravian karst czech republic and the carnic alps austria based on conodont and foraminifer biostratigraphy microfacies analysis field gamma ray spectroscopy grs carbon isotopes and element geochemistry is presented in this paper the study is focused on the interval from the middle palmatolepis gracilis expansa zone late famennian to the siphonodella sandbergi zone early tournaisian in lesni lom moravian karst a positive 13 c excursion in the bisphatodus costatus protognathodus kockeli interregnum from a distinct laminated carbonate horizon is correlated with a carbon isotope excursion from the grune schneid section of the carnic alps and is interpreted as the equivalent of the hangenberg black shales and a local expression of the global hangenberg event sensu stricto higher up at both sections a significant increase in the terrigenous input which is inferred from the grs signal and elevated concentrations of terrigenous elements si ti zr rb al etc provides another correlation tieline and is interpreted as the equivalent of the hangenberg sandstone both horizons are discussed in terms of relative sea level fluctuations and palaeoceanographic changes recent studies show that conodont biostratigraphy is facing serious problems associated with the taxonomy of the first siphonodellids their dependence on facies and discontinuous occurrences of protognathodids at the d c boundary therefore the correlative potential of geochemical and petrophysical signatures is high and offers an alternative for the refining of the problematic biostratigraphic division of the d c boundary

devonian carboniferous transition containing a hangenberg black shale equivalent in the pho han formation on cat ba island northeastern vietnam abstract on cat ba island in northeastern vietnam the devonian to carboniferous d c transition consists mainly of ramp carbonates intercalated with black shale beds beds 1 to 176 in the pho han formation and is one of the few records of the d c transition of the eastern paleotethys the three main facies of the sequence are facies 1 alternations of whitish gray to gray limestone and marl facies 2 calcirudite bed 115b and facies 3 alternations of dark gray limestone and organic carbon rich black shale beds 115c 120 and 126 129 the latest famennian siphonodella praesulcata subzone conodont assemblage of s praesulcata palmatolepis gracilis palmatolepis sigmoidalis and rhodalepis polylophodontiformis was recognized in beds 113 115c beds 105 112 commonly contain palmatolepis expansa p gracilis and p sigmoidalis bed 119 yielded a basal carboniferous index conodont siphonodella sulcata in beds 116 118 solenoporids such as pseudochaetetes elliotti and parachaetetes sp were characteristic species in organic carbon rich dark gray limestone facies 1 is characterized by bioclastic peloidal and intraclastic grainstone and packstone containing massive normal grading and cross laminations and is interpreted to represent deep ramp carbonates above storm wave base facies 2 is represented by typical lag deposits overlying a transgressive surface facies 3 comprises organic carbon rich black shale and minor scour filling bioclastic peloidal and intraclastic packstone and may represent a marginal basin plain environment surrounding a carbonate ramp the alternations of organic carbon rich black shale and dark gray packstone facies 3 show no evidence of bioturbation and have high toc contents 0 18 5 73 wt a minor succession within the transgressive lag deposits from bed 115b of facies 2 to beds 115c 120 in the lower part of facies 3 is equivalent to the hangenberg black shale s l in the middle part of the siphonodella praesulcata to siphonodella sulcata zones because beds 115b 120 characterized by no evidence of bioturbation and high toc contents are interpreted to be accumulated in anoxic to dysoxic conditions

conodont zonation and the devonian carboniferous famennian tournaisian boundary in the naltas section eastern taurides turkey abstract conodont faunas from the devonian carboniferous naltas section eastern taurides turkey are presented the faunas include important marker species of the latest devonian earliest carboniferous interval belonging to the genera siphonodella bispathodus polygnathus pseudopolygnathus apatognathus and branmehla four conodont zones comparable to the standard conodont zonation are established in the studied succession from the oldest to the youngest 1 bispathodus ultimus 2 siphonodella praesulcata zones upper famennian 3 siphonodella sulcata and 4 siphonodella bransoni zones lower tournaisian the devonian carboniferous boundary in the eastern taurides is recognized by the first appearance of siphonodella sulcata

tracing paleoredox conditions across the devonian carboniferous boundary event a case study from carbonate dominated settings of belgium the czech republic and northern france the devonian carboniferous boundary was coeval with the hangenberg crisis which is regarded as a first order mass extinction event related with large sea level changes and widespread anoxia this study aims to trace the geochemical paleoproductivity and paleoredox proxies across the devonian carboniferous carbonate dominated successions of the namur dinant basin belgium northern france and the moravo silesian basin czech republic located in the variscan rhenohercynian zone the research was focused on the distribution of oxides sio2 al2o3 fe2o3 cao na2o k2o tio2 mno and trace elements th u v zr mo zn pb ni cu measured by icp oes and icp ms respectively the enrichment factors of mo and u and their ratios were used as the main paleoredox proxies whereas the enrichment factors of zn cu pb and ni were employed to trace the paleoproductivity changes high values of zr al2o3 0 001 tio2 al2o3 0 06 and fe ti 20 and low values of al al fe mn 035 coinciding with an increase of paleoredox proxies suggest a possible volcanic and hydrothermal source of nutrients related to late devonian and early carboniferous extensional magmatism in the rhenohercynian domain although a relationship between higher paleoproductivity and enhanced continental runoff of volcanic material cannot be excluded the studied devonian carboniferous boundary sections from the namur dinant basin gendron celles ardennes quarry reveal three levels with similar vectors of mo and u enrichments the pre crisis famennian pattern is typical for weakly restricted basins with fe mn redox cycling accompanying vertical fluctuations of the oxic anoxic chemocline close to the sediment water interface with the influence of particulate shuttle the mo ef and u ef patterns corresponding to the unrestricted or weakly restricted basin with alternating suboxic to anoxic conditions are considered to represent the transgressive hangenberg black shale event the lower tournaisian mo ef and u ef patterns fall along a vector in the direction of the strongly restricted marine conditions with prevailing suboxic conditions in the moravo silesian basin lesni lom section the pre crisis famennian mo ef and u ef vector indicates an unrestricted marine trend which converges with that of restricted systems redox conditions range from suboxic to euxinic in the tournaisian mo ef and u ef oscillate between oxic and anoxic conditions and fall along a vector of strongly restricted marine conditions increased isolation of both studied basins in the early tournaisian is regarded as a reflection of a significant eustatic fall during the hangenberg crisis linked to a severe episode of the gondwana glaciation these paleohydrographic patterns have correlative potential that should be considered for a revised devonian carboniferous boundary definition

geotechnical aspects of soil slips in alpine regions abstract slope movements are due to many different causes numerous investigations carried out during the last ten years have led to the supposition that almost all slope movements and particularly those occurring in soils are conditioned by a significant combination of factors for the alpine regions quantity duration and kind of precipitation have to be considered as direct mechanical causes combined with such contributing factors as geological and soil mechanical properties aspect vegetation slope inclination and slope morphology they will determine the type dimensions and process of slope movements the detailed investigation of 140 slope movements in slightly cohesive soils show that the process of movement is represented by sliding and flow events in particular it was found out that shallow scars with planar slides predominate so that the supposition of an infinite slope model for slope stability appears to be justified in many cases debris flows and debris avalanches continued downslope of the source area of the scars