the permian triassic transition and the onset of mesozoic sedimentation at the northwestern peri tethyan domain scale palaeogeographic maps and geodynamic implications the main aim of this paper is to review middle permian through middle triassic continental successions in european secondly areas of middle late permian sedimentation the permian triassic boundary ptb and the onset of triassic sedimentation at the scale of the westernmost peri tethyan domain are defined in order to construct palaeogeographic maps of the area and to discuss the impact of tectonics climate and sediment supply on the preservation of continental sediment at the scale of the western european peri tethyan basins the upper permian is characterised by a general progradational pattern from playa lake or floodplain to fluvial environments in the northern variscan belt domain areas of sedimentation were either isolated or connected to the large basin which was occupied by the zechstein sea in the southern variscan belt during the late permian either isolated endoreic basins occurred with palaeocurrent directions indicating local sources or basins underwent erosion and or there was no deposition these basins were not connected with the tethys ocean which could be explained by a high border formed by corsica sardinia palaeorelief and even parts of the kabilia microplate the palaeoflora and sedimentary environments suggest warm and semi arid climatic conditions at the scale of the whole study area an unconformity more or less angular is observed almost everywhere between deposits of the upper permian and triassic except in the central part of the germanic basin the sedimentation gap is more developed in the southern area where in some basins upper permian sediment does not occur the large sedimentary supply erosion and or lack of deposition during the late permian as well as the variable palaeocurrent direction pattern between themiddle late permian and the early triassic indicate a period of relief rejuvenation during the late permian during the induan all the intra belt basins were under erosion and sediment was only preserved in the extra belt domains the northern and extreme southern domains in the northern domain the central part of the germanic basin sediment was preserved under the same climatic conditions as during the latest permian whereas in the extreme southern domain it was probably preserved in the tethys ocean implying a large amount of detrital components entering themarinewaters mesozoic sedimentation began in the early olenekian the ephemeral fluvial systems indicate arid climatic conditions during this period three distinct areas of sedimentation occur a northern and southern domain separated by an intra belt domain the latter accumulated sediments during the early middle permian and experienced erosion and or no deposition conditions between the middle late permian and the beginning of mesozoic sedimentation dated as anisian to hettangian at the top of the lower triassic another tectonically induced more or less angular unconformity is observed the hardegsen unconformity which is dated as intra spathian and is especially found in the north european basins this tectonic activity created new source areas and a new fluvial style with marine influences at the distal part of the systems during the anisian and ladinian continental sedimentation was characterised by a retrogradational trend in other words the fluvial system evolved into fluvio marine environments attesting to a direct influence of the tethys ocean in the southern and northern domains both at the end of the olenekian spathian and during the anisian the presence of palaeosols micro andmacrofloras indicate less arid conditions throughout this domain

climatic control on the late permian main dolomite ca2 deposition in northern margin of the southern permian basin and implications to its internal cyclicity

neogene and quaternary history of vegetation climate and plant diversity in amazonia the neotropical amazonian and andean plant diversity developed mainly during the tertiary in amazonia miocene oral diversity seems considerably higher than today during the neogene tropical taxa entered newly created montane area and montane taxa entered the tropical lowlands the general decrease of temperature during the upper neogene and especially during the quaternary glacial periods may have caused considerable extinctions in the lowlands representation of pollen of apparently principally montane taxa podocarpus hedyosmum in miocene pliocene and quaternary sediments of amazonia and surroundings is still di cult to interpret in terms of temperature decrease at low elevation changes in precipitation may have profound impact on the composition of vegetation communities ilex and melastomataceae increase signi cantly in many glacial pollen records increase of weinmannia in amazonian pollen records seems the best indicator of downward migration of montane vegetation belts a temperature lowering at sea level of 4 5 13c during the last glacial maximum lgm seems reasonable it may have caused a downslope migration of some 700 m of the lower montane vegetation belt lower montane arboreal species may have been able to grow in higher elevation areas 500 m of amazonia increasing background pollen values of montane taxa in the area di erence between a cool and wet middle pleniglacial 60 28 ka bp and a cold and dry upper pleniglacial 28 14 ka bp thus including the lgm is evident in andean and amazonian records statements about environmental conditions of the ice age amazon should be speci ed chronologically the middle pleniglacial is a time of accumulation of uvial sediments the upper pleniglacial is a time of incision of the rivers in their sediments sedimentation started again in the lateglacial since ca 13 ka bp and the holocene when lake levels rose again based on simpli ed considerations of precipitation changes and evaporation we estimate that lgm rainfall may have been reduced by values of ca 45 10 amazonian and cordilleran lakes dried up dry rain forest was locally replaced by savanna savanna forest or cerrado type vegetation dry rain forest savanna forest and pure savanna was locally replaced by extensive semi desert dune formations lower rio branco area in present day central amazonia the present day centers of higher rainfall 2500 mm surrounded by areas of lower rainfall are refuge areas of the very wet rain forest and of the very high plant diversity 300 plant species per 0 1 ha and they should have been that equally or more during the dry climate intervals plant diversity of drier forests is in the order of 100 150 species per 0 1 ha both extinction and speciation in isolation under precipitation and temperature stress may have taken place in these refugia 2000 elsevier science ltd all rights reserved

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

nearshore euxinia in the photic zone of an ancient sea part ii the bigger picture and implications for understanding ocean anoxia abstract biomarker palaeontological and isotopic evidence suggests that the late permian carbonate seas i e the northern npb and southern spb permian basins of northern pangea were characterized by significant spatial and temporal variations in the palaeowater column redox state this is particularly the case with regard to the deposition of the lopingian zechstein cycle 2 carbonate rocks a shelf to basin reconstruction of environmental conditions was achieved by analysing nearly 400 core samples from 49 wells this allowed an evaluation of the spatial variations in facies and broad oceanographic conditions at the basin scale specifically in the lower slope and shallow basin facies of the northern margin of the spb present day northern poland and eastern germany highly variable concentrations of the green sulphur bacterial biomarkers chlorobactane and isorenieratane and their likely degradation products c 15 to c 31 2 3 6 aryl isoprenoids indicative of photic zone euxinia and homohopane indices indicative of anoxia combined with the presence of a benthic fauna and bioturbation indicate a variable but occasionally anoxic euxinic water column locally in lagoonal facies in the northern and southern margin of the spb euxinic conditions also developed but these were likely associated with localised conditions or benthic production in association with microbialites the presence of gammacerane in the eastern spb south eastern germany and eastern poland suggests elevated salinities there compatible with the restricted configuration of the basin however a lack of these signatures in basinal settings of the eastern spb indicates that strongly reducing conditions were restricted to the lower slope and shallow basin locations and restricted lagoons and were not developed in the basin centre moreover this anoxia euxinia in marginal settings is restricted to the north eastern part of the spb the south eastern part of the spb se poland in contrast is devoid of evidence for pze the southern margin of the spb is also characterized by generally oxic suboxic conditions with local anoxia limited to more restricted embayments and elevated salinities limited to restricted oxic anoxic lagoons in the western spb ne england and adjacent offshore and the npb outer moray firth offshore scotland the water columns were oxic suboxic overall it appears that high but episodic primary bioproductivity of organic matter was concentrated on or even limited to the lower slopes of the spb s north eastern margin and the restricted lagoons and shallow basin of its southern margin leading to the formation of source rocks for petroleum in these areas in addition the temporal and geographical restriction of anoxia appears to have prevented the accumulation of large and more widespread quantities of organic matter in fact toc contents exhibit a poor correlation with ecological and anoxia indicators crucially this work confirms that the strong evidence for pze observed in shelf and lower slope shallow basin facies of the north eastern spb need not be associated with widespread basin scale anoxia this conclusion has implications for organic matter burial carbon cycling and biotic crises during other times in earth history

lake deposits of moderate salinity as sensitive indicators of lake level fluctuations example from the upper rotliegend saline lake middle late permian northeast germany abstract the rotliegend saline lake periodically covered wide areas of the southern permian basin in northwest europe during the permian the sedimentology mineralogy and geochemistry of lake deposits were studied to document very high frequency lake level fluctuations and to evaluate their triggers increased precipitation and marine ingressions into the basin resulted in lake extension increased run off is documented by intercalated fluvial deposits in low salinity deposits of the lake because lake deposits reflect mainly deposition in relatively wet climate phases they are not correlatable to halite deposits in other basin areas decreased precipitation is followed by shrinkage of the lake desiccation at its margins and higher lake salinity due to concentration of the brine carbonate and anhydrite contents of lake deposits increased considerably before the areas fell dry but halite is not preserved in the study area falling lake level is also reflected by the occurrence of wave ripples reflecting decreased water depth and finally by desiccation and formation of evaporite crusts not only the mineralogical content but also the colour of lake claystones changes with varying salinity anhydrite and carbonate free red claystones were replaced by violet to green and grey anhydritic and calcareous claystone or marls with increasing salinity the amount of boron adsorbed on illite also corresponds to changes in salinity and can therefore be used as a palaeosalinity indicator rare earth element concentrations within lake deposits do not reflect variations in salinity but different palaeogeographical settings marine ingressions into the lake are neither reflected by the amount of boron adsorbed onto illite nor by rare earth element contents of the lake deposits highly saline deposits are partly characterised by intensive deformation which can be interpreted as seismites or dissolution breccias

the role of detrital anhydrite in diagenesis of aeolian sandstones upper rotliegend the netherlands implications for reservoir quality prediction the rotliegend upper permian reservoir interval in the southern permian basin spb contains low permeability streaks corresponding to anhydrite cemented intervals an integrated study was conducted using core cuttings thin sections and well log data from a gas exploration well and two geothermal wells that target the zone of interest this study aims at understanding the origin and nature of these low permeability streaks as well as their impact on reservoir properties and to establish a predictive model of their spatial distribution high resolution xrf core scanning analysis allowed to extrapolate spot observations in thin sections to the entire core diagenetic history includes grain rearrangement and anhydrite haematitic clay coatings dolomite rims quartz overgrowths kaolinite and second generation carbonates as cementing phases coupling of all data reveals the detrital origin of the anhydrite gypsum grains which were deposited together with the coarse grained sand fraction in an aeolian sandflat environment such partially or completely dissolved grains acted as local sources of anhydrite cement and as nuclei for precipitation explaining its preferential occurrence in coarsegrained laminae thick gypscretes in the vicinity likely supplied the anhydrite gypsum grains a conceptual model is proposed including the location of nearby gypscretes and the prevailing west southwest aeolian transport direction on the southern rim of the spb

marine incursions and the influence of andean tectonics on the miocene depositional history of northwestern amazonia results of a palynostratigraphic study abstract new palynological and sedimentological data permit the age of neogene sediments in northwestern amazonia to be established more precisely and indicate that major environmental changes occurred in the area during this time based on a study of borehole samples the age of the solimoes formation solimoes basin northwestern brazil is determined as miocene and five pollen zones are distinguished which are correlated with existing zonations for northern south america in addition 30 new sporomorphs are described which belong to the following 12 genera psilamonocolpites retimonocolpites retitricolpites retibrevitricolpites psilatriporites nov gen bombacacidites psilatricolporites retitricolporites rugutricolporites psilastephanoporites nov gen psilastephanocolporoties and heterocolpites a correlation is made between the brazilian wells and some of the studied outcrops in colombian and peruvian amazonia based on palynological marker species the presence of coastal elements such as mangroves zonocostites indicates that during the miocene this area was influenced by marginal marine conditions caused by several marine incursions these incursions may be related to global sea level fluctuations miocene marine phases also are known from sites elsewhere in northern south america which at present like northwestern amazonia are entirely ruled by continental conditions sediment composition shows that during the early miocene the guyana shield was the major source area of sediment input in the basins of northwestern amazonia in the interval from early to middle miocene the andes became the major sediment source area the change in provenance is related to the uplift of the eastern cordillera this event caused a major change in palaeoenvironment and palaeogeography in northwestern amazonia which was characterized by the reverse of a northwestward directed fluvial system into an eastward directed fluvial lacustrine system with an estuarine character

sequence stratigraphy of carbonate evaporite basins models and application to the upper permian zechstein of northeast england and adjoining north sea the successions of carbonate evaporite basins which are periodically cut off from the world ocean are considered in terms of their sequence stratigraphy two basin types are distinguished those where incomplete drawdown takes place and those showing complete drawdown and wholesale basin desiccation it is argued that following relative sea level falls sequences begin with the evaporites precipitated as marginal lowstand gypsum wedges in the first basin type and as lowstand basin centre halite fills in the second the evaporites pass up into carbonate sediments which are mainly deposited on shallow water platforms around the basin during transgressive and highstand systems tracts the concepts and models developed are applied to the zechstein upper permian strata of northeast england and adjoining north sea seven sequences are proposed with some containing thin parasequences the sequence approach to carbonate evaporite basins which considers both basin margin and basin centre facies gives a more encompassing perspective of sedimentation than the traditional cycle concept with its emphasis on the basin centre

grain size control of river suspended sediment geochemistry clues from amazon river depth profiles residual solid products of erosion display a wide range of size density shape mineralogy and chemical composition and are hydrodynamically sorted in large river channels during their transport we characterize the chemical and isotopic variability of river sediments of the amazon basin collected at different water depths as a function of grain size absolute chemical concentrations and sr and nd isotopic ratios greatly varies along channel depth the al si ratio tightly linked to grain size distribution systematically decreases with depth mostly reflecting dilution by quartz minerals a double normalization diagram is proposed to correct from dilution effects elements define fan shaped patterns and can be classified in three different groups with respect to hydrodynamic sorting during transport in the amazon 1 poorly sorted insoluble elements like al fe th and rees 2 well sorted insoluble elements like zr and ti mainly carried by heavy minerals and 3 alkali na to cs and alkali earth elements mg to ba for which a large variety of patterns is observed related for alkali to their variable affinity for phyllosilicates sr isotopes show that the amazon river at the mouth is stratified the madeira and solimoes derived sediments being preferentially transported near the channel surface and at depth respectively the comparison between the solimoes and madeira rivers shows how the interplay between grain sorting weathering and crustal composition controls the composition of the suspended river sediments

holocene environmental changes in the central amazon basin inferred from lago calado brazil abstract holocene environments have been reconstructed by sedimentological mineralogical geochemical and high resolution pollen analysis of a 1190 cm long core from lago calado near manaus in central amazonia the sediment core dated by eight ams radiocarbon dates has a basal age of 8330 50 14 c yr bp and documents the landscape development from a river valley before 8280 14c yr bp to a lake environment this change is related to the rise of the central amazonian water level controlled by the postglacial sea level rise pollen analytical results show the formation of a local mauritia palm swamp along the river margin between 8280 and 7700 14c yr bp at that time highly diverse terra firme unflooded upland amazon rainforest and poorly developed varzea igapo inundated forests along the river characterized the vegetation the expansion of varzea igapo forests and a strong presence of aquatic plants started at 7700 14c yr bp reflecting the rise of the amazonian water level and the formation of the lago calado the occurrence of abundant poaceae and cyperaceae pollen in the lake sediments since 7770 14c yr bp suggest both the local colonization of unflooded mud banks around the lake margin and the formation of flooding meadows open exposed unflooded mud areas periodically colonized by herbs are related to seasonal amazonian high and low water stands in respect to the abundance of poaceae pollen during the early and mid holocene these open areas must have been large suggesting brief annual high and extensive annual low amazonian water stands after 4070 14c yr bp the proportion of varzea igapo forest areas was larger than before herbs were less abundant probably due to the smaller area of unflooded mud banks the amazonian water levels must have been higher and the period of the annual high water stands was probably longer than before since 2080 14c yr bp the largest proportion of varzea igapo forests is recorded reflecting the highest amazonian water level herbs were rare suggesting that open unflooded mud areas around the lake were relatively small this may perhaps also indicate that the seasonal period of the amazonian high water level was the longest since 2080 14c yr bp the increase of cecropia poaceae and alternanthera during the last 150 yr suggests stronger human impact on the local vegetation changes to higher amazonian water levels are related to the rise of the atlantic sea level relatively short annual high water levels during the early holocene and relatively long annual high water levels since 4070 and especially since 2080 14c yr bp can be interpreted as a climate change from a drier early holocene with lower annual rainfall rates and longer dry periods until 4070 14c yr bp to a wetter late holocene

permian and triassic rifting in northwest europe the permo triassic roughly coincided with the life span of pangaea so far as europe is concerned pangaea s creation began in the early carboniferous visean when the northward drifting megacontinent gondwana began to collide with the iberian portion of the slower moving laurussia while proto tethys was subducted beneath the southern margin of central europe creation was complete by the end of the carboniferous or early in the permian with the final development of the variscan orogenic belt which trends from brittany eastward through central europe and with the addition of western siberia along the line of the ural orogen ziegler 1989 despite or perhaps because of its bulk pangaea was not a stable megacontinent no sooner had it formed than it tried to break apart again the disintegration of pangaea had already started before the end of the triassic with the westerly extension of tethys between iberia and africa though not yet underlain by oceanic crust and by early in the jurassic rifting was taking place between africa and the americas in the newly forming central atlantic ocean ziegler 1988 indeed e w extensional movements within a proto atlantic ocean possibly began as early as the late carboniferous haszeldine russell 1987 whilst mid permian extension is well documented in east greenland surlyk et al 1984 these extensional movements may have propagated southward to initiate fracturing in the viking and central grabens of the north sea along which the late permian zechstein sea was to break into the subsiding rotliegend basins and towards the central atlantic where a shallow seaway eventually developed early in the jurassic thus in the northern half of pangaea the continued existence of the former laurussia was already at risk in the permian although crustal separation in the north atlantic which possibly started in the rockall trough in the early cretaceous was finally achieved along the line of the reykjanes ridge only in the paleocene these major events on the periphery of what is now europe separately and jointly were factors that probably controlled a whole sequence of tectonic events within the continent which in turn controlled its patterns of mostly terrestrial sedimentation climatically the northward drift of laurussia had carried nw europe from a region of equatorial rain forest during the later carboniferous to the latitudes of a trade wind desert like the modern sahara in the permian the late permian basins of upper rotliegend and zechstein deposition were arid rotliegend sediments are characterized by dune sand and the saline mudstones of a semipermanent desert lake and the zechstein by shallow water carbonates and anhydrite and deeper water halite during the triassic however brackish water fluvial and lacustrine sediments occupied the basinal areas although even here halite horizons e g rrt muschelkalk and keuper in the north sea area associated with local transgressions from tethys testify that arid conditions were never far away

a multiproxy palaeoecological record of holocene lake sediments from the rio tapajos eastern amazonia abstract two sediment cores up to 42 m in length were raised from the wide deep section of the lower tapajos river amazonia referred to as lago tapajos these cores reveal a history of subtle environmental change that began with the formation of lago tapajos as sea level rose about 11 000 years ago the sediments of the lake were deposited fairly quickly at a rate of ca 4 m per millennium and are uniformly fine grained with low organic content the fossil pollen record derived from these sediments reveals that forest surrounded this site throughout the holocene the largest change in the core took place between ca 5500 and 4200 cal years bp and reflects a transition from coarser to finer sediments coincident with the change in sediment is a slight transition in the pollen spectra with an increase in poaceae abundance at the expense of the pioneer tree cecropia cecropia a tentative explanation is offered in which increased human activity possibly spurred by climatic change resulted in the formation of some local grasslands however despite the apparent actions of humans there is no indication of basin wide transformation of landscapes in this record the holocene persistence of forest as the dominant landscape matrix around lago tapajos is supported by low 13 c values and by the constant geochemistry and mineralogy of the lake sediments

sulfur cycle in buried evaporites sulfur isotopes are potent indicators of the way in which sulfur behaves chemically during diagenesis we have studied sulfur isotope ratios 34s 32s from a number of minerals and compounds across the permian triassic boundary in the khuff formation abu dhabi the 34s in dissolved marine sulfate increased by 10 from the late permian to the early triassic despite precipitation of gypsum from permian and triassic seawater and its subsequent dehydration to anhydrite at depths greater than about 1000 m the primary marine stratigraphic sulfur isotope variation has been preserved in anhydrite in the khuff formation a combination of biostratigraphic and absolute age data show that this 10 shift occurred over 2 m y gypsum dehydration to anhydrite has not involved significant isotopic fractionation or diagenetic redistribution of material in the subsurface the sulfur isotope variation across the permian triassic boundary is also present in elemental sulfur and h2s at depths greater than 4300 m formed by reaction of anhydrite with hydrocarbons via thermochemical sulfate reduction this demonstrates that sulfate reduction has not led to isotope fractionation it also demonstrates that significant mass transfer has not occurred at least in the vicinity of the permian triassic boundary even though elemental sulfur and h2s are both fluid phases at depths greater than 4300 m thus despite two major diagenetic processes that converted the sulfur in gypsum into elemental sulfur and h2s by 4300 m burial and the potentially mobile nature of some of the reaction products the primary differences in sulfur isotopes have been preserved in the rocks and fluids all reactions occurred in situ there was no significant sulfur isotope fractionation and only negligible sulfur was added subtracted or moved internally within the system

origin of polyhalite deposits in the zechstein upper permian zdrada platform northern poland polyhalite deposits in the zechstein upper permian of northern poland occur in the lower werra anhydrite in the zdrada sulphate platform the polyhalite appears to be a very early replacement of anhydrite the replacement was caused by the halite precipitating brines which contained potassium and magnesium ions the formation of polyhalite was preceded by the syndepositional anhydritization of the original gypsum deposit which has often preserved its primary textures this anhydritization on the platform and its slopes was a reaction of the precipitated gypsum in a hydrologically open evaporite basin with brines of salt basins adjacent to the sulphate platform these brines when nearly saturated with respect to halite and potassium and magnesium rich reacted with anhydrite to precipitate polyhalite along the slopes of the zdrada platform the oxygen and sulphur isotopic compositions of sulphate evaporites indicate that marine solutions were the only source of sulphate ions supplied to the zechstein basin and that anhydrite was transformed to polyhalite by reaction with marine brines more concentrated than those that precipitated precursor calcium sulphate minerals

ammonoid stratigraphy and sedimentary evolution across the permian triassic boundary in east greenland east greenland is a classical area for the study of the permian triassic transition and the succession is one of the most expanded in the world new ammonoid data from the wordie creek formation have allowed us to better reconstruct the history of the east greenland basin from semi isolated basins with an endemic fauna during latest permian earliest triassic h triviale h martini zones time to well connected open marine shelf basins during the early triassic m subdemissum o commune w decipiens and b rosenkrantzi zone times the east greenland zonation can be correlated with boreal zonations in arctic canada svalbard and northeastern asia it allows precise relative dating and correlation of important events across the permian triassic boundary the new ammonoid data indicate that deposition was continuous across the permian triassic boundary and developed as a marine mudstone mudstone contact in basinal areas of hold with hope northern and southern jameson land correlation of the ammonoid stratigraphy with the fad of hindeodus parvus which defines the base of the triassic in global stratotype section and point gssp in meishan china suggests that the hypophiceras triviale zone is to be referred to the uppermost permian whereas the h martini zone is lowermost triassic accordingly the end permian marine and terrestrial extinctions and associated isotope changes as well as the subsequent adaptive radiations in east greenland took place in latest permian time new boreal faunas and floras were well established and diversified in the hypophiceras triviale zone prior to the beginning of the triassic and the permian triassic boundary in its present definition is no longer reflecting major changes in the earth system it would have been fortunate if a gssp were defined in a protracted section at a point of major environmental perturbations marked by isotope excursions chemical anomalies and mass extinction rather than in the strongly condensed section like meishan at a point which post dates all significant events

sequence stratigraphy and cyclic development of basal zechstein carbonate evaporite deposits with emphasis on zechstein 2 off platform carbonates upper permian northeast germany abstract although the basal zechstein is classically subdivided into two cycles z1 and z2 lower part it can alternatively be subdivided into three complete third order depositional sequences zs1 zs3 and the associated lowstand systems tract transgressive systems tract of a fourth sequence zs4 third and higher order sea level fluctuations influenced the depositional and diagenetic history of the carbonate evaporite alternations within the basal zechstein the main subject of the present study the zechstein 2 carbonate stassfurt carbonate or ca2 is interpreted to encompass both transgressive predominantly in slope and basinal settings and highstand systems tracts of zechstein sequence zs3 as well as part of the lowstand systems tract of the fourth zechstein sequence zs4 in northeastern germany hydrocarbon reservoirs of the ca2 developed along both northern and southern margins of the southern permian basin on top of the topography of the zechstein 1 cycle z1 this z1 topography resulted from deposition of the werra anhydrite a1 the highstand systems tract of the second zechstein sequence zs2 the northern ca2 carbonate platform is consistently narrow and fringed by coated grain and composite grain bars and shoals it is characterized by a steep fault controlled slope which precluded the formation of in situ shallow water grain dominated carbonates during relative sea level lowstands displaced shallow water coated grain and composite grain packstones wackestones may however occur as slope fan deposits turbidites in contrast the southern carbonate platform is wide tectonically dissected and fringed by grain dominated shallow water carbonates coated grain and composite grain bars and shoals zechstein 2 shallow water carbonates detectable by basal zechstein seismic anomalies also developed on pre existing topographical highs in off platform positions three depositional cycles ca2 cycles i ii and iii most probably reflecting high amplitude fourth order sea level fluctuations can be identified within the stassfurt carbonate our observations suggest that sea level variations possibly reflecting cyclicity in the milankovitch frequency band 0 1 0 4 ma and the pre zechstein topography pronounced during formation of the werra anhydrite were the most important factors in controlling the depositional as well as the diagenetic history of the zechstein 2 carbonate in off platform positions

holocene environmental changes from the rio curua record in the caxiuana region eastern amazon basin abstract holocene environments have been reconstructed by multiproxy studies of an 850 cm long core from rio curua dating to 8000 14 c yr b p the low energy river lies in the eastern amazon rain forest in the caxiuana national forest reserve 350 km west of belem in northern brazil sedimentological mineralogical and geochemical dates demonstrate that the deposits correspond to two different environments sediments of an active river before 8000 14 c yr b p and later a passive river system the pollen analytical results indicate four different local and regional holocene paleoenvironmental periods 1 a transition to a passive fluvial system and a well drained terra firme unflooded upland amazon rain forest with very limited development of inundated forests varzea and igapo 7990 7030 14 c yr b p 2 a sluggish river with a local mauritia palm swamp and similar regional vegetation as before 7030 5970 14 c yr b p 3 a passive river forming shallow lake conditions and with still abundant terra firme forest in the study region 5970 2470 14 c yr b p and 4 a blocked river with high water levels and marked increase of inundated forests during the last 2470 14 c yr b p increased charcoal during this last period suggests the first strong presence of humans in this region the atlantic sea level rise was probably the major factor in paleoenvironmental changes but high water stands might also be due to greater annual rainfall during the late holocene

depositional environment and organic geochemistry of the upper permian ravnefjeld formation source rock in east greenland the upper permian ravnefjeld formation in east greenland is composed of shales that laterally pass into carbonate buildups and platforms of the wegener halvo formation the ravnefjeld formation is subdivided into five units that can be traced throughout the upper permian depositional basin two of the units are laminated and organic rich and were deposited under anoxic conditions they are considered good to excellent source rocks for liquid hydrocarbons with initial average toc total organic carbon values between 4 and 5 and hi hydrogen index between 300 and 400 the cumulative source rock thickness is between 15 and 20 m the source rocks are separated and enclosed by three units of bioturbated siltstone with a toc of less than 0 5 and an hi of less than 100 the e siltstones were deposited under relatively oxic conditions the organic geochemistry of the source rocks is typical for marine source rocks with some features normally associated with carbonate evaporite environments low pr ph pristane phytane low cpi carbon preference index distribution of tricyclic and pentacyclic terpanes the establishment of anoxic conditions and subsequent source rock deposition was controlled by eustatic sea level changes the subenvironment paleogeographic setting influx of carbonate material water depth salinity has some influence on a number of bulk parameters toc hi relations toc ts total sulfur relations and in particular biomarker parameters such as pr ph and terpane ratios all the basal shales or shales in the vicinity of carbonate buildups or platforms are characterized by low pr ph high c23 tricyclic terpanes and high c35 and c33 hopanes

87sr 86sr record of permian seawater abstract a population of 169 permian articulate brachiopod shells was analysed for their 87 sr 86 sr ratios 51 of these characterised as well preserved and stratigraphically well defined are utilized for delineation of the permian seawater strontium isotope trend the 87 sr 86 sr curve shows values of about 0 7080 in the lowermost permian asselian followed by a gradual decline to 0 70685 in the capitanian and a minor rise in the dzhulfian and lower dorashamian to values of 0 70715 just below the permian triassic boundary the early permian decrease in the strontium isotope curve that commences in the early sakmarian is coincident with the advancing deglaciation of the gondwana and with the increased aridity in large parts of the pangaea these factors may have led to a reduced continental weathering of rb rich silicate rocks and thus to the decline in seawater 87 sr 86 sr starting with the artinskian the opening of the neotethys and the associated widespread basaltic volcanism supplied low radiogenic strontium to seawater from an enhanced hydrothermal flux in the capitanian basaltic volcanism in the entire palaeotethys ceased and this may have been the reason for a slightly more radiogenic seawater isotopic composition during the lopingian higher input of riverine sr due to expansion of humid areas may have been a contributory factor

late permian non marine marine transitional profiles in the central southern permian basin northern germany the transition from rotliegend to zechstein within the southern permian basin is one from continental desert to a marine environment during the upper rotliegend ii a huge playa lake existed there this lake was temporarily influenced by precursors of the zechstein transgression therefore the mega playa evolved into a sabkha system one of these early marine ingressions is known from an outcrop in schleswig holstein laminated silt and claystones deposited within a standing water body are intercalated in siltstones of a salt flat environment the lake sediments are characterised by high frequency cyclicity shown by the sedimentary record and also by palaeontological data the section contains fresh water as well as brackish marine and marine fauna climatically forced cycles interact with marine incursions after the zechstein transgression had flooded the basin completely sedimentation was controlled by sea level fluctuations two sections in the southern north sea and in schleswig holstein are presented in this paper cyclicities with different frequencies controlled the sedimentation of the kupferschiefer t1 and the werra carbonate ca1 sediments of the north sea sequence were deposited within a shallow bay at the margin of an elevation therefore the high frequency cyclicity became obvious within the sedimentary patterns and in the faunal content

forest changes in the amazon basin during the last glacial maximum we report here the discovery of forest beds in the amazon basin radiocarbon dated to the wisconsin wurm glaciation these are the first dates from the last glaciation determined on amazonian samples the locality is in ecuador at 1 100 m elevation near the upper limit of the present amazonian rainforest both pollen spectra and podocarpus wood in the deposits suggest that vegetation comparable to the present andean forest grew at least 700 m lower than it does now suggesting a temperature depression of at least 4 5 c for the amazon lowlands

problems of a late palaeozoic glaciation in australia and subsequent climate in the permian the most recent information suggests two periods of glaciation separated by a considerable time interval the first is found in the namurian early carboniferous and may extend into the beginning of the late carboniferous evidence for the carboniferous glaciation is largely or entirely redeposited striated clasts known only from the new england area of northeastern new south wales these are considered to represent montane type glaciation associated with a developing alpine chain after a long interval glacial deposits are then found in many parts of australia in the asselian the lowest stage of the permian and the glaciation may extend into the beginning of the sakmarian the following stage in western australia a number of major fluctuations are recorded in the asselian the end of the glaciation seems to be associated with a worldwide eustatic rise in sea level in the tastubian the lower stage of the sakmarian after the tastubian no direct verifiable evidence indicates glaciation in the permian in australia or any other part of the world in australia there is no clear evidence on the climate in the interval between the two glacial periods but in south america and other parts of the world a warm interval is reported at this time most of the glacial debris is now found in sedimentary basins which were developing contemporaneously with the glaciation and is of a wet based type glaciers were active on steep hinterland carrying debris in adjacent water covered basins but how far the ice may have spread over lower lying land areas in not clear there is no real evidence of a thick dry based ice sheet like that of present antarctica after the tastubian there are a number of major fluctuations in climate during the rest of the permian at times seasonal ice and or perhaps icebergs may have been active but fluctuations which were cool or warm temperate or in some places in australia even subtropical or tropical are found in the sterlitamakian upper sakmarian beginning and end of the baighenzhinian upper artinskian kungurian kazanian and dzhulfian all separated probably by colder and in some cases considerably colder periods comparison of the marine faunas of the carboniferous and permian suggests that the levipustula fauna may not represent as cold sea water as the eurydesma fauna

the isotopic composition of strontium and sulfur in seawater of late permian zechstein age abstract the paleozoic minima of 87 sr 86 sr ratios and 34 s values in seawater are observed in anhydrite layers of the stassfurt a 2 and aller a 4 cycles of evaporation of late permian age in germany these minima were probably caused by extremely low rates of continental runoff and bacterial sulfate reduction thereafter conditions changed suddenly with a steeply increasing supply of radiogenic sr and of nutrients into seawater the latter induced a large growth in the production of organic material in bacterial activity in sediments and in the flow of isotopically heavy sulfur back into the oceans this large change in the cycles of s and sr as well as of c and o within the relatively short zechstein period 2 5 ma reflects a considerable modification of the plate tectonic and environmental conditions shortly before the beginning of the mesozoic era the ochoan deposition in the usa is probably of the same age as the stassfurt leine evaporation in w europe

early triassic conchostracans crustacea branchiopoda from the terrestrial permian triassic boundary sections in the moscow syncline abstract the permian triassic boundary marks the greatest mass extinction in earth s history in order to understand the real causes of this severe extinction event multidisciplinary investigations around the globe are required here the terrestrial permian triassic boundary sections in the vladimir region central russia were sampled bed by bed for conchostracan study in the early triassic intervals the following taxa were recognized for the first time cornia germari beyrich 1857 euestheria gutta lutkevitch 1937 magniestheria mangaliensis jones 1862 palaeolimnadiopsis vilujensis varentsov 1955 and rossolimnadiopsis novozhilov 1958 the wide distribution of c germari demonstrates their high value for biostratigraphy since this species was also reported from the lower buntsandstein subgroup in the germanic basin as well as from early triassic deposits in hungary greenland and siberia the assumption of an early triassic age of the studied sections is also supported by associated tupilakosaurus bone fragments which point to the tupilakosaurus wetlugensis zone in the earliest triassic

tree ring analysis elucidating palaeo environmental effects captured in an in situ fossil forest the last 80 years within an early permian ecosystem abstract the early permian chemnitz fossil lagerstatte leukersdorf formation chemnitz basin se germany represents a diverse t 0 assemblage of a fossil forest ecosystem around the sakmarian artinskian transition 290 6 1 8 ma which was preserved by pyroclastic deposits of a multi phased volcanic eruption the multi aged plant community consists of predominantly hygrophilous elements which grew on an alluvial plain mineral substrate under sub humid conditions representing a wet spot environment strong seasonality triggered the formation of annual tree rings in arborescent woody plants such as pycnoxylic gymnosperms medullosan seed ferns and calamitaleans from several hundred fossil trees the 53 best preserved specimens were selected and investigated in detail by measuring 2 081 tree rings in individual sequences of up to 77 rings ring sequences were analysed by standard dendrochronological methods to determine both annual growth rates and mean sensitivity morphological and statistical analyses on single tree rings reveal different tree ring types according to the different plant groups pycnoxylic gymnosperms have distinct and regular tree rings whereas medullosan seed ferns and calamitaleans show indistinct and regular tree rings as well as so called event rings results reveal differences between plant groups regarding their physiological reactions or adaptations to seasonal fluctuations in comparison to pycnoxylic gymnosperms both medullosan seed ferns and calamitaleans exhibit reduced growth rates and more sensitive reaction to environmental perturbances as water deficiency pointing to comparably lower adaptation to seasonally dry palaeoclimate in this context event rings are in many cases traced back to plant physiological stress during particularly severe drought periods altogether these fossil trees serve as sensitive environmental archives which shed light on growth conditions several decades back in time from the entombing eruption

marine ingressions into the middle late permian saline lake of the southern permian basin rotliegend northern germany possibly linked to sea level highstands in the arctic rift system abstract a huge saline lake existed in the southern permian basin spb of northwest europe during late wordian to early wuchiapingian more than 2500 m thick continental siliciclastics and evaporites of the upper rotliegend ii were deposited before the marine zechstein transgression flooded the basin marine deposition took place in the arctic rift system between east greenland and the fennoscandian shield at that time interval sediments of the foldvik creek group reflect relative sea level fluctuations short termed pre zechstein ingressions from the boreal realm into the spb are known by the marine lamellibranch liebea reichei however sedimentological analysis of different saline lake horizons show that the marine influenced saline lake horizon does not differ lithologically from other saline lake claystone layers in the rotliegend succession the 87 sr 86 sr ratios of anhydrite 0 7089 0 7100 reflect deposition in a continental setting in contrast to this s isotopic values more than 11 7 cdt reflect marine pre zechstein ingressions into the spb in the middle niendorf and munster members s isotopic values of anhydrite can be used as an indicator for marine influence in the spb the pre zechstein ingressions superimpose the climatic triggered lake level fluctuations of the rotliegend saline lake two marine ingressions can be integrated into a set of regularly recurring abnormities in the depositional evolution these important evolutionary steps the saline lake formation the garlstorf ingression the p ameland and bahnsen lake level highstands the niendorf ingression and the zechstein transgression show a periodicity of more or less 1 ma one million year cyclicity is also known from deposits of the arctic rift system in east greenland wegener halvo and ravnefjeld formations a correlation of the upper rotliegend ii deposits with the succession of east greenland is proposed based on the assumption that the marine ingressions as well as the exceptionally intensive saline lake expansions could be linked to sea level highstands in the arctic rift system the result is the first correlation of upper rotliegend ii deposits with marine strata

modern pollen rain characteristics of tall terra firme moist evergreen forest southern amazonia the paucity of modern pollen rain data from amazonia constitutes a significant barrier to understanding the late quaternary vegetation history of this globally important tropical forest region here we present the first modern pollen rain data for tall terra firme moist evergreen amazon forest collected between 1999 and 2001 from artificial pollen traps within a 500 x 20 m permanent study plot 14 degrees 34 50 s 60 degrees 49 48 w in noel kempff mercado national park ne bolivia spearman s rank correlations were performed to assess the extent of spatial and inter annual variability in the pollen rain whilst statistically distinctive taxa were identified using principal components analysis pca comparisons with the floristic and basal area data of the plot stems 10 cm d b h enabled the degree to which taxa are over under represented in the pollen rain to be assessed using r rel values moraceae urticaceae dominates the pollen rain 64 median abundance and is also an important constituent of the vegetation accounting for 16 of stems 10 cm d b h and ca 11 of the total basal area other important pollen taxa are arecaceae cf euterpe melastomataceae combretaceae cecropia didymopanax celtis and alchornea however 75 of stems and 67 of the total basal area of the plot 10 em d b h belong to species which are unidentified in the pollen rain the most important of which are phenakospermum guianensis a banana like herb and the key canopy emergent trees erisma uncinatum and qualea paraensis

origin transport and deposition of leaf wax biomarkers in the amazon basin and the adjacent atlantic paleoenvironmental studies based on terrigenous biomarker proxies from sediment cores collected close to the mouth of large river systems rely on a proper understanding of the processes controlling origin transport and deposition of biomarkers here we contribute to the understanding of these processes by analyzing long chain n alkanes from the amazon river system we use the dd composition of long chain n alkanes from river bed sediments from the amazon river and its major tributaries as well as marine core top samples collected off northeastern south america as tracers for different source areas the d13c composition of the same compounds is used to differentiate between long chain n alkanes from modern forest vegetation and petrogenic organic matter our d13c results show depleted d13c values 33 to 36 in most samples indicating a modern forest source for most of the samples enriched values 31 to 33 are only found in a few samples poor in organic carbon indicating minor contributions from a fossil petrogenic source long chain n alkane dd analyses show more depleted values for the western tributaries the madeira and solimoes rivers 152 to 168 while n alkanes from the lowland tributaries the negro xingu and tocantins rivers 142 to 154 yield more enriched values the n alkane dd values thus reflect the mean annual isotopic composition of precipitation which is most deuterium depleted in the western amazon basin and more enriched in the eastern sector of the basin samples from the amazon estuary show a mixed long chain n alkane dd signal from both eastern lowland and western tributaries marine core top samples underlying the amazon freshwater plume yield dd values similar to those from the amazon estuary while core top samples from outside the plume showed more enriched values although the variability in the river bed data precludes quantitative assessment of relative contributions our results indicate that long chain n alkanes from the amazon estuary and plume represent an integrated signal of different regions of the onshore basin our results also imply that n alkanes are not extensively remineralized during transport and that the signal at the amazon estuary and plume includes refractory compounds derived from the western sector of the basin these findings will aid in the interpretation of plant wax based records of marine sediment cores collected from the adjacent ocean

the capitanian guadalupian middle permian mass extinction in nw pangea borup fiord arctic canada a global crisis driven by volcanism and anoxia until recently the biotic crisis that occurred within the capitanian stage middle permian ca 262 ma was known only from equatorial tethyan latitudes and its global extent was poorly resolved the discovery of a boreal capitanian crisis in spitsbergen with losses of similar magnitude to those in low latitudes indicated that the event was geographically widespread but further non tethyan records are needed to confirm this as a true mass extinction the cause of this crisis is similarly controversial whilst the temporal coincidence of the extinction and the onset of volcanism in the emeishan large igneous province in china provides a clear link between those phenomena the proximal kill mechanism is unclear here we present an integrated fossil pyrite framboid and geochemical study of the middle to late permian of the sverdrup basin at borup fiord ellesmere island arctic canada as in spitsbergen the capitanian extinction is recorded by brachiopods in a chert limestone succession 30 40 m below the permian triassic boundary the extinction level sees elevated concentrations of redox sensitive trace metals mo v u mn and contemporary pyrite framboid populations are dominated by small individuals suggestive of a causal role for anoxia in the wider boreal crisis mercury concentrations a proxy for volcanism are generally low throughout the succession but are elevated at the extinction level and this spike withstands normalization to total organic carbon total sulfur and aluminum we suggest this is the smoking gun of eruptions in the distant emeishan large igneous province which drove high latitude anoxia via global warming although the global capitanian extinction might have had different regional mechanisms like the more famous extinction at the end of the permian each had its roots in large igneous province volcanism

channel floodplain geomorphology along the solimoes amazon river brazil across the cratonic landscape of brazil the solimoes amazon river transports to its delta plain 1240 mt of suspended sediment derived from andean erosion and reworks another 3200 mt of floodplain sediments distribution of these sediments has resulted in a variable along stream pattern of geomorphology the upstream reaches are characterized by sediment erosion in the main channel and deposition in floodplain channels that are an order of magnitude smaller in discharge than the main channel sediment deposition in and migration of the floodplain channels erases oxbow lakes of the main channel and yields an intricate scroll bar topography that forms the boundaries of hundreds of long narrow lakes in contrast downstream reaches are characterized by channels restricted by stabilizing long term levee building and floodplain construction dominated by overbank deposition overbank deposition buries the scroll bar topography resulting in a flat floodplain covered by a patchwork of large more equant shallow lakes on the basis of estimated rates of recycling of floodplain sediments the modern floodplain of the brazilian amazon could have been recycled in 5000 yr and is recycled more rapidly in the upstream than the downstream reaches the cratonic interior is interrupted by structural arches that bound intracratonic basins four of these arches cross the valley of the main river system at intervals of several hundred kilometres and impart a tectonic imprint on the channel floodplain geomorphology at this spatial scale structural arches appear to exert a primary influence by promoting entrenchment of the river as it passes through zones of deformation thus restricting channel movement for example as the river crosses the purus arch the valley narrows to 20 km compared to an average of 45 km the water surface gradient decreases sediment is deposited and yet the rate of channel migration is negligible hence the effect of the arches is to create a landscape where on the spatial scale of hundreds of kilometres the river is confined and entrenched in its valley is straight and is relatively immobile local valley tilting apparently unrelated to the arch structures also imprints the geomorphology in particular a tilted valley in the upstream reaches appears to have caused avulsions which have left behind the only large scale oxbow type features on the brazilian amazon river floodplain

river tributaries as sediment sinks processes operating where the tapajos and xingu rivers meet the amazon tidal river the amazon river is the largest fluvial source of freshwater and sediment to the global ocean and has the longest tidally influenced reach in the world two major rivers the tapajos and xingu enter the amazon along its tidal reach however unlike most fluvial confluences these are not one way conduits through which water and sediment flow downstream toward the sea the drowned river valleys rias at the confluences of the tapajos and xingu with the amazon river experience water level fluctuations associated not only with the seasonal rise and fall of the river network but also with semidiurnal tides that propagate as far as 800 km up the amazon river superimposed seasonal and tidal forcing distinct sediment and temperature signatures of amazon and tributary waters and antecedent geomorphology combine to create mainstem tributary confluences that act as sediment traps rather than sources of sediment hydrodynamic measurements are combined with data from sediment cores to determine the distribution of tributary derived and amazon derived sediment within the ria basins characterize the sediment transport mechanisms within the confluence areas and estimate rates of sediment accumulation within both rias the tapajos and xingu ria basins trap the majority of the sediment carried by the tributaries themselves in addition to ca 20 mt yr 1 of sediment sourced from the amazon river these findings have implications for the interpretation of stratigraphy associated with incised valley systems such as those that dominated the transfer of sediment to the oceans during lowstands in sea level this article is protected by copyright all rights reserved

long range high resolution stratigraphic correlation of rotliegend fluvial fan deposits in the central dutch offshore abstract the rotliegend feather edge area in the central part of the endorheic southern permian basin in the dutch offshore is characterized by a predominance of mud prone evaporite bearing playa and lake deposits with a subordinate amount of interbedded thin fluvial sheet sandstones the distribution and lateral facies changes of the sandstone bodies have been analyzed by generating a long range high resolution chronostratigraphic correlation framework the correlation technique of pattern matching of gr logs was applied supported by calculating spectral trend curves flooding events are the primary near synchronous correlation surfaces which can be traced up to and over 100 km the basin setting of the southern permian basin the studied sandstone depositional architecture logs and sedimentary characteristics core are analogous to the depositional setting of laterally amalgamated terminal lobes of dryland river systems in an endorheic basin such as the holocene altiplano basin in bolivia present day lake eyre australia and the miocene ebro basin spain the integrated approach has yielded a stratigraphic reservoir architecture framework in which the reservoir sandstones with net sand up to 10 m have been identified as amalgamated terminal splay sandstone sheets formed at the end of dryland river pathways alternating with lacustrine mudstone layers deposited during short duration high magnitude flooding in intermittent wet climate periods

palaeoclimatic and site specific conditions in the early permian fossil forest of chemnitz sedimentological geochemical and palaeobotanical evidence abstract as significant indicators of deep time palaeoclimate a number of new palaeontological pedological and geochemical characteristics are provided for the chemnitz fossil lagerstatte to depict more precisely its environmental conditions for the first time several lines of evidence indicate that this fossil forest instantaneously preserved by volcanic deposits once received an annual precipitation of around 800 1100 mm but grew on a nearly unweathered palaeosol although the composition of this rich and diverse t0 assemblage suggests a hygrophilous dense and multi aged vegetation dominated by conservative lineages the habitat was affected by environmental disturbances and pronounced seasonality repeated changes in local moisture availability are suggested by geochemical proxies the co occurrence to intergrowth of calcic and ferric glaebules in the palaeosol and developmental traits of perennial vegetational elements specific substrate adaptation is reflected by different root systems and cyclic growth interruptions recorded in the stems branches and roots of long lived woody plants many differentially adapted terrestrial animals complete the more comprehensive reconstruction of a late sakmarian ecosystem and its climatic and preservational controls albeit spatially confined this diverse in situ record may contribute to understand wetland dryland dynamics of sub tropical northern hemisphere pangaea

deglaciation sequences in the permo carboniferous karoo and kalahari basins of southern africa a tool in the analysis of cyclic glaciomarine basin fills the late westphalian to artinskian glaciomarine deposits of the karoo and kalahari basins of southern africa consist of massive and stratified diamictite mudrock with ice rafted material sandstone silty rhythmite shale and subordinate conglomerate forming a cyclic succession recognizable across both basins a complete cycle comprises a resistant basal unit of apparently massive diamictite overlain by softer bedded stratified diamictite sandstone and mudrock with a total thickness of as much as 350 m four major cycles are observed each separated by bounding surfaces lateral facies changes are present in some cycles the massive diamictites formed as aprons and fans in front of the ice grounding line whereas the stratified diamictites represent more distal debris flow fans the sandstones originated in different environments as turbidite sands small subaqueous outwash channel sands and delta front sands the rhythmites and mudrock represent blanket deposits derived from turbid meltwater plumes cycles represent deglaciation sequences which formed during ice retreat phases caused by eustatic changes in the karoo and kalahari basins evidence for shorter term fluctuation of the ice margin is present within the major advance retreat cycles hardly any sediment was deposited during lowstand ice sheet expansion whereas a deglaciation sequence was laid down during a sea level rise and ice margin retreat with the volume of meltwater and sediment input depending on temporary stillstands of the ice margin during the retreat phase the duration of the cycles is between 9 and 11 ma suggesting major global tectono eustatic events smaller cycles probably linked to orbital forcing were superimposed on the longer term events a sequence stratigraphic approach using the stacking of deglaciation sequences with the ice margin advance phases forming bounding surfaces can be a tool in the framework analysis of ancient glaciomarine basin fills

conchostracans in continental deposits of the zechstein buntsandstein transition in central germany taxonomy and biostratigraphic implications for the position of the permian triassic boundary within the zechstein group abstract the end permian mass extinction marks the largest biotic crisis in the geologic record the stratigraphic position of this boundary in continental deposits is still under discussion in the present study conchostracans from the zechstein buntsandstein late permian to early triassic transition in central germany have been taxonomically reinvestigated in order to better understand their utility for fine scale biostratigraphy in continental permian triassic boundary sections the studied material was obtained from both collections and recent sampling activities in classical key sections and new outcrops of the zechstein and buntsandstein groups the sedimentary environments of the conchostracan occurrences are interpreted as lacustrine to fluvial facies depending on the paleogeographic position within the basin of the respective sections the conchostracan fauna in the zechstein buntsandstein transition consists of euestheria gutta palaeolimnadiopsis vilujensis cornia germari estheriella marginostriata estheriella costata estheriella nodosocostata magniestheria mangaliensis and euestheria nordvikensis based on comparison with the early triassic conchostracan record in the moscow syncline the palaeolimnadiopsis vilujensis euestheria gutta association in the upper part of the fulda formation indicates both its early triassic age and a position of the continental permian triassic boundary within the zechstein group

clay mineral composition of river sediments in the amazon basin abstract clay minerals are important in evaluating the maturity of suspended sediments weathering intensity and source area however there are processes that can change the mineral assemblage such as river transportation deposition remobilization and tributary inputs in terms of water discharge and sediment yield the amazon is one of the largest rivers in the world most of the suspended sediments come from the andes crossing the lowlands before reaching the ocean this study measures the spatial distribution of clay mineral assemblages over the entire amazon basin the results obtained show the main features of the amazon river main stem and larger tributaries from their sources to their confluence clay mineral composition highlights the evolution of the madeira and maranon solimoes river which start in the andes with high illite chlorite content downstream smectite contents increase moreover all shield tributaries show high kaolinite content the lower amazon river is characterized by relative high smectite content different from the andean sources the clay mineral results show that suspended sediments of the amazon river have three main sources 1 the andes mountains 2 the amazon shields and 3 the piedmont basins especially the pastaza alluvial megafan and the fitzcarrald arch basin lateral bank erosion plays also a significant role by the introduction of more mature sediments into the river enriched in smectite

the structural evolution of the northern viking graben and its bearing upon extensional modes of basin formation recent advances in the understanding of rift basin formation coupled with the increasing public availability of seismic and well data across the northern viking graben 60 61 n have enabled a detailed analysis of its development two rifting episodes can be recognized late permian early triassic and bathonian ryazanian major regional unconformities thought to be primarily tectonic rather than eustatic in origin separate and subdivide the rifting episodes the earlier episode involved extension about a n s axis ensuing triassic mid jurassic thermal subsidence was accommodated on steep faults during the later episode a new ne sw fault trend was superimposed on pre existing patterns major block rotation marking active rifting ceased at the end of the ryazanian during the second post rift episode there was a progressive migration of active faulting towards the basin margins and as a result a widening with time of the area undergoing subsidence asymmetric subsidence of the central part of the basin was hinged at the western margin of the horda platform and accommodated to the nw on major faults within the tampen spur factors for the second rifting episode were calculated both by relating subsidence to extension and by measuring observed extension values calculated by both methods increase consistently towards the basin axis for both rifting and thermal subsidence phases but are greater for the latter phase subsidence patterns are similar for both rifting and thermal subsidence episodes so that there is vertical stacking of relatively thick sequences in the axis of the northern viking graben these factors preclude the application of models involving uniform and non uniform stretching and also preclude oblique extension depth dependent stretching is preferred

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

an abrupt extinction in the middle permian capitanian of the boreal realm spitsbergen and its link to anoxia and acidification the controversial capitanian middle permian 262 ma extinction event is only known from equatorial latitudes and consequently its global extent is poorly resolved we demonstrate that there were two severe extinctions amongst brachiopods in northern boreal latitudes spitsbergen in the middle to late permian separated by a recovery phase new age dating of the spitsbergen strata belonging to the kapp starostin formation using strontium isotopes and d 13 c trends and comparison with better dated sections in greenland suggests that the first crisis occurred in the capitanian this age assignment indicates that this middle permian extinction is manifested at higher latitudes redox proxies pyrite framboids and trace metals show that the boreal crisis coincided with an intensification of oxygen depletion implicating anoxia in the extinction scenario the widespread and near total loss of carbonates across the boreal realm also suggests a role for acidification in the crisis the recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors and an increased mollusk dominance resulting in an assemblage reminiscent of younger mesozoic assemblages the subsequent end permian mass extinction terminated this late permian radiation

late quaternary vegetation and climate change in the amazon basin based on a 50 000 year pollen record from the amazon fan odp site 932 hemipelagic sediments from the amazon deep sea fan odp site 932 5 12 7 n 47 1 8 w and continental shelf provide a 50 000 yr long pollen record of amazon basin vegetation the age model for hole 932a is constrained by eight magnetic remanence intensity features one paleomagnetic excursion and three ams14c dates alchornea melastomataceae myrtaceae and moraceae urticaceae are dominant taxa in the pollen record between 40 200 and 19 800 cal yr b p andean taxa such aspodocarpusandhedyosmum increase in abundance between 19 800 and 11 000 cal yr b p and prior to 40 200 cal yr b p the holocene pollen assemblage derived from amazon river and continental shelf sediments is dominated by secondary growth taxa such ascecropia climatic factors influencing the development of glacial and interglacial tropical vegetation are considered by comparing marine with terrestrial records of vegetation change this comparison shows that the amazon basin forests were not extensively replaced by savanna vegetation during the glacial period contradicting the refugia hypothesis

late pleistocene temperature depression and vegetation change in ecuadorian amazonia abstract paleoecological pollen phytolith and wood analyses of sediments radiocarbon dated 33 000 to 26 000 yr b p from two sites in ecuadorian amazonia provide data that suggest a cooling of ca 7 5 c below present in equatorial lowlands from 33 000 to 30 000 yr b p a period of warning followed in which novel species assemblages a blend of montane and lowland floral components persisted for at least 4000 years these data of forest community change from sites lying within the postulated glacial rain forest napo refugium provide the strongest paleoecological refutation of the refugial hypothesis yet obtained the large temperature depression at ca 30 000 yr b p allows the possibility that if maximum cooling at the equator was synchronous with the last glacial maximum lgm of the northern hemisphere freezing temperatures would have been experienced in parts of lowland amazonia between 25 000 and 18 000 b p

sedimentology and palynofacies of the zechstein 2 carbonate upper permian northwest germany implications for sequence stratigraphic subdivision abstract the zechstein 2 carbonate stassfurt carbonate or ca2 of the second zechstein cycle has been subdivided into third order and higher order sequences using sedimentology and palynofacies analysis as complementary tools this combination of tools provides a logical approach to the correlation of parasequences across different depositional settings in a platform to basin transect the ca2 reservoir overlies the anhydrites of the first zechstein cycle z12 the werra anhydrite a12 and is sealed by the anhydrites of the second zechstein cycle z2 the basal anhydrite a2 the ca2 can be subdivided into platform upper slope middle slope lower slope and basinal facies these facies can be further subdivided into a total of twenty six subfacies types the ca2 comprises a nearly complete third order sequence zs3 and part of the lowstand systems tract of the fourth zechstein sequence zs4 it can be further subdivided into seven parasequences identified by subfacies succession gamma ray log response and palynofacies interpretation indicating higher order intra ca2 relative sea level fluctuations sea level fluctuations at third order and higher order scale are reflected by cyclic changes in palynomaceral assemblages transgressive deposits including the maximum flooding surface are characterized by a high proportion of vitrinitic and inertinitic frequently blade shaped palynomacerals whereas various types of degraded palynomacerals occur most frequently during lowstand and highstand progradation phases intertidal carbonates at the base of the ca2 third order lowstand wedge are particularly distinct due to the abundance of palynomorphs resembling colonial green algae plaesiodictyon spp the proposed chronostratigraphic subdivision of the ca2 into third and high order sequences improves the prediction of lateral and vertical reservoir facies distribution

fluid rock interactions in a geothermal rotliegend permo carboniferous reservoir north german basin abstract comprehensive data on the chemical composition of reservoir rocks and geothermal brines from the geothermal well doublet gro schonebeck north german basin drilled into a rotliegend sedimentary and permo carboniferous volcanic rock reservoir were sampled over the past years they were characterized with respect to their major and minor elemental composition including various isotope ratios the study considered the impact of drilling and reservoir operations on fluid composition and aimed at determining fluid rock interactions to gain information on fluid origin and hydraulic pathways the highly saline fluids up to 265 g l tds show 18 o and d of water 2 7 5 6 and 3 1 15 respectively as well as 34 s of sulfate 3 6 5 and 87 sr 86 sr ratios 0 715 0 716 that resemble rotliegend brines from an area located around 200 km in the west the altmark halogen ratios indicated that brines developed predominantly by evaporation of meteoric water primary brine together with halite dissolution brine secondary brine indication for mixing with zechstein brine or with younger meteoric water was not found no geochemical distinction was possible between fluids deriving from different rock formations dacites or sedimentary rocks respectively this is due to the evolution of the sediments from the effusive rocks resulting in a similar mineralogical and chemical composition and due to a hydraulic connectivity between the two types of rock this connection existed probably already before reservoir stimulation as indicated by a set of faults identified in the area that could connect the rotliegend formation with both the volcanic rocks and the lower units of the zechstein additional geochemical indication for a hydraulic connectivity is given by 1 the very high heavy metal contents mainly cu and pb in fluids and scaling that derive from the volcanic rocks and were that were also found in increased amounts up at the zechstein border kupferschiefer formation 2 the 87 sr 86 sr isotope ratios of fluid samples correspond to the ratios determined for the sedimentary rocks indicating that initially the fluids developed in the sedimentary rocks and circulated later when faults structures were created by tectonic events into the volcanic rocks

suspended sediments of the modern amazon and orinoco rivers abstract the amazon and orinoco rivers are massive transcontinental conveyance systems for suspended sediment they derive about 90 of their sediment from the andes that support their western headwaters transport it for thousands of kilometers across the breadth of the continent and deposit it in the coastal zones of the atlantic at their points of maximum suspended sediment discharge the amazon transports an average of 1100 1300 10 6 tons per year and the orinoco transports about 150 10 6 tons per year relations of sediment discharge to water discharge are complicated by unusual patterns of seasonal storage and remobilization increased storage and reduced transport of sediment in the middle orinoco during periods of peak water discharge and storage of suspended sediment in the lower amazon during rising discharge and resuspension during falling discharge spatial distributions of suspended sediment in cross sections of both rivers are typically heterogeneous not only in the vertical sense but also in the lateral the cross channel mixing of tributary inputs into the mainstem waters is a slow process that requires several hundred kilometers of downriver transport to complete considerable fine grained sediment is exchanged between rivers and floodplains by the combination of overbank deposition and bank erosion

modern pollen signatures of amazonian rivers and new insights for environmental reconstructions abstract paleoenvironmental reconstructions based on amazonian fluvial and marine pollen data are often hindered due to the scarcity of modern calibration data in amazonia rivers are the main pathways for pollen from upland and flooded forests to continental and marine sediment sinks linking pollen assemblages transported by rivers to watershed vegetation is crucial to interpret palynological archives in order to constrain the interpretation of palynological archives we analysed the pollen content of 36 riverbed sediment samples distributed from the mouth of the ica river ca 68ow to the amazon estuary ca 49ow with support of grain size and major element analyses of the inorganic sedimentary content the palynological analysis shows a strong imprint of the lowland floodplain vegetation as the main source of the riverborne pollen the upper reaches of the amazon river present abundant cecropia reflecting early successional stages induced by intense floodplain disturbance the middle and lower reaches of the amazon river exhibit a progressive increase in herbs mainly represented by poaceae and cyperaceae related to wider floodplains covered by seasonally inundated vegetation floodplain forests of whitewater rivers varzeas are palynologically characterized by iriartea mauritia ilex pseudobombax acalypha and luehea laetia with high frequency of cecropia or herbs and montane taxa at the black and clearwater rivers the igapo floodplain forests provide high percentages of symmeria myrtaceae and alchornea and can be distinguished by sapium sebastiana piranhea amanoa pouteria ferdinandusa genipa attalea astrocaryum and eschweilera which suggest conditions of higher stability and mature forests contribution from the non flooded uplands andean mountains and savannas cerrado occur but their signals are blurred by the high pollen production of the lowland floodplains our data provide a calibration set for environmental reconstructions of river influenced deposits across the amazon including offshore areas of the most iconic riverine dominated landscape in the world

acoustic emission microstructure and damage model of dry and wet sandstone stressed to failure twenty three uniaxial compression tests were performed on dry and wet flechtingen sandstone from germany compressive strength of wet core is 60 of the strength of dry core before fracture the transverse p wave speed drops by 13 and the pulse amplitude by 22 for wet and 37 for dry cores accumulated strain energy doubles for dry core acoustic emissions ae are detected with 10 sensors for 19 cores ae activity starts at 84 of the fracture strength of wet cores 55 mpa and at 91 of the strength of dry cores 87 mpa the ratio of located to recorded ae is 0 37 for dry and 0 13 for fully wet cores ae hypocenter patterns document the development of two opposite fracture cones the negative slope of cumulative ae amplitude frequency distribution drops by 50 before failure in dry cores the slope of the wet core drops and recovers energy discrimination of ae detected by a broadband sensor resolves different stages of damage and captures the onset of the dilatant throughgoing macrofracture using the analogy to visible light microfracturing events are separated into high energy short pulses blue ae and low energy pulses with long duration times red ae blue ae are explained by intragranular grain breakage red ae by multiple stick slip on crack planes or grain boundaries deformed cores show highly fractured calcite cement and mostly intact quartz grains the stochastic damage model for brittle composites developed highlights that microfracturing of the sandstone is controlled by the amount and distribution of the weak mineral calcite

variation in 87 sr 86 sr of permian seawater an overview the strontium isotope ratio 87sr s6sr of seawater has changed significantly through time in response to variations in the input of sr to the oceans from various crust and upper mantle sources with differing 87sr 86sr values an important aspect of this temporal variation is the empirical finding that while the 87sr 86sr of seawater may vary through time at any given time the sr isotope ratio of the oceans is everywhere the same isotopic uniformity is achieved because the marine residence time of sr 4 x 106 yr is long e g veizer 1989 compared to the oceanic circulation time 103 yr the oceans therefore are well mixed with respect to both sr and sr isotope ratio and all coeval marine derived carbonates sulfates and phosphates will possess the same initial 87sr s6sr value consequently the temporal changes in the 87sr s6sr of seawater can be used to correlate and date marine strata and can provide insight into the global processes that have shaped our world

sequence stratigraphy basin morphology and sea level history for the permian kapp starostin formation of svalbard norway based on seven measured sections from svalbard the marine strata of the permian kapp starostin formation are arranged into seven transgressive regressive sequences tr1 tr7 of c 4 5 ma average duration each bound by a maximum regressive surface facies including heterozoan dominated limestones spiculitic cherts sandstones siltstones and shales record deposition within inner middle and outer shelf areas the lowermost sequence tr1 comprises most of the basal voringen member which records a transgression across the gipshuken formation following a hiatus of unknown duration temperate to cold storm dominated facies established in inner to middle shelf areas between the latest artinskian and kungurian prolonged deepening during sequences tr2 and tr3 was succeeded by a long term shallowing upward trend that lasted until the latest permian tr4 tr7 a major depocentre existed in central and western spitsbergen while to the north dickson land remained a shallow platform leading to a shallow homoclinal ramp in ne spitsbergen and nordaustlandet the middle permian extinction late capitanian is recorded near the base of tr6 in deeper parts of the basin only elsewhere this sequence is not recorded likewise the youngest sequence tr7 extending to the upper formational contact of latest permian age is found only in the basin depocentre comparison with age equivalent strata in the sverdrup basin of canada reveals a remarkably similar depositional history with for example two third order sea level cycles recorded in the late permian of both regions in keeping with the global record sequence stratigraphy may therefore be a powerful correlative tool for onshore and offshore permian deposits across nw pangaea