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

construction and evolution of submerged deltaic bodies on the high energy se african coastline the interplay between relative sea level and antecedent controls abstract this paper investigates the interplay between allocyclic controls and antecedent topography in the evolution of submerged coastal landforms including a back stepped delta using high resolution tools we examine the wave dominated thukela shelf and define the major seismic units key features identified comprise incised valleys scoured into bedrock that have overspilled to form lagoons at depths of 50 m these are in turn overlain by two prograding and backstepped sandy delta systems at 40 m and 32 m depth respectively the deltas interfinger with muddy prodelta deposits and are truncated by the holocene ravinement overlain by the contemporary prodelta of the thukela river system a bedrock high separates two physically separate strato morphological zones landward a sediment stripped steep and shallow nearshore zone and seaward a gentle zone downdip where the deltaic accumulations are sited delta development was favoured during sea level stillstands at 40 m and 32 m respectively the step back of the deltas corresponds to sharp increases in the rate of sea level rise associated with meltwater pulses the overall gentle palaeo bathymetric gradient has moderated erosion associated with rising sea level preserving a sandy back stepping delta and a draping mud clinoform submerged delta positioning relates to underlying incised valleys suggesting a synchronous transgressive evolution of the drainage and the delta incised valley network positioning is further governed by late pliocene aged growth faults in the basement rocks the geological framework has acted as a recurring primary control to the geomorphic evolution of the area partitioning accommodation for sediment accumulation and moderating the efficiency of ravinement

a continental drift flipbook abstract forty six miniature plate tectonic reconstructions are presented that can be assembled into a flipbook that illustrates the movement of the continents since the late precambrian 750 m yr ago six principal lines of evidence have been used to reconstruct the past positions of the continents 1 linear magnetic anomalies produced by sea floor spreading 2 paleomagnetism 3 hotspot tracks and large igneous provinces 4 the tectonic fabric of the ocean floor mapped by satellite altimetry 5 lithologic indicators of climate e g coals salt deposits tillites and 6 the geologic record of plate tectonic history i discuss the probable uncertainties associated with the plate tectonic reconstructions and give an estimate of the uncertainty in the positions of the continents back through time

climate warming in the latest permian and the permian triassic mass extinction high resolution oxygen isotope records document the timing and magnitude of global warming across the permian triassic p tr boundary oxygen isotope ratios measured on phosphate bound oxygen in conodont apatite from the meishan and shangsi sections south china decrease by 2 in the latest permian translating into low latitude surface water warming of 8 c the oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates suggesting that the addition of isotopically light carbon to the ocean atmosphere system by siberian traps volcanism and related processes resulted in higher greenhouse gas levels and global warming the major temperature rise started immediately before the main extinction phase with maximum and harmful temperatures documented in the latest permian meishan bed 27 the coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems in addition very warm climate conditions in the early triassic may have played a major role in the delayed recovery in the aftermath of the permian triassic crisis

climate simulation of the latest permian implications for mass extinction life at the permian triassic boundary ca 251 ma underwent the largest disruption in earth s history paleoclimatic data indicate that earth was significantly warmer than present and that much of the ocean was anoxic or euxinic for an extended period of time we present results from the first fully coupled comprehensive climate model using paleo geography for this time period the coupled climate system model simulates warm high latitude surface air temperatures related to elevated carbon dioxide levels and a stagnate global ocean circulation in concert with paleodata indicating low oxygen levels at ocean depth this is the first climate simulation that captures these observed features of this time period

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

changing fluvial environments across the permian triassic boundary in the karoo basin south africa and possible causes of tetrapod extinctions abstract the karoo supergroup is a 12 km thick succession of sedimentary rocks that accumulated in a large intracratonic retroarc foreland basin in southwestern gondwana the strata record 100 million years of almost continuous sediment accumulation from the permo carboniferous 300 ma through to the early jurassic 190 ma under a range of climatic regimes and within several tectonically controlled sub basins alluvial sediments dominate the succession from the late permian onwards fossils of synapsid reptiles and early dinosaurs are sufficiently common to be used in a ten fold biostratigraphic subdivision of these strata the permian triassic boundary in the karoo succession is marked by a major extinction of the herbivorous dicynodonts which co incides with a rapid change in fluvial facies this study uses field observations of the sedimentary facies palaeosols and in situ fossils of well exposed p tr boundary sequences in the southern karoo basin to provide evidence of environmental changes that may have caused the tetrapod extinctions in the main karoo basin below the p tr boundary sequence the sediments comprise drab greenish grey mudrocks with a few thick 3 12 m multistoried laterally accreted fine grained sandstone bodies the mudrocks host hydromorphic palaeosols with palustrine carbonate horizons and mostly disarticulated skeletal remains of dicynodon assemblage zone fauna above a transition zone of approximately 20 m thickness these strata change into reddish brown mudrocks with numerous thin 0 5 5 m ribbon sandstone bodies and more continuous sheet sandstones calcic palaeosols with rhizocretions nodular horizons and pervasive calcareous encrustation of articulated skeletons of lystrosaurus and associated fauna of the lystrosaurus assemblage zone within a 20 m thick interval of the transitional strata fossils of dicynodon and lystrosaurus occur together the facies transition that co incides with the latest permian dicynodont extinction is interpreted as a change in fluvial style from meandering to low sinuosity channels with general drying of the floodplain habitats and redistribution of vegetation belts the horsetails in particular became significantly reduced in areal distribution the changes in fluvial style in the karoo basin at the end of the permian were triggered by a pulse of thrusting in the southerly source area dated at 247 ma 2 ma which brought about rapid progradation of a large sandy braided fan system the katberg sandstone fm into the central parts of the basin a concomitant basinward migration of depositional environments allowed the lystrosaurus communities that were adapted to dry floodplains to colonise the entire basin to the detriment of most of the wet floodplain dicynodon fauna that lived there

geomorphology and preservation potential of coastal and submerged aeolianite examples from kwazulu natal south africa abstract the distribution and geomorphology of aeolianite outcrop on the coast of kwazulu natal south africa are described in the context of its preservation potential in the geological record aeolianite on the contemporary coast comprises discontinuous widely spaced outcrops less than 100 m in longshore extent and typically 50 60 m wide that reflects the combined action of subaerial weathering and physical abrasion in the coastal zone since the mid holocene approximately 7000 yrs the dominant morphological component is an intertidal erosional platform that slopes gently landward it is fronted by a notch in the mid intertidal zone 0 m msl and contains active erosional potholes on its seaward margin the platform surface is encrusted by a variety of marine organisms landward of and contiguous with the intertidal surface are small elevated outcrops of aeolianite in the supratidal zone these comprise a 3 m high seaward scarp with a basal notch in the high intertidal zone 1 m msl gullies in the scarp trap coarse clasts of eroded aeolianite as well as bedrock the upper surface of the supratidal aeolianite is planar with large potholes within which accumulations of coarse clasts and oyster shells have been cemented the upper surface is interpreted as a remnant of an intertidal platform formed at a higher mid holocene sea level the supratidal outcrop is subject to weathering and disintegration major joints divide the outcrop into cuboid blocks with axes of 3 4 m eroded blocks on the seaward face that exceed 1 m diameter remain in situ and become locked in place by repeated shaking smaller blocks that collapse from the seaward face accumulate in small gullies or are dispersed the facet most likely to be preserved in the geological record is the planar intertidal platform the morphology of aeolianite on the contemporary coast is markedly different from submerged aeolianite ridges on the adjacent shelf which are of higher relief wider and more laterally extensive preservation potential of aeolianite under subaerial conditions is low and the widespread high relief aeolianite on the shelf is attributed to rapid inundation or burial during transgression

morphodynamic evolution self organisation and instability of coarse clastic barriers on paraglacial coasts abstract beaches and barriers on many mid to high latitude coasts comprise mixtures of fine and coarse clastic materials forming a distinctive morphodynamic environment in many cases the sediments are derived primarily from limited glacigenic deposits and the coasts are considered paraglacial over relatively long time scales decades to centuries coarse clastic barriers on such coasts show evidence of self organisation through large scale morphological evolution and facies differentiation this process involves gradual reworking partitioning and textural sorting of material toward transport minima long intervals of slow evolution are punctuated by episodes of rapid reorganisation involving breakdown of stable barrier structures and facies patterns remixing of sediment and accelerated migration of transgressive systems drift aligned systems develop longshore cell structure sometimes leading to breaching and segmentation and may evolve toward progressively greater swash alignment under appropriate circumstances swash aligned systems may experience catastrophic transformation when appropriate environmental triggers lead to threshold exceedance in the morphodynamics of the shore system adjacent barriers may show quite different behaviour depending on the antecedent states of individual coastal cells while appropriate parameterisations and sediment budget formulations allow us to model the long term evolution of some barrier structures the non linear dynamics that appear to dominate large scale behaviour may limit predictability the identification of stability threshold criteria remains an important research priority

simulations of permian climate and comparisons with climate sensitive sediments abstract we use a climate model to simulate two intervals of permian climate the sakmarian ca 280 ma at the end of the major permo carboniferous glaciation and the wordian ca 265 ma we explore the climate sensitivity to various levels of atmospheric co2 concentration and to changes in geography and topography between the two periods the model simulates large seasonality and high aridity in the continental interiors of both hemispheres for both periods the northern summer monsoon weakens and the southern monsoon strengthens between the sakmarian and the wordian owing to changes in geography and topography the northern middle and high latitudes cool in winter between the sakmarian and wordian associated with northward shift of the continents this high latitude cooling strengthens the winter westerlies and shifts the maximum storm track precipitation south in the southern hemisphere the winter westerlies weaken from the sakmarian to the wordian starting the simulations with no permanent i

seismic stratigraphy and morphology of the holocene progradational system beneath bohai bay bohai sea lobate evolution of a multi sourced subaqueous fluviodeltaic complex abstract since 6 kyr bp the subaerial deltas of the yellow the yanshan and the taihang river systems evolved along the bohai bay coast forming several lobate progradational systems associated with frequent avulsions of these river systems their subaqueous parts consist of a multi sourced subaqueous deltaic complex in bohai bay but little is known about the complex s subsurface structure morphology and evolutionary history here we investigate these characteristics using a dense high resolution seismic survey using stratigraphic superposition seismic geometry and the results of previous studies we identified nine seismic units sus in the post last glacial maximum stratigraphy which are interpreted from bottom to top as 1 fluvial lacustrine sediments su0 2 marine sands combined with estuarine coastal deposits su1 and 3 a subaqueous fluviodeltaic complex sus2 8 these units correspond to the lowstand system tract the transgressive and or highstand system tracts and the normal regressive system tract respectively and evolved as a function of eustatic fluctuations the subaqueous fluviodeltaic complex is characterized by a discrete and spatially confined lobate architecture which is indicative of step wise switching of subaqueous lobes two sets of progradational systems ps a northern one sus2 3 and a southern one sus4 8 were observed within the complex tapering in opposite directions and bounded by an erosional unconformity r3 these characteristics indicate that the two ps were sourced from different river systems and prograded at different times r3 forms the base of the southern ps but cross cuts the northern ps indicating that it is a diachronous surface marks the preexisting seafloor which was further reworked eroded by the progradation of the southern ps in each ps the internal subaqueous lobes correlated well with the onshore lobes superlobes of the subaerial deltas suggesting the lobate evolution of the complex is driven predominantly by alternating erosion and deposition caused by the variation in fluvial supply which appears to be linked to the frequent avulsions of the major river systems in addition to the multi sourced supply based on the dipping geometries and the locations of the depocenters we hypothesize that 1 the northern ps is the seaward extension of the ancient haihe river s northern branch 2 the bulk of southern ps in the middle and southern bohai bay is correlated with the principal body of the yellow river subaqueous delta 3 the majority of the volume of the northern ps in northern bohai bay consists of the modern haihe river subaqueous delta

late quaternary stratigraphic evolution of the inner continental shelf in response to sea level change santa catarina brazil abstract the inner continental shelf 0 50 m water depth off santa catarina southern brazil was investigated using seismic stratigraphic methods to identify and interpret the major seismic stratigraphic units and to reconstruct the late quaternary evolution of the inner shelf and coast the stratigraphy comprises a bedrock basement overlain by a thick 30 m unit that comprises in the distal portion laminated muds and sands and in the coast proximal zone offlapping deltaic deposits whose upper surface has been reworked to form alongshore prograding barrier spits deposition of this unit is tentatively attributed to sea levels 20 m msl during the late pleistocene mis 5a or 5c a normal fault in the muddy units with a vertical offset of 3 5 m indicates episodic tectonic activity cut into this unit is a profusion of incised valleys associated with sea level fall ultimately to 120 m at the last glacial maximum lgm the associated subaerial unconformity is only preserved close to shore where it has escaped subsequent wave ravinement this coupled with the well preserved incised valleys implies the underlying substrate to be weakly cohesive material mud the incised valleys display a variety of infilling sediments interpreted variously as basal fluvial sediments estuarine basin infill muds and marginal bar or barrier associated sands deposited during the postglacial marine transgression during a sea level stillstand at ca 50 m a 3 5 km wide planar surface was cut into the unconsolidated coastal plain sediments forming a terrace on which a thick sequence of sands accumulated this unit is regionally developed and the acoustic signature implies it to comprise littoral sand including a large aeolianite component the accumulation of sand on this mainland beach dune system is attributed to establishment of a mature littoral system with strong longshore drift the fact that it rests on an erosional surface that truncates incised valleys suggests the unit to be holocene in age it is interpreted to have been deposited during a still stand in the holocene and to have undergone aggradation and cementation until it was overstepped by sea level rise its surface and the coastal plain to landward were then subject to wave ravinement and a thin ca 5 6 m layer of modern marine sands was deposited on the eroded surface sea level rise continued to the regional glacio isostatic highstand of ca 5 5 m after which regressive strandplains developed in response to a renewed mature longshore drift system similar to that prevailing during the 50 m stillstand of sea level in the intervening period rapid shoreline translation over the low gradient surface inhibited the development of the longshore transport system the three shoreline systems identified show marked differences that relate to sea level change and the influence of the underlying topography shoreline 1 pleistocene highstand developed by localised wave reworking of delta deposits and involved a series of alongshore prograding barrier spits on a shoreline of alternating high relief bedrock and littoral sands in coastal re entrants shoreline 2 50 m was a major accumulation of beach and dune sand deposited as a mainland attached beach dune system on a low lying coastal plain environment shoreline 3 the modern coast comprises a series of headland embayment beaches strandplains and transgressive dunes with a strong bedrock control and a well developed longshore drift system delivering sediment northward

coastal dynamics under conditions of rapid sea level rise late pleistocene to early holocene evolution of barrier lagoon systems on the northern adriatic shelf italy this multidisciplinary case study of two preserved barrier systems combined the analysis of radiocarbon datings grain size distributions high resolution seismics and shelf bathymetry with reconstructions of palaeo environmental conditions tides waves sea level change and forward modelling of barrier lagoon systems to provide an integrated view of the coastal transgressive evolution of a large sector of the northern adriatic shelf between 15 and 8 ka bp palaeoenvironmental reconstructions point to increased tidal amplitude low energy wave climate and high rates of sea level rise up to 60 mm a during the formation of the oldest preserved barrier system not vert similar90 m water depth 14 3 cal ka bp a younger barrier system 42 m water depth 10 5 cal ka bp formed under conditions of lower tidal amplitude higher wave energy and a lower rate of sealevel rise 10 mm a forward modelling suggests that the probability of barrier island overstepping during transgression is inversely proportional to tidal amplitude if all other factors are assumed equal the oldest barrier lagoon system developed under conditions of large tidal amplitude which permitted rapid transgression however this system apparently failed to keep up with the anomalously high rate of sea level rise resulting from melt water pulse 1a the youngest barrier system appears to have drowned in place due to antecedent topography as the barrier system transgressed over an ancient pleistocene alluvial plain the rapid increase in backbarrier accommodation caused an abrupt disequilibrium between shoreface and backbarrier sedimentation which led to barrier overstepping although barsim modelling indicates that tidal deposition can reduce the probability of barrier overstepping there are other driving mechanisms in our case extremely rapid sea level rise and antecedent topography which are more determinative in explaining the transgressive coastal evolution of barrier lagoon systems in the northern adriatic sea grain size analysis of shoreface deposits sampled above the transgressive ravinement surface across the northern adriatic shelf indicate a distinct relation between the sediment grain size and the rate of sea level rise during deposition which implies that progressive sorting must have been highly effective

global coal gap between permian triassic extinction and middle triassic recovery of peat forming plants early triassic coals are unknown and middle triassic coals are rare and thin the early triassic coal gap began with extinction of peat forming plants at the end of the permian ca 250 ma with no coal known anywhere until middle triassic 243 ma permian levels of plant diversity and peat thickness were not recovered until late triassic 230 ma tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal bearing sequences are present also in early triassic rocks nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers insects or tetrapod herbivores which became cosmopolitan and much reduced in diversity across the permian triassic boundary instead we favor explanations involving extinction of peat forming plants at the permian triassic boundary followed by a hiatus of some 10 m y until newly evolved peat forming plants developed tolerance to the acidic dysaerobic conditions of wetlands this view is compatible not only with the paleobotanical record of extinction of swamp plants but also with indications of a terminal permian productivity crash from delta sup 13 c sub org and total organic carbon of both nonmarine and shallow marine shales 205 refs 3 figs more 3 tabs less

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

outer to inner shelf response to stepped sea level rise insights from incised valleys and submerged shorelines abstract shorelines respond to rising sea level through processes such as erosion landward migration and in situ drowning i e overstepping submerged and preserved shorelines on the continental shelf play a key role in examining coastal response to rising sea levels as they provide important information on how modern shorelines may evolve in time and space within the context of changing climate and post glacial sea level rise this study identifies and assesses the response of a continental shelf to stepped rises in sea level with particular focus on the stepwise evolution of incised valleys and shorelines from the shelf edge to the inner shelf multibeam bathymetry from the mid outer allows for the analysis of seafloor morphology including the protea banks reef a palaeo shoreline complex and the adjacent incised sediment starved continental shelf six seismic units and intervening surfaces are identified using interpretations from sub bottom profiles these include the incised acoustic basement variable incised valley fill successions aeolianite ridges and post transgressive shoreface and associated sediments that withstood wave ravinement processes the incised valleys of the outer shelf are manifested as distinctive seafloor depressions filled at their bases by fluvial deposits overlain in the unfilled valley by deposits derived from cascading subaqueous dunes which comprise the upper most post transgressive sediments a core intersecting the dune material yields a maximum age of deposition of 1191 1263 cal yr bp 68 range synchronous with a period of higher than present sea levels in the region suggesting reworking and redistribution of coastal sediment as shelf sediment post transgression during the stepped rises in sea level the shoreface has disconnected from the contemporary shoreline and is preserved by means of topographic barriers formed by antecedent topography as relict shoreface deposits we provide a new perspective of shoreline response to stepped rises in sea level by integrating the seismic architecture of incised valley fills and shorelines across the continental shelf thus allowing for the assessment of variation in rates of relative sea level rise since the last glacial maximum

a new paleoclimate classification for deep time in deep time climates are mainly classified by climatically sensitive deposits paleontological evidences and modeling however they only have limited applicability in deep time studies here we propose a new paleoclimate classification based on the widely used koppen climate classification the proposed new classification is simple and quantitative but bridges the gap between modern and deep time climate studies the new classification is closely related to but differs from that of koppen by changing some limits a world map using the new classification shows the same patterns as the world map of the koppen climate classification using the new classification we are able to solve a long standing problem about the climates of east asia during the eocene we found that east asia shared the same climate type ca subtropical at all studied locations supporting the hypothesis of monsoon or monsoon like climate that prevailed there during the eocene

sequence stratigraphy of continental triassic strata of southernmost brazil a contribution to southwestern gondwana palaeogeography and palaeoclimate abstract the continental triassic succession of southernmost brazil comprises two second order depositional sequences the sanga do cabral early triassic and the santa maria middle to late triassic supersequences the first one includes ephemeral low sinuosity fluvial deposits developed on a low gradient plain based on fossil tetrapods especially procolophonids an upper induan age is estimated for this sequence facies association of the santa maria supersequence indicates low sinuosity fluvial rivers deltas and lakes this supersequence can be further subdivided into three third order sequences age provided by palaeovertebrate biostratigraphic data as follows santa maria 1 ladinian santa maria 2 carnian to early norian and santa maria 3 probably raethian or early jurassic sequences the gondwanides paroxysms i and ii in the sierra de la ventana cape fold belt are directly related to the development of both supersequences the source area of the sanga do cabral supersequence was located to the south it consisted of an uplifted peripheral bulge situated landward of the retro foreland system from where older sedimentary rocks were eroded the source area of the santa maria supersequence was also positioned southwards and related to the uplifted sul rio grandense and uruguayan shields the santa maria supersequence stratigraphic architecture is comparable to the triassic rift basins of western argentina diagenesis facies and palaeontology of the studied succession suggest a dominantly semiarid climate during the triassic

cape capture geologic data and modeling results suggest the holocene loss of a carolina cape for more than a century the origin and evolution of the set of cuspate forelands known as the carolina capes hatteras lookout fear and romain off the eastern coast of the united states have been discussed and debated the consensus conceptual model is not only that these capes existed through much or all of the holocene transgression but also that their number has not changed here we describe bathymetric lithologic seismic and chronologic data that suggest another cape may have existed between capes hatteras and lookout during the early to middle holocene this cape likely formed at the distal end of the neuse tar pamlico fluvial system during the early holocene transgression when this portion of the shelf was flooded ca 9 cal calibrated kyr b p and was probably abandoned by ca 4 cal kyr b p when the shoreline attained its present general configuration previously proposed mechanisms for cape formation suggest that the large scale rhythmic pattern of the carolina capes arose from a hydrodynamic template or the preexisting geologic framework numerical modeling however suggests that the number and spacing of capes can be dynamic and that a coast can self organize in response to a high angle wave instability in shoreline shape in shoreline evolution model simulations smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of cape capture the suggested former cape in raleigh bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self organization hypothesis cape capture may be a widespread process in coastal environments with large scale rhythmic shoreline features its preservation in the sedimentary record will vary according to geologic setting physical processes and sea level history

late quaternary sea level change in south africa abstract a late quaternary sea level curve for south africa is presented on the basis of new and published data from a range of sea level indicators and a variety of locations available evidence suggests that sea level in south africa broadly follows that described from the caribbean but that deviations occur during sea level highstands during the last interglaciation oxygen isotope stage 5 and the late holocene coastal emergence produced higher sea levels in south africa than those identified in the caribbean during the same time intervals this is tentatively ascribed to predicted lithospheric deformation in continental margin settings

submerged shoreline preservation and ravinement during rapid postglacial sea level rise and subsequent slowstand submerged shorelines hold much potential for examining the interplay between the rate of sea level rise and geomorphic setting and informing the development of models of contemporary shoreline behavior this paper describes the sedimentary architecture of a submerged barrier shoreline complex off durban south africa the complex consists of several barriers that have survived the postglacial transgression and associated erosive ravinement processes the main shoreline sequence 60 m dates to 11 690 90 calibrated cal yr b p and rests on a pleistocene lagoonal deposit 35 395 592 cal yr b p the entire barrier shoreline complex is truncated by a strongly diachronous wave ravinement surface the ravinement surface seaward of the main 60 m shoreline is steep but the gradient declines across and landward of the subordinate landward shoreline complexes the steep ravinement surface is attributed to fast sea level rise possibly associated with meltwater pulse 1b while the gentle ravinement surface is associated with a subsequent slowing of the rate of sea level rise to 0 15 mm yr 1 preservation of the main barrier and back barrier deposits through overstepping is associated namely with rapid transgression and increased back barrier accommodation the smaller barriers landward of the main barrier were preserved through overstepping related to gentle antecedent gradients despite more intense ravinement during a very slow rise in sea level slowstand this process was assisted by a sediment deficit the resulting post transgressive drape is also influenced by antecedent topography created by the barriers themselves damming along the landward sides of overstepped barriers thickens the drape and creates a temporal disconnect between the migration of the shoreface and more landward elements of the littoral system in examining the rates of shoreline migration associated with the overstepped barrier system these are far greater than those calculated for the predicted rates of shoreline change on similarly steep coastal profiles future rates of shoreline migration appear to be insufficient to cause overstepping and rollover or erosional responses are more likely

sedimentation in a river dominated estuary the mgeni estuary on the wave dominated east coast of south africa occupies a narrow bedrock confined alluvial valley and is partially blocked at the coast by an elongate sandy barrier fluvial sediment extends to the barrier and marine deposition is restricted to a small flood tidal delta sequential aerial photography sediment sampling and topographical surveys reveal a cyclical pattern of sedimentation that is mediated by severe fluvial floods which exceed normal energy thresholds during severe floods up to 10x 103 m3 s 1 lateral channel confinement promotes vertical erosion ofbed material eroded material is deposited as an ephemeral delta in the sea after floods the river gradient is restored within a few months through rapid fluvial deposition and formation of a shallow braided channel over an extended period approximately 70 years the estuary banks and bars are stabilised by vegetation and mud deposition subsequent downcutting in marginal areas transforms the channel to an anastomosing pattern which represents a stable morphology which adjusts to the normal range of hydrodynamic conditions this cyclical pattern of deposition produces multiple fill sequences in such estuaries under conditions of stable sea level the barrier and adjacent coastline prograde temporarily after major floods as the eroded barrier is reformed by wave action but excess sediment is ultimately eroded as waves adjust the barrier to an equilibrium plan form morphology deltaic progradation is prevented by a steep nearshore slope and rapid sediment dispersal by wave action and shelf currents during transgression estuarine sedimentation patterns are controlled by the balance between sedimentation rates and receiving basin volume if fluvial sedimentation keeps pace with the volume increase of a basin an estuary may remain shallow and river dominated throughout its evolution and excess fluvial sediments pass through the estuary into the sea only if the rate of volume increase of the drowned river valley exceeds the volume of sediment supply are deep water environments formed under such conditions an estuary becomes a sediment sink and infills by deltaic progradation and lateral accretion as predicted by evolutionary models for microtidal estuaries bedrock valley geometry may exert an important control on this rate of volume increase independently of variations in the rate of relative sea level change if estuarine morphology is viewed as a function of the balance of wave tidal and fluvial processes the mgeni estuary may be defined as a river dominated estuary in which deltaic progradation at the coast is limited by high wave energy it is broadly representative of other river dominated estuaries along the natal coast and a conceptual regional depositional model is proposed refinement of a globally applicable model will require further comparative studies of river dominated estuaries in this and other settings but it is proposed that river dominated estuaries represent a distinct type of estuarine morphology

impacts of global warming on permo triassic terrestrial ecosystems geologists and palaeontologists have expressed mixed views about the effects of the end permian mass extinction on continental habitats and on terrestrial life current work suggests that the effects on land were substantial with massive erosion following the stripping of vegetation associated with long term aridification and short term bursts of warming and acid rain wildfires at the permo triassic boundary contributed to the removal of forests and the prolonged absence of forests from the earth s surface for up to 10 myr these physical crises on land impinged on the oceans suggesting tight interlocking of terrestrial and marine crises levels of extinction on land may well have been as high as in the sea and this is certainly the case for tetrapods the mass extinction seems to have been less profound for plants and insects but it is hard at present to disentangle issues of data quality from reductions in abundance and diversity several killing agents have been proposed and of these tetrapods may have succumbed primarily to acid rain mass wasting and aridification plants may have been more affected by the sudden effects of heating and wildfires and the crisis for insects has yet to be explored

sedimentation on the narrow 8km wide oceanic current influenced continental shelf off durban kwazulu natal south africa abstract the narrow transform margin of southeast africa and its associated sedimentological and hydrodynamic setting differs to other documented continental margins the durban bluff continental shelf is extremely narrow and steep 8 km wide with a gradient ranging from 2 to 8 characterised by a wave and oceanic current dominated regime seismic sequence boundary 2 developed during the last interglacial regression spans the entire shelf separating the holocene sediment wedge seismic unit h from underlying pleistocene deposits a wave ravinement surface marks the holocene transgression comprising a pavement lag of well sorted gravels and bioclastics overlain by inshore reef derived carbonate rich sediments and offshore by quartzose mid shelf sands the shelf sands represent the transgressive holocene to modern sediment wedge forming a seaward thinning unit stacked against the pleistocene blood reef aeolianite beachrock substrate the sediment wedge is dynamic and constantly redistributed by currents associated with the durban eddy inshore of the agulhas current and bottom surge associated with high swells and marine storm events these have been instrumental in shaping large scale shoreface attached and detached sand ridges the presence of mud lenses in the vicinity of blood reef represents deposition from turbid flood waters with preservation facilitated by the morphology of the durban bluff and blood reef palynological results reflecting the local subtropical vegetation and recently introduced neophytes together with radiocarbon dates provide a very recent age for this sediment supporting a terrestrial origin and deposition from a single large flood event

marine geology of the sodwana bay shelf southeast africa abstract the geostrophic current controlled northern zululand shelf displays a unique assemblage of interesting physical sedimentological and biological phenomena the shelf in this area is extremely narrow 3 km and is characterised by submarine canyons coral reefs and steep gradients on the continental slope three submarine canyons occur in the study area and are classified as mature or youthful phase canyons depending on the degree to which they breach the shelf these canyons originated as mass wasting features which were exploited by palaeo drainage during sea level regressions shelf lithology is dominated by a series of coast parallel patch coral reefs which have colonised beachrock and aeolianite sequences that extend semi continuously from 5 to 95 m and delineate late pleistocene palaeocoastline events the unconsolidated sediment on the shelf is either shelf sand mainly terrigenous quartz grains or bioclastic sediment large scale subaqueous dunes commonly form in the unconsolidated sediment on the outer shelf due to the agulhas current flow these dunes occur as two distinct fields at depths of 35 to 70 m the major sediment transport direction is towards the south but occasional bedload parting zones exist where the bedform migration direction changes from south to north

late permian to early triassic environmental changes in the panthalassic ocean record from the seamount associated deep marine siliceous rocks central japan abstract in order to infer the late late permian to early early triassic environmental changes in a pelagic realm of the panthalassic ocean the stratigraphic variations of toc wt and 13corg of the ptb siliceous rock section 3 5 m in thickness were examined the study section crops out in the mino terrane central japan and consists of the upper upper permian chert changhsingian and lower lower triassic induan black claystone intermittently with thin chert beds the succession is reconstructed as sediments on the lower slope of a mid panthalassic seamount the major extinction event of permian radiolarians mee occurs at the top of the changhsingian chert our analysis shows that the toc content is markedly higher in the induan black claystone than the changhsingian chert toc values rapidly increase across the ptb the onset of the increase in toc values corresponds to mee the rapid and profound increase in toc values implies the sudden onset of oceanic anoxia as well as the rapid increase in primary production at the ptb 13corg values are generally higher in the changhsingian chert than the induan claystone and chert the stepwise drop of 13corg values characterizes their excursion of the study section the largest scale drop occurs prior to mee the minimum 13corg value is recorded at the base of the induan claystone the flux of 13c depleted gasses related to the siberian traps could have significantly contributed to the marked drop of 13corg values due to the weakened ocean circulation under the predominant condition of global warming oceanic anoxia suddenly took place at the end of the permian the anoxic condition in the surface layer was the most likely kill mechanism for permian radiolarians the anoxic condition persisted into the induan but was intermittently weakened the episodic relaxation of the anoxic condition in the induan resulted in intermittent and transient blooming of radiolarians and deposition of radiolarian chert with lowered toc values these biotic and depositional records of the study section imply the mid panthalassic ocean was under the more hospitable conditions favored by the earlier recovery of radiolarians relative to the tethys ocean and pangean marginal seas

preservation of a drowned gravel barrier complex a landscape evolution study from the north eastern english channel abstract landscape response to post glacial relative sea level during the quaternary is documented using an integrated dataset of multibeam bathymetry and 2d seismic reflection profiles from the hastings bank area in the north eastern english channel mapping of nine seismic stratigraphic units calibrated to lithological information from multiple vibrocores has enabled the interpretation of fluvial shoreface barrier washover fan back barrier and tidal environments of deposition the interpreted landscape evolution is as follows i fluvial incision of bedrock during sea level lowstand ii progradation of a shoreline and then development of a barrier complex as sea level rose iii recycling and breaching of the barrier iv rapid drowning of the barrier complex v landward migration of the shoreline through continued sea level rise and vi complete abandonment and submarine preservation of the barrier complex during sea level highstand the previously undocumented yet exceptionally well preserved drowned barrier complex at hastings bank records phases of barrier initiation breakdown and retreat and documents coastal response to high rates of relative sea level rise initial development of the barrier complex required a sufficient supply of sediment maintained by offshore sources to keep pace with rising sea level which permitted progradation of a shoreline and development of a barrier complex inherited topography in the north eastern english channel is an important factor in the development of the barrier complex phases of barrier breakdown occur when sediment supply is outpaced by a rapid increase in accommodation controlled by existing basement morphology and rising sea levels subsequently the barrier responds through internal reorganisation by breaching and reworking of existing sediment bodies barrier retreat is characterised by a phase of sediment surplus overstepping under rapid rates of sea level rise where increased water depths limit wave reworking followed by a phase of discontinuous retreat where the shoreline steps back through sediment deficit overstepping hastings bank presents a rare opportunity to examine the conditions and processes that control barrier response to sea level rise and to assess the preservation potential of barrier deposits as a function of the style of retreat

submergent shorelines in the sw pacific evidence for an episodic post glacial transgression high resolution seismic profiles supported where possible by radiocarbon dates and regional stratigraphic data indicate that the last post glacial transgression in the sw pacific was episodic comprising major stillstands punctuated by rapid rises in sea level on the terrigenous continental shelf east of south island new zealand a succession of shorelines s8 s1 are recognized as follows s8 c 113 m 18 000 yr bp s7 c 88 m 17 000 yr bp s6 c 75 m 15 000 yr bp s5 c 56 m 12 000 yr bp s4 c 46 m 11 000 yr bp s3 c 28 m 9 500 yr bp s3a c 24 m 9 000yr bp s2 c 9 m 7 500yr s1 0 m 6 500yr bp with the exception of s8 and possibly s2 the shorelines are associated with wedges of sediment the size and presence of which imply that 1 sea level stabilized at some shorelines for a considerable period of time up to i 2 000 yr and 2 the intervening rises of sea level estimated to have been at least 10 12 m lo3 yr were too rapid to allow the reworking of the wedges into a transgressive sediment sheet as favoured in some current models on the great barrier reef shelf off queensland australia shorelines s8 sl have also been recognized with a further shoreline feature s4a occurring at c 39 m shorelines sla 0 m o yr bp slb 2 3 m 6 000 yr bp and slc 0 m 6 500 yr bp are recognized as discrete aspects of the post 6 500 yr bp sea level behaviour in north eastern australia the rapid rise in sea level at least between shorelines s5 12 000 yr bp and 53 9 500 yr bp is known to have outpaced reef growth causing in situ drowning of reefs located along the deeper shorelines all modern reefs so far drilled and dated began their development at or above s3 28 m 9 500 yr bp some of the shorelines particularly s5 appear to correlate between the northern and southern hemispheres on the basis of age succession and general depth of occurrence suggesting 1 that they may be global features controlled by the post glacial pattern of ice sheet decay and 2 that hydro isostatic adjustment may exert only a minor control on the depth of particular shorelines at least during the earlieg parts of the post glacial transgression

wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western united states a comparison panfish j t and peterson f 1988 wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western united states a comparison in g kocurek editor late paleozoic and mesozoic eolian deposits of the western interior of the united states sediment geol 56 261 282 wind directions for middle pennsylvanian through jurassic time are predicted from global circulation models for the western united states these predictions are compared with paleowind directions interpreted from eofian sandstones of middle permsylvanian through jurassic age predicted regional wind directions correspond with at least three quarters of the paleowind data from the sandstones the rest of the data may indicate problems with correlation local effects of paleogeography on winds and lack of resolution of the circulation models the data and predictions suggest the following paleoclimatic developments through the time interval studied predominance of winter subtropical high pressure circulation in the late pennsylvanian predominance of summer subtropical high pressure circulation in the permian predominance of summer monsoonal circulation in the triassic and earliest jurassic and during the remainder of the jurassic influence of both summer subtropical and summer monsoonal circulation with the boundary between the two systems over the western united states this sequence of climatic changes is largely owing to paleogeographic changes which influenced the buildup and breakdown of the monsoonal circulation and possibly owing partly to a decrease in the global temperature gradient which might have lessened the influence of the subtropical high pressure circulation the atypical humidity of triassic time probably resulted from the monsoonal circulation created by the geography of pangaea this circulation is predicted to have been at a maximum in the triassic and was likely to have been powerful enough to draw moisture along the equator from the ocean to the west

extending the database of permian palaeo wildfire on gondwana charcoal remains from the rio do rasto formation parana basin middle permian rio grande do sul state brazil abstract macroscopic charcoal has been recovered from a bonebed from the barro alto outcrop middle permian guadalupian rio do rasto formation in the southernmost part of the parana basin brazil during this time a global biotic crisis was taking place and changes in the palaeofloristic composition can be observed records of palaeowildfires from the guadalupian period are scarce on a global scale in the parana basin low plant diversity compared to the entirety of gondwana persists and just a few plant bearing localities have so far been described from the northern part of the basin in the studied locality macroscopic charcoal could be detected in an outcropping bonebed and the occurrence of palaeo wildfires was confirmed besides representing the first palaeobotanical data for the guadalupian of the southern part of the parana basin the charcoal remains analyzed here are also a significant record of the local environmental conditions during the increase in aridity observed during the guadalupian and lopingian in gondwana this contributes to the understanding of regional changes that took place during this interval

offshore transport of sediment during cyclonic storms hurricane ike 2008 texas gulf coast usa extreme storms can have a large impact on coastal sediment budgets and the character of strata preserved in the geologic record here we investigate the impact of a cyclonic storm surge flood and ebb on sediment transport in a microtidal beach barrier shelf system hurricane ike made landfall on the texas united states coast on 13 september 2008 the accompanying storm surge flooded galveston bay with up to 5 m of water above sea level the surge flood and ebb preferentially flowed over a low elevation bay fronting spit known as the bolivar peninsula destroying buildings and eroding sediments surge waters also flowed through bolivar roads tidal inlet the main passageway through the barrier system that separates the gulf and the bay bathymetry chirp data and samples were collected in bolivar roads tidal inlet 9 to 10 d after the storm and we compare them here to data collected 4 mo prior additional data were collected offshore of bolivar peninsula in october 2008 our results document the dominance of the storm surge ebb in forcing sediment transport through the inlet which is not considered in models of beach barrier evolution shoreface sands appear to have been incised by the storm and advected with beach barrier sediments sufficiently offshore by the storm surge ebb that they cannot be reincorporated indicating a significant loss to the barrier system9s sediment budget as a result of a single storm

gas emissions due to magma sediment interactions during flood magmatism at the siberian traps gas dispersion and environmental consequences we estimate the fluxes of extremely reduced gas emissions produced during the emplacement of the siberian traps large igneous province due to magma intrusion in the coaliferous sediments of the tunguska basin using the results of a companion paper iacono marziano et al submitted to epsl and a recent work about low temperature interaction between magma and organic matter svensen et al 2009 we calculate co ch4 dominated gas emission rates of 7 1015 2 1016 g yr for a single magmatic volcanic event these fluxes are 7 to 20 times higher than those calculated for purely magmatic gas emissions in the absence of interaction with organic matter rich sediments we investigate by means of atmospheric modelling employing present geography of siberia the short and mid term dispersion of these gas emissions into the atmosphere the lateral propagation of co and ch4 leads to an important perturbation of the atmosphere chemistry consisting in a strong reduction of the radical oh concentration as a consequence both co and ch4 lifetimes in the lower atmosphere are enhanced by a factor of at least 3 at the continental scale as a consequence of 30 days of magmatic activity the short term effect of the injection of carbon monoxide and methane into the atmosphere is therefore to increase the residence times of these two species and in turn their capacity of geographic expansion the estimated co and ch4 volume mixing ratios i e the number of molecules of co or ch4 per cm3 divided by the total number of molecules per cm3 in the low atmosphere are 2 5 ppmv at the continental scale and locally higher than 50 ppmv the dimension of the area affected by these high volume mixing ratios decreases in the presence of a lava flow accompanying magma intrusion at depth complementary calculations for a 10 year duration of the magmatic activity suggest i an increase in the mean ch4 volume mixing ratio of the whole atmosphere up to values 3 to 15 times higher than the current one and ii recovery times of 100 years to bring back the atmospheric volume mixing ratio of ch4 to the pre magmatic value thermogenic methane emissions from the siberian traps has already been proposed to crucially contribute to end permian early triassic global warming and to the negative carbon isotopic shift observed globally in both marine and terrestrial sediments our results corroborate these hypotheses and suggest that concurrent high temperature co emissions also played a key role by contributing to increase i the radiative forcing of methane and therefore in its global warming potential and ii the input of isotopically light carbon into the atmosphere that generated the isotopic excursion we also speculate a poisoning effect of high carbon monoxide concentrations on end permian fauna at a local scale

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

coal in a carbonate sequence stratigraphic framework the upper permian heshan formation in central guangxi southern china microfacies and sedimentological analyses of the upper permian coal bearing heshan formation in the heshan coalfield of central guangxi suggest that these coal measures formed in a marine carbonate platform setting low volatile bituminous coals with very high organic sulphur overlie either palaeosols or locally developed cherts the petrography and geochemistry of the coals suggest formation in low lying mires in which marine influence increased upwards in the heshan and overlying dalong formations four third order sequences are described based on the recognition of four sequence boundaries higher order sequences within each of these third order sequences are also documented and within sequence iii coal seams are developed above higher order transgressive surfaces representing the deposits formed during the lag time between initial flooding of the platform and the onset of carbonate production in the heshan formation the coals with greatest thickness occur immediately above third order transgressive surfaces it is argued that in some coal bearing siliciclastic free marine carbonate platform settings accommodation creation rates and peat accumulation rates are balanced hence greater coal accumulation can be achieved at the transgressive surface rather than at the maximum flooding surface

permian phytogeography in gondwana abstract phytogeographic patterns based on multivariate techniques multidimensional scaling are proposed for the permian vegetation of gondwana this approach requires a data set with broad geographic coverage based on generic composition and with good time control in general strong phytogeographic differentiation can be observed throughout the permian in order to identify short term phytogeographic patterns the permian period was informally divided into five time slices in the permian stage i earliest permian the vegetation was strongly influenced by glacial conditions a very impoverished vegetation is seen except in patagonia and parts of south america four units were identified patagonia nothosouthamerica australia and indo africa by far patagonia was the most diverse and had the most favourable climatic conditions perhaps as a result of palaeogeographic separation from western gondwana nothosouthamerica which included plant assemblages from nw argentina and brazil perhaps as two subunits is a mid latitude area with glacial influence in the brazilian sector indo africa had a much lower diversity occupying high latitudes whereas australia had the lowest diversity of all the vegetational regions in stage i the early permian stage ii shows a more diversified and expanded plant cover vegetation of eastern and western gondwana was differentiated patagonia and south america including a brazilian and nw argentinean unit had the richest plant assemblages whereas africa indo australia and antarctica as separate units are less diverse probably due to late glacial influence by the late early permian stage iii gondwana shows much more ameliorated climatic conditions basically due to drifting into more temperate latitudes as well as increased moisture resulting in expansion of peat forming areas this is immediately reflected in the vegetation as shown by diversified plant assemblages even in antarctica nonetheless a differentiation is again observed between eastern gondwana patagonian and south american units and the western sector indo australian and antarctic units whereas africa would probably represent an ecotone beginning in the late permian stage iv there was a decrease in the number of plant assemblages and diversity indicating a deterioration in climate resulting from generally drier conditions latitudinal differentiation can be observed with antarctica as a polar unit afro australia at high latitudes whereas the south american indian and patagonian units are located in middle latitudes finally in permian stage v latest permian a south american unit can be differentiated clearly from the rest africa and indo australia antarctica is interpreted again as a discrete unit in the stage v time slice eastern gondwana returns to more humid climatic conditions allowing the formation of extended peat swamps whereas the western sector is affected by seasonal and strong droughtness this kind of phytogeographic approach has proven useful for detecting some palaeogeographic problems such as those involving the patagonian subcontinent in this regard palaeogeographic reconstructions and palaeoclimatic models should be tested against these phytogeographic patterns

altered river morphology in south africa related to the permian triassic extinction the permian triassic transition in the karoo basin of south africa was characterized by a rapid and apparently basin wide change from meandering to braided river systems as evidenced by preserved sedimentary facies this radical changeover in river morphology is consistent with geomorphic consequences stemming from a rapid and major die off of rooted plant life in the basin evidence from correlative nonmarine strata elsewhere in the world containing fluvial permian triassic boundary sections suggests that a catastrophic terrestrial die off of vegetation was a global event producing a marked increase in sediment yield as well as contributing to the global 13 c excursion across the permian triassic boundary

rollover drowning and discontinuous retreat distinct modes of barrier response to sea level rise arising from a simple morphodynamic model we construct a simple morphodynamic model to investigate the long term dynamic evolution of a coastal barrier system experiencing sea level rise using a simplified barrier geometry the model includes a dynamic shoreface profile that can be out of equilibrium and explicitly treats barrier sediment overwash as a flux with barrier behavior primarily controlled by the maximum potential overwash flux and the rate of shoreface response the modeled barrier system demonstrates four primary behaviors height drowning width drowning constant landward retreat and a periodic retreat height drowning occurs when overwash fluxes are insufficient to maintain the landward migration rate required to keep pace with sea level rise on the other hand width drowning occurs when the shoreface response rate is insufficient to maintain the barrier geometry during overwash driven landward migration during periodic barrier retreat the barrier experiences oscillating periods of rapid overwash followed by periods of relative stability as the shoreface resteepens this periodic retreat which occurs even with a constant sea level rise rate arises when overwash rates and shoreface response rates are large and of similar magnitude we explore the occurrence of these behaviors across a wide range of parameter values and find that in addition to the maximum overwash flux and the shoreface response rate barrier response can be particularly sensitive to the sea level rise rate and back barrier lagoon slope overall our findings contrast with previous research which has primarily associated complex barrier behavior with changes in external forcing such as sea level rise rate sediment supply or back barrier geometry

the burning of gondwana permian fires on the southern continent a palaeobotanical approach abstract fossil charcoal has widely been accepted as a direct indicator for the occurrence of palaeo wildfires in upper palaeozoic sediments of euramerica and cathaysia records of these remains are relatively common and regionally and stratigraphically more or less homogeneously distributed in terrestrial sequences on the other hand just a few records have been published for the permian of gondwana and only recently has it been demonstrated that macroscopic charcoals are also common here most permian macroscopic charcoal from gondwana is gymnospermous and has been reported from coal bearing strata macroscopic charcoal occurrences are spread out in different sequences and also in distinct stratigraphic intervals in the permian e g parana basin sakmarian artinskian of brazil karoo basin artinskian of south africa damodar basin lopingian of india and dead sea area changhsingian of jordan they range from peri glacial post glacial to warm temperate climatic systems throughout the permian macro and micro charcoal occurrences are compared to inertinite incidences to support the pyrogenic origin for these coal macerals and to provide an up to date overview on the known evidences of permian wildfires on gondwana in space and time

permo carboniferous climate early pennsylvanian to late permian climate development of central europe in a regional and global context a well justified stratigraphical correlation of continental successions and new palaeogeographic reconstruction of pangaea reveal new insights into the northern pangaean climate development influenced by palaeogeography palaeotopography glacio eustatic sealevel changes and ocean currents the overall permo carboniferous aridization trend was interrupted by five wet phases these are linked to the gondwana icecap the aridization and weakening of wet phases over time were not only caused by the drift of northern pangaea to the arid climatic belt but also by the successive closure of the rheic ocean which caused the expansion of arid semi arid environments in the lower middle permian the end of the gondwana glaciation rearranged ocean circulation leading to a cold coast parallel ocean current west of northern pangaea blocking moisture coming with westerly winds the maximum of aridity was reached during the roadian wordian the trans pangaean mountain belt was non existent its single diachronous parts never exceeded an average elevation of 2000 m the maximum elevation shifted during time from east to west the hercynian orogen never acted as an orographic east west barrier and the inter tropical convergence zone was widely displaced causing four seasons dry summer winter wet spring autumn at the equator and a strong monsoon system the climate history of the european realm during the late carboniferous pennsylvanian and permian is stored in many solitary basins fig 1 within the hercynian orogen and the foreland basin the story of westphalian climate is well known because of the numerous investigations of the coal bearing variscan foredeep the younger westphalian is characterized by a slight aridization abbink van kronijnenburgvan cittert 2003 oplustil 2004 which was accompanied by an increase of seasonality nevertheless the environment was strongly influenced by the ocean and epi continental seas with multiple transgression events the last extensive marine ingression was the aegir mansfield band westphalian b c the post westphalian climate development is more differentiated and

chronology of quaternary coastal aeolianite deposition and the drowned shorelines of southwestern western australia a reappraisal abstract aeolianite successions of low gradient continental margins commonly show complex records of coastal dune deposition linked to a wide range of sea level positions and climatic periods of the middle and late pleistocene recording both regional and broader scale drivers of sediment production coastal dune development and landform preservation to better characterise the general pattern of sedimentation that occurs over quaternary glacial interglacial cycles on low gradient temperate carbonate continental shelves we examine the morphology stratigraphy and age of aeolianite deposits in the perth region western australia this includes an analysis of well defined drowned coastal landforms preserved on the adjacent shelf new and previously published optical ages provide a preliminary timeframe for the deposition of aeolianite in the perth region and on rottnest island 17 km offshore an extensive aeolianite ridge near perth representing a former barrier has optically stimulated luminesence osl ages that range from 120 12 to 103 10 ka mis 5e 5a in the context of associated age uncertainties osl ages for an exposure in the same ridge 2 5 km inland record the onlap of much older aeolianite osl age 415 70 ka by shell rich estuarine beds osl age 290 30 ka a further 5 5 km inland from the coast two thick aeolianite units separated by a well developed palaeosol have stratigraphically consistent osl ages of 310 30 and 155 20 ka in contrast aeolianite units that form the northern coast of rottnest island have osl ages of 77 12 ka and 27 5 ka the new osl ages and previously reported tl and u th ages indicate that the bulk of the island comprises dunes deposited around the end of the last interglacial sensu lato mis 5a 4 and during the last glacial mis 4 2 accumulating over a last interglacial coral reef and basal calcarenite drowned barrier and dune landforms preserved on the adjacent continental shelf reveal that barriers were formed during periods of intermediate sea level e g mis 3 and significant dune mobility occurred when the shelf was subaerially exposed the pattern of shelf sedimentation discernible in the perth region large scale coastal carbonate dune deposition during periods of high and intermediate sea level and reactivation during glacial lowstands is largely consistent with published stratigraphic and age data for large scale aeolianite deposits on other low gradient carbonate shelves based on these data a general model is proposed for the cycle of quaternary sedimentation and landform evolution that occurs on these shelves which are dynamic sedimentary environments with coastal landforms and sedimentary successions that are very sensitive to erosion and sediment reworking

the seismic stratigraphy of the inner shelf of southern namibia the development of an unusual nearshore shelf stratigraphy abstract this paper investigates the complex interplay between allocyclic autocyclic and antecedent controls on the development of the proximal portions of a wave dominated gravel rich submerged delta the inner shelf of the orange river delta of southern namibia is investigated using seismic stratigraphic methods and vibracore data in conjunction with onshore electromagnetic data the aim is to define and interpret the major seismic stratigraphic units and to examine the controls on the stratigraphic evolution of the area the stratigraphy comprises a crystalline bedrock and sedimentary rock basement the contact of which exhibits a break in slope in the palaeo bathymetry surface the basement is truncated by a subaerial unconformity which includes two palaeo channels incised into a bedrock palaeo promontory offshore of the modern orange river mouth the incision of these channels is attributed to episodic periods of river rejuvenation linked to tectono eustatic events of the late cretaceous and end neogene during which sea level dropped below the shelf break the ensuing smaller glacio eustatic sea level oscillations of the quaternary led to the formation of bypass valleys which did not incise the existing channels and allowed remnants of original old course channel fill to remain in the lower sequences of the valley fill north and offshore of the bedrock palaeo promontory the basement is overlain by a widespread thick up to 3 m gravel lag associated with repeated ravinement events that represent multiple cycles of subaerial and wave ravinement erosion including those of the last post glacial transgression this gravel lag represents the proximal portion of the world s largest diamond placer deposit gravel spit barrier and linear beach facies occur between 70 and 55 msl and are interpreted to have developed under high rates of coarse sediment supply during a stillstand preceding mwp 1b a constructional phase of delta progradation followed interposed with backstepping which we consider representative of the final shoreline trajectory from mwp 1b through 1d the overlying thick up to at least 70 m fine sandy to muddy clinoform unit is the proximal portion of the modern delta of the orange river which has prograded during the holocene and episodically accumulates fine sediments during flood events in modern times gravel deposits are winnowed by cyclical erosion processes in combination with the oceanographic regime to strongly partition the grain sizes of the shelf stratigraphy gravel deposits e g lags and barrier beaches etc are preserved by inheritance of the sediment stock and by later sheltering from wave energy due to antecedent topography where gravel beaches and deltas formed their preservation in the stratigraphy is enhanced due to existing low gradient palaeo slope and punctuated rises in sea level which overstepped the shelf geomorphology

shifts in late paleozoic atmospheric circulation over western equatorial pangea insights from pedogenic mineral δ18o compositions the d 18 o values of pedogenic calcites phyllosilicates and iron oxyhydr oxides from fossil soils throughout the southwestern united states show systematic paleolatitudinal and temporal trends that indicate a significant change in soil moisture conditions and atmospheric circulation patterns over southwestern euramerica throughout latest pennsylvanian and early permian time a progressive depletion of as much as 6 in mineral 18 o values with increasing distance northward to 108 of the paleoequator indicates a weakening or disruption of zonal easterly flow over the study area by latest pennsylvanian time furthermore elevated d 18 o values suggest a proximal source of paleoprecipitation over the study area perhaps due to initiation of reversed equatorial flow over tropical southwestern euramerica coupling of the geographic and temporal trends defined by pedogenic mineral d 18 o values with those defined by climatically sensitive paleosol pedotypes in the study area along with overall elevated mineral d 18 o values provides some of the strongest evidence that northern hemisphere monsoonal circulation was well established over pangea by early permian time

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

topographic and hydrodynamic controls on barrier retreat and preservation an example from dogger bank north sea abstract barrier retreat can occur due to in place drowning overstepping or rollover depending on the interplay of controls such as sea level rise sediment supply coastal hydrodynamic regime and topography offshore sedimentary archives of barriers active during rapid holocene sea level rise provide important records of marine transgression which are vital analogues to support appropriate mitigation strategies for future coastal realignment under projected relative sea level rise scenarios this study analyses the sedimentary archive at dogger bank which is a formerly glaciated area in the north sea dogger bank experienced marine transgression due to early holocene rapid relative sea level rise an integrated dataset of vibrocores and high resolution seismic reflection data permits a stratigraphic framework to be established which reveals the buried coastal geomorphology of the southern dogger bank for the first time a transgressive stratigraphy was identified comprising a topographically complicated basal glacial and terrestrial succession overlain by two phases of barrier and tidal mudflat deposition prior to shallow marine sedimentation barrier phase a was a recurved barrier drowned in place and discontinuously overstepped to barrier phase b which experienced continuous overstepping by linking barrier elevations to relative sea level curves the timing of each barrier phase was established both barrier phases retreated during periods of rapid sea level rise with abundant sediment supply coastal hydrodynamics increasing wave energy and antecedent topography with spatially variable accommodation are suggested to be the main reason for differing retreat mechanisms rather than the rate of sea level rise antecedent coastal geomorphology plays a critical role in erosional and depositional patterns during transgression and therefore on the timing rate and location of marine inundation which needs to be included in models that aim to forecast hazards in coastal areas

relict and contemporary influences on the postglacial geomorphology and evolution of a current swept shelf the eastern cape coast south africa abstract few stratigraphic models of continental shelves incorporate the process of geostrophic current sweeping consequently its role in the stratigraphic record is often overlooked we examine the narrow current swept eastern cape shelf of south africa using a combination of geophysical techniques seafloor sampling and video observations and interpret the role of current action on the transgressive stratigraphy of this steep subtropical shelf during the last glacial maximum fluvial valleys incised the acoustic basement rocks during the subsequent transgression two distinct shorelines were formed and preserved at 105 m and 60 m their development and preservation is linked to i high sediment supply from adjacent fluvial sources ii early diagenesis and iii alternating sea level stillstands and periods of rapid sea level rise during melt water pulses 1a and 1b respectively the deeper shoreline formed in a sandy wide coastal plain setting with limited bedrock influence whereas the shallower shoreline comprised alternating rock headlands and embayments like the contemporary coast differences in antecedent topography and geology are responsible for the temporal variability in shoreline type coastal squeeze is exacerbated with increasing bedrock control as the shoreline migrates landward between the two shoreline complexes in the mid shelf the transgressive stratigraphy records initial valley infill by progradation of coast parallel sandy spits these are capped by a stiff lagoonal mud deposited as ongoing sea level rise overspilled the valley interfluves onlapping the adjacent aeolianites the uppermost stratigraphy comprises mounds of rhodoliths which interfinger with a sandy inner to middle shelf highstand wedge after sea level reached its present position ca 7 4 ka yr bp the shelf became subject to reworking by the high energy geostrophic agulhas current this has had the following major effects on the shelf stratigraphy 1 the topographic relief of the cemented palaeo shorelines has been emphasised by removal of the post transgressive cover and 2 the shelf no longer acts as a depocenter instead the seabed consists of rhodoliths gravel streamers bedrock or gravel hash of the wave ravinement surface given the necessary antecedent conditions such as accommodation sediment supply and favourable diagenetic climate prominent shorelines can form and be preserved on the shelf strong current sweeping emphasises these morphological features on subtropical shelves

strange bedfellows a deep water hermatypic coral reef superimposed on a drowned barrier island southern pulley ridge sw florida platform margin abstract the southeastern component of a subtle ridge feature extending over 200 km along the western ramped margin of the south florida platform known as pulley ridge is composed largely of a non reefal coastal marine deposit modern biostromal reef growth caps southern pulley ridge spr making it the deepest hermatypic reef known in american waters subsurface ridge strata are layered lithified and display a barrier island geomorphology the deep water reef community is dominated by platy scleractinian corals leafy green algae and coralline algae up to 60 live coral cover is observed in 60 75 m of water although only 1 2 of surface light is available to the reef community vertical reef accumulation is thin and did not accompany initial ridge submergence during the most recent sea level rise the delayed onset of reef growth likely resulted from several factors influencing gulf waters during early stages of the last deglaciation 14 kyr b p including cold low salinity waters derived from discrete meltwater pulses high frequency sea level fluctuations and the absence of modern oceanic circulation patterns currently reef growth is supported by the loop current the prevailing western boundary current that impinges upon the southwest florida platform providing warm clear low nutrient waters to spr the rare discovery of a preserved non reefal lowstand shoreline capped by rich hermatypic deep reef growth on a tectonically stable continental shelf is significant for both accurate identification of late quaternary sea level position and in better constraining controls on the depth limits of hermatypic reefs and their capacity for adaptation to extremely low light levels

factors controlling shelf sediment dispersal along the southeast african continental margin abstract four major factors control sediment dispersal along the southeast african continental margin 1 morphology of the upper continental margin 2 wave regime and wind driven circulation 3 influence of the agulhas current and 4 sediment supply these factors interact on various scales to produce a unique regional sediment dispersal pattern the continental shelf is very narrow and the adjacent slope extremely steep the shelf platform is interrupted by a number of structural offsets and locally the shelf break is dissected by numerous submarine canyons the nearshore zone down to about 60 m waterdepth is dominated by a high energy swell regime and in most places is underlain by a thin wedge of sandy sediment this wedge appears to have achieved dynamic equilibrium with the prevailing energy regime and additional sediment is rapidly dispersed and fed into a sandstream situated on the central shelf where the agulhas current dominates sediment transport along some parts of the coast the sediment wedge is dammed behind a drowned coastal dune ridge within the sandstream sediment is transported alongshelf until a structural offset is reached where sediment spills over the shelf break four major localities for off shelf transport are recognized between maputo and port elizabeth most of the suspended load appears to be expelled from the system without being deposited on the shelf in the lee of each offset a clockwise gyre is developed which produces return flow currents capable of moving sediment northward thereby creating bedload partings in the vicinity of these partings depositional features are observed that are similar to those normally associated with tidal regimes e g bedforms migrating in opposite directions most of the bedload sediment entering the system is eventually deposited in well defined sinks situated in the lee of structural offsets this model applies only to inter glacial high sea level situations accompanied by strong western boundary flow of the agulhas current

depositional history of estuarine infill during the last postglacial transgression gulf of cadiz southern spain abstract the late pleistocene and holocene evolution of the estuaries in the gulf of cadiz is interpreted for the first time using drill cores logs trenches and 38 new radiocarbon data and the results compared with the shelf the odiel tinto and guadalete rivers deposited conglomerates during a highstand that did not reach the present sea level dated at ca 25 30 ka isotopic stage is 3 corresponding to a relatively humid period in the area rivers incised these coarse grained deposits during the last main lowstand at ca 18 ka when sea level dropped to 120 m and the coastline lay 14 km seawards from the present the erosional surface is a sequence boundary and the flooding surface of the postglacial eustatic rise overlain by the valley fill deposits of the transgressive and highstand phases of the last fourth and fifth order depositional sequences recognised in the shelf the first marine influence in the estuaries during the transgression occurs at 25 30 m at ca 10 000 years bp according to fossil assemblages the transgressed basins changed from brackish to more open marine as the sea rose until ca 6500 years bp when it reached the maximum flooding and the sandy estuarine barriers ceased to retrograde toward the muddy central basins then the rate of eustatic rise decreased drastically and the estuarine filling followed a two fold pattern governed by the progressive change from vertical accretion to lateral centripetal progradation at ca 4000 years bp the fluvial input surpassed the already negligible rate of rise causing partial emergence of tidal flats and spit barriers in the largely filled estuarine basins prevalence of coastal progradation upon vertical accretion at ca 2400 years bp caused accelerated expansion of tidal flats and rapid growth of the sandy barriers further changes since the 16th century reflect widespread anthropic impacts

the upper hawkesbury river new south wales australia a holocene example of an estuarine bayhead delta holocene deposits of the hawkesbury river estuary located immediately north of sydney on the new south wales coast record the complex interplay between sediment supply and relative sea level rise within a deeply incised bedrock confined valley system the present day hawkesbury river is interpreted as a wave dominated estuarine complex divisible into two broad facies zones i an outer marine dominated zone extending 6 km upstream from the estuary mouth that is characterized by a large subtidal sandy flood tidal delta ocean wave energy is partially dissipated by this flood tidal delta so that tidal level fluctuations are the predominant marine mechanism operating further landward ii a river dominated zone that is 103 km long and characterized by a well developed progradational bayhead delta that includes distributary channels levees and overbank deposits this reach of the hawkesbury river undergoes minor tidal level fluctuations and low fluvial runoff during baseflow conditions but experiences strong flood flows during major runoff events fluvial deposits of the hawkesbury river occur upstream of this zone the focus of this paper is the hawkesbury river bayhead delta history of deposition within this delta over the last c 12 ka is interpreted from six continuous cores located along the upper reaches of the hawkesbury river detailed sedimentological analysis of facies whole core x ray analysis of burrow traces and a chronostratigraphic framework derived from 10 c 14 dates reveal four stages of incised valley infilling in the study area 1 before 17 ka bp a 0 1 m thick deposit of coarse grained fluvial sand and silt was laid down under falling to lowstand sea level conditions 2 from 17 to 6 5 ka bp a 5 10 m thick deposit composed of fine grained fluvial sand and silt muddy bayhead delta and muddy central basin deposits developed as the incised valley was flooded during eustatic sea level rise 3 during early highstand between 6 5 and 3 ka bp a 3 8 m thick bed of interbedded muddy central basin deposits and sandy river flood deposits formed in association with maximum flooding and progradation of sandy distributary mouth bar deposits commenced 4 since 3 ka bp fluvial deposits have prograded toward the estuary mouth in distributary mouth bar interdistributary bay and bayhead delta plain environments to produce a 5 15 m thick progradational to aggradational bayhead delta deposit at the mouth of the hawkesbury estuary subaqueous fluvial sands interfinger with and overlie marine sands the hawkesbury river bayhead delta depositional succession provides an example of the potential for significant variation of facies within the estuarine to fluvial segment of incised valley systems

septarian carbonate concretions in the permian rio do rasto formation birth growth and implications for the early diagenetic history of southwestern gondwana succession abstract between the late carboniferous and early triassic the southwestern gondwana supercontinent was characterized by the development of a huge intracratonic basin a large confined epeiric sea and the accumulation of a transgressive regressive sequence were formed by continuous subsidence related to tectonic effects caused by the sanrafaelic orogeny and the consequent generation of accommodation space the permian rio do rasto formation documents the last progradational cycle related to the complete continentalization of this epeiric sea the basal member of the rio do rasto formation serrinha is believed to have been deposited in a shallow epicontinental water body subjected to storms and influenced by episodic deltaic incursions one of the most remarkable characteristics of the serrinha member is the presence of carbonate concretions hosted in mudstones and very fine sandstones here we combine sedimentological and petrographic descriptions coupled with geochemical and stable carbon and oxygen isotopic data to elucidate the nature of these carbonate concretions the non deformed internal structure decreasing proportion of carbonate cements relative to detrital grains toward the concretion edges core to rim isotopic variations and perhaps most importantly the preservation of a well developed cardhouse fabric support an early diagenetic origin for these structures at shallow burial depths of tens of meters stable isotope analyses of micritic calcite cements and calcites filling the septarian fractures reveal major negative excursions in both 18 o and 13 c values oxygen isotope ratios obtained for the micritic calcite cements vary between 12 1 and 2 6 the calcite filling septarian fractures also exhibit negative values of 18 o 14 2 to 13 8 with an average of 14 the 13 c values of micritic calcite cements range from 5 0 0 2 the carbon isotopic data from the calcite filling septarian fractures are also negative 4 4 to 3 3 the 18 o signatures suggest that the early diagenetic carbonate concretions precipitated in a shallow freshwater environment rather than in a marine setting the 13 c values suggest that the carbon isotopes were derived from a source with slightly depleted 13 c supporting at least a partial organogenic contribution with weak sulfate reduction rates typical of freshwater systems sedimentological analysis shows that the epicontinental water body in which the serrinha member was deposited was constantly supplied by rivers and meteoric waters which suggests that an enormous freshwater basin with restricted marine connections to the panthalassa ocean once existed

evolution of an incised valley coastal plain estuary under low sediment supply a give up estuary the literature on incised river valley sedimentology is dominated by studies of sediment rich systems in which the valley has been filled during and or shortly after drowning in contrast the holocene evolution of the kosi lagoon south africa an incised coastal plain river valley took place under very low sedimentation rates which have produced a distinctive stratigraphy and contemporary sedimentary environments the findings are based on a synthesis of the results of studies of seismic stratigraphy sediment distribution morphodynamics and geomorphology barrier migration was prevented by a high pre holocene dune barrier against which holocene coastal deposits accumulated in an aggradational sequence holocene evolution of the back barrier involved i drowning of the incised valley ii wave induced modification of the back barrier shoreline leading to segmentation during the highstand and iii marine sedimentation adjacent to the tidal inlet segmentation has divided the estuary into a series of geochemically and sedimentologically distinctive basins connected by channels in the estuarine barriers the seismic stratigraphy of the back barrier essentially lacks a transgressive systems tract shoreline modification and deposition having been accomplished during the highstand the lack of historical geomorphological change suggests that the system has achieved morphological equilibrium with ambient energy conditions and low sediment supply this study presents a classification for estuarine incised valley fills based on the balance between sea level rise and sedimentation in which kosi represents a give up estuary where much of the relict incised channel form is drowned and preserved it exhibits a fundamentally different set of evolutionary processes and stratigraphic sequences to those of the better known incised valley systems in which sedimentation either keeps pace with sea level keep up estuaries or occurs after initial drowning catch up estuaries

submerged barrier shoreline sequences on a high energy steep and narrow shelf abstract late pleistocene holocene shoreline sequences and associated shelf stratigraphy are described from a high gradient high wave energy shelf although shoreline preservation by overstepping is considered unlikely in such an environment as a result of intense ravinement during shoreline translation the development and preservation of two distinct shorelines at 100 m and 60 m are evident and attributed to century to millennial scale periods of stillstand during these periods shoreline equilibrium forms developed characterised by early diagenesis of beachrock and aeolianite between these features the shelf is dominated by erosional surfaces reflecting ravinement during periods of slowly rising sea level where shorelines are not preserved areas of scarping in the ravinement surface at similar depths to the adjoining shorelines represent rocky headlands separating the sandy coastal compartments where the depositional shorelines formed shoreline preservation by overstepping was facilitated by rapid relative sea level rise associated with meltwater pulses 1a and 1b although the features preserved are likely to represent only the cemented cores of the coastal dunes and linear beachrock outcrops formed the steep antecedent shelf gradient fostered the erosion of significant portions of the shorelines by ravinement with loose sediment re organised into a thick post ravinement drape the removal of shorelines during ravinement was countered by the rapid rate of sea level rise and early sub tropical diagenesis it is clear that due to the combined effects of subtropical diagenesis long periods of stillstand and drowning by meltwater pulses the governing controls on shoreline preservation can be over ridden by combinations of local climatic and global eustatic factors

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

geomorphic and stratigraphic signals of postglacial meltwater pulses on continental shelves selective development and preservation of major shoreline complexes on the continental shelf provide geomorphic evidence in support of alternating periods of holocene sea level stillstand and rapid rise during meltwater pulses on a tectonically stable far fi eld setting the southeast african shelf regionally developed well preserved shoreline complexes occur at 100 m and 60 m within an overall shelf sequence dominated by transgressive ravinement non preservation of shorelines the development of geomorphically mature submerged shorelines with equilibrium forms is attributed to extended periods of sea level stability and their preservation is the result of early cementation followed by very rapid sea level rise several centimeters per year that caused overstepping meltwater pulses 1a and 1b are recorded in the shelf stratigraphy and geomorphology setting aside local infl uences of topography and sediment supply we hypothesize that shelf stratigraphies should preferentially preserve shorelines at water depths associated with the stillstands or slowstands immediately preceding meltwater pulses a reappraisal of shelf stratigraphy and geomorphology in particular the preservation potential of former shorelines is required in the light of contemporary understanding of postglacial sea level history

andean uplift ocean cooling and atacama hyperaridity a climate modeling perspective abstract located along the west coast of subtropical south america the atacama desert features an extremely dry climate in sharp contrast with relatively wet conditions over the central andes and farther east the atacama s hyperaridity has been attributed to its subtropical location the cold waters over the adjacent southeast pacific ocean and the presence of the andes cordillera although geological evidence reveals less dry conditions in the remote past the timing of the arid to hyperarid transition is a matter of controversy several studies suggest that such transition occurred between 19 and 13 ma fostered by the concurrent uplift of the andes during the lower middle miocene other studies however suggest a much earlier 25 ma or later 2 1 ma transition associated with global or regional ocean cooling here we use plasim a simple global climate model to study the effect of the andean surface uplift and sea surface temperature changes upon atacama aridity in one set of experiments the continental topography was scaled by a factor ranging from 0 9 to 0 1 decreasing the height of the andes did not increase precipitation over the atacama region but rather decrease the precipitation over the central andes and the interior of the continent these results consistent with previous modeling studies suggest that the andean uplift was not an important ingredient in the onset of atacama hyperaridity even if both events overlapped in time a globally uniform sea surface warming does not result in a significant increase of precipitation over the atacama in contrast a regional warming over the subtropical southeast pacific very effectively increase precipitation along the west coast of south america by decreasing the subsidence and the dry advection at low levels it suggested that a reinforcement of the humboldt current since the late miocene and particularly during the pliocene pleistocene transition was crucial in the drying of the atacama desert that culminated with the present day hyperarid conditions

the effect of global warming and global cooling on the distribution of the latest permian climate zones abstract the end permian biotic crisis is commonly associated with rapid and severe climatic changes these climatic changes are commonly suggested to have originated from solid earth carbon degassing leading to global warming but aerosol and ash induced cooling induced by lava degassing has been suggested as well the application of an earth system model of intermediate complexity has enabled a visualisation of the major climatic shifts on the supercontinent pangaea caused by rapid temperature changes due to changed radiative properties from greenhouse gases the reconstructed reference climate was validated by latest permian climate indicative sediments to investigate the possible climatic shifts from a set of 22 reconstructions which varied with temperature a minimum global annual mean temperature of 18 2 c for the late permian climate prior to the climatic perturbation event was determined starting from this pre event setup global warming and global cooling scenarios were simulated the response of the end permian climate system to temperature increase and decrease show marked differences while global cooling is followed by major climatic changes in the high latitudes and replacement of boreal biomes by tundra and polar frost the changes during global warming are less pronounced with only locally increasing aridity compensated by humidisation in other regions the different behaviour of the climatic belts under warm and cold conditions is accompanied by different climate sensitivities caused by different strength of the snow cover albedo feedback thus changes in the energy balance of the latest permian surface troposphere system have a 30 higher perturbation potential during cold climate conditions than during warmhouse conditions therefore substantial global cooling resulting in coldhouse climate conditions and an annual global mean temperature below 18 c is more efficient in perturbing the earth palaeoclimate during the end permian warmhouse the results suggest that global cooling mechanisms as injection of sulphur aerosols and ash particles from the siberian traps large igneous province into the late permian palaeoatmosphere have a higher climate perturbation potential than a warming due to carbon greenhouse gases with a similar magnitude of radiative forcing

drowned shelf edge deltas barrier islands and related features along the outer continental shelf north of the head of de soto canyon ne gulf of mexico abstract four drowned shelf edge delta complexes two drowned shelf deltas three drowned barrier islands large areas of hardground and fields of bedforms on the mid and outer continental shelf and uppermost slope north of the head of de soto canyon ne gulf of mexico were mapped with high resolution multibeam echosounder deltas formed not during the last eustatic low stand but during one or more interstadials when eustatic sea levels were only 60 to 80 m below present sea level the barrier islands and deltas must have been cemented prior to rapid falls of eustatic sea level that occurred during global glaciations cementation is necessary to have preserved the barrier islands from erosion and subsequent destruction by the rapid sea level rise during the last deglaciation the preservation of the relict bathymetry is so good that features that superficially resemble trough blowouts are found in association with one of the relict barrier islands asymmetric bedforms on the midshelf in water depths of 50 to 60 m indicate transport directions to the sw but asymmetric bedforms in water depths of the upper slope between 100 and 120 m on the s and se flanks of the drowned shelf edge deltas indicate a different current direction a separate flow that is a continuation of a sw flowing current that was previously found on the upper slope off nw florida

disruption of playa lacustrine depositional systems at the permo triassic boundary evidence from vyazniki and gorokhovets on the russian platform abstract permo triassic sections at vyazniki and gorokhovets provide evidence on terrestrial events at or close to the permo triassic boundary the time of the largest ever mass extinction the sedimentary succession records the overrun of a muddy playa lacustrine depositional system by major channel belts transporting sand grade sediments biostratigraphy of sections at vyazniki and gorokhovets zhukov ravine shows that this event occurred either at the very end of the permian or 8 m above in the sections the timing and nature of this event which records increased sediment flux from the ural mountains is closely comparable with that from the southern uralian foreland basin the vyazniki and gorokhovets sections are 800 km from the mountain front and in a separate depositional basin which strengthens the case that increased sediment flux from the urals at the permo triassic boundary is related to devegetation of upland catchments increasing sediment yield and a switch toward low frequency but high magnitude discharge events increasing sediment delivery the interbedding of fluvial and aeolian deposits provides further evidence for climatic instability and extremes in the early triassic supplementary material detailed reports on the ostracodes and fossil fish remains from the zhukov ravine sections are available at http www geolsoc org uk sup18402

initial observations of the subsurface structure and short term variability of the seaward deflection of the gulf stream off charleston south carolina a recurring seaward deflection of the surface layer of the gulf stream has been observed near 32 n latitude off the coast of the southeastern united states it has been suggested that a ridge and trough bottom feature the so called charleston bump on the upper continental slope off the georgia south carolina coast produces the deflection through a bottom steering effect present data indicate that the deflection is great enough to direct the gulf stream s shoreward surface thermal front to the east and even south of east about 70percnt of the time air deployed expendable bathythermograph surveys have been made with sufficient coverage to provide several synoptic three dimensional views of the gulf stream s thermal frontal zone in the region between savannah georgia and cape hatteras north carolina these views show the subsurface structure of the seaward deflection to exhibit large short term variability during wintertime conditions february 1979 the greatest deflection 090 true of the near surface front occurred at a time when the deeper front was more aligned 080 true with local topography within the few days following this observation the deflection angle at all depths decreased to near or below 070 true two large amplitude gulf stream meanders progressed northeastward away from the deflection region during this time period deflection angles at all levels during late summertime conditions november 1979 were observed to be near 070 true a simple kinematical model which incorporates growing propagating gulf stream meanders is proposed to explain the deflection s short term variability a dome shaped volume of cold water was observed to be located over the upper continental slope immediately downstream of the deflection the existence and persistence of this cold dome suggest that upwelling is important in its maintenance a hypothesis consistent with its hydrographic properties

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

formation and preservation of an overstepped segmented lagoon complex on a high energy continental shelf the duration of shoreline occupation at a given sea level coastal response to sea level change and the controls on preservation of various shoreline elements can be recognized by detailed examination of submerged shorelines on the continental shelf using bathymetric and seismic observations this article documents the evolution and preservation of an incised valley and lithified barrier complex between 65 m and 50 m mean sea level on a wave dominated continental shelf the barrier complex is preserved as a series of aeolianite or beachrock ridges backed by laterally extensive back barrier sediments the ridges include prograded cuspate lagoonal shoreline features similar to those found in contemporary lagoons the incised valley trends shore parallel behind the barrier complex and records an early phase of valley filling followed by a phase of extensive lagoonal sedimentation beyond the margins of the incised bedrock valley sea level stability at the outer barrier position ca 65 m enabled accumulation of a substantial coastal barrier that remained intact during a phase of subsequent slow sea level rise to 58 m when the lagoon formed these lagoonal sediments are stripped seawards by bay ravinement processes which caused the formation of several prograded marginal cuspate features an abrupt rise in sea level to 40 m correlated with melt water pulse 1b enabled the preservation of thick lagoonal sediments at the top of the incised valley fill and preservation on the sea bed of the cemented core of the barriers this situation is unique to subtropical coastlines where early diagenesis is possible the overlying sandy sediment from the uncemented upper portion of the barriers is dispersed by ravinement partly burying the ridges and protecting the underlying sediments the high degree of barrier or shoreline preservation is attributed to rapid overstepping of the shoreline early cementation in favourable climatic conditions and the protection of the barrier cores by sand sheet draping

magnitude and timing of episodic sea level rise during the last deglaciation a succession of elevated ridge deposits on the south florida margin was mapped using high resolution seismic and side scan sonar imaging in water depths ranging from 50 to 124 m the ridges are interpreted to be subtidal shoal complexes and paleoshorelines eolian dune or beach formed during the last sea level transgression oolitic and skeletal grainstones and mixed skeletal peloidal ooid packstones were recovered using a research submersible all of the grains are of shallow water or intertidal origin and both marine and nonmarine cements were identified formation and preservation of these features are attributed to episodic and rapid changes in the rate of the deglacial sea level rise at the onset of the termination 1a 18o excursion this high resolution record of sea level change appears to be related to deglacial processes operating on submillennial time scales and supports increasing evidence of rapid episodic fluctuations in ice volume climate and ocean circulation patterns during glacial interglacial transitions

spatial and temporal variations in incised valley systems from the durban continental shelf kwazulu natal south africa abstract the evolution of several incised valley systems from the kwazulu natal shelf is compared over time these represent the shelf extension of the collective durban harbour drainage system and the mgeni mhlanga and mdloti rivers two main ages of incision are apparent early santonian cretaceous and late pleistocene holocene the early valleys formed by tectonic controls namely phases of higher frequency base level fall superimposed on lower frequency higher order transgression the results are complex networks of stacked compound valleys that have been exploited by some of the younger networks formed by glacio eustatic fall prior to the last glacial maximum lgm of 18 ka bp the valley fills have evolved from high energy basal fluvial deposits low energy central basin fines mixed energy estuarine mouth plug deposits clay rich flood deposits through capping sandy shoreface deposits the earliest fills are dominated by central basin deposits and were underfilled as a result of low gradient and limited sediment supply the more recent late pleistocene holocene fills have significantly thicker fluvial deposits as a result of increased gradient and stream competence during the later stages of valley and shelf evolution the youngest valleys show a situation of differential evolution along the valley length due to varying rates of sea level rise in the holocene initial rapid sea level rise caused drowning and overstepping of the outer segment of the incised valley whereas slower rates of sea level rise in the late holocene caused shoreface ravinement of the inner mid segments of the valley this differential exposure to accommodation has resulted in a sedimentological partitioning between tide dominated facies in the outer valley segment and river dominated facies in the inner segment cf cooper 2001

spatial variability of late holocene and 20th century sea level rise along the atlantic coast of the united states accurate estimates of global sea level rise in the pre satellite era provide a context for 21 st century sea level predictions but the use of tide gauge records is complicated by the contributions from changes in land level due to glacial isostatic adjustment gia we have constructed a rigorous quality controlled database of late holocene sea level indices from the u s atlantic coast exhibiting subsidence rates of 0 8 mm a 1 in maine increasing to rates of 1 7 mm a 1 in delaware and a return to rates 0 9 mm a 1 in the carolinas this pattern can be attributed to ongoing gia due to the demise of the laurentide ice sheet our data allow us to defi ne the geometry of the associated collapsing proglacial forebulge with a level of resolution unmatched by any other currently available method the corresponding rates of relative sea level rise serve as background rates on which future sea level rise must be superimposed we further employ the geological data to remove the gia component from tide gauge records to estimate a mean 20 th century sea level rise rate for the u s atlantic coast of 1 8 0 2 mm a 1 similar to the global average however we fia distinct spatial trend in the rate of 20 th century sea level rise increasing from maine to south carolina this is the fi rst evidence of this phenomenon from observational data alone we suggest this may be related to the melting of the greenland ice sheet and or ocean steric effects

drowned coastal deposits with associated archaeological remains from a sea level slowstand northwestern gulf of maine usa drowned terrestrial wetland environments such as lakes marshes and beaches were thought to be rare in formerly glaciated regions like the gulf of maine united states in the northwestern gulf of maine postglacial relative sea level changes include a slowstand between 11 5 ka and 7 5 ka when the ocean rose 5 m this period of sea level stability permitted erosion of glacial materials and concomitant construction of spits and sheltered wetland habitats attractive to human occupation between 17 m and 22 m below modern sea level this work underscores the importance of a well constructed sea level chronology to predict the location of drowned terrestrial environments and associated cultural resources

effects of rapid global warming at the paleocene eocene boundary on neotropical vegetation temperatures in tropical regions are estimated to have increased by 3 to 5 c compared with late paleocene values during the paleocene eocene thermal maximum petm 56 3 million years ago event we investigated the tropical forest response to this rapid warming by evaluating the palynological record of three stratigraphic sections in eastern colombia and western venezuela we observed a rapid and distinct increase in plant diversity and origination rates with a set of new taxa mostly angiosperms added to the existing stock of low diversity paleocene flora there is no evidence for enhanced aridity in the northern neotropics the tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide in contrast to speculations that tropical ecosystems were severely compromised by heat stress

world peat occurrence and the seasonality of climate and vegetation abstract the climatic controls on present day peat formation are examined in order to develop a uniformitarian tool for refining paleoclimate studies and to create a retrodictive model for the coals of the geologic record a peat database has been compiled for the world and the resulting patterns are compared with aspects of precipitation and temperature drawn from a gridded data set precipitation continuity through the annual cycle is important for biologic productivity in the terrestrial realm it is expressed in terms of the number of months with average precipitation above 40 mm temperature is limiting at higher latitudes where the potential growing season may be defined by the number of months with mean temperature exceeding 10 c a map predicting the growing season has been constructed from these rainfall and temperature statistics which compares very well with actual vegetation persistence through the year as measured directly from satellite instruments however biologic production will not result in peat accumulation unless groundwater levels are maintained through the growing season our peat prediction map therefore shows the percentage of time that precipitation occurs during the potential growing season present day peat accumulations are well predicted by this map

causes and consequences of extreme permo triassic warming to globally equable climate and relation to the permo triassic extinction and recovery permian waning of the low latitude alleghenian variscan hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high co2 atmosphere and global warming the correspondingly reduced delivery of nutrients to the biosphere caused further increases in co2 and warming melting of polar ice curtailed sinking of o2 and nutrient rich cold brines while pole to equator thermal gradients weakened wind shear and associated wind driven upwelling lessened further diminishing productivity and carbon burial as the earth warmed dry climates expanded to mid latitudes causing latitudinal expansion of the ferrel circulation cell at the expense of the polar cell increased coastal evaporation generated o2 and nutrient deficient warm saline bottom water wsbw and delivered it to a weakly circulating deep ocean warm deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling wsbw with the loss of polar sinking the ocean was rapidly filled with wsbw that became increasingly anoxic and finally euxinic by the end of the permian rapid incursion of wsbw could have produced 20 m of thermal expansion of the oceans generating the well documented marine transgression that flooded embayments in dry hot pangaean mid latitudes the flooding further increased wsbw production and anoxia and brought that anoxic water onto the shelves release of co2 from the siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse increasingly frequent and powerful cyclonic storms mined upwelling high latitude heat and released it to the atmosphere that heat trapped by overlying clouds of its own making suggests complete breakdown of the dry polar cell resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest permian coal forests that could not migrate any farther poleward because of light limitations loss of water stored by the forests led to aquifer drainage adding another 5 m to the transgression non peat forming vegetation survived at the newly moist poles climate feedback from the coal forest extinction further intensified warmth contributing to delayed biotic recovery that generally did not begin until mid triassic but appears to have resumed first at high latitudes late in the early triassic current quantitative models fail to generate high latitude warmth and so do not produce the chain of events we outline in this paper future quantitative modeling addressing factors such as polar cloudiness increased poleward heat transport by deep water and its upwelling by cyclonic storms and sustainable mid latitude sinking of warm brines to promote anoxia warming and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data

sudden changes in fluvial style across the permian triassic boundary in the eastern iberian ranges spain analysis of possible causes abstract the sedimentary record of the late permian and early triassic of the eastern iberian ranges shows four major sudden or very rapid vertical changes in fluvial style the late permian sedimentary cycle starts with the boniches formation of alluvial fan braided fluvial origin which grades vertically over within a few metres into the alcotas formation deposited by low to high sinuosity avulsion prone rivers with extensive floodplains the alcotas formation contains calcimorphic soils plant remains and pollen and spore assemblages however the upper third of the unit is devoid of all organic remains and soils and is characterized by a dominant red colour the sandstone levels were deposited by high sinuosity meandering rivers this major change took place during the late permian and is probably coeval with the emplacement of the emeishan basaltic large igneous province lip in se china rocks of the boniches and alcotas formations are separated by an angular unconformity from the overlying strata which consist of the late permian conglomeratic hoz del gallo formation of alluvial fan gravel braided fluvial origin and the sandy canizar formation of low sinuosity sandy river origin the permian triassic boundary lies probably between the upper part of the hoz del gallo formation and the first metres of the canizar formation late permian pollen and spore assemblages have been found in the hoz del gallo formation but the canizar formation is barren with the exception of an anisian middle triassic assemblage at the top tectonic extensional pulses in the iberian basin caused the changes observed between the lower and upper parts of the boniches formation at the base of the hoz del gallo formation and between the lower and upper part of this formation the changes observed in the uppermost part of the alcotas formation are not easily explained by tectonic causes nor those in the passage from the hoz del gallo formation to the canizar formation similar sedimentary characteristics of the sandy canizar formation such as amalgamated sandstone bodies erosion and reactivation surfaces dominant trough cross stratification tabular geometry absence of plant remains and pollen and spores and absence of silts and clays to those of coeval formations in places as far away as australia south africa and brazil suggest a global rather than local cause for these abrupt changes in fluvial style this global cause was probably die off of plant cover over extensive areas of the catchment related to the end of the permian mass extinction and possibly related to the emplacement of the west siberian basaltic large igneous province lip responsible for drastic atmospheric and marine changes

hercynian high altitude phenomena in the french massif central tectonic implications abstract stratified slope deposits diamictite and sedimentary structures such as water escape craters ghosts of ice crystals and solifluction flowage in the stephanian autunian of the french massif central are related to high altitude periglacial effects the clay mineral assemblage dominated by the association illite chlorite irregular interlayed clays and the slight weathering of feldspathic clasts and granite gneiss pebbles favour the prevalence of a cold to temperate climate at this time rather than a hydrolyzing climate of humid equatorial or tropical type the flora and entomofauna also indicate a seasonally varying climate with cold winters favouring the development of periglacial phenomena at high altitude in view of the equatorial paleogeographic position of the hercynian belt this type of climate could exist only at altitudes higher than 4500 m the tectonic implications of these altitudes are examined through a comparison with the present day himalayas and tibetan plateau

tempo of the end permian event high resolution cyclostratigraphy at the permian triassic boundary the permian triassic p t boundary is marked by the most severe mass extinction in the geologic record high resolution cyclostratigraphy on a 10 4 yr scale across the p t boundary in a core from the carnic alps austria revealed significant cycles in the ratio 40 10 4 7 2 3 m identified with milankovitch cycles of 412 100 40 20 k y eccentricity 1 and 2 obliquity and precession wavelet analysis indicates continuity of deposition across the boundary with an average accumulation rate of 10 cm k y the dramatic faunal changes at the p t boundary can be constrained within an interval of 60 k y possibly 8 k y with the accompanying sharp negative global carbonisotope shift within 30 k y suggesting a catastrophic cause

early cementation and accommodation space dictate the evolution of an overstepping barrier system during the holocene abstract the morphology and stratigraphic features of a well preserved drowned barrier system located on the western coast of sardinia mediterranean sea are presented here the barriers were mapped using a multibeam echosounder the digital terrain model of the seabed revealed five sub parallel barriers in a depth range of 18 37 m with a distance of 300 m between each single barrier direct inspection by scuba diving revealed that the barriers consist of beachrocks topped by seagrass meadows growing on a biogenic hardground the inner most barrier is limited landward by a steep cliff 10 m high bordering the back barrier area about 200 km of seismic lines were collected along the barrier system using a 0 4 1 0 kj sparker source and a 3 5 khz chirp subbottom profiler the seismic data calibrated with vibrocores allowed us to recognize the subaerial topographic surface of the last glacial maximum as well as several seismic units interpreted as the pliocene marine sediments the pre holocene deposits and the holocene barrier lagoon complex composed of shoreface barrier lagoonal deltaic and beach deposits despite the relatively high seabed gradient 0 3 0 4 and the relatively low rate of sea level rise 10 15 mm y 1 the barriers were well preserved due to the early diagenetic processes which led to a rapid cementation with the formation of beachrocks and the subsequent overstepping with the rise of the sea level the development of the overstepping barrier system is strictly related to the antecedent subaerial topography which is in turn related to the tectonic setting of the area the pliocene seismic unit was lowered by a direct fault at the entrance of the gulf forming a depression filled by sediments the overstepping barrier system developed following the increase of the seabed gradient and was limited landward by the above mentioned depression which increased the accommodation space following the sea level rise and the barrier formation this depression was filled by lagoonal sediments washover fans and sediments coming from the rivers the age model of barrier evolution based on previous sea level rise curves during the holocene supported by radiocarbon data highlighted that the whole system evolved over a time period of 1 ka while the time elapsed from this formation to the drowning of single barriers was estimated to be in the order of magnitude of centuries scenarios of short term evolution of modern barrier lagoon systems of the adjacent coastal sector under conditions of accelerated sea level rise according to church et al 2013 2013 ipcc report and rahmstorf 2007 projections were elaborated the study of this ancient analogue suggests that the processes of adaptation of coastal systems to the rising sea level would require times evaluable from centuries to millennia

palaeo environment in an ancient low latitude arid lacustrine basin with loessite the smith bank formation early triassic in the central north sea uk continental shelf acknowledgements this work was conducted as part of the triassic mudstones joint industry project which was sponsored by bp conocophillips eon e p esso exploration and production uk limited gdf suez e p uk ltd jx nippon maersk oil shell and total the guidance of prof steve hillier of the james hutton institute in quantitative mineralogical analysis is acknowledged with gratitude dr stuart jones and an anonymous referee are thanked for their incisive and constructive reviews that significantly helped in the revision of the manuscript

permo triassic boundary superanoxia and stratified superocean records from lost deep sea pelagic cherts of japan and british columbia canada recorded a long term and worldwide deep sea anoxic oxygen depleted event across the permo triassic or paleozoic and mesozoic boundary 251 2 million years ago the symmetry in lithostratigraphy and redox condition of the boundary sections suggest that the superocean panthalassa became totally stratified for nearly 20 million years across the boundary the timing of onset climax and termination of the oceanic stratification correspond to global biotic events including the end guadalupian decline the end permian extinction and mid triassic recovery

quantitative analysis of the stratigraphic architecture of incised valley fills a global comparison of quaternary systems abstract facies models of the internal fills of incised valleys developed in shelf and coastal settings during cycles of relative sea level change are largely conceptual descriptive and qualitative in form moreover they are commonly bespoke to individual examples here a database driven quantitative statistical analysis of 87 late quaternary incised valley fills ivfs has been undertaken to assess the general validity and predictive value of classical facies models for ivfs and to investigate the relative importance of possible controls on their stratigraphic organization based on datasets from the published literature stored in a sedimentological database the geometry and proportion of systems tracts and of architectural elements of different hierarchies within ivfs are quantified these variables were analysed to assess how they vary in relation to parameters that represent potential controlling factors relative sea level stage continental margin type drainage basin area valley geometry basin physiography and shoreline hydrodynamics the stratigraphic organization of the studied coastal plain ivfs is generally consistent with that represented in facies models the primary control being the rate and magnitude of relative sea level change however results from this study demonstrate significant variability in the stratigraphic architectures of ivfs which is not accounted for by existing models variations in the facies architecture of coastal plain and cross shelf valley fills can be attributed to controls other than sea level and expressed in relationships with continental margin type basin physiography catchment area river system size and shoreline hydrodynamics the following primary findings arise from this research i compared to their counterparts on passive margins coastal plain ivfs hosted on active margins contain on average a higher proportion of fluvial deposits and a lower proportion of central basin estuarine deposits estuarine deposits tend however to be thicker this suggests a control on ivf stratigraphic architecture exerted by distinct characteristics of the tectonic setting of the host continental margins notably basin physiography rates and mode of sediment supply and nature of sediment load ii the thickness and proportion of lowstand systems tract are positively correlated with coastal plain ivf dimensions likely reflecting the role of drainage basin area in dictating the scale of the fluvial systems that carved and infilled the valleys iii positive correlations are observed between the thickness of fluvial deposits bayhead delta deposits and central basin estuarine deposits versus coastal plain ivf dimensions and valley catchment area this suggests a control exerted by the river system scale on sediment supply rates and on the accommodation determined by valley size iv positive correlations between the thickness and proportion of barrier complex deposits within cross shelf ivfs versus mean shelf gradient indicate that the geometry of the shelf might control the establishment and preservation of barrier island environments in incised valleys located on the shelf v correlations between the width of coastal plain ivfs and present day mean tidal range at the shoreline indicate that tidal dynamics may contribute to the widening of the incised valleys positive correlation is observed between the proportion of tide dominated elements in highstand ivf deposits and ivf width suggesting possible effects of interplays between hydrodynamic conditions and the geometry of incised valleys on their infills this study highlights the complexity of the internal fills of incised valleys which must be considered when attempting the application of facies models of ivfs to rock record interpretations or as predictive tools in subsurface studies

siberian gas venting and the end permian environmental crisis abstract the end of the permian period is marked by global warming and the biggest known mass extinction on earth the crisis is commonly attributed to the formation of the siberian traps large igneous province although the causal mechanisms remain disputed we show that heating of tunguska basin sediments by the ascending magma played a key role in triggering the crisis our conclusions are based on extensive field work in siberia in 2004 and 2006 heating of organic rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated 100 000 gt co2 the gases were released to the end permian atmosphere partly through spectacular pipe structures with kilometre sized craters dating of a sill intrusion by the u pb method shows that the gas release occurred at 252 0 0 4 million years ago overlapping in time with the end permian global warming and mass extinction heating experiments to 275 c on petroleum bearing rock salt from siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases the results indicate that global warming and ozone depletion were the two main drivers for the end permian environmental crisis we demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a large igneous provinces causes an environmental crisis or not we propose that a similar mechanism could have been responsible for the triassic jurassic 200 ma global warming and mass extinction based on the presence of thick sill intrusions in the evaporite deposits of the amazon basin in brazil