the pangaea megamonsoon records evidence from the triassic mungaroo formation northwest shelf of australia abstract an integrated analysis in this study of paleogeographic paleontologic seismic and sedimentologic data has been used to explain the effect of the pangaean megamonsoon on the whole triassic especially the middle late triassic mungaroo formation in the north carnarvon basin northwest shelf of australia our results show that the three triassic formations from bottom to top locker shale mungaroo formation and brigadier formation comprise a complete depositional cycle and correspond to an undeveloped strong and weak monsoon periods respectively during the strong monsoon period of the mungaroo formation the palynological evidences exhibited mixture spore pollen characteristics of the hygrophytic assemblage spore pollen from the pteridophyte spores seed ferns and cycads pollen in humid environment of lowlands and coastal plain and the xerophytic assemblage pollen from the drought tolerant plants of the interior mountainous areas the sedimentary evidences of the mungaroo formation show low angle shingled progradational seismic reflection configuration the highly seasonal variations in precipitation during deposition of the mungaroo formation exhibited typical sandwiched depositional characteristics of coarse channels sandstone fining upward fluvial aggradational cycles facs with poor to moderately sorting and angular to subangular roundness organic mudstone and coal seam interbedded finally in contrast to today s typical examples of poyang lake delta a shallow water braided delta conceptual depositional model of the mungaroo formation is formed with a large proximal and distal delta plain and small delta front the model results serve mainly to indicate the importance of various climate forming factors climate topography eustatic whereas tectonic activity unlikely played any significant role in this process

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

vegetation communities of a high palaeolatitude middle jurassic forest in new zealand abstract fossil evidence of a high southern palaeolatitude approximately 75 78 south middle jurassic temaikan forest from gondwana is investigated from the murihiku supergroup exposed at kawhia harbour north island new zealand horizons of fossilised tree stumps preserved in growth position and rooted within coal rich layers at bedding contacts are exposed within cross bedded medium grained sandstone on the present day shore platform interbedded siltstone and fine grained sandstone contain terrestrial palynomorphs fossilised leaves and other macroflora material including cones and seeds the sediments are interpreted as three fluvial facies vegetated bar top major sheet flood and channel fill and migration within a sandy braided river palaeoenvironment the fossil flora suggest the original vegetation was multi layered and dominated by gymnosperms and ferns lycopods bryophytes fungi and algae also grew on the forest floor and in bar top pools a model of plant communities is presented reflecting changing habitats up the side of interdistributary bars the model is based on stratigraphically successive taphocenoses within vegetated bar top facies and the preferred growing conditions and life forms of comparable modern relatives lycopods and bryophytes on the saturated channel banks became less frequent higher up the bar on the damp partially drained soil preferred by ferns and cycad trees favouring the drier bar top arborescent gymnosperms thrived around probably ephemeral pools containing lycopods bryophytes and algae the characteristics of this fossil forest at kawhia harbour compare well to a similar middle jurassic site at curio bay in south island new zealand and other high southern palaeolatitude fossil floras from the late mesozoic a humid warm climate with high average annual rainfall and large storms is interpreted from the kawhia harbour fossil forest for the new zealand middle jurassic these palaeoclimatic conditions are comparable to the modern mesothermal zone

sea level anomalies exacerbate beach erosion sea level anomalies are intra seasonal increases in water level forced by meteorological and oceanographic processes unrelated to storms the effects of sea level anomalies on beach morphology are unknown but important to constrain because these events have been recognized over large stretches of continental margins here we present beach erosion measurements along onslow beach a barrier island on the u s east coast in response to a year with frequent sea level anomalies and no major storms the anomalies enabled extensive erosion which was similar and in most places greater than the erosion that occurred during a year with a hurricane these results highlight the importance of sea level anomalies in facilitating coastal erosion and advocate for their inclusion in beach erosion models and management plans sea level anomalies amplify the erosive effects of accelerated sea level rise and changes in storminess associated with global climate change

evaluating proxies for estimating subaerial beach volume change across increasing time scales and various morphologies proxies such as changes in beach profiles and shoreline positions are commonly used in management and research for estimating changes in subaerial beach volume however the accuracy of these proxies across increasing time scales and complex morphologies is unclear volume changes associated with along beach morphologic variability may not be captured well by changes in profiles while volume changes associated with across beach morphologic variability may not be captured well by measuring shoreline change this study assesses the impacts of morphologic variations associated with beach cusps and nourishment material on volume change estimates from profiles and shoreline change at 0 5 to 3 5 year time periods results indicate that profiles spaced 150 m apart and the shoreline change proxy will likely estimate volume change inaccurately over periods 1 year at beaches that are consistently eroding or accreting and contain cusps however over longer time periods 1 3 5 years estimates of volume change from both proxies improved at those types of beaches volume changes at the edges of nourishment areas are not captured well by profiles when the nourishment material is graded to a ramped morphology which minimizes across beach morphologic variability the shoreline change proxy does accurately estimate volume changes both proxies estimate volume changes inaccurately at beaches where volume changes oscillate between erosion and accretion on both short and long time scales because the magnitude of small scale changes in volume from the formation and erosion of morphologic features such as cusps and berms will always be similar to the longer term net volume change this study suggests that decadal records of shoreline change which are commonly developed using aerial photography can be used to help identify the best proxy for estimating volume change however recent anthropogenic modifications that impact patterns of beach sedimentation including nourishment terminal groins and inlet channel dredging makes decadal records less useful copyright 2013 john wiley sons ltd

structure of a corystosperm fossil forest from the late triassic of argentina abstract a palaeoecological study of a standing late triassic forest containing 150 silicified stumps from the rio blanco formation of mendoza province argentina is described a mapped portion of the forest floor provides quantitative data tree density mean separation of trees and basal area per stump which along with taxonomic and sedimentologic information allowed the reconstruction of a plant community that grew along river banks and within proximal floodplain environments analysis of architectural and phenological data from monotypic forest indicates an evergreen community composed of a corystosperm genus with a canopy height of c 13 21 m the corystosperm taxon elchaxylon like rhexoxylon has polyxylic axes with centripetal secondary xylem but does not generate perimedullar bundles and the centrifugal secondary xylem produces an undivided solid pycnoxylic cylinder vegetation analysis shows that the forest has a clustered distribution pattern with high density forest density ranges between 727 and 1504 trees ha but there are first order clusters with elevated density mean nearest neighbour distance of 1 85 m the histogram of diameter classes based on 131 stumps suggests an earlier colonization by few older pioneers the largest ones followed by establishment of a large younger cohort of coeval trees based on 9 series and 139 rings the mean ring width and mean sensitivity ms were 3 47 mm and 0 31 respectively ms values and the presence of false rings indicate the forest community responded to stressed ecosystems the growth rings are very erratic and range from 0 27 to 8 94 mm for fossil growth analysis it was assumed that wider rings would suggest a warmer climate and the considerable range in growth rates would indicate variability in the limiting factors among subsequent cycles

in situ fossil forest from the upper fremouw formation triassic of antarctica paleoenvironmental setting and paleoclimate analysis abstract a structural and ecological study of a standing triassic forest containing 99 silicified trunks from the fremouw formation of antarctica is detailed utilizing quantitative methods forest density total forest cover per hectare mean separation of trees and basal area per stump were obtained this information integrated with sedimentologic taxonomic fossil wood and biomechanical data has allowed the reconstruction of a plant community that grew at very high paleolatitudes 70 75 s the paleoforest grew along river banks levees and within proximal floodplain environments where a taphocoenosis of permineralized stumps and compression impression foliage of the dicroidium type has been preserved in particular the intimate association of this leaf type with dense conifer like wood provides additional confirmation that the dicroidium foliage morphotype was attached to several types of stems this riparian forest stand was apparently in a mature stage prior to the beginning of preservation tree ring analysis as well as additional indirect evidence indicates that this middle triassic ecosystem in antarctica experienced a season very suitable for plant growth resulting from an overall favorable climatic regime this conclusion contrasts with earlier paleoclimate models based on physical parameters in which temperature ranges would make plant or animal growth at these latitudes almost impossible finally antarctic climatic change from latest permian through late triassic is considered in the context of tectonic and paleogeographic reconstructions of the east antarctic craton

a crested theropod dinosaur from antarctica jurassic fossil vertebrates collected from the falla formation in the central transantarctic mountains included a partial skull and postcranial elements of a crested theropod cryolophosaurus ellioti gen nov sp nov the theropod bears some resemblance to the large tetanurans of the middle to late jurassic but also has primitive ceratosaurian features elements from a prosauropod teeth from scavenging theropods a pterosaur humerus and a tritylodont molar were also recovered the presence of this fauna suggests that a mild climate existed at high paleolatitude in this area of gondwana during the early jurassic

the southern oscillation index wave climate and beach rotation short embayed beaches bounded by headlands are a common feature along the southern and central coastline of new south wales australia many of these embayed beaches have experienced severe erosion at their southern end over the last decade previous studies have suggested that this erosion may be the result of an oscillatory medium term phenomenon known as beach rotation the present study was undertaken with the objectives of 1 establishing definitive links between the southern oscillation index soi wave climate and beach rotation and 2 determining the physical processes governing beach rotation data from two similar new south wales beaches were analysed using time series analysis techniques and image processing techniques using argus video images in this study the results indicate that the northern end of this type of beach accretes during el nino phases while the southern end erodes resulting in a net clockwise rotation of the beach the opposite occurs during la nina phases resulting in a net anti clockwise rotation of the beach the beach response at the northern and southern ends lags soi trend shifts by 3 and 17 months respectively waves are predominantly incident from the southeast during both el nino and la nina phases offshore wave height is positively correlated with the soi while offshore wave direction is negatively correlated with the soi on average the number of storms per year doubles from el nino to la nina based on these links between beach width fluctuations soi and incident wave conditions a conceptual model of beach rotation is presented the model describes the combinations of cross shore and longshore sediment transport and hydrodynamic processes that are expected to result in the observed clockwise and anti clockwise beach rotation during el nino and la nina phases respectively

structure of a near polar latitude forest from the new zealand jurassic a tidal platform at curio bay near the southernmost point of the south island new zealand preserves the petrified remains of an in situ middle jurassic forest the forest grew close to the palaeo polar circle but data are not precise enough to tell on which side it lay a mapped portion of the forest floor provides data on tree density and population structure allowing comparison with recent forests and with records of other fossil forests the forest has tree densities similar to many forests growing in low to mid latitudes today it appears to have had emergents projecting through a low canopy and a well developed undergrowth of smaller gymnosperms and osmundaceous ferns no aspect of the forest structure uniquely distinguishes it from that of non polar latitude forests an extended discussion is given on reconstructing tree height from stump diameter on the basis of this a reinterpretation of the structure of an early cretaceous fossil forest from alexander island antarctica is offered

sand size versus beachface slope an explanation based on the constructal law article i nfo article history the relationship between beachface slope and sand grain size has been established based on multiple observations of beach characteristics in many parts of the world we show that this observational result may be understood in the light of the constructal law bejan 1997 a model of wave run up and run down along the beachface swash was developed to account for superficial flows together with flows through the porous sand bed of average porosity 0 35 the permeability of which may be related to grain diameter and sphericity 0 9 for sand grains through the kozeny carman equation then by using the constructal law we minimized the time for completing a swash cycle under fixed wave height and sand grain diameter as the result a relationship involving sand grain size beachface slope and open ocean wave height has been obtained and then discussed and validated against experimental data in addition this relationship has also been used to illuminate beachface dynamic processes namely the reshaping of sandy beachfaces in response to changes in wave height though the model used in this work may be improved further the results appear to show as with other natural systems that beachface morphing in time may be understood based on a unifying principle the constructal law

triassic climates state of the art and perspectives abstract the climate of the triassic period was characterized by a non zonal pattern dictated by a strong global monsoon system with effects that are most evident in the tethys realm this strong monsoonal regime is related to the aggregation of the pangaean supercontinent which by triassic time was already completed climate oscillations existed within this framework the harsh hot house climatic conditions that characterized the late permian and perhaps precipitated the end permian mass extinction were probably maintained during the early triassic and may account for the impoverished but distinctive faunal and floral lower triassic associations although metazoan reef builders were probably the most affected group carbonate production remained high at least in the western tethys realm the middle triassic was characterized locally by humid episodes although their geographical distribution has yet to be clarified the carnian pluvial event marks an episode of increased rainfall documented worldwide was the most distinctive climate change within the triassic different hypotheses have been proposed for its causes changes of atmospheric or ocean circulation driven by plate tectonics a peak of the global monsoon due to maximum continent aggregation or triggering by the eruption of a large igneous province subsequently the late carnian and norian seem to have been climatically stable although minor climatic changes have recently been described even from this time period finally the end triassic extinction event is also associated with climate change specifically warming and increased rainfall but this evidence comes mostly from the northern parts of the central atlantic magmatic province and the global pattern of climate change at the triassic jurassic boundary has still to be resolved many facets of triassic climate are intriguing and deserve further research however palaeoclimate studies on the triassic have so far been carried out only locally with different proxies those proxies will require inter calibration in order to depict correctly the temporal and geographical patterns of triassic climate

hurricane induced beach change derived from airborne laser measurements near panama city florida this study used airborne laser data to investigate spatial variations in shoreline migration beach width subaerial volume and subaqueous volume change due to a hurricane event five separate airborne laser data sets of panama city fl area beaches were collected during a seven month period before and after landfall of hurricane ivan contour shorelines were extracted from digital elevation models interpolated from these laser measurements and were used to measure changes in shoreline position and beach width the shoreline migrated 16 m landward due to hurricane ivan and migrated 10 m seaward following hurricane ivan no significant spatial relationship was found between shoreline migration before and after the hurricane linear relationships between a time series of beach width and subaerial volume were found at many locations however utilization of a single coefficient to represent all relationships is problematic due to the spatial variability in the linear relationship differences in two bathymetric data sets for summer and fall show that only a small portion of sediments were transported beyond an active zone and most sediments remain within the active zone despite the occurrence of a hurricane

rip currents mega cusps and eroding dunes abstract dune erosion is shown to occur at the embayment of beach mega cusps o 200 m alongshore that are associated with rip currents the beach is the narrowest at the embayment of the mega cusps allowing the swash of large storm waves coincident with high tides to reach the toe of the dune to undercut the dune and to cause dune erosion field measurements of dune beach and rip current morphology are acquired along an 18 km shoreline in southern monterey bay california this section of the bay consists of a sandy shoreline backed by extensive dunes rising to heights exceeding 40 m there is a large increase in wave height going from small wave heights in the shadow of a headland to the center of the bay where convergence of waves owing to refraction over the monterey bay submarine canyon results in larger wave heights the large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale the strongly refracted waves and narrow bay aperture result in near normal wave incidence resulting in well developed persistent rip currents along the entire shoreline the alongshore variations of the cuspate shoreline are found significantly correlated with the alongshore variations in rip spacing at 95 confidence the alongshore variations of the volume of dune erosion are found significantly correlated with alongshore variations of the cuspate shoreline at 95 confidence therefore it is concluded the mega cusps are associated with rip currents and that the location of dune erosion is associated with the embayment of the mega cusp

spatial and temporal variations of sediment size on a mixed sand and gravel beach abstract mixed sand and gravel beaches have been the subject of comparatively few studies in the uk this paper describes the sediment distribution before during and after a programme of beach nourishment along a section of mixed sand and gravel beach forming part of the pevensey bay coastal defences in east sussex uk the beach was recharged in september 2002 and beach profiles were measured along three cross shore transects from august 2002 to february 2003 sediment samples were taken along the transects between august and november 2002 and a total of 147 sediment samples were analysed 40 before nourishment and 107 after nourishment the majority of the sediment samples were strongly bimodal with mean sizes varying between a minimum of 0 18 mm 2 48 for the sand fraction and a maximum of 27 mm 4 74 for the gravel the recharge material was also bimodal but contained more fine sediment than the natural beach material particularly on the upper beach the recharge sediment had grain sizes and sorting similar to some of the natural material but lower bimodality parameters than any of the natural sediment the sediment distributions after recharge contained significantly more fine sediment particularly on the upper beach over time the beach profile lowered and fine sediment appeared to be selectively transported seawards from the beachface

morphological changes beach inundation and overwash caused by an extreme storm on a low lying embayed beach bounded by a dune system nw mediterranean abstract the geomorphological evolution of a low lying micro tidal sandy beach in the western mediterranean pals beach was characterized using airborne light detection and ranging lidar data data were collected in prior to and six months after the impact of an extreme storm with a return period of approx 50 years with the aim of characterizing the beach s response to the storm the use of repeated high resolution topographic data to quantify beach geomorphic changes has allowed assessment of the accuracy of different proxies for estimating beach volume changes results revealed that changes in the shoreline position cannot accurately reproduce beach volume changes on low lying beaches where overwash processes are significant observations also suggested that volume estimations from beach profiles do not accurately represent subaerial volume changes at large profile distances on beaches with significant alongshore geomorphological variability accordingly the segmentation of the beach into regularly spaced bins is proposed to assess alongshore variations in the beach volume with the accuracy of the topographic data the morphological evolution of pals beach during the study period showed a net shoreline retreat 4 m and a significant sediment gain on the subaerial beach 7 5 m 3 m the net gain of sediment is mostly due to the impact of the extreme storm driving significant overwash processes that transport sediment landwards increasing volume on the backshore and dunes the increase of volume on the foreshore and the presence of cuspate morphologies along the shoreline also evidence post storm beach recovery observed morphological changes exhibit a high variability along the beach related to variations in beach morphology changes in the morphology and migration of megacusps result in a high variability in the shoreline position and foreshore volume changes on the other hand larger morphological changes on the backshore and larger inundation distances occur when the beach and the dunes are lower favouring the dominance of overwash the observed storm induced morphological changes differ from predicted beach storm impacts because of spatial and temporal variations in the beach morphology suggesting that detailed morphological parameters and indicators used for predicting beach vulnerability to storms should be regularly updated in order to represent the pre storm beach conditions finally observed morphological changes in pals bay evidenced a different behaviour between natural and urban areas with better post storm beach recovery on natural areas where the beach is not artificially narrowed

depositional setting and paleobotany of permian and triassic permineralized peat from the central transantarctic mountains antarctica abstract silicified peat is known from two sites in the central transantarctic mountains both are within a 2 km thick permo triassic sandstone shale sequence that was deposited by braided streams in a rapidly subsiding foreland basin along the paleo pacific margin of antarctica upper permian permineralized peat occurs as scattered boulders just above a channel form sandstone in the upper part of the buckley formation on skaar ridge overlooking the beardmore glacier these boulders are erosional remnants of fine grained deposits that accumulated in shallow lakes or swamps on a flood plain at fremouw peak the peat occurs near the top of the fremouw formation in strata that are probably middle to late triassic in age the peat consists of large blocks that were rafted into a sandy braided stream channel during a flood and then stranded and buried as flood waters receded both sites are characterized by exceptionally well preserved plant material although the composition and diversity of the two floras are very different permineralization apparently took place rapidly and was enhanced by the dissolution of siliceous volcanic detritus that is abundant in both formations

changes to monterey bay beaches from the end of the 1982 83 el nino through the 1997 98 el nino abstract the shoreline of monterey bay ca usa demarcates the landward extent of the monterey bay national marine sanctuary along the length of that shoreline nine beaches were profiled 34 times between 1983 and 1998 the resulting data set provides an understanding of processes that affect beach volume width and shape monterey bay which is open to high energy waves generated in the pacific ocean comprises a range of beach environments that respond in a dramatic way to major storms such as the anomalously large el ninos in 1982 83 and 1997 98 this study relates the profile characteristics of the beaches to storminess shoreline location and geomorphic setting because the large el ninos occurred at the start and end of the study the surveys cover both periods of nearly constant beach size and periods of extreme erosion and the data show both the extent of erosion and accretion and the nature of the transition between the two periods

palaeobotanical evidence for a warm cretaceous arctic ocean the cretaceous period was a time of global warmth1 4 mid cretaceous equatorial temperatures were similar to today s5 but the equator to pole temperature gradient is the subject of some controversy5 7 although it is unlikely that the poles were ice free8 10 fossil evidence3 5 11 12 indicates that near polar temperatures were much higher than they are today little is known moreover about oceanic poleward heat transport and this makes it hard to model the cretaceous climate or to evaluate the extent to which it provides an analogue for a greenhouse world warmed by increased atmospheric co2 alone here we use relationships between leaf physiognomy such as shape and size and modern climate to determine cretaceous climate conditions in the arctic region from fossil leaves we find that the arctic ocean was relatively warm remaining above 0 c even during the winter months this implies that there was significant poleward heat transport during all seasons

mid el nino erosion at nourished and unnourished southern california beaches wave conditions in southern california during the 2015 2016 el nino were similar to the 2009 2010 el nino previously the most erosive minimum beach widths and subaerial sand levels in a 7 year record as of february 2016 torrey pines beach had eroded slightly below 2009 2010 levels threatening the shoulder of a major highway however cardiff solana and imperial beaches nourished with imported sand in 2012 were on average 1 2 m more elevated and more than 10 m wider than in 2009 2010 monthly subaerial sand elevation observations showed that the nourished beaches remained consistently wider than unnourished beaches under similar wave conditions in contrast to a 2001 nourishment at torrey pines built with native sized sand that was removed from the beach face during a single storm these relatively coarse grained nourishments protected shorelines for several years and during the significant wave attack of the 2015 2016 el nino as of february 2016

historical changes in the shoreline and littoral processes on a headland bay beach in central chile abstract we applied parabolic and logarithmic adjustments and methods of cartographic overlay to the sandy littoral of concon bay central chile to determine the changes associated with the shoreline and their relation with littoral processes in a typical bay on an active continental margin and with a microtidal regime a set of historical reference points was built by means of aerial photographs and topographies for the period 1945 2008 given the form of the shoreline to the southern section of the bay we applied the classical logarithmic formula of yasso 1965 and the functions incorporated in the coastal modeling system sistema de modelamiento costero smc of the universidad de cantabria in the northern section a method of map overlay was applied the oluca sp model of the smc was used to determine the influence of waves refraction on the types of changes of the shoreline information on waves 1985 2006 mean sea level 2001 2006 and variations in the mean size of beach sediment were used to relate the changes in the plan form of the bay there has been little spatio temporal variability in the shoreline of the bay over the last 65 years the southern section had a mean shoreline retreat rate of 0 55 m year 1945 2008 in spite of the large variability produced in an estuary dominated by waves the best adjustment was obtained with the logarithmic function in the northern section the mean accretion rate was 0 39 m year 1954 2008 the plan form and the historical changes of the shoreline are closely associated with the seasonal changes of the waves and the presence of rocky thresholds in the area the mean sea level did not produce important effects in the types of change

morphodynamics of a field of crescent shaped rippled scour depressions northern monterey bay ca abstract despite the prevalence of rippled scour depression rsd on the world s continental shelves and their importance as nursery habitats for many commercially important species the processes responsible for their formation and geomorphic evolution are still not well understood most studies that focused on rsd evolution have been based on data acquired over multiple years to decades and often during calmer summer months here multiple geophysical seafloor mapping surveys of a field of rsd s off santa cruz california usa were conducted over the course of two winters with distinctly different oceanographic forcing these results were compared to time series oceanographic measurements made within the survey area and put into the context of long term trends from survey data collected during previous decades although the migration of these features across the seafloor occurs on decadal time scales significant change was detected within a given year depending on the wave climate and fluvial sediment input rsds shrank up to 16 or grew up to 28 in a span of a few months such change was predominantly the result of redistribution of fine grained sediment input to the system by local rivers migration of the seafloor features appears to be the result of accumulation of fine grained sediment at the boundary between the rsd and the surrounding fine grained cap

reversing storm hotspots on sandy beaches spatial and temporal characteristics coastal erosion hotspots are defined as sections of coast that exhibit significantly higher rates of erosion than adjacent areas this paper describes the spatial and temporal characteristics of a recently identified type of coastal erosion hotspot which forms in response to storms on uninterrupted sandy coasts largely free from human intervention these are referred to here as reversing storm hotspots because the erosion is reversed by accretion of a similar magnitude to the storm induced erosion the accretion occurs within a few days or weeks of fair weather after the storm reversing storm hotspots observed here on two us east coast beaches have a longshore length averaging 3 86 km a cross shore excursion magnitude of erosion or accretion averaging 15 4 m and a time scale of days to weeks associated with individual storm events these spatial and temporal scales clearly distinguish reversing storm hotspots from previously described forms of longshore variability in erosion including those attributed to several types of shoreline undulations and hotspots associated with long term shoreline change

continental shelf gis for the monterey bay national marine sanctuary abstract a marine sanctuary is an environment where the interests of science and society meet land and marine managers need access to the best scientific data available that describe the environment and environmental processes in sanctuaries the sidescan sonar imagery bathymetry sample analyses and other data discussed in the papers in this volume have been made available as a u s geological survey cdrom publication

rainfall patterns and the distribution of coals and evaporites in the mesozoic and cenozoic abstract paleoclimatologists have adequately demonstrated over the last twenty years that the distribution of climatically sensitive sediments can be related to present day climatic zones that are roughly parallel to latitude for example coals were deposited at paleolatitudes that correspond to the present day rainy zones at the equator and at about 55 n and 55 s indicating that those zones were present in the past from this it can be concluded that atmospheric circulation has not been radically different from its present configuration despite some apparently great differences in some climatic parameters such as the equator to pole temperature gradient nevertheless the zonal model for predicting the distribution of climatically sensitive sediments is not wholly adequate although general atmospheric circulation may not have been radically altered from its present pattern it would have differed in some respects because the paleogeography was different from the present geography therefore we have constructed what we believe are more realistic maps of the distribution of rainfall through time these maps are based on maps of atmospheric circulation that have been successfully used to predict the distribution of some petroleum source beds and phosphorites we have compared the predicted distribution of rainfall to the distribution of coals and evaporites for each of seven geologic stages the circulation rainfall maps were more successful than the zonal model for predicting the distribution of evaporites and coals for times when the paleogeography would have maximized the development of a monsoonal circulation which most effectively disrupts the general zonal pattern for times when a monsoonal circulation would not have been important the zonal model adequately predicted the distribution of these rocks

long term cliff retreat and erosion hotspots along the central shores of the monterey bay national marine sanctuary abstract quantification of cliff retreat rates for the southern half of santa cruz county ca usa located within the monterey bay national marine sanctuary using the softcopy geographic information system gis methodology results in average cliff retreat rates of 7 15 cm yr between 1953 and 1994 the coastal dunes at the southern end of santa cruz county migrate seaward and landward through time and display net accretion between 1953 and 1994 which is partially due to development in addition three critically eroding segments of coastline with high average erosion rates ranging from 20 to 63 cm yr are identified as erosion hotspots these locations include opal cliffs depot hill and manresa although cliff retreat is episodic spatially variable at the scale of meters and the factors affecting cliff retreat vary along the santa cruz county coastline there is a compensation between factors affecting retreat such that over the long term the coastline maintains a relatively smooth configuration the softcopy gis methodology significantly reduces errors inherent in the calculation of retreat rates in high relief areas e g erosion rates generated in this study are generally correct to within 10 cm by removing errors due to relief displacement although the resulting root mean squared error for erosion rates is relatively small simple projections of past erosion rates are inadequate to provide predictions of future cliff position improved predictions can be made for individual coastal segments by using a mean erosion rate and the standard deviation as guides to future cliff behavior in combination with an understanding of processes acting along the coastal segments in question this methodology can be applied on any high relief coast where retreat rates can be measured

confirmation of carboniferous clastic swamp communities tropical lowlands dominated by arborescent lycophytes are the principal foci for our understanding of carboniferous peat and non peat accumulating coastal swamps1 2 suggested palaeoeco logical interpretations of various lycophytes and accessory vegetation have been based on transported compression assemblages3 4 and palynomorphs5 6 or in situ permineralized peats7 where transported macrodetritus resulting in compression assemblages is used to reconstruct past vegetational patterns taphonomic factors tend to bias the preserved flora8 11 taken alone or out of depositional context the heterogeneity of an assemblage most probably bears little or no relationship to that of the original contributing communities gastaldo9 suggests that reconstructions should be based on the autecology of erect in situ plants because with peats permineralized in situ precise resolution in time of laterally equivalent vegetation is difficult here i document an erect in situ early pennsylvanian lycophyte swamp which provides the first confirmatory evidence for previously hypothetical ecological amplitudes

synchronised patterns of erosion and deposition observed at two beaches abstract a similarity in the observed variability through time of two or more individual beaches here quantified by synchronous changes in shoreline position and subaerial sand volume can have significant implications to the increased focus worldwide on the need for expanded coastal monitoring if it can be established that one or a select few beach sites exhibit regionally representative behaviour in response to varying and or changing wave and other climatic forcing then this will assist to guide the extent and scope of the ongoing monitoring effort required in this study two beaches located on the southeast australian coastline of similar size and orientation but separated by 35 km were simultaneously monitored and compared for a period spanning 3 years intensive sub aerial surveys were conducted each month at both sites using atv mounted rtk gnss the purpose was to establish whether detailed embayment wide patterns of erosion and deposition quantified at either site were indicative of the behaviour observed at the other during the data collection period storm wave events caused substantial fluctuations in monthly sub aerial sand volumes in the range of 60 70 of mean volume including month to month changes at the berm and episodic foredune erosion and recovery principal component analysis of the two beaches revealed that both were dominated by oscillation corresponding north south behaviour rather than rotation contrasting north south behaviour over this three year period comparison of alongshore averaged volume time series between the two sites indicated a similar total range 68 m3 m and 78 m3 m and the average difference between the two sites 4 5 m3 m was found to be of the order of 50 of the average monthly change 9 7 m3 m and 10 2 m3 m corresponding spatial patterns in the occurrence of erosion accretion along the two sites were also compared and found to closely correspond five synchronised snap shot observations from historical aerial photogrammetry and surveys at both sites spanning the period 1974 to 2011 one per decade suggest coherence between the sites extends beyond the three year intensive monitoring period reported here

oxygen and carbon isotope and sr ca signatures of high latitude permian to jurassic calcite fossils from new zealand and new caledonia abstract calcite fossils from new zealand and new caledonia provide insight into the permian to jurassic climatic history of southern high latitudes southern hl and triassic southern intermediate latitudes southern il these results permit comparison with widely studied coeval sections in low latitudes ll and il oxygen isotope ratios of well preserved shell materials indicate a partially pronounced sea surface temperature sst gradient in the permian whereas for the triassic no indication of cold climates in the southern hl is found the late jurassic of new zealand is characterized by a slight warming in the oxfordian kimmeridgian and a subsequent cooling trend in the tithonian systematic variations in the 13c values of southern hl samples are in concert with those from ll sections and confirm the global nature of the carbon isotope signature and changes in the long term carbon cycle reported earlier systematic changes of sr ca ratios in late triassic brachiopods falling from 1 19 mmol mol in the oretian early norian to 0 67 mmol mol in the warepan late norian and subsequently increasing to 1 10 mmol mol in the otapirian rhaetian are observed also sr ca ratios of late jurassic belemnite genera belemnopsis and hibolithes show synchronous changes in composition that may be attributed to secular variations in the seawater sr ca ratio for the two belemnite genera an increase from 1 17 mmol mol in the middle heterian oxfordian to 1 78 mmol mol in the mangaoran late middle tithonian and a subsequent decrease to 1 51 mmol mol in the waikatoan late tithonian is documented

sand mining impacts on long term dune erosion in southern monterey bay abstract southern monterey bay was the most intensively mined shoreline with sand removed directly from the surf zone in the u s during the period from 1906 until 1990 when the mines were closed following hypotheses that the mining caused coastal erosion it is estimated that the yearly averaged amount of mined sand between 1940 and 1984 was 128 000 m 3 yr which is approximately 50 of the yearly average dune volume loss during this period to assess the impact of sand mining erosion rates along an 18 km range of shoreline during the times of intensive sand mining 1940 1990 are compared with the rates after sand mining ceased 1990 2004 most of the shoreline is composed of unconsolidated sand with extensive sand dunes rising up to a height of 46 m vulnerable to the erosive forces of storm waves erosion is defined here as a recession of the top edge of the dune recession was determined using stereo photogrammetry and lidar and gps surveys long term erosion rates vary from about 0 5 m yr at monterey to 1 5 m yr in the middle of the range and then decrease northward erosion events are episodic and occur when storm waves and high tides coincide allowing swash to undercut the dune and resulting in permanent recession erosion appears to be correlated with the occurrence of el ninos the calculated volume loss of the dune in southern monterey bay during the 1997 98 el nino winter was 1 820 000 m 3 which is almost seven times the historical annual mean dune erosion of 270 000 m 3 yr the alongshore variation in recession rates appears to be a function of the alongshore gradient in mean wave energy and depletions by sand mining after cessation of sand mining in 1990 the erosion rates decreased at locations in the southern end of the bay but have not significantly changed at other locations

sediment dynamics and the burial and exhumation of bedrock reefs along an emergent coastline as elucidated by repetitive sonar surveys northern monterey bay ca abstract two high resolution bathymetric and acoustic backscatter sonar surveys were conducted along the energetic emergent inner shelf of northern monterey bay ca usa in the fall of 2005 and the spring of 2006 to determine the impact of winter storm waves beach erosion and river floods on biologically important siliclastic bedrock reef habitats the surveys extended from water depths of 4 m to 22 m and covered an area of 3 14 km 2 45 8 of which was bedrock gravel and coarse grained sand and 54 2 was fine grained sand our analyses of the bathymetric and acoustic backscatter data demonstrates that during the 6 months between surveys 11 4 of the study area was buried by fine grained sand while erosion resulted in the exposure of bedrock or coarse grained sand over 26 5 of the study area the probability of burial decreased with increasing water depth and rugosity the probability of exhumation increased with increasing wave induced near bed shear stress seabed slope and rugosity much of the detected change was at the boundary between bedrock and unconsolidated sediment due to sedimentation and erosion burying or exhuming bedrock respectively in a number of cases however the change in seabed character was apparently due to changes in sediment grain size when scour exposed what appeared to be an underlying coarser grained lag or the burial of coarser grained sand and gravel by fine grained sand these findings suggest that in some places a burial and exhumation of nearshore bedrock reefs along rocky energetic inner shelves occurs over seasonal timescales and appears related to intrinsic factors such as seabed morphology and extrinsic factors such as wave forces and b single acoustic surveys typically employed for geologic characterization and or habitat mapping may not adequately characterize the geomorphologic and sedimentologic nature of these types of environments that typify most of the pacific ocean and up to 50 of the world s coastlines

towards a sediment budget for the santa cruz shelf a conceptual model is presented for the northern monterey bay continental shelf in which coarse sediment moves southward along the coast in the littoral zone while fine sediment moves to the north by advection and diffusion along the midshelf data from measurements and estimates of various sediment sources and sinks show that the midshelf mudbelt is the dominant sink for fine grained sediment introduced into monterey bay the principal sources of the fine sediment are the three rivers that enter monterey bay the san lorenzo pajaro and salinas rivers accumulation rates in the midshelf mudbelt are high relative to documented yields of rivers and cliff erosion and also are high relative to other documented mud accumulations of the west coast continental shelves

fine grained splay deposition in the avulsion belt of the lower saskatchewan river canada abstract in or about 1883 a northward avulsion of the meandering lower saskatchewan river at the cumberland marshes initiated a broad belt of alluvial sedimentation that has continued to evolve to the present and now covers some 500 km2 the avulsion belt comprises a complex alluvial terrain dominated by individual and coalesced splays and associated wetlands connected by networks of active and abandoned channels of various sizes the windy lake splay a predominantly fine grained feature typical of large parts of the avulsion belt was examined to investigate the relationships between splay evolution and facies development the splay now largely inactive mostly formed over a 35 year period depositing nearly 2 m of sediment over a 7 2 km2 area the splay surface is ch racterized by stable well defined anastomosed distributary channels that separate interchannel wetland basins heights of channel levees diminish downstream and the levees merge with channel mouth bars whose progradation forms the locus of lakeward channel extension and the base for subsequent subaerial levee deposition the anastomosed channel pattern was created when the mouth bars of separate distributary channels merged during progradation vibracore and soil probe profiles show the splay to be dominated by upward coarsening lacustrine prodeltaic mouth bar facies sequences capped by levees and organic rich interchannel wetland deposits channels now containing sand only sporadically in narrowed or slightly migrated reaches will eventually fill with fine sediment when abandonment s complete the windy lake splay is typical of stage iii splays smith et al 1989 whose deposits and associated lacustrine fills form at least half of the avulsion belt thin widespread predominantly upward coarsening sequences capped by either nondepositional horizons or true overbank fines may be characteristic of many avulsive suites in the ancient alluvial record

temporal and spatial variations in sand budgets with application to southern monterey bay california abstract often in calculating a sediment budget there is an unknown contribution which is ascribed to the residual of the balance and the budget cannot be fulfilled the temporal and spatial variations and sediment size within a littoral cell provide additional information to define sediment budgets the approach here is to consider only medium to coarse sand grain size 0 25 mm over a long time period during significant changes of natural and anthropogenic inputs and losses that allow calculating several budgets to isolate the unknown inputs and outputs to close the system considering only medium to coarse sand eliminates including the cross shore transport of fine sand by waves which is poorly quantified to demonstrate these concepts shoreline recession rates measured over a 101 year time period are used to calculate sediment budgets for southern monterey bay california littoral cells the coarse sandy shoreline is backed by extensive bluffs and dunes that reach 44 m in elevation intensive sand mining of coarse sand derived directly from the beach and surfzone started in 1927 and continues today a contribution of about 100 k m 3 year of medium to coarse sand from the salinas river is calculated from measured shoreline accretion for the period 1910 1945 starting when the river first flowed into the littoral cell prior to damming of the river and significant losses owing to sand mining sediment budgets are calculated for 1940 1989 and 1989 2011 to spatially identify the loss of about 200 k m 3 year attributed to different mining operations that captured the littoral transport the primary contributions of medium to coarse sand to the littoral system is approximately 180 k m 3 year from the eroding dunes and beaches only a quarter of the dune sand is found to be compatible with the coarser beach sand with the finer fraction carried offshore a conclusion is that sand mining is the cause of the observed high recession rates

permian triassic boundary in the central transantarctic mountains antarctica the permian triassic boundary occurs within a relatively complete terrestrial sequence in the shackleton glacier area of the central transantarctic mountains the boundary is within a 7 to 10 m thick interval between the permian glossopteris flora and the lower triassic lystrosaurus fauna this interval representing on the order of 200 k y records some of the events that occurred in the transition from the permian to triassic in the best documented section at graphite peak in the beardmore glacier region protohaploxypinus microcorpus zone palynomorphs which we assign to the latest permian record the declining glossopteris flora and occur near the top of the buckley coal measures just below a previously reported major negative 13c excursion in the shackleton glacier area the permian glossopteris flora including fossil wood roots and leaves occurs within the lower part of the fremouw formation the antarctic lystrosaurus assemblage of early triassic age has several species in common with the south african fauna that lived 20 to 35 closer to the equator the migration of vertebrates from southern africa into antarctica in the early triassic supports hypotheses of runaway greenhouse warming possibly related to co2 emissions from siberian flood basalts and large methane gas releases changes in flora bracketing the first of the major negative 13c anomalies near the boundary in antarctica and in east greenland support the hypothesis that a global event perhaps through mutations caused by enhanced ultraviolet radiation may have played a role in the destruction of floras

possible role of oceanic heat transport in early eocene climate increased oceanic heat transport has often been cited as a means of maintaining warm high latitude surface temperatures in many intervals of the geologic past including the early eocene although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically determining how additional oceanic heat transport would take place has yet to be accomplished that the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked using early eocene climate as an example we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early eocene conditions our interpolation of early eocene paleotemperature data indicate that an approximately 30 increase in poleward heat transport would be required to maintain eocene high latitude temperatures this increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early eocene rates either oceanic processes were very different from those of the present to produce the early eocene climate conditions or oceanic heat transport was not the primary cause of that climate we believe that atmospheric processes with contributions from other factors such as clouds were the most likely primary cause of early eocene climate

annual and interannual changes on a reef fringed pocket beach kailua bay hawaii abstract historical aerial photographs and topographic survey sheets are used to establish a 70 year shoreline history 1926 1996 for kailua beach oahu hawaiian islands the shoreline has migrated seaward over this period at an average rate of 0 5 m yr with a maximum net accretion along the beach of 58 7 m and a maximum net erosion of 13 2 m net accretion has taken place even while sea levels have risen on the order of 0 1 m semi annual and monthly beach profile surveys 1995 1999 at seven transects reveal short term variations of shoreline position sand volume and beach shape a relationship between beach width and corresponding sand volume fluctuations established from the beach profile data is applied to the historical shoreline change data to establish a history of sand volume fluctuations results show that kailua has experienced a net accretion of 673 000 m3 of sand over the period 1926 1996 with average annual rates of volume change varying between 6 8 m3 m yr and 0 1 m3 m yr the most recent period 1989 1996 shows a net volume increase of 41 000 m3 given the lack of sand inputs at the ends of the beach exchange with offshore deposits is a likely mechanism for long term accretional trends seasonal fluctuations in kailua beach morphology dominate the variability with a response to seasonal wave state that varies along the length of the beach in magnitude and sign at least four alongshore zones are observed with the first and third zones exhibiting high low sand volumes during the summer winter and the second and fourth zones exhibiting opposite behavior with high low volumes during the winter summer although seasonal sand accumulation varies along the beach the overall beach profile is largely maintained moreover changes in sand volume occur in phase over the subaqueous and subaerial sections of the beach this behavior suggests that longshore rather than cross shore sand transport is important at annual time scales a simple seasonal transport pattern is proposed to account for these observed fluctuations which depends in part on the topography of the offshore reef

biodiversity and terrestrial ecology of a mid cretaceous high latitude floodplain alexander island antarctica the biodiversity and terrestrial ecology of the late albian triton point formation fossil bluff group alexander island antarctica is analysed to improve our understanding of polar biomes during the mid cretaceous thermal optimum this formation was deposited on a high latitude 75 s floodplain and consists of two facies associations a lower braided alluvial plain unit and an upper coastal meander belt unit analysis of fossil plants in well exposed palaeosols reveals the existence of spatially complex plant communities braidplains supported patchy low density 91 trees ha stands of podocarp and taxodioid conifers on floodbasin substrates and conifer cycadophyte fern angiosperm thickets in riparian settings coastal meander belts supported medium density 568 trees ha podocarp araucarian conifer forests on mature floodbasin soils and fern angiosperm ginkgo thickets in riparian settings growth ring analysis indicates plants experienced stressful growing conditions on the braidplain characterized by high frequency flood events but more favourable growing conditions on the coastal plain additional vegetation disturbances were caused by arthropod fungal attack frost and wildfire in terms of structure composition ecology and productivity these predominantly evergreen broad leafed conifer forests bear similarities to the extant temperate rainforests of new zealand

seasonal morphodynamics of the subaerial and subtidal sections of an intermediate and mesotidal beach abstract this study provides a detailed insight into the seasonal morphological evolution of the subaerial and subtidal sections of an intermediate and mesotidal beach in relation to the nearshore wave conditions for this purpose fortnightly to monthly topographic and bathymetric measurements were collected on ensenada beach baja california mexico from november 2012 to february 2016 wave data were concurrently measured at 20 m water depth enabling the correlation of the observed morphological changes to the hydrodynamic forcing the seasonal morphological variability of the beach comprised 200 000 m 3 70 m 3 m 1 and resulted primarily from the cross shore exchange of sediment the volumetric fluctuations alongshore were up to 100 000 m 3 and event driven and played an inportant role in the overall sediment balance in association with the incoming wave conditions the subaerial and subtidal beach sections experienced a strong seasonal variability the subaerial beach reached the maximum volumes in the end of summer september october and minimum in winter january february while the opposite response was obtained for the subtidal beach with the largest and smallest volumes occurring during the same months in winter and summer respectively the morphological fluctuations of the upper and lower beach sections were associated with the preceding monthly averaged wave conditions the subtidal volume variations were highly and positively correlated to the wave height and period while the subaerial section was highly but negatively correlated to the same variables the morphological beach response to energetic waves was more rapid than to low energy conditions the largest subaerial erosion and subtidal accretion happened in three months october january while the subaerial accretion and subtidal erosion occurred smoothly over nine months january october the total beach volume subaerial and subtidal lacked of seasonal variability and an annual loss of 50 000 m 3 17 m 3 m 1 occurred from august 2014 to august 2015 indicating that the beach remained fairly stable over that period of time the largest volumetric variations of 300 000 m 3 105 m 3 m 1 occurred during the beginning of the 2015 2016 el nino winter

behaviour of beach profiles during accretion and erosion dominated periods beach profiles have been surveyed at monthly intervals between 1972 and 1988 at moruya on the south coast of new south wales australia four profile sites have been used as a data set to provide an understanding of changes to beach volume width and shape moruya beach represents a moderately high energy microtidal environment which responds in a dramatic way to major storm events such as those experienced in the mid 1970s this study distinguishes between profile characteristics associated with such a period erosion dominated or edp compared with periods when accretion dominated adp accompanied by foredune expansion in both height and width