the response of the southwest western australian wave climate to indian ocean climate variability knowledge of regional wave climates is critical for coastal planning management and protection in order to develop a regional wave climate it is important to understand the atmospheric systems responsible for wave generation this study examines the variability of the southwest western australian swwa shelf and nearshore wind wave climate and its relationship to southern hemisphere climate variability represented by various atmospheric indices the southern oscillation index soi the southern annular mode sam the indian ocean dipole mode index dmi the indian ocean subtropical dipole iosd the latitudinal position of the subtropical high pressure ridge strp and the corresponding intensity of the subtropical ridge stri a 21 year wave hindcast 1994 2014 of the swwa continental shelf was created using the third generation wave model simulating waves nearshore swan to analyse the seasonal and inter annual wave climate variability and its relationship to the atmospheric regime strong relationships between wave heights and the strp and the stri a moderate correlation between the wave climate and the sam and no significant correlation between soi dmi and iosd and the wave climate were found strong spatial seasonal and inter annual variability as well as seasonal longer term trends in the mean wave climate were studied and linked to the latitudinal changes in the subtropical high pressure ridge and the southern ocean storm belt as the southern ocean storm belt and the subtropical high pressure ridge shifted southward northward wave heights on the swwa shelf region decreased increased the wave height anomalies appear to be driven by the same atmospheric conditions that influence rainfall variability in swwa

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

role of geological inheritance in australian beach morphodynamics the australian coast contains 10 685 beaches which occupy 49 of the 30 000 km coast and average 1 37 km in length their relatively short length is largely due to the presence of bedrock calcarenite and laterite which form boundaries to many of the beaches as well as occurring as rocks reefs and islands along and off the beaches this geological inheritance plays a major role in australian beach systems determining their length and through wave refraction and attenuation influencing beach location shape type morphodynamics and circulation which in turn influence sediment transport and the backing dune and barrier systems this paper uses a database covering every australian beach to review the role of headlands rocks and reefs on australian beaches major effects are the short average beach length reduction in breaker height resulting in lower energy beach types wave refraction resulting in increased beach curvature the presence of topographic rips on moderate and higher energy beaches and megarips during high wave conditions and the interruption of and or trapping of longshore sand transport leading to beach rotation

seasonal changes in beach morphology along the sheltered coastline of perth western australia abstract seasonal change in beach morphology is traditionally ascribed to a variation in the incident wave energy level with calm conditions in summer resulting in wide beaches with pronounced subaerial berms and energetic conditions in winter causing narrow beaches with nearshore bar morphology the coastline of perth western australia is characterised by a large seasonal variation in the incident wave height and local beaches exhibit a distinct seasonal change in morphology however these morphological changes are better explained by a seasonal reversal in the littoral drift direction than by variations in the incident wave energy conditions in summer when northward sediment transport prevails due to sea breeze activity beaches located south of coastal structures headlands or rocky outcrops become wider due to the accumulation of sediment against the obstacle these beaches will subsequently erode in winter during storms when the longshore sediment transport is toward the south in contrast beaches located north of obstacles will become narrower during summer and wider during winter the usefulness of the dimensionless fall velocity h b w s t where hb is the breaker height ws is the sediment fall velocity and t is the wave period as a predictor of presence absence of bar morphology and beach type was investigated it was found that fluctuates around the threshold of bar formation 1 5 2 over a variety of time scales daily weekly and seasonally these temporal variations in in conjunction with the relatively low wave energy level that characterises the coast negates the development of beach and nearshore morphology that is in equilibrium with the hydrodynamic conditions as a result bar occurrence and beach type can not be readily predicted using along the perth coast

a global analysis of austral summer ocean wave variability during sam enso phase combinations anticipating and mitigating wave related hazards rely heavily on understanding wave variability drivers here we describe wave conditions related to concurrent southern annular mode sam and el nino southern oscillation enso phases during the austral summer to identify such conditions significant wave height hs and peak wave period tp daily anomalies were composited during different sam enso phase combinations over the last four decades 1979 2018 surface wind anomalies were also composited to assist in the interpretation of wave conditions the composites show significant wave variability across all ocean basins and in several semi enclosed seas throughout the different sam enso phase combinations the southern indian and pacific oceans generally experience the strongest tp anomalies during combinations of sam phases with el nino and the weakest tp anomalies during combinations of sam phases with la nina the anomalously large waves observed in the south western pacific tasman sea and the southern ocean previously ascribed to enso conditions seem to be instead associated with the sam variability sam related atmospheric conditions are found to be able to modulate the intensity of enso related winds over the south china sea which in turn alter the magnitude of waves in that region these and other wave anomaly structures described here especially those contrasting the behaviour expected for a given enso phase such as the one found along the california coast stress the importance of understanding relationships between wave parameters and climate patterns interactions

glaciation and tectonics in an active intracratonic basin the late palaeozoic itarare group parana basin brazil the parana basin 1 600 000 km2 is the largest intracratonic basin in southern south america and contains a thick 1300 m permo carboniferous glacial succession the itarare group this paper describes over 1700 m of drill core recovered during recent exploration for oil and gas itarare group sediments consist of massive and stratified diamictites interbedded with massive and graded sandstones and massive and laminated mudstones facies are interpreted as the product of sediment gravity flows in a glacially influenced marine basin three stratigraphic formations can be defined across the basin each consisting of a lowermost sandstone rich member overlain by a diamictite rich member examination of itarare group rocks both in core and outcrop shows that depositional processes were influenced by active faulting and downslope resedimentation on relatively steep and unstable substrate slopes primary glacial deposits such as tillites and associated striated pavements occur along the present eastern outcrop belt which probably coincided with the eastern basin margin during deposition of the itarare group ice masses fringing the eastern southern african and western bolivian basin margins supplied sediment to the basin in the form of fluvio glacial deltas fans and floating ice tongues this sediment was then resedimented downslope as debris flows and turbidites both stratigraphic relationships and the regional distribution of facies types identify a clear pattern of basin subsidence and step wise expansion by outward faulting within late proterozoic mobile belts the position of successive basin margins can be related to specific lineament structures in the underlying basement asymmetric expansion of the parana basin occurred along the northern and southern basin margins during deposition of the itarare group this expansion probably reflects shallow crustal adjustments activated by collisional movements along the andean margin of south america during the hercynian orogeny

on the development of electron microprobe zircon fission track geochronology abstract the fission track method has been applied for decades to quantify rates and timing of processes in the shallow crust the most widely used approach the external detector method involves counting fission tracks a decay product resulting from the spontaneous fission of 238 u and a paired set of induced tracks parent proxy from the thermal neutron irradiation of 235 u we propose an alternate method of dating zircons that utilizes an electron microprobe to directly measure uranium concentration u and image the number of spontaneous fission tracks or etch figures that intersect the surface of the crystal using an electron backscatter detector the electron microprobe fission track ep ft method is used to date six zircon samples four of which are widely used as standards fish canyon tuff peach springs tuff buluk member of the bakata formation tuff tardee rhyolite mt dromedary complex hypabyssal granite and browns park formation tuff all samples yield ages that overlap within two standard deviations of published reference ages determined using other radiometric techniques i e k ar 40 ar 39 ar and u pb and also by the traditional fission track external detector method to correct for poorly constrained parameters such as the spontaneous fission decay constant weight to volume percent conversions etching efficiency and selection bias we calculate a preliminary z proportionality factor of 4469 661 1 the ep ft technique avoids the hazard and expense of thermal neutron irradiation allows simultaneous chemical compositions to be determined removes the step of counting an external detector manually and will likely allow much higher track densities to be counted than would be normally possible with optical microscopy the technique is ideal for dating moderate to high u zircons 100 ppm u

in situ u pb sr nd and hf isotopic analysis of eudialyte by la mc icp ms abstract eudialytes are a group of complex na ca zirconosilicate minerals that generally occur in peralkaline agpaitic syenites given that eudialytes are easily altered and commonly contain inclusions of earlier crystallized minerals in situ laser ablation is considered as the most suitable method to determine their u pb ages and sr nd and hf isotopic compositions electron microprobe and la icp ms analysis of eudialytes from nepheline syenites from ilimaussaq greenland khibiny and lovozero russia saima china tamazeght morocco kipawa and mont saint hilaire canada pocos de caldas brazil and langesund fjord norway indicate that this mineral typically has high contents of u pb nb ta zr hf and rare earth elements ree analysis of an in house standard eudialyte by both solution and laser ablation methods demonstrates that precise and accurate u pb ages can be obtained from eudialyte after correction for the common pb content the high sr nd and hf contents in eudialyte coupled with the generally low rb sr and lu hf ratios also permit the precise determination of in situ sr nd and hf isotopic ratios by la mc icp ms methods however some eudialytes with rb sr ratio of 0 02 and yb sr 0 1 and lu hf 0 08 or yb hf 0 4 0 5 cannot be used for in situ sr and hf isotopic measurement eudialyte is the only mineral investigated to date for which it is possible to determine simultaneously u pb ages and sr nd and hf isotopic compositions

durango apatite fission track dating using length based age corrections and neutron fluence measurements by natural thorium thin films and natural u doped glasses calibrated through natural uranium thin films abstract in this work we present an approach for neutron fluence measurements based on natural thorium thin films and natural uranium doped glasses calibrated through natural uranium thin films to be used for dating with the fission track method ftm this neutron dosimetry approach allows the employment of ftm even when dating is carried out using low neutron thermalization facilities besides it makes possible the determination of the th u ratio of the mineral to be dated durango apatite which is often employed in ftm as an age standard was analyzed this apatite presented a fairly high th u ratio 29 9 1 7 th fissions were 18 12 and 10 of the total for irradiations where thermal to fast neutron flux ratios were 2 4 4 4 and 5 2 respectively these results show that th fission must be considered for this apatite when not well thermalized irradiation facilities are used the ratio between spontaneous and induced track length ls li close to 0 89 indicates a certain amount of rejuvenation of the age of durango apatite therefore its apparent age should be corrected the application of a technique based on track length measurements produced a corrected age of 29 7 1 1 ma consistent with the independent reference age of this apatite 31 4 0 5 ma this result represents a support for viability of the neutron dosimetry approach studied in this work for ftm

decadal changes of wind stress over the southern ocean associated with antarctic ozone depletion using 40 yr ecmwf re analysis era 40 data and in situ observations the positive trend of southern ocean surface wind stress during two recent decades is detected and its close linkage with spring antarctic ozone depletion is established the spring antarctic ozone depletion affects the southern hemisphere lower stratospheric circulation in late spring early summer the positive feedback involves the strengthening and cooling of the polar vortex the enhancement of meridional temperature gradients and the meridional and vertical potential vorticity gradients the acceleration of the circumpolar westerlies and the reduction of the upward wave flux this feedback loop together with the ozone related photochemical interaction leads to the upward tendency of lower stratospheric zonal wind in austral summer in addition the stratosphere troposphere coupling facilitated by ozone related dynamics and the southern annular mode cooperates to relay the zonal wind anomalies to the upper troposphere the wave mean flow interaction and the meridional circulation work together in the form of the southern annular mode which transfers anomalous wind signals downward to the surface triggering a striking strengthening of surface wind stress over the southern ocean

late quaternary sedimentary processes and ocean circulation changes at the southeast greenland margin a study has been made of late quaternary depositional processes and bottom current activity on the southeast greenland margin using seismic sub bottom profiling and deep tow side scan sonar data as well as sediment core information the seabed data demonstrate the occurrence of strong southerly bottom currents prevailing on the slope and rise well defined longitudinal bedforms indicate maximum mean near bottom current velocities of up to at least 1 0 m s at the depth stratum of labrador sea water 800 1500 m similarly strong currents occur in denmark strait overflow water dsow at the base of the slope whereas more basinward the maximum dsow flow speed is lower iceberg plow marks were found down to about 700 m water depth both at the shelf edge and on the lower slope and rise the seafloor morphology is indicative of downslope sediment transport and mass flow deposition which is concluded to be a typically glacial feature after generally more sluggish deep water circulation during the last glacial maximum dsow basin ventilation was re established shortly before 13 3 ka on the shelf in front of the retreating greenland ice margin permanent or semi permanent sea ice conditions prevailed until about 12 5 ka at that time increased irminger current activity had resulted in warming and east greenland current egc controlled iceberg drift increased no evidence was found for a return to extreme glacial conditions or a ceasing of dsow flow during the younger dryas abundant coarse ird collected at greater water depth from shallow sub seabed strata has a provenance mainly in the northern part of east greenland 68 73 n which demonstrates the existence of a pre holocene egc system initially extending to beyond the shelf edge

an analysis of the cross shore beach morphodynamics of a sandy and a composite gravel beach in this paper beach profile surveys acquired over more than a decade at a sandy beach narrabeen beach new south wales australia and a composite sand gravel beach milford on sea christchurch bay uk are analysed to compare and contrast cross shore morphodynamics of the two beach types the different behavioural characteristics of the two beach types at decadal inter annual and intra annual time scales are investigated comparisons of beach profiles with dean s equilibrium profile and vellinga s erosion profile show that the dean s profile satisfactorily represents the time mean profiles of both beach types statistical and empirical orthogonal function eof analyses confirm the generally accepted model that the inter tidal zone is the most morphodynamically active region on a sandy beach whereas the swash zone is the most dynamic region on a mixed sand gravel beach the results also imply that during storms composite sand gravel beaches may become unstable due to cutback of the upper beach while sandy beaches are more likely to be unstable as a result of beach lowering due to sediment transport from the inter tidal zone to the sub tidal zone during storms eof results also show that milford on sea beach is in a state of steady recession while the narrabeen beach shows a cyclic erosion accretion variability a multivariate technique canonical correlation analysis cca shows that on the composite beach a strong correlation exists between incident wave steepness and profile response which could be attributed to the unsaturated surf zone whereas on the sandy beach any correlation is much less evident

observations of gravel beach dynamics during high energy wave conditions using a laser scanner the work described in this publication was supported by the epsrc project arcoes adaptation and resilience of the uk energy system to climate change epsrc reference ep 1035390 1 and by epsrc grant ep h040056 1 in partnership with the channel coastal observatory cco the full text is under embargo until 01 01 16

assessment of hirnantian synglacial eustacy and palaeogeography in a tectonically active setting the welsh basin uk the hirnantian stratigraphy of wales is critically assessed against the global evidence for two major hirnantian synglacial eustatic lowstands the evidence for two separate lowstands of relative sea level is locally suggestive in shelf sequences but generally only permissive in the basin nowhere can the possible candidate lowstands be separated biostratigraphically and thus basinwide correlation that might rule out local tectonic control is impossible to prove consistent with palaeolatitude evidence and a situation far removed from the gondwana margin there is no facies evidence e g dropstones for local glacial conditions and the diamictites are of mass flow origin sequence stratigraphic reasoning proves helpful in the correlation of the basinal succession in central wales with the shelf sequences along the tywi lineament and the variscan front and suggests that the first appearance of normalograptus persculptus in wales does not correspond with the base of the persculptus biozone extensive new palaeocurrent data and sedimentological restudy is combined with review of earlier knowledge to argue for significant revisions to previous palaeogeographic maps for generalized lowstand conditions notably along the bala lineament the variscan front and the central wales inliers

spatial patterns of variability in antarctic surface temperature connections to the southern hemisphere annular mode and the southern oscillation 1 the 17 year 1982 1998 trend in surface temperature shows a general cooling over the antarctic continent warming of the sea ice zone with moderate changes over the oceans warming of the peripheral seas is associated with negative trends in the regional sea ice extent effects of the southern hemisphere annular mode sam and the extrapolar southern oscillation so on surface temperature are quantified through regression analysis positive polarities of the sam are associated with cold anomalies over most of antarctica with the most notable exception of the antarctic peninsula positive temperature anomalies and ice edge retreat in the pacific sector are associated with el nino episodes over the past two decades the drift towards high polarity in the sam and negative polarity in the so indices couple to produce a spatial pattern with warmer temperatures in the antarctic peninsula and peripheral seas and cooler temperatures over much of east antarctica

late ordovician global warming the boda event there is substantial evidence for mid ashgillian global warming before the latest ordovician hirnantian glaciation as shown by the movement of previously lower latitude benthic faunas such as trilobites and brachiopods to progressively higher latitudes and by an increase in endemic faunas at low latitudes this is shown by faunal dynamics on several paleocontinents and endorsed by published evidence of warmer water sediments from gondwana and elsewhere we term this global warming the boda event

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

spectral wave characteristics over the head bay of bengal a modeling study information on spectral wave characteristics is an essential prerequisite for ocean engineering related activities and also to understand the complex wave environment at any given location to the best of our knowledge there are no comprehensive studies attempted so far to study the wave spectral characteristics over the head bay of bengal a low lying deltaic environment the present study is an attempt to describe the spectral characteristics of wave evolution across different locations over this deltaic region based on numerical simulations therefore it implements a multi scale nested modeling approach using two state of art wave models wam and swan and forced with era interim winds spanning the year of 2016 model computed integrated wave parameters are validated against wave rider buoy data as well as remotely sensed saral altika and merged altimeter data analysis of the monthly averaged one dimensional spectrum reveals a single peak during the southwest monsoon and existence of double peaks from november to january and occasionally up to march variance energy density undergoes inter seasonal variation and attains its maxima during the month of july transformation of swell wave energy as a function of depth is found to be mostly associated with physical processes such as wave bottom interaction and attenuation by opposing winds during the northeast ne monsoon fetch restriction for the evolution of wind seas from the ne modification in wind shear stress by opposing swells and bottom effects remarkably contribute to the reduction in wind sea energy at shallow water depths this study indicates that the influence of swells is higher along the eastern side of the basin as compared to the western side and marginally higher variance is also observed over the east except during february april the two dimensional wave spectra exhibit differential wave systems approaching from various directions attributed to a reflected swell system from the south southeast throughout the year southwest swells reversing wind seas following local winds and reflected wind seas from the land boundary

the late ordovician diamictic formations from southwestern europe north gondwana glaciomarine deposits abstract this paper presents a review and a discussion of the clast bearing formations diamicts which occur in the uppermost part of the ordovician succession of numerous regions in southwestern europe lithology facies stratigraphic setting and age are discussed the strong similarities of these formations with contemporaneous glaciomarine deposits of the northern and northwestern margins of the african ice sheet and the late ordovician paleogeographic pattern based upon paleomagnetic data lead to the conclusion that the south european clast bearing formations are glaciomarine deposits supplied with clasts by floating icebergs released from the african ice sheet the proposed paleogeographic model confirms the close connection between southwestern europe and gondwana during early palaeozoic times

radiation effects in zircon the widespread distribution of zircon in the continental crust its tendency to concentrate trace elements particularly lanthanides and actinides its use in age dating and its resistance to chemical and physical degradation have made zircon the most important accessory mineral in geologic studies because zircon is highly refractory it also has important industrial applications including its use as a lining material in high temperature furnaces however during the past decade zircon has also been proposed for advanced technology applications such as a durable material for the immobilization of plutonium or when modified by ion beam irradiation as an optic waveguide material in all of these applications the change in properties as a function of increasing radiation dose is of critical importance in this chapter we summarize the state of knowledge on the radiation damage accumulation process in zircon

genesis of mg fe carbonates from the sierra menera magnesite siderite deposits northeast spain evidence from fluid inclusions trace elements rare earth elements and stable isotope data the mg fe carbonate deposits of sierra menera underneath exploited goethite gossan are located in the iberian range of northeasten spain within the late ordovician dolomitic formation of the sierra menera unit mgo and feo contents of the carbonates range between 13 74 and 44 02 and 5 52 and 41 73 wt percent respectively corresponding to the breunnerite and pistomesite members the morphology petrographic mineralogical and geochemical characteristics of the mg fe carbonates are consistent with a metasomatic hydrothermal origin by replacement of a dolomitic protolith as the result of the influx of hot fe mg rich fluids under acid and reducing conditions these deposits have similarities to alpine type magnesite deposits austria slovakia western carpathian mountains pyrenees and mississippi valley type fe deposits basque cantabrian basin northern spain the mg fe carbonates have normalized rare earth element ree patterns characterized by low light ree heavy ree ratios and positive eu anomalies dolomite rocks that host mg fe occurrences have been recrystallized to saddle dolomite crystals and have less fractionated normalized ree patterns but are also characterized by positive eu anomalies these patterns are distinct from the pristine host dolomite which has ree distribution typical of marine carbonates based on ree fluid inclusion and stable isotope data the mg fe carbonates are interpreted to have been formed by interaction between hot 100 150 c 18o enriched and saline 20 wt nacl equiv iron rich hydrothermal fluids and marine carbonates recrystallization of the host dolomite resulted from moderate to low fluid rock ratios 10 the mg fe carbonates were partially replaced by late dolomite redolomitization due to the action of more dilute solutions although this event resulted in 18o depletion ree patterns and 13c values of the precursors were preserved

assessment of southern oscillation sea level pressure indices abstract monthly sea level pressure anomalies at easter island rapa tahiti and darwin for the period 1951 79 are analysed to reveal their temporal characteristics and the coherence and time lead lag relationships among them for interannual scale oscillations the pressure variations at rapa and easter island lead those at tahiti and those of opposite phase at darwin by 2 8 months where the large lead times are associated with lower frequency oscillations of the four stations rapa has the smallest percentage of its variance in the range of periods containing the southern oscillation darwin has the largest spatial smoothing by combining stations enhances the percentage of variance in the longer periods combining tahiti and darwin gives a substantial increase combining rapa and easter island much less normalization of the time series through division by the monthly standard deviations is also treated the combination of tahiti and darwin is recommended as a southern oscillation index for diagno

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

chemical stratigraphy of the parana lavas south america classification of magma types and their spatial distribution a new classification scheme has been developed to assign the lava flows of the parana continental flood basalt province south america into geochemically distinct magma types with six basaltic major and trace element abundances and or ratios by mapping out the spatial distribution of these magma types within the lava sequences it has been possible to determine the internal stratigraphy of the lava pile on a regional scale previous studies on road profiles traversing the well exposed coastal serra geral escarpment of southern brazil are summarised together with results from some new sampled sections more widespread stratigraphical investigations of the parana lavas have been hampered by the lack of sufficient topographic relief and the cover of sedimentary rocks however access to drill core chippings from nine boreholes in the central parana region has provided a unique opportunity to investigate the stratigraphy of the otherwise inaccessible deeper levels of the lava pile and to map out stratigraphic variations in three dimensions the borehole samples have indicated cated a stacking of units of different magma types all overlapping towards the north which suggests that the main locus of magmatism moved northwards with time within the parana basin this migration could be related to the northward propagation of rifting during the initiation of the south atlantic ocean maps of the surface distribution of samples of each magma type show a pattern consistent with the stratigraphy inferred from the boreholes although suggesting that the shift in magmatism may have been towards the northwest on the basis of geochemical similarities between magma types and their inferred stratigraphical relationships it is proposed that the parana can be divided into two principal magmatic centres 1 an older one in the south comprising the gramado esmeralda and urubici magma types and 2 a younger one developed about 750 km to the north formed by the pitanga paranapanema and ribeira magma types

precise k ar 40ar 39ar rb sr and u pb mineral ages from the 27 5 ma fish canyon tuff reference standard the accuracy of ages measured using the 40ar 39ar technique is affected by uncertainties in the age of radiation fluence monitor minerals at present there is lack of agreement about the ages of certain minerals used as fluence monitors the accuracy of the age of a standard may be improved if the age can be measured using different decay schemes this has been done by measuring ages on minerals from the oligocene fish canyon tuff fct using the k ar 40ar 39ar rb sr and u pb methods k ar and 40ar 39ar total fusion ages of sanidine biotite and hornblende yielded a mean age of 27 57 0 36 ma the weighted mean 40ar 39ar plateau age of sanidine and biotite is 27 57 0 18 ma a biotite feldspar rb sr isochron yielded an age of 27 44 0 16 ma the u pb data for zircon are complex because of the presence of precambrian zircons and inheritance of radiogenic pb zircons with 207pb 235u 0 4 yielded a discordia line with a lower concordia intercept of 27 52 0 09 ma evaluation of the combined data suggests that the best age for fct is 27 51 ma

indices of the southern hemisphere zonal wind abstract the time and spatial variation of the southern hemisphere 500 hpa zonal wind has been examined using spectral analysis bandpass filtering and empirical orthogonal function eof analysis applied to a 15 year sample of australian hemispheric analyses spectral analysis of the entire 15 year record of the 500 hpa zonal mean westerly wind shows significant peaks only on the seasonal and interannual time scales the mean segmented spectra for each season failed to show any additional significant peaks at higher frequencies or any significant differences between seasons the primary pattern of variation revealed by eof analysis shows similar behavior on synoptic to seasonal time scales with compensating departures occurring at intervals of 20 latitude the first eof has opposing peaks near 40 and 60 s and shows an equivalent barotropic pattern when correlated with individual grid point values at 500 hpa and mean sea level pressure correlations of the zonal pattern with regional anomalies reveal

tropical and extratropical origin storm wave types and their influence on the east australian longshore sand transport system under a changing climate tropical expansion is potentially an amplifier of coastal change in the subtropics through directional wave climate shifts the storm wave climate and directional wave power distribution along the southeast australian shelf seas is investigated with respect to tropical extent forty years of storm wave observations from nine midshelf wave buoys are evaluated using synoptic storm wave typing a robust latitudinal and along shelf gradient in storm wave types and wave propagation patterns exists the tropical origin storms produce a shore normal propagation pattern along the seas reduce the connectivity of coastal compartments through minor headland bypassing events or episodically reversing the net northward transport in contrast the extratropical origin storms produce a shore oblique propagation pattern from the southern tasman to the coral sea and are an important control on the connectivity of regional longshore sand transport through episodic major headland bypassing events between compartments and the maintenance of down drift coastlines in dynamic equilibrium future climate change projections indicate that the recent trend in the expansion of the latitudinal extent of the tropics in the south west pacific region will continue throughout this century the combined impacts of a projected 2 5 poleward shift on the storm wave climate is a significant reduction in net northward longshore sand transport and the efficiency of headland bypassing events on the north and central coasts of new south wales we project a 30 reduction in longshore sand transport for the dominant extratropical origin storm events together with a 5 increase in reversed net southward longshore sand transport for tropical origin storm events

ocean beach tasmania a swell dominated shoreline reaches climate induced recessional tipping point global sea level rise since the nineteenth century is expected to eventually cause recession of many shores however most swell exposed sandy beaches have not yet shown such response this study analysed a 70 year air photo and beach profile record for swell dominated ocean beach western tasmania to show an abrupt change of long term shoreline position variability circa 1980 from episodic erosion and accretion since at least 1947 to persistent recession with no recovery up to the present dating of back dune peats exposed in the dune scarp showed that recent shoreline recession exceeds any in the last 1800 years investigation of potential causes identified recent onset sea level rise slr on a tectonically stable coast and increasing winds driving increased wave setup as drivers with sufficient explanatory power to account for the observed changes although data limitations and residual uncertainties mean additional contributing factors such as interdecadal wave direction changes cannot be ruled out we hypothesise that ocean beach has experienced earlier recession in response to slr and other climate change effects than many other beaches owing to exposure to a very high energy stormdominated wave climate littoral drift efficiently delivering eroded sand to a large capacity active sand sink and low variability in swell wave directions and inter annual sea levels we hypothesise that sea level rise with higher onshore wind speeds generating increased wave setup at ocean beach since before the 1980s has increased upper beach erosion event frequency until the formerly stable or gaining sand budget reversed to deficit a major storm or storm cluster abruptly tipped the beach into its current recessional mode when its sand budget was close to deficit factors causing an early shoreline response to sea level rise at this site are applicable more widely as potential indicators of beaches likely to respond earlier than others to climate induced changes including not only slr but also wind climate changes

beach erosion and recovery during consecutive storms at a steep sloping meso tidal beach this study analyses beach morphological change during six consecutive storms acting on the meso tidal faro beach south portugal between 15 december 2009 and 7 january 2010 morphological change of the sub aerial beach profile was monitored through frequent topographic surveys across 11 transects measurements of the surf swash zone dimensions nearshore bar dynamics and wave run up were extracted from time averaged and timestack coastal images and wave and tidal data were obtained from offshore stations all the information combined suggests that during consecutive storm events the antecedent morphological state can initially be the dominant controlling factor of beach response while the hydrodynamic forcing and especially the tide and surge levels become more important during the later stages of a storm period the dataset also reveals the dynamic nature of steep sloping beaches since sub aerial beach volume reductions up to 30 m3 m were followed by intertidal area recovery 2 z 3 m with rates reaching 10 m3 m however the observed cumulative dune erosion and profile pivoting imply that storms even of regular intensity can have a dramatic impact when they occur in groups nearshore bars seemed to respond to temporal scales more related to storm sequences than to individual events the formation of a prominent crescentic offshore bar at 200 m from the shoreline appeared to reverse the previous offshore migration trend of the inner bar which was gradually shifted close to the seaward swash zone boundary the partially understood nearshore bar processes appeared to be critical for storm wave attenuation in the surf zone and were considered mainly responsible for the poor interpretation of the observed beach behaviour on the grounds of standard non dimensional morphological parameters copyright 2011 john wiley sons ltd

cbathy a robust algorithm for estimating nearshore bathymetry 1 a three part algorithm is described and tested to provide robust bathymetry maps based solely on long time series observations of surface wave motions the first phase consists of frequency dependent characterization of the wave field in which dominant frequencies are estimated by fourier transform while corresponding wave numbers are derived from spatial gradients in cross spectral phase over analysis tiles that can be small allowing high spatial resolution coherent spatial structures at each frequency are extracted by frequency dependent empirical orthogonal function eof in phase two depths are found that best fit weighted sets of frequency wave number pairs these are subsequently smoothed in time in phase 3 using a kalman filter that fills gaps in coverage and objectively averages new estimates of variable quality with prior estimates objective confidence intervals are returned tests at duck nc using 16 surveys collected over 2 years showed a bias and root mean square rms error of 0 19 and 0 51 m respectively but were largest near the offshore limits of analysis roughly 500 m from the camera and near the steep shoreline where analysis tiles mix information from waves swash and static dry sand performance was excellent for small waves but degraded somewhat with increasing wave height sand bars and their small scale alongshore variability were well resolved a single ground truth survey from a dissipative low sloping beach agate beach or showed similar errors over a region that extended several kilometers from the camera and reached depths of 14 m vector wave number estimates can also be incorporated into data assimilation models of nearshore dynamics

low frequency changes of sediment volume on the beachface at warilla beach new south wales 1975 1985 abstract characteristic patterns of shore parallel and shore normal movements of sediment on a sandy beach are described in this study the sediment movements are apparent as low frequency variations in the volume of sediment stored above mean low water spring tide mlwst level on warilla beach n s w they were determined by an empirical orthogonal function eof analysis of beach profile records the profiles were surveyed from eighteen stations along a 2 km long beach at least monthly generally fortnightly for over 10 years from july 1975 until august 1985 results from the eof analysis confirm and substantially extend an earlier study of warilla beach when the first 5 years of the beach survey record was examined the importance of low frequency beachface change identified in the earlier shorter study was confirmed from the extended data set zones of maximum variability linked with rip current activity are consistent in both studies and similar patterns of alongshore sediment movement in the swash zone were determined from both analyses the principal differences between the two sets of results highlight beachface responses to processes operating in different time scales amplitude spectra from time series describing the characteristic modes of sediment movement along and across the beachface have periodicities of 2 0 1 7 and 1 0 years beach changes with periods close to 3 years are apparent in the record but cannot be resolved by standard spectral analysis techniques each period is associated with a characteristic pattern of beach change the triennial and 1 7 year cycles with alongshore sediment transport and the biennial cycle with onshore offshore sediment exchange eigenvectors from the eof analysis identify the characteristic patterns of beach change from survey data specified to highlight the shore parallel sediment movement along 0 5 m deep horizontal segments of beach and shore normal sediment movement along the beach profiles in the analysis of shore parallel variation in beach profile configuration the fundamental eigenvectors explain between 70 and 80 of beachface variance in each instance and different patterns of sediment movement were identified for each horizontal slice on the upper part of the beachface all eigenvectors identified a zone of low variability along the shoreline skirting a rockwall below berm crest in the swash and intertidal zones of the beach and away from the rockwall the northern half of the beach was highly variable second mode eigenvectors cellular flux modes explain a further 5 to 14 of the variance and describe sediment exchanges between discrete zones in each horizontal segment of the beachface zones of greatest variability occurred landward of places where rip currents frequently develop conversely zones of low variability are coincident with areas of beachface in the lee of places where inshore bars frequently form analysis of sediment movement along each profile is consistent with the beach changes described the fundamental eigenvectors account for 91 to 99 of the variance on each profile they describe an onshore offshore movement of sediment through the intertidal zone of the beach

maximum extent of ice sheets in morocco during the late ordovician glaciation new field data demonstrate that during the late ordovician hirnantian glaciation an ice sheet expanding northwestwards over the anti atlas range reached into the southern meseta of northern morocco its growth to a glacial maximum position resulted in extensive subglacial erosion and deformation including the development of soft sediment striated surfaces and streamlined subglacial bedforms preserved between the high atlas of marrakech and rehamna these features imply that this ice mass extended 200 km further than previously thought and increase its size by at least ca 190 000 km2 comparable in area to the uk correlation between a measured section in the high atlas of marrakech and that of the southern meseta identifies sedimentary evolution within an ice contact system common to both these findings imply that the west african craton and northern morocco were in full glaciological communication during the latest ordovician palaeogeographic reconstruction shows that beyond the ice sheet south and southeastward palaeoslopes persisted on the shelf a palaeohigh beyond the main ice sheet was a major source for sand feeding delta systems that grew along the shelf as far as the shelf break this palaeohigh probably formed as a result of rift shoulder uplift and supported a satellite ice mass in the eastern meseta a thick 350 m underflow dominated deep marine fan was fed both from this shelf delta system and from glaciogenic debris derived from the main ice sheet the occurrence of this unexpected deep marine area in northern morocco implies that continued northward advance of the ice sheet was hampered by a dramatic break in bathymetry two depositional units are recognised across the meseta containing four distinct sedimentary cycles each recognised as a glacioeustatic response to the waxing and waning of ice masses elsewhere in west gondwana

statistical characteristics of gravity waves observed by an all sky imager at darwin australia 1 an all sky airglow imager with a cooled charge coupled device camera in place at darwin 12 4 s 131 0 e australia since october 2001 has been used to obtain two dimensional gravity wave images in the mesopause region using airglow images of the oi 557 7 nm emission altitude 96 km and oh band 720 910 nm 86 km emissions obtained for october 2001 to august 2002 we investigated the wavelengths phase velocities and propagation directions of gravity waves wave occurrence in oh images 60 90 is higher than in oi images 30 70 for all seasons the waves have wavelengths of less than 90 km peak 30 50 km and phase velocities of less than 90 m s peak 30 60 m s most of the waves propagate in the meridional direction and the directionality strongly depends on the season in winter waves propagate both poleward and equatorward while in summer almost all waves propagate poleward an examination of airglow imaging statistics at adelaide 35 s 138 e australia obtained by walterscheid et al 1999 leads us to conclude that this clear directionality is caused by the location of the wave sources and by the wave ducting processes that is poleward waves in summer come from an equatorial convective source through a thermal duct structure the effect of wind filtering on the waves is also discussed for zonal wave propagation

subtropical sst dipole events in the southern indian ocean sea surface temperature sst anomalies in the subtropical southern indian ocean show interannual dipole events that are seasonally phase locked to the austral summer a positive phase of the event is characterized by cold sst anomalies in the eastern part i e off australia and warm sst anomalies in the southwestern part south of madagascar such an event is found to produce above normal rainfall over many regions in south central africa the cooling of sst in the eastern part is mainly caused by the enhanced evaporation this is associated with stronger winds along the eastern edge of the subtropical high which is strengthened and shifted slightly to the south during the event on the other hand relative decrease in the seasonal latent heat loss due to reduced evaporation dominates the warming in the southwestern part evolution of such subtropical dipole events shows quite a contrast to that of the tropical dipole events discovered recently in the indian ocean

stratigraphic evidence for hirnantian glaciation in the alborz mountain ranges northeastern iran abstract the author examined the high latitude hirnantian diamictites of the ghelli formation and the early silurian olive gray shales of the niur formation exposed in the northeastern alborz mountains iran these 404 m thick glacial deposits can be divided into three progradational retrogradational cycles each potentially controlled by the regional advance and retreat of the hirnantian ice sheet the glaciated source area was west of the study area in the arabian shield region where numerous tunnel valleys have been reported time calibration was performed based on a high quality biostratigraphic control mainly derived from the chitinozoan biozones tanuchitina fistulosa acanthochitina barbata armoricochitina nigerica ancyrochitina merga tanuchitina elongata spinachitina oulebsiri and spinachitina fragili s the land derived miospores present in most chitinozoan assemblages often abundant seem associated with global sea level changes during the late ordovician glaciation the ghelli formation s high abundance of terrestrial miospores and low abundance of marine palynomorphs suggests its deposition in a shallow marine environment additionally rhythmic bedded tidalites of claystone and sandstone indicate the growth of early land plants producing cryptospores on adjacent flooded areas based on marine palynomorphs chitinozoans and acritarchs the northeastern alborz mountains glacial deposits were dated as hirnantian the niur formation was assigned to the earliest llandovery rhuddanian glacial deposits and marine palynomorphs suggest the presence of hirnantian ice caps in the alborz mountains at the margin of the arabian plate and indicate the peripheral extension of the late ordovician ice sheet several biostrome beds forming pelmatozoan bryozoan mud mounds mainly comprising bryozoans echinoderms tentaculites and subordinate trilobites were found in the glacial deposits of the ghelli formation suggesting carbonate deposition during the hirnantian these carbonate beds are not related to the boda warming event which happened over the gondwana landmass in the katian interval the glacial deposits of the alborz mountain ranges are thus not correlated to those of the gondwana paleocontinent climatic amelioration is more likely than local reduction of clastic input to be responsible for the biostrome beds in the glacial member of the ghelli formation namely a short lived episode of global warming during the hirnantian interval the milankovitch cycles four new chitinozoan species namely armoricochitina persianense n sp tanuchitina alborzensis n sp spinachitina iranense n sp and hyalochitina jajarmensis n sp are described and illustrated biometric data are also provided for the iranian s oulebsiri and a nigerica

downstream changes of alpine zircon fission track ages in the rhone and rhine rivers zircons from 13 sediment samples from the rhone and rhine drainages were dated by the fission track method to study downstream changes in detrital fissiontrack grain age distributions in large river systems draining the european alps the orogen parallel rhone river shows a zircon fission track grain age distribution similar to that in its alpine source areas this signal is well preserved because there are alpine sources along its full length and input from non alpine sources is small in contrast only the headwaters of the north flowing rhine river are located in the alps as a consequence alpine derived zircons which are distinguished by young fission track ages become progressively diluted downstream by older ages from zircon sources external to the alps nevertheless the alpine component is persistent and can easily be detected in sediments more than 1000 km downstream at the rhine delta these results demonstrate that fission track dating of detrital zircons can provide useful information about orogenic processes even where sediments have been transported hundreds of kilometers from the orogenic source crossing ephemeral lakes and subsiding basins deposits along the lower reaches of the river appear to have a short residence time 1 myr and thus many of these deposits serve to smooth out variations in the supply of sediment from fast eroding heterogeneous sources in the alpine headwaters of these drainages for the rhone and the rhine rivers we show that fast erosion in the alps accounts for most of the sediment load this finding supports a widespread observation that the sediment in most large continental drainages is usually derived from a small part of the drainage where uplift relief and erosion rates are greatest

the wave climate of the southern ocean abstractthe wave climate of the southern ocean is investigated using a combined dataset from 33 years of altimeter data in situ buoy measurements at five locations and numerical wave model hindca

southern australian rainfall and the subtropical ridge variations interrelationships and trends 1 monthly values of the latitude and intensity mean maximum pressure of the subtropical ridge str averaged across australian longitudes 105 155 e have been related to variations and trends in rainfall over southern australia south of 30 s for 1958 2005 there is an abrupt shift of latitude of the subtropical ridge over australia at the onset of winter in the cooler part of the year the intensity of the str is more closely related to rainfall variations and correlations between latitude and rainfall are a by product of the relationship of intensity with both latitude and rainfall whereas in summer the latitude of the str is more closely related to rainfall the decline in southern australian rainfall in recent decades which has occurred principally in autumn appears related to a trend towards a more intense str rather than a trend in the latitude of the str

spatial variability of sea level pressure and 500 mb height anomalies over the southern hemisphere abstract the spatial variability of mean sea level pressure slp and 500 mb height anomalies over the southern hemisphere during summer djf and winter jja is determined using eigenvector analysis based on daily synoptic maps from 1972 to 1979 the patterns of spatial distribution of pressure and height anomalies are further verified and examined by means of station data and the eigenvectors are compared between the seasons and to those found for the northern hemisphere the first eigenvector shows that midlatitude anomalies of slp and 500 mb height are of an opposite sign to those found over and around antarctica the pattern is highly barotropic and suggests strengthening and weakening of the zonal wind in alternating latitude belts the 500 mb height differences are calculated for five midlatitude to antarctic station pairs using data from the late 1950 s onward these latitudinal height differences are also used to describe the association between the hemispheric westerlies and the southern oscil

graptolite biostratigraphy of the lower silurian llandovery shelf deposits of the western iberian cordillera spain eight lower silurian graptolite biozones triangulatus convolutus linnaei turriculatus cris pus griestoniensis tullbergi and spiralis and three subzones runcinatus gemmatus palmeus and hispani cus have been recognized in the sierra menera nevera and tremedal massifs in the castilian branch of the iberian cordillera western iberian cordillera early silurian rhuddanian low diversity normalograp tid faunas are also present and these together with the rich graptolite faunas of the aeronian triangulatus and convolutus biozones come from black shaly intercalations within the quartzose sandstones of the upper part of the los puertos quartzite telychian graptolite biozones have been recognized in the succeeding black shale sequence of the badenas formation diachroneity of the transition from sandstones to black shales is dated by graptolites it ranges from about the base to at least the top of the linnaei biozone we sug gest that the lower silurian black shales of the western iberian cordillera were deposited in a shallow shelf environment not much deeper than that of presumably storm influenced sandstones of the los puertos quartzite

tropical cyclone track characteristics as a function of large scale circulation anomalies abstract factors that contribute to intraseasonal variability in western north pacific tropical cyclone track types are investigated it is hypothesized that the 700 mb large scale circulation can affect tropical cyclone track characteristics by enhancing or excluding genesis in certain regions and concurrently prohibiting or favoring recurving versus straight tracks a track type climatology indicates that genesis location alone may explain some of the variability in track type although some genesis regions have no preference for straight moving or recurving tracks a formation north of 20 n or east of 150 e and north of 10 n favors a recurvature track these recurving storms are classified as recurving north and recurving storms that form in regions with nearly equal probability of straight or recurving tracks are classified as recurving south a compositing technique is used to define anomalous 700 mb large scale circulations that exist during the formation of tropical cyclones that subsequently fol

the impact of temperate reefs on 34years of shoreline and vegetation line stability at yanchep southwestern australia and implications for coastal setback coastal setbacks are used to protect populations and infrastructure and involve determining baselines and historic trends in shoreline movements assessing these movements can be difficult on coasts with especially complex geomorphology such as due to rock and coral reefs reefs are often assumed to provide coastal protection and stability however little is known about the spatial variability of beach dynamics on beaches with reefs over inter annual and decadal time scales spatial variability in inter annual vegetation line and shoreline stability was assessed on three adjacent beaches at yanchep southwestern australia using 34 years 1974 2008 of aerial photographs over 96 of the study area beach width narrowed over the 34 years this trend was statistically significant on 83 of the middle beach 43 of the northern beach and only 29 of the southern beach the maximum mean annual change in beach width was 1 7 m yr 1 at the south end of the southern beach the first mode of the empirical orthogonal function eof explained 45 of the variability alongshore and correlated significantly p 0 05 with the 90th percentile of annual wave height and annual mean sea level beach rotation and reef controlled currents resulted in cellular beach morphodynamics and vegetation line and shoreline movements varied greatly alongshore on one occasion the beach widened by more than 50 m inter annually while other areas eroded by 50 m the southern beach that was fronted by the most continuous and highest supratidal section of reef was the most temporally variable even the vegetation line here moved by up to 20 m inter annually so cannot be assumed to be a stable baseline for setback the impact of reefs on inter annual shoreline and vegetation line stability should be considered in future guidelines for determining coastal setback

late ordovician glaciation in southern turkey abstract we present a new survey of several palaeozoic sections in both the taurus range and the border folds that documents typical glacial features including a glacial pavement and striated dropstones halevikdere formation and demonstrates the former presence of an ice sheet in southern and south eastern turkey evidence for the late ashgill hirnantian age of this episode is provided by macro and microfossils found within the glacial formation the extension of ice related deposits into the northernmost part of the arabian platform mardin region implies a much wider distribution of the ordovician ice sheet than was previously believed and strongly suggests that southern turkey lay close to egypt during the lower palaeozoic

historical trends in southern ocean storminess long term variability of extreme wave heights at cape sorell tasmania 1 atmospheric re analyses indicate increased southern ocean so storminess over the past few decades a southern australia waverider record provides a 23 year record of storm waves generated in the so statistical models to estimate long term trends in frequency and intensity of severe storm waves based on time dependent versions of the peak over threshold model are applied to investigate so storminess trends significant increase in frequency of storm wave events observed in the corrected era 40 re analysis significant wave height h s record is supported by increasing frequency of synoptic storms which drive large wave events at the site in both era 40 and ncep ncar re analyses however buoy data show a small decrease in storm wave event frequency consistent with previous studies investigating trends in so mean h s from altimeter records re analysis winds with apparent increasing trend may have influenced prior so research conclusions particularly related to weakening of the so co 2 sink

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

further investigation of the initial fission track length and geometry factor in apatite fission track thermochronology the external detector method edm is a widely used technique in fission track thermochronology ftt in which two different minerals are concomitantly employed spontaneous tracks are observed in apatite and induced ones in the muscovite external detector they show intrinsic differences in detection and etching properties that should be taken into account in this work new geometry factor values g in apatite were obtained by directly measuring the ed is ratios and independently determined gqr ed is values through the measurement of projected lengths five mounts two of which were large area prismatic sections and three samples composed of random orientation pieces have been used to determine the g values a side effect of applying edm is that the value of the initial confined induced fission track l 0 is not measured in routine analyses the l 0 value is an important parameter to quantify with good confidence the degree of annealing of the spontaneous fission tracks in unknown age samples and is essential for accurate thermal history modeling the impact of using arbitrary l 0 values on the inference of sample thermal history is investigated and discussed the measurement of the l 0 value for each sample to be dated using an extra irradiated apatite mount is proposed this extra mount can be also used for determining the g value as an extension of the ed is ratio method eight apatite samples from crystalline basement with grains at random orientation were used to determine the g values the results found are statistically in agreement with the values found for apatite samples from durango mexico measured in prismatic section and also measured at random orientation there was no observable variation in efficiency regarding crystal orientation showing that it is relatively safe using non prismatic grains especially in samples with paucity of grains as it is the case of most basin samples implications for the calibration and for the calibration of the direct spectrometer based fission track dating are also discussed

diamictite and oolitic ironstones a sedimentary association at ordovician silurian transition in the north gondwana margin new evidence from the inner nappe of sardinia variscides italy abstract the contact between the silurian black phyllite and the cambro ordovician underlying rocks has been investigated over different tectonic units affected by green schist facies metamorphism in the inner nappe zone of the sardinia variscides in spite of strain and metamorphism the field work highlighted the occurrence of diamictic sediments in the canaglia tectonic unit the diamictite consists of dark massive metamorphic claystone bearing chamositic ooliths chamositic nodules and millimetre to centimetre sized clasts dispersed or gathered in clusters within the muddy matrix in the argentiera tectonic unit the diamictite consists of angular clasts ranging in size from few millimetres to several decimetres scattered within a finely laminated black sericitic meta argillite field data textural and compositional analyses suggest a glacio marine environment for the formation of the diamictites the canaglia diamictite deposited in a protected glacial influenced shore compositionally it can be defined as ironstone in the upper part it hosts a horizon of clast supported conglomeratic hard ironstone mostly made of magnetite which testifies for sub aerial reworking the source of the iron is to be related to local glacio eustatic driven emergence of upper ordovician alkaline mafic volcanics these are widespread in the uppermost ordovician of the canaglia unit possibly linked to the rifting stage that invested the north gondwana margin before the uppermost ordovician early silurian sea level rise the argentiera diamictite deposited beyond the iron rich diamictite in the outer euxinic shelf that was reached by rain out of rafted debris

glacimarine sedimentary processes and facies on the polar north atlantic margins abstract major contrasts in the glaciological oceanic and atmospheric parameters affecting the polar north atlantic both over space between its eastern and western margins and through time from full glacial to interglacial conditions have lead to the deposition of a wide variety of sedimentary facies in these ice influenced seas the dynamics of the glaciers and ice sheets on the hinterlands surrounding the polar north atlantic have exterted a major influence on the processes rates and patterns of sedimentation on the continental margins of the norwegian and greenland seas over the late cenozoic the western margin is influenced by the cold east greenland current and the svalbard margin by the northernmost extent of the warm north atlantic drift and the passage of relatively warm cyclonic air masses in the fjords of spitsbergen and the northwestern barents sea glacial meltwater is dominant in delivering sediments in the fjords of east greenland the large numbers of icebergs produced from fast flowing outlets of the greenland ice sheet play a more significant role in sedimentation during full glacials sediments are delivered to the shelf break from fast flowing ice streams which drain huge basins within the parent ice sheet large prograding fans located on the continental slope offshore of these ice streams are made up of stacked debris flows large scale mass failures turbidity currents and gas escape structures also rework debris in continental slope and shelf settings even during interglacials both the margins and the deep ocean basins beyond them retain a glacimarine overprint derived from debris in far travelled icebergs and sea ice under full glacial conditions the glacier influence is correspondingly stronger and this is reflected in the glacial and glacimarine facies deposited at these times

u th he geochronology of single zircon grains of known tertiary eruption age we performed a systematic study of u th he ages of volcanic zircons of known eruption age to establish a reliable protocol for zircon he dating and to validate the resulting ages using laser he extraction and dissolution by lithium borate flux melting we analyzed many aliquots of single zircon grains separated from four rapidly cooled rocks fish canyon tuff accepted age 27 8 0 7 ma buluk tuff 16 3 0 2 ma tardree rhyolite 58 4 0 7 ma and utaosa rhyolite 2 52 0 02 ma he ages of fish canyon tuff buluk tuff and utaosa rhyolite zircons are in good agreement with their reference ages mean emission corrected ages were 28 6 1 4 1 16 1 0 8 and 2 61 0 18 ma respectively however the zircon he ages of tardree rhyolite are irreproducible and consistently too old with a mean he age of 78 8 7 0 ma spontaneous fission track densities of tardree rhyolite zircons indicate that about 80 of these zircons are strongly zoned in u with high track density i e high u content in the core and low density on the rim this causes an overestimation of the ejection correction that likely explains the erratic and excessively high he ages from these zircons assessment of the degree and style of u zonation within a zircon population is thus prudent before application of the u th he method step heating experiments indicate that for most zircons he extraction is 99 complete after 1 h at 1300 c however for as yet unknown reasons occasional grains seem to retain substantial amounts of he under these conditions

stratigraphic evidence for the hirnantian latest ordovician glaciation in the zagros mountains iran abstract high latitude hirnantian diamictites dargaz formation and lower silurian kerogenous black shales sarchahan formation are locally exposed in the zagros mountains the glaciogenic dargaz deposits consist of three progradational retrogradational cycles each potentially controlled by the regional advance and retreat of the hirnantian ice sheet glacial incisions of sandstone packages change laterally from simple planar to high relief

sedimentary facies and depositional architecture of ice contact glaciomarine systems abstract the characteristics of ice contact glaciomarine systems are reviewed based on a range of weichselian and holocene examples from the fjordal basins in norway and svalbard these depositional systems occur as large morphological ridges end moraines including push moraines which are coarse grained and show large scale foreset bedding the paper addresses some of the major problems with regard to the recognition classification and stratigraphic analysis of these systems the ice proximal glaciomarine systems are classified here into three categories 1 ice contact submarine fans 2 ice contact deltas and 3 glaciofluvial deltas this classification integrates morphological and sedimentological criteria and renders these glaciomarine systems not only easier to recognize in the stratigraphic record but also possible to compare with common non glacial deltaic systems the emphasis is on the criteria for the recognition of the ice contact glaciomarine systems i e ice contact fans and ice contact deltas and their discrimination from common gilbert type deltas and fan deltas the review further focuses on ice contact glaciomarine systems as highly sensitive recorders of glacier dynamics and climatic fluctuations it is shown that both the periods of ice front stability and changes in the ice front position as well as the magnitude and rate of those changes are all recorded in the ice contact depositional system the sedimentary record further reflects glacio isostatic sea level changes and local palaeogeography a new conceptual model is suggested which places these ice contact glaciomarine systems in a dynamic stratigraphic context the model integrates sedimentary facies and their depositional architecture in an allostratigraphic framework and is meant to be a guide for the analysis of the sedimentary record of ice contact systems

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

lightning development associated with two negative gigantic jets 1 we report observations of two negative polarity gigantic jets sufficiently near very high frequency vhf lightning mapping networks that the associated lightning characteristics and charge transfer could be investigated in both cases the gigantic jet producing flash began as ordinary intracloud lightning with upper level channels attempting to exit the cloud and then produced the upward gigantic jet neither flash had developed channels to ground confirming that the major charge transfer during gigantic jets occurred between the cloud and ionosphere the leader progression of one event was detected at altitudes above 20 km demonstrating the possibility of detecting and tracking the propagation of negative jets above the cloud with vhf techniques citation lu g et al 2011 lightning development associated with two negative gigantic jets geophys res lett 38 l12801

facies and allostratigraphy of high latitude glacially influenced marine strata of the early permian southern sydney basin australia the sydney basin of new south wales australia is a foreland basin containing a thick up to 10 km permo triassic succession the southern margin of the basin exposes strata deposited during late palaeozoic glaciation of south eastern gondwana the early permian wasp head pebbley beach snapper point formations and wandrawandian siltstone were deposited between 277 and 258 ma on a polar glacially influenced continental margin adjacent to ice sheets located over east antarctica and eastern australia sedimentary facies together with related ichnofacies and fauna can be grouped into six facies associations that record marine sub environments ranging from high energy storm dominated inner shelf to turbidite dominated upper slope settings cold marine conditions with near freezing bottom water temperatures are recorded by glendonites ice rafted debris most likely deposited by icebergs occurs in almost all facies associations an allostratigraphic approach emphasizing the recognition of bounding discontinuities i e erosion surfaces and marine flooding surfaces is used to subdivide the early permian stratigraphy into facies successions three types of succession can be identified and record changes in the relative influence of allocyclic controls such as basin tectonics sediment supply and glacio eustatic sea level variation together sedimentological and allostratigraphic data allow reconstruction of the depositional history of the south western margin of the sydney basin initial marine sedimentation characterized by sediment gravity flows and storm deposited sandstones of the lower wasp head formation occurred adjacent to a faulted basin margin overlying successions within the upper wasp head pebbley beach and snapper point formations record aggradation in inner to outer shelf settings along a storm and glacially influenced continental margin tectonic subsidence and basin flooding is recorded by deeper water turbidites of the wandrawandian siltstone

fluvial coastal nearshore and shelf deposition in the upper proterozoic to lower cambrian addy quartzite northeastern washington abstract quartzose and lesser argillaceous strata of the approximately 1300 m thick upper proterozoic to lower cambrian addy quartzite of northeastern washington record shelf coastal and continental sedimentation on an actively subsiding relatively young passive margin the lower 400 to 500 m of the addy quartzite was deposited immediately following the initiation of subsidence in a wave dominated coastal and eventually storm dominated shelf environment this sequence records relative sea level rise that culminated in high stand conditions these sediments grade upwards into approximately 150 m of fluvial strata that record progradation of terrestrial environments during a period of relative sea level fall and a regional low stand the upper 700 m of the addy quartzite fines upwards from nearshore to shallow marine dominated sediments into shelf dominated deposits this sequence marks the reestablishment of net sea level rise the overall fining upwards trend displayed by the addy quartzite indicates that regional subsidence of the newly formed passive margin was one of the most important factors controlling addy sedimentation however variation seen in this trend throughout the addy quartzite indicates that rates of sea level rise associated with subsidence fluctuated and occasionally even reversed causes for the variation are inferred to be related to variations in subsidence rates and sediment supply textural and compositional data suggest addy detritus was derived from relatively proximal recycled sedimentary source terranes and more distal continental crystalline terranes

storm driven changes in rip channel patterns on an embayed beach this paper introduces a semi automatic computer algorithm designed to detect rip current channels in video imagery as a case study this method is applied to 3 3 years of video data from an embayed beach to demonstrate the link between antecedent surf zone morphology wave energy and up down transitions in beach state an objective measure of rip channel change was developed to define six significant rip reconfiguration events and relate these events to wave energy over the period of study no complete resets of the nearshore morphology occurred the analysis indicates that direct correlation of rip patterns with the instantaneous wave conditions is not a useful way to demonstrate how rips and waves interact the average wave energy over a period of ten days combined with storm duration were good indicators of rip channel change demonstrating that in general beach morphology responds with a time lag to changes in forcing rip channels with a short cross shore length and narrow alongshore spacing responded faster to changes in wave conditions than rips with a long cross shore length and wider alongshore spacing to force changes in the rip morphology longer rip channels required wave events of higher energy and or a longer duration offshore islands protect the beach under certain wave approach angles sometimes resulting in a dual width surf zone which was narrow at the sheltered end and wide at the exposed end of the beach the wider surf zone end was characterised by three dominant and persistent rip channels whereas the narrow surf zone section contained a number of smaller rips which evolved rapidly under wave forcing our observations demonstrate the importance of rip channel size in controlling the response time of nearshore morphology

response to the comment by w h schwarz et al on joint determination of 40k decay constants and 40ar 40k for the fish canyon sanidine standard and improved accuracy for 40ar 39ar geochronology by p r renne et al 2010

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

late ordovician carbonate productivity and glaciomarine record under quiescent and active extensional tectonics in ne spain abstract carbonate productivity and glaciomarine deposits of the ordovician silurian transition display different sedimentary architectures in the iberian and hesperian chains of ne spain as a result of quiescent and active extensional tectonics on platforms fringing north gondwana the late katian carbonate productivity of the iberian platform reflects the onset of bryozoan pelmatozoan meadows and mud mound complexes throughout an intra shelf ramp whereas carbonate nucleation of prominent carbonate factories took place on the top of isolated palaeo highs in the hesperian platform in both cases the end of carbonate productivity is associated with glacioeustatic regression subaerial exposure and karstification predating widespread precipitation of iron ore deposits in the vicinity of palaeohighs the hirnantian glacioeustatic transgression is represented lithostratigraphically by the orea formation in the iberian platform the formation consists of two distinct depositional sequences bounded by the progradation of conglomeratic channels and is dominated by the record of massive and crudely stratified diamictites with tabular geometries and deposited subaqueously as rain out facies in contrast the hesperian platform is rich in disrupted diamictites which form strongly deformed units interpreted as submarine slumps associated with active synsedimentary faults in both cases the anomalous occurrence of massive diamictites rich in boulder to sand sized carbonate dropstones and displaying rapid variations in density and size suggests that distinct iceberg drift lanes existed indicating current activity in the open sea

wave spectral energy variability in the northeast pacific 1 the dominant characteristics of wave energy variability in the eastern north pacific are described from noaa national data buoy center ndbc buoy data collected from 1981 to 2003 ten buoys at distributed locations were selected for comparison based on record duration and data continuity long period lp t 12 s intermediate period 6 t 12 s and short period t 6 s wave spectral energy components are considered separately empirical orthogonal function eof analyses of monthly wave energy anomalies reveal that all three wave energy components exhibit similar patterns of spatial variability the dominant mode represents coherent heightened or diminished wave energy along the west coast from alaska to southern california as indicated by composites of the 700 hpa height field the second eof mode reveals a distinct el nino southern oscillation enso associated spatial distribution of wave energy which occurs when the north pacific storm track is extended unusually far south or has receded to the north monthly means and principal components pcs of wave energy levels indicate that the 1997 1998 el nino winter had the highest basin wide wave energy within this record substantially higher than the 1982 1983 el nino an increasing trend in the dominant pc of lp wave energy suggests that storminess has increased in the northeast pacific since 1980 this trend is emphasized at central eastern north pacific locations patterns of storminess variability are consistent with increasing activity in the central north pacific as well as the tendency for more extreme waves in the south during el nino episodes and in the north during la nina

a comparison of extreme wave analysis methods with 1994 2010 offshore perth dataset abstract this study took the hourly wave height records collected 10 km southwest of rottnest island offshore of perth western australia from 1994 to 2010 as a testing ground and compared the results obtained by the goda method commonly used in costal engineering community the generalised extreme value gev and generalised pareto distribution gpd methods which are currently the standard practice in mainstream extreme statistics the results highlight the merits and limitations associated with those methods and formulas it is recommended that the coastal engineering community should embrace the gpd distribution as one of the credible candidates due to its merits in the threshold selection techniques and the nature of the distribution the conventional distributions recommended by goda could be the other candidates provided a properly selected threshold value the final selection of the distributions should be made based on the goodness of fit test demonstrated in this study finally the extreme wave heights for offshore perth are recommended based on 1994 to 2010 dataset

experimental study on hydrothermal annealing of fission tracks in zircon abstract increasing temperature causes fading of fission tracks fts in minerals which has been quantified by many laboratory heating experiments in atmosphere in order to elucidate whether or not ft annealing at hydrothermally pressured conditions is the same as that at atmospheric condition we performed zircon heating experiments using a hydrothermal synthetic apparatus for reliable comparison we annealed the same zircon samples using the same temperature monitor and analyzed them using the same experimental procedure as the previous experiment at atmosphere yamada et al chem geol isot geosci sect 122 1995 249 the observed ft annealing characteristics are indistinguishable between atmospheric and hydrothermally heating it is therefore implied that the annealing kinetics of ft in zircon previously established can be applied to thermal history analysis of rocks that were subjected to hydrothermal conditions in nature such as those in fault and subduction zones

apatite fission track chronometry using laser ablation icp ms abstract comparison is made of apatite fission track ft ages measured by using conventional thermal neutron irradiation and laser ablation inductively coupled plasma mass spectrometry la icp ms to determine sample uranium content spontaneous track densities were determined on specified apatite grains from the durango fish canyon tuff and mount dromedary complex age standards neutron induced track densities and icp ms uranium values were determined for the same specified grains ages determined using the two approaches show reasonable consistency indicating the possibility of routine fission track analysis using la icp ms uncertainties and assumptions in the la icp ms approach include the laser ablation of chemically etched mineral surfaces the suitability of reference materials for calibration and the derivation of ft ages using the alternatives of selection of a f value or a revised zeta comparative approach the use of la icp ms in ft chronometry would dramatically increase the speed of analysis and hence sample throughput as well as avoiding the need for neutron irradiation and the production transport and handling of radioactive samples with the acknowledged dependency of ft annealing in apatite on composition such grain by grain multi element analysis could provide a more robust definition of the specific track annealing characteristics of each apatite crystal

modern and palaeozoic iron ooids a similar volcanic origin abstract the discovery of an unconsolidated deposit of iron ooids of a kind not previously described and in the vicinity of a volcanic island in indonesia has shed new light on the genesis of many ancient iron oolites the discovery shows that iron ooid formation is geologically a rapid process the ooids form by chemical precipitation of cryptocrystalline iron oxyhydroxides on available grains on the seafloor from seawater enriched with fe al and si the enrichment can be a result of hydrothermal fluids volcanic ash falls into shallow basins or rapid weathering of fresh volcanic rocks ordovician iron ooids from northern europe are strikingly similar to the modern ooids in chemical composition ree distributions and internal structures the differences in mineralogy can be explained as diagenetic transformation reactions under different environments a model for the formation of the ordovician iron ooids in northern europe from volcaniclastic material is presented which could be applicable to other ancient oolites in the world

rock topography causes spatial variation in the wave current and beach response to sea breeze activity we hypothesized that beach profiles that are perched on natural rock structures would be better protected from waves and currents than profiles that are not fronted by rock in southwest western australia many beaches such as at yanchep are perched on quaternary limestone yanchep lagoon is fronted by a low crested limestone reef that partially encloses a coastal lagoon the spatial variation of waves and currents around the rock structures were quantified during the sea breeze cycle at locations 1 offshore 2 20 m seaward of the reef 3 inside the lagoon and 4 in the surf zone the spatial variation in the beach profile response was measured at two beach profiles 1 the exposed profile that was not fronted directly seaward by outcropping limestone and 2 the sheltered profile which was fronted seaward by submerged limestone at 2 m water depth and that was near the lagoon exit at the end of the limestone reef the sheltered profile had greater volume changes during the cycle of the sea breeze whilst the exposed profile recovered more by overnight accretion when wind decreased the lagoonal current drove the strong response of the sheltered profile and may have contributed to the lack of overnight recovery of the beach together with the seaward rock formation impeding onshore sediment transport the different direction and speed responses of bottom currents in the surf zone fronting the two profiles reflected the local variation in geology the influence of the jet exiting the lagoon and wave refraction around the reef that was measured with gps drifters and wave ray tracing using xbeach major spatial variation in waves currents and beachface behavior at this perched beach shows the importance of the local geological setting

comparison of long medium and short term variations of beach profiles with and without submerged geological control abstract victoria beach cadiz spain comprises a rocky flat outcrop in its northern zone and a sand rich southern zone these natural features allowed for a 5 year monitoring period and subsequent analysis of two different profiles one in each zone based on differences in bottom contours topo bathymetric data were analysed using empirical orthogonal functions eofs to determine changes over the short medium and long term several morphologic phenomena were identified generalised erosion seasonal or summer winter tilting of the profile around different hinge points berm development and its posterior destruction etc in terms of their importance in explaining the variability of the collected data for both profiles it is worth mentioning that both profiles undergo parallel regression in the medium term thus the 1st eigenfunction enabled us to identify the true regression of the beach shoreline independent of seasonal or summer winter slope changes reconstruction of profiles using eof components demonstrated that though accretion periods in the medium term were similar for both types of profiles the accretion speed was much faster in the sand rich profile than in the reef protected profile 1 01 m 3 day versus 0 33 m 3 day moreover the seasonal erosion rate and the subsequent shoreline retreat for the sand rich profile were much larger than for the reef protected profile 121 m 3 year versus 29 m 3 year analysis in the short term changes induced by a single day s storm showed an instantaneous tilting of the profile with the mobilised sand volume being much greater for the sand rich than for the reef protected profile 68 m 3 m versus 12 m 3 m in brief we can assume that the wave energy attenuation provoked by the existence of a reef flat acted as a geological control for profile evolution which is essentially different for both profiles among the most important differences special attention should be given to the larger slope smaller mobilised sand volume and slower accretion rate of the reef flat profile versus the non protected profile

a new approach for electron microprobe zircon fission track thermochronology abstract fission track thermochronology ftt has been applied for decades to quantify rates and timing of processes in the shallow crust the most widely used approach is the external detector method edm in this conventional approach an age is obtained by counting both the fossil 238u spontaneous fission and the induced 235u induced fission tracks using an optical microscope the induced tracks are obtained through the irradiation of the sample with thermal neutrons in the nuclear reactor which causes fission of 235u based on the studies carried out by gombosi et al 2014 we present an alternative method of dating zircons using electron probe microprobe analysis epma to measure uranium concentration u the electron microprobe analysis fission track epma ft method was applied to three samples of rapidly cooled zircons the fish canyon tuff pocos de caldas syenite and serra geral zircons the analyses were performed using two approaches 1 using the age equation described in gombosi et al 2014 and 2 using a new age equation calibration developed for this work the results using the gombosi et al 2014 age equation were 26 7 4 1 ma 80 6 12 8 ma and 130 9 20 1 ma respectively and the results using the age equation from this work were 27 8 1 9 ma 83 8 7 7 ma and 136 12 ma respectively the uncertainty of the age is affected mainly by 238u concentration and s the spontaneous fission track density determinations other factors can affect the uncertainty of the age but their contributions are smaller for all samples the yield ages found by the two methods are consistent and overlap within two standard deviations of published reference ages determined from other radiometric techniques i e k ar 40ar 39ar and or u pb and traditional ftt by the edm

late ordovician glaciomarine deposits orea shale in the sierra de albarracin spain abstract a description and interpretation is given of marine fragment bearing arenaceous shales occuring near the ordovician silurian boundary in northeast spain these deposits known as the orea shales have been reported before as non glacial or questionably glaciomarine sedimentary features and scanning electron microscopical examination of quartz grains however reveal that much of the debris has been supplied by ice rafting paratillite close similarity between these spanish deposits and coeval normandian paratillites supports the theory that the iberian peninsula and northwest france belonged to one depositional realm probably forming a microcontinent armorica separated from the glaciated gondwanaland

interplay of orbital forcing and tectonic pulses in the cambrian iberian platform ne spain the stratigraphy of carbonate shale couplets cycles and cycle stacking patterns in a cambrian shallow water platform iberian chains ne spain are related to sea level changes driven by orbital forcing and by tectonic pulses the interplay of both effects can be discriminated in the iberian fault controlled platform in which the tectonic activity can be analysed by accurate and detailed biostratigraphic correlations based on trilobite zonation the stratigraphic hierarchy of rhythmically interbedded limestones and shales in two coeval but structurally separated geodynamic settings yields cycle ratios of 1 44 1 this ratio is supported by time thickness and spectral analysis which is based on a graphic method of analysis the map of grey lines the cycle ratio seems to be evidence for orbital forcing by obliquity and precession cycles predicted for early paleozoic time carbonate shale couplets the smallest rhythmic units recognisable in the field represent short term periodic fluctuations in supply of terrigenous sediments and carbonate productivity of uncertain origin which could be associated with one of several harmonics of the former orbital cycles the pulsating tectonic activity was approximated by using a quantitative analysis of tectonically induced subsidence shaw method recurrence frequencies of tectonic pulses were estimated and dated by biostratigraphy as a result tectonic disturbances in the cambrian iberian platform show an episodic periodicity comparable to that of orbital eccentricity cycles which could mask their recognition