high pressure 2000 mpa kyanite and glaucophane bearing pelitic schist and eclogite from cordillera de la costa belt venezuela in the cretaceous melange of the cordillera de la costa belt introduction north central venezuela there are knockers of eclogite barroisitetwo belts of high pressure hp low temperature lt bearing eclogite and pelitic glaucophane schist these occur in a metamorphic rocks are exposed in the caribbean mounmetamorphic melange matrix that locally consists of marble sertain system of northern venezuela which is part of the pentinite amphibolite actinolite schist feldspathic schist and gneiss complex east west trending boundary zone between the graphitic schist chloritoid schist and garnet bearing mica schist caribbean and south american plates e g menendez the protoliths for these various rock types exhibit a wide age range 1966 1967 these two belts are the cordillera de la cambrian to early cretaceous recently discovered knockers of costa and villa de cura belts both of which were pelitic glaucophane schist contain mg glaucophane paragonite metamorphosed during the mid cretaceous presumably kyanite garnet talc graphite rutile quartz in a subduction zone related to the mid cretaceous the coexistence of kyanite and mg glaucophane suggests minimum leeward antilles volcanic arc e g pindell 1993 from p 2000 mpa at t 600 c eclogite knockers from the same jurassic to eocene time north and south america were outcrop contain garnet and clinopyroxene which yield 500 c for diverging and new proto caribbean sea floor was created cores 700 c for rims and p 1200 mpa the assemblage between them e g pindell 1993 therefore the leegarnet biotite phengite albite within schists of the melange matrix ward antilles arc as well as the entire caribbean mounof this locality indicates metamorphic conditions of t tain system are allochthonous and formed far to the 450 520 c at p 1800 mpa because all lithologies in this west as part of the farallon north south american plate outcrop record high p conditions this metamorphic melange formed boundary zone e g pindell 1993 before or during peak metamorphism in a mid cretaceous subduction although the two hp lt belts have similar metazone morphic ages they differ greatly in lithology and metamorphic history the cordillera de la costa belt consists of oceanic and passive continental margin rocks intermixed with paleozoic granites and granitic gneisses in this belt the eclogites and blueschists were retrograded to epidote amphiboliteand greenschist facies assemblages following an apparent p t path typical for

sediment dynamics of an artificially deepened mesotidal coastal lagoon an environmental magnetic investigation of tauranga harbour new zealand abstract tauranga harbour new zealand s largest barrier enclosed coastal lagoon comprises two sub basins with separate catchments inlets and tidal channel systems this study sets out to assess and investigate the sediment dispersal system of tauranga harbour using standard environmental magnetic and sedimentological methods compilations of rock magnetic and grain size data of surficial sediments collected from inflowing rivers various estuarine environments estuaries tidal flats and tidal channels and the adjacent nearshore mirror the net and differential sediment fluxes into and through the two sub basins of this lagoon for all studied depositional environments the magnetogranulometric ratios sirm and arm are positively correlated with magnetic mineral content sirm arm in the sense that larger magnetic particles are associated with higher magnetic enrichment grain size analyses show that magnetic enrichment during particle transport and deposition can result from grain size as well as from grain density fractionation the periodically changing accumulation erosion conditions provide for a selective retention of specific grain sizes and an enhancement of the heavier magnetic mineral particles magnetic crystal size and clastic grain size correlate poorly over the whole study area but group within similar depositional environments coarser magnetic and clastic grain sizes and higher magnetite enrichment in the southern sub basin can be reconciled with episodic flood runoff of the wairoa river and a much larger artificially deepened southern tidal inlet which likely enables higher tidal current velocities our approach of combining magnetic and clastic grain size could be successfully implemented to establish a conceptual model of sediment dynamics and gravitational sorting within tauranga harbour

calculated greenschist facies mineral equilibria in the system cao feo mgo al 2 o 3 sio 2 co 2 h 2 o the kinetic problems associated with the experimental determination of reactions among complex solidsolution phases at low temperatures have hindered our understanding of the phase relations in greenschist facies rocks in the absence of reliable experimental data we have used the new expanded internally consistent thermodynamic dataset of holland and powell 1990 to present calculated phase equilibria for the system cao feo mgo al2o3 sio2 h2o co2 cafmasch with quartz in eccess in the range 400 500 c at low to intermediate pressures involving the minerals amphibole chlorite anorthite clinozoisite dolomite chloritoid garnet margarite andalusite and calcite by solving independent sets of non linear equations formed from equilibrium relationships we calculate not only the loci of reactions in pressuretemperature x co2 space but also the compositions of coexisting minerals in terms of the substitutions femg 1 and fe mg sial 1al 1 invariant univariant and divariant equilibria are calculated and discussed in relation to naturally occurring greenschist facies metabasic and siliceous dolomitic mineral assemblages we thus avoid the use of activity corrected curves so commonly presented in the literature as a substitute for genuine univariant phase diagram boundaries

coesite and pure pyrope in high grade blueschists of the western alps a first record and some consequences a pyrope quartzite originally described by vialon 1966 from the dora maira massif was resampled and reinvestigated garnet up to 25 cm in size phengite kyanite talc and rutile are in textural equilibrium in an undeformed matrix of polygonal quartz the garnet is a pyrope almandine solid solution with 90 to 98 mol mg end member it contains inclusions of coesite which has partially inverted to quartz resulting in a typical radial cracking of the host garnet around the inclusions several lines of evidence show that coesite crystallised under nearly static pressure conditions and that the whole matrix has once been coesite

tidal distortions and flood dominance at five small tidal inlets in southern maine maximum and mean flood current velocities exceeded ebb current velocities by an average of more than 20 cm s 1 at five small inlets along the southern coast of maine distortion of the tidal wave as it interacts with these shallow inlets such that the rising tide duration averages 3 22 h less than the falling tide duration may be the cause of flood current dominance at these inlets tide records from three locations at ogunquit inlet located along the southern coast of maine show that the 29 day average tide duration asymmetry increases from a rising tide that is 0 07 h longer than the falling tide for the offshore record to a rising tide that is 2 15 and 5 15 h shorter than the falling tide for the inlet throat and bay records respectively previous field studies and numerical models of tidal asymmetry have not examined tidal distortion in very shallow inlets where the channels shoal to depths shallower than the forcing tide amplitude at the inlets investigated in this paper channels are shallower than the ocean tide amplitude by an average of 30 cm a model is presented that explains how the shallow inlet bathymetry truncates the ocean tide and produces an inlet tide characterized by an extended falling tide and a shortened rising tide duration the dominance of flood tidal currents at these inlets produces net landward sediment transport

calculated mineral equilibria in the pelite system kfmash k 2 o feo mgo al 2 o 3 sio 2 h 2 o

climate sensitivity and mass balance evolution of gran campo nevado ice cap southwest patagonia a degree day model extended for surface mass balance calculations has been applied to derive the sensitivity of gran campo nevado ice cap gcn southwest patagonia to climate change seasonal sensitivity characteristics were computed using automatic weather station data gathered in the period 2000 05 results indicate pronounced mass balance sensitivity to temperature during the summer with monthly values of 0 27 0 01 m w e k 1 monthly sensitivity to a 10 precipitation perturbation fluctuates around 0 03 m w e the sensitivity characteristics obtained were used to model the surface mass balance evolution of gcn during the 20th and 21st centuries based on monthly means of air temperature and precipitation derived from bias corrected weather station data and statistically downscaled re analysis and general climate model data surface mass balance shows a persistently negative trend ranging from around 1 m w e a 1 at the beginning of the 20th century down to almost 1 5 m w e a 1 during the first years of the 21st century with only a few positive years occurring occasionally during the second half of the 20th century the scenario for the end of the 21st century totals approximately 4 5 m w e a 1 i e an estimated ice volume loss for gcn of 59 km 3 during 1900 2099

calcic amphibole equilibria and a new amphibole plagioclase geothermometer reply to the comment of poli and schmidt although only aliv appears in our thermometer expression this in no way infers that we believe tschermakite or katophorite kaersutite and other substitutions to be unimportant a careful reading of our earlier papers makes it clear that the reverse is true e g holland and richardson 1979 will et al 1990a b guiraud et al 1990 indeed in b and h p 211 we state that natural and synthetic amphiboles are dominated by a combination of edenite pargasite hornblende and hastingsite substitutions what we endeavoured to point out was that because of the nature of reaction 1 and the use of mixing on sites activity models the extent of al substitutions on m2 or na on m4 do not materially influence our expression for k1 and consequently our thermometer certainly any sophisticated activity model for amphibole explicitly should account for all cross site interactions between m tl and a site cations as alluded to by p and s in reference to docka et al 1987 as well as o3 site anions however such a day currently is well away and mixing on sites with modifications as outlined above and to be detailed in t j b holland and j d blundy in preparation seems rather promising for the purposes of amphibole thermometry we do not share the rather negative and pessimistic outlook on activity models and thermobarometry implicit in p and s comments

shoreline recovery on wave dominated sandy coastlines the role of sandbar morphodynamics and nearshore wave parameters abstract this study quantifies and characterises the temporal variability of shoreline recovery on a high energy sandy coastline using a 10 year dataset of daily shoreline and sandbar positions from a coastal imaging station at narrabeen collaroy beach australia following a total of 82 individual storm events rates of the cross shore return of the shoreline to its pre storm position were analysed observed rates during shoreline recovery were characterised by an overall mean of 0 2 m day temporal variability in rates was most evident at shorter timescales of 1 2 weeks and included rates most frequently between 0 and 0 3 m day less frequent more rapid rates of up to 2 m day and also minor landward movements this temporal variability was significantly correlated with nearshore forcing parameters describing the ratio of wave height to wave period the cross shore proximity and attachment of the sandbar to the shoreline and the rate of cross shore sandbar migration these findings are summarised in a new conceptual model that characterises temporal phases and rates of shoreline recovery corresponding to stages of onshore sandbar migration following a storm from fully detached storm deposited sandbar morphology through to complete sandbar welding with the shoreline more gradual shoreline recovery rates are observed with fully detached and semi attached sandbar conditions in contrast more rapid rates of shoreline recovery occur when sandbars are closer and attached to the shoreline observed to be on average 3 4 times greater than for detached sandbars in conditions with attached and semi attached sandbars shoreline recovery rates are negatively correlated to the forcing of nearshore wave steepness and dimensionless fall velocity and coupled with concurrent rates of onshore sandbar migration the findings provide insight into key parameters influencing shoreline recovery following storms

evidence of glaucophane schist facies metamorphism in the east karkonosze complex west sudetes poland in the east karkonosze complex karkonosze riesengebirge which occurs at the northern margin of the bohemian massif rocks of the glaucophane schist facies and transitions between the glaucophane schist facies greenschist facies and epidote amphibolite facies are present they belong to the leszczyniec volcanic formation lvf of cambrian ordovician age and to the mainly metasedimentary czarnow schist formation csf of ordovician silurian age similar high pressure low temperature rocks occur in the southern karkonosze and in the kaczawa mountains within metavolcanic formations of approximately the same age petrographic and electron probe studies show complex relationships between minerals including chemical zoning in the east karkonosze three stages of metamorphism pre dating contact metamorphism by late variscan lowermost upper carboniferous granite intrusion were distinguished stage 1 ocean floor amphibolite facies observed only in part of the lvf stage 2 high pressure low temperature variably glaucophane schist facies high pressure greenschist facies and epidote amphibolite facies stage 3 medium pressure greenschist facies accompanied by strong deformations glaucophane schist facies rocks formed in stage 2 survived the later stages of metamorphism only in the southern part of east karkonosze i e in lasocki range and r chory using the maruyama et al 1986 geobarometer the glaucophane bearing rocks formed at 6 5 7 kb those with crossite at 5 6 kb and rocks with magnesioriebeckite riebeckite at 4 5 kb other estimates for glaucophane bearing rocks give somewhat higher values of pressure i e 7 12 kb at temperatures between 300 and 530 c the highest temperatures are recorded in the glaucophane and garnet bearing rocks stilpnomelane may occur in all of these rocks the subduction obduction episode responsible for this high pressure low temperature metamorphism is considered to have taken place in the early variscan although no geochronology is yet available to confirm this

the daily scale entrance dynamics of intermittently open closed estuaries intermittently open closed estuaries ioce are a dynamic form of estuary characterised by periodic entrance closure to the ocean entrance closure is a function of the relative balance between on and offshore sediment transport with closures occurring during periods of low fluvial discharge whereby the estuary ebb tidal prism is reduced although the broad scale processes of entrance closure are becoming better understood there remains limited knowledge on channel morphodynamics during an individual closure event in this study the entrance dynamics of three ioce on the coast of victoria australia were monitored over a daily timescale following both artificial and natural openings the influence of changing marine and fluvial conditions on the relative sedimentation rate within the entrance channel was examined ioce in victoria showed two distinct modes of entrance closure a lateral accretion whereby the estuary gradually closes by longshore drift driven spit growth during low river flows and b vertical accretion where the channel rapidly aggrades under high 2 m near normal waves during storms when fluvial discharge and wave heights simultaneously increase large swells will not always close the mouth due to an increase in the ebb tidal prism the estuary water depth and the maximum channel dimensions following opening were not proportional to the opening duration with this being a function of the wave and fluvial conditions occurring following lagoon drainage based on the findings of this work implementing a successful artificial entrance opening is dependent on reduced onshore sedimentation rates which occur when wave energy is low 2 m hs relative to river flow copyright

climatic interpretation of alpine snowline variations on millennial time scales abstract the depression of snowlines or equilibrium line altitudes of alpine glaciers is often used by glacial geologists to infer variations in mass balance the climatic interpretation of snowline depression however is complicated by the number of factors that control glacier mass balance the simple lapse rate method of temperature interpretation ignores the effects of changes in radiation and snow accumulation the statistical approach to temperature interpretation which regresses precipitation and temperature against snowline altitude neglects the effect of radiation the most comprehensive approach for the climatic interpretation of snowline depression couples the heat and mass balances of a glacier surface a sensitivity analysis that utilizes the coupled heat and mass balance approach indicates that the 1000 m variation in snowline of alpine glaciers on glacial to interglacial time scales could be a result of significant changes in temperature and to a lesser extent changes in insolation snowline variations are sensitive only to relatively large changes in annual accumulation which should also be evident in other proxy records of moisture change the approaches outlined here provide glacial geologists with a summary of how various climatic forcings associated with glaciation may be quantified from snowline data

chloritoid bearing rocks associated with blueschists and eclogites northern new caledonia chloritoid bearing metasedimentary rocks occur in close proximity to blueschists and eclogites in the tertiary high pressure metamorphic belt of northern new caledonia the typical assemblage of chloritoid bearing rocks in the epidote zone is quartzchlorite muscovite garnet chloritoid in the omphacite zone epidote is an additional member of the chloritoid bearing assemblage paragonite is rare plagioclase was not detected and rutile and ilmenite are the fe ti oxide phases chloritoid glaucophane is not a common assemblage chloritoid bearing rocks have relatively low ca k na al ratios and the chloritoids are relatively mg rich with mg mg fe up to about 0 4 a comparison of the mineral assemblages and mineral chemistry with experimental and computed phase equilibria suggest an upper temperature limit near 560 c in the omphacite zone and a minimum temperature limit near 450 c at 10 kbar an empirical garnet chlorite fe mg exchange thermometer does not yield consistent results for the higher grade rocks suggesting ts ranging from 390 to 535 c in the omphacite zone and 420 465 c in the epidote zone the distribution coefficient kd fe mg ctd fe mg chl for chloritoid and chlorite ranges from 3 9 to 6 4 values which are lower than those 10 from lower greenschist facies rocks but are near those of upper greenschist facies and albite epidote amphibolite facies

evidence for a variscan suture zone in the vendee france a petrological study of blueschist facies rocks from bois de cene in the bois de cene area blueschist facies rocks characterized by glaucophane and or chloritoid provide evidence for a suture zone in the variscan this terrain is considered to be the eastern equivalent of the ile de groix high pressure metamorphic terrain petrological study of the two characteristic types of rocks found in the area shows that the primary high pressure paragenesis was modified during a retrogression which followed substantial decompression probably at constant or decreasing temperature the simplest interpretation is that this retrogression followed tectonic emplacement within a nappe pile

buoyancy driven lacustrine calving glaciar nef chilean patagonia glaciar nef a 164 km 2 eastern outlet of hielo patagonico norte the northern patagonia icefield terminates in a proglacial lake that has formed in conjunction with 20th century glacier retreat the terminus is inferred to be transiently afloat a hinge calving mechanism is proposed in which buoyant forces impose a torque on the glacier tongue resulting in the release of coherent sections of the glacier tongue as tabular icebergs a simple model shows how torque and tensile stress reach a maximum at the up glacier limit of the buoyant zone and that glacier thinning causes this point to migrate up glacier empirical evidence supporting this model includes elevated thermo erosional notches 6 5 m above lake level and the ubiquitous presence since 1975 of tabular icebergs with surface areas 0 3 km 2 flow speeds of 1 2 1 3 m d 1 were measured near the terminus in february 1998 extrapolations from these short term data yield a calving rate of 785 835 m a 1 and a calving flux of 232 10 6 m 3 a 1 or 0 2 km 3 a 1 the calculated mean water depth at the terminus is 190 m this calving rate is higher than at grounded temperate glaciers calving in fresh water but is nevertheless almost an order of magnitude less than calving rates at both grounded and floating tidewater glaciers

tectonic setting petrology and geochronology of jadeite glaucophane and chloritoid glaucophane schists from north west turkey the north west turkish blueschists represent a subducted passive continental margin sequence dominated by metaclastic rocks and marble the depositional age of the blueschist protoliths are probably palaeozoic to mesozoic while the age of the high pressure low temperature metamorphism is late cretaceous blueschists are tectonically overlain by a volcanosedimentary sequence made up of accreted oceanic crustal material that locally shows incipient blueschist metamorphism and by spinel peridotite slices the metaclastic rocks with regional jadeite and glaucophane which comprise the lower part of the blueschist unit make up an over 1000 m thick coherent sequence in the kocasu region of north west turkey rare metabasic horizons in the upper parts of the metaclastic sequence with sodic amphibole iawsonite but no garnet indicate lawsonite blueschist facies metamorphism the blueschist metaclastics in the kocasu region are practically free of calcium and ferric iron and closely approximate the nfmash system in bulk composition two low variance mineral assemblages with quartz and phengite are jadeite glaucophane chlorite paragonite and chloritoid glaucophane paragonite the metaclastics comprise up to several metres thick layers of jadeite schist with quartz phengite and nearly 100 mol jadeite phase relations in the metaclastics show that the chloritoid glaucophane assemblage even in fe2 rich compositions is stable in the jadeite stability field in the nfash system the above assemblage without the accompanying garnet has a narrow thermal stability field mineral equilibria in the metaclastics involving chloritoid glaucophane jadeite paragonite and chlorite indicate metamorphic p t conditions of 20 2 kbar and 430 30 d c yielding geothermal gradients close to 5d c km 1 one of the lowest geotherms recorded blueschists in the kocasu region which have been buried to 70 km depth are tectonically overlain by the volcanosedimentary sequence and by peridotite buried not deeper than 30 km phengites from two jadeite schists were dated by ar ar laser probe they give an age of 88 5 0 5 ma interpreted as the age of metamorphism blueschists and the overlying peridotite bodies are intruded by 48 53 ma old granodiorite bodies that were emplaced at 10 km depth this suggests that the exhumation of blueschists by underplating of cold continental crust and normal faulting at the blueschist peridotite interface occurred during the late cretaceous to palaeocene 88 53 ma

anomalous glacier responses to 20th century climatic changes in darwin cordillera southern chile there is an asymmetric pattern response of glaciers in darwin cordillera 54 55 s 69 71 w to the climate of the 20th century this asymmetry is suggested here as a cause of an increased wind activity which has a pronounced orographic effect although climatic records for the last 50 years show a warming trend as well as no trend in precipitation in the area some glaciers are advancing the area is characterized by strong climatic gradients with high rates of precipitation on the southwestern side of the range and dry conditions on the northern side glaciers on the northern and eastern sides show a general trend of receding fronts with a few exceptions these glaciers have gradually and uninterruptedly been shrinking since the turn of the century on the southern rim the present extents of some glaciers are similar to their 20th century maximum extents these are in turn similar or close to the holocene maximum the most extreme sites are the glaciers on either side of mount darwin which is 2469 m high the north facing glacier ventisquero marinelli has retreated several hundred metres per year over the last two decades while the south facing glaciers in the pahia pia basin have advanced during the same period in this study the frontal changes over the last 50 years of 20 glaciers have been analysed aerial photographs verticals from 1943 and 1984 have been used as well as oblique aerial photographs from 1993 the general result is that glaciers with accumulation areas facing south and west show somewhat stable fronts while glaciers facing east and north show receding fronts

relative geobarometry from high pressure rocks of quartzofeldspathic composition from the sesia zone western alps italy in the sesia zone of the western alps italy early alpine blueschist to eclogite facies metamorphism of rocks of quartzofeldspathic composition has produced the same high pressure assemblage of quartz na pyroxene na amphibole paragonite phengite zoisite garnet magnetite sphene and fe sulphide the qfs assemblage over an area 150 km2 relative gradients in pressure and temperature over this region are reflected in the variations in mineral chemistries of the individual phases of the quartzofeldspathic assemblage through continuous reactions mineralogical discontinuities do not occur in the qfs assemblage of this region increases in the jadeite content of the pyroxenes xjd 0 48 to xjd 0 93 and in the glaucophane content of the amphiboles xgl 0 89 to xgl 0 96 occur from the southwest to the northeast of the region studied analysis of coexisting garnets and pyroxenes indicate that the compositional variation of amphiboles and pyroxenes is associated with a decrease in the grossular component of the coexisting garnet zoned pyroxenes and garnets together with the regional trends in mineral chemistries suggest that the evolution of the qfs assemblage with increasing pressure may be modelled by pressure sensitive continuous reactions in which amphibole zoisite and the more jadeitic pyroxene constitute the high pressure assemblage chemographic constraints permit the positioning in pressure temperature space of the compositional isopleths of those model continuous reactions involving these phases which meet the textural and chemical criteria observed in the natural assemblages the low dp dt slope 20 bars c of these isopleths causes the continuous reactions to be useful for geobarometric calculations at pressures above the absolute breakdown of albite to jadeite plus quartz in addition the pseudobinary loops for the other continuous reactions which are potentially useful geobarometers and involve either the naalca 1mg 1 exchange or the mgca 1 exchange are calculated comparison of mineral chemistries with the isopleths yields a relative barometric scheme for the localities studied with these barometric observations it is possible to show that the p t path which the sesia body travelled towards the final recorded state was one of increasing pressure other blueschist and eclogite occurrences from syros and sifnos which contain rocks of quartzofeldspathic composition are also examined

structure petrology and metamorphic history of the nome group blueschist terrane salmon lake area seward peninsula alaska an 80 mi 2 area adjacent to salmon lake mapped at a scale of 1 36 680 includes a section of the nome group schist that is at least 2 000 m thick it is relatively intact with relict primary lithologic layering and not melange like or highly disrupted by faults the nome group metasediments include pelitic schist graphitic quartzite pure and impure marble calcareous schist chlorite albite schist chloritic quartz albite and mafic schists metaigneous rocks include fe ti rich metabasite and granitic to tonalitic orthogneiss the protoliths are precambrian to paleozoic in age and radiometric ages indicate that the high pressure metamorphism of the nome group is late jurassic blueschist facies assemblages occur in nome group metabasites and in most metasedimentary schists the blueschists are synkinematic they formed during an episode of widely distributed penetrative deformation and mesoscopic intrafolial isoclinal folding of consistent orientation the nome group of the salmon lake area underwent a prograde monocyclic polyfacial high p t metamorphism initial metamorphism was in the lower t regime of the lawsonite glaucophane field 300 c 7 kb and prograded with increasing t and p into the epidote almandine glaucophane field through an apparent p t maximum as indicated by the assemblage glaucophane omphacite garnet 420 c 9 10 kb the later stages of the metamorphism were characterized by increased t p likely during initial stages of decompression and the return of the normal geothermal gradient to the transition between the blueschist facies and the high p albite epiclote barroisite field 450 to 525 c 7 8 kb this high p t cycle was followed by an incipient static retrogressive metamorphism at low greenschist facies conditions during the later uplift of the nome group in the late cretaceous and early tertiary

the 20th century advance of glaciar pio xi chilean patagonia glaciar pio xi the largest glacier in south america has experienced an advance during the 20th century unlike virtually all other glaciers in patagonia which are retreating rapidly climatological records of the last 80 years are analyzed together with ice velocity and meteorological measurements collected during november 1995 near the tidewater front of glaciar pio xi ice speeds of up to 50 m d 1 were measured the maximum occurring during a period when air temperatures were high

high pressure metamorphism in the nappes of the valle dell orco traverse western alps collisional belt a detailed field and petrological study of rocks from nappes cut by the valle dell orco italian western alps in particular the sesia lanzo composite unit has revealed geological and metamorphic histories which started in pre alpine times and lasted up to the alpine subduction collisional processes during these processes the nappes sustained an early high p low t stage and a later low p greenschist facies stage but followed partly distinctive p t time trajectories this paper discusses the kinematic evolution and the thermal history of the alpine belt from the early subduction underthrust to the later exhumation stage the metamorphic crystallization is often governed by incomplete and or local equilibrium and the pervasive syn metamorphic deformation and the composition of the syn metamorphic fluid phase if present have exerted an effective local control on reaction kinetics

processes controlling morphodynamics of artificially breached barriers abstract naturally and artificially breached tidal inlets can promote fast morphological changes along the adjacent detrital barriers as they evolve in response to the contemporaneous wave regime inlet migration results in downdrift barrier erosion while updrift sand accumulation and concomitant barrier extension are commonly observed this study addresses the performance of placement of a sandfill designed to create an artificial dune along the updrift tip of a sand barrier aiming to constrain inlet migration stabilize its location and reduce sand transfers from the ocean into the lagoon induced by storm overtopping of the barrier herein we investigate the patterns of inlet drifting and processes regulating the progressive loss of efficiency of this soft engineering solution we show that besides updrift inlet migration which occurs with temporary reversal of the prevailing direction of drift currents meandering of the ebb channels that envelop the flood delta is quite effective in triggering or enhancing erosion of the updrift barrier tip in periods when the inlet main channel is migrating in the opposite direction this additional erosional process which acts along the back barrier facade is responsible for the increase of the erosion rate of the artificial dune and regardless of the direction of wave induced drift direction of the inlet this finding discloses the relevance of taking into account not only the oceanic processes waves but also processes operating on the lagoonal side of the barriers in future engineering operations designed for tidal inlet management

glacier change and climate forcing in recent decades at gran campo nevado southernmost patagonia digital terrain models of the southern chilean ice cap gran campo nevado reflecting the terrain situations of the years 1984 and 2000 were compared in order to obtain the volumetric glacier changes that had occurred during this period the result shows a slightly negative mean glacier change of 3 80 m the outlet glacier tongues show a massive thinning whereas the centre of the ice cap is characterized by a moderate thickening thus a distinct altitudinal variability of the glacier change is noticed hypothetically this could be explained by the combined effects of increased precipitation and increased mean annual air temperature both to verify and to quantify this pattern of climatic change the mean glacier change as well as its hypsometric variation are compared with the results of a degree day model the observed volumetric glacier change is traced back to possible climate forcing and can be linked to an underlying climate change that must be comparable with the effects of a precipitation offset of at least 7 8 and a temperature offset of around 0 3 k compared to the steady state conditions in the period 1984 2000

new insights into embayed beach rotation the importance of wave exposure and cross shore processes although embayed beach rotation has been viewed and modeled as an alongshore sediment transport process acting on a uniform beach profile recent research suggests a more complex response whereby alongshore variability in cross shore sediment fluxes may be more significant this study utilizes 5 years of fully three dimensional beach surveys at narrabeen collaroy beach se australia to quantify the control of alongshore nonuniform wave exposure and cross shore processes on embayed beach rotation empirical orthogonal function analysis of the alongshore variability in subaerial beach volume width and berm slope confirms that the dominant mode of subaerial beach variability is an onshore offshore sediment exchange that is strongly controlled r 0 8 by the alongshore gradient in breaker wave height and coincides with a uniform flattening steepening of the berm slope a secondary rotation like signal is observed in both the subaerial beach volume width data and significantly the berm slope this inverse flattening steepening of the berm slope between beach extremities is most likely a proxy for differing cross shore processes within the surf zone between the exposed and sheltered ends of the embayment particularly with regards to dissipation of storm wave energy by offshore sandbars and beach recovery following storms analysis of the corresponding wave data reveals two distinct time scales of wave forcing characteristic of short term erosion and longer term recovery processes a new conceptual model is presented of three differing modes of embayed beach rotation with the newly identified beach rotation mode controlled by offshore sandbars considered of particular importance at embayments where headland sheltering of oblique waves is pronounced

singularities in nckfmash na2o cao k2o feo mgo al2o3 sio2 h2o a new petrogenetic grid is presented for the system nckfmash na2o cao k2o feo mgo al2o3 sio2 h2o in which ca is incorporated in garnet and caalna 1si 1 solid solution is considered for both the plagioclase and white mica structures a compatibility diagram for plagioclase bearing metapelitic assemblages within the nckfmash system also has been derived a dominant feature of the nckfmash grid is the singularities and associated singular reactions which occur along plagioclase margarite and plagioclase paragonite bearing univariant equilibria the singularities represent compositional coplanarities which occur in response to the caalna 1si 1 substitution occurring at different rates in plagioclase and white mica this is controlled by a fundamental difference in the mixing within the two mineral structures the singularities give rise to a number of intriguing phase diagram features including azeotropes from the results presented here it is predicted that the occurrence of margarite and paragonite in pelitic rocks is controlled by equilibria related to the singularities the presence of these white micas is strongly dependent upon bulk composition and plagioclase bearing margarite paragonite free assemblages typical of barrovian type terranes are predicted for bulk compositions of mg mg fe 0 4 and ca ca na 0 4 at for example 5 5 kbar

calculated mineral equilibria in the greenschist blueschist eclogite facies in na 2 o feo mgo al 2 o 3 sio 2 h 2 o the new greatly expanded internally consistent dataset of holland and powell includes thermodynamic data for a wide range of mineral end members in common rock forming minerals in particular including femg 1 substitutions in glaucophane garnet chloritoid and carpholite and femg 1 and mgsial 1al 1 substitutions in talc and chlorite moreover we have the uncertainties and correlations for these data with the data we have calculated the full pressure temperature phase diagram for the system na2o feo mgo al2o3 sio2 h2o nfmash for quartz or coesite and h2o in excess in the range 300 800 c and 5 50 kbars by solving the set of non linear equations formed by the equilibrium relationships for an independent set of equations between the end members in an assemblage in nfmash the compositions of the minerals and pt can be calculated thus the changes in mgsial 1al 1 along nmash reactions and fesial 1al 1 along nfash reactions are calculated and the changes in femg 1 and mgsial 1al 1 along nfmash reactions are calculated from this information it is straightforward to generate pt diagrams for specific rock compositions mineral assemblages and mineral compositional changes in the phase diagram are discussed in relation to greenschist blueschist and eclogite facies assemblages in metapelitic rocks it is found that the correspondence between the predictions of the phase diagrams and the observations on rocks is remarkably good when semiquantitative extensions of the phase diagram to include ca mgfe 1 nasica 1al 1 fe3 al 1 and kna 1 substitutions are taken into account the agreement is essentially complete

controls of local geology and cross shore longshore processes on embayed beach shoreline variability 10 shoreline variability along the 3 6 km long narrabeen beach embayment in se australia is 11 investigated over a 5 year period we apply the one line shoreline change model lx shore 12 which couples longshore and cross shore processes and can handle complex shoreline 13 planforms non erodible emerged headlands and submerged rocky features the model 14 skilfully reproduces the three dominant modes of shoreline variability which are by 15 decreasing order of variance cross shore migration rotation and a third mode possibly 16 related to breathing model results confirm previous observations that longshore processes 17 primarily contribute to the rotation and third modes on the timescales of months to seasons 18 while cross shore processes control the shoreline migration on shorter timescales from hours 19 storms to months additional simulations simplifying progressively the bathymetry show 20 how the inherent geology strongly modulates the spatial modes of shoreline variability the 21 offshore central rocky outcrop is found to limit the rotation in contrast the submerged rocky 22 platforms that extend from the headlands enhance the shoreline rotation mode and increase 23 alongshore variability of the cross shore migration mode owing to increased alongshore 24 variability in wave exposure offshore wave transformation across large scale submerged 25 rocky features and headland shape are therefore critical to contemporary shoreline dynamics 26 2

the alpine geodynamic evolution of penninic nappes in the eastern central alps the eastern central alps consist of several pennine nappes with different tectonometamorphic histories the tectonically uppermost units oceanic avers bundnerschiefer continental suretta and tambo nappes oceanic vals bundnerschiefer show cretaceous early tertiary w directed thrusting with associated blueschist facies metamorphism related to subduction of the pennine units beneath the austroalpine continental crust this event caused eclogite facies metamorphism in the underlying continental adula nappe the gross effect was crustal thickening the tectonically lower continental simano nappe is devoid of any imprint from this event in the course of continent continent collision high t metamorphism and n directed movements occurred both affected the whole nappe pile more or less continuously from amphibolite to greenschist facies conditions crustal thinning commenced during the regional temperature peak a final phase is related to differential uplift under retrograde p t conditions further thinning of the crust was accommodated by e to ne directed extensional deformation

morphodynamics of intermittently open closed coastal lagoon entrances new insights and a conceptual model abstract ocean entrances to coastal lakes and lagoons are a complex sensitive and important part of the coastal environment they provide estuarine water exchange between inland waterways and the open ocean and are increasingly the focus of intense urban and industrial development coastal lagoons that are only intermittently connected to the ocean are particularly sensitive during periods of closure water quality issues are exacerbated along with the increased risk of flooding mechanical clearance was undertaken in 2006 at the ocean entrance to narrabeen lagoon sydney australia historically this site has intermittently opened and closed both naturally and mechanically with the ingress of marine sand into the entrance restricting water exchange between the estuary and the ocean this instantaneous reset of the system provided a unique opportunity to monitor and quantify generic inlet sedimentation processes and mechanisms an intensive data collection campaign was undertaken for one entire year following the clearance this dataset includes current and water level measurements calculation of the alongshore sediment supply and regular highly detailed morphological surveys of the infilling lagoon entrance system this contribution utilises this unique dataset to quantify the sediment ingress volumes rates and pathways within the accreting flood tide delta of the lagoon entrance it was found that ingress of sand into the system proceeds via a rapid landward infilling process as opposed to backfilling toward the ocean with the evolution of the flood tide delta occurring in distinct phases the location of the divergence point of the flood tidal current the amount of available accommodation space within the entrance system and the influence of storm events were found to be key factors in the evolving morphodynamics of this intermittently open closed coastal lagoon

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

some remarks on the stability of blueschists and related high p low t assemblages in continental orogens the thermal evolution of the crust in continental orogens is sensitive to the deformation in the mantle part of the lithosphere a point obscured in models that apply a boundary condition of constant basal heat flux within the mantle lithosphere we show that for part of the plausible range of conductivities and heat source distributions within the continental lithosphere the maximum or potential temperatures in thickened continental crust typical of collision zones do not necessarily exceed the stability field of the high p low t facies such as blueschists provided the mantle lithosphere is also thickened during the deformation the appropriate range of parameters includes conductivities towards the upper limit of the plausible range k 2 2 w m i k l together with low crustal heat production rates with distributions concentrating heat production in the upper crust and relatively thin initial lithosphere these observations suggest that at least some of the high p low t assemblages found within continental orogens for example in the dalradian of the scottish sw highlands may reflect the thermal response to whole lithospheric thickening and do not necessarily reflect thermal regimes attendent with subduction or unusually rapid excavation

intermittently closed open lakes and lagoons their global distribution and boundary conditions abstract intermittently closed open lakes and lagoons icolls are a particularly dynamic form of estuary characterised by periodic entrance closure to the ocean closure occurs when a subaerial sand berm stabilises across the entrance channel during times of low fluvial discharge icolls are of global importance as they provide valuable ecological habitats for many species and are associated with a wide range of management issues due to their cycle of entrance closure and opening icolls are found to be more widespread globally than previously described with 1477 of these estuaries being identified in this study this constitutes an estimated 3 of the world s estuaries and 15 of all estuaries along microtidal coastlines icolls are concentrated along microtidal to low mesotidal coastlines in the mid latitudes and predominantly on coasts with temperate climates this distribution is related to greater wave heights as driven by high intensity winds and a longer fetch distance the highest proportion of icolls are present in australia 21 all global icolls south africa 16 and mexico 16 in australia a comparison with fluvial input found that it is less important than marine processes in determining icoll formation and that icolls are associated with a relative tidal range of

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

a calculated petrogenetic grid for the system k2o feo mgo al2o3 sio2 h2o with particular reference to contact metamorphosed pelites a petrogenetic grid is presented for the system kfmash k o feo mgo a1 0 sio h o including biotite muscovite k feldspar chlorite chloritoid staurolite cordierite garnet ortho amphibole orthopyroxene spinel andalusite sillimanite kyanite quartz and corundum with h o in excess which was calculated using the computer program thermocalc and the powell and holland internally consistent thermodynamic dataset by removing the normal constraint of having quartz in excess both quartz bearing and quartz absent equilibria are shown quartz absent equilibria are particularly relevant at high t and low p conditions because of their common occurrence at these conditions the calculated mineral assemblage and mineral compositional variations in terms of femg and fe mg siall exchange vectors are broadly compatible with observations on natural rocks particularly when non kfmash components are taken into account

hydro morphological modelling of small wave dominated estuaries small intermittently open or closed estuaries are characteristic of the coasts of south africa australia california mexico and many other areas of the world however modelling attention has tended to focus on big estuaries that drain large catchments and serve a wide diversity of interests e g agriculture urban settlement recreation commercial fishing in this study the development of a simple parametric system dynamics model to simulate the opening and closure of the mouths of small wave dominated estuaries is reported in the model the estuary is conceived as a basin with a specific water volume to water level relationship connected to the sea by a channel of fixed width but variable sill height changes in the form of the basin are not treated in the model while the dynamics of the mouth channel are central to the model the magnitude and direction of the flow through the mouth determines whether erosion or deposition of sediment occurs in the mouth channel influencing the sill height the model is implemented on the great brak estuary in south africa and simulations reveal that the raised low water levels in the estuary during spring tide relative to neap tide are occasioned by the constriction of the tidal flow through the shallow mouth freshwater inflows to the estuary are shown to be significant in determining the behaviour of the inlet mouth a factor often ignored in studies on tidal inlets further it is the balance between freshwater inflows and wave events that determines the opening or closure of the mouth of a particular estuary

phase relations in the greenschist blueschist amphibolite eclogite facies in the system na 2 o cao feo mgo al 2 o 3 sio 2 h 2 o ncfmash with application to metamorphic rocks from samos greece calculated phase equilibria among the minerals sodic amphibole calcic amphibole garnet chloritoid talc chlorite paragonite margarite omphacite plagioclase carpholite zoisite clinozoisite lawsonite pyrophyllite kyanite sillimanite quartz and h2o are presented for the model system na2o cao feo mgo al2o3 sio2 h2o ncfmash which is relevant for many greenschist blueschist amphibolite and eclogite facies rocks using the activity composition relationships for multicomponent amphiboles constrained by will and powell 1992 equilibria containing coexisting calcic and sodic amphiboles could be determined the blueschist greenschist transition reaction in the ncfmash system for example is defined by the univariant reaction sodic amphibole zoisite calcic amphibole chlorite paragonite plagioclase quartz h2o occurring between approximately 420 and 450 c at 9 5 to 10 kbar the calculated petrogenetic grid is a valuable tool for reconstructing the pt evolution of metabasic rocks this is shown for rocks from the island of samos greece on the basis of mineral and whole rock analyses pt pseudosections were calculated and together with the observed mineral assemblages and reaction textures are used to reconstruct pt paths for rocks from northern samos pseudomorphs after lawsonite preserved in garnet the assemblage sodic amphibole garnet paragonite chlorite zoisite quartz and the retrograde appearance of albitic plagioclase and the formation of calcic amphibole around sodic amphibole constrain a clockwise pt path that reaches its thermal maximum at some 520 c and 19 kbar the derived pt trajectory indicates cooling during exhumation of the rocks and is similar to paths for rocks from the western part of the attic cycladic crystalline complex rocks from eastern samos indicate lower pressures and are probably related to high pressure rocks from the menderes massif in western turkey

ductile thrusting recorded by the garnet isograd from blueschist facies metapelites of the ile de groix armorican massif france

the geomorphology and evolution of intermittently open and closed estuaries in large embayments in victoria australia abstract intermittently open and closed estuaries ioce are common landforms on open ocean microtidal coasts they are often viewed as evolutionary end members of open estuaries where all the accommodation space has been infilled by sediment while ioce are typically recognised to form in wave dominated microtidal environments they can also form within embayments where the relative balance between waves and tides is highly spatially and temporally variable this study examines the geomorphology and infill of two such embayed ioce in victoria southern australia in order to assess how these systems compare to their open ocean counterparts in order to gain an understanding of the boundary conditions of such landforms it is found that ioce s can occur in embayments where there is sufficient energy to form a beach berm the infill of these systems broadly follows the transgressive stillstand pathways of open coast systems but the facies are modulated by the size of the catchment and open ocean wave exposure these boundary conditions also affect the evolution of the coastal plain in which the embayed ioce may form and in turn the estuary planform the entrance dynamics of these estuaries are highly variable and it appears that they may switch between permanently open or closed states in relation to modification of boundary conditions such as roughness it is inferred that the relative tidal range rtr of the marine environment at the estuary mouth is an important determination of entrance condition with the observed systems being close to the maximum rtr value on the open coast at which these landforms can exist

shoreline change mapping using crowd sourced smartphone images abstract shoreline change information is critical for effective management of the coastal zone this study presents a low cost method for mapping shoreline change that harnesses smartphone images collected by the community and uploaded to social media platforms a smartphone camera cradle installed overlooking a coastal region is used to constrain the crowd sourced camera extrinsic parameters and accompanying signage instructs participants on how to share their image to social media using a site specific hashtag identifier surveyed ground control points solve for the focal length of the smartphone lens and more accurately resolve the camera extrinsic parameters shoreline position is subsequently mapped on georectified images using an edge detection technique based on the red and blue colour channels a validation of the method was conducted at two sandy beaches in se australia and resulted in strong community participation 400 images submitted over 7 months by 198 individual contributors concurrent shoreline surveys using rtk gnss indicated that shoreline accuracy using this crowd sourced approach is comparable to that of established coastal imaging systems with cross shore shoreline accuracy best for these two elevated validation sites camera elevation 17 3 m 27 1 m above msl in the camera nearfield rmsd 1 4 m and rmsd ranging between 2 6 and 3 9 m over coastal stretches spanning up to 1 km minimal differences in shoreline accuracy were observed between low resolution images characteristic of those uploaded to social media and higher resolution images sourced from the smartphone the successful application of this low cost approach combined with the proliferation of smartphones and social media usage open up new possibilities for crowd sourced shoreline change mapping at suitable coastal locations worldwide

sedimentary facies and landform genesis at a temperate outlet glacier soler glacier north patagonian icefield glasser n f hambrey m j 2002 sedimentary facies and landform genesis at a temperate outlet glacier soler glacier north patagonian icefield 49 1 43 64

low differential stress during high pressure metamorphism the microstructural record of a metapelite from the eclogite zone tauern window eastern alps constraints on the state of stress at deep levels of convergent plate boundaries can be obtained from the microstructural record of high pressure metamorphic rocks provided that this record has remained unchanged during exhumation the inclusion patterns in poikiloblastic garnet of a metapelite from the eclogite zone of the tauern window eastern alps reveal a foam microstructure of quartz controlled by grain boundary free energy the garnet blasts show concentric chemical zonation thermobarometry based on correlation between compositional domains in garnet chloritoid and phengite coexisting with kyanite rutile and quartz shows that garnet growth commenced before peak p t conditions close to 25 kbar and 600 c had been reached and continued during the early stage of decompression this implies that the microstructure of quartz controlled by grain boundary free energy persisted continuously during the latest stage of burial to ca 80 km depth and the early stage of exhumation involving detachment from the downgoing slab and release into the subduction channel the foam structure of the overgrown quartz indicates that the differential stress was too low to drive dislocation creep during that period when the rock crossed the interface between the plates with a high differential stress resulting in tectonic overpressure or significant shear heating being ruled out outside the protective garnet the interfacial free energy controlled quartz microstructure has been destroyed completely due to dynamic recrystallization during deformation by dislocation creep this happened while the crustal slice was exhumed to a depth of about 45 km the preservation of this synkinematic quartz microstructure indicates a tectonic scenario where the final cooling was rapid and no marked stress peak was associated with the brittle plastic transition

phase petrology and p t conditions of mafic blueschists from the meliata unit west carpathians slovakia blueschists occurring as layers in calcite marbles of the meliata unit occur along the so called roznava tectonic line situated in the southern part of the gemericum slovakia mineral assemblages and compositions from seven blueschists localities and one occurrence of amphibolite facies rocks overprinted by blueschist metamorphism were investigated the most common minerals in the blueschists are blue amphibole epidote and albite some fe2 and al rich rocks also contain garnet and chloritoid respectively na pyroxene with a maximum 50 jadeite component was also found the blue amphiboles correspond mostly to crossite and also to glaucophane and ferroglaucophane in some samples almandine and spessartine rich garnet has very low mgo content 3 wt the si content in phengite ranges between 3 3 and 3 5 pfu calculated on the basis of 11 oxygens the zoning patterns of blue amphibole garnet and chloritoid suggest their formation during a prograde stage of metamorphism the p t conditions of metamorphism are estimated to be about 380 460 c and 10 13 kbar pressures of 7 5 8 5 kbar and temperatures of 350 370 c were obtained for some actinolite and aegirine rich rocks apart from chlorite other mafic minerals formed during retrograde metamorphism are biotite and occasionally also actinolite

a study of non linear tidal propagation in shallow inlet estuarine systems part i observations the offshore tide becomes strongly distorted as it propagates into shallow estuarine systems observations of sea surface elevation and horizontal currents over periods ranging from three days to one year at nine stations within nauset inlet estuary document the non linear interaction of the off shore equilibrium tidal constituents despite strong frictional attenuation within the estuary the overtides and compound tides of m2 s2 and n2 in particular reach significant amplitude resulting in strong tidal distortion high frequency forced constituents in sea surface are phase locked consistently leading the forcing tides by 60 70 resulting in a persistent distortion where falling tide is longer than rising tide forced constituents in currents are more nearly in phase with equilibrium constituents producing flood currents which are shorter but more intense than ebb currents a compound fortnightly tide msf modulates the mean water level such that lowest tides occur during neap phase instead of spring phase this fortnightly tide can be contaminated by storm surge changing the phase characteristics of this constituent implications of the overtides compound tides and lower frequency tides on near bed suspended and dissolved material transport are profound

a low variance mineral assemblage with talc and phengite in an eclogite from the saxonian erzgebirge central europe and its p t evolution a light coloured fine grained eclogite sample from near the village of hammerunterwiesenthal in the erzgebirge nw bohemian massif preserves the low variance mineral assemblage of garnet omphacite phengite talc amphibole clinozoisite quartz rutile and accessory phases porphyroblasts of amphibole clinozoisite and phengite formed during a late stage iii of metamorphism paragonite joined the assemblage late in this stage iiib the chemical zonation of the minerals was carefully studied various geothermobarometric methods were applied especially involving phengite and talc the constrained p t path for the eclogite starts at about 480 c and 25 kbar stage ib followed by a significant temperature rise stage ii at slightly increasing pressure at the peak p t conditions of 720 c and 27 kbar blastesis of amphibole clinozoisite and phengite was caused by infiltrating hydrous fluids the resulting density reduction may have allowed buoyant uplift of the eclogite subsequently significant cooling occurred at high pressures stage iiib is characterized by p t conditions around 520 c and 18 kbar at reduced water activities this unusual late p t evolution might explain the freshness of the eclogite including the preservation of chemical zonation on the micrometre scale

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

detailed dynamic geometric and supraglacial moraine data for glaciar pio xi the only surge type glacier of the southern patagonia icefield chilean government through centers of excellence base financing program of comision nacional de investigacion y tecnologica de chile conicyt

pressure temperature time paths of regional metamorphism i heat transfer during the evolution of regions of thickened continental crust the development of regional metamorphism in areas of thickened continental crust is investigated in terms of the major controls on regional scale thermal regimes these are the total radiogenic heat supply within the thickened crust the supply of heat from the mantle the thermal conductivity of the medium and the length and time scales of erosion of the continental crust the orogenic episode is regarded as consisting of a relatively rapid phase of crustal thickening during which little temperature change occurs in individual rocks followed by a lengthier phase of erosion at the end of which the crust is at its original thickness the principal features of pressure temperature time ptt paths followed by rocks in this environment are a period of thermal relaxation during which the temperature rises towards the higher geotherm that would be supported by the thickened crust followed by a period of cooling as the rock approaches the cold land surface the temperature increase that occurs is governed by the degree of thickening of the crust its conductivity and the time that elapses before the rock is exhumed sufficiently to be affected by the proximity of the cold upper boundary for much of the parameter range considered the heating phase encompasses a considerable portion of the exhumation decompression part of the ptt path in addition to the detailed calculation of ptt paths we present an idealized model of the thickening and exhumation process which may be used to make simple calculations of the amount of heating to be expected during a given thickening and exhumation episode and of the depth at which a rock will start to cool on its ascent path an important feature of these ptt paths is that most of them lie within 50 c of the maximum temperature attained for one third or more of the total duration of their burial and uplift and for a geologically plausible range of erosion rates the rocks do not begin to cool until they have completed 20 to 40 per cent of the total uplift they experience considerable melting of the continental crust is a likely consequence of thickening of crust with an average continental geotherm a companion paper discusses these results in the context of attempts to use metamorphic petrology data to give information on tectonic processes 1984 oxford university press

glaciar perito moreno patagonia climate sensitivities and glacier characteristics preceding the 2003 04 and 2005 06 damming events mass balance and climate sensitivity of glaciar perito moreno gpm one of the main outlet glaciers of hielo patagonico sur southern patagonia icefield were investigated field measurements were carried out from 1995 to 2003 including ice ablation and velocity at stakes seismic profiling bathymetry of the lake near the calving fronts and meteorological data the database was complemented by satellite observations to derive the motion field by interferometric data map glacier boundaries and snowlines from multi year time series of radar images and obtain glacier topography from the shuttle radar topography mission in september 2003 gpm started to dam the southern arm of lago argentino resulting in a maximum rise of the lake level of 9 35 m before the dam burst in march 2004 the ice dam formed again in august 2005 bursting in march 2006 analysis of mass fluxes indicates no long term trend in mass balance this behaviour contrasting with most retreating glaciers in the vicinity can be attributed to a particular glacier geometry monthly climate sensitivity characteristics for glacier mass balance were derived using a degree day model showing similar importance of both temperature and precipitation also the reconstruction of the mass balance for the last 50 years from local climate data shows a near steady state condition for gpm with some small fluctuations such as a slightly positive balance after 1998 that may have triggered the minor advance leading to damming events in 2003 and 2005

short term changes in the morphodynamic states of beaches and surf zones an empirical predictive model a time series of 6 5 years of daily observations of beach states and wave characteristics from southeastern australia was analyzed with the aim of determining the degree to which time varying beach state can be explained and predicted the six commonly occurring beach states dissipative longshore bar trough rhythmic bar and beach transverse bar and rip low tide terrace and reflective discussed earlier were related by means of discrete discriminant analyses to the parameter hb wst where hb is breaker height ws is the fall velocity of the beach sand and t is peak breaker period using a total of 1545 cases two values were used in the analyses the immediate value occurring on the day the particular state was observed and a weighted mean value expressing recently antecedent conditions the immediate value made a negligible contribution to explaining day to day beach state observations however the antecedent conditions showed a strong relationship and provide a successful means of prediction by examining cases where the time derivatives of both state and were near zero it was possible to define the equilibrium conditions associated with each state directions of change erosional or accretionary are predicted in terms of departures of from the equilibrium value appropriate to the beach state prevailing at the time change begins