apatite fission track thermochronometry from central alberta implications for the thermal history of the western canada sedimentary basin apatite separated from 47 cretaceous and tertiary drill core and surface samples from the foreland basin strata of the western canada sedimentary basin wcsb have been analyzed for their apatite fission track aft age and confined track length distribution thermal histories of the fission track data were then estimated using a constrained random search inversion technique based on the durango apatite annealing model most importantly this technique provides an estimate of the peak postdepositional temperature experienced by each sample with error bounds determined by the precision of the fission track data most apatite samples retain at least some tracks that formed prior to the time of maximum cenozoic burial assumed to be coincident with maximum temperature seven apatite samples were fully annealed during burial during or following the laramide orogeny and provide a minimum age of 42 ma for heating lower cretaceous samples from near the deformation front were fully annealed and attained temperatures of at least 119 138 c during maximum burial in contrast stratigraphically equivalent samples at the northeastern end of the transect near the cold lake heavy oil and tar sand deposits did not exceed 80 c paleogeothermal gradients calculated using bounded estimates of the peak temperatures experienced by the samples together with maximum burial estimates from coal moisture studies range from 20 c km near the deformation front to as high as 60 c km near the cratonic edge of the basin this variation has the same trend as present geothermal gradients which range from 30 c km to 45 c km but indicates a greater contrast at the end of the laramide the results are consistent with the concept of heat transport by basinal scale fluid flow

single crystal 40ar 39ar age variation in muscovite of the gassetts schist and associated gneiss vermont appalachians an exposure near gassetts vermont contains lithologies varying from staurolite kyanite grade aluminous schists with paragonitic muscovite to potassic gneiss with phengitic muscovite single crystal laser fusion 40 ar 39 ar ages for paragonitic and phengitic muscovite yield similar distributions with ranges between 366 4 and 326 4 ma intracrystalline ages vary from ca 394 4 to 330 4 ma thus we find that the intracrystalline core rim age distribution of relatively large single crystals essentially encompasses the range of ages obtained through total fusion of smaller crystals consistent with models for development of diffusion profiles and 40 ar closure during cooling with a diffusion dimension controlled by the physical grain size however some of the larger crystals studied particularly those with prominent microscopic defects features readily evident such as internal grain boundaries and twin planes yield relatively young ages and lack significant core rim age discordance furthermore the overall distribution of single crystal ages in the two samples is bimodal and we suggest that this age distribution reflects metamorphic deformation and recrystallization event s superimposed on early generation muscovite thus the mean age of muscovite in these samples typical of k ar and 40 ar 39 ar incremental heating analysis of bulk mineral separates has little relationship to any single hypothetical closure temperature in view of the similar results we obtain for muscovite of contrasting composition the net effects of variations in grain size deformational character and growth history are interpreted to be more important in forming the observed variations in age than are the chemical substitutions in these samples

crustal structure of the western new england appalachians and the adirondack mountains we present an interpretation of the crustal velocity structure of the new england appalachians and the adirondack mountains based on a seismic refraction wide angle reflection experiment in eastern north america extending from the adirondacks in new york state through the northern appalachians in vermont and new hampshire to central maine modeling of the eastern portion of the profile within the new england appalachians shows a subhorizontal layered crust with upper crustal velocities ranging from 5 5 to 6 2 km s a midcrustal velocity of 6 4 km s and a lower crustal velocity of approximately 6 8 km s crustal thickness increases from 36 km beneath maine to 40 km in vermont little evidence is seen for structures at depth directly related to the white mountains or the green mountains a major lateral velocity change in the upper and mid crust occurs between the appalachians and the adirondacks this boundary projecting to the surface beneath the champlain valley dips to the east beneath the green mountains and extends to a depth of 25 km below the eastern edge of the connecticut valley synclinorium in vermont the tahawus complex a series of strong horizontal reflections at 18 24 km depth beneath the adirondack highlands is seen to dip eastward beneath vermont upper crustal rocks in the adirondack mountains have poisson s ratios of 0 28 0 01 that can be correlated with the marcy anorthosite pois son s ratios of 0 24 0 01 calculated for rocks of the connecticut valley synclinorium indicate a siliceous upper crust in vermont the lower crust is considered to be best represented by intermediate to mafic granulites a high poisson s ratio 0 26 0 27 tends to support a mafic lower crust in the new england appalachians this seismic refraction wide angle reflection experiment provides further evidence for the obduction of the allochthonous western appalachian units onto grenvillian crust above a zone of detachment that penetrates at least to midcrustal depths and was the locus of successive paleozoic thrusting

geochronologic studies in central new england ii post acadian hinged and differential uplift sup 40 ar sup 39 ar analyses of muscovite biotite and k feldspar from central new england reveal a remarkable pattern of mineral ages the ages are progressively younger from central to western new hampshire and rise sharply near the vermont border to ages more typical of post acadian cooling this distribution is attributed to differential uplift via isostatic rebound of an anomalously thickened crust at the bronson hill anticlinorium this explanation requires that between 6 and 8 km of normal fault motion has occurred on structures in western new hampshire not previously recognized to have accommodated this kind or magnitude of displacement this hinged differential uplift occurred from approximately 360 170 ma and is consistent with a time constant for rebound of approximately 80 m y

one dimensional thermal modelling of acadian metamorphism in southern vermont usa one dimensional thermal 1dt modelling of an acadian devonian tectonothermal regime in southern vermont usa used measured metamorphic pressures and temperatures and estimated metamorphic cooling ages based on published thermobarometric and geochronological studies to constrain thermal and tectonic input parameters the area modelled lies within the vermont sequence of the acadian orogen and includes i a western domain containing garnet grade pre silurian metasedimentary and metavolcanic rocks from the eastern flank of an acadian composite dome structure rayponda sadawga dome and ii an eastern domain containing similar but staurolite or kyanite grade rocks from the western flank of a second dome structure athens dome approximately 10 km farther east using reasonable input parameters based on regional geological petrological and geochronological constraints the thermal modelling produced plausible p t paths and temperature time t t and pressure time p t curves information extracted from p t t modelling includes values of maximum temperature and pressure on the p t paths pressure at maximum temperature predicted ar closure ages for hornblende muscovite and k feldspar and integrated exhumation and cooling rates for segments of the cooling history the results from thermal modelling are consistent with independently obtained pressure temperature and ar cooling age data on regional metamorphism in southern vermont modelling results provide some important bounding limits on the physical conditions during regional metamorphism and indicate that the pressure contemporaneous with the attainment of peak temperature was probably as much as 2 5 kbar lower than the actual maximum pressure experienced by rocks along various particle paths in addition differences in peak metamorphic grade garnet grade versus staurolite grade or kyanite grade and peak temperature for rocks initially loaded to similar crustal depths differences in calculated exhumation rates and differences in 40ar 39ar closure ages are likely to have been consequences of variations in the duration of isobaric heating or crustal residence periods and tectonic unroofing rates modelling results are consistent with a regional structural model that suggests west to east younging of specific acadian deformational events and therefore diachroneity of attainment of peak metamorphic conditions and subsequent 40ar 39ar closure during cooling modelling is consistent with the proposition that regional variations in timing and peak conditions of metamorphism are the result of the variable depths to which rocks were loaded by an eastward thickening thrust nappe pile rooted to the east new hampshire sequence as well as by diachronous structural processes within the lower plate rocks of the vermont sequence

archaean granulites of the limpopo belt zimbabwe one slow exhumation or two rapid events the peak of high temperature low pressure anticlockwise granulite facies metamorphism in the northernmost part of the northern marginal zone of the limpopo belt has been dated at 2591 4 ma using conventional u pb zircon geochronology on a syntectonic charnockite intrusion the thermal peak of 800 c at 0 5 gpa reflects a strong perturbation of the geotherm and was reached during compressional deformation and coincides with vast granite intrusion into the overlying craton the coincidence of the temperature t maximum and compression is thought to be a response to lithospheric mantle thinning that resulted in granite emplacement and a consequent change in upper crustal rheology after initial exhumation and cooling these high temperature low pressure rocks resided at a comparatively shallow depth 10 km for 620 ma field microstructural and geochronological investigation of a low temperature overprint establishes that reworking and final exhumation occurred at 1 97 ga along discrete greenschist facies thrusts the 40ar 39ar laser ablation of hornblende and biotite and pb pb step leaching of sphene are shown to be useful geochronometers in dating the low grade assemblages our results indicate that early proterozoic deformation lasted 10 to 20 ma however a number of ages intermediate between the events at 2 6 and 2 0 ga have been reported for the northern marginal zone these include pb pb garnet ar ar step heating amphibole and u pb zircon ages such ages suggest that these minerals were partially rejuvenated below their commonly believed closure temperature reinterpreting these intermediate ages as partial overprint or inheritance was possible in the northern marginal zone due both to the large time gap between the two tectonometamorphic events and the use of a multimethod multichronometer approach these observations call for great caution when extrapolating mineral ages into cooling histories especially so when the resulting cooling is slower than thermally and or mechanically possible and suggests that the geochronometry in other regions that underwent multiple tectono metamorphic events may need to be reassessed

a numerical study of circulation in a coastal reef lagoon system 1 a coupled wave circulation numerical model was used to simulate the distribution of wave energy as well as the circulation induced by wave breaking wind and tidal forcing within a coral reef system in kaneohe bay oahu hawaii modeled wave current and wave setup fields were compared with field measurements collected on the forereef reef flat and reef channels and in the lagoon over a 4 week period the predicted wave height transformation across the reef lagoon system was in good agreement with field observations using single parameter spatially uniform values to describe both wave breaking and frictional dissipation the spatial distribution of the resulting wave setup field drove a persistent wave driven flow across the reef flat that returned to the ocean through two deeper channels in the reef both the magnitude and direction of these currents were well described using a spatially uniform hydraulic roughness length scale notably the model lends support to field observations that setup within the coastally bounded lagoon was a substantial fraction of the maximum setup on the reef 60 80 which generated relatively weak cross reef wave driven flows 10 20 cm s 1 compared with reefs having mostly unbounded lagoons e g many atolls and barrier reefs numerical experiments conducted using lagrangian particle tracking revealed that residence times within kaneohe bay are extremely heterogeneous typically ranging from 1 month within its sheltered southern lagoon

atmospheric forcing intensifies the effects of regional ocean warming on reef scale temperature anomalies during a coral bleaching event 1 we investigate how local atmospheric conditions and hydrodynamic forcing contributed to local variations in water temperature within a fringing coral reef lagoon system during the peak of a marine heat wave in 2010 2011 that caused mass coral bleaching across western australia a three dimensional circulation model regional ocean modeling system roms with a built in air sea heat flux exchange module coupled ocean atmosphere experiment coare was coupled with a spectral wave model simulating waves nearshore swan to resolve the surface heat exchange and wave driven reef circulation in coral bay ningaloo reef using realistic oceanic and atmospheric forcing the model predictions were in good agreement with measured time series of water temperature at various locations in the coral reef system during the bleaching event through a series of sensitivity analyses we found that the difference in temperature between the reef and surrounding offshore waters dt was predominantly a function of both the daily mean net heat flux qnet and residence time whereas diurnal variations in reef water temperature were dependent on the diurnal fluctuation in the net heat flux we found that reef temperatures were substantially higher than offshore in the inner lagoon under normal weather conditions and over the entire reef domain under more extreme weather conditions 0 7 c 1 5 c although these temperature elevations were still less than that caused by the regional ocean warming 2 c 3 c the arrival of peak seasonal temperatures in the summer of 2010 2011 when net atmospheric heat fluxes were positive and abnormally high caused substantially higher thermal stresses than would have otherwise occurred if offshore temperatures had reached their normal seasonal maxima in autumn when net atmospheric heat fluxes were negative or cooling therefore the degree heating weeks calculated based on offshore temperature substantially underestimated the thermal stresses experienced by the reef in the period leading up to the observed bleaching

the kashiru pollen sequence burundi palaeoclimatic implications for the last 40 000 yr b p in tropical africa abstract a continuous pollen record from a central african highland site 3 28 s 29 34 e with 15 radio carbon dates spans at least the last 40 000 yr both modern and fossil pollen have been investigated a clear pattern of changes in vegetation and climate is suggested prior to 30 000 yr b p the occurrence of the montane conifer forest including the upper forest limit indicates climatic conditions colder and drier than now but more humid than in late glacial time between 30 000 and 15 000 yr b p grassland with afroalpine indicators expanded down to 2500 2000 m altitude as a result of dry and most probably cool climate the montane forest persisted in refuges although much reduced forest vegetation with the same floristic composition as today appeared after 13 250 200 yr b p suggesting more humid conditions the occurrence of a possible short term humid episode about 21 500 yr b p is correlated with some high lake level stages in east africa and with organic deposits in deep sea cores from the mediterranean and the atlantic ocean

microstructure metamorphism thermochronology and p t t deformation history of the port aux basques gneisses south west newfoundland canada the port aux basques gneisses comprise three lithostratigraphic units separated by major fault zones the grand bay complex the port aux basques complex and the harbor le cou group a similar regionally developed polyphase history of penetrative deformation characterizes each of these units thickening during d1 produced rare recumbent folds f1 and an axial planar schistosity s1 overprinted by d2 recumbent folds f2 and transposed during development of a locally penetrative differentiated crenulation cleavage s2 in western sectors of the area d2 was associated with nw directed reverse shearing the ne trending structural grain reflects d3 transpression partitioned into dextral transcurrent movement along major shear zones and development of upright to steeply inclined periclinal folds f3 and a variably penetrative schistosity s3 amphibolite facies metamorphism increases in grade from west to east across the area microstructures including porphyroblast matrix foliation relations and internal textural unconformities in garnet indicate episodic porphyroblast nucleation and growth which reflect a prograde traverse sequentially across univariant reactions during syntectonic metamorphism garnet kyanite and staurolite porphyroblasts are wrapped by the s2 foliation but each may contain trails of inclusions that define s1 commonly these trails preserve early stages of s2 crenulation cleavage development progressive and sequential reaction out of kyanite staurolite and muscovite in favour of sillimanite garnet biotite and k feldspar and the development of an increasing volume of anatectic migmatite in south eastern sectors of the area record syn to late d2 peak metamorphic conditions microstructural relationships and petrogenetic grid considerations indicate clockwise trajectories in p t space for units of the port aux basques gneisses peak metamorphic conditions are estimated to have been 620 650 c at 8kbar in the west and 700 750 c at 8 kbar in the east titanite from an upper amphibolite facies calc silicate gneiss yields u pb ages of c 420 ma interpreted to date cooling shortly after the thermal peak in these gneisses variable d3 strain was associated with some recrystallization of hornblende and micas 40ar 39ar hornblende plateau isotope correlation ages range from c 419 to c 393 ma from east to west across the area and are interpreted to record cooling through c 500 c coeval with or soon after d3 deformation the range in ages may record the effects of heterogeneous d3 deformation and differential uplift from south east to north west associated with displacement on major shear zones 40ar 39ar muscovite plateau ages cluster at c 390 ma and date cooling through c 375 c during regional exhumation cooling rates are moderate to fast and may indicate a component of tectonic exhumation the port aux basques gneisses are a product of silurian collisional tectonics the higher grade of metamorphism in comparison with adjacent areas of the canadian appalachians is interpreted to reflect greater thickening due to juxtaposition of the st lawrence promontory laurentian margin with the cabot promontory avalonian margin during closure of the iapetus ocean

variable variscan thermal rejuvenation in the st malo region cadomian orogen france evidence from 40ar 39ar mineral ages abstract the st malo region in north west france contains migmatites and anatectic granites derived by partial melting of metasedimentary protoliths during cadomian orogenesis at c 540 ma previously reported rb sr model ages for muscovite and biotite range from c 550 to c 300 ma and suggest variable resetting of mineral isotopic systems these rocks display microscopic evidence for variably intense cadomian intracrystalline plastic strain but record no obvious evidence of penetrative palaeozoic regional deformation 40ar 39ar mineral ages have been determined to evaluate better the extent timing and significance of palaeozoic overprinting eleven muscovite concentrates and one whole rock phyllite have been prepared from various units exposed in the st malo and adjacent mancellian regions in the mancellian region muscovite from two facies of the bonnemain granite complex record 40ar 39ar plateau ages of c 527 and 521 ma an internally discordant 40ar 39ar release spectrum characterizes muscovite from protomylonitic granite within the cadomian alexain deux evailles ize granite complex and probably records the effects of variscan displacement along the north armorican shear zone muscovite concentrates from anatectic granite and from cadomian mylonites along ductile shear zones within the north western sector of the st malo region exhibit internally discordant 40ar 39ar release spectra which suggest variable and partial late palaeozoic rejuvenation by contrast muscovite concentrates from samples of variably mylonitic brioverian metasedimentary rocks exposed within the south eastern sector of the st malo region display internally concordant apparent age spectra which define plateaux of 326 320 ma a whole rock phyllite sample from brioverian metasedimentary rocks exposed along the eastern boundary of the st malo region displays an internally discordant argon release pattern which is interpreted to reflect the effects of a partial late palaeozoic thermal overprint muscovite from the plelan granite part of the variscan plelan bobital granite complex yields a 40ar 39ar plateau age of c 307 ma the 40ar 39ar results indicate that cadomian rocks of the st malo region have undergone a widespread and variable palaeozoic carboniferous rejuvenation of intracrystalline argon systems which apparently did not affect the mancellian region this rejuvenation was not accompanied by penetrative regional deformation and was probably of a static thermal hydrothermal origin the heat source for rejuvenation was probably either the result of heating during variscan extension or advection from variscan granites which are argued to underlie the st malo region

the combined influence of hydrodynamic forcing and calcification on the spatial distribution of alkalinity in a coral reef system 1 we investigated the influence of hydrodynamic forcing waves tides alongshore currents and winds and net calcification by coral reef organisms on the spatial distribution of total alkalinity ta in a fringing reef system through a combination of field measurements and numerical modeling a field experiment was conducted over 10 days in coral bay ningaloo reef western australia during which we measured wave heights currents and tides as well as the spatial distribution of ta across the fore reef reef crest and lagoon we used observed changes in ta on the adjacent reef flat along with synoptic measurements of cross reef transport to estimate in situ rates of net calcification gcv using a control volume approach based on the gcv estimated we simulated light driven diurnal variations in benthic net calcification within a three dimensional ocean circulation model roms regional ocean modeling system by coupling roms with a spectral wave model simulating waves nearshore we were able to simulate currents within coral bay reef lagoon system that were in good agreement with the field observations and demonstrate that circulation with the system was wave dominated both the field measurements and numerical model output confirmed that both residence time r and ta varied primarily with offshore wave heights and location within the bay however variations in ta were also affected by the nonlinear interaction between rates of net calcification that varied as a function of diurnally changing light and water residence time that varied as a function of offshore wave heights

oxygen isotopes in tree rings of abies alba the climatic significance of interdecadal variations we determined the 18o variations in the latewood of tree rings from four silver firs abies alba mill for the period 1840 1997 at a mountain site in switzerland establishing the longest available tree ring record for 18o in central europe the isotope ratios were determined on whole wood with a rapid continuous flow pyrolysis technique thus avoiding cellulose extraction we found significant correlations with 18o tree ring records from the same region although these involved different materials cellulose extracted from whole rings rather than latewood and different species this indicates that physical factors are more important than biological influences as a determinant of 18o in tree rings the isotope tree ring chronology was highly correlated with the oxygen isotope variations in the june july precipitation for the period 1972 1992 r 0 72 and 18o in whole wood of tree rings is therefore well suited for the reconstruction of 18o in precipitation we found a slow quasi periodic variation of the 18o series with a periodicity of 24 years which is correlated to variations in the july temperature this could be caused by fluctuations in the large scale atmospheric circulation over europe and the north atlantic which may result in a change in source and flow path of atmospheric moisture affecting the isotope ratio of precipitation in switzerland although a significant correlation with summer temperature was found p 0 01 the low correlation coefficient r 0 31 indicates that the 18o variations cannot be explained by temperature variations alone however even when considering that the factors influencing 18o in precipitation are not yet fully understood our study shows the potential of tree rings to provide long records of 18o in precipitation for continental areas which will improve our understanding of the causes of natural perturbations of the climate system

supplemental material zircon and monazite geochronology in the palmer zone of transpression south central new england usa constraints on timing of deformation high grade metamorphism and lithospheric foundering during late paleozoic oblique collision in the northern appalachian orogen analytical methods for zircon u pb and monazite th pb sims geochronology zircon u pb la icp ms geochronology data tables and supporting previous work

metamorphic thermal and tectonic evolution of central new england mountain skitchewaug and big staurolite nappes reactivation of a new detailed tectonic model is presented for the acadian orogenic this fabric during thrusting is recorded in some rocks of the big belt of central new england vermont and new hampshire that staurolite nappe by rotated garnets that grew during near isothermal accounts for a wide range of petrological and structural observations loading only the sillimanite isograd crosses the fall mountain three belts are considered the eastern vermont merrimack and skitchewaug nappe boundary metamorphic breaks across the skitintervening bronson hill belts specific observations in eastern chewaug big staurolite nappe boundary at the base of the big vermont that are accounted for in the model include the following staurolite nappe and at the margin of the keene and alstead domes p t paths are clockwise with maximum pressures near the athens require post metamorphic thrusting when p t conditions were in chester and strafford domes of 8 11 kbar but with maximum the greenschist facies these observations can be explained by a pressures decreasing to 3 5 kbar at the boundary with the bronson relatively simple model involving in sequence thrusting from east to hill belt differential exhumation of the vermont domes relative to west commencing in central new hampshire at 400 410 ma the rocks in easternmost vermont is required by the recorded differences preservation of the low grade belt along the vermont new hampin maximum pressure 5 6 kbar 15 20 km and the present day shire border requires that crustal thickening in vermont was not geographical separation 7 10 km specific observations in new caused by emplacement of new hampshire nappes onto eastern hampshire that are explained include the following p t paths in vermont and that the nappes of western new hampshire had time the merrimack belt are counter clockwise with maximum pressures to cool before final juxtaposition against the low grade belt cooling of 4 5 kbar and are related to high regional heat flow and heat ages constrain this final juxtaposition to have occurred in the transfer by early acadian plutons p t paths in the bronson hill carboniferous suggesting that the acadian was a prolonged event belt are intimately associated with structural position an early spanning as much as 100 myr contact metamorphism is evidenced in the skitchewaug and fall mountain nappes near contacts with the early acadian bethlehem gneiss 400 410 ma peak metamorphic temperature rises upwards in the nappe sequence an inverted metamorphic sequence

dissolution and replacement creep a significant deformation mechanism in mid crustal rocks abstract zoning patterns and zoning truncations in metamorphic minerals in a granodioritic orthogneiss indicate that strain and s c fabrics in these rocks were produced by dissolution precipitation and replacement processes even at epidote amphibolite facies metamorphic conditions the metamorphic fabric is defined by alternating layers and folia dominated by quartz feldspars and biotite epidote zoning patterns in most metamorphic plagioclase orthoclase epidote and sphene are truncated at boundaries normal to the shortening direction suggesting dissolution interfaces of relict igneous orthoclase phenocrysts that face the shortening direction are embayed and replaced by biotite epidote and myrmekitic intergrowths of plagioclase and quartz metamorphic plagioclase grains are also replaced by epidote we interpret these microstructures to reflect strain enhanced dissolution the cores of many grains show asymmetric overgrowths with at least two generations of beards all oriented on the ends of grains that face the extension direction we interpret these textures to reflect precipitation of components dissolved by deformation enhanced dissolution while biotite and quartz probably deformed by dislocation creep the overall deformation was accommodated by dissolution perpendicular to the shortening direction and precipitation parallel to it these chemical processes must have been activated at lower stresses than the dislocation creep predicted from extrapolations of data from experiments in dry rocks thus wet crust is likely to be weaker than calculated from these experimental studies

assessing the drivers of spatial variation in thermal forcing across a nearshore reef system and implications for coral bleaching we examined the seasonal and spatial variability in the temperatures of nearshore reef waters over 19 months across coral bay at ningaloo reef western australia local deviations in the mean daily temperature of nearshore reef waters from offshore values dt were a linear function of the combined effect of net atmospheric heating qnet and offshore wave height and period hs ffiffiffiffiffi tp p whereas intra annual variation in local heat exchange was driven mainly by seasonal changes in shortwave radiation intra annual variation in local cooling was driven mostly by changes in relative humidity r2 5 0 60 and wind speed r2 5 0 31 that exhibited no apparent seasonality we demonstrate good agreement between nearshore reef temperatures modeled from offshore sea surface temperatures offshore wave forcing and local atmospheric heat fluxes with observed temperatures using a simple linear model r2 5 0 31 0 69 root mean square error 5 0 4 0 9uc using these modeled nearshore reef temperature records we show that thermal stresses across the reef reached between 16uc weeks and 22uc weeks in the summer of 2011 when a mass coral bleaching event was reported and between 12uc weeks and 13uc weeks in the following summer of 2012 when no mass bleaching was reported after compensating for differences between observed and modeled thermal stresses we found that maximum thermal stresses across the reef likely reached as high as 18 34uc weeks in the summer of 2011 the approach used here could thus improve our ability to predict spatial variation in thermal stress and bleaching across other wavedriven nearshore reef systems

two dimensional modelling of wave dynamics and wave forces on fringing coral reefs abstract two dimensional numerical modelling of swell wave dynamics on idealized fringing reefs is performed using swan covering a wide range of bathymetries climate forcing conditions and water depths over the reefs the results illustrate the impact of reef geometry and bathymetry coral species and sea level rise on key hydrodynamic parameters on the reef and on forces on corals the modelling demonstrates that one dimensional models underestimate the wave action on the reef flat wide short reefs and narrow long reefs have similar wave heights at the centre of the reef flat for a given reef length the wave height first decreases with increasing reef width then increases to a local maximum when reef width is approximately equal to the reef length and then decreases for further increases in width this pattern is a result of combined dissipation and refraction processes which combine to lead to different zones of cross reef wave transformation provided that a reef retains its hydrodynamic functions in breaking and refracting the waves sea level rise enhances the wave heights and wave orbital velocities on the reef flat if vertical coral growth does not keep pace with sea level rise loss of the hydrodynamic functions of the reef may occur on deeper reefs and result in a reduction of near bed velocities with sea level rise hydrodynamic forces on corals vary by coral species and slr changes the magnitude of the forces on different species in different ways which may lead to less favourable conditions for certain coral species for long period swell the intermediate size corals are drag dominated and behave similarly to branching corals whereas for short period swell their behavior is similar to that of the inertia dominated massive corals for intermediate corals different responses to slr may therefore be expected for different overall regional wave climates over time this process may contribute to changes in the structural complexity of reefs the influence of sea level rise on the forces on corals on the reef flat is different under swell and cyclonic wind conditions since wind influences wave period in the latter case

40ar 39ar dating of silurian and late devonian cleavages in lower greenschist facies rocks in the westminster terrane maryland usa 40 ar 39 ar dating of muscovite biotite and k feldspar combined with microstructural analysis of lower greenschist facies polymetamorphic phyllitic rocks and marbles were successfully used to decipher the thermal and tectonic histories of the westminster and adjacent terranes in western maryland the presence of unreset detrital muscovite in some samples demonstrates that temperatures in these rocks never exceeded the closure temperature for argon diffusion in muscovite 350 50 c minor biotite in some arkoses constrains the minimum metamorphic temperatures to 320 c these data show an early silurian ca 430 ma cleavage in the western part of the westminster terrane and a late devonian event ca 370 ma in the eastern westminster and adjacent potomac terranes these two cleavage domains are separated by the ne trending newly identified parrs ridge fault zone we propose that the sinistral transpressive collision of the carolina terrane with laurentia emplaced the western portion of the westminster terrane in the pennsylvania embayment along the martic fault where it was folded and cleaved at ca 430 ma but otherwise largely sheltered from later deformation the later late devonian dextral transpressive accretion of the outboard potomac terrane thrust rocks of the eastern westminster and potomac terranes to the west causing late devonian 360 370 ma s 2 cleavage in these rocks but only minimal discrete overprinting s 3 cleavages in rocks farther west final juxtaposition and thermal convergence of these terranes occurred along reactivated dextral strike slip faults in the alleghanian at ca 300 ma

presence of a long term lithospheric thermal anomaly evidence from apatite fission track analysis in northern new england abstract apatite fission track aft ages from 56 samples of paleozoic and mesozoic crystalline rocks in new hampshire northeastern vermont and western maine range from 70 to 140 ma and reflect widespread early to late cretaceous cooling the regional aft age distributions determined in this study suggest that reactivation of preexisting orogen parallel faults and the presence of a long lived thermal anomaly in the lithospheric mantle controlled the late unroofing history of this part of the northern appalachians a northeast trending zone of young dominantly late cretaceous aft ages 70 118 ma extends from southwestern new hampshire through the central white mountain region and continues into northern new hampshire northeastern vermont and western maine providing evidence for regional nw se extension and cooling at this time significantly older aft ages 125 140 ma in the region bounded by the bill little ammonoosuc and northey hill faults in northwestern new hampshire suggest a normal sense r

interpreting paleoclimate from l8o and 2h in plant cellulose comparison with evidence from fossil insects and relict permafrost in southwestern ontario the oxygen isotope content of terrestrial plant cellulose is related to that of the source waters by a two step process involving evapotranspirative leaf water enrichment and equilibrium isotopic exchange between leaf water and atmospheric carbon dioxide a combination of two models that describe these steps yields consistent agreement between measured and predicted climatic and isotopic data humidity is the dominant influence on variations in the cellulose 18o enrichment relative to the source water a good first order approximation of the average daytime relative humidity during the growth season at a site can be based on the linear correlation that exists between humidity and cellulose enrichment without explicit consideration of factors such as temperature 18o of atmospheric vapour and leaf boundary layer dynamics the value of the combined model for paleoclimatic reconstruction has been tested using fossil wood from a late glacial site at brampton ontario estimates of the past relative humidity

morphological characterisation of reef types in torres strait and an assessment of their carbonate production coral reefs represent major accumulations of calcium carbonate caco3 the particularly labyrinthine network of reefs in torres strait north of the great barrier reef gbr has been examined in order to estimate their gross caco3 productivity the approach involved a two step procedure first characterising and classifying the morphology of reefs based on a classification scheme widely employed on the gbr and then estimating gross caco3 productivity rates across the region using a regional census based approach this was undertaken by independently verifying published rates of coral reef community gross production for use in torres strait based on site specific ecological and morphological data a total of 606 reef platforms were mapped and classified using classification trees despite the complexity of the maze of reefs in torres strait there are broad morphological similarities with reefs in the gbr the spatial distribution and dimensions of reef types across both regions are underpinned by similar geological processes sea level history in the holocene and exposure to the same wind wave energetic regime resulting in comparable geomorphic zonation however the presence of strong tidal currents flowing through torres strait and the relatively shallow and narrow dimensions of the shelf exert a control on local morphology and spatial distribution of the reef platforms a total amount of 8 7million tonnes of caco3 per year at an average rate of 3 7kg caco3m 2yr 1 g were estimated for the studied area extrapolated production rates based on detailed and regional census based approaches for geomorphic zones across torres strait were comparable to those reported elsewhere particularly values for the gbr based on alkalinity reduction methods however differences in mapping methodologies and the impact of reduced calcification due to global trends in coral reef ecological decline and changing oceanic physical conditions warrant further research the novel method proposed in this study to characterise the geomorphology of reef types based on classification trees provides an objective and repeatable data driven approach that combined with regional census based approaches has the potential to be adapted and transferred to different coral reef regions depicting a more accurate picture of interactions between reef ecology and geomorphology

spectral wave dissipation over a barrier reef 1 a 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at kaneohe bay oahu hawaii wave heights and velocities were measured at several locations on the fore reef and the reef flat which were used to estimate rates of dissipation by wave breaking and bottom friction dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites this is attributed to the rough surface generated by the reef organisms which makes the reef highly efficient at dissipating energy by bottom friction results were compared to a spectral wave friction model which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site on the fore reef dissipation was due to the combined effect of frictional dissipation and wave breaking however in this region the magnitude of dissipation by bottom friction was comparable to wave breaking despite the existence of a well defined surf zone there under typical wave conditions the bulk of the total wave energy incident on kaneohe bay is dissipated by bottom friction not wave breaking as is often assumed for sandy beach sites and other coral reefs

intracontinental subduction and hinged unroofing along the salmon river suture zone west central idaho the salmon river suture zone in west central idaho juxtaposes volcanic arc rocks of the wallowa terrane directly against cratonic north america detailed metamorphic studies along a 10 km traverse perpendicular to the suture indicate that the arc and two crystalline fragments thrust upon it each record different pressure temperature p t histories from lowest to highest structural level the wallowa terrane shows only subgreenschist metamorphism the rapid river plate rrp records unroofing and cooling from 8 kbar and 550 c to 6 kbar and 475 500 c and the pollock mountain plate pmp shows evidence for polymetamorphism and records burial and heating paths to final equilibration conditions of 9 11 kbar and 600 625 c ar ar hornblende ages combined with the p t data suggest that currently exposed levels of the rrp and pmp were juxtaposed against one another at 15 20 km depth at or prior to 118 ma indicating that 10 20 km of uplift and hence also the onset of collision related metamorphism occurred before 118 ma correlation of the metamorphic and age data with geometric constraints from the initial sr 0 706 line and the dimensions of the rrp and pmp permit construction of large scale retrodeformable sections of the west side of the suture from late jurassic through late cretaceous time the abrupt nature of the sr 0 706 line implies that the arc continent boundary extends vertically through most of the crust which requires sharp downwarping of the arc lithosphere in order to account for the pmp metamorphic data narrow zoned overgrowths on pmp garnets record this burial event and require initially rapid 3 km m y uplift rates in order to be preserved we suggest that the onset of rapid uplift resulted from the separation of the negatively buoyant lithospheric root from the downwarped arc allowing buoyant rise of fragments of thickened crust detachment of the root is suggested to change the environment of crustal shortening from one in which footwalls of thrusts or shear zones sink to one in which hanging walls rise this mechanism represents an alternative to cessation of shortening or onset of tectonic denudation as an explanation for the transition from burial to uplift of high pressure metamorphic terrains subsequent uplift appears to have been slow and to have occurred in a hinged fashion such that mineral and whole rock ages decrease systematically towards the suture zone the consumption of lithosphere during 40 km of shortening between two crustal blocks implies that the salmon river suture is the trace of an intracontinental subduction zone burial and collision apparently began before about 130 ma and thus any precollision strike slip faulting or tectonic escape of intervening terranes was likely accomplished in jurassic and earliest cretaceous time

nearshore circulation in a tropical fringing reef system 1 the role of waves tide and wind on the circulation of a fringing reef system was investigated using data collected during a 6 week field experiment in a section of ningaloo reef off western australia the high correlation observed between current velocities and wave height throughout the system revealed the dominant role wave breaking plays in driving the overall reef lagoon circulation whereas the modulation of the currents at tidal frequencies suggested that the wave driven currents responded to tidal variations in the mean water level over the reef the influence of the various forcing mechanisms on the current field was investigated for both high and low frequency bands wave breaking was found to be the dominant forcing mechanism for the low frequency subtidal currents with the subtidal flow pattern consisting of a cross reef flow over the reef alongshore flow in the lagoon and water exiting back to the ocean through the main channel the tides controlled the high frequency current variability via two mechanisms one associated with the ebb flood cycle of the tides and the second associated with tidal modulations of the wave driven currents wind forcing and buoyancy effects were both found to be negligible in driving the circulation and flushing of the system during the observation period flushing time scale estimates varied from as low as 2 h to more than a day for the wide range of observed incident wave heights the results suggest that the circulation of ningaloo reef will be strongly influenced by even a small mean sea level rise

isotopic hydrology and paleohydrology of the madagi kenya natron tanzania basin during the late quaternary abstract three generations of stromatolites mark the recent extension of paleolakes in the magadi natron basin on the border between tanzania and kenya the last two generations are observed some 50 m above the modern lakes level they are respectively attributed to the beginning of the last interglacial and to the pleistocene holocene transition analysis of the morphology and texture of the stromatolites reveals an ecological zonation between 0 and 10 14 m below the shoreline their relatively high 18o and 13c values reflect a long residence time for the paleolake water which would have been favorable to the establishment of an isotopic equilibrium between atmospheric co2 and the dissolved inorganic carbon despite deep carbon inputs in relation to carbonititic volcanism a study of the 18o 2h and 13c contents in the hydrothermal springs perennial rivers and lacustrine brines indicates that during the last period of significant renewal of the deep saline groundwater precipitation was depleted in heavy isotopes when compared to modern precipitation this difference corresponds to a drop of about 600 1000 m in altitudinal hydroclimatic zones finally a comparison between the modern and paleohydrological data leads us to believe that the stabilization of the paleolake shorelines at the same altitude can be attributed to control by the water table level in the aquifer of the basaltic plateaus east of the basin

monazite geochronology in central new england evidence for a fundamental terrane boundary monazite crystallization ages have been measured in situ using sims and emp analysis of samples from the bronson hill anticlinorium in central new england in west central new hampshire each major tectonic unit nappe displays a distinctive p t path and metamorphic history that requires significant post metamorphic faulting to place them in their current juxtaposition and monazite ages were determined to constrain the timing of metamorphism and nappe assembly monazite ages from the low pressure high temperature fall mountain nappe range from c 455 to 355 ma and y zoning indicates that these ages comprise three to four distinct age domains similar to that found in the overlying chesham pond nappe the underlying skitchewaug nappe contains monazite ages that range from c 417 to 307 ma 40 ar 39 ar ages indicate rapid cooling of the chesham pond and fall mountain nappes after 350 ma which is believed to represent the time of emplacement of the high level chesham pond and fall mountain nappes onto rocks of the underlying skitchewaug nappe garnet zone rocks from western new hampshire contain monazite that display a range of ages c 430 340 ma both the metamorphic style and monazite ages suggest that the low grade belt in western new hampshire is continuous with the vermont sequence to the west rocks of the big staurolite nappe in western new hampshire contain monazite that crystallized between c 370 and 290 ma and the same unit along strike in northern new hampshire and central connecticut records ages of c 257 300 ma conspicuously absent from this nappe are the older age populations that are found in both the overlying nappes and underlying garnet zone rocks these monazite ages confirm that the metamorphism observed in the big staurolite nappe occurred significantly later than that in the units structurally above and below these data support the hypothesis that the big staurolite nappe represents a major tectonic boundary along which rocks of the new hampshire metamorphic series were juxtaposed against rocks of the vermont series during the alleghanian

a laser microprobe mass spectrometric study of ar kr k cl and br in an unconformity garnet associated fluid inclusions staurolite and micas from vermont u s a abstract garnet prophyroblasts in paragonite schist of the pinney hollow fm on the west limb of the athens mantled gneiss dome in vermont exhibit apparent angular unconformities cores of garnets contain inclusions of chloritoid rutile and ilmenite that define a foliation which is truncated at a high angle by the foliation in the rims electron microprobe traverses across a garnet indicate that the core rim boundary is the beginning of a steep compositional gradient in ca mg mn and fe that characterizes the rim following electron microprobe study a sample was irradiated in a nuclear pile and then studied by laser microprobe noble gas mass spectrometry ar isotopes were measured in garnet and in adjacent micas and staurolite and ar plus kr isotopes were measured in fluid inclusions fi in quartz in garnet and in fi trapped 40 ar 36 ar varies between 300 and 2000 with no simple correlations indicated between trapped ar isotope ratios and k cl and 84kr or petrographic features similar trapped ar occurs in the core and rim of garnet and in fi in quartz most fi indicate 40 ar e cl 10 3 and cl 36 ar 6 atom ratios br abundances in fi are usually too low to be measured indicating br cl 3 atom ratio 84 kr 36 ar in fi varies between 0 02 and 0 08 gases extracted from laser craters in white micas in schist outside the garnet indicate mean 40 ar 39 ar ages of 362 5 ma and in biotites 332 7 ma with k bearing inclusions in the garnet rim yielding ages close to 360 ma in the garnet core interpretation of 40 ar 39 ar ages is ambiguous due to the combination of low concentrations of in situ radiogenic 40ar and comparatively large amounts of trapped 40are poorly correlated with other parameters measured

numerical modeling of an estuary a comprehensive skill assessment i numerical simulations of the hudson river estuary using a terrain following three dimensional model regional ocean modeling system roms are compared with an extensive set of time series and spatially resolved measurements over a 43 day period with large variations in tidal forcing and river discharge the model is particularly effective at reproducing the observed temporal variations in both the salinity and current structure including tidal spring neap and river discharge induced variability large observed variations in stratification between neap and spring tides are captured qualitatively and quantitatively by the model the observed structure and variations of the longitudinal salinity gradient are also well reproduced the most notable discrepancy between the model and the data is in the vertical salinity structure while the surface to bottom salinity difference is well reproduced the stratification in the model tends to extend all the way to the water surface whereas the observations indicate a distinct pycnocline and a surface mixed layer because the southern boundary condition is located near the mouth the estuary the salinity within the domain is particularly sensitive to the specification of salinity at the boundary a boundary condition for the horizontal salinity gradient based on the local value of salinity is developed to incorporate physical processes beyond the open boundary not resolved by the model model results are sensitive to the specification of the bottom roughness length and vertical stability functions insofar as they influence the intensity of vertical mixing the results only varied slightly between different turbulence closure methods of k e k and k kl

the distribution style and intensity of alleghanian metamorphism in south central new england petrologic evidence from the pelham and willimantic domes abstract alleghanian metamorphism in south central new england is characterized by late pennsylvanian documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm kyanite mathrm muscovite mathrm staurolite end document grade heterogeneous reconstitution of migmatitic documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepack

fluid inclusion evidence for an anticlockwise metamorphic p t path in central massachusetts acadian late silurian to early devonian metamorphism in the central maine terrane cmt in central massachusetts is characterized by an early low p high t buchan type metamorphism followed by thickening at high temperature 650d c and then by cooling to 100 200d c below peak recorded temperatures before eventual unroofing mineralogical and textural evidence for this path includes sillimanite pseudomorphs after early andalusite abundant cordierite in pelitic lithologies replacement of low p cordierite bearing assemblages by high p garnet bearing assemblages and recrystallization of mylonites associated with late shear zones to form lower t and higher p assemblages peak conditions in the highest grade rocks were 685 780d c and 5 6 kbar the cooling path passed through 550d c at about 6 5 kbar the well constrained p t path documented from geological and mineralogical evidence for the cmt offers an unusual opportunity to examine characteristics of fluid inclusions that have experienced a long lived metamorphic event spanning a broad range of p t conditions fluid inclusion data from the cmt document a range of fluid compositions co2 rich mixed co2 n2 rich n2 rich and h2o rich and densities during metamorphism densities of co2 fluid inclusions range from 0 20 to 1 03 g cm 3 medium density co2 fluid inclusions are contained in quartz inclusions within garnets in partial melt leucosomes and in quartz grains within migmatites fluid inclusions within the quartz inclusions indicate trapping conditions of 650 700d c at pressures below 5 kbar other co2 fluid inclusions from matrix quartz yield isochores which pass through 700d c and 5 2 kbar the highest density inclusions associated with rocks containing the late high p assemblages have isochores which pass below the estimated p t conditions for recrystallization of the mylonite fluid inclusion evidence suggests an early low p heating event followed by thickening at high temperature and then by nearly isobaric cooling to about 500d c with later decompression this interpretation is also consistent with previously published petrological models and supports an anticlockwise p t path for the cmt of south central massachusetts

petrology of the regional sillimanite zone west central new hampshire u s a with implications for the development of inverted isograds abstracr sillimanite from the regional sillimanite zone in west central new hampshire is fibrolitic and overprints f2 folds nappe stage of earlier mica foliation regional sillimanite zone samples show no evidence for earlier staurolite parageneses despite the fact that staurolite is abundant at lower grade because sillimanite was produced directly from garnet chlorite by the prograde heating reaction garnet chlorite muscovite quartz sillimanite biotite h20 the pressure at which this reaction occurs is sensitive to the mno and cao contents of garnet and phase equilibrium arguments reveal that at the regional pressures of west central new hampshire 2 4 kbar staurolite parageneses are only possible in rocks with low mno cao the inferred p t path is counterclockwise with nearly isobaric initial heating at 2 kbar followed by loading t heating to a peak metamorphic temperature of 600 t 25 c at 4 kbar followed by nearly isobaric cooling garnets were compositionally homogenized near the metamorphic peak but subsequent cooling was rapid 100 c m y these data argue against the folded isotherm model of chamberlain 1986 instead the present distribution of metamorphic grades is interpreted to be the result of regional stacking of high grade thrust sheets on lower grade rocks followed by depression of high grade rocks to lower structural levels

implications of low temperature cooling history on a transect across the colorado plateau basin and range boundary west central arizona fission track ages of apatite and zircon from metamorphic plutonic and sedimentary rocks along a 80 km transect across the colorado plateau basin and range boundary in west central arizona show differences in the low temperature cooling histories between the provinces the transect extends from cypress mountain in the colorado plateau transition zone to the eastern buckskin mountains in the basin and range along the northeast margin of the basin and range province metamorphic rocks exposed in the footwall of a major detachment fault system yield zircon and apatite fission track ages of 16 10 ma these ages are similar to k ar fusion ages of biotite and age minima of k feldspar on 40ar 39ar age spectra and collectively indicate rapid cooling one k feldspar age spectrum has an age maximum of about 22 8 ma an age minimum of 11 8 ma and a spectrum whose shape is suggestive of reheating possibly in middle miocene time the heating event was probably related to hydrothermal activity during emplacement of cu and mn deposits in and above the detachment fault zone effects of this heating are only locally detected in rocks above the detachment fault in the poachie range fission track ages of apatite and zircon are 60 50 and 80 70 ma respectively the disparity between the apatite and zircon ages indicates that the rocks cooled slowly in late cretaceous and early tertiary time probably due to gradual uplift and erosion total uplift and denudation in the area of the poachie range since cretaceous time is 6 km or more to the northeast of the range fission track ages of apatite and zircon increase and diverge indicating that apparent uplift decreased in that direction the apatite ages from the poachie range are concordant with early tertiary hornblende ages determined in other studies of lower plate rocks near the southwest end of the transect the ages represent cooling of crystalline rocks after cretaceous regional metamorphism and magmatism near bagdad 20 km northeast of the poachie range 2 km or less of erosion has occurred since intrusion of high level plutons and dikes and caldera formation in late cretaceous time remnants of an erosion surface that developed in middle tertiary time are preserved in the transition zone volcanic and sedimentary rocks at least as old as early miocene were deposited on the erosion surface and filled valleys cut into it dissection of these deposits began about 8 ma we interpret these data combined with those from other studies to indicate that in cretaceous time southward thrusting and later extensive magmatism in the middle crust led to thickening and heating of the crust the cretaceous igneous rocks at bagdad are high level manifestations of this magmatism uplift and slow cooling occurred in late cretaceous and early tertiary time in late oligocene and early miocene time during northeast southwest extension middle crustal rocks moved southwest put from beneath the southwest margin of the transition zone tectonic denudation rapidly exposed the crust that had been brought up from a depth of 10 km or more and rapidly cooled in the eastern buckskin and harcuvar mountains middle miocene reheating occurred locally in the lower plate along the detachment and in nearby parts of the upper plate

paleohydrology of a canadian shield lake inferred from 18o in sediment cellulose oxygen and carbon isotope analyses on cellulose in the postglacial sediment of weslemkoon lake southern ontario show that the cellulose came mainly from aquatic plants or algae rather than from terrestrial sources if a wholly aquatic source is assumed the oxygen isotope content permits inferences of lake water 18o values over the past 10 000 years by accounting for the isotopic fractionation that occurs during cellulose synthesis chronological control is provided by pollen analysis and six 14c dates our reconstruction shows lake water 18o fluctuated from about 5 lower than present in the early postglacial to 5 or more above present values during the mid postglacial these broad secular shifts reflect a combination of fluctuating mean annual 18o of local precipitation evaporative isotopic enrichment of surface waters and snowmelt bypass effects the first two factors reflect the changing paleotemperature and paleohydrology respectively whereas the third factor is a more speculative interp

oxygen isotopes in cellulose from modern and quaternary intertropical peatbogs implications for palaeohydrology abstract cellulose 18o values were measured in modern peatbog plants in recent peats and in mountain peatbog cores from burundi in a study of the hydrologic control of the frsol 18o 16o ratio in intertropical peat cellulose modern plants and waters were collected under various altitudes 800 2500 m a s l with mean annual relative humidity ranging from 0 72 to 0 82 the water 18o values i vary between 4 and 2 5 the cellulose water enrichment is of 25 3 0 5 for aquatic plants of 24 6 emergent plant species the scatter in the cellulose 18o values in vary between 4 and 2 5 the cellulose water enrichment is cellulose 18o values of emergent plantss tend to decrease with increasing elevation 0 6 to 0 07 per 100 m and relative humidity 0 5 to 0 1 per mean emergent plant 18o values are approximated within 0 6 by available cellulose 18o models relating cellulose 18o to the relative humidity h and the environmental water 18o except in a large swampy system peats were subsampled in core ka 2 kashiru burundi 3 28 s 29 34 e 890 cm long 2240 m a s l altitude and for control in the topmost 50 cm of core ku 2 kuruyangwe 3 35 s 29 41 e 2020 m a s l altitude similar 18o vaues 26 to 28 5 were found in the topmost 50 cm of both cores they compare well with the mean 18o for modern emergent plants at kashiru ams 14c dating showed that core ka 2 spans the last 30 ka celluloses are mainly derived from emergent plants and yield 18o values ranging from 19 to 29 with the highest values between 2 1 and 0 ka and the lowest values 19 to 23 5 between 6 and 4 5 ka for the period between 6 and 4 5 ka the models yield a decrease in in of 4 to 2 5 relative to present for an h increase of 6 to 11 before 11 7 ka the models yield a in value close to the present value for an h increase of 6

morphological constraints to wave driven circulation in coastal reef lagoon systems a numerical study 1 the response of the wave driven circulation within coastally bounded reef lagoon systems to varying lagoon and channel morphology was investigated using a two dimensional coupled wave circulation numerical model numerical experiments were conducted using a series of coastal reefs that incorporated a wide range of different lagoon depths and channel widths with the morphology of both the reef forereef and reef flat and incident wave forcing held constant the wave driven circulation was found to increase substantially as dimensionless reef morphology parameters characterizing the relative lagoon depth and channel width were each independently increased analysis of the wave setup fields revealed that this increased flow was due to an enhancement of the cross reef water level gradient resulting from a sharp reduction in the lagoon setup as the frictional resistance on the lagoon channel return flow was diminished this follows similar trends observed in existing field and laboratory studies of wave driven reef flows analysis of flushing time scales computed for each reef lagoon geometry predicted the existence of optimal dimensionless lagoon depths and channel widths for a reef system to establish maximal coastal flushing overall the circulation and flushing of coastal reef lagoon systems was found to be largely controlled by the particular morphology of the lagoon and channel region rather than solely by the morphology of the forereef and reef flat that has been the primary focus of analytical models developed to predict wave setup and circulation on reefs

late cretaceous reactivation of the norumbega fault zone maine evidence from apatite fission track ages apatite fission track ages from opposite sides of the norumbega fault zone in southern maine reveal a significant early cretaceous time temperature discontinuity across the structure ages west of the fault zone range from 113 to 89 ma while those to the east are significantly older ranging from 159 to 140 ma modeling of track length distributions reveals that at 120 ma an 55 c difference in temperature existed between opposite sides of the fault zone currently exposed at the surface this discontinuity is best explained by an episode of significant to 2 km of net vertical separation east side down vertical movement along the norumbega fault zone in late cretaceous time the modeling suggests contemporaneous cooling and that final movement along the fault zone occurred ca 80 ma these results when combined with earlier structural and thermochronological studies suggest that faults mapped within the norumbega fault zone were intermittently active from middle devonian to late cretaceous time and that the structure is a fundamental zone of crustal weakness the prolonged period of activity likely reflects stresses associated with late paleozoic dextral transgression early mesozoic rifting associated with the initial opening of the north atlantic ocean basin and processes associated with the late mesozoic uplift and exhumation of the northern appalachian orogen

obtaining equilibrium oxygen isotope fractionations from rocks theory and examples a generalized approach for retrieving equilibrium isotope fractionations from natural rocks is proposed in which models of prograde reaction histories and retrograde diffusional exchange are used to identify coexisting minerals with similar isotope closure temperatures examples using literature data and new analyses from 32 natural amphibolite facies schists demonstrate both the feasibility and limitations of obtaining equilibrium oxygen isotope fractionations from minerals in natural rocks by screening samples according to the theoretical models natural data are shown to have highly consistent mineral fractionations 2 reproducibilities of 0 16 to 0 54 that within uncertainty reproduce experimental determinations among the minerals quartz biotite muscovite and calcic amphibole this correspondence indicates that the proposed theoretically based selection criteria improve the likelihood of measuring equilibrium fractionations the new data further corroborate the expected progressive enrichment of 18o in the orthosilicates with increasing al si relative to fe mg ky grt 1 05 st grt 0 6 and st cld 0 3 at 525 575 c in contrast typical samples that fail to satisfy screening criteria exhibit fractionations involving quartz biotite and amphibole that are strongly disequilibrium because of exchange during cooling theoretical screening of samples prior to isotope analysis allows robust independent assessment of theoretical and experimental determinations of equilibrium isotope fractionations

partitioning of deformation along an orogen and its effects on porphyroblast growth during orogenesis an identical succession of foliation inflection intersection axis trends in porphyroblasts fias is present in three separate areas affected by acadian deformation and metamorphism along 130 kms of the appalachians from east central vermont to north central massachusetts the fias trend successively nw se sw ne w e nnw sse and ssw nne and appear to have formed during the same succession of deformations which have been dated in se vermont as follows not yet dated pre 425 ma 425 to 404 ma 404 to 385 ma and 385 to 360 ma respectively the two areas that are furthest apart in east central vermont and north central massachusetts have strikingly similar total distributions of fias in garnet porphyroblasts that show a somewhat inverse relationship to those observed in the chester athens dome area of se vermont that separates them that is the number of samples containing the first formed fia set is greatest for the two regions lying furthest apart and decreases in younger sets whereas the number of samples containing the first fia set is the least in the central region and increases for more recently developed sets partitioning of deformation into zones of progressive shearing and shortening has been demonstrated to control the sites of development of differentiated crenulation cleavage versus porphyroblast growth and sites of porphyroblast growth on one limb of a regional fold versus the other we argue that partitioning of the deformation around competent feldspathic gneiss bodies at an orogen scale produced the variation in the number of samples containing the various fia sets between the central and outer areas described above porphyroblasts most commonly grew during sw ne directed shortening to the north and south of the chester athens dome region of the appalachians but only rarely grew in the latter region this suggests that deformation at this time partitioned around an outlier of competent basement feldspathic gneiss that underlies the chester athens dome region and this protected the rocks above and in the strain shadow to the nw and se from the effects of the great bulk of the deformation that occurred over the period of time during which nw se trending fias formed we attribute the increase in the number of samples containing progressively younger fias in the chester athens dome area during subsequent periods of nw se n s wsw ene and wnw ese directed shortening to the rise in temperature and pressure recorded in the rocks above the chester athens dome with peak conditions occurring during the development of the nnw sse oriented fia set between 404 and 385 ma as the temperature and pressure increased the gneiss below would have become less competent allowing the deformation associated with the succession of fia sets to partition more pervasively through the dome core this provided more sites for porphyroblast nucleation and growth and hence the number of samples recording these fia sets increased the concomitant decrease in the number of samples in which porphyroblasts grew in the rock within the areas to the north and south with successive fias possibly resulted from a progressive increase in competency of these rocks as the number of porphyroblasts increased

wave breaking hydrodynamics within coral reef systems and the effect of changing relative sea level this paper considers the hydrodynamics of wave driven flow across a coral reef and the resultant flushing of its lagoon current depth coefficients are introduced that describe the fractional change of across reef and lagoonal current with change in the relative local sea level i e the depth of water over the reef flat the coefficients are derived from an analytical hydrodynamic model and compared with data from two reefs the first is ningaloo reef in northwest australia which is a typical barrier reef with a narrow coastal lagoon and the second is kaneohe bay in oahu hawaii where the reef is both unusually deep and wide the current depth coefficients are shown to be sensitive to the form of the frictional law on the reef flat and can be deduced from measurements of the astronomical tidal currents in the lagoon both quadratic and linear friction laws are considered for the reef flat and good agreement obtained with a linear law based on the high frequency motion due to surface gravity waves

metamorphic p t paths from calcic pelitic schists from the strafford dome vermont usa metamorphism of the gile mountain formation and waits river formation in the strafford dome and townshend brownington syncline in east central vermont records two nappe style events d1 and d2 followed by doming d1 formed a muscovite biotite ilmenite schistosity subparallel to compositional layering so and was followed by heating to garnet grade the temperature and pressure at the end of d1 are estimated to be c 450d c and 6 8 kbar d2 variably crenulated and folded s1 during a nearly isothermal pressure increase of 1 2 kbar calculated from compositions of garnet which have inclusions trails with progressive crenulation and rotation of the s1 fabric similar p t paths are computed for most of the area suggesting that the later schistosity developed during emplacement of a regional nappe 3 6 km thick there is a general lack of d3 dome stage microstructures near the strafford willoughby arch staurolite and kyanite overgrew s2 in pelites and plagioclase with increasing xan overgrew s2 in calcic pelites reflecting post d2 heating to a maximum of 550 600d c metamorphic pressures at the end of d2 are fairly constant on the west side of the dome indicating minor dome stage uplift in contrast pressures at the thermal peak of metamorphism decrease by more than 4 kbar east of the dome the observed pattern of isotherms and isobars is mainly the result of post metamorphic differential uplift and unroofing finally a minor retrograde metamorphism produced the assemblage albite epidote k feldspar muscovite chlorite with grade increasing east toward the connecticut river

mass transfer limitation of nutrient uptake by a wave dominated reef flat community maximum rates of phosphate nitrate and ammonium uptake by a reef flat community were estimated from rates of frictional dissipation that were calculated from the attenuation of waves propagating over the kaneohe bay barrier reef flat time averaged flow speeds across the entire study area ranged from 0 08 to 0 22 m s 21 observed decreases in wave energy fluxes and near bottom orbital velocities gave a mean estimate for the bottom friction coefficient cf of 0 22 6 0 03 friction coefficients were used to estimate nutrient mass transfer coefficients of 5 9md 21 for phosphate and 9 16 m d 21 for ammonium and nitrate wave heights offshore of kaneohe bay were also used to estimate an annual phosphate mass transfer coefficient of 8 6 2md that was determined from measured changes in phosphate concentrations across the reef flat we conclude that rates of phosphate uptake by the kaneohe bay barrier reef flat community are occurring near the limits of mass transfer net primary production is a major pathway by which mass and energy flow into coral reef ecosystems the uptake of dissolved nutrients is often the rate limiting step for net pri mary production in marine ecosystems thus a knowledge of the kinetics of nutrient uptake by coral reef communities is necessary for assessing how nutrient loading rates change in response to natural or anthropogenic increases in nutrient concentrations bilger and atkinson 1992 proposed that nutrient uptake by shallow reef communities was limited by mass transfer the physical transfer of nutrients across con centration boundary layers covering the surfaces of reef au totrophs these authors used mass transfer correlations for rough surfaces taken from the engineering literature to cor relate maximum rates of nutrient uptake with the frictional characteristics of experimental reef communities subse quent studies demonstrated the ability of such mass transfer correlations to predict nutrient uptake kinetics for experi mental reef communities within closed recirculating flumes atkinson and bilger 1992 bilger and atkinson 1995 thomas and atkinson 1997 and a large experimental me socosm atkinson et al 2001 the results of these studies made it clear that shallow water reef communities are ca pable of taking up nutrients from the water column at rates that are limited by mass transfer however it had not yet been demonstrated whether in situ rates of nutrient uptake

probing the depths of oliverian magmas implications for paleozoic tectonics in the northeastern united states oliverian magma series gneisses 442 454 ma in the cores of domes in southwestern new hampshire have an igneous mineralogy that crystallized at pressures p of 9 11 kbar and temperatures t of 650 775 c whereas the cover ammonoosuc volcanics has the same formation age 453 2 ma yet is clearly extrusive a significant crustal section 30 km thick must have originally separated the two units a recognition that demands tectonic reinterpretation of this classic orogen acadian age ca 400 ma metamorphism at p 4 6 kbar t 625 c is well documented in the cover but the absence of expected diffusional reequilibration in oliverian garnets indicates that they never exceeded 550 c after formation juxtaposition of the oliverian magma series gneisses and their cover must have occurred after the cover had cooled below 550 c and was likely via either neo acadian or alleghanian thrusting

combining compositional zoning and foliation intersection axes fias in garnet to quantitatively determine early p t t paths in multiply deformed and metamorphosed schists north central massachusetts usa quantitative compositional and microstructural analysis of garnet porphyroblasts in kyanite staurolite garnet grade rocks from the northeastern flank of the pelham dome north central massachusetts distinguishes the effects of acadian deformation and metamorphism from extensive overprinting alleghanian shearing the p t conditions and the metamorphic path during the acadian were determined using samples preserving well defined stages in a lengthy tectonic history revealed by a succession of five foliation intersection axis trends preserved within porphyroblasts fias this acadian succession extends at least 120 km to the north into rocks where no evidence has been found of an alleghanian overprint for each sample where garnet first nucleated during one of these stages in the tectonic history the pt of core growth was determined by plotting the intersection of the mn fe and ca isopleths calculated for the core composition on a p t pseudosection for that sample using thermocalc combining the pt data from all these samples indicates that the temperature and pressure increased throughout acadian orogenesis causing episodic garnet growth during the alleghanian locally intense shearing especially against the margin of the pelham dome formed the dominant schistosity which truncated all foliations defined by inclusion trails in porphyroblasts and obliterated all remains of acadian deformation and metamorphism in the rock matrix shearing was accompanied by near complete homogenization of the compositional zoning in garnet porphyroblasts and an associated apparent increase in the temperature of the matrix to 700 c in those rocks lying directly adjacent to the pelham dome and resulted from the rocks of the northfield syncline being thrust a large distance southwards over the gneisses in the dome

regional scale mid jurassic to late cretaceous unroofing from the adirondack mountains through central new england based on apatite fission track and u th he thermochronology abstract apatite fission track aft ages of 178 to 70 ma for 108 samples from the adirondack mountains and eastern new york state vermont western massachusetts and connecticut and western new hampshire indicate that widespread unroofing occurred throughout the region during the middle jurassic to late cretaceous additionally u th he ages of 167 to 85 ma were determined on nine of those samples and support cooling rates of 1 8 2 2 c m yr from 100 to 65 c during the middle jurassic to late cretaceous assuming a geothermal gradient of 25 c km unroofing rates for the region were estimated to be on average 0 07 0 08 km m yr the aft age discontinuities between the high peaks region and the fault dissected southeastern adirondack mountains and along the ammonoosuc fault in the connecticut river valley between vermont and new hampshire suggest differential unroofing that may have been accommodated by fault reactivation syn post late cretaceous time after the youngest aft ages 82 and 70 ma resp

the ryoke plutonometamorphic belt crustal section of the cretaceous eurasian continental margin abstract the ryoke belt comprising low pressure regional metamorphic rocks and low level granitoids expresses a deep in the crust of the cretaceous eurasian continental margin before the opening of japan sea the petrological p t estimation of the metamorphic rocks indicates the condition of upper to middle crust level the zonally arranged areal distribution of the san yo shallow facies to ryoke deep facies granitic provinces from back arc side to fore arc side is concordant with the occurrence of the associated low grade to high grade regional metamorphic rocks they are regarded as an upper to middle crustal section of the cretaceous eurasian continental margin these metamorphic rocks are derived mainly from the jurassic accretionary complex in the migmatitic high grade part the metasedimentary rocks were just being transformed into continental crust isotopic ages of these metamorphic and granitic rocks show an along arc variation of the systematic eastward younging from 100 ma to 70 ma for 800 km it cannot be interpreted with the steady state subduction model and indicates that the orogeny was caused by an episodic event presumably the subduction of kula pacific ridge beneath the eurasian continent during cretaceous the present juxtaposition of the ryoke and the sanbagawa paired metamorphic belts inevitably needs a secondary displacement from their birthplace two possibilities should be examined along arc transcurrent movement or across arc overthrusting

characterizing carbon isotopic variability in sphagnum to understand more fully the nature of isotopic fractionation in mosses and to explore the potential of stable isotope analyses of selected peat constituents for palaeoenvironmental research we present results from a study of inter and intra plant 13c variability in sphagnum spp subdivisions of stem pendant and horizontal branch elements of modern sphagnum capillifolium plants revealed consistent and statistically significant differences in their isotopic composition sequential downstem analysis of a further cohort of four modern sphagnum capillifolium plants also reveals evidence of common forcing on the isotopic composition of sequentially formed stem and branch increments this relationship was tested further by analysis of a series of branch and stem samples manually recovered from sphagnum fuscum preserved within a late holocene ad 2003 1970 peat monolith from a european mire the high degree of isotopic coherence observed between plants supports the analysis of sphagnum in palaeoecological

episodic circulation and exchange in a wave driven coral reef and lagoon system we examined the role of wave driven circulation relative to wind and buoyancy forcing in a coral reef lagoon system circulation measurements in paopao bay moorea french polynesia during austral summer show the importance of waves in driving flows over the reef crest through the lagoon and out the reef pass tides were comparatively weak due to proximity to amphidromic points and exhibited an unusual spring neap cycle where the major lunar tide modulated the major solar tide and the overall tidal phase stayed approximately constant wind had only a secondary effect compared to surface waves a simple fluid mass balance indicated rapid flushing of the shallow back reef and export through the reef pass and a reef capture zone width of 2 3 km the reef pass circulation dynamics exhibited two layer baroclinic exchange flow when waves were small which was suppressed during large wave events the unusually weak tidal forcing provided an opportunity to more closely investigate wave driven circulation dynamics as expected theoretically there was a wave driven setup of the free surface across the shallow lagoon which drove a highly frictional flow evident by a large drag coefficient cp 0 1 diverging from extant theory the observed setup varied strongly with significant wave height and period overall the circulation and exchange between this coral reef system and the adjacent open ocean were largely determined by episodic remote forcing events and differed significantly from periodic tidal exchange mechanisms

contrasting styles of taconian eastern acadian and western acadian metamorphism central and western new england the two major early to middle palaeozoic tectonic metamorphic events in the northern appalachians were the taconian middle to late ordovician in central to western areas and the acadian late silurian to early middle devonian in eastern to west central areas this paper presents a model for the acadian orogenic event which separates the acadian metamorphic realm into eastern and western belts based on distinctively different styles we propose that the acadian metamorphism in the east was the delayed consequence of taconian back arc lithospheric modification east of the taconian island arc thick accumulations of late ordovician and silurian sediments coupled with plutons rising along a magmatic arc produced crustal thermal conditions appropriate for anomalously high t low p metamorphism accompanied by major crustal anatexis in this zone upward melt migration was coupled with subsequent e w crustal shortening possibly due to outboard collision with the avalon terrane to produce mechanical conditions that favoured formation of fold and thrust nappes and resultant tectonic thickening to the west and probably to the east as well the basis for the distinction between the eastern and western acadian events lies in the contrasting styles of metamorphism accompanying each evidence for contrasting metamorphic styles consists of 1 estimated metamorphic field gradients mfgs based on thermobarometric studies and 2 petrological evidence for contrasting p t trajectories west of the acadian metamorphic front the taconian zone has an mfg in which peak temperatures of 400 600 c were reached at pressures of about 4 6 kbar with both p and t increasing to the east near its western edge the western acadian metamorphic overprint has a similar mfg to the taconian and is mainly discriminated by 40ar 39ar dating and microtextural evidence east of this narrow zone the western acadian overprint is characterized by progressively higher temperatures 600 725 c and pressures 6 5 10 kbar or more to the east yielding an overall mfg that lies along or slightly above the kyanite sillimanite boundary on a p t diagram there is little or no plutonism accompanying western acadian metamorphism in contrast thermobarometry in the eastern acadian east of the bronson hill belt yields high t intermediate p conditions for the highest grade rocks known in new england t 650 750 c p 4 5 6 5 kbar for granulite facies assemblages which apparently formed along an anticlockwise p t path the bronson hill belt lies geographically between the eastern and western acadian zones and shows transitional petrological behaviour anomalously high temperatures at intermediate pressures but a clockwise path with decompression cooling radiometric dating indicates peak taconian conditions may have been achieved as early as 475 ma in the taconian hinterland and as late as 445 ma in the taconian foreland including the taconic allochthons eastern acadian magmatism may have started as early as 425 ma and most nappe stage deformation and metamorphism in the eastern acadian zone appears to have ended by about 410 ma tectonic thickening in the western acadian including the western counterparts of the nappe stage deformation documented in the eastern acadian must pre date attainment of peak metamorphic conditions dated at 395 385 ma dome stage deformation clearly post dates peak metamorphism and deforms metamorphic isograds the end of western acadian deformation is well constrained by 370 375 ma radiometric ages of late pegmatites and granitoids which cross cut all structures

p t t paths and differential alleghanian loading and uplift of the bronson hill terrane south central new england late paleozoic u pb ages of sphene and 4 0 ar 3 9 ar cooling ages of amphibole and muscovite from rocks of the bronson hill terrane in connecticut and central massachusetts reflect a late paleozoic alleghanian overprinton acadian metamorphic rocks prograde alleghanian sphenes crystallized during the late pennsylvanian and eliminate the possibility that amphibole ages reflect delayed permian cooling from devonian acadian metamorphism fourteen new amphibole ages from connecticut form a north to south trend of decreasing age from 294 to 245 ma while in massachusetts four new amphibole ages together with three others from the literature produce a random carboniferous pattern seven new muscovite ages support existing data indicating uniform cooling throughout the bronson hill terrane through 350 c in the early triassic the rate of permian cooling defined by amphibole muscovite pairs increases from 4 c my in northern connecticut to 50 c my near long island sound hinged loading and hinged but delayed exhumation in the southern part of the bronson hill terrane with the hinge in central connecticut explain these ages and cooling rates as well as a southerly increasing metamorphic field gradient one dimensional thermal modeling indicates that loading of bronson hill rocks must have begun by the late mississippian the time of peak alleghanian metamorphic temperature decreases southward from early permian in northern connecticut to late permian to the south these results demonstrate that the metamorphic effects of the alleghanian orogeny are not restricted to the avalon terrane of southeastern new england on the contrary the alleghanian orogeny reset 4 0 ar 3 9 ar mineral ages recrystallized minerals partially melted felsic rocks and transposed fabrics at least as far west as the bronson hill terrane in south central new england

seasonal circulation and temperature variability near the north west cape of australia 1 the circulation and temperature variability on the inner shelf near the north west cape of australia off ningaloo reef was investigated using field data obtained from two moorings deployed from 2004 to 2009 the results revealed that alongshore currents on the inner shelf were on average only weakly influenced by the offshore poleward southward leeuwin current flow i e monthly averaged alongshore current velocities were 0 1 m s 1 or less the presence of a consistent summer time wind driven equatorward northward counter flow on the inner shelf referred to in the literature as the ningaloo current was not observed instead the shelf waters were strongly influenced year round by episodic subtidal current fluctuations time scale 1 2 weeks that were driven by local wind forcing analysis of the current profiles showed that periods of strong equatorward winds were able to overcome the dominant poleward pressure gradient in the region leading to upwelling on the inner shelf contrary to prior belief these events were not limited to summer periods the forcing provided by these periodic wind events and the associated alongshore flows can explain much of the observed temperature variability with timescales 1 month that influences ningaloo reef

consistent slow exhumation in a late cenozoic glaciated landscape the presidential and carter ranges of the white mountains in new hampshire usa abstract to investigate the ability of the onset of quaternary glaciations to drive an acceleration in erosion rates we compare short timescale 103 104 yr erosion rates using the in situ terrestrial cosmogenic nuclide tcn 10be to longer time scale exhumation rates 106 107 yr using the apatite u th he method in the presidential and carter ranges of the white mountains in new hampshire usa our results are generally consistent with but refine previous studies using similar techniques resulting u th he ages and thermal modeling from mt washington in the presidential range n 4 91 7 to 117 3 ma suggest that exhumation rates from the late cretaceous to the present were slow

deuterium excess in an east antarctic ice core suggests higher relative humidity at the oceanic surface during the last glacial maximum a continuous deuterium excess profile d d 8 18o was obtained from the dome c ice core spanning 32 000 yr it exhibits significant variations over this period in particular d was 4 5 lower around 18 000 yr bp than over the past 7 500 yr interpreted as reflecting higher relative humidity estimated 90 over the oceanic areas providing moisture for antarctic precipitation

observations of spatial flow patterns at the coral colony scale on a shallow reef flat 1 although small scale spatial flow variability can affect both larger scale circulation patterns and biological processes on coral reefs there are few direct measurements of spatial flow patterns across horizontal scales 1 had similar spatial patterns to wakes while higher frequency variations 0 05 0 1 hz kc 1 had no observable spatial structure on the reef flat both drag and inertial forces exerted by coral colonies could have significant effects on flow but within different frequency ranges drag dominates for low frequency flow variations and inertial forces dominate for higher frequency variations including the wave band our scaling analyses suggest that spatial flow patterns at colony and patch scales could have important implications for both physical and biological processes at larger reef scales through their effects on forces exerted on the flow turbulent mixing and dispersion

assessing the role of orogen parallel faulting in post orogenic exhumation low temperature thermochronology across the norumbega fault system maine as a part of a regional effort to determine the extent of low temperature thermochronological discontinuities across major orogen parallel faults in northern new england 41 apatite fission track

oxygen isotope geochemistry of the amphiboles isotope effects of cation substitutions in minerals abstract the occurrence of coexisting amphiboles in rocks and the likelihood of concurrent isotope closure allows equilibrium oxygen isotope fractionations among the amphiboles to be recovered from natural samples oxygen isotope analyses of mineral separates using laser fluorination show that coexisting amphiboles increasingly partition 18o in the order hornblende gedrite 0 9 previously published data for hornblende actinolite glaucophane and garnet show that act hbl 0 2 gln grt 1 and hbl grt 0 thus glaucophane strongly partitions 18o relative to the calcic amphiboles the fractionation between two amphiboles of arbitrary composition can be predicted from the known fractionations for mica endmembers pyroxene endmembers and exchange components such as caal nasi 1 naal camg 1 camg 1 mgfe 1 femn 1 kna 1 kal si 1 and fe3 al 1 applications of the exchange component method reproduce measured amphibole fractionations to within 0 1 to 0 2 whereas other predictive methods cause misfit for typical metamorphic hornblende of 0 5 at 575 c although the isotope effects of cation exchanges may be small at high t they magnify dramatically for minerals formed in surficial diagenetic and low t metamorphic environments different composition clays are predicted to have equilibrium 18o differences of 2 9 if the isotope fractionation can be determined for one mineral endmember then calibrated exchanges allow accurate prediction of the isotope fractionations for intermediate compositions of most ortho ring chain and sheet silicates

exhumation and tilting of the western metamorphic belt of the coast orogen in southern southeastern alaska the uplift history of the western metamorphic belt in southern southeastern alaska can be traced using emplacement depths and cooling ages of mid cretaceous plutons which intruded the metamorphic belt during the period 101 ma to 89 ma during the period 101 ma to 94 ma the rocks of the metamorphic belt now at the surface were buried to a depth of approximately 30 km pressure data indicate that by 89 ma the western portion of the metamorphic belt was at a shallower crustal level 23 km within the study area while the eastern side remained at a depth of approximately 30 km cooling curves constructed from minerals in mid cretaceous plutonic rocks indicate that the western side of the metamorphic belt cooled earlier than the eastern side an observation consistent with the inferred uplift history southwestward transport of metamorphic belt rocks within the hanging walls of thrust and high angle faults may have provided one mechanism for uplift during mid to late cretaceous time the eastern portion of the western metamorphic belt cooled rapidly at 55 ma probably in response to a period of rapid uplift the coast shear zone an early tertiary high angle fault with west side up displacement bounds the east side of the metamorphic belt we suggest tertiary uplift occurred by tilting of the metamorphic belt due to movement along this fault

geochronology at the namew lake ni cu orebody flin flon area manitoba canada thermal history of a metamorphic terrane intermediate composition orthogneisses of the southward extension of the flin flon greenstone belt surround the ultramafic host rock of the namew lake ni cu deposit in northern manitoba the gneiss

quantitative estimates of full glacial temperatures in equatorial africa from palynological data this paper presents a new reconstruction of the mean annual temperature obtained from a high altitude pollen sequence in equatorial africa 3 28 s 29 34 e 2240 m it has been achieved with an extended modern african reference data set by adding spectra from 228 new sites and using another selection for pollen taxa the purpose of this paper is to test how the obtained temperature value depends upon the availability of modern analogues the results are in good agreement with those previously published reinforcing the validity of the method the mean standard error is reduced by 0 3 c the mean temperature for the holocene appears 1 4 c warmer than the present and the last glacial maximum 25 18 kyrs bp cooling is better specified at 3 1 9 c a conservative value more consistent with reconstructed sea surface temperature in the equatorial ocean

influences of reaction history and chemical diffusion on p t calculations for staurolite schists from the littleton formation northwestern new hampshire geothermometry from staurolite grade pelitic assemblages may fail to reflect peak temperatures of metamorphism because of 1 prograde gamet consuming reactions and 2 diffusional reequilibration during cooling in response to retrograde reactions gamet dissolution during staurolite formation leads to sharp compositional gradients within a few micrometers of garnet rims these gradients may then be modified by diffusion on cooling and lead to anomalous temperature estimates calculated from thermo barometers involving garnet numerical simulations of mineral growth and diffusion were used to examine these effects for a prograde metamorphic sequence from the salmon hole brook syncline northwestern new hampshire in higher grade assemblages mineral textures indicate that staurolite grew by the consumption of gamet and gamet biotite temperature estimates fall in the range 515 t 30 c interbedded layers containing garnet and biotite but not staurolite yield temperature estimates of 565 t 25 c in the eastern portion of the syncline rocks containing kyanite staurolite garnet biotite assemblages indicate temperatures of 550 t 25 c hypothetical growth and reaction histories that adhere to the modal mineralogical and known geochronological constraints were developed using a thermodynamically rigorous treatment of mineral modes and compositions incorporating calculations for multicomponent diffusion in garnet these models demonstrate that temperature estimates from staurolite schists may underestimate actual thermal maxima by more than 50 c gamet growth accompanying the reaction staurolite kyanite biotite garnet can lead to higher absolute temperature estimates but these may still be at least 50 c lower than actual peak temperatures simulations also demonstrate that fe enrichment in biotite accompanying retrograde production of chlorite may lead to calculated temperatures that are 10 50 c higher than would occur where only diffusional exchange operated on cooling evidence from additional metamorphic terranes suggests that this reaction model has wide applicability

monazite ages in the chesham pond nappe sw new hampshire u s a implications for assembly of central new england thrust sheets four distinct generations of monazite growth have been identified in samples from the chesham pond nappe and three monazite compositional domains 2 3 and 4 have been correlated with both temperature and mineral assemblage domain 1 cores were interpreted previously to be detrital relics or vestiges of an earlier acadian metamorphism the four monazite domains have been dated by in situ isotope and chemical methods the following are chemical ages of each domain weighted average 2 standard errors of the mean 400 10 ma domain 1 381 8 ma domain 2 372 6 ma domain 3 352 14 ma domain 4 heating and cooling rates derived from combining monazite ages monazite thermometry and 40ar 39ar closure temperatures are approximately 10 15 c m y for heating from 470 to 740 c approximately 8 c m y for cooling from 740 to 375 c and approximately 1 2 c m y for cooling from 375 to 150 c temperature time paths calculated with monazite ages and monazite thermometry indicate that 1 plutonism at ca 400 ma was the likely heat source for the formation of monazite domain 1 and 2 monazite domains 2 4 were produced during a regional low pressure high temperature metamorphism active between 380 350 ma the regional metamorphism is ascribed to lithospheric mantle delamination followed by asthenospheric mantle upwelling which heated a wide area of the merrimack basin southwestern new hampshire central massachusetts central connecticut to temperatures in excess of 725 c monazite ages in the chesham pond nappe and adjacent structural units to the west constrain the commencement of nappe overthrusting to roughly 355 ma