an energy dispersive miniprobe multielement analyzer emma for direct analysis of trace elements and chemical age dating of single mineral grains abstract an energy dispersive miniprobe multielement analyzer emma was designed and constructed for the analysis of trace elements as cr cu fe ga ge hf mn ni pb rb se sr th y u zn in small individual mineral grains such as apatite garnet monazite sphene zircon and other accessory minerals the instrument is sensitive ppm for most elements rapid 3 6 min per analysis non destructive and essentially no sample preparation is required with respect to single zircon grains as small as 50 m with mass as low as a few g for example the detection limits for u th and pb are on the order of 10 ppm 5 10 times better than the electron microprobe here the emma is used to illustrate the variation in hf and y concentrations in single zircon grains from pegmatites granites basalts carbonatites and kimberlites also the instrument is used for chemical age dating u th total pb of 1 single zircon grains from the berdyshevsky intrusive complex ukraine and 2 single monazite grains from a small placer deposit within the transition zone between the saxothuringikum and moldanubikum bavaria germany the average age of the single zircon grains from berdyshevsky granite determined using emma 2 19 0 17 ga 1 is consistent with the u pb zircon intrusion age of this complex 2 14 0 07 ga and monazite data ranging from 1 95 to 2 48 ga with respect to the pegmatite from this complex the average age of 1 93 0 09 ga found with emma is geologically consistent with zircon and monazite ages ranging from 1 90 to 2 29 ga regarding the monazite grains from the placer the age dates obtained using emma 328 28 ma are comparable to the isotopic ages conventional u pb and pb pb step leaching which yielded ages of 312 3 and 324 12 ma respectively

u pb dating of monazite and its application to geological problems monazite is an underutilized mineral in u pb geochronological studies of crustal rocks it occurs as an accessory mineral in a wide variety of rocks including granite pegmatite felsic volcanic a

metamorphic field gradients in the central alps metamorphic field gradients were determined across the entire amphibolite grade central alps c 50 100 km p t were calculated from 116 samples acquired from our own field work from samples provided to us by others and from rocks with mineral compositions described in the literature only fluid conserved equilibria were used to determine p t the use of an internally consistent thermodynamic database and mineral solid solution models makes the results robust and reduces relative errors the results are presented in contour maps temperature increases from 500 to 550 c along the limit of amphibolite grade metamorphism in the north and west to c 675 c toward the south at the insubric line near the town of bellinzona maximum recorded pressures of c 7 kbar are in a central region c 20 km north of the insubric line and decrease both to the north 5 5 kbar and south 4 5 kbar the p t results indicate that there is a relatively large area that reached conditions in the sillimanite stability field but developed neither sillimanite nor fibrolite this is interpreted as a result of kinetic constraints on nucleation and growth because of the small amounts of thermal overstep 40 c of the kyanite sillimanite phase boundary comparison of p t conditions with carbonate isograds in the region indicate that fluids present during metamorphism were not dominated by a homogeneous external source examination of the two dimensional distribution of pressure and temperature in the context of thermal and tectonic models indicates that two thermal pulses aected the central alps during the tertiary in the second heat aected only the southern parts of the area and overprinted the previously established p t gradients

textural chemical and isotopic insights into the nature and behaviour of metamorphic monazite monazite is a mineral of choice for dating metamorphism in amphibolite and granulite grade metapelites however there exist a number of difficulties that complicate the interpretation of monazite geochronological data and prevent its application to many geological problems the two main obstacles addressed in this contribution are firstly the minor but significant e g 1 30 ma dispersal in duplicate isotope dilution thermal ionisation mass spectrometry id tims u pb age data commonly recorded from a single rock and secondly the difficulty of attaching monazite age data to pressure and temperature information through a multidisciplinary approach utilising tims and laser ablation multicollector inductively coupled plasma mass spectrometry la mc icpms isotope data quantitative and qualitative emp chemical analyses of monazite and textural studies we assess the significance of pb loss older components and continuous and episodic monazite growth in the generation of dispersed age data three samples from the canadian cordillera and one sample from the himalaya of pakistan are examined each sample exhibits an age dispersion of between 1 and 12 ma for single crystal and multi grain tims u pb monazite age determinations consideration of the closure temperature for pb diffusion in monazite and the metamorphic temperatures experienced by these samples suggests diffusive pb loss did not play a significant part in generating this age dispersal the la mc icpms study indicates that an older component 100 ma older than the tims ages contributed to the age dispersal in three of the four samples in all the samples however chemical analyses identified that the majority of monazites examined exhibited significant intra crystalline zoning in y content the la mc icpms analysis of one sample that was constrained to zones of distinct y content indicates that these zones are of distinct age we suggest that monazite grown before the appearance of garnet and during garnet breakdown is relatively rich in y whereas monazite grown after garnet is relatively poor in y a combination of these chemical data with textural observations suggests that once monazite had entered the mineral assemblage it grew or recrystallised episodically throughout the prograde and retrograde paths of the metamorphic event this behaviour contributes to and in one of the samples controls the observed age dispersal this recognition allows the generation of pressure temperature time points by combining textural and chemical information of monazite with in situ age determinations and pressure temperature information from garnet thus the episodic growth of compositionally distinct monazite throughout a metamorphic event provides the geochronologist with a very valuable chronological tool

microprobe monazite geochronology understanding geologic processes by integrating composition and chronology abstractmonazite is a light rare earth element lree bearing phosphate mineral that is present in a wide variety of rock types has an extremely variable composition reflecting host rock conditions and is a robust geochronometer that can preserve crystallization ages through a long history of geological events monazite crystals typically contain distinct compositional domains that represent successive generations of monazite which in turn can provide a detailed record of the geologic history of its host rocks the electron microprobe can be used to characterize the geometry of compositional domains analyze the composition of each domain and when carefully configured determine the u th total pb age for domains as small as 5 m in width these data allow the monazite to be linked with and place timing constraints on silicate processes in the host rocks current applications span a broad range of geologic processes in igneous metamorphic hydrothermal and sedimentary rocks

nondestructive chemical dating of young monazite using xrf 1 design of a mini probe age data for samples from the central alps and comparison to u pb tims data the analytical capabilities of an improved mini xrf instrument for trace element analysis are explored to obtain u th pb ages for single monazite grains as small as 50 m the detection limits for u th and pb with counting times of 10 min are 10 ppm counts collected for 40 min are sufficient to date single monazite grains as young as 15 ma the precision of the age data depends essentially on the counting statistics of the main x ray peak npb l 1 2 used to analyze for lead the age uncertainty is proportional to the age of the grain the total contents of th and u and the squared integration time the reliability of the chemical dating method is tested using monazite separates from amphibolite facies metamorphic monazite samples from the central alps for which the chemical ages are compared to mass spectrometric u pb tims ages we show that populations of analyses obtained using the new instrument on single grains as young as 25 30 ma agree within error with the tims data for monazite separates with complex age patterns such as polymetamorphic samples yielding discordant isotopic ages the statistical analysis of chemical age data obtained from populations of 26 50 grains is advantageous in that it may provide additional insight into the reasons for the discordancy chemical th u pb dating of monazite by the xrf method offers considerably improved accuracy and precision compared with chemical dating by electron microprobe which typically becomes impractical for samples less than 100 200 ma in age conversely the minimum grain size required for the new instrument 50 m is well above the spatial resolution of the electron microprobe 2 m a companion paper scherrer et al this volume describes further developments towards microanalysis by xrf with improved spatial resolution

replacement of primary monazite by apatite allanite epidote coronas in an amphibolite facies granite gneiss from the eastern alps accessory monazite crystals in granites are commonly unstable during amphibolite facies regional metamorphism and typically become mantled by newly formed apatite allanite epidote coronas this distinct textural feature of altered monazite and its growth mechanism were studied in detail using backscattered electron imaging in a sample of metagranite from the tauern window in the eastern alps it appears that the outer rims of the former monazites were replaced directly by an apatite ring with tiny thorite intergrowths in connection with ca supply through metamorphic fluid around the apatite zone a proximal allanite ring and a distal epidote ring developed this concentric corona structure with the monazite core regularly preserved in the center shows that the reaction kinetics were diffusion controlled and relatively slow quantitative electron microprobe analyses suggest that the elements released from monazite breakdown p ree y th u were diluted and redistributed in the newly formed apatite allanite and epidote overgrowth rings and were unable to leave the corona this supports the common hypothesis that these trace elements are highly immobile during metamorphism furthermore microprobe data suggest that the preserved monazite cores lost little possibly none of their radiogenic lead during metamorphism thus metastable monazite grains from orthogneisses appear to be very useful for constraining u th pb protolith ages on the basis of these findings and a review of literature data it seems that monazite stability in amphibolite facies metamorphic rocks depends strongly on lithologic composition while breaking down in granitoids monazite may grow during prograde metamorphism in other rocks such as metapelites

lewisian crustal history from in situ sims mineral chronometry and related metamorphic textures abstract a combination of detailed petrography and in situ sims 207 pb 206 pb micro chronometry of monazite has been carried out on samples from the lewisian high grade metamorphic terrain northwest scotland two episodes of granulite facies metamorphism have been recognized the thermal maxima of which are estimated at or before 2760 12 ma 2 and at 2526 8 ma respectively pegmatites at scourie crystallised at 2480 ma the amphibolite facies metamorphism of the main laxfordian event is estimated at 1752 12 ma and the formation of kyanite and staurolite is associated with this event the oldest ages of 2760 ma have been obtained from micro inclusions of monazite in garnet it appears that garnet which has a high closure temperature for the u pb system plays an important role in the behaviour of the monazite u pb system it serves to shield monazite from reaction with the other phases and to armour monazine from diffusive pb loss or from resetting

post granulite facies monazite growth and rejuvenation during permian to lower jurassic thermal and fluid events in the ivrea zone southern alps u pb analyses of single monazite grains from two granulite facies metapelites in the ivrea zone southern alps reveal the presence in both samples of at least three different ages and prove that earlier interpretations of supposedly concordant monazite data as cooling ages are unwarranted one group of monazite data defines a subconcordant discordia line with an upper intercept age of 293 4 5 8 ma and a lower intercept age of 210 14 ma the upper intercept is interpreted as the real cooling age of the monazites the lower intercept is interpreted as an episode of fluid driven pb loss indicated by the presence of internal and external corrosion structures not only of the monazites but also of the zircons in the same samples that are also rejuvenated at 210 12 ma another group of monazite data lies above the concordia the presence of excess 206pb indicates that these crystals have grown below the monazite blocking temperature thus after the granulite facies metamorphism the age of growth of the new monazite crystals is approached by their 207pb 235u ages that range between 273 and 244 ma the two groups of post cooling age post 293 4 5 8 ma monazite data correspond to two distinct late and post variscan geotectonic regimes that affected the southern alps 1 permian transtension with decompression and anatectic melting 2 upper triassic to lower jurassic rifting with geographically dispersed hydrothermal activity and alkaline magmatism

geochronology and geochemistry of multiple generations of monazite from the wepawaug schist connecticut usa implications for monazite stability in metamorphic rocks u pb isotope analyses rare earth and trace element analyses and petrographic observations are presented for monazites from the wepawaug schist in southern connecticut usa two samples of kyanite zone schist were collected less than a meter apart each sample contains a different variety of monazite with distinct morphology chemistry and pb isotopic composition one sample preserves a largely amphibolite facies mineralogy including kyanite staurolite garnet biotite and chlorite with little textural evidence of later shearing monazites from this sample are xenoblastic with about 1 wt tho2 0 3 wt cao and a more lree enriched pattern than monazites from the second sample these xenoblastic monazites preserve textural evidence of a retrograde reaction to apatite which involves chlorite indicating that these monazites became unstable during retrograde chloritization of biotite these monazites give strongly discordant u pb ages which fit a chord with an upper intercept age of 411 18 ma interpreted as the minimum growth age of these xenoblastic monazites perhaps during amphibolite facies metamorphism the second sample contains s c banding evidence of dynamic recrystallization and abundant retrograde chlorite this sample contains idioblastic monazites with about 3 wt tho2 0 8 wt cao and with less fractionated ree patterns these monazites give close to concordant u pb ages with a mean 207pb 206pb age of 388 2 ma this age is interpreted as probably representing the time of monazite growth during retrogression of the sample from an amphibolite to greenschist facies mineralogy

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

u pb single zircon pb evaporation and sm nd isotopic study of a granulite domain in se madagascar madagascar is a poorly known precambrian domain at the eastern border of the mozambique belt strongly affected by the pan african orogeny this large island represents a key part of gondwanaland and the accurate dating of the major metamorphic event is critical for the reconstruction of that supercontinent in the southeastern zone of the island metamorphism has reached high temperature and low pressure conditions 850 c and 5 kbar with moderate retrogression a u pb conventional multigrain single zircon stepwise pb evaporation and sm nd geochronological study on meta felsic rocks has shown that basement of at least lower proterozoic age was strongly metamorphosed around 570 580 ma this tectometamorphic event nearly obliterated any pre pan african zircon isotopic memory the granulite facies metamorphism is associated with the syn metamorphic emplacement of the anosyan charnock ites and granites a strong channelized fluid contribution at 545 ma has produced the re crystallization of biotite apatite

monazite geochronology of uhp and hp metamorphism deformation and exhumation nordoyane western gneiss region norway u th pb monazite geochronology is combined with previous structural analysis and quantitative estimates of metamorphic conditions to date the thermotectonic evolution of uhp and hp plates 820 c 39 kbar 780 c 18 kbar metamorphosed during the late silurian early devonian collision between baltica and laurentia the upper plate contains a microdiamond bearing kyanite garnet graphite gneiss and associated kyanite eclogites independently indicating probable diamond forming conditions in situ dating of monazite in the microdiamond sample using the shrimp ii at the geological survey of canada yielded ages of 415 6 8 ma for those included in garnet and 398 6 ma for those in the matrix these ages compare to 408 0 5 6 and 397 5 4 4 ma determined using the electron microprobe at the university of massachusetts both methods also identified complexly zoned detrital cores up to 150 micrometers in diameter with ages of 1100 950 ma and scattered grains with ages of 900 500 ma but no ages of 1680 1650 ma equivalent to the local baltica basement were found agreement between the two techniques allowed evaluation of monazite age domains 198 analyses from the microdiamond rock and a kyanite garnet sillimanite mylonite produced from it using a combination of high resolution element imaging and trace element analysis of u th pb and y this comparison yielded three mean ages of 407 0 2 1 ma 394 8 2 3 ma and 374 6 2 7 ma combining this geochronology with previous p t estimates we propose that the uhp unit reached its maximum depth of 125 km at a maximum age of 407 ma when monazite was included in garnet and experienced 65 km of exhumation at an average rate of 10 9 mm year during top southeast thrusting that brought it into contact with the hp unit following these events both units were exhumed together at an average rate of 3 8 mm year until reaching a depth of 37 km at 395 ma where these rocks experienced extensive re equilibration and top west and left lateral shearing after 395 ma these units continued to be exhumed at an average rate of 0 8 to 1 4 mm year until 375 ma the time of last equilibration of asymmetric monazite porphyroclasts in the mylonite the exhumation histories of these units record a change in mechanism from syncollisional exhumation through late to post orogenic collapse that was a consequence of plate reorganization

late devensian to early holocene palaeoenvironmental changes in the viking bank area northern north sea abstract lithological and macrofaunal analysis of vibrocores collected from northwest of the viking bank enables the devensian to holocene strata to be subdivided into eight informal units three of which occur widely in the northern north sea for the viking bank area it is suggested that sea level was more than 100 110 m below that at present between 15 500 and 13 600 bp a time when some parts of the area were dry land and others covered by a shallow high arctic sea sea level may have been even lower more than 140 m below its present level prior to 15 500 bp during the windermere interstadial 13 000 11 000 bp polar water was replaced by atlantic water and the environment was low arctic with a regime of strong tidal currents sea level at approximately 12 000 bp had risen to some 80 100 m below present the loch lomond stadial and early holocene generally were characterised by high arctic followed by boreo arctic to boreal faunas relatively low energy conditions and probably rapidly rising sea level

patterns of isostatic land uplift during the holocene evidence from mainland scotland preliminary results of a lengthy and detailed investigation into middle and late holocene raised shorelines in mainland scotland indicate that three shorelines are sufficiently widely distributed to permit an examination of their extent and of the patterns of uplift which they indicate the shorelines are the storegga tsunami shoreline reached at c 7100 14c years bp at the culmination of the main postglacial transgression and the blairdrummond shoreline reached after the main postglacial shoreline at c 2000 4200 14c years bp at the time of a tsunami believed to have been caused by the second storegga submarine slide the main postglacial shoreline reached at c 5800 6850 14c years bp the main postglacial shoreline previously believed to be the highest holocene raised shoreline in scotland is now believed to be overlapped around the periphery of the uplifted area by the later blairdrummond shoreline isobase models based upon quadratic trend surface analysis of available comparable height dat

format and philosophy for collecting compiling and reporting microprobe monazite ages microprobe monazite dating has been increasingly used to constrain the timing of deformation and metamorphism because of the potential to date very small monazite domains down to 5 m or less in structural and petrologic context this paper presents an analytical strategy presentation format and error considerations for microprobe monazite dating the strategy involves high resolution compositional mapping to delineate compositional domains within monazite crystals then for each compositional domain a series of th u and pb analyses are made and a single date and error are calculated the number of analyses in each domain is determined by the desired statistical precision of the date results from several monazite grains are typically combined and along with textural relationships are used to build an argument that the dates constrain the age of a deformation or metamorphic event the total error involves three components short term random error dominated by counting statistical uncertainty short term systematic error uncertainty in background correction conductive coating variation and calibration and long term systematic error uncertainty in standard composition mass absorption factors decay constants etc in homogeneous compositional domains short term random errors 2 of less than 10 m y can be obtained from five to ten analyses however short term systematic error mainly background estimation uncertainty would typically result in a doubling of the magnitude of random error microprobe dates are presented as a single gaussian probability distribution for each domain along with representative compositional maps it is recommended that a consistency standard be analyzed during each analytical session and the results be reported along with those from the unknown this proposed strategy and format are compatible with those of other geochronological techniques they incorporate analytical limitations associated with trace as opposed to major element microprobe analysis and will allow better comparisons to be made between labs and between different geochronological techniques

monazite paragenesis and u pb systematics in rocks of the eastern mojave desert california u s a implications for thermochronometry abstract studies of the paragenesis and u pb systematics of monazite in rocks from the eastern mojave desert california corroborate its potential usefulness as a prograde thermochronometer and in dating granite inheritance unmetamorphosed latham shale and its equivalents at grades ranging from greenschist to upper amphibolite facies are virtually identical in composition monazite is absent in the shale and low grade schists but it is abundant in schists at staurolite and higher grades lower grade schists instead include minute th and ce oxides and unidentified ce poor lree phosphates that apparently are lower temperature precursors to monazite thus monazite originates when the pelite passes through lower amphibolite facies conditions monazites from three upper cretaceous granites yield ages that are strongly discordant upper intercepts of 1 6 1 7 ga are similar to those defined by u pb data for coexisting zircons and coincide with a period of copious magmatism in the mojave crust as the host upper cretaceous granitic magmas were all above 700 c effective closure of the restitic monazites to pb loss must be well in excess of this temperature u pb compositions of monazite from proterozoic granitoids and schist also indicate high pb retentivity taken together these studies support the suggestion that monazite can be an effective prograde thermochronometer at least in pelites it is not usually retained as a detrital mineral but rather forms during moderate temperature metamorphism its u pb system should not be reset by subsequent higher grade metamorphism

spatial patterns of soil n alkaneδd values on the tibetan plateau implications for monsoon boundaries and paleoelevation reconstructions 1 between 2010 and 2011 this project collected and analyzed forty nine superficial soil samples for wax derivedn alkane d values dwax along a south to north transect of the tibetan plateau from the southern plateau and nepalese himalayas passing through the nam co basin to qilian mountains twenty two paired river water samples were also collected from northeastern tibet during this period and analyzed for d drw the drw and dwaxvalues become progressively more negative northward from 27 5 n and reach a minimum at 30 6 n nam co basin north of the nam co basin to 35 n isotope values increase due to increasing contributions from the year round westerlies and recycled moisture from the plateau relatively high and constant dwax and drw values prevail in areas north of 35 n in northeastern tibet results show that these dwaxvalues vary considerably with location and relate closely to the influences of the summer monsoon and circulation changes these changes track the spatial variability of isotopes from modern river water and precipitation at large spatial scales paleoelevation reconstructions should take into account the impact of mixing between continental and monsoon derived moisture on the relationships with elevation and dwax and linear isotopic lapse rates for central northeastern tibet based on extended and more sensitive relative to 18o dwax and drw values we infer that in the past the westerlies reached further south to the north piedmont of the nyainqentanglha range and that indian summer monsoon moisture pushes across the tanggula mountains and approaches the kunlun mountains

nondestructive chemical dating of young monazite using xrf 2 context sensitive microanalysis and comparison with th pb laser ablation mass spectrometric data a newly developed xrf microprobe at the institute of mineralogy and petrology university of bern switzerland has been applied for precise chemical th u pb dating of individual monazite grains separated from pb free polished petrographic thin sections the nondestructive nature of the xrf measurement permitted a comparative study of dating methods by sequentially applying chemical dating by electron microprobe analysis empa chemical dating by xrf microprobe analysis and isotopic 208pb 232th dating by laser ablation plasma ionisation multi collector mass spectrometry la pimms analysis as an example the 2 precision achieved with the xrf microprobe for well characterised reference material monazite fc 1 tims age 54 3 1 ma xrf age 55 3 2 6 ma doubly polished to 30 m in thickness is below 5 after 90 min integration time 50 kv 30 ma at a spatial resolution of 90 m at 38 m spatial resolution the uncertainty is 35 for the same integration time the sample characteristics are 200 300 ppm of pb xrf 3 8 5 1 wt of th empa and 0 4 1 4 wt u empa combined with an electron microprobe and conventional optical microscopy the xrf microprobe is thus a competitive low cost and nondestructive alternative to more costly isotopic methods the xrf microprobe is easy to use and maintain

electron microprobe dating of monazite because monazite is extremely rich in u and th radiogenic pb pb accumulates very quickly and reaches in about 100 ma a level where it is possible to analyse it with the electron probe assuming that common pb is negligible and that partial loss of pb has not occurred the simultaneous measurement of u th and pb allows to obtain a geologically meaningful age from a single electron probe analysis here we present the results of two years of systematical investigations aiming to define both the limits and potential of this method a specific statistical method to deal with the large number of data which can be obtained on a single sample is described and several guidelines illustrated by examples are suggested to optimize the method electron probe measurements carried out on samples of known age from 200 ma to 3 1 ga yield ages that always fall inside the confidence interval of the isotopically determined age demonstrating that this method is reliable the younger age limit is approximately 100 ma although it can be younger in some favourable cases in old monazites extremely high pb contents have been found up to 5 wt indicating that monazite can tolerate high radiation doses without experiencing lead loss the final precision on the age for a normal monazite is 30 50 ma for a total counting time of 600 s a complete dating procedure can be completed in less than 1 h first results indicate that old ages can be preserved in monazite either in small relict cores in crystals or by the coexistence of several generations of monazites in a sample this method has all the advantages of the electron probe it is non destructive has an excellent spatial resolution monazites as small as 5 i m can be dated and because it is possible to work on normal polished thin sections the petrographical position of the dated crystal is known this method offers a large number of geologists access to an in situ dating technique at moderate cost

versatile monazite resolving geological records and solving challenges in materials science monazite is ubiquitous in the geological realm overstreet 1967 its compositional and isotopic response to changes in intensive and extensive rock parameters has made it an increasingly important component of integrated pressure temperature deformation composition time p t d x t studies particularly in complex poly metamorphic terranes janots et al 2012 kelly et al 2012 langille et al 2012 the utility of monazite also includes its role in understanding igneous sedimentary and hydrothermal systems dumond et al 2008 mahan et al 2010 aleinikoff et al 2012 and more recently as a means for examining repositories of radioactive waste oelkers and montel 2008 since the broader potential applications of monazite as a geochronometer were described by parrish 1990 several significant developments have since occurred that allow for the routine compositional and isotopic analysis of monazite by a variety of techniques these include technological advances in electron probe microanalysis epma suzuki and adachi 1991 montel et al 1996 pyle

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

significance of in situ sims chronometry of zoned monazite from the lewisian granulites northwest scotland abstract in situ studies of lewisian metamorphic monazites show them to be strongly zones in th content th u ratio and 207 pb 206 pb age traverses across compositional zones of individual monazites by sims and empa show that there are no resolvable shifts between 232 th 238 u and 208 pb 206 pb ratios and between th and pb contents in any of the profiles obtained furthermore the difference in 208 pb 232 th ages between two zones of monazites in the same thin section is indistinguishable from the difference in 207 pb 206 pb ages determined by sims these observations together with simple models suggest that transport of pb relative to th and u did not occur significantly during younger e g the laxfordian events in the lewisian and the ages preserved in these zoned monazites are close to concordant moreover monazites having different compositions yield indistinguishable 207 pb 206 pb ages which suggests that the closure temperature of the u pb system in these monazites is not significantly dependent upon their composition consequently the pattern of age distribution observed in the monazites is taken to reflect the metamorphic history of the lewisian the results are consistent with the recent interpretations of the lewisian thermal history which suggest two high grade metamorphic events separated by 200 ma

holocene coastal evolution and sea level change on the southern coast of england a review data collected recently from select areas within the eastern central and western english channel are used to reconstruct the holocene evolution and sea level history of the southern coast of england rapid sea level rise in the early holocene produced a ubiquitous vertical and lateral expansion in the marine influence from ca 6800 cal calendar yr bp the rate of sea level rise declined and a shift from minerogenic to organogenic sedimentation is also widely recorded a further decline in the rate of sea level rise occurred in the late holocene during which time the eastern and central english channel experienced coastal inundation and a return to minerogenic sedimentation explanations for this apparent contradiction include the effects of this decline on the accumulation of minerotrophic peat and changes in sediment supply sea level index points from the eastern channel generally plot below those from the central and western channel indicating differential crustal movement although sediment compaction and tidal range also may be responsible for apparent altitudinal variation between these areas despite an increase in the quantity and quality of the data available from this region over the past 20 yr these and a number of other important issues require further clarification copyright 2003 john wiley sons ltd

sedimentary evolution of the north norfolk barrier coastline in the context of holocene sea level change holocene sediments of the north norfolk coast nnc between weybourne and hunstanton have been studied using geophysical sedimentological biofacial and dating techniques new cores and refraction seismic data have defined the topography of the pre holocene surface and show that the nnc sediment prism is underlain by an east west trending quaternary trough probably a palaeo river valley the age of the holocene fill has been dated using radiocarbon and luminescence dates while sedimentation rates were constrained by and compared with modern rates using radionuclide data the holocene sediments are divided into a sandy barrier lithofacies association lfa and a muddy silty peat back barrier lfa the oldest holocene sediments are peats formed on an undulating till surface these peats were forming by 11 10 cal ka bp and continued to form until at least 7 cal ka bp in a number of places as holocene sea level rose marine mudflat and saltmarsh environments began to form between 7 and 6 cal ka bp east of holkham and around 6 cal ka bp or younger west of holkham a marked erosion surface between the barrier and back barrier lfa in the holkham to burnham overy area is imperfectly dated at 3 cal ka bp but suggests the sediment prism has thinned by about 3 km over 6 to c 3cal ka bp this surface probably records the westward progress of laterally migrating tidal channels that caused back barrier sediment erosion along with shoreface processes as sea level rose small scale regressive and transgressive saltmarsh sequences occur at different elevations along strike but cannot be correlated suggesting that the control on saltmarsh and mudflat development is autocyclic rather than allocyclic generally transgressive and regressive events are related to disposition of coastal barriers and these are superimposed on a general facies evolution governed by regional sea level change predictions about how this barrier coastline might respond to increased rates of regional sea level change caused by global warming or climatic events like increased storminess require an understanding of how specific segments of the coastline have responded over millennial time scales this longer term evolution provides the baseline information for decision making and management strategy it is likely that sandy sediment supply is limited on the nnc and this implies that the barriers will continue to move landward probably at increased rates relative to today suggesting that parts of the nnc will become more vulnerable to erosion and flooding

electron microprobe dating of monazites from high grade gneisses and pegmatites of the kerala khondalite belt southern india monazites of five samples one leptynitic garnet biotite gneiss one khondalite one augen gneiss and two pegmatites from the central and northern part ponmudi unit of the kerala khondalite belt kkb in southern india were analyzed with the electron microprobe dating technique monazites in the augen gneiss and the pegmatites yield grain sizes between 200 800 m th abundances are rather low 10 wt and the distribution of th u and pb within single grains is fairly homogeneous contrasting to this monazites in the leptynitic gneiss and the khondalite are small 150 m they often display very complex th u pb patterns and contain high th concentrations up to 20 wt the statistical treatment of individual ages from the investigated samples revealed three populations of lower proterozoic 1 9 ga upper proterozoic 580 ma and ordovician age 470 ma as well as mid proterozoic ages between 0 8 1 7 ga which are not regarded to be of geological significance lower proterozoic ages are preserved in the cores of monazites from leptynitic gneisses and khondalites they fairly agree with sm nd model ages for similar rocks of the kkb and give a minimum age for first monazite growth or complete homogenization the prominent pan african population with mean values between 540 and 580 ma is present in the leptynitic gneiss the khondalite and the augen gneiss and in line with published isotope ages for the kkb the ordovician population finally marks the emplacement of granitic pegmatites subsequent to the pan african high grade metamorphic event there is an obvious discrepancy between khondalites and leptynitic gneisses on the one hand and augen gneisses on the other concerning the presence of lower proterozoic ages while these are abundant in the former often rimmed by upper proterozoic ages they are completely absent in the latter it appears unlikely that lower proterozoic ages were completely reset during a pan african event exclusively in the augen gneisses while they were preserved in leptynitic gneisses and khondalites it is further concluded that the augen gneisses are of magmatic origin and were derived from porphyritic granites thus the upper proterozoic age of 605 37 ma calculated for the investigated sample approximates the time of magma emplacement which slightly precedes the peak stage of pan african high grade metamorphism in the kkb and of monazite crystallization from the granitic melt a characteristic feature of the investigated monazites is the resetting of lower proterozoic and pan african ages to significantly younger values due to partial pb loss monazites not shielded by other minerals e g garnet suffered selective mobilization of pb along fractures or at their rims while th and u concentrations remained almost unchanged the results presented in this study indicate that this was mainly due to fluid rock interaction it is concluded that thermal diffusion of pb even at the suggested temperatures of 900 c only had minor influence on the th u pb composition in monazite and that the closure temperature for this system must be significantly higher than previously assumed 750 c

late devensian and holocene records of relative sea level changes in northwest scotland and their implications for glacio hydro isostatic modelling raised tidal marshes and isolation basins lakes that were once connected to the sea in northwest scotland record changes in relative sea level following deglaciation during the late devensian to the present the kentra to arisaig area which was covered by relatively thick ice c 900 m at the last glacial maximum lgm shows a regression from a marine limit between 36 5 m od and 40 m od at c 15 9 kyr cal bp range 15 6 16 3 kyr cal bp through to an early holocene minimum a range of sites in the same area record a mid holocene maximum indicative of mean sea level c 6 5 m above present the maximum is not a well developed and short duration highstand as predicted by a number of models but is an extended period 8 0 5 0 kyr cal bp with sea level within c 1 m of the maximum sites to the north in kintail show no late devensian record because much of the area lies within the younger dryas ice limit the altitude of the mid holocene maximum in kintail is not well constrained but occurred 7 9 8 1 kyr cal bp further north sites on the applecross peninsula record a late devensian fall in sea level and a holocene maximum for mean sea level no higher than c 3 0 m above present in coigach the furthest north of the new sites and well outside the younger dryas ice limit there is no evidence recorded of late devensian sea levels above present the holocene maximum here was around c 2 5 m above present these observations of sea level change all standardised to change in mean sea level relative to present constrain the glacio hydroisostatic rebound model parameters earth models comprising three mantle layers with lateral viscosity and elastic parameters give a satisfactory description of rebound the parameters h lithosphere thickness 65 km g 6 upper mantle viscosity 4 1020 pa 14c seconds and g lower mantle viscosity 1022 pa 14c seconds give the best overall agreement but discrepancies between observations and predictions remain an increase of 10 in ice thickness north of the great glen compared to the previous optimum ice model provides good agreement for many sites but important discrepancies remain for the northern sites and indicate inadequacies in the model of the british ice sheet several alternative ice models are examined but the various combinations of earth and ice model illustrate the non uniqueness of the solution a combination of more extensive ice limits especially onto the hebridean shelf and west shetland shelf and some changes to ice thicknesses over the mainland should produce a better agreement but the spatial coverage of observations remains a limitation to producing a unique solution the characteristics of the holocene highstand age duration and amplitude at the di erent sites refutes the assumption that globally deglaciation ceased abruptly 7000 yr ago the observations are consistent with an ice model that includes c 3 m of melting over the last 7000 yr 2000 elsevier science ltd all rights reserved

palaeotidal modelling of continental shelves marine implications of a land bridge in the strait of dover during the holocene and middle pleistocene

a three dimensional method for calculating independent chemical u pb and th pb ages of accessory minerals abstract previous theoretical considerations on the chemical u th total pb dating method failed to distinguish between thorogenic and uranogenic lead however it can be shown that the data points are located on a plane in the three dimensional tho2 pbo uo2 space the calculation of the best fit plane yields a slope in the tho2 pbo and uo2 pbo coordinate projections and an initial pbo value from the two slopes th pb and u pb ages can be calculated independently the method described in this paper is applied to monazites from the hercynian g4 granite of the fichtelgebirge germany th pb and u pb ages were calculated at 323 20 ma and 304 15 ma respectively the intercept value close to zero indicates that no significant amounts of common lead are present in the monazites studied

palaeogeographical changes in response to glacial interglacial cycles as recorded in middle and late pleistocene seismic stratigraphy southern north sea offshore stratigraphic records from the north sea contain information to reconstruct palaeo ice sheet extent and understand sedimentary processes and landscape response to pleistocene glacial interglacial cycles we document three major middle to late pleistocene stratigraphic packages over a 401 km2 area norfolk vanguard boreas offshore wind farm offshore east anglia uk through the integration of 2d seismic borehole and cone penetration test data the lowermost unit is predominantly fluviatile yarmouth roads formation marine isotope stage mis 19 13 including three northward draining valleys the middle unit swarte bank formation records the southernmost extent of tunnel valley fills in this area of the north sea providing evidence for subglacial conditions most likely during the anglian stage mis 12 glaciation the yarmouth roads and swarte bank deposits are truncated and overlain by low energy estuarine silts and clays brown bank formation mis 5d 4 smaller scale features including dune scale bedforms and abrupt changes in cone penetration test parameters provide evidence for episodic changes in relative sea level within mis 5 the landscape evolution recorded in deposits of mis 19 5 are strongly related to glacial interglacial cycles although a distinctive aspect of this low relief ice marginal setting are opposing sediment transport directions under contrasting sedimentary process regimes

country rock monazite response to intrusion of the searchlight pluton southern nevada we investigated how monazite grains in country rocks responded to the intrusion of the miocene searchlight pluton in southern nevada country rock samples were collected from the roof zone and along transects on the flanks wallrock of the 16 to 17 ma pluton deep wallrock ireteba granite monazite grains have patchy secondary growth zones of searchlight age overprinting primary growth zones of ireteba age 66 ma shallow wallrock proterozoic gneiss zircon grains define a discordia with an upper intercept age of 1 74 0 02 ga corresponding to crystallization of the protolith proterozoic gneiss monazite grains define a discordia with an upper intercept age of 1 64 0 02 ga and a poorly defined lower intercept age of 75 61 ma that may correspond to the ireteba intrusion emp analyses show that patchy secondary zones in proterozoic gneiss monazite grains were contemporaneous with intrusion of the ireteba granite not the searchlight pluton oxygen isotopes in ireteba monazite hydrogen and oxygen isotopes in whole rocks from the ireteba transect and oxygen isotopes in whole rocks from the proterozoic gneiss transect show no systematic pattern related to the contact no geochemical data support the hypothesis that hydrothermal fluids associated with intrusion of the searchlight pluton caused monazite in the proterozoic gneiss or ireteba granite wallrock to partially recrystallize ireteba samples with the most intensely altered monazite were at the greatest paleodepths at the time of searchlight intrusion and are the most deformed suggesting that strain caused ireteba monazite grains to partially recrystallize in proterozoic gneiss country rock monazite grains are present on the flanks but absent from the roof zone suggesting that high fluid fluxes in the roof may have destroyed monazite strong focusing of hydrothermal fluid and heat into the roof zone prevented the development of a well defined contact metamorphic aureole in ireteba granite and proterozoic gneiss wallrocks

a late miocene pliocene origin for the central himalayan inverted metamorphism abstract perhaps the best known occurrence of an inverted metamorphic sequence is that found immediately beneath the himalayan main central thrust mct generally thought to have been active during the early miocene however in situ 208 pb 232 th dating of monazite inclusions in garnet indicates that peak metamorphic recrystallization of the mct footwall occurred in this portion of the central himalaya at only ca 6 ma the apparent inverted metamorphism appears to have resulted from activation of a broad shear zone beneath the mct which tectonically telescoped the young metamorphic sequence this explanation may resolve some outstanding problems in himalayan tectonics such why the mct and not the more recently initiated thrusts marks the break in slope of the present day mountain range it also renders unnecessary the need for exceptional physical conditions e g high shear stress to explain the generation of the himalayan leucogranites

holocene tides of the wash u k the influence of water depth and coastline shape changes on the record of sea level change abstract tidal simulations are conducted using a numerical model to investigate the relative influence of water depth and coastline shape changes on the holocene tides of the wash tidal input to this model is obtained by running a nested series of models commencing with a model of the northeast atlantic results of both types of simulations are compared with those of other simulations incorporating all the palaeogeographic information available on both past water depths and coastline shapes around the wash the model employs six harmonic tidal constituents to obtain mean high water of spring tides mhwst altitudes the wash was a depositional embayment during the holocene and results of model simulations are compared with sea level indicators in the stratigraphy which record past mhwst altitudes tidal simulations for water depths reduced by 2 5 and 10 m compared with present sea levels generally give lower tidal amplitudes around the wash than found at present mhwst altitudes simulating the coastline shape for 3000 4000 and 5000 yrs b p utilising present water depths show similar patterns of tidal changes to those obtained from the palaeogeographic simulations however reduced water depth tidal simulations accord more closely with the palaeogeographic simulation results in terms of the magnitude of changes to mhwst altitudes than the palaeocoastline simulations this is due to the fact that the rise in mean sea level during the holocene is far greater than any change in the amplitude of tides in the wash palaeogeographic simulation model results for mhwst agree within experimental errors with sea level curve altitudes reasons for discrepancies include inaccuracies in model parameters or measurement errors in obtaining mhwst altitudes from the stratigraphy overall tidal heights increase with sea level rise towards the present day alterations to coastline shape and non uniform water depth changes for example due to sediment movements or coastal defence schemes must be taken into consideration when assessing changes to the tidal regime for different sea levels in coastal embayments in order to determine both the pattern and magnitude of tidal changes this applies to both past and possible future tidal simulations

holocene isostatic uplift of the south shetland islands antarctic peninsula modelled from raised beaches we present new isobases constraining the holocene isostatic uplift of the south shetland islands northern antarctic peninsula based on evidence from raised shorelines holocene shorelines were described and surveyed at fifteen sites to determine the spatial variability of relative sea level rsl change across the south shetland islands and provide new spatial rsl change corrections for the region results show that the highest shoreline is a transgressive feature correlated by geomorphological evidence on most exposed coastlines of the archipelago its surveyed height was corrected for local variability in wave energy by subtracting the measured altitude of the present day shoreline these corrected surveyed heights of the highest raised beach were modelled using quadratic polynomial trend surface analysis to constrain differing rates of regional isostatic uplift we present two isobase models of isostatic uplift since formation of the highest holocene raised beach circa 7360 7000 years ago these models suggests a maximum uplift of ca 20 m was centred on an area north of greenwich island with isobases implying an elongate zone of uplift orientated east southeast to west northwest along the spine of the island chain this corresponds well with previously published geomorphologically based estimates of palaeo ice extent and the deglaciation history of the south shetland islands and gives new context to the palaeo ice extent and glacial history of the region

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

new models of north west european holocene palaeogeography and inundation this paper presents new 500 year interval palaeogeographic models for britain ireland and the north west french coast from 11000 cal bp to present these models are used to calculate the varying rates of inundation for different geographical zones over the study period this allows for consideration of the differential impact that holocene sea level rise had across space and time and on past societies in turn consideration of the limitations of the models helps to foreground profitable areas for future research

modeling the contribution of m2 tidal amplification to the holocene rise of mean high water in the gulf of maine and the bay of fundy abstract increase in the m2 principal lunar semi diurnal component of the tidal range is an important contributor to the postglacial rise of the high tide level in the gulf of maine and the bay of fundy in addition to relative sea level rise the increase occurred as the shape of this semi enclosed embayment changed with sea level rise and its natural period approached resonance with the m2 tide a three dimensional tide model 3dens predicts the following m2 tidal ranges averaged for the gulf of maine bay of fundy as a percentage of the present range 54 59 at 7000 yrs b p 73 at 5000 yrs b p 78 at 4000 yrs b p 85 at 3000 yrs b p 94 at 2000 yrs b p and 98 at 1000 yrs b p with a predicted sea level rise of 0 15 0 90 m by the year 2100 m2 tidal range may increase 0 3 1 9

monazite th pb age depth profiling the significant capabilities of the ion microprobe for thermochronometric investigations of geologic materials remain largely unexploited whereas sup 208 pb sup 232 th spot analysis allows approximately 10 mm scale imaging of pb loss profiles or overgrowths in sectioned monazite grains the spatial resolution offered by depth profiling into the surface region of natural crystals is more than two orders of magnitude higher the authors document here the ability of the high resolution ion microprobe to detect sup 208 pb sup 232 th age differences of 1 m y with better than 0 05 micro m depth resolution in the outer micron of tertiary monazites from the hanging wall of the himalayan main central thrust age gradients on this scale are inaccessible to ion microprobe spot analysis or conventional thermal ionization mass spectrometry interpretation of the near surface sup 208 pb distributions with available monazite pb diffusion data illustrates the potential of the approach for recovering continuous high temperature thermal history information not previously available

electron microprobe observations of pb diffusion in metamorphosed detrital monazites electron microprobe analyses have been made on monazite grains from paragneiss samples in the andalusite sillimanite transition 620 15 c and sillimanite orthoclase 680 15 c zones of the cretaceous ryoke metamorphic belt southwest japan monazites from pelitic gneisses are of metamorphic origin euhedral to subhedral and chronologically homogeneous giving chemical th u total pb isochron chime ages of 98 8 3 3 98 0 3 2 ma two psammitic gneisses of individual metamorphic grade contain both metamorphic monazite grains and detrital ones as old as ca 1700 ma most detrital monazite grains are heterogeneous in the tho2 and uo2 concentrations and have multiple or single rims as young as ca 100 ma several detrital monazite grains are well rounded in form exhibit homogeneous th and u distributions and show a pb diffusion profile in the margin the width of the diffusion zones is approximately constant throughout grains from each psammitic gneiss 18 22 m for 620 c and 48 58 m for 680 c assuming the isothermal diffusion of pb from homogeneous monazite spheres during a 5 ma duration of peak metamorphism we obtain diffusion coefficients of 1 9 0 3 10 21 and 1 5 0 3 10 20 cm2 s at 620 c and 680 c respectively these data derive an activation energy of 2 44 2 85 1 26 105 j mol and a frequency factor of 3 4 10 7 8 5 10 12 2 2 107 cm2 s taking account of uncertainties of 15 c in the temperatures and of 20 in the diffusion coefficients the diffusion parameters obtained from natural samples in this study provide a reliable insight into the closure temperature for pb in monazite that has been poorly understood so far

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

mantle viscosity and ice age ice sheet topography ice age paleotopography and mantle viscosity can both be inferred from observations of earth s response to the most recent deglaciation event of the current ice age this procedure requires iterative application of a theoretical model of the global process of glacial isostatic adjustment results demonstrate that the iterative inversion procedure converges to a paleotopography that is extremely close to that from the ice 4g model the accompanying mantle viscosity profile is furthermore shown to reconcile the requirements of aspherical geoid anomalies related to the mantle convection process thus resolving a fundamental issue concerning mantle rheology the combined model also explains postglacial sea level histories for the east coast of the united states

towards improved empirical isobase models of holocene land uplift for mainland scotland uk a new approach to modelling patterns of glacio isostatic land uplift during the holocene in mainland scotland uk is described the approach is based upon altitude measurements at the inner margin or locally highest point of raised estuarine surfaces dated by radiocarbon assay supported by microfossil analyses 2241 altitudes have been analysed by a technique new to studies of former sea levels gaussian trend surface analysis and isobase models for four holocene shorelines the holocene storegga slide tsunami shoreline abandoned rapidly circa 7900 sidereal years bp the main postglacial shoreline abandoned during circa 6400 7700 sidereal years bp the blairdrummond shoreline abandoned during circa 4500 5800 sidereal years bp and a speculative fourth shoreline the wigtown shoreline abandoned during circa 1520 3700 sidereal years bp are shown in a series of maps the implications of the shoreline patterns for glaicio isostasy in the area are discussed it is maintained that the statistical technique used enables broad estimates to be made of nearshore sea surface change

denudation history of the high t p ryoke metamorphic belt southwest japan constraints from chime monazite ages of gneisses and granitoids chime chemical th u total pb isochron method monazite ages were determined for gneisses and granitoids from the eastern and western parts of the ryoke belt separated by about 500 km the monazite ages for the gneisses are concentrated between 102 and 98 ma and are interpreted as the time of monazite formation under lower amphibolite facies conditions the peak metamorphism seems to be contemporaneous with the emplacement of the geologically oldest plutons that are dated at c 95 ma in both the eastern and western parts in the eastern part plutonism continued from c 95 ma to c 68 ma at intervals of 2 10 ma whereas in the western part it ceased at c 85 ma the chime monazite ages agree well with the relative age of granitoids derived from intrusive relationships of granitoids in both parts these lines of evidence are incompatible with a current view that the plutonometamorphism in the ryoke belt becomes younger towards the east the chime monazite ages coupled with available data on the depth at which the ryoke metamorphism took place and the emplacement of individual plutons show that the western part was eroded more rapidly about 1 5 mm year 1 than the eastern part about 0 8 mm year 1 over the time span from 91 to 85 ma the denudation rates agree well with those in active orogenic belts like the alps and himalayas

developing detailed records of relative sea level change using a foraminiferal transfer function an example from north norfolk uk this paper provides a brief overview of the transfer function approach to sea level reconstruction using the example of two overlapping sediment cores from the north norfolk coast uk the advantages and limitations of the transfer function methodology are examined while the selected cores are taken from different sites and display contrasting patterns of sedimentation the foraminiferal transfer function distils comparable records of relative sea level change from both sequences these reconstructions are consistent with existing sea level index points from the region but produce a more detailed record of relative sea level change transfer functions can extract sea level information from a wider range of sedimentary sub environments this increases the amount of data that can be collected from coastal deposits and improves record resolution the replicability of the transfer function methodology coupled with the sequential nature of the data it produces assists in the compilation and analysis of sea level records from different sites this technique has the potential to bridge the gap between short term instrumental and long term geological or geophysical records of sea level change

tides in the northeast atlantic considerations for modelling water depth changes abstract a two dimensional tidal model of the northeast atlantic is used to simulate the m 2 s 2 2 m 4 ms 4 and m 6 tides for present sea level and with mean water level lowered or raised by a uniform number of metres over the model area m 2 s 2 tides predict the present spring tidal range although the other constituents are needed to predict spring tides in shallow water areas the accuracy of the assumptions made in modelling is assessed the relative amplitudes of the different tidal constituents vary in a non linear manner depending on model water depth changes in the northeast atlantic tides are relatively minor for tidal simulations with water depths 30 m below to 5 m above present levels however the situation is more complicated in the shallower waters of the northwest european shelf examples are given from a number of locations results from the northeast atlantic model are used to run larger scale models of morecambe bay on the west coast of britain and the wash on the east coast the tidal changes within these embayments highlight the local nature of the variations in the amplitude of different tidal constituents and the importance of the scale at which modelling is carried out

on the postglacial isostatic adjustment of the british isles and the shallow viscoelastic structure of the earth summary observations of postglacial relative sea level rsl history at sites beyond the margins of the main accumulations of wu rm wisconsin devensian ice may be invoked to test the accuracy of global models of the glacial isostatic adjustment process the existing database of rsl time series for the british isles forms a continuous network of sites that sample the coasts of scotland england and wales fairly uniformly and which may be especially important in this regard not only are these 14c data for the holocene epoch of very high quality in terms of our knowledge of the coastal environment and relationship to palaeo sea level of each age measurement but they are especially numerous and relate to an island that was itself partly glaciated in the north essentially ice free in the south and located well outboard of the massive ice sheet that covered fennoscandia at the last glacial maximum lgm taken together the time series from 55 distinct locations allow us to perform a fairly stringent test of the recently formulated ice 4g vm2 global model of the isostatic adjustment process even without modification this model has been shown to fit most of the time series in the uk data set rather well in order to satisfy very recently published a priori constraints on the maximum thickness of the scottish ice sheet however we find that the lithospheric thickness the feature of the radial viscoelastic structure to which the rebound data from scotland are most sensitive must be somewhat reduced whereas the assumed thickness of the lithosphere in ice 4g vm2 was near to 120 km best fits to the scottish data require a lithospheric thickness near to 90 km this reduced value for lithospheric thickness agrees exceedingly well with the latest estimates of this earth property based on the inversion of oceanic geoid and topography data as the asymptotic thickness characteristic of the oldest ocean floor this would appear to be the best possible a priori estimate for the thickness of the cratonic lithospheres upon which the largest ice sheets of the late pleistocene are known to have rested we also demonstrate explicitly that inferences of the shallow viscoelastic structure beneath the british isles are strongly influenced by the details of the history of deglaciation at remote locations at antarctica in particular

holocene relative sea level movements along the north norfolk coast uk abstract relative changes in holocene sea level are reconstructed from foraminiferal assemblages in seven cores recovered from the intertidal zone of north norfolk eastern england a total of 33 radiocarbon and infra red stimulated luminescence dates provide a detailed chronological framework for these changes a transfer function approach developed from modern uk foraminiferal datasets establishes a series of 21 new sea level index points for this coastline which are combined with 18 existing index points and a further number of limiting values errors associated with changing tidal ranges through the holocene are reduced by adopting recently developed tidal models for this period this new approach allows the use of foraminiferal assemblages to be extended from the upper saltmarsh environment traditionally used for sea level studies to lower elevations in the tidal frame and include clastic detrital sediments the results confirm the previously observed trend of continuously rising sea levels in this area during the last 10 000 years which is consistent with a glacial isostatic adjustment model relative sea level rsl rises from an observed minimum of approximately 13 50 m od at about 7500 cal bp to approximately 4 0 m at about 5300 cal bp which equates to a mean rise of c 4 3 mm yr 1 subsequently rsl rose gradually to present levels although there is evidence that a minor reverse in this trend occurred between 4000 and 2000 cal bp when sea level fell by about 1 m to c 3 5 m the rate of land subsidence for north norfolk is 0 54 0 03 mm yr 1 inverse of late holocene sea level rise

holocene coastal change and geoarchaeology at howick northumberland uk the recent discovery of one of the earliest mesolithic occupation sites in northern britain at howick on the northumberland coast in association with multiperiod archaeological evidence nearby highlights the importance of uk coastal settings as focii of human occupation through the holocene environmental evidence from a nearby river valley 8 15 m of sediment ranging in age from about 12 000 cal bp to the present records local and regional environmental change twenty four radiocarbon dates based on plant macrofossils provide a strong chronological framework calcareous microfossil assemblages foraminifera ostracods have been recovered from the fine grained sediments recording a change from marine through to brackish and eventually freshwater conditions between about 8200 and 6500 cal bp a preliminary pollen study of the core has permitted a reconstruction of the regional vegetation as it responded to climatic amelioration and human influence upon the landscape radiocarbon dating and sedimentological evidence indicates a major hiatus between approximately 11 000 and 8000 years bp including the period of mesolithic occupation represented by a 30 cm layer of coarse sands and sandstone pebbles probably the result of a significant high energy event dated to about 8300 cal bp although not a typical tsunami deposit the age and context suggests that this may be associated with the storegga slide event already well documented along the eastern coast of scotland the sedimentary and biological remains at howick record environmental change over much of the holocene and are compared with other environmental change records from the region to provide an environmental framework for the archaeology of this coastline

low sea level tidal origin of celtic sea sand banks evidence from numerical modelling of m2 tidal streams abstract numerical modelling of m 2 tidal streams in the celtic sea with a sea level lowered by 100 m indicates tidal currents about twice as strong as those at present such currents would have been sufficient to generate and maintain the linear tidal sand banks now found in that region as moribund bedforms furthermore an indicated clockwise rotation of the major axes of the tidal ellipses at a sea level lowered by 100 m with respect to the present day is in the correct sense to further the comparison with modern examples of actively maintained linear tidal sand banks

a new holocene relative sea level curve for western brittany france insights on isostatic dynamics along the atlantic coasts of north western europe abstract this study presents new relative sea level rsl data that were obtained in the finistere region western tip of brittany france and the implications those data have for the understanding of the isostatic dynamics across north western europe and more specifically along the atlantic and channel coasts new stratigraphic sequences were obtained and analyzed to derive 24 new sea level index points in which 6 are basal these new data considerably increase the knowledge we have of the rsl evolution along the coasts of western brittany since the last 8 kyr b p from this new dataset rsl was estimated to rise continuously over the last 8 kyr with a major inflection at ca 6 kyr cal bp our results show large vertical discrepancies between the rsl records of brittany and south western uk with the latter plotting several meters below the new data from this comparison we suggest that the two regions underwent a very different pattern and or amplitude of subsidence during the last 8 kyr which has implications for the spatial and temporal pattern of the peripheral bulge of the european ice sheets we compared our data against predictions from glacio isostatic adjustment models gia models there are large misfits between rsl observations and the predictions of the global ice 5g vm2a peltier 2004 glac1 b tarasov and peltier 2002 tarasov et al 2012 briggs et al 2014 and regional uk models biis bradley et al 2009 bradley et al 2011 kuchar kuchar et al 2012 which can t be resolved through significant changes to the deglaciation history and size of the british irish ice sheet paleo tidal modelling corrections indicate regional changes in the tidal ranges played a negligible role in the data model misfits hence we propose that the misfits are due to some combination of i unaccounted mass loss of far field ice sheets antarctic ice sheet or laurentide ice sheet ii unresolved differences in the deglaciation history and size of the fennoscandian ice sheet or more likely iii significant lateral variations in the earth s structure across the english channel

analysis and interpretation of holocene sedimentary sequences in the humber estuary the interpretation of the holocene evolution of the humber estuary has been made possible only through integrated multidisciplinary studies involving inter alia drilling to obtain sedimentary records of the holocene estuary fill multi element carbon nitrogen sulphur and stable carbon isotope geochemistry heavy and clay mineralogy palaeomagnetism radio carbon dating and pollen diatom and foraminiferal studies eight chemostratigraphic suites and 14 palaeo environments have been recognized sediment types environments of deposition and provenance change in response to rising sea level showing a range from freshwater fluvial deposition of locally derived terrestrial sediment to intertidal and subtidal deposition of sediments from marine sources the methods used are illustrated with reference to sediment cores from inner and outer estuary locations the results show that holocene environmental characterization is most secure when a number of different but complementary techniques are used the integration of radiocarbon dates with palaeomagnetic and geochemical data improves the understanding of the presence and significance of time breaks which is crucial to constraining sedimentation rates and material budgets

partial resetting of the upb isotope system in monazite through hydrothermal experiments an sem and upb isotope study abstract natural monazites of different grain sizes were treated experimentally under hydrothermal conditions and their u pb isotope systematics measured before and after the runs runs were carried out with monazite grain size fractions ranging from 40 to 125 m in diameter and on 207 pb 206 pb ages close to 380 ma u concentrations remained always unchanged all recrystallized monazites from the powdered starting material define a discordia with intercept ages of 379 3 2 3 and 7 18 ma the latter indicating the hydrothermally induced pb loss at the time of the experiment sem observations of monazite grains from hydrothermally treated grain size fractions exhibited only minor dissolution features confined to the grain surfaces run products from monazite powders showed recrystallization and grain growth induced by a dissolution precipitation mechanism increasing temperature resulted in a distinct enlargement of grain sizes at 650 and 750 c a dissolution precipitation process in presence of a fluid phase rather than pb volume diffusion acts as a very efficient mechanism for the resetting of the u pb isotope system of monazites even at low temperatures this process is most important in shear zones where channelized fluid flow may occur

periwinkle littorina littorea intrashell δ18o and δ13c records from the mid holocene limfjord region denmark a new high resolution palaeoenvironmental proxy approach shells of the common intertidal gastropod littorina littorea both of recent and mid holocene origin were analysed along their growth spirals for seasonally induced variations in stable oxygen and carbon isotope compositions the subfossil specimens are from the stone age kitchen midden in ertebolle northern denmark dated between 5970 95 and 5070 90 bp the recent specimens were collected along a west east salinity gradient within the limfjord a limfjord mixing line of 0 25 parts per thousand change in delta 18 o v smow for each salinity unit was determined the recent littorina periwinkles display a calcite relationship of 0 22 parts per thousand change in shell delta 18 o per degrees c change in temperature as derived from the littorina equilibrium equation versus v pdb delta 18 o littorina delta 18 o water 5 250 0 224t degrees c by using this linearity together with maximum winter isotopic results we extracted a littorina growth stop isotherm equivalent to a temperature of 3 7 1 degrees c in order to constrain the climate and salinity in the limfjord region during the mid holocene we used this regression derived growth stop isotherm as a boundary condition the subfossil shells indicate a summer surface water temperature close to 22 1 degrees c together with a salinity of 31 1 psu these results suggest a more pronounced water exchange between the central limfjord and the north sea during the late atlantic time and in terms of temperature they indicate 2 4 degrees c warmer conditions than today

th pb ion microprobe dating of allanite allanite which is a common accessory mineral in a wide variety of rock types typically contains high concentrations of th and u thus an in situ method of u th pb dating of this phase would have broad application we describe a method to permit th pb ages of allanite to be determined with approximately 10 accuracy using a high resolution ion microprobe knowledge of the composition and substitution mechanisms of this complex mineral is key to understanding the relative ion ization efficiencies of th and pb the chemical compositions of three allanite samples used as age standards cima d asta pluton 275 5 1 5 ma atesina volcanic complex 276 3 2 2 ma la posta pluton 94 2 ma were determined using an electron microprobe permitting an assessment of matrix effects on ionization an ion microprobe calibration curve involving elemental and oxide species of th and pb i e 208 pb th vs tho 2 th yields highly scattered apparent ages when allanite age standards with different fe contents are used however a three dimensional plot of 208 pb th vs tho 2 th vs feo sio improves the accuracy of the calibration to about 10 even though this level of uncertainty is substantially greater than that expected for u th pb ion microprobe analyses of zircon or monazite th pb ages of allanite can still be used to address important geologic questions we used this method to date two metamorphic allanite grains from the footwall of the main central thrust nepal himalaya and an allanite grain from the pacoima canyon pegmatite california allanite inclusions in garnet from nepal yield significantly older ages than the coexisting monazite indicating that allanite formation in these rocks records a previous metamorphic cycle that predates slip along the fault the pacoima canyon allanite grain yields a younger age than that reported for zircon implying pb loss during cooling of the pegmatite

quaternary shelf sea palaeoceanography recent developments in europe abstract high quality palaeoceanographic reconstructions based on sequences preserved in shallow marine environments demonstrate that these constitute significant archives of climatic and oceanographic change such sequences are important first because their often very high resolution sometimes laminated nature enables high frequency cycles to be resolved and provides the basis for establishing spatial and temporal variability in the marine radiocarbon reservoir effect second sea level index points from shelves are important for the validation of glacio hydro isostatic geophysical models and for understanding sea level change during early deglaciation third shallow marine sequences contain excellent records of land ocean interaction often preserving paired terrestrial marine proxies in the same stratigraphic sequence a new development in shelf sea palaeoceanography is documenting the long term dynamics of shelf sea stratification this is the dominant hydrodynamic phenomenon of tide dominated shelf seas in the middle and high latitudes and has a profound influence on productivity and therefore global change through the carbon cycle detailing the evolution of seasonal stratification during eustatic highstands is therefore of relevance to the climate system

glacial rebound of the british isles ii a high resolution high precision model summary observations of ice movements across the british isles and of sea level changes around the shorelines during late devensian time after about 25 000 yr bp have been used to establish a high spatial and temporal resolution model for the rebound of great britain and associated sea level change the sea level observations include sites within the margins of the former ice sheet as well as observations outside the glaciated regions such that it has been possible to separate unknown earth model parameters from some ice sheet model parameters in the inversion of the glaciohydro isostatic equations the mantle viscosity profile is approximated by a number of radially symmetric layers representing the lithosphere the upper mantle as two layers from the base of the lithosphere to the phase transition boundary at 400 km the transition zone down to 670 km depth and the lower mantle no evidence is found to support a strong layering in viscosity above 670 km other than the high viscosity lithospheric layer models with a low viscosity zone in the upper mantle or models with a marked higher viscosity in the transition zone are less satisfactory than models in which the viscosity is constant from the base of the lithosphere to the 670 km boundary in contrast a marked increase in viscosity is required across this latter boundary the optimum effective parameters for the mantle beneath great britain are a lithospheric thickness of about 65 km a mantle viscosity above 670 km of about 4 5 lo2 pa s and a viscosity below 670 km greater than 4 x lo2 pas

holocene sea level database for the atlantic coast of the united states we have constructed a database of holocene relative sea level rsl observations for the atlantic coast of the united states the database contains 492 index points which locate the position of rsl in time and space and 344 limiting dates which constrain the minimum or maximum limit of former sea level the majority of the index points in the database are from 6 ka bp to present with only 7 older than 6 ka bp spatially index points are distributed between maine and south carolina but there is an absence of data from georgia and the atlantic coast of florida the database is sub divided into 16 regions based on the distance from the former laurentide ice sheet and are classified depending upon their susceptibility to compaction the index points and limiting data demonstrate that rsl did not exceed present 0 m during the holocene except potentially in regions 1 and 2 eastern maine and southern maine rates of rsl change were highest during the early holocene and have decreased over time due to the diminishing response of the earth s mantle to glacial isostatic adjustment and reduction of ice equivalent meltwater input along the atlantic coast of the united states the linear rate of rsl rise prior to 4 ka bp ranged from 0 5 to 4 5 mm a 1 compared to 0 6 1 8 mm a 1 from 4 ka bp to ad 1900 the database suggests minimal 0 3 mm yr changes in these rates of rsl rise during the late holocene deglaciation of the laurentide ice sheet caused the spatial variability captured by the database the maximum rate of late holocene and ongoing rsl rise occurred in mid atlantic regions new jersey and inner delaware because of collapse of the peripheral forebulge

glacial rebound of the british isles i preliminary model results summary observations of sea level change from localities around the british coastline indicate that major spatial and temporal variations have occurred over the past 15000 10000yr these observations provide a valuable data set for testing models of glacial rebound and for estimating the earth s response to surface loading as well as for placing broad constraints on models of the ice sheet over the northern british isles in late devensian time simple models have been developed to examine the criteria required for a high precision rebound model suitable for an inversion of the observations of sea level change for earth and ice model parameters for such a model to have a precision of better than 1 m these requirements include 1 introduction of the fennoscandian and more distant ice sheets into the model both as contributions to the sea level rise and to the crustal deformation of the associated changing ice and water loads 2 an expansion of the ice and meltwater loads to very high spherical harmonic degree including terms up to about 240 for the water load term 3 the development of higher iteration solutions of the sea level equation in order to model accurately the meltwater load contribution to sea level change 4 the introduction of loading cycles before the attainment of the last glacial maximum for both the british ice sheet and the other major but more distant ice sheets and 5 the introduction of time dependent coastlines during the period of rapid global sea level rise the sea level predictions are strongly dependent on both earth model and ice model parameters but because observations are available from a wide range of locations within and beyond the former ice sheet margins some separation of the two types of parameters is possible for example the models exclude the possibility that a substantial ice load occurred over the north sea between scotland and norway in late devensian time and that the maximum ice thickness over northern great britain is unlikely to have exceeded about 1500 m during the last glacial maximum the earth model parameters that can be resolved are the lithospheric thickness and the upper mantle viscosity a high resolution model incorporating the above model criteria and used to infer ice and earth model parameters from the observations of sea level change is developed in the accom panying paper

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

holocene relative sea level changes in the inner solway firth abstract bio and lithostratigraphic data from four sites from the inner solway firth allow an accurate reconstruction of holocene rsl changes in the estuary radiocarbon assays give eleven new sea level index points providing a total of 24 reliable index points for the inner solway firth these data show a consistent pattern of rapid rsl rise during the early holocene culminating in a mid holocene sea level maximum then a gradual fall to the present day level detailed analysis of this dataset quantifies for the first time differential crustal movement between the north and south shores of the solway firth these data are used to test the accuracy of quantitative isostatic rebound models of lambeck and peltier and show there is good general agreement between the data and the models especially during the early holocene the models predict the mid holocene sea level peak slightly later than shown by the data c 500 and c 2000 yr this may be partly due to lack of resolution in the models and for the south solway the maximum altitude at this peak is 1 and 2 5 m too high in the two models the data are also compared to the isobase models of the main postglacial shoreline showing slight diachroneity between the north and south shore but otherwise general agreement with the postulated age and indicating that the altitude of this feature is 1 3 m higher than suggested by the models

why this revolution explaining the major technical shift in southwestern europe during the 7th millennium cal bc during the course of the 7th millennium cal bc a major change occurred in stone working techniques and tool types among the lithic industries of mesolithic hunter gatherers in north africa and western europe these mutations not only affected the function and shape of certain tools but also modified volume management and the techniques used for blade removal this article proposes a new exploration of this shift which is the most important during the mesolithic in europe based on the interrogation of a database of 570 sites using very strict ordering criteria the examination of the first occurrences of these industries region by region reveals a diffusionist process that seems to begin in north africa tunisia at the end of the 8th or the very beginning of the 7th millennium cal bc before spreading progressively towards the atlantic ocean the data are not yet reliable enough to understand the process beyond the north of the loire river northern france it then underwent a regional stylistic diversification everywhere this technical mutation has not been recorded for bone tools or personal ornaments it was not accompanied by a transformation in social organization such as for cemeteries during the early mesolithic an analysis of the available data also calls into question all the economic changes sometimes evoked for these periods climatic change does not have a direct impact on this phenomenon apart from portugal which is on the geographic fringe of this shift the 6200 cal bc climatic crisis clearly occurred after this diffusion and had no direct effect on its development on the other hand the geographic modifications induced by the holocene warming clearly affected the extension of this phenomenon to western europe with the marine transgression

flandrian sea level changes in the fenland ii tendencies of sea level movement altitudinal changes and local and regional factors stratigraphic micropalaeontologic and radiocarbon data show that since c 6500 bp the fenland has been influenced by 7 periods of positive sea level tendencies and by 6 periods of negative sea level tendencies despite the numerous problems associated with the reconstruction of past altitudes of sea level the periods of positive sea level tendencies were clearly characterised by a rise in sea level the development of transgressive overlaps and a landward movement of the coastline the periods of negative sea level tendencies were characterised by the development of regressive overlaps a seaward movement of the coastline and a reduced or negative rate of sea level rise the various altitudinal errors do not permit the incontrovertible distinction of periods of falling sea levels all changes within the fenland were not synchronous and local factors influenced the exact nature of each sea level indicator dominant regional and local factors have been identified for different areas and different time periods the chronological and spatial characteristics of the sequences within the fenland are best explained by a palaeocoastline without supratidal barriers controlling sedimentation the data indicate an average crustal subsidence in the fenland of 0 9m 1000 years since c 6500 bp and the pattern of positive and negative tendencies of sea level movement is also seen in the chronologies for north west england and north east scotland