derivation of δ18o from sediment core log data implications for millennial scale climate change in the labrador sea sediment core logs from six sediment cores in the labrador sea show millennial scale climate variability during the last glacial by recording all heinrich events and several major dansgaard oeschger cycles the same millennial scale climate change is documented for surface water 18o records of neogloboquadrina pachyderma left coiled hence the surface water 18o record can be derived from sediment core logging by means of multiple linear regression providing a paleoclimate proxy record at very high temporal resolution 70 years for the labrador sea sediment core logs contain important information about deepwater current velocities and also reflect the variable input of ice rafted debris from different sources as inferred from grain size analysis the relation of density and p wave velocity and magnetic susceptibility for the last glacial faster deepwater currents which correspond to highs in sediment physical properties occurred during iceberg discharge and lasted from several centuries to a few millennia those enhanced currents might have contributed to increased production of intermediate waters during times of reduced production of north atlantic deep water hudson strait might have acted as a major supplier of detrital carbonate only during lowered sea level greater ice extent during coldest atmospheric temperatures over greenland deepwater currents increased during iceberg discharge in the labrador sea then surface water freshened shortly thereafter while the abrupt atmospheric temperature rise happened after a larger time lag of 1 kyr the correlation implies a strong link and common forcing for atmosphere sea surface and deep water during the last glacial at millennial timescales but decoupling at orbital timescales

do swarms of migrating barchan dunes record paleoenvironmental changes a case study spanning the middle to late holocene in the pampa de jaguay southern peru swarms of barchan dunes are common in arid environments unlike immobile or slowly moving dunes whose stratigraphy can be used to reconstruct paleoenvironmental changes the high migration rate of barchans seems to prohibit their use as geoarchives in this paper a possible use of barchan swarms for paleoenvironmental reconstructions is presented the approach is based on dune migration in a case study based on 500 dunes in the pampa de jaguay aeolian transport corridor in coastal southern peru middle to late holocene changes in the supply of aeolian material are inferred from calculating the time of dune initiation at the coastline limitations posed by the assumptions underlying this approach are discussed

late holocene diatom biostratigraphy and sea level changes in the southeastern beaufort sea late holocene sediments from the atkinson point area were analysed to provide quantitative reconstructions of recent sea level changes in the southeastern beaufort sea the succession of diatom assemblages in five cores revealed paleoenvironmental changes induced by the transgression of the beaufort sea during successive periods of lacustrine conditions breaching and flooding of thermokarst lakes by the sea and the landward migration of sandy spits based on radiocarbon dates and quantitative paleodepth determinations a relative sea level curve for the late holocene has been developed despite a loss of temporal precision due to old carbon contamination an envelope of sea level change has been defined for the last 2 ka bp suggesting a sea level rise in the order of 1 1 mm a 1 for the last millennium this paper presents the first sea level reconstruction inferred from a diatom based transfer function it represents an improvement over traditional methods which were limited to qualitative estimates of

dating methods and geomorphic evidence of palaeoenvironmental changes at the eastern margin of the south peruvian coastal desert 14 30 s before and during the little ice age abstract the atacama desert is known to be one of the driest places on earth however in the study area between ica and nasca south peru 75 76 w 14 15 s palaeoclimate proxies show several semi arid phases during the holocene a more humid period during the early holocene favoured an open grass land which allowed the accumulation of desert loess eitel b hecht s machtle b schukraft g kadereit a wagner g kromer b unkel i reindel m 2005 geoarchaeological evidence from desert loess in the nazca palpa region southern peru palaeoenvironmental changes and their impact on pre columbian cultures archaeometry 47 137 158 the paracas and nasca cultures existing in that region between the 9th century bc and 7th century ad had propitious conditions to evolve and to settle close to the rivers fed by the monsoonal precipitation in the cordillera occidental culminating aridity after 600 ad might have caused the collapse of the nasca civilization the onset of semi arid climate towards the end of the late intermediate period 14th century ad allowed a reoccupation of the area here we present 14c and osl data from sediments of river terraces a debris flow and loess snails scutalus sp indicating appreciable geomorphic activity between 1390 and 1714 cal ad this phase is isochronous to the little ice age period on the northern hemisphere and to an increase in the ice accumulation on the quelccaya glacier in the peruvian altiplano thompson l g mosley thompson e bolzan j f koci b r 1985 a 1500 year record of tropical precipitation in ice cores from the quelccaya ice cap peru science 229 971 973

single zircon u pb ages and geochemistry of granitoid gneisses from sw poland evidence for an avalonian affinity of the brunian microcontinent seven granitoid gneisses from the contact zone between the eastern margin of the variscan belt and the brunian microcontinent in sw poland have been dated by ion microprobe and 207 pb 206 pb single zircon evaporation methods the zircons define two age groups for the gneiss protoliths 1 late neoproterozoic c 576 560 ma and 2 early palaeozoic c 488 503 ma granites the granitoid gneisses belonging to the basement of the brunian microcontinent contain abundant mesoproterozoic to latest palaeoproterozoic inherited material in the range of 1200 1750 ma the gneisses of the variscan crustal domain lack mesoproterozoic inherited zircon cores trace element geochemistry of proterozoic gneisses reveals features resembling either volcanic arc or post collisional granites the studied rocks are geochemically similar to other proterozoic orthogneisses derived from the basement of the brunian microcontinent gneisses with early palaeozoic protolith ages are geochemically comparable to granitoid gneisses widespread in the adjacent sudetic part of the bohemian massif and are considered characteristic of peri gondwanan crust our data prove the dissimilarity between the brunia plate and the westerly terranes of the variscan belt the occurrence of granitic gneisses with late neoproterozoic protolith ages and widespread mesoproterozoic inheritance in our dated samples support an east avalonian affinity for the brunian microcontinent in contrast the abundance of gneisses derived from an early palaeozoic granitic protolith and devoid of mesoproterozoic zircon cores supports the armorican affinity of the variscan domain bordering on the brunia plate from the west structural evidence shows that the eastern segment of the variscan belt is juxtaposed against the brunian microcontinent along a n s trending tectonic contact possibly equivalent to the rheic suture

holocene relative sea level changes and coastal vegetation history at kentra moss argyll northwest scotland abstract a late holocene fall in relative sea level in northwest scotland from ca 1 3mm yr 1 to ca 1 0 mm yr 1 is interpreted from lithostratigraphic biostratigraphic chronostratigraphic and numerical analyses of fossil tidal marsh and acidic peat bog communities elevated by isostatic uplift pollen diatom and stratigraphic data from contemporary depositional environments are used to define the indicative range 0 2 m and reference water level mean high water of spring tides or highest astronomical tide of thirteen dated sea level index points no holocene intertidal sediments are recorded above 7 7 m od and all sea level index points are younger than ca 4 kyr b p in parts of kentra moss beyond the limit of holocene intertidal clastic sedimentation raised bog communities were established by at least 8 3 kyr b p these age and altitude parameters differ from those interpolated for the main postglacial shoreline but support a regional model in which isostatic uplift continues at present in the kentra moss area

is there a relationship between magmatic fabrics and brittle fractures in plutons a view based on structural analysis anisotropy of magnetic susceptibility and thermo mechanical modelling of the tanvald pluton bohemian massif abstract the present study focuses on the thermal and mechanical aspects of cooling of plutonic systems with respect to their internal structure analysis of the tanvald pluton and the nearby liberec granite the krkonose jizera plutonic complex bohemian massif using the anisotropy of magnetic susceptibility ams method indicates the decoupled magnetic fabrics formed by different processes in these two plutons two regional sets of vertical fractures cut across the plutons and their host rocks they are interpreted as having been formed as opening mode fractures joints after emplacement and cooling our thermo mechanical finite element modelling indicates that the thermal stresses within the tanvald pluton were compressive and that fracture criteria were not met during pluton cooling these results imply that the emplacement depth and confining pressure significantly affect the state of stress within a pluton during cooling and may play a crucial role in the formation of early fractures in plutons consequently the formation of early fractures during pluton cooling is driven by external conditions overriding the role of internal magmatic fabrics we argue that no genetic geometric or temporal correlation can exist between magmatic fabrics and fractures in granitoid plutons and thus that the original concept of hans cloos based on fabric joints relationships should be reconsidered instead an alternative classification of fractures in plutons should include cooling fractures syntectonic fractures uplift fractures and post uplift fractures

shrimp u pb zircon geochronology of the strzelin gneiss sw poland evidence for a neoproterozoic thermal event in the fore sudetic block central european variscides zircon ages recorded in gneissic rocks have recently been used as criteria to define and correlate various tectonic units and crustal blocks in the central european variscides a shrimp u pb zircon geochronological study of the strzelin gneiss in the fore sudetic block sw poland indicates the presence of 1 inherited zircon cores of palaeo to mesoproterozoic 206pb 238u ages between ca 2 000 and 1 240 ma and 2 zoned rims of neoproterozoic age with two distinct means of 600 7 and 568 7 ma the proterozoic age range of the cores suggests that different precambrian crustal elements were the source for the protolith of the gneiss a likely scenario is the erosion of various proterozoic granites and gneisses sedimentation after 1 240 ma and partial resistance of the original components to subsequent metamorphic dissolution and or anatectic resorption in neoproterozoic times the zoned zircon rims of both of the younger neoproterozoic ages are indistinguishable in the cathodoluminescence images the data are interpreted in terms of two different thermal events inducing zoned zircon overgrowth at ca 600 and 568 ma in general the new results confirm earlier assumptions of the proterozoic age of the gneiss protoliths and indicate their similarity to orthogneisses in the east sudetes tectonic domain e g the velke vrbno and desna gneisses the neoproterozoic dates are different from the age of 504 3 reported earlier for the go ciecice gneiss from a neighbouring locality in the strzelin massif the new data strongly indicate a moravo silesian bruno vistulian affinity for the strzelin gneiss and support the hypothesis that the strzelin massif lies within the tectonic boundary zone between the west and east sudetes domains which represents the northern continuation of the moldanubian thrust

numerical model of the geothermal regime on the beaufort shelf arctic canada since the last interglacial 1 a finite element geothermal model is developed for the outer mackenzie delta beaufort sea shelf to predict permafrost evolution since the last interglacial 130 116 kabp cal the purpose is to reconcile sparse observations of the depth and extent of ice bonded permafrost with sediment properties and the paleoenvironment sea level curves determine as a function of time areas of the shelf that were subaerially exposed promoting permafrost aggradation and areas that were submerged promoting permafrost degradation assuming as a model starting point that a paleoclimate similar to today persisted through the last interglacial permafrost subsequently aggrades in depth and advances seaward from the present shoreline to the shelf slope bathymetric break by the last glacial maximum lgm 26 kabp cal modeled permafrost exhibits reduced growth in depth and seaward progression that correlate with early and middle wisconsin stillstands in sea level following the lgm and rise in sea level offshore permafrost degrades and permafrost base rises 100 m to its present depth of 600 m the offshore limit of modeled ice bonded permafrost lies at the 95 m isobath within 1 km of the bathymetric shelf slope break the model replicates features of offshore permafrost body observed seismically and demonstrates that warm outflow from the mackenzie river depresses the upper surface of offshore permafrost by tens of meters to the 20 m isobath although pleistocene permafrost predated the wisconsinan the model demonstrates that the paleoenvironment of the last 125 000 years is sufficient to develop the depth seaward extent and principal features of the permafrost body

fragile landscapes fragile civilizations how climate determined societies in the pre columbian south peruvian andes abstract this paper presents alternating periods of geo ecological fragility and stability in a highly sensitive environmental setting the desert margin area of southern peru 14 5 s there we have to state that fragility was dominantly triggered by climatic changes which induced several oscillations of the desert margin during the mid holocene the study area received the holocene maximum of precipitation soil formation occurred and the desert retreated as loess paleosoil formation documents in contrast the titicaca region further south east experienced extreme drought at that time this regional antagonism between humid and dry conditions was a result of meridional shifts in moisture transport across the andes and occurred also during pre columbian times considering a coincidence between environmental and cultural changes we state that success and decline of civilizations were dominated by hydrological oscillations triggering fertility as well as a critical loss of natural resources fragile periods i e periods of geomorphological activity occurred contemporaneous with cultural transitions in response to spatial changing resources cultural foci were shifted so the success of pre columbian civilizations was closely coupled to areas of geo ecological favorability which were directly controlled by distinct regional impacts of large scale circulation mechanisms including el nino southern oscillation enso this spatial view on non uniform environmental and cultural changes has not been thoroughly considered before therefore for the first time this paper offers geomorphological evidence for diachronous andean agri cultural development which was geographically determined

coastal retreat and shoreface profile variations in the canadian beaufort sea the coastline of the southern canadian beaufort sea consists primarily of unconsolidated bluffs although the sea is ice free for 3 months of the year and wave energy is restricted by pack ice the coast is undergoing regional retreat with erosion rates as high as 10 m a 1 in some locations simple and multiple regression analyses were carried out to determine the degree of correlation between the mean retreat rate measured at various locations and the different parameters that may control shoreline recession sediment texture ground ice content cliff height wave energy and shoreface gradient revealed medium to poor correlation with erosion rates showing that the recessive evolution of the coastline can not be explained solely by wave induced and subaerial processes the comparison of nearshore echo sounding records from 1987 with bathymetry from 1971 showed substantial erosion up to 1 m of the submarine profile between 12 and 15 m of water there is strong evidence that this erosion has been caused by sea ice gouging on the seafloor from depths of 5 to 9 m accretion has taken place possibly induced by ice push processes and inshore of the 5 m isobath wave and current erosion of the shoreface has occurred these results suggest that the erosion of the inner shelf by ice gouging drives the erosion observed inshore on the coastal bluffs and nearshore zone as the shoreface profile strives for a state of dynamic equilibrium

multistage magma emplacement and progressive strain accumulation in the shallow level krkonose jizera plutonic complex bohemian massif 1 field relationships combined with new u pb zircon geochronology suggest that the shallow level krkonose jizera plutonic complex northern bohemian massif was assembled successively from bottom to top starting with emplacement of the separately evolved s type tanvald granite 317 3 2 1 ma followed by at least two voluminous batches of the i type porphyritic liberec 319 5 2 3 ma and jizera 320 1 3 0 ma and 319 3 3 7 ma granites the intrusive sequence was completed by uppermost minor intrusions of the equigranular harrachov 315 0 2 7 ma and krkonose granites the i type granites exhibit an unusually complex pattern of superposed feldspar phenocryst and magnetic fabrics as revealed from the anisotropy of magnetic susceptibility ams the outer liberec granite preserves margin parallel foliations and lineations interpreted to record emplacement related strain captured by cooling from the pluton floor and walls in contrast the inner jizera harrachov and krkonose granites were overprinted by synmagmatic strain resulting from dextral movements along regional strike slip faults cutting the opposite ends of the plutonic complex late stage felsic dikes in the liberec and jizera granites reorient from horizontal to vertical lineation perpendicular attitude in response to changing the least principal stress direction whereas mafic schlieren do not do so representing only randomly oriented small scale thermal mechanical instabilities in the phenocryst framework in general this case example challenges the common approach of inferring pluton wide magma flow from interpolated foliation lineation and schlieren patterns more likely magmatic fabrics in large plutons record complex temporal succession of superposed strains resulting from diverse processes at multiple scales

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

multiple magmatic fabrics in the sazava pluton bohemian massif czech republic a result of superposition of wrench dominated regional transpression on final emplacement abstract the sazava pluton 354 ma of the central bohemian plutonic complex was emplaced syntectonically into the upper crustal neo proterozoic and lower paleozoic host rock along the se margin of the tepla barrandian zone bohemian massif czech republic the host rock is characterized by transpressional fabric dominated by steep se nw dipping foliations and subhorizontal ne sw stretching lineations associated with flattening to a plane strain ellipsoid the strain intensity degree of oblateness and temperature conditions of deformation increase in the host rock towards the pluton margin in the pluton quartz microfabric indicates progressive cooling of the syntectonically emplaced magma the ams method revealed multiple magmatic fabrics and lateral variations in the shapes of the ams ellipsoid and the magnetic fabric intensity in the pluton the central part of the pluton yields prolate shapes of the ams ellipsoid and a low degree of anisotropy with preserved steep magnetic lineations whereas along the pluton margins oblate ams ellipsoids are associated with a high degree of anisotropy we interpret the multiple fabrics and the partially decoupled fabric pattern between the host rock and the pluton as being a result of superposition of regional tectonic strain during highly oblique transpression on emplacement related intrusive strain where outer solidified and more rigid edges of the pluton enabled preservation of older steep fabrics in its interior

interpreting magmatic fabric patterns in plutons abstract most plutons have widespread magmatic fabrics the interpretation of which remains controversial we propose a method to constrain likely causes of fabric patterns the application of which indicates the following 1 preserved fabric patterns often form after chamber construction and only rarely provide information about ascent or emplacement 2 fabrics are poor recorders of total strain and are easily reset preserving only the last increment of strain during crystallization 3 in magmatic systems mechanically decoupled from host rocks patterns may result from strain during internally driven flow filter pressing or porous flow in relatively static chambers or by final increments of strain during emplacement 4 with greater emplacement depths fabric patterns increasingly reflect strain caused by regional deformation and 5 given that magmatic fabrics are easily reset and reflect only the last increment of strain of comparatively weak materials they may provide a relatively direct record of paleostress in orogenic belts

en echelon vein array development in extension and shear a subdivision of en echelon vein arrays is proposed based on the geometry of sets of transcurrent arrays from the lower carboniferous rocks in the se midlands of ireland the parameter vein zone angle is proportional to the array orientation for arrays developed through secondary failure in shear zones shear arrays for arrays developed during propagation of an extension vein extension arrays is proportional to the overlap of veins in the array p o criteria for field distinction together with the different methods of kinematic interpretation that are required for the two types of arrays are described for shear arrays the average trends of the two members of the conjugate set are calculated and the axis of principal shortening strain z bisects these the average trend of extension arrays is parallel to that of extension veins and is therefore normal to the maximum extensional strain axis x

u pb ages from sw poland evidence for a caledonian suture zone between baltica and gondwana faunal and palaeomagnetic evidence suggests the existence of a c 3000 km wide tornquist sea between gondwana and baltica in early ordovician times which narrowed to 50 2 ma an unmetamorphosed ophiolite gives a 420 20 2 ma age whilst in two other terranes amphibolite facies island arc lavas have fossiliferous lower ludlow 424 415 ma sequences all are unconformably overlain by unmetamorphosed upper devonian conglomerates a sinistral transpressive regime is observed in regionally extensive mylonite zones titanite and zircon ages 338 2 3 and 339 4 ma record variscan magmatism the data suggest considerable narrowing of the tornquist sea during the ordovician continuing ocean floor and island arc activity in the silurian and final sinistral transpressive closure by the mid devonian

a sea level curve for the canadian beaufort shelf radiocarbon dated peat and peaty clay samples from geotechnical boreholes in the canadian beaufort continental shelf have been used to reconstruct a late quaternary relative sea level rsl curve the samples were carefully selected and evaluated using palynological techniques to ensure that reasonable age error limits could be given to each sample the dated samples were then related to the local geological setting using seismic profiles to determine the environment of deposition the resulting data show a rise of 140 m in rsl since 27 000 years bp a minor lowering of rsl at some time between 20 000 and 10 000 years bp is inferred from acoustic data contributions from basin subsidence sediment loading and consolidation account for 35 m of the total rsl rise the rsl curve is interpreted in the light of recent models of the isostatic and eustatic responses of the earth s crust at the laurentide ice sheet margin ice may have been more extensive during the middle wisconsinan than previously thought a

diatoms as quantitative paleodepth indicators in coastal areas of the southeastern beaufort sea arctic ocean abstract surface sediment diatom assemblages in depth profiles along the southeastern beaufort sea coasts canada were analysed to describe the relationship between species distribution and water depth of deposition the 74 coastal stations sampled were distributed in several sedimentary environments from salt marshes to the inner shelf the relationship between diatom species distribution and water depth was examined using canonical correspondence analysis cca and partial cca the water depth accounted for 9 7 of the variance in the data set the diatom water depth relationship is believed to be controlled by the shoreface circulation which results in a shift in the relative abundance of the epipsammon epipelon and plankton along the water depth gradient upper shoreface assemblages are dominated mainly by epipelic species and a few number of epipsammic taxa whereas deeper environments are dominated by planktonic species a transfer function was derived using weighted averaging regression and calibration to reconstruct the water depth of deposition over the coastal interval from mean sea level to a maximum of 14 m depth on the coastal shelf of the southeastern beaufort sea the transfer function allows relative sea level to be predicted from fossil diatom assemblages with a root mean square error of 1 43 m this model is likely to produce reliable water depth inferences along the southeastern beaufort sea coasts and in other shallow sandy microtidal environments dominated by low energy waves and influenced by freshwater discharge the transfer function was used to provide quantitative paleodepth inferences for late holocene sediments from the atkinson point area based on fossil diatom assemblages

shear criteria in granite and migmatite deformed in the magmatic and solid states microstructural criteria for the determination of the sense of shear in rocks homogeneously deformed in the partially melted state are similar to those which apply to solid state deformation sense of shear determination is either direct deduced from the sense of rotation of markers or indirect involving the obliquity between the shear and foliation planes or between the successive foliations imprinted at different stages of progressive deformation this study is a by product of the detailed structural and microstructural investigation of a high grade metamorphic rock pile variscan vosges massif france which underwent subhorizontal shearing during partial melting and further solidification depending on the rock chemistry on the position in the pile and the relative timing of progressive deformation layered migmatites and homogeneous granites were variously deformed in the partially melted and solid states the sense of shear obtained from these rock types using the criteria presented here consistently gives a top to sw direction

tidal marsh stratigraphy sea level change and large earthquakes i a 5000 year record in washington u s a abstract many of the estuaries of the pacific northwest of the u s a and canada contain stratigraphic sequences typified by alternating peat mud couplets recent studies in this region interpret such couplets as the product of repeated large magnitude s or 9 earthquakes on the cascadia subduction zone the resultant pattern of land level movements is described by a model the earthquake deformation cycle of coseismic land subsidence followed by land uplift during interseismic strain accumulation however peat mud couplets similar to those recorded in the pacific northwest are found on other less tectonically active temperate latitude coasts such as northwest europe and the atlantic coast of the u s a where they have been interpreted as the product of non seismic coastal processes in this paper we apply the methods and scientific framework common to sea level investigations in northwest europe to a sequence of peat mud couplets recorded in the lower johns river an estuary in southern washington to provide a test of the earthquake deformation cycle stratigraphic investigations of the intertidal sediments along the lower johns river using lithological pollen diatom and foraminiferal data show evidence for eight coastal submergence events during the last 5000 years to evaluate the earthquake deformation cycle we assess the lateral extent of peat mud couplets the synchroneity of submergence the presence of tsunami deposits accompanying submergence and the suddenness and amount of submergence each submergence is shown to be accompanied by changes in coastal sedimentation broadly commensurate with those predicted by the earthquake deformation cycle demonstrating the continued intermittent seismic activity of the cascadia subduction zone throughout the mid and late holocene quantitative analyses of contemporary and fossil biostratigraphic data using twinspan and detrended correspondence analysis enable us to estimate the magnitude of submergence accompanying each peat mud couplet one event was accompanied by submergence of about 1 5 m or more four events by intermediate submergence of about 1 0 5 m and a further three events by submergence of

mangrove pollen of indonesia and its suitability as a sea level indicator we investigated the mangroves of southeast sulawesi indonesia to assess their potential as proxies for reconstructing sea level during the holocene initial investigations confirmed that the mangrove species demonstrate zonations parallel to the shoreline and are dominated by the family rhizophoraceae with avicennia heritiera and sonneratia also important constituents of the mangroves we investigated the vertical distributions of pollen assemblages at three sites partial cca analysis demonstrated that at all three sites elevation was a significant control on the distribution of pollen assemblages in surface samples we combined the three contemporary transects to develop a regional transfer function to explain the relationship between the surface assemblages and elevations using the maximum likelihood ml method the developed transfer function indicated mangrove pollen can be used as a precise indicator of past sea levels with an error of 0 22 m the transfer function was applied to two fossil cores from the wakatobi marine national park and evaluated using the modern analogue technique both cores showed similar patterns in changes of palaeo mangrove elevation and had modern analogues in the contemporary training set we conclude that mangrove pollen is a suitable proxy for reconstructing sea level in tropical environments

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

granite tectonics revisited insights from comparison of k feldspar shape fabric anisotropy of magnetic susceptibility ams and brittle fractures in the jizera granite bohemian massif in the jizera granite of the krkonose jizera plutonic complex northern bohemian massif contrasting patterns of magmatic k feldspar fabrics and brittle fractures characterize different structural levels of the pluton the uppermost exposed level at 800 1 100 m above sea level is dominated by flat foliation that overprints two steep foliations in contrast k feldspar shape fabric in an underground tunnel 660 m above sea level shows complex variations in orientation and intensity magnetic fabric carried by coaxial contributions of biotite magnetite and maghemite is homogeneous along the examined section of the tunnel and is decoupled from the k feldspar fabric the jizera granite is crosscut by two regional sets of subvertical fractures ne sw and nw se and by near surface exfoliation joints the multiple fabrics are inferred to reflect a complex magmatic strain history at different structural levels of the pluton bearing little or no relationship to the fracture network in contrast to the original concept of hans cloos granite tectonics we conclude that no simple genetic relationship exists between fabrics and fractures in plutons an alternative classification of fractures in plutons thus should avoid relationships to magmatic fabrics and should instead consist of cooling syntectonic uplift and post uplift fractures

timing of post collisional volcanism in the eastern part of the variscan belt constraints from shrimp zircon dating of permian rhyolites in the north sudetic basin sw poland the final stages of the variscan orogeny in central europe were associated with voluminous granitic plutonism and widespread volcanism four samples representative of the main rhyolitic volcanic units from the stephanian permian continental succession of the north sudetic basin in the eastern part of the variscan belt were dated using the sims shrimp zircon method three samples show overlapping 206 pb 238 u mean ages of 294 3 293 2 and 292 2 ma and constrain the age of the rhyolitic volcanism in the north sudetic basin at 294 292 ma this age corresponds to the early permian sakmarian stage and is consistent with the stratigraphic position of the lava units the fourth sample dated at 288 4 ma reflects a minor younger stage of sub volcanic activity in the artinskian the silicic activity was shortly followed by mafic volcanism the rhyolite samples contained very few inherited zircons possibly owing to limited contribution of crustal sources to the silicic magma or owing to processes involved in anatectic melting and magma differentiation e g resorption of old zircon by zr undersaturated melts the shrimp results and the stratigraphic evidence suggest that the bimodal volcanism terminated the early short lived 10 15 ma and vigorous stage of basin evolution the permian volcanism in the north sudetic basin may be correlated with relatively late phases of the regional climax of late palaeozoic volcanism in central europe constrained by 41 published shrimp zircon age determinations at 299 291 ma the permian volcanism and coeval plutonism in the ne part of the bohemian massif can be linked to late variscan post collisional extension

the 40ar 39ar ages from the west sudetes ne bohemian massif constraints on the variscan polyphase tectonothermal development

geochronology and nd sr systematics of lusatian granitoids significance for the evolution of the variscan orogen in east central europe a variety of pre variscan granitoids and two variscan monzogranites occurring in the central and western parts of the lusatian granodiorite complex lgc saxonia were dated by the single zircon evaporation method complemented by whole rock nd isotopic data and rb sr whole rock and mineral ages the virtually undeformed pre variscan granitoids constitute a genetically related mostly peraluminous magmatic suite ranging in composition from two mica granodiorite muscovitebearing biotite quartz diorite tonalite and granodiorite to biotite granodiorite and monozogranite

a model for a continental accretionary wedge developed by oblique collision the ne bohemian massif structural and metamorphic investigations of the northeastern margin of the bohemian massif indicate three main sequential devonian carboniferous tectonic events 1 devonian rifting 2 early carboniferous oblique underthrusting and formation of a continental accretionary wedge 3 eduction of the wedge and late carboniferous transpression devonian rifting of the brunia microcontinent resulted in the formation of two crustal scale boudins associated with the development of two syn rift devonian basins this extensional template strongly influenced the nature of the ensuing variscan contractional deformation early carboniferous 350 330 ma progressive highly oblique underthrusting of the two crustal boudins beneath the lugian terrane to the west generated syn deformational barrovian metamorphism and the formation of a continental accretionary wedge the wedge was further compressed by continued underthrusting of brunia which resulted in the successive vertical extrusion eduction of an upper and lower allochthon derived from the more deeply underthrust crustal boudin the eduction was terminated by a late carboniferous 330 310 ma transpressional event resulting from continued plate convergence release of mantle derived magma during late stage eduction thermally softened the transpressional zones in the more external parts of the wedge the resultant differential displacements gave rise to extensional unroofing of the internal part of the wedge

deducing the ancestry of terranes shrimp evidence for south america derived gondwana fragments in central europe we present here an example of how the sensitive high resolution ion microprobe shrimp zircon dating method can provide a terrane specific geochronological fingerprint for a rock and thus help to reveal major tectonic boundaries within orogens this method applied to inherited zircons in a ca 580 ma metagranitoid rock from the eastern bohemian massif has provided for the first time in the central european variscan basement unequivocal evidence for mesoproterozoic and late paleoproterozoic geologic events ca 1 2 ga 1 5 ga and 1 65 1 8 ga the recognition of such zircon ages has important consequences because it implies that parts of the precambrian section of variscan central europe were originally derived from a grenvillian cratonic province as opposed to the common assumption of an african connection a comparison with previously published shrimp data suggests however that these mesoproterozoic and late paleoproterozoic zircon ages may be restricted to the moravo silesian unit in the eastern variscides whereas the saxothuringian and moldanubian zones appear to contain a typical north african i e neoproterozoic plus eburnian inherited zircon age spectrum this finding supports new tectonic concepts according to which variscan europe is composed of a number of completely unrelated terranes with extremely different paleogeographic origins the moravo silesian unit can be best interpreted as a peri gondwana terrane which was situated in the realm of the amazonian cratonic province by the late precambrian comparable to the avalonian terranes of north america and the united kingdom

crustal scale en echelon p shear tensional bridges a possible solution to the batholithic room problem the apparent paradox of voluminous granitoid emplacement in an overall compressional magmatic are has been somewhat alleviated by the idea of pluton emplacement in tension cracks and dilational jogs within arc parallel strike slip fault systems as an alternative hypothesis we propose that an en echelon p shear array provides a continuous batholith scale zone of dilation along the trend of active magmatism and that it is favored by transpressional tectonics in the sierra nevada california the late cretaceous granitoids of the cathedral range intrusive epoch are consistent with emplacement into bridges between p shears because 1 they are elongated oblique to the magmatic trend consistent with p shear orientation within a dextral system 2 they were all emplaced within 5 10 m y along a 300 km trend resulting in a displacement rate of 1 cm yr across the arc and 3 syn to late magmatic dextral shear zones bound and crosscut the plutons as in a p shear tensional bridge

enechelon sigmoidal vein arrays hosted by faults abstract the morphology of enechelon sigmoidal veins generally supports an extension fracture origin for host fractures nevertheless a shear fracture origin has been proposed in some cases mainly on geometric arguments often without morphological support this study describes a system of sigmoidal enechelon quartz veins in a deformed greywacke which displays morphological evidence that the veins are hosted by faults the veins occur in the hinge zone of an upright horizontal antiform and their configuration is consistent with both faulting and vein opening occurring during folding the formation of close spaced vertical dextral faults transformed thick massive greywacke beds into a discontinuous multilayer structure of rock bridges between faults as the length to thickness ratio of the multilayer structure increased the deformation mechanism changed to one of rotation and bending of rock bridges along sinistral shear displacement zones resulting in sigmoidal openings between rock bridges morphological features which indicate that the host fractures are faults include 1 continuity of host fractures well past the tips of the sigmoidal veins and shear displacement of markers by unopened host fractures 2 pinnate extension veins emanating from host fractures particularly near terminations and 3 shear quartz fibres on host fractures basic kinematic analysis shows that shear displacement with opposite shear sense to the array must occur before sigmoidal forms develop as the curvature produces contractional jogs which are incompatible with vein opening recognition of these features may assist in determining the role of shear displacement on host fractures of sigmoidal enechelon vein arrays

stoped blocks in plutons paleo plumb bobs viscometers or chronometers abstract stoped blocks potentially provide information about paleohorizontal during emplacement of plutons and about the timing of and viscosities and kinematics during magmatic fabric formation in the mount stuart batholith washington we have examined magmatic fabrics patterns around stoped blocks in tonalite located near the pluton roof and completed 1 1 scale three dimensional mapping of fabric patterns around stoped blocks in diorite located 1000 m below the roof in both settings no structural record of magma ascent early emplacement or settling of the blocks is preserved instead fabric formation largely post dates the settling and trapping of stoped blocks two dimensional finite difference thermal modeling and calculations of sinking rates support short

evidence of climatic change from oxygen and carbon isotope variations in sediments of a small arctic lake canada radiocarbon dating of the organic rich sediments of lake illisarvik in the outer mackenzie delta indicates that formation of the lake occurred approximately 9500yr bp with maximum expansion around 6000 yr bp sedimentation rates have remained relatively constant at an average of 0 3mm yr 13c results on biogenic and inorganic carbonates and organics indicate a change from dominantly terrestrial organics 27 to 28 0 to submerged aquatic vegetation or plankton 18 to 23 0 upon formation of the lake 9500yr bp and a dramatic return to dominantly terrestrial organics at 5800yr bp 13c 27 to 30 0 this latter shift is accompanied by a drastic reduction in the macroflora and fauna populations 18o results suggest that a warmer climate than today existed prior to the shift at 5800yr bp

holocene sea level change in the severn estuary southwest england a diatom based sea level transfer function for macrotidal settings the recent growth in the use of microfossil based transfer functions in late quaternary sea level reconstructions reflects their potential to accurately quantify palaeo sea level changes this study details the development of a diatom based sea level transfer function for the severn estuary southwest england a macrotidal setting that experiences the second highest tidal range in the world this setting presents difficulties in representing the full tidal range from mean sea level msl to highest astronomical tide hat however two separate transects were merged successfully and a statistically significant relationship between contemporary diatom assemblages and altitude m o d was established a diatom based transfer function for palaeoaltitude was developed using weighted averaging wa tolerance downweighted weighted averaging wa tol and weighted averaging partial least squares wa pls wa tol produced the lowest prediction errors for altitude and the transfer function was applied to a fossil diatom data set from gordano valley a site adjacent to the severn estuary 2007 sage publications

sequential granite emplacement a structural study of the late variscan strzelin intrusion sw poland the strzelin massif in sw poland central european variscides records a protracted igneous evolution with three main magmatic stages 1 tonalitic i 2 granodioritic and 3 tonalitic ii granitic in the northern part of this massif the strzelin intrusion proper comprises three successively emplaced rock types a medium grained biotite granite 303 2 ma a fine grained biotite granite 283 8 ma and a fine grained biotite muscovite granite based on field evidence the third variety postdates both types of the biotite granites the structural data from the three granites including their parallel approximately e w striking and steeply dipping lithological contacts and ene wsw trending subhorizontal magmatic lineations suggest that the emplacement of all three successive granite varieties was controlled by an active long lived strike slip fault striking ese wnw with a dextral sense of movement after the emplacement of the youngest biotite muscovite granite the intrusion underwent brittle extension which produced q joints striking nnw sse to n s and dipping at 55 70 wsw to w and showing evidence of broadly n s directed sinistral displacements the structural observations supported by new geochronological data indicate that the internal structure of the composite granitoid intrusion including the faint magmatic foliation and lineation formed in a long lived strike slip setting different from the subsequent post emplacement extensional tectonics that controlled the development of brittle structures

the development of contrasting structures during the cooling and crystallisation of a syn kinematic pluton structural elements of a syn kinematic pluton in the pilbara craton of western australia reflect evolving rheology during progressive crystallisation representing a transition from magmatic through high temperature sub solidus to low temperature deformation magmatic elements include 1 nne trending sub vertical kilometre scale folds outlined by xenolith trains that have a magmatic axial planar foliation defined by aligned k feldspar 2 cross cutting ene trending sub vertical shear zones intruded by numerous metre scale granite sheets and 3 a narrow concordant magmatic k feldspar foliation in the granite host rock adjacent to the shear zones microstructures such as fractured feldspars healed by quartz that is continuous with matrix grains further suggest that deformation occurred while the pluton was magmatic high temperature structural elements include checkerboard sub grain boundaries in quartz whereas deformation at lower temperatures is indicated by kinked feldspar recrystallised microcline and undulose quartz a nne trending sub vertical sub solidus foliation defined by elongate quartz aggregates overprints all the above mentioned features generation of these sequential structural elements correspond to the transition from newtonian fluid through bingham type to newtonian solid behaviour as the crystal fraction of the felsic magma increased the orientation of the structures is consistent with a regional ese wnw shortening direction throughout magma crystallisation this study indicates how evolving magma rheology and regional strain regimes control the micro to macro structural elements of a syn tectonic pluton

age determination of petra s engineered landscape optically stimulated luminescence osl and radiocarbon ages of runoff terrace systems in the eastern highlands of jordan abstract the unfavourable mountainous environment of the petra region in southern jordan was modified by ancient engineers to supply the nabataean roman city of petra with food and water the area was reclaimed by installing extended runoff terrace systems and hydraulic structures the agricultural terrace systems have so far been dated based on surface pottery and the chronology of the systems is under debate in this study optically stimulated luminescence osl and radiocarbon dating techniques were successfully applied to date these terrace systems samples were taken from the fills of agricultural terraces and underneath their walls to determine the chronology of the construction use and abandonment of the agricultural terraces the results suggest that runoff farming in the petra region started around the beginning of the common era and construction use and maintenance lasted at least until 800 ad

incremental emplacement and syn tectonic deformation of late triassic granites in the qinling orogen structural and geochronological constraints abstract granitoids are important components of major orogenic belts and provide important information about the regional geodynamic evolution the emplacement mechanism of granite plutons and its relationship with regional tectonics has long been discussed although it still remains debated the qinling orogen within the central china orogen was marked by the emplacement of numerous late triassic granitic plutons although the petrology geochemistry and geochronology of these intrusions have been addressed in various studies their tectonic setting remains controversial particularly since the structural aspects not been evaluated in detail in this study we attempt to reconstruct the emplacement process of the late triassic dongjiangkou pluton in the south qinling belt field observations show extensive syn plutonic deformations both in the pluton and its contact zones microstructural observations demonstrate that fabrics in the pluton were mainly acquired during submagmatic flow to high t solid state deformation zircon u pb ages reveal that the pluton is a composite intrusion which is composed of two juxtaposed small plutons with distinct ages 210 ma and 200 ma al in hornblende thermobarometer indicates that the pluton was formed at depths ranging from 4 7 km to 8 8 km with an increasing depth trend from the inner unit to the outer unit distribution of the internal fabrics shows two concentric patterns which are concordant with pluton margins at the pluton scale and were probably induced by the regional sinistral transpression integrating these analyses an incremental emplacement model is proposed for the syn tectonic pluton this model not only solves the room problem but also accounts for the zoned petrological features of the pluton combined with previous studies we suggest that the late triassic granite plutons in the qinling orogen were emplaced under a syn collisional convergence setting and that the granite magmatism was probably controlled by regional tectonics additionally the incremental emplacement model may be a common mechanism for the late triassic granite plutons

on curved laminae graded layers convection currents and dynamic crystal sorting in the ploumanac h brittany subalkaline granite curved layered objects in a subalkaline potassic intrusive granite are analyzed biotite laminae and cyclic reverse size and modal layers are encountered in an annular zone both cyclic and intermittent layers are observed in rhythmic arrangement truncation the bifurcation curvature of layers with ladle shape represents the action of magmatic currents as would convection cells or fluid dynamic fingers emphasis is put on the bagnold effect related to such currents which would explain the reverse size grading of layers this kind of size sorting hydrodynamic occurs in highly viscous granitic magma simple convection seems more likely than diffusive convection

evidence from north west canada for an early holocene milankovitch thermal maximum according to the milankovitch theory of global climatic change maximum summer solar radiation at high latitudes of the northern hemisphere occurred at 10 000 yr bp refs 1 2 in particular it predicts summer solstice radiation greater by 9 10 preliminary climate simulation experiments with these increased values of radiation confirm that high latitude land surfaces received maximal insolation at 10 000 yr refs 3 4 paradoxically however the large volume of fossil pollen and other evidence from north america indicates a maximum of holocene warmth at 7 000 6 000 yr ref 5 and a recent review of the evidence from new england suggests that the warming began at 9 000 and ended at 5 000 yr but also stresses the difficulties of interpretation in terms of climate change6 we summarize here data from sites in the north west corner of mainland canada fig 1 that directly support the milankovitch hypothesis

irrigation agriculture and the sedimentary record in the palpa valley southern peru abstract irrigation agriculture is an ancient and widespread feature in regions where allogenic rivers flow through arid landscapes this paper reports the results of sedimentological pedological investigations in the palpa valley in the coastal desert of southern peru where sediment laden river water is used for irrigation an adapted facies classification is used to deduce a generalised stratigraphical sequence of the valley bottom sediments chronological constraints from radiocarbon dating and archaeological finds are used to reconstruct sedimentation rates for fossil to recent irragric anthrosols actualistic case studies are used to quantify present day irrigation sedimentation the investigations result in a clarification of the sedimentological and geomorphic history of this valley and a quantification of irrigation related sedimentation irragric anthrosols date back more than 3500 years and provide direct evidence for the beginning of irrigation agriculture in this region it is concluded that i the up to approximately 4 m thick fine grained sediments in the palpa valley bottom totaling a volume of 21 4 mio m3 are a result of long lasting human impact and have to be considered as artefacts of prehistoric and historic irrigation agriculture in the hyperarid coastal desert ii the fine grained sediments represent a geoarchive which holds information on the history of irrigation agriculture as well as information on possible natural disturbance by extreme fluvial events iii the identification of irragric anthrosols has implications for archaeological and paleoenvironmental reconstructions

prism and basal plane parallel subgrain boundaries in quartz a microstructural geothermobarometer empirical data on quartz subgrain patterns from various metamorphic rocks show that at least up to 10 kbar in the stability field of low quartz prismatic subgrain boundaries are dominant whereas basal subgrain boundaries are not developed in the high quartz stability field both prismatic and basal subgrain boundaries occur and form typical rectangular chessboard patterns the likely reason behind the different occurrence of these subgrain patterns is that in high quartz prismatic glide becomes as easy as or probably even easier than basal glide the two types of subgrain patterns can be clearly distinguished by optical microscopy consequently the occurrence of chessboard subgrain patterns in quartz represents a practicable geothermobarometer the possibilities of its application are far reaching and include the specification of deformation conditions at high grade metamorphism the recognition of syntectonic intrusions and the distinction between pluton emplacement at lower and at higher crustal levels

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

comment on dorr and zulauf elevator tectonics and orogenic collapse of a tibetan style plateau in the european variscides the role of the bohemian shear zone int j earth sci geol rundsch 2010 99 299 325 the present comment disproves the tectonic model of a late devonian early carboniferous tibetan style collisional plateau in the tepla barrandean tb part of the bohemian massif which later collapsed by thermal weakening of the underlying crust contrary to this model the tb neither reveals major crustal thickening nor uplift and erosion and eastern continuations of the tb were during the relevant time span areas of open marine sedimentation late devonian early carboniferous marine sediments widespread also in the armorican and central massifs of france testify to low topography in central parts of the variscan orogen notional traces of a permo carboniferous ice cap on the french massif central do not support the plateau model because they are questionable and much younger than the inferred plateau stage of the tb the relative uplift of high grade metamorphic rocks to the nw and the se of the tb is not due to sinking of an elevated tb but instead to the hydraulic and buoyant expulsion of hp material from the saxo thuringian and moldanubian subduction channels the rise of lower grade ht rocks along the southwestern margin of the bohemian massif was effected by late carboniferous transpression the high temperature and the resulting low viscosity of the rising materials were probably not caused by variscan mantle delamination but relate to lithospheric thinning and heating at the tip of the westward propagating tethys rift

submagmatic microfractures in granites microstructures in hercynian granite plutons of the pyrenees indicate fracturing of plagioclase crystals in the presence of melt this is represented mainly by quartz and or feldspar that fills fractures electron microprobe analyses demonstrate that in compositional agreement with the rims of the zoned plagioclase the feldspar infillings are more sodic with decreasing melt fraction fracturing resulted from concentration of stress at contacts between grains while the granite was submagmatic i e when the melt was below the critical fraction for magmatic flow material compositionally far from eutectic is petrologically the best candictate to develop submagmatic fractures because during cooling the volume fraction of melt remains low for a large temperature range a strong tendency for microfractures to be oblique to flow foliation may constitute a new criterion for shear sense in magmas

episodic construction of the tatra granitoid intrusion central western carpathians poland slovakia consequences for the geodynamics of variscan collision and rheic ocean closure the tatra granitoid pluton central western carpathians poland slovakia is an example of composite polygenetic intrusion comprising many magmatic pulses varying compositionally from diorite to granite the u pb la mc icp ms zircon dating of successive magma batches indicates the presence of magmatic episodes at 370 368 365 360 355 and 350 340 ma all together covering a time span of 30 ma of magmatic activity the partial resorption and recycling of former granitoid material petrological cannibalism was a result of the incremental growth of the pluton and temperature in the range of 750 850 c the long lasting granitoid magmatism was connected to the prolonged subduction of oceanic crust and collision of the proto carpathian terrane with a volcanic arc and finally with laurussia closing the rheic ocean the differences in granitoid composition are the results of different depths of crustal melting more felsic magmas were generated in the outer zone of the volcanic arc whilst more mafic magmas were formed in the inner part of the supra subduction zone the source rocks of the granitoid magmas covered the compositional range of metapelite amphibolite and were from both lower and upper crust the presence of the inherited zircon cores suggests that the collision and granitoid magmatism involved crust of cadomian consolidation age c 530 and 518 ma forming the proto carpathian terrane crust of avalonian affinity 462 426 ma and melted metasedimentary rocks of volcanic arc provenance

holocene climate effects on the development of a peatland on the tuktoyaktuk peninsula northwest territories abstract six cores were collected from a small peatland on the tuktoyaktuk peninsula yielding up to 1 8 m of organic material and 1 2 m of ice rich material stratigraphic relationships radiocarbon dating and pollen plant macrofossil and isotopic analyses are used to reconstruct the developmental history of the peatland organic matter began to accumulate in the basin about 7200 yr b p during a period when the climate is thought to have been warmer than present initially the permafrost table was probably below the bottom of the basin and an open water mineral wetland with emergent and submergent aquatic vegetation occupied the site enriched 18 o values from ice samples confirm the existence of an open water body with a water balance strongly affected by evaporation transformation to a graminoid fen peatland was underway by 6300 yr b p permafrost and ice began to form in the peatland at this time low centered polygons probably began to develop by 4700 yr b p and subsequently evolved into the high centered polygons which characterise the southwestern part of the peatland today peat accumulation in the polygons has been extremely slow for the last 4000 years the eastern wetter part of the basin has largely remained unchanged since its inception about 7000 yr b p development of the peatland may be linked to permafrost formation that was controlled by regional climate changes during the holocene

the role of long term human impact on avulsion and fan development this study aims to understand mainly qualitatively the long term role of human impact on avulsion processes and the development of fluvial mega fans in semi arid environments in this paper we refer to human impact as the direct influences of actions on the river s hydraulics i e flow regulation flow diversion and channel engineering in five case studies drawn from the khuzestan plains in southwest iran we have analysed the setup and triggering conditions of specific avulsions that occurred in the past timescale of millennia and identified the role of human interference in their causation our analysis is based on the integration of historical archaeological geomorphological and geological data through this study we demonstrate that avulsions in the khuzestan plains are the result of long term and complex interplay between multiple human induced and natural causes in similar ways human induced actions may play important roles during different phases of avulsion development the success of an avulsion in the post triggering phase may be defined by human induced setup causes as well as morphodynamic processes we suggest that present day flood events may be partly inherited from long term human alterations of the natural processes these finding could have implications for any fluvial system e g distributive fluvial systems deltas where avulsion plays a major role in their development and research tends to emphasize on natural mechanisms copyright 2016 john wiley sons ltd

late cretaceous age of fractures in the sierra nevada batholith california regional sets of steeply dipping joints and faults are common throughout the sierra nevada batholith yet relatively little is known about how or when they formed within some east northeast striking left lateral fault zones in the mount abbot quadrangle of the central sierra nevada the host granodiorite is hydrothermally altered to a lower greenschist assemblage that contains muscovite the muscovite yields a mean k ar and sup 40 ar sup 39 ar age of 79 ma which provides a minimum age for the faulting field relations show that these faults developed from earlier formed mineralized joints so these ages also provide a minimum age for the jointing published ages of biotite hornblende and zircon from the host granodiorite of lake edison are 80 ma k ar 85 ma k ar and 90 ma u pb respectively the geochronology field relations and hydrothermal mineral assemblages together suggest that the mineralized joints and faults all formed between 85 and 79 ma soon after the host pluton was emplaced

morphology of the canadian beaufort sea coast a study of the canadian beaufort sea coast alaskan yukon border to baillie island was conducted to provide a regional summary of a coastal morphology b coastal stability and c coastal processes a total of 2077 km of coastline was mapped using aerial photographs low altitude and oblique aerial video imagery and information from previous field studies the coast can be adequately characterized by six repetitive coastal types four of which are erosional landforms and comprise 60 of the coast ice rich cliffs ice poor cliffs low tundra cliffs and inundated tundra two repetitive coastal types are accretional landforms and comprise 40 of the coast barrier islands and spits and deltas the deltas in the study area are retreating rapidly and therefore over 80 of the coast is considered erosional and less than 20 accretional over 1000 measurements of coastal stability indicate wide scale coastal retreat most sections of the coast show mean coastal retreat rates in excess of 1 m yr 1 despite very low annual wave exposure levels near active areas of the mackenzie river delta mean retreat rates are in excess of 2 m yr 1 and a maximum retreat rate of 18 m yr 1 was documented near shallow bay the presence of significant quantities of ice in the coastal sediments both in the form of pore ice and massive ice beds appears to be the primary cause of the wide scale regional retreat of the coast although a relative sea level rise in the region may also be important

holocene sea level changes and crustal movements in morecambe bay northwest england holocene stratigraphy from skelwith pool on the northern side of morecambe bay is described diatom and pollen analyses and radiocarbon dating have been undertaken for three sampling sites from which eight sea level index points have been obtained these index points come from a small homogeneous area and similar palaeoenvironments some published sea level index points from morecambe bay have been re evaluated and validated by means of diatom analysis an enhanced sea level database with 28 index points has been used for the reconstruction of holocene sea level history relative sea level rose rapidly around 6870 6510 bc at a maximum rate of 36 7 mm yr 1 subsequently the rate of sea level change has varied between 8 mm yr 1 and 12 mm yr 1 the rate of relative sea level changes for the last 3500 years is not clear uplift driven by deglaciation is believed to have been interrupted in the early holocene by a rapid rise in relative sea level uplift restarted at 6510 bc but soon declined as glacio isostatic recovery ended around 3800 bc in the morecambe bay area since then crustal movements in the morecambe bay area have been minimal factors affecting the attitudes of the index points such as sediment compaction of the basal peat and variations in palaeotidal range during the holocene have been considered 1996 john wiley sons ltd

holocene sea level history of the canadian beaufort shelf new radiocarbon ages pertaining to the holocene sea level history of the canadian beaufort shelf are presented the ages were obtained on samples of freshwater and tidal marsh peat beds from offsho