geochronology of early to middle paleozoic tectonic development in the southwest newfoundland gander zone southwest newfoundland s gander zone was once considered part of the collided eastern margin of an early paleozoic iapetus ocean distinguished from the rest of the gander zone by the extensive exposure of a polydeformed amphibolite to greenschist facies sequence considered devonian in age overlying presumed precambrian basement it was later found that truly devonian strata were confined to the cape ray fault system the local northwestern boundary of the zone u pb zircon isotopic ages of 452 13 51 ma and 458 22 29 ma on metavolcanic rocks in the upper part of the sequence southeast of the fault system indicate that ordovician and possibly older rocks underlie the gander zone itself a temporal framework for the three main stages of regional deformation corresponding to pre metamorphic recumbent folding d 1 and transpression d 2 and d 3 is presented using u pb and 40 ar 39 ar dates of granitoid and metamorphic rocks d 1 is bracketed as late o

a freshwater old carbon offset in lake baikal siberia and problems with the radiocarbon dating of archaeological sediments evidence from the sagan zaba ii site abstract lake baikal in eastern siberia is one of the largest and deepest freshwater lakes in the world and its diverse fauna were extensively utilized by local human populations over many millennia the regional culture history models primarily are based on radiocarbon dates on human skeletal remains and in some cases also on dates on sediments from habitation sites analyses of a set of 113 radiocarbon dates from the sagan zaba holocene hunter gatherer and pastoralist habitation site 52 6825 n 106 4760 e on the western coast of lake baikal demonstrates two critical problems in the dating of these sets of materials first comparison of ams radiocarbon dates on terrestrial mammal and baikal seal bones from sagan zaba reveals the existence of a freshwater radiocarbon offset in the seal remains of at least 700 radiocarbon years radiocarbon dates on skeletal remains from humans who consumed the aquatic fauna also should be expected to carry an old carbon offset second comparison of radiocarbon dates made on sediment samples with those made on terrestrial mammal bones demonstrates major inconsistencies the primary problem with these samples is that the carbon being dated in them is of unclear relationship to human activities of interest at the site therefore the still common practice in this region of radiocarbon dating sediments to establish archaeological chronologies should be abandoned the ams radiocarbon dating of bone from species which clearly fed outside of lake baikal s aquatic environments should provide more reliable age estimates for human activities at archaeological sites

slip along the sultanhani fault in central anatolia from deformed pleistocene shorelines of palaeo lake konya and implications for seismic hazards in low strain regions

crustal structure measurements near fram ii in the pole abyssal plain abstract an extensive refraction profiling program was carried out during the fram ii experiment march may 1980 in the eastern arctic ocean two structural areas were covered north of the ice camp 86 n 24 w into the basin of the pole abyssal plain and south onto the flanks of the morris jesup rise digital multichannel data on an 800 by 800 m 24 channel hydrophone array and a single 2 component ocean bottom seismometer obs were recorded for offsets from 2 5 to 100 km arrival times amplitudes and phase velocities of the seismic signals recieved on the hydrophone array were determined using high resolution array processing from these measurements and the obs data preliminary velocity structural models of the crust have been derived for the purposes of this paper 2 refraction lines have been analyzed a 40 km line on a flat region of the pole abyssal plain and an 86 km line on a slightly dipping region taken as the drifting ice camp shoaled on the morris jesup rise these preliminary analyses yield a sedimentary layer with a gradually increasing velocity 1 5 2 km thick this cover overlays a crust with a thin layer 2 and yields a total ocean bottom to mantle thickness of 4 7 km

paleomagnetism of diabase dikes from the bonavista bay area of northeastern central newfoundland paleomagnetic results are reported for a swarm of diabase dikes from the northeastern gander zone of the newfoundland appalachians sixty eight cores were collected from 19 dikes cutting the variou

chronology of a sedimentary sequence from the land ocean interaction zone in the north jiangsu basin abstract the north jiangsu basin njb located in the western part of the north jiangsu south yellow sea basin is a critical region providing invaluable archives about the evolution processes of the land ocean interchange and climatic environments in a coastal zone chronology is of crucial importance to reconstruct the timing of sea level eustacy and shoreline changes as well as the evolution of the regional environment by means of numerical dating to determine the age of sedimentary strata in the sea land interaction zone of the njb however sediment dating in the njb remains controversial due to limitations in the quantity and quality of chronological data therefore the sediments in the jianhu gangxi gx profile of the njb were analyzed in this study by applying both fine grained quartz optically stimulated luminescence osl dating and 14c dating the results were used to discuss the processes of regional environment evolution the osl dating of fine grained quartz components in sediments was found to be a reliable method to determine deposition ages of sediments in the land sea interaction zone in the njb the combination of osl and accelerator mass spectrometry 14c dating techniques allowed a reliable and high resolution chronological framework for the gx profile since the last glaciation the sedimentary environment in the eastern portion of the njb changed significantly in particular 1 between 13 and 7 25 ka b p the area of interest was dominated by lacustrine deposition within a stable sedimentary environment with low deposition rates 2 from 7 25 to 6 45 ka b p marine transgression events occurred and the deposition rate increased rapidly in an area of land sea interaction 3 after 6 45 ka b p a regression event occurred and the study area transformed into a lowland lake environment

glacially influenced deep marine sedimentation of the late precambrian gaskiers formation newfoundland canada the late proterozoic conception group exposed on the avalon peninsula in newfoundland canada is a 4 km thick turbidite succession containing a conformable 300 m thick sequence of diamictites the gaskiers formation near the base massive and crudely stratified diamictites form beds up to 25 m thick which have a tabular geometry with slightly erosive basal contacts and are interbedded with mudstones and fine grained thin bedded turbidites these diamictites are interpreted as submarine debris flow deposits disrupted diamictites form strongly deformed units that contain large complexly folded rafts of mudstone and turbidite facies these diamictite units are interpreted as submarine slumps diamictites contain glacially striated and faceted clasts clasts and matrix are predominantly of volcanic provenance one outcrop shows interbedded volcanic agglomerate and diamictite and volcanic bombs can also be identified the interbedding of diamictites with turbidites and the stratigraphic context provided by the thick sequences of turbidites below mall bay formation and above drook formation indicate a deep marine slope setting of diamictite deposition diamictite facies record remobilization and downslope transfer of large volumes of unstable volcanic and glacial debris initially deposited in a shallower water marginal marine zone the regional tectonic framework suggests the conception group accumulated in a deep southward opening ensialic rift basin with active but waning volcanic centres to the north the gaskiers formation may be representative of other late precambrian glacially influenced diamictite sequences that were deposited around the north atlantic region and in europe these deep marine diamictite sequences characterized by debris flows turbidites and slump deposits can be contrasted with more extensive shallow marine shelf diamictite sequences found in association with dolomites and tidally influenced shallow water facies in other basinal settings

kinematic history of the narragansett basin massachusetts and rhode island constraints on late paleozoic plate reconstructions the formation of the narragansett basin of rhode island and massachusetts and the polyphase deformation geometry of the pennsylvanian age basin sediments can be explained by collision and strike slip interactions between an avalonian microcontinent the european north american plate and the african plate during the late paleozoic sinistral movement between an avalonian microcontinent and the european north american plate resulted in formation of pull apart basins subsequently africa moved toward north america along an east west trending dextral megashear zone and collided with the eastern margin of southern north america the narragansett basin is located on the avalonian microcontinent near the suture with the north american continent and in the transition zone between the megashear and the collision tectonic regimes the basin shape stratigraphy and sedimentary relationships can be explained by the coalescence of two composite grabens which formed at different times the thicker northern graben is only affected by one deformation whereas the southern graben shows evidence of four distinct phases of postrifting deformation the first two coaxial folding deformations of the basin sediments are attributed to the closure of the basin complex during collision of africa and north america the third and fourth deformations are interpreted as sinistral r riedal and dextral shears respectively associated with the east west trending megashear system a prograde barrovian metamorphic front started in the western portion of the southern graben slightly after the first deformation and migrated northward and eastward where it is synchronous with the second deformation

chronology of tectonothermal activity in the western avalon zone of the newfoundland appalachians the ackley granite was intruded into variably deformed and metamorphosed rocks within the gander and avalon zones of the newfoundland appalachians biotite and hornblende from the pluton record internally concordant 40ar 39ar age spectra that define total gas dates of 352 356 ma these are similar to a previously reported 355 5 ma rb sr whole rock isochron age and indicate relatively rapid post magmatic cooling a feature consistent with the post kinematic character of the pluton in the western avalon zone recrystallized sericitic metavolcanic rocks from the late precambrian love cove and marys town groups display variably discordant whole rock 40ar 39ar age spectra however the samples yield well defined plateau ages of 353 400 ma 11 samples which are interpreted to closely date the regional metamorphism and associated deformation in the western avalon zone this chronology is similar to that of the easternmost gander zone indicating that deformation and metamorphism in the western avalon zone

application of 34s analysis for elucidating terrestrial marine and freshwater ecosystems evidence of animal movement husbandry practices in an early viking community around lake mývatn iceland carbon and nitrogen stable isotope ratios 13c and 15n have been used widely in archaeology to investigate palaeodiet sulphur stable isotope ratios 34s have shown great promise in this regard but the potential of this technique within archaeological science has yet to be fully explored here we report 34s 13c and 15n values for 129 samples of animal bone collagen from skutusta ir an early viking age landnam settlement in north east iceland this dataset represents the most comprehensive study to date of its kind on archaeological material and the results show a clear offset in 34s values between animals deriving their dietary resources from terrestrial mean 5 6 2 8 freshwater mean 2 7 1 4 or marine mean 15 9 1 5 reservoirs with the three food groups being significantly different at 2 this offset allows reconstruction of the dietary history of domesticated herbivores and demonstrates differences in husbandry practices and animal movement trade which would be otherwise impossible using only 13c and 15n values for example several terrestrial herbivores displayed enriched bone collagen 34s values compared to the geology of the lake m vatn region indicating they may have been affected by sea spray whilst being pastured closer to the coast before being traded inland additionally the combination of heavy 15n values coupled with light 34s values within pig bone collagen suggests that these omnivores were consuming freshwater fish as a significant portion of their diet arctic foxes were also found to be consuming large quantities of freshwater resources and radiocarbon dating of both the pigs and foxes confirmed previous studies showing that a large freshwater radiocarbon 14c reservoir effect exists within the lake overall these stable isotope and 14c data have important implications for obtaining a fuller reconstruction of the diets of the early viking settlers in iceland and may allow a clearer identification of the marine and or freshwater 14c reservoir effects that are known to exist in human bone collagen

influence of deformation and fluids on ar retention in white mica dating the dover fault newfoundland appalachians abstract white mica 40ar 39ar analyses may provide useful constraints on the timing of tectonic processes but complex geological and thermal histories can perturb ar systematics in a variety of ways ductile shear zones represent excellent case studies for exploring the link s between dynamic re neo crystallization of white mica and coeval enhanced fluid flow and their effect on 40ar 39ar dates white mica 40ar 39ar dates were collected from compositionally similar granites that record different episodes of deformation with proximity to the dover fault a terrane bounding strike slip shear zone in the appalachian orogen newfoundland canada 40ar 39ar data were collected in situ by laser ablation and by step heating single crystals results were compared to each other and against complementary u pb zircon and monazite and k ar fault gouge analysis although step heat 40ar 39ar is a widely applied method in orogenic settings this dataset shows that relatively flat step heat 40ar 39ar spectra are in contradiction with wide spreads in in situ 40ar 39ar dates from the same samples and that plateau dates in some cases yielded mixed dates of equivocal geological significance this result indicates that the step wise release of ar from white mica likely homogenizes and obscures spatially controlled ar isotope reservoirs in white mica from sheared rocks in contrast in situ laser ablation 40ar 39ar analysis preserves the spatial resolution of 40ar reservoirs that have been variably reset by deformation and fluid interaction this study therefore suggests that laser ablation is the best method for dating the timing of deformation recorded by white mica final interpretation of results should be guided by microstructural analysis estimation of deformation temperature chemical characterization of white mica and complementary chronometers overall the dataset shows that granitic protoliths were emplaced between 430 and 422 ma u pb zircon high strain deformation along the wing pond shear zone occurred between ca 422 405 ma u pb monazite and 40ar 39ar subsequent patchy ar loss in white mica occurred locally during low t shear

radiocarbon reservoir effects in human bone collagen from northern iceland human bone collagen from a series of icelandic human pagan graves was radiocarbon 14c dated to aid understanding of early settlement landnam chronologies in northern iceland these individuals potentially consumed marine protein the 14c age of samples containing marine carbon requires a correction for the marine 14c reservoir effect the proportion of non terrestrial sample carbon was quantified via measurement of carbon stable isotopes 13c using a simple mixing model based on 13c measurements of archaeofaunal samples non terrestrial carbon was also quantified in six pig bones from the archaeofaunal dataset assuming all non terrestrial carbon in human and pig bone collagen was marine derived calibrated age ranges calculated using a mixed intcal09 marine09 calibration curve were consistent with an early settlement date close to landnam but several samples returned pre landnam age ranges measurements of nitrogen stable isotopes 15n strongly suggest that many of the human bone collagen samples contain freshwater diet derived carbon icelandic freshwater systems frequently display large freshwater 14c reservoir effects of the order of 10 000 14c years and we suggest that the presence of freshwater carbon is responsible for the anomalously early ages within our dataset in pig samples the majority of non terrestrial carbon is freshwater in origin but in human samples the proportion of freshwater carbon is within the error of the marine component 10 this presents a major obstacle to assessing temporal patterns in the ages of human remains from sampled graves although the majority of grave ages are within the same broad calibrated range

synthesis of palaeozoic deformational events and terrane accretion in the canadian appalachians plate tectonic theory predicts that most deformation is associated with subduction and terrane accretion with some deformation associated with transform transcurrent movements deformation associated with subduction varies between two end members 1 where the tectonic regime is dominated by subduction of oceanic lithosphere containing small terranes a narrow surface zone of accretionary deformation along the subduction zone starts diachronously on the subducting plate at the trench as material is transferred from the subducting plate to the over riding plate and 2 where continent continent collision is occurring a wide surface zone of accretionary deformation starts synchronously or with limited diachronism palaeozoic deformational events in the canadian appalachians correspond to narrow diachronous events in the ordovician and silurian whereas devonian carboniferous and permian deformational events are widespread and broadly synchronous along the western side of the canadian appalachians the taconian deformational event starts diachronously throughout the ordovician and corresponds to the north north west accretion of the notre dame ascot weedon st victor and various ophiolitic massifs volcanic arc and peri arc terranes over cratonic north america within the eastern half of the central mobile belt the late cambrian early ordovician penobscotian deformational event corresponds to the south easterly accretion of the exploits subzone various volcanic are and peri arc terranes over the gander zone continental rise in the centre of the orogen the late ordovician silurian beothukan deformational event corresponds to the south easterly accretion of the notre dame over the exploits gander subzones along the south eastern side of the central mobile belt the silurian ganderian deformational event corresponds to the north north east sinistral transcurrent accretion of the avalon composite terrane microcontinent over the gander exploits zones along the south eastern half of the orogen the late silurian middle devonian acadian deformation event corresponds to the westerly accretion of the meguma terrane intradeep or continental rise over the avalon composite terrane affecting the entire orogen the late devonian carboniferous and permian acadian alleghanian deformational events correspond to the east west convergence between laurentia and gondwana continent continent collision

structure of the earth oceanic crust and uppermost mantle the past four years have witnessed the introduction of a variety of new instruments and methods for the study of the seismic structure of the oceanic crust and lithosphere the application of these and existing tools has led to the discovery of a number of new phenomena and to a fuller understanding of the genesis and evolution of the oceanic ithosphere borehole seismic instrumentation has become more widely employed ocean bottom seismographs while generally decreasing in number have become significantly more reliable and useful and multichannel seismic systems have been employed in innovative experiments ranging from studies of fracture zones to the regular detection of magma chambers beneath rise axes the techniques available for the analysis of seismic data have become more sophisticated waveforms collected in seismic experiments can now be used directly in constructing and evaluating seismic velocity models and travel time data are regularly inverted directly for structure trial and error modeling has become increasingly unimportant marine seismologists are becoming increasingly involved in understanding the coupling between the ocean and the underlying oceanic lithosphere this has led to a more complete understanding of seafloor noise processes and the partitioning of energy between acoustic and elastic waves

implications of a freshwater radiocarbon reservoir correction for the timing of late holocene settlement of the elk hills kern county california abstract uncertainties regarding the magnitude of freshwater radiocarbon reservoir effects can introduce random errors into dates on archaeological freshwater carbonates as a result many archaeologists avoid dating freshwater shells unless no other datable materials are available the chronology of prehistoric occupation of the former naval petroleum reserve no 1 npr 1 at elk hills kern county has been established with 50 radiocarbon dates on freshwater mussels gonidea and anodonta sp characterization of any freshwater radiocarbon reservoir effect is crucial for the accurate interpretation of inferred settlement and subsistence changes on the elk hills paired charcoal and freshwater mussels sampled from closely associated contexts were dated to identify a freshwater reservoir effect paired anodonta and gonidea sp shells were dated to investigate interspecific differences in fractionation results indicate that a 340 20 14 c yr correction should be applied to conventional 14 c dates on freshwater carbonates in the buena vista basin before calendar calibration evidence of interspecific differences is inconclusive dates recalibrated with the reservoir correction indicate that widespread occupation of the elk hills is correlated with increasing precipitation towards the end of the medieval climatic anomaly and during the little ice age suggesting that slough resource exploitation may have been driven by regional population pressure rather than drought related declines in aquatic productivity

nares strait a suture zone geophysical and geological implications abstract the motion of greenland relative to ellesmere island along nares strait is determined from poles of rotation which provide control for the motion independent of local geology and geophysics the plate kinematics around the north atlantic ocean the norwegian and greenland seas and the eurasian basin of the arctic ocean constrain motion along nares strait these motions are checked by examining the stability characteristics of the triple junctions these junctions are found to be stable the motion along nares strait between anomalies 34 and 13 is a combination of strike slip and compression the regional geology is found to support the plate reconstructions the local geology of the nares strait area is reviewed and found not to refute the predicted motions the geophysical and geological data are interpreted in terms of the wilson cycle the opening and closing of an ocean the nares strait area has the characteristics of a cryptic suture a join between regions of collided continental crust

mediaeval lead pollution in the river ouse at york england the city of york in northern england has a long history of being flooded by the river ouse excavations of a 9 m sedimentary profile were carried out by the york archaeological trust on the site of a pumping station associated with a flood prevention scheme at north street on the south west bank of the river ouse this profile records evidence of human activity and episodic river sedimentation over a period from the 2nd to the 14th century ad anthropogenic materials in the profile include waterfront timber and wattle structures and dumps of organic domestic debris and industrial waste evidence of historic floods is preserved in interleaved alluvial deposits this study reports on the degree of lead pb contamination at the site from roman to mediaeval times and the sources of both alluvial and manufactured lead deposited in the profile archaeological sedimentological geochemical and mineralogical evidence suggest that yorkshire dales mining activity during the 9th 13th centuries ad may have both directly and indirectly caused lead contamination of the alluvial deposits at north street

provenance and paleodrainage patterns of upper jurassic and lower cretaceous synrift sandstones in the flemish pass basin offshore newfoundland east coast of canada upper jurassic to lower cretaceous synrift sandstones from two industry exploratory wells in the flemish pass basin were studied for provenance using heavy mineral proxies these sandstones were deposited during the north atlantic rifting stage at which time rifting intensified between iberia and the grand banks several heavy mineral methods were used including in situ u pb geochronology and morphological and chemical analysis of detrital zircons chemical discrimination of detrital tourmalines and heavy mineral ratios clastic bed load material entering the northern flemish pass basin during the tithonian to berriasian was connected to transport systems reaching west as far as 400 to 500 km 249 311 mi source areas to the west included igneous rocks and associated cover sequences of the avalon zone as well as the magmatic rocks metasedimentary rocks and associated cover sequences present in the central mobile belt the eastward directed input of bed load material into the basin is considered to have resulted in the concentration of sandstone units along its western margin with deteriorating reservoir grade toward the east given the regional extent of drainage systems it is likely that similar constraints apply to equivalent sandstones in the adjacent east orphan basin by the valanginian barremian paleodrainage orientations had switched and bed load material began to enter the flemish pass basin from more proximal areas to the southeast with the avalon zone basement overall no evidence exists to support sediment sourcing from the iberian margin or the flemish cap galicia bank continental fragment to the east and material from these areas is instead interpreted to have been shed into the incipient atlantic ocean or bay of biscay also no evidence exists to support sourcing from grenville basement farther to the west implying that a drainage divide may have existed somewhere between central and western newfoundland west of which material was presumably being transported to the south or southwest

the yermak plateau formed at a triple junction the yermak plateau is an arcuate marginal plateau located seaward of northwestern spitsbergen the plateau is divided into two zones based on bathymetric trends and magnetic characteristics that have roughly coincident boundaries north of latitude 82 n where the bathymetric contours trend ne the magnetic amplitudes are large whereas the southern portion strikes nnw and exhibits a subdued magnetic signature beneath the northern section of the plateau crustal refraction velocities of 5 0 km s 1 underlain by 7 2 km s 1 are recorded while farther south velocities of 4 3 6 0 and 8 0 km s 1 are measured the 6 0 km s 1 velocity is similar to ones reported on the continental shelf south of spitsbergen dredged material gravity heat flow and seismic reflection and refraction data indicate the northern region of the plateau is oceanic and formed in conjunction with the morris jesup rise in contrast the southern section is thinned continental crust formed by the initial rifting process at a triple junction north of greenland plate reconstructions for anomalies 24 and 13 are consistent with this interpretation little space is required for the yermak plateau at anomaly 24 because it is composed of oceanic and thinned continental crust the development of the yermak plateau and the morris jesup rise paired aseismic ridges took place when the north american eurasian and greenland plates were moving independently

age and origin of the dover fault tectonic boundary between the gander and avalon zones of the northeastern newfoundland appalachians the dover fault forms a tectonic boundary between northern portions of the gander and avalon zones of the newfoundland appalachians a systematic geochronological investigation across the mylonitic

freshwater reservoir effect and the radiocarbon chronology of the cemetery in ząbie poland in the 3rd millennium bc an island on the anskie lake in north eastern poland was seasonally settled by a group of people practicing a syncretic burial ritual exhibiting indigenous and foreign patterns they left behind a small cemetery consisting of at least six graves 14c dates made for samples of human bones until 2009 did not coincide with the expected age of the graves under a new pilot program in 2010 2013 a series of radiocarbon measurements was made for the human bones and an artefact of red deer antler along with analyses of the stable isotopes ratios of carbon 13c and nitrogen 15n in the collagen the results indicate a significant proportion of freshwater food in the diet which caused the radiocarbon dates to be too old due to the freshwater reservoir effect fre based on the dating of the antler unaffected by fre and comparative analysis the reservoir offset for one of the graves was estimated to 740 radiocarbon years the results although limited by a low number of investigated humans and animals indicate indirectly a specialization in the exploitation of local water resources such an economic strategy seems to be characteristic for the societies inhabiting the coasts of the baltic sea and littoral zones of large lakes in the final neolithic and at the beginning of the early bronze age

understanding the variability in freshwater radiocarbon reservoir offsets a cautionary tale abstract freshwater resources in past diets can lead to inaccuracies when attempts are made to ascertain their radiocarbon ages or those of the consumers radiocarbon reservoir effects may lead to significant age offsets when the bones or other tissues of these consumers are radiocarbon dated a number of recent studies have investigated freshwater reservoir offsets however no study thus far has satisfactorily obtained a ubiquitous freshwater reservoir correction due to variability in the ecosystems analysed this study tests the possibility of predicting freshwater reservoir effects from the carbonate alkalinity of the water with measurements on modern fish bone and water samples a predictive capability would be especially valuable in the absence of well preserved archaeological fish bone we surveyed samples from lakes and rivers in varying geological settings in britain and ireland modern fish bone and water samples were analysed to investigate modern radiocarbon offsets from the atmosphere archaeological fish bone was also analysed to examine past reservoir offsets at selected sites stable carbon and nitrogen isotope values were measured to aid in interpretation of any variability in the offsets large freshwater reservoir offsets were measured in some modern and archaeological samples maximum offset 1638 14 c years the freshwater reservoir offsets in the fish bone were highly correlated with alkalinity of water in modern lake sites analysed however a high amount of variation within and between fish species was also evident in the results precluding the possibility of providing regional corrections for freshwater reservoir offsets from alkalinity although this still may provide a general guideline the variability is thought to be due to differences in the diet of individual fish

the indian bay formation fossiliferous early ordovician volcanogenic rocks in the northern gander terrane newfoundland and their regional significance the first reported fossiliferous rocks in the northern gander terrane of the newfoundland appalachians occur at indian bay big pond in an area previously mapped as unfossiliferous quartzose sedimentary rocks of the gander group brachiopods trilobites and bryozoans in argillaceous tuff indicate a late arenigian late early ordovician age the rocks associated with the fossils are similar to coeval rocks of the dunnage terrane in newfoundland but are atypical of the gander terrane the sequence that includes the fossiliferous rocks at indian bay big pond is here named the indian bay formation the indian bay formation may overlie the gander group stratigraphically but structural geophysical and geochemical data suggest that the rocks of the indian bay formation are contained in a klippe thrust onto the gander terrane

marine or estuarine radiocarbon reservoir corrections for mollusks a case study from a medieval site in the south of england abstract mollusk shells are frequently radiocarbon dated and provide reliable calibrated age ranges when the regional marine reservoir correction is well established for mollusks from an estuarine environment the reservoir correction may be significantly different than the regional marine reservoir correction due to the input of bedrock or soil derived carbonates some mollusk species such as oysters are tolerant of a significant range of salinities which makes it difficult to determine which reservoir correction is appropriate a case study is presented of an anomalous radiocarbon age for an oyster shell paint dish found in the fabric of the ruined nave walls of st mary s church shoreham by sea west sussex england stable isotopes 18 o and 13 c were used to establish the type of environment in which the oyster had lived paired marine and terrestrial samples from a nearby medieval site were radiocarbon dated to provide an appropriate reservoir correction

freshwater radiocarbon reservoir age in the lower yellow river floodplain during the late holocene the radiocarbon concentration of the dissolved inorganic carbon dic pool of most freshwater bodies such as lakes and rivers tends to be depleted with respect to that of the contemporaneous atmosp

plutonic and hydrothermal events in the ackley granite southeast newfoundland as indicated by total fusion 40ar 39ar geochronology results of total fusion 40ar 39ar dating eight biotites four muscovites and one hornblende of magmatic and hydrothermal stages of the high silica chemically zoned ackley granite indicate three distinct episodes of magmatic activity viz 410 378 374 and 355 ma and that the metallogenic system w sn mo evolved synchronously with only one of the magmatic phases the oldest suite is indicated by two biotite dates at 410 4 4 4 and 392 5 7 6 ma which are themselves considered as representing partial resetting related to a tectonothermal event of acadian age thus the 410 ma age offers the best estimate of intrusion although it must be considered a minimum the main magmatic pulse for the ackley granite is indicated by dates between 378 and 374 ma with most of these phases occurring in the southern part of the complex concordant hornblende biotite ages 374 8 3 8 and 372 3 4 8 ma respectively for one of the southern phases rencontre lake granite suggests rapid cooling for this part o

new age data refine extent and duration of paleozoic and neoproterozoic plutonism at ganderia avalonia boundary newfoundland devonian and younger plutonic suites of the appalachian orogen in newfoundland form a curvilinear belt straddling the boundary between ganderia and avalonia and exhibit a general pattern of younging to the southeast however many individual plutonic suites within this belt remain undated or have ages that are poorly constrained this study reports u pb sensitive high resolution ion microprobe shrimp data from zircon and 40ar 39ar data from hornblende biotite and muscovite which collectively improve definition of post tectonic plutonic events in southeastern newfoundland but at the same time raise new questions for further study u pb zircon shrimp determinations provide valuable new geochronological information for the deadman s bay granite 390 4 ma the gander lake granite 378 4 ma the terra nova granite 384 4 ma the old woman stock 376 4 ma and the easternmost unit tolt phase of the composite ackley granite 372 4 ma the pass island granite long considered part of this

a silurian u pb age for the cape st mary s sills avalon peninsula newfoundland canada implications for silurian orogenesis in the avalon zone mafic sills from cape st mary s on the avalon peninsula of newfoundland give an u pb baddeleyite age of 441 2 ma this age corresponds with the earliest ages recorded for the climactic silurian orogenic event that dominantly affected rocks of the central mobile belt in newfoundland the age is consistent with but in no way necessitates that the avalon and gander zones were juxtaposed during the silurian because sills tend to form in poorly lithified and undeformed sedimentary rocks it is unlikely that cambrian sediments hosting the sills were affected by ordovician orogenic events that strongly affected central newfoundland negative nb and ti anomalies on mid ocean ridge basalt normalized diagrams show that the sill geochemistry is consistent with formation in a transpressional tectonic environment mafic magmas clearly associated with the silurian event share these chemical and tectonic affinities thus both the age and geochemical data are consistent with but do not require a link between the gand

geochemistry of siluro devonian tobique volcanic belt in northern and central new brunswick canada tectonic implications siluro devonian volcanic rocks of the northwestern mainland appalachians are found mainly in the tobique belt of new brunswick where they consist predominantly of bimodal mafic felsic suites erupted in a continental rift environment the axis of the tobique rift trends north northeast south southwest obliquely to the regional northeast southwest trend of the appalachians these geometric relationships are interpreted as being the result of rifting in a sinistral shear regime produced during emplacement of the avalon terrene the basaltic rocks are continental tholeiites and transitional basalts derived from a heterogeneous upper mantle source that was enriched in incompatible elements relative to the primordial mantle the mantle source was probably affected by the subduction processes

inversion of refraction data from the fram and nansen basins of the arctic ocean abstract as a part of the fram 2 experiment march may 1980 six refraction lines were shot in the pole abyssal plain or fram basin of the eastern arctic ocean during the fram 4 experiment march may 1982 four refraction lines were also shot in the nansen basin just northeast of the yermak plateau the fram 2 lines at 86 n 24 w cover both the abyssal plain region and the northern flank of the morris jessup rise near magnetic anomalies 22 and 23 the fram 4 lines near 83 n 15 20 e are on slightly younger crust at anomaly 12 in this paper we introduce new methods for processing and inversion of arctic refraction data and contrast the results from these tectonically similar regions on opposite sides of the spreading center at the arctic mid ocean nansen ridge in both experiments the data were recorded digitally on a two dimensional array of 24 hydrophones located 93 m below the floe camps these multi channel data are processed by high resolution array processing techniques to yield velocity spectra over the short 1 km apertures of the arrays these velocity spectra are transformed to tau slowness and offset slowness parameterizations and are inverted by 1 1 velocity depth migration 2 2 tau sum 3 3 extremal inversion techniques to obtain crustal velocity models down to the moho without the ability of the array processing to discern late breaking primaries multiples and shear arrivals the sparsely shot lines with 5 15 offsets over the 30 100 km line lengths would not be invertible by these methods these results demonstrate the effectiveness of arrays in determining crustal structure under the constraints of arctic ice pack environment

the evolution of the avalonian plate abstract the avalon platform of newfoundland is the type locality of the avalonian plate that is characterized by late precambrian volcanic and clastic rocks marine at the bottom and terrestrial at the top all are intruded by 650 550 ma granites late precambrian rocks in the southern british isles are similar in both areas northeastern parts of the belt are affected by deformation and metamorphism that have orogenic aspects the orogeny is referred to as the avalonian in newfoundland and monian in britain to the southeast of the avalonian rocks in europe lies another late precambrian cadomian orogenic belt of rocks as a part of the pan african orogenic belt the cadomian and avalonian belts extend into north africa morocco since these belts are ophiolite bearing it is suggested that the plate was bordered by oceanic domains it is therefore proposed that a microcontinental volcanic arc that was generated in the late precambrian was orogenically deformed by collision with north america europe and africa and survived as a coherent terrain until the late carboniferous

timing of arrival of the avalon zone in the northeastern appalachians a new look at the straddling granite the straddling granite was previously thought to straddle the hermitage bay dover fault system which marks the boundary between the avalon and gander zones of eastern newfoundland and hence to fix the earliest juxtaposition of these two zones before 504 12 ma more detailed investigation shows that these rocks are divisible into two distinct geochemical suites the indian point granite to the west and the hardy9s cove intrusive suite to the east of the samples that provided the 504 ma isochron five were obtained from the hardy9s cove suite and one from within the fault zone hence the isochron must be taken as representing only a typical date for plutonic rocks within the avalon zone the indian point granite intrudes the gaultois granite dated at 350 18 ma and is thus considerably younger than the hardy9s cove suite these observations now allow for juxtaposition of the avalon and gander zones to have been as late as early carboniferous

devonian dikes from north central newfoundland a radiometric paleomagnetic study 40ar 39ar age spectra have been obtained for biotites and hornblendes representing a suite of diabase dikes from the northern part of newfoundland s gander zone a primary apparent age of 375 10 ma is suggested a value probably very close to the age of intrusion a number of the age spectra are discordant this perhaps results from a disturbing event 180 ma ago magnetic analysis of the dike swarm has yielded four paleopoles three of these magnetizations appear to be carried by multi domain magnetite the other by hematite if the magnetite magnetizations are primary they possibly reflect a period of aberrant geomagnetic field behaviour at about the time given above on the other hand if the hematite magnetization is primary the data can be interpreted in terms of the displaced terrain model of kent and opdyke however our data imply that the relative southern displacement of acadia in the devonian may be smaller than these authors have suggested

40ar 39ar incremental release ages of biotite from a progressively remetamorphosed archean basement terrane in southwestern labrador abstract gneisses within an archean basement terrane adjacent to the southwestern portion of the labrador trough were variably retrograded during a regional metamorphism of grenville age ca 1000 ma biotites from non retrograded segments of the gneiss terrane record 40 ar 39 ar plateau and isochron ages which date times of cooling following an episode of the kenoran orogeny 2376 2391 ma a suite of gneiss samples displaying varying degrees of retrograde alteration was collected across the grenville metamorphic gradient biotites in these samples show no petrographic evidence of retrograde alteration however they do record internally discordant 40 ar 39 ar age spectra although the extent of internal discordance is variable the overall character of the release patterns is similar with younger apparent ages recorded in intermediate temperature gas fractions the total gas dates range from 2257 27 ma northwest to 1751 23 ma southeast suggesting that variable quantities of radiogenic argon were lost from the archean biotites during grenville metamorphism the saddle shaped nature of the discordant spectra indicates that argon loss was not accomplished through single stage volume diffusion processes biotites in portions of the gneiss terrane which were completely recrystallized during grenville metamorphism are petrographically and texturally distinct a representative of this phase records a 40 ar 39 ar plateau age of 2674 28 ma this date is markedly inconsistent with regional constraints on the timing of grenville metamorphism and indicates the presence of extraneous argon components both the extraneous and radiogenic argon components must have been liberated in constant proportions during experimental heating because the argon isotopic data yield a well defined 40 ar 36 ar vs 39 ar 36 ar isochron corresponding to an age 2658 23 ma similar to that defined by the plateau portion of the spectrum the 40 ar 39 ar biotite dates suggest that the effects of grenville metamorphism extent 15 20 km northward into the superior province the limit of this overprint is approximately coincident with the northernmost development of grenville age thrust faults in the archean terrane therefore it is proposed that the northern margin of the grenville province in southwestern labrador should be located along the northernmost grenville thrust fault because this represents both a structural and a thermal discontinuity

spatial variability of 14c reservoir effects in tibetan plateau lakes abstract radiocarbon dating of lake sediments is often hampered by the presence of a lake reservoir effect lre also dead carbon or old carbon effect especially in dry and cold regions with a sparse plant cover in the catchment the tibetan plateau became a hotspot of the palaeoenvironmental and climate research community in recent years and the assessment of present day lres is a crucial prerequisite for the establishment of reliable radiocarbon age depth relationships for lake sediment cores this paper examines the spatial variability of lres within individual lakes through a discussion of new data for lake donggi cona and a compilation of previously published data for five additional lakes where lre data are available for different sites lake reservoir effects for lake donggi cona on the northeastern tibetan plateau were determined for shells of aquatic snails collected alive close to the lake s shore the largest determined lre of 20 000 14 c years is significantly larger than previously reported lres from the central part of the lake and larger than any previously published lre for the tibetan plateau relatively low lres in the central regions of lakes higher lres towards the margins and high lres in tributaries and spring waters are apparently a common pattern of tibetan plateau lakes the differences in lres within individual lakes or catchment areas are attributed to the more prolonged exchange of the lake water s dissolved inorganic carbon with the atmospheric co 2 in central lake regions on the one hand and the increasing influence of 14 c free or poor stream and groundwater due to the dissolution of carbonaceous basement rocks towards its margins generally higher lres were recorded in the three tectonically active lake regions of the six examined catchments and it is speculated that rising crustal co 2 further contributes to the lres in these catchments in addition to these observations and inferences elevated 14 c levels of the atmosphere as a result of nuclear bomb testing are often ignored if lres for modern materials are reported by convention relative to the atmospheric 14 c activity of the year 1950 lre data reported in this way represent unrealistic minimum estimates

the massabesic gneiss complex new hampshire a study of a portion of the avalon terrane geochemical data from the 625 ma massabesic gneiss complex of southern new hampshire show strong affinities for other avalonian rocks of southern new england and suggest continental rifting in the late proterozoic migmatized paragneiss the dominant rock type in the complex has major and trace element compositions that are compatible with graywackes from continental arcs the para gneiss also has strong lithologic metamorphic and isotopic similarities to the rocks of the hope valley zone of connecticut avalon suggesting a possible hope valley massabesic correlation at 625 ma the paragneiss end values are similar to avalonian crust in other locations of the orogen two types of amphibolite are present in minor amounts in the paragneiss of the massabesic gneiss complex the first type is a paramphibolite and consists of calc silicate layers in the massabesic paragneiss the second type is metaigneous major and trace element abundances reveal that the protoliths of the orthoamphibolites range from continental rift alkaline basalts and tholeiites to n type morbs orthoam phibolite end 625 ma values range from 2 4 to 4 as expected of rift related magmas derived from partial melting of a depleted mantle source and have the same values as iapetus ocean floor rocks of similar age orthoamphibolite major and trace element geochemical characteristics overlap those of the middlesex fells amphibolites of the esmond dedham zone of eastern massachusetts avalon which range from alkaline to transitional basalts erupted in a continental rift setting the compositions of orthoam phibolites define a potential magmatic continuum produced by batch partial melting of the mantle initiated during continental rifting and proceeded to ocean basin forma tion the inferred continuity of mafic magmatism from the esmond dedham mid dlesex fells formation to the massabesic gneiss complex and hope valley zone suggests that these zones are not distinct lithotectonic zones but are parts of a single landmass massachusetts avalon esmond dedham represents the continental section of avalon where the alkaline to transitional magmas of the early rifting stages are preserved according to our tectonic reconstruction the massabesic gneiss complex is the oceanward continental margin represented by volcanoclastic sediments with the morbs representing the initiation of ocean basin development the leading edge of this landmass of which the massabesic gneiss complex is the only observable remnant collided with laurentia during the acadian orogeny the inboard thicker more continental trailing edge that is platform avalon esmond dedham collided later during the alleghanian orogeny