history and isostatic effects of the last ice sheet in southern british columbia abstract the late wisconsinan cordilleran ice sheet covered british columbia southern yukon territory and parts of alaska washington idaho and montana its major source areas were the high mountain ranges of the canadian cordillera and flow was strongly controlled by topography the last ice sheet began to develop about 30 000 25 000 14c yr ago but it did not achieve its maximum extent until 15 000 14 000 14c yr bp ice sheet growth was interrupted locally by stillstands and retreat ice sheet decay was rapid and was characterized by complex frontal retreat at the periphery accompanied locally by brief readvances and by downwasting and stagnation by 10 000 14c yr bp

geochemical reconstruction of pacific decadal variability from the eastern north pacific during the holocene determining climate variations over the holocene requires high resolution records with well developed age models a 40 m long marine sediment core raised from effingham inlet an anoxic fjord on the west coast of vancouver island british columbia canada yields such a record forty six 14c accelerator mass spectrometry ams dates determined from terrestrial plant material form the age model downcore sampling at both 5 cm 20 year and 1 5 cm 7 year resolution indicates that high frequency oceanographic variability has prevailed at this site over the last 10 000 years spectral analysis of wt opal a proxy for diatom productivity in the basin reveals the bidecadal and pentadecadal periods of the pacific decadal oscillation pdo north pacific index npi that are related to changes in the strength of the aleutian low coherence analysis between the effingham inlet data and 18o records from jellybean lake a high elevation site in southwest yukon indicates regional coherence at periods of 45 7

regional mapping of pre metamorphic spilitization and associated chemical mobility in greenschist facies metabasalts of the sw scottish highlands abstract both spilitic and non spilitic metabasaltic sills are hosted by greenschist facies metasediments in the sw scottish highlands spilitization is mainly characterized by enrichment in na 2 o elevated modal plagioclase and epidote segregations mapping of the spatial distribution of spilitic metabasalts reveals an ancient sub sea floor fluid cell centred on the extrusive tayvallich volcanics fluid circulation was most extensive at shallow levels where most sills were spilitized we attribute this to pervasive flow of saline fluid which was thermally driven by the cooling suite of lava flows and sills spilitization below this lithostratigraphic depth was restricted to only a few sills their spilitization is largely unrelated to specific properties of these sills e g width chemistry or host lithology we conclude that fluid channelling was an intrinsic property of sub sea floor fluid flow either at deeper levels or earlier during fluid circulation by profiling of the size distributions of relic phenocrysts in a partly spilitized sill we conclude that spilitization proceeds with the symmetric propagation of a spilitization front from the sill margins towards the sill interior based on chemical profiling across the margin of an epidote segregation we conclude that spilitization is associated with chemical transport on scales ranging from 0 1 to 10 m

late quaternary sea levels and crustal movements coastal british columbia late quaternary sea level fluctuations on the british columbia coast have been established from studies of terrestrial and marine sediments and landforms these studies indicate that the sea level history of mainland british columbia and eastern vancouver island is very different from that of the queen charlotte islands and western vancouver island specifically in the former areas there was a rapid rise of submerged coastal lowlands between about 13 000 and 10 000 years ago emergence culminated about 6000 9000 years ago depending on the locality when the sea relative to the land was 12 m or more lower than at present in some areas during middle and late holocene time relative sea level rose on the mainland coast and at least locally on eastern vancouver island resulting in inundation of coastal archaeological sites and low lying terrestrial vegetation tidal records and precise levelling suggest ongoing submergence of at least part of this region in contrast shorelines on the queen charlotte i

isolation basins sea level changes and the holocene history of the greenland ice sheet abstract isolation basins are natural topographic depressions that at various times in their history may be connected to or isolated from the sea by changes in relative sea level rsl they provide a valuable source of data for tracking large scale tens of meters changes in rsl over millennia as well as quiet water depositional environments where abrupt changes caused by tsunami iceberg roll or storms may be recorded in this paper we review isolation basins as sources of rsl data with a particular focus on their use in greenland to constrain the holocene history of the ice sheet a new rsl curve from disko fjord west greenland is presented which shows that local ice free conditions were established at c 11 k cal yr bp after which rsl fell rapidly from a marine limit at c 80 m to reach close to present sea level by c 4 k cal yr bp we compare this record with other isolation basin rsl data from six other sites in disko bugt and note a strong northwest southeast differential rebound across the area during the early and mid holocene that reflects variations in ice load history we compare the disko bugt data with other previously published isolation basin rsl records from sisimiut central west greenland nanortalik south greenland and ammassalik southeast greenland rsl fell below present during the early holocene at nanortalik c 10 k cal yr bp and during the mid to late holocene elsewhere before rising to present these differences reflect variations in the timing and amount of greenland ice load change since the last glacial maximum as well as non greenland processes notably the collapse of the laurentide forebulge and also changes in ice equivalent sea level isolation basin data have relatively small age and height uncertainties compared with other rsl indicators enabling them to resolve between different earth and ice sheet models especially during periods of large ice load and rsl change

marine and limnic radiocarbon reservoir corrections for studies of late and postglacial environments in georgia basin and puget lowland british columbia canada and washington usa models of late glacial environmental change in coastal areas are commonly based on radiocarbon ages on marine shell and basal lake sediments both of which may be compromised by reservoir effects the magnitude of the oceanic reservoir age in the inland waters of the georgia basin and puget lowland of northwestern north america is inferred from radiocarbon ages on shell wood pairs in saanich inlet and previously published estimates the weighted mean oceanic reservoir correction in the early and mid holocene is 720 90 yr slightly smaller than but not significantly different from the modern value the correction in late glacial time is 950 50 yr valley head sites yield higher reservoir values 1200 130 yr immediately after deglaciation the magnitude of the gyttja reservoir effect is inferred from pairs of bulk gyttja and plant macrofossil ages from four lakes in the region incorporation of old carbon into basal gyttja yields ages from bulk samples that are initially about 600 yr too old the reservoir age declines to less than 100 yr after the first millennium of lake development when these corrections are accounted for dates of deglaciation and late glacial sea level change in the study area are pushed forward in time by more than 500 yr

mineralogical controls on metamorphic fluid flow in metabasaltic sills from islay scotland abstract in this study we show that mineralogy was the primary control of metamorphic fluid flow in the well studied metabasaltic sills in the sw scottish highlands here basaltic sills have been partially carbonated by h 2 o co 2 fluids at greenschist facies conditions this has led to mineral zonation with carbonate poor sill interiors separated from carbonate rich sill margins by reaction fronts although deformation set the stage for metamorphic fluid flow in the sw scottish highlands by causing the preferred alignment of mineral grains metamorphic fluid flow was not coupled with active deformation but occurred later utilizing the pre existing mineral alignment as a means of accessing the sill interiors the sills which were studied were partially carbonated with well preserved reaction fronts they were selected because atypically for the sw scottish highlands they are mineralogically heterogeneous making them ideal for a study of mineralogical controls of metamorphic fluid flow their mineralogical heterogeneity reflects chemical heterogeneity arising from magmatic flow differentiation and spilitization which occurred before greenschist facies metamorphism magmatic flow differentiation resulted in parts of the sill containing large crystals with no preferred alignment large up to 3 cm plagioclase phenocrysts were concentrated in the sill interior whereas large up to 1 cm amphibole after pyroxene grains formed cumulate layers close to the sill margins these large randomly oriented crystals were replaced by an interface coupled dissolution precipitation mechanism replacement is constant volume and with hydration and carbonation affecting the cores of these minerals while the rims are remained intact and unaltered this finding points to intra granular metamorphic fluid flow in contrast inter granular metamorphic fluid flow was facilitated by mineral alignment on different scales pre metamorphic spilitization produced layers of epidote called segregations whereas regional deformation caused preferred alignment mainly of amphibole and chlorite epidote undergoes a series of volume changes during greenschist facies metamorphism this created porosity which produced preferred pathways for metamorphic fluids affecting the advancement of fluid driven reaction fronts preferred alignment of amphibole and chlorite also affected the advancement of reaction fronts in this case fluid flow was preferentially parallel to the foliation in both cases inter granular metamorphic fluid flow utilized a pre existing fabric albeit on different scales these results show intra granular metamorphic fluid flow in unfoliated rock and inter granular metamorphic fluid flow in foliated rock in both cases metamorphic fluid flow occurred after deformation controlled by pre existing mineralogical heterogeneities such as grain composition and shape anisotropy as well as preferred alignment of mineral grains

differential behaviour of the rb sr and k ar systems of spilitic flows and interbedded metasediments the spilite group of erquy brittany france paleomagnetic implications the erquy series cotes du nord france consists in its upper part of spilitic pillow lavas with some interbedded volcano sedimentary horizons

late pleistocene coastal paleogeography of the queen charlotte islands british columbia canada and its implications for terrestrial biogeography and early postglacial human occupation molluscs sediment lithology and published sub bottom profiles are used to deduce sea levels outline the influence of glacially induced crustal displacement and reconstruct the paleoenvironment of the northeast pacific late quaternary coastline geo spatial modelling shows subaerially exposed land that could have been inhabited by plants and animals and also coastally migrating early north american peoples ice free terrain present by at least 13 790 150 14 c years bp a land bridge and edible molluscs are identified queen charlotte islands qci late pleistocene coastal paleogeography may assist in explaining the biogeography of many terrestrial plant and animal species along the broader northeastern pacific margin and provide evidence for researchers seeking late pleistocene early holocene glacial refugia late pleistocene early holocene coastlines that are not drowned and that may harbour early archaeological sites are identified along the western qci where migrants probably first travelled and the westernmost british columbia mainland where the effects of glacial ice were reduced

dolomitic breccia veins as evidence for extension and fluid flow in the dalradian of argyll veins of red dolomite occur extensively in the dalradian rocks of argyll scotland and adjacent areas the veins represent brittle extensional deformation preferentially reactivating caledonian quartz veins the dolomite is associated with reddening of the adjacent dalradian country rock which it partially replaced dolomite was also precipitated in overlying old red sandstone and probably dates to late carboniferous early permian fluid inclusion studies show that the veining involved moderate temperature 75 to 115 c fluids stable isotope data suggest that these fluids were basinal brines traces of chalcopyrite paragenetically late in the veins may reflect the mineralization which occurs more widely in the dalradian rocks of argyll the red colour of the dolomite is due to abundant haematite crystallites that grew in the dolomite crystal fabric palaeomagnetic analysis yields a consistent late permian early triassic age for the haematite growth in the dolomite veins and the reddened dalradian country rocks this age represents the time of haematite precipitation from iron rich dolomite that may have been related to deep oxidizing weathering gold anomalies associated with reddened basement rock must be of this age or younger

annual record of particle fluxes geochemistry and diatoms in effingham inlet british columbia canada and the impact of the 1999 la nina event abstract sediment traps were deployed inside the anoxic inner basin of effingham inlet and at the oxygenated mouth of the inlet from may 1999 to september 2000 in a pilot study to determine the annual depositional cycle and impact of the 1999 la nina event within a western canadian inlet facing the open pacific ocean total mass flux geochemical parameters carbon nitrogen opal major and minor element contents and stable isotope ratios and diatom assemblages were determined and compared with meteorological and oceanographic data deposition was seasonal with coarser grained terrestrial components and benthic diatoms settling in the autumn and winter coincident with the rainy season marine sedimentary components and abundant pelagic diatoms were coincident with coastal upwelling in the spring and summer despite the seasonal differences in deposition the typical temperate zone thalassiosira skeletonema chaetoceros bloom succession was muted a july 1999 total mass flux peak and an increase in biogenous components coincided with a rare bottom water oxygen renewal event in the inlet likewise there were cooler than average sea surface temperatures ssts just outside the inlet and unusually high abundances of a previously undescribed cool water marine diatom fragilariopsis pacifica sp nov within the inlet each of these occurrences likely reflects a response to the strong la nina that followed the year after the strongest ever recorded el nino event of 1997 1998 by the autumn of 1999 ssts had returned to average and f pacifica had all but disappeared from the remaining trap record indicating that oceanographic conditions had returned to normal oxygenation events were not witnessed in the inlet in the years before or after 1999 suggesting that a rare oceanographic and climatic event was captured by this sediment trap time series the data from this record can therefore be used as a benchmark for identifying anomalous environmental conditions on this coast

paleomagnetic evidence for long term 104 year memory and periodic behavior in the earth s core dynamo process a new paleomagnetic secular variation psv record from the late quaternary wilson creek beds of mono lake california contains a distinctive periodic vector waveform that follows and is almost certainly related to the mono lake excursion a comparison of all published psv results from the wilson creek beds suggests that the magnetic field at mono lake went through an interval 36 000 28 000 ybp of very low amplitude psv followed by the mono lake excursion 28 000 27 000 ybp and four subsequent recurrences 27 000 12 500 ybp of the excursion waveform with relatively diminished amplitudes lower than the excursion amplitude but higher than psv amplitudes at mono lake since 12 500 ybp this pattern clearly suggests that the mono lake excursion is related to typical psv it also suggests that the core dynamo process responsible for psv is capable of near impulse onset persistence over a time scale of 15 000 years and quasi periodic behavior that is non wave length dispersive in time

a general review of volcanogenic massive sulphide deposits in china abstract volcanogenic massive sulphide deposits in china have for the past forty years been an important source of cu zn pb and sulphur and of a number of associated elements such as au ag and co the areal distribution of the deposits is determined by the different geological settings in which they occur and which range in time from archean to triassic host rock lithologies comprise felsic mafic and ultramafic metavolcanic rocks with or without subsidiary intercalated metasedimentary rocks four groups of ore associations based on chemical composition have been distinguished cu cu zn cu fe and pb zn cu only one deposit of economic significance hongtoushan has been recognised so far in an archean greenstone belt this ore is hosted by metafelsic volcanic rocks of a calc alkaline suite the proterozoic was an important period for the formation of two groups of volcanogenic massive sulphide deposits in china early proterozoic cu fe deposits such as dahongshan and lalachang are predominantly distributed in graben like depressions within cratons late proterozoic cu zn deposits e g xiqiu and liujiaping occur mainly along the edges of the craton the ores of all proterozoic deposits are hosted by quartz keratophyre the most important metallogenic epoch for this type of ores in china was the lower palaeozoic and is represented by a number of deposits situated in the northern qilian caledonian orogenic belt within this belt the various groups of deposits can be related to specific plate tectonic settings cu zn or pb zn cu ores occur in quartz keratophyric tuffite with or without intercalated sediments of island arc environments houyanshan zheyaoshan xiaotieshan cu ores are hosted by spilite generated probably in back arc basin settings honggou while cu zn ores presumably occur in metabasalts of oceanic ridge or off axis settings yendonggou volcanogenic massive sulphides are relatively unimportant in the late palaeozoic both with regard to size and numbers but a rather unusual and important cu zn deposit hosted by ultramafic rocks deerni is ascribed to this epoch an important pb zn cu deposit gacun that is comparable with the kuroko deposits was formed in the early mesozoic yidun orogenic belt which is considered to represent a mature arc environment the ores are hosted by rhyolites within calc alkaline volcanites of dominantly andesitic and rhyolitic composition the very important sedex type stratabound and stratiform base metal deposits in china seem to have occurred mainly at times when the volcanogenic massive sulphide deposits became relatively unimportant for instance the early proterozoic early palaeozoic and early mesozoic are the main periods for the formation of volcex type massive sulphides while the middle proterozoic and middle late palaeozoic are most important for sedex type stratiform base metal sulphides

first report of lower permian basalts in south tibet tholeiitic magmatism during break up and incipient opening of neotethys abstract the neo tethys ocean began to form at early permian times when continental flood basalts were emplaced in various areas of the newly formed indian passive margin exposed today in the so called tibetan sedimentary zone of the himalaya lower permian mafic volcanic rocks which have long been known from various himalayan localities from kashmir to arunachal pradesh are here for the first time reported to occur also in south tibet bhote kosi basalts of the gyirong county the basalts unconformably overlie lowermost permian diamictites with locally intervening black shales and debris flow deposits and are followed in turn by chert bearing quartzarenites and silty to phosphatic marls yielding brachiopods of roadian wordian age the age of the lavas can thus be bracketed as late early permian post sakmarian and pre roadian the geochemistry of these subalkalic tholeiites akin to morbs testifies to their similarity not only with the adjacent nar tsum spilites of central nepal but also with the panjal traps and abor volcanics of the western and eastern himalayas respectively the geochemical signature of lower permian volcanic rocks is in fact uniform all along the himalayan range and markedly different from that of basaltic rhyolitic alkalic products sporadically emplaced during the previous rifting stage rift volcanism in the tethys himalaya began in the early carboniferous and came to an end in sakmarian times in the early permian initial submergence of the rift shoulders and sediment starvation were followed by tholeiitic magmatism which is therefore interpreted as following break up and incipient sea floor spreading in the neotethys ocean roughly contemporaneous emplacement of continental flood basalts of similar geochemical signature along a 2000 km long rift axis would in fact suggest extensive mantle melting at the transition from continental rifting to break up and opening of the neotethys between northern gondwana and the peri gondwanian blocks

ice core record of rising lead pollution in the north pacific atmosphere 1 a high resolution 8000 year long ice core record from the mt logan summit plateau 5300 m asl reveals the initiation of trans pacific lead pb pollution by ca 1730 and a 10 fold increase in pb concentration 1981 1998 mean 68 9 ng l above natural background 5 6 ng l attributed to rising anthropogenic pb emissions from asia the largest rise in north pacific pb pollution from 1970 1998 end of record is contemporaneous with a decrease in eurasian and north american pb pollution as documented in ice core records from greenland devon island and the european alps the distinct pb pollution history in the north pacific is interpreted to result from the later industrialization and less stringent abatement measures in asia compared to north america and eurasia the mt logan record shows evidence for both a rising pb emissions signal from asia and a trans pacific transport efficiency signal related to the strength of the aleutian low

magnetic hysteresis parameters and day plot analysis to characterize diagenetic alteration in gas hydrate bearing sediments 1 the j meter coercivity spectrometer is a machine capable of rapid and simple measurement of magnetic hysteresis isothermal remanence acquisition and magnetic viscosity of rocks and sediments the j meter was used to study a suite of samples collected from strata in the gas hydrate bearing japex jnoc gsc mallik 5l 38 well 69 5 n 134 6 w in the mackenzie delta of the northwestern canadian arctic the day plot of magnetic hysteresis ratios for these samples is exotic in that the points do not plot along a hyperbola as is usually observed rather they plot as a scatter which is shown to contour into vertical slices using coercivity field hc or saturation magnetization js and horizontal slices using the relative quantity of superparamagnetism jspm js optical microscopy reveals that the magnetic minerals are detrital magnetite and authigenic greigite greigite is dominant in sands which in situ had 70 gas hydrate saturation and in silts in which gas hydrate growth was blocked by insufficient porosity we infer that the silts were the accumulation sites for solutes which had been excluded from the pore waters in neighboring coarser grained sediments during the course of gas hydrate formation consequently we conclude that magnetic properties are related to gas hydrate related processes and as such may have potential as a method of remote sensing for gas hydrate deposits

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

timing of meltwater pulse 1a and climate responses to meltwater injections the temporal relationship between meltwater pulse 1a mwp 1a and the climate history of the last deglaciation remains a subject of debate by combining the greenland ice core project d18o ice core record on the new greenland ice core chronology 2005 timescale with the u th dated barbados coral record we conclusively derive that mwp 1a did not coincide with the sharp bolling warming but instead with the abrupt cooling of the older dryas to evaluate whether there is a relationship between meltwater injections north atlantic deep water nadw formation and climate change we present a high resolution record of nadw flow intensity from eirik drift through the last deglaciation it indicates only a relatively minor 200 year weakening of nadw flow coincident with mwp 1a our compilation of records also indicates that during heinrich event 1 and the younger dryas there were no discernible sea level rises and yet these periods were characterized by intense nadw slowdowns shutdowns clearly deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead our results emphasize that the location of meltwater pulses may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

holocene earthquake records from the cascadia subduction zone and northern san andreas fault based on precise dating of offshore turbidites abstract we present preliminary evidence for a 10 000 year earthquake record from two major fault systems based on sediment cores collected along the continental margins of western north america new stratigraphic evidence from cascadia demonstrates that 13 earthquakes ruptured the entire margin from vancouver island to at least the california border since the eruption of the mazama ash 7700 years ago the 13 events above this prominent stratigraphic marker have an average repeat time of 600 years and the youngest event 300 years ago coincides with the coastal record we also extend the record of past earthquakes to the base of the holocene at least 9800 years ago during which 18 events correlate along the same region the sequence of holocene events in cascadia appears to contain a repeating pattern of events a tantalizing first look at what may be the long term behavior of a major fault system the northern california margin cores show a cyclic record of turbidite beds that may represent holoce

were they all giants perspectives on late holocene plate boundary earthquakes at the northern end of the cascadia subduction zone abstract the relative magnitude of plate boundary earthquakes at the northern end of the cascadia subduction zone was assessed from the temporal concordance between the ages of coseismically buried late holocene soils in southwest washington their counterparts in central and southern cascadia offshore turbidites and paleoseismic deposits on the west coast of vancouver island only three of the seven buried soils in southwest washington that can be reliably traced as buried soils or paleotsunami deposits in the coastal lowlands of south central and southern cascadia have well dated counterparts in northern cascadia the three wide ranging events date from cascadia earthquakes y 250 cal bp u 1260 cal bp and n 2520 cal bp all three likely ruptured the entire plate margin and therefore potentially qualify as giants m w 9 deposits that may derive from tsunamis generated by earthquakes s 1570 cal bp l 2870 cal bp and j 3360 cal bp can also be found in northern cascadia but the ages of these deposits are not yet well enough constrained to determine whether they are coeval with their southern counterparts earthquake w 850 cal bp appears to be present in the northern cascadia paleoseismic record but yields considerably older ages than in central cascadia and may be missing from southernmost cascadia the onshore record of an offshore turbidite t2 displays a similar spatio temporal pattern to that of earthquake w

tectonic setting of the bela ophiolites southern pakistan abstract the bela ophiolites consist of a 3 5 km thick sequence of basaltic pillow lava inter flow sedimentary rocks chert argillite limestone and diabase gabbro sills debris of serpentinite up to kilometer sized blocks serpentinite carbonate breccia and less commonly of basalt gabbro peridotite pelagic limestone and their metamorphic equivalents occur throughout the ophiolite sequence and may form extensive horizons the age of the ophiolites as indicated by pelagic microfauna is aptian early maestrichtian the lava flows belong to a spilite keratophyre basaltic andesite suite of tholeiites enriched in fe tio 2 and other trace elements the lava flows although similar to the e type morb differ in details such as la ta ratio ranges 9 62 18 04 for the bela lavas versus 10 15 for the morb the diabase gabbro sills are similar to the associated lava flows however due to their relative enrichment in certain elements e g fe ti hf th and ta etc they may represent more fractionated late melts a comparison of the stratigraphic and structural features of the bela ophiolites with modern oceanic environments reveals that these ophiolites probably originated in a large oceanic fracture zone leaky transform this is based on lithotectonic features such as the common occurrence of debris of foliated serpentinite and serpentinite carbonate breccia bearing rocks in the ophiolite sequence and on geodynamic considerations the fracture zone ancestral to the bela ophiolites probably acted as a boundary between the indian and the neo tethys plates during the cretaceous analogous to the present day owen fracture zone which separates the indian and the arabian plates this ancestral fracture zone was destroyed when transform movement gave way to oblique convergence culminating in the ophiolite obduction in paleocene early eocene time the ophiolite obduction on the west indian continental margin was preceded by alkaline wpb type volcanism which is represented by the porali basalts the bibai lavas and the deccan basalts

effects of productivity glaciation and ventilation on late quaternary sedimentary redox and trace element accumulation on the vancouver island margin western canada variations in chalcophile and redox sensitive trace elements are examined at high resolution intervals from a 50 kyr long sediment core md02 2496 from the vancouver island margin enrichments of ag cd re u and mo above lithogenous levels signifying sedimentary suboxia and anoxia occurred during the early holocene and bolling allerod and during warm interstadial events of marine isotope stage mis 3 down core trace element profiles co vary with productivity proxy records opal caco3 and marine organic carbon and with sedimentary nitrogen isotope ratios which reflect variably enriched nitrate upwelled from intermediate waters that were transported northward from the eastern tropical north pacific the similarity of the md02 2496 record with records from the southern portion of the california current system ccs and to the greenland ice core oxygen isotope record during warm climate intervals suggests that sedimentary redox conditions along the california current responded to local productivity to north atlantic climate change and to tropical pacific surface water processes via long distance teleconnections concentrations of trace elements and productivity proxies were relatively depleted during the younger dryas cool stadial events of mis 3 and in two episodes of glaciomarine sedimentation from 14 7 to 30 5 kyr bp last glacial maximum lgm and from 44 to 50 4 kyr bp cordilleran ice sheet advancement onto the vancouver island continental shelf during the lgm led to intervals of increased terrigenous sedimentation and greatly reduced productivity not seen in the southern portion of the ccs and along with ventilation of north pacific intermediate waters resulted in brief sedimentary oxic conditions

metamorphic gradients in burial metamorphosed vesicular lavas comparison of basalt and spilite in cretaceous basic flows from central chile partial spilitization of a 9 km thick pile of flood basalts with highly vesicular flow tops gave rise to patterns of secondary mineralogy at different scales a a local pattern of mineralogical variation from the almost unaltered bottom towards the altered top of each flow and b an overall pattern comparing flow tops throughout the pile with changes in mineralogical composition within a sequence of metamorphic zones and facies the local patterns mimic the trend of the overall pattern but are of opposite direction and telescoped thus a gradual ordering and andepletion of the secondary albite and increases in the fe al ratio of epidote and pumpellyite upwards within individual flows are comparable in range to corresponding overall changes downwards throughout several kilometres the mineralogical changes within the flows diminish in range towards the more altered deeper part of the pile

port eliza cave north american west coast interstadial environment and implications for human migrations abstract the timing of late pleistocene glacial advance retreat relative sea level and environmental viability between 25 and 12 5 ka 14 c yrs bp remain a key issue in the feasibility of a coastal migration route for the first north americans this is discussed on the basis of stratigraphic radiometric and faunal data for port eliza cave a raised sea cave on the west coast of vancouver island british columbia ice cover is indicated by the occurrence of 2 m of laminated clay representing deposition in a subglacial lake from immediately below this clay a diverse vertebrate fauna of marmot vole marten cervid and various species of birds and fish was recovered yielding ages of 18 16 ka these dates and others from the region show that ice cover on the outer coast was brief from ca 15 5 14 ka the fish species indicate that relative sea level was close to the cave and that salmon runs were likely present the terrestrial vertebrate fauna is consistent with a cool open parkland environment with maximum summer temperatures cooler than present these conditions lasted until at least 16 ka with a diverse fauna and favorable climate humans could have survived here on a mixed marine terrestrial diet confirming the viability of the coastal migration hypothesis for this portion of the route

lithofacies and seismic reflection interpretation of temperate glacimarine sedimentation in tarr inlet glacier bay alaska abstract high resolution seismic reflection profiles of sediment fill within tarr inlet of glacier bay alaska show seismic facies changes with increasing distance from the glacial termini five types of seismic facies are recognized from analysis of huntec and minisparker records and seven lithofacies are determined from detailed sedimentologic study of gravity vibro and box cores and bottom grab samples lithofacies and seismic facies associations and fjordfloor morphology allow us to divide the fjord into three sedimentary environments ice proximal iceberg zone and ice distal the ice proximal environment characterized by a morainal bank depositional system can be subdivided into bank back bank core and bank front subenvironments each of which is characterized by a different depositional subsystem a bank back subsystem shows chaotic seismic facies with a mounded surface which we infer consists mainly of unsorted diamicton and poorly sorted coarse grained sediments a bank core depositional subsystem is a mixture of diamicton rubble gravel sand and mud seismic reflection records of this subsystem are characterized by chaotic seismic facies with abundant hyperbolic diffractions and a hummocky surface a bank front depositional subsystem consists of mainly stratified and massive sand and is characterized by internal hummocky facies on seismic reflection records with significant surface relief and sediment gravity flow channels the depositional system formed in the iceberg zone environment consists of rhythmically laminated mud interbedded with thin beds of weakly stratified diamicton and stratified or massive sand and silt on seismic reflection profiles this depositional system is characterized by discontinuously stratified facies with multiple channels on the surface in the proximal zone and a single channel on the largely flat sediment surface in the distal zone the depositional system formed in the ice distal environment consists of interbedded homogeneous or laminated mud and massive or stratified sand and coarse silt this depositional system shows continuously stratified seismic facies with smooth and flat surfaces on minisparker records and continuously stratified seismic facies which are interlayered with thin weakly stratified facies on huntec records

siliceous microfossil record of late holocene oceanography and climate along the west coast of vancouver island british columbia canada diatoms silicoflagellates and biogenic silica bsi were analyzed from two piston cores recovered from effingham inlet british columbia relatively productive marine conditions from 4850 to 4000 cal yr bp were followed by a transition to the modern ocean climate regime marked by a decreased siliceous microfossil production since 2800 cal yr bp this change in the northeast pacific climate was characterized by an apparent cooling associated with higher rainfall and lower light levels the reduced abundance of most spring summer bloom diatom taxa skeletonema thalassiosira chaetoceros was coupled with a decreased abundance of diatoms normally associated with incursions of offshore water into coastal inlets this pattern reflected a weaker summer upwelling along vancouver island associated with the insolation related increase in the strength of the aleutian low and a weakened north pacific high after ca 2800 cal yr bp diatom assemblages also indicated more frequent periods of relatively low spring summer surface water salinity and a disruption of the typical bloom sequence indicative of increased climatic variability a period of warmer and drier climate conditions and possibly increased coastal upwelling offshore occurred ca 1450 1050 cal yr bp the most recent 500 yr are marked by reduced diatom production and the appearance of three distinct diatom biomarkers in the stratigraphic record rhizosolenia setigera ca ad 1940 minidiscus chilensis ca ad 1860 thalassionema nitzschioides morphotype a ca ad 1550 the oceanographic changes recorded in effingham inlet are correlative with other marine and terrestrial paleoenvironmental records in the northeast pacific ocean

late pleistocene terrestrial deposits on the continental shelf of western canada evidence for rapid sea level change at the end of the last glaciation a paleosol with in situ rooted plant remains has been found in a core at a water depth of 95 m on the central continental shelf of british columbia fluvial sediments associated with the paleosol are sharply overlain by lagoonal or shallow pond sediments these in turn are overlain by shallow marine ediments radiocarbon dates on wood fragments and root recovered from the cored sediments indicate that relative sea level was at least 95 m lower 10 500 yr b p and that the core site was rapidly transgressed by the sea shortly thereafter this rapid transgression was contemporaneous with an equally rapid regression at the heads of fiords on the british columbia mainland to the east the two are probably genetically linked and a result of late pleistocene deglaciation and the migration and collapse of a glacial forebulge our evidence indicates that large areas of the british columbia continental shelf were subaerially exposed 11 10 ka this may have facilitated the southward migration of early humans from beringia into mid continental north america at the end of the pleistocene

short paper the depositional age of the dalradian supergroup u pb and sm nd isotopic studies of the tayvallich volcanics scotland zircons from a keratophyre associated with the tayvallich volcanics in the dalradian rocks of the sw scottish highlands have been dated by u pb methods yielding an age of 595 4 ma this age indicates that most or all of the dalradian is precambrian in age and that dalradian sedimentation may have lasted for about 200 million years the age also constrains the time interval between cessation of dalradian sedimentation and subsequent crustal thickening and regional metamorphism during the grampian orogeny sm nd isotopic data for the tayvallich volcanins and related metadolerite sills yield initial ond values of 2 to 4 which are thought to reffect the effects of melting of lithospheric mantle

volcanic facies analysis of a subaqueous basalt lava flow complex at hruskovec nw croatia evidence of advanced rifting in the tethyan domain abstract the hruskovec quarry of basaltoid rocks is situated on the northwestern slopes of mt kalnik within the zagorje mid transdanubian zone a part of the north western dinarides the basaltoids are inter bedded with radiolarites of the middle and upper triassic age langobardian carnian norian spilites altered diabases and meta basalts form part of triassic volcanic sedimentary sequence made of sandstones shales micritic limestone altered vitric tuffs and radiolarian cherts incorporated tectonically into the jurassic cretaceous melange the architecture of the 2 km long and 100 m high pile of the extrusive basaltoid rocks is interpreted as a subaqueous basaltic lava flow the presented research deals with a variety of volcanic facies of the subaqueous basaltic lava flow which consists of several facial units 1 coherent pillow lavas with massive core the bending rims around the massive core 30 50 cm thick are dissected by polygonal columnar joints radiating from the pillow centres 2 closely packed pillows densely packed and contorted pillows due to emplacement accommodation clearly younging upward 3 pillow fragment breccia clast supported matrix poor monomict breccia formed proximal to the axis of the extrusion 4 isolated pillow breccia matrix supported clast poor breccia made of lava pipes and tubes within a matrix of fine grained sideromelan granules and shards 5 pyjama style pillows spherical decimetre to meter size pillow lava balls grown and chilled in isostatic state i e in a state of diminished density contrast within water soaked sediments named after peculiar alternating basaltic shelves inside the sphere which are encrusted with white secondary minerals 6 peperite and peperitic hyaloclastites blocky and globular peperites developed at the contact of soft wet sediment and hot intruding magma discovery of peperite and peperitic hyaloclastites within the triassic radiolarian cherts shales and micritic limestone with registration of conodonts index microfossils links their origin to magmatism during advanced rifting in a progressively subsiding basin during the triassic it precludes an affiliation of the subaqueous basaltic lava flow with the dismembered ophiolite formation a product of oceanization created in jurassic cretaceous times which is a commonly stated alternative explanation the basaltic rocks and their sedimentary hosts may be correlated with advanced triassic rifting and related volcanic sedimentary successions in the dinarides albanides helenides and further along the tethyan orogenic belt

geothermometry geobarometry and the al2sio5 triple point at mt moosilauke new hampshire the distribution of aluminum silicate minerals in pelitic schists constrains pressure and temperature conditions during the acadian orogeny to have been approximately those of the al 2 sio 5 invariant point thus providing an excellent opportunity to evaluate the internal consistency of a variety of published geothermometers and geobarometers with the al 2 sio 5 invariant point of holdaway 1971 four fluid independent equilibria yield p t estimates consistent with holdaway 1971 two fluid dependent equilibria yield internally consistent but unrealistically high temperatures our data are consistent with the conclusions that 1 only pyrope grossular mixing in the quaternary garnet system is significantly non ideal and 2 the activity coefficient for the anorthite component in plagioclase is approximately 2 at triple point p t conditions modified journal abstract

mobility of gold during metamorphism of the dalradian in scotland abstract mobility of au and related metals during metamorphism has been suggested to be the source of metals enriched in orogenic au deposits this study investigates the mobility of au as and sb during metamorphism of the dalradian metasedimentary rocks of scotland the metamorphic processes in the dalradian of scotland are extremely well studied and the terrane is an ideal area to investigate mobility of these metals our results show that of the 25 major and trace elements analysed only au as sb s and volatile contents as shown by loss on ignition loi values show systematic variation with the metamorphic grade of the samples average au concentrations decrease from 1 1 0 55 ppb and 0 72 0 34 ppb in chlorite and biotite zone rocks down to 0 4 0 22 ppb and 0 34 0 13 ppb in kyanite and sillimanite zone rocks average as concentrations decrease from 4 8 ppm range 0 5 to 17 8 ppm and 1 96 1 9 ppm in chlorite and biotite zone rocks down to 0 24 0 15 ppm and 0 2 0 12 ppm in kyanite and sillimanite zone rocks average sb concentrations decrease from 0 18 0 15 ppm and 0 11 0 10 ppm in chlorite and biotite zone rocks down to 0 04 0 02 ppm in both kyanite and sillimanite zone rocks sulphur and loi concentrations also show significant decreases mass balance calculations indicate that compared to chlorite and biotite zone samples sillimanite zone samples have an average mass loss of 62 14 94 4 and 74 14 for au as and sb respectively every 1 km3 of chlorite biotite zone mixed psammitic pelitic protolith rock that is metamorphosed to sillimanite zone conditions would release 1 5 t au 8613 t as 270 t sb and 1 02 mt s the mobility of these elements is strongly controlled by the paragenesis of sulphide minerals pyrite sphalerite galena and cobaltite as well as gersdorffite decrease in abundance with increasing metamorphic grade in the dalradian metasedimentary rocks a critical aspect of the sulphide paragenesis is the transition of pyrite to pyrrhotite this transition is complete by mid greenschist facies in the loch lomond samples but is more gradual at glen esk occurring between biotite and sillimanite zones the au as and sb content of the sulphide assemblage also decreases with increasing metamorphic grade and we suggest that this is a controlling factor on the mobility of these metals from the dalradian metasedimentary rocks during metamorphism chlorite may be an important host mineral for as in the greenschist facies rocks breakdown of chlorite indirectly drives the mobility of au as and sb as this produces the bulk of metamorphic fluid that drives transition between pyrite and pyrrhotite we suggest that there is potential for significant undiscovered mineralisation in the central and sw highlands of scotland however as the total mass of gold mobilised is lower than observed in other metasedimentary terranes such as the otago and alpine schist s new zealand very efficient fluid focussing and trapping mechanisms would be required to form large deposits in the dalradian of scotland

geochemical and diatom signatures of bottom water renewal events in effingham inlet british columbia canada abstract sediments from effingham inlet vancouver island british columbia hold a valuable high resolution holocene record of paleoclimatic and paleoceanographic conditions in the northeast pacific ocean accurate interpretation of this record requires that the depositional environment be well understood in order to assess deposition within the fjord over the last 1500 years two cores a soutar box core and a kasten core were analyzed for fossil diatoms and biogeochemical properties the cores contain varved sequences intercalated with homogeneous mud layers and a seismite we show that homogeneous mud units related to periods of bottom water renewal are geochemically distinct from the seismite and that these bottom renewal events are favored when brackish rather than marine surface water conditions are present the seismite deposited in ad 1946 has lower opal and higher organic carbon concentrations and higher organic carbon nitrogen ratios reflecting greater terrestrial material input in contrast homogeneous mud units are marked by a lower organic c n and more isotopically heavy 13 c values suggesting a stronger marine influence major metals and trace element data also confirm that the source material of these units differs from that of the ad 1946 seismite fossil diatom assemblages within the homogeneous mud units are characterized by a decreased abundance of typical marine spring bloom taxa skeletonema costatum chaetoceros spp thalassiosira spp coupled with an increased abundance of the brackish water taxon cyclotella choctawhatcheeana reduced surface salinity enhances stratification of the water column which in turn favors an intensified two layer estuarine exchange across the shallow sills and associated bottom water renewal the homogeneous mud units are produced through transport of sediment into the fjord coupled with a reworking of the upper layers of the sediment column therefore these units represent a recorder of past changes in regional oceanography and climate

regional fluid flow and gold mineralization in the dalradian of the sperrin mountains northern ireland gold vein mineralization occurs in the metamorphosed and deformed dalradian neoproterozoic rocks of the sperrin mountains northern ireland two structures exerted a control on the location of the mineralization the north south omagh lineament and the west northwest east southeast curraghinalt lateral ramp in the footwall of the northeast southwest omagh thrust these are caledonian structures resulting from the thrusting of dalradian rocks over a possibly still active ordovician arc cathodoluminescence microscopy distinguishes four phases of vein quartz in the curraghinalt gold prospect fluid inclusion studies and stable isotope geochemistry have defined the probable fluids responsible for the precipitation of each quartz phase and associated sulfide and precious metal mineralization the initial phase q1 appears to have been associated with the main caledonian metamorphic event ca 470 ma and is nonauriferous the second phase q2 forms an extensive cement to brecciated early quartz and is believed to have involved a fluid 15 wt co 2 10 wt nacl kcl equiv with a significant magmatic component of 470 to 400 ma which underwent phase separation and dilution with a cooler formation water this process resulted in precipitation of the main phase of gold mineralization characterized by an assemblage of electrum pyrite arsenopyrite chalcopyrite tennantite tetrahedrite and various tellurides similar fluids are observed on a regional scale concentrated within the hanging wall of the omagh thrust indicating an extensive fluid flow event the relative abundance of gold at the curraghinalt and cavanacaw prospects is thought to be due to higher fluid fluxes in favorable zones of dilation and closer proximity to the fluid source the deposit was subsequently reactivated with the precipitation of later quartz q3 q4 from a formation water believed to be resident in the dalradian metasediments which mixed with a low temperature high salinity basinal brine probably during carboniferous basin inversion brine flow resulted in the remobilization of earlier electrum reducing its fineness and also introduced base metal sulfides carbonates and barite again brine flow is localized by the omagh thrust indicating the long lived role of this structure in controlling regional fluid migration

younger dryas environments and archaeology on the northwest coast of north america abstract this paper reviews the current archaeological and palaeo environmental evidence from the younger dryas period on the northwest coast of north america sea level histories are region specific ranging from 100 m lower to 150 m higher than modern at ca 12 200 cal bp the mid point of the younger dryas palaeo environmental evidence shows temperature decrease across the study area but in some regions this is accompanied by greater precipitation and glacial advance whereas in other conditions were drier terrestrial vegetation reflects this variability with northern areas in particular showing evidence for expansion of herb and shrub tundra and southern areas marked by increased mountain hemlock and other species marine intertidal and terrestrial fauna indicate productive ecosystems with some sub regional changes such as extirpation of deer and bison perhaps associated with the younger dryas onset stable isotope analysis of bear remains show these species which are a good ecological analogue for humans exploited both marine and terrestrial resources despite patchy and dynamic marine and terrestrial environments these results suggest a challenging yet viable environment for humans archaeological evidence for younger dryas human occupation is currently limited to six sites of which four are associated with karst caves the earliest of these are in haida gwaii where bear hunting is dated to at least 12 650 cal bp during the heart of the younger dryas interval other sites in southeast alaska and in the fraser river lowlands date to around 12 100 cal bp in puget sound the presence of ca 13 000 cal bp clovis surface collections and the emerging data from the pre clovis ayer pond bison butchery site suggest pre younger dryas occupation the northwest coast was open to population movement from both the north and south in the poorly known interval before the younger dryas when conditions may have been more moderate and stable the sub regional variation and the scale of environmental change in the younger dryas especially sea level fluctuation makes discovery of pleistocene archaeological sites challenging the younger dryas may therefore be seen as something of a worst case scenario for both the human occupation and the archaeological investigation of the northwest coast

rb sr and sm nd isotopic dating of an early precambrian spilite keratophyre sequence in the wutaishan area north china preliminary evidence for nd isotopic homogenization in the mafic and felsic lavas during low grade metamorphism the spilite keratophyre sequence in the wutaishan area north china has been dated by zircon from the quartzkeratophyre and a volcanic crystallization age of 2522 ma liu dunyi et al 1985 was obtained this volcanic rock sequence experienced a low grade metamorphism of greenschist facies during 1800 2000 ma however combined sm nd whole rock data from the volcanic rock sequence if interpreted in terms of an isochron gives a younger age of 2250 182 ma if separately calculated sm nd isochrons for quartz keratophyre and spilite yield two consistently younger ages of 1977 385 ma and 1981 178 ma these sm nd isochron ages are consistent with a rb sr age of 1871 98 ma and with the time of regional greenschist facies metamorphism consequently we interpret the 2250 ma alignment on the sm nd diagram as an errorchron the two sm nd metamorphic ages suggest that partial homogenization of nd isotopic composition in water rich spilite keratophyric meta volcanics can be achieved during low grade metamorphism as a result of ree mobility using the nd values at the time of metamorphism and the average 147sm 144nd ratios of the spilite and the quartzkeratophyre initial nd values of 2 6 3 5 and 3 0 6 1 respectively are estimated at the time of volcanic eruption 2522 ma similar positive initial nd values for the spilites and quartz keratophyres suggest that they might have been derived from the same depleted mantle source or that the quartz keratophyres are derived from a short lived mafic source

rapid sea level change and coastal evolution on the pacific margin of canada a rapid regression occurred off the northern pacific margin of canada approximately between 14 600 and 12 500 14c years b p contemporary with the deglaciation of the continental shelf primarily due to the rapid isostatic rebound sea level had reached a maximum lowering of greater than 150 m and remained low until approximately 12 400 14c years b p after which a rapid transgression occurred at 12 500 14c years b p the shelf tilt across the northern pacific margin of canada ranged between 50 m of submergence at prince rupert on the british columbia mainland to greater than 150 m of emergence on the western edge of the queen charlotte islands this regressive transgressive cycle lasted only from 5200 to 5500 14c years a result of the development and collapse of a glacioisostatic forebulge sediment supply wave action and tidal current energy are the primary factors that controlled the coastal response to these late quaternary relative sea level changes plate tectonics on the other hand played a secondary role in coastal evolution during deglacial regression extensive glacial outwash and glaciomarine deposition occurred except on the outer coast where sediment was transferred to the shelf break during the transgression of the shelf the sediment supply was primarily restricted to the erosion of the previously deposited deglacial deposits resulting in the formation of drowned wave cut terraces spit platforms and modification of estuarine environments as the sea level rose in steps the present unconsolidated coastline is mostly erosional during the most recent enso event the sea level rise of up to 0 4 m resulted in as much as 12 m of coastal retreat

records of seasonal flux in holocene laminated sediments gulf of california holocene laminated sediments from guaymas basin gulf of california mexico have in the past been described as annual couplets of sedimentation couplets comprise an alternation of diatom and terrigenous rich sediment reflecting winter and summer flux to the sediment respectively new data from backscattered electron imagery bsei show that a three component pattern of sedimentation is preserved comprising 1 a lithogenic lamina consisting of clays silt and minor diatomaceous material deposited during the summer and autumn wet season 2 a mixed flora diatomaceous lamina deposited during the early winter collapse of the thermocline and onset of water column mixing and 3 a near monospecific flora lamina of chaetoceros resting spores or more rarely skeletonema costatum representing deposition from or at the end of the spring coastal upwelling bloom recent sediment trap biogenic and terrigenous flux data also show three to four major flux events per year direct comparisons are possible between bsei records and recent sediment trap flux data to facilitate high resolution palaeoceanaographic and palaeoclimatic reconstructions throughout the holocene

evidence for abrupt climate changes in annually laminated marine sediments annually laminated sediments from marine or lacustrine settings represent valuable high resolution archives of climate change that record variation due to changing precipitation and run off from land or variation in biological productivity and flux in the water column because of their annual resolution such sediments may capture abrupt changes of interannual to decadal scales rivaling corals and ice cores in resolution laminated sediments often occur intermittently in the sediment column and the onset and cessation of laminae commonly record the abrupt crossing of thresholds related to climate change for example in the degree of oxygenation of bottom waters such records from marginal basins and continental margins have been pivotal in demonstrating that abrupt changes hitherto documented only in high latitude ice cores are synchronous with climatic change at low latitudes these insights into global teleconnections have improved our understanding of the mechanisms of rapid climate change in deep sea settings the discovery of the episodic occurrence of laminated diatom rich sediments in the equatorial pacific and southern ocean provides evidence for massive climate related biogeochemical excursions tied to abrupt changes in the input distribution and availability of nutrients in the oceans

postglacial evolution of a pacific coastal fjord in british columbia canada interactions of sea level change crustal response and environmental fluctuations results from mona core md02 2494this article is one of a series of papers published in this special issue on the theme polar climate stability network the sedimentary record in a 40 9 m giant calypso piston core md02 2494 raised from the inner basin within effingham inlet british columbia canada during the 2002 marges ouest nord americaines mona campaign spans from 14 360 14 c years bp 17 300 calibrated calendar cal years bp to about nine centuries before present the core ar chives changes in sedimentation and sea level immediately following deglaciation of the late wisconsin fraser glaciation which peaked about 15 000 14 c years bp the presence of the mazama ash in the core anchors a detailed chronology based on 49 radiocarbon dates and seven pleistocene paleomagnetic secular variation correlations diatom assemblages identify a marine freshwater marine transition in the basin which occurred 11 630 14 c years bp 13 500 cal years bp at this time a bedrock sill presently at 46 m depth was briefly exposed as sea level fell and then rose again during iso static crustal adjustments these data constrain a new sea level curve for the outer coast of vancouver island covering the past 12 000 14 c years bp 14 000 cal years bp providing new information on the nature of deglaciation along the west coast of canada and informing interpretations of regional paleoceanographic records and mantle viscosity models

late quaternary geology and geochronology of the central continental shelf of western canada piston cores and high resolution seismic profiles from queen charlotte sound have yielded new information on the late quaternary history of this part of the western canada continental shelf cores in three major troughs goose island mitchell s and moresby up to 130 km apart sample a similar sedimentary sequence this sequence comprises five units the lowest unit a which is up to 40 m thick is a laminated to massive mud containing coarse ice rafted debris deposited between pre 13 6 ka and 12 9 ka during deglaciation of queen charlotte sound this unit is overlain by a sequence of stratified sediments units b1 b3 up to 20 m thick deposited during the transition from the pleistocene to the holocene unit b1 directly overlies and is similar to unit a but lacks ice rafted detritus unit b2 is sandy mud locally gravelly deposited during a period of lagging and winnowing from about 12 9 to 10 2 ka when sea level in queen charlotte sound was lower relative to the land than it is today unit b3 is a laminated to massive mud similar to unit b1 deposited when water depths in queen charlotte sound rapidly increased at the end of the pleistocene due to the combined effect of eustatic sea level rise and forebulge collapse the sedimentary sequence is capped by up to 10 m of mud unit c which is more organic rich and contains more clay than any of the other units it was accumulating under present day conditions as early as 9 7 k y ago

preparation and analysis techniques for studies of laminated sediments laminated sediments commonly represent the highest resolution continuous records available of marine and lacustrine variability to exploit this information effectively careful sampling and preparation procedures must be followed thus the method of analysis chosen must have sufficient resolution to recover the data the scanning electron microscope because of its good spatial resolution is an ideal tool for analyzing laminated sediment fabric backscattered electron imagery produces preserved flux data on intra annual time scales which enables high resolution fabric studies palaeoenvironmental reconstructions and compilation of data for time series analysis this contribution summarizes the techniques used for laminated sediment fabric investigation and discusses the use of the scanning electron microscope including the best preparation method for thin sections and the procedure for backscattered electron imagery analysis

holocene sea level change on the central west coast of vancouver island british columbia a new holocene relative sea level rsl curve is proposed for the central west coast of vancouver island based on topographic surveys of coastal landforms and the stratigraphy of coastal deposits six study sites are described on vargas island and esowista and ucluth peninsulas and 23 previously unpublished radiocarbon ages that constrain mean sea level msl position are presented a long term rise in rsl from an early holocene 7000 bp lowstand below 3 m asl is documented from dates on tree stumps in the intertidal zone and salt marsh peats and forest floor deposits buried by marine sands and gravels submergence culminated in a stillstand from 6000 to 4800 bp marked by the development of a strandline at 6 m asl msl 3 2 m asl a fall in rsl is documented by a strandline at 4 0 4 5 m asl which dates from 2700 to 2000 bp msl 2 0 m asl little is known of the dynamics of emergence between 4800 and 2700 bp or from 2000 bp to the present although the absence of strandlines below 4 m asl sugges

an assessment of the megathrust earthquake potential of the cascadia subduction zone the active tectonic setting of the southwest coast of canada and the pacific northwest coast of the united states is dominated by the cascadia subduction zone the zone can be divided into four segments where oceanic lithosphere is converging independently with the north american plate the winona and the explorer segments in the north the larger juan de fuca segment that extends into both canada and the united states and the gorda segment in the south the oceanic lithosphere entering the cascadia subduction zone in all segments is extremely young less than 10 ma of the other six zones around the pacific where young 20 ma lithosphere is being subducted five have had major thrust earthquakes megathrust events on the subduction interface in historic time an estimation based on potential area of rupture gives maximum possible earthquake magnitudes along the cascadia subducting margin of 8 2 for the winona segment 8 5 for the explorer segment 9 1 for the juan de fuca segment and 8 3 for the so

late quaternary sediments and geomorphic history of northern vancouver island british columbia materials from two glacial intervals and one nonglacial interval have been identified on northern vancouver island british columbia the oldest pleistocene unit termed older drift consists of glaciomarine silt and clay 38 000 years bp in age that overlie a till that has only been recorded in well logs older drift is tentatively correlated with dashwood drift of the semiahmoo glaciation early wisconsin or older no sediments of the succeeding olympia nonglacial interval mid wisconsin have been found in the area it is thought that this interval was characterized by a period of degradation in which olympia age sediments were deposited in transient sedimentary environments and subsequently eroded in part during the fraser glaciation late wisconsin the youngest pleistocene unit termed port mcneill drift includes advance deposits till and deglacial sediments all deposited during fraser glaciation ice of this glaciation did not cover most of northern vancouver island until after 20 600

determining the post glacial evolution of a northeast pacific coastal fjord using a multiproxy geochemical approachthis article is one of a series of papers published in this special issue on the theme polar climate stability network a 40 32 m piston core recovered from effingham inlet on the west coast of vancouver island provides the basis for a high resolution geochemical study of the last deglaciation and the holocene glacial retreat basin isolation sea level rise and productivity variations are determined using proxies for sediment composition k al fe al mg al grain size ti al zr al sedimentary redox conditions mo al u al and productivity wt organic carbon wt opal as local ice retreated and marine waters inundated the basin coarse grained glacimarine sediments were replaced by finer grained laminated opal rich sediments during meltwater pulse 1a the dominance of local crustal rise over eustatic sea level rise resulted in the progressive restriction of ocean circulation in effingham inlet and the formation of a temporary freshwater lake the transition into stable holocene conditions was initiated at 12 700 bp which corresponds to the onset of the younger dryas as identified by the greenland ice

post glacial sea levels on the western canadian continental shelf evidence for rapid change extensive subaerial exposure and early human habitation grounded piedmont type glaciers inundated and isostatically loaded the deep troughs which indent the western canadian continental shelf as far west as the shelf edge glaciers do not appear to have covered the offshore banks east of the queen charlotte islands haida gwaii ice retreated from the shelf at approximately 13 500 14c yr b p rapid emergence of the crust followed the ice retreat and resulted in a relative fall of sea level at 10 400 14c yr b p relative sea level on the continental shelf was more than 100 m below that of today and large areas of the queen charlotte basin were subaerially exposed eustatic sea level rise coupled with subsidence of a glacioisostatic forebulge allowed sea levels to rise very rapidly and reach the present shoreline on the queen charlotte islands haida gwaii by about 9100 14c yr b p dated shoreline deposits shells submerged wood remnants and barnacles on stone tools at elevations between 110 m and 14 m suggest a sea level rise of 6 3 cm per year between 12 200 and 11 000 calender years our reconstructions of the paleogeography and paleoenvironments suggest a hospitable environment for human habitation existed in areas that are now submerged stone tools excavated from intertidal deposits support this interpretation significant local variations in the depth of synchronous shorelines are described and attributed to localized differences in isostatic load the documented rates of crustal adjustment are much greater than those used in conventional geophysical forebulge models regional high resolution seismic reflection data 3400 line km shows little evidence for post glacial faulting and suggest that most crustal adjustments appear to have been isostatically rather than tectonically driven subaerial exposure and subsequent sea level transgression were the dominant post glacial processes that determined the morphology texture and paleoenvironment of the western canadian continental shelf

a new high resolution radiocarbon bayesian age model of the holocene and late pleistocene from core md02 2494 and others effingham inlet british columbia canada with an application to the paleoseismic event chronology of the cascadia subduction zone annually laminated sediments from the anoxic inner basin of effingham inlet pacific coast of vancouver island british columbia canada yield a high resolution 42 m paleoenvironmental record from the present to about 14 ka 14c bp 17 ka cal bp a new age model based on 68 radiocarbon dates from twigs and small plant material from the 40 m core md02 2494 and 2 m freeze cores from the surface is anchored by the mazama ash and varve counting a poisson process sedimentation model is used applying a new method to determine the poisson k value giving a realistic age model compatible with the multi proxy core data twenty one seismites which are lithofacies in the effingham cores that may be representative of seismically triggered mass wasting events are identified and dated precisely then compared with the chronology of the deep sea turbidite record farther south in the cascadia subduction zone csz to determine if regional sediment disturbances can be identified with 16 proposed correlations

rb sr mineral ages for the grenvillian metamorphic development of spilites from the dalsland supracrustal group sw sweden rb sr isotope systematics have been investigated of epidote actinolite albite and biotite concentrates from 4 spilite samples from the precambrian basement directly w of lake vanern in sw sweden the rocks belong to the dalsland supracrustal group whose basal conglomerate was deposited on an erosion surface with a maximum age of c 1 200 ma epidote wr and actinolite wr tie lines in a nicolaysen diagram give ages with an average of 990 10 la ma which is thought to represent the metamorphic culmination biotite wr lines yield an average age of 900 15 1 ma which indicates the time at which the rock complex cooled through the isotopic closure temperature of biotite estimated at c 250 c the average cooling rate in this period was very low 1 2 c ma initial sr isotopic ratios of the 4 spilite samples vary from 0 7040 to 0 7080 and are thought to reflect interaction of mantle derived basalts with seawater

all age depth models are wrong but how badly the uncertainty and error associated with fitted age depth models were investigated by fitting a range of models to sets of simulated radiocarbon dates based on varved sediments and comparing the modelled relationship with the varve timescale with large numbers of dates cubic smooth splines out perform other models with few dates no model reliably provides a good fit to reality and calculated confidence intervals are over optimistic c 2003 elsevier ltd all rights reserved

volcanology of the 2350 b p eruption of mount meager volcanic complex british columbia canada implications for hazards from eruptions in topographically complex terrain the pebble creek formation previously known as the bridge river assemblage comprises the eruptive products of a 2350 calendar year b p eruption of the mount meager volcanic complex and two rock avalanche deposits volcanic rocks of the pebble creek formation are the youngest known volcanic rocks of this complex they are dacitic in composition and con tain phenocrysts of plagioclase orthopyroxene amphi bole biotite and minor oxides in a glassy groundmass the eruption was episodic and the formation com prises fallout pumice bridge river tephra pyroclastic flows lahars and a lava flow it also includes a unique form of welded block and ash breccia derived from col lapsing fronts of the lava flow this merapi type brec cia dammed the lillooet river collapse of the dam triggered a flood that flowed down the lillooet valley the flood had an estimated total volume of 10 9 m 3 and inundated the lillooet valley to a depth of at least 30 m above the paleo valley floor 5 5 km downstream of the blockage rock avalanches comprising mainly blocks of plinth assemblage volcanic rocks an older formation making up part of the mount meager vol canic complex underlie and overlie the primary vol canic units of the formation both rock avalanches are unrelated to the 2350 b p eruption although the post eruption avalanche may have its origins in the over steepened slopes created by the explosive phase of the eruption much of the stratigraphic complexity evident in the pebble creek formation results from deposition in a narrow steep sided mountain valley containing a major river

new accelerator mass spectrometry radiocarbon ages for the mazama tephra layer from kootenay national park british columbia canada charcoal fragments recovered from the mazama air fall tephra layer in cores from dog and cobb lakes kootenay national park british columbia yielded accelerator mass spectrometry ages of 6720 70 and 6760 70 14c years bp respectively these two new ages together with other previously published radiocarbon ages on charcoal and twig fragments from mazama air fall deposits indicate that the climactic eruption of mount mazama occurred 6730 40 14c years bp

late quaternary deglaciation and sea level history of eastern juan de fuca strait cascadia abstract eastern juan de fuca strait of southwestern british columbia northwestern washington state is near the western and southern terminus of late wisconsinan glaciation in north america seismic reflection profiles bathymetric data sediment core data and 41 new radiocarbon dates provide insight into the history of ice retreat and sea level change in the eastern portion of the strait the retreating ice margin appears to have passed through the area between 14 460 200 and 13 595 145 14c yr glacial marine sediments date between 12 889 50 and 11 110 50 14c yr bp wave eroded unconformities drowned prograded deposits and a partially isolated low stand basin are evidence attributed to low stand sea levels following deglaciation and five new control points on the local eustatic sea level curve are assigned based on radiocarbon dating of these features sea level change was rapid from 75 m immediately after deglaciation to possibly 60 4 m at 9920 60 14c yr bp after this time gradual sea level transgression took place relative sea level reached its approximate present position by 5470 115 14c yr bp since then relative sea level has remained constant suggesting eustatic rise is balanced by crustal uplift

a high resolution marine palynological record from the central mainland coast of british columbia canada evidence for a mid late holocene dry climate interval abstract sediments collected in a 12 m long core vec02a04 obtained from frederick sound in the seymour belize inlet complex of british columbia were deposited between ca 4540 cal yr bp and ca 1090 cal yr bp in primarily dysoxic conditions the sediments are characterized by alternating intervals of fine grained massive and laminated units laminated sediments consist of light coloured diatom rich layers deposited during summer and dark coloured mineral rich layers deposited during winter laminated sediments are most common in portions of the core deposited between ca 2840 cal yr bp and ca 1820 cal yr bp and correspond to a decline in the relative abundance and pollen accumulation rate of cupressaceae pollen between ca 3190 cal yr bp and ca 2250 cal yr bp the preservation of laminated units and decline of cupressaceae pollen at this time suggest that a drier and possibly cooler climate punctuated otherwise wet and temperate late holocene conditions in the seymour belize inlet complex we correlate the occurrence of the mid late holocene dry climate interval documented in frederick sound to dynamics in the relative position and intensity of the aleutian low pressure system and suggest that climate change associated with dynamics of this semi permanent air mass affected primary productivity and vegetation of the seymour belize inlet complex

a sea level database for the pacific coast of central north america a database of published and new relative sea level rsl data for the past 16 ka constrains the sea level histories of the pacific coast of central north america southern british columbia to central california our reevaluation of the stratigraphic context and radiocarbon age of sea level indicators from geological and archaeological investigations yields 600 sea level index points and 241 sea level limiting points we subdivided the database into 12 regions based on the availability of data tectonic setting and distance from the former cordilleran ice sheet most index 95 and limiting points 54 are 7 ka older data come mainly from british columbia and san francisco bay the stratigraphic position of points was used as a first order assessment of compaction formerly glaciated areas show variable rsl change where data are present highstands of rsl occur immediately post deglaciation and in the mid to late holocene sites at the periphery and distant to formerly glaciated areas demonstrate a continuous rise in rsl with a decreasing rate through time due to the collapse of the peripheral forebulge and the reduction in meltwater input during deglaciation late holocene rsl change varies spatially from falling at 0 7 0 8 mm a 1 in southern british columbia to rising at 1 5 0 3 mm a 1 in california the different sea level histories are an ongoing isostatic response to deglaciation of the cordilleran and laurentide ice sheets

late quaternary glaciation and postglacial stratigraphy of the northern pacific margin of canada abstract areas of southeastern alaska and the queen charlotte islands of the northwestern pacific coast of north america were considered to be ice free during the late wisconsinan glaciation and glacial refugia existed however a glacier extended from mainland north america to the shelfbreak in dixon entrance separating alaska and the queen charlotte islands glacial retreat to the east began sometime after 15 000 to 16 000 14 c yr b p and ice had completely left dixon entrance by 13 500 to 13 000 14 c yr b p a rapid sea level regression occurred soon after deglaciation began due to isostatic rebound with relative sea level falling to approximately 150 m below present in central dixon entrance decreasing the size of the inlet by about 30 percent by 12 400 14 c yr b p the late quaternary glacial and postglacial stratigraphic sequence is more than 100 m thick overlying older pleistocene sediments and tertiary bedrock a late wisconsinan diamicton is overlain by glaciomarine muds formed between approximately 14 400 and 13 000 14 c yr b p contemporaneous with the deposition of the glaciomarine muds an extensive outwash deposit formed off the northern coast of the queen charlotte islands to a present depth of 150 m during the sea level lowstand and subsequent transgression a reworked sand unit was deposited over much of the seafloor to depths greater than 450 m the unit is exposed at the seafloor over much of the region suggesting that seabed hydrodynamic energy levels were high after 13 000 14 c yr b p and remain so today

drowned forests and archaeology on the continental shelf of british columbia canada we have used high resolution digital terrain imaging and sea floor sampling to reveal drowned late glacial to early postglacial terrestrial landscapes at water depths as great as 150 m in situ tree stumps and shellfish rich paleobeaches are present on these drowned landscapes a stone tool encrusted with barnacles and bryozoa was recovered from a drowned delta flood plain now 53 m below mean sea level this is the first tangible evidence that the formerly subaerial broad banks of the western north american continental shelf may have been occupied by humans in earliest holocene and possibly late glacial time analyses 14 c of the drowned terrestrial and intertidal deposits were used to refine the local sea level curve which shows very rapid change within this glacio isostatically dynamic region

genesis and mobility of the h2o co2 fluid phase during regional greenschist and epidote amphibolite facies metamorphism a petrological and stable isotope study in the scottish dalradian during high pressure low temperature greenschist and epidote amphibolite facies metamorphism in dalradian rocks of the sw scottish highlands mineral assemblages in metabasites and calcareous metasediments were dominantly controlled by infiltration of hydrous fluids consequently mineral assemblages capable of buffering the fluid phase composition were rare equilibrium prograde h 2 o co 2 fluids usually contained less or much less than about 1 2 mol co 2 three fluid infiltration events are recognized during prograde greenschist facies metamorphism metabasic sills were infiltrated by large volumes of co 2 bearing hydrous fluid carbon isotope studies indicate that the co 2 was locally derived by widespread oxidation of graphite or other organic carbon in adjacent metasediments this may have occurred under approximately lower greenschist facies conditions as a result of mixing of fluids of varying f o 2 initiated by thermal expansion of water during heating decompression and consequent hydraulic fracturing in the epidote amphibole facies garnet zone dehydration reactions in metabasites generated large quantities of water which removed carbonate from metabasites on a regional scale and infiltrated calcareous metasediments to produce assemblages containing grossular diopside k feldspar amphibole clinozoisite and sphene a late retrograde infiltration of co 2 bearing hydrous fluid under lower greenschist facies conditions generated assemblages containing k feldspar chlorite rutile dolomite in calcareous rocks and albite prophyroblast schists in zones of intense secondary deformation large scale infiltration of fluid into greenschist facies metadolerite sills was intimately related to and possibly controlled by penetrative deformation and in the absence of a penetrative deformation grain boundary diffusion by itself was an ineffectual mechanism of fluid transport

the filon norte orebody tharsis iberian pyrite belt a proximal low temperature shale hosted massive sulphide in a thin skinned tectonic belt the filon norte orebody tharsis iberian pyrite belt is one of the largest pyrite rich massive sulphide deposits of the world the present structure of the mineralization consists of an internally complex low angle north dipping thrust system of variscan age there are three major tectonic units separated by thick fault zones each unit with its own lithologic and hydrothermal features they are internally organized in a hinterland dipping duplex sequence with high angle horses of competent rocks igneous and detritic rocks and massive sulphides bounded by phyllonites the mineralization is within the lower unit and is composed of several stacked sheets of massive sulphides and shales hosting a stockwork zone with no obvious zonation the intermediate unit is made up of pervasively ankeritized shales and basalts spilites here hydrothermal breccias are abundant the upper unit is the less hydrothermally altered one and consists of silicified dacites and a diabase sill the tectonic reconstruction suggests that the sequence is inverted and the altered igneous rocks were originally below the orebody carbon oxygen and sulphur isotopes in the massive sulphides and hydrothermal rocks as well as the mineral assemblage and the paragenetic succession suggest that the sulphide precipitation in the sea floor took place at a low temperature 150 c without indication at least in the exposed section of a high temperature copper rich event sporadic deep subsea floor boiling is probably responsible for the formation of hydrothermal breccias and the wide extension of the stockwork its co au enrichment is interpreted as being related with the superposition of some critical factors such as the relationship with black shales the low temperature of formation and the boiling of hydrothermal fluids the present configuration and thickness of the orebody is due to the tectonic stacking of a thin and extensive blanket 2 4 km2 of massive sulphides with low aspect ratio they were formed by poorly focused venting of hot modified seawater equilibrated with underlying rocks into the seafloor massive sulphide precipitation took place by hydrothermal fluid quenching bacteriogenic activity and particle settling in an unusual restricted euxinic and shallow basin brine pool with a low detritic input but with important hydrothermal activity related to synsedimentary extensional faulting resedimentation of sulphides seems to be of major importance and responsible for the observed well mixed proximal and distal facies the tectonic deformation is largely heterogeneous and has been mostly channelled along the phyllonitic tectonized shales deformation bands thus sedimentary and diagenetic textures are relatively well preserved outside the deformation bands in the massive sulphides superimposed variscan recrystallization is not very important and only some early textures are replaced by metamorphic tectonic ones the stockwork is much more deformed than the massive sulphides the deformation has a critical effect on the present morphology of the orebody and the distribution of the ore minerals this deposit is a typical example of the sheet like shale hosted anoxic low temperature and zn rich massive sulphides developed in a ensialic extensional basin

basin dewatering near salt domes and formation of brine plumes a previous study noted the occurrence of a subsurface brine plume with more than 160 g l sodium chloride perched above welsh salt dome in southwestern louisiana plumes of saline groundwaters have been reported above other gulf coast salt domes as well the u s geological survey code sutra was used to model the formation of brine plumes around a generic salt dome by basin dewatering along the flanks of the dome and also to study the gravitational instability of a brine plume initially perched above a dome in the absence of an externally impressed driving force for upwelling the simulations take into account the effect of salt concentration gradients on brine density the first set of simulations showed that a brine plume initially perched above a salt dome sank rapidly in the absence of an overpressured section where observed perched brine plumes above salt domes must therefore be either 1 young 2 ma if formed by basin dewatering and vertical fluid expulsion along the flanks of salt domes or 2 formed by a continuous mechanism the second set of simulations modeled the dewatering of a thick initially overpressured sedimentary section extending from a depth of 3 km to a depth of 10 km the deflation rate of the overpressured section profoundly depended on whether or not a permeable conduit along the flank of the dome existed which could collect water expelled radially inward to the flank of the dome from the overpressured sediments and focus it upward along the flank of the dome in most simulations the volume of compaction water was limited to only 10 of the total volume of overpressured sediment around the dome and there was an ample amount of compaction water for a perched brine plume to form in fact when a perched brine plume formed it formed very quickly in 0 01 m y after a negligible degree of deflation of the overpressured section it is conceivable that if cycles of conduit sealing and seal rupturing occurred perched brine plumes could be formed several times during deflation conditions necessary for the formation of a perched brine plume are as follows 1 waters must be focused laterally toward the dome within in the overpressured section 2 there must be a conduit of sediment with relatively high vertical permeability along the flank of the dome and 3 sediments above the dome must be more permeable than sediments along the flank of the dome for some simulations the average linear velocity of upward flow along the flanks of the dome was 3 m yr possibly of large enough magnitude to cause a thermal anomaly if perched brine plumes form by basin dewatering the thermal buoyancy effects associated with such a thermal anomaly may make the plumes rise to depths shallower than indicated in the simulations here the inability of the code sutra to simultaneously model heat and solute transport did not permit an evaluation of this

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

post glacial sea level change along the pacific coast of north america abstract sea level history since the last glacial maximum on the pacific margin of north america is complex and heterogeneous owing to regional differences in crustal deformation neotectonics changes in global ocean volumes eustasy and the depression and rebound of the earth s crust in response to ice sheets on land isostasy at the last glacial maximum the cordilleran ice sheet depressed the crust over which it formed and created a raised forebulge along peripheral areas offshore this combined with different tectonic settings along the coast resulted in divergent relative sea level responses during the holocene for example sea level was up to 200 m higher than present in the lower fraser valley region of southwest british columbia due largely to isostatic depression at the same time sea level was 150 m lower than present in haida gwaii on the northern coast of british columbia due to the combined effects of the forebulge raising the land and lower eustatic sea level a forebulge also developed in parts of southeast alaska resulting in post glacial sea levels at least 122 m lower than present and possibly as low as 165 m on the coasts of washington and oregon as well as south central alaska neotectonics and eustasy seem to have played larger roles than isostatic adjustments in controlling relative sea level changes

a 20 000 year record of ocean circulation and climate change from the santa barbara basin much of the evidence for climate driven fluctuations in ocean circulation during the past 20 000 years has come from studies of the north atlantic region1 6 the extent to which such interactions have occurred in other ocean basins and any associated teleconnec tions between basins is poorly understood here we present high resolution palaeoclimate and palaeoceanographic records from a 20 000 year sedimentary sequence from the santa barbara basin on the eastern margin of the north pacific ocean the sequence shows oscillations of the benthic environment between low oxygen conditions laminated sediments during periods of warm climate and higher oxygen conditions non laminated bioturbated sediments during cool intervals age differences between coexisting benthic and planktonic foraminifers indicate climate related changes in the age and source and hence oxygen content of basin bottom waters relatively young bottom waters are associated with the cooler intervals and are considered to reflect high proportions of intermediate waters derived from proximal sources conversely older bottom waters are associated with the warmer intervals and were derived from more distal sources these climate driven variations in ocean circulation appear to be synchronous with the main ocean climate fluctuations in the north atlantic region1 6 suggesting that a tight coupling mechanism operates between the two basins

the indian ocean nodule field petrotectonic evolution and ferromanganese deposits abstract the indian ocean nodule field ionf is significant from several points of view roughly bordered by 10 s to 16 30 s and 72 e to 80 e and located within the central indian ocean basin ciob the field hosts the world s second largest and second high grade manganese nodule deposit after the equatorial nodule belt in the north pacific ocean moreover the crust underlying this field is characterised by unique morphotectonic signatures owing to its formation between 60 and 49 ma under three variable spreading conditions fast intermediate and slow from the indian ocean ridge system iors the nodule field has been surveyed both extensively more than 0 4 million km2 area and intensively comprising of a large geophysical data set and geological sample inventory during the last two decades several morphotectonic features such as seamounts hills ridge normal lineaments and ridge parallel lineations have disturbed the apparently smooth topographic gradient 1 7000 of the seafloor here variations in the rate of spreading and formation of new oceanic crust along the ridge crest during more than one episode of india eurasia collision are imprinted in the ionf based on the nature of the ridge parallel lineations which are related to the rate of crustal accretion the field is divided in to four sectors a b c and d from north to south sectors a and c were formed at a fast rate of spreading 90 95 mm year half rate and sectors b and d were formed at an intermediate 55 mm year and slow 26 mm year rates respectively the predominance of tensional stress in sectors a and c caused asymmetrical flexuring of the seafloor resulting in widely spaced faults and folds with low amplitude and large wavelength in contrast the seafloor flexuring in sector d are closely spaced long symmetrical and of high amplitude the timing and intensity of the collision of india with eurasia is constrained by the variable intensity of these flexures suggesting probably a soft touch at 58 ma and the hard collision at about 51 ma the nodule field hosts several seamounts both as isolated entities and in linear chains which are arranged parallel to the flow lines along the direction of absolute motion of the indian plate the distribution morphology and growth patterns of a majority of these seamounts are related to spreading rate suggesting their formation at the ridge crest however many of the seamounts show more than one stage of growth with local intraplate volcanism contributing to the enlargement of the larger ancient seamounts varieties of volcanics such as tholeiitic basalts spilites ferrobasalts and pumice occur within the ionf the alteration of some of these volcanics has resulted in palagonitisation of the glass and formation of zeolites subsequently during its journey away from the ridge crest to the abyssal areas the crust underlying the nodule field witnessed intraplate volcanism this is evident from the addition of younger rocks at the base of the ancient seamounts inconsistent growth of volcanoes eruption of ferrobasalt corresponding to the areas of high amplitude magnetic zones and presence of volcanogenic hydrothermal materials vhm of 10 ka age these findings collectively hint that the ionf is geodynamically unstable and may have been volcanically active in the recent past during the last 8 ma growth of authigenic ferromanganese deposits in the form of manganese nodules and crusts has occurred in the nodule field the deposits occur at an average water depth of 5000 m the basinal geomorphology intraplate tectonic deformations and volcanic eruptions considerably influence the formation development morphology mineralogy and composition of these deposits the data show that the large seamounts reverse faults and fracture zones fzs supply rock fragments as seeds for the nodule formation the hydrogenous precipitation from the overlying water column is the primary source of metal accumulation in the nodules the secondary relatively weak intraplate eruptions along the base of ancient seamounts or lineaments subsurface igneous activity and diagenetic remobilisation of metals have also played significant role in the growth and enrichment of the deposit based on a large data set we estimate the contribution of various physico chemical parameters and model the probable conditions of formation of the ferromanganese deposits in the ionf the model also hints at the location where the resource exploitation should be rewarding

distribution of diatom surface sediment assemblages within effingham inlet a temperate fjord on the west coast of vancouver island canada abstract twenty nine surface sediment samples from effingham inlet a small fjord on the west coast of vancouver island british columbia were analyzed for diatoms this fjord has been selected for paleoceanographic investigation due to the presence of laminated sediments resulting from the dysoxic to anoxic bottom water conditions in the inner and outer basins of the inlet distributional patterns of the diatom microflora reflected proximity to littoral regions phytoplankton production and marine influence from outside the fjord principal components and cluster analyses of the microflora established four diatom assemblages with a clear separation between the inner and outer basin diatom floras inner basin stations were characterized by elevated absolute abundance with assemblages dominated by spring early summer bloom taxa including skeletonema costatum thalassiosira nordenskioeldii and thalassiosira pacifica chaetoceros spp resting spores were abundant throughout effingham inlet with the exception of the stations closest to the fjord head stations located in the outer basin and towards the fjord mouth had relatively lower absolute abundance yet showed a higher relative and absolute abundance of thalassionema nitzschioides rhizosolenia setigera coscinodiscus radiatus ditylum brightwellii odontella longicruris and paralia sulcata in relation to the inner basin many of these latter taxa are often associated with late summer and autumn conditions in fjords along coastal british columbia oceanographic data for effingham inlet suggest that increased offshore penetration is more likely to occur from summer to early fall with a more restricted offshore influence in the inner basin diatom surface sediment assemblages in effingham inlet appear to reflect incursions of offshore waters into the fjord absolute abundance estimates and the preservation of lightly silicified taxa suggest excellent preservation of fossil material in the sediments of the predominantly anoxic inner basin preservation in the outer basin is reduced reflecting more frequent recharge by oxygenated waters spilling over the outer sill into the basin our findings suggest the inner basin should be an optimal site for reconstruction of diatom production with records from the outer basin providing more consistent information about offshore influence and coastal upwelling conditions over the holocene estimates of diatom abundance within the inner basin sediment may serve as a good proxy of production although proxy tracers of bottom water conditions and sedimentological analyses must be coupled to the diatom record to ensure depositional conditions were not influencing valve preservation or abundance our results suggest that fjords can serve as good environments for paleoceanographic reconstructions of both inshore and offshore conditions although careful site selection and understanding of processes affecting the microfossil record are essential

postglacial rebound at the northern cascadia subduction zone postglacial rebound is the response of the earth to the decay of ice sheets a postglacial rebound model explains crustal tilting and rapid uplift at the northern cascadia subduction zone that occurred during retreat of the cordilleran ice sheet observations explained by the model include the shoreline tilts of two proglacial lakes that formed at 13 5 14 ka 14c yr ago and rapid sea level fall land uplift at 12 12 5 ka modelled mantle viscosity values range from 5 1018 to 5 1019 pa s and are consistent with previous viscosity inferences from observations of crustal deformation following subduction zone earthquakes 1018 1019 pa s no lower limit to subduction zone mantle viscosity is apparent from our model but viscosity values equal to or larger than 1020 pa s are de nitely ruled out our modelled subduction zone viscosity values are smaller than most upper mantle viscosity estimates derived from postglacial rebound studies of tectonically less active regions 1020 1021 pa s the rapid observed uplift at 12 ka requires in addition to a low mantle viscosity rapid unloading from a sudden collapse of remaining coastal portions of the southern cordilleran ice sheet the sudden collapse provides 0 18 m of global eustatic sea level rise approximately 0 7 of the sea level rise associated with melt water pulse ia predictions of a global postglacial rebound model ice 3g with a 1021 pa s upper mantle viscosity were previously applied to geodetic data from this region to isolate signals associated with the earthquake cycle owing to the low viscosity values and resulting rapid recovery of glacial deformation our model predicts present day postglacial rebound uplift rates at least 10 times smaller than ice 3g less than about 0 1 mm yr as the ice 3g adjustments were substantial this indicates the need for re evaluation of the geodetic data 2000 elsevier science ltd all rights reserved

modern to late holocene deposition in an anoxic fjord on the west coast of canada implications for regional oceanography climate and paleoseismic history laminated sediments preserved in the anoxic inner basin of effingham inlet on the pacific coast of vancouver island british columbia canada yield a high resolution sediment deposition record spanning about 6000 yr the varying thickness of diatom terrigenous mud varves in sediment cores from the basin can be interpreted in terms of annual changes in surface productivity and freshwater input within the inlet similarly the occurrence of unlaminated mud units homogenites intercalated amongst the laminated sediments can be interpreted in terms of oceanic and climatic changes these units appear to be associated with coastal upwelling events that result infrequently in highly oxygenated oceanic water penetrating to the bottom of the inner and outer basins of the inlet the sedimentary record also contains massive and graded mud units considered to arise from debris flows and turbidity currents some of which were probably initiated by seismic events including a major event about 4500 14 c yr bp which may be earthquake related a total of seventeen oceanographic surveys of the inlet beginning in 1995 characterize the modern seasonal coastal upwelling regime and a unique bottom water oxygenation event which was

a new geobarometer for the assemblage biotite muscovite chlorite quartz the equilibrium thermodynamics of the reaction 4kmga1si40 o oh mg5a1 si30 o oh muscovlte chlorite muscovite biotite ka13si 0 oh 3kmg3aisi 0 0 oh 7si0 4h o quartz fluid can be formulated as a geobarometer thermo dynamic data for the mg a1 celadonite end member of muscovite is derived from the reversed mineral equilibria experiments of velde i 965 using the calculation method of powell 1978 giving afh 1298 5823 5 kj s 1298 0 3060kjk v 1298 13 8kjkbar

high resolution dinoflagellate cyst record of environmental change in effingham inlet british columbia canada over the last millennium abstract we present a high resolution sedimentary record of dinoflagellate cysts spanning the last 900 years recovered from effingham inlet a glacial fjord on the west coast of vancouver island canada the combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters together with restricted bottom water circulation in the silled fjord fosters the preservation of laminated sediments in the inner basin of effingham inlet geochemical data are used to assess the sedimentary facies of the core which is composed primarily of laminated units 50 2 occasionally interrupted by seismites 39 5 and homogenous units 10 2 the chronology of the 2 m long core is based on varve counting and fifteen 14c dates and is anchored by a seismite previously dated at ad 1946 the dinoflagellate cyst assemblages are diverse total of 47 taxa abundant average concentrations of 102 900 cyst g 1 of dry sediment and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples overall cyst assemblages are characterized by operculodinium centrocarpum 36 2 accompanied by brigantedinium spp 18 0 and dubridinium spp 6 6 multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of the medieval climate anomaly from the base of the record ad 1090 to 1230 the little ice age ad 1230 to late 19th century and warming in the second half of the 20th century the timing of these intervals are consistent with the regional paleoclimate and help constrain past climatic and oceanographic variability on the west coast of vancouver island the origin of homogenous units in the sedimentary record of effingham inlet and paleoseismicity in the region are also discussed

volcanic red bed copper mineralisation related to submarine basalt alteration mont alexandre quebec appalachians canada two types of native copper occur in upper silurian basaltic rocks in the mont alexandre area quebec appalachians 1 type 1 forms micrometric inclusions in plagioclase and is possibly magmatic in origin whereas 2 type 2 occurs as coarse grained patches rimmed by cuprite in altered porphyritic basalt type 1 has higher contents of sulphur 2 000 20 263 ppm and arsenic 146 6 017 ppm and a broader range of silver abundances 65 2 186 ppm ag than type 2 149 1 288 ppm s 90 146 as 65 928 ppm ag no mineral inclusions of sulphide or arsenide in native copper were observed at the electron microprobe scale primary igneous fabrics are preserved but the basaltic flows are pervasively oxidised and plagioclase is albitised chlorite replaces plagioclase and forms interstitial aggregates in the groundmass and has fe fe mg ratios ranging from 0 29 to 0 36 with calculated temperatures between 155 c and 182 c copper sulphides in vacuoles and veinlets are associated with malachite fibro radiating albite and yarrowite cu9s8 with up to 0 3 wt ag bulk rock concentrations of thallium and lithium range from 70 to 310 ppb and 10 to 22 ppm respectively and thallium is positively correlated with fe2o3 such concentrations of thallium and lithium are typical of spilitisation during heated seawater basalt inter action spilitisation is consistent with the regional geolog ical setting of deepwater facies sedimentation but is different from current models for volcanic red bed copper which indicate subaerial oxidation of volcanic flows the volcanic red bed copper model should be re examined to account for native copper mineralisation in basalts altered by warm seawater

interaction between local tectonics and glacial unloading on the pacific margin of canada abstract variations in late quaternary coastal deformation along the pacific margin of canada reflect not only differences in glacial history but also local non glacial tectonics a forebulge developed to the north in the queen charlotte basin qcb from 13 2 until after 9 7 ka bp resulting in exposure of the currently submerged shelf whereas similar exposure was not evident to the south in the georgia basin a semi quantitative effective elastic lithosphere thickness of between 10 and 20 km is estimated for the qcb we propose that this warm relatively thin lithosphere combined with tectonic movement influenced crustal displacement particularly the decoupling of the north american plate along the queen charlotte qc fault which may have allowed the qcb to behave like a hinge in response to glacial unloading this would explain large magnitude crustal tilting 2 1 m km 1 observed adjacent to the qc fault the 50 m of depression observed in the early and mid holocene may imply that the western edge of the north america plate flexed down below present elevation producing a second wave of response to ice loading and unloading

laminated sediments as palaeo indicators as society at large becomes increasingly concerned with the issues surrounding global climate change so the pressure on the scientific community to produce models and predictions of climate variability increases in many respects however that branch of science concerned with climate change is in its infancy while recent meteorological and oceanographic studies have shed light on the processes and mechanisms of atmospheric and oceanic circulation this has produced only a snapshot perspective of global change limited by the range of instrumental or historical records on the other hand palaeoclimatic and palaeoceanographic studies have been mainly on coarser millennial timescales that have a more academic and less immediate appeal the palaeorecords which have the required temporal interannual decadal resolution are limited to tree rings ice cores coral records and laminated marine or lacustrine sediments this volume is concerned with the wide ranging application of lacustrine and marine laminated sediments as palaeo indicators

interannual to multidecadal timescale climate variations in the northeast pacific abstract analysis of five long term coastal air temperature records reconstructed from tree ring growth patterns indicate that the climate of the northeast pacific ocean has oscillated at three dominant timescales over the last 400 years the well known 2 8 yr el nino southern oscillation enso timescale a 20 40 yr interdecadal timescale and a 60 80 yr multidecadal timescale the latter oscillation has been the dominant mode of air temperature variability along the west coast of north america over the last 400 years during this period there have been conspicuous temporal modulations of the enso and the interdecadal signals low frequency temperature oscillations at periods greater than 10 years in the northeast pacific have been significantly coherent and in phase from southern california to british columbia however with the exception of the enso signal higher frequency variability has been weakly coherent along the west coast recent work suggests that the interdecadal oscillation is a worldwi