maintenance of near surface stratification in doubtful sound a new zealand fjord abstract the surface waters of doubtful sound a glacially carved fjord in south western new zealand feature a quasi permanent low salinity layer lsl the lsl is maintained year round by the extreme precipitation in the catchment 7 m yr 1 and discharge from a hydroelectric power station 450 m 3 s 1 the robust stable lsl has been shown to play a major role in controlling intertidal and subtidal community structure by contrast little is known about the dynamics of the lsl itself the work presented here elucidates the response of the lsl to perturbations in the wind stress and rainfall frequency domain analysis of salinity data collected from an array of moored instruments revealed that the lsl responded to perturbations in both the winds and rainfall however the specific roles of the wind stress and rain could not be adequately resolved in these analyses by contrast simulations of the response of the lsl using a three dimensional primitive equation model revealed that strong up fjord directed wind events set up a storm surge at the head of the fjord this surge significantly deepens the lsl at the head of the fjord and retards or reverses estuarine circulation the subsequent relaxation of the surge after the abatement of the wind stress resulted in a redistribution of buoyancy throughout the fjord over a two day period it is shown that the development and relaxation of the storm surge is a major process controlling the maintenance of the near surface stratification

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

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

carbonate dissolution and temporal abundances of foraminifera in long island sound sediments the dynamics of benthic foraminifera assemblages can be used to examine carbonate dissolution processes in nearshore sediments and as a general assay of physical chemical factors affecting survival of juvenile benthos abundances of total foraminifera live and dead fluctuate regularly throughout the year in long island sound lis mud deposits with highest numbers in spring summer and lowest in winter essentially all forams disappear each year pore water undersaturation with respect to carbonate minerals coincides with periods of rapid disappearance of forams and suggests that these fluctuations reflect a balance between the rate of production recruitment and the rates of death and dissolution of the calcareous tests of the animals reworking by macrofauna in lis central basin sediments inhibits accumulation or depletion of pore water solutes and is responsible for minimizing pore water carbonate saturation states quantitative estimates of seasonal patterns of foram dissolution with a simple mass balance model give a minimum average annual flux of caz in lis sediments of 6 mmol ca2 m 2 d 1 due solely to foraminifera dissolution abandoned tests have a maximum mean residence time of 86 13 d dissolution precipitation of forams may significantly affect benthic zco fluxes and likely accounts for a large proportion 30 during some seasons or at some locales other organisms with carbonate tests of similar size particularly juvenile bivalves may also be affected by periods of undersaturated pore waters conditions promotinn dissolution of tests may represent an important source of mortality for calcareous meiofauna

may 18 1980 mount st helens deposits in south coldwater creek washington beginning at 0832 pacific daylight time pdt mount st helens washington produced a rockslide debris avalanche and a lateral explosion blast that generated a laterally directed pyroclastic surge called here a blast surge the resulting deposits are thickest in the east west trending valley of north fork toutle river immediately north of the volcano but are almost as thick in south coldwater creek a small tributary of the toutle river in the lee of an east west trending ridge johnston ridge just north of the north fork toutle river the avalanche surmounted johnston ridge 300 m relief and flowed down the valley of south coldwater creek closely following the avalanche and in part contemporaneously with it the blast surge left thin up to 0 5 m deposits on johnston ridge and thick up to 15 m deposits in south coldwater creek these deposits have a lower layer layer a1 which is friable massive poorer in fines particles 1 16 mm and more poorly sorted than the upper layer layer a2 layer a2 is less friable because it contains more silt and clay sized material beneath layer a1 is a zone containing a small percentage of debris from the blast surge mixed with products eroded from the underlying surface this zone designated as layer a0 is a poorly mixed layer containing schlieren of soil shattered volcanic fragments and considerable quantities of organic material layer a1 is strongly sorted and fines depleted and is interpreted to have been deposited from just behind the turbulent head of the blast surge layer a2 is interpreted to have been deposited from the body of the blast surge which is believed to have been less turbulent than the head layer a0 is interpreted to have formed by shearing at the base of the head of the blast surge in the region between the front and the back of the head of the blast surge it is concluded that a strongly fines depleted basal layer of a pyroclastic flow or surge deposit underlain by a thin sheared zone is the signature of an extremely high velocity particulate density current

a high resolution 800 year glaciomarine record from russkaya gavan a novaya zemlya fjord eastern barents sea sediment core asv 987 from russkaya gavan a tidewater fjord on the northwestern coast of 13 novaya zemlya provides the first multicentury record of sedimentary and hydrographic glaciomarine 14 environments in russian arctic with a century scale resolution age is constrained by seven 14 c ages 15 securing an especially robust control for the period between c ad 1370 and 1600 based on sediment struc 16 ture grain size depositional rates foraminiferal assemblages and stable isotopes in foraminiferal tests 17 we reconstruct the changes in fjord sedimentation and circulation in relation to the history of a tidewater 18 glacier connected to the main novaya zemlya ice complex we conclude that a noticeable glacier advance 19 occurred c ad 1400 contemporaneous with a change in north atlantic atmospheric circulation inferred sea late holocene

climate change and decadal to centennial scale periodicities recorded in a late holocene ne pacific marine record examining the role of solar forcing abstract we present a decadal scale late holocene climate record based on diatoms biogenic silica and grain size from a 12 m sediment core vec02a04 obtained from frederick sound in the seymour belize inlet complex of british columbia canada sediments are characterized by graded massive and laminated intervals laminated intervals are most common between c 2948 2708 cal yr bp and c 1992 1727 cal yr bp increased preservation of laminated sediments and diatom assemblage changes at this time suggest that climate became moderately drier and cooler relative to the preceding and succeeding intervals spectral and wavelet analyses are used to test for statistically significant periodicities in time series of proxies of primary production total diatom abundance biogenic silica and hydrology grain size preserved in the frederick sound record periodicities of c 42 53 60 70 82 89 241 243 and 380 yrs are present results are compared to reconstructed sunspot number data of solanki et al 2004 using cross wavelet transform to evaluate the role of solar forcing on ne pacific climate significant common power of periodicities between c 42 60 70 89 241 243 and of 380 yrs occur suggesting that celestial forcing impacted late holocene climate at frederick sound replication of the c 241 243 yr periodicity in sunspot time series is most pronounced between c 2900 cal yr bp and c 2000 cal yr bp broadly correlative to the timing of maximum preservation of laminated sedimentary successions and diatom assemblage changes high solar activity at the suess de vries band may have been manifested as a prolonged westward shift and or weakening of the aleutian low in the mid late holocene which would have diverted fewer north pacific storms and resulted in the relatively dry conditions reconstructed for the seymour belize inlet complex

preliminary report on the activity at unzen volcano japan november 1990 november 1991 dacite lava domes and pyroclastic flows abstract the eruption of unzen volcano commenced on 17 november 1990 phreatic and phreatomagmatic eruptions occurred by early may 1991 no large scale explosive eruptions preceded the extrusion of lava domes lava domes appeared in a summit crater on 20 may 1991 and they grew on the steep slope of mt fugen at unzen volcano rockfalls from the margins of the domes frequently generated pyroclastic flows major pyroclastic flows occurred on 3 june 8 june and 15 september 1991 the 3 june pyroclastic flow killed forty three persons many of the pyroclastic flows seem to have resulted from the simple rockfalls except one flow on 8 june which was accompanied by an explosion from the crater many of the rockfalls that generated pyroclastic flows were witnessed as of november 1991 unzen volcano was still active with a nearly constant magma supply rate of about 0 3 106 m3 d the total magma output exceeded 45 106 m3 by the beginning of november 1991 the volume of the lava domes is more than 23 106 m3

late holocene atlantic bottom water variability in igaliku fjord south greenland reconstructed from foraminifera faunas a high resolution record of late holocene subsurface water mass characteristics in outer igaliku fjord south greenland is presented based on benthic foraminifera faunas from core po 243 451 collected from a water depth of 304 m strati cation with atlantic water masses present in the lower part of the water column is suggested to have prevailed during the last 3200 cal years except for a period referred to as the mediaeval warm period mwp during the mwp c ad 885 1235 the outer part of igaliku fjord experienced enhanced vertical mixing and a high hydrodynamic energy level which we ascribe to increasing wind stress through this period corresponding to the period of the norse settlement the transition from the mwp to the little ice age lia shows a two step pattern with a short climatic amelioration around ad 1520 before maximum cooling occurred the intensified wind stress and the overall environmental change are suggested to have contributed to the loss of the norse settlement in greenland periods with strong stratification and marked in uence of atlantic subsurface water masses around 2 6 1 3 ka bp and during the lia are correlated to north atlantic holocene ice rafting events reported by bond et al 1997

the valle del bove mount etna its origin and relation to the stratigraphy and structure of the volcano abstract the valle del bove is a major horseshoe shaped depression some 5 km in diameter and over 1000 m deep carved into the eastern flank of mount etna volcano the origin of the valle del bove has been a subject of debate for over a century but recent models relate it to the collapse of the ancient trifoglietto ii centre of etna either by caldera collapse or phreatomagmatic explosive activity careful morphological analysis shows the valle del bove to have formed after the post trifoglietto ii ellittico and leone centres and therefore to be considerably younger than the trifoglietto ii centre it has also been argued that the pyroclastic deposits that occur on the flanks of the volcano in close spatial relationship with the valle del bove were produced by the same event these pyroclastics are divided on the basis of age and composition into two groups the upper and lower tephra deposits the stratigraphy petrology and radiocarbon date of the lower tephra deposits indicate a trifoglietto ii age at least 20 000 years before the formation of the valle del bove the upper tephra deposits have a strong phreatomagmatic character and are closest in age to the valle del bove there is no evidence however to link them with its formation morphological study shows the valle del bove to consist of a series of coalescing scallops indicative of formation by landsliding the material removed by slope failure and subsequent fluvial transport followed a valley to the coast where it forms a fan shaped accumulation the chiancone consisting of volcaniclastics of fluvial and mudflow origin it is argued that the valle del bove did not result from simple caldera collapse but formed from a series of collapses caused by gravitational slope failure the chiancone is considered to be the product of this collapse

late holocene paleoceanographic evidence of the influence of the aleutian low and north pacific high on circulation in the seymour belize inlet complex british columbia canada foraminiferal and thecamoebian faunas from the seymour belize inlet complex sbic a fjord network situated on the mainland coast of british columbia were studied to assess climatic cycles and trends impacting the area through the ad 850 ad 2002 interval ocean circulation patterns prevalent in the sbic are strongly linked to precipitation which is closely linked to the relative strength and position center of action coa of the seasonally developed aleutian low al and north pacific high nph atmospheric circulation gyres through interpretation of cluster analysis and ordination methods a period of weak estuarine circulation was recognized to have impacted the sbic area between ad 850 and ad 1500 during this time waters in the sbic were dysoxic to anoxic and the sediment water interface was comprised of a depauperate foraminiferal fauna consisting of low diversity agglutinated forms these reduced oxygen conditions came about as a result of diminished precipitation in the sbic catchment as the coa of the al progressively migrated westward over time resulting in greatly reduced estuarine circulation and only infrequent and feeble incursions of well oxygenated open ocean water into the sbic basin by ad 1575 following a gradual transition period of 75 years when circulation patterns in the inlet were unstable very strong estuarine circulation developed in the sbic concomitant with the onset of the little ice age lia in western canada in the sbic this interval was characterized by higher levels of precipitation which greatly enhanced estuarine circulation resulting in frequent incursions of cold well oxygenated ocean currents into the bottom waters of the sbic and the development of a diverse calcareous foraminiferal fauna this circulation pattern began to break down in the late 19th century ad and by ad 1940 conditions similar to those that existed in the inlet prior to ad 1500 had redeveloped a process that continues at present

isolation basin records of late quaternary sea level change central mainland british columbia canada isolation basin records from the seymour belize inlet complex a remote area of central mainland british columbia canada are used to constrain post glacial sea level changes and provide a preliminary basis for testing geophysical model predictions of relative sea level rsl change sedimentological and diatom data from three low lying 4 m elevation basins record falling rsls in late glacial times and isolation from the sea by 11 800 11 200 14c bp a subsequent rsl rise during the early holocene 8000 14c bp breached the 2 13 m sill of the lowest basin woods lake but the two more elevated basins sill elevations of 3 6 m remained isolated at 2400 14c bp rsl stood at 1 49 0 34 m above present mtl falling rsls in the late holocene led to the final emergence of the woods lake basin by 1604 36 14c bp model predictions generated using the ice 5g model partnered with a small number of different earth viscosity models generally show poor agreement with the observational data indicating that the ice model and or earth models considered can be improved upon the best data model fits were achieved with relatively low values of upper mantle viscosity 5 1019 pa s which is consistent with previous modelling results from the region the rsl data align more closely with observational records from the southeast of the region eastern vancouver island central strait of georgia than the immediate north bella bella bella coola and prince rupert kitimat and areas to the north west queen charlotte sound hecate strait underlining the complexity of the regional response to glacio isostatic recovery

crumbling of dacite dome lava and generation of pyroclastic flows at unzen volcano recent modelling of volcanic eruptions has shown that the efficiency of subsurface degassing of magmas determines whether magma erupts explosively or effuses quietly1 2 slow uprise of magma is often accompanied by effective degassing leading to the extrusion of lava flows and domes although lava dome extrusion is one of the less explosive modes of eruption it is often accompanied by explosive pyroclastic activities3 5 the 1991 eruption of unzen volcano provided an opportunity to observe at close range several types of small scale pyroclastic flow glowing avalanches originating from lava domes most of the pyroclastic flows are of merapi type caused by blocks falling from a collapsing dome others are of pelean type originating in an explosion from the side of a dome the lavas apparently show variable degrees of self explosivity we suggest that variable degrees of degassing of the magma produced a wide range of excess pore pressures in the extruded lava domes resulting in both merapi type and pelean type pyroclastic flows from the domes

late holocene sedimentation in saanich inlet british columbia and its paleoseismic implications eight piston cores of sediment spanning the last 1500 years were collected from saanich inlet an anoxic fiord on southern vancouver island to obtain information on sedimentation and prehistoric earthquake activity the cores consist mainly of fine grained varved sediments but include massive layers deposited by subaqueous debris flows the debris flows may have been triggered by earthquakes or by the buildup of fine sediment on the walls of the inlet cesium 137 and 2bopb data i4c ages and varve counts were used to date and correlate massive layers in the eight cores the uppermost massive layer in two cores may record a magnitude 7 2 earthquake that occurred in 5946 near comox british columbia 200 km north northwest of saanich inlet seven older layers are found in two or more cores and are about 200 440 550 800 850 1050 1100 1100 1150 and 1450 1500 years old two of these older layers may correlate with previously documented earthquakes in the region there is an average of one massive layer per 116 varves in the core with the greatest number of such layers which is broadly consistent with the expected periodicity of moderate to large earthquakes in the region on average one earthquake producing local modified mercalli intensity vii or viii per century saanich inlet may contain a proxy record of all moderate and large earthquakes that have affected southwestern british columbia during holocene time but some of the massive layers do not appear to correlate from core to core and undoubtedly are nonseismically generated deposits

climate shift at 4400 years bp evidence from high resolution diatom stratigraphy effingham inlet british columbia canada abstract diatom paleoecology and climatic interpretations were assessed from a 15 cm long laminated sediment slab extracted from an anoxic fjord in southwest british columbia the slab spans at least 62 years of deposition determined from counting varves and is dated at approximately 4400 years bp the slab shows a sedimentation pattern where thick diatom rich varves at the bottom become thinner and more silty toward the top thin section analysis reveals that the thicker varves contain a distinct succession of diatoms representing seasonal deposition throughout each year annual scale subsampling shows that the abundance of coastal marine diatoms namely a weakly silicified form of skeletonema costatum decreased over the 62 year period while benthic and brackish water diatoms such as planothidium delicatulum and achnanthes minutissima increased with the concomitant increase in silt the increase in such benthic species and silt along with the presence of 1 cm thick nonlaminated intervals is interpreted to represent deposition during progressively increasing precipitation over time these sedimentation patterns and changes in diatom assemblages may signify a change in the relative intensities of the aleutian low al and north pacific high nph atmospheric pressure systems thicker diatomaceous varves at the bottom of the slab reflect a stronger nph system with associated coastal upwelling and enhanced diatom production the thinner silty varves at the top of the slab suggest that the al system was prevalent resulting in greater amounts of precipitation and reduced upwelling the findings of this study show that significant natural environmental change can occur within a twenty year time frame and can provide a basis for the study of modern change in the ocean atmosphere system over the northeast pacific ocean

late holocene sedimentary response to solar and cosmic ray activity influenced climate variability in the ne pacific marine laminated sediments along the ne pacific coast effingham inlet vancouver island provide an archive of climate variability at annual to millennial scales a 7 75 m portion of piston core tul99b 03 was deposited during a 3045 year interval 1440 4485 years before present ybp under primarily anoxic conditions darker clay laminae were deposited under higher precipitation conditions in winter and diatom dominated laminae were laid down when marine productivity was higher in the spring through autumn wavelet transform and other time series analysis methods were applied to sediment color i e gray scale values line scans obtained from x ray images and compared with global records of cosmogenic nuclides 14 c and 10 be as well as the ice drift index hematite stained grains record to detect cycles trends and nonstationarities in the climate and sedimentary pattern our results show that the marine sedimentary record in the ne pacific responded to abrupt changes and long term variability in climate that can be linked to external forcing e g solar and cosmic irradiance specifically a strong cooling in the ne pacific at 3550f160 ybp can be correlated to a weakening of high frequency 50 150 years pulses in sun activity at the gleissberg cycle band similar to what occurred at the onset of the dlittle ice aget at 1630 ad three intervals of unusually low sun activity at 2350 2750 and 3350 ybp are characterized by thick clay rich annual sedimentation that we interpret as representative of unusually wet conditions these intervals of higher precipitation conditions may have been related to a regional intensification of the aleutian low al caused by an eastward migration of the center of action coa of the al which occurs during intervals of solar minima dryer conditions in the region occur when the coa of al migrates westward and the coa of the north pacific high nph migrates northward during intervals of solar maxima a cyclicity of 50 85 33 36 and 22 29 years in the sediment color record lamination thickness and 14 c cosmogenic nuclide characterized the relatively warm interval from 3550 to 4485 ybp this record is similar to that of present day low and highfrequency variants of the pacific decadal oscillation and aleutian low d 2004 elsevier b v all rights reserved

estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes apparently benign silicic domes or lava flows can travel for several kilometres and then suddenly collapse to generate pyroclastic phenomena capable of causing widespread destruction as happened recently at mount unzen in japan1 two sources have been proposed for the energy that propels such pelean or merapi type2 pyroclastic flows gravitational col lapse supplemented by heating and expansion of air and sudden expansion of pressurized gases from inside the lava flow if gravity controls the energy transfer then areas likely to be affected can be predicted on the basis of topography3 and the resulting deposits will bear a simple relationship to the part of the lava flow from which they issued but if gas pressure adds a significant contribution hazard assessment becomes more difficult because gas decompression adds velocities beyond those acquired by gravitational forces putting much larger areas at risk and forming pyroclastic deposits that are much more difficult to relate to their source here we estimate the initial velocities of pyroclastic flows generated by dome disintegration for a range of lava compositions and volatile contents and offer a conceptual framework for correlating the dynamics of dome front collapse with the resulting sediment record our results indicate that explosive decompression at distal portions of domes can cause velocities comparable to gravitational collapse especially in cases where volatiles become locally concentrated above equilibrium values

a 1500 year record of temperature and glacial response inferred from varved iceberg lake southcentral alaska we present a varve thickness chronology from glacier dammed iceberg lake in the southern alaska icefields radiogenic evidence confirms that laminations are annual and record continuous sediment deposition from a d 442 to a d 1998 varve thickness is positively correlated with northern hemisphere temperature trends and more strongly with a local 600 yr long tree ring width chronology varve thickness increases in warm summers because of higher melt runoff and sediment transport as expected but also because shrinkage of the glacier dam allows shoreline regression that concentrates sediment in the smaller lake varve thickness provides a sensitive record of relative changes in warm season temperatures relative to the entire record temperatures implied by this chronology were lowest around a d 600 warm between a d 1000 and a d 1300 cooler between a d 1500 and a d 1850 and have increased dramatically since then combined with stratigraphic evidence that contemporary jokulhlaups which began in 1999 are unprecedented since at least a d 442 this record suggests that 20th century warming is more intense and accompanied by more extensive glacier retreat than the medieval warm period or any other time in the last 1500 yr

cyclic variation and solar forcing of holocene climate in the alaskan subarctic high resolution analyses of lake sediment from southwestern alaska reveal cyclic variations in climate and ecosystems during the holocene these variations occurred with periodicities similar to those of solar activity and appear to be coherent with time series of the cosmogenic nuclides 14c and 10be as well as north atlantic drift ice our results imply that small variations in solar irradiance induced pronounced cyclic changes in northern high latitude environments they also provide evidence that centennial scale shifts in the holocene climate were similar between the subpolar regions of the north atlantic and north pacific possibly because of sun ocean climate linkages

a review of current testate rhizopod thecamoebian research in canada thecamoebians are a diverse group of testate rhizopods present in a variety of lacustrine and terrestrial habitats among this group certain agglutinating forms primarily arcellacea have tests that are highly resistant to decay and thus fossilize well although the canadian fossil record of thecamoebians extends back as far as the carboniferous the group is particularly common in quaternary lacustrine and peatland environments from temperate to arctic regions of the country research on thecamoebians during the past few years has resulted in great progress on realizing the potential of this group as an important new class of paleoenvironmental indicator applied research on thecamoebian faunas in canada has emphasized aspects of paleolimnology e g eutrophication ph temperature oxygen levels monitoring of land use changes monitoring effectiveness of remediation efforts in contaminated substrates paleo sea level reconstruction paleo water table assessment and paleoclimatic reconstruction 2002 elsevier science b v all rights reserved

regional atmospheric circulation change in the north pacific during the holocene inferred from lacustrine carbonate oxygen isotopes yukon territory canada analyses of sediment cores from jellybean lake a small evaporation insensitive groundwater fed lake provide a record of changes in north pacific atmospheric circulation for the last 7500 yr at 5 to 30 yr resolution isotope hydrology data from the southern yukon indicate that the oxygen isotope composition of water from jellybean lake reflects the composition of mean annual precipitation 18op recent changes in the 18o of jellybean sedimentary calcite 18oca correspond to changes in the north pacific index npi a measure of the intensity and position of the aleutian low al pressure system this suggests that 18op variability was related to the degree of fractionation during moisture transport from the gulf of alaska across the st elias mountains and that holocene shifts were controlled by the intensity and position of the al following this model between 7500 and 4500 cal yr b p long term trends suggest a predominantly weaker and or westward al between 4500 and 3000 cal yr b p the al shifted eastward or intensified before shifting westward or weakening between 3000 and 2000 cal yr b p rapid shifts eastward and or intensification occurred 1200 and 300 cal yr b p holocene changes in north pacific atmospheric circulation inferred from jellybean lake oxygen isotopes correspond with late holocene glacial advances in the st elias mountains changes in north pacific salmon abundance and shifts in atmospheric circulation over the beaufort sea

paleoenvironments of the strait of georgia british columbia during the last deglaciation microfaunal and microfloral evidence the strait of georgia is situated between vancouver island and the western canadian mainland it was deglaciated quickly around 12 500 14c yr bp by in situ downwasting the subsequent marine invasion has left glacimarine sediments with foraminifers diatoms and dinocysts characterizing successive paleoenvironments recognizable basinwide the first paleoenvironment represents near ice conditions under the influence of the turbid meltwater plume marked by low algal productivity and few foraminifers mostly elphidium excavatum just off the plume the second environment shows a peak of nonionellina labradorica possibly resulting from an observed sudden increase in diatom numbers mostly ice dwelling forms implying a long annual sea ice cover further away cassidulina reniforme increases n labradorica decreases while other calcareous foraminifer species colonize the area there are fewer ice diatoms more marine planktonic diatoms and dinocysts become more abundant finally after 12 000 14c yr bp calcareous foraminifers are gradually replaced because of dissolution of calcium carbonate by a low diversity arenaceous assemblage at the same time abundant planktonic diatoms and dinocysts indicate warmer surface temperature the succession of fossils and environments compares well with modern horizontal off glacier successions observed in fjords of the european arctic

dinoflagellate cyst based reconstructions of mid to late holocene winter sea surface temperature and productivity from an anoxic fjord in the ne pacific ocean abstract published contemporary dinoflagellate distributional data from the ne pacific margin and estuarine environments n 136 were re analyzed using canonical correspondence analysis cca and partial canonical correspondence analysis pcca these analyses illustrated the dominant controls of winter temperature and productivity on the distribution of dinoflagellate cysts in this region dinoflagellate cyst based predictive models for winter temperature and productivity were developed from the contemporary distributional data using the modern analogue technique and applied to subfossil data from two mid to late holocene 5500 calendar years before present present cores tul99b03 and tul99b11 collected from effingham inlet a 15 km long anoxic fjord located on the southwest coast of vancouver island that directly opens to the pacific ocean through barkley sound sedimentation within these basins largely comprises annually deposited laminated couplets each made up of a winter deposited terrigenous layer and spring to fall deposited diatomaceous layer the effingham inlet dinoflagellate cyst record provides evidence of a mid holocene gradual decline in winter sst ending with the initiation of neoglacial advances in the region by 3500 cal bp a reconstructed late holocene increase in winter sst was initiated by a weakening of the california current which would have resulted in a warmer central gyre and more el nino like conditions

the impact of climate and shore level displacement on the late holocene environmental development of havstens fjord and koljo fjord swedish west coast koljo fjord and havstens fjord on the swedish west coast are like many silled fjords in scandinavia characterized by strong stratification and stagnant bottom water with periodically occurring low oxygen and anoxic conditions high organic production together with a stable water column very low tidal activity and existence of the sill create an ideal foundation for low oxygen conditions to develop the aim of this study was to find out how the fjord environments developed during the later part of the holocene and especially how and when the low oxygen conditions evolved to achieve these goals sediment cores were dated 210 pb and 14 c and x rayed the distribution of benthic foraminifera was analysed and their content of the stable isotopes delta 18 o and delta 13 c was investigated in both fjords the climate proved to be of importance for the environment and it seems that increased freshwater runoff increased the primary production between 500 bc and ad 500 increasing freshwater runoff not only increased primary production but at least since ad 1880 also made the water stratification stronger and the deep water more stagnant stagnant conditions are the main cause of the development of periodic anoxia and formation of laminated sediments in koljo fjord from ad 1930 to 1980 and in havstens fjord from ad 1950 in koljo fjord the isostatic land rise and the shallow sill are the most important reasons for a general change from an almost normal saline deep water environment to a brackish environment in ad 500 at that time the sill depth passed the pycnocline mean depth of 15 m for koljo fjord this is a threshold value of the depth for the quality of the deep water marine or brackish

linkages between holocene paleoclimate and paleohydrogeology preserved in a yucatan underwater cave abstract three sediment cores spanning the last 4200 years from aktun ha cave on the yucatan peninsula mexico demonstrate that underwater caves can document changes to regional hydrogeology and climate benthic microfossils testate amoebae foraminifera organic matter geochemistry 13 c 15 n c n and particle size distributions were analyzed however microfossil paleoecology proved the most useful for indicating three salinity phases in the aktun ha sediment cores phase 1 4300 yr bp contains predominantly foraminifera physalidia simplex 78 that indicate the meteoric lens flooding the cave was initially brackish salinity 3 5 g l 1 phase 2 2800 4300 cal yr bp has both freshwater testate amoebae centropyxis spp 40 and p simplex 42 which indicates a slight freshening of the meteoric lens to 1 5 2 g l 1 phase 3 lagenodifflugia vas and difflugia oblonga with a reduction in p simplex 10 this last faunal shift represents the initiation of modern freshwater conditions in the cave 1 5 g l 1 this final freshening is synchronous with a significant reduction in the c n ratio e g core 2 27 to 19 which suggests an expansion of primary productivity in the adjacent cenote the 15 n values ranged from 1 5 to 3 5 with observed cycles likely from intervals of increased terrestrial om input into the cave during high rainfall events e g hurricanes the observed paleoenvironmental shifts in the cave correlate well with regional precipitation patterns aquifer recharge and storm activity caused by southward migration of the intertropical convergence zone therefore regional climate change impacted eastern yucatan groundwater during the mid to late holocene however decelerating holocene sea level rise and aquifer occlusion are likely contributing factors these results demonstrate that underwater cave sediments and microfossils can be useful proxies for aquifer evolution and climate change

small volcanic edifices and volcanism in the plains of venus the most widespread terrain type on venus consists of volcanic lowland plains several styles of volcanism are represented in the plains the most extensive volcanic units consist of flood lavas the largest of which have volumes of the order of thousands of cubic kilometers as with terrestrial flood lavas they are inferred to have erupted at high effusion rates they show a range of radar backscatter characteristics indicating different surface textures and ages small edifices on the plains occur mainly in clusters associated with fracture belts the majority are shield volcanoes that may be up to a few tens of kilometers across but are generally 10 km or less in diameter volcanic cones have the same size range volcanic domes have diameters up to several tens of kilometers and volumes of the order of 100 km3 these are interpreted as being constructed of lava erupted with a relatively high effective viscosity and thus possibly composed of more silicic lava for many domes the flanks were unstable during and afte eruption and suffered gravity sliding that produced steep scalloped outer margins because of the high atmospheric pressures on venus explosive activity is less likely to occur than on earth however n a few plains areas there is evidence of pyroclastic deposits surrounding craters indicating that volatile contents in some of the magmas may be high in comparison to earth the clusters of small volcanic edifices are considered to be analogous to plains volcanism similar to that of the snake river plain of idaho there may also be analogues with terrestrial volcanic clusters associated with mid oceanic ridges

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

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 6000 yr varve record of holocene climate in saanich inlet british columbia from digital sediment colour analysis of odp leg 169s cores abstract high resolution grey value time series were extracted from digital images of varved sediments in saanich inlet british columbia odp sites 1033 and 1034 results allowed reconstruction of a 6000 yr long record with annual resolution composite records were compiled for sites 1033 and 1034 by correlation of massive beds which represent gravity flows and of characteristic features in the varve patterns the varve count age scale was calibrated with published radiocarbon ages results demonstrate that the odp leg 169s record is virtually complete saanich inlet varve record has the potential to provide a high resolution climate record temporal variation in varve thickness is interpreted to reflect regional precipitation history with thick varves representing wet conditions long term changes in varve thickness during the past 6000 yr coincide with known changes in global climate but without an obvious one to one correlation between wet dry in saanich inlet and warm cold periods elsewhere varve thickness indicates that the climate around saanich inlet was wet from the start of the varved sequence at 6000 to 3250 yr bp between 2100 and 1750 yr bp roman warm period and from 500 yr bp onward including during little ice age

foraminifera climatic change and pollution a study of late holocene sediments in drammensfiord southeast norway benthic foraminifera are shown to reflect both natural including climatic and human induced environmental alterations over the last 1500 years in drammensfjord norway today drammensfjord is a 124 m deep partly anoxic hyposaline basin salinity 32 o separated from the adjoining oslo fjord by a sill at 10 m water depth it has been affected by human induced organic pollution for more than a century based on major faunal trends sediment characteristics and concentrations of plant fragments and pollen grains four environmental zones are distinguished the faunal composition of zones 1 3 before ad 500 to about ad 1850 reflects the natural environmental development from a period with frequent deep water renewals and diverse calcareous dominated assemblages to periods with increasing river flow which impeded effective deep water renewals and gave rise to agglutinated assemblages of low diversity increasing human induced organic flux over the last 130 140 years has elevated the redox cline the

rheologic properties and kinematics of emplacement of the chaos jumbles rockfall avalanche lassen volcanic national park california the chaos jumbles is a rockfall avalanche deposit that was emplaced by three separate events 300 years ago deposits from each event are distinguishable on the basis of morphology size variation of large dacitic surface clasts and by the color of both the matrix and entrained dacitic blocks steep lateral and distal deposit margins and surface features such as folds and apparent strike slip faults indicate that each rockfall avalanche had a finite yield strength and was being actively deformed and sheared throughout the body of the moving deposit rather than strictly along a basal surface kinematic analysis of the three deposits indicates that each had a very low apparent coefficient of friction and was emplaced at velocities of up to 100 m s these data suggest that each rockfall avalanche can be modeled as a pseudoplastic material undergoing flow parallel compression above a frictionless base this model allows calculation of deposit volumes ranging from 1 2 to 1 7 108 m3 and also suggests that a future rockfall avalanche from the same location would have a more restricted runout than the previous events

modern distribution of salt marsh foraminifera and thecamoebians in the seymour belize inlet complex british columbia canada foraminifera and thecamoebian distribution along two marsh transects in the waump wir 16 and wawwat l wir 12 indian reserves in the seymour belize inlet complex north coastal british columbia were investigated based on q and r mode cluster analysis of the faunal distributions three high abundance low diversity faunal assemblages were identified the freshwater brackish and high salt marsh assemblages the freshwater assemblage is dominated by the soil thecamoebian species cyclopyxis kahli a significant presence of centropyxids and nebela collaris the brackish assemblage is characterized by abundant centropyxids and less than 10 foraminifera the high salt marsh assemblage is characterized by the dominance of balticammina pseudomacrescens the results of this study show the high potential of combined thecamoebian foraminifera analyses for paleo sea level research under lower salinity marsh conditions

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

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

late holocene environmental change at treeline in the northern coast mountains british columbia canada an integrated stratigraphic paleoecological and geochronological study of lake and fen sediments just beyond the terminus of berendon glacier provides insights into late holocene climate vegetation and glacier change in the northern coast mountains of british columbia cores collected from two small lakes in the foreland of berendon glacier and pits dug in a nearby fen record little lee age and older glacier advances the first little ice age advance in this area began more than 500 years ago and peaked in the early 17th century an earlier neoglacial advance began about 2800 3000 cal yr ago and may have lasted for hundreds of years there is also evidence for an intervening advance of even smaller magnitude around 1200 1300 cal yr ago the advances are broadly synchronous with those in other parts of western north america indicating that they were caused by regional possibly global changes in climate plant communities within the study area did not change dramatically during the late holocene the ranges of some plants however likely retracted or extended near treeline in response to changes in mean temperatures of perhaps 1 2degreesc as a well as changes in summer snow cover the greatest changes in vegetation occurred within and just beyond the forefields of berendon frank mackie and other nearby glaciers the largest climate shifts of the last 3000 years took place during the late little ice age and the last century climate warmed about 1 2degreesc during the 20th century accompanied by a rise in treeline an increase in coniferous tree cover in the subalpine zone and an increase in the temperature and biological productivity of ponds these trends are likely to continue if climate as expected continues to warm c 2004 elsevier ltd all rights reserved less

the impact of air mass circulation dynamics on late holocene paleoclimate in northwestern north america paleoclimate records from northern british columbia southwestern yukon and adjacent alaska suggest that late holocene climate may have been influenced by specific air mass circulation dynamics the aleutian lowpressure index alpi is a measure of sea level pressure fluctuations in the pacific northwest associated with the aleutian low al pressure system in this study we show that the al has a strong influence on historical climate change in the study area and explore the relationships between alpi polarity and changes in late holocene paleoclimate records analyses of weather station data in the study area indicate positive correlations r 0 63 between mean wintertime december march temperature and alpi values total wintertime snowfall accumulation and total precipitation show moderate and weak negative correlations respectively a late holocene increase in exotic western hemlock tsuga heterophylla pollen has been observed in regional paleoclimate studies a sustained positive alpi phase during the late holocene is considered as a causative mechanism under such conditions warm maritime air masses would more frequently penetrate inland potentially resulting in eastward pollen transfer enhanced growing conditions at coastal sites and an increase eastwards in the range limit of these species this study indicates that apparent conflicts in the timing and magnitude of late holocene climate change may be the result of a strong regional climate forcing mechanism that exhibits both temporal and geographical variation r 2002 elsevier science ltd and inqua all rights reserved