climate evolution during the holocene a study with an earth system model of intermediate complexity an earth system model of intermediate complexity mobidic has been used to simulate the transient variations in continental temperature sea surface temperature sst thermohaline circulation thc and sea ice cover over the last 9000 years 9 kyr experiments were designed to determine a the deviation of the climatic system with respect to equilibrium over the last 9 kyr b the individual contributions of oceans and vegetation to climatic changes as well as the potential synergies between these components and c the relative importance of precession obliquity and co2 concentration changes during this period results show a monotonous cooling trend in the northern high latitudes between 9 kyr bp and the present day both over the oceans and the continents north of 60 n this cooling is noticed throughout the year but the largest variations appear in spring and summer up to 6 c over continents along with this cooling the model exhibits a southward shift of the northern treeline by about 600 km most of this shift takes place between 4 and 1 kyr bp during this period reorganisations of the boreal forest introduce a lag of about 200 years in the system with respect to a state in equilibrium with the external forcing sensitivity experiments illustrate the strong impact of this vegetation shift both on the oceans and the continents especially in spring and early summer however the model exhibits a weak synergy between vegetation and ocean throughout the holocene finally a sensitivity study to the forcing components shows the dominant role of the astronomical forcing with respect to co2 as well as the non linear behaviour of climate in response to obliquity and precession

lateglacial vegetation dynamics in the eastern baltic region between 14 500 and 11 400 cal yr bp a complete record since the bolling gi 1e to the holocene abstract this paper discusses a complete record of vegetation history since the bolling gi 1e warming 14 500 cal yr bp up to the holocene in latvia to date this is the only complete record of such age in the eastern baltic area and the northernmost area for which bolling records are present combining pollen evidence pollen accumulation rates par and plant macrofossil data we assess the local and regional vegetation development and we attempt to separate the true lateglacial vegetation signal by removing the obviously redeposited thermophilous pollen however we remove not only their signal we discuss the possibilities of separating the redeposition signal of the so called local lateglacial trees pine and birch by looking at their corrosion and degradation the results show that the bolling warming in the eastern baltic area was a treeless tundra community consisting of the shrubs betula nana dryas octopetala and salix polaris the older dryas cold spell is clearly recognised as a decline in the total concentration of plant macrofossils and pars at between 14 200 and 13 500 cal yr bp at 13 460 cal yr bp the b nana macrofossils disappear and tree birch betula sect albae appears marking the start of tree birch forest the presence of pine forest is confirmed by a variety of macrofossils including bark wood needles and seeds since 13 400 cal yr bp at the same time at which pine stomata are found the first identified pine stomata finds are associated with a pinus par over 3000 grains cm 2 yr 1 and pine macrofossil finds with a pinus par over 4000 grains cm 2 yr 1 during the warmest period of the gi 1a allerod at 13 000 12 700 cal yr bp a pine forest with deciduous trees birch betula pendula and aspen populus tremula developed in the study area the younger dryas gs 1 cooling strongly affected the floral composition in eastern latvia the par of the tree taxa declined abruptly from a maximum value at 12 700 to below 1000 grains cm 2 yr 1 at 12 600 cal yr bp the response time for the pine forest to collapse was 100 years according to the par data pine macrofossils disappear simultaneously with the pollen signal at 12 600 cal yr bp yet occasional pinus stomata are recorded throughout the younger dryas gs 1 the landscape was treeless shrub tundra again with d octopetala s polaris b nana and juniperus present picea is introduced in the region within the cold younger dryas and is represented by stomata 12 400 12 200 cal yr bp needles seeds and wood since 12 050 cal yr bp up to the holocene the pleistocene holocene boundary at 11 650 cal yr bp is marked by changes both in vegetation composition and sediment type the organic rich gyttja accumulated instead of silts and clays and the start of the holocene warm period permitted forest re expansion in eastern latvia

timing of lateglacial vegetation dynamics and respective palaeoenvironmental conditions in southern estonia evidence from the sediment record of lake nakri this paper investigates a detailed well dated lateglacial floristic colonisation in the eastern baltic area ca 14 000 9000 cal a bp using palynological macrofossil loss on ignition and 14c data during 14 000 13 400 cal a bp primarily treeless pioneer tundra vegetation existed tree birch betula sect albae macro remains and a high tree pollen accumulation rate indicate the presence of forest tundra with birch and possibly pine pinus sylvestris l trees during 13 400 12 850 cal a bp palaeobotanical data indicate that the colonisation and development of forested areas were very rapid arising within a period of less than 50 years thus far there are no indications of conifer macrofossils in estonia to support the presence of coniferous forests in the lateglacial period signs of greenland interstadial 1b cooling during 13 100 cal a bp are distinguishable biostratigraphic evidence indicates that the vegetation was again mostly treeless tundra during the final colder episode of the lateglacial period associated with greenland stadial 1 approximately 12 850 11 650 cal a bp this was followed by onset of the holocene vegetation with the expansion of boreal forests in response to rapid climatic warming copyright 2011 john wiley sons ltd

mapping of alteration zones with seismic amplitude data and well logs in the hard rock environment of the keefe lake area athabasca basin canada abstract optical televiewer otv and full wave sonic fws data sets acquired in two boreholes from the keefe lake property of atom energy inc aei provided a unique opportunity to study the lithologic units through analysis of p and s wave velocities and elastic rock properties derived from them poisson s ratio lambda and mu this approach is a first attempt to describe petrophysical properties for the sandstone sediments and underlying crystalline proterozoic rocks of the eastern athabasca basin wireline measurements penetrated through the entire 180 m thickness of the basin fill and deep into the basement 357 m and 552 m intersecting several fracture and alteration zones such zones are considered possible locations of uranium mineralization in the athabasca basin seismic attributes amplitude envelope and cosine instantaneous phase can be used in the hard rock environment the characteristic values of fracture and alteration zones can by analyzed by crossplotting the elastic properties

succession of arboreal taxa during the late glacial in south eastern poland climatic implications abstract this paper presents and discusses vegetation changes between ca 14 910 and 11 620 cal bp which are recorded in the deposits of a small mire located in south eastern poland particular attention is paid to arboreal taxa changes in arboreal vegetation are reconstructed on the basis of pollen analysis including pollen accumulation rate par and analysis of plant macrofossils these being supported by radiocarbon chronology before the onset of the gi 1 warming 14 910 310 14 810 280 cal bp a mosaic of pinus and betula wood patches and or isolated stands of trees along with heliophilous juniperus thickets were dispersed within patches of herb steppe and tundra communities thermal amelioration at the gs 2 gi 1 transition ca 14 810 280 14 510 200 cal bp led to the spread of salix and to a lesser extent of tree birches betula pines pinus and hippophae rhamnoides in the light of par values from ca 14 550 210 cal bp there were open pine birch woodlands there which ca 14 270 160 cal bp turned into dense forests cold oscillations such as gi 1d gi 1c2 and gi 1b dated in the profile at ca 14 190 120 13 870 140 13 740 120 13 490 80 and 13 120 12 870 60 cal bp respectively are visible as declines in the par of arboreal taxa from ca 13 770 120 cal bp picea abies whose nearest glacial refugia were located in the western carpathians probably reached the site surroundings 50 n in the younger dryas gs 1 climate deterioration caused a decline in birch population in the first phase a slight retreat of forests and the simultaneous expansion of artemisia poaceae steppe communities and juniperus thickets the par values reflect a division of the younger dryas into two distinct phases an older phase more severe for tree populations probably due to longer and cooler winters and a younger phase with milder winters which begun ca 11 960 110 cal bp

biogeography of pleistocene conifer species from the ziegler reservoir fossil site snowmass village colorado article i nfo article history received 7 november 2013 available online xxxx pleistocene biogeography of conifer species is poorly known in much of western north america we conducted morphological studies on 201 conifer cones and cone fragments recovered from pleistocene sediments at the ziegler reservoir fossil site 2705 m near snowmass village colorado the basin formed 155 130 ka contains fossil bearing lacustrine palustrine and colluvial sediments spanning approximately 85 ka using a suite of mor phological characters particularlycone scale bracts we differentiated species of abies picea a ndpseudotsuga all fossil abies specimens were assignable based on bract morphology to abies concolor which is currently absent from central colorado nearest populations are 160 km southwest of the site a concolor occurs only in sedi ments of mis 5d and 5c pseudotsuga menziesii and picea engelmanniicones occurred in sediments corresponding to mis 5e 5d 5c and 5a a fourth conifer species occurring in sediments of mis 5e 5d 5c and 5a is difficult to assign to any extant species bract morphology is similar to picea pungens which grows near the site today but scale morphology is unlike p pungens these fossils may represent ancestral p pungens an extinct variant or an extinct sister species

seismic reflection imaging of mineral systems three case histories mineral deposits can be described in terms of their mineral systems i e fluid source migration pathway and trap source regions are difficult to recognize in seismic images many orebodies lie on or adjacent to major fault systems suggesting that the faults acted as fluid migration pathways through the crust large faults often have broad internal zones of deformation fabric which is anisotropic this coupled with the metasomatic effects of fluids moving along faults while they are active can make the faults seismically reflective for example major gold deposits in the archaean eastern goldfields province of western australia lie in the hanging wall block of regional scale faults that differ from other nearby faults by being highly reflective and penetrating to greater depths in the lower crust coupled thermal mechanical and fluid flow modeling supports the theory that these faults were fluid migration pathways from the lower to the upper crust strong reflections are also recorded from two

stevens and earlier miocene turbidite sandstones southern san joaquin valley california a thick marine turbidite succession dominantly coarse sandstone underlies the southern part of the san joaquin valley sands are pebbly to fine grained commonly poorly sorted quartzose to arkosic and are interbedded with dark shales bearing deep water foraminifers graded bedding is common and with the depths of 2 000 to 6 000 ft 610 to 1 830 m implied by the fauna is taken to indicate a turbidity current origin for most of the sands the upper middle and lower miocene turbidite section was revealed by extensive coring at paloma and is similar to the more widespread and oil and gas productive upper miocene stevens sandstone the central basin stevens was deposited as channel sands on deep sea fans derived from several discrete troughs or canyons on the eastern and southeastern margin of the basin prior to their burial by prograding santa margarita sand sand channels and lobes in the bakersfield arch area were controlled locally by compaction structures the rising paloma anticline deflected stevens sands for a time and the very last sands were guided also by incipient folds on the outer bakersfield arch coarse stevens conglomerates and sands shed from the emergent temblor range were deflected by the buena vista hills elk hills and other anticlinal shoals and were deposited in intervening gaps as thick oil productive channel sands they merge with sands from the east side in flowing axially into the di tal northwestern basin facies recognized in the subsurface include a meander channel facies developed in the prograded muddy slope area upstream from the massive braided sand facies

integration of modern and past pollen accumulation rate par records across the arctic tree line a method for more precise vegetation reconstructions abstract in order to assess the potential role of the boreal forest in the early to mid holocene global dynamics it is critical that the tree line reconstructions are based on precise palaeorecords pollen accumulation rate par calculations provide a technique for estimating past plant population densities independently for each species when considering tree lines an important concept is the threshold par value for the absence presence and dominance of the most common tree species such threshold values are often based on modern lake sediment core top par values in northern fennoscandia records obtained through pollen monitoring now add an important element to these studies as they allow more precise definitions of the temporal and spatial limits of par values here we compare modern par values based on pollen monitoring data with sediment core top data to evaluate the robustness of the threshold values for the major tree species of finnish lapland we apply these threshold values to two fossil par records from this tree line region and as an example of the potential of the approach map the vegetation patterns in the area at 7000 cal yr bp the results indicate that the extent of the mid holocene tree line advance in northern fennoscandia was substantially less than climate vegetation model simulations have predicted despite their value and potential in vegetation reconstructions the use of par values requires careful validation of the data we stress the importance of basin size of precise and reliable sediment dating age depth modelling and assessment of the sedimentary processes in each study basin as prerequisites for par based studies

sediment focusing in mirror lake new hampshire1 analyses of multiple sediment cores from mirror lake new hampshire dated by 14c and pollen show that between 14 000 and 11 000 b p silts and sands were deposited over 85 of the basin after 11 000 b p organic rich sediments were focused into the deeper parts of the basin and no sediment accumulated in water 5 m deep late glacial particulate inorganic inputs were 33 times greater than modern losses from forested watersheds at hubbard brook after trees became established inorganic inputs fell sharply to modern levels late glacial organic inputs were a half the average during the last 11 000 years at four of the sites studied accumulation rates reached a maximum between 7000 and 4000 b p the precise date varies from site to site suggesting that it would be misleading to link peak accumulation in a single core to events in the watershed after 4000 b p organic sediment accumulation rates declined at all four sites parallel declines in accumulation rates of both pollen and inorganic sediments suggest that this decline is due to the process of sediment focusing rather than to a change in decomposition rates or in organic inputs related to autochthonous or allochthonous primary production

shallow high resolution seismic imaging at the ansil mining camp in the abitibi greenstone belt volcanic rocks in and around the ansil mining camp host a large number of massive sulfide mineral deposits a high resolution seismic reflection profile was shot across the camp with the objective of mapping the contacts between the different volcanic units at which most of the ore bodies have been found numerous exploration boreholes define the geology to a depth of 1600 m and allow a precise comparison with the recorded reflections geophysical logs obtained in one deep borehole suggest that reflection coefficients between the andesite rhyolite units of the volcanic stratigraphy are around 0 05 but few corresponding reflections can be identified in the seismic data those reflections in the surface seismic profile that can be correlated with the subsurface geology originate from diorite sills at which reflection coefficients are between 0 05 and 0 11 we suggest that reflections are observed from the diorite sills because the sills were intruded as sheets some along fault planes resulting in inte

holocene tree line dynamics and inferred climatic changes in the abisko area northern sweden based on macrofossil and pollen records lake sediment records of pollen and macroscopic plant remains of terrestrial origin provide evidence of long term changes in forest composition close to the altitudinal tree line in the abisko area northernmost sweden a dominance of mountain birch betula pubescens ehrh ssp tortuosa ledeb nyman with a field layer of ferns grasses and sedges suggests that an oceanic climate with relatively high precipitation existed during the early holocene macrofossils of mountain birch were found 300 400 m above the present tree line which corresponds to a 1 5 2 c higher summer temperature than at present scots pine pinus sylvestris was present to some extent at altitudes above its present limit during the early holocene a pronounced expansion of pine took place above its present limit around 6300 cal bp 5500 bp this is interpreted as a result of successively drier and more continental climatic conditions a decreased abundance of pine from c 5200 cal bp 4700 bp followed by a gradual retraction of

postglacial vegetation history of the mackenzie river basin abstract three radiocarbon dated cores from small lakes provide pollen records of postglacial vegetation change in the central mackenzie river basin these data are combined with previously published records to reconstruct vegetation development from central alberta to the mackenzie delta the paleoecological data demonstrate that a continuous corridor of herb and shrub dominated vegetation extended between beringia and the great plains of north america from deglaciaiton until about 10 000 yr b p the initial vegetation was replaced by spruce forests between 10 000 and 8500 yr b p significant vegetation change continued until approximately 500 yr b p when the muskeg dominated landscape typical of the present subarctic was established the initial herb and shrub vegetation was likely a reprise of conditions which existed during earlier pleistocene deglaciations these conditions may have provided a favorable environment for animals adapted to nonforested vegetation and promoted migration southward from beringia and northward from the great plains during the last deglaciation and earlier pleistocene deglaciations the sequence of postglacial vegetation change in the mackenzie basin likely reflects a combination of climatic change edaphic change and plant migration patterns and interactions

upper miocene stevens sandstone san joaquin basin california reinterpretation of a petroliferous sand rich deep sea depositional system deep marine sands of the upper miocene stevens sandstone one of the most important hydrocarbon producing units in the united states were deposited by sediment gravity flows in the bakersfield arch area of the southern san joaquin basin the stevens sandstone historically has been considered to be a thick turbidite succession shed off the southern sierra nevada as four fans in a long lived submarine fan system fed in large part by several large submarine canyons access to previously unavailable proprietary two dimensional and three dimensional seismic data sets carefully calibrated by well log and core data permits a more complete understanding of the depositional architecture of this highly petroliferous deep marine depositional system we conclude that these units were deposited in a structurally controlled sand rich deep sea system which was fed by a delta system that lacked major submarine canyons the uppermost sand unit the upper stevens sandstone developed as a deep sea braid plain in the area of the present bakersfield arch within the braid plain curvilinear features detected on horizon slices through a three dimensional seismic data cube are interpreted as braided channel form deposits hydrocarbon production established along these linear trends may reflect improved reservoir quality localized by channel sedimentary processes

kinematic history of the boulder lefroy shear zone system and controls on associated gold mineralization yilgarn craton western australia the boulder lefroy shear zone developed in the ca 2 7 to 2 65 ga archean greenstone sequence of the kalgoorlie terrane in the yilgarn craton is remarkable for the number and importance of gold deposits it hosts these include from south to north the following gold districts with tons of contained au st ives 253 t hampton boulder jubilee 123 t golden mile 1 821 t plus mount charlotte 219 t and paddington broad arrow 112 t detailed structural studies reveal that the shear zone system developed in two main stages the first related to a phase of north northwest south southeast trending folding and thrusting regional d 2 and the second related to sinistral shearing regional d 3 that reactivated and linked the preexisting north north west south southeast trending network of thrust planes sinistral movement resulted in only limited displacement less than 12 km and evolved from a ductile shearing in broad zone toward semibrittle shearing along narrow planes regional d 4 the structures suggest a temporal evolution from crustal thickening during d 2 through lateral escape during d 3 to the development of brittle structures during d 4 the fimiston and oroya lodes at the golden mile in kalgoorlie are also exceptional in their gold endowment and associated alteration and were most likely developed during d 2 all other deposits along the shear zone system were formed within 25 m y of the fimiston and oroya lodes late in the tectonic history of the terrane either during d 3 or d 4 intense mineralization within and around the shear zone resulted from multiscale focusing of mineralizing fluids at a regional scale fluids were focused into the shear zone system and its large anticlines which expose deeper mafic and ultramafic rocks at a local scale fluids were further focused into structural pathways resulting from strain induced permeability in rocks with contrasting rheology

interpretation of the reflections in the siljan ring area based on results from the gravberg 1 borehole abstract during 1985 about 80 km of surface multichannel seismic reflection data were collected across the meteorite impact in the siljan ring area in central sweden the area consists mainly of granitic and gneissic rock ranging in age from 1400 to 2000 million years with remnants of palaeozoic sedimentary rocks preserved by downfaulting after a meteorite impact at 360 ma thereby forming a circular ring about 40 km in diameter dolerite intrusions ranging in age from 850 to 1700 million years are also present the seismic data revealed several high amplitude laterally continuous sub horizontal reflections in the northern part of the structure the high amplitude reflections and a possible intermediate low velocity zone were contributing factors in choosing the site for the gravberg 1 deep earth gas test well drilling and vertical seismic profiling vsp found that the reflectors were associated with dolerite sills which had intruded into the granite and which range in thickness from a few metres up to 60 m and with a pre impact area extent of at least 800 km 2 studies of amplitude and frequency versus offset afvo show the observations are compatible with a model of simple granite dolerite granite layering

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

structural controls on submarine fan geometry and internal architecture upper la jolla fan system offshore southern california la jolla fan offshore of san diego california is a well studied example of submarine fan sedimentation yet the internal architecture of the fan has remained poorly known high resolution seismic data recorded in a 1 by 2 mi 1 6 by 3 3 km grid over much of the fan allow better understanding of upper and middle fan features and processes and of structural controls on fan sedimentation three bathymetrically prominent conduits supply sediment to the upper la jolla fan system from stream and nearshore littoral drift cell sources la jolla canyon and contiguous la jolla fan valley is the main feeder to the fan seismic profiling data confirm the previously reported erosional character of the channel and constructional nature of flanking levees these data also reveal that the position of the channel is controlled by the geometry of a buried hard rock structure newport canyon channel northerly feeder to the upper la jolla fan system is a single well defined channel with flanking constructional levees where it lies in a structurally controlled trough in contrast the channel splays into multiple broad poorly defined channels where sedimentation is unconstrained a buried pliocene pleistocene ancestral version of newport channel displays the same structural control the position of loma sea valley southern feeder to la jolla fan system is tightly controlled by the structure of the steep flank of coronado bank thus loma sea valley trends parallel with the shore and is fed by an orthogonal set of tributary channels which drains the san diego shelf to the east at intersections with these tributaries abnormal thicknesses of sediment partially clog loma sea valley these channel fills may be analogous to those occurring in terrestrial trunk stream intermittent tributary systems like the colorado river in the grand canyon seismic data demonstrate that the la jolla fan system comprises a complex interleaved set of sediment wedges derived from multiple sources and woven around the wrench tectonic fabric of uplifts and basins of the southern california borderland thus la jolla fan system presents an expansion from the simple radial growth pattern of fan sedimentation to a complex fan system built of a number of smaller interwoven radial growth components despite these complexities lithofacies patterns are in part predictable for the la jolla fan system fault bounded uplifts form long lived barriers to sediment dispersal and enhance channel development along their flanks multistory channel complexes detectable seismically commonly occur in these structurally controlled positions adjacent to wrench elated uplifts

middle miocene tectonic uplift of southern san joaquin basin california calculations of the tectonic component of the subsidence history of california s southern san joaquin basin indicate 200 400 m of abrupt tectonic uplift during the relizian about 15 ma this uplift can be explained as an isostatic response to the movement of thin young lithosphere south of the subducted mendocino fracture zone to a position under the basin the calculated uplift cannot be a result of extension and subsidence caused by instability of the mendocino triple junction but earlier early miocene subsidence of the basin may have resulted from triple junction related extension marine strata deposited in the san joaquin basin during the middle miocene are rich sources of petroleum so the inferred uplift and facies shifts may have important implications for ex loration

holocene paleoclimate data from the arctic testing models of global climate change to evaluate the spatial variability of arctic climate change during the present interglacial cape project members compiled well dated terrestrial marine and ice core paleoenvironmental records spanning the past 10 12 thousand years ka six tundra biomes of increasing summer temperature requirements were defined based on regionally coherent pollen assemblages using a rule based approach pollen spectra were converted to tundra forest tundra or forest biomes ranked by their average growing season requirements marine sea surface reconstructions were based on proxy data following a similar rule based approach from these data based reconstructions departures in summer temperatures from modern normals were calculated in 1 ka time slices through the holocene to test predictive models data based summer temperature reconstructions were compared with general circulation model gcm simulations for 10 ka and 6 ka ago paleodata and model results both show that warming occurred earlier across beringia and asia relative to lands adjacent to the north atlantic and that late holocene cooling was most apparent in the north atlantic region however the gcm over predicts the magnitude of mid holocene warming over northern asia and underestimates the intensification of the north atlantic drift in the early holocene strong spatial variability in environmental response during the holocene despite symmetric insolation forcing suggests that any future changes whether caused by anthropogenic or natural factors are unlikely to result in a uniform change across the arctic adding additional complexity to forecasts of global impacts

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

using supervirtual first arrivals in controlled source hardrock seismic imaging well worth the effort varied applications of seismic interferometry have arisen in the last decade however the potential of the method to improve reflection seismic processing in hardrock environments has not explicitly been regarded therefore in this paper we investigate the potential of retrieving the first arrivals originally hindered by high noise level in the exploitation of controlled source data acquired over the iron oxide apatite rich deposit at grangesberg sweden and its mining induced structures the supervirtual first arrivals retrieved using interferometry methodologies allowed first breaks to be picked more extensively than in the original data revised static corrections significantly improved the linearity of the first arrivals and continuity of reflections in the source gathers especially reflections considerably enhanced in the source gathers stacked constructively in the final section comparison with geological data supported by traveltime forward modelling indicates that these reflections represent the unmined part of the deposit other reflections at shallower depth are interpreted as anthropogenic faults possibly located at lithological contacts tomographic inversion was also run using the augmented traveltime data the greater resolution and penetration of this new tomographic image allowed better bridging with the results of the reflection seismic section velocity anomalies depict the presence of mining induced structures and a potential brewery fault which is believed to put at risks an urban area even though the potential of first arrival retrieval seems to be case dependent this study illustrates that interferometry may substantially improve the accuracy of static corrections and subsequent stack for hardrock imaging as well as in the penetration and resolution of traveltime tomograms

seismic processing inversion and avo for gold exploration case study from western australia abstractwe investigate the potential of using high resolution seismic methods for rock characterization and for targeting of gold deposits at the st ives gold camp the application of seismic methods in hard rock environments is challenged by complex structures intrinsically low signal to noise ratio regolith distortions and access restrictions if these issues can be addressed then the unparalleled resolving power of reflection seismic can be used for mineral exploration appropriate spatial sampling of the wavefield combined with a survey geometry design and rigorous data processing to incorporate high fold and long offsets are necessary for creation of high quality seismic images in the hard rock environment of western australia accurate static corrections and multiphase velocity analysis are essential processing steps this is followed by a rigorous quality control following each processing step in such a case we show that the role of reflection seismic could be lifted from mere identificatio

tectonic depositional and diagenetic history of monterey formation miocene central san joaquin basin california the miocene monterey formation in the central san joaquin basin of california consists of biogenic siliceous rocks with a significant terrigenous clastic component correlation of electric logs in conjunction with analysis of outcrop sections core samples and paleontologic data suggests that deposition of the monterey was controlled by an interplay of basin geometry san andreas related tectonics fluctuations in sea level and changes in climate the basin is bounded on the east by the sierran magmatic arc complex and on the west by the san andreas fault during the late saucesian through early mohnian 20 10 ma the basin was reshaped by tectonism related to the migrating mendocino triple junction creating a broad gently sloping shelf to the east that cut off the supply of clastics to the central basin with the subsequent evolution of the san andreas fault the salinian block was emplaced along the western basin margin restricting the seaway and permitting low oxygen nutrient rich waters to occupy the basin as a result laminated organic rich fine grained pelagic to hemipelagic sediments of the monterey formation were deposited a warmer climate during saucesian through luisian time with less intensive upwelling le to more calcareous less siliceous sedimentation a cooling trend during late miocene time 10 5 ma increased upwelling activity diatom productivity in the water column and deposition of diatomaceous debris although turbidites accumulated on the basin floor and terrigenous clastics were deposited on the eastern shelf relatively undiluted diatomaceous deposits developed on outer shelves and slopes atop anticlinal banks generated by wrench tectonism and in some areas of the basin floor a mid mohnian eustatic sea level rise caused fine grained deposition to extend onto the eastern shelf slightly later a mid late mohnian period of exceptionally cool temperatures resulted in the most extensive development of upwelling related siliceous sediments throughout the basin with diagenesis these deposits formed the siliceous shales and porcelanites of the monterey formation high sedimentation rates coincident with a eustatic drop in sea level led to clastic progradation in latest miocene time as the basin filled analysis of organic matter from cores of the monterey formation shows that kerogen type reflects overall sedimentation trends samples from northern and eastern areas contain abundant terrestrial organic matter whereas samples from western areas mostly contain marine kerogens source potential is thus strongly influenced by geographic locality as well as lithology maturity of kerogen was assessed using vitrinite reflectance thermal alteration indices and pyrolysis techniques the latter two appear to be the more reliable indicators of organic matter maturity in the monterey formation of the san joaquin valley although much of the monterey formation in the study area may be thermally immature portions are probably generating hydrocarbons today in deep synclinal areas

vegetation and environmental responses to climate forcing during the last glacial maximum and deglaciation in the east carpathians attenuated response to maximum cooling and increased biomass burning the carpathian mountains were one of the main mountain reserves of the boreal and cool temperate flora during the last glacial maximum lgm in east central europe previous studies demonstrated lateglacial vegetation dynamics in this area however our knowledge on the lgm vegetation compo sition is very limited due to the scarcity of suitable sedimentary archives here we present a new record of vegetation fire and lacustrine sedimentation from the youngest volcanic crater of the carpathians lake st anne lacul sf ana szent anna tto examine environmental change in this region during the lgm and the subsequent deglaciation our record indicates the persistence of boreal forest steppe vegetation with pinus betula salix populus and picea in the foreland and low mountain zone of the east carpathians and juniperus shrubland at higher elevation we demonstrate attenuated response of the regional vegetation to maximum global cooling between 22 870 and 19 150 cal yr bp we find increased regional biomass burning that is antagonistic with the global trend increased regional fire activity suggests extreme continentality likely with relatively warm and dry summers we also demonstrate xerophytic steppe expansion directly after the lgm from 19 150 cal yr bp and regional increase in boreal woodland cover with pinus and betula from 16 300 cal yr bp plant macrofossils indicate local 950 m a s l establishment of betula nana and betula pubescens at 15 150 cal yr bp pinus sylvestris at 14 700 cal yr bp and larix decidua at 12 870 cal yr bp pollen data furthermore support population genetic inferences regarding the regional presence of some temperate deciduous trees during the lgm fagus sylvatica corylus avellana fraxinus excelsior our sedimentological data also demonstrate intensified aeolian dust accumulation between 26 000 and 20 000 cal yr bp

rapid vegetation response to lateglacial and early holocene climatic fluctuation in the south carpathian mountains romania abstract high resolution pollen conifer stomata and plant macrofossil analyses of two glacial lake sediments 1740 and 1990 m a s l are used to reconstruct lateglacial lg and early holocene eh vegetation and tree line changes in the retezat mountains our results show that during the lg tree line was between 1750 and 1800 m a s l formed by larix decidua pinus mugo and picea abies early lg spread to high altitudes suggests refugia of these tree species in the mountain the younger dryas cooling resulted in regional steppe tundra expansion but tree line position and composition showed little change the abundance of trees and shrubs decreased at 1740 m a s l but species richness increased with the arrival of pinus cembra our data support climate model hindcasts for only modest decrease in accumulated growing season heat at mid high altitudes regionally the pollen records suggest enhanced aridity and seasonality in the eh tree line reached 2000 m a s l higher than today by 11 100 cal yr bp p mugo p cembra p abies established around the upper lake suggesting rapid increase in summer temperatures the eh maximum of l decidua between 11 200 10 600 cal yr bp was connected to high summer insolation high altitude expansion of abies alba between 10 600 10 300 cal yr bp suggested summer mean temperatures 2 8 c higher then today in comparison with other mountain sites in europe lg interstadial tree line was at similar altitude in the s alps and 350 m higher in the pirin mountains lg tree line fluctuation had similar low amplitude in the se alps retezat and pirin mts suggesting relatively weak influence of the north atlantic thermohaline circulation changes on growing season temperatures

surface pollen deposition on glacier forelands in southern norway ii spatial patterns across the jotunheimen jostedalsbreen region this paper presents the results of a study of surface pollen deposition on 26 glacier forelands in the jostedalsbreen jotunheimen region of southern norway numerical techniques including two way indicator species analysis twinspan detrended correspondence analysis dca and canonical correspondence analysis cca are used to identify distinct plant assemblages to examine the pollen vegetation relationship and to distinguish broad trends in the data the source of pollen is fundamental the majority of samples especially those from sparsely vegetated sites are dominated by arboreal pollen up to 90 of the total land pollen tlp sum most with a long distance source however indicator taxa notably salix and empetrum although present at low frequencies can hold the key to the true nature of the local vegetation indicator taxa produce strong correlations between their presence in the vegetation and representation in the pollen spectra at times essential to distinguish plant communities mult

lake store finnsjoen a key for understanding lateglacial early holocene vegetation and ice sheet dynamics in the central scandes mountains the lateglacial lg deglaciation and vegetation development in the scandes mountains has been debated for a century here we present new evidence from microfossils radiocarbon dated plant macrofossils and sedimentary ancient dna from laminated sediments in lake store finnsjoen 1260 m a s l at dovre central norway combined with previous results from three other dovre lakes this allows for new interpretations of events during and immediately after the lg deglaciation the finnsjoen sediments present the first uninterrupted record of local vegetation development in the scandes mountains from the late younger dryas yd ca 12 000 cal years bp to the early holocene around 9700 cal years bp the local vegetation in late yd early holocene was extremely sparse with pioneer herbs e g artemisia norvegica beckwithia campanula cf uniflora koenigia oxyria papaver saxifraga spp and dwarf shrubs betula nana salix including salix polaris from 11 300 cal years bp local vegetation rapidly closed with dominant dryas saxifraga spp and silene acaulis from ca 10 700 cal years bp open birch forests with juniper empetrum nigrum and other dwarf shrubs developed pine forests established within the area from 10 300 cal years bp we identified the cold preboreal oscillation pbo not earlier described from pollen data in south norway around 11 400 cal years bp by a regional pollen signal distinct local vegetation changes were not detected until the post pbo warming around 11 300 cal years bp apparently the earlier warming at the yd holocene transition at 11 650 cal years bp was too weak and short lived for vegetation closure at high altitudes at dovre for the first time we demonstrate a regional glacier readvance and local ice cap formations during the yd in the scandes mountains in two of the deep lakes with small catchments yd glaciation blocked sedimentation without removing old sediments and caused a hiatus separating sediments of the ice free lg interstadial lgi from those of the ice free holocene period both regional glaciers and local ice caps caused hiati ice free pre yd conditions at dovre followed by a yd readvance point to a scenario that is intermediate between the maximum ice model postulating a thick glacier during the entire lg and the minimum ice model postulating thin and multi domed early lg ice

types of submarine fan lobes models and implications different lobe models imply significantly different reservoir geometries thus one must apply the proper lobe model to ancient fan sequences braided suprafan lobes are characterized by stacked channel sand bodies with good lateral and vertical communication and they constitute excellent reservoir facies depositional lobes composed of sheet like sand bodies with good lateral and moderate vertical communication exhibit properties of good reservoir facies fanlobes which refer to meandering channels and associated levee facies of large mud rich submarine fans such as the mississippi fan are characterized by offset stacked sand bodies with poor lateral and vertical communication these lenticular sands have the potential to be moderately good reservoir facies ponded obes which represent mud rich slump facies of slope environments comprise poor reservoir facies because of low sand content and poor sand body connectivity furthermore the presence of contorted mud layers in ponded lobes is expected to hinder fluid flow external mounded reflections in seismic profiles often are interpreted as lobes however there are no definite seismic criteria to delineate mud rich lobes from sand rich lobes

july mean temperature and annual precipitation trends during the holocene in the fennoscandian tree line area pollen based climate reconstructions july mean temperature and annual precipipation during the last 9900 cal yr bp were recon structed from pollen assemblages preserved in a sediment core from northern finland quantitative recon structions were performed using a modern pollen climate calibration model based on weighted averaging partial least squares regression the predictive ability of the model was evaluated against modern meteoro logical data using leave one out cross validation the prediction error for july mean temperature is c 1 0 c and for annual precipitation 340 mm the july mean temperatures during the earliest holocene were low c 1 1 0 c and annual precipitation was high c 600 800 mm between 8200 and 6700 cal yr bp july mean temperatures reached their maxima 12 5 13 0 c which are c 1 4 1 7 c higher than at present at the same time precipitation decreased during the late holocene july mean temperatures declined and the last 2000 years have been the coolest since the early holocene precipitation has slightly increased the spatial coherence between our results and of several other climate reconstructions from northern europe indicates that the holocene climate was strongly influenced by north atlantic oceanic and atmospheric circulation patterns we propose that the distinctly oceanic climate of the early holocene was due to enhanced westerly latitudinal airflow which was replaced at c 8200 cal yr bp by a more meridional flow pattern and by the development of predominantly anticyclonic summer conditions

pollen representation source area and basin size toward a unified theory of pollen analysis abstract the concepts of pollen source area and of production and dispersal biases in pollen representation are quantified by means of a simple theoretical model source areas and relative pollen representation are shown to depend on basin size according to functions that describe the amount of pollen remaining airborne at increasing distances from single pollen sources the form of these functions is determined by physical processes standard formulas for elevated sources do not apply but the integrated form of sutton s equation for particle dispersal from a ground level source gives useful approximations applicable to pollen transport over a forest canopy simulations using this equation yielded source areas that increased realistically with basin size showed substantial differences between source areas for pollen grains with different deposition velocities and predicted that lighter pollen grains should become better represented with increasing basin size all of these predictions are qualitatively consistent with present knowledge of the characteristics of pollen assemblages in different depositional environments the model further allows parameters that can be estimated by statistical calibration methods to be predicted from underlying physical quantities this extension suggests procedures for testing the theory with quantitative data on surface pollen and forest composition preliminary results showed reasonable agreement between estimated and predicted values of dispersal indices for the most abundant taxa in pollen spectra from the northern midwestern united states

tectono eustatic controls on reservoir compartmentalisation and quality an example from the upper miocene of the san joaquin basin california abstract systematic changes in stratigraphic architecture and reservoir quality of upper miocene stevens sandstones at north and south coles levee fields san joaquin basin reflect tectono eustatic controls on deposition two depositional sequences 330 500 m thick are present in the coles levee stevens the upper sequence contains sandstones deposited by sediment gravity flows in water depths of 300 500 m backstepping retrogradational reservoir compartments in this sequence overlie vertically stacked to prograding compartments although the backsteps are the better reservoirs with higher permeabilities and porosities the vertically stacked to prograding compartments are volumetrically more important curiously the upper stevens section is sand rich 60 80 ss on structural highs that were also palaeotopographic highs thicker sections with less and characterise the flanks these sand distributions are anomalous since sediment gravity flows preferentially deposit in bathymetric lows apparently the flanks of stevens palaeohighs subsided faster than the crests consequently accomodation increases were greatest on the flanks and resulted in aggradation with preservation of section less accommodation on the crests resulted in progradation with erosion and reworking through lobe switching processes some sand reached all parts of the depocenter subsequent progradation with erosion of shale interbeds and attendant reworking by density currents created sand rich sections in slowly subsiding areas crests concurrent aggradation preserved shale interbeds and created shale dominated sections in rapidly subsiding areas flanks greater compaction of thicker shale dominated flanks equalised thicknesses of flank and crest sections thus the reservoir architecture represents the integrated effects of compensation lobe switching accommodation subsidence sea level and compaction

shear zones fault networks and archean gold conjugate ductile shear zones developed mostly on granite greenstone margins are a dominant structural feature of the yilgarn craton these greenstone belt scale shear zones lack both gold deposits and gold related alteration previous interpretations of the shear zones as part of a linked system as craton scale terrane boundaries or as crustal scale pathways for gold mineralizing fluids all appear equivocal instead gold mineralizing fluids in the yilgarn craton illustrated here by the gold rich yandal belt were focused by a network of middle to upper crustal brittle faults in the late archean the faults are 040 to 060 trending dextral and 090 to 120 trending sinistral the maximum compression direction is about 075 gold mineralization occurs in laminated and other schistosity parallel quartz veins where brittle faults refract along earlier subsidiary within greenstone ductile shear zones and in quartz veins within late archean faults

reconstructing the palaeoenvironments of the early pleistocene mammal faunas from the pollen preserved on fossil bones abstract we carried out a systematic investigation on the pollen content of sediment adhering to skeletal elements of large mammals which originate from the long lacustrine record of leffe early pleistocene of the italian alps three local faunas were discovered during mining activities along the intermediate part spanning from 1 5 to 0 95 ma of the basin succession the excellent pollen preservation allowed testing the reproducibility of the pollen signal from single skeletons a clear palaeoenvironmental patterning consistent with the ecological preferences of the considered mammal species emerged from the canonical correspondence analysis of pollen types diagnostic for vegetation communities edaphic factors related to seasonal river activity changes and to the development of swamp forests in the riverbanks are significantly associated to the occurrences of hippopotamus cf antiquus whereas finds of mammuthus meridionalis belong to fully forested landscapes dominated by conifer or mixed forests of oceanic warm to cool temperate climate rhinoceros habitats include variable forest cover under different climate states distinct cool temperate partially open vegetation could be recognized for large deer included cervalces cf carnutorum a palynostratigraphic correlation between individual spectra and a reference palynostratigraphic record allowed assignment of many fossil remains to a precise stratigraphic position this procedure also shown that the leffe local faunas include specimens accumulated under different environmental and climate states as a consequence of high frequency climate changes characterizing the late villafranchian early pleistocene

seismic methods in mineral exploration and mine planning a general overview of past and present case histories and a look into the future abstractdue to high metal prices and increased difficulties in finding shallower deposits the exploration for and exploitation of mineral resources is expected to move to greater depths consequently seismic methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration these methods also can be used with varying degrees of success to directly target mineral deposits at depth we review important contributions that have been made in developing these techniques for the mining industry with focus on four main regions australia europe canada and south africa a wide range of case studies are covered including some that are published in the special issue accompanying this article from surface to borehole seismic methods as well as petrophysical data and seismic modeling of mineral deposits at present high resolution 2d surveys mostly are performed in mining areas but there is a general increasing trend in the use of 3

estimates of yet to find impact crater population on earth abstract one hundred and seventy six craters on earth are currently accepted as resulting from bolide impact this list is growing at a rate of approximately two craters per year because of new discoveries and revised interpretations here we take the subset of craters most relevant to sedimentary basin exploration and utilization phanerozoic kilometre scale craters and tackle the question of how many remain to be found in phanerozoic strata on earth a surprising range in predictions of crater numbers is obtained from published crater population functions reaching two orders of magnitude variation for craters in the range 1 5 km diameter this range in predictions is largely due to variations in treatment of impactor breakup in the atmosphere also required is quantification of the total area and timespan of phanerozoic sediment currently preserved on earth an estimate of 8 87 10 15 km 2 a is derived here together with a relatively conservative crater population function this yields a prediction of 845 craters subtracting the 131 known phanerozoic craters larger than 1 km leaves a predicted population yet to find of 714 of which 228 are larger than 2 5 km uncertainties subsets of this population and spatial distribution are also considered

palynology after y2k understanding the source area of pollen in sediments pollen grains preserved in lake and bog sediment provide a record of past vegetation that has been an important source of information about climate and land cover during the quaternary period yet from the beginning questions have been raised about the source area of pollen in sediment interpretation has been hampered by the lack of well developed theory treating the relationship between the spatial distribution of trees on the landscape and the percentages of pollen in sediment within the past decade however new theory models and empirical data show how heterogeneous vegetation is represented by pollen the distinction between local and regional pollen is explained by the prentice sugita dispersal deposition models which predict how the ratio of regional to local pollen changes with lake size sugita s model simulating a landscape with heterogeneous vegetation predicts the size of the relevant source area the area of vegetation reflected in between lake variations in pollen loading while demo

late glacial vegetation and climate oscillations on the southeastern tibetan plateau inferred from the lake naleng pollen profile we present a late glacial pollen record 17 700 to 8500 cal yr bp from a lake naleng sediment core lake naleng is located on the southeastern tibetan plateau 31 10 n 99 75 e 4200 m along the upper tree line variations in the summer monsoon are evident from shifts in vegetation that correspond to late glacial climate trends from other monsoon sensitive regions alpine steppe was recorded between 17 700 and 14 800 cal yr bp indicating low effective moisture at the study site expansion of alpine meadows followed by advances in the position of tree line around lake naleng suggest that climate became warmer and wetter between 14 800 and 12 500 cal yr bp probably representing an enhancement of the asian monsoon climatic cooling and reduced effective moisture are inferred from multivariate analysis and the upward retreat of tree line between 12 500 and 11 700 cal yr bp the timing and nature of these shifts to warm wet and then cold dry climatic conditions suggest that they correspond to the bolling allerod and younger dryas intervals abies betula forests representing warm and moist conditions spread during the early holocene

a model of pollen source area for an entire lake surface a model of pollen deposition on the surface of an entire basin is developed to estimate pollen source area and results are compared with those for a point at the center of a basin i c prentice 1985 quaternary research 23 76 86 1988 vegetation history pp 17 42 kluwer academic this model is more appropriate for approximating the source area of pollen in lake sediment since mixing in lake water and focusing of sediment redistribute pollen originally deposited over the entire surface in general the pollen source radius for the entire basin surface is 10 30 smaller than the source radius for a point at the center the difference in the source radius is more profound for heavier pollen types such as spruce and sugar maple than for lighter types such as oak and ragweed the average pollen input to the entire surface is more strongly influenced by nearby pollen sources than pollen deposition at the center the pollen record from a lake may therefore provide different spatial resolution than the record from a bog of similar radius

holocene climate reconstructions from the fennoscandian tree line area based on pollen data from toskaljavri due to its location on the eastern north atlantic seaboard the fennoscandian tree line area is an ideal area to use biological proxies to assess the relative roles of the scandinavian ice sheet and of oceanic atmospheric and astronomic forcings on regional climate history here we report pollen based july mean temperature tjul and annual precipitation pann reconstructions from a sediment core from a high altitude tree line lake in northwestern finland the reconstructions suggest that at 9600 8300 cal yr b p tjul values were low but steadily rising while pann was high the period of warmest summers with tjul values ca 1 8 1 6 c higher than at present occurred at ca 8000 6500 cal yr b p since then climate has become gradually cooler tjul values during the medieval warm period ca 1400 1000 cal yr b p were ca 0 8 c higher that at present but decreased rapidly to the low little ice age levels at 800 cal yr b p we compare these results with an earlier pollen based climate reconstruction from the same region the reconstructions indicate a similar general holocene tjul pattern with lower values in the reconstruction from the high altitude lake however most of the small scale variations are not synchronous suggesting that they may represent noise rather than signal in our data c 2002 university of washington

estimating phytolith influx in lake sediments abstract so far no phytolith extraction protocols have been tested for accuracy and repeatability here we aim to display a phytolith extraction method combining the strengths of two widely used protocols supplemented with silica microspheres as exogenous markers for quantifying phytolith concentrations phytolith concentrations were estimated for samples from two sedimentary sequences in which numerical age depth models make it possible to calculate phytolith influxes phytolith numbers per cm2 per yr analysis of replicates confirmed the statistical robustness the repeatability and the very few biases of our extraction technique for small phytoliths since the relationship between grass silica short cells and microspheres was kept stable furthermore we demonstrated that silica microspheres are robust exogenous markers for estimating phytolith concentrations the minimum number of items i e phytoliths plus silica microspheres that must be counted to estimate phytolith concentrations and thus influxes depends on the ratio of phytoliths to microspheres r and is minimized when r 1 nevertheless we recommend using ratios r 1 in order to avoid having the counting process become excessively time consuming because microspheres are easier to identify and count than phytoliths