evidence of arc related svecofennian magmatic activity in the southwestern margin of the east european craton in poland abstract the precambrian basement of northeastern poland forms the western part of the present day east european craton the central part of this area with moderately uniform potential fields of variably oriented magnetic and gravity anomalies has been penetrated by a six boreholes samples from which consist of calc alkaline granodiorite orthogneiss okuniew 1 calc alkaline monzonite rajsk 1 and 2 and calc alkaline orthoamphibolite lomza 1 2 and 3 geochemical features of the most drilled rocks particularly depletion in th u nb p and ti relative to primitive mantle and position on trace element discrimination diagrams y vs nb y nb vs rb hf rb ta and la y nb are consistent with a volcanic arc environment the results of u pb age measurements show that arc related magmatic activity took place between 1 82 and 1 80 ga these data may be compared to analytical results from the transcandinavian igneous belt in the southwestern part of the east european craton where continental crust was formed in several arc systems mainly between 1 91 and 1 86 ga overall the data suggest a general decrease in the age of the intrusive rocks towards the south southwest of the east european craton

development of partial rock veneers by root throw in a subalpine setting rock veneers stabilize hillslope surfaces occur especially in areas of immature soil and form through a variety of process sets that includes root throw near westcliffe colorado usa data were collected from a 20 500 m transect on the east slope of the sangre de cristo mountains ages of pit mound complexes with rock fragments exposed at the surface by root throw ranged from recent freshly toppled tree to unknown complete tree decay calculations based on dimensions of the pit mound complexes estimated time of tree toppling sizes of exposed rock fragments and percentage rock covers at pit mound complexes as well as within the transect area indicate that recent rates of root throw have resulted in only partial rock veneering since late pleistocene deglaciation weathering of rock fragments prevents development of an extensive rock veneer and causes a balance achieved within an estimated 700 years between the rates of rock fragment exposure by root throw and clast disintegration by chemical reduction the estimated rate of rock fragment reduction accounts for part of the fluvial sediment yields observed for forested subalpine areas of western north america copyright 2005 john wiley sons ltd

lake devlin and pinedale glacial history front range colorado abstract glacial lake devlin was an ice margin lake that formed during pinedale time when the north boulder creek valley glacier blocked the mouth of a tributary near the downvalley limit of glaciation the lake was about 2 km long and as much as 60 m deep and was fed by meltwater from small valley glaciers it accumulated sediment apparently without interruption for about 10 000 yr the inception of lake devlin between 23 500 and 21 000 yr b p provides a limiting date for the maximum expansion of pinedale ice because the lake could not form until the north boulder creek glacier had advanced to within 2 km of its downvalley limit the maximum lowering of timberline which occurred about 19 000 yr b p is assumed to coincide with the pinedale glacial maximum apparent timberline elevations determined from picea pinus pollen ratios suggest that ice front positions during the time between 23 000 and 19 000 yr b p may have been only slightly less extensive than at the pinedale maximum lake devlin drained catastrophically about 13 000 yr b p which was after ice had receded from the outlet area pinedale glaciation in the front range began about or after 30 000 yr b p and final deglaciation occurred between 15 000 and 12 000 yr b p

ferro potassic a type granites and related rocks in ne poland and s lithuania west of the east european craton the present study of monzodiorite quartz monzodiorite monzonite quartz syenite granodiorite and rapakivi like granite surrounding the suwalki ketrzyn and sejny anorthosite norite and gabbro plutons or forming separate bodies in northern poland and southern lithuania has resulted in the recognition of a specific suite with amcg affinity the bodies belonging to the mazury and veisiejai complexes are aligned to e w trending lineaments in southern lithuania and northern poland with a continuation through the baltic sea into south central sweden in the west and into nw belarus in the east the rocks of the suite form a continuous series ranging from 45 to 75 sio2 with no indication of the classical daly gap between mafic and felsic rocks the mazury and veisiejai complexes chemically belong to the ferro potassic alkali calcic type of rocks and are comparable with the amcg suite e g in rogaland southern norway the most acidic varieties of the granitoids approach the classic rapakivi granites in their petrogenetic characteristics elevated contents of incompatible elements and ree and hence have a type affinities the granitoids are assigned to the post collisional granite field the overall evolution from mafic to acidic rocks is characterized by well defined trends which most probably represent a liquid line of descent fractional crystallization with or without assimilation and hybridization can account for the continuous evolution from mafic to acidic members the formation of the suite is concentrated in the timespan covering almost 50 myr from 1 55 to 1 5 ga the most felsic rocks yield ages of ca 1 5 ga which are very similar to the kabeliai granites further east in southeastern lithuania cooling and local mylonitization proceeded until 1 4 ga hornblende and biotite 40 ar 39 ar ages

limits of windthrow driven hillslope sediment flux due to varying storm frequency and intensity the uprooting and toppling of trees during storms transports soil exhumes bedrock and thus influences the evolution of hillslopes given predicted increased storminess due to future climate change we adapt a forest gap model forgem to explore windthrow driven sediment transport in a douglas fir forest under increasingly severe wind regimes in order to better assess potential future impacts on soil erosion larger trees are more sensitive to wind loading and are therefore preferentially toppled as storm frequency and intensity increase because larger trees have larger root plate volumes and can move large volumes of sediment increased wind velocities lead to an increase in sediment flux with increasingly stormier conditions however the proportion of large trees dwindles the net effect of these two countervailing trends is that sediment transport increases as average annual rates of windthrow approach eight trees per hectare but begins to decline thereafter our results highlight the complex relationship between climate and sediment transport particularly when it is mediated by the biota

the fennoscandia sarmatia junction in belarus new inferences from a pt study abstract in eastern belarus the ne striking junction zone between the fennoscandian and sarmatian crustal segments of the east european craton rather abruptly separates the ca 2 0 ga osnitsk mikashevichi igneous belt omb developed on the continental margin of sarmatia from a 2 0 1 9 ga old palaeoproterozoic composite terrane in the northwest the latter consists of the central belarus belt cb and the vitebsk granulite domain vg the ne trending minsk fault subdivides the cb into lithologically different northwestern and southeastern sub terranes the northwestern sub terrane of the cb is dominated by ca 2 0 ga metabasalts containing numerous tonalite trondhjemite granodiorite ttg intrusions the southeastern cb and the vg in contrast are mainly composed of metasedimentary rocks with only minor ca 1 98 ga andesitic to dacitic metavolcanics in the vg these rocks have been penetrated and contact metamorphosed by 1 96 ga cordierite bearing granites subalkaline granites and quartz syenites of ca 1 8 ga age form numerous intrusions in the southeastern part of the cb the present study of the pt conditions of metamorphism as related to the chronologies demonstrates contrasting tectonothermal evolutions in the two major parts of the overall cb vg composite terrane separated by the minsk fault in the northwestern cb the metavolcanics have been exposed to prograde metamorphism with peak temperatures varying from 640 to 725 c at depths reaching 28 30 km these peak conditions were attained approximately 1 90 ga ago during concomitant emplacement of ttg type melts a retrograde stage in the amphibolite facies lasted until ca 1 70 1 67 ga in the vg xenoliths of metapelite enclosed in 1 96 ga high temperature granites document regional pre granitic metamorphism at ca 610 c and 6 7 kbar as well as some subsequent retrogression the contact metamorphism associated with the granites resulted in heating to ca 670 c upon which followed cooling and substantial decompression in part presumably effected by the ascent of the granite melts ultimate cooling of the granites and their metapelitic xenoliths can be followed through temperatures dropping from ca 530 to 420 c at pressures decreasing from ca 3 8 to 2 kbar the metamorphic and magmatic histories of the rocks in the vg agree in many regards with those recorded from the adjacent omb the substantial differences now discovered between the tectonothermal evolutions in various parts of the overall cb vg composite terrane suggest a more complex structure and development histories than those hitherto assumed both for the fennoscandia sarmatia junction zone and the cb the role of the minsk fault is still conjectural it may either represent the upper steep part of a listric thrust fault active during the stacking of the oceanic island island arc sub terrane against the sarmatian buttress or a much later fault that uplifted the northwestern cb and juxtaposed it with the southeastern cb sub terrane and the vg after subduction and compression had ceased

soil deepening by trees and the effects of parent material abstract in some cases biomechanical effects of individual trees may locally deepen or thicken regolith especially in relatively shallow soils this biogeomorphic ecosystem engineering phenomenon is at least partly contingent on the geological setting the purpose of this research was to gain further insight into the biogeomorphic phenomenon and to assess the relative importance of biomechanical and geological effects earlier studies in the ouachita mountains of arkansas showed that individual trees locally thicken the regolith via mechanisms associated with root penetration of bedrock however that work was conducted mainly in areas of strongly dipping and contorted rock where joints and bedding planes susceptible to root penetration were thought to be common and accessible this project extended the research to the cumberland plateau region of kentucky where flat level bedded sedimentary rocks are dominant soil depth beneath trees was compared to that of non tree sites by measuring depth to bedrock beneath rotted tree stumps and at adjacent sites with 1 0 m while soil thickness beneath stumps was greater in the ouachita mountains compared to the kentucky sites in both regions soils beneath stumps are significantly deeper than adjacent soils further there were no statistically significant differences in the difference between stump and adjacent sites between the two regions this suggests the local deepening effects of trees occur in flat bedded as well as steeply dipping lithologies

pedologic and geomorphic impacts of a tornado blowdown event in a mixed pine hardwood forest abstract biomechanical effects of trees on soils and surface processes may be extensive in forest environments two blowdown sites caused by a november 2005 tornado in the ouachita national forest arkansas allowed a case study examination of bioturbation associated with a specific forest blowdown event as well as detailed examination of relationships between tree root systems soils and underlying bedrock the sites occur within mixed shortleaf pine and hardwood forests more than 95 of trees in the severe blowdown areas were either uprooted or suffered trunk break with uprooting more common than breakage within the most heavily damaged areas all uprooted trees were pines while all trees left standing were hardwoods root wads of uprooted trees had a mean surface area of about 3 m 2 and volume of about 2 m 3 though individual sizes were quite variable nearly 4 of the ground surface area was affected by uprootings with a soil volume equivalent to a disturbance of the entire surface area to a depth of 2 4 cm tree size as measured by diameter at breast height was significantly related to the area and volume of root wads r 2 0 55 0 71 respectively with volume of uprooted soil varying as diameter to the 3 power suggesting that the timing of blowdown events relative to tree age or growth stage significantly influences the area of disturbance and the mass and volume of material involved in 93 of cases the roots of the uprooted trees contacted or penetrated the underlying bedrock and in all those cases bedrock was quarried by uprooting only 11 of the tree throws showed evidence of general lateral root turning at the soil bedrock interface in most cases roots penetrated bedrock along joints the propensity for tree roots to penetrate bedrock joints facilitate weathering and excavate bedrock during uprooting supports the idea that tree roots play a predominant role in locally deepening soils

the healing of disturbed hillslopes by gully gravure results of accelerated erosion on certain constructed surfaces in southeastern arizona appear similar to those described by bryan 1940 as gully gravure twenty cross section excavations in eight rills incised into silt rich lacustrine and fluvial deposits reveal partial filling of the rills by debris derived from overlying fluvial sand gravel and cobbles interstices of the coarse material gradually fill with fine grained erosion products decreasing permeability of the fill and deflecting subsequent runoff to the margins of the fill rills and rill fillings thus increase in width with time and complete veneering of the surface by coarse debris ultimately may occur through incision filling lateral planation and armoring channels of the dissected surface heal and the new hillslope approaches an equilibrium condition natural hillslopes in the area with similar geologic conditions have inclinations of 16 22 have generally unbroken veneers of coarse debris and appear subject to the same erosional processes identified at constructed hillslopes field measurements and the revised universal soil loss equation rusle were used to estimate soil loss on natural and constructed hillslopes results suggest that erosion may be almost three orders of magnitude greater on steep non veneered nonvegetated constructed surfaces than on natural hillslopes attributes of stable natural hillslopes provide criteria for the design of stable constructed hillslopes

new pollen and beetle analyses at the mary jane site colorado evidence for late glacial tundra conditions analyses of fossil pollen and beetles from a late pinedale peat deposit from the upper fraser river colorado allow a reassessment of previously published paleoenvironmental evidence from the site between 13 800 and at least 12 600 yr b p the environment was an open tundra indicative of a cold dry climate scattered spruce trees were probably present at the site by the end of the record ca 12 300 yr b p

the north eastern polish anorthosite massifs petrological geochemical and isotopic evidence for a crustal derivation deeply buried 1 5 ga polish anorthosites accessible only by bore holes reveal diagnostic features of some massif type anorthosites polybarism jotunitic parent magma diapirically emplaced in the mid crust together with the rapakivi granites of the ew trending mazury complex intruded along a major crustal discontinuity geochemical modelling and isotope data corroborate recent experimental work on the basaltic system in dry conditions the source rock of the parental magma is a gabbronorite necessarily lying in the lower crust since no archaean crust is known in the region high initial 188 os 187 os ratios for sulphide oxide isochrons and negative end values are best accounted for by melting a 2 0 ga mafic crust

a late paleoproterozoic 1 80 ga subduction related mafic igneous suite from lomza ne poland the lomza orthoamphibolites in the crystalline basement of ne poland dated at 1802 9 ma by shrimp zircon u pb are characterized by high incompatible and ree element contents these features the low nb and the position of the rock compositions on la y nb zr nb zr and zr nb y tectonomagmatic discrimination diagrams suggest that the metavolcanics formed in a subduction setting possibly within a continental margin island arc the likely extension of the belt of paleoproterozoic mafic magmatism from latvia and lithuania into ne poland provides convincing evidence for the existence of an active plate margin in that region at that time

the accretionary svecofennian orogen insight from the babel profiles abstract the babel profiles b c 1 7 form a 1200 km long nearly continuous cross section through the svecofennides the near vertical marine reflection profiles display a wide range of crustal structures that can be associated with both the accretionary svecofennian orogeny 1 96 1 75 ga and the following subjotnian and jotnian rift stages 1 65 1 11 ga the svecofennian accretionary orogeny took place when a number of micro plates with island arc affinities and surface expression of a large archipelago accreted to the continental karelian plate some of the accreting terranes seem to have had older cores that have acted as crustal indentors during the collision babel profiles 3 and 4 image a series of collisional terrane boundaries between karelian continental margin savo arc sa and central finland arc cfa in the north the karelian margin has been both over and underthrust by the savo arc cfa comprises a folded thrust package on top of a continental nucleus and the savo arc the associated subduction zone and accretionary prism are interpreted to lie to the south underneath the bothnian basin area where prominent ne dipping lower to middle crustal reflections are found along babel profiles 1 and 4 an oblique collision of the central finland arc and the continent resulted in the development of the strike slip fault on the young hot savo arc babel profiles 1 6 7 and c image the internal architecture of the southern and central finland arcs the unusually thick crust 55 60 km hosts unreflective high density mafic intrusions acting as a crustal indentor a highly reflective antiform structure developed on the southern side of it southern finland arc complex sfa is an imbrication structure comprising stacked slices of arc related crust on an older continental nucleus bergslagen nucleus prior to the collision the sfa suffered from gravitational collapse during which the crust was thinned profile b images the architecture of the central and southern swedish svecofennides the sormland terrane sob is interpreted as the accretionary prism of the southern finland arc squeezed between the svecofennian collage in the north and the advancing continent to the south the southern continent island arc is characterised by ne dipping crustal reflections and moho offsets as well as step wise increasing thickness of the crust after the final collision large volumes of mantle derived material intruded the crust as large mushroom shaped plutons they are interpreted as the heat source for the tib magmatism in southern and western scandinavia

effects of rock fragments on soil erosion by water at different spatial scales a review this paper reviews the various effects of rock fragments on soil erosion by water since these effects are scale dependent they are investigated at three different nested spatial scales the microplot 4 10 6 100m2 the mesoplot 10 2 102 m2 and the macroplot 101 104 m2 for each scale the corresponding process mechanisms are discussed particular attention is paid to the effects of rock fragment cover on the intensity of soil erosion processes at the mesoplot scale i e on interrill areas rock fragments at the soil surface can have negative as well as positive effects on sediment yield these ambivalent effects are conditioned by the type of fine earth porosity soil surface slope vertical position and size of rock fragments and by the occurrence of horseshoe vortex erosion at the microplot scale i e the soil surface area which is covered by a single rock fragment and at the macroplot scale i e upland areas where both interrill and rill erosion takes place rock fragments at the soil surface have a negative effect on sediment yield in these two scales rock fragments can thus be considered as natural soil surface stabilizers at the macroplot scale the mean decrease of relative interrill and rill sediment yield with rock fragment cover can be expressed by an exponential decay function the scatter of the data indicates that a given rock fragment cover can have different efficiencies in reducing interrill and rill sediment yield depending on the varying intensities of the hydrological and erosion subprocesses these findings have implications for erosion modelling and soil conservation

the effects of bioturbation on soil processes and sediment transport abstract plants and animals exploit the soil for food and shelter and in the process affect it in many different ways for example uprooted trees may break up bedrock transport soil downslope increase the heterogeneity of soil respiration rates and inhibit soil horizonation in this contribution we review previously published papers that provide insights into the process of bioturbation we focus particularly on studies that allow us to place bioturbation within a quantitative framework that links the form of hillslopes with the processes of sediment transport and soil production using geometrical relationships and data from others work we derive simple sediment flux equations for tree throw and root growth and decay

boulder deposits and the retreat of mountain slopes or gully gravure revisited observations on mountains composed chiefly of shale and capped with tuscarora sandstone in the valley and ridge province of southwest virginia suggest that slopes retreat by a process similar to but different from bryan s 1940 gully gravure the process appears to operate as follows bouldery alluvium protects the floors of hollows on the mountain flanks in each hollow the junction between the boulder armored floor and the base of the unprotected shale side slope is the locus of greatest erosion runoff from rainstorms that have recurrence intervals of the order of 10 to 10 years incises gullies along the margins of the bouldery deposits but lacks the competence to disturb the deposits periodically however runoff from catastrophic rainstorms that have recurrence intervals of the order of perhaps 10 years mobilizes the bouldery alluvium and deposits it in the gullies the armored floor thus shifts laterally subsequently new gullies are incised adjacent to the old ones the result is the later

desert pavement evolution an example of the role of sheetflood patches of young well developed desert pavement were found atop bare rock on the pisgah basalt flow california these particular stone mosaics formed directly atop the flow no soil is present or ever has been therefore soil expansion and aeolian processes played no significant role in their creation or maintenance the unusual setting at pisgah allows sheetflood to be the sole agent responsible for the lateral movement of surface stones into these mosaics the pisgah mosaics thus represent an end member case of desert pavement types and they may represent a previously unrecognized initial substage of accretionary mantle formation

the role of trees in the geomorphic system of forested hillslopes a review abstract forested hillslopes form a special geoecosystem an environment of geomorphic processes that depend strongly on forest ecology including the growth and decay of trees changes in structure disturbances and other fluctuations hence the following various functions of trees are reviewed here their role in both biomechanical and biochemical weathering as well as their importance for the hillslope geomorphic subsystem and for transport of soil material via tree uprooting and root growth special attention is paid to tree uprooting a process considered the most efficient and most frequent biogeomorphological indicator of bio physical activity within forest in complex terrain trees have varied implications for soil formation in different environments boreal to tropical forests and altitudes in this paper an attempt has been made to emphasize how trees not only modulate geomorphic processes but also how they act as a direct or indirect agent of microrelief formation the most striking example of which being widespread and long lasting pit and mound microtopography based on the analyzed literature it seems that some problems attributed to forest ecology can have a fundamental effect on forested hillslope dynamics a relationship which points to the need for its integration and interpretation within the field of geomorphology the biology of individual trees has a key influence on the development of e g rock faces weathering front migration and changes in the soil biomantle within upper and lower forest belts additionally forms and sediments depend largely on the horizontal and vertical extent volume and structure of root systems as well as on active processes taking place in the root zone and rhizosphere furthermore although trees to a large extent stabilize slope surfaces their presence can also have a dual effect on slope stability due to tree uprooting a process which in some circumstances can trigger mass movements e g debris avalanches so far several attempts at quantifying the influence of trees on slopes have been made via the use of mathematical equations enabling researchers to calculate 1 the root plate volume of uprooted trees 2 the amount of soil displacement due to tree root growth and 3 rates of erosion sedimentation and soil creep in light of the reviewed literature the most urgent issue appears to be the need for a thorough study of the interactions and feedbacks occurring between trees and geomorphic systems e g soil mixing and biotransport by trees in different climate zones altitudes and time frames especially in terms of the development of forest ecosystems during the holocene

isotopic evidence for palaeoproterozoic accretion in the basement of the east european craton abstract the precambrian basement in the western part of the east european craton eec consists of a series of arcuate tectonic belts metamorphosed in amphibolite and granulite facies these are separated from each other by crustal discontinuities generally trending nne ssw in conjunction with previously published sm nd and u pb isotopic data the results reported now show that the basement between the baltic and ukrainian shields is palaeoproterozoic in age it was formed between 2 1 and 1 8 ga ago igneous rocks from the various arcuate belts generally have positive initial nd values between 1 and 3 thus they are essentially juvenile and contain little material derived from older continental crust most metasedimentary rocks in contrast contain a distinct component of older crustal materials this is demonstrated by initial nd values ranging from 1 to 3 and by the results of u pb multigrain and single grain sims analyses of detrital zircons the oldest magmatic activity in the region occurred 2 1 2 0 ga ago in the southeast along the margin of the archaean protocontinent of sarmatia two subsequent episodes of volcanism in the tectonic belts farther west have been dated at ca 2 0 and 1 87 ga using the u pb zircon approach the proterozoic volcanic rocks are thus younging towards the northwest away from sarmatia the high grade metamorphism that has been dated employing u pb in monazite and zircon is also younging from the southeast to the northwest its ages range from 1 95 to less than 1 79 ga the available data are explained best by accretionary plate tectonics these involved repeated episodes of generation of juvenile continental crust along and outboard of the margin of the dominantly archaean craton in sarmatia an andean type of geodynamic setting between 2 1 and 2 0 ga ago was succeeded by the formation of several island arcs and accretion of these onto the older continent between 2 0 and 1 8 ga subsequent compression of the newly formed crust lasted until ca 1 7 ga

contrasting source components of the paleoproterozoic svecofennian metasediments detrital zircon u pb sm nd and geochemical data abstract the paleoproterozoic svecofennian orogen in the fennoscandian shield can be regarded as one entity or as a collage of several accretionary units to test for the possible occurrence of a suture zone dividing the svecofennian orogen into central and southern parts we report new ion microprobe data on clastic zircons of nine samples of metasediments whole rock sm nd and geochemical data were acquired to characterize the source components of the metasediments the central svecofennian metasediments in finland can be divided to lower and upper types with inferred deposition ages at 1 92 1 91 and 1 90 1 88 ga respectively both types are immature and show a derivation from an unweathered orogenic source the lower central svecofennian metasediments show a dominant proterozoic age population at 1 93 2 02 ga and a variation in end 1 9 values from about 3 to 0 5 which is mainly explained by variable amounts of archean detritus 30 45 the upper central svecofennian metasediments have end 1 9 at about 0 similar to values obtained from adjacent volcanic and plutonic arc rocks one meta arkose is tentatively classified as a molasse type sediment with a source dominated by earlier svecofennian sediments southern svecofennian metasediments can be divided into mature and less mature types with dominant deposition ages at 1 90 1 88 ga and end 1 9 values from 3 to 1 mature quartzites seem to occur at least in two stratigraphic levels where the upper quartzites have maximum deposition ages at 1 87 1 86 ga a characteristic feature of some southern svecofennian metasediments is a dominant proterozoic age population at 2 0 2 1 ga coincident deposition of mature and immature sediments and volcaniclastic rocks indicate that different sources weathered and non weathered basement and syn depositional volcanic centers produced simultaneously detritus to a large subsiding basin mature pelites and quartzites suggest a long residence time and stable passive margin or cratonic environment the tectonic setting and possible provenance areas for the central and southern svecofennian metasediments are also discussed as a conclusion the metasediments from the central and southern parts of the svecofennian orogen show different lithological characteristics and have contrasting source components the presented isotope data indicate a different evolution of these parts prior to 1 89 ga and the existence of a suture zone between them as proposed in earlier studies

breaking ground pedological geological and ecological implications of soil bioturbation abstract soil and its biota are fundamental components of the critical zone earth s living skin that most directly sustains life within that zone geologically rapid soil and saprolite displacement by biota particularly invertebrate meso and macrofauna affects a large proportion of earth s soils this was first recognised by late 19th century observers on both sides of the atlantic ocean who regarded bioturbation as fundamental to soil formation throughout much of the 20th century however the agronomical focus of soil scientists and the dominant paradigm of landscape evolution relegated bioturbation as a result many aspects of bioturbation are still not widely appreciated only in the last few decades has a re evaluation commenced in a range of disciplines primary effects of bioturbation which we quantify herein include soil production from saprolite the formation of surface mounds soil burial and downslope transport rates of bioturbation can be as rapid as sustained maximum rates of tectonic uplift in concert with surface geomorphic processes bioturbation alters fundamental properties of soil including particle size distribution porosity the content of carbon and other nutrients and creep flux rate the precise influence of biotic mixing is regulated by its depth function earth s incredibly diverse soil biota also perform a number of functions at a range of spatial and temporal scales that extend beyond soil to landscape evolution ecosystem engineering niche construction and carbon cycling understanding these linkages which have operated since the evolution of trees in the devonian period is of growing importance as we seek a fuller picture of earth s history to predict and manage its future

surface processes and interactions with forest vegetation on a steep mudstone slope stolowe mountains sw poland abstract in this study we recognize complex physical biotic abiotic interactions on a steep forested slope in the moderately elevated mountain terrain of the sudetes central europe using geomorphological pedological and dendrochronological methods on the forested hillslopes of mt rogowa kopa the evidence of disturbance in natural systems is widespread in the geomorphic subsystem its most obvious manifestation is the origin and disappearance of pit and mound microtopography resulting from tree uprooting 82 pit and mound associations have been mapped on a test slope providing quantitative data for calculating sediment flux the flux is around 2 10 4 m 3 m 1 year 1 hence less than suggested in the literature but within the same order of magnitude nevertheless in the long term such a transport rate is comparable with the one typical for creep while it affects a greater thickness of hillslope regolith tree bending and abrupt changes in tree ring width are indicators of disturbed tree growth causally linked to soil creep of mudstone derived regolith eccentric growth is best recorded in wet years and in younger trees which have to adapt to the pre existing pit and mound surface topography we offer a conceptual model that links biotic and abiotic factors and discuss implications of the widespread tree uprooting we suggest that veneers of angular clasts and occasional larger boulders are not necessarily residuals of washed pleistocene solifluction mantles but may result from root plate degradation after uprooting recent catastrophic wind events may through tree uprooting lead to structural changes in cover deposits so that they lose their inherited periglacial signatures

fluvial processes and vegetation glimpses of the past the present and perhaps the future abstract most research before 1960 into interactions among fluvial processes resulting landforms and vegetation was descriptive since then however research has become more detailed and quantitative permitting numerical modeling and applications including agricultural erosion abatement and rehabilitation of altered bottomlands although progress was largely observational the empiricism increasingly yielded to objective recognition of how vegetation interacts with and influences geomorphic process a review of advances relating fluvial processes and vegetation during the last 50 years centers on hydrologic reconstructions from tree rings plant indicators of flow and flood frequency parameters hydrologic controls on plant species regulation of sediment movement by vegetation vegetative controls on mass movement and relations between plant cover and sediment movement extension of present studies of vegetation as a regulator of bottomland hydrologic and geomorphic processes may become markedly more sophisticated and widespread than at present research emphases that are likely to continue include vegetative considerations for erosion modeling response of riparian zone forests to disturbance such as dams and water diversion the effect of vegetation on channel and bottomland dynamics and rehabilitation of stream corridors research topics that presently are receiving attention are the effect of woody vegetation on the roughness of stream corridors and hence processes of flood conveyance and flood plain sedimentation the development of a theoretical basis for rehabilitation projects as opposed to fully empirical approaches the effect of invasive plant species on the dynamics of bottomland vegetation the quantification of below surface biomass and related soil stability factors for use in erosion prediction models and the effect of impoundments on downstream narrowing of channels and accompanying encroachment of vegetation bottomland vegetation partially controls and is controlled by fluvial geomorphic processes the purposes of this paper are to identify and review investigations that have related vegetation to bottomland features and processes to distinguish the present status of these investigations and to anticipate future research into how hydrologic and fluvial geomorphic processes of bottomlands interact with vegetation

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

non pegmatitic deposits of beryllium mineralogy geology phase equilibria and origin non pegmatitic occurrences of be minerals constitute a diverse set of geologic environments of considerable mineralogical and petrological interest they currently provide the majority of the world s be ore and emeralds and they contain the greatest resource of these commodities of the approximately 100 be minerals known see chapter 1 by grew appendix a most occur in hydrothermal deposits or non pegmatitic igneous rocks where their distribution varies systematically with the setting and origin table 1 fig 1 view this table table 1 beryllium minerals in non pegmatitic deposits formulas use and occurrence 1 figure 1 chemography of the principal solid phases in the beo al2o3 sio2 h2o f2o 1 bash system with the projected positions of helvite group and alkali be silicates also shown are generalized fields for some of the major types natural of occurrences cf table 1 fig 4 see text for discussion beryllium minerals are best known from geologic systems associated with felsic magmatism they also occur in a variety of settings that lack evident igneous associations environments range from the surface to the deep crust and host rocks range from feldspathic to carbonate to ultramafic in composition genetically related igneous rocks are felsic and share low calcium and high f contents but are diverse in composition setting and origin compositions range from strongly peraluminous to peralkaline and can be silica undersaturated beryllium minerals also occur in metamorphic and basinal environments and are redistributed by surface processes table 2 summarizes the types and significance of major groups of occurrences by their lithologic associations figure 2 shows the global distribution of some important examples and regional belts for most types at least one example has been described in some detail and can be used to help evaluate general patterns however

palaeoproterozoic upb zircon ages from belorussia new geodynamic implications for the east european craton abstract the crust in the northwest of the east european craton has traditionally been regarded as part of an archaean nucleus in eastern europe recent correlation with the baltic shield in scandinavia however suggests the need of reappraisal to study this problem zircons from three boreholes in the basement of the russian platform in belorussia belarus have been dated by the u pb and pb pb methods the ages indicated by two u pb discordias are 1982 26 ma for a metadacite from the central belorussian belt of volcanic arc igneous rocks and 1800 7 ma for mafic granulite from the baltic belorussian granulite belt largely built up of mafic igneous rocks for another central belorussian metadacite a pb pb age of 1975 10 ma was obtained in previous stratigraphies of belorussia all three dated rocks have been considered to be important components of an archaean even early archaean crust analyses of abraded crystal cores of complex zircons in one sample and separated core and rim zircons in another do not suggest substantially older ages of the core materials together with previous ages of granitoids and charnockites which had however been explained as a result of late magmatism and metamorphism and therefore not characterizing the age of the crust our data indicate the dominance of palaeoproterozoic rocks in the basement of the northwestern part of the east european craton that adjoins the tornquist line boundary between central and northeastern europe in conjunction with the results of a finnish estonian study of similarly allegedly archaean but in actual fact proterozoic rocks in southern estonia our results suggest the existence of large palaeoproterozoic crustal belts extending all the way from the finnish gulf to eastern poland this implies a substantial revision of established concepts on the precambrian geology in the northeastern half of the european continent

geological geochemical and geochronological evidence for a new palaeoproterozoic terrane in southeastern sweden the geological and geochronological relationships between a rhyolite belonging to the transscandinavian igneous belt tib and an intrusive suite the backaby intrusion southeast sweden have been investigated by means of bedrock mapping geochemistry and radiometric age determinations u pb on zircons field relations suggest that the rhyolite rests unconformably on the backaby intrusion which previously has been correlated with 1 9 ga granitoids within the svecofennian domain the rhyolite yielded an age of 1800 8 ma and a tonalite belonging to the backaby intrusion basement yielded an age of 1834 3 ma the age of the rhyolite is slightly older 10 15 ma than adjacent granitoids belonging to the transscandinavian igneous belt and is considered as the earliest magmatic expression of tib in the area the age and the geochemical trends for the backaby intrusion is significantly different from that of the surrounding tib granitoids and indicate a rock forming event at about 1830 1840 ma in southeastern sweden represented by the oskarshamn jonkoping belt this event is significantly younger than the older svecofennian rocks within the svecofennian domain proper indicating a hitherto unidentified geological terrane in southeastern sweden

relict colluvial boulder deposits as paleoclimatic indicators in the yucca mountain region southern nevada early to middle pleistocene boulder deposits are common features on southern nevada hillslopes these darkly varnished ancient colluvial deposits stand but in stark contrast to the underlying light colored bedrock of volcanic tuffs and they serve as minor divides between drainage channels on modern hillslopes to demonstrate the antiquity of these stable hillslope features six colluvial boulder deposits from yucca mountain nye county nevada were dated by cation ratio dating of rock varnish accreted on boulder surfaces estimated minimum ages of these boulder deposits range from 760 to 170 ka five additional older deposits on nearby skull and little skull mountains and buckboard mesa yielded cation ratio minimum age estimates of 1 38 ma to 800 ka an independent cosmogenic chlorine 36 surface exposure date was obtained on one deposit which confirms an estimated early to middle quaternary age these deposits have provided the oldest age estimates for unconsolidated hillslope deposits in the southwestern united states we suggest that the colluvial boulder deposits were produced during early and middle pleistocene glacial pluvial episodes and were stabilized during the transition to drier interglacial climates by comparison to modern periglacial environments winter minimum monthly temperatures of 3 to 5 c were necessary to initiate freeze thaw conditions of such vigor to physically weather relatively large volumes of large boulders from the upper hillslopes of the yucca mountain area these conditions imply that early and middle pleistocene glacial winter temperatures were at least 1 to 3 c colder than existed during the last pleistocene glacial episode and 7 to 9 c colder than present we conclude that at least several early and middle pleistocene glacial episodes were colder and perhaps wetter than glacial episodes of the late pleistocene in the southern great basin geomorphic processes necessary to form these colluvial boulder deposits are not active on modern hillslopes in the southern great basin in addition the lack of young relatively unvarnished colluvial boulder deposits on these hillslopes suggests that boulder forming conditions did not exist during the late pleistocene in this region modern semiarid hillslope processes primarily erode colluvium during infrequent high intensity storms the preservation of old thin hillslope deposits and the less than 2 m incision by hillslope runoff adjacent to these deposits however indicate that extremely low denudation rates have occurred on resistant volcanic hillslopes in the southern great basin during quaternary time

cosmogenic 3he surface exposure dating of stone pavements implications for landscape evolution in deserts the formation of stone pavements a ubiquitous gravel armor mantling landforms in arid regions of the world has been previously attributed to erosion by wind and water or alternating shrinking and swelling of soil horizons implying that gravel is concentrated at the land surface in a time transgressive manner a newly proposed model for pavement evolution differs from these models in that pavement clasts are continuously maintained atthelandsurfaceinresponsetodepositionandpedogenicmodificationofwindblowndust in situ cosmogenic 3 he surface exposure ages on volcanic and alluvial landforms in the mojave desert of california are used to understand pavement evolution over geologic time scales and to test this new model these exposure ages are stratigraphically consistent show internal consistency at each site and for stone pavements adjacent to pristine continuously exposed volcanic bedrock are indistinguishable at the 1 level we conclude that stone pavements are born at the surface and that pavements may provide one of the longest term records of geologic hydrologic and climatic processes operating on desert surfaces

age and ϵ nd constraints on the palaeoproterozoic tectonic evolution in the baltic sea region abstract the metamorphic precambrian basement in the western part of the east european craton eec has previously been considered to be archaean in age recent u pb and sm nd studies in estonia poland and belarus have however revealed a vast area of palaeoproterozoic crust in order to survey the crustal ages in latvia and lithuania and to establish the relationships of these territories with adjacent regions of the eec particularly those exposed in the baltic and ukrainian shields three new u pb zircon age determinations and 21 nd whole rock analyses were performed in latvia a granodiorite yielded an intrusion age of 1816 5 ma and a felsic metavolcanic rock an age of metamorphism at 1810 2 ma with indications of a minimum protolith age of ca 1840 ma in lithuania a metasediment yielded a multigrain u pb zircon age of 2302 200 100 ma very similar to multigrain zircon ages of svecofennian metasediments in scandinavia the nd survey of various rock types demonstrated relatively little variation with depleted mantle model ages between 2 4 and 1 9 ga for the igneous rocks and between 2 5 and 2 0 ga for the metasedimentary ones this indicates only minor influence of archaean crust but close isotopic similarity to rocks of the same lithologies in the svecofennian domain of sweden and finland together with recent u pb and sm nd results from other parts of the eec the present study suggests a close relationship between the palaeoproterozoic crust in estonia western latvia and western lithuania and the southern part of the svecofennian domain within the baltic shield all these regions have u pb zircon ages of rock formation between 1 90 and 1 82 ga and were subjected to a major metamorphic event between 1 83 and 1 81 ga these ages contrast with ages between 2 0 and 1 9 ga for similar rocks farther east and southeast i e closer to the ukrainian shield altogether the current results reaffirm an accretionary character of the palaeoproterozoic crust in the western part of the eec as previously concluded by other investigators in addition there is basis to suggest that the crust in western latvia and lithuania was formed during the late stages of the svecofennian orogeny and thus can be correlated with juvenile late svecofennian crust in southeastern sweden

spatial distribution of surface rock fragments along catenas in semiarid arizona and nevada usa improved techniques for estimating soil erosion by water have shown that soil surface cover is a major component in the estimate of soil loss erosion prediction models require the user to input slope gradient and soil profile descriptions if equations expressing the relations between slope gradient soil profile rock fragment content and surface rock fragment cover were embedded in these models then direct user input could be reduced field measurements of slope gradient soil profile rock fragment content surface rock fragment cover and vegetation type and cover were made on 12 soil slope complexes on catenas in southeastern arizona usa correlation analysis showed that both slope gradient and soil profile rock fragment content were significantly p 0 01 correlated to surface rock fragment cover additional analysis indicated that the combined effects of slope gradient and soil profile rock content were better defined by a soil slope factor ssf two equations were developed to estimate surface rock fragment cover a logarithmic relation using slope gradient as the independent variable and a hyperbolic equation using the ssf as the independent variable these equations were used to estimate surface rock fragment cover from a soil slope complex in southern nevada the ssfrfc equation gave better estimates of the measured surface rock fragment cover these relations developed for catenas in southeastern arizona may be site specific but they do show that a relation exists for this semiarid area and suggest that similar relations may exist in areas with similar geology and climate such as parts of africa asia australia and south america development of simple relations describing important erosion processes will improve erosion estimates while simultaneously decreasing time and costs associated with using erosion prediction models