sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

an alternative interpretation of the cayman trough evolution from a reidentification of magnetic anomalies magnetic data were collected during the wilkes 1973 and seacarib ii 1987 cruises to the cayman trough a new interpretation of magnetic data is carried out an isochron pattern is drawn up from our anomaly identifications an early eocene age 49 ma ypresian for cayman trough opening is proposed instead of the late oligocene or middle eocene ages suggested by previous studies our plate tectonic reconstruction is simpler and fits the on land geology jamaica and cuba and the tectonics our reconstruction shows a southward propagation of the spreading centre between magnetic anomalies 8 and 6 26 and 20 ma the trough width increases by 30 km in this period the southward propagation of the cayman spreading centre from the middle oligocene to the early miocene induced the development of the restraining bend of the swan islands the formation of a 1 km high scarp on the eastern trace of the cayman trough transform fault walton fault and the formation of a pull apart basin hendrix pull apart magnetic anomalies and magnetization maps give information about the deformation and the rocks the proposed evolutionary model of the cayman trough from the inception of seafloor spreading to the present configuration is presented in relation to the tectonic escape of the northern boundary of the caribbean plate from the maastrichtian to the present

diagenesis of siliciclastic and volcaniclastic sediments in the cretaceous and miocene sequences of the nw african margin dsdp leg 47a site 397 abstract the lower cretaceous and miocene sequences of the nw african passive continental margin consist of siliciclastic volcaniclastic and hybrid sediments these sediments contain a variety of diagenetic carbonates associated with zeolites smectite clays and pyrite reflecting the detrital mineralogical composition and conditions which prevailed during opening of the north atlantic in the lower cretaceous siliciclastic sediments siderite 6 to 0 7 18 o pdb 19 6 to 0 6 13 c pdb was precipitated as thin layers and nodules from modified marine porewaters with input of dissolved carbon from the alteration of organic matter microcrystalline dolomite layers lenses nodules and disseminated crystals 3 0 to 2 5 18 o pdb 7 2 to 4 9 13 c pdb predominate in slump and debris flow deposits within the lower miocene sequence during the opening of the atlantic volcanic activity in the canary islands area resulted in input of volcaniclastic sediments to the middle and upper miocene sequences calcite is the dominant diagenetic carbonate in the siliciclastic bioclastic volcaniclastic hybrid and in the volcaniclastic sediments which commonly contain pore rimming smectite diagenetic calcite 22 to 1 6 18 o pdb 35 7 to 0 8 13 cpdb was precipitated due to the interaction of volcaniclastic and bioclastic grains with marine porewaters phillipsite is confined to the alteration of volcaniclastic sediments whereas clinoptilolite is widely disseminated occurring essentially within foraminiferal chambers and formed due to the dissolution of biogenic silica

the 1996 ad delta collapse and large turbidite in lake brienz abstract in spring 1996 ad the occurrence of a large mass transport was detected by a series of events which happened in lake brienz switzerland turbidity increase and oxygen depletion in deep waters release of an old corpse into surface waters and occurrence of a small tsunami like wave this mass transport generated a large turbidite deposit which is studied here by combining high resolution seismic and sedimentary cores this turbidite deposit correlates to a prominent onlapping unit in the seismic record attaining a maximum of 90 cm in thickness it is longitudinally graded and thins out towards the end of the lake basin thickness distribution map shows that the turbidite extends over 8 5 km2 and has a total volume of 2 72 106 m3 which amounts to 8 7 yr of the lake s annual sediment input it consists of normally graded sand to silt sized sediment containing clasts of hemipelagic sediments topped by a thin white clay sized layer the source area the exact dating and the possible trigger of this turbidite deposit as well as its flow mechanism and ecological impact are presented along with environmental data river inflow wind and lake level measurements the combined results indicate that no particular cause i e earthquake explosion flood wind storm lake level change seiche or sediment dredging triggered the 1996 ad large turbidite deposit instead it was due to a delta slope failure most likely caused by normal sediment accumulation

hiatal duration of correlative sequence boundaries from oligocene pliocene mixed carbonate siliciclastic sediments of the south florida platform abstract sequence boundaries defined by regional unconformities in mixed carbonate siliciclastic sediments have a variable duration from the margin to the interior of the florida platform factors controlling the timing and duration of these unconformities include a combination of global eustatic and regional mechanisms sediment supply current intensification integrated chronostratigraphies developed from a transect of continuous cores in the south central interior to the southern margin of the florida platform show an increase in duration of the hiatal gaps along correlative sequence boundaries toward the platform edge two sequence boundaries are correlated across the south florida platform and mark formation contacts the lower sequence boundary sb a marks the suwannee limestone arcadia formation contact and is of significantly less duration in the platform interior southwest peninsular florida 2 0 m y than at the south platform margin middle florida keys 8 1 m y the hiatal gap along the upper sequence boundary sb b marking the arcadia formation overlain by miocene pliocene sediments that vary in age and composition regionally records the same increase from the central part of the platform southwest florida arcadia fm peace river fm 1 6 m y to the south platform edge lower florida keys arcadia fm stock island fm 11 5 m y eustatic fluctuations affected the relative sedimentation rates of the mixed sediments in the platform interior and at the margin most notably the large eustatic fall at the end of the early oligocene terminated carbonate deposition of the suwannee limestone sb a sediment accumulation on the platform interior was more temporally continuous than at the margin because of greater siliciclastic input from the north the strengthening of marine currents beginning in the middle miocene limited sediment accumulation across the southern platform margin sb b and possibly caused erosion of the margin carbonates increasing the duration of the hiatal gap on top of the arcadia formation

compilation of non annually resolved holocene proxy climate records stacked holocene peatland palaeo water table reconstructions from northern britain abstract the number and range of holocene palaeoclimate reconstructions from various regions of the world have increased dramatically over the last decade the data density for many regions and proxies now offers the potential of robust regional scale reconstructions that avoid the problems of records from individual sites and improve communication between palaeoclimate subdisciplines and climate modellers however there are problems with chronological uncertainties and quantification of proxies which make compilation of multiple records difficult here we explore a stacking and tuning approach to the derivation of regional records from peatland climate proxies to test its applicability to non annually resolved terrestrial records twelve individual records from northern britain based on water table reconstructions from testate amoebae analysis were divided into four regions records were detrended normalised and compared within regions to identify clear correlative events the original chronologies of the records were tuned using both these events and independent age markers the stacked record for northern britain indicates pronounced changes to wet conditions at 3600 2760 and 1600 cal yr bp with more minor changes at 3060 2050 1260 860 550 and 260 cal yr bp the main wet phases are highly correlated with mid european lake highstands wider north atlantic climate change inferred from ocean and ice core records and solar variability tuning and stacking of non annual terrestrial palaeoclimate records is a new approach to the compilation and reconciliation of individual records within coherent climatic regions and provides a tool for upscaling of palaeoclimate records for climate model data comparisons

formation processes of framboidal pyrite abstract pyrite framboid formation may be the result of four consecutive processes 1 nucleation and growth of initial iron monosulfide microcrystals 2 reaction of the microcrystals to greigite fe 3 s 4 3 aggregation of uniformly sized greigite microcrystals i e framboid growth and 4 replacement of greigite framboids by pyrite the uniform morphology uniform size range and ordering of the microcrystals in individual framboids as well as the range of observed framboid structures from irregular aggregates to densely packed spherical aggregates and polyframboids are consequences of these processes using dlvo theory derjaguin landau verwey and overbeek we have evaluated the stability of colloidal iron monosulfide suspensions with ionic strengths typical of marine and lacustrine waters in addition to van der waals attractive and double layer repulsive forces a term is included to account for the ferrimagnetic properties of greigite numerical models predict that magnetically saturated greigite particles 0 1 m in diameter will rapidly aggregate in either marine or fresh water the aggregation model is in agreement with the sequence of greigite formation followed by pyrite framboid formation established in a previous experimental study sweeney and kaplan 1973 and is consistent with the occurrence of framboids composed of other magnetic minerals e g greigite magnetite and magnesioferrite based on the temperature dependent magnetic properties of greigite and aging experiments in hydrothermal solutions this mechanism for framboid formation via precursor greigite could operate to temperatures of 200 c consistent with the occasional occurrence of pyrite framboids in the paragenesis of metalliferous ore deposits

origin of clay rich beds in turonian chalks from lower saxony germany a rare earth element study abstract the mineralogy and ree geochemistry of thin clay rich beds from turonian chalks of lower saxony germany has been studied two types of clay rich beds are present the first is of volcanic origin and is characterised by 1 a ree signature similar to marine argillized volcanic ash bands and 2 a silicate mineralogy dominated by smectite with minor corrensite the second type is of continental origin and is characterised by 1 a ree signature similar to continental shale and 2 a silicate mineralogy dominated by smectite with minor heulandite clinoptilolite the use and misuse of these widespread clay rich horizons in the turonian stratigraphy of lower saxony is discussed

the disturbance regime of an early holocene swamp forest in the czech republic as revealed by dendroecological pollen and macrofossil data abstract a unique remnant of forest dating back to the period 9733 7897 yr bc and consisting of hundreds of tree bases was discovered in the czech republic we aimed to reveal the complex disturbance history of this sub fossil forest using dendrochronology and to describe its detailed plant species composition changes using palaeobotanical techniques analysing such early holocene forest dynamics should help us understand the ability of the forest community to actively adapt to climate change and generally to understand the role of dynamic instability in ecosystem evolution we anatomically identified woody species in 488 samples and determined the ages growth suppressions releases and fire scars in 116 well preserved tree ring series using a modern boundary line approach this image of the forest structure and dynamics was supplemented with analyses of pollen spectra and plant macrofossils in excavated profiles in order to achieve accurate dating we dated 87 samples using 14c and synchronized tree ring series and compared them with an existing pinus sylvestris chronology the developmental trajectory of the forest was unique and did not match the general trend of postglacial pine growth in central europe palaeobotanical proxies indicated that during the circa 2000 years the forest persisted this early holocene ecosystem passed through several phases reflected in the species composition of the vegetation as well as in habitat conditions nevertheless the dominance of pine and the complex fine scale disturbance regime were relatively robust and did not change fundamentally low severity fires and short term changes in soil moisture regime were crucial disturbance agents in the ecosystem stand replacing disturbances were not found up to the gradual collapse of the forest around 8300 yr bc replaced by a swamp community the disturbance regime was relatively stable suggesting a mitigating effect of changing climate due to the predominance of pine in the forest

the magnitude of error in conventional bulk sediment radiocarbon dates from central north america abstract although the carbon reservoir problem with bulk sediment radiocarbon dates from lakes has long been recognized many synoptic studies continue to use chronologies derived from such dates for four sites in central north america we evaluate chronologies based on conventional radiocarbon dates from bulk sediment versus chronologies based on accelerator mass spectrometry ams radiocarbon dates from terrestrial plant macrofossils the carbon reservoir error varies among sites and temporally at individual sites from 0 to 8000 yr an error of 500 2000 yr is common this error has important implications for the resolution of precise event chronologies

dendrochronological evidence for a lower water table on peatland around 3200 3000 bc from subfossil pine in northern scotland tree ring analysis of subfossil pinus sylvestris l from nine new peatland sites located beyond the species current northern limit in scotland established a regional chronology called wrath 9 the chronology has been provisionally dated against irish pine chronologies and provides the first annual resolution picture of scots pine expansion from c 3200 bc and subsequent demise from c 3000 bc pine germination and growth is suggested to be associated with a widespread fall in bog water tables that indicates a regional climatic control bog pines progressively declined in number rather than died out in a single event reflecting their growth in a marginal habitat close to a critical ecological threshold the use of tree ring sequences from in situ bog pine macrofossils provides a higher resolution insight into past conditions than possible with existing radiocarbon and pollen based chronologies

pine stumps in irish peats is their occurrence a valid proxy climate indicator we investigate the temporal and spatial distribution of pine pinus sylvestris stumps preserved in peat deposits to test whether their occurrence can be used as an indicator of climatic shifts to drier conditions radiocarbon dates of sub fossil stumps were collected from the literature along with environmental data throughout the island of ireland data were analysed using non parametric statistical techniques there was no distinct geographical pattern observed in the distribution of pine stumps on bog surfaces tree ages ranged from 66 to 500 years with 85 7 of these 300 years pines occurred on bogs from ca 8500 to 500 cal a bp the temporal distribution during the holocene was characterized as a mid holocene peak in sites supporting pine with two gaps either side of this peak our current understanding of past climate dynamics failed to explain this temporal distribution the onset mid holocene peak and cessation of bog sites supporting the presence of bog pines appears to be driven by changes in pine seed and bog surface area availability during the holocene rather than changes in climate we conclude that variability in the occurrence of irish bog pines is not a valid climate proxy as factors other than climate influence their presence and thereby disrupt the climate signals

holocene peatland development and hydrological variability inferred from bog pine dendrochronology and peat stratigraphy a case study from southern sweden dendrochronological analysis was applied to subfossil remains of scots pine pinus sylvestris l buried in a south swedish peat deposit in combination with peat stratigraphy this approach was explored for its potential to provide information on the local hydrological and depositional history at the site forming the basis for a regional palaeohydrological analysis a 726 year ring width chronology was developed and assigned an absolute age of 7233 6508cal a bp 5284 4559 bc through cross dating with german bog pine chronologies whereas two short additional records of older ages were radiocarbon dated registration of growth positions of individual trees allowed assessment of the spatial dynamics of the pine population in response to hydrological changes and peatland ontogeny annually resolved growth variability patterns in the pine population reveal several establishment and degeneration phases probably reflecting fluctuations in bog surface wetness a major establishment phase at 7200 6900 cal a bp reflects the onset of a period of lowered groundwater level also indicated by increased peat humification and a development consistent with regional temperature and lake level reconstructions revealed from other proxies this study demonstrates that subfossil bog pine populations may provide annually to decadally resolved reconstructions of local groundwater variability which are highly relevant in a long term palaeoclimatic context copyright c 2012 john wiley sons ltd

questioning carbonate diagenetic paradigms evidence from the neogene of the bahamas carbonate diagenetic models have been heavily influenced by numerous studies of exposed quaternary limestones as a result meteoric diagenesis is often assumed to be the principle means of altering aragonite rich sediments into calcitic limestones however these models are limited by the scarcity of examples of aragonite rich sediments buried in seawater that have never been influenced by meteoric fluids the bahamas transect cores recovered originally aragonite rich sediments deposited in deep water beyond the easy reach of meteoric waters and provide an opportunity to test current diagenetic paradigms the bahamas transect consists of seven cores drilled in the prograding western margin of great bahama bank the two proximal cores clino and unda were drilled on the platform top and recovered shallow water platform to reef facies overlying deeper margin and proximal slope facies the five distal cores were drilled by odp leg 166 in up to 660 m of water and recovered carbonate slope facies all studied sections are neogene to pleistocene in age diagenetic environments were identified based on petrographic and scanning electron microscopy sem observations xrd mineralogy carbon and oxygen stable isotopic data and trace elements the upper 100 150 m of the two proximal cores were altered in meteoric to mixing zone diagenetic environments but all other intervals were altered exclusively in marine pore fluids during seafloor marineburial and deep burial diagenesis several of the findings of this study question current carbonate diagenetic paradigms these include 1 large scale sea level lowstands may not have chemically active meteoric lenses as we found no meteoric alteration at the 3120 m elevation of the latest pleistocene lowstand rather phreatic meteoric diagenesis appears restricted to within w10 m of the land surface 2 mixing zone diagenesis includes aragonite dissolution and minor lmc cementation but does not show the cavernous porosity or dolomitization predicted by mixing zone diagenetic models current models are based on coastal mixing zones which do not appear to be applicable to these more inland and perhaps more typical locations 3 marine burial diagenesis produces a mature limestone with fabrics formerly considered diagnostic for meteoric diagenesis such as moldic porosity aragonite neomorphism blocky calcite spar and calcite microspar however oxygen stable isotopic data average n 18 o 1x indicate alteration in marine pore fluids only the character of marine burial diagenesis is partially controlled by the nature of the sediment being altered we have identified two end member styles an open system style characterized by dissolution of aragonite without significant cementation and a more closed system style with aragonite dissolution

reconstructed water tables from two ombrotrophic mires in eastern central sweden compared with instrumental meteorological data water level changes for the last 125 years were reconstructed from two ombrotrophic mires in eastern central sweden using testate amoebae assemblages the reconstructed water tables show the same o

the climate of scotland over the last 5000 years inferred from multiproxy peatland records inter site correlations and regional variability the mid to late holocene climates of most of scotland have been reconstructed from seven peat bogs located across north south and east west geographical and climatological gradients the main techniques used for palaeoclimatic reconstruction were plant macrofossil colorimetric humification and testate amoebae analyses which were supported by a radiocarbon based chronology aided by markers such as tephra isochrons and recent rises in pine pollen and in spheroidal carbonaceous particles scps field stratigraphy was undertaken at each site in order to show that the changes detected within the peat profiles were replicable proxy climate records were reconstructed using detrended correspondence analysis dca of the plant macrofossil data and a mean water table depth transfer function on the testate amoebae data these reconstructions coupled with the humification data were standardised for each site and used to produce a composite record of bog surface wetness bsw from each site the results show coherent wet and dry phases over the last 5000 years and suggest regional differences in climate across scotland specifically between northern and southern scotland distinct climatic cycles are identified all of which record a millennial scale periodicity which can be correlated with previously identified marine and ice core holocene cycles the key role of the macrofossil remains of sphagnum imbricatum a taxon now extinct on many sites is discussed in relation to the identified climatic shifts

impact of the 1960 major subduction earthquake in northern patagonia chile argentina abstract the recent sedimentation processes in four contrasting lacustrine and marine basins of northern patagonia are documented by high resolution seismic reflection profiling and short cores at selected sites in deep lacustrine basins the regional correlation of the cores is provided by the combination of 137cs dating in lakes puyehue chile and frias argentina and by the identification of cordon caulle 1921 22 and 1960 tephras in lakes puyehue and nahuel huapi argentina and in their catchment areas this event stratigraphy allows correlation of the formation of striking sedimentary events in these basins with the consequences of the may june 1960 earthquakes and the induced cordon caulle eruption along the liquine ofqui fault zone lofz in the andes while this catastrophe induced a major hyperpycnal flood deposit of ca 3 106 m3 in the proximal basin of lago puyehue it only triggered an unusual organic rich layer in the proximal basin of lago frias as well as destructive waves and a large sub aqueous slide in the distal basin of lago nahuel huapi a very recent mega turbidite in the two distal basins of reloncavi fjord located close to the lofz suggests that 1960 co seismic movements in this area may have triggered the remobilization of ca 187 106 m3 of marine sediments

prehistoric earthquake history revealed by lacustrine slump deposits five strong paleoseismic events were recorded in the past 15 k y in a series of slump deposits in the subsurface of lake lucerne central switzerland revealing for the first time the paleoseismic history of one of the most seismically active areas in central europe although many slump deposits in marine and lacustrine environments were previously attributed to historic earthquakes the lack of detailed three dimensional stratigraphic correlation in combination with accurate dating hampered the use of multiple slump deposits as paleoseismic indicators this study investigated the fingerprint of the well described a d 1601 earthquake i vii viii mw 6 2 in the sediments of lake lucerne the earthquake triggered numerous synchronous slumps and megaturbidites within different subbasins of the lake producing a characteristic pattern that can be used to assign a seismic triggering mechanism to prehistoric slump events for each seismic event horizon the slump synchronicity was established by seismic stratigraphic correlation between individual slump deposits through a quasi three dimensional high resolution seismic survey grid four prehistoric events dated by accelerator mass spectrometry 14c measurements and tephrochronology on a series of long gravity cores occurred at 2420 9770 13 910 and 14 560 calendar yr ago these recurrence times are essential factors for assessing seismic hazard in the area the seismic hazard for lakeshore communities is additionally amplified by slump induced tsunami and seiche waves numerical modeling of such tsunami waves revealed wave heights to 3 m indicating tsunami risk in lacustrine environments

lake sediments record high intensity shaking that provides insight into the location and rupture length of large earthquakes on the alpine fault new zealand abstract understanding the seismic hazard posed by large earthquakes requires paleoseismic investigation because most faults have not ruptured repeatedly during the period of historic records however determining the location and length of fault ruptures using paleoseismic data remains challenging our study demonstrates that lake sediments record the high intensity shaking that occurs proximal to fault rupture allowing the location and length of ruptures to be reconstructed in two lakes adjacent to the alpine fault new zealand seismic shaking is recorded as subaqueous mass wasting derived turbidites formed by coseismic subaqueous slope failures which are overlain by sets of hyperpycnites representing elevated fluvial sediment fluxes from earthquake induced landslides precise radiocarbon age models show that shaking events are synchronous between the two lake sites and correlate with the timing of known alpine fault earthquakes modelled shaking intensities for the last two alpine fault earthquakes show that subaqueous mass wasting occurs when shaking intensities exceed modified mercalli scale mm vi vii and that fluvial sediment fluxes from earthquake induced landslides occur when shaking intensities exceed mm ix the data demonstrate that lake records distinguish between strong mm vi and violent mm ix shaking at a lake site the ability to map the spatial extent of mm ix shaking provides new insights into the timing and extent of rupture for the last five earthquakes on the alpine fault the study demonstrates that lake deposits constrain the spatial extent of rupture during large earthquakes and may yield long records of the spatial and temporal patterns of fault rupture

submarine paleoseismology of the northern hikurangi subduction margin of new zealand as deduced from turbidite record since 16 ka abstract paleoseismic studies seek to characterise the signature of pre historical earthquakes by deriving quantitative information from the geological record such as the source magnitude and recurrence of moderate to large earthquakes in this study we provide a 16 000 yr long paleo earthquake record of the 200 km long northern hikurangi margin new zealand using cm thick deep sea turbidites identified in sediment cores cores were collected in strategic locations across the margin within three distinct morphological re entrants the poverty ruatoria and matakaoa re entrants the turbidite facies vary from muddy to sandy with evidence for rare hyperpycnites interbedded with hemipelagites and tephra we use the oxal probabilistic software to model the age of each turbidite using the sedimentation rate of hemipelagite deduced from well dated tephra layers and radiocarbon ages measurements on planktonic foraminifera turbidites are correlated from one core to the other using similarity in sedimentary facies petrophysical properties and ages results show that 46 turbidites are synchronous along the entire margin amongst them 41 are interpreted as originating from the upper continental slope in response to earthquake triggered slope failures between 390 170 to 16 450 310 yr bp using well established empirical relationships that combine peak ground acceleration magnitude and location of earthquakes we calculate that synchronous slope failures were triggered by the rupture of 3 of the 26 known active faults in the region each capable of generating mw 7 3 to 8 4 earthquakes two are crustal reverse faults and one is the subduction interface the 41 mw 7 3 earthquakes occurred at an average recurrence interval of 400 yr over the last 16 000 yr among them twenty are interpreted as subduction interface earthquakes that occurred at an average recurrence interval of 800 yr with alternating periods of high activity and low return times 305 610 yr and quiescence periods with high return times 1480 2650 yr based on turbidite paleoseismology we propose that subduction interface earthquakes were of lower magnitude during active periods mw 7 5 than during quiescence periods mw 8 2

late holocene pinewoods persistence in the gredos mountains central spain inferred from extensive megafossil evidence macro and megafossil studies are of great value in palaeoecology because such evidence is spatially precise directly radiocarbon dated and usually taxon specific here we present new macro and megafossil data from ten sites from the gredos mountains central iberian peninsula that suggest persistent forest cover through the late holocene with a widespread belt of pinewoods in the highlands of the central iberian mountains well preserved pine cones found at several sites revealed that both pinus sylvestris and pinus nigra were present in the area during the middle and late holocene at locations of important biogeographical interest the p sylvestris forests represent one of the southernmost locations of its entire range p nigra was not known to have occurred in central spain during the holocene it was found at the westernmost edge of its range in siliceous soils a rare environment compared with the rest of its distribution finally we explored the potential for obtaining a long pine chronology from central iberia using tree ring measurements and radiocarbon dating of pine subfossil logs

late holocene palaeoclimate variability the significance of bog pine dendrochronology related to peat stratigraphy the puścizna wielka raised bog case study orawa nowy targ basin polish inner carpathians abstract the results of dendrochronological and palynological analyses of subfossil pine trees occurring in the peat deposits of the pu cizna wielka raised bog polish carpathians southern poland the only site with numerous subfossil pine trees in the mountainous regions of central europe presently known indicate that the majority of the tree populations grew in the peat bog during the periods ca 5415 3940 cal bp and 3050 2560 cal bp several forestless episodes dated to 5245 5155 cal bp 4525 4395 cal bp and 3940 3050 cal bp were preceded by tree dying off phases caused by an extreme periodical increase in humidity and general climate cooling trends these events are documented based on analyses of pollen and non pollen palynomorph assemblages dendrochronological analyses of the trees as well as numerous radiocarbon datings of the sediment horizons occurring within the peat bog profile the phases of germinations and in turn of tree and shrub invasions of the peat bog areas have been closely connected to drying and occasional warming of the regional climate the last of the forestless periods began about 2600 years ago and continued up to the very recent times currently as a result of desiccation of the peat bog and the lowering of the groundwater level due to improved water drainage system pine trees have returned the peat bog again these results demonstrate that studies of subfossil bog pine trees are quite effective in documenting and reconstructing periods of humidity fluctuation that occurred within the carpathian region over the last several millennia

the paleoclimatic interpretation of clay minerals in sediments a review abstract the application of paleoclimatic interpretation to clay minerals from continental and marine sediments is reviewed and the advantages of this method are indicated levels relatively rich in chlorite illite palygorskite and quartz are interpreted as corresponding to relatively dry periods while more humid periods lead to more intensive weathering and consequently to the dominance of clay minerals more advanced in the relative stability scale such as kaolinite smectite is taken to indicate a climate with contrasting seasons and a pronounced dry season using this and similar schemes the paleoclimates of areas adjoining the mediterranean basin north sea north atlantic southern arctic equatorial and north west pacific and north phillipine sea are reconstructed clay minerals in sediments particularly marine sediments can be useful indicators of paleoclimatic conditions while they do not produce direct indications of climatic parameters they provide integrated records of overall climatic impact occasionally they may be superior to the more conventional paleoclimatic methods such as pollen or oxygen isotope analysis the limitations imposed on the paleoclimatic interpretation of clay minerals in sediments are discussed on the basis of examples the distinction between authigenic and detrital clay minerals is shown to be problematic particularly with regard to smectite the relationship between climatic parameters and clay mineral formation is complicated by the intervention of extra climatic factors such as topography geomorphology lithology and time post depositional diagenetic changes may not be recognized differentiation during transport due to size sorting or differential flocculation may overlap climate induced differentiation the association of clay mineral assemblages with specific source areas presents difficulties due to dispersal pathways that are affected by type of transport agency i e water ice or wind transport agencies are not constant with time by an interdisciplinary approach with the paleoclimatic information derived from clay minerals being correlated with that obtained from the analysis of microfossils and oxygen isotope data many of these limitations can be overcome

clinoptilolite as a new proxy of enhanced biogenic silica productivity in lower miocene carbonate sediments of the bahamas platform isotopic and thermodynamic evidence abstract massive clinoptilolite authigenesis was observed at about 1105 meters below sea floor mbsf in lower miocene well compacted carbonate periplatform sediments from the great bahama bank ocean drilling program odp leg 166 site 1007 the diagenetic assemblage comprises abundant zeolite crystallized within foraminifer tests and sedimentary matrix as well as mg smectites in carbonate rich deposits the formation of the zeolite requires a supply of silica thus the objective of the study is to determine the origin of the silica supply its diagenetic evolution and consequently the related implications on interpretation of the sedimentary record in terms of local or global paleoceanographic change for lack of evidence for any volcaniclastic input or traces of si enriched deep fluids circulation an in situ biogenic source of silica is validated by isotopic data and chemical modeling for the formation of such secondary minerals in shallow water carbonate sequences geochemical and strontium isotopic data clearly establish the marine signature of the diagenetic zeolite as well as its contemporaneous formation with the carbonate deposition sr model ages of 19 6 23 2 ma the test of saturation for the pore fluids specifies the equilibrium state of the present mineralogical assemblage seawater rock modeling specifies that clinoptilolite precipitates from the dissolution of biogenic silica which reacts with clay minerals the amount of silica opal a involved in the reaction has to be significant enough at least 10 wt to account for the observed content of clinoptilolite occurring at the most zeolite rich level modeling also shows that the observed amount of clinoptilolite 19 reflects an in situ and short term reaction due to the high reactivity of primary biogenic silica opal a until its complete depletion the episodic occurrence of these well lithified zeolite rich levels is consistent with the occurrence of seismic reflectors particularly the p2 seismic sequence boundary located at 1115 mbsf depth and dated as 23 2 ma the age range of most zeolitic sedimentary levels biostratigraphic ages of 21 5 22 ma correlates well with that of the early miocene glaciation mi 1 and mi 1a global events thus the clinoptilolite occurrence in the shallow carbonate platform environment far from volcanogenic supply or in other sensitive marine areas is potentially a significant new proxy for paleoproductivity and oceanic global events such as the miocene events which are usually recognized in deep sea pelagic sediments and high latitude deposits

lithologic controls on calcite recrystallization in cenozoic deep sea sediments abstract interpretations of calcite strontium calcium records in terms of ocean history and calcite diagenesis require distinguishing the effects on deep sea calcite sediments of changes in ocean chemistry of different mixes of calcite depositing organisms as sediment contributors through time and space and of the loss of sr during diagenetic calcite recrystallization in this paper sr ca and 18 o values of bulk calcium carbonate sediments are used to estimate the relative extent of calcite recrystallization in samples from four time points core tops 5 6 9 4 and 37 1 ma at eight ocean drilling program sites in the equatorial atlantic ceara rise and equatorial pacific ontong java plateau and two eastern equatorial pacific sites the possibility that site to site differences in calcite sr ca at a given time point originated from temporal variations in ocean chemistry was eliminated by careful age control of samples for each time point with sample ages differing by less than the oceanic residence times of sr and ca the sr ca and 18 o values of 5 6 and 9 4 ma samples from the less carbonate rich eastern equatorial pacific sites and ceara rise site 929 appear to be less diagenetically altered than the sr ca and 18 o values of contemporaneous samples from the more carbonate rich sites it is evident from these data that both sr ca and 18 o in bulk calcite have been diagenetically altered in some samples 5 6 ma and older these data indicate that noncarbonate sedimentary components like clay and biogenic silica have partially suppressed recrystallization at the lower carbonate sites sr ca data from the less altered carbonate poor sites indicate higher oceanic sr ca relative to today at 5 6 and 9 4 ma

tectonic controls on carbonate sequence formation in an active strike slip setting serranilla basin northern nicaragua rise western caribbean sea abstract the serranilla basin is a flat floored semi circular bathymetric depression 100 100 km 1100 1200 m deep at the western end of the northern nicaragua rise nnr in the caribbean sea it is bound to the north by the cayman trough an area of active sea floor spreading and is part of the northern caribbean plate boundary zone ncpbz single channel high resolution seismic data were calibrated to rock dredges and odp site 1000 to define the geologic evolution and attempt to tie sequence formation within the basin to tectonic developments in this part of the caribbean five seismic sequences were identified within the basin the two lower sequences a and b are interpreted as neritic and shallow periplatform deposits which infill three distinct basins that make up the early to late miocene serranilla basin the three upper sequences c through e are interpreted as periplatform and pelagic deposits interspersed with turbidites and in some areas megabreccias faulting is prevalent in sequences a through c in the central basin and becomes progressively younger toward the south disrupting the seafloor in places and perhaps indicating renewed activity along the pedro fracture zone the timing of sequence boundary formation has been correlated to tectonic activity along the ncpbz and closure of the central american seaway possible mechanisms of sequence boundary formation include tectonic tilting within the basin in conjunction with increased turbidite deposition carbonate platform drowning and subsequent back stepping associated with circulation changes resulting from tectonic gateway closure and megabreccia deposition associated with bank demise although a direct genetic relationship is not proven regional tectonic changes are considered more important than eustatic sea level changes in controlling depositional sequence formation in the serranilla basin

models for the coupled sr sulfate budget in deep sea carbonates a numerical model for the sr and sulfate budgets during deposition of deep sea carbonate sediments was developed and used to fit porewater sr2 and so42 data from dsdp sites 593 590 574 573 572 516 and 289 the sr and sulfate budgets are coupled whenever the porewaters become saturated with respect to celestite srso4 models for the porewater sr and sulfate at sites 593 590 516 and 289 suggest that porewater sr concentrations are controlled by the precipitation of celestite and predict maximum celestite concentrations of the order of 0 02 wt for sediments at sites 593 590 and 289 and trace amounts of celestite at site 516 the actual amount of celestite predicted by the model is not well constrained because it depends on the as yet poorly known value of the equilibrium distribution coefficient for sr between calcite and porewaters the fact that celestite has been found in sediments from sites 590 and 593 is used to derive an upper bound for the sr distribution coefficient that suggests that all laboratory determined values for the sr distribution coefficient between calcite and porewater are too large the occurrence of celestite at sites 593 590 516 and 289 does not significantly change earlier estimates of the rates of solution reprecipitation of calcite and its consequences in terms of shifting the sr content or sr isotopic composition of the bulk sediment from what the sediment incorporated when originally deposited the sulfate data at sites 593 and 590 are best fit by invoking a flow of porewater within the sediments of the order of 75 m ma the sr and sulfate concentrations in porewaters from sites 572 573 and 574 never reach celestite saturation and thus the two budgets are decoupled both the sr and the sulfate data require that all three sites have abundant unaltered seawater flowing in the underlying basement and can only be modeled if seawater concentrations of sr and sulfate are imposed as boundary conditions at both the sediment water interface and the bottom of the section model sulfate profiles for sites 572 573 and 574 confirm prior estimates of the rate of porewater flow at these sites that were made using sr data

phyllosilicates and zeolite assemblages in the carbonate periplatform of the great bahama bank origin and relation to diagenetic processes odp leg 166 sites 1006 and 1007 abstract the western flank of the great bahama bank drilled during odp leg 166 at seven sites represents a prograding carbonate sequence from late oligocene to holocene eberli et al proc odp init reports 166 1997 the signatures of the detrital input and of diagenetic alteration are evident in clay enriched intervals from the most distal sites 1006 and 1007 in the straits of florida mineralogical and chemical investigations xrd tem sem icp ms run on bulk rocks and on the clay fractions enable the origin and evolution of silicate parageneses to be characterized plio pleistocene silt and clay interbeds contain detrital clay assemblages comprising chlorite illite interstratified illite smectite smectite kaolinite and palygorskite the greater smectite input within late pliocene units than in pleistocene oozes may relate either varying source areas or change in paleoclimatic conditions and weathering intensity the clay intervals from miocene upper oligocene wackestone sections are fairly different with prevalent smectite in the fine fraction whose high crystallinity and mg contents that point towards an authigenic origin the lower miocene section below 1104 mbsf at depths where compaction features are well developed is particularly characterized by abundant authigenic na k clinoptilolite filling foraminifer tests the authigenic smectite and clinoptilolite paragenesis is recorded by the chemical trends both of the sediment and the interstitial fluid this diagenetic evolution implies si and mg rich fluids circulating in deeper and older sequences for lack of any local volcaniclastic input the genesis of zeolite and the terms of water rock interaction are discussed the location of the diagenetic front correlates with that of the seismic sequence boundary p2 dated as 23 2 ma this correspondence may allow the chronostratigraphic significance of some specific seismic reflections to be reassessed

geochemistry of eolian dust in pacific pelagic sediments implications for paleoclimatic interpretations geochemical data rees th sc were determined for the operationally defined eolian dust oded fraction 63 m of late quaternary sediment samples n 57 from the north and equatorial pacific ocean paleoclimate studies commonly have assumed that this sediment fraction represents eolian materials from continental source regions this study shows on the basis of geochemical data published mineralogical data and mixing models that the oded fraction actually is a mixture of materials from two endmember sources the continental crust eolian transported weathering products and the oceanic crust primarily volcanogenic material mixing model results show that the average ash content is significant in the oded fraction equatorial pacific 43 north pacific 24 we have used this information to reconsider and refine the results of previous paleoclimate studies in the northwest pacific the flux of the eolian fraction is greater during glacial stages and shows a latitudinal maximum between 35 n and 42 n eolian fluxes are greatest during interglacial periods in the equatorial pacific these results are consistent with previous interpretations in contrast to previous assumptions eolian mass accumulation rates may not be a valid indicator of paleo aridity because they are correlated with grain size furthermore the relative abundance of the two endmembers is correlated with the average grain size of the dust fraction the continental crust component is associated with larger grains this compositional effect should be considered in future studies which commonly utilize grain size as a proxy indicator of paleo wind intensity

late quaternary lacustrine paleo seismic archives in north western alps examples of earthquake origin assessment of sedimentary disturbances abstract the late quaternary sedimentary fills of several lakes of the north western alps are revealed to be possible paleo seismological archives in a moderately active seismo tectonic region the strongest historically reported events can be correlated with specific layers whose textures result from different processes i mass failures of sub aqueous slope deposits especially delta foresets evolving into hyperpycnal currents influenced by seiche effects and or multiple reflections on lake basin slopes ii in situ liquefaction and flowage and iii micro fracturing based on identification of the sedimentary signature of a well documented historical earthquake the paleoseismic interpretation can be extrapolated back to 16 000 yrs bp with a reconstruction of a time series and textural identification of slope failure related turbidites the most frequent earthquake signature the obtained time series are compatible with historical seismicity in terms of recurrence interval

reconstructing holocene climate from tree rings the potential for a long chronology from the scottish highlands despite promising research in the 1980s showing the potential of scots pine pinus sylvestris l for the reconstruction of past summer temperatures in the scottish highlands little dendroclimatic work has been attempted in this region since this reflects in part the limited number of sparsely distributed remnant natural semi natural pine woodlands in the scottish highlands and the lack of old growth forest therein on average most of the pine trees dated in this region are around 225 years in age here we present the first results of an ongoing interdisciplinary initiative to develop a long scottish chronology through the acquisition of modern historical and subfossil pine material from the native pinewoods historic structures and lakes of the scottish highlands radiocarbon dating of 25 subfossil pine timbers recovered from lake sediments identified the presence of preserved material covering the last 8000 years with initial clusters focused on the last two millennia and early mid holocene alth

6700 yr sedimentary record of climatic and anthropogenic signals in lake aydat french massif central a 19 meters long sedimentary record that was retrieved in lake aydat french massif central covers the last 6700 yrs at a high resolution a multi proxy approach density magnetic susceptibility xrf rock eval analyses pollen and non pollen palynomorphs analyses and historical archives study was used to characterise and tentatively propose a model of the sedimentation the important deposition rate results from the narrow and incised fluvial valley dammed by a lava flow ca 8550 years ago two contrasted periods of sedimentation 6700 200 3180 90 cal bp and 1770 60 cal bp now are characterized the lower unit mid holocene displays a fine and regular lamination and holds a single major flood deposit this unit is capped by an erosive mass wasting deposit triggered ca 1770 60 cal bp the upper unit late holocene is made of organic rich and fine grained faintly laminated sediment with numerous interbedded flood deposits 56 events and layers resulting from blooms of diatoms the sedimentation was principally controlled by climatic forcings solar activity until ca 1100 cal bp accompanied by detritic events linked to human activities around the lake then a more detrital input attested by numerous and recurrent flood deposits can be linked to the intensification of a persistent anthropogenic impact on the catchment two phases of lake eutrophication are highlighted a first phase between 1200 1130 cal bp as a result of increased anthropogenic pressure and the current phase that could have started ca 150 cal bp

lake sediments as natural seismographs earthquake related deformations seismites in central canadian lakes abstract central canada experiences numerous intraplate earthquakes but their recurrence and source areas remain obscure due to shortness of the instrumental and historic records unconsolidated fine grained sediments in lake basins are natural seismographs with the potential to record ancient earthquakes during the last 10 000 years since the retreat of the laurentide ice sheet many lake basins are cut into bedrock and are structurally controlled by the same precambrian basement structures shear zones terrane boundaries and other lineaments implicated as the source of ongoing mid plate earthquake activity a regional seismic sub bottom profiling of lakes gull muskoka joseph rousseau ontario wanapitei fairbanks vermilion nipissing georgian bay mazinaw simcoe timiskaming kipawa parry sound and lake of bays encompassing a total of more than 2000 kilometres of high resolution track line data supplemented by multibeam and sidescan sonar survey records show a consistent sub bottom stratigraphy of relatively thick lowermost lateglacial facies composed of interbedded semi transparent mass flow facies debrites slumps and rhythmically laminated silty clays mass flows together with cratered kettled lake floors and associated deformations reflect a dynamic ice contact glaciolacustrine environment exceptionally thick mass flow successions in lake timiskaming along the floor of the timiskaming graben within the seismically active western quebec seismic zone wqsz point to a higher frequency of earthquakes and slope failure during deglaciation and rapid glacio isostatic rebound though faulting continues into the postglacial lateglacial faulting diapiric deformation and slumping of coeval lateglacial sediments is observed in parry sound lake muskoka and lake joseph which are all located above prominent precambrian terrane boundaries lateglacial sediments are sharply overlain by relatively thin rhythmically laminated and often semi transparent postglacial silty clay laminations postglacial neotectonic activity is recorded by co seismic water escape structures faults slumps and debris flows in lake simcoe above a terrane boundary and especially within lakes timiskaming and kipawa recording ongoing deformation within the wqsz high resolution seismo stratigraphic data presented here support the model that ongoing mid plate earthquake activity is a consequence of brittle deformation of the upper crust of the north american plate such activity appears to have been greatest during deglaciation but continues today

reconstructing historical seismicity from lake sediments lake laffrey western alps france sediment archives from a mountain lake are used as indicators of seismotectonic activity in the grenoble area french western alps 45n sedimentological analysis texture and grain size characteristics exhibits several layers resulting from instantaneous deposits in lake laffrey six debris flow events up to 8 cm thick can be attributed to slope failure along the western flank of the basin dating with 210 pb and 137 cs gamma counting techniques and the reconnaissance of historical events provide a constrained age depth model over the last 250 years five of such debris flow deposits could be related to historical earthquakes of msk intensities greater than vi over an area of 60 km one debris flow deposit triggered at the beginning of the last century can be related to an historical landslide possibly triggered by the artificial regulation of the lake level

turbidites as records of intense palaeoearthquakes in lake biwa japan abstract some 20 turbidites were collected in the uppermost 3 m of surface sediments in lake biwa southwest japan these turbidites correlate in age to historical earthquakes that caused severe loss of lives and property near lake biwa the age of each turbidite was estimated precisely based on sedimentation rate by weight and the age of tephra markers below the turbidites the magnitudes and epicentres of major historical earthquakes during the last 1300 years are available from historical documents empirical equations relating intensity distance to the epicentre and magnitude enable us to calculate the ground shaking at lake biwa from these historical earthquakes earthquakes having intensity stronger than grade iv l on the japan meteorological agency jma earthquake scale that is 44 gal acceleration at lake biwa all coincide with the turbidite ages this intensity is apparently the lower threshold for turbidity current initiation in lake biwa

provenance of the detrital component of deep sea sediments from the sw pacific ocean based on mineralogy geochemistry and sr isotopic composition abstract clay mineralogy and chemical and strontium isotope compositions have been used to determine the detrital components of deep sea sediments from the sw pacific ocean continental detritus derived mainly from the new zealand landmass is characterised by high illite and chlorite contents and 87 sr 86 sr ratios close to 0 7110 this material eroded from the eastern margin of both islands is transported into deeper water by turbidity currents and hemipelagic processes and is carried northwards by the strong western boundary current as far north as the samoan basin due to the great distance from source and unfavourable prevailing winds the contribution of aeolian dust from the australian deserts to the sediment appears to be relatively small particularly in the northernmost part of the region in the vicinity of the oceanic volcanic islands of tonga samoa and the cook islands volcaniclastic material including heavy minerals pyroxene and magnetite pumice glass shards proximally and smectite clays distally is dispersed into the sediments by turbidity currents and airfall in areas of very low sedimentation distant from landmasses the sediments contain significant amounts of authigenic material rsos characterised by high concentrations of transition metals and rare earth elements strontium isotopes together with trace element compositions have proved particularly useful in determining the relative proportions of the detrital types the contrasting 87 sr 86 sr ratios and sr contents of the various source rocks permit the use of binary mixing relationships whch indicate that sediments less than 35 km from the cook islands contain 80 volcanic detritus and those more than 1200 km away contain up to 20 volcanic detritus

subfossil bog pine chronologies from the puścizna wielka raised bog orawa basin southern poland abstract subfossil wood of the scots pine pinus sylvestris l appearing in the peat sediments in southern poland presents material for the construction of long tree ring chronologies that are of potential utility in palaeoclimatic reconstructions over 600 subfossil pine samples in form of discs were taken for dendrochronological analyses from the pu cizna wielka peat bog the only economically exploited bog in the carpathians based on these samples five floating chronologies covering ca 1700 years were constructed they were dated with the wiggle matching technique to the years 3485 3295 25 3205 2575 25 2445 2200 50 2210 1990 40 1100 610 10 cal bc these results indicate that the trees grew on the valley bog during the initial phase of its development the vast majority of the trees analysed grew on the peat bog between ca 3500 and ca 2000 cal bc with breaks in the record dated to ca 3290 3200 cal bc ca 2570 2450 cal bc pines invaded the peat bog in drier periods whereas a high groundwater level presumably related to increased precipitation was a factor determining mortality of the trees this study therefore fills a geographical gap in the coverage by subfossil pine records as there are no studies on subfossil pine trees from peat bogs in central eastern europe

cenozoic sedimentation and clay mineralogy in the northern part of the magellan trough central pacific basin abstract assemblages of clay sized minerals in twelve deep sea cores from the northern part of the magellan trough in the central pacific basin clearly show that authigenic smectite together with clinoptilolite formed subsea in situ and predominated throughout palaeogene time clastic clay minerals such as chlorite illite and kaolinite increased at the expense of smectite in sediments deposited since the pliocene most of the authigenic smectites are of the di octahedral iron rich type the most probable origin of the authigenic smectites is formation from precursors such as volcanic glass as part of this process biogenic silica evidently contributed to the formation of smectite and zeolites as clinoptilolite the presence of a tri octahedral saponite and the tem morphology of some smectites on the other hand suggests that not all of the smectite studied was formed subsea in situ but that some had an allogenic origin systematic vertical changes in the assemblage of clay sized minerals suggest that the authigenesis of submarine smectite and clinoptilolite prevailed in conditions of reduced aridity and weak wind activity throughout the palaeogene in the study area however allogenic clay minerals such as chlorite and illite increased since the olduvai event under conditions of severe aridity and strong wind activity caused by global climatic change the west northwest movement of the pacific plate must have partly played a role in deposition of the clastic clay sized minerals from the asian continent by westerlies in the study area the widespread occurrence of cenozoic hiatuses in the study area is attributed to the influence of antarctic bottom water aabw the latter must have influenced non deposition of the clay sized minerals at times during the cenozoic

a plate tectonic model for the mesozoic and early cenozoic history of the caribbean plate abstract we present a model in which the caribbean plate is an intra american feature formed along the caribbean spreading center as opposed to the current model that considers the caribbean plate as a far travelled crustal segment that formed in the pacific region paleomagnetic data which cover an age range from jurassic through paleocene indicate the ophiolite complexes in costa rica and panama formed in an equatorial position the ophiolites did not fundamentally change their position relative to south america since their origin basaltic rocks of the lower part of the ophiolites are of mid ocean ridge type suggesting formation at a spreading center they are interpreted to have formed as part of the proto caribbean crust at a spreading axis in an intra american position during jurassic and early cretaceous times the upper part of the ophiolites is mainly built up by island arc and intraplate basalts the island arc basalts evolved at the central american landbridge which started in the middle cretaceous the intraplate basalts are related to the caribbean plateau basalt which thickened and stiffened the caribbean crust in middle cretaceous to probably campanian times changes in relative plate motions along the middle american convergent plate margin are reflected by orientations and time sequences of paleostress tensors calculated from fault slip data in southern mexico and costa rica kinematic indicators from mylonite zones display sinistral movement along secondary shear zones within the southern mexican crustal complexes and along the northern boundary of the chortis block in the motagua polochic fault system this reflects the eastward drift of the chortis block since the beginning of the cenozoic at this time the chortis block became part of the caribbean plate which moved more than 1000 km towards the east relative to the north and south american plates during the cenozoic

high resolution reconstruction of wetness dynamics in a southern boreal raised bog finland during the late holocene a quantitative approach a high resolution plant macrofossil analysis was applied to investigate wetness dynamics in a southern finnish boreal bog kontolanrahka during the last 5000 years the chronological control and the age depth model were based on 40 ams radiocarbon dates pollen analysis provided information on regional scale vegetation changes macrofossil analysis revealed prominent changes in vegetation assemblages during the late holocene indicating fluctuations in water table the reconstruction suggests that at the coring point which nowadays is a relatively wet lawn habitat type has repeatedly varied between transient communities similar to those currently represented in dry hummocks very wet lawns and even hollows in order to quantify historical changes in water table generalized additive models gam were used to investigate the current relationships between surface plant species and water table depth modern water table measurements and a survey of associated plant communities along moisture gradients prov

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

mechanisms of mg phyllosilicate formation in a hydrothermal system at a sedimented ridge middle valley juan de fuca we present results of a detailed mineralogical and geochemical study of the progressive hydrothermal alteration of clastic sediments recovered at odp site 858 in an area of active hydrothermal venting at the sedimented axial rift valley of middle valley northern juan de fuca ridge these results allow a characterization of newly formed phyllosilicates and provide constraints on the mechanisms of clay formation and controls of mineral reactions on the chemical and isotopic composition of hydrothermal fluids hydrothermal alteration at site 858 is characterized by a progressive change in phyllosilicate assemblages with depth in the immediate vent area at hole 858b detrital layers are intercalated with pure hydrothermal precipitates at the top of the section with a predominance of hydrothermal phases at depth sequentially downhole in hole 858b the clay fraction of the pure hydrothermal layers changes from smectite to corrensite to swelling chlorite and finally to chlorite in three pure hydrothermal layers in the deepest part of hole 858b the clay minerals coexist with neoformed quartz neoformed and detrital components are clearly distinguished on the basis of morphology as seen by sem and tem and by their chemical and stable isotope compositions corrensite is characterized by a 24 a stacking sequence and high si and mg contents with fe fe mg ratio of 0 08 we propose that corrensite is a unique possibly metastable mineralogical phase and was precipitated directly from seawater dominated hydrothermal fluids hydrothermal chlorite in hole 858b has a stacking sequence of 14 a with fe fe mg ratios of 0 35 the chemistry and structure of swelling chlorite suggest that it is a corrensite chlorite mixed layer phase the mineralogical zonation in hole 858b is accompanied by a systematic decrease in 18o reflecting both the high thermal gradients that prevail at site 858 and extensive sediment fluid interaction precipitation of the mg phyllosilicates in the vent region directly controls the chemical and isotopic compositions of the pore fluids this is particularly evident by decreases in mg and enrichments in deuterium and salinity in the pore fluids at depths at which corrensite and chlorite are formed structural formulae calculated from tem edx analyses were used to construct clay h2o oxygen isotope fractionation curves based on oxygen bond models our results suggest isotopic disequilibrium conditions for corrensite quartz and swelling chlorite quartz precipitation but yield an equilibrium temperature of 300 c 30 for chlorite quartz at 32 m below the surface this estimate is consistent with independent estimates and indicates steep thermal gradients of 10 11 m in the vent region

palaeolimnology of lake sapanca and identification of historic earthquake signals northern anatolian fault zone turkey abstract lake sapanca is located on a strand of the northern anatolian fault zone nafz turkey where a series of strong earthquakes ms 6 0 have occurred over the past hundred years identifying prehistoric earthquakes in and around lake sapanca is key to a better understanding of plate movements along the nafz this study contributes to the development of palaeolimnological tools to identify past earthquakes in lake sapanca to this end several promising proxies were investigated specifically lithology magnetic susceptibility grain size thin section and laser analysis geochemistry pollen concentration diatom assemblages 137cs and 210pb sedimentological indicators provided evidence for reworked turbidite like or homogeneous facies event layers in several short cores

chemistry of surface sediment along a north south transect across the equator in the central indian basin an assessment of biogenic and detrital influences on elemental burial on the seafloor nineteen surface sediment samples collected along a north south transect across the equator in the central indian basin cib were analysed for their major minor and rare earth element ree composition in absence of the element flux data we demonstrate here the association of various elements and their preferential sinks using inter elemental associations in sediment exhibiting latitudinal dissimilarity biogenic sedimentation north of the equator 1 to 4 n latitudes is dominated by carbonate ooze whereas south of the equator 4 to 14 s latitudes is dominated by siliceous ooze carbonate ooze deposition 60 caco3 above 4400 m and its drastic reduction to 80 of their respective total content in all the three sediment zones these observations suggest a close link between ba and a mn oxide phase on the other hand nearly overlapping latitudinal trends of alxs with carbonate in areas north of the equator and opal south of the equator strong positive correlation of alxs with opal r 0 8 similar ratios between carbonate free opal and alxs 16 in both biogenic sediments suggest a close link between productivity and alxs the alxs proportion in both biogenic sediment types is around 28 of the total al suggesting nearly the same level of primary productivity along the transect 4 n to 14 s which supports the estimates of berger berger w h 1989 global maps of the ocean productivity in w h berger v s smetacek g wefer eds productivity of the ocean present and past dahlem workshop reports wiley chichester pp 429 455 and kabanova kabanova j g 1968 primary production of the northern part of the indian ocean oceanology 8 214 255 i e 70 g cm 2 y 1 the rees exhibit mutual coherence in the sediment r 0 7 however they display an increasing affinity towards mn r increases from 0 6 to 0 8 and decreasing affinity towards ti r decreases from 0 8 to 0 3 with increasing atomic number such a subtle but systematic variation within ree group suggests preferential burial of heavy ree by mn oxide phase and light ree by detrital phase

the record of historic earthquakes in lake sediments of central switzerland deformation structures in lake sediments in central switzerland can be attributed to strong historic earthquakes the type and spatial distribution of the deformation structures reflect the historically documented macroseismic intensities thus providing a useful calibration tool for paleoseismic investigations in prehistoric lake sediments the swiss historical earthquake catalogue shows four moderate to strong earthquakes with moment magnitudes of mw 5 7 to mw 6 9 and epicentral intensities of i0 vii to i0 ix that affected the area of central switzerland during the last 1000 years these are the 1964 alpnach 1774 altdorf 1601 unterwalden and 1356 basel earthquakes in order to understand the effect of these earthquakes on lacustrine sediments four lakes in central switzerland sarner see lungerer see baldegger see and seelisberg seeli were investigated using high resolution seismic data and sediment cores the sediments consist of organicand carbonate rich clayey to sandy silts that display fine bedding on the centimeter to millimeter scale the sediments are dated by historic climate and environmental records 137 cs activity and radiocarbon ages deformation structures occur within distinct zones and include large scale slumps and rockfalls as well as small scale features like disturbed and contorted lamination and liquefaction structures these deformations are attributed to three of the abovementioned earthquakes the spatial distribution of deformation structures in the different lakes clearly reflects the historical macroseismic dataset lake sediments are only affected if they are situated within an area that underwent groundshaking not smaller than intensity vi to vii we estimate earthquake size by relating the epicentral distance of the farthest liquefaction structure to earthquake magnitude this relationship is in agreement with earthquake size estimations based on the historical dataset d 2004 elsevier b v all rights reserved

sedimentary records of past earthquakes in boraboy lake during the last ca 600 years north anatolian fault turkey abstract multiproxy sedimentological analyses along 4 9 m long sequence of boraboy lake which is located on the central eastern part of the north anatolian fault naf reveal the sedimentary traces of past large earthquakes in the region the lake has a relatively large catchment area 10 km2 compared to its size 0 12 km2 which renders sedimentation sensitive to heavy rain storm events accordingly the background sedimentation which is composed of faintly laminated reddish yellowish brown clayey silt is frequently interrupted by organic rich intercalations probably due to heavy rain storm events transporting terrestrial plant remains from the densely vegetated catchment in addition to frequent organic rich intercalations the background sedimentation is interrupted by four mass wasting deposits mwd of which thickness range is between 15 and 50 cm high resolution itrax xrf data confirms higher homogeneity along the mwds e1 e4 compared to the background sedimentation based on 137cs and 210pbxs dating and radiocarbon chronology three mwds detected in boraboy sequence e2 e3 and e4 temporally correlate with large historical earthquakes along the naf the 1943 tosya ms 7 6 and or 1942 niksar erbaa ms 7 1 the 1776 amasya merzifon and the 1668 north anatolian ms 7 9 earthquakes the youngest mwd in the sequence e1 which is dated to early 2000s does not correlate with any strong earthquake in the region this mwd was probably a single mass wasting event due to routine overloading and oversteepening on the delta front formed by the main inlet of the lake in subaqueous paleoseismology coevality of multi location mass wasting events is used as a criterion to assign a seismic triggering mechanism and to rule out mass wasting events due to routine overloading oversteepening of subaqueous slopes within this context boraboy sequence provides a valuable example to discuss sedimentological imprints of single vs multi source mwds

snapshots in time precise correlations of peat based proxy climate records in scotland using mid holocene tephras mid holocene tephra layers have been located and geochemically analysed from seven ombrotrophic bogs in scotland the tephras found in these scottish peats occur as stratigraphically discrete horizons not visible to the naked eye and originate from volcanic activity in iceland identifying and geochemically typing the tephra layers can enable precise correlations between sites on regional scales depending on the spatial extent of the airfall events dispersal of both the glen garry and hekla 4 tephras is excellent over scotland enabling snapshot views of the past at the time of these tephra depositions palaeoecological analyses have also been undertaken on these bogs providing detailed reconstructions of past changes in bog vegetation and surface wetness a proxy for past climates correlations between the ombrotrophic bogs at the time of the glen garry tephra revealed significant differences between the proxy climate records in the north and the south of scotland suggesting asynchronous changes between northern scotland and the rest of great britain

historical seismicity of the mont dore volcanic province auvergne france unraveled by a regional lacustrine investigation new insights about lake sensitivity to earthquakes lake sediments are relevant natural seismographs over long time scale however because tectonic events are not systematically recorded in lake sediments one forthcoming challenge for paleoseismology is to better assess lake sensitivity to earthquakes to this end a limnogeological investigation including hydroacoustic mapping techniques core sampling and multi proxy sediment analyses has been conducted within four small volcanic lakes located in the mont dore province auvergne france an area with a moderate seismo tectonic activity results show the existence of several gravity reworking processes in the lakes over the last millennium around ad 1300 the occurrence of synchronous events in lakes pavin chauvet montcineyre and guery 100 km 2 area highlights an undocumented earthquake as a common trigger for slope failures in disconnected basins at regional scale the record of this tectonic event may have been favored by human induced increase in sediment load chauvet and montcineyre and or after an abrupt lake level drop pavin affecting the sediment stability in addition synchronous turbidites and mass wasting deposits mwd recorded in lakes pavin and guery provide evidence for a seismic activity during the xix th century potential triggers are historical earthquakes that occurred either in the mont dore area or in the southern part of the limagne fault at this time despite moderate seismic activity in this intraplate volcanic domain these results highlight the role of tectonics as a major trigger in the sedimentary processes dominating these lacustrine infills within the diversity of studied sites it appears that lake sensitivity to earthquakes was not constant over time this sensitivity can be expressed as a combination of external factors namely earthquake magnitude and lake epicenter distance and internal factors such as lake morphology nature of sediment lake level fluctuations and human induced changes in catchment sedimentary load

holocene landslides and a 3500 year record of pacific northwest earthquakes from sediments in lake washington lake washington which forms the eastern boundary of seattle is located in a tectonically active area containing several strands of the seattle fault high resolution seismic reflection profiling sidescan swath imagery and sediment coring were used to define deformation of holocene lake sediments and the distribution geometry age and causes of submarine landslides numerous large block slides sediment slumps and debris flows are present throughout the lake and large landslides obscure the surficial structure of seattle fault strands as they pass through the lake in addition most bays along the lake margin are the headwalls of large submarine slides submerged forests show evidence of deep seated block failures that have exposed glacial sediments and tertiary rocks the massive submarine block slides and retrogressive submarine slope failures were triggered most likely by large m b 7 earthquakes on the seattle fault and or large to great m b 8 temblors occurring elsewhere in cascadia buried landslides suggest that submarine slope failures and mass wasting occurred more than once in the last 11 000 yr sediments in lake washington preserve a record of episodic deposition of turbidites possibly caused by seismically induced submarine landslides magnetic susceptibility profiles on 36 gravity cores show a characteristic series of magnetic peaks that can be traced throughout the lake x radiography and grain size analyses suggest that the magnetic peaks represent anomalous detrital layers that in some cases are turbidites the areal extent and magnetic signatures of many of the deposits suggest multiple sources which is consistent with numerous local landslides caused by large earthquakes radiocarbon dating and correlation of the downcore magnetic profiles establish a sediment record in which episodic sedimentary disturbances occurred seven times in the last 3500 yr if these deposits are seismically induced turbidites seismites then large earthquakes have occurred about every 300 500 yr in the puget sound region

a comprehensive pollen and tephra based chronostratigraphic model for the late glacial and holocene period in the french massif central this paper discusses about 250 conventional c 14 ages obtained on peat and gyttja samples that apply to pollen features or tephra beds in the massif central region of france a method to estimate the migration periods of eight late glacial to holocene pollen features typical of the massif central is described a review of all c 14 ages pertaining to tephras of this region enabled the most appropriate age or age range of the tephras to be estimated the chronostratigraphic relationships between pollen features and tephras are discussed and a new comprehensive stratigraphic model is presented the model shows that pollen features are diachronous and should not be used therefore as proxy stratigraphic markers copyright c 1996 inqua elsevier science ltd

linking the oxygen isotope record of late neogene eustasy to sequence stratigraphic patterns along the bahamas margin results from a paleoceanographic study of odp leg 166 site 1006 sediments abstract during odp leg 166 the recovery of cores from a transect of drill sites across the bahamas margin from marginal to deep basin environments was an essential requirement for the study of the response of the sedimentary systems to sea level changes a detailed biostratigraphy based on planktonic foraminifera was performed on odp hole 1006a for an accurate stratigraphic control the investigated late middle miocene early pliocene sequence spans the interval from about 12 5 ma biozone n12 to approximately 4 5 ma biozone n19 several bioevents calibrated with the time scale of berggren et al 1995a b were identified the odp site 1006 benthic oxygen isotope stratigraphy can be correlated to the corresponding deep water benthic oxygen isotope curve from odp site 846 in the eastern equatorial pacific shackleton et al 1995 proc odp sci res 138 337 356 which was orbitally tuned for the entire pliocene into the latest miocene at 6 0 ma the approximate stratigraphic match of the isotopic signals from both records between 4 5 and 6 0 ma implies that the paleoceanographic signal from the bahamas is not simply a record of regional variations but indeed represents glacio eustatic fluctuations the odp site 1006 oxygen and carbon isotope record based on benthic and planktonic foraminifera was used to define paleoceanographic changes on the margin which could be tied to lithostratigraphic events on the bahamas carbonate platform using seismic sequence stratigraphy the oxygen isotope values show a general cooling trend from the middle to late miocene which was interrupted by a significant trend towards warmer sea surface temperatures sst and associated sea level rise with decreased ice volume during the latest miocene this trend reached a maximum coincident with the miocene pliocene boundary an abrupt cooling in the early pliocene then followed the warming which continued into the earliest pliocene the late miocene paleoceanographic evolution along the bahamas margin can be observed in the odp site 1006 13c values which support other evidence for the beginning of the closure of the panama gateway at 8 ma followed by a reduced intermediate water supply of water from the pacific into the caribbean at about 5 ma a general correlation of lower sedimentation rates with the major seismic sequence boundaries ssbs was observed additionally the ssbs are associated with transitions towards more positive oxygen isotope excursions this observed correspondence implies that the presence of a ssb representing a density impedance contrast in the sedimentary sequence may reflect changes in the character of the deposited sediment during highstands versus those during lowstands however not all of the recorded oxygen isotope excursions correspond to ssbs the absence of a ssb in association with an oxygen isotope excursion indicates that not all oxygen isotope sea level events impact the carbonate margin to the same extent or maybe even represent equivalent sea level fluctuations thus it can be tentatively concluded that ssbs produced on carbonate margins do record sea level fluctuations but not every sea level fluctuation is represented by a ssb in the sequence stratigraphic record

multiphase silurian bentonites in the baltic palaeobasin abstract the mineral composition of altered volcanic ash beds bentonites deposited in marine environments is typically characterized by smectite or illite smectite type clay minerals silurian bentonites from an unmetamorphosed normal marine sedimentary sequence in the eastern baltic palaeobasin however show a complex and varied mineral composition with illite smectite k feldspar and kaolinite as the dominant authigenic phases the whole rock xrd study of 52 bentonite beds from two drill cores ruhnu and ohesaare southwestern estonia reveals a range of compositions varying between different beds as well as laterally within a single bed the observed variations are found to reflect the bentonite development and diversification during initial stages of volcanic ash transformation and diagenesis that was probably overprinted by a later k metasomatic event

evidence for an extreme climatic event on achill island co mayo ireland around 5200 5100 cal yr bp a range of detailed palaeoenvironmental analyses carried out on a series of three peat profiles from achill island co mayo western ireland reveal evidence for an extreme climatic event probably a storm or series of storms around 5200 5100 cal yr bp that caused the deposition of an extensive layer of silt across blanket peat this event followed a period of relatively dry climate during which neolithic communities expanded in the region there was a subsequent period of continuing dry conditions allowing extensive colonisation of the peat by pinus before a shift to wetter conditions characteristic of the later holocene the extreme climatic event is possibly linked to human abandonment of the area comparable to that observed from the work on the internationally significant ceide fields in the same region

a 3400 year lacustrine paleoseismic record from the north anatolian fault turkey implications for bimodal recurrence behavior high resolution physical geochemical and geochronological analyses on the sedimentary sequence of yenicaga lake located in a fault bounded basin along the north anatolian fault reveal fingerprints of paleoearthquakes a robust sediment chronology spanning the last 3400 years is constructed by radiocarbon dating and time stratigraphical correlation with the precisely dated sofular cave speleothem record yenicaga sedimentary sequence contains 11 seismically induced event deposits characterized by siliciclastic enriched intervals some of the event deposits are also associated with implications of sudden lake deepening which may be related to coseismic subsidence the paleoearthquake series having an average recurrence interval of ca 260 years are interrupted by two possible seismic gaps of ca 420 and 540 years

giant earthquakes in south central chile revealed by holocene mass wasting events in lake puyehue abstract very high resolution reflection seismic profiling 3 5 khz revealed nine holocene mass wasting events in lake puyehue south central chile these events are made up of numerous coeval mass wasting deposits and some homogenites which are radiocarbon dated the two youngest mass wasting events could be attributed to the giant ad 1960 and ad 1575 valdivia earthquakes the most extensive event took place around 1660 cal yr bp evaluation of all possible slope failure processes led us to infer that giant earthquakes roughly comparable to the ad 1960 valdivia earthquake mw 9 5 are the most likely trigger mechanisms of all mass wasting events in lake puyehue these occurred with a mean recurrence rate of 1000 yr although relatively aperiodically ranging between 500 and 2000 yr quantitative comparison of mass wasting events related to historically reported earthquakes ad 1960 and ad 1575 showed significant differences although these earthquakes are assumed to have had a comparable strength a lowered background sedimentation rate could be responsible for this variable earthquake recording which highlights the importance of a thorough assessment of the depositional history before using lacustrine records for quantitative paleoseismic analysis

sediment yield during late glacial and holocene periods in the lac chambon watershed massif central france a sediment budget for the late glacial and holocene periods was calculated for the lac chambon watershed which is located in a formerly glaciated temperate crystalline mountain area it appears that over 15 500 years 1 69 per cent of eroded particles have been displaced by gravity processes and then stored within the watershed compared to 31 per cent that have been displaced by running water and evacuated outward 2 the mean mechanical erosion due to gravity processes on the slopes amounted to 16 1 6 m and only developed on a quarter of the watershed surface whereas the mean mechanical erosion due to running water amounted 1 24 0 37 m and involved the whole watershed surface the mean sediment yields due to gravity processes on slopes were 2300 1360 1770 960 and 380 100 m 3 km 3 a 1 respectively for basalts and basic and acidic trachyandesites values of sediment yield due to running water were 49 15 120 36 and 79 24 m 3 km 2 a 1 respectively during the bolling allerod the younger dryas and the pre boreal boreal periods they were 56 17 and 166 50 m 3 km 2 a 1 during the sub atlantic period before and after 1360 a bp respectively these values reflect variations in the natural environment and the impact of human induced deforestation 1997 by john wiley sons ltd

icelandic volcanic ash and the mid holocene scots pine pinus sylvestris decline in the north of ireland no correlation tephra linked pollen and dendrochronological studies were performed on mid holocene subfossil peats and pines and two lowland raised bogs in the north of ireland the results demonstrated that at these sites contrary to recent findings in the north of scotland there was no temporal link between the decline in pine pollen and tephra from the eruption of the icelandic volcano hekla h4

chemical transport to the seafloor of the equatorial pacific ocean across a latitudinal transect at 135 w tracking sedimentary major trace and rare earth element fluxes at the equator and the intertropical convergence zone we have analyzed the major trace and rare earth element composition of surface sediments collected from a transect across the equator at 135 w longitude in the pacific ocean comparing the behavior of this suite of elements to the caco3 opal and corg fluxes which record sharp maxima at the equator previously documented at the same sampling stations enables us to assess the relative significance of the various pathways by which trace elements are transported to the equatorial pacific seafloor the 1 1 high biogenic source at the equator associated with equatorial divergence of surface water and upwelling of nutrient rich water and 2 2 high aluminosilicate flux at 4 n associated with increased terrigenous input from elevated rainfall at the intertropical convergence zone itcz of the tradewinds are the two most important fluxes with which elemental transport is affiliated the biogenic flux at the equator transports ca and sr structurally bound to carbonate tests and mn primarily as an adsorbed component trace elements such as cr as pb and the rees are also influenced by the biogenic flux at the equator although this affiliation is not regionally dominant normative calculations suggest that extremely large fluxes of ba and p at the equator are carried by only small proportions of barite and apatite phases the high terrigenous flux at the itcz has a profound effect on chemical transport to the seafloor with elemental fluxes increasing tremendously and in parallel with ti normative calculations however indicate that these fluxes are far in excess of what can be supplied by lattice bound terrigenous phases the accumulation of ba is greater than is affiliated with biogenic transport at the equator while the p flux at the itcz is only 10 less than at the equator this challenges the common view that ba and p are essentially exclusively associated with biogenic fluxes many other elements including mn pb as and rees also record greater accumulation beneath the itcz than at the equator thus adsorptive scavenging by terrigenous paniculate matter or phases intimately associated with them appears to be an extremely important process regulating elemental transport to the equatorial pacific seafloor these findings emphasize the role of vertical transport to the sediment and provide additional constraints on the paleochemical use of trace elements to track biogenic and terrigenous fluxes

a 7500 year peat based palaeoclimatic reconstruction and evidence for an 1100 year cyclicity in bog surface wetness from temple hill moss pentland hills southeast scotland analyses of plant macrofossils peat humification and testate amoebae were used to reconstruct a proxy climate record spanning the last 7500 years from an ombrotrophic bog temple hill moss in southeast scotland the plant macrofossil data were subjected to detrended correspondence analysis dca which modelled effectively the significant wet shifts within the record a mean water table depth transfer function was applied to the testate amoebae data to provide quantifiable changes the three proxy records show coherent phase changes which are interpreted as variability in past effective precipitation two tephra horizons glen garry and lairg a were used in conjunction with radiocarbon dates to construct an age depth model producing a robust geochronology from which a time series was calculated the palaeoclimatic reconstruction identified major wet shifts throughout the holocene with specific events occurring around cal 6650 5850 5300 4500 3850 3400 2800 2450 1450 1350 and 250 150 bp spectral analysis of the plant macrofossil dca and colorimetric humification data produced a millennial scale periodicity of 1100 years the same periodicity has also been found in a palaeoclimatic reconstruction from a site in cumbria walton moss and may be linked with millennial scale periodicities found in oceanic palaeoclimatic records