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

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

melange genesis and ophiolite emplacement related to subduction of the northern margin of the tauride anatolide continent central and western turkey the tauride anatolide continent stretching for c 900 km across western and central turkey is one of the world s best example of a subducted exhumed passive margin within a collisional orogen twelve widely separated areas were studied and correlated to develop a new plate tectonic model a metamorphosed rifted continental margin of triassic lower cretaceous age tauride anatolide platform is overlain by upper cretaceous cenomanian lower maastrichtian pelagic sediments and then by both tectonic melange subduction complexes and sedimentary melange foredeep gravity complexes the melanges are overthrust by unmetamorphosed ophiolitic rocks commonly peridotites with swarms of diabase gabbro dykes and are underlain by metamorphic soles new geochemical evidence from basaltic blocks in the melange indicates predominantly subduction influenced within plate and mid ocean ridge type settings the dykes cutting the ophiolites were probably intruded during early stage intra oceanic arc genesis the metamorphosed continental margin melanges and ophiolites in the north anatolides are correlated with unmetamorphosed equivalents in the taurides further south e g beysehir and lycian nappes oceanic crust of triassic late cretaceous age formed between the gondwana related tauride anatolide continent in the south and the eurasia related sakarya microcontinent in the north following late triassic early cretaceous passive margin subsidence the continental margin was covered by cenomanian turonian pelagic carbonates c 98 90 ma ophiolites formed in an intra oceanic subduction zone setting in response to northward subduction probably within a two stranded ocean with the inner tauride ocean in the se and the izmir ankara erzincan ocean in the north nw metamorphic soles relate to intra oceanic subduction c 95 90 ma oceanic sedimentary igneous rocks accreted to the advancing supra subduction oceanic slab the tauride anatolide continental margin then underwent diachronous collision with the trench c 85 ma deeply subducted and metamorphosed at hp lt c 80 ma accretionary ophiolitic and exhumed hp lt rocks were gravity reworked into a southward migrating flexural foredeep and progressively overridden c 70 63 ma slices of the upper part of the platform and its margin detached and were thrust southwards as the tauride lycian and beysehir nappes together with regional scale ophiolites the continental margin and melange were simultaneously exhumed during maastrichtian early paleocene 70 63 ma and transgressed by shallow water sediments beginning in the late maastrichtian in the east c 64 ma and the mid late paleocene c 60 ma further west remnant oceanic crust was consumed during early cenozoic time followed by mid eocene 45 40 ma diachronous continental collision and a second phase of regional deformation rather than being progressive there were two stages of collision first upper cretaceous ophiolite emplacement driven by continental margin subduction trench collision and secondly eocene collision of the tauride and sakarya eurasian continents

a 14 000 year sediment yield record from western germany based on annually laminated lake sediments the reconstruction of sediment yield data for the catchment of lake holzmaar 205 8 ha in the eifel mountains western germany is based on high resolution geochemical and physical analyses of an absolutely dated sediment record this technique provides flux rates of allochthonous minerogenic deposition for the last 13 840 years the pleistocene holocene transition is characterized by instable soils and vegetation caused by adjustment of the catchment to interglacial climatic conditions these instabilities are the reason for elevated mean sediment yields in the catchment of 16 t km 2 yr 1 until 9800 cal bp during most of the holocene erosive processes are insignificant and sediment yields are very low 1 5 t km 2 yr 1 since humans cleared the forests for agriculture and early industrial purposes the natural environment has been disturbed and sediment yields increased to mean values of 14 t km 2 yr 1 during the last 2750 years comparisons of reconstructions from the eifel area with similar data from southern sweden and with measured data from lakes reservoirs and monitoring sites suggest that quantitative reconstructions based on lake holzmaar sediments may be regarded as reliable despite uncertainties related to the methods of reconstruction applied

sediment yields and sources in a welsh upland lake catchment during the past 800 years estimates of suspended sediment yield over the past 800 years have been derived from a whole basin study of lake sediments in llyn geirionydd north wales magnetic and physical sediment properties were used to correlate a suite of cores to a master chronology based on 210pb and 14c dates the sources of sediment within the catchment were identified by comparing the magnetic and heavy metal properties of sediments soils and stream sediments mean suspended sediment yields range from 6 to 18 t km 2 yr 1 with high yields in the periods 1765 1830 and 1903 1985 corresponding to mining activities in the catchment the impact of earlier deforestation agricultural expansion or climatic change on sediment yields is low although there is evidence that agricultural activities increased levels of peak stream discharge afforestation in the 20th century does not appear to have significantly increased sediment yield sediment sources have remained fairly constant through time they appear to be widespread and dominated by stream channel sides rather than point sources except during the mining phases when spoil material has dominated the sediment load sediment loads to the lake today are still dominated by sediment derived from unvegetated spoil heaps

geomagnetic and mineral magnetic characterization of the anthropocene geomagnetic and mineral magnetic data provide geological indices that are both independent of human impact i e geomagnetic and respond to human induced environmental impact i e mineral magnetic we provide the first discussion of such magnetic events for help in defining the anthropocene within the holocene a potential geomagnetic marker for the anthropocene is the low dipole latitude at c 2700 cal a bp which is associated with distinct palaeosecular variation features in northerly mid to high latitude sites mineral magnetic records from lake and marine sediments identify major deforestation and soil delivery events from catchment systems in many parts of the world during the last 4000 years in europe clusters of these events occur around both 2600 cal a bp and ad 1100 the former coinciding with a low in geomagnetic field dipole latitude and peak intensity mineral magnetic records in peats and lake sediments can reflect particulate pollution from fossil fuel burning the expansion of major coal burning began c ad 1800 in western europe and eastern north america but around ad 1900 this expanded due to more widely distributed coal use and this event is the most clear mineral magnetic marker for the base of the anthropocene

tectonics and magmatism in turkey and the surrounding area this volume contains 23 papers from a range of international contributors describing recent research into the tectonics and magmatism of turkey and its surroundings this region is sited at the collision zone between eurasia and afro arabia and as such provides an extraordinarily complete and well exposed record of the staged tectonic evolution of this sector of the alpine himalayan orogen the geological history of this area involves separation of continental fragments from the margin of gondwana their migration across the tethyan oceans the subsequent closure of these oceans and finally the development of the neotectonic regime which continues to evolve to the present day such a comprehensive record is relevant to the understanding of collisional zones worldwide the volume is divided into five sections tethyan evolution neotethyan ophiolites post tethyan basin evolution neotectonics and igneous activity the first two sections deal with tethyan oceans whose growth and subsequent closure dominated the geodynamic framework in the mesozoic and cenozoic the subsequent sections deal with more recent geological developments from the balkan peninsula in the west to the transcaucasus in the east that followed consumption of the tethyan oceans there is a broad mix of papers throughout the volume wide ranging review papers on ocean development and extensional tectonics are followed by detailed descriptions of petrology and geochemistry and geographically focused studies on basin evolution specific aspects of extensional and strike slip tectonics and discussions of the relationship of magmatic activity to the tectonic development of the area tectonics and magmatism in turkey and the surrounding area presents up to date results and ideas from a large number of international contributors on a wide range of current research activity in this region it is essential reading for all geoscientists with an interest in both academic and applied aspects of eastern mediterranean geology

forest disturbance in the central north island new zealand following the 1850 bp taupo eruption the 1850 bp taupo eruption covered c 30 000 km2 of the central north island with airfall deposits and c 20 000 km2 with ignimbrite this paper reviews pollen and charcoal analyses of lake and peat sediment cores from sites at various distances and directions from the taupo vent to establish the effects of this eruption on the surrounding forests forests within range of the ignimbrite were destroyed and forests located up to 170 km east of the vent suffered variable degrees of damage from ashfall stands of pteridium esculentum and other seral taxa flourished immediately after the eruption fires occurred during the eruption and continued for several decades after the degree and nature of vegetation disturbance above the taupo tephra varied according to the thickness of ashfall local topographical features and probably the vigour of the forest revegetation was complete within 200 years of the eruption even at sites overwhelmed by the taupo ignimbrite post eruption forests were similar to those exi

middle cretaceous calcareous nannofossil biogeography and preservation in the atlantic and indian oceans implications for paleoceanography abstract the quantitative study of calcareous nannofossil preservation and biogeographic distribution puts constraints on paleoceanographic models for the atlantic and indian oceans during the middle cretaceous we establish a dissolution ranking of middle cretaceous calcareous nannofossils based on susceptibility to dissolution a positive correlation of organic carbon content of the sediments and the relative abundance of watznaueria indicates that much of the carbonate dissolution was caused by the release of carbon dioxide during oxidation of organic matter the depth distribution of the most dissolution resistant species watznaueria barnesae shows relative abundance maxima at the deepest sites and a maximum where intermediate waters impinge on slopes this reflects stagnant oxygen poor bottom waters and possibly a mid water oxygen minimum zone with increased deposition and catabolic breakdown of organic matter factor analyses are performed on various data sets for three different time slices ranging in age from late aptian to early albian middle albian and late albian to cenomanian the resulting factors can be related to paleoceanographic conditions such as colder water at high latitudes high fertility upwelling conditions and neritic conditions for all three time intervals a wide tropical to subtropical zone was flanked by boreal and austral zones upwelling conditions probably existed along the north african margin and over the falkland plateau zonal upwelling is tentatively postulated for the northwestern and northeastern margin of the north atlantic in the middle albian and for the eastern margin of the north atlantic off western europe for the late albian to cenomanian we speculate on surface water current patterns location of upwelling regions and haline driven deep circulation for the middle cretaceous

aalenian early bathonian middle jurassic radiolarian assemblages in the tavas nappe within lycian nappes in the western taurides sw turkey the first dating of carbonate platform drowning abstract stratigraphic sections kizilca and kizilca north in the tavas nappe western taurides turkey records the event of carbonate platform drowning in the western tethyan realm our detailed biostratigraphic study of radiolarians and other microfossils places the important temporal constraints on this event and indicates that drowning occured in the geochronological interval from early jurassic hettangian sinemurian through to middle jurassic early bathonian the basal part of the kizilca section is represented by platform carbonates with abundant benthic foraminifera and algae of hettangian sinemurian to pliensbachian age toward the upper part of the section the occurrence of brecciated limestones with some ammonites and belemnites reveals that the drowning event began in the pliensbachian the first radiolarian assemblages of early middle to late aalenian age were obtained from the overlying units characterized by pelagic limestones and chert alternation just after the subsidence of the platform ribbon chert sedimentation began in the late aalenian as indicated by the radiolarians successively early late bajocian and latest bajocian early bathonian radiolarian assemblages were obtained from overlying chert with mudstone silicified mudstones similar to that observed in the kizilca section the kizilca north section include successively pelagic limestones pelagic limestone chert alternation and chert mudstone alternation of late aalenian to early middle bajocian age according to radiolarian biostratigraphy all of these observations indicate that a continuous stratigraphy recorded the drowning event without a large gap from hettangian sinemurian to early bathonian in the tavas nappe this drowning event has close similarities with coeval events in other tethyan realms in terms of mechanism facies characteristics and fossil assemblages therefore this study can aid correlation studies of the tavas nappe with the jurassic paleogeography worldwide

fingerprints and age models for widespread new zealand tephra marker beds erupted since 30 000 years ago a framework for nz intimate abstract the role of tephras in the nz intimate project is a critical one because most high resolution palaeoclimatic records are linked and dated by one or more tephra layers in this review first we document eruptive distributional and compositional fingerprinting data both mineralogical and geochemical for 22 key marker tephras erupted since 30 000 years ago to facilitate their identification and correlation we include new glass compositional data the selected marker tephras comprise 10 from taupo and nine from okataina volcanoes rhyolitic one from tuhua volcano peralkaline rhyolitic and one each from tongariro and egmont volcanoes andesitic second we use four approaches to develop 2 age models for the tephras youngest to oldest 1 calendar ages for kaharoa and taupo y were obtained by wiggle matching log derived tree ring sequences dated by 14c 2 whakaipo v was dated using an age depth model from peat 3 14 tephras in the montane kaipo peat sequence waimihia s unit k whakatane tuhua mamaku rotoma opepe e poronui c karapiti b okupata konini waiohau rotorua rerewhakaaitu were dated by simultaneously wiggle matching stratigraphic position and 51 independent 14c age points against intcal04 using bayesian probability methods via both oxcal and bpeat and 4 the five oldest tephras erupted before ca 18 000 cal yr bp were dated by calibrating limited numbers of 14c ages using intcal04 okareka or comparison curves of the expanded cariaco basin sequence te rere kawakawa oruanui poihipi okaia kawakawa oruanui tephra the most widely distributed marker tephra was erupted probably ca 27 097 957 cal yr bp potential dating approaches for the older tephras include their identification in antarctic ice cores if present or annually laminated sediments for which robust calendar age models have been constructed high precision ams 14c dating on appropriate material from environmentally stable sites systematic luminescence dating or new radiometric techniques e g u th he if suitable minerals are available and errors markedly reduced further application of bayesian age modelling to stratigraphic sequences of 14c ages possibly augmented with luminescence ages may help refine age models for pre holocene tephras with the largest errors finally we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the new zealand region which is a key objective of australasian and southern hemisphere intimate projects

middle and late holocene paleotemperatures reconstructed from oxygen isotopes and gdgts of sediments from lake pupuke new zealand abstract quantitative holocene temperature reconstructions for southern hemisphere terrestrial environments are still restricted to few records and multi proxy methods are rarely applied to the same system here we test the applicability and comparability of temperature reconstructions inferred from different methodological approaches we combined sedimentary cellulose and diatom oxygen isotope data from lake pupuke north island new zealand to derive a record of lake water temperatures this record is complemented with mean annual air temperatures derived from the branched gdgt index mbt measured on the same sedimentary record the datasets of both reconstructions show little temperature variation for the period 1320 7110 cal bp the exceptions are a warmer period culminating between 1700 and 1600 cal bp reflected in both proxies and centennial scale intervals with cooler water temperatures at 3380 and 2750 cal bp recorded in the oxygen isotope based temperature reconstruction but not in the mbt inferred air temperature estimates we suggest that variations in lake circulation are the likely reason for deviations between temperature reconstructed from different proxies

environmental changes and human impact as recorded in a sediment sequence offshore from a viking age town birka southeastern sweden the viking age town of birka which existed between ad 750 and 975 on the island of bjorko in the malar archipelago of the baltic sea is known as the oldest centre used for large scale international trading in sweden birka had a strong defence town rampart hillfort and a water palisade studies of lithology and microand macroremains in a sedimentary sequence accumulated offshore from birka outside the water palisade revealed a stratigraphically distinct refuse stratum referred to as the birka layer we argue that the bulk material of the birka layer emanates from human activities in the town e g latrine cleanings cuttings of shore vegetation cleaning of ditches and storage areas and domestic animal dung organic remains from vegetation and animals deposited during activities on the ice offshore from the town e g winter markets may also have contributed to the composition the material constituting the birka layer started to accumulate after the construction of the protecting water pali

late pleistocene and holocene paleoenvironments of chalco lake central mexico abstract in order to establish paleoenvironmental conditions during the late quaternary four cores from the basin of mexico central mexico were drilled in chalco lake located in the southeastern part of the basin the upper 8 m of two parallel cores were studied using paleomagnetic loss on ignition pollen and diatom analyses based on 11 14c ages the analyzed record spans the last 19 000 14c yr b p volcanic activity has affected microfossil abundances both directly and indirectly resulting in absence or reduction of pollen and diatom assemblages important volcanic activity took place between 19 000 and 15 000 yr b p when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry cold climate during this interval abrupt environmental changes with increasing moisture occurred from 15 000 until 12 500 yr b p the lake level increased and the pollen indicates wetter conditions the highest lake level is registered from 12 500 to ca 9000 yr b p the end of the pleistocene is characterized by an increase in humidity from 9000 until ca 3000 yr b p chalco lake was a saline marsh and the pollen record indicates warmer conditions after 3000 yr b p the lake level increased and human disturbance dominates the lacustrine record

influence of sediment source and type on the magnetic susceptibility of fiord and shelf deposits baffin island and baffin bay n w t volume and mass magnetic susceptibility are measured on recent and late quaternary sediments from the fiords and shelf of eastern baffin island baffin bay and the northern labrador sea major changes in hinterland bedrock geology are associated with order of magnitude changes in magnetic susceptibility the fiords that head into the proterozoic foxe fold belt have mass magnetic susceptibilities ms of 2 4 10 7 m3 kg compared with 25 60 10 7 m3 kg in sediments derived from archean gneisses and granites another low ms region is the middle reach of frobisher bay ms studies in cambridge mcbeth and itirbilung fiords included analyses of surface samples and samples from lehigh 3 m and piston 11 m cores lehigh cores had higher ms values on average than the piston cores suggesting a coarsening in texture or an increase in the flux of magnetic minerals during the last 0 3 3 ka an analysis of the ms logs of 17 piston cores indicated that six broad patterns of ms can be recognized based on a

abrupt environmental oscillations during the early weichselian recorded at lago grande di monticchio southern italy abstract this study presents multi proxy data from a new core from lago grande di monticchio italy extending back to about 100 000 calendar years bp the time scale of this record is independent from deep sea and ice core chronologies and has been established from a combination of varve counts and high resolution sedimentation rate calculations based on microscopic sediment investigation this paper focuses on environmental variability between 100 000 and 65 000 calendar years bp several abrupt cold periods have been recognised and correlated to other terrestrial as well as to ice core and deep sea records the longest of the monticchio cold phases corresponds to marine isotopic stage 5b and lasted from ca 87 000 to 84 000 calendar years bp two shorter events about 1000 years long occurred during the transition from interstadial to full glacial conditions between 79 000 and 75 000 calendar years bp the increased frequency of cold events during this time interval probably indicates a higher degree of climatic instability in periods of major changes dating discrepancies between monticchio grip and deep sea chronologies range between a few hundred to a few thousand years however these differences in dating are not constant but vary significantly for different sections of the records nevertheless the good match of environmental fluctuations at monticchio with atmospheric variability at the greenland summit as well as variations in the oceanic circulation pattern suggests a close link of the mediterranean to the atlantic climate regime

late cretaceous carbon and oxygen isotope stratigraphy nannofossil events and paleoclimate fluctuations in the haţeg area sw romania abstract this study presents carbon and oxygen isotope fluctuations identified in marine red marlstones and claystones of the fizesti formation from the se ha eg area southern carpathians romania biostratigraphy based on calcareous nannoplankton allow the identification of nannofossil standard zones and subzones cc16 cc17 up to cc20 and respectively uc11c up to uc15b indicating that the investigated deposits are latest coniacian late early campanian in age throughout the studied succession 13c values fluctuate between 1 4 and 2 65 while 18o values are between 3 and 4 in the middle santonian within the uc12 calcareous nannofossil zone we found a slight positive carbon isotope excursion with values increasing by 0 3 up to a value of 2 44 which we assume to represent the regional expression of the horseshoe bay event originally recognized in the english chalk in the uppermost santonian just below the first occurrence of the crinoid marsupites testudinarius within the uc13 calcareous nannofossil zone we recorded a 13c increase from 2 38 up to 2 63 correlative with the hawks brow event firstly described in uk the most significant 13c increase identified by us up to 2 63 is coincident with the last occurrence of the crinoid marsupites testudinarius the santonian campanian boundary and represents the regional expression of the worldwide distributed santonian campanian boundary event the santonian campanian boundary is associated with a slight positive excursion for 18o in the lower part of the campanian stage 13c values progressively decrease to around 1 5 a decrease of the water surface temperature in the region is suggested for the lower part of the santonian an assumption based on the significant shift to less negative values of 18o and on the mixed tethyan and boreal character of the identified nannofloras from the santonian campanian boundary interval upwards the temperatures were rising leading to an arid and warm climate in the region this climate mode continued probably into the maastrichtian when the ha eg area became part of an island situated in the northern tethys realm

palaeogeography and geodynamic evolution of the gosau group of the northern calcareous alps late cretaceous eastern alps austria abstract the sedimentation of the late cretaceous gosau group of the northern calcareous alps records the complex geodynamic evolution of the northern part of the austroalpine microplate the tectonically controlled sedimentation and facies distribution were mainly governed by the oblique subduction of the pennic ligurian ocean below the austroalpine margin most of the gosau successions comprise two distinct sedimentary complexes the lower gosau subgroup upper turonian campanian is characterized by terrestrial to shallow marine facies associations alluvial fan and fan delta deposits shallow marine sandstones and sandy limestones and storm influenced nearshore and shelf deposits during the early santonian sea level highstand a great part of the northern calcareous alps was covered by a shallow shelf sea palaeotransport directions point to source areas situated both to the north and to the south of the northern calcareous alps the upper gosau subgroup upper santonian eocene comprises deep water hemipelagic and turbiditic deposits rapid subsidence into bathyal to abyssal depths started diachronously from the northwest santonian to the southeast maastrichtian after a short phase of deformation and erosion abyssal deposits in the northern parts of the northern calcareus alps and north directed palaeotransport indicate a tilting of the slope towards the north this subsidence pulse is attributed to an event of subcrustal tectonic erosion probably triggered by the subduction of a topographic high of the south penninic ocean the relationships of the gosau group of the austroalpine unit to late cretaceous deposits of the carpathians and southern alps are discussed in the framework of a plate tectonic model

using rat gnawed seeds to independently date the arrival of pacific rats and humans in new zealand the pacific rat rattus exulans was transported throughout the south pacific with voyaging humans thus the earliest dated evidence of pacific rat can be used to infer first human contact until recently it was considered that rats arrived in new zealand with humans in the thirteenth century ad however controversial radiocarbon dates on pacific rat bones now suggest that rats reached the remote islands of new zealand with people c ad 50 150 these dates are anomalous because they imply human contact with new zealand more than 1000 years before any archaeological evidence for human presence and precede settlement of tropical eastern polynesia the ancestral homeland of maori the first new zealanders the early rat bone dates are controversial for other technical reasons which have been debated in the literature here distinctive rat gnawed seed cases preserved in sediments are used as a proxy to independently date the arrival of the pacific rat and humans in new zealand this method effectively b

a new interpolation method to measure delta evolution and sediment flux application to the late holocene coastal plain of the argens river in the western mediterranean abstract rapid environmental changes along the mediterranean coasts influenced the sedimentary dynamics shoreline position and human settlements in deltaic areas over the last millennia an innovative and multiproxy approach using geostatistical modelling was developed to estimate geomorphic evolution and sediment fluxes in deltaic areas while palaeoecological conditions and environmental changes were assessed from geochemistry and cluster analyses of molluscan fauna this method was applied to the coastal plain of the argens river in southern france depositional environments of prodelta delta front river channel floodplain marsh and abandoned channel were identified from the study of facies associations the late holocene sediment flux in the argens river bayhead delta ranged from 15 800 2300 to 52 000 8500 m3 yr 1 the highest rate of sediment deposition between 2500 and 2000 cal yr bp was associated with increased river flooding in southeastern france a general decrease in subaqueous sediment flux over the past 2500 years was primarily controlled by a decrease in accommodation space and delta slope from 500 to 0 cal yr bp a sharp increase in subaerial sediment flux probably due to hydroclimatic change was contemporaneous with a period of high flood frequency during the little ice age a southward shift of the north atlantic westerlies combined with either a negative phase of the east atlantic west russian pattern or a negative phase of the east atlantic pattern coupled to a northward migration of the intertropical convergence zone could have led to increased fluvial activity in the lower argens valley during the late holocene

use of electrical conductivity to analyze depositional environments example of a holocene delta sequence on the nobi plain central japan abstract the usefulness of electrical conductivity ec of stirred holocene deltaic sediments from three cores from the nobi plain japan was assessed as a proxy for marine transgression and regression lack of correlation of ec with mud content for the sediments with 20 mud suggested that permeability was a negligible factor marine deposits showed high ec 0 9 ms cm terrestrial deposits low ec

records of southern and central baltic sea eutrophication in δ 13 c and δ 15 n of sedimentary organic matter abstract the baltic sea catchment area has seen considerable agricultural and industrial development over the last century but observational evidence of eutrophication is ambiguous we examined organic carbon accumulation rates and the stable isotope signature of 13 c and 15 n in organic matter in four 210 pb dated short sediment cores from the southern and central baltic sea to search for sedimentary records of increased nutrient input and biological production organic carbon accumulation rates vary little through time in the cores from the oder estuary and the arkona basin but increase significantly in the bornholm basin and in the gotland deep records over the last 40 years 15 n in the sediments show distinct increases over the last 80 50 years in the oder estuary arkona basin and bornholm basin with the greatest increase near the mouth of river oder the gotland deep record shows increasing 15 n values from 1900 to 1975 and decreased 15 n values during the last 20 years the 15 n records are interpreted to trace the effects of eutrophication in nearshore and basinal sediments over the last 100 years and the magnitude of 15 n increase may be a measure for its extent the switch to lower 15 n values in the gotland basin sediment core after initially increasing values coincides with increasing abundance of summer blooms of nitrogen fixing cyanobacteria as observed in monitoring programs 13 c toc values of organic matter increase in the oder estuary over the last 80 years and over the last 30 years in the bornholm basin and gotland basin the tendency to heavier 13 c indicates decreasing isotope fractionation during massive plankton blooms that this effect is not well documented in the sediments of the arkona basin may be due to enhanced degradation processes in the permanently mixed water column a comparison of organic carbon concentrations and 13 c toc and 15 n from early litorina stage around 7 000 years bp and modern sediments from the gotland sea suggests that the trophic state of the baltic sea was comparable to that of the modern environment productivity was nitrate based in spring and based on nitrogen fixation in summer much higher organic carbon concentrations and 13 c enrichment in modern sediments are indications of enhanced productivity compared to early litorina times

documentation of the physical properties of annually laminated varved sediments at a sub annual to decadal resolution for environmental interpretation this paper describes a method to digitize high resolution physical properties of annually laminated lake sediments we modified a water acetone epoxy exchange method in order to preserve all the fine structural details that varved sequences provide by applying sediment microstratigraphical investigations x ray radiography sem and semi automatic image analysis we were able to establish detailed information about varve composition and structure mineral magnetic measurements were also applied for comparison by comparing all available physical data at high resolution it will be possible to identify environmental changes that has occurred in the lake drainage basin

palaeozoic early tertiary tethyan evolution of melanges rift and passive margin units in the karaburun peninsula western turkey and chios island greece

k ar dating of some infra ophiolitic metamorphic soles from the eastern mediterranean new evidence for oceanic thrustings before obduction abstract k ar dating on separated minerals from the infra peridotitic metamorphic soles outcropping beneath various eastern mediterranean ophiolite complexes pindos nappe in greece lycian antalya beysehir hoyran mersin and pozanti karsanti nappes in the taurides belt turkey baer bassit nappe in syria shows that the main metamorphic recrystallization of those rocks occurred 25 30 m y prior to the tectonic emplacement of the ophiolite complexes onto a continental platform these data support the hypothesis of an early slicing of the oceanic crust before its obduction advocated recently by several authors

thin tephra layers in peat revealed by x radiography x radiography has been found to provide a rapid economical non destructive method of locating very thin fine grained tephra of icelandic origin in scottish peats tephra layers form time parallel marker horizons or isochrones that are of great archaeological significance because they cover large areas offer precise chronological control for associated material and occur at times of significant cultural and environmental changes not all of the discrete deposits of recent volcanic fallout in scotland are sufficiently dense to show clearly on x radiographs but those which do provide particularly clear easily located marker horizons with many applications in palaeoenvironmental studies the tephra layer in caithness produced by fallout from a c 4000 by eruption of hekla provides a particularly good example of the use of x radiography to locate volcanic ash the method also reveals other structures of archaeological and palaeoenvironmental significance butler 1992 journal of archaeological science 19 151 161

palaeoenvironmental changes in southern patagonia during the last millennium recorded in lake sediments from laguna azul argentina marked environmental changes in the southern patagonian steppe during the last 1100 years are detected by a multi proxy study of radiocarbon dated sediment cores from the crater lake laguna azul 52805vs 69835vw a prominent shift in carbon isotope records occurred between ad 1670 and ad 1890 induced by a change to cooler climate conditions with a concurrent lake level rise a second perturbation of the lake ecosystem started with a fire event around ad 1830 the fire event triggered increased soil erosion initiating a change of the diatom assemblages this shift in diatom assemblages may have been enhanced by shrinkage of littoral habitats and higher nutrient supply in the course of permanent european settlement at the end of the 19th century the introduction of neophytes by european sheep farmers is confirmed by the permanent occurrence of rumex pollen in the sediment record since the beginning of the 20th century d 2005 elsevier b v all rights reserved

multi proxy evidence of late holocene human induced environmental changes at lake pupuke auckland new zealand abstract new zealand was the last major landmass in the world to be colonised by people despite the short time depth of human presence in the country there is ongoing debate about the date of earliest arrival of people that resulted in the emergence of two contrasting colonisation hypotheses the early hypothesis and the short prehistory to decide between both hypotheses we employed a range of multi proxy investigations geochemistry stable isotopes and mineral magnetism on a lacustrine sequence from lake pupuke a maar lake in the city of auckland and an area potentially among the first places in new zealand to have been colonised by early people the environmental history reconstructed from the multi proxy evidence identified a clear lack of catchment disturbance from c 2000 b p until several decades before the eruption of the rangitoto volcano the nature and abruptness of disturbance unambiguously point to anthropogenic forcings and are likely to mark the onset of prehistoric human colonisation at the site linear interpolation between independently dated tephrochronostratigraphic marker beds present in the sediments allowed to date this event to c 610 cal yr b p this date is in compliance with the short prehistory for this region

tephras and new zealand archaeology establishing an accurate date for earliest polynesian settlement in new zealand is essential for understanding patterns of settlement and associated enviromental impacts and the processes and rates of cultural change in eastern polynesia tephra deposits from five volcanic centres together with exotic sea rafted pumice provide isochronous constraints on the timing of earliest settlement and human impacts in northern new zealand a local basaltic tephra from rangitoto island auckland and locally distributed andesitic tephras from egmont volcano directly date human occupation toc ad 1400 1450 distal andesitic tephras tufa trig formation from mt ruapehu tongariro volcanic centre help constrain the timing of earliest anthropogenic deforestation signals in hawke s bay sea rafted loisels pumice s although of uncertain stratigraphic reliability in places overlies cultural remains that can be no younger thanc ad 1350 along the east coast north island the regionally extensive rhyolitic kaharoa tephra which erupted from okataina volcano between c ad 1300 1390 is the critical settlement layer datum for dating prehistory in the north island no human artefacts are recorded beneath it and the earliest inferred environmental impacts by humans are dated to c ad 1280 just prior to its deposition this maximum date matches the earliest radiocarbon dates derived for both settlement and human impacts from archaeological and natural sites c ad 1250 and implies that the onset of deforestation was essentially contemporaneous with initial settlement the widespread rhyolitic taupo tephra which erupted from taupo volcanoc ad 200 provides an isochronous benchmark well before earliest settlement the tephra may coincide approximately with a putative earlier transient contact in new zealand based on pacific rat bone rattus exulans dates more precise calendrical dates on the tephras via dendrochronology or ice core records or other dating methods would help refine assessment of the timing of earliest settlement while extending the distributional range of critical tephra layers through application of crypto tephra analysis could lead to a greater understanding of settlement patterns

high resolution stable isotope records from the upper cretaceous rocks of italy and spain glacial episodes in a greenhouse planet high resolution 13c and 18o records from upper albian to lower santonian pelagic carbonates of the contessa quarry section in italy exhibit large positive oxygen isotopic excursions of 1 in the lower cenomanian and upper turonian coniacian strata within the uncertainties of biostratigraphic correlation these positive excursions appear to correspond to times of large sea level regressions in global sequence stratigraphic sea level curves several lines of evidence suggest that the major 18o excursions in contessa reflect episodes of global cooling and not differential diagenesis numerical models of oxygen isotope exchange during diagenesis show that a high contrast in the degree of alteration would be required to produce these signals as artifacts of diagenesis and lithological data provide no evidence for such large contrasts in the degree of alteration furthermore although precise correlation with a section in the south of spain is hampered by stratigraphic complexities the general sequence of major positive 18o excursions is reproduced it is unlikely that differential diagenesis would produce similar artifacts in multiple sites one explanation for the link between episodes of global cooling and sea level falls is that global cooling events led to polar ice sheet accumulation lowering sea level although ice free conditions have been inferred from evidence for a much warmer climate in late cretaceous time our results suggest that the relationship between continental high latitude ice sheets and overall climatic warmth warrants further examination

rapid post settlement floodplain accumulation in northland new zealand many river systems within new zealand and globally have experienced rapid acceleration in floodplain sedimentation in response to anthropogenic catchment disturbance creating significant issues i e flooding and water quality reconstruction of past river responses to environmental and anthropogenic driven changes in sedimentation and erosion can provide valuable insights into these river dynamics this research uses lidar data sedimentology radiocarbon chronology xrf analysis and gpr to examine pre and post settlement alluviation of the kaeo river and floodplain sedimentation in northland new zealand in kaeo rapid rates of post settlement floodplain aggradation equating to over 4 m of interbedded sand and silt alluvium in a partly confined valley setting have created considerable contemporary flooding issues radiocarbon dates indicate that terrestrially sourced sedimentation commenced at 7680 7570 cal yr bp and continued at an average rate of 1 mm yr 1 under conditions of limited accommodation space the holocene floodplain has accumulated at a faster average rate 8 13 5 mm yr 1 in the last several hundred years in response to anthropogenic catchment disturbance following m ori and european settlement this response mirrors the general trend for northland floodplains where there has been rapid accumulation of floodplains 3 10 mm yr 1 in the last 1000 yr

holocene river dynamics in northland new zealand the influence of valley floor confinement on floodplain development abstract valley floor mapping sedimentology and 14c dating have been used to reconstruct the fluvial history at eight floodplain sites spread throughout northland a region removed from the main areas of tectonic and volcanic activity in new zealand we present a probability based record of holocene river behaviour for northland using 14c dated holocene fluvial deposits and compare this with independent palaeoclimate proxy records from the north island holocene floodplain evolution and fluvial behaviour have been conditioned by the degree of valley floor confinement in the most and least confined valley settings holocene floodplain evolution has involved the development of a single floodplain surface at partly confined sites the river terrace and floodplain geomorphology are more complex region wide progressive floodplain alluviation through the mid to late holocene and a period of increased river activity between 3500 and 2800 cal ybp in response to climatically driven increases in sediment supply was followed by a period of valley floor incision and terrace formation beginning after 1900 cal ybp in partly confined valley settings this was followed by the aggradation of a lower holocene floodplain surface with rapid rates of vertical accretion in response to post settlement catchment disturbance the results of this study indicate that valley floor confinement has played a major role in controlling northland holocene river floodplain development producing a continuum of floodplain and river terrace landforms in response to climatically and anthropogenically driven variations in sediment flux

reassessing the age of karpathos ophiolite dodecanese greece consequences for aegean correlations and neotethys evolution while the neogene history of the eastern mediterranean region is now fairly well understood our knowledge of older regional palaeogeographies is less accurate especially the positions of blocks and nappes constituting the aegean islands prior to the cenozoic our study focuses on the ophiolite exposed on the island of karpathos dodecanese which is located in the aegean fore arc at a pivotal position between the western and eastern ophiolites of the mediterranean region and where conflicting late jurassic and late cretaceous ages have led to diverging tectonic and palaeogeographic interpretations to test these ages we targeted the radiolarian cherts that depositionally overlie the ophiolite and extracted diagnostic radiolarian assemblages of aptian 125 113 ma early middle albian 113 105 ma and turonian 93 9 89 8 ma ages these results suggest that previous late cretaceous k ar isotopic ages from 95 3 4 2 ma to 81 2 1 6 ma may have been reset by late cretaceous metamorphism or affected by argon loss overall the new early cretaceous ages show that the karpathos ophiolite should not be correlated with the pindos nappes of greece or the ophiolites of cyprus or syria but rather with the lycian nappes of turkey and their root located in the izmir ankara erzincan suture zone therefore the karpathos ophiolite represents a remnant of the northern neotethys not the pindos ocean or the proto eastern mediterranean basin

biochronology of jurassic and early cretaceous radiolarites from the lycian melange sw turkey and implications for the evolution of the northern neotethyan ocean new radiolarian ages for blocks of radiolarian cherts associated with other blocks of distal pelagic facies and ophiolitic lithologies within the lycian melange sw turkey indicate deposition during mid jurassic to early cretaceous time radiolarites overlying pink pelagic limestones of an allochthonous carbonate unit accumulated during the midto late jurassic on the basis of structural evidence the lycian melange is inferred to have been rooted within the northern neotethys to the north of the tauride anatolide microcontinent the lycian radiolarites can be compared with other dated radiolarites from the izmir ankara suture the root zone of the northern neotethyan ocean based on all the available radiolarian data it is inferred that radiolarites accumulated within the northern neotethys in western turkey from late triassic mid carnian to late norian to midcretaceous cenomanian time the radiolarites were later detached from their inferred oceanic basement and accreted within a subduction complex during the late cretaceous turonian maastrichtian and emplaced over the northern margin of the tauride anatolide continent together with slices of continental margin and ophiolitic lithologies following the development of mesozoic radiolarian biostratigraphical schemes during the last 25 years radiolarian biochronology has become invaluable for reconstructing the palaeogeography palaeoceanography and tectonic evolution of tethyan oceanic basins and margins de wever 1989 robertson et al 1991 de wever et al 1994 danelian robertson 1997 2001 radiolarites in the tethyan realm commonly occur within melanges that are interpreted as parts of accretionary prisms related to subduction of ocean crust robertson 2002 2004 radiolarian ages from such melanges provide valuable age constraints on related geological processes including spreading intra plate volcanism and tectonic accretion e g al riyami et al 2001 beccaletto et al 2005 here we will present the first radiolarian evidence from the lycian melange an east west trending late mesozoic accretionary complex in sw turkey collins robertson 1997 fig 1 this melange forms part of the wellknown lycian nappes in sw turkey de graciancky 1972 poisson 1977 1984 collins robertson 1998 the root zone of the melange is considered to lie to the north of the regional basement represented by the tauride anatolide platform collins robertson 1998 2003 and is inferred to lie within the izmir ankara suture zone to the north of the menderes massif robertson pickett 2000 robertson et al 2004 we will also review the limited available data for radiolarites from comparable tectonic units within the izmir ankara suture zone and the bey daglari we conclude by considering the implications of the available radiolarian evidence for the evolution of the mesozoic tethyan ocean

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

magnetic properties of lake sediments from lake chalco central mexico and their palaeoenvironmental implications lake chalco 99 0 w 19 5 n in the basin of mexico was formed during the pleistocene after the emplacement of the chichinautzin volcanic field that closed the former drainage system the lake sediment record has been influenced by a number of factors including glacial interglacial cycles local volcanism erosion of soils and anthropogenic disturbances the magnetic properties of the lake sediments and the associated tephra layers of the last 16500 yr have been studied it is found that the magnetic properties of the lake chalco sediments are very distinctive magnetic concentration varies by a factor of 1000 and magnetic stability also varies over an extremely wide range the predominant magnetic mineral is titanomagnetite in addition to an imperfect antiferromagnetic phase possibly goethite an unusually large range of coercivities is found in certain of the tephras down core variations in magnetic properties closely follow climatic environmental changes previously established by other proxy methods the late pleistocene and late holocene lake sediments display a higher concentration of magnetic minerals than the early middle holocene sediments in the non volcanic sediments fluctuations in the magnetic concentration reflect changes in both the intensity of erosion as represented by ferrimagnetic and paramagnetic minerals and by the maturing of soils as represented by geothite copyright 2000 john wiley sons ltd

paleoenvironmental reconstruction of the semi arid chaco region of argentina based on multiproxy lake records over the last six hundred years abstract in this paper we analyze the paleoclimatic and paleoenvironmental evolution of laguna yema in semi arid chaco region of argentina over the past six hundred years high resolution multiproxy studies of lake sediments utilize analyses of lithology mineralogy geochemistry palynology and are constrained by radiocarbon and gamma spectrometry dating laguna yema sediments were mainly composed of well stratified fine sediments silts and clays with variable proportions of quartz clays illite and feldspar microcline and albite twelve light and heavy geochemical elements were registered most elements al si k ti fe rb ba and br are associated with illite and albite different material transport processes related to the changes in aridity and humidity of the basin were identified using the main mineralogical origins of geochemical elements palynological records indicate cycles of contraction and expansion of the lake with an increase in concentration of alternanthera aquatica during wet periods expansion of lake and an increase in ambrosia poaceae and fern spores during dry periods contraction of lake these changes are linked to fluctuations in moisture conditions in the subandean mountains and semi arid chaco regions in response to interactions between the south american monsoon system sams and the south american low level jet sallj which send warm and humid air to northern argentina in a regional context the laguna yema records are in accordance with the analyses of the temporal and spatial pattern of moisture distribution for the last six centuries

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

extracting a primary holocene crytoptephra record from pupuke maar sediments auckland new zealand post depositional reworking of volcanic glass shards is a common problem in tephrochronological studies distinguishing between primary and reworked tephra is challenging particularly in cryptotephra investigations that depend on identifying peaks of glass shard concentrations in sediment sequences rather than discrete macroscopic tephra layers here we investigated macro and cryptotephra in sediments of lake pupuke new zealand to identify primary from reworked tephra and thus refine the record of tephra fall events in the region over the last ca 9 cal ka geochemical fingerprinting stratigraphic correlation 14c ages and x ray fluorescence and magnetic susceptibility core scanning were employed to filter out reworked tephra and thus establish a new holocene tephrochronological framework for the region five primary macrotephra layers and 18 primary cryptotephra were identified confidence levels are attached to the newly identified cryptotephra and geochemical characterization of well dated rhyolite tephra was used to establish an associated age model our results suggest that holocene tephra fall from both local and distal volcanoes affected auckland more frequently than previously documented with a possible average frequency of at least once every 424 years furthermore the study demonstrates the importance of identifying the extent of post depositional reworking to establish the veracity of the cryptotephra record

characteristics of sedimentary varve chronologies a review abstract we constructed a varve data base vdb to study the worldwide distribution of varved sediment records and the fidelity of their varve chronologies clusters of lakes with varved sediments exist in central north america in the canadian arctic and in northern and central europe among the 108 sites included in the vdb varved records are typically 200 500 cm long and cover a period of 1000 2000 years their varve chronologies are often based on counting of annual layers from fresh sediment surfaces and photographs or from epoxy embedded sediment blocks and thin sections the vdb indicates that chronological errors associated with counting sedimentary varves fall generally between 1 and 3 but only 57 of published records are providing quantitative error estimations for their chronologies with a careful documentation of varves and by applying radiometric dating methods to surface sediments as well as using historical events as time markers there is the potential of having centennial long varved records with a very precise age depth control however it is unrealistic to expect errors significantly below 1 from several millennia long sections we found no indication that varve chronologies would have been substantially more accurate and precise in some parts of the world than in others or statistically dependent on varve thickness or temporal extension of a varved sequence according to the vdb close to 90 of the published varve chronologies have been cross checked with some independent dating methods

obduction subduction and collision as reflected in the upper cretaceous lower eocene sedimentary record of western turkey late cretaceous early eocene tethyan evolution of western turkey is characterized by ophiolite obduction high pressure low temperature metamorphism subduction arc magmatism and continent continent collision the imprints of these events in the upper cretaceous lower eocene sedimentary record of western anatolia are studied in thirty eight well described stratigraphic sections during the late cretaceous period western turkey consisted of two continents the pontides in the north and the anatolide taurides in the south these continental masses were separated by the izmir ankara neo tethyan ocean during the convergence the pontides formed the upper plate the anatolide taurides the lower plate the arc magmatism in the pontides along the black sea coast is biostratigraphically tightly constrained in time between the late turonian and latest campanian ophiolite obduction over the passive margin of the anatolide tauride block started in the santonian soon after the inception of subduction in the turonian as a result large areas of the anatolide tauride block subsided and became a region of pelagic carbonate sedimentation during the campanian the leading margin of the anatolide tauride block was buried deeply and was deformed and metamorphosed to blueschist facies during campanian times the campanian arc volcanic rocks in the pontides are conformably overlain by shaley limestone of maastrichtian palaeocene age however maastrichtian sedimentary sequences north of the tethyan suture are of fore arc type suggesting that although arc magmatism ceased by the end of the campanian age continent continent collision was delayed until palaeocene time when there was a change from marine to continental sedimentation in the fore arc basins the interval between the end of the arc magmatism and continent continent collision may have been related to a northward jump of the subduction zone at the end of campanian time or to continued obduction during the maastrichtian

implications of jurassic chert identified in the tokat complex northern turkey the tokat complex is a strongly deformed tectono sedimentary mixture of low grade metamorphic rocks with abundant recrystallized limestone and relatively rare serpentinite and radiolarian chert in blocks of variable size samples from the radiolarian chert blocks found in highly crushed zones each of which corresponds to a thrust sheet within an imbricate thrust zone have yielded a tithonian fossil assemblage they are interpreted as tectonic inclusions emplaced within the tokat complex after its main post early permian pre liassic metamorphism and were derived from the rifting and opening of a neotethyan ocean the presence of tithonian blocks within low grade metamorphic rocks of the tokat complex shows that tethys ocean was in existence in this region by latest jurassic time we also suggest that the presence of ophiolitic slices imbricated with the pontide basement tokat complex explains the swarm of north anatolian fault zone nafz splays in this region where the nafz likely followed a major pre existing crustal weakness

the beysehir hoyran hadim nappes genesis and emplacement of mesozoic marginal and oceanic units of the northern neotethys in southern turkey the beysehir hoyran hadim nappes crop out over 700 km from nw to se above a regionally autochthonous tauride carbonate platform the beysehir hoyran nappes begin with a thrust sheet c 400 m of mainly redeposited carbonates quartzose sandstones and mudstones of mid late triassic age interpreted as a proximal slope base of slope succession above is a thrust sheet c 1 km of middle upper triassic intermediate acidic extrusive rocks volcaniclastic rocks and minor pelagic carbonates interpreted as a continental rift thin

development of concepts concerning the genesis and emplacement of tethyan ophiolites in the eastern mediterranean and oman regions this article uses evidence mainly from the eastern mediterranean and oman to help understand the origin and emplacement of ophiolites field studies in these regions emphasize the diversity of ophiolite related sedimentary and tectonic processes topics to be discussed here include the sedimentary covers of ophiolites their metamorphic soles related melanges and emplaced continental margin slope rise units modes of ophiolite emplacement will also be considered and tectonic reconstructions that have a direct bearing on the origin and emplacement of ophiolites the writer argues that there is compelling evidence that many ophiolites formed by spreading above intraoceanic subduction zones evidence from their intact sedimentary covers however indicates that such subduction was only incipient in most cases as directly associated volcanic arcs or back arc basins are rare metamorphic soles record fragments of oceanic lithosphere derived from settings ranging from open ocean to continental slope rise settings underlying melanges record the subduction of most of the ocean lithosphere formed at spreading ridges continental margin units beneath ophiolites demonstrate that these ophiolites were formed in ocean basins that were mainly initiated by continental rifting in the eastern mediterranean and oman regions ophiolite emplacement was commonly achieved by trench margin collision although strike slip transpression and large scale accretion along subducting margins played a role in some cases taking account of the mesozoic palaeotectonic setting of the eastern mediterranean region it is widely believed that ophiolites of two main ages mid jurassic and late cretaceous were formed in several small oceanic basins separated by rifted microcontinents the history of tethys in pre mesozoic time remains more open to question lastly giant subduction related ophiolites as in oman cyprus or the balkans may not be forming anywhere in the world ocean today but may instead relate to rare events in earth history when regional to global plate boundaries were drastically reorganised

processes of late cretaceous to late miocene episodic thrust sheet translation in the lycian taurides sw turkey the lycian taurides of sw turkey consist of an allochthonous mesozoic passive margin succession that was episodically detached from its autochthon and translated southeastwards between latest cretaceous to late miocene times a combination of structural analysis sedimentology palaeontology and geochemistry allows subdivision of this orogenic event into 1 latest cretaceous trench passive margin collision causing ophiolite obduction and detachment of the koycegyiz thrust sheet 2 mid late eocene continent continent collision renewing southeastwards thrusting and causing detachment of the teke dere thrust sheet and yavus thrust sheets 3 miocene extensional collapse of the orogen with southeastwards translation of the allochthon coeval with rift basin formation in the hinterland

lycian melange southwestern turkey an emplaced late cretaceous accretionary complex the lycian thrust belt is an important part of the tethyan orogenic belt in the eastern mediterranean region it includes a unit of internally disrupted thin skinned thrust sheets layered tectonic melange and a melange rich in ophiolitic material ophiolitic melange the layered tectonic melange is dominated by mesozoic distal deep water sedimentary rocks and the ophiolitic melange includes disrupted thrust sheets of early mesozoic shallow water limestone and blocks of basalt of both mid ocean ridge and within plate geochemical affinities a complete record of closure of a tethyan oceanic basin began with late cretaceous intraoceanic subduction followed by latest cretaceous trench continental collision and ended with mid tertiary continental collision and orogenic collapse

environmental magnetism past present and future environmental magnetism involves the application of rock and mineral magnetic techniques to situations in which the transport deposition or transformation of magnetic grains is influenced by environmental processes in the atmosphere hydrosphere and lithosphere the first explicit description of environmental magnetism as a distinct field was in 1980 since that time environmental magnetism has become a broad field that is finding application in an ever increasing array of scientific disciplines in this review of the present state of environmental magnetic studies we divide the field into three broad but arbitrary categories the first involves the use of mineral magnetic assemblages in the geological record to study physical processes in depositional environments this category includes the correlation of sediment cores using magnetic susceptibility measurements studies of geomagnetic field behavior the analysis of depositional and postdepositional mechanical processes that affect sediments and the examination of magnetic parameters that might represent proxies for paleoclimatic variation the second category encompasses studies of the processes responsible for variations in the magnetic minerals brought into a sedimentary environment these provenance investigations include studies of changes in catchment derived sediment in lakes fluctuations in contributions from terrigenous aeolian and glaciogenic components in deep sea sediments and the origin of atmospheric particulates the final category addresses in situ changes and transformations of magnetic minerals in sedimentary environments including pedogenesis authigenetic diagenetic formation of ferrimagnetic phases dissolution of magnetic minerals due to reductive diagenesis and contributions of biomagnetism to sedimentary magnetism because environmental magnetism can address problems in so many disciplines and because many of these problems may be inaccessible to other techniques it is likely that the scope of environmental magnetism will continue to expand rapidly environmental magnetism is capable of providing important data for studies of global environmental change climatic processes and the impact of humans on the environment all of which are major research initiatives in the international scientific community these factors suggest that environmental magnetism has a bright and diverse future

annually laminated lake sediments and the study of quaternary environmental changes a review abstract annually laminated lake sediments non glacial varves have in recent years been discovered in increasing abundance especially since the development of in situ freezer samplers so far the majority of examples have been found in three main areas eastern north america northern and central europe and east and central africa a much more widespread distribution seems highly probable however the formation of annual laminations in freshwater lakes is governed by a number of factors the most important of which appears to be morphometry seasonality of sediment supply which may be controlled by physical biological or even cultural processes in the lake or in its catchment is also clearly significant four main types of laminations here termed ferrogenic calcareous biogenic and clastic have so far been recorded although it is quite clear that others exist special field and laboratory techniques are needed in order that the particular properties of varved sediments may be fully exploited annually laminated sediments have so far been applied to the investigation of a number of aspects of the quaternary these include the study of a geochronology b climatic change c vegetation history especially the role of fire in forest ecosystems d the calculation of rates of sediment influx to lakes and of rates of erosion from their catchments and e the monitoring of processes in the modern environment such as heavy metal pollution eutrophication and acid rain annually laminated lake sediments combine an internal independent chronology with the preservation of discrete visible increments of seasonal and annual sedimentation given this unique property and the likelihood that many more examples will be discovered the prospects for further applications of studies of these sediments to the investigation of the quaternary seem very good indeed

neotethyan evolution of eastern greece pagondas melange evia island inferred from radiolarian biostratigraphy and the geochemistry of associated extrusive rocks this paper presents new radiolarian biostratigraphic and igneous metamorphic geochemical data for a mesozoic volcanic sedimentary melange on the island of evia euboea or evvoia eastern greece this melange includes dismembered thrust sheets and blocks of radiolarian chert and basalt biostratigraphic age data show that radiolarites interbedded with basalt derived coarse clastic sediments near the base of a coherent succession were deposited in middle and late triassic time late ladinian carnian norian geochemical evidence shows that associated extrusive rocks of inferred triassic age range from enriched alkaline basalts to transitional basalts and more depleted mid ocean ridge type basalts amphibolite facies meta basalts from the metamorphic sole of the over riding evia ophiolite exhibit similar chemical compositions both the basalts and the meta basalts commonly show an apparent subduction related influence e g relative nb depletion that may have been inherited from a previous subduction event in the region the basalts are interpreted to have erupted during middle late triassic time late ladinian carnian related to initial opening of a neotethyan ocean basin adjacent to a rifted continental margin radiolarites located stratigraphically higher in the coherent succession studied are dated as middle jurassic late bathonian early callovian similar aged radiolarites are depositionally associated with ophiolitic rocks including boninites in some other areas of greece and albania during initial ocean basin closure bajocian bathonian the adjacent shallow water carbonate platform pelagonian zone disintegrated to form basins in which siliceous sediments were deposited and highs on which shallow water carbonates continued to accumulate this facies differentiation is seen as a response to crustal flexure as the neotethyan ocean began to close the over riding pagondas melange and other similar units in the region are interpreted as accretionary prisms related to subduction of neotethyan oceanic crust in middle late jurassic time these melanges were emplaced probably diachronously during oxfordian kimmeridgian time when the passive margin collapsed creating a foredeep ahead of advancing thrust sheets of melange and ophiolites

continental climate response to orbital forcing from biogenic silica records in lake baikal changes in insolation caused by periodic changes in the earth s orbital parameters provide the primary forcing for global ice ages1 6 but it is not clear to what extent the climates in continental interiors are controlled directly by regional variations in insolation and to what extent they are driven instead by the highly nonlinear response of the oceans and ice sheets here we investigate this question using the record of biogenic silica in lake baikal as a proxy for climate change in this high latitude mid continental region we find a good correlation between this record and that of marine oxygen isotopes4 over the past 250 kyr the baikal record exhibits both a strongly nonlinear component manifested in a 100 kyr periodicity and weaker direct insolation components manifested in the 41 kyr obliquity and 23 and 19 kyr precession orbital cycles these results show that even though extreme continental climates such as this are influenced directly by insolation variations they are dominated by the nonlinear rhythm of the oceans and ice sheets

carbon and oxygen isotope stratigraphy of the english chalk and italian scaglia and its palaeoclimatic significance a detailed carbon and oxygen isotope stratigraphy has been generated from upper cretaceous coastal chalk sections in southern england east kent culver cliff isle of wight eastbourne and seaford head sussex norfolk coast and the british geological survey bgs trunch borehole norfolk data are also presented from a section through the scaglia facies exposed near gubbio italian apennines wherever possible the sampling interval has been one metre or less both the chalk and scaglia carbon isotopic curves show minor positive excursions in the mid cenomanian mid and high turonian basal coniacian and highest santonian lowest campanian there is a negative excursion high in the campanian in chalk sections that span that interval the well documented cenomanian turonian boundary spike is also well displayed as is a broad positive excursion centred on the upper coniacian a number of these positive excursions correlate with records of organic carbon rich deposition in the atlantic ocean and elsewhere the remarkable similarity in the carbon isotope curves from england and italy enables cross referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the turonian coniacian and santonian stages the oxygen isotope values of the various chalk sections although showing different absolute values that are presumably diagenesis dependent show nonetheless a consistent trend the east kent section which is very poorly lithified indicates a warming up to the cenomanian turonian boundary interval then cooling thereafter regional organic carbon burial documented for this period is credited with causing drawdown of co 2 and initiating climatic deterioration inverse greenhouse effect data from other parts of the world are consistent with the hypothesis that the cenomanian turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth

late holocene climate variability from lake pupuke maar auckland new zealand abstract spectral analyses of quasi annual organo diatomaceous laminae couplets in an auckland maar lake indicate brief sub decadal scale episodes with strong spectral power and long periods of weak to no spectral power between c 1700 to c 550 cal yr bp laminae couplet thickness appears to be a function of changes in wind flow over the basin with enhanced wind flow deepening the mixing zone and providing additional nutrients for laminae formation aeolian dust from australia amplifies the wind signal spectral signals in the high power episodes are focused in

relationship of environmental changes in central sri lanka to possible prehistoric land use and climate changes abstract a radiocarbon dated pollen analysed peat sequence from the horton plains 2000 m a s l in central sri lanka together with physical and chemical parameters organic carbon mineral magnetics carbon isotopes and phytoliths indicates major environmental changes during the last 24 000 years the results suggest that a mobile life form i e a hunter forage culture predominated in an open landscape associated with xerophytic vegetation e g chenopodium spp at 17 5 ka bp incipient management of cereal plants and slash and burn techniques seem to have prevailed between 17 5 and 13 ka bp which was indigenous and associated with grazing evidence of systematic cereal cultivation in the form of oat and barley pollen grains is found from the late pleistocene 13 ka bp this is the earliest evidence of farming activities noted in sri lanka as well as in south asia after 13 ka bp cereal cultivation was associated with an increase in humidity with a later abrupt increase in aridity agricultural land use decreased from 8 to 3 6 ka bp when the area appears to have been almost deserted after a severe middle holocene arid phase i e 5 4 3 6 ka bp the agricultural activity with a limited extension was again initiated by 2 9 ka bp during the next 900 years cultivation ceased allowing the upper montane rain forest to dominate between 0 2 and 0 15 ka bp new phases of agricultural activities were undertaken and potato cultivation took place lately between 1950 and 1969 ad

biostratigraphic data from the cetmi melange northwest turkey palaeogeographic and tectonic implications abstract the cetmi accretionary melange is cropping out in the biga peninsula of northwest turkey it is characterised by an isolated position relatively far from the accretion complexes of the nearest suture zones which raises the question of its lateral correlations a detailed biostratigraphic investigation of the limestone and radiolarite blocks and the matrix of the cetmi melange allowed to propose a solution for this palaeogeographic problem scarce red nodular limestones in the han bulog facies represent the oldest lithology in the melange their late scythian ladinian age is based on chiosella gondolleloides the co occurrence of gladigondolella sp and nicoraella cf kockeli and paragondolella fuelopi light grey limestone blocks are a characteristic feature of the cetmi melange they occur in two distinct facies facies a consists of packstone to grainstone and is characterised by unsorted and poorly washed pelbiosparites facies b consists of wackestone to packstone and is characterised by poorly washed biopelmicrites to biopelsparites the foraminiferal assemblage of facies a containing triasina hantkeni is of late norian to rhaetian age the foraminiferal assemblage of facies b never contains t hantkeni and is characteristic of a late triassic carnian to norian rhaetian age radiolarian cherts are widely distributed in the cetmi melange they record fully pelagic sedimentation from the upper bajocian to the aptian the matrix of the cetmi melange consists of brown to black shales sometimes silty or siliceous intercalated with dark grey greywackes palynomorphs of one sample of brownish silty shale yielded an early to middle albian age based on the co occurrence of several dinoflagellate cysts the age of the matrix representing the youngest lithology within the melange and of the unconformable overlaying section latest albian cenomanian indicate that the melange forming process stopped between the early albian and the latest albian cenomanian at a regional scale the cetmi melange has little in common with the melanges from the izmir ankara and intra pontide sutures of northwestern turkey precluding a direct correlation on the other hand the cetmi melange shares several characteristics with the melange like units of the eastern rhodope zone bulgaria and greece like a major cenomanian transgression the reworking of triassic limestones and middle jurassic lower cretaceous radiolarians and the absence of jurassic cretaceous passive margin lithologies the occurrence of rhodopian units on the biga peninsula suggests that the studied units represent an isolated fragment of the rhodope zone in nw turkey

radiocarbon age of the kaharoa tephra a key marker for late holocene stratigraphy and archaeology in new zealand the kaharoa eruption the most recent rhyolitic volcanic event in new zealand resulted in the deposition of the compositionally distinctive kaharoa tephra over at least 30 000 km2 of northern and eastern north island the tephra forms an isochronous marker bed for various late holocene stratigraphic and palaeoen vironmental studies but is particularly important for evaluating the chronology of new zealand s notably short prehistory because it was erupted within the last millennium close to the time of first polynesian colonization we derive a definitive radiocarbon age previously ambiguous for the kaharoa tephra of 665615 bp using cluster analysis of 22 radiocarbon ages relevant to the kaharoa eruptive episode the error weighted mean age obtained on unscreened ages minus outliers is supported by statistically identical ages obtained from three sets of screened ages selected to minimize the effects of inbuilt age or contamination based on the intercepts method and 1 sigma range of northern hemisph

the use of mineral magnetic analyses in identifying middle and late holocene agriculture a study of peat profiles in smaland southern sweden a transect of profiles from the bratamossen bog near the village of axlarp in the province of smaland southern sweden was investigated with respect to magnetic properties human impact pollen indicators and loss on ignition the bog is situated close to an area with clearance cairns an indication of abandoned arable fields there are also graves from the bronze age and the early iron age close to the bog a variety of analytical methods were used to reconstruct the land use history of this area since c 6000 14 c years bp while pollen analysis was used to detect changes in vegetation the magnetic analyses reflected how the soils in the landscape were affected by these changes the pollen analysis showed that the area became deforested and that forest vegetation was succeeded by pasture and arable land magnetic analyses indicated soil erosion as a consequence of agricultural activity the conventional technique of determining the minerogenic content by loss on ignition yielded no valuable information

cortex a shipboard xrf scanner for element analyses in split sediment cores abstract the cortex corescanner texel is a non destructive xrf system for the logging of split sediment cores it is a seaworthy instrument that remains active during heavy weather conditions the scanner produces reliable counts for k to sr highly correlated with concentrations measured with atomic absorption spectrometry aas the option to scan al si and elements heavier than sr is in preparation a core section of 1 m can be scanned at 2 cm intervals within an hour a maximum resolution of 1 mm can be achieved at present each region and sedimentary environment requires separate calibration in the nearby future the generator settings will be standardized which may result in the development of a standard calibration procedure because of the high resolution of its semi quantitative records the cortex is a useful tool for detailed time series analysis inter core correlation and shipboard analysis

the palaeoenvironments of coastal lagoons in the southern baltic sea i the application of sedimentary corg n ratios as source indicators of organic matter abstract c n ratios of organic matter sources in coastal lagoons and their drainage areas in the southern baltic sea region are investigated to determine the origin of organic matter i e terrigenous or marine in the sediments of the lagoons these ratios are compared with 13c values in the area terrestrial plants in the study area show c n ratios between 10 and 85 whereas aquatic macrophytes have values in the range of 6 to 44 peat and shore vegetation have c n ratios between 15 and 16 and plankton shows values close to 6 in conjunction with 13c values the c n ratios in the sediments allow the reconstruction of the holocene palaeoenvironments and palaeoecology in the lagoons oder estuary and greifswalder bodden distinct stages in the development of the water bodies resulting from sea level changes in the region can be derived post glacial lake stages with sandy sedimentation lacustrine phases with high autochthonous productivity terrestrial stages with peat formation sedimentation as a result of marine transgression and brackish sedimentation after the formation of sand spits and barrier islands the application of corg ntot ratios instead of corg norg does not have any significant influence on the interpretation of the data and may thus be used in the coastal sediments of the southern baltic sea after having applied the test procedures presented in this study

radiolarian evidence for the stratigraphy and palaeo oceanography of the deep water passive margin of the indian plate karamba formation indus suture zone ladakh himalaya abstract new radiolarian biostratigraphical information sheds light on the mesozoic sedimentary tectonic and palaeoceanographic evolution of a south tethyan margin in northern india radiolarian cherts studied here form part of deformed deep water successions within the indus suture zone ladakh himalaya these are defined as the karamba formation and interpreted as the stratigraphically higher and palaeogeographically more distal parts of a passive margin lamayuru group this formation includes radiolarites pelagic carbonates redeposited limestones ferruginous shales sandstones and abundant mafic extrusive rocks radiolarian assemblages of early and late middle jurassic mid cretaceous mid albian to cenomanian and late cretaceous santonian age were obtained from four measured sequences results indicate i long intact jurassic cretaceous successions rather than disrupted melange are present in the karamba formation ii extensive basic volcanism took place during the middle jurassic and can be correlated with an extensional phase affecting the nw indian continental margin iii non calcareous radiolarian rich sediments accumulated during the middle jurassic reflecting the influence either of a broad jurassic equatorial upwelling zone or a more localised coastal upwelling system after drowning of the zanskar clastic shelf in the late albian sedimentation on the distal shelf and upper slope was restricted by bottom current activity late albian cenomanian radiolarites of the karamba formation are contemporaneous with stratigraphie gaps and glauconite phosphorite deposition on the zanskar shelf a well developed eastward boundary current off the northern margin of india may have persisted until near the end of the late cretaceous during the late albian cenomanian current activity and coastal upwelling were probably strong and radiolarian rich sediments accumulated on the distal margin beneath the ccd pelagic limestones accumulated during the turanian over the entire margin possibly related to eustatic sea level rise and consequent reduction in bottom current activity intense oceanic circulation apparently was renewed during the coniacian santonian as indicated by sedimentary hiatuses in the zanskar shelf succession and accumulation of carbonate free radiolarian ooze in the karamba formation

structure and petrology of tauride ophiolites and mafic dike intrusions turkey implications for the neotethyan ocean cretaceous neotethyan ophiolites occur in four east west trending subparallel zones within the tauride tectonic belt in southern turkey the ophiolites of the inner intermediate and outer zones tectonically overlie the mesozoic platform carbonates of the tauride belt and are commonly underlain by a cenomanian ophiolitic melange these ophiolites consist mainly of tectonized mantle rocks mafic ultramafic cumulates and gabbros and commonly lack sheeted dike complexes and extrusive rocks of a complete ophiolite sequence metamorphic soles that are several hundred meters thick occur as thrust faulted slices beneath these ophiolites and show well developed metamorphic field gradients ophiolitic units and the metamorphic soles are intruded by mafic dike swarms that are truncated at the contact with the underlying melange unit dike rocks are made of subalkalic basalt to andesite typical of evolved island arc tholeiites they display large compositional variations with sio 2 content between 50 and 60 wt and mgo between 8 and 4 wt and contain higher ti augite phenocrysts and significantly less calcic plagioclase than their host cumulates the majority of the analyzed dike rocks show a slight depletion in light rare earth elements ree with low la smn ratios and are depleted in both high field strength hfs and heavy rees while enriched in large ion lithophile elements lile relative to normal mid ocean ridge basalt morb these characteristics suggest a mantle source that underwent previous melt extractions and subsequent metasomatism by lile and light ree enriched fluids geochemical modeling of trace elements shows that melting occurred at relatively low pressures under hydrous conditions and that it may have required the existence of an asthenospheric window in which the dike magmas developed through tapping and mixing of melts generated within a rising melting column starting slightly within the garnet stability field or in a transitional zone between the garnet and spinel stability fields at about 60 km depth this asthenospheric window was probably created during subduction of a neotethyan ridge system magmas ascending from the melt column within this window generated dikes that crosscut the metamorphic soles and were injected into the overlying mantle wedge and oceanic lithosphere the new 40 ar 39 ar hornblende dates of 92 90 ma and 90 91 ma from the metamorphic soles and dike swarms respectively show that evolution of these two geologic units was closely related in time and space and that they formed at the same intraoceanic subduction zone within the inner tauride seaway these data suggest that the tauride ophiolites within the three zones to the north originated from the same root zone situated north of the tauride carbonate platform and that they constitute remnants of a single ophiolitic nappe sheet derived from the inner tauride seaway within the neotethyan ocean

production sedimentation and isotopic composition of organic matter in lake ontario organic matter and its carbon and nitrogen isotopic composition were measured in sequential sediment trap and core samples from the rochester basin of lake ontario to evaluate their usefulness in reconstructing historic changes in lake productivity the greatest flux of organic matter from the epilimnion occurred during late summer and coincided with whiting events indicating that calcite precipitation is an effective mechanism for sedimenting organic matter carbon isotopes of organic matter were low prior to the onset of stratification increased to maximum values in late summer and then decreased following fall overturn this pattern is controlled mainly by the timing of stratification and primary productivity which preferentially removes 12co2 from the epilimnion the physiological effect of decreased carbon isotopic fractionation with decreasing supplies of co2 aq may have also contributed to increased 13corgc nitrogen isotopes showed a seasonal pattern opposite to that of carbon whereby 15n values were low during the summer stratified period and high for the remainder of the year seasonal variability in 15norgn probably reflects changes in the source of sedimented organic particles which is dominated by isotopically depleted phytodetritus during the stratified period and isotopically enriched organic matter from heterotrophic or detrital sources during the mixed period a comparison of organic carbon accumulation rates and 13corgc between sediment cores collected in 1987 and 1993 1994 confirms earlier predictions that diagenetic processes reduce the mass accumulation of organic carbon in the zone of oxic pore waters but will not change the 13corgc values all cores analyzed for 13corgc display the reproducible pattern of a progressive increase in the 19oos peaking in the early to mid 1970s and then decreasing to the present this pattern matches the historical trends of phosphorus loading to the basin suggesting that 13c of organic carbon is a reliable proxy for paleoproductivity and responds to spring phosphorus supplies in the water column the 15n of sedimentary organic matter increased linearly from 1840 to 1960 at a rate of 0 3ppt per decade and remained relatively constant thereafter except for an increase in the upper few centimeters of sediment the increase in 15norgn reflects a combination of factors including early forest clearance by europeans increased sewering by municipalities after 1940 and increased nitrate utilization as productivity increased in the lower great lakes increased rates of denitrification in the central basin of upstream lake erie from the 1930s to the early 1970s may have also contributed to the rise in 15norgn values

natural and human induced environmental changes preserved in a holocene sediment sequence from the etoliko lagoon greece new evidence from geochemical proxies abstract a key feature of greece is the large amount of historical and archaeological records the sedimentary record of the etoliko lagoon aetolia western greece offers an ideal opportunity to study human environment interaction and to disentangle natural and anthropogenic imprints in the sedimentary record by applying an interdisciplinary approach of combining geoscientific methods xrf loi grain size analysis with archaeological and historical records the 8 8 m long sedimentary sequence eto1c reveals the palaeoenvironmental history of the lagoon and its catchment since 11 670 cal bp with a thorough chronology based on 14 c age depth modelling including varve counting different evolutionary stages were put in a chronological context these stages include a lake period 11 670 8310 cal bp followed by a period of sporadic saltwater intrusion 8310 1350 cal bp as a result of continuing transgression phases of limnic predominance associated with freshwater inflow of episodically activated distributaries around 5230 cal bp still occurred by 1350 cal bp ongoing sea level rise had connected the lagoons of etoliko and messolonghi and freshwater influence had ceased with the onset of settlement activity in the late helladic 1700 1100 cal bc humans took advantage of the prevailing environmental landscape a sudden increase in coarse sedimentation correlates with the history of human occupation with its peak of prosperity from the late helladic until the end of the hellenistic period 30 cal bc

dating initial maori environmental impact in new zealand abstract over the last decade there has been an intense debate as to whether new zealand prehistory is long 1500 yr short

the late quaternary vegetational and climatic history of easter island easter island occupies an exceptionally isolated position in the south pacific ocean it is entirely volcanic and is famous for its giant statues late quaternary sediments have been investigated in three craters rano raraku rano aroi and rano kao giving a continuous record over the past 30 ka pollen records indicate that the island was formerly forested palynological and sedimentological evidence suggests a late pleistocene climate slightly cooler and drier than the present deforestation by people occurred mainly between 1200 and 800 yr bp this may have led to an ecological disaster and to the decline of the megalithic civilization the depauperation of the present native flora owes more to human activity than to isolation

radiolarian biochronology of mesozoic deep water successions in nw syria and cyprus implications for south tethyan evolution new radiolarian biostratigraphical data have shed light on the mesozoic tectonic evolution of south tethys in the baer bassit region of nw syria radiolarian assemblages of late triassic middle jurassic and early cretaceous age were extracted from radiolarites in five measured sections the results are compared with published radiolarian ages from the mamonia complex western cyprus these two areas are interpreted as preserved fragments of the conjugate margins of a small south tethyan oceanic basin formed by triassic rifting in the southerly i e arabian margin proximal successions were dominated by shallow water derived carbonate whereas distal successions reveal seamount type alkaline peralkaline volcanism dated as both late triassic and middle jurassic early cretaceous along the inferred northern margin i e western cyprus proximal successions are dominantly terrigenous whereas distal settings include late triassic oceanic crust and seamount type lavas

late cretaceous campanian carbon isotope events sea level change and correlation of the tethyan and boreal realms abstract carbon stable isotope stratigraphy provides unique insights into environmental change during the campanian the longest 83 5 71 3 ma but least well understood stage of the late cretaceous a new carbon isotope 13c profile for a 500 m thick campanian basal maastrichtian tethyan pelagic hemipelagic section near el kef northern tunisia is calibrated using data from a biostratigraphically well constrained succession at kalaat senan the general shapes of the tunisian 13c reference curve and published tethyan 13c profiles from elles tunisia and bidart sw france and a boreal curve for the trunch borehole eastern england are remarkably similar in all three areas a positive carbon isotope event of 0 2 13c in the mid campanian dated at 78 7 ma and a negative excursion of 0 4 in the upper campanian at 74 8 ma can be correlated between tunisia and england a positive excursion of 0 3 at 83 7 ma spans the santonian campanian boundary these isotope events enable precise inter regional correlations that are consistent with published nannofossil data review of campanian sea level data from north africa the middle east and northern europe indicates that major shifts in 13c profiles coincide with changes in eustatic sea level relatively stable 13c values in the lower campanian and their long term fall through the upper campanian reflect high and then falling eustatic sea levels and increased carbonate production short term 600 kyr positive excursions record greater organic productivity and or organic matter preservation and decreased carbonate fluxes during periods of rapid sea level rise and the drowning of carbonate platforms excursions were terminated by falling nutrient supply and increased carbonate deposition associated with epicontinental sea expansion and renewed carbonate platform growth during the late transgression and highstand negative excursions are linked principally to reworking of marine and terrestrial organic matter during rapid sea level fall carbon isotope stratigraphy is a powerful tool for correlation which can be used to test the validity of campanian global biostratigraphic frameworks and improve our understanding of the nature and timing of late cretaceous sea level change

preservation of organic matter and alteration of its carbon and nitrogen isotope composition during simulated and in situ early sedimentary diagenesis abstract the carbon and nitrogen isotope composition of organic matter has been widely used to trace biogeochemical processes in marine and lacustrine environments in order to reconstruct past environmental changes from sedimentary organic matter it is crucial to consider potential alteration of the primary isotopic signal by bacterial degradation in the water column and during early diagenesis in the sediments in a series of oxic and anoxic incubation experiments we examined the fate of organic matter and the alteration of its carbon and nitrogen isotopic composition during microbial degradation the decomposition rates determined with a double exponential decay model show that the more reactive fraction of organic matter degrades at similar rates under oxic and anoxic conditions however under oxic conditions the proportion of organic matter resistent to degradation is much lower than under anoxic conditions within three months of incubation the 13c of bulk organic matter decreased by 1 6 with respect to the initial value the depletion can be attributed to the selective preservation of 13c depleted organic compounds during anoxic decay the 15n values continuously decreased to about 3 below the initial value the decrease probably results from bacterial growth adding 15n depleted biomass to the residual material in the oxic experiment 15n values increased by more then 3 before decreasing to a value indistinguishable from the initial isotopic composition the dissimilarity between oxic and anoxic conditions may be attributed to differences in the type timing and degree of microbial activity and preferential degradation in agreement with the anoxic incubation experiments sediments from eutrophic lake lugano are on average depleted in 13c 1 5 and 15n 1 2 with respect to sinking particulate organic matter collected during a long term sediment trap study

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

a 750 year fire history based on lake sediment records in central yellowstone national park usa a 750 year fire history was reconstructed for the central plateau of yellowstone national park from the deep water sediments of five lakes the charcoal record from a large lake provided a chronology of regional fires data from four small lakes were used to study local and extralocal fires the co occurrence of abundant charcoal and high magnetic susceptibility values at the same stratigraphic level was used as evidence of a local catchment fire and a charcoal peak without high magnetic susceptibility was ascribed to an extralocal fire or a local fire without a related erosion event the fire history was compared with the dendrochronologic fire record for the last 450 years and the close agreement provided the justification to extend the chronology back in time large areas of the region burned in ad 1988 c 1700 c 1560 and c 1440 from c 1220 to 1440 and c 1700 to 1987 intermediate to small areas burned the near absence of fires in the twentieth century prior to the large fires of 1988 is evi

lacustrine varve formation through time abstract studies using sediment traps in lakes reveal that the seasonal flux of sediment regulates both the composition and timing of deposition of materials that reach the bottoms of lakes if the bottom waters of a lake are partly or totally anoxic the seasonally deposited materials are preserved as annual groupings of laminae varves common components that form individual laminae consist of allochthonous clastic material derived from the drainage basin precipitated carbonate minerals diatom frustules iron rich and manganese rich flocs autochthonous organic detritus and autochthonous and allochthonous materials resuspended from the bottom the style of varving has changed over geologic time reflecting changes in biologic evolution and types of materials available precipitated iron rich laminations were common in the middle precambrian graded sets of clastic organic laminations persisted through the precambrian prior to the evolution of bioturbating benthic organisms glaciolacustrine varves appear to have retained their distinctive character through time carbonate rich varves occurred sporadically in the precambrian and phanerozoic with the exception of diatoms major components of modern lacustrine varves were present through the paleozoic and mesozoic and yet varves are rare in strata of these ages and may have accumulated in marine to brackish water environments diatoms were introduced into lacustrine systems in early tertiary time and are common components of varves from then on diatom laminae combined with a greater chance for geologic preservation of younger lake deposits have increased the number of geologically young occurrences of varved sediments however seasonal associations of modern varve components and the processes they represent are present in ancient deposits and provide clues to the interpretation of ancient environments

testing models of late palaeozoic early mesozoic orogeny in western turkey support for an evolving open tethys model field evidence from north south transects tests three tectonic models for tethys in western turkey for when a late palaeozoic ocean was closing and an early mesozoic ocean opening in model 1 a palaeozoic ocean subducted southwards rifting continental fragments from gondwana and opening a triassic neo tethys to the south closure and collision occurred by latest triassic time in model 2 a wide palaeozoic tethys subducted northwards with an active eurasian margin and a passive gondwana margin the northern gondwana margin rifted in the triassic fragments either remained nearby taurides or drifted northwards e g karakaya attached to a north subducting plate new oceanic crust replaced palaeo tethys with neotethys and back arc marginal basins opened along the south eurasian margin e g kure in model 3 a palaeozoic ocean also subducted northwards opening wide marginal basins a wide southern neotethys opened along the gondwana margin rifted eurasian anatolides and gondwana taurides fragments collided in mid tethys by latest triassic time field evidence from the pontides supports north dipping subduction models model 2 or 3 above key features are a south vergent hp lt accretionary prism magmatic arc and back arc basin system bordering the eurasian margin also evidence from the tauride mountains favours model 2 over model 3 critically the anatolides and taurides appear to have a common history and were unlikely to have been located on opposite sides of tethys as in model 3

lacustrine responses to tephra deposition examples from mexico one of the major problems with palaeoclimate investigations in volcanic regions is that tephra inputs to lakes can cause changes in proxies analogous to those of climate forcing we review the range of impacts thought to be associated with tephra deposition distinguishing between direct effects on lake ecosystems and indirect changes to catchment nutrient cycles to achieve better understanding of these complex responses we have used high resolution diatom analysis from around 17 tephra layers in three mexican lakes a positive response to the tephra inputs has been identified for over half of these layers the most common response was for diatom concentrations to increase after tephra deposition also in plankton dominated systems fragilaria spp replaced stephanodiscus spp and aulacoseira spp an increase in the supply of silica to the lakes through their catchments is probably the cause of the diatom changes in the lakes studied direct effects of the tephra inputs to these lakes can be excluded as they would not generate changes of sufficient longevity the impact of these tephras which lasted for several decades was insufficient to perturb the underlying long term climate forcing of these lake systems c 2004 elsevier ltd all rights reserved