magnetic properties of variably serpentinized peridotites and their implication for the evolution of oceanic core complexes serpentinization of ultramafic rocks during hydrothermal alteration at mid ocean ridges profoundly changes the physical chemical rheological and magnetic properties of the oceanic lithosphere there is renewed interest in this process following the discovery of widespread exposures of serpentinized mantle on the seafloor in slow spreading oceans unroofing of mantle rocks in these settings is achieved by displacement along oceanic detachment faults which eventually results in structures known as oceanic core complexes occs however we have limited understanding of the mechanisms of serpentinization at the seafloor and in particular their relationship with the evolution of occs since magnetite is a direct product of serpentinization the magnetic properties of variably serpentinized peridotites can provide unique insights into these mechanisms and their evolution in the oceanic lithosphere here we present new results from an integrated rock magnetic paleomagnetic and petrological study of variably serpentinized peridotites from the first fossil occ recognized in an ophiolite integration with existing data from mid ocean ridge related abyssal peridotites recovered from several scientific ocean drilling sites yields the first magnetic database from peridotites extending across the complete range 0 100 of degrees of serpentinization variations in a range of magnetic parameters with serpentinization and associated paleomagnetic data provide i key constraints on the mechanism s of serpentinization at mid ocean ridges ii insights on the potential for serpentinized peridotites to contribute to marine magnetic anomalies and iii evidence that leads to a new conceptual model for the evolution of serpentinization and related remanence acquisition at occs

origin and emplacement of an inferred late jurassic subduction accretion complex euboea eastern greece in northern euboea central eastern greece an up to 3 km thick polygenetic melange pagondas complex is structurally interleaved between a triassic jurassic carbonate platform pelagonian zone and an overriding harzburgitic ophiolite the melange mainly comprises late triassic shallow water limestone and calciturbidites radiolarites triassic jurassic tholeiites alkaline basalts and minor andesites the units concerned range from kilometre sized thrust sheets and detached blocks to broken formation and structureless or bedded matrix supported conglomerates diamictite the melange includes remnants of neotethyan oceanic lithosphere overlain by radiolarites hemipelagic carbonates and distal calciturbidites derived from a mesozoic carbonate platform tholeiites were erupted at a triassic jurassic spreading axis whilst within plate type alkali basalts are interpreted mainly as seamounts kilometre scale detached blocks of shallow water coralline limestone are identified as collapsed atolls formed within an ocean and or along the rifted continental margin volcaniclastic sediments are locally interbedded with radiolarite and reflect post volcanic erosion of the ocean floor intra oceanic convergence began apparently in late early jurassic time giving rise to the euboea ophiolite above an inferred westwards dipping subduction zone the pagondas complex then developed as an accretionary prism the subduction trench later collided with the pelagonian passive margin driving the hot euobea ophiolite over the accretionary complex to produce amphibolites and greenschists of the metamorphic sole trench margin collision then drove the entire supra subduction zone complex apparently eastwards downflexing the pelagonian carbonate platform to form a foredeep in which late jurassic kimmeridgian tithonian radiolarian sediments accumulated during emplacement the accretionary complex was disrupted and partly resedimented as debris flows turbiditic volcaniclastic sandstone and shale in a foredeep or foreland basin setting

possible giant metamorphic core complex at the center of artemis corona venus hundreds of circular features on venus known as coronae are characterized by annular fractures and commonly associated radial fractures and lava flows coronae are thought to have been produced by buoyant mantle diapirs that flatten and spread at the base of the lithosphere and cause fracturing uplift and magmatism the interior of artemis corona by far the largest corona at 2100 km diameter is divided in half by a northeast trending deformation belt that contains numerous rounded ridges resembling antiforms the largest of these ridges located at the center of artemis corona is 5 km high on its steep northwest flank where it is adjacent to a flat bottomed 10 km wide trough interpreted as a rift valley the 280 km long antiformal ridge is marked by perpendicular grooves that cross the 50 km wide ridge and extend southeastward as far as 120 km across adjacent plains the grooves abruptly terminate northwestward at the rift trough the large antiformal ridge terminates southwestward at a transform shear zone that parallels the grooves these features rift valley antiformal uplift grooves and transform shear zone are morphologically and geometrically similar to grooved elevated submarine metamorphic core complexes on the inside corners of ridge transform intersections of slow spreading ridges on earth as with submarine core complexes the grooved surface on venus is interpreted as the footwall of a large displacement normal fault and the grooves are inferred to be the product of plastic molding of the footwall to irregularities on the underside of the hanging wall followed by tectonic exhumation of the molded grooves and conveyer belt like transport up and over the large antiform and across the southeastern plains according to this interpretation the trend of the grooves records the direction of extension which is perpendicular to the thrusts at the leading edge of the annular thrust belt 1000 km to the southeast both may have formed at the same time as a result of uniform southeastward displacement of the southeastern half of the interior of artemis corona the location of this grooved core complex at the center of artemis corona may reflect genesis above the buoyant ascending tail of the corona producing mantle diapir

mirdita zone ophiolites and associated sediments in albania reveal neotethys ocean origin the mirdita ophiolite zone in albania is associated with widespread melanges containing components of up to nappe size we dated matrix and components of the melange by radiolarians conodonts and other taxa the components consist of radiolarites pelagic limestones and shallow water limestones all of triassic age as well as ophiolites triassic radiolarite as a primary cover of ophiolite material proves middle triassic onset of mirdita ocean floor formation the melange contains a turbiditic radiolarite rich matrix radiolaritic flysch dated as late bajocian to early oxfordian it formed as a synorogenic sediment during west directed thrusting of ophiolite and sediment cover nappes representing ocean floor and underplated fragments of the western continental margin the tectonic structures formed during these orogenic events younger kimmeridian or eohellenic orogeny are sealed by late jurassic platform carbonates the geological history conforms with that of the inner dinarides and adjoining areas we therefore correlate the mirdita pindos ophiolite zone with the vardar zone and explain its present position by far distance west directed thrusting

structure and geochemistry of tethyan ophiolites and their petrogenesis in subduction rollback systems suprasubduction zone ssz ophiolites in orogenic belts represent oceanic crust generation in subduction rollback cycles during the closing stages of basins prior to terminal continental collisions mantle flow and slab rollback result in one or more episodes of arc splitting and basin opening producing a collage of protoarc and forearc oceanic lithosphere in suprasubduction zone settings the jurassic cretaceous ssz tethyan ophiolites in the eastern mediterranean region i e mirdita pindos troodos kizildag oman generally have penrose type oceanic crust and contain well developed sheeted dike complexes indicative of magmatic extension beneath narrow rift zones during their seafloor spreading evolution igneous accretion of these ssz tethyan ophiolites involved upper plate extension and advanced melting of previously depleted asthenosphere in host basins showing a progressive evolution from morb like to iat island arc tholeiite to boninitic extremely refractory protoarc assemblages however there are some distinct differences in the geochemical evolution of these tethyan ophiolites that appear to have resulted from variations in their subduction zone geodynamics whereas a major part of the kizildag and troodos lavas shows island arc affinity similar to their counterparts in the pindos and mirdita ophiolites a significant component of the oman lavas indicates morb affinity and the majority of the kizildag and oman data plot within the mantle array between n morb and e morb on the nb yb th yb discriminant diagram furthermore the troodos and oman lavas do not show any particular th enrichment in their multi element patterns suggesting that fluid melt input from subducted sediments was not that significant in generation of their magmas although all ophiolites exhibit geochemical features indicating increased subduction influence during the melt evolution of their younger extrusive sequences and dike intrusions as evidenced by their negative nd values their overall characteristic trace element patterns seem to have been strongly affected by the maturity of the subduction systems in which they developed

petrological and organic geochemical investigation of recent peats with known environments of deposition abstract a series of recent peat samples from tropical sub tropical and temperate locations were investigated using coal petrographical and organic geochemical techniques maceral and biomarker compositions were examined to see if they correlated or diverged from the known environment of deposition of the peats the proportion of humotelinite was related to the water depth and the frequency of dry periods the ph and trophic level have a modifying influence on the preservation of tissues furthermore the proportions of sclerotinite in the peats seem to reflected the oxygen status in the mire which was also mirrored in the abundance of humic and fulvic acids a facies diagram was calculated for the peat samples to see how maceral indices would fare in interpreting their known environments of deposition the results proved to be generally unsuccessful as the herbaceous and woody peats did not always give the predicted high humodetrinite and humotelinite compositions respectively the aliphatic hydrocarbon fraction from the extracts of the peat samples show that mainly odd numbered n alkanes are present diterpenoids triterpenoids and hopanoids were found in most samples and were mainly unsaturated in nature the relative proportion of hopanoids in pears appears to be related to bacterial activity in acidic environments de a triterpenoids were also detected in the peat stage of diagenesis in an angiosperm dominated peat type mariscus polycyclic aromatic triterpenoids were present in the aromatic fraction of the extract their occurrence and proportion appears to be related to the degree of humification in a taxodium peat mono di and triaromatic diterpenoids were detected the presence of these aromatic biomarkers indicate the rapid formation of these compounds in the peat stage mainly mediated by microbial activity

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

root related rhodochrosite and concretionary siderite formation in oxygen deficient conditions induced by a ground water table rise sedimentological mineralogical stable carbon and oxygen isotope determinations and biomarker analyses were performed on siderite concretions occurring in terrestrial silts to understand their formation and to characterize the sedimentary and diagenetic conditions favouring their growth high 13c values 6 4 on average indicate that siderite precipitated in an anoxic environment where bacterial methanogenesis operated the development of anoxic conditions during shallow burial was induced by a change in sedimentary environment from flood plain to swamp related to a rise of the ground water table large amounts of decaying plant debris led to efficient oxygen consumption within the pore water in the peat oxygen depletion in combination with a decrease in sedimentation rate promoted anoxic diagenetic conditions under the swamp and favoured abundant siderite precipitation this shows how a change in sedimentary conditions can have a profound impact on the early diagenetic environment and carbonate authigenesis the concretions contain numerous rhizoliths they are cemented with calcium rhodochrosite a feature which has not been reported before the rhodochrosite cement has negative 13c values 16 5 on average and precipitated in suboxic conditions due to microbial degradation of roots coupled to manganese reduction the exceptional preservation of the epidermis exodermis and xylem vessels of former root tissues indicates that the rhodochrosite formed shortly after the death of a root in water logged sediments rhodochrosite precipitated during the initial stages of concretionary growth in suboxic microenvironments within roots while siderite cementation occurred simultaneously around them in anoxic conditions these suboxic microenvironments developed because oxygen was transported from the overlying oxygenated soil into sediments saturated with anoxic water via roots acting as permeable conduits this model explains how separate generations of carbonate cements having different mineralogy and isotopic compositions which would conventionally be regarded as cements precipitated sequentially in different diagenetic zones during gradual burial can form simultaneously in shallow burial settings where strong redox gradients exist around vertically oriented permeable root structures

oceanic core complex development in modern and ancient oceanic lithosphere gabbro localized versus peridotite localized detachment models abstract drilling and submersible studies of the atlantis bank southwest indian ridge and the atlantis massif mid atlantic ridge oceanic core complexes reveal gabbro localized and peridotite localized end member models of strain localization and deformation during core complex development in which the gabbroic fault rocks exhibit extensive and rare high temperature ductile deformation fabrics respectively both models emphasize a footwall cored by gabbroic intrusions therefore precluding an amagmatic origin of core complex formation we test these models by using relict oceanic core complexes preserved in the western mirdita ophiolite in albania the puka and krabbi massifs display traits of the peridotite localized detachment model whereby amagmatic tectonic extension is not required for the formation of this category of core complexes

branched gdgt based paleotemperature reconstruction of the last 30 000 years in humid monsoon region of southeast china abstract the use of bacterial branched glycerol dialkyl glycerol tetraethers brgdgts to reconstruct mean annual air temperatures maats and environmental ph from soils has sparked significant interest in the terrestrial paleoclimate community however the reconstruction of these climate proxies from peat bogs is rare in monsoonal regions of the east asia this research was carried out on a core from the shuizhuyang szy peat bog located in fujian province branched gdgt brgdgt indexes were used for reconstructing the paleoclimate of the last 30 cal ka the aim was to evaluate quantitatively the maat and ph values since the last glacial maximum lgm in the subtropical zone of china results show that the cbt mbt derived maat at mis 3 is about 15 6 c on average which is followed by a significant fall at the lgm 11 7 12 1 c the temperature difference between the lgm and the present day value is as high as 5 8 c the synchronous variation of biomarker and pollen proxies indicates that replacement of subtropical evergreen broadleaved forests by cold tolerant deciduous broadleaved forests was driven by the significant drop in air temperature our results also indicate that the younger dryas event lasted from about 12 9 to about 11 3 cal ka and cooling event at 3 2 cal ka in the late holocene was detected showing the sensitivity of peat bogs to rapid cooling our ph reconstructions indicate that the ph of the bog rose during heinrich 1 and bolling allerod periods probably due to low precipitation and were lowest in the holocene thermal maximum between 8 ka and 2 5 ka probably due to higher precipitation the decoupling of reconstructed maat and ph during particularly deglaciation and yd periods supports the hypothesis that the variations in temperature and precipitation are not always synchronous

comparison of the paleoclimatic significance of higher land plant biomarker concentrations and pollen data a case study of lake sediments from the holsteinian interglacial abstract a sediment core from the dethlingen paleolake holsteinian interglacial northern germany was subjected to integrated organic geochemical and palynological paleobotanical analyses in order to reconstruct past environmental conditions the fractionated lipid extracts were investigated using gas chromatography mass spectrometry gc ms and gc combustion isotopic ratio ms ring a aromatized pentacyclic triterpenoids most likely glutinane derivatives were the only higher plant derived pentacyclic triterpenoids found the saturated ring a degraded triterpenoid des a lupane was the most abundant aliphatic hydrocarbon throughout the core based on published pollen data which imply the strong presence of betula and alnus around the paleolake the des a lupane would be expected to originate mainly from lupane type precursors synthesized by betulaceae the carbon isotopic composition of des a lupane varied from 28 2 to 30 6 and no significant trend or isotopic shift was observed however the discrepancy between the variation in pollen data and biomarker concentration i e quasi absence of diterpenoids in the core argues for a scenario in which the two proxies represent different components of the vegetation in the catchment area of the paleolake

paleoclimate influence on early diagenesis of plant triterpenes in the dajiuhu peatland central china abstract aromatic derivatives of vascular plant triterpenoids are common in recent and ancient sediments coal and petroleum understanding their early diagenetic alterations and their relation with environmental conditions can facilitate their applications in paleoenvironmental reconstructions here we present a high resolution record of aromatic triterpenes in a holocene peat core collected in the dajiuhu peatland central china these aromatic triterpenes are derivatives of plant triterpenoids with oleanane ursane and lupane carbon skeletons and exist in three different structural groups aromatic des a triterpenes aromatic pentacyclic triterpenes and c ring cleaved aromatic triterpenes such a high diversity of aromatic triterpenes in a young peat deposit is compelling evidence for rapid microbial mediation of these important degradation pathways during very early diagenesis of particular importance is the occurrence of c ring cleaved aromatic triterpene and aromatic des a triterpenes in the dajiuhu peat samples which until now have not been identified in recent sediments the downcore profile shows that the microbial aromatization process of oleanoids positively correlates with paleoclimate change during dry or warm intervals highly aromatized products such as tetraaromatic triterpenes become predominant over their triaromatic homologs in contrast triaromatic triterpenes become dominant during wet or cold intervals in addition this study provides further evidence to support that the climate pattern in the middle reaches of the yangtze river is different from that in north china during 13 9 4 ka these findings suggest that aromatic triterpenes can be valuable tools for holocene paleoenvironmental reconstructions

reply to d pană s discussion on the eastern carpathians ophiolites romania remnants of a triassic ocean lithos 108 2009 151 171

mesozoic tertiary tectonic evolution of albania in its regional eastern mediterranean context abstract research carried out since the opening of albania to the western geological community in the 1990s allows the geology and tectonics of this small balkan country to be integrated into an overall interpretation of neotethys in the eastern mediterranean region specifically greece and the former yugoslavia region albanian geology is most famous for the occurrence of contrasting ophiolites of jurassic age the country is sub divided into three main geotectonic units those in the west i e sazani ionian kruja krasta cukali and the albanian alps relate to the western margin of apulia effectively part of north africa from early mesozoic time onwards in the east is the korabi zone interpreted as a microcontinent located further northeast within neotethys between the two is the mirdita zone dominated by two contrasting jurassic ophiolites the western type ophiolite and the eastern type ophiolite taking account of evidence from greece and former yugoslavia the following tectonic evolution is proposed from early mesozoic time onwards neotethys in albania existed as a northward continuation of the pindos oceanic basin in greece pindos mirdita ocean a korabi microcontinent was rifted off apulia in the early mid triassic followed by passive margin subsidence until late middle jurassic time a rifted slow spreading mor type ophiolite formed within the western pindos mirdita oceanic basin in late triassic early late jurassic time using present co ordinates the shkoder peje scutari pec lineament in the north of albania is interpreted as an important transform fault zone that influenced the regional tectonic evolution during the entire mesozoic early tertiary rift drift emplacement history of the pindos mirdita ocean taking account of evidence from the greek and former yugoslavia ophiolites the easterly albanian ophiolites formed within the pindos mirdita ocean above a westward dipping intra oceanic subduction zone in the early late jurassic metamorphic soles were formed during initial intra oceanic displacement ca 162 174 m y and underlying melanges originated as subduction accretion complexes the mor western type ophiolite evolved into the iat boninitic eastern type ophiolite after subduction began during tithonian berriasian time trench margin collision emplaced the ophiolites eastwards over the korabi margin coupled with redeposition of ophiolitic and continental margin material as exotic blocks debris flow deposits and turbidites these were emplaced onto the upper surface of the ophiolitic thrust sheet during the latest stages of emplacement onto the korabi microcontinent following collision in the east oceanic crust remained within a small remnant pindos mirdita oceanic basin passive conditions were restored in the mid late cretaceous with shallow water carbonate deposition on microcontinental units and both pelagic and redeposited carbonates in basinal settings from the maastrichtian onwards africa eurasia convergence resulted in large scale westward thrusting deforming the apulian foreland in oligo miocene time the suture zone was re activated in oligo miocene time as the albanie thassalie piggy back type basin in central and southern albania albania as a whole was rotated 45 clockwise as part of the western aegean arc in post eocene time coastal and offshore albania experienced strong subsidence after early miocene time forming the periadriatic basin including the tirana depression interpreted as a foredeep related to continuing regional convergence southern albania experienced extensional tectonics in plio quaternary time related to southward roll back of the aegean active margin

δ13c values and radiocarbon dates of microbial biomarkers as tracers for carbon recycling in peat deposits this paper describes the first application of compound specific stable carbon isotope and radiocarbon isotope analyses to the investigation of microbial processes in peat deposits

slow spreading accretion and mantle denudation in the mirdita ophiolite albania the mirdita ophiolite in albania occupies a n s corridor which escaped most alpine and cenozoic deformation possibly due to a thick ophiolitic basement the sheeted dike complex strikes ns and dips steeply indicating that the ridge was oriented parallel to the ns corridor and that the ophiolite has not been significantly tilted although differential motion between individual massifs cannot be excluded classically the western massifs have been considered lherzolitic and the eastern massifs harzburgitic detailed structural mapping reveals that the deep mantle section was harzburgitic and that the major differences between the two are restricted to the uppermost mantle and lower crustal section these are typically ophiolitic in the eastern massifs being composed of a thick dunitic transition zone rich in basaltic impregnations and chromite deposits overlain by a lower crust of layered gabbros in contrast in the western massifs the uppermost mantle is composed of highly strained to mylonitic lherzolites which originate from more depleted harzburgites by impregnation and tectonic dispersion of melt during deformation occurring at 1000 800 c layered gabbros are locally absent and the crust can be reduced to diabase dikes or sills and extrusives the diabase intrusions are locally sheared together with peridotites and metamorphosed to amphibolites the contrast between the eastern and western massifs is ascribed to successive episodes of magmatic and amagmatic spreading in a slow spreading environment the low t high strain deformation of the western massifs is localized in the dome shaped envelopes of these massifs this structure and even the present day topography of the western massifs evoke the turtleback domes described along the mid atlantic ridge mar and explained by mantle denudation tucholke et al 1998

organic geochemistry of the lower miocene oberdorf lignite styrian basin austria its relation to petrography palynology and the palaeoenvironment abstract in the oberdorf trough at the northwestern margin of the styrian basin austria an up to 36 m thick lower miocene ottnangian lignite seam occurs within the fluvial koflach voitsberg formation previous results indicate that the lignite originated in a topogenous mire within a wet forest swamp palaeoenvironment differences in soluble organic matter som yield of borehole samples from the lignite seam are related to free lipids present in plant waxes or resins and the presence of thermally labile polymers indicated by the contents of liptinite macerals i e resinite suberinite and liptodetrinite the n alkane distribution patterns are dominated by high molecular weight lipids with marked odd over even predominance originating from plant waxes a contribution of algae to the even numbered short chain lipids observed in considerable amounts in the footwall sediments is proposed terpenoid biomarkers characteristic for conifers and angiosperms were detected consistent with palynomorphic spectra which are dominated by forest swamp pollen taxodiaceae cupressaceae and pollen from plants living in a mixed mesophytic forest excellent relationships between higher plant biomarker composition and palynologic data indicate that the organic geochemical results reflect the varying inputs of coniferales vs angiosperms the data further imply that cuparene may be used for taxonomical differentiation of coniferales families organic geochemical data provide evidence that the content of land plant derived biomarkers is controlled by the input of resin rich conifers concentrations of hopanoids dominated by hop 17 21 ene generally increase towards the top of the lignite a section characterised by high extents of aromatisation of triterpenoid biomarkers the results suggest that the aromatisation of angiosperm derived biomarkers may be governed by the activity of anaerobic rather than by aerobic bacteria however changes in the depositional environment and palynologic facies during peat formation probably influenced the origin and fate of angiosperm derived triterpenoids the results indicate how biomarker composition may contribute to the evaluation of environmental changes cross correlations of organic geochemical parameters with palynological data and petrography based facies indicators will provide further insights in the peat forming vegetation and biogeochemical activities in the mire

southeastern lewis hills bay of islands ophiolite geology of a deeply eroded inside corner ridge transform intersection the lewis hills massif bay of islands ophiolite newfoundland preserves a deeply eroded transform fault a major low angle extensional mylonite zone is next to the transform assemblage and probably merges laterally into it the mylonite developed in a high temperature environment and occurs at the top of relatively rigid lithospheric mantle the lithospheric mantle represents exhumed older arc type basement of the little port complex that is also exposed across the transform in the western lewis hills it differs dramatically from an asthenospheric mantle unit of the bay of islands complex exposed in the eastern lewis hills that formed in a spreading ridge environment the fossil ridge transform segment and associated low angle normal fault in the lewis hills formed at an inside corner structural setting similar to recently discovered core complexes at oceanic ridge transform intersections however the lewis hills segment developed in a setting where a spreading center propagated across a transform margin and rifted older arc type lithosphere factors that contributed to formation of the low angle detachment fault are the lithospheric nature of the mantle basement rheological weakening and strain focusing by intrusive sills and weak lateral coupling realized by the extensional transform assemblage

tethyan vs cordilleran ophiolites a reappraisal of distinctive tectono magmatic features of supra subduction complexes in relation to the subduction mode abstract supra subduction zone ssz ophiolites deserve special attention because they represent fundamental markers of intraoceanic convergence and generation of new lithosphere above subduction zones moreover owing to their structural characteristics and location in the overriding plate these complexes are far better represented and preserved than mid ocean ridge basalt morb ophiolites in orogenic belts in terms of their structure tectonics and magmatic features ssz ophiolites may be classified in two main types 1 tethyan complexes such as those of the albanide hellenide belt which mostly consist of complete and extensive volcanic dyke plutonic and mantle sections with prevalent island arc tholeiitic iat affinity and the significant presence of boninites obducted as relatively intact lithospheric slabs onto collisional continental margins 2 cordilleran complexes including the circum caribbean ophiolites of guatemala cuba and venezuela mostly represented by dismembered sections of arc volcanic plutonic and subordinate mantle sequences with tholeiitic to calc alkaline iac magmatic affinity and acidic differentiates commonly associated with metamorphic subduction complexes and tectonically emplaced onto or juxtaposed against the continental margin within polygenetic terranes these two types appear to be related to significantly different subduction modes and intraoceanic plate dynamics whereby ssz ophiolites were generated the tethyan complexes can best be compared with west pacific type subduction with accentuated steepening and retreat of the subducted slab accompanied by progressive decoupling of the converging plates intense mantle diapirism and tensional events in the upper plate with generation of large iat sheeted dike complexes in open oceanic spreading systems continuous slab sinking and roll back allow increasing asthenospheric diapirism and interarc spreading from the arc axis to the forearc region with generation of boninites and back arc basin basalts babb with intermediate morb iat composition by contrast the genesis of the cordilleran complexes requires a subduction mode characterized by a steady state regime with moderate and constant dip of the subducted slab and limited extension in the backarc region the magmatic evolution of these ophiolites from iat to iac and the significant presence of rhyodacite and tonalite differentiates coherently indicate a more mature stage of arc magmatism as well as the occurrence of efficient differentiation processes developing under nearly closed system conditions in independent magma chambers tethyan complexes are likely to be obducted as large and relatively intact slabs onto the continental margins through the interposition of metamorphic soles which represent relics of the morb lithosphere underplating the ssz ophiolites on the other hand the common emplacement of cordilleran complexes within polygenetic terranes appears to be controlled by prolonged accretionary mechanisms that trap against the continental margin parts of the arc structure subduction complexes melanges and volcanoclastic products

high resolution evidence from southern china of an early holocene optimum and a mid holocene dry event during the past 18 000 years abstract computer models suggest that the holocene optimum for east asian summer monsoon precipitation occurred at different times in different regions of china previous studies indicate that this time transgressive holocene optimum should have been experienced about 3000 yr ago in southern china in this study we describe a section which allows us to test this timing directly we have closely examined high resolution eutrophic peat mud sequences covering the past 18 000 cal yr at dahu jiangxi on the southern boundary of the mid subtropical zone in china late pleistocene successions in the dahu record indicate cooler and much wetter conditions relative to synchronous events in north central china our results indicate that the holocene optimum occurred between ca 10 000 and 6000 cal yr ago in southern china consistent with the global pattern conditions were relatively dry and cold from 6000 to 4000 cal yr ago our data also support the conclusion that the last deglaciation to early holocene in the south was much wetter resulting in the formation of dense broad leaved forests which could have acted to moderate land temperature 10 000 to 6000 cal yr ago yielding a stable early holocene climate after 6000 cal yr forest reduction led to unstable land temperatures and possibly to a northerly shift of the subtropical high pressure system whatever the mechanism these changes resulted in decreased precipitation between 6000 and 4000 cal yr b p in southern china

comment on the paper mesozoic tertiary tectonic evolution of albania in its regional eastern mediterranean context by robertson and shallo tectonophysics 316 2000 197 254

resource assessment of undiscovered seafloor massive sulfide deposits on an arctic mid ocean ridge application of grade and tonnage models abstract norway has started ongoing initiatives related to deep sea mining these include the evaluation of mineral resources within its sovereign territorial waters on the deep ocean floor of the arctic region i e the mohns ridge 71 73 n among the variety of possible seabed resources seafloor massive sulfides sms attract particular interest owing to the significant development potential and the general lack of knowledge of the sms deposits the present study aims at assessing mineral resources i e cu zn au and ag from a number of undiscovered sulfide deposits with the help of a revised model for mafic hosted volcanogenic massive sulfide vms deposits that adequately corresponds to geological settings of slow spreading ridges application of the model requires a priori knowledge of the seafloor terrain to depict favorable geologic environments for the occurrence of sms deposits in such context estimates are conducted for the easily accessible volcanically active parts of the ridge where 11 undiscovered deposits are expected in these areas total metal endowments are calculated to be on average 447 000 tonnes using a monte carlo simulation that combines the probabilistic estimates of number of undiscovered deposits with the grade and tonnage models estimates of in place metal resources are generated in cumulative distribution form to present expected amount of undiscovered metals at 90 confidence intervals

reconstructing plate boundaries in the jurassic neo tethys from the east and west vardar ophiolites greece and serbia jurassic subduction initiation in the neo tethys ocean eventually led to the collision of the adria africa and eurasia continents and the formation of an 6 000 km long alpine orogen spanning from iberia to iran reconstructing the location and geometry of the plate boundaries of the now disappeared neo tethys during the initial moments of its closure is instrumental to perform more realistic plate reconstructions of this region of ancient ocean basins in general and on the process of subduction initiation neo tethyan relics are preserved in an ophiolite belt distributed above the dinaric hellenic fold thrust belt here we provide the first quantitative constraints on the geometry of the spreading ridges and trenches active in the jurassic neo tethys using a paleomagnetically based net tectonic rotation analysis of sheeted dykes and dykes from the west and east vardar ophiolites of serbia maljen and ibar and greece othris pindos vourinos and guevgueli based on our results and existing geological evidence we show that initial middle jurassic 175 ma closure of the western neo tethys was accommodated at a n s trending west dipping subduction zone initiated near and parallel to the spreading ridge the west vardar ophiolites formed in the forearc parallel to this new trench simultaneously the east vardar ophiolites formed above a second n s to nw se trending subduction zone located close to the european passive margin we tentatively propose that this second subduction zone had been active since at least the middle triassic simultaneously accommodating the closure of the paleo tethys and the back arc opening of neo tethys

dynamics of intraoceanic subduction initiation 1 oceanic detachment fault inversion and the formation of supra subduction zone ophiolites subduction initiation is a critical link in the plate tectonic cycle intraoceanic subduction zones can form along transform faults and fracture zones but how subduction nucleates parallel to mid ocean ridges as in e g the neotethys ocean during the jurassic remains a matter of debate in recent years extensional detachment faults have been widely documented adjacent to slow spreading and ultraslow spreading ridges where they cut across the oceanic lithosphere these structures are extremely weak due to widespread occurrence of serpentine and talc resulting from hydrothermal alteration and can therefore effectively localize deformation here we show geochemical tectonic and paleomagnetic evidence from the jurassic ophiolites of albania and greece for a subduction zone formed in the western neotethys parallel to a spreading ridge along an oceanic detachment fault with 2 d numerical modeling exploring the evolution of a detachment ridge system experiencing compression we show that serpentinized detachments are always weaker than spreading ridges we conclude that owing to their extreme weakness oceanic detachments can effectively localize deformation under perpendicular far field forcing providing ideal conditions to nucleate new subduction zones parallel and close to or at spreading ridges direct implication of this is that resumed magmatic activity in the forearc during subduction initiation can yield widespread accretion of suprasubduction zone ophiolites at or close to the paleoridge our new model casts the enigmatic origin of regionally extensive ophiolite belts in a novel geodynamic context and calls for future research on three dimensional modeling of subduction initiation and how upper plate extension is associated with that

migration of neolithic settlements in the dongting lake area of the middle yangtze river basin china lake level and monsoon climate responses the vast dongting lake in the middle yangtze river basin china was occupied by chinese neolithic settlements starting 10 000 years ago and rice cultivation there is probably the earliest in the world the numerous neolithic settlements identified by previous archaeological surveys represent the five major neolithic cultural stages i e the pengtoushan 9000 7900 cal yr bp zaoshixiaceng 7900 6800 cal yr bp daxi 6800 5500 cal yr bp qujialing 5500 5000 cal yr bp and shijiahe 5000 4000 cal yr bp using sedimentological and geoarchaeological approaches this paper analyses the drivers of basin scale settlement relocation in relation to lake level fluctuations and monsoon climate variations in the holocene the relocation of neolithic sites around the lake shoreline and on the adjacent floodplain together with radiocarbon dated stratigraphy clearly indicates that the shape of the lake basin was an incised and elongated valley occupied by a lake in the early holocene which became a broad

the variation of summer monsoon precipitation in central china since the last deglaciation abstract two stalagmites c996 1 and c996 2 collected from the jiuxian cave in the shaanxi province in central china have been studied with u series dating and stable isotope analysis thirty eight 230 th dating results showed that the stalagmite c996 1 was continuously deposited through the last 8 5 ka bp thousand years before present present 1950 ad and c996 2 was deposited through the last 19 ka bp excluding two growth hiatuses between 8 3 and 5 7 ka bp and 15 4 and 11 9 ka bp with a relatively stable boundary condition we interpret the 18 o of speleothem calcite as most indicative of the amount of summer monsoon precipitation although temperature and other factors might have some minor impact the 18 o records show notable changes within the last glacial maximum lgm resembling other east asian monsoon records such as those from the hulu and sanbao caves suggesting that significant monsoonal climate changes occurred in eastern asia as far north as the qinling mountains during the lgm interval a comparison of our records to precisely dated contemporaneous speleothem records from other caves shows that the increasing trend of 18 o during the holocene commenced as early as 7 5 ka bp in the low latitude monsoonal area i e the hoti cave while at higher latitudes this shift occurred later such as 7 0 ka bp in the dongge cave 5 3 ka bp in the heshang cave 4 7 ka bp in the sanbao cave and 4 5 ka bp in the jiuxian cave these results imply an asynchronous change of the summer monsoon precipitation occurred in east asia during the holocene the asynchrony may be related to the responses of a coupled tropical and subtropical monsoon system to changes of the insolation and the differences in thermal forcing which result from the complex geographical configuration the variation of sea surface temperature sst in the western tropical pacific may also have important impacts on the summer monsoon precipitation changes in central and northern china because it affects the northwestern pacific subtropical high a monsoon front regulator more robust tests are needed to confirm this phenomenon and to evaluate the contribution of different factors in detail

aliphatic and aromatic terpenoid biomarkers in cretaceous and paleogene angiosperm fossils from japan abstract the distributions of aliphatic and aromatic terpenoids in cretaceous and paleogene angiosperm fossils from japan were investigated aliphatic a ring degraded oleanane ursane and lupane were found in all samples in addition aliphatic gymnosperm derived diterpenoids were detected in significant quantities aromatic oleanane type triterpenoids were the major components with ursane and lupane type triterpenoids being minor compounds in all angiosperm fossils in a cretaceous gymnosperm fossil major components included aliphatic labdane isopimarane and abietane type diterpenoids aromatic abietane type diterpenoids and chrysene and picene type polyaromatic hydrocarbons pahs trace amounts of oleanane ursane and lupane type triterpenoids were also identified it is likely that the aromatic triterpenoids were introduced to the gymnosperm fossil from the angiosperm derived material in the sediments we defined an angiosperm gymnosperm index al agi as an alternative to the aliphatic triterpenoid diterpenoid ratio proposed in the literature the al agi index may underestimate the angiosperm contribution because the aliphatic angiosperm derived triterpenoids are more readily converted to aromatic counterparts than the diterpenoids during diagenesis an aromatic angiosperm gymnosperm index ar agi can be calculated using aromatic diterpenoids and triterpenoids we suggest that ar agi is best calculated using only the oleanane ursane and lupane type aromatic triterpenoids and that the chrysene and picene type pahs be excluded

peatland development and climate changes in the dajiuhu basin central china over the last 14 100 years abstract peatlands are one of the optimal archives for paleoclimate research and their records contain a detailed history of climatic and environmental variations during their formation here we collected a peat profile from the dajiuhu basin in central china and analyzed several geochemical proxies such as total organic carbon toc total nitrogen tn titanium ti and aluminum al to investigate the history of peat development the results show that the peat growth was initiated after around 12 8 cal ka bp at the sampling site and the toc and tn contents kept stable during the holocene except during the periods of 10 5 9 0 cal ka bp and recent 1 5 cal ka bp however compared with other toc records in the dajiuhu basin the history of peat development varied greatly in different sampling sites indicating that the peat development in the dajiuhu basin probably responds to both climate changes and local geological and hydrological conditions investigations of the interactions between climate change and peat development record in this study suggest that peat development presented significant responses to the large and rapid decreases in east asian summer monsoon intensity such as the 9 2 ka monsoon weakening event however the obvious long term decreasing trend of monsoon precipitation during the mid late holocene did not lead to the degradation of the dajiuhu peat probably resulting from relatively stable temperature in addition the sharp decrease of toc and tn values in the surface 15 cm of dajiuhu peat was probably attributed to increased human activity

paleotemperature variability in central china during the last 13 ka recorded by a novel microbial lipid proxy in the dajiuhu peat deposit the asian summer monsoon is a very important climatic component affecting the land ecosystem on the eastern asian continent here we assess microbe derived lipid biomarker evidence from a well date

emplacement of the jurassic mirdita ophiolites southern albania evidence from associated clastic and carbonate sediments sedimentology can shed light on the emplacement of oceanic lithosphere i e ophiolites onto continental crust and post emplacement settings an example chosen here is the well exposed jurassic mirdita ophiolite in southern albania successions studied in five different ophiolitic massifs voskopoja luniku shpati rehove and morava document variable depositional processes and palaeoenvironments in the light of evidence from comparable settings elsewhere e g n albania n greece ophiolitic extrusive rocks pillow basalts and lava breccias locally retain an intact cover of oceanic radiolarian chert in the shpati massif elsewhere ophiolite derived clastics typically overlie basaltic extrusives or ultramafic rocks directly the oldest dated sediments are calpionellid and ammonite bearing pelagic carbonates of latest jurassic berrasian age similar calpionellid limestones elsewhere n albania n greece post date the regional ophiolite emplacement at one locality in s albania voskopoja calpionellid limestones are gradationally underlain by thick ophiolite derived breccias containing both ultramafic and mafic clasts that were derived by mass wasting of subaqueous fault scarps during or soon after the latest stages of ophiolite emplacement an intercalation of serpentinite rich debris flows at this locality is indicative of mobilisation of hydrated oceanic ultramafic rocks some of the ophiolite derived conglomerates e g shpati massif include well rounded serpentinite and basalt clasts suggestive of a high energy shallow water origin the berriasian pelagic limestones at voskopoja experienced reworking and slumping probably related to shallowing and a switch to neritic deposition mixed ophiolite derived clastic and neritic carbonate sediments accumulated later during the early cretaceous mainly barremian aptian in variable deltaic lagoonal and shallow marine settings these sediments were influenced by local tectonics or eustatic sea level change terrigenous sediment gradually encroached from neighbouring landmasses as the ophiolite was faulted or eroded an aptian transgression was followed by regression creating a local unconformity e g at boboshtica a turonian marine transgression initiated widespread upper cretaceous shelf carbonate deposition in the regional context the southern albania ophiolites appear to have been rapidly emplaced onto a continental margin in a subaqueous setting during the late jurassic late oxfordian late tithonian this was followed by gradual emergence probably in response to thinning of the ophiolite by erosion and or exhumation the sedimentary cover of the south albanian ophiolites is consistent with rapid relatively short distance emplacement of a regional scale ophiolite over a local pelagonian korabi microcontinent

segmentation and crustal structure of the western mid atlantic ridge flank 25 25 27 10 n and 0 29 m y we conducted a detailed geological geophysical survey of the west flank of the mid atlantic ridge between 25 25 n and 27 10 n and from the ridge axis out to 29 ma crust acquiring hydrosweep multibeam bathymetry hawaii mr1 sidescan sonar imagery gravity magnetics and single channel seismic reflection profiles the survey covered all or part of nine spreading segments bounded by mostly nontransform right stepping discontinuities which are subparallel to flow lines but which migrated independently of one another some discontinuities alternated between small right and left stepping offsets or exhibited zero offset for up to 3 4 m y despite these changes the spreading segments have been long lived and extend 20 m y or more across isochrons a large shift 9 in relative plate motion about 24 22 ma caused significant changes in segmentation pattern the nature of this plate boundary response together with the persistence of segments through periods of zero offset at their bounding discontinuities suggest that the position and longevity of segments are controlled primarily by the subaxial position of buoyant mantle diapirs or focused zones of rising melt within segments there are distinct differences in seafloor depth morphology residual mantle bouguer gravity anomaly and apparent crustal thickness between inside corner and outside corner crust this demands fundamentally asymmetric crustal accretion and extension across the ridge axis which we attribute to low angle detachment faulting near segment ends cyclic variations in residual gravity over the crossisochron run of segments also suggest crustal thickness changes of at least 1 2 km every 2 3 m y these are interpreted to be caused by episodes of magmatic versus relatively amagmatic extension controlled by retention and quasiperiodic release of melt from the upwelling mantle detachment faulting appears to be especially effective in exhuming lower crust to upper mantle at inside corners during relatively amagmatic episodes creating crustal domes analogous to turtleback metamorphic core complexes that are formed by low angle detachment faulting in subaerial extensional environments

the peridotites of the kukes ophiolite albania structure and kinematics abstract structural study of the kukes ultramafic massif which belongs to the albanian mirdita zone is of great interest for reconstruction of alpine tectonic environments from bottom to top the following lithological succession is observed in the ultramafic mafic section harzburgites harzburgites with dunitic lenses dunites an intermediate zone and gabbros the ultramafic rocks are apparently weakly deformed the textures indicate a high temperature deformation and slight locally superimposed low temperature deformation this is confirmed by olivine lattice preferred orientation which indicates that 010 100 was the activated glide system in olivine i e at high temperature the kinematics of deformation have been determined from the lattice preferred orientation of olivine an inversion of the shear sense occurs at the base of the dunite zone and is interpreted as being due to asthenospheric flow a simple geometric reconstruction indicates that the kukes ultramafic massif could correspond to the eastern flank of a nnw sse orientated paleo ridge

dynamics of intraoceanic subduction initiation 2 suprasubduction zone ophiolite formation and metamorphic sole exhumation in context of absolute plate motions analyzing subduction initiation is key for understanding the coupling between plate tectonics and the underlying mantle here we focus on suprasubduction zone ssz ophiolites and how their formation links to intraoceanic subduction initiation in an absolute plate motion frame ssz ophiolites form the majority of exposed oceanic lithosphere fragments and are widely recognized to have formed during intraoceanic subduction initiation structural petrological geochemical and plate kinematic constraints on their kinematic evolution show that ssz crust forms at fore arc spreading centers at the expense of a mantle wedge thereby flattening the nascent slab this leads to the typical inverted pressure gradients found in metamorphic soles that form at the subduction plate contact below and during ssz crust crystallization former spreading centers are preserved in forearcs when subduction initiates along transform faults or off ridge oceanic detachments we show how these are reactivated when subduction initiates in the absolute plate motion direction of the inverting weakness zone upon inception of slab pull due to e g eclogitization the sole is separated from the slab remains welded to the thinned overriding plate lithosphere and can become intruded by mafic dikes upon asthenospheric influx into the mantle wedge we propound that most ophiolites thus formed under special geodynamic circumstances and may not be representative of normal oceanic crust our study highlights how far field geodynamic processes and absolute plate motions may force intraoceanic subduction initiation as key toward advancing our understanding of the entire plate tectonic cycle

variability of monsoon climate in east asia at the end of the last glaciation abstract high resolution paleomonsoon proxy records from peat and eolian sand paleosol sequences at the desert loess transition zone in china denote a rapid oscillation from cold dry conditions 11 200 10 60014c yr b p to cool humid conditions 10 600 10 20014c yr b p followed by a return to cold dry climate 10 200 10 00014c yr b p variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern asia during the younger dryas interval late glacial climate in the chinese desert loess belt that lies downwind from europe was strongly influenced by cold air from high latitudes and from the north atlantic via the westerlies the inferred precipitation variations were likely caused by variations in the strength of the siberian high which influenced the pressure gradient between land and ocean and therefore influenced the position of the east asian monsoon front

geodynamic evolution of ophiolites from albania and greece dinaric hellenic belt one two or more oceanic basins all the geological constraints for an exhaustive reconstruction of the triassic to tertiary tectonic history of the southern dinaric hellenic belt can be found in albania and greece this article aims to schematically reconstruct this long tectonic evolution primarily based on a detailed analysis of the tectonic setting the stratigraphy the geochemistry and the age of the ophiolites in contrast to what was previously reported in the literature we propose a new subdivision on a regional scale of the ophiolite complexes cropping out in albania and greece this new subdivision includes six types of ophiolite occurrences each corresponding to different tectonic units derived from a single obducted sheet these units are represented by 1 sub ophiolite melange 2 triassic ocean floor ophiolites 3 metamorphic soles 4 jurassic fore arc ophiolites 5 jurassic intra oceanic arc ophiolites and 6 jurassic back arc basin ophiolites the overall features of these ophiolites are coherent with the existence of a single though composite oceanic basin located east of the adria pelagonian continental margin this oceanic basin was originated during the middle triassic and was subsequently early jurassic affected by an east dipping intra oceanic subduction this subduction was responsible for the birth of intra oceanic arc and back arc oceanic basins separated by a continental volcanic arc during the early to middle jurassic from the uppermost middle jurassic to the early cretaceous an obduction developed during which the ophiolites were thrust westwards firstly onto the neighboring oceanic lithosphere and then onto the adria margin

evidence for jurassic subduction from the northern calcareous alps berchtesgaden austroalpine germany the closure of the western part of the neotethys ocean started in late early jurassic the middle to early late jurassic contraction is documented in the berchtesgaden alps by the migration of trench like basins formed in front of a propagating thrust belt due to ophiolite obduction these basins propagated from the outer shelf area hallstatt realm to the interior continent hauptdolomit dachstein platform realm the basins were separated by nappe fronts forming structural highs this scenario mirrors syn orogenic erosion and deposition in an evolving thrust belt active basin formation and nappe thrusting ended around the oxfordian kimmeridgian boundary followed by the onset of carbonate platforms on structural highs starved basins remained between the platforms rapid deepening around the early late tithonian boundary was induced by extension due to mountain uplift and resulted in the reconfiguration of the platforms and basins erosion of the uplifted nappe stack including obducted ophiolites resulted in increased sediment supply into the basins and final drowning and demise of the platforms in the berriasian the remaining early cretaceous foreland basins were filled up by sediments including siliciclastics the described jurassic to early cretaceous history of the northern calcareous alps accords with the history of the western carpathians the dinarides and the albanides where 1 age dating of the metamorphic soles prove late early to middle jurassic inneroceanic thrusting followed by late middle to early late jurassic ophiolite obduction 2 kimmeridgian to tithonian shallow water platforms formed on top of the obducted ophiolites and 3 latest jurassic to early cretaceous sediments show postorogenic character

oceanic core complexes and ancient oceanic lithosphere insights from iapetan and tethyan ophiolites canada and albania abstract oceanic ridges are extensional environments characterized by brittle to ductile normal faulting and episodic magma supply studies in modern oceanic settings suggest that the interplay of low angle detachments and high angle normal faults locally lead to the exhumation of lower crust and upper mantle peridotites to the seafloor as oceanic core complexes along the mid atlantic ridge core complexes typically occur in inside corners of intersections between the ridge axis and major transform faults the core complexes were exhumed by movement along long lived detachment faults that extend for 10s of km and that are crosscut by high angle normal faults oriented parallel to the rift axis ridge segments with abundant detachments would be characterized by lithosphere having little or no upper crust similar features in ophiolites may also reflect the dominance of amagmatic extension this contribution presents two examples of fossilized oceanic core complexes preserved in the canadian appalachian and albanian dinaride ophiolite belts in the canadian appalachians the southern quebec ophiolites experienced two paleozoic orogenies after their obduction onto the laurentian margin although locally obscured by tectonic fabrics and structures the original relationships between the ophiolitic mantle the overlying plutonic section and onlapping ordovician siliciclastic rocks are well preserved in the thetford mines ophiolite which also shows similarities with lithological and structural features of the mirdita ophiolite where conformable contacts between the sedimentary cover sequence debris flows and flysch deposits and the mantle and crustal sections are superbly exposed the jurassic mirdita ophiolite in albania underlies ca 4000 km2 and was only slightly affected by the tertiary alpine orogeny of eastern europe well exposed sections of the ophiolite suggest that the oceanic mantle was exhumed prior to obduction and locally records the formation of an oceanic core complex mafic cumulates of the mirdita ophiolite have been totally excised in places and exhumation related shear zones are preserved in the krabbi puka massif the shear zones are manifested both within the mantle and at the contact with overlying basalts the ophiolitic sedimentary sequence was deposited on basalts sheeted dykes or gabbros and typically consists of debris flows intercalated with and overlain by slumped oceanic sedimentary rocks the lithological and structural characteristics of both the thetford mines and the mirdita ophiolites are consistent with extensional tectonism crustal excision and lower crust upper mantle exhumation during formation both ophiolites are believed to have originated during asymmetrical oceanic extension in a suprasubduction zone setting with preservation of the upper plate lower plate segments during obduction

conifer and angiosperm biomarkers in clay sediments and fossil plants from the miocene clarkia formation idaho usa the aliphatic lipids and terpenoids of conifer and angiosperm macrofossils and the clay sediment from a new site p 37 of the miocene clarkia formation idaho usa were analyzed to evaluate the preservation of characteristic conifer and angiosperm biomarkers in the sediment series of aliphatic lipids terpenoids and steroids similar to the biomarkers found in type locality clarkia p 33 were the predominant compounds in the sediment and in the fossils long chain aliphatic lipids were major compounds in the fossil plants and the sediment but a differentiation of angiosperm and conifer sources is not possible due to their common distribution among all vascular plants in addition to previously reported terpenoids diterpenoids of a conifer origin and several angiosperm derived polar triterpenoids of the oleanane lupane ursane and friedelane classes are reported here for the first time from the clarkia sediments the conifer shoots taxodium glyptostrobus calocedrus contained characteristic conifer biomarkers such as abietane type diterpenoids while characteristic angiosperm triterpenoids were predominant in the angiosperm leaves betula quercus lithocarpus the biomarker compositions of the taxodium and glyptostrobus shoots match the terpenoid patterns previously reported from fossil seed cones of the same genera although conifer macrofossils contribute about 45 to the flora of site p 37 characteristic conifer biomarkers occurred in the sediment in only low amounts while the angiosperm derived triterpenoids were present in comparatively higher abundances the results indicate that the conifers are under represented compared to the angiosperms according to the terpenoid composition of the sediment extract this may be due to the presence of small angiosperm derived particles leaf detritus wax in the sediment and or migration of leaf waxes from the angiosperm leaves into the sediment in contrast the diterpenoids are trapped in the resinous woody tissue of the conifers and are thus disseminated less into the sediment

holocene east asian monsoon variability links to solar and tropical pacific forcing 1 sedimentary geochemical records from subalpine retreat lake subtropical taiwan document the unstable east asian monsoon eam climate over the past 10 300 years with a weak eam between 10 3 and 8 6 ky b p eam intensity peaks between 8 6 and 7 7 ky b p and then gradually decrease in response to summer insolation heat and moisture transport our proxy record reveals several weak monsoon intervals that correlate to low sea surface temperatures in the western tropical pacific and cold events in the north atlantic linking the tropical pacific north atlantic and polar climates because weak eam events at 8 2 5 4 and 4 5 2 1 ky b p also correspond to low values of atmospheric methane and periods of reduced north atlantic deep water formation we therefore suggest that centennial to millennial scale monsoon variability during the holocene in the northern subtropics is globally mediated via a sun ocean monsoon north atlantic linkage

the vardar zone as a suture for the mirdita ophiolites albania constraints from the structural analysis of the korabi pelagonia zone the dinarides hellenides result from underthrusting of the adriatic margin during africa europe convergence in albania they consist of 1 a western zone of nappes derived from adria 2 a central belt made up of the mirdita ophiolites and 3 an eastern zone the korabi pelagonia zone of variscan basement overlain by permian to mesozoic rift deposits and carbonates some authors interpret the korabi pelagonia zone as a microcontinent between the mirdita pindos oceanic basin to the west and the eastern vardar oceanic basin to the east other regard the korabi pelagonia zone as a tectonic window below a single ophiolitic nappe this contribution argues for a far traveled thrust sheet the mirdita ophiolites are 165 160 ma the metamorphic sole yielded 40ar 39ar ages of 171 to 162 ma the korabi pelagonia zone is subdivided into the korabi and gjegjan subzones the structural analysis of these rocks supports the rooting of the mirdita ophiolites in the western vardar zone the post variscan cover sequence of the korabi subzone records two phases of deformation d1 is associated with a se dipping to flat lying schistosity axial planar to nw verging folds and thrust faults related to ophiolite obduction d2 is a postobduction nne trending crenulation cleavage published zircon fission track analyses yielded 150 125 ma suggesting that regional metamorphism is early cretaceous or older k ar mica ages from correlative rocks of macedonia cluster between 148 and 130 ma indicating that d1 is late jurassic a west directed obduction is favored as is a rooting east of the mirdita ophiolites because of the top to the west structural polarity of obduction related deformation

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

chinese stalagmite δ 18 o controlled by changes in the indian monsoon during a simulated heinrich event carbonate cave deposits in india and china are assumed to record the intensity of monsoon precipitation because the 18 o of the carbonate tracks the isotopic signature of precipitation these records show spatially coherent variability throughout the last ice age and suggest that monsoon strength was altered during the millennial scale climate variations known as dansgaard oeschger events and during the heinrich cooling events here we use a numerical climate model with an embedded oxygen isotope model to assess what caused the shifts in the oxygen isotope signature of precipitation during a climate perturbation designed to mimic a heinrich event our simulations show that a sudden increase in north atlantic sea ice extent during the last glacial period leads to cooling in the northern hemisphere reduced precipitation over the indian basin and weakening of the indian monsoon the precipitation is isotopically heavier over india and the water vapour exported to china is isotopically enriched our model broadly reproduces the enrichment of 18 o over northern india and east asia evident in speleothem records during heinrich events we therefore conclude that changes in the 18 o of cave carbonates associated with heinrich events reflect changes in the intensity of indian rather than east asian monsoon precipitation

distribution of aliphatic des a triterpenoids in the dajiuhu peat deposit southern china abstract aliphatic des a triterpenoids have been tentatively assigned in samples taken from a 260 cm thick peat sequence from the dajiuhu basin of southern china using gas chromatography mass spectrometry gc ms the compounds possessing the carbon skeletons of oleanane ursane or lupane are generally considered as the microbial degradation products of plant triterpenoids under anoxic conditions abundant aliphatic des a triterpenoids were observed only in peat samples during the transitional period from the last glaciation to the early holocene 9 5 11 6 cal 14 c ka bp among these des a lupane is the only saturated ring a degraded compound whilst mono and di unsaturated des a triterpenes are dominated by oleanane and ursane derivatives the mono and di unsaturated des a triterpenes show a strong correlation r 2 0 94 in abundance indicating that they may be derived from the same source or process des a lupane shows no correlation in abundance with the mono or di unsaturated des a triterpenes r 2 des a triterpenoids corresponds to the interval with relatively high sedimentation rate 0 3 mm per year these data indicate that the abundance of aliphatic des a triterpenoids in the dajiuhu peat deposit in the early holocene may result from the prevailing reducing conditions in the water table or surficial sediment and or rapid preservation of the early diagenetic products our study highlights the potential application of des a triterpenes in the reconstruction of palaeoenvironments based on peat sequences

cryptic abundance of long chain iso and anteiso alkanes in the dajiuhu peat deposit central china abstract long chain 2 methyl and 3 methyl alkanes occur widely in modern plants and in recent and ancient sediments but their presence in peat deposits has not been reported here we document an early holocene enrichment of long chain 2 methyl alkanes in the dajiuhu peat deposit accompanied by traces of 3 methyl alkanes the 2 methyl alkanes showed a strong odd even predominance and were dominated by c 27 and c 29 homologs their 13 c values were 5 7 less negative than those of the n alkanes with the same carbon numbers our previous paleoenvironmental reconstruction for this peat sequence indicated that the interval enriched in long chain 2 methyl alkanes corresponded to a period with a very wet climate although not resolved possible sources of the long chain 2 methyl alkanes with relatively enriched 13 c composition include submerged aquatic plants utilizing bicarbonate or heterotrophic microbes in the peatland and its catchment

moisture conditions during the younger dryas and the early holocene in the middle reaches of the yangtze river central china the last glacial interglacial climate transition in east asia was characterized by an intensified monsoon but knowledge about hydrological responses at a regional scale during this transitional period is limited here we provide a novel lipid based paleohydrological record for this period from the dajiuhu peat deposit central china high water levels and persistent wet conditions during the younger dryas 12 5 11 6 ka and the early holocene 10 5 9 9 ka were inferred on the basis of enrichments of sterenes a group of unstable intermediate diagenetic products derived from biogenic sterols that are most likely preserved under a waterlogged peatland surface these two wet intervals were accompanied by temperature decreases indicated by an increase in pollen abundance from cold favoring conifer trees and a decrease in total hardwood tree pollen this cold and wet climate pattern which is different from the concordant cold dry pattern documented in north china was probably caused by the regional influen

fault zone guided waves from explosions in the san andreas fault at parkfield and cienega valley california fault zone guided waves were successfully excited by near surface explosions in the san andreas fault zone both at parkfield and cienega valley central california the guided waves were observed on linear three component seismic arrays deployed across the fault trace these waves were not excited by explosions located outside the fault zone the amplitude spectra of guided waves show a maximum peak at 2 hz at parkfield and 3 hz at cienega valley the guided wave amplitude decays sharply with observation distance from the fault trace the explosion excited fault zone guided waves are similar to those generated by earthquakes at parkfield but have lower frequencies and travel more slowly these observations suggest that the fault zone wave guide has lower seismic velocities as it approaches the surface at parkfield we have modeled the waveforms as s waves trapped in a low velocity wave guide sandwiched between high velocity wall rocks resulting in love type fault zone guided waves while the results are nonunique the parkfield data are adequately fit by a shallow wave guide 170 m wide with an s velocity 0 85 km sec and an apparent q 30 to 40 at cienega valley the fault zone wave guide appears to be about 120 m wide with an s velocity 0 7 km sec and a q 30

evidence from the oman ophiolite for sudden stress changes during melt injection at oceanic spreading centres the system of dikes in the uppermost mantle below oceanic spreading centres bears witness to the processes involved in the supply of melt to the ridge such systems cannot be studied on currently active ridges but can be seen in ophiolites in particular the oman ophiolite allows us to examine segments of a fast spreading ridge1 here we present a statistical analysis of the orientation of intrusions in the uppermost mantle section of the oman ophiolite spreading centres which points to the existence of two systems dikes whose azimuth is parallel to the sheeted dikes which we thus consider as related to the extensional lithospheric stress field and sills roughly parallel to the moho2 branching contemporaneous dikes and sills are frequently observed we suggest that these relations can be explained by repeated sudden changes of the dominant stress field from lithospheric to asthenospheric such changes could result from the episodic relaxation of lithospheric stress in response to tension fracturing of the lithospheric lid related to sudden melt surges this episodic behaviour is recorded in the sheeted dike complex with each dike each about one metre wide representing one of these fractures

holocene land cover dynamics in the curuai floodplain inferred from lacustrine biomarkers this study on curuai floodplain central amazonia sediments last 5600 cal yr bp focused in rock eval re hydrogen hi and oxygen oi indices tmax s2 curve and tps2 organic petrography and molecular biomarkers n alkanes hopanes pentacyclic triterpene methyl ethers ptmes and derivatives of pentacyclic triterpenes such as des a lupane and aromatic derivatives analyses between 5600 and 5100 cal yr bp the environment was waterlogged and dominated by emersed plants paq 0 27 0 38 the influence of the amazon river was low terrestrial vs aquatic ratio t a 0 8 cpi values 3 4 and high contents of ptme 0 22 1 54 g g sed and aromatics 21 53 g g sed indicated a strong contribution of terrestrial material and anoxic om deposition conditions between 5100 and 5000 cal yr bp more humid conditions due to heavier rainfalls were observed early in this period terrestrial biomarker contents 253 g g sed of aromatics paq 0 17 increased due to input of watershed erosion material this provoked a rapid burial and good preservation of terrestrial om cpi 3 4 5 from 5000 cal yr bp a strong sedimentation of carbonate minerals oi 1600 mg co2 g 1 masked the om signal and affecting re parameters paq 0 18 t a ratio 0 4 and the decrease of c31 c31 hopanes 1 18 indicate increasing aquatic conditions up to 2700 cal yr bp cpi ratio 1 2 and degraded phytoclasts suggest intense degradation during transport to the sedimentation location the ptmes results showed that from 3000 yr cal bp the poaceae genuses were different from those found at the bottom middle holocene suggesting a change of vegetation the last 600 cal yr bp were marked by the seasonal influence of the amazon river during periods of low water level the organic petrography and cpi values 1 0 evidenced om degradation and the return of rather drier conditions

the jurassic south albanian ophiolites mor vs ssz type ophiolites abstract within the western belt of the southern albanian ophiolites the voskopoja ophiolite consists of three subunits voskopoja morava and rehove these are predominantly lherzolites with minor harzburgites and dunites in the mantle section above come ultramafic and mafic cumulates including wehrlites troctolites and olivine gabbros gabbronorites are restricted to the morava subunit isotropic clinopyroxene gabbros extrusives and sediments are present only in rehove and voskopoja the volcanic section is dominated by basaltic breccias including megablocks with sheeted dykes pillow lavas and isolated dykes the basaltic breccias grade upwards into sandstones in turn interlayered with argillites and cherts of jurassic age the basalts are predominantly clinopyroxene plagioclase basalts either aphyric or plagioclase phyric geochemically they are divided into four groups 1 an intermediate ti and zr group with low ni hereafter called low ni group 2 an intermediate ti zr group with high ni hereafter called high ni group 3 a high ti zr group and 4 a low ti zr group the high ni content in group 2 is interpreted as originating from olivine and spinel xenocrysts apart from the high ni content groups 1 and 2 are comparable with the volcanics of the low to high ti intermediate ophiolites by contrast group 3 is more comparable to the high ti ophiolitic extrusives in the western ophiolite belt of northern albania group 4 consists ssz type basalts and is widespread in the volcanics of the eastern ophiolite belt comparison of the ultramafic mafic cumulates and the basaltic volcanics with those in the northern part of the western belt in albania and the pindos ophiolite indicates that there is a systematic variation in petrography and geochemistry from north to south in the western belt with an increasingly distinct ssz signature towards the south ultramafic and mafic cumulates as well as basalts from the shebenik massif in the eastern belt are similar to those of voskopoja implying a genetic relationship

contrasted distributions of triterpene derivatives in the sediments of lake caco reflect paleoenvironmental changes during the last 20 000 yrs in ne brazil lipid fractions extracted from sediment layers deposited in a small brazilian lake during the last 20 000 yrs were investigated by gas chromatography mass spectrometry considerable differences in the distribution and the amount of triterpene derivatives in the aliphatic as well as in the aromatic fractions were observed all along the series although no precise identification of these compounds was undertaken our interpretation of mass spectral data allowed us to discriminate between des a triterpenes mono and triaromatic derivatives of pentacyclic triterpenes and a series of compounds tentatively identified as diaromatic derivatives of tetracyclic triterpenes the largest compound diversity was found in the lowest levels of the series dated back to the end of the last glacial maximum when good preservation of terrestrial plant debris was ensured by rapid burial in a semi arid climate then except for a period corresponding to the younger dryas only des a lupane was detected in significant amounts the high predominance of des a lupane is interpreted to result from the development of a belt of eleocharis sp spike rush that filtered most of organic inputs from the catchment and was the site of des a lupane production and exportation towards the lake centre during the younger dryas a strong influx of des a lupane is attributed to the destruction of the spike rush belt consecutive to the lowering of the lake level under drier conditions the temporary destruction of this barrier allowed other triterpene derivatives to reach the lake the distinct dynamics of des a and aromatic triterpene derivatives under variable medium conditions led us to hypothesis that these two families of compounds derive from distinct pools that contributed differently to the sediment depending on environmental and climatic conditions des a lupane was most probably produced in sub aquatic conditions within the belt of spike rush conversely aromatic derivatives of triterpenes could have resulted from the degradation of their biological precursors within reducing micro environments in the catchment

biomarkers and geochemical indicators of holocene environmental changes in coastal lake sarbsko poland organic rich samples from the holocene sedimentary sequence of lake sarbsko were investigated to reconstruct variations in the aquatic system in response to environmental change the aims were to i identify organic matter om sources ii examine changes in soluble om composition in relation to fluctuations in limnological conditions and iii validate the sensitivity of organic geochemical indicators in tracing environmental changes diatom frustules are abundant in all samples alginite macerals and terrigenous organic matter further contribute to the sedimentary om organic petrography total organic carbon toc n ratio values and high content of biogenic silica sio2 biogenic argue for a predominant algal source of om in contrast the n alkane distributions high relative abundance of c29 steroid hydrocarbons and high content of detrital quartz in the sediments provide evidence for the input of terrigenous material as a major om source within the basin the terpenoid biomarker composition indicates a contribution from conifers and angiosperms from the diterpenoids in the samples a contribution from species of the coniferales family pinaceae is concluded toc s and mg ca values as well as steroid hopanoid concentration ratios reflect enhanced water salinity in this coastal lake due to ingression of brackish water from the baltic sea during the atlantic and sub atlantic periods as indicated by the positive relationship between d 13 c of toc and mg ca d 13 c values are influenced by changing contribution of marine vs freshwater phytoplankton additional isotopic heterogeneity in d 13 c may result from differences in terrigenous om supply vs autochthonous om production in the lake the isotopic composition of calcites supports the establishment of freshwater conditions in the lake during the sub boreal period pristane phytane and fe mn ratios are interpreted to reflect differences in the redox conditions oxygenation of bottom waters was temporarily variable with highest levels of oxygen availability during the sub boreal freshwater lake high contents of hopanoid hydrocarbons argue for enhanced microbial activity in the water column and sediment the occurrence of 2b methyl hopanes is related to the presence of cyanobacteria or methylotrophic bacteria

oleananes in oils and sediments evidence of marine influence during early diagenesis abstract the oleananes as markers for the angiosperms provide valuable source and age information when present in an oil nevertheless they are not quantitatively related to the land plant input and indeed their presence reflects only a small leak in diagenetic processes leading primarily to aromatic oleanoids because they are minor products the abundance of oleananes in terrigenous oils and sediments may be highly sensitive to changes in early diagenetic conditions here we present evidence that contact of plant matter with seawater during early diagenesis enhances the expression of oleananes in a mature sediment or oil oleananes are absent or present at very low concentrations in samples from the base of an eocene coal seam affected by postdepositional seawater intrusion however their abundance increases toward the top of the seam in correlation with organic sulphur dibenzothiophene phenanthrene and the homohopane index similarly in deltaic sediments from the south sumatra basin oleanane hopane is strongly correlated with indicators of marine influence such as c 27 c 29 steranes and the homohopane index in each case increasing oleanane abundance is accompanied by a reduction in the extent of aromatisation and for the south sumatra basin the proportion of a ring contracted oleananes an angiosperm derived miocene coal from the philippines deposited under freshwater conditions shows abundant aromatic oleanoids but no oleananes these results show that oleananes need to be used with caution as age and source markers in fluvio deltaic and lacustrine petroleum systems on the other hand their sensitivity to early diagenetic conditions may make them useful in locating effective source rocks in such systems

tectonic units of the alpine collision zone between eastern alps and western turkey abstract we present a map that correlates tectonic units between alps and western turkey accompanied by a text providing access to literature data explaining the concepts used for defining the mapped tectonic units and first order paleogeographic inferences along strike similarities and differences of the alpine eastern mediterranean orogenic system are discussed the map allows 1 for superimposing additional information such as e g post tectonic sedimentary basins manifestations of magmatic activity onto a coherent tectonic framework and 2 for outlining the major features of the alpine eastern mediterranean orogen dinarides hellenides anatolides and taurides are orogens of opposite subduction polarity and direction of major transport with respect to alps and carpathians and polarity switches across the mid hungarian fault zone the dinarides hellenides taurides and apennines consist of nappes detached from the greater adriatic continental margin during cretaceous and cenozoic orogeny internal units form composite nappes that passively carry ophiolites obducted in the latest jurassic earliest cretaceous or during the late cretaceous on top of the greater adriatic margin successions the ophiolites on top of composite nappes do not represent oceanic sutures zones but root in the suture zones of neotethys that formed after obduction suturing between greater adria and the northern and eastern neotethys margin occupied by the tisza and dacia mega units and the pontides occurred in the latest cretaceous along the sava izmir ankara erzincan suture zones the rhodopian orogen is interpreted as a deep crustal nappe stack formed in tandem with the carpatho balkanides fold thrust belt now exposed in a giant core complex exhumed in late eocene to miocene times from below the carpatho balkan orogen and the circum rhodope unit its tectonic position is similar to that of the sakarya unit of the pontides we infer that the rhodope nappe stack formed due to north directed thrusting both rhodopes and pontides are suspected to preserve the westernmost relics of the suture zone of paleotethys

aliphatic and aromatic triterpenoid hydrocarbons in a tertiary angiospermous lignite abstract the hydrocarbon biomarker assemlage of a liptinite rich early tertiary angiospermous lignite has been characterized the biomarker fistribution for the lignite confirms the low maturity and previous paleobotanic interpretations the aliphatic hydrocarbon fraction consists predominantly of n alkanes showing a strong odd carbon predominance and numerous de a triterpenoids and triterpenoids derived from higher plants bacterially derived triterpenoids were represented primarily by homohopanes and hopenes the aromatic hydrocarbon fraction contains a series of mono di and triaromatic de a triterpenoids and mono tri and tetraaromatic triterpenoids derived from higher plants the concentration and abundance of monoaromatic triterpenoids containing one to three additonal degress of unsaturation have not seen previously observed in a single deposit as such a diagenetic scheme for angiosperm derived triterpenoids is presented which confirms and extends previous hypothesis

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

concordant monsoon driven postglacial hydrological changes in peat and stalagmite records and their impacts on prehistoric cultures in central china asian monsoon records are widely documented but specific proxies of monsoonal rainfall are limited we present here two new independent proxy records from peatland and stalagmite archives that indicate a high degree of concordance between monsoon driven hydrological changes occurring since the last deglaciation in a broad region of central china the wet periods elevated the water table in the dajiuhu peatland as recorded by reduced mass accumulation rates of hopanoids biomarkers for aerobic microbes confirmed by molecular phylogenic analyses the hopanoid based reconstruction is supported by the first report of the environmental magnetism parameter arm sirm anhysteretic remanent magnetization saturation isothermal remanent magnetization ratio of fine magnetic particles to total ferrimagnetic particles in a stalagmite from heshang cave in central china heavy rainfall resulted in the enhanced transport of coarse particles to the cave and thus low arm sirm values in the stalagmite the hydrological conditions inferred from the two records reveal three relatively long wet periods in central china 13 11 5 k y ago 9 5 7 0 k y ago and 3 0 1 5 k y ago archaeological evidence for the hydrological impacts on regional populations comes from the observation that temporal shifts among six distinctive cultures of the neolithic period to the iron age in central china occurred during wet periods or flood episodes spatiotemporal distributions of 1600 prehistoric settlement sites correlate with the proxy inferred fluctuating hydrological conditions with enhanced flooding risk forcing major relocations of human settlements away from riparian zones

lipid stratigraphy of a flandrian peat bed northumberland uk comparison with the pollen record a flandrian peat bed near low hauxley northumberland uk was studied both optically and geochemically to compare the pollen and lipid records of changing plant input during its accumulation a pr

molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction a 40 cm deep sphagnum dominated peat monolith from bolton fell moss in northern england was systematically investigated by lipid molecular stratigraphy and compound specific 13c and d analysis using gas chromatography gc gc mass spectrometry gc ms gc combustion isotope ratio ms gc c irms and gc thermal conversion irms gc tc irms techniques 210pb dating showed the monolith accumulated during the last ca 220 yr a period encompassing the second part of little ice age while the distributions of lipids including n alkan 1 ols n alkan 2 ones wax esters sterols n alkanoic acids alkandioic acids and hydroxy acids display relatively minor changes with depth the cooler climate event was recorded in the concentrations of n alkanes and organic carbon cpi values of n alkanes and n alkanoic acids and the ratio of 5 n alkylresorcinols sterols superimposed on the fossil fuel effect the relatively cooler climate event was also recorded by 13c values of individual hydrocarbons especially the c23n alkane a major compound in certain sphagnum spp the d values of the c29 and c33n alkanes correlated mainly with plant composition and were relatively insensitive to climatic change in contrast the c23n alkane displayed variation that correlated strongly with recorded temperature for the period represented by the monolith agreeing with previously reported deuterium records in tree ring cellulose spanning the same period in scotland germany and the usa with more negative values occurring during the second part of little ice age these biomarker characteristics including the compound specific 13c and d records provide a new set of proxies of climatic change potentially independent of preserved macrofossils which will be of value in deeper sections of the bog where the documentary records of climate are unavailable and humification is well advanced

postglacial climate change record in biomarker lipid compositions of the hani peat sequence northeastern china abstract the peat sequence at hani in northeastern china accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system the molecular compositions of n alkanes n alkanols and n alkanoic acids extracted from the hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat forming vegetation long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n alkane distributions throughout the hani peat sequence the paleoclimate integrity of these biomarker molecules appears to be well preserved most of the n alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants in contrast n alkanoic acid distributions are dominated by secondary components that record the importance of post depositional microbial activity in this peat sequence which evidently can be extensive in a percolation mire elevated n alkane paq values and c23 c29 ratios which are both molecular proxies for water loving plants record an especially moist local climate in the bolling allerod 14 5 to 12 9 ka younger dryas 12 9 to 11 5 ka and pre boreal 11 5 to 10 5 ka portions of the hani peat sequence depressed paq values and c23 c29 ratios and larger n alkane average chain length values indicate that the holocene climatic optimum 10 5 to 6 ka was a period of warmer climate with lower effective precipitation which contrasts with evidence of wetter climates in most of east asia

influence of floral assemblage facies and diagenesis on petrography and organic geochemistry of the eocene bourgas coal and the miocene maritza east lignite bulgaria abstract numerous differences in the petrography and organic geochemistry of two tertiary low rank coal deposits of bulgaria formed within comparable depositional environments are outlined different floral assemblages are indicated as the main sources of organic matter for the eocene bourgas sub bituminous coals a warm climate plant community dominated by angiosperms is reflected in the biomarker composition whereas a coniferous flora was the main source of the resinous organic matter of the miocene maritza east lignite the results are in agreement with palaeobotanical data these differences in the peat forming vegetation of the paleogene compared to the neogene of bulgaria are attributed to decreasing temperature during the tertiary the abundance of resinous compounds relative to lipids from plant waxes long chain n alkanes as well as the preservation of plant tissue are mainly controlled by gymnosperm angiosperm ratios pristane phytane and diasterenes sterenes ratios reflect variations in redox conditions and the ph of the depositional environments caused by eustatic sea level changes freshwater inflow or varying ground water table changing eh and ph values are associated with differences in microbial activity controlling the extent of gelification of plant tissue bacteria most probably contributed to the aromatisation of triterpenoids in the mire enhanced thermal maturation of organic matter during diagenesis is reflected in higher contents of n alkanes and the presence of alkyl naphthalenes in the bourgas coals alkyl naphthalenes are thought to have been formed from pentacyclic triterpenoids rather than from resinous compounds

source rock potential of the lowest coal seams of the marcelina formation at the paso diablo mine in the venezuelan guasare basin evidence for the correlation of amana oils with these paleocene coals abstract the aims of this work were to carry out a combined petrographic palynofacies and organic geochemical study of twelve drill core samples collected from the lowest coal seams in the paleocene marcelina formation paso diablo mine guasare basin northwestern venezuela to characterize crude oil samples from three wells in the nearby amana field and to evaluate oil source correlations of these crude oils with the paso diablo coal extracts the coals under study were classified as high volatile bituminous a or at the b a boundary and showed vitrinite contents between 50 0 and 89 4 vol liptinites ranging from 1 4 to 24 2 vol and inertinites in the 6 2 30 8 vol range results from organic geochemical investigations indicate that the guasare coals were generated in a limno telmatic to telmatic zone under fluctuating oxygen conditions a type iii kerogen with relatively high hydrogen content and a thermal maturity corresponding to the early oil window are proposed for these coals as supported by rock eval and petrographic data as well as biomarker interpretations oil generation potential from marcelina formation coals is probably due to the perhydrous nature of the vitrinite high bitumen contents and considerable liptinite concentrations mainly oil prone resinites and exsudatinites palynofacies observations denote a dominance of psilate pollen grains related to angiosperm plants and as expected type iii kerogens or humic coals in the studied seams the parent material of which contained a significant contribution of algae the non detection of 18 h oleanane does not preclude the fact that angiosperms are the dominant plants in the guasare paleomire on the other hand the characterization of the amana oils suggests that they all fall into a unique oil family the presence of 25 norhopanes in them could indicate paleobiodegradation and mixing from various hydrocarbon charges in the reservoir thus the crude oils from the amana field seem to be a mixture of one or more oil charges from the early mature marine carbonate source rocks of the la luna formation deposited under anoxic reducing conditions and a later pulse of hydrocarbon generation which originated from an unknown so far nonmarine source rock in this regard hydrocarbon liquid derived from the lowest marcelina coal seams may be tentatively identified as the latter oil charge also this work delineates some components of a currently subcommercial and hypothetical tertiary petroleum system identified and named as marcelina misoa c5 in the lake maracaibo region finally the coalbed gas contents of sampled coals were determined

petrology and organic geochemistry of peat samples from a raised bog in kalimantan borneo abstract two peat cores from the margin and centre of a tropical raised bog from the sebangau river near palangkaraya in kalimantan indonesia were investigated to illustrate the changes during peatification using coal petrographic and organic geochemical techniques these methods included a maceral analysis on polished peat blocks under reflected white and blue light excitation using the brown coal maceral nomenclature soxhlet extraction was carried out and an estimate of the humic composition was undertaken on the residues gc and gc ms analysis of the alkane and aromatic fractions were also made to identify biomarkers present in the peat results of this study show that peats from the margin of the raised bog were more decomposed than peats from the centre tissue content extract yield and alkaline insoluble acid soluble humic acid fraction support these results not only were there differences between the two locations of the peat cores but also differences arose with respect to depth in both cores the basal peats were more decomposed than the peats from the upper layers this was a result of their differing environments of deposition i e the basal peats were deposited under relative mesotrophic conditions and a more seasonal climate whereas the peats from the upper layers were deposited under acidic and oligotrophic conditions the biomarker composition of the alkane fraction included long chain n alkanes from n c 23 to n c 35 with an odd over even predominance and interestingly n alkanes from n c 36 to n c 40 with an even over odd predominance peaking at n c 38 pentacyclic triterpenoids were mainly represented by 17 21 h homohopane and hop 17 21 ene biomarkers in the aromatic fraction included polyaromatic triterpenoids derived from and amyrin