seasonal diurnal and storm scale hydrochemical variations of typical epikarst springs in subtropical karst areas of sw china soil co2 and dilution effects summary two year continuous ph conductivity temperature and water stage of the two typical epikarst springs nongla spring and maolan spring about 200 km apart in subtropical karst areas of sw china were presented our primary study objective was to understand how karst systems respond hydrochemically to recharge at different time scales and what the biogeochemical processes and controlling factors in the sw china epikarst environment are a thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of co 2 partial pressures and calcite dolomite saturation levels on a continuous basis marked seasonal diurnal and storm scale variations were observed for ph conductivity co 2 partial pressures and calcite dolomite saturation indexes of the springs indicating that both springs are dynamic and variable systems however the coefficients of variation of these hydrogeochemical features tends to be in the order of seasonal storm scale diurnal the seasonal and diurnal variations of these features higher conductivity and lower ph in summer and at daytime lower conductivity and higher ph in winter and at nighttime tend to co vary with temperature which influences the production of co 2 in soils thus being the driving force for the variations soil co 2 effect the storm scale fluctuations occur during the spring summer rainy days due to the storm events depending on the rainfall intensities however there are differences in magnitudes and direction of the variations of these features at very high rainfall intensity the dilution effect dominates the variations characterized by the decrease in both conductivity and calcite dolomite saturation of the springs while soil co 2 effect determines the variations at lower rainfall intensity characterized by increase in co 2 partial pressure and conductivity but decrease in ph and calcite dolomite saturation in a word the hydrodynamic aspects together with hydrobiogeochemical characteristics need to be taken into account to correctly explain the hydrochemical variations of the epikarst springs results from the study demonstrate the need to redesign hydrogeochemical sampling strategies for epikarst springs in karst areas with monsoon climate like sw china i e with remarkable seasonal matching fluctuations in temperature rainfall and vegetation

thinned continental crust below northern evoikos gulf central greece detected from deep seismic soundings abstract in march 1996 a wide aperture reflection refraction profiling warrp seismic survey was carried out across the maliakos sporades and northern evoikos basins central greece two onshore offshore seismic lines were recorded using 14 ocean bottom seismographs obs and 10 land stations as an energy source we used one sleevegun of 60 l volume operating at 120 bar pressure the results acquired by kinematic two point raytracing modelling of the time sections provided evidence of a thinned stretched continental crust of only 20 km thickness below the central part of the northern evoikos basin this basin was developed by the separation of the island of evia with continental crust of approximately 30 km thickness from the greek mainland by transtension and stretching of the crust forming the north evia and the sperchios valleys along the maliakos north sporades basin the crust thins from 34 km at the mainland to 22 km below the sporades basin the crust at the northern part of the island of evia and the trikeri straits is 30 32 km thick and of normal continental structure it is separated by an intercrustal discontinuity between an upper and lower crust the sediments thicken significantly towards the sporades basin where they obtain maximum thicknesses of the order of 8 10 km the igneous and metamorphic crust thins significantly in the basin maintaining however its continental character along the entire section the transition from the maliakos trikeri straits to the sporades basin is controlled by a steep listric fault that downthrows the basin crust by more than 6 7 km the crustal transition of the thinned sporades basin to the 30 km thick crust of the northern evia and the maliakos straits is poorly understood simple or pure shear stretching cannot have developed this margin and we favour the assumption that it denotes the limit of two different crustal domains these were merged together during a compressive tectonic episode prior to the present day extension and stretching of the aegean sea that was activated 5 ma ago

isotopic and geochemical evidence of palaeoclimate changes in salton basin california during the past 20 kyr 1 δ18o and δ13c records in lake tufa deposits abstract investigation of 18 o and salt content of surface waters in the salton basin california shows that there is a strongly positive correlation between 18 o values and salt contents and that the 18 o of salton sea is much heavier than that of its input waters due to strong evaporation using a steady state 18 o model we have discussed the 18 o of lake cahuilla an ancient lake in the basin under through flowed closed and overflowed situations an ams 14 c dated stable isotope record of a 60 cm lake tufa slice lc 1 from the ancient shoreline of lake cahuilla indicates that the lake experienced closed and or overflowed conditions between 1 300 and 20 500 yr bp the variations in 18 o and 13 c values of lc 1 ranging from 8 52 to 2 50 pdb and from 0 8 to 3 76 respectively reflect changes in the relative humidity in salton basin and variations in the colorado river inflow and hence climatic conditions in the colorado river drainage basin the tufa record exhibits palaeoclimates of salton basin as follows 1 relatively dry climate between 20 and 18 kyr bp was followed by a wet climate between 18 and 17 kyr bp 2 decreasing effective moisture precipitation evaporation from 17 to 16 kyr bp corresponded to heinrich 1 event whereas effective moisture increased at ca 15 5 kyr bp during the trans us wet period contrasting patterns between the lc 1 record and the greenland ice core and chinese speleothem records during the bolling allerod interstadial from 15 2 to 11 7 kyr bp may be caused by age uncertainty of the lc 1 record further study of this interval is needed 3 wet warm early holocene corresponding to the maximum effective moisture period perhaps brought about by the strengthening of north american monsoon 4 toward 2 kyr bp the climate became dryer apparently resulting from weakening of the monsoons especially around 6 2 and 2 5 kyr bp 5 a wet regime occurred in the basin during the medieval warm period

seismic imaging of melanges pieniny klippen belt case study discussion we appreciate the attempts of marzec et al 2019 to investigate the geological structure of the pieniny klippen belt pkb by means of seismic reflection profiling but in our opinion the authors main conclusions contradict the results of previous studies without being constrained by the new data below we comment on some of the problems that led to the misinterpretation

uranium series dating of carbonate tufa deposits associated with quaternary fluctuations of pyramid lake nevada abstract uranium series dating of dense tufa deposited in a small cave at former lake margins and in large tufa mounds clarifies the timing of lake level variation during the past 400 000 yr in the pyramid lake basin a moderate sized lake occasionally overflowed the emerson pass sill at elevation of 1207 m between ca 400 000 and 170 000 and from ca 60 000 to 20 000 yr b p as shown by230th 234u ages of the cave samples 230th excess ages of tubular tufas and average isochron plot ages of shoreline deposited tufas by comparison modern pyramid lake is 50 m below this sill there is a lack of tufa record during the intervening period from ca 170 000 to 60 000 yr b p after ca 20 000 yr pyramid lake underwent abrupt changes in level and based on previous14c ages reached its highest elevation ca 1335 m at ca 14 000 yr b p the youngest uranium series ages are comparable with previously reported14c ages

u th dating of freshwater travertine from middle velino valley central italy paleoclimatic and geological implications abstract six travertine bodies outcropping along the middle velino valley central italy have been studied and dated using the u th method in order to obtain new chronological constraints for the recent geological evolution of the area the lithological and sedimentological characteristics of travertines have been described showing that such deposits can be referred to waterfall pool terraces and gentle slopes environment travertines have formed during warm periods and can be referred to marine oxygen isotope stages 5 3 and 1 travertine deposition seems to stop around 5 ka bp according to other european and italian sites pollen stratigraphy and ostracod assemblages from the close sequence of valle di castiglione characterized by the same climatic conditions of velino valley have confirmed that periods of velino valley travertine deposition were effectively characterized by warm and wet climatic conditions seismic activity strongly active in the area since the middle pleistocene has deeply influenced the location and the discharge of springs which have deposited the travertines influencing in turn the shape and size of travertine bodies

230th 234u dating of holocene tufas possibilities and problems high resolution chronologies in continental carbonate deposits such as tufas are required for detailed palaeoclimatic and environmental studies this work set out to establish if high resolution u series dating of detritus rich holocene tufas is routinely possible the study centres on a paludal holocene tufa from southern england that already has an existing holocene chronology based on 14c and supported by biostratigraphy against which to compare u series dates the results show that significant detrital contamination combined with low initial u concentrations and short time for ingrowth of radiogenic 230th make high resolution u series dating of holocene tufa very difficult moreover a single 230th 232th initial value to correct for the presence of detrital 230th is not appropriate at the study site a finding that may apply to most holocene tufas total sample dissolution of coeval samples demonstrates considerable variability in the isotopic composition of the detritus the total sample dissolution data are too scattered to constrain chronologies at the required resolution and may indicate the incorporation of a 230th rich component in the detritus

passive and active margin history of the northern tatricum western carpathians slovakia the tatricum an upper crustal thrust sheet of the central western carpathians comprises pre alpine crystalline basement and a late paleozoic mesozoic sedimentary cover the sedimentary record indicates gradual subsidence during the triassic early jurassic initial rifting a jurassic early cretaceous extensional tectonic regime with episodic rifting events and thermal subsidence periods and middle cretaceous overall flexural subsidence in front of the orogenic wedge prograding from the hinterland passive rifting led to the separation of the central carpathian realm from the north european platform a passive margin rimmed by peripheral half graben was formed along the northern tatric edge facing the vahic south penninic oceanic domain the passive versus active margin inversion occurred during the senonian when the vahic ocean began to be consumed southwards below the tatricum it is argued that passive to active margin conversion is an integral part of the general shortening polarity of the western carpathians during the mesozoic that lacks features of an independent wilson cycle an attempt is presented to explain all the crustal deformation by one principal driving force the south eastward slab pull generated by the subduction of the meliatic triassic jurassic tethys oceanic lithosphere followed by the subcrustal subduction of the continental mantle lithosphere

evaporation induced 18o and 13c enrichment in lake systems a global perspective on hydrologic balance effects growing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time one of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions however endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined as a consequence isotopic researchers are often required to assume values for multiple parameters including temperature of carbonate formation or lake water delta o 18 in order to interpret changes in hydrologic conditions here we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions through integration of multiple large datasets we show that lake carbonate delta o 18 values and the lake waters from which they are derived are often shifted by 10 parts per thousand relative to source waters discharging into the lake the global pattern of delta o 18 and delta c 13 covariation observed in 70 of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where delta o 18 and delta c 13 covariation is absent aridisol pedogenic carbonates show similar isotopic responses to evaporation and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed recent advances in stable isotope research techniques present unprecedented opportunities to overcome the underdetermined nature of stable isotopic data through integration of multiple isotopic proxies including dual element c 13 excess values and clumped isotope temperature estimates we demonstrate the utility of applying these multi proxy approaches to the interpretation of paleohy droclimatic conditions in ancient lake systems understanding past present and future hydroclimatic systems is a global imperative significant progress should be expected as these modern research techniques become more widely applied and integrated with traditional stable isotopic proxies c 2015 elsevier ltd all rights reserved

local seismic array observations at north evoikos central greece delineate crustal deformation between the north aegean trough and corinthiakos rift abstract in order to better constrain and define the microseismic activity at the north evoikos gulf and its surrounding area we deployed an onshore offshore seismic array consisting of 31 three component seismic digital stations the array was active from 30 june to 24 october 2003 and covered an area of 2500 km 2 we located more than 2000 seismic events ranging from 0 7 to 4 5 m l by using six stations as a minimum in order to define the foci parameters recorded seismicity delineated three major zones of deformation from south to north the eretria parnis eastern corinthiakos zone the psachna viotia zone and the northern sporades north evia bralos zone alignments of the recorded seismicity follow the tectonic trends and their orientation in the above zones the whole area accommodates the stress field between the north aegean trough and the corinthiakos gulf rate of deformation intensifies from north to south as revealed also by historical and instrumental seismicity the successive change of orientation between the two stress fields fragments the crust in relatively small units and the fault systems developed do not permit the generation of major earthquakes in the north evoikos area and its immediate vicinity this is also supported by the instrumental seismicity of the last century larger events reported in historical times are probably overestimated most seismic activity is crustal subcrustal events were recorded mainly below the lichades area and are interpreted as the consequence of the subduction of the ionian oceanic lithosphere below the hellenides the lichades volcano is the most northern end of the hellenic volcanic arc at present the highest seismic activity is associated with the psachna region of north evia that has been continuously active since 2001 considering however the development of the seismic activity during the last decade there has been a sequence of large events i e parnis in 1999 skyros in 2001 and psachna in 2001 2003 this demonstrates the fact that the tectonic deformation in all this area is intense and important for the accommodation of the stress field of the north aegean trough to that of the corinthiakos rift

aegean crustal thickness inferred from gravity inversion geodynamical implications since oligo miocene times the aegean domain has undergone regional extension due to the southward retreat of the hellenic subduction zone boundary conditions have been more recently modified by the westward extrusion of anatolia a new map of the aegean crustal thickness inferred from gravity inversion is proposed here to better constrain the variations in space and time of crustal thinning that has accumulated since oligo miocene times moho topography is obtained by inversion of satellite marine gravity data data are first corrected for terrain anomalies and deep mantle effects african subducting slab they are then filtered between 50 and 300 km to avoid short wavelength intracrustal effects results are consistent with previous 2d geophysical studies seismic refraction receiver functions and show that an overall regional isostatic compensation of the crust holds for the aegean area with a mean crustal thickness of 25 km three different provinces north aegean cyclades and cretan sea can be identified thinner crust is observed both in the north aegean region ne sw trending of thinning with crustal thickness lower than 24 km and in the cretan sea crustal thickness of 22 23 km between these two regions the cyclades are marked by a rather flat moho at 25 km a two stage model of the aegean extension could well explain the observed crustal thickness variation from oligocene to middle miocene gravitational collapse of the hellenides due to the southward retreat of the african slab reduced the aegean continental crust from 50 km by reference to continental greece and anatolia to a mean value of 25 km at the scale of the whole aegean from upper miocene to present the westward extrusion of anatolia modified the extension and the associated crustal thinning in the north aegean domain during this second episode crustal thinning related to the southward retreat of the african slab tends to localize in the cretan sea the cyclades likely behave as a rigid block translated toward the south west without significant deformation in agreement with the gps velocity field and the lack of major earthquakes d 2004 elsevier b v all rights reserved

seismic imaging of melanges pieniny klippen belt case study the authors present results of the first high resolution deep seismic reflection survey in the pieniny klippen belt pkb in poland this survey sheds new light on the matter of olistostromes and the melange character of the pkb the sedimentary mass transport deposits represented by olistoliths and olistostromes manifest themselves by different petrophysical parameters of rocks velocity density and resistivity and seismic attributes seismic attributes are very effective in the interpretation of the geology of complex melanges the authors used selected attributes low pass filter energy energy gradient dip steered median filter prewitt filter laplacian edge enhancing filter and square root of the energy gradient these attributes emphasize changes of the seismic image inside melange zones the distinguished olistoliths are now inside imbricated thrust structures and they are tectonically rearranged polygenetic melanges in the pkb originated as a result of sedimentary and tectonic processes the pkb in the investigated area forms several north vergent thrust sheets belonging to the zlatne and hulina nappes both nappes contain large chaotic non reflective olistoliths as well as the smaller mainly high reflective olistoliths olistoliths are arranged parallel to the flysch layering and thrusts the results presented confirm the postulated two olistostrome belts within the pkb structure

crustal investigation of the hellenic subduction zone using wide aperture seismic data abstract we present the results of a wide aperture seismic onshore offshore study crete seismic experiment in the cretan region as part of the hellenic arc compressional system three seismic lines were carried out on and around the island of crete in order to investigate the crustal structure of the region up to 119 three component recording stations were deployed on each profile that observed seismic energy generated by a 48 l airgun array and eight 20 kg landshots a total of 6208 shots were fired upon completing the fieldwork the vertical components of all stations were evaluated 300 common receiver gather crg sections of the ocean bottom seismographs obs and land stations as well as 100 common source gather csg sections of the land shots and selected airgun shots were compiled and modeled in order to generate a 2d p wave velocity depth model for each profile the accuracy of the model depends on the depth and position along the profiles and does not exceed 5 for both depth and p wave velocity we identified strong lateral variations in crustal and sedimentary thickness mainly in a north south direction but also along strike east west the crust is continental and has a maximum thickness of 32 5 km below northern central crete its subdivision in an upper v p 5 8 6 3 km s locally up to 6 5 km s and a lower v p 6 4 6 9 km s part is justified by a first order discontinuity with v p velocity a contrast of up to 0 6 km s the eastern part of crete shows a significantly thinner crust of 24 to 26 km to the north the crustal thickness decreases to 15 km below the central cretan sea the prominent decrease of the moho depth north of central crete is interpreted to represent the northern end of a microcontinent that was subducted in oligocene times and later surfaced by buoyant escape stockhert et al 1999 thomson et al 1999 the p t t d history of the high pressure rocks of crete greece denudation by buoyant escape in exhumation processes normal faulting ductile flow and erosion ring u lister g willet s brandon m eds spec publ of the geol soc of london p 154 to the south and southwest of the island the continental crust gradually thins to a minimum of 17 km and at approximately 100 km off the southern coast of crete it is in contact with oceanic crust below the mediterranean ridge upper mantle velocities were determined to be 7 7 km s below the cretan sea and 8 0 km s south of crete below the continental cretan crust a 6 to 7 km thick layer with v p velocities between 6 6 and 7 1 km s was identified on each line and could be followed by reflections to a depth of 42 km it is decoupled from the overlying continental crust at central crete and is interpreted as oceanic crust presently under subduction towards the nne below the aegean sea

role of the olistostromes and olistoliths in tectonostratigraphic evolution of the silesian basin in the outer west carpathians abstract the silesian series deposited in the proto silesian and silesian basins and preserved within the silesian nappe represents most complete continuous basinal sedimentary succession late jurassic early miocene within the outer carpathians it contains intercalations of numerous olistostromes that occurred during every stage of flysch basin evolution from rift and post rift through orogenic to postorogenic stage the olistostromes represent sediments of sub marine debris flows and avalanches they are of different size and composition and were derived from ridges and their slopes bordering proto silesian and silesian basins 0however the main source was the tectonically active southern slope and adjacent ridges the silesian and bukowiec ridges composition of olistostromes is an important source of knowledge about the geological structure and history of ridges and basin slopes which now are not preserved some large olistoliths and olistoplaques have been incorrectly interpreted as thrust sheets so detail studies of their true origin allowed correct interpretation of local tectonics

variations in the crustal structure beneath western turkey summary we use teleseismic receiver functions to investigate the crustal structure at two locations in westernturkey using seismic data recorded on small arrays of temporary broad band seismographs the results from these analyses are compared with receiver function results from the gdsn station anto on the anatolian plateau in central turkey the crust is 30 km thick in the region of western turkey where active normal faulting reveals present day extension in the upper crust and alkali basaltic volcanism reveals recent extension within the subcrustal lithosphere the crust is 34 km thick further east where crustal extension is still evident but less pronounced in the anatolian plateau which is not currently extending the crust is 38 km thick the level of extension estimated from these measurements of crustal thickness implies a b factor of 1 2 this value agrees with the amount of extension estimated in the upper crust from the integrated seismic strain rate b factor of 1 3 from surface faulting b factor of 1 25 and from the amount of extension in the subcrustal lithosphere estimated from the volcanism b factor 2 all indicating that the extension is approximately uniformly distributed vertically throughout the lithosphere the moho transition in this region appears to thin slightly as the degree of extension increases westwards

variable structural styles and tectonic evolution of an ancient backstop boundary the pieniny klippen belt of the western carpathians the pieniny klippen belt pkb and adjoining zones form a narrow but lengthy belt that separates the cretaceous nappe stack of the central austroalpine and the cenozoic accretionary wedge of the external western carpathians flysch belt the pkb shares units and structures of both in addition to the distinctive oravic units derived from a continental fragment in the middle penninic position in map view the northward convex pkb consists of two branches the western one striking roughly sw ne and the eastern one oriented in the nw se direction the western branch experienced a continuous nw se convergence and forward accretion of units derived from the foreland plate during the late cretaceous up to oligocene the developing accretionary wedge was supported by the backstop of the central carpathians in contrast the eastern branch originated by separation of pkb units and their dextral translation along the ne margin of the central carpathian block in the late eocene during the miocene reorganization of plate movements in the carpathian area the situation reversed the eastern formerly dextral transform margin was converted to the frontal backstop of the eastern part of the accretionary wedge in contrast the western previously orthogonally convergent branch was affected by along strike sinistral movements despite these considerable kinematic changes the pkb remained fixed to both backstop edges and records deformation structures and associated sediments differentiated into several evolutionary stages

physical properties and state of the crust and upper mantle of the eastern mediterranean sea deduced from geophysical data abstract by evaluating the geophysical information available for the eastern mediterranean sea ems a crustal thickness map and some conclusions as to the nature of the crustal type were drawn it was found that the ionian abyssal plain is floored by an oceanic type of crust which is 14 km thick and covered by sediments of the order of 8 km thick the herodotus abyssal plain in the levantine sea is floored by a crust 22 km thick and covered by sediments ranging between 10 and 15 km thick the eastern mediterranean rise extending more or less continuously from the apulian plateau to rhodes and the south of the antalya basin is of a thickness ranging between 28 and 34 km the thickness of its sedimentary cover is of the order of 10 km the borders of the eastern mediterranean sea are built up of thick continental crust for example the hellenides of western greece range between 40 and 44 km thick and western turkey has a similar crustal thickness the crust of sicily also exceeds 40 km whereas the southern and eastern borders of the ems are approximately 30 32 km thick tectonically the northern border of the ems is built up of active continental margins defined by the calabrian hellenic and cyprus antalya arcs whereas the southern border represents a passive continental margin controlled mainly by subsidence and stretching to the east the dead sea megashear limits the area the deep basins of the eastern mediterranean sea are tectonically controlled by subsidence and partial stretching the mediterranean ridge or rise is still an area of dispute regarded by some authors as a subsiding continental fragment and separated from the hellenic arc by the hellenic trench whereas others consider it to be a zone of crustal shortening thickened mainly by thrusting both the western and southwestern borders of the mediterranean rise and the hellenides are controlled by compressional processes similar to those deforming the calabrian arc the stravo and pliny trenches to the east southeast border of the hellenic arc are partly affected by strike slip movements various plate tectonic models of the area have been proposed by several authors though the complexity of the deformation hardly permits reliable reconstructions the lack of reliable paleomagnetic information and the absence of linear magnetic anomalies do not favour the application of plate tectonic concepts vertical processes due to the uprising of lithothermal systems below the hellenic and calabrian arcs may also be regarded as the driving force controlling the present day deformation

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

cyanobacterial tufa calcification in two freshwater streams ambient environment chemical thresholds and biological processes abstract calcareous freshwater streams near bad urach southwest germany were studied to determine the environmental limits to cyanobacterial calcification daily variations in temperature ph calcium concentration and alkalinity were measured at seasonal intervals from september 1993 to january 1995 in two small woodland streams with lengths of 1 0 and 1 5 km the principal cause of supersaturation in these fast flowing streams is inorganic carbon dioxide outgassing from resurging groundwater locally enhanced by turbulence at waterfalls and cascades photosynthetic uptake of carbon dioxide and temperature effects are negligible nonetheless organic substrates particularly cyanobacteria dominated microbial mats and biofilm significantly localize precipitation by providing suitable nucleation sites precipitation rates on artificial substrates up to 2 2 mm yr on limestone correlate with high saturation index values copper substrates inhibited microbial colonization and received negligible encrustation tufa formation and external calcium carbonate encrustation of cyanobacteria are conspicuous where the annual wateq4f saturation index exceeds 0 8 and are slightly below 0 7 calcium carbonate impregnation of cyanobacterial sheaths has not been observed we infer that in these fast flowing streams cyanobacteria utilize co2 in photosynthesis whereas elsewhere in sluggish freshwater cyanobacteria utilize hco3 leading to sheath impregnation by calcium carbonate even where saturation index is only 0 2 0 3 thus photosynthetic influence on cyanobacterial calcification appears to be negligible in fast flowing co2 rich streams and cyanobacterial calcification takes the form of external encrustation in slow flowing co2 poor streams and lakes cyanobacteria preferentially utilize bicarbonate and sheath impregnation can result modern tropical marine carbonate shelves have saturation indices commonly in the range 0 62 0 82 and cyanobacterial calcification is negligible extrapolation suggests that cyanobacterial calcification could occur in present day seas if saturation index exceeded 0 8 this level corresponding with heavy calcification in the freshwater streams studied may have been widespread in marine environments in the geological past at times when calcified cyanobacteria and environmentally influenced non skeletal calcium carbonate precipitates were abundant

stable isotope record of palaeoclimatic change in a british holocene tufa a 9 5 m long continuous core through holocene tufa deposits in derbyshire uk was analysed for oxygen and carbon stable isotope variations with a view to palaeoclimatic and palaeoenvir onmental interpretation the depositional environment of the tufa is well understood and dated using 14c and biostratigraphy it is argued that smooth variations of up to 1 in 18o of the tufa calcites are caused by changes in the isotopic composition of regional rainfall which in turn were caused mainly by changes in air temperature palaeoclimate in general lower 13c values for calcite correspond with higher 18o values suggesting a stronger component of soil derived carbon during warmer climatic phases a stable isotope approach to reading terrestrial palaeoclimatic records is of widespread application to holocene and older tufa deposits which are common in carbonate bedrock regions

tsunami potential of moderate earthquakes the july 1 2009 earthquake mw 6 45 and its associated local tsunami in the hellenic arc on july 1 2009 a mw 6 45 earthquake ruptured south of crete island greece along the hellenic arc triggering a local tsunami eyewitness reported the tsunami from myrtos and arvi south eastern crete and from the north of chrisi islet located to the southeast of crete the earthquake occurred offshore about 80 km south of crete where routine earthquake locations are poor the hypocentre is relocated using a 2 d velocity model and several local 1 d velocity models epicentral locations obtained by using the different velocity models show very minor variations instead relocated hypocentres can be grouped into two sets of solutions 1 those with a shallower depth depth 25 km either in the upper plate or along the plate interface models accounting for either homogeneous or heterogeneous slip on the causative fault are tested with the heterogeneous one better reproducing the observations in terms of number of tsunami waves reaching the shoreline and duration of the sea disturbance the short travel time about 10 min of the first tsunami arrival at the southern coast of crete represents a big challenge for tsunami early warning systems operating in the area

receiver function study of the hellenic subduction zone imaging crustal thickness variations and the oceanic moho of the descending african lithosphere summary we use data from recently installed broad band seismographs on the islands of crete gavdos santorini naxos and samos in the hellenic subduction zone to construct receiver function images of the crust and upper mantle from south of crete into the aegean sea the stations are equipped with sts 2 seismometers and they are operated by gfz potsdam university of chania and eth zurich teleseismic earthquakes recorded by these stations at epicentral distances between 35 and 95 have been used to calculate receiver functions the receiver function method is a routinely used tool to detect crustal and upper mantle discontinuities beneath a seismic station by isolating the p s converted waves from the coda of the p wave converted p s energy from the oceanic moho of the subducted african plate is clearly observed beneath gavdos and crete at a depth ranging from 44 to 69 km this boundary continues to the north to nearly 100 km depth beneath santorini island because of a lack of data the correlation of this phase is uncertain north of santorini beneath the aegean sea moho depths were calculated from primary converted waves and multiply reflected waves between the moho and the earth s surface beneath southern and eastern crete the moho lies between 31 and 34 km depth beneath western and northern crete the moho is located at 32 and 39 km depth respectively and behaves as a reversed crust mantle velocity contrast possibly caused by hydration and serpentinization of the forearc mantle peridotite the moho beneath gavdos island located south of crete in the libyan sea is at 26 km depth indicating that the crust south of the crete microcontinent is also thinning towards the mediterranean ridge this makes it unlikely that part of the crust in crete consists of accreted sediments transported there during the present day subduction process which began approximately 15 ma because the backstop i e the boundary between the current accretionary wedge of the mediterranean ridge and the crete microcontinent is located approximately 100 km south of gavdos a seismic boundary at 32 km depth beneath santorini island probably marks the crustal base of the crete microcontinent a shallower seismic interface beneath santorini at 20 25 km depth may mark the depth of the detachment between the crete microcontinent and the overlying aegean subplate the moho in the central and northern aegean at naxos and samos is observed at 25 and 28 km depth respectively assuming a stretching factor of 1 2 1 3 crustal thickness in the aegean was 30 35 km at the inception of the extensional regime in the middle miocene

stable isotopes of holocene calcareous tufa in southern poland as paleoclimatic indicators abstract the isotopic composition of oxygen in freshwater calcareous tufa seems to be a sensitive indicator of past climatic changes results of measurements of c 18 o and c 13 c in tufa samples dated with the 14 c method are used to reconstruct holocene climatic changes in southern poland values of c 18 o obtained on tufa samples from four sites raclawka rzerzu nia trzebienice sieradowice representing different hydrodynamic conditions of tufa sedimentation seem to form a selfconsistent series these values with some simplifying assumptions concerning the course of tufa sedimentation were therefore used to estimate mean annual temperatures in the interval ca 9500 2000 yr b p when the resulting curve of thermal changes in southern poland is compared with changes of deposition and erosion of tuffaceous sediments and with results of other methods of reconstruction of paleoclimate in central europe a reasonable agreement among the different specific methods is seen

high resolution records of rainfall events from clay bands in tufa individual rainfall events are recorded as thin clay bands in annually laminated freshwater carbonate tufa runoff from rainfall events entrains clay that then adheres to the tufa surface a specimen collected from southwest japan exhibits 100 clay bands formed during a 15 yr period from 1988 to 2002 the chronology of the clay bands was determined by using the temperature dependent cycle of oxygen isotope ratios in the carbonate and the clay content was quantified by electron probe microanalysis si x ray strength the obtained si x ray strength curve and actual rainfall record follow a nearly identical pattern the clay content of each band correlates with rainfall amount rainfall of 50 mm week produced sufficient amounts of suspended cave clay to produce clay bands in the tufa because the clay bands survive postdepositional alteration this new method can be applied to ancient tufa deposits and has great potential as a high resolution rainfall record for use in climate studies

ams radiocarbon dating of late quaternary glacial landforms source of the urumqi river tien shan a pilot study of 14c dating on inorganic carbon abstract carbonate coatings on roche moutonnees and till clasts and calcite in the fine matrix of late quaternary glacial landforms were dated by using accelerating mass spectrometry ams radiocarbon dating at the source area of the urumqi river tien shan the values of 13 c and the sedimentary properties of tills and coatings show that the precipitation of inorganic carbon in calcite in the till matrix is synchronous with till formation the carbon dating of the fine matrix of till and the coatings on till clasts can be used to determine or estimate the ages of glacial moraines as the inorganic carbon in fine matrix and coatings may preserve well with no or little fractionation the largest scaled moraine near wangfeng road maintenance station was dated to be 19 23 ka the age of the local last glaciation maximum was therefore coincident with the global last glaciation maximum the moraine at glacier observatory which was formerly believed to be the product of neoglaciation seems to be the relics of a lateral moraine also formed during the last glaciation

continuity and episodicity in the early alpine tectonic evolution of the western carpathians how large scale processes are expressed by the orogenic architecture and rock record data

the late holocene tufa decline in europe over much of europe it has been postulated that in the late holocene since c 2500 bp there was a marked decline in the deposition of tufa there has been considerable debate about the causes of this phenomenon with some authors postulating the importance of natural climatic changes and others asserting that miscellaneous human influences have been crucial this article discusses the role that various changes both natural and anthropogenic may have played and suggests ways in which the large number of possible hypotheses can be tested

how fast does tufa grow very high resolution measurement of the tufa growth rate on artificial substrates by the development of a contactless image based modelling device

calcite supersaturation and precipitation kinetics in the lower colorado river all american canal and east highline canal in situ ph determinations and analysis of major ions in solution indicated that the lower colorado river is supersaturated with respect to calcite throughout the entire daily cycle in both winter and summer although the ion activity product was 4 to 6 times greater than the calcite solubility product there was no detectable precipitation chemical analyses of water samples taken along 350 km of the river and canals from parker dam to the salton sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows laboratory kinetic studies indicated that calcite crystal growth rates with colorado river water are about 30 of the rate for pure ca hco3 waters and about 70 of that for synthetic colorado river water calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite critical supersaturation levels necessary for heterogeneous nucleation do not occur a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime h2co3 levels

reply to the seismic imaging of melanges pieniny klippen belt case study discussion we welcome the discussion by jurewicz et al 2020 whose main criticism focused on the fact that the authors main conclusions contradict the results of previous studies however this statement refers perhaps to the geological setting since we are not aware of any previous studies providing seismic imaging of melanges in the pieniny klippen belt pkb we did not consider the critical remarks by plasienka et al 2017 because we believe that sufficient answers were provided by golonka et al 2017 we are grateful to jurewicz et al 2020 for pointing out the erroneous term tectonic olistolith that we will correct it in future work the discussion is based on two sets of problems regional geology and interpretations of seismic data

discussion of olistostromes of the pieniny klippen belt northern carpathians j golonka m krobicki a wa kowska m cieszkowski a l czka reply we welcome the comments by our slovakian colleagues and their critique of our results particularly as we have discussed and published papers together several times about our ideas sometimes more or less disputable aubrecht et al 2003 2006 krobicki et al 2003 krobicki aubrecht golonka 2003 golonka et al 2006 pienkowski et al 2008 we are pleased to see such warm reaction to our work paper which is focused on one of the rudimentary questions in the pieniny klippen belt pkb area how many what kind of olistoliths olistostromes occur within the inner structure of the pkb and when and why did they originate mostly during the palaeogene part of the mesozoic cenozoic history of this region we expected this discussion earlier the content of our paper was presented at the 6 th meeting of the central european tectonic studies group ceteg in upohlav pieniny klippen belt slovakia cieszkowski et al 2008 and later at the xix congress of the carpathian balkan geological association in thessaloniki greece cieszkowski et al 2010 golonka et al 2010 some ideas were also briefly mentioned in the paper by cieszkowski et al 2009 in a journal issue edited by d plasienka we assume that the comments are based on recent investigation because the authors list the grants received to conduct the research therefore the submitted comments sometimes present a point of view different from that published previously by some of the authors of the comments ra jm see aubrecht et al 2003 krobicki aubrecht golonka 2003 wierzbowski et al 2006 pienkowski et al 2008 the statement certainly there are many still unresolved problems in the geology of the pkb and it ought to be said that the co authors of this discussion also do not fully agree with all interpretations formulated and illustrated by the first author perhaps explains this controversy of course we agree that there are many still unresolved problems in the geology of the pkb we also agree with the statement olistostromes and olistoliths are quite frequent but not omnipresent we depicted the distribution of the olistoliths and their relationship to the non olistolith tectonic units of the pkb in golonka et al 2015 figs 3 8

sedimentary basins evolution and olistoliths formation the case of carpathian and sicilian regions abstract comparative research carried out within two different basins one in the carpathians of poland late jurassic to early miocene and another in the apenninic maghrebian mountain chain of sicily triassic miocene indicate significant similarity not only in their evolution but also in the sedimentary features of horizons with olistoliths the olistolith bearing units are genetically related to stages of tectonic evolution and are independent of the size of the basins and of duration of these stages however the observed differences in composition and size of olistoliths suggested among the others relationship with the size of source areas and thickness of their sedimentary cover

holywell coombe folkestone a 13 000 year history of an english chalkland valley abstract holywell coombe is a valley cut into the scarp face of the north downs chalk cuesta near folkestone kent its geological importance stems from a highly fossiliferous sequence of lateglacial and holocene deposits that line the valley floor these have yielded a molluscan succession of particular importance providing a record of environmental change throughout the past 13 000 radiocarbon years waterlogging of the basal deposits has prevented oxidation leading to the preservation of a range of organic fossils such as plant and insect remains that normally do not survive in calcareous environments this enables linkage between faunal and vegetational records allowing the differential rates of response of particular groups to be critically compared the importance of the site was revealed in 1968 in trial pits connected with an aborted channel tunnel project resurrection of plans to build a tunnel led in 1987 to major rescue excavations and multidisciplinary investigations the results of which are reviewed here a three dimensional picture of the valley infill was established from a network of 180 boreholes critical parts of the sequence were investigated in specially excavated trenches and sections exposed during construction of the tunnel systematic sampling at a number of locations within the valley provided a palaeontological record from the full stratigraphical succession a number of lateglacial and holocene soils were found to be represented in the sequence including that formed during the allerod phase of the lateglacial interstadial the molluscan zonation scheme previously defined at holywell coombe and applicable over large areas of southern britain and possibly further afield has been refined and dated with greater precision the lateglacial sequence has been extended back to the early part of the lateglacial interstadial by this study and the site chronology is now underpinned by over 35 new radiocarbon dates quantitative palaeoclimatic reconstructions from beetle remains using the mutual climatic range method cover the period between 13 000 and 9000 yr bp the earliest sediments marsh deposits with thermophilous insect taxa and a species poor molluscan assemblage date from around 13 000 12 000 yr bp just before the end of this period changes in beetle faunas record climatic cooling heralding slope instability and the accumulation of thick colluvial deposits by 11 500 yr bp the climate had stabilized and slope movement had ceased allowing the formation of the allerod soil there followed a major deterioration to the arctic climate of the younger dryas during which renewed erosion from the valley sides brought further material onto its floor burying and sealing the earlier sediments the beginning of the holocene saw the onset of tufa formation around two dominant springs in the upper valley there was progressive development of forest hazel dominated woodland being established by 9500 yr bp there is some evidence for thinning of the forest canopy during the late mesolithic and neolithic but the major clearance occurred during the early bronze age causing renewed instability on slopes and consequent hillwash accumulation this final depositional phase continued with pauses marked by soil formation in the early bronze age and the iron age to the present day the hillwash seals structures relating to prehistoric human activity including plough marks and contains an extensive sequence of artefacts

tracing tectonic deformation using the sedimentary record the study of sediments and sedimentary basins in terms of their tectonic environment requires a multidisciplinary approach and has increasingly drawn both techniques and objectives from fields outside sedimentology the application of different theoretical experimental and empirical resources provided by structural geology geochemistry geophysics scale modelling and field geology complement sedimentological methods with the combined aim of achieving a deeper understanding of the origins evolution and significance of sedimentary sequences in terms of their tectonic history studies presented in this volume range across a wide spectrum from the analysis of sedimentary sequence architecture at basin scale down to the chemical properties of individual grains and include studies from a range of tectonic settings the volume will be of interest to those involved with or contemplating studies involving the linkages between tectonics and sedimentation as well as a wider audience to whom the results of such studies may provide fresh insight

thickness and stable isotopic characteristics of modern seasonal climate controlled sub annual travertine laminas in a travertine depositing stream at baishuitai sw china implications for paleoclimate reconstruction a continuous high resolution monthly record of stable isotopes 13c and 18o in a well laminated freshwater travertine deposited at baishuitai sw china from may 1998 to november 2001 was presented the travertine exhibits clear annual bands with coupled brown white color laminations throughout field investigation it was found that the thin 1 5 2 2 mm brown porous lamina was formed in the monsoonal rainy season from april to september whereas the thick 5 8 mm dense white lamina was formed in the dry season from october to march the comparisons of lamina thickness and stable isotope signals in the travertine with the meteorological records allow us to constrain the relevant geochemical processes in the travertine formation under different climate conditions and to relate climate variables to their physicochemical proxies in the travertine record sympathetic variations in lamina thickness 13c and 18o along the sampled profile reflect changes in hydrogeochemistry showing that thin lamina and low 13c and 18o values occur in warm and rainy seasons the decreased amount of calcite precipitation and low 13c values during the warm and rainy seasons is caused by dilution of overland flow after rainfall the low 18o values are believed to be related to the rainfall amount effect in subtropical monsoonal regions this process is thought to be markedly subdued whenever the amount of rainfall is lower than a given threshold accordingly distinct minima in lamina thickness 13c and 18o are interpreted to reflect events with above average rainfall possibly heavy floods and vice versa this study demonstrates the potential of freshwater travertine to provide valuable information on seasonal or even monthly rainfall variations

late quaternary paleoclimate in semiarid northeastern brazil from u series dating of travertine and water table speleothems abstract fossil travertine and subaqueous speleothems in presently dry caves suggest periods of enhanced ground water recharge during the quaternary period in semiarid northeastern brazil travertine deposits and water table speleothems were dated by the 230 th 234 u technique yielding new evidence for the timing of past periods of increased rainfall the travertine was deposited in two distinct phases extensive in situ deposits during marine isotope stage 2 and fragmentary indurated deposits dating to ca 400 000 yr b p possibly marine isotope stage 10 or 12 dating of water table speleothems showed that the regional water table was 13 1 m above the present level at the last glacial maximum a second site yielded ages suggesting a still higher water table during marine isotope stage 6 these new data demonstrate that northeastern brazil did not follow the general pattern of a dry last glacial maximum as suggested by other continental records in amazonia and southeastern brazil and as depicted in recent general circulation model gcm simulations our results thus indicate that significant variability in regional rainfall patterns occurred in the area during glaciations and caution against overgeneralization of paleoclimate patterns

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

the western carpathians interaction of hercynian and alpine processes abstract the complicated structural and rheologic properties of western carpathian lithosphere reflect the complex geodynamic history of the carpathian orogen based on critical analysis of earlier models new interpolation of existing geophysical data and results of integrated modelling a new map of the lithosphere thickness for the carpathian pannonian region has been constructed the map allows for the distinction of a frontal orogen collision zone in the ne from increased lithosphere thickness as well as a zone of oblique collision with the bohemian massif in the west where lithosphere is not significantly thickened the moho discontinuity beneath the western carpathian hinterland danube and east slovak basins as defined by deep reflection seismic profiling is relatively shallow this probably reflects recent crustal extension related to oblique collision between the european plate and the alcapa block and an increase of the asthenospheric updoming from the middle miocene onward crustal thickness reflects the combined effects of deep seated orogenic processes and mantle thermal evolution beneath the pannonian basin system in this study we focus particularly the structures of 1 the late alpine collision and neogene back arc basin development including deep seated contacts between colliding plates a zone of slab detachment the compressional accretionary wedge of the outer western carpathian flysch belt and extensional structures produced by subduction rollback and asthenosphere upwelling 2 early alpine structures related to cretaceous thrust stacking including subhorizontal reflection packages interpreted as multi generational extensional structures the underplated intra penninic oravic continental ribbon and ophiolite traces of the meliatic oceanic suture and 3 north dipping reflectors interpreted as remnant hercynian lithotectonic fragments with opposed vergency to the subducted alpine units

palaeogeographic evolution of the pieniny klippen basin using stratigraphic and palaeomagnetic data from the veliky kamenets section carpathians ukraine abstract a 40 m thick carbonate succession of the bajocian to berriasian age from the veliky kamenets quarry novoselica area pieniny klippen belt ukraine resembles both the czorsztyn and niedzica successions of the pieniny klippen belt traditionally considered ridge slope related deposits a total of 176 individually oriented cores collected from the bottom to the top of the sequence with sampling density dependent on inferred sedimentation rates show multicomponent remanent magnetization with magnetite as a main magnetic carrier thermal demagnetization revealed two main components of natural remanent magnetization nrm a low blocking temperature component s of normal polarity is considered of posttectonic probably thermoviscous origin due to overheating by neogene volcanics a stable high blocking temperature nrm component p shows dual polarity distribution and is considered primary it was possible to recognize 23 polarity zones that have been correlated with a biostratigraphic scale since two significant sedimentary gaps occur at 422 and 860 cm the main hiatus ms from the base the latter comprising the middle callovian early oxfordian time span 6 8 ma an obtained pattern of magnetic reversals presented in this study cannot be considered complete a palaeolatitude of 41 5 is calculated for the mid jurassic part below ms similar to that expected for the european craton at the kamenets locality the mid oxfordian limestone directly overlying the ms has palaeolatitudes around 28 6 this implies a relatively fast opening of the oceanic domain to the north from the kamenets block this conclusion combined with similarity of the kamenets sequence to ridge related sediments of the pieniny klippen belt makes it possible to speculate on the existence of the kamenets ridge a new term a structure of uncertain although possible structural links to the czorsztyn ridge palaeomagnetic declinations suggest 100 counterclockwise rotation of the whole section before the neogene

hydrochemical variations during flood pulses in the south west china peak cluster karst impacts of caco3 h2o co2 interactions high resolution measurements of rainfall water level ph conductivity temperature and carbonate chemistry parameters of groundwater at two adjacent locations within the peak cluster karst of the guilin karst experimental site in guangxi province china were made with different types of multiparameter sonde the data were stored using data loggers recording with 2 min or 15 min resolution waters from a large perennial spring represent the exit for the aquifer s conduit flow and a nearby well measures water in the conduit adjacent fractured media during flood pulses the ph of the conduit flow water rises as the conductivity falls in contrast and at the same time the ph of groundwater in the fractures drops as conductivity rises as ca 2c and hco3 were the dominant 90 ions we developed linear relationships both r 2 0 91 between conductivity and those ions respectively and in turn

mesozoic plate tectonic reconstruction of the carpathian region abstract palaeomagnetic palaeobiogeographic and structural comparisons of different parts of the alpine carpathian region suggest that four terranes comprise this area the alcapa tisza dacia and adria terranes these terranes are composed of different mesozoic continental and oceanic fragments that were each assembled during a complex late jurassic cretaceous palaeogene history palaeomagnetic and tectonic data suggest that the carpathians are built up by two major oroclinal bends the alcapa bend has the meliata oceanic unit correlated with the dinaric vardar ophiolite in its core it is composed of the western carpathians eastern alps and southern alcapa units transdanubian range bukk this terrane finds its continuation in the high karst margin of the dinarides further elements of the alcapa terrane are thought to be derived from collided microcontinents czorsztyn in the n and a carbonate unit tisza in the se the tisza dacia bend has the vardar oceanic unit in its core it is composed of the bihor and getic microcontinents this terrane finds its continuation in the serbo macedonian massif of the balkans the bihor getic microcontinent originally laid east of the western carpathians and filled the present carpathian embayment in the late palaeozoic early mesozoic the vardar ocean occupied an intermediate position between the western carpathian austroalpine transdanubian high karst margin and the bihor getic serbo macedonian microcontinent the vardar and pindos oceans were opened in the heart of the mediterranean adriatic microcontinent in the late permian middle triassic vardar subducted by the end of jurassic causing the bihor getic serbo macedonian microcontinent to collide with the internal dinaric western carpathian margin an external penninic vahic ocean tract began opening in the early jurassic separating the austroalpine western carpathian microcontinent and its fauna from the european shelf further east the severin ceahlau magura also began opening in the early jurassic but final separation of the bihor getic ribbon and its fauna from the european shelf did not take place until the late middle jurassic the alcapa and the tisza dacia were bending during the albian maastrichtian the two oroclinal bends were finally opposed and pushed into the gates of the carpathian embayment during the palaeogene and neogene at that time the main n s shortening in distant alpine and hellenic sectors was linked by a broader right lateral shear zone along the former vardar suture

earthquake mechanisms and active tectonics of the hellenic subduction zone summary we use improved focal mechanisms and centroid depth estimates of earthquakes combined with gps velocities to examine the tectonics of the hellenic subduction zone and in particular the processes occurring at both ends of the hellenic arc nubia aegean convergence is accommodated by shallowly dipping thrust faulting along the subduction zone interface as well as by steeper splay faults in the overriding material from a comparison of observed and expected seismic moment release over the last 100 yr combined with existing knowledge of the longer term documented historical record we confirm earlier suggestions that most 80 per cent of this convergence is accommodated aseismically that is that the subduction zone is uncoupled this conclusion is robust even allowing for rare very large earthquakes on splay faults such as that of ad 365 and also allowing for the contribution of small earthquakes the downgoing nubian plate deforms by arc parallel contraction at all depths from 200 km seaward of crete to at least 100 km within the subducting slab extensional t axes of earthquakes are aligned downdip within the descending slab suggesting that even if the aseismic prolongation of the slab has reached the 670 km mantle discontinuity it does not transmit stresses to shallower depths shallow thrust faulting earthquakes on the subduction interface show a divergence of slip vectors round the arc and gps measurements show that this is accommodated mainly by e w extension on normal faults in the overriding aegean material the eastern end of the subduction zone south of rhodes displays distributed deformation in the overriding material including a mixture of strike slip and splay thrust faulting and probably involves rotations about a vertical axes here slip on the interface itself is by thrust faulting with slip vectors oblique to the arc but parallel to the overall nubia aegean convergence there is no evidence for slip partitioning in the traditional sense in the west the subduction zone terminates in a distributed zone of parallel ne sw strike slip faults of which the most prominent is the kefalonia transform fault ktf a flexural gravity anomaly confirms that the deep bathymetric escarpment of the ktf is a lateral ramp formed as the ionian islands are emplaced sw onto the apulian lithosphere and enhanced by minor thrust faulting with slip vectors perpendicular to the scarp distributed parallel strike slip faults both sw and ne of mainland central greece terminate in e w graben in central greece which accommodate the overall ne sw shear by clockwise block rotation central greece therefore acts as a relay zone between the strike slip faulting of the ne aegean and the ionian islands western peloponnese

response of dissolved inorganic carbon dic and δ13cdic to changes in climate and land cover in sw china karst catchments abstract monthly hydrochemical data and 13c of dissolved inorganic carbon dic in karst water samples from september 2007 to october 2012 were obtained to reveal the controlling mechanisms on dic geochemistry and 13cdic under different conditions of climate and land cover in three karst catchments banzhai dengzhanhe and chenqi in guizhou province sw china dic of karst water at the banzhai site comes mainly from carbonate dissolution under open system conditions with soil co2 produced by root respiration and organic carbon decomposition with lowest 13c values under its dense virgin forest coverage weaker carbonate bedrock dissolution due to sparse and thin soil cover results in lower 13cdic pco2 dic and ec and lower cation and anion concentrations at the chenqi site larger soil co2 input from a thick layer of soil results in high pco2 and dic and low ph sic and 13cdic in the karst water at the dengzhanhe site a lesser soil co2 input due to stronger karst rock desertification and strong gypsum dissolution contribute to higher 13cdic high ec and high cation and anion concentrations soil co2 inputs controlled by biological activity and available soil moisture carbonate bedrock dissolution dilution and degassing effects vary seasonally following rainfall and temperature changes consequently there are seasonal cycles in hydrochemistry and 13cdic of the karst water with high pco2 and low ph ec sic and 13cdic values in the warm and rainy seasons and vice versa during the cold and dry seasons a strongly positive shift 3 in 13cdic occurred in the drought year 2011 indicating that 13cdic in groundwater systems can be an effective indicator of environmental and or climate changes

lithospheric structure of the aegean obtained from p and s receiver functions combined p and s receiver functions from seismograms of teleseismic events recorded at 65 temporary and permanent stations in the aegean region are used to map the geometry of the subducted african and the overriding aegean plates we image the moho of the subducting african plate at depths ranging from 40 km beneath southern crete and the western peloponnesus to 160 km beneath the volcanic arc and 220 km beneath northern greece however the dip of the moho of the subducting african plate is shallower beneath the peloponnesus than beneath crete and rhodes and flattens out beneath the northern aegean observed p to s conversions at stations located in the forearc indicate a reversed velocity contrast at the moho boundary of the aegean plate whereas this boundary is observed as a normal velocity contrast by the s to p conversions our modeling suggests that the presence of a large amount of serpentinite more than 30 in the forearc mantle wedge which generally occurs in the subduction zones may be the reason for the reverse sign of the p to s conversion coefficient moho depths for the aegean plate show that the southern part of the aegean crustal thickness of 20 22 km has been strongly influenced by extension while the northern aegean sea which at present undergoes the highest crustal deformation shows a relatively thicker crust 25 28 km this may imply a recent initiation of the present kinematics in the aegean western greece crustal thickness of 32 40 km is unaffected by the recent extension but underwent crustal thickening during the hellenides mountains building event the depths of the aegean moho beneath the margin of the peloponnesus and crete 25 28 and 25 33 km respectively show that these areas are also likely to be affected by the aegean extension even though the cyclades crustal thickness of 26 30 km were not significantly involved in this episode the aegean lithosphere asthenosphere boundary lab mapped with s receiver functions is about 150 km deep beneath mainland greece whereas the lab of the subducted african plate dips from 100 km beneath crete and the southern aegean sea to about 225 km under the volcanic arc this implies a thickness of 60 65 km for the subducted african lithosphere suggesting that the aegean lithosphere was not significantly affected by the extensional process associated with the exhumation of metamorphic core complexes in the cyclades

study of the crustal thickness and the subducting lithosphere in greece from gravity data the area of greece has experienced a complex tectonic history dominated by the subduction of the african plate beneath eurasia in this study the variations of the crustal thickness in the area of greece were obtained by means of the multiple source werner deconvolution mswd method applied to gravity data thicknesses of 40 49 km are estimated beneath the hellenides mountain belt to the west eastward thinning of the crust to thicknesses ranging from 25 km in the north to 30 km in the south is seen in the aegean region these results are in good agreement with recent seismological results demonstrating that the mswd method successfully treated the problem using the crustal model we derived we computed the gravity effect of the crust and extracted it from the bouguer anomaly we also extracted the gravity effect of the subducting lithosphere from the bouguer anomaly producing a residual map where most of the original gravity variation has been successfully removed the remaining anomalies appear related to near surface features and an area of low velocity mantle in the central aegean sea

gravity data inversion for moho depth modeling in the hellenic area the main objective of this study is the determination of the moho discontinuity in the hellenic area based on gravity data inversion high resolution 2 arcmin and accuracy 2 to 3 mgal gravity data were used in the computations following the parker oldenburg iterative method and a low pass filter was applied to gravity information towards the convergence of the final solution to determine the cut off wavenumber of the filter we tested different mean depths and density contrasts of the crust and the mantle mohorovicic discontinuity the selected density contrast and mean depth of the mohorovicic discontinuity are those which agree with the moho depth interpreted from deep seismic imaging data by comparing the moho depth estimated covering both land and marine areas and including the ionian and aegean sea with those interpreted from previous studies it is shown that our solution is consistent with the available seismic data interpretation moreover the resolution of the gravity data and the appropriate filtering used in this study contributed to the representation of local features of the moho discontinuity finally area dependent discrepancies detected between the moho depths of the current solution and those derived from previous studies are extensively discussed

gravity modelling of the hellenic subduction zone a regional study abstract the hellenic subduction zone is clearly expressed in the arc shaped distribution of earthquake epicenters and gravity anomalies which connect the peloponnesos with crete and anatolia in this region oceanic crust of the african plate collides northward with continental crust of the aegean microplate which itself is pushed apart to the south west by the anatolian plate and at the same time is characterised by crustal extension the result is an overall collision rate of up to 4 cm year and a retreating subduction process recent passive and active seismic studies on and around crete gave first but not in all details consistent structural results useful for supporting gravity modelling this was undertaken with the aim of presenting the first 3d density structure of the entire subduction zone gravity interpretation was based on a bouguer map newly compiled using data from land marine and satellite sources the anomalies range from 170 mgal cretan sea to 10 mgal mediterranean ridge 3d gravity modelling was done applying the modelling software igmas the computed bouguer map fits the low frequency part of the observed one which is controlled by variations in moho depth less than 20 km below the cretan sea and extending 30 km below crete and the extremely thick sedimentary cover partly up to 18 km of the mediterranean ridge the southernmost edge of the eurasian plate with its more triangular shaped backstop area was traced south off crete only 50 to 100 km further to the south the edge of the african continent was traced as well in between these boundaries there is african oceanic crust which has a clear arc shaped detachment line situated at the eurasian continental edge the subduction arc is open towards the north its slab separates hotter mantle material lower density below the updoming moho of the cretan sea from colder one higher density in the south subjacent to the upper continental crust of crete is a thickened layer of lower crust followed by the subducted oceanic crust with some mantle material as intermediate layer the depth of the oceanic moho below crete is 50 km the presence and structure of subducted or underplated sediments remains uncertain

estimation of hypocentral parameters of regional earthquakes using a fuzzy logic approach this study presents improvements on the hypocentral location method using the fuzzy logic approach proposed by lin and sanford bulletin of the seismological society of america 91 82 93 2001 in resolving regional earthquakes location in addition to trying to determine epicentral parameters of the earthquake focal depths are also attempted utilizing this method in a three dimensional 3d space in this study instead of p and s wave models a trapezoidal membership function constructed by the direct use of travel time difference between the two stations for p and s arrival times was utilized in this procedure it is not necessary to precisely know the velocity structure of the studied area in order to map the uncertainties in arrival times into the fuzzy logic space the location determination process was performed with the defuzzification of only the grid points having the membership value of 1 obtained by normalizing all the maximum fuzzy output values of the highest values which gives more reliable epicentral locations for both real and synthetic earthquakes the results show that this method for epicentral estimation works well if the depth of the earthquake is sufficiently shallow and according to the distance between the event and seismic network in this method of hypocenter determination firstly epicenter coordinates are determined then the hypocenter location is found by considering only the epicentral area in 3d in the case of very shallow events e g h 10 km the estimation of the focal depth using this method seems to fail causing faulty results in the hypocenter coordinates however the estimation of epicentral coordinates is successful in giving a more reasonable epicentral location otherwise the obtained results would be reversed consequently the deeper the focal depth the better the hypocenter location but a worse epicenter determination this method is only valid in the hypocentral location of the earthquake occurring in the upper crust because only primarily the arrivals of pg and sg on the seismograms and a half space velocity model are used the hypocenter locations of some selected shallow earthquakes that occurred in the south east of the aegean sea have been determined by this method with results that are highly comparable with those obtained by other seismic agencies

geodetic constraints on the tectonic evolution of the aegean region and strain accumulation along the hellenic subduction zone article i nfo we present evidence that gps velocity estimates of plate motions and fault slip rates agree to within uncertainties with geologic estimates during the most recent phase of the geologic evolution of the e mediterranean region post late miocene on this basis we use the gps differential velocities to estimate the timing of initiation of the principal structures in nw turkey the n aegean sea and central greece including the marmara sea the gulfs of evia goe and corinth goc and the kephalonia transform fault ktf we interpret these ages to indicate that the north anatolian fault propagated across the n aegean opening the goe and goc and initiating the ktf during the past 1 4 ma we further suggest that aegean extension that was earlier more distributed across the aegean basin became focused on this new fault system allowing the southern aegean and peloponnisos to translate sw with little internal deformation as observed today with gps this change in tectonic configuration may account for the clear geologic evidence for crustal thinning throughout the s aegean in apparent contradiction with low present day strain rates we further show that the low present day strain rate along the southern edge of the aegean micro plate requires substantial aseismic slip along the plate interface below crete consistent with the low level of historic subduction type earthquakes along this segment of the subduction zone

the quaternary travertine deposits of europe and asia minor abstract a summary is provided of the published information relating to all aspects of quaternary travertine formation in europe west of the ural mountains the deposits have been divided into two broad groups the meteogene travertines which result primarily from the degassing of soil borne aqueous co 2 and thermogene deposits resulting from the degassing of thermally generated co 2 meteogene deposits are rare above latitude 58 n and in regions where the mean annual air temperature is below 5 c a significant positive correlation exists between mean air temperature and travertine deposit thickness the combined effects of temperature and rainfall are used to provide a zoned map showing the travertine forming potential of limestones within the region information from 14 c dating indicates that deposition reached a maximum in the period 5 10 ka bp and is currently limited by land and water management practices in the populated areas thermogene deposits occur in regions of high co 2 discharge resulting from tectonic activity such as italy and turkey where there is much vulcanism these travertines are frequently more massive and less readily weathered than meteogene deposits fully referenced information is provided for 320 important mostly well studied sites 227 meteogene 93 thermogene of which 156 are currently active

the taravilla lake and tufa deposits central iberian range spain as palaeohydrological and palaeoclimatic indicators 21 pages 8 figures 3 tables available online oct 13 2007 issue title lake systems sedimentary archives of climate change and tectonics egu general assembly

the crust of the western mediterranean ridge from deep seismic data and gravity modelling summary we present a crustal cross section of the western mediterranean ridge from the african margin to the aegean sea constrained by the morphology of the ridge new seismic reflection and refraction results obtained during a two ship cruise performed in december 1988 pasiphae cruise the distribution of seismicity and gravity modelling morphologically the western mediterranean ridge can be divided into three main units from the sirte abyssal plain to the hellenic trench a broad outer unit a narrow central unit and an inner unit the seismic front orgeaward extent of the interplate seismicity between the african lithosphere and the cretan arc is located 50 km seaward of the hellenic trench seismicity is thus distributed widely over the innermost unit of the ridge suggesting that brittle material is present at shallow depth beneath the inner portion of the mediterranean ridge the refraction results of the pasiphae cruise show that the crust in the ionian basin and beneath the outer and central units of the western mediterranean ridge is oceanic and that the moho discontinuity progressively deepens towards the hellenic arc in agreement with the accretionary prism model high velocity material occurs at shallow depth beneath the innermost unit of the ridge gravity modelling also indicates a significant increase in density beneath the inner unit we consequently interpret the inner unit of the ridge as the backstop of the western mediterranean ridge prism possibly composed of peloponnesus thrust sheets

discussion of olistostromes of the pieniny klippen belt northern carpathians d plasienka j michalik j sotak r aubrecht comment in their recent paper golonka et al 2015 described the cretaceous and palaeogene olistostromes and other types of mass transport deposits occurring within the pieniny klippen belt pkb of the western carpathians after a short introduction into the olistostrome concept and an overall description of the pkb structure the authors presented their views on the composition and evolution of the pkb with olistostromes as the leading phenomenon although novel in some aspects the model they present is largely oversimplified and partly erroneous in our opinion in the following we shall comment on the several most disputable statements and interpretations offered in the discussed paper

land sea correlation of middle pleistocene temperate sub stages using high precision uranium series dating of tufa deposits from southern england abstract high precision u series dating allows a direct correlation to be made between terrestrial records of the penultimate interglacial marine oxygen isotope stage 7 mis 7 in britain and sub stage climate forcing in the marine oxygen isotope sequence u series ages of surficial tufa deposits are of sufficient precision to correlate discrete episodes of temperate conditions with individual warm sub stages within mis 7 furthermore detailed biostratigraphy allows periods of faunal turnover to be correlated with cold climates and lowered sea level ecological and environmental conditions in britain during mis 7 are therefore driven by the short lived sub stage climate forcing that is observable in the marine isotope record it is clear that interglacial climates are highly dynamic producing multiple climatic optima and a diverse range of environments within single warm episodes consequently sub stage records of climate forcing are crucial frameworks for reconstructing terrestrial records of environmental change

hydrochemical and isotope characteristics of spring water and travertine in the baishuitai area sw china and their meaning for paleoenvironmental reconstruction a method of combining hydrochemical data logging and in situ titrating with measurement of stable carbon and oxygen isotopes was used to reveal the hydrochemical and isotopic characteristics in the baishuitai travertine scenic area of sw china it was found that the travertine forming springs have a very high concentration of calcium and bicarbonate and accordingly very high co2 partial pressures which are not likely to be produced by biological activity in soil alone further analysis of the stable carbon isotopes of the springs shows that the high pressure of co2 is mainly related to an endogenic co2 source that means the baishuitai travertine is endogenic in origin this is contrast to the commonly accepted saying that the travertine deposition in this study simply is a product of warm and humid conditions in a karst ecological environment rapid co2 degassing from the water is triggered by the much higher partial pressures in water than that of the surrounding air consequently as the waters flow downstream of the spring the ph increases the waters become supersaturated with respect to calcite and travertine is deposited the preferential release of 12co2 to the atmosphere results in a progressive increase of travertine 13c downstream this is concluded with a preliminary discussion of variation in travertine forming water temperatures according to differences in stable oxygen isotopic compositions of the travertine formed in different epochs at baishuitai it was found that the change in water temperature is as high as 13 c i e from 23 c at about 2500 years b p to 10 c at present this may mainly reflect that the effect of geothermal source on water temperature is decreasing the problems involved in paleoenvironmental reconstruction with endogene travertine are also discussed they are the impacts of dead carbon in radiocarbon dating and the enrichment in 13c of travertine by endogenic co2 and degassing of co2 from water which has to be considered in paleovegetation reconstruction when using 13c data of the endogene carbonate deposits

two ship deep seismic soundings in the basins of the eastern mediterranean sea pasiphae cruise summary new results from a two ship refraction and oblique reflection deep seismic cruise are presented to discuss the nature of the crust in the ionian sirte and herodotus abyssal plains these expanding spread profiles were processed and analysed in both the x t and p domains arrival times of reflected and refracted branches are matched by ray tracing in both domains in spite of a shallow evaporitic sequence messinian evaporites deposited on top of a thick sedimentary pile responsible for velocity inversions on many profiles we obtain excellent velocity control down to moho depth pmp and pn 8 4 8 6 km s 1 arrivals are observed the three basins have a relatively thin crust 8 to 11 km overlain by a thick sedimentary cover up to 10km in the herodotus abyssal plain the moho boundary and main crustal units identified in the basins can be followed beneath the calabrian prism to the west and beneath the mediterranean ridge to the east the crustal structure is of oceanic type for both the ionian and sirte basins where typical oceanic layer 2 and 3 are recognized the thin crust of the herodotus basin may be interpreted either as oceanic or thinned continental crust about 10 km thick the top of the crust of the herodotus basin is much deeper therefore the herodotus basin is probably significantly older than the ionian basin triassic versus early cretaceous in age

δ13c δ18o and deposition rate of tufa in xiangshui river sw china implications for land cover change caused by climate and human impact during the late holocene

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

age and paleoclimatic implications of the bet shean travertines abstract from 41 000 to over 22 000 yr b p a massive and areally extensive spring travertine was deposited in the bet shean valley israel this travertine is coeval with the ami az member of the lisan formation which represents a high lake stand the travertine deposition is contemporaneous with a more active hydrologic regime associated with wetter conditions in the arid zones of the southern levant adjacent to southern israel these wetter conditions facilitated formation of a widespread spring tufa and also enhanced the water levels of lake lisan

new paleomagnetic results from the upper cretaceous red marls of the pieniny klippen belt western carpathians evidence for general ccw rotation and implications for the origin of the structural arc formation abstract the pieniny klippen belt pkb is a narrow arcuate structure separating the central and outer western carpathians formed during several cenozoic deformational stages the primary aim of this study was to obtain paleomagnetic constraints for the mechanism of formation of the arc we investigate albian santonian red pelagic marls from 14 localities distributed along a strike length of ca 400 km ams measurements reveal a pattern characteristic of weakly deformed sedimentary rocks and magnetic lineations do not correlate with the general strike of the pkb paleomagnetic analysis revealed well defined hematite based ancient magnetization components at 13 localities which are dated using fold and inclination tests a within locality fold test is negative for two localities exhibiting large ccw rotations of similar magnitude situated at the two ends of the pkb remanences of pre folding age were documented for 11 localities with an overall mean paleomagnetic direction of d 311 i 53 and 95 11 the indicated general ccw rotation most probably took place during the miocene together with western central and outer carpathians paleolatitudes for the pkb indicate a considerable separation from the southern margin of stable europe leaving space for coordinated rotation a paleomagnetic oroclinal test involving all localities with primary magnetizations was negative when localities with monoclinal steep dips are omitted due to possible declination bias the overall mean paleomagentic direction does not change significantly but correlation is observed between the general trend of the pkb and the paleomagnetic declinations thus we conclude that the present shape of the arc can be partly due to oroclinal bending this must have happened before oligocene since paleomagnetic declinations for neighboring paleogene basins in the central and outer western carpathians reveal a uniform ccw rotation of ca 50 magnitude irrespective of the position of the localities in relation to the carpathian arc

the strain rate field in the eastern mediterranean region estimated by repeated gps measurements we use the combined gps velocity field of the eastern mediterranean for the period 1988 to 1996 to determine crustal deformation strain rates in a region comprising the hellenic arc the aegean sea and western anatolia we interpret the velocity field and determine the strain rate tensor by the spatial derivatives of the collocated motion vectors the region following the line marmara sea north aegean trough northern central greece and the central ionian islands is associated with strong right lateral shear motion with maximum shear strain rates of 180 nano strain a 180 10 9 a in the central aegean sea n s oriented extensional processes prevail reaching 100 nano strain a the southern aegean is characterized by relatively small strain rates maximum extensional components of the strain rate tensor reaching 150 nano strain a in a n s direction are found in central greece the hellenic arc is associated with moderate arc parallel extension and strong compression perpendicular to it projections of the strain rates parallel to the major fault zones reveal that the northern aegean is governed by the westward continuation of the north anatolian fault zone which is associated with strong dextral shearing maximum 220 nano strain a accompanied by numerous large earthquakes in this century

three detailed radiocarbon dated holocene tufa and alluvial fan mollusc successions from southern ontario the first in northeastern north america abstract fossil mollusc remains particularly those of land snails provide a wealth of detailed information concerning local quaternary paleoenvironments and regional paleoclimatic conditions however this important resource is generally overlooked in north america and consequently quantitative well dated terrestrial mollusc successions are extremely rare here in an attempt to redress this imbalance a project examining the holocene molluscan faunal history of northeastern north america has been initiated thus far detailed mollusc successions and associated radiocarbon age determinations have been obtained from three sites in southern ontario two alluvial fans chine drive fan and cudia park fan both from the scarborough bluffs east of toronto and a tufa west river road near cambridge the observed land snail successions to provide an initial view of the molluscan faunal history of this region during the period from the late glacial to the mid holocene between approximately 10 500 and 5000 radiocarbon years bp yr bp the molluscan data have also been used to reconstruct the paleoenvironmental history of southern ontario during this time documenting the progression from exposed open habitats characterised by species such as vertigo modesta vallonia albula columella columella and vitrina angelicae limpida to closed woodland biotopes indicated by the presence of taxa including carychium nannodes nesovitrea binneyana paravitrea multidenta and helicodiscus parallelus this study has already demonstrated the potential of this technique in the study of quaternary climatic and environmental change in eastern north america and represents a strong foundation for extending the analysis of fossil land snail successions to other sites throughout this region it has also provided new and important insights into the establishment of the modern molluscan fauna which are essential to the understanding of present day distributional patterns and environmental associations

are two elements better than one dual isotope ratio detrending of evaporative effects on lake carbonate paleoelevation proxies 1 stable isotope based proxy methods enhance our ability to interpret geodynamical histories for tectonic provinces via paleoelevational reconstructions these methods require that the unmodified isotopic composition of meteoric water is recorded by authigenic minerals a critical assumption that has not been tested across wide ranging environmental and topographical contexts here we show that quaternary lake carbonate 18o values are not strongly nor significantly correlated with regional elevation due to the isotopic modification of in flow waters following entry into the lake environment these modifications are largely caused by surface water evaporation and can result in 3 km errors in paleoelevation estimates if not accounted for however our analysis suggests that positive shifts in surface water 18o are accompanied by similar magnitude shifts in 13c dic this positive co variation in 18o and 13c may be used to detrend lake carbonate compositions for the effects of surface water evaporation using a parameter we define here as the 13c excess when tibetan lakes are excluded from the data set 13c excess values are significantly correlated with mean up slope hypsometric altitude with an error of 500 m application of the13c excess approach to cenozoic lake carbonate records from the western u s cordillera both challenges and reinforces previous paleoelevational interpretations based on 18o alone

the 2008 methoni earthquake sequence the relationship between the earthquake cycle on the subduction interface and coastal uplift in sw greece ah is supported by a shell exploration studentship this study forms part of the nerc and esrc funded project earthquakes without frontiers under grant nej02001x 1 and was partly funded by the nerc grant looking inside the continents from space

greek tectonics and seismicity abstract the validity of existing tectonic models for the area of greece is examined in the light of the new recalculated parameters for earthquakes of the region makropoulos and burton 1981 relocated hypocentral positions are extracted from the catalogue to form radial and vertical distance depth cross sections centred on a reference point near the mid point of the aegean volcanic arc and these are used to form a three dimensional topography of the base of earthquake occurrence below 60 km isodepth maps are extracted from this topography as both three and two dimensional map presentations these maps reveal several significant features of deep seated tectonic processes in the region isodepths exceeding 150 km are seen in the northwest aegean and these are more closely linked to the sporadhes and gulf of thermaicos rather than the north aegean trough the 150 km isodepths are also seen in the northeast aegean straddling the dardanelles in the northeastern part of the peloponnesus gulf of saronikos and eastern gulf of corinth in the southern peloponnesus towards crete and extending from north of kos to south of rodos the largest extent of deepest activity is seen south of rodos and this continues towards southwest of turkey the subduction zone of the hellenic arc is clear but smooth benioff zones are not the norm and these data show that structural complexity is more readily observed it is concluded that none of the proposed tectonic models completely explain the observed activity over the whole area and rather than propose yet another model places where further work is still particularly necessary are identified

dead carbon in stalagmites carbonate bedrock paleodissolution vs ageing of soil organic matter implications for 13c variations in speleothems twenty one 14c accelerator mass spectrometric analyses were obtained for three holocene stalagmites from the uamh an tartair cave sutherland scotland in order to estimate the past dead carbon proportion dcp results show that the dcp increases from 22 to 38 from 3780 years ago to the present because 13c variation is small within each sample it is concluded that this dcp increase is the product of the ageing of soil organic matter related to peat bog development above the cave that produced older soil co2 and not from a more intense dissolution of the surrounding carbonates which would have led to a 13c increase comparison with samples from other sites in europe shows no intersite correlation between dcp and 13c but a relatively good intersite correlation is observed between dcp and average site temperature thus temperature may be a major factor controlling the production of old soil organic matter co2 and therefore the dead carbon content of seepage water in contrast to the scotland stalagmites two other holocene samples from sites in southern france and belgium exhibit a good correlation between 13c and dcp which can be explained in terms of variations in the intensity of limestone dissolution consequently 13c variations observed in stalagmites are not always due to changes in the vegetation type c3 c4 as has been commonly assumed 13c 12c variations in speleothem calcite may also be controlled by the soil organic matter age and in some cases by the intensity of the limestone dissolution conversely a largely constant speleothem 13c signal as observed for the scotland stalagmites does not necessarily imply that surface climate and vegetation conditions were stable since the dcp variations in this case are clearly related to the peat bog development during stalagmite growth

climatic significance of seasonal trace element and stable isotope variations in a modern freshwater tufa abstract we present a continuous 14 yr long 1985 to 1999 high resolution record of trace element mg sr ba u and stable isotope 13c 18o variations in a modern freshwater tufa from northwestern queensland australia by utilizing the temperature dependence of the 18o signal an accurate chronology was developed for the sampled profile which allowed a comparison of the chemical records with hydrological and meteorological observations as a consequence it was possible to constrain the relevant geochemical processes relating climate variables such as temperature and precipitation to their chemical proxies in the tufa record temperatures calculated from the mg concentrations of the tufa samples provide close approximations of average annual water temperature variations furthermore we demonstrate that temporal changes in mg ca water can be estimated using an empirically derived equation relating mg ca water to the sr ba ratio measured in the tufa samples by means of this relationship it is theoretically possible to determine the mg ca ratio of paleowaters and hence to derive reliable estimates of former water temperatures from the mg concentrations of fossil tufas from the study area sympathetic variations in sr ba and 13c along the sampled profile record changes in water chemistry which are most probably caused by variable amounts of calcite precipitation within the vadose zone of the karst aquifer this process is thought to be markedly subdued whenever the amount of wet season precipitation exceeds a given threshold accordingly distinct minima in sr ba and 13c are interpreted to reflect years with above average rainfall the pronounced seasonal and annual variability of the u concentration along the profile is thought to primarily record changes in the u flux from the soil to the water table we suggest that during intensive rain events u is transported to the phreatic zone by complexing organic colloids giving rise to conspicuous u maxima in the tufa after above average wet seasons this study demonstrates the potential of freshwater tufas to provide valuable information on seasonal temperature and rainfall variations if tufa deposits turn out to be reasonably resistant to secondary processes combined investigation of speleothems and tufas from the same area could become a promising approach in future research while speleothems offer continuous records of long term paleoenvironmental changes tufas could provide high resolution time windows into selected periods of the past

a 3 d density velocity model between the cretan sea and libya abstract a 3 d density model for the cretan and libyan seas and crete was developed by gravity modelling constrained by five 2 d seismic lines velocity values of these cross sections were used to obtain the initial densities using the nafe drake and birch empirical functions for the sediments the crust and the upper mantle the crust outside the cretan arc is 18 to 24 km thick including 10 to 14 km thick sediments the crust below central crete at its thickest section has values between 32 and 34 km consisting of continental crust of the aegean microplate which is thickened by the subducted oceanic plate below the cretan arc the oceanic lithosphere is decoupled from the continental along a nw se striking front between eastern crete and the island of kythera south of peloponnese it plunges steeply below the southern aegean sea and is probably associated with the present volcanic activity of the southern aegean sea in agreement with published seismological observations of intermediate seismicity low density and velocity upper mantle below the cretan sea with 3 25 103 kg m3 and vp velocity of compressional waves around 7 7 km s which are also in agreement with observed high heat flow density values point out at the mobilization of the upper mantle material here outside the hellenic arc the upper mantle density and velocity are 3 32 103 kg m3 and vp 8 0 km s respectively the crust below the cretan sea is thin continental of 15 to 20 km thickness including 3 to 4 km of sediments thick accumulations of sediments located to the ssw and sse of crete are separated by a block of continental crust extended for more than 100 km south of central crete these deep sedimentary basins are located on the oceanic crust backstopped by the continental crust of the aegean microplate the stretched continental margin of africa north of cyrenaica and the abruptly terminated continental aegean microplate south of crete are separated by oceanic lithosphere of only 60 to 80 km width at their closest proximity to the east and west the areas are floored by oceanic lithosphere which rapidly widens towards the herodotus abyssal plain and the deep ionian basin of the central mediterranean sea crustal shortening between the continental margins of the aegean microplate and cyrenaica of north africa influence the deformation of the sediments of the mediterranean ridge that has been divided in an internal and external zone the continental margin of cyrenaica extends for more than 80 km to the north of the african coast in form of a huge ramp while that of the aegean microplate is abruptly truncated by very steep fractures towards the mediterranean ridge changes in the deformation style of the sediments express differences of the tectonic processes that control them that is subduction to the northeast and crustal subsidence to the south of crete strike slip movement between crete and libya is required by seismological observations