application of satellite magnetic anomaly data to curie isotherm mapping a boundary condition on temperature at depth in the continental crust can in principle be obtained by mapping of the curie isotherm where it forms the base of the magnetic crust an approach to mapping magnetic crustal thickness using satellite magnetic anomaly data is described because magnetic crustal thickness is small with respect to satellite altitude inversion of the anomaly data yields magnetization models expressing regional variations in the vertical integral of magnetization this parameter is inversely correlated with regional heat flow in the western united states suggesting that areas of low apparent magnetization are areas of thin magnetic crust resulting from a shallow curie isotherm for a simple model of a uniformly magnetized magnetic crust or intra crustal layer curie depth is linearly related to apparent magnetization if the relation can be calibrated by two or more curie depth estimates regional apparent curie isotherm configuration can be mapped in an alternative approach a family of curie depth models can be computed using assumed magnetization values in each case the curie depth configuration is used as a boundary condition in a thermal model that model is selected which gives a heat flow distribution best fitting observations conductive heat flow models for a traverse across the rio grande rift using a finite element technique and for a map grid using a one dimensional thermal model approximation are given as examples

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

comparison of the quaternary travertine sites in the denizli extensional basin based on their depositional and geochemical data abstract in the denizli basin turkey located in the western anatolian extensional province travertine and tufa deposition has been an ongoing process for at least 600 000 years travertine bodies which are 30 to 75 m thick and each covers areas of 1 to 34 km2 are up to 1 km3 in volume today spring waters in this area have temperatures of 19 to 57 c are of the ca mg hco3 so4 type in the pamukkale kelkaya and pinarbasi areas and the ca mg so4 hco3 type at cukurbag thermal waters along the northern margin of the basin are generally hotter than those in the east southeast and south the 18o and d values of the spring waters indicate a meteoric origin the average temperatures of the hydrothermal systems in the denizli basin appear to have decreased from pleistocene to holocene travertine which formed from the hotter water is more widespread than the tufa that formed in the cooler spring waters deposition of the travertine which formed largely on slopes in depressions and along fissure ridges mostly on northern basin margins was controlled by the interplay between various intrinsic and extrinsic parameters the travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded crystalline crust raft and pisoid travertines found in some of the northern sites the aragonitic samples rich in sr are typically found around the spring orifices and along the central axis of the fissure ridges the stable isotope values of the travertine found in the northwest and southeast parts of the basin are different the 13c values of the northern travertine deposits are more positive 3 7 to 11 7 vpbd than those found in the south southeast areas 4 to 5 8 vpdb in contrast the travertine and tufa in the southeastern areas have higher 18o values 15 2 to 7 8 vpdb than those of the northern areas 16 6 to 4 8 vpdb available evidence indicates that spring activity and associated travertine precipitation in the denizli basin were controlled largely by tectonic activity rather than by climatic conditions

interaction between the deep fluids and the shallow groundwaters on vulcano island italy the aim of this work is to study the interactions processes between the fluids of deep origin and the shallow groundwaters of the vulcano porto area during 1995 13 well waters were sampled three times may july and november and analysed for major and some minor elements b br and nh4 and for dissolved gases the close relationship of these waters with the deep magmatic source is highlighted by the composition of the dissolved gases furthermore the areal distribution of dissolved species is controlled mainly by the gas fluxes from depth and by the presence of a deeper thermal aquifer the distribution of major anomalies in the parameters measured in the groundwaters in fact overlaps the soil gas fluxes distribution that are related to the existence of preferential upflow routes of fumarolic fluids through weak structural lines in the volcanic edifice

atmosphere driven ice sheet mass loss paced by topography insights from modelling the south western scandinavian ice sheet abstract marine terminating glaciers and ice streams are important controls of ice sheet mass balance however understanding of their long term response to external forcing is limited by relatively short observational records of present day glaciers and sparse geologic evidence for paleo glaciers here we use a high resolution ice sheet model with an accurate representation of grounding line dynamics to study the deglaciation of the marine based south western norwegian sector of the scandinavian ice sheet and its sensitivity to ocean and atmosphere forcing we find that the regional response to a uniform climate change is highly dependent on the local bedrock topography consistent with ice sheet reconstructions our simulations suggest that ocean warming is able to trigger initial retreat in several fjords but is not sufficient to explain retreat everywhere widespread retreat requires additional ice thinning driven by surface melt once retreat is triggered the underlying bedrock topography and fjord width control the rate and extent of retreat while multi millennial changes over the course of deglaciation are modulated by surface melt we suggest that fjord geometry ice ocean interactions and grounding line dynamics are vital controls of decadal to centennial scale ice sheet mass loss however we postulate that atmospheric changes are the most important drivers of widespread ice sheet demise and will likely trump oceanic influence on future ice sheet mass loss and resulting sea level rise over centennial and longer time scales

a 10be production rate calibration for the arctic we present a baffin bay 10 be production rate calibration derived from glacial deposits in western greenland and baffin island and test our results against published 10 be calibration datasets to develop an arctic 10 be production rate our calibration comprises i 10 be measurements from moraine boulders linked to a 14 c dated moraine at jakobshavn isfjord in western greenland ii an independent and previously published 10 be production rate at jakobshavn isfjord and iii re measured 10 be concentrations from a baffin island calibration site that is included in the north eastern north america dataset combined we calculate a sea level high latitude 10 be production rate for the baffin bay region of 3 96 0 07 atoms g 1 a 1 lal stone scaling model after testing the baffin bay rate against calibration sites in norway and north eastern north america we calculate a more conservative arctic production rate of 3 96 0 15 atoms g 1 a 1 the baffin bay and arctic 10 be production rates are indistinguishable from the north eastern north america 10 be production rate 3 91 0 19 atoms g 1 a 1 and yield overall uncertainties of 2 3 7 1s these production rates reduce systematic uncertainties in 10 be based chronologies of ice margin change and allow 10 be based chronologies to be more confidently compared with high resolution climate records such as those from greenland ice cores copyright 2013 john wiley sons ltd

stable isotope geochemical study of pamukkale travertines new evidences of low temperature non equilibrium calcite water fractionation abstract in this paper we present the first detailed geochemical study of the world famous actively forming pamukkale and karahayit travertines denizli basin sw turkey and associated thermal waters sampling was performed along downstream sections through different depositional environments vent artificial channel and lake terrace pools and cascades of proximal slope marshy environment of distal slope 13 c travertine values show significant increase from 6 1 to 11 7 pdb with increasing distance from the spring orifice whereas the 18 o travertine values show only slight increase downstream from 10 7 to 9 1 pdb mainly the co 2 outgassing caused the positive downstream shift 6 in the 13 c travertine values the high 13 c values of pamukkale travertines located closest to the spring orifice not affected by secondary processes suggest the contribution of co 2 liberated by thermometamorphic decarbonation besides magmatic sources based on the gradual downstream increase of the concentration of the conservative na k cl evaporation was estimated to be 2 5 which coincides with the moderate effect of evaporation on the water isotope composition stable isotopic compositions of the pamukkale thermal water springs show of meteoric origin and indicate a local meteoric water line of denizli basin to be between the global meteoric water line craig 1961 and western anatolian meteoric water line imsek 2003 detailed evaluation of several major and trace element contents measured in the water and in the precipitated travertine along the pamukkale mm section revealed which elements are precipitated in the carbonate or concentrated in the detrital minerals former studies on the hungarian egerszalok travertine kele et al 2008a b 2009 had shown that the isotopic equilibrium is rarely maintained under natural conditions during calcite precipitation in the temperature range between 41 and 67 c in this paper besides the detailed geochemical analyses along downstream sections we present new evidences of non equilibrium calcite water fractionation in lower temperature range 13 3 to 51 3 c our measurements and calculations on natural hot water travertine precipitations at pamukkale and egerszalok revealed that the 18 o travertine is equal with the 18 o hco3 at the orifice of the thermal springs which means that practically there is no oxygen isotope fractionation between these two phases high rate of co 2 degassing with rapid precipitation of carbonate could be responsible for this as it was theoretically supposed by o neil et al 1969 thus for the determination of the deposition temperature of a fossil travertine deposit we propose to use the water bicarbonate oxygen isotope equilibrium fractionation instead of the water travertine fractionation which can result 8 9 c difference in the calculated values our study is the first detailed empirical proof of o neil s hypothesis on a natural carbonate depositing system the presented observations can be used to identify more precisely the deposition temperature of fossil travertines during paleoclimate studies

late glacial and holocene 10be production rates for western norway we present a new regional calibration of the 10be production rate from two well dated surfaces insouthern norway a rock avalanche with 14c dated wood and a precisely dated younger dryas moraine c

new improved equations for and sio2 geothermometers by outlier detection and rejection abstract we present new improved equations for three still widely used na k na li and sio 2 geothermometers obtained by statistical treatment of the data and application of outlier detection and rejection as well as theory of error propagation and compare them with those by fournier and others new equations are also developed for estimating errors associated with the use of these new geothermometric equations and comparing them with the performance of the original equations the errors in the use of the new na k equation for temperatures ranging from 80 to 350 c vary from about 19 to 34 which is lower than the corresponding errors 24 43 for the original fournier equation similarly for temperatures ranging from about 50 to 320 c our new equation for na li geothermometer for cl 2 2 geothermometer we have proposed a linear equation for the temperature range of 210 to 310 c sio 2 295 ppm which shows considerably smaller total propagated errors 2 3 than for the original equation 5 29

hydrogeochemistry of thermal and mineralized waters in the diyadin agri area eastern turkey abstract the diyadin geothermal area located in the eastern part of anatolia turkey where there has been recent volcanic activity is favorable for the formation of geothermal systems indeed the diyadin geothermal system is located in an active geodynamic zone where strike slip faults and tensional cracks have developed due to n s regional compression the area is characterized by closely spaced thermal and mineralized springs with temperatures in the range 30 64 c and flowrates 0 5 10 l s thermal spring waters are mainly of ca na hco 3 and ca mg so 4 types with high salinity while cold groundwater is mostly of ca na mg hco 3 type with lower salinity high contents of some minor elements in thermal waters such as f b li rb sr and cs probably derive from enhanced water rock interaction thermal water samples collected from diyadin are far from chemical equilibrium as the waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters the temperatures of the deep geothermal reservoirs are estimated to be between 92 and 156 c in diyadin field based on quartz geothermometry while slightly lower estimates are obtained using chalcedony geothermometers the isotopic composition of thermal water 18 o 2 h 3 h indicates their deep circulating meteoric origin the waters are likely to have originated from the percolation of rainwater along fractures and faults to the deep hot reservoir subsequent heating by conduction due to the presence of an intrusive cupola associated with the tendurek volcano is followed by the ascent of deep waters to the surface along faults and fractures that act as hydrothermal conduits modeling of the geothermal fluids indicates that the fluid is oversaturated with calcite aragonite and dolomite which matches travertine precipitation in the discharge area likewise the fluid is oversaturated with respect to quartz and chalcedony indicating the possibility of siliceous precipitation near the discharge areas a conceptual hydro geochemical model of the diyadin thermal waters based on the isotope and chemical analytical results has been constructed

hot spring systems geobiology abiotic and biotic influences on travertine formation at mammoth hot springs yellowstone national park usa multiple abiotic and biotic factors combine in nature to influence the formation of calcium carbonate limestone deposits systems geobiology studies of how micro organisms respond to or sometimes even control the coupled effects of environmental change and mineralization will permit more accurate interpretation of the fossil record of ancient microbial life mammoth hot springs in yellowstone national park usa serves as a natural laboratory for tracking how the dynamic interplay of physical chemical and biological factors come together to form hot spring limestone called travertine systematic downstream correlations occur at mammoth hot springs between travertine deposition geomorphology crystalline structure and geochemistry microbial communities mat morphology pigmentation and phylogenetic and metabolic diversity and spring water conditions temperature ph geochemistry and flow field based microscale and mesoscale experimentation indicates that microbes directly influence travertine growth rate and crystalline structure at the macroscale time lapse field photography and numerical modelling suggest that travertine terrace geomorphology is influenced strongly by hydrology heat dispersion and geochemistry these results from mammoth hot springs allow establishment of a conceptual framework across broad spatial and temporal scales in which to track how multiple geological and biological factors combine to control caco3 crystal precipitation and the resulting formation of travertine deposits

biotic and inorganic control on travertine deposition at bullicame 3 spring viterbo italy a multidisciplinary approach abstract a multidisciplinary characterization of an active thermal spring in central italy has been undertaken with the aim of i ascertaining whether microbiological activity plays a relevant role in hot depositing travertines and ii establishing an experimental protocol able to identify similar effects in fossil travertines water gas and travertine samples were investigated by chemical icp ms sem eds physical dta dtg isotopic 18o d and 13c mineralogical xrpd and spectroscopic epr techniques twenty four samples three for each phase were collected every 5 c temperature drop along a 100 m long artificial channel near viterbo bullicame 3 latium central italy a microbiological characterization was carried out in parallel sampling the channel every 10 c temperature drop the bullicame 3 system is revealed to be composed of two markedly different subsystems a water gas interface where a kinetically fast exchange allows equilibrium of components both in water and in gases a solid water interface where travertine precipitation occurs influenced by microbiological activity a peculiar lattice shrinking of calcite was identified as well as an anomalous value of the zero field splitting parameter from the epr measurements the interpretation of these anomalies is confirmed by the identification of calcifying cyanobacteria throughout the channel path our results point out that microbiological activity can play a significant role in travertine deposition from hot springs furthermore the proposed approach representing a tool to identify crystal chemical remnants of past microbiological activity could be applicable to fossil travertines

a tentative 2d thermal model of central india across the narmada son lineament nsl abstract this work deals with 2d thermal modeling in order to delineate the crustal thermal structure of central india along two deep seismic sounding dss profiles namely khajuriakalan pulgaon and ujjan mahan traversing the narmada son lineament nsl in an almost north south direction knowledge of the crustal structure and p wave velocity distribution up to the moho obtained from dss studies has been used for the development of the thermal model numerical results reveal that the moho temperature in this region of central india varies between 500 and 580 c the estimated heat flow density value is found to vary between 46 and 49 mw m2 the curie depth varies between 40 and 42 km and is in close agreement with the curie depth 40 4 km estimated from the analysis of magsat data based on the present work and previous work it is suggested that the major part of peninsular india consisting of the wardha pranhita godavari graben basin bastar craton and the adjoining region of the narmada son lineament between profiles i and iii towards the north and northwest of the bastar craton are characterized with a similar mantle heat flow density value equal to 23 mw m2 variation in surface heat flow density values in these regions are caused by variation in the radioactive heat production and fluid circulation in the upper crustal layer

depositional facies and aqueous solid geochemistry of travertine depositing hot springs angel terrace mammoth hot springs yellowstone national park u s a petrographic and geochemical analyses of travertine de positing hot springs at angel terrace mammoth hot springs yellow stone national park have been used to define five depositional facies along the spring drainage system spring waters are expelled in the vent facies at 71 to 73 8c and precipitate mounded travertine composed of aragonite needle botryoids the apron and channel facies 43 728c is floored by hollow tubes composed of aragonite needle botryoids that encrust sulfide oxidizing aquificales bacteria the travertine of the pond facies 30 62 8c varies in composition from aragonite needle shrubs formed at higher temperatures to ridged networks of calcite and aragonite at lower temperatures calcite ice sheets calcified bubbles and aggregates of aragonite needles fuzzy dumbbells pre cipitate at the air water interface and settle to pond floors the prox imal slope facies 28 54 8c which forms the margins of terracette pools is composed of arcuate aragonite needle shrubs that create small microterracettes on the steep slope face finally the distal slope facies 28 30 8c is composed of calcite spherules and calcite feather crys tals despite the presence of abundant microbial mat communities and their observed role in providing substrates for mineralization the com positions of spring water and travertine predominantly reflect abiotic physical and chemical processes vigorous co 2 degassing causes a 12 unit increase in spring water ph as well as rayleigh type covariations between the concentration of dissolved inorganic carbon and corre sponding d 13 c travertine d 13 c and d 18 o are nearly equivalent to aragonite and calcite equilibrium values calculated from spring water in the higher temperature 50 738c depositional facies conversely

crustal structure along mehmadabad billimora profile in the cambay basin india from deep seismic soundings abstract deep seismic sounding dss investigations were carried out along a 220 km long n s profile from mehmadabad 22 50 n 72 46 e to billimora 20 46 n 72 58 e in the cambay basin india for studying the detailed crustal structure in the region seismic refraction as well as narrow and wide angle reflection travel time data were obtained for various crustal boundaries starting from the sedimentary section down to the moho by continuous profiling analysis of reversed reflection and refraction travel time data has yielded crustal velocity depth functions for the mehmadabad broach and broach navsari sections along the profile which are significantly different from each other the average velocities at depths in the magmadabad broach section have been found to be considerably lower than those in the broach navsari section by about 25 at 5 km 17 at 10 km 7 at 20 km and 2 at the moho depth and even deeper down in the upper mantle the presence of a relatively thicker sedimentary section especially in the jambusar broach area as revealed by the reversed refraction data analysis is responsible for this gross difference in the average velocity functions for the two parts of the profile and the same have therefore been used for obtaining the detailed crustal depth along the profile the cambay basin which is well known to be bounded by step faults on the eastern and western margins is also dissected into seven major crustal blocks in the n s direction from mehmadabad to billimora the various crustal blocks identified are from the north 1 i mehmadabad block 2 ii tarapur block 3 iii petlad katana block 4 iv jambusar broach block 5 v kosamba block 6 vi surat block and 7 vii navsari billimora block these blocks are displaced up or down relative to the adjacent blocks due to movements along the faults bounding them most of the faults have been found to extend quite deep and to affect the moho boundary considerably as is quite evident from the relief of the moho found along the profile further the seismic activity observed in the region during historical as well as modern times suggests that these deep faults may even be currently active the jambusar broach block which is well known as a broad regional syncline with the maximum thickness of cenozoic sediments has been found to be a major graben revealing a maximum crustal thickness of 38 40 km the granitic basement in this graben is also the deepest at 6 0 6 5 km depth towards the north and south of this major graben the moho as well as the granitic basement are found to be at relatively shallower depths in various crustal blocks the boundary velocity at the moho has been found to be 8 1 8 2 km sec whereas at the granitic basement level there seems to be a lateral velocity variation from 5 7 to 6 3 km sec the crustal depth section obtained in the present study reveals a close relationship between the deep and shallow structural features in this region the deccan traps which form the basement of the overlying tertiary sediments over most part of the profile vary in thickness from 1 0 to 1 8 km however the trap surface rises to very shallow depths on the southern part of the profile the boundary velocity in the deccan traps has been found to vary between 4 8 and 5 2 km sec in the anklesvar kosamba area there is also evidence for the presence of a 1 2 km thick layer of mesozoic sediments with a velocity of about 4 0 km sec underlying the 1 1 km thick deccan traps layer

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

the deep accumulation of 10be at utsira southwestern norway implications for cosmogenic nuclide exposure dating in peripheral ice sheet landscapes cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories we scrutinize a recently published data set of cosmogenic 10be data from erratic boulders in norway used to constrain the deglaciation of the western scandinavian ice sheet to 20 ka our model of the 10be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of 10be during long lasting ice free periods that resulted in 10be ages 10 too old we suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon produced 10be and were derived from bedrock depths 2 5 m and most likely 4 m the implication of our finding is that for landscapes that experience long ice free periods between brief maximum glacial phases glacial erosion of 5 m is required to remove detectable traces of inherited 10be

fjord insertion into continental margins driven by topographic steering of ice fjords line mountainous continental margins where icesheets and glaciers once stood a two dimensional model simulation suggests that fjords can be eroded within one million years primarily in response to topographic ice steering and erosion from ice discharge subsequent glaciers that form on these landscapes are smaller and exhibit greater responses to climate change

elastic thickness and isostatic coherence anisotropy in the south indian peninsular shield and its implications 1 we present measurements of the mechanical strength of the lithosphere of the south indian peninsular shield sips values of effective elastic thickness te were obtained from azimuthally averaged coherence measurements 2 k between bouguer gravity and topography using a multitaper method mtm and a mirrored periodogram method mpm values of te from mtm 11 16 km are consistently lower than those from mpm 20 31 km and are contained within the seismogenic thickness ts substantiating earlier measurements in shield regions that have been tectonically inactive for a long time the 2d coherence function 2 k calculated with the mtm reveals little mechanical anisotropy in the sips we conduct analyses of different provinces within the sips and show how the results correlate with maximum horizontal stress orientations hmax and heat flow measurements local processes appear to influence the strength of the sips lithosphere more profoundly than processes occurring at the plate boundary

pn velocity and cooling of the continental lithosphere average upper mantle p sub n velocities and heat flow were computed within continental physiographic provinces in north america from published data p sub n velocity and heat flow data display an inverse relationship and were found to correlate with a statistically significant correlation coefficient temperatures at the crust mantle boundary were estimated from the heat flow values and these were used to demonstrate a correlation between p sub n velocity and temperature of upper mantle material the value of partialp sub n partialt p thus obtained 4 4 x 10 sup 4 to 8 1 x 10 sup 4 km s sup 1 sup 0 c sup 1 is within the range of temperature derivatives determined from laboratory studies of ultramafic rocks this dependence of p sub n velocity on temperature implies that one possible explanation for the observed geographical distribution in upper mantle seismic velocity is that the variation in p sub n velocity is primarily a temperature effect combined with the relationship between heat flow and crustal age for continents the p sub n versus heat flow correlation suggests a relationship between p sub n velocity and crustal age probably due to progressive cooling of the continental lithosphere after a thermotectonic event

marine 14c reservoir ages for 19th century whales and molluscs from the north atlantic abstract in order to compare radiocarbon dates on marine and terrestrial samples the former have to be corrected for a reservoir age we present reservoir ages from dating 21 whales collected 1860 1901 and recalculating dates of 23 molluscs collected 1857 1926 most of the whales were caught along the coast of norway but one is from france and one from iceland we assume the former mainly lived in the north and equatorial atlantic and in the norwegian sea whales feed only on pelagic organisms and will provide the reservoir age for the open ocean surface water however they travel long distances and will integrate the reservoir ages of the different water masses along their way molluscs dated from norway spitsbergen and arctic canada are stationary and monitor the sea water passing their dwelling site but some also take up carbon from particulate food or sediment pore water coastal water also often contains some continental carbon we present two different views on how to analyze and interpret the data mangerud recommends to use reservoir ages based on a combination of the whale and mollusc dates i e 380 30 and 360 30 yr relative to intcal04 and british oak respectively and a r value of 20 30 for the surface water in the n atlantic and norwegian sea bondevik and gulliksen maintain that the reservoir age and r along the norwegian coast is latitude dependant with r values increasing from 3 22 in the south to 105 24 at spitsbergen whales reflecting north atlantic open ocean surface water have lower r 7 11 than most molluscs

asynchronous response of marine terminating outlet glaciers during deglaciation of the fennoscandian ice sheet this is the accepted manuscript version published version is available at http dx doi org 10 1130 g35299 1

the deglaciation of the americas during the last glacial termination this paper reviews current understanding of deglaciation in north central and south america from the last glacial maximum to the beginning of the holocene together with paleoclimatic and paleoceanographic data we compare and contrast the pace of deglaciation and the response of glaciers to major climate events during the global last glacial maximum glgm 26 5 19 ka average temperatures decreased 4 to 8 c in the americas but precipitation varied strongly throughout this large region many glaciers in north and central america achieved their maximum extent during the glgm whereas others advanced even farther during the subsequent heinrich stadial 1 hs 1 glaciers in the andes also expanded during the glgm but that advance was not the largest except on tierra del fuego hs 1 17 5 14 6 ka was a time of general glacier thickening and advance throughout most of north and central america and in the tropical andes however glaciers in the temperate and subpolar andes thinned and retreated during this period during the bolling allerod interstadial b a 14 6 12 9 ka glaciers retreated throughout north and central america and in some cases completely disappeared many glaciers advanced during the antarctic cold reversal acr 14 6 12 9 ka in the tropical andes and patagonia there were small advances of glaciers in north america central america and in northern

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

changes in north atlantic radiocarbon reservoir ages during the allerod and younger dryas estimates of the radiocarbon age of seawater are required in correlations between marine and terrestrial records of the late quaternary climate we radiocarbon dated marine shells and terrestrial plant remains deposited in two bays on norway s west coast between 11 000 and 14 000 years ago a time of large and abrupt climatic changes that included the younger dryas yd cold episode the radiocarbon age difference between the shells and the plants showed that sea surface reservoir ages increased from 400 to 600 years in the early yd stabilized for 900 years and dropped by 300 years within a century across the yd holocene transition

quaternary glaciations in southern fennoscandia evidence from southwestern norway and the northern north sea region abstract based on records from the northern north sea and southern norway quaternary fennoscandian glaciations are described and discussed maximum glaciation defined as the presence of shelf edge glaciation an ice stream flowing out of the norwegian channel and most likely an ice divide over the central part of fennoscandia sweden gulf of bothnia occurred for the first time in the late cenozoic at ca 1 1 myr the fedje glaciation this glaciation was followed by a ca 600 kyr period with at least two glaciations with ice extension somewhat larger than the younger dryas event in the region the first maximum glaciation of the bruhnes chron was during isotope stage 12 and was followed by repeated maximum glaciations within each of the light isotopic stages until stage 2 during the weichselian the southwestern part of the fennoscandian ice sheet reached maximum position three times sometime between 22 and 28 37 and 50 and 60 and 80 ka limited glaciations probably occurred during stadials between the early and middle weichselian interstadials between 500 ka and 1 1 myr and most likely also prior to 1 1 myr deep norwegian sea ice rafted detritus ird records reflecting contributions from several different ice sheets fennoscandian barents sea iceland and greenland each with large variations in history of ice extent to their respective margins yet to some degree they reflect the glaciation of the northern north sea region with an increasing ird input around 1 1 myr and a relatively low input of north sea components during some cycles around the b m boundary maximum glaciations occurred during insolation minima in the earlier part of the middle pleistocene however not all such minima are reflected by maximum glaciation in southern parts of fennoscandia the relatively poor chronological control and non continuous character of the data on weichselian interstadials stadials precludes a clear relationship to atmospheric changes recorded in greenland ice cores as well as to precession and or obliquity cycles in insolation

late weichselian vegetation climate and floral migration at liastemmen north rogaland south western norway palynological results from liastemmen indicate a tripartite division of the late weichselian in the pleniglacial period from deglaciation ca 14000 bp to ca 13000 bp artemisia dominated pioneer vegetation on disturbed mineral soil was strongly influenced by cold winters and katabatic winds the late weichselian interstadial ca 13000 bp ca 11000 bp comprises a salix shrub consolidation phase and from ca 12700 bp a tree birch phase in the last 500 years of this period july and january means are estimated to about 16 c and between 2 c and 6 c respectively in the younger dryas stadial ca 11000 bp ca 10200 bp artemisia dominated vegetation returns three brief climatic deteriorations ca 12 250 bp 11 700 bp and 11 300 bp unfavourable to woody vegetation on humus soils are demonstrated within the interstadial critical climatic factors include cool winters and strong winds exposing vegetation and soil to frost drought and erosion the oldest and strongest oscillation probably involving local deforestation is correlated with the older dryas deterioration boreal circumpolar eurasiatic and arctic alpine plants dominated the late glacial flora for the majority of the late glacial taxa a northward migration is demonstrated this may also apply for papaver radicatum pinguicula alpina and primula scandinavica all with bicentric distributions in norway today

a comparison of heat flow from the gondwana continents with velocities of gondwana plates geodynamic implications abstract the velocities of the lithospheric plates generally differ from each other and the cause of the super mobility of the indian subcontinent is an unresolved problem as the lithospheric plates and the sub lithospheric mantle form the two key elements of plate tectonic movement the thermal characteristics of the three constituent plates of gondwanaland i e the indian african and australian landmasses have been compared in this study it has been clearly shown that the mean surface heat flow values q s in those gondwana terrains of india which remained unaffected by tectonic and igneous activity during the last 150 m y i e after the break up of gondwanaland are either equal to or mostly lower by 5 22 mw m 2 than those in similar terrains of australia and even the immobile african continent and that q s values for the terrains of these landmasses which were affected by such activity during the last 150 m y are uniformly equal it is inferred that the indian lithosphere is neither hotter nor thinner than that beneath the above mentioned continents and that the sub lithospheric upper mantle beneath the indian peninsula is not hotter or less viscous than that beneath the african and australian shields these results and inferences evidently imply that the thermal regime and the other related parameters of the continental lithosphere do not contribute to the mobility of the plates to which it is attached that the rapid movement of the indian landmass is not coupled with the thermal characteristics of its lithosphere and that the drag force which the present studies have shown to be insignificant would not have been lower on the base of the indian lithosphere than beneath the african and australian landmasses accordingly the earlier reported postulate that the high velocity of the indian landmass is due to its thin and hot continental lithosphere and less viscous upper mantle is not valid the paleo reconstruction indicates the existence of the reunion and kerguelen plumes one on each side of the indian landmass it is likely that these plumes created in the sub lithospheric mantle favourable conditions which worked together with forces that resulted from slab pull and ridge push to give a high velocity to the indian landmass

evaluation of groundwater hydrochemical characteristics and mixing behavior in the daying and qicun geothermal systems xinzhou basin this paper examines groundwater hydrochemical characteristics during mixing between thermal and non thermal groundwater in low to medium temperature geothermal fields a case study is made of daying and qicun geothermal fields in the xinzhou basin of shanxi province china the two geothermal fields have similar flow patterns with recharge sourced from precipitation in mountain areas heated through a deep cycle before flowing into overlying quaternary porous aquifers via fractures hydrochemical features of 60 ground and surface water samples were examined in the context of hydrogeologic information the average temperatures of the deep geothermal reservoirs are estimated to be 125 degrees c in daying field and 159 degrees c in qicun field based on na k mg geothermometry while slightly lower estimates are obtained using silica geothermometers hydrochemical features of thermal water are distinct from cold water thermal groundwater is mainly cl center dot so 4 na type with high tds while non thermal groundwater is mostly hcl 3 ca center dot mg and hco 3 ca type in the daying and qicun regions respectively hydrogeochemical processes are characterized by analyzing ion ratios in various waters higher contents of some minor elements in thermal waters such as f si b and sr are probably derived from extended water rock interaction and these elements can be regarded as indicators of flow paths and residence times mixing ratios between cold and thermal waters were estimated with cl na and b concentrations using a mass balance approach mixing between ascending thermal waters and overlying cold waters is extensive the proportion of water in the quaternary aquifer derived from a deep thermal source is lower in daying geothermal field than in qicun field 5 3 7 3 vs 6 3 49 3 mixing between thermal and non thermal groundwater has been accelerated by groundwater exploitation practices and is enhanced near faults shallow groundwater composition has also been affected by irrigation with low temperature thermal water c 2009 elsevier b v all rights reserved

origin and evolution of intracratonic thermal fluids from central western peninsular india abstract the chemical and isotopic composition of several thermal springs and associated gas phases in a large sector of central western peninsular india has been investigated such springs have meteoric isotopic signature and emerge after very well developed convective circulation at depth along important tectonic structures such as the son narmada tapti rift zone and the west coast fault chemical components in both gas and liquid phases and geothermometric estimations suggest that such springs are not related to the presence of any active hydrothermal systems at shallow depth in any of the studied areas the hottest convective water emerges at tattapani at near boiling point for water at atmospheric pressure 90 c in association with an n2 rich gas phase of clear meteoric signature since such fluids do not carry any corrosive components they could be conveniently exploited for industrial purposes such as drying processes from a tectonic point of view the presence of thermal emergences scattered in a wide area along geologically well defined structures which also generate frequent moderate earthquakes suggests that such structures are active although the isotopic composition of thermal springs points to a meteoric origin their feeding aquifers are not topographically driven as in most active alpine orogenic belts the relative high quantity of total helium in the associated gas phase suggests also that they are really deep old long circulating waters we propose for such waters the term intracratonic thermal waters since the isotopic signature of he in the gas phase does not show any release of primordial 3he in any of the areas of spring emergence based on the quite low 3he 4he ratio in the gas phase we suggest also that in spite of its morphological shape the narmada son tapti rift zone cutting the indian subcontinent in two is more related to paleo suture rather than to a mid continental rift system

too young or too old evaluating cosmogenic exposure dating based on an analysis of compiled boulder exposure ages cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods and glacial boulder exposure ages are now routinely used to constrai

estimation of effective elastic thickness from gravity and topography data under the deccan volcanic province india abstract effective elastic thickness eet under the deccan volcanic province is estimated based on admittance and coherence between the gravity field and the topography the observed admittance function shows a good fit for the regional compensation model with an eet of 10 2 km the effect of a long wavelength geoidal gravity anomaly on the computation of eet has been investigated and found not to significantly influence the value of eet although a considerable change in compensation depth was noticed the estimated eet is less than the thickness of the seismically active layer in this region these results are consistent with observations in other parts of the world that eet should be smaller than the depth of the 350 100 c isotherm

source parameters of two rift associated intraplate earthquakes in peninsular india the bhadrachalam earthquake of april 13 1969 and the broach earthquake of march 23 1970 abstract the bhadrachalam earthquake of april 13 1969 and the broach earthquake of march 23 1970 are two major intraplate earthquakes associated with paleorift zones in the stable continental region of peninsular india these two events shook very large portions of the peninsula and casualties were reported for the broach earthquake ancient rifts have recently been identified as a major seismogenic tectonic feature for intraplate seismicity in stable continental regions p wave first motions and waveforms of long period teleseismic p and sh waves have been modeled to constrain the focal mechanisms and to determine the source parameters for the earthquakes previous investigators proposed multiple fault plane solutions for each of the events in this paper some of the early solutions are eliminated and the best source mechanism is derived for each earthquake for the bhadrachalam earthquake the focal mechanism determined is predominantly strike slip strike 245 dip 72 rake 358 the strike direction of the ne sw trending nodal plane is in good agreement with the trend of the observed isoseismals and is probably the fault plane the seismic moment is 4 59 1024 dyne cm and the moment magnitude mw is determined to be 5 7 the focal depth and the static stress drop are estimated to be 10 km and 17 bar respectively the strike slip motion represents a reactivated fault motion under the present day stress field for the broach earthquake the focal mechanism determined is reverse faulting with a strike slip component strike 273 dip 58 rake 130 the direction of the e w striking nodal plane is in good agreement with the mapped narmada fault dislocation direction of fissures and the trend of the isoseismals the seismic moment and moment magnitude are determined to be 1 39 1024 dyne cm and 5 4 respectivety the focal depth and the stress drop are estimated to be 11 km and 9 bar respectively the reverse motion of this event represents an inverted slip or tectonic inversion within a rift zone under the present day compressional stress field some rift associated earthquakes are characterized by large multiple shocks with significant strike slip motions the two indian earthquakes however occurred as regular main shock aftershock sequences and represent a different mode of strain release these two earthquakes also represent events with low stress drops and relatively long recurrence intervals the interpretation of this last observation is uncertain and needs more study in the future

geochemistry of carbon dioxide in six travertine depositing waters of italy abstract the chemical compositions of six travertine depositing hot spring waters in italy are described with emphasis on the carbon dioxide system all springs contained high concentrations of co 2 20 mm l 1 with equilibrium partial pressures well above those which could have been formed in contact with a soil atmosphere after surfacing the co 2 is rapidly lost to the atmosphere with evasion rates close to the springs ranging from 0 45 4 41 mm m 2 s 1 partial pressures of c02 showed an exponential decline with distance which is consistent with the static film model where temperature and turbulence are constant downstream co 2 transfer coefficients which ranged from 66 to 360 cm h 1 were consistent with moderately turbulent flow however there was no correlation between turbulence measured as the mean shear stress and co 2 evasion rate the channels investigated had all been modified by man and most possessed even widths and gradients all waters became increasingly supersaturated with aragonite and calcite downstream and both of these minerals were present in fresh travertine deposits the supersaturation was driven almost exclusively by gas evasion comparison of daytime and nighttime evasion rates demonstrated that photosynthetic activity was an insignificant source of co 2 flux in the reaches investigated carbon dioxide evasion is therefore primarily responsible for the supersaturation and probably also the deposition of travertine at these sites the caco 3 content of the travertines ranged from 91 3 to 96 0 wt with 1 7 4 1 caso 4 traces of organic matter and acid insoluble minerals

landform assemblages and sedimentary processes along the norwegian channel ice stream abstract several regional and detailed bathymetric datasets together with 2d and 3d seismic data are compiled to investigate the landform assemblages and sedimentary processes along the former path of the norwegian channel ice stream ncis at the broad scale the glacial geomorphology and sedimentary architecture reveals three different zones along the ice stream path characterized by 1 glacial erosion in the onset zone and inner shelf area 2 sediment transport through the main trunk of the ice stream across the mid shelf and 3 a zone of deposition towards the outer continental shelf edge along the first 400 km of the ice stream bed outer oslofjord skagerrak stavanger a major overdeepening is associated with suites of crag and tail features at the transition from the crystalline bedrock to the sedimentary bedrock together with evidence of glaciotectonic thrusting in the form of hill hole pairs here we interpret extensive erosion of both sedimentary rocks and quaternary sediments this zone is succeeded by an approximately 400 km long zone through which most of the sediments eroded from the inner shelf were transported rather than being deposited we infer that sediment was transported subglacially and is likely to have been advected downstream by soft sediment deformation the thickness of till of inferred weichselian age generally varies from 0 and 50 m and this zone is characterized by mega scale glacial lineations msgls which we interpret to be formed in a dynamic sedimentary system dominated by high sediment fluxes but with some localized sediment accretion associated with lineations towards the shelf break the north sea fan extends to the deep norwegian sea and reflects massive sedimentation of glacigenic debris onto the continental slope numerous glacigenic debris flows accumulated and constructed a unit up to 400 m thick during the last glacial maximum the presence of these three zones erosion transport deposition is consistent with observations from other palaeo ice streams and their significance arises from their potential to feedback and impact on ice stream dynamics

a 10be chronology of south western scandinavian ice sheet history during the lateglacial period we present 34 new cosmogenic 10be exposure ages that constrain the lateglacial bolling preboreal history of the scandinavian ice sheet in the lysefjorden region south western norway we find that the classical lysefjorden moraines earlier thought to be entirely of younger dryas age encompass three adjacent moraines attributed to at least two ice sheet advances of distinctly different ages the 10be age of the outermost moraine 14 0 0 6 ka n 4 suggests that the first advance is of older dryas age the innermost moraine is at least 2000 years younger and was deposited near the end of the younger dryas 11 4 0 4 ka n 7 after abandonment of the innermost lysefjorden moraine the ice front receded quickly towards the head of the fjord where recession was interrupted by an advance that deposited the trollgaren moraine at 11 3 0 9 ka n 5 10be ages from the inboard side of the trollgaren moraine suggest final retreat by 10 7 0 3 ka n 7 the late culmination of the younger dryas advance contrasts with other sectors of the scandinavian ice sheet where the margin appears to have culminated earlier during the younger dryas stadial followed by retreat during the middle and late part of the younger dryas

geothermal fields of china abstract there are over 2500 known occurrences of geothermal phenomena in china these lie mainly in four major geothermal zones xizang tibet yunnan taiwan east coast and north south hot water has also been found in boreholes in major mesozoic cenozoic sedimentary basins this paper presents a summary of present knowledge of these geothermal zones the geological settings of geothermal occurrences are associated mainly with magmatic activity fault uplift and depressional basins and these are described by examples of each type increased multipurpose utilisation of geothermal resources is planned and examples are given of current usages

chemical and stable isotope composition of recent hot water travertines and associated thermal waters from egerszalok hungary depositional facies and non equilibrium fractionation abstract combined petrographical mineralogical geochemical and stable isotope analyses were conducted on an actively forming egerszalok travertine mound to determine the factors that govern carbonate precipitation and thus influence the use of travertines in paleoclimate reconstruction stable isotope analyses of oxygen carbon and hydrogen demonstrate both biological and abiological factors to control travertine deposition processes of morphology related outgassing had major effects upon isotopic composition continuous co 2 degassing and temperature change of the thermal water between the spring orifice and distal parts of the system caused stable carbon and oxygen isotope compositions of the precipitating travertines to increase from 2 7 to 4 3 relative to v pdb and from 10 5 to 14 7 relative to v smow respectively the travertines at the spring orifice t 67 c are composed of almost pure calcite with a 13 c value of 2 7 relative to v pdb enabling classification as intermediate between thermometeogene and thermogene in lower temperature water away from the spring orifice various amounts of aragonite 5 35 with higher sr concentrations precipitate from solution this phenomenon is exceptional in hot spring carbonate deposits and could be explained by fast carbonate precipitation due to the morphology related outgassing oxygen and hydrogen isotope measurements of the thermal water confirmed evaporation to be causing limited kinetic isotope fractionation however 18 o values of the travertine do show isotope shifts away from the equilibrium fractionation curve which is most probably related to the rapid calcite precipitation and transportation along the flow path our data closely follow the temperature 18 o calcite water relationship observed for other travertine localities this is slightly displaced from the experimental curve and determines an empirical travertine curve our study shows that this shift may result in an approximately 8 c difference in paleotemperature calculations depending upon which fractionation curve is used

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

evidence of early deglaciation 18 000 cal a bp and a postglacial relative sea level curve from southern karmoy south west norway

erratum late glacial and holocene 10be production rates for western norway 1 calculation of the sea level high latitude production rate based on the samples from the herdla halsnoy younger dryas end moraine required accounting for the isostatic rebound of the site following deglaciation lohne et al 2007 in the process of calculating exposure ages of samples from nearby sites it was realized that the original calibration of the production rates from halsnoy were calculated using a correction based on the relative sea level history 70m maximum plus the eustatic sea level history 50m at maximum i e that the amount of isostatic depression had been over corrected sea level high latitude be production rates based on the correct relative sea level history are presented below in a corrected version of table 2 2 in the original publication the combined production rates were determined using a chi squared minimization based on the data from both calibration sites however because the two studied sites have significantly different ages halsnoy 11650 100 and oldedalen 6070 111 and therefore integrate production over different lengths of time it is inappropriate to determine a sea level high latitude production rate for the entire data set using the chi squared minimization instead the arithmetic mean of the production rates from the two sites is the more appropriate average production rate we present in the corrected table 2 below both the updated production rate values for the samples from halsnoy and average production rates using the arithmetic mean and standard deviation of the production rates from the two sites we apologize for any inconvenience caused references

surface heat flow and igneous intrusion in the cambay basin india abstract heat flow values from some additional locations in the cenozoic cambay basin have been determined together with the previously published data they show that the heat flow is moderate 55 67 mw m in the southern part of the basin towards broach and ankleswar and that there is a clear trend of high heat flow 75 93 mw m 2 range of average values for six different widely separated locations in a part of the basin located north of the mahisagan river between cambay and mehsana along a stretch of about 140 km conductive steady state geotherms calculated using observed high surface heat flow values and appropriate models show beneath the cambay mehsana area a large degree of melting in the lower crust and upper mantle which is not suggested by the existing geodata considering this aspect and taking into account the existence of a normal crust about 37 km thick below the cambay tarapur and ahmedabad mehsana blocks as obtained from deep seismic soundings it has been inferred that the heat flow anomaly is due to transient thermal perturbations introduced from tectonic activity in the form of magmatic intrusions a careful analysis of heat flow gravity and other related geodata point out and support the possibility of a miocene pliocene basic intrusive body at a depth of around 10 km under the cambay mehsana area further the consistent trend of the thermal and gravity fields indicates thinning of the postulated intrusive body from cambay towards mehsana

resistivity structure of the central indian tectonic zone citz from multiple magnetotelluric mt profiles and tectonic implications the central indian tectonic zone citz is a major tectonic feature extending across the indian subcontinent it was formed in the paleoproterozoic when the bastar craton and the bundelkhand craton were sutured together this region is recognized in the geological record as a persistent zone of weakness with many tectonothermal events occurring over geologic time the weakness of this region may have caused the late cretaceous early tertiary deccan volcanism to have been localized in the citz the zone is still tectonically active as evidenced by sustained levels of seismic activity this paper presents the first systematic investigation of the resistivity structure of the citz using multiple magnetotelluric mt transects two dimensional 2d resistivity models were generated for five north south profiles that cross the citz and encompass an area of 60 000 km2 the models were based on the joint inversion of transverse electric te transverse magnetic tm and tipper hz data all the profiles showed a low resistive 10 80 m middle to lower crust beneath the citz with a crustal conductance of 300 800 s the presence of an interconnected fluid phase and or hydrous metallic minerals appears to be the most likely explanation for the elevated conductivity that is observed beneath the citz the presence of fluids is significant because it may indicate the cause of persistent weakness at crustal depths a northward dip of both the crustal conductive layer and coincident seismic reflections favor a northward polarity of the subduction process associated with the formation of the citz

collapse of marine based outlet glaciers from the scandinavian ice sheet abstract we present a reconstruction of the timing and retreat rates of more than 2000 m thick younger dryas yd fjord glaciers in western norway using a detailed chronology of 10 be exposure ages from lateral moraines and 14 c dated end moraines a primary conclusion is that ice margins retreated up the 120 170 km long fjords at mean rates of 240 340 m yr 1 during the early holocene we further show that part of the south western sector of the scandinavian ice sheet collapsed in two distinct steps the first step occurred between 19 5 and 18 5 ka bp as break up of the norwegian channel ice stream which drained the ice sheet during the last glacial maximum lgm the second step was the rapid retreat up the fjords mentioned above dated to 11 6 11 1 ka bp during the intervening 7000 years no net retreat occurred despite oscillations of the ice margin this stepwise ice margin retreat strongly contrasts with the more monotonic decay of the ice sheet as a whole indicating that water depths set the pace for climate triggered ice margin retreat in this part of the ice sheet calving and melting of marine margins has dominated mass loss from modern ice sheets in recent decades however the mechanisms and long term 100 1000 yr rate of ice front retreat is less certain and empirical examples such as those given here may help in developing better numerical models

age of the fjord stade moraines in the disko bugt region western greenland and the 9 3 and 8 2 ka cooling events abstract retreat of the western greenland ice sheet during the early holocene was interrupted by deposition of the fjord stade moraine system the fjord stade moraine system spans several hundred kilometers of western greenland s ice free fringe and represents an important period in the western greenland ice sheet s deglaciation history but the origin and timing of moraine deposition remain uncertain here we combine new and previously published 10 be and 14 c ages from disko bugt western greenland to constrain the timing of fjord stade moraine deposition at two locations 60 km apart at jakobshavn isfjord the northern of two study sites we show that jakobshavn isbrae advanced to deposit moraines ca 9 2 and 8 2 8 0 ka in southeastern disko bugt the ice sheet deposited moraines ca 9 4 9 0 and 8 5 8 1 ka our ice margin chronology indicates that the greenland ice sheet in two distant regions responded in unison to early holocene abrupt cooling 9 3 and 8 2 ka as recorded in central greenland ice cores although the timing of fjord stade moraine deposition was synchronous in jakobshavn isfjord and southeastern disko bugt within uncertainties we suggest that jakobshavn isbrae advanced while the southeastern disko bugt ice margin experienced stillstands during the 9 3 and 8 2 ka events based on regional geomorphology and the distribution of 10 be ages at each location the contrasting style of ice margin response was likely regulated by site specific ice flow characteristics jakobshavn isbrae s high ice flux results in an amplified ice margin response to a climate perturbation both warming and cooling whereas the comparatively low flux sector of the ice sheet in southeastern disko bugt experiences a more subdued response to climate perturbations our chronology indicates that the western greenland ice sheet advanced and retreated in concert with early holocene temperature variations and the 9 3 and 8 2 ka events although brief were of sufficient duration to elicit a significant response of the western greenland ice sheet

high moho temperature in the indian shield abstract moho temperatures in the indian shield region are estimated using step exponential and power law models of the depth variation of radiogenic heat with temperature dependent thermal conductivity the moho temperatures and heat flows are around 550 600 c and 0 8 hfu 33 mwm 2 in the southern part of the indian shield and 850 900 c and 0 95 hfu 40 mwm 2 in its northern part it is argued that such high temperatures and their lateral variations may contain signatures of deccan trap volcanism and himalayan orogeny the implications of the temperature estimates on some related crustal parameters viz p n wave velocity curie isotherm depth and melting point temperature at moho depth are also indicated

geothermal structure in a seismoactive region of central india the geothermal structure beneath a seismoactive region of central india has been determined by using two independent geophysical parameters i e p n velocity and curie point depth which are temperature dependent p n velocity has been determined by reanalyzing deep seismic sounding dss records obtained for this region surface heat flow has been computed using the p n velocity data from this region and found to be 55 5 mw m 2 curie point depths have been derived from the magnetic satellite data in this region and reveal an identical value of heat flow of around 56 4 mw m 2 we estimated temperatures of 600 700 c at a moho depth of 39 km by using surface heat flow ranging from 50 to 60 mw m 2 and a simple 1 d geothermal model the present study suggests the presence of a brittle ductile transition high strength zone ranging in depth from 20 to 35 km where the temperatures range from 350 to 550 c we also suggest that the nucleation of earthquakes in this region took place in a relatively high strength zone this is supported by the fact that the focal depths of all the recent earthquakes from 1978 to 2000 of magnitude 3 5 lie in this zone of high strength

tectonic stress field in the indian subcontinent a map of maximum horizontal compressive stress orientation in the indian subcontinent has been prepared using orientations derived from three different stress indicators borehole elongation breakouts in situ hydraulic fracturing measurements and earthquake focal mechanisms most part of the subcontinent appears to be characterized by a compressional stress regime thrust and strikeslip faulting imposed by plate boundary forces although shmax orientations do not in general show clear correlation with the direction of motion of the indian plate four provinces are recognized on the basis of regionally consistent orientations these are the midcontinent stress province the southern shield the bengal basin and the assam wedge their boundaries have been determined taking into consideration regional tectonics and seismicity central and northern india including the shillong plateau stretching up to the great himalaya pakistan and nepal are included in a broad midcontinent stress province characterized by nne ene oriented shmax the mean orientation of shmax in this province is n23 e subparallel to the direction of compression expected to arise from the net resistive forces at the himalayan collision zone suggesting that it is largely determined by the tectonic collision processes much of southern india mysore plateau and the high grade metamorphic terrain south of the plateau appears to be part of a second stress province characterized by nw oriented shmax these appear close to those of the intraplate stress field prevailing in the central indian ocean a third stress province was recognized in the bengal basin including parts of west bengal tripura manipur and mizoram in northeastern india and most of bangladesh this province extends eastward from the marginal fault in the western margin of the bengal basin to the indo burma subduction zone and is bounded on the north by the e w striking dauki fault shmax within the sedimentary pile of the bengal basin is oriented in e w direction while p axes of earthquakes within the basement and the crust beneath the basin and within the subducted slab of the indian plate beneath the indo burman ranges generally trend north n30 e shmax orientations within the sedimentary pile of the basin are parallel to the local approximately e w direction of the convergence of indian and burmese plates suggesting a casual relation to the resistive forces at the subduction zone in the indo burma region interestingly the stress field in the basement and the crust beneath the bengal basin and in the subducted slab is similar to the one prevailing in the midcontinent stress province assam wedge stress region occupies the northeastern corner of the indian plate including upper assam arunachal pradesh and much of nagaland this region subducts beneath a sharply bent continental collision boundary consisting of the northeastern limb of the himalayan and northern limb of the indo burman fold belts as a result the stress field in this province is depth differentiated and most likely responsible for the absence of consistent shmax directions

metastability mechanical strength and the support of mountain belts exhumed high pressure rocks from the caledonian root zone in norway provide analogues for processes occurring today under southern tibet allowing large scale geophysical observations from gravity and earthquakes to be linked with the mechanical properties of metastable rocks under high mountains metastability is essential for the survival of thick mountain roots and hence of high mountains and is in turn controlled by water if water is absent dry granulite formed from earlier melting episodes is both stable and strong and likely to survive in the eclogite stability field of deep root zones for hundreds of million years but if hydrous fluid is introduced the transformation of granulite to eclogite is relatively rapid and accompanied by a dramatic loss of strength in norway this transformation was initiated by water infiltration along fractures formed by earthquakes the same process as marked by deep earthquakes may be occurring today beneath southern tibet

geological contacts thermal springs and earthquakes in peninsular india abstract the occurrence of thermal springs in peninsular india shows a distinct pattern that is related to geological contacts tectonic units and earthquakes it is observed that most of these thermal springs occur either near the contact of two geological units or along prominent tectonic units in the peninsular shield the seismicity map of peninsular india from historical times up to 1990 for earthquakes of magnitude 3 5 indicates a striking correlation between seismicity and thermal springs the b values which characterize the thermal spring areas of the western coast are higher 0 8 1 1 than those obtained in similar areas in the rest of the peninsular shield 0 47 0 6 this indicates that the stresses are released by frequent micro to moderate earthquakes in the thermal springs area along the west coast of india whereas in peninsular india the stress release is through infrequent moderate earthquakes

hydrochemical evolution and reaction simulation of travertine deposition of the lianchangping hot springs in yunnan china located in western yunnan of china the lianchangping hot springs are of so 4 hco 3 ca na type with total dissolved solids tds ranging from 3560 to 4240 mg l large amounts of travertine are deposited near the hot springs with a variety of travertine morphology including travertine terrace slope and ridge travertine is precipitating along the slope near one of the spring s thresholds chemical compositions of the hot water samples collected along travertine slope show that p co 2 p co 2 tds and contents of hco 3 and ca decrease downstream along the travertine slope due to travertine deposition the initial milliequivalent ratio of ca 2 hco 3 is greater than 1 5 before travertine precipitation and there is an increasing trend in the ratio downstream along the travertine slope high levels of sulphate are probably the result of gypsum dissolution in the sediments widespread in the lianchangping area the spring waters issuing from the land surface are slightly supersaturated with respect to calcite dolomite fluorite kaolinite halite plagioclase and carbon dioxide hydrochemical evolution of the lianchangping spring water along the slope is calculated with the phreeqc interactive 2 12 5 sets of minerals and gases reacted in appropriate amounts are recognized through reaction simulation quantitatively accounting for the variations in chemical compositions especially depositing minerals along the flow path on the travertine slope

hydrocarbon prospects across narmada tapti rift in deccan trap central india inferences from integrated interpretation of magnetotelluric and geochemical prospecting studies abstract as the mesozoic sediments contribute most of the oil and gas reserves of the world we present an integrated interpretation approach using magnetotellurics mt and surface geochemical prospecting studies to demarcate hydrocarbon prospective gondwana mesozoic formations underneath the deccan flood basalts of late cretaceous age across narmada tapti rift between bhusawal and barwah in central india the mt interpretation shows deep 5 km basement structure between southern and central part of the mt profile however it gradually becomes shallower to either ends of the profile with a predominant basement depth reduction in the northern end compared to the southern end the geophysical results suggest thick 2 3 5 km mesozoic sediments in the area characterized by deep basement structure the geochemical analysis of the near surface soil samples indicate higher concentrations of light gaseous hydrocarbons constituents over the area marked with thick sub basalt mesozoic formations analyses of the geochemical data imply that these hydrocarbons are genetically related generated from a thermogenic source and these samples fall in the oil producing zone the temperature depth estimations in the region supports favorable temperature conditions 80 120 c for oil generation at basement depths

tectonics and thermal structure of western satpura india abstract increased seismicity and occurrences of hot springs having surface temperature of 36 58 c are observed in the central part of india 74 81 e 20 25 n where the ne trending middle proterozoic aravalli mobile belt meets the ene trending satpura mobile belt earlier deep seismic sounding dss studies along thuadara sendhwa sindad profile in the area has showed mesozoic sediments up to around 4 km depth covered by deccan trap and the moho depth with a boundary velocity p n of 8 2 km s in the present study surface heat flow of 48 4 mw m 2 has been estimated based on p n velocity which agrees with the value of heat flow of 52 4 mw m 2 based on curie point isotherms estimates the calculated temperature depth profile shows temperature of 80 120 c at the basement which is equivalent to oil window temperature in mesozoic sediments and around 570 635 c at moho depth of 38 43 km and the thermal lithosphere is about 110 km thick which is comparatively higher than those of adjoining regions the present study reveals the brittle ductile transition zone at 14 41 km depth temperature around 250 600 c where earthquake nucleation takes place

on the mechanism and source parameters of the deep crustal jabalpur earthquake india of 1997 may 21 constraints from aftershocks and changes in static stress summary the 1997 may 21 jabalpur earthquake mb 6 0 occurred in the lower crust of the ene wswtrending narmada son palaeorift zone in central india known as the narmada son lineament nsl we correlate the aftershock distribution of this earthquake with the computed changes in static stress caused by slip on the earthquake rupture in order to constrain some of the source parameters of the main event we estimate that the downdip edge of the earthquake rupture extended up to a depth of about 38 km and that the majority of the aftershocks occurred due to unclamping in the hangingwall near the downdip edge of the rupture considering the intermediate to moderately high heat flow in the region we suggest that 1 high pore pressure in the lower crust which developed due to the dehydration of the serpentinite body during previous episodes of thermo tectonic processes 2 a lower frictional coefficient possibly arising due to fractured rocks at depth 3 a higher strain rate and 4 the favourable influence of n s compression due to the motion of the indian plate are responsible for the infrequent earthquakes in the lower crust of the nsl zone

lateglacial retreat chronology of the scandinavian ice sheet in finnmark northern norway reconstructed from surface exposure dating of major end moraines abstract we report results from a comprehensive surface exposure dating campaign in eastern finnmark located in the northernmost part of norway and close to the norwegian russian border this is a palaeo glaciologically important region as it sits near the proposed border zone between the former scandinavian and barents sea ice sheets however until now the deglaciation history has few direct dates onshore and the chronology of ice front retreat is instead found by correlating ice marginal deposits with isostatically raised shorelines and marine sediment cores we measured the content of 10 be n 22 and 36 cl n 17 from boulders located at the crest of major moraine ridges at four localities kjaes kongsfjorden vardo and kirkenes these are key localities of existing regional reconstructions of ice recession in this area despite some spread in age results from each locality due to methodological challenges associated with surface exposure dating the large numbers of samples from each site except kjaes still allow for obtaining clusters of similar ages which are used for arriving at a likely chronology of ice front retreat our results show that the kongsfjorden and vardo moraines were deposited 14 3 1 7 ka and 13 6 1 4 ka respectively and thus point to a older dryas age of the proposed outer porsanger deglaciation sub stage moraine ridges belonging to the main sub stage near kirkenes were dated to 11 9 1 2 ka corresponding well with the ice retreat chronology farther west in northern norway and suggesting that the maximum younger dryas ice sheet extent was attained in the late younger dryas along a more than 500 km long stretch in northernmost scandinavia

large variation of curie depth and lithospheric thickness beneath the indian subcontinent and a case for magnetothermometry summary a first order estimate of curie depth and lithospheric thickness variation beneath the indian region has been obtained using the available geothermic data the curie depth is found to vary from 18 to 68 km and the lithospheric thickness from 38 to 186 km these estimates conform well with the mags at and seismological findings both the parameters exhibit covariancy and suggest the possibility of approximating heat flow values and lithospheric thickness in geothermally uncharted areas using curie point geotherm depths derived from air satellite borne magnetic anomalies interestingly the areas with shallow curie depth and lithospheric thickness are found to be associated with a thin crust higher heat flow higher geothermal gradients and positive gravity anomalies and vice versa large thickness estimate of magnetic crustal layer extending below the moho demands a new conceptual understanding the study has brought out a good case for wider use of magneto thermometry and provides understanding of the geodynamic evolution of the indian subcontinent

groundwater evolution in the continental intercalaire aquifer of southern algeria and tunisia trace element and isotopic indicators abstract the geochemical processes taking place along an 800 km flow line in the non carbonate continental intercalaire aquifer ci aquifer in north africa are described using chemical major and trace element and isotopic indicators the aquifer is hydraulically continuous from the atlas mountains in algeria to the chotts of tunisia and the geochemical evidence corroborates this the highest discharge temperature is 73 c but silica geothermometry indicates a maximum temperature of 94 c at depth chloride concentrations increase from 200 to 800 mg l 1 and the br cl ratios confirm the dissolution of non marine evaporites or interstitial waters as the main source of salinity fluoride concentrations are low and are likely to be derived from rainfall recording oscillations in source radiocarbon ages except near outcrop are at or near detection limits and the 18o and 2h values indicate a cooler recharge regime with rainfall having lower primary evaporation than today this is shown by the fact that mean isotope ratios of ci waters are around 3 lighter than the present day weighted mean value for rain major ion ratios and most trace elements indicate that despite the complex structure and stratigraphy uniform evolution with continuous water rock interaction takes place along the flow lines which are only disturbed near the tunisian chotts by groundwater converging from additional flow lines the ageing of the water can also be followed by the smooth increase in several indicator elements such as li k and mn which are least affected by solubility controls similarly the influence of marine facies in the tunisian sector may be recognised by the changing mg ca and higher br cl as well as trace element indicators the groundwaters are oxidising up to 300 km from outcrop dissolved o2 has persisted for at least 20 ka and within this zone the concentrations of several elements forming oxy anions such as u and cr increase and no3 remains conservative beyond 300 km from outcrop the groundwaters are reducing and contain high fe concentrations the basin contains huge reserves of fresh brackish waters but these need careful development due to the limiting high salinity and scaling tendency resulting from the high temperatures and mineral super saturation caused during abstraction as well as high concentrations of some harmful elements such as cr in the oxidising section

lithospheric thickness and mechanical strength of the indian shield abstract we determined the relative mechanical strength of the indian subcontinent by a robust coherence method based on multitaper spectral analysis on overlapping windows of equal size representing the elastic properties of the lithosphere by a transitional coherence wavelength we bypass the need to input rheological variables such as young s modulus or poisson s ratio which have been shown to vary on other continents we compare our measurements in terms of age and find that regions underlain by proterozoic basement are on average stronger than regions of archaean age this is in stark contrast to the common assumption that mechanical strength should increase progressively with time this suggests they are indeed mechanically distinct and that the transitional coherence wavelength adequately captures this distinction between regions of relative strength difference conversions of these values to absolute effective elastic thickness show a greater overlap which is due to the many strong assumptions required in obtaining such absolute values and argues against their usage as a robust and well constrained property of the elastic lithosphere

submarine landforms and the reconstruction of fast flowing ice streams within a large quaternary ice sheet the 2500 km long norwegian svalbard margin 57 80 n morphological interpretation of regional and detailed bathymetric data sets on the 2500 km long norwegian shelf from the north sea 57 n to svalbard 80 n has revealed a dynamic ice flow pattern along the western marginof the scandinavian and barents svalbard ice sheets about 20 cross shelf troughs with megascale glacial lineations msgl elongate ridges and grooves oriented parallel to trough long axes are interpreted as former pathways for fast flowing ice streams studies of large scale margin morphology and seismic profiles have identified large submarine fans at the mouths of several major cross shelf troughs less dynamic ice probably existed on shallower banks the two largest paleo ice streams were the norwegian channel ice stream and bear island trough ice stream each 150 200 km wide at the mouth the lengths of individual msgl vary from hundreds of meters to several tens of kilometers and the distance between ridges varies from 0 1 to 3 km msgl amplitudes reach 15 m but are commonly 10 m the onset of msgl and hence fast ice flow is generally close to the outer coast at the border zone between crystalline rocks and softer sedimentary rocks transverse submarine ridges on various scales commonly parallel to the shelf edge reflect either the maximum ice sheet position or the recessional pattern of the ice sheet lateral ice stream moraines several tens of kilometers long have also been mapped along the sides of several cross shelf troughs identifying the border zone between fast ice flow and stagnant or slow flowing ice on intervening banks

submarine slide scars and mass movements in karmsundet and skudenesfjorden southwestern norway morphology and evolution abstract shallow seismic sections multibeam bathymetric images and geotechnical investigations of the seafloor in karmsundet and skudenesfjorden sw norway have revealed the occurrence of large slide scars and associated mass movement deposits the slide escarpments are up to 30 40 m high and 8 km long with up to 20 10 6 m 3 of sediment released during a single event of retrogressive sliding the slide scars show a range of associated seafloor topography reflecting various modes of sediment displacement the variation in the escarpment morphology and sediment deformation style can be attributed to the varied intensity of liquefaction sliding involved mud deposits of allerod younger dryas to early holocene age but partly also deposits older than ca 12 000 14 c years bp the sediment failures were probably triggered by seismic reactivation of a local fault by postglacial regional isostatic rebound prior to failure the seafloor deposits were undercompacted and metastable due to high pore pressure the presence of shallow gas and the relatively steep local slope created by the formation of a major scour trough by sea currents minor gravitational sliding may still occur along some of the escarpments although engineering slope stability analysis indicates that the deposits can be regarded as stable in the present day conditions of static load and the anticipated weak sporadic earthquakes with an occurrence likelihood of 10 4 year and a peak acceleration of 0 25 g

elevation changes of the fennoscandian ice sheet interior during the last deglaciation the dynamics of ice sheet interiors during the last deglaciation are poorly constrained hindering evaluation of ice sheet models we provide direct evidence of fennoscandian ice sheet fis interior behaviour during deglaciation through surface exposure dating our results demonstrate early thinning of the fis prior to the younger dryas yd 12 8 11 7 ka interior thinning in central norway was concurrent with retreat along the coastline exposing ice free mountainous tracts potentially as early as 20 15 ka the fis then formed moraines in these ice free tracts during the yd this is contrary to current hypotheses advocating a landscape fully covered by cold inactive ice during this period present empirical and model reconstructions fail to capture rapid interior down wastage increasing uncertainties in ice sheet volume estimates and sea level contributions

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

travertines depositional morphology and the bacterially constructed constituents abstract investigation of travertine accumulations throughout central italy and the west central u s has shown that the carbonate is precipitated in response to both inorganic and organic processes individual deposits range up to 85 m thick and hundreds of square kilometers in areal extent all of the carbonate is low magnesian calcite water chemistry temperature and morphology of the accumulation greatly influence the constituents comprising these deposits harsh environmental situations favor inorganic deposits while increasingly more moderate conditions result in the formation of a greater abundance of organically precipitated material morphological variations of travertine deposits recognized include 1 waterfall or cascade 2 lake fill 3 sloping mound fan or cone 4 terraced ound and 5 fissure ridge gross morphology internal stratification and constituents comprising these deposits vary systematically depending upon the type of accumulation and chemistry of the waters bacterially precipitated calcite forms a large percentage of the carbonate in many travertine accumulations exceeding 90 of the framework grains comprising some of the lake fill deposits bacteria are among the first taxa to inhabit and reproduce in harsh spring environments and produce a variety of fascinating constituents the bacteria are primarily rods generally 0 2 m in diameter and less than 1 0 m in length the rods readily decay resulting in calcite crystals loaded with micropores the basic building block of bacterially constructed travertine is a clump of bacteria averaging 20 m in diameter enclosed in a single crystal of calcite aggregates of these crystals produce a variety of deposits including 1 crudely laminated carbonate mud 2 finely laminat d layers of mud 3 intraclasts 4 foam rock and 5 shrubs the shrubs are most striking commonly forming layers 1 3 cm thick but also producing bacterial pisoids at some locales bacterial stromatolites composed of layers of shrubs alternating with finely laminated layers of bacterial mud comprise essentially the entire deposit the shrub layers are the result of flourishing summer growth of bacteria and furthermore show remarkable daily laminae 0 1 0 5 mm thick the importance of bacteria in the formation of travertine and their universally recognized abundance in modern sediments provides an impetus for a reexamination of the role of bacteria in the origin of other types of ancient deposits

hydrogeochemical and isotopic investigation of the bursa oylat thermal waters turkey the oylat spa is located 80 km southeast of bursa and 30 km south of inegol in the marmara region with temperature of 40 c and discharge of 45 l s the oylat main spring is the most important hot water spring of the area southeast of the spa the forest management spring has a temperature of 39 4 c and discharge of 2 l s the goz spring 2 km north of the spa which is used for therapy of eye disease and cold waters of the saadet village springs with an acidic character are the further important water sources of the area ec values of main spring and forest management hot spring 750 780 s cm are lower than those of saadet and goz spring waters 2 070 1 280 s cm and ionic abundances are ca na k mg and so4 hco3 cl the oylat and sizi springs have low na and k contents but high ca and hco3 concentrations according to aih classification these are ca so4 hco3 waters based on the results of 18o 2h and 3h isotope analyses the thermal waters have a meteoric origin the meteoric water infiltrates along fractures and faults gets heated and then returns to surface through hydrothermal conduits oylat waters do not have high reservoir temperatures they are deep circulating recharge waters from higher enhanced elevations 13cdic values of the main spring and forest management hot spring are 6 31 and 4 45 respectively indicating that 13c is derived from dissolution of limestones the neutral ph thermal waters are about 18 7 in 34s while the sulfate in the cold waters is about 17 practically identical to the value for the neutral ph thermal waters however the goz and saadet springs acid sulfate waters have much lower 34s values 4

deposition and diagenesis of mammoth hot springs travertine yellowstone national park wyoming u s a strata forming a 113 m long core through mammoth hot springs record the holocene evolution of this travertine accumulation from deposition as part of a lacustrine to a terraced mound environment the deposit is readily divided into four intervals 113 67 m carbonate cemented volcaniclastic with intercalated layers of travertine 67 60 m moderately pure travertine with some volcaniclastics 60 50 m carbonate cemented volcaniclastic rich interval and 50 0 m essentially pure travertine lithologic composition sedimentary structures and the rare ostracode fossils indicate that the lower 67 m predominantly accumulated in a lacustrine environment whereas the upper 40 m are terraced mound deposits all of the travertine is calcite some after aragonite layers of shrubs oncoids and peloids all bacterial in origin form the dominant allochems within the travertine stable isotopic carbon and oxygen values n 128 are strongly positively correlated and decrease up core 4 and 8 respectively reflec

early break up of the norwegian channel ice stream during the last glacial maximum 10be dating last glacial maximum abstract we present 18 new cosmogenic 10 be exposure ages that constrain the breakup time of the norwegian channel ice stream ncis and the initial retreat of the scandinavian ice sheet from the southwest coast of norway following the last glacial maximum lgm seven samples from glacially transported erratics on the island utsira located in the path of the ncis about 400 km up flow from the lgm ice front position yielded an average 10 be age of 22 0 2 0 ka the distribution of the ages is skewed with the 4 youngest all within the range 20 2e20 8 ka we place most confidence on this cluster of ages to constrain the timing of ice sheet retreat as we suspect the 3 oldest ages have some inheritance from a previous ice free period three additional ages from the adjacent island karmoy provided an average age of 20 9 0 7 ka further supporting the new timing of retreat for the ncis the 10 be ages from utsira and karmoy suggest that the ice stream broke up about 2000 years earlier than the age assignment based on 14 c ages on foraminifera and molluscs from marine sediment cores we postulate that the scandinavian ice sheet flowed across the norwegian channel to denmark and onto the north sea plateau during early phases of the lgm when the ncis started to operate this ice supply to the north sea was cut off and the fast flow of the ncis also led to a lowering of the ice surface along the norwegian channel and thereby drawdown of the entire ice sheet this facilitated rapid calving of the ice front in the north sea and we reconstruct a large open bay across the entire northern north sea by 20 ka based on our 10 be ages in the

geothermal studies in the hyderabad granitic region and the crustal thermal structure of the southern indian shield based on temperature measurements in three boreholes one specially drilled for the purpose and thermal conductivity determinations heat flow density values were determined for three sites in the archaean hyderabad granitic batholith a mean heat flow density value of 40 1 s d mw m 2 has been obtained the heat generation in its rocks 5 57 w m 3 is significantly higher than in average crustal rocks it has been proposed that the hyderabad batholith has a layered structure with a thin 1 km surface layer of high radioactivity these results together with the already reported data have been used to estimate the conductive steady state temperature within and at the base of the crust of the southern indian shield yielding values of the same order as found in the western australian shield