shallow marine carbon and oxygen isotope and elemental records indicate icehouse greenhouse cycles during the early jurassic 1 for much of the mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences we present a carbon and oxygen isotope and elemental record for part of the early jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the cleveland basin uk the invertebrate isotope record is supplemented with carbon isotope data from fossil wood which samples atmospheric carbon new data elucidate two major global carbon isotope events a negative excursion of 2 at the sinemurian pliensbachian boundary and a positive excursion of 2 in the late pliensbachian the sinemurian pliensbachian boundary event is similar to the slightly younger toarcian oceanic anoxic event and is characterized by deposition of relatively deepwater organic rich shale the late pliensbachian strata by contrast are characterized by shallow marine deposition oxygen isotope data imply cooling locally for both events however because deeper water conditions characterize the sinemurian pliensbachian boundary in the cleveland basin the temperature drop is likely of local significance in contrast a cool late pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions both the large scale long term and small scale short duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy isotope events and the sea level cycles are concluded to reflect processes of global significance supporting the idea of an early jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 ma

strong biological controls on sr ca ratios in aragonitic marine bivalve shells 1 it is well known that skeletal remains of carbonate secreting organisms can provide a wealth of information about past environments sr ca ratios have been successfully used as a temperature proxy in corals and sclerosponges previous work on aragonitic bivalve shells has not been conclusive but suggests a major control of growth rate on sr ca ratios as many studies have used bivalve growth rates to determine temperature we tested if sr ca ratios could predict temperature through its relationship with growth rate shells from the two species of clams from the same family veneroidea studied here saxidomus giganteus and mercenaria mercenaria show vastly different seasonal sr ca profiles a strong relationship between average annual sr ca ratios and annual growth rate was found in s giganteus shells from both washington r2 0 87 and alaska r2 0 64 usa but not in m mercenaria shells from north carolina usa furthermore the sr ca growth rate relationship was also evident upon a more detailed inspection of subannual growth rates in s giganteus r2 0 73 although there were significant positive correlations between sr ca ratios and temperature in s giganteus shells the correlations were weak 0 09 r2 0 27 and thus sr ca ratios cannot be used as a reliable temperature proxy in these species of aragonitic bivalves it is clear from this study that sr ca ratios are not under thermodynamic control in either clam species since thermodynamics predict a negative correlation between sr ca ratios and temperature in aragonite this points toward dominance of biological processes in the regulation of sr2 this is also reflected by the largely differing sr ca partition coefficients dsr in these shells dsr 0 25 when compared to inorganic coral and sclerosponge studies dsr 1 all of which show a negative dependence of sr ca on temperature we suggest that caution be taken when using sr ca in any biogenic aragonite as a temperature proxy when the dsr greatly deviates from one as this indicates the dominance of biological controls on sr ca ratios

nonlinear forecasting analysis of inflation deflation patterns of an active caldera campi flegrei italy the ground level in pozzuoli italy at the center of the campi flegrei caldera was monitored by tide gauges between 1970 and 1976 and then continuously since 1982 tide gauges offer a long record of a variable that is believed to be related to the activity of an underlying shallow magma chamber previous work suggests that the dynamics of the campi flegrei system as reconstructed from the tide gauge record is chaotic and low dimensional according to this suggestion in spite of the complexity of the system at a time scale of days the ground motion is driven by a deterministic mechanism with few degrees of freedom however the interactions of the system may never be describable in full detail our new analysis of the tide gauge record from january 1987 to june 1989 using nonlinear forecasting confirms low dimensional chaos in the ground elevation record at campi flegrei and suggests that nonlinear forecasting could be a useful tool in volcanic surveillance

u th pb zircon ages of some keweenawan supergroup rocks from the south shore of lake superior new single crystal zircon u th pb ages for plutonic and rhyolitic keweenawan supergroup rocks from the south shore of lake superior provide geochronological constraints on magmatic evolution associated with the 1 1 ga midcontinent rift analyses of a granophyric phase of the mineral lake intrusion and the mellen granite both parts of the mellen intrusive complex and a laterally extensive rhyolite from the top of the kallander creek volcanics have weighted average 207pb 206pb ages of 1102 0 2 8 ma n 2 1100 9 1 4 ma n 5 and 1098 8 1 9 ma n 4 respectively analyses of a pyroclastic rhyolite flow at the top of the porcupine volcanics result in variable 207pb 206pb ages that range from 1080 to 1137 ma this rhyolite exhibits a continuum between morphologically complex and simpler prismatic zircon crystals the latter yielding concordant analyses having a weighted average 207pb 206pb age of 1093 6 1 8 ma n 2 four prismatic zircons from an aphyric rhyolite of the chengwatana volcani

triassic polyphase deformation in the feidong zhangbaling massif eastern china and its place in the collision between the north china and south china blocks the feidong zhangbaling massif is located between the dabieshan and sulu areas along the tan lu fault in eastern china five tectonic metamorphic events are distinguished there the earliest deformation d1 corresponds to a southward compression that occurred during subduction of the south china block below the north china block top to the south shearing is coeval with late permian early triassic blueschist facies metamorphism and possibly with the development of south verging recumbent folds in the neoproterozoic paleozoic sedimentary cover of the south china foreland the main ductile deformation d2 is an extensional one characterized by top to the north shearing coeval with the early stage of exhumation of the high pressure rocks a top to the nw ductile shearing and microfolds overturned to the northwest belong to a second deformational phase of exhumation d3 which is distinct from the main event d2 previous 40ar 39ar mica dates ranging between 245 and 212 ma suggest late permian early triassic ages for the d1 to d3 events the d4 event produced ne sw trending folds in the sedimentary cover interpreted as gravity collapse structures a late cretaceous brittle extensional event d5 controls the opening and infill of continental half grabens in the study area the tan lu fault is a cretaceous brittle normal fault the lack of ductile deformation presented along the tan lu fault suggests that it did not play a significant role in the exhumation of high pressure metamorphic rocks

giant bivalves tridacna gigas as recorders of enso variability we compare monthly resolved oxygen isotope records derived from a giant bivalve shell tridacna gigas and massive parkes corals collected along the northern coast of papua new guinea this intercomparison study demonstrates that delta o 18 profiles obtained from these different aragonite secreting organisms collected from within a 30 km range are correlated in great detail and record the timing and amplitude of seasonal and interannual enso related variations in sea surface temperature sst and water isotopic composition which is closely related to rainfall furthermore the t gigas record is shown to be close to isotopic equilibrium with the local sea water in contrast to the corals which are approximately 4 parts per thousand offset these results reveal that living and fossil t gigas clam shells have the potential to yield reliable records of past changes in seasonality and enso variability as well as mean climate conditions in particular since the non porous shells are generally more resistant to diagenesis than coral skeletons they may provide robust estimates of past tropical climate for periods and locations where unaltered corals are absent crown copyright c 2011 published by elsevier b v all rights reserved

stable isotope fractionation in benthic foraminifera from the peruvian continental margin abstract stable isotope ratios of the carbonate tests of benthic foraminifera are now widely used to reconstruct past changes in ocean circulation and chemistry such studies depend on the accuracy with which changing environmental conditions are recorded and preserved in the tests of foraminifera found in deep sea deposits assessment of this aspect of the method is best accomplished through rigorous study of modern core tops collected from a wide range of depths and bottom water temperatures stable isotope analyses of eighteen taxa of benthic foraminifera from surface sediments of the peru continental margin indicate that most foraminifera are slightly depleted in 18o relative to the benthic foram uvigerina peregrina for at least five taxa we observed subparallel 18 o temperature relationships with slopes nearly equal to that predicted by shackleton 1974 for uvigerina for seven taxa isotopic analysis of six size fractions in the range 210 590 mm reveals that with the exception of u peregrina variation between different size classes for each species is small for 18 o and for 13 c a slight inverse correlation between foraminiferal 18o and 13c content implies a complex interplay of biological and environmental factors which control isotopic composition

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

oxygen and carbon isotope ratios of lampsilis cardium unionidae from two streams in agricultural watersheds of iowa usa abstract climate archives preserved as seasonal variation in oxygen and carbon isotope ratios 18o and 13c in unionid shells potentially provide records of pre instrumental environmental conditions in mid to high latitude continental regions this study measured 18o and 13c values of biogenic carbonate and 18owater to investigate the timing of growth line formation and to examine the utility of lampsilis cardium as an environmental archive we tested the hypotheses that 1 l cardium precipitates its shell in isotopic equilibrium with the environment during biomineralization and 2 growth lines form seasonally during winter months these questions were addressed by monitoring water chemistry by tagging l cardium to record growth and by combining sclerochronology and stable isotope geochemistry temperature and 18owater were measured fortnightly from september 2002 to july 2004 with a break in sampling from december 2003 to february 2004 in two iowa rivers boone river and buffalo creek these data were used to calculate expected 18o values to compare to measured shell values one hundred fifty four individuals were marked at the postero dorsal margin in september 2002 and june 2003 to monitor growth seven recaptured shells collected in july 2004 were analyzed for shell 18o and 13c across three growth lines including growth lines prior to the initial marking period from the growing edge toward the umbo comparison of shell 18o with expected values revealed precipitation of 18o in equilibrium with the ambient environment from early spring to early fall winter values were not recorded due to winter growth cessation change in temperature or reaching a threshold temperature appeared to control the onset and cessation of growth moreover the locations of seasonal growth lines corresponded to winter growth cessation allowing the assignment of calendar years to growth lines seasonal growth lines were distinguished from non seasonal disturbance lines by their seasonal location inferred from the 18o time series recorded in shell growth thus we can faithfully reconstruct ontogeny through time and environmental and climate conditions from mid to high latitudes using l cardium variation in 13cshell followed a more or less sinusoidal trend similar to the seasonal profiles of 18oshell suggesting that seasonal processes influenced the variation in carbon isotopes reduced amplitudes and more negative 13cshell values with increasing age suggest that kinetic and or metabolic isotope effects become important through ontogeny as observed in other bivalves the profiles of 13cshell potentially record local differences in landscape vegetation however specific factors influencing 13cshell are unknown and further study of water quality are required to fully assess the variation of 13cshell as an environmental proxy

oxygen isotope records of the australian flat oyster ostrea angasi as a potential temperature archive abstract the response of the oxygen isotope ratio 18o in shells of the australian native flat oyster ostrea angasi to changes in water temperature has been assessed using growth experiments conducted for one year at two locations on the east coast of australia the analysed 18o of the oyster shells 18oshell closely follows the predicted oyster shell 18o constructed from measured 18o in the water 18owater and water temperature influxes of freshwater that occur in the estuarine habitats of o angasi can modify the 18owater and consequently 18oshell salinity fluctuations can also cause interruptions to shell growth in this species this can cause overestimated temperatures in o angasi 18oshell temperature reconstructions a 18oshell temperature calibration was established for o angasi yielding the relationship t c 13 97 3 57 18oshell 18owater 0 17 18oshell 18owater 2 n 79 r2 0 79 which within the experimental uncertainties of the data is similar to other published biogenic carbonate paleotemperature equations

mineral deposits of the mesoproterozoic midcontinent rift system in the lake superior region a space and time classification abstract the mesoproterozoic midcontinent rift system mrs of north america hosts a diverse suite of magmatic and hydrothermal mineral deposits in the lake superior region where rift rocks are exposed at or near the surface historically hydrothermal deposits such as michigan s native copper deposits and the white pine sediment hosted stratiform copper deposit were major mrs metal producers on going exploration for and potential development of copper nickel sulfide deposits hosted by the duluth complex of minnesota and the opening of the eagle nickel mine in michigan indicate an expanding interest in mrs magmatic deposits mrs hydrothermal and magmatic mineral deposits many of which are significant past present and likely future providers of critical minerals here are placed into a space and time metallogenic framework to construct this framework regional mrs mineral deposits extracted from the u s geological survey mineral resources data system mrds and the ontario ministry of energy northern development and mines mineral deposit inventory mdi were supplemented by other known and recently recognized mineral deposits described in the literature all mineral deposits were classified by deposit type host rock age and type and estimated timing of mineralization deposits were then put into a tectonic evolutionary framework stages for the mrs which shows that deposits formed within discrete spatial and temporal stages of rift evolution each stage of rift evolution is characterized by specific mineral deposit types that are largely confined both by their physical location in rift rocks and type and timing of mineralization examples include mrs nickel rich conduit type magmatic sulfide deposits which are restricted to an early magmatic stage mrs history when magma compositions were characterized by ni rich picrites and high mg basalts in contrast contact type magmatic sulfide deposits with cu ni were derived from more evolved al rich tholeiitic magmas that dominated a later time of voluminous magmatic activity hydrothermal sediment hosted stratiform chalcocite mineralization along the margins of western lake superior in michigan is economic only where fluid flow through red beds was concentrated by structures along the margins of a post volcanic mrs sedimentary basin widespread native cu and native ag mineralization occurred about 40 million years after formation of host basalt lava flows and interflow sedimentary rocks these descriptions of the diverse mineral deposits in the lake superior region cataloged within the space of the local and regional geology and over the more than 60 million year mineralizing history of the mrs are indicative of the complex and at times overlapping magmatic and hydrothermal mineral systems that operated within this major large igneous province

slow dense replenishments of a basic magma chamber the layered series of the newark island layered intrusion nain labrador the newark island layered intrusion is a composite layered intrusion within the nain anorthosite complex labrador the intrusion comprises a lower layered series ls dominated by troctolites olivine gabbros and oxide rich cumulates and an upper hybrid series hs characterized by a wide range of mafic granitic and hybrid cumulates and discontinuous layers of chilled mafic rocks wiebe 1988 the hs crystallized from a series of replenishments of both silicic and basic magmas the ls crystallized from periodically replenished basic magmas the ls has a lower zone that consists mainly of olivine plagioclase cumulates and contains minor cryptic reversals in mineral compositions that resulted from replenishments of relatively primitive magma an upper zone is dominated by olivine plagioclaseaugite ilmenite cumulates cumulus titanomagnetite and pyrrhotite occur within some oxide rich cumulates and the stratigraphically highest layers contain cumulus apatite at intermediate levels in the sequence cumulus inverted pigeonite occurs in place of olivine several prominent regressions in the stratigraphy of the upper zone are marked by fine grained troctolitic layers with much higher mg no 100 mgo mgo feo and anorthite than underlying cumulates these layers coarsen upward and grade back to oxide bearing olivine gabbros within thicknesses ranging from 10 cm to 15 m dikes that cut the ls have major and trace element compositions that strongly suggest that they are feeders for the replenishments in the lower zone when olivine and plagioclase were the only cumulus phases replenishments were less dense than the resident magma and rose as plumes and mixed with it precipitation of cumulus oxides in the upper zone lowered the density of resident magma so that subsequent replenishments were more dense than resident magma replenishments that occurred after oxides began to precipitate had small injection velocities these post oxide injections flowed along the interface between resident magma and the cumulate pile and precipitated flow banded fine grained troctolites

the igneous petrology and magmatic evolution of the midcontinent rift system klewin k w and shirey s b 1992 the igneous petrology and magmatic evolution of the midcontinent rift system in p a ziegler editor geodynamics of rifting volume ii case history studies on rifts north and south america and africa tectonophysics 213 33 40 the 1100 ma midcontinent rift system of north america is one of the world s great igneous provinces containing over one million km3 of mafic volcanic and plutonic rocks volcanic rocks range from picrite to rhyolite although tholeiitic basalt predominates plutonic rocks range from peridotite to granite with plagioclase rich gabbros and troctolites being most abundant the igneous history of the rift can be divided into early and late stages flows of the early stage form a trend having low alumina high magnesia picrite as the primitive endmember whereas flows from the late stage form a trend having high alumina olivine tholeiite as the primitive endmember the early basalts have enriched nd isotopic compositions and were derived largely from old heterogeneous subcontinental lithosphere the late basalts have chondritic to depleted nd isotopic compositions and were derived from large degree partial melts of a mantle plume that had mixed with isotopically depleted asthenospheric mantle apparently melting began initially in the subcontinental lithosphere as it was stretched subsequently a lower mantle plume which had entrained asthenospheric mantle during its ascent rose beneath the rift and melted at large degrees to yield the voluminous later basalts

a key to the past element ratios as environmental proxies in two arctic bivalves 2016 elsevier b v understanding rapid climate change in the arctic and its ecosystem implications requires more information on the environment at temporal resolutions and time periods not available from instrumental records such information can be acquired through geochemical proxy records but sub annual records are rare we analyzed shell material of bivalve mollusks serripes groenlandicus and ciliatocardium ciliatum placed on oceanographic moorings for one year in two arctic fjords to assess the potential use of shell elemental ratios as environmental proxies li ca mg ca li mg li sr mn ca sr ca mo ca and ba ca were determined using laser ablation inductively coupled plasma mass spectrometry combining data from moorings with previously derived sub annual shell growth models allowed us to relate the elemental ratio patterns to oceanographic parameters temperature salinity and fluorescence shell ba ca profiles were characterized by abrupt peaks occurring 11 to 81 days after the phytoplankton bloom as indicated by an index of seawater fluorescence li ca and mg ca values exhibited significant logarithmic relationships with shell growth rate indicated by marginal r2 values of 0 43 and 0 30 respectively these ratios were also linearly related to temperature with marginal r2 values of 0 15 and 0 17 respectively mn ca and sr ca ratios exhibited variability among individuals and their temporal pattern was likely controlled by several unidentified factors mo ca patterns within the shells did not demonstrate correlations with any of the oceanographic parameters our results reflect complex relationships between elemental ratios and bivalve metabolism methodological limitations as well as contemporaneous environmental processes suggesting that none of the studied elemental ratios can be used as unequivocal proxies of seawater temperature salinity paleoproductivity or shell growth rate despite this ba ca and li ca can be used as sub annual temporal anchors in further studies because the variability of these elements was synchronized in each fjord

use of stable oxygen isotope determinations from brachiopod shells in palaeoenvironmental reconstruction abstract stable oxygen isotope analyses were obtained from fossil brachiopod shells from a shallow marine deposit of upper pleistocene age approximately 80 ka in new zealand as part of a palaeoenvironmental investigation bulk analyses of entire shells of calloria inconspicua yielded highly variable results a range of 2 30 rendering these data of limited use as palaeoenvironmental proxies attempts to obtain consistent oxygen isotope values by removing areas of the brachiopod shell thought to be prone to oxygen isotope disequilibrium effects vital effects revealed that the matching anterior portions of ventral and dorsal valves from the same individual which were secreted at the same time also yielded different oxygen isotope ratios the dorsal valve 18o values were higher and less variable than those obtained from the ventral valve of the same individual the investigation was then extended to living representatives of the same species from a similar shallow water habitat from the south island of new zealand the pattern of dorsal valves yielding higher and less variable oxygen isotope values than matching areas of the ventral valves was repeated in seven out of eight individuals investigated although there was considerable variation in the absolute values from specimen to specimen contrary to common practice therefore it seems that in this species it is the much thinner and lighter dorsal valve that provides a more consistent isotopic measurement if converted into absolute temperature estimates the dorsal valve measurements correspond to a temperature midway between the mean and maximum annual temperature experienced by this species in its present day habitat which may make it acceptable as a palaeoenvironmental indicator the high level of variation between individuals including an inferred temperature from one ventral valve above the mean maximum temperature experienced indicates that a range of individuals needs to be investigated in any palaeoenvironmental investigation to avoid misleading interpretations however intra and inter specimen variation in isotopic composition may provide valuable palaeobiological information on growth rates metabolism and possibly also pathological conditions in the past

contrasting shell growth strategies in two mediterranean bivalves revealed by oxygen isotope ratio geochemistry the case of pecten jacobaeus and glycymeris pilosa abstract high resolution stable isotope ratio data 18 o 13 c were used to study growth strategies of two bivalve species pecten jacobaeus calcitic shell and glycymeris pilosa aragonitic shell from the north adriatic sea the principal objectives of this study were to identify the period of the year when the growth line is formed in the shell of two target species to identify the main growing season of these two species to identify the environmental drivers of shell growth and to evaluate the potential applicability of 18 o and 13 c values for the reconstruction of environmental variability samples were collected from the north adriatic sea by commercial bean trawl p jacobaeus december 2013 and january 2014 n 4 and scuba diver glycymeris pilosa march 2016 n 3 samples for the oxygen 18 o and carbon 13 c isotope composition of the calcium carbonate were collected by drilling the outer shell layer across several annual cycles temporal and spatial temperature and salinity values inside the investigated area were simulated using the 3d numerical ocean model roms the 18 o cycles corresponded to the number of seasonal growth marks observed on the external shell surface of both target species thereby confirming the annual periodicity of these growth patterns in february 2012 extreme cooling of the water column accompanied by dense water formation occurred in the adriatic sea an event recorded by p jacobaeus shells this study indicates that p jacobaeus and g pilosa have contrasting shell growth strategies pecten jacobaeus grows during winter and slows shell growth during the warmest part of the year and thereby may be an interesting archive for winter conditions due to its longevity and continuous growth during the warmest part of the year g pilosa is a promising archive for the reconstruction of summer seawater temperatures

environmental controls on the stable isotopic composition of mercenaria mercenaria potential application to paleoenvironmental studies 1 we have investigated the environmental controls of seasonally resolved records of oxygen and carbon isotopes of modern mercenaria mercenaria bivalves collected live from five coastal sites along the east coast of north america seasonal profiles of 18o and 13c obtained by subsampling the incremental growth layers of aragonite were compared with in situ historical records of temperature and salinity we show that m mercenaria 18o profiles track accurately the seasonal variations of water temperature and that variations in growth rates do not affect the shell 18o values growth rates are strongly reduced or interrupted below water temperatures ranging from 8 to 10 c implying that only bivalves sampled in tropical areas track the full amplitude of seasonal variations although further measurements of water 18o and a better understanding of seasonal variations of the water 18o salinity relationships are necessary mercenaria mercenaria bivalves appear to precipitate their shell close to isotopic equilibrium whereas the amplitude of the seasonal profiles of 18o reflects variations in water temperature the annual average 18o decreases with latitude reflecting the trend of rainfall and riverwater 18o with latitude over the northern american continent

tropical atlantic seasonal dynamics in the early middle eocene from stable oxygen and carbon isotope profiles of mollusk shells there are disagreements whether the tropical sea surface temperature during the warm early to early middle eocene was equal to the present temperature or significantly lower in order to determine the sea surface temperature of the eastern tropical atlantic in the early middle eocene we have established 18o and 13c profiles along the transect of growth of excellently preserved shells of turritella gastropods and a macoma bivalve from tropical west africa this method makes possible a distinction between the winter and the summer temperature the 18o and 13c data indicate sea surface temperatures of 29 31 c which declined to 23 25 c during seasonal upwelling these conditions are similar to those of today and suggest that significant seasonal dynamics prevailed in the early middle eocene tropics the new data further contradict that the tropics cooled during the generally warm early to early middle eocene as inferred in studies on foraminifera 18o

where is the north china south china block boundary in eastern china the qinling dabieshan belt results from the collision of the north china and south china blocks the eastern extension of the belt the sulu area consists of several stacked units from top to bottom these are 1 a weakly metamorphosed slate sandstone unit of neoproterozoic paleozoic age 2 a gneiss quartzite unit metamorphosed under high pressure p conditions 3 a marble amphibolite unit 4 an ultrahigh p unit that was very deeply subducted and then exhumed and 5 a migmatitic dome resulting from the melting of ultrahigh p rocks all these units underwent the same deformation which was characterized by a top to the northwest extensional ductile shearing during their exhumation granulite facies restites in the migmatite are not significantly different from granulitized eclogites derived from the ultrahigh p rocks the migmatite exhibits the same structural and petrologic evolution as that determined for the other units the resemblance of petrologic and structural features and the lack of ocean basin rock shows that the boundary between the north china block and south china block must be placed north of the sulu area

fossil clams from a serpentinite hosted sedimented vent field near the active smoker complex rainbow mar 36 13 n insight into the biogeography of vent fauna hydrothermal circulation at ultramafic hosted sites supports a large variety of high and low temperature hydrothermal vents and associated ecosystems the discovery of abundant fossil vesicomyid and thyasirid shell accumulations at the ridge crest approximately 2 5 km east of the active rainbow vent field on the mid atlantic ridge mar 36 degrees 13 n increased our knowledge regarding the diversity of vent communities at slow spreading ridges bivalve molluscs of the family vesicomyidae were represented by the genus phreagena here we present the first record of this genus in the atlantic ocean this second vesicomyid species known from the mar phreagena sp was found to be associated with a thyasira species that is affiliated with t southwardae at the logatchev vent field on the mar and with t vulcolutre in the gulf of cadiz these two clams have close relationships with seep taxa along the continental margin and were likely associated with sedimented vent fields delta o 18 and delta c 13 analyses of the shells suggested that the burrowing bivalve thyasira could incorporate isotopically light carbon derived from the oxidation of methane in the sediment while the signature of phreagena sp shells denoted a different carbonate source c 14 dating of the shells denoted that the hydrothermal activity in the rainbow area began at least similar to 25 5 kyr bp which is similar to the model of the hydrothermal vent field distribution that was proposed for the logatchev hydrothermal site the results provide new insight regarding the diversity of chemosynthetic fauna on the mar over geologic time ultramafic hosted on axis sedimented vent fields extend the range of habitats for chemosynthetic communities underlying the need to further explore the geology of these types of environments on slow spreading ridges and to determine their role in the ecology of deep sea vent communities

stable isotope and minor element proxies for eocene climate of seymour island antarctica 1 abundant and well preserved marine macrofossils on seymour island antarctica provide a valuable resource to establish paleoenvironmental conditions at high southern latitudes during the warm paleogene stable isotope minor element and 8 7 sr 8 6 sr compositions have been measured for the aragonite bivalve cucullaea from the eocene la meseta formation the 8 7 sr 8 6 sr stratigraphy suggests an early to late eocene age for the la meseta formation sea surface temperature estimates based on 1 8 o values range from 14 5 to 15 5 c in the early and middle eocene to 10 5 c in the late eocene high resolution sampling along growth structures provides estimates of seasonality in temperature which decrease considerably up section to address the relative contribution of temperature and ice volume or salinity to the 1 8 o record sr ca was measured and evaluated as a potential independent paleothermometer for cucullaea

geochronology and geochemistry of the giant qian echong mo deposit dabie shan eastern china implications for ore genesis and tectonic setting abstract the qian echong mo deposit is a giant porphyry deposit in the dabie shan of eastern china molybdenum mo mineralization mainly occurs as numerous veinlets in altered schists with the development of potassic phyllic argillic and propylitic alteration assemblages a buried granite porphyry stock and locally exposed dikes are spatially and genetically related to the mo mineralization zircon crystals from exposed quartz porphyry rhyolitic porphyry and granite porphyry dikes as well as a buried granite porphyry dike yield weighted average 206 pb 238 u ages of 128 9 1 1 ma mswd 0 30 2 n 13 127 42 0 94 ma mswd 0 58 2 n 17 127 44 0 98 ma mswd 1 6 2 n 16 and 126 6 1 4 ma mswd 0 67 2 n 15 respectively the buried granite porphyry stock yields a zircon u pb weighted average age of 124 7 1 6 ma mswd 1 5 2 n 16 which is slightly younger than the exposed dikes but within error of the age of the buried granite porphyry dike five molybdenite samples from the ores yield re os isotope ages of 123 31 1 02 to 128 49 1 40 ma which are consistent with the u pb ages for the igneous rocks these age data constrain magmatic hydrothermal activity at the qian echong mo deposit to a period of about six million years from 129 to 123 ma this period overlaps the recognized regional mo mineralization event in the dabie shan of 142 111 ma which took place during the post collisional tectonism subsequent to amalgamation of the yangtze and north china blocks the qian echong granite porphyry stock and dikes have high contents of sio 2 k 2 o and al 2 o 3 and low contents of tio 2 mgo and cao showing a peraluminous high k calc alkaline to shoshonite affinity with obvious lree enrichment and a negative eu anomaly the rocks have a high initial 87 sr 86 sr of 0 70729 to 0 71788 and highly negative e nd t values of 16 2 to 26 1 with t dm2 nd ages of 2 24 to 3 03 ga their 206 pb 204 pb t 207 pb 204 pb t and 208 pb 204 pb t values range from 16 017 to 16 701 15 252 to 15 368 and 37 095 to 37 578 respectively this sr nd pb isotopic signature indicates that the causative granitic intrusions for the qian echong deposit were mainly melts with components of both the northern dabie complex and the taihua and xiong er groups that are part of the precambrian basement of the north china block the melts were generated during the tectonic extrusion of the dabie shan and their emplacement onto the basement of the north china block the qian echong mo deposit is unique based upon the crustal source for the causative porphyry localization of most mineralization in the surrounding schist country rocks and the co 2 rich ore forming fluid thus we propose the qian echong deposit to represent a new sub type of porphyry mo deposit herein termed collisional or dabie type porphyry deposit

reconstruction of seasonal temperature variability in the tropical pacific ocean from the shell of the scallop comptopallium radula we investigated the oxygen isotope composition d 18 o of shell striae from juvenile comptopallium radula mollusca pectinidae specimens collected live in new caledonia bottom water temperature and salinity were monitored in situ throughout the study period external shell striae form with a 2 day periodicity in this scallop making it possible to estimate the date of precipitation for each calcite sample collected along a growth transect the oxygen isotope composition of shell calcite d 18 oshell calcite measured at almost weekly resolution on calcite accreted between august 2002 and july 2003 accurately tracks bottom water temperatures a new empirical paleotemperature equation for this scallop species relates temperature and d 18 oshell calcite

paired li ca and δ18o peaks in bivalve shells from the gulf of panama mark seasonal coastal upwelling abstract paired lithium to calcium li cashell and oxygen isotope 18oshell ratios were measured in four aragonitic megapitaria aurantiaca bivalve shells from the tropical eastern pacific and evaluated with respect to their linkage to seasonal coastal upwelling the li cashell and 18oshell of two specimens from the upwelling dominated gulf of panama are positively correlated and consistently reveal large seasonal variations of up to 300 mol mol and 3 respectively the li cashell and 18oshell of two shells from the adjacent non upwelling gulf of chiriqui are not correlated and show a reduced seasonal variability rarely exceeding 20 mol mol and 1 0 respectively in some m aurantiaca specimens the li cashell shows a weak positive correlation with growth increment width indicating that physiological growth rate effects might in part control the background li cashell unambiguous seasonal 18oshell signals used for a precise chronology for a live collected specimen from the gulf of panama imply that distinct parallel peaks in li cashell and 18oshell mark the cold and highly productive coastal upwelling season during february to april a comparison with environmental data reveals a negative correlation between li cashell and water temperature and a strong positive correlation between li cashell and chlorophyll a in the gulf of panama while a causal link between li cashell and temperature remains uncertain we argue that li cashell peaks in m aurantiaca are consistent with the concept of an incorporation of additional li provided by diatom dominated phytoplankton blooms during coastal upwelling our findings suggest that li cashell in m aurantiaca may serve as a new proxy for seasonal coastal upwelling the potential of which should be tested for other mollusk species and upwelling regions

a grenville age layered intrusion in the subsurface of west texas petrology petrography and possible tectonic setting the nellie intrusion is a thick more than 4420 m mafic to ultramafic layered intrusion with a radiometric age of 1163 ma rock types change abruptly with stratigraphic height and include norite pyroxenite gabbronorite hornblende gabbro gabbro anorthosite harzburgite and lherzolite norite is most abundant but gabbro and hornblende gabbro are locally abundant rare olivine rich layers are also present the general order of crystallization was olivine orthopyroxene plagioclase clinopyroxene and hornblende mg s expressed as 100 mg mg fe range from 76 3 to 85 8 for olivine 56 7 to 84 9 for orthopyroxene 62 5 to 90 3 for clinopyroxene and 52 4 to 82 8 for amphibole mg s vary with height and display abrupt reversals which indicate open system addition of new mafic magma eleven cyclic units were identified on the basis of evidence for injection of basaltic magma these can be grouped into three megacyclic units the abundance of orthopyroxene and mineral compositional evidence for

mollusc and brachiopod skeletal hard parts intricate archives of their marine environment the biogenic carbonate hard parts of fossil bivalves cephalopods and brachiopods are among the most widely exploited marine archives of phanerozoic environmental and climate dynamics research the advent of novel analytical tools has led many workers to explore non traditional geochemical and petrographic proxies and work performed in neighbouring disciplines sheds light on the complex biomineralization strategies applied by these organisms these considerations form a strong motivation to review the potential and problems related to the compilation and interpretation of proxy data from bivalve cephalopod and brachiopod hard parts from the viewpoint of the sedimentologist and palaeoceanographer specific focus is on the complex biomineralization pathways of a given dissolved ion or food particle from its aquatic environment via the digestion and biomineralization apparatus in molluscs and brachiopods and its incorporation into a biomineral given that molluscs and brachiopods do not secrete their hard parts from seawater but rather from their mantle and periostracum this paper evaluates differences and similarities of seawater versus that of body fluids cephalopods bivalves and brachiopods exert a strong biological control on biomineralization that to some degree may buffer their shell geochemistry against secular changes in seawater chemistry disordered amorphous calcium carbonate precursor phases later transformed to crystalline biominerals may be significant in carbonate archive research due to expected geochemical offset relative to the direct precipitation of stable phases a reasonable level of understanding of the related mechanisms is thus crucial for those who use these skeletal hard parts as archives of the palaeo environment the impact of what is commonly referred to as biological factors on the geochemistry of mollusc and brachiopod hard parts is explored for conventional isotope systems such as carbon oxygen strontium and traditionally used element to calcium ratios in particular the often used 13ccarb or the mg ca and sr ca elemental proxies are fraught with problems an interesting new research field represents the analysis calibration and application of non traditional proxies to mollusc and brachiopod hard parts examples include the carbonate clumped isotope 47 approach and the analysis of the isotopes of ca mg n li s or element to ca ratios such as li ca or b ca and rare earth elements based on considerations discussed here a series of do s and don ts in mollusc and brachiopod archive research are proposed and suggestions for future work are presented in essence the suggestions proposed here include experimental work also field experiments making use of recent archive organisms or where possible a reasonable recent analogue in the case of extinct groups moreover the detailed understanding of the architecture of mollusc and brachiopod hard parts and their ultra structures must guide sampling strategies for geochemical analyses where feasible a detailed understanding of the diagenetic pathways and the application of multi proxy and multi archive approaches should form the foundation of fossil carbonate archive research the uncritical compilation of large data sets from various carbonate shelled organisms collected at different locations is not encouraged

response of central european sst to atmospheric pco2 forcing during the oligocene a combined proxy data and numerical climate model approach abstract co 2 induced global warming will affect seasonal to decadal temperature patterns expected changes will be particularly strong in extratropical regions where temperatures will increase at faster rates than at lower latitudes despite that it is still poorly constrained how precisely short term climate dynamics will change in a generally warmer world particularly in nearshore surface waters in the extratropics i e the ecologically most productive regions of the ocean on which many human societies depend specifically a detailed knowledge of the relationship between p co 2 and seasonal sst is crucial to understand interactions between the ocean and the atmosphere in the present investigation we have studied for the first time how rising atmospheric p co 2 levels forced surface temperature changes in central europe paleolatitude 45 n during the mid oligocene from ca 31 to 25 ma a time interval of earth history during which global conditions were comparable to those predicted for the next few centuries for this purpose we computed numerical climate models for the oligocene winter summer annual average assuming an atmospheric carbon dioxide rise from 400 to 560 ppm current level to two times pre industrial levels pal and from 400 to 840 ppm three times pal respectively these models were compared to seasonally resolved sea surface temperatures sst reconstructed from 18 o values of fossil bivalve shells glycymeris planicostalis g obovata palliolum pictum arctica islandica and isognomon maxillata sandbergeri and shark teeth carcharias cuspidata c acutissima and physogaleus latus collected from the shallow water deposits of the mainz and kassel basins germany multi taxon oxygen isotope based reconstructions suggest a gradual rise of temperatures in surface waters upper 30 to 40 m on average by as much as 4 c during the rupelian stage followed by a 4 c cooling during the chattian stage seasonal temperature amplitudes increased by ca 2 c during the warmest time interval of the rupelian stage with warming being more pronounced during summer 5 c than during winter 3 c according to numerical climate simulations the warming of surface waters during the early oligocene required a co 2 increase by at least 160 ppm i e 400 ppm to 560 ppm given that atmospheric carbon dioxide levels predicted for the near future will likely exceed this value significantly the early oligocene warming gives a hint of the possible future climate in central europe under elevated co 2 levels

detecting time averaging and spatial mixing using oxygen isotope variation a case study abstract in principle bivalve mollusks living at the same time and in the same place will experience the same temperature and salinity regimes and will have identical annual oxygen isotope 18 o profiles bivalve mollusks living at different times or in different places are more likely to have different annual 18 o profiles thus differences in annual 18 o profiles can be used to detect temporal or spatial mixing we devised eight metrics to quantitatively compare sclerochronologically calibrated annual 18 o profiles from different shells difference in maximum value difference in minimum value difference in amplitude the number of non contemporaneous isotopic enrichment events nnee the average fortnightly difference ad the standard deviation of the average fortnightly differences sdd the maximum fortnightly difference maxd and the number of fortnights separating the minimum values these metrics vary among northern gulf of california shells from four temporal and spatial categories 1 same time and same place 2 same time and different place 3 different time and same place and 4 different time and different place different time different place comparisons include comparisons of live collected shells with shells alive during times of colorado river flow and shells from a pleistocene interglacial deposit the same time same place comparison has the most similar metric values whereas comparisons among the different time different place shells are usually the least similar between shell oxygen isotope differences can reveal temporal or spatial mixing of shells that would be undetectable with radiocarbon or amino acid racemization dating application of the technique to a holocene deposit with shells in life position reveals that the bivalves were alive at different times despite indistinguishable radiocarbon ages two adjacent but disarticulated pleistocene shells appear to be both temporally and spatially mixed the method can detect temporal or spatial mixing in any shell material unaffected by diagenesis regardless of the age of the specimens

crystallization sequence and magma chamber processes in the ferrobasaltic sept iles layered intrusion canada the sept iles layered intrusion quebec canada 564 ma is a large plutonic body with a diameter of 80 km and a thickness of 6 km made up from its base to top of a layered series with troctolite and gabbro and an upper border series with anorthosite capped by cupolas of a type granite chilled margin compositions suggest a ferrobasaltic parental magma close to that of the skaergaard intrusion but much richer in iron and titanium samples from drill cores and surface sampling of the 4 7 km thick layered series reveal a succession of massive troctolites and layered gabbros that contain 24 fe ti oxide layers cm to m thick and many anorthositic autolithic blocks the sequence of crystallization in the layered series is plagioclase an72 34 and olivine fo75 21 followed by magnetite and ilmenite then ca rich pyroxene and finally apatite an olivine gap is observed between fo66 and fo59 the saturation of fe ti oxides before ca rich pyroxene is interpreted to be the result of the high feot and tio2 contents and the low cao content of the parental magma contamination by old continental crust has occurred during crystallization of the layered series as indicated by sr isotopic compositions 87sr 86sr564 0 70360 0 70497 the differentiation trend of the intrusion is interrupted by two large and many small reversals to more primitive compositions of cumulus phases cr content of magnetite and lower sr isotope ratios these reversals and the intermittent disappearance of some phases are interpreted as resulting from magma chamber replenishments by undifferentiated primitive basaltic magma and mixing with the resident magma the author 2010 published by oxford university press all rights reserved for permissions please e mail journals permissions oxfordjournals org

experimental study of liquid evolution in an fe rich layered mafic intrusion constraints of fe ti oxide precipitation on the t f o 2 and t ϱ paths of tholeiitic magmas the newark island layered intrusion a composite intrusion displaying a similar fractionation sequence to the skaergaard has both dikes which preserved liquids fed into the intrusion and chilled pillows of liquids resident in the chamber this study reports experimentally determined one atmosphere liquid lines of descent of these compositions as a function of oxygen fugacity which varies from qfm quartz fayalite magnetite to 0 5 log10 units above iw iron wustite these experiments reveal a strong oxygen fugacity dependence on the order of appearance and relative abundances of the fe ti oxide minerals titanomagnetite saturates prior to ilmenite at qfm but the order is reversed at lower oxygen fugacities in the layered series of the newark island intrusion ilmenite arrives shortly before titanomagnetite and the titanomagnetite ilmenite ratio decreases monotonically after the cumulus appearance of titanomagnetite comparison of the crystallization sequence in the intrusion with that of the experiments requires that the oxygen fugacity in the intrusion increased relative to qfm before titanomagnetite saturation and decreased afterward but always remained between the qfm and iw buffers similar trends in the modes of the fe ti oxides ilmenite and titanomagnetite in the skaergaard kiglapait and somerset dam intrusions along with fe2o3 feo ratios in morbs suggest that such a temperature oxygen fugacity path may be typical of tholeiitic magma differentiation calculations of the temperature density paths of the experimental liquids indicate that at all possible oxygen fugacities the density must have decreased abruptly after fe ti oxide saturation accordingly liquids replenishing the intrusion after fe ti oxide saturation should pond at the bottom of the chamber quenching against older cumulates field observation at the newark island intrusion confirm this prediction the similarities in the fractionation paths of several other layered intrusions to that of the newark island intrusion suggest that the density of the liquids in these intrusions also decreased after fe ti oxide saturation experiments on a suggested initial skaergaard liquid are consistent with this model

assessing the reproducibility and reliability of estuarine bivalve shells saxidomus giganteus for sea surface temperature reconstruction implications for paleoclimate studies studies using oxygen isotopes y 18 o of mollusk shells to determine paleotemperature need to assume water y 18 o values which could severely influence calculated temperatures we analyzed aragonitic shells of the butter clam saxidomus giganteus deshayes 1839 to determine the reproducibility of the isotopic signal between individuals and to assess how precisely temperature could be calculated given known salinity and temperature furthermore carbon isotopes are also investigated as an environmental proxy the abundance of well preserved s giganteus shells in archeological and geological deposits in northwestern north america makes them a particularly suitable species for paleoclimate studies seasonally resolved stable oxygen isotope profiles in three s giganteus shells collected from the same site in puget sound washington usa were well correlated 0 77br 2 b0 87 although there were differences up to 0 58x in high resolution y 18 o profiles of the three shells the difference between the average y 18 o of each shell was less than half of this 0 19x and half of what has been reported for between colony coral variability y 13 c profiles on the other hand were more complex with shell y 13 c being about 2 5x lower than expected equilibrium values however this roughly conforms to the idea that about 10 of the shell carbon originates from metabolic co2 both y 18 o and y 13 c indicate that s giganteus do not grow during periods of reduced salinity despite the excellent reproducibility of y 18 o between shells and the fact that salinity effects were duly considered calculated temperature still differed from instrumental temperature applying different salinity y 18 o water relationships to average shell y 18 o and considering salinity from the shell collection site and a nearby offshore station resulted in calculated average water temperatures ranging from 1 7 to 6 4 8c warmer than measured although we could not determine if s giganteus precipitate their shells in isotopic equilibrium we believe that the difficulty in predicting temperature arose from not being able to accurately determine

late quaternary climatic variability in northern patagonia argentina based on δ18o of modern and fossil shells of amiantis purpurata bivalvia veneridae abstract amiantis purpurata is a common warm temperate water bivalve species distributed from southern brazil to northern patagonia argentina which has a rich and well preserved fossil record in the san matias gulf smg dating back to the late quaternary this study aims to establish a purpurata shells as a new palaeoarchive of past marine conditions in south america we compared the stable oxygen and carbon profiles 18oshell 13cshell of eleven specimens of a purpurata from different geological times modern late holocene and interglacial late pleistocene and additionally present in situ oxygen isotope values of seawater within smg 18owater using both sets of information we calculated and reconstructed palaeowater temperatures for the late holocene and compared them to modern water temperatures our findings indicate that a purpurata records past environmental parameters such as water temperatures on a seasonal scale and can therefore be considered a suitable candidate for future palaeoenvironmental reconstructions in northern patagonia this study is the first step towards further stable isotope analyses on fossil a purpurata shells which will show whether and if so to what extent important global climate events such as the neoglacial early holocene the hypsithermal middle holocene and the little ice age late holocene occurred in south america

fluid inclusion and h o c isotope geochemistry of the yaochong porphyry mo deposit in dabie shan china a case study of porphyry systems in continental collision orogens the yaochong porphyry mo deposit in xinxian county henan province china is located in the hong an terrane that is the western part of the dabie orogen the dabie orogen is part of a 1 500 km long triassic continental collision belt between the north china block and the south china block four types of vein are present paragenetically from early to late they are as follows stage 1 quartz k feldspar pyrite magnetite vein stage 2 quartz k feldspar molybdenite pyrite vein stage 3 quartz polymetallic sulfides k feldspar vein and stage 4 quartz carbonate fluorite vein four compositional types of fluid inclusion pure co2 co2 bearing aqueous and solid bearing are present in quartz from the first three stages only low salinity aqueous fluid inclusions occur in quartz from the last stage all the estimated salinities are 13 1 wt nacl eq and no halite crystals were identified homogenization temperatures for the fluid inclusions from stages 1 to 4 are in the ranges of 262 501 202 380 168 345 and 128 286 c respectively and estimated depths decrease from 6 9 to 8 9 km through 6 2 7 2 to 4 7 km quartz separates from the veins yielded a 18o value of 7 7 11 2 corresponding to 18oh2o values of 1 3 to 6 9 using temperature estimates from fluid inclusion data dh2o values of fluid inclusion vary from 80 to 55 and 13cco2 from 2 3 to 2 7 suggesting that the ore fluids evolved from magmatic to meteoric sources we conclude that the ore forming fluid system at yaochong was initially high temperature high salinity and co2 rich and then progressively evolved to co2 poor lower salinity and lower temperature by mixing with meteoric water which results in ore precipitation

upwelling signals in radiocarbon from early 20th century peruvian bay scallop argopecten purpuratus shells abstract we quantified 14c 18o and 13c cycles along ontogeny within four bay scallop argopecten purpuratus shells collected from callao bay salaverry and sechura bay peru following the 1907 1908 non el nino years and the 1925 1926 el nino 14c and 13c generally covary 14c and 18o vary inversely simultaneous decreases in 14c and increases in 18o in non el nino shells are followed by constant 14c and gradually decreasing 18o which we interpret as evidence for discrete marine upwelling events followed by warming of the initially cold upwelled water upwelling changes from el nino events are detectable with difficulty in mollusk shell 14c

changes of shell microstructural characteristics of cerastoderma edule bivalvia a novel proxy for water temperature abstract shells of bivalves potentially provide an excellent archive for high resolution paleoclimate studies however quantification of environmental variables specifically water temperature remains a very challenging task here we explore the possibility to infer water temperature from changes of microstructural characteristics of shells of the common cockle cerastoderma edule the size and elongation of individual microstructural units i e prisms in the outer shell layer of seven three to five year old specimens collected alive from the intertidal zone of the north sea near texel the netherlands and schillig germany were measured by means of automatic image processing growth patterns circatidal ciralunidian and fortnightly increments and lines shell oxygen isotope values and mark and recovery experiments were used to place the shell record in a precise temporal context irrespective of the locality and ontogenetic age size and elongation of the prisms increased non linearly with water temperature small 0 12 0 05 m 2 and round prisms elongation 2 42 0 31 were formed at temperatures of ca 10 c late april whereas larger 0 33 0 11 m 2 and more elongated prisms 3 26 0 28 occurred during hot summer ca 22 c no clear cut or consistent correlation existed between microstructural characteristics and growth rate as well as a variety of other environmental variables such as salinity chlorophyll a and turbidity based on these findings a model was constructed from three shells at texel that enables reconstruction of water temperature with a precision of 1 7 1 0 c from prism size and elongation sst 9 02 17 25 p s 1 10 p e this model was successfully tested at four shells from schillig the new temperature proxy can be of particular interest for paleoclimate studies in nearshore settings when non recrystallized c edule shells are available future studies are required to verify our findings and check if other species with the same and different microstructures show similar relationships with water temperature

inflation of long valley caldera from one year of continuous gps observations a permanent global positioning system receiver at casa diablo hot springs long valley caldera california was installed in january 1993 and has operated almost continuously since then the data have been transmitted daily to the jet propulsion laboratory for routine analysis with data from the fiducial laboratories for an international natural sciences network flinn by the jpl flinn analysis center results from these analyses have been used to interpret the on going deformation at long valley with data excluded from periods when the antenna was covered under 2 5 meters of snow and from some periods when anti spoofing was enforced on the gps signal the remaining time series suggests that uplift of the resurgent dome of long valley caldera during 1993 has been 2 5 1 1 cm yr and horizontal motion has been 3 0 0 7 cm yr at s53w in a no net rotation global reference frame or 1 5 0 7 cm yr at s14w relative to the sierra nevada block these rates are consistent with uplift predicted from frequent horizontal strain measurements spectral analysis of the observations suggests that tidal forcing of the magma chamber is not a source of the variability in the 3 dimensional station location these results suggest that remotely operated continuously recording gps receivers could prove to be a reliable tool for volcano monitoring throughout the world

the shell of the queen scallop aequipecten opercularis l as a promising tool for palaeoenvironmental reconstruction evidence and reasons for equilibrium stable isotope incorporation abstract the queen scallop aequipecten opercularis has been an important part of the marine fauna of the northeast atlantic region since the miocene and is a suitable candidate for palaeoenvironmental studies using stable isotopes modern shells were investigated to determine if carbonate is precipitated in isotopic equilibrium in this species and to confirm that growth continues through the year specimens of a opercularis were cultured under monitored semi natural conditions over an autumn winter period and the analyses of these specimens were supplemented with isotope data from preserved indigenous north sea specimens the results indicated that the cultured specimens grew in relatively low temperatures that oxygen isotopes of shell exterior carbonate were precipitated in isotopic equilibrium and that a large proportion of the ambient temperature range was recorded in shell carbonate the indigenous north sea specimens exhibited a good correspondence to predicted oxygen isotope values for summer the isotopic record related to winter was however somewhat truncated due to growth decelerations in the specimens carbon isotopes of shell exterior carbonate were calculated as being derived primarily from external sources and showed comparatively little influence from metabolically derived carbon this suggests that carbon isotopes were at least close to equilibrium with ambient waters the limited incorporation of metabolic products suggests that a opercularis would be a good monitor of changing carbon isotope ratios in seawater dissolved inorganic carbon the occurrence of equilibrium shell precipitation is explained using a pteriomorph shell calcification model which proposes that transport of ions through the periostracum caused the composition of the extrapallial fluid to be effectively the same as seawater carbonate secretion is therefore not influenced significantly by biological vital effects

reconstructing intra annual growth of freshwater mussels using oxygen isotopes abstract intra annual growth rates from the bivalve mollusk lampsilis cardium unionidae were reconstructed using measured oxygen isotope 18o profiles together with high resolution environmental records mussels from a single cohort 2007 were grown in two different settings at the columbus zoo aquarium freshwater mussel conservation research center mrc located in central ohio usa outside specimens were collected from sediment laden cages deployed in the o shaughnessy reservoir a single inside specimen was collected from the raceways in the mrc measured 18ocarb profiles from these specimens were calibrated with a predicted oxygen isotope envelope i e the daily range of potential 18ocarb values calculated from hourly water temperatures and weekly 18owater samples collected in 2010 this exercise suggests the outside specimens commenced 2010 shell deposition in late april and ceased in latest october six month growing season in contrast the inside growing season lasted only three months early july and early september calculated daily growth rates from both sites were faster early in the year but highly episodic throughout maximum daily growth rates for the outside and inside specimens were 300 and 436 m day respectively analysis of annual growth rates from the entire cohort suggests the inside specimens grew slower following transplantation in subsequent years however their growth rates were nearly identical to the outside population our results suggest that despite the fact that both populations have similar annual growth rates they have different intra annual growth patterns thus caution should be exercised when extrapolating intra annual growth patterns from cultured specimens to natural populations

stable carbon and oxygen isotope compositions of mollusc shells from britain and new zealand abstract stable carbon and oxygen isotope analysis of the carbonate shells of two fossil mollusc species from the plio pleistocene of new zealand and two recent species from the west coast of scotland has revealed an unexpectedly high degree of variability for each species and a positive correlation between 13 c and 18 o in each case this phenomenon may be due to kinetic isotope effects which are inherent in fastgrowing shells or areas of shell if this is the case then equilibrium isotope partitioning may not have had time to occur before the completion of calcite precipitation kinetic effects would tend to favour the lighter isotopes of both carbon and oxygen it is therefore the highest 13 c and 18 o values that are most likely to reflect equilibrium with the environment very small carbonate particles often give particularly low 13 c and 18 o values these results have implications for the use of isotopic data in environmental reconstruction based on fast growing shells and may also be applicable to other carbonate precipitating organisms

the eagle and east eagle sulfide ore bearing mafic ultramafic intrusions in the midcontinent rift system upper michigan geochronology and petrologic evolution 1 the eagle and east eagle intrusions are small subvertical dike like mafic ultramafic bodies that cut proterozoic sedimentary strata in the baraga basin in northern michigan the eagle intrusion hosts a newly discovered magmatic ni cu pge deposit the nearby east eagle intrusion also contains sulfide mineralization but the extent of this mineralization has yet to be determined by further drilling both intrusions contain olivine bearing rocks such as feldspathic peridotite melatroctolite and olivine melagabbro sulfide accumulations range from disseminated at both eagle and east eagle to semimassive and massive at eagle u pb baddeleyite dating gives a crystallization age of 1107 2 5 7 ma for the eagle intrusion coeval with eruption of picritic basalts at the base of the volcanic succession in the midcontinent rift system mrs the fo contents of olivine cores in the eagle and east eagle intrusions vary between 75 and 85 mol higher than those of olivine in larger layered intrusions in the mrs such as the duluth complex the feo mgo ratios and al2o3 contents of the parental magmas for the eagle and east eagle intrusions inferred from olivine and spinel compositions are similar to those of picritic basalts in the base of the mrs volcanic succession these petrochemical data suggest that the eagle and east eagle intrusions are the intrusive equivalents of high mgo basalts that erupted in the early stages of continental magmatism associated with the development of the rift variations in mineral compositions and incompatible trace element ratios suggest that at least three major pulses of magmas were involved in the formation of low sulfide rocks in the eagle intrusion lower fo contents of olivine associated with semimassive sulfides as compared to that of olivine in low sulfide rocks suggest that the magma associated with the semimassive sulfide was more fractionated than the parental magmas of the low sulfide rocks in the eagle intrusion accumulation of suspended olivine crystals and sulfide droplets from ascending magmas as they passed through wide parts of the conduits at eagle and east eagle played a critical role in the genesis of olivine rich rocks and sulfide ores in the intrusions the eagle ni cu pge deposit typifies the conduit style of magmatic sulfide deposition that is associated with continental basaltic magmatism

spondylus gaederopus a new mediterranean climate archive based on high resolution oxygen and carbon isotope analyses abstract the presented study evaluates the potential of the mediterranean bivalve spondylus gaederopus linne 1758 as a palaeoclimatic archive its fixosessil life in water depths 18 o and carbon 13 c isotope data obtained from high resolution sampling of a modern s gaederopus from rhodes greece collected alive in 4 m water depth in spring 2002 suggest that the outer calcitic shell layer as well as the inner aragonitic shell layer is precipitated in equilibrium with seawater due to the complexity of the outer calcitic shell layer with its spines and prickles a chronological sampling of this part of the shell is not possible in contrast the inner aragonitic shell layer with its well developed growth bands allows a fast chronologic sampling 18 aragonite growth bands were sampled from the inner shell layer of the studied specimen corresponding to 9 years of growth with 9 10 samples per year carbon stable isotopes 13 c ar yield mean values of 0 70 0 6 and show a remarkable negative shift of about 1 8 from about 1 6 to about 0 2 through time this ontogenetic depletion in 13 c might be related to physiological developments like sexual maturity as it is the case in other bivalves seasonal variations with an average amplitude of 0 85 are superimposed on the observed secular trend these cycles show an increase in amplitude that has not been described before and cannot be explained so far oxygen isotopes 18 o ar exhibit mean values of 1 11 0 5 clearly pronounced seasonal cycles with an average amplitude of 1 45 show the same wavelength as the carbon cycles but run out of phase the 18 o ar correlates well with sea surface temperature and correlation fits best during summer periods deviations between measured and predicted 18 o ar input data sea surface temperature seawater 18 o show that maximal discrepancies occur during winter periods these discrepancies can be best explained by a decrease in local seawater 18 o due to increased freshwater influx on rhodes maxima in precipitation hence river runoff occur during winter months

oxygen isotope fluctuations in a modern north sea oyster crassostrea gigas compared with annual variations in seawater temperature implications for palaeoclimate studies abstract a total of 181 oxygen isotope values from sequential samples of the left shell of a modern pacific oyster crassostrea gigas that lived on a sub tidal oyster bank in the list basin north sea germany shows periodically varying values between 1 3 and 2 5 in order to test whether these 18 o fluctuations reflect seawater temperature changes the isotope values of the shell were compared to actual seawater temperature variations from the region c gigas serves as an excellent proxy for temperature of palaeoseawater and the results show that the examined oyster precipitated its shell in 18 o equilibrium with the ambient seawater a cessation of the oyster shell calcification starts at water temperatures below 6 c at lower temperatures than previously thought for crassostrea for palaeoclimate investigations the termination of shell production is important because the lowest temperatures might not be represented in the shell higher water temperatures are therefore potentially over represented in time spans when the shell grows faster and mean oxygen isotope values may potentially bias the mean seawater temperatures of annual variations towards higher temperatures

u pb zircon and sm nd isotopic study of the huangtuling granulite dabie sulu belt china implication for the paleoproterozoic tectonic history of the yangtze craton sims data demonstrate archean 2 9 to 2 7 ga and paleoproterozoic 1991 43 ma ages for rounded detrital zircon cores and unzoned rims respectively in a graulite sample collected from huangtuling dabie sulu orogenic belt china the granulite rocks in this locality have pelitic compositions and represent an exposure of the northern margin of the yangtze craton the rounded zircon cores show oscillatory zoning and have th u ratios 0 17 0 78 systematically higher than those of the unzoned luminescent rims 0 005 0 03 the age of the detrital zircon cores and whole rock nd isotope model age suggest that the huangtuling granulite was possibly derived from a provenance dominated by archean rocks similar to the kongling complex exposed 200 km in the southwest multiple phases of metamorphism have been identified for the granulites with the dominant granulite facies mineral assemblage defining an early clock wise metamorphic p t path orthopyroxene plagioclase and whole rock material define a linear trend in a 147sm 144nd 143nd 144nd diagram corresponding to an age of 1926 146 ma this result and the u pb data for the zircon rims suggest that a collisional event may have occurred along the northern margin of the yangtze craton at 2 0 ga inviting further study on whether the yangtze craton was involved in the assembly of the recently proposed paleo mesoproterozoic supercontinent columbia

the potential of combined mg ca and δ18o measurements within the shell of the bivalve pecten maximus to estimate seawater δ18o composition the combined use of 18o and another independent palaeotemperature proxy from the same carbonate biomineral archive forms the basis of a much desired palaeosalinity proxy by circumventing the main source of uncertainty in interpreting 18o palaeorecords i e variations in the isotopic composition of seawater contrary to the 18o proxy transferring the mg ca temperature proxy to marine bivalves has proved problematic since a strong seawater temperature control on shell calcite mg ca has rarely been observed in this study a preliminary evaluation of the combined use of 18ocalcite and mg ca from pecten maximus inner shell calcite to estimate 18owater is reported new mg ca data obtained by milling the inner shell regions from p maximus specimens grown in laboratory aquaria under constant seawater temperatures between 10 and 20 c exhibit a strong relationship between mg ca and temperature mg ca 2 56 0 42 0 17 0 03 t r2 0 77 p 0 001 n 54 while the relationship between sr ca and temperature was not strong r2 0 30 p 0 001 n 54 using specimens grown in a separate aquaria validation experiment estimated mg ca derived seawater temperature was within 0 48 c of measured seawater temperature while estimated 18owater was within 0 05 to 0 15 of measured seawater 18o composition depending on the 18o temperature equation used and with uncertainty estimates of 0 63 and 0 35 such observations indicate the strongest potential to date for the development of valid temperature and 18owater salinity proxies in bivalves from the combined application of mg ca and 18ocalcite in the inner shell regions of p maximus further studies for a wide range of pectinid species ages and different natural environmental settings are needed to validate the observations of this study

exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification throughout much of earth s history marine carbonates have represented one of the most important geological archives of environmental change several pivotal events during the phanerozoic such as mass extinctions or hyperthermal events have recently been associated with ocean acidification nevertheless well defined geological proxies for past ocean acidification events are at best scarce here experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry c 13 o 18 and mg 26 to stressful environments in particular to sea water acidification in this study the common blue mussel mytilus edulis was cultured from early juvenile stages to one year of age at four ph regimes ph nbs 72 to ph 80 shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments specimens exposed to low ph environments show patches of disordered calcitic fibre orientation in otherwise well structured shells furthermore the electron backscattered diffraction analyses reveal that under acidified conditions the c axis of the calcite prisms exhibits a bimodal or multi modal distribution pattern similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions in contrast this study found no evidence that different ph regimes affect shell carbon oxygen or magnesium isotope ratios based on these observations it is proposed that i stressful environments in this case low sea water ph predictably affect bivalve biomineralization patterns and ii these findings bear potential as a novel petrographic proxy for ancient sea water acidification an assessment of the applicability of these data to well preserved fossil shell material from selected time intervals requires additional work

late pleistocene monsoon variability in northwest thailand an oxygen isotope sequence from the bivalve margaritanopsis laosensis excavated in mae hong son province abstract long continuous records of late quaternary environmental change are rare in southeast asia yet they are crucial for understanding the nature of early human dispersal and occupation in the australasian region we present a new record of palaeomonsoon activity extending back to 35 000 bp years before the present based on the analysis of oxygen isotope ratios 18 o in the freshwater bivalve margaritanopsis laosensis excavated from the tham lod and ban rai rockshelters in mae hong son province northwest thailand long term changes in the m laosensis 18 o record reflect changes in the 18 o of the river water in which these organisms grew and correlate well with changes in speleothem 18 o records of east asian monsoon rainfall from hulu cave and dongge cave in china the new northwest thailand 18 o sequence indicates wetter and relatively unstable climatic conditions from 35 000 to 20 000 bp followed by drier conditions from 20 000 to 11 500 bp a period of peak aridity occurred around 15 600 bp during heinrich event 1 suggesting that the intertropical convergence zone shifted southward when the north atlantic region cooled however there is little evidence for the younger dryas event at 12 800 11 500 bp after 9 800 bp precipitation increased substantially and climatic variability declined our findings provide an improved baseline against which to gauge interactions between early humans and climate change in southeast asia for example there was no significant change in the prehistoric flake stone technology used at tham lod and ban rai despite the bivalve 18 o evidence for substantial climate change in the region also the climatic impact of the younger dryas event appears to have been less intense in northwest thailand compared to the cooling and drying observed in china and may explain why agriculture made a relatively late appearance in thailand possibly involving migrants from china

the ormer haliotis tuberculata a new promising paleoclimatic tool abstract this study aimed to investigate the environmental controls on the oxygen isotope composition of shells of the european abalone haliotis tuberculata seasonal 18 o profiles from the outer prismatic layer of four abalone shells collected live in northwest brittany france in 2002 and 2012 were compared to local temperatures and salinities according to the findings herein 18 o variations in abalone shells corresponded to seasonal variations and thus shell composition represented a reliable tool for aging and growth studies seawater temperatures estimated from the abalone collected in 2012 reflected the in situ measured temperatures but the reconstructed temperatures from shells of the three specimens collected in 2002 deviated from measured temperatures by 2 5 c this overestimation of temperatures corresponded to a kinetic effect related to very high annual abalone growth rates thus it could be corrected by applying 0 53 to the 18 o shell this methodology was then applied to a fossil 6000 cal yr bp collected in the bay of biscay given the worldwide distribution of both live and fossilized abalones the results of the present study showed that this genus represents a promising paleoclimatic tool

exploring the calcium isotope signature of arctica islandica as an environmental proxy using laboratory and field cultured specimens abstract the calcium isotope composition 44 40ca of the aragonitic bivalve arctica islandica grown in laboratory and field cultures was investigated in terms of environmental and biological controls to explore its potential as a palaeoceanographic proxy while we found no significant effect of salinity on ca isotope fractionation the relationship between 44ca 40ca ratios of a islandica and temperature was best explained by a generalised additive model which describes the temperature versus ca isotope relationship as a nonlinear second degree polynomial with an optimum temperature of 15 c since 44ca 40ca ratios clearly increase with increasing temperature up to 15 c the temperature versus ca isotope relation can be approximated through a linear fit up to 15 c the slope of this linear temperature dependent ca isotope fractionation resembles previous calibrations of inorganic and biogenic aragonites providing insights into fractionation processes during bivalve biomineralization our findings suggest that the observed biologically induced ca isotope fractionation occurs when ca is transported from seawater to the site of mineralization most likely during the passage through the epithelial mantle the observed evidence for strong vital effects indicates limited use of ca isotopes in a islandica as a temperature proxy

structural and stratigraphical constraints on the kinematics history of the southern tan lu fault zone during the mesozoic anhui province china abstract the tan lu fault zone tlfz extends in a nne ssw direction for more than 2000 km in eastern china it has been considered either as a major sinistral strike slip fault as a suture zone or as a normal fault we have conducted a structural analysis of the southern segment of this fault zone stlfz in the anhui province the ages triassic to palaeocene of the formations affected by the faults have been re appraised taking into account recent stratigraphical studies to better constraint the ages of the successive stages of the kinematics of the stlfz subsequently the kinematics of the faults is presented in terms of strain stress fields by inversion of the striated fault set data finally the data are discussed in the light of the results obtained by previous workers we propose the following history of the stlfz kinematics during the mesozoic at the time of collision a nne orientated tan lu margin probably connected two margins located north of the dabie and sulu collision belts during the middle late triassic the scb has been obliquely subducted below the ncb along this margin which has acted as a compressional transfer zone between the dabie and sulu continental subduction zones the stlfz has been initiated during the early jurassic and has acted as a sinistral transform fault during the jurassic following which the ncb scb collision stopped a nw trending extension related to metamorphic domes was active during the basal early cretaceous 135 130 ma it has been followed by a nw se compression and a ne sw tension during the middle late early cretaceous 127 to 105 ma possibly 95 ma at that time the tlfz was a sinistral transcurrent fault within the eastern part of the asian continent during the late cretaceous palaeocene the stlfz was a normal fault zone under a wnw ese tension

li ca enrichments in great scallop shells pecten maximus and their relationship with phytoplankton blooms article i nfo phytoplankton dynamics in coastal oceans is a major component of the global biogeochemical carbon cycle and is currently affected by global change through modifications in levels of primary productivity and com position of phytoplankton communities despite many attempts no straightforward geochemical proxy has been found yet in marine biogenic carbonates for reconstruction of past phytoplankton dynamics with high temporal resolution here we report on sub weekly variations of lithium to calcium ratios li cashell along the axis of maximum growth of great scallop shells pecten maximus collected alive between 1999 and 2007 in the bay of brest northwest france inter individual variability of li cashell time series was very low suggesting an environmental control on the incorporation of li within shells conversely inter annual variability of li cashell was high with limited seasonal li cashell variations in 2001 and 2007 and the presence of li enrichments from may to july in 1999 and 2004 comparison of these results with shell growth measure ments increment width and environmental parameters suggests i that shell calcification rate is likely the main factor controlling incorporation of li in pecten maximus shell calcite ii that seawater temperature has only a weak positive influence on li cashell of this species over the range 8 18 c and iii that during diatom blooms additional amounts of li may be trapped in the shell following dissolution of li rich frustules of ed ible species in the digestive tract of scallops being responsible for li cashell peaks therefore we suggest that li cashell ratio may be a novel proxy for timing and magnitude of diatom blooms in coastal ecosystems anal ysis of ancient shells may thus provide useful information on past phytoplankton dynamics and on the im portance of recent shifts observed from diatoms to non siliceous phytoplankton in coastal areas affected by anthropogenic activities

seasonality in sea surface temperatures from δ18o in cladocora caespitosa modern adriatic to late pleistocene gulf of corinth high resolution stable isotope analysis of coral skeletons is an established method to help reconstruct seawater growth temperatures for palaeoenvironmental reconstructions here we investigated the temperate colonial mediterranean scleractinian coral cladocora caespitosa we first studied modern adriatic corals from mljet croatia where growth temperatures were known a clear sinusoidal cyclicity is present in the d18o of the modern coral skeletons with average cycle minima 3 3 and average maxima 1 6 cyclicity approximately matches the number of seasonal growth band pairs in each sample implying a genetic link between d18o cyclicity and factors that determine seasonal growth band development here mainly water temperature a derived and calibrated species specific d18o temperature relationship was then used to reconstruct growth temperatures from fossil c caespitosa this was applied to well preserved material collected from late pleistocene deposits mis 1 5 and 7 around the gulf of corinth greece clear seasonal d18o signals are seen in all the fossil samples mis 5e was the warmest period studied with a lower than modern seasonal temperature range the early to mid holocene probably experienced the lowest temperatures while conditions in mis 7a c were probably the wettest with most freshwater input into the gulf

thermal dependency of shell growth microstructure and stable isotopes in laboratory reared scapharca broughtonii mollusca bivalvia we experimentally examined the growth microstructure and chemistry of shells of the bloody clam scapharca broughtonii mollusca bivalvia reared at five temperatures 13 17 21 25 and 29 c with a constant pco2 condition 450 atm in this species the exterior side of the shell is characterized by a composite prismatic structure on the interior side it has a crossed lamellar structure on the interior surface we previously found a negative correlation between temperature and the relative thickness of the composite prismatic structure in field collected specimens in the reared specimens the relationship curve between temperature and the growth increment of the composite prismatic structure was humped shaped with a maximum at 17 c which was compatible with the results obtained in the field collected specimens in contrast the thickness of the crossed lamellar structure was constant over the temperature range tested these results suggest that the composite prismatic structure principally accounts for the thermal dependency of shell growth and this inference was supported by the finding that shell growth rates were significantly correlated with the thickness of the composite prismatic structure we also found a negative relationship between the rearing temperature and 18o of the shell margin in close quantitative agreement with previous reports the findings presented here will contribute to the improved age determination of fossil and recent clams based on seasonal microstructural records

ice elevation near the west antarctic ice sheet divide during the last glaciation 1 interior ice elevations of the west antarctic ice sheet wais during the last glaciation which can serve as benchmarks for ice sheet models are largely unconstrained here we report past ice elevation data from the ohio range located near the wais divide and the onset region of the mercer ice stream cosmogenic exposure ages of glacial erratics that record a wais highstand 125 m above the present surface date to 11 5 ka the deglacial chronology prohibits an interior wais contribution to meltwater pulse 1a our observational data of ice elevation changes compare well with predictions of a thermomechanical icesheet model that incorporates very low basal shear stress downstream of the present day grounding line we conclude that ice streams in the ross sea embayment had thin lowslope profiles during the last glaciation and interior wais ice elevations during this period were several hundred meters lower than previous reconstructions citation ackert r p jr s mukhopadhyay b r parizek and h w borns 2007 ice elevation near the west antarctic ice sheet divide during the last glaciation geophys res lett 34 l21506 doi 10 1029 2007gl031412

petrology of the late carboniferous punta falcone gabbroic complex nothern sardinia italy the punta falcone gabbroic complex represents an evolved high alumina basalt which rose from the mantle through the lower crust and subsequently intruded a granite magma in middle crustal levels during the calc alkaline magmatic activity which took place in the sardinian and corsican islands in the carboniferous the gabbroic complex has a stratified sub vertical structure and consists of three zones developing from the bottom to the top of the magma chamber an interaction zone can be recognized along contacts with the surrounding granite stock and it is characterized by finer grained and more evolved rocks than the interior of the gabbroic complex processes occurring in its interior zone have been substantially different from those occurring in its marginal interaction zone petrographical and geochemical features indicate that the differentiation of the interior of the gabbroic complex can be accounted for by low pressure closed system in situ crystallization the different gabbroic units represent mixtures between cumulus phases and trapped liquid plagioclase pyroxenes and successively plagioclase calcic amphibole oxides nucleated and grew in situ on the floor and walls of the chamber floating of plagioclase towards the top of the magma chamber resulted in the accumulation of the denser liquid at the bottom compaction phenomena and convective fractionation processes permitted the development of the pile of cumulus crystals with their trapped liquid and the migration of part of this evolved liquid towards the top of the magma chamber on the basis of major and trace element modelling a mathematical artifice has been developed to evaluate cumulus intercumulus processes that occurred in the interior of the gabbroic complex accordingly the formation of the different units can be modelled by mixtures between the parental magma and different percentages of minerals formed during the first stages of crystallization contemporaneously with the differentiation of the interior zone the envelope of fine grained rocks enclosing and grading into the coarser inner part of the gabbroic complex experienced both chemical and physical processes chemical processes resulted in the evolution of the marginal interaction zone by crystal fractionation plus contamination by the acid magma physical processes were closely related to the thermodynamic instability of this marginal zone and consisted of mingling and back veining phenomena which developed interdigitations of granite veins along contacts in addition an increase of the melt fraction of the granite magma superheated by the latent heat of crystallization of the mafic magma caused the occurrence of tilting of the mafic magma chamber and resulted in the development of the sub vertical structure of the gabbroic complex

shell of the great scallop pecten maximus as a high frequency archive of paleoenvironmental changes 1 we investigate the environmental and biological controls on oxygen isotope ratios in the shells of modern pecten maximus bivalves collected alive in the bay of brest france seasonal 18o profiles obtained by drilling the daily calcite ridges deposited at the surface of the left valve were compared with in situ measurements of temperature and salinity we show that p maximus 18o values accurately track seasonal variations in bottom water temperature shell growth rate has no significant effect on shell 18o values our study demonstrates that daily variations in water temperature can be reconstructed within about 0 5 c temperatures estimated with the paleotemperature equation established in this study were compared with temperatures derived from previously published equations the comparison indicates that the most commonly used paleotemperature equation for biogenic calcite epstein et al 1953 provides inaccurate temperature estimates but the kim and o neil 1997 equation established from abiogenic calcite precipitation provides results very similar to ours and should therefore be used for scallop individuals coming from populations where proper empirical calibration cannot be done pecten maximus bivalves precipitate calcite in isotopic equilibrium with seawater produce large daily growth striae are stenohaline and are well preserved in archeological and geological deposits making them an excellent high frequency archive of paleoenvironmental change

composition of stable isotopes in geoduck panopea abrupta shells a preliminary assessment of annual and seasonal paleoceanographic changes in the northeast pacific abstract we tested the suitability of using panopea abrupta geoduck shells to evaluate changes in both annual and seasonal sea surface temperature geoducks are long lived and deposit annual growth increments within their shell each winter making them potentially excellent paleoceanographic archives shells were sampled by thin section from the hinge plate region where the first 20 30 years of growth provide relatively wide annual increments suitable for sampling for isotopic analysis the geoducks used in this study were collected in ad 2000 from west of protection island located at the eastern end of the strait of juan de fuca the isotopic record is compared to the historic instrumental record as well as the thickness of geoduck growth increment measurements which were also correlated with water temperature strom a francis r c mantua n j miles e l peterson d l 2004 north pacific climate recorded in growth rings of geoduck clams a new tool for paleoenvironmental reconstruction geophysical research letters 31 p lo6206 doi 10 1029 2004gl019440 the annual average oxygen isotopic values from two geoduck clams whose first years of growth correspond to the early historic instrumental record ad 1920 appear to be recording trends in sea surface temperature intra annual sampling of annual growth increments indicates that the shells also appear to be recording seasonal changes in sea surface temperature preliminary analysis of carbon isotopic data on both the annual and seasonal timescales indicate the potential for assessing productivity changes in ambient seawater

unraveling environmental histories from skeletal diaries advances in sclerochronology high resolution proxy archives from aquatic settings are essential to better understand processes and mechanisms of global change during the last decade it has become increasingly evident that calcified tissues of bivalve mollusks and cold water corals in particular can significantly increase our knowledge of seasonal to multi decadal paleoclimate and paleoenvironmental variability in the extratropical oceans and coastal marine settings daily tidal fortnightly and annual growth patterns of periodically formed skeletal hard parts provide a means to place the proxy record in a precise temporal context their extreme longevity coupled with the running similarity between growth increment time series of contemporaneous bivalves opens the possibility of constructing stacked chronologies covering centuries to millennia which provide information on decadal climate and environmental variability and magnitudes of climate variability through time a current major research focus is on how to translate geochemical properties of the skeletons into quantifiable environmental proxy data and how to eliminate the adverse influence of vital effects on the proxy records this special issue presents the most recent advances in the field of sclerochronology specifically calcified tissues of bivalve mollusks cold water corals and tropical shallow water corals the majority of the contributions deal with the potential reconstruction of temperature ph and productivity through the analysis of variable growth rates sr ca mg ca ba ca u ca li ca 13c 18o and 44 40ca four papers present composite chronologies of two long lived bivalve species and discuss inherent decadal climate variability and one study demonstrates that sclerochronology can shed light on socioeconomic patterns of past human populations as well as resource use and resource management by people

late paleocene arctic ocean shallow marine temperatures from mollusc stable isotopes late paleocene high latitude 80 n arctic ocean shallow marine temperatures are estimated from molluscan 18o time series sampling of individual growth increments of two specimens of the bivalve camptochlamys alaskensis provides a high resolution record of shell stable isotope composition the heavy carbon isotopic values of the specimens support a late paleocene age for the youngest marine beds of the prince creek formation exposed near ocean point alaska the oxygen isotopic composition of regional freshwater runoff is estimated from the mean 18o value of two freshwater bivalves collected from approximately coeval fluviatile beds over a 30 34 range of salinity values assumed to represent the tolerance of c alaskensis the mean annual shallow marine temperature recorded by these individuals is between 11 and 22 c these values could represent maximum estimates of the mean annual temperature because of a possible warm month bias imposed on the average 18o value by slowing or cessation of growth in winter months the amplitude of the molluscan 18o time series probably records most of the seasonality in shallow marine temperature the annual temperature range indicated is approximately 6 c suggesting very moderate high latitude marine temperature seasonality during the late paleocene on the basis of analogy with modern chlamys species c alaskensis probably inhabited water depths of 30 50 m the seasonal temperature range derived from 18o is therefore likely to be damped relative to the full range of annual sea surface temperatures high resolution sampling of molluscan shell material across inferred growth bands represents an important proxy record of seasonality of marine and freshwater conditions applicable at any latitude if applied to other regions and time periods the approach used here would contribute substantially to the paleoclimate record of seasonality

an aquaculture based method for calibrated bivalve isotope paleothermometry to quantify species specific relationships between bivalve carbonate isotope geochemistry 18oc and water conditions temperature and salinity related to water isotopic composition 18ow an aquaculture based methodology was developed and applied to mytilus edulis blue mussel the four by three factorial design consisted of four circulating temperature baths 7 11 15 and 19 c and three salinity ranges 23 28 and 32 parts per thousand ppt monitored for 18ow weekly in mid july of 2003 4800 juvenile mussels were collected in salt bay damariscotta maine and were placed in each configuration the size distribution of harvested mussels based on 105 specimens ranged from 10 9 mm to 29 5 mm with a mean size of 19 8 mm the mussels were grown in controlled conditions for up to 8 5 months and a paleotemperature relationship based on juvenile m edulis from maine was developed from animals harvested at months 4 5 and 8 5 this relationship t c 16 19 0 14 4 69 0 21 18oc vpbd 18ow vsmow 0 17 0 13 18oc vpbd 18ow vsmow 2 r2 0 99 n 105 p 0 0001 is nearly identical to the kim and o neil 1997 abiogenic calcite equation over the entire temperature range 7 19 c and it closely resembles the commonly used paleotemperature equations of epstein et al 1953 and horibe and oba 1972 further the comparison of the m edulis paleotemperature equation with the kim and o neil 1997 equilibrium based equation indicates that m edulis specimens used in this study precipitated their shell in isotopic equilibrium with ambient water within the experimental uncertainties of both studies the aquaculture based methodology described here allows similar species specific isotope paleothermometer calibrations to be performed with other bivalve species and thus provides improved quantitative paleoenvironmental reconstructions

coastal upwelling in norway recorded in great scallop shells the shells of bivalve mollusks have been shown to contain a wealth of information about the environment in which the organisms lived as well as about their life histories shells of the great scallop pecten maximus were collected in 1987 and 1988 at 15 25 m depth close to the austevoll islands norway a sharp slowdown in growth was detected in 1986 for all age classes resulting in a growth rate decrease of nearly 45 over 10 d measurements of stable isotopes 18o and 13c in four specimens suggested that this slowdown was concurrent with a drop in water temperature in situ measurements of environmental parameters temperature salinity wind and data from a numerical coastal model system norkyst 800 confirmed that a temperature drop of 3 c occurred in july 1986 due to a sudden change in wind direction and speed along the western coast of norway these northerly winds parallel to the coast induced an upwelling of deep cold water along the coast thus the present study demonstrated a clear relationship between regional climatic phenomena acting on an oceanographic process and the growth of a benthic invertebrate bivalve shells should be used to describe and characterize local upwelling events for example in terms of duration and intensity in current environments and in paleoenvironments

structural analysis and paleoenvironmental potential of dog cockle shells glycymeris glycymeris in brittany northwest france to compensate for the lack of high resolution data on variation in environmental parameters before the establishment of monitoring networks we evaluated dog cockle shells glycymeris glycymeris mollusca bivalvia as archives for temperature and climate perturbations such as the north atlantic oscillation nao over the last 50 years oxygen isotope compositions were measured from annual increments of shells collected from the bay of brest and the chausey islands in northwestern france simultaneously sclerochronological analyses were performed on the same shells oxygen isotopic ratios measured in shells collected from the bay of brest were compared to in situ temperature and salinity data from monitoring stations and buoys in order to build a specific paleotemperature equation r2 0 87 p 0 001 for the dog cockle the specific equation was used to estimate sea surface temperatures around the chausey islands between 1966 and 1994 standardized growth indices sgi calculated through sclerochronological methods were strongly correlated to oxygen isotope derived temperatures the sgi however did not capture the area s predominant climate pattern the nao this study demonstrates that dog cockle shells can be used for long term high resolution reconstructions of past sea surface temperatures

air humidity and lake δ18o during the latest paleocene earliest eocene in france from recent and fossil fresh water and marine gastropod δ18o δ13c and 87sr 86sr detailed isotopic 18 o 13 c 87 sr 86 sr analyses have been performed on aragonitic fresh water brackish water and marine gastropod shells of latest paleocene earliest eocene age from northwestern europe fresh water shells e g viviparus lymnaea from sparnacian deposits in the paris basin show relatively high 18 o values in the range 4 to 0 1 large intrashell 18 o variability typically 3 is consistent with significant seasonal variation in precipitation and or temperature we also present intrashell isotopic profiles for 22 recent fresh water shells mainly viviparidae representing the major middle to low latitude climate zones e g sweden france portugal lake chad ceylon gambia congo lake victoria new guinea distinct isotopic patterns reflecting humidity and temperature characterize each of the climate zones comparing the results for recent and fossil shells suggests that the climate in northern france during sparnacian time was warm subtropical with a pronounced seasonal drought the 18 o composition of sparnacian lake water has been estimated from the fossil fresh water shell 18 o and by using seasonal temperatures derived from 18 o profiles of fully marine shells the best estimate of the 18 o composition of sparnacian lake water compared with eocene mean ocean water is 1 this is consistent with paleorain 18 o values of 3 to 5 similar to present mean rain 18 o standard mean ocean water values close to 4 in portugal at 40 n the paleolatitude of the paris basin during earliest eocene time the evaporated nature of sparnacian lake water contradicts hypotheses of globally equable humid conditions in the warm early eocene and instead suggests that dry subtropical highs occurred over the eastern parts of the oceans similar to today the results of this study demonstrate the potential of fossil fresh water carbonates to reconstruct the development of subtropical highs and hadley cell circulation in the past

postsubduction porphyry cu au and epithermal au deposits products of remelting of subduction modified lithosphere porphyry cu mo au and some epithermal au deposits are formed from hydrothermal fluids exsolved from cooling water rich calc alkaline magmas emplaced in volcanoplutonic arcs above subduction zones these magmas originate by partial melting of the metasomatized asthenospheric mantle wedge however there is increasing evidence for the existence of a suite of porphyry cu au and epithermal au deposits related to magmas generated after subduction beneath the arc has ceased associated magmas tend to be mildly alkaline relatively sulfur poor and emplaced as isolated complexes rather than in voluminous volcanoplutonic arcs they are likely formed by remelting of previously subduction modified arc lithosphere triggered by postsubduction lithospheric thickening lithospheric extension or mantle lithosphere delamination metasomatized mantle lithosphere or hydrous lower crustal cumulates residual from first stage arc magmatism contain small amounts of chalcophile and siderophile element rich sulfides and constitute a fertile source for hydrous au rich but relatively sulfur poor magmas during later remelting the recognition that porphyry cu au and related epithermal au systems can also form in postsubduction and collisional tectonic settings expands the range of geological environments and geographical terranes that are prospective for such deposits

an explanation of the effect of seawater carbonate concentration on foraminiferal oxygen isotopes abstract stable oxygen isotope ratios of foraminiferal calcite are widely used in paleoceanography to provide a chronology of temperature changes during ocean history it was recently demonstrated that the stable oxygen isotope ratios in planktonic foraminifera are affected by changes of the seawater chemistry carbonate system the 18 o of the foraminiferal calcite decreases with increasing co 3 2 concentration or p h this paper provides a simple explanation for seawater chemistry dependent stable oxygen isotope variations in the planktonic foraminifera orbulina universa which is derived from oxygen isotope partitioning during inorganic precipitation the oxygen isotope fractionation between water and the dissolved carbonate species s h 2 co 3 hco 3 co 3 2 decreases with increasing p h provided that calcium carbonate is formed from a mixture of the carbonate species in proportion to their relative contribution to s the oxygen isotopic composition of caco 3 also decreases with increasing p h the slope of shell 18 o vs co 3 2 of orbulina universa observed in culture experiments is 0 0022 mol kg 1 1 spero et al 1997 whereas the slope derived from inorganic precipitation is 0 0024 mol kg 1 the theory also provides an explanation of the nonequilibrium fractionation effects in synthetic carbonates described by kim and o neil 1997 which can be understood in terms of equilibrium fractionation at different p h the results presented here emphasize that the oxygen isotope fractionation between calcium carbonate and water does not only depend on the temperature but also on the p h of the solution from which it is formed

global carbon isotopic events associated with mass extinction and glaciation in the late ordovician mass extinctions and glacioeustatic sea level changes in the lower part of the hirnantian final stage of the ashgill are accompanied by shifts in marine stable isotope compositions previously published stable isotope changes have been used to identify the onset and demise of the gondwana glaciation and to suggest relationships between biotic changes and carbon cycling within the oceans however the existing isotopic data set had limitations because it was derived from ordovician low latitude settings and from carbonates or organic carbon in separate areas we report new data from ordovician high latitude carbonates and demonstrate parallel shifts in organic and carbonate 13c from baltica brachiopod shells from a high palaeolatitude periglacial setting in argentina have elevated 13c values similar to those described previously from low latitude sites the new data demonstrate that the positive hirnantian 13c excursion previously only recognised from low palaeolatitude areas was widespread and probably global in extent the poor preservation state of the brachiopods unfortunately prevented the determination of a reliable oxygen isotopic value from the same material preliminary carbon isotopic data from thermally immature organic matter from estonia provide the first indication of a synchronous shift in organic and inorganic 13c in sediments from the same basin this work provides new data of critical importance for constraining models of end ordovician palaeoceanography and climate change

gradients in seasonality and seawater oxygen isotopic composition along the early permian gondwanan coast se australia abstract oxygen isotope compositions of marine carbonates are commonly employed for understanding ancient temperatures but this approach is complicated in the very distant past due to uncertainties about the effects of diagenesis and the isotopic composition of seawater both locally and globally microsampled accretionary calcite from two species of the fossil bivalve eurydesma sowerby and morris 1845 collected from sediments of cisuralian age in high latitude marine sediments along the se coast of australia records cyclic seasonal fluctuations in shell 18 o values during growth demonstrating the primary nature of the isotope signal and thus allowing investigation of early permian seawater isotopic composition and water temperature in the high southern latitudes the mean and seasonal range of 18 o carb decreases poleward across about 10 of paleolatitude 67 s 77 s the presence of co occurring dropstones and stratigraphically associated glendonites constrains winter temperatures across the region to near freezing thus permitting calculation of realistic estimates of water composition and summer temperatures summer 18 o carb values indicate water temperatures between 5 c and 12 c with warmer values at lower latitudes the decrease in both mean sea surface temperature and seasonal amplitude with increasing latitude on the gondwanan coast is much like that observed along high latitude coastlines today calculated 18 o water decreases toward the pole likely associated with an increasing contribution of isotopically light fresh water derived from summer snow melt the gradient in 18 o water is similar to that documented over a similar span of latitude on the modern se greenland coast we infer the presence of a north flowing coastal current of cold o 18 depleted water that entrains progressively greater amounts of more typical seawater as it moves away from the pole 18 o values in se australia however are about 3 lower than those off greenland suggesting comparatively lower salinity water or more o 18 depleted glacial ice runoff in the permian gondwanan high latitudes perhaps augmented by more depleted negative global average seawater conditions in southeastern australia during the largest of the permian deglaciations were warmer than present day antarctica at similar latitudes but may approximate those of early mid miocene antarctica with frozen winters but summers closer to 10 c

winter and summer temperatures of the early middle eocene of france from turritella δ18o profiles the mean annual range of temperature is from a climatological point of view at least as important as the mean annual temperature in order to examine intra annual temperature variations in the warm early cenozoic we have analyzed stable oxygen and carbon isotopes along the transect of growth on excellently preserved specimens of the gastropod turritella imbricataria and the bivalve venericardia imbricata from sedimentary rocks of early middle eocene age ca 46 ma in the paris basin turritella shell growth is fast throughout the year and the isotopic records give the first detailed information about early middle eocene seasonal variations the oxygen isotope profiles indicate winter temperatures of about 14 c and summer temperatures of up to 28 c i e a seasonality indistinguishable from the present situation but an annual temperature some 10 c higher our results contradict the opinion that the climate during this period was more equable than that of today

geochemistry of north shore hypabyssal dikes and sills in the midcontinent rift of minnesota an example the 47th avenue sill this study presents geochemical data for several of the numerous small to large dikes and sills including the 47th avenue sill exposed along the shore of lake superior in and north of duluth minnesota these intrusions are late magmatic features of the proterozoic midcontinent rift system and together form the north shore hypabyssal group the dikes are geochemically distinct from the sills and when the two are exposed together the younger dike intrudes the older sill dikes are primitive with mg up to 68 have positive end values and are oriented approximately north south with steep westerly or near vertical dips the older sills are more evolved usually have end values near or below 0 and have the same gentle easterly dip as the thick sequence of north shore volcanic group flows they intrude dike compositions correlate best with a mixture of widespread basalt compositions types 4 and 5 with primitive geochemistry and positive end values whereas sill compositions are similar to widespread ba

investigation of li ca variations in aragonitic shells of the ocean quahog arctica islandica northeast iceland interannual and intra annual variations in lithium to calcium ratio were investigated with high temporal resolution in the aragonitic outer shell layer of juvenile arctica islandica mollusca bivalvia collected alive in 2006 off northeast iceland li ca shell ranged between 7 00 and 11 12 mol mol 1 and presented well marked seasonal cycles with minimum values recorded at the annual growth lines a general pattern was a progressive increase in li ca shell from march to may followed by a plateau in june and a decrease down to minimum values in july august li ca shell was correlated with d 18 o shell derived temperature but the strength of this relationship was weak r 2 p shell in a islandica may most likely be explained 1 by calcification rate and or 2 by significant river inputs of li rich silicate particles flowing to the sea as soon as snow melts in the first case li ca shell may be a useful proxy for addressing seasonal variations of growth rate in bivalves that lack discernable microgrowth patterns abrupt decreases of li ca shell may in turn help identify growth retardations due to harsh environmental conditions alternatively if li ca shell variations are linked to particulate li inputs by rivers this could be a new proxy for the intensity of mechanical weathering of icelandic basalts with interesting perspectives for the reconstruction of frequency and intensity of past jokulhlaups subglacial outburst floods further works including experimental studies are needed to test these hypotheses