u pb zircon and 40 ar 39 ar geochronology of sericite from hydrothermal alteration zones new constraints for the timing of ediacaran gold mineralization in the sukhaybarat area western afif terrane saudi arabia the sukhaybarat east and red hill deposits in the northeastern part of the arabian shield are mesothermal vein type gold deposits hosted by late cryogenian ediacaran intrusive rocks of the idah suites diorite tonalite granodiorite and at sukhaybarat east also by ediacaran metasedimentary rocks gold mineralization comprises quartz arsenopyrite veins sukhaybarat east quartz carbonate pyrite veins red hill and subordinate gold base metal sulfide veins in the red hill deposit alteration is complicated due to multiple overprinting hydrothermal events and is characteristically affected by pervasive pink quartz k feldspar hematite alteration which is overprinted by potassic alteration characterized by a quartz biotite carbonate muscovite sericite rutile apatite assemblage this assemblage is associated with molybdenite veins which appear to form late in the paragenetic sequence and may represent either evolution of the ore fluid composition or a later unrelated mineralized fluids hydrothermal alteration at the sukhaybarat east deposit is dominated by quartz carbonate sericite arsenopyrite assemblages zircon from ore hosting tonalite at sukhaybarat east yields a u pb age of 629 6 ma and biotite from the same rock gives an 40ar 39ar age of 622 23 ma the 40ar 39ar age is within the uncertainty range for the u pb age of the host intrusion and is interpreted as a minimally disturbed cooling age for the tonalite in the red hill area granodiorite was emplaced at 615 5 ma whereas muscovite sericite separated from a mineralized sample of a quartz carbonate pyrite vein that was overprinted by molybdenite bearing veinlets yields an 40ar 39ar age of 597 8 ma we interpreted this age to represent the maximum age of the molybdenite mineralization and the probable minimum age of gold mineralization in the red hill deposit

evidence from u th dating against northern hemisphere forcing of the penultimate deglaciation milankovitch proposed that summer insolation at mid latitudes in the northern hemisphere directly causes the ice age climate cycles1 this would imply that times of ice sheet collapse should correspond to peaks in northern hemisphere june insolation but the penultimate deglaciation has proved controversial because june insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier2 3 4 5 6 7 8 there is a clear signature of the penultimate deglaciation in marine oxygen isotope records but dating this event which is significantly before the 14c age range has not been possible here we date the penultimate deglaciation in a record from the bahamas using a new u th isochron technique after the necessary corrections for recoil mobility of 234u and 230th and a small age correction for sediment mixing the midpoint age for the penultimate deglaciation is determined to be 135 2 5 kyr ago this age is consistent with some coral based sea level estimates but it is difficult to reconcile with june northern hemisphere insolation as the trigger for the ice age cycles potential alternative driving mechanisms for the ice age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean atmosphere system or changes in atmospheric co2 concentration controlled by a process in the southern hemisphere

history of stage 5 sea level in bermuda review with new evidence of a brief rise to present sea level during substage 5a abstract oxygen isotope substage 5e is represented by the devonshire formation in bermuda the occurrence of these coastal marine deposits to about 5 m indicates pleistocene sea level data in bermuda do not need tectonic corrections a few published u series coral dates suggest that a conglomerate spencer s point formation may have formed during substage 5c geologic mapping however indicates that the eolianite beneath the conglomerate is pre rather than post devonshire formation in age as was previously thought and the aminostratigraphy of marine sheels also confirms the correlation of the spencer s point and devonshire formations substages 5c and 5a are represented by the southampton formation large eolianites comprise the bulk of this formation they are onlapped by a few small younger marine 1 m and eolian deposits aminostratigraphy confirms that these late southampton age deposits are significantly younger than the devonshire formation and u series dates indicate a substage 5a age the setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms this evidence that sea level in bermuda was at about present datum late in substage 5a agrees with interpretations of neotyrrhenian deposits of mediterranean shorelines but not with inferences from the deep sea oxygen isotope record or with data from uplifted coral reefs

east european loess palaeosol sequences palynology stratigraphy and correlation abstract in this paper the results of pollen analyses of the loess palaeosol sequences lps of the east european plain are presented environment and vegetation evolution during the time of loess and soil formation has been characterized by pollen data of the reference sections of the upper oka likhvin chekalin section the upper don strelitsa section the middle kuma otkaznoe section the middle dniester molodova and ketrosy sections and the middle desna arapovichi section regions palaeomagnetic studies indicate that the sediment sequence studied spans at least the last 800 ka the palynological climate proxies show a pattern of periodic variations comprising nine interglacial and eight glacial stages on the basis of palynological results coupled with the electron spin resonance esr chronostratigraphic data on mollusc shell bearing marine and terrestrial deposits the reconstruction periodization and distant correlation of palaeoclimatic events and deposits of glacial periglacial and extraglacial zones of northern eurasia over the last 600 000 years have been carried out based on palaeoenvironmental evidence it has been established that the full interglacial conditions revealed are centred at about 580 400 310 220 and between 145 and 70 ka a broad correspondence between the long palynological sequence directly esr dated warm climate related events and other palaeoenvironmental records described in the literature is noted at least for the 11 upper marine isotope stages mis 11 1

a shear instability seeding mechanism for quasiperiodic radar echoes the quasiperiodic echoes with periods in the range of 1 10 minutes originally discovered at the middle and upper atmosphere mu radar in japan in the early 1990s are now known to be a common feature of midlatitude sporadic e a possible role of shear instabilities and the associated kelvin helmholtz structure in seeding the plasma instabilities that produce the radar echoes is suggested in this paper the proposed mechanism has the advantage that the seed structure is generated in situ as part of the same neutral wind structure that serves to initiate the generation of the sporadic e layer in addition the range of observed periods can easily be explained since the kelvin helmholtz structure is embedded in the shear flow and moves with the mean flow in the shear layer the period observed in the ground based frame is simply a product of the horizontal wavelength and the mean flow velocity at the center of the disturbance finally a typical feature of the radar observations has been that the quasiperiodic structure often ebbs and wanes in intensity over a period of 30 to perhaps 60 min recent simulations of unstable neutral shears show that the timescale for the build up and eventual restabilization of the shear flow is 30 40 min comparable to the timescale found in the observations

re os molybdenite age of the cu mo skarn ore deposit at suoerkuduke in east junggar nw china and its geological significance the suoerkuduke cu mo ore is a medium sized skarn deposit in the east junggar orogen of the southern altaids xinjiang northwest china we measured re os isotopes of a molybdenite veinlet from the

incompleteness of the geological record in middle upper pleistocene key sections of the northern caspian lowland abstract pleistocene key sections of the northern caspian lowland are characterized by the incompleteness of the geological record which is presented in depositional breaks their duration causes and types depositional breaks occurred in all periods of the middle and the late pleistocene and occupied various time intervals usually quite continuous from 180 ka cherny yar to 100 110 ka alexandrov gay gorky erik kopanovka enotaevka rarely shorter about 15 40 ka seroglazovka mergenevo period of accumulation in these sections is small 3 5 44 ka and covers only 1 2 9 average 3 4 for presented deposits and less than 10 from all chronological record the total chronological assessment of the geological record incompleteness in all studied sections estimated as more than 90 in all studied sections accumulation rates for holocene upper khvalynian lower khvalynian upper khazarian chernoyarian and lower khazarian are lower than the average for this region incompleteness is usually characterized by erosion of river waters of the volga and ural system but more often by abrasion of the khvalynian and the khazarian transgressive waters another cause of incompleteness of the geological record is long continuous periods without significant deposition this is often observed in subaerial conditions in the vast watershed area

radar studies of long wavelength waves associated with mid latitude sporadic e layers the cornell university portable radar interferometer cupri a 50 mhz doppler radar system was operated during may and august september 1983 on the island of st croix 17 7 n 64 8 w to study the plasma instabilities associated with nighttime sporadic e layers two events on may 7 and august 22 show evidence of large amplitude waves with apparent horizontal wavelengths of 10 12 km and periods of 2 6 min these apparent wavelengths are upper limits for the true wavelengths the cupri beam was directed over arecibo puerto rico and on may 7 concurrent electron density profiles within the cupri scattering volume were measured by the arecibo observatory s 430 mhz radar during the stronger event of august 22 radar echoes were received from several altitudes up to 130 km large mean doppler velocities at times exceeding 250 m s were observed during this event and the power spectra closely resemble those obtained at the magnetic equator during type 1 conditions we believe 1 that the mid latitude large scale waves are generated by the same gradient drift instability mechanism responsible for equatorial large scale waves and 2 that the type 1 3 m waves can be generated at mid latitudes with drift velocities well below the sound speed because of the very sharp plasma density gradients associated with metallic ion sporadic e layers

a fluid inclusion and stable isotope study of the pebble porphyry copper gold molybdenum deposit alaska abstract the hydrothermal fluid evolution in the supergiant pebble porphyry cu au mo deposit in southwest alaska has been constrained using fluid inclusion and light stable isotope data the deposit is related to 90 ma granodiorite porphyry intrusions and mineralization occurs primarily in sodic potassic potassic and advanced argillic alteration zones throughout the deposit vein quartz hosts intermediate density fluid inclusion assemblages with an average salinity of 9 5 wt nacl equivalent and homogenization temperatures of 377 to 506 c pressure corrections result in trapping temperatures with a maximum of 610 c this early fluid exsolved from a crystallizing magma at depth and underwent phase separation under varying conditions during cooling and depressurization forming two distinct fluid compositions the two fluids formed two hydrothermal alteration assemblages which have different metal signatures in the hydrothermal core in the eastern part of the system high density quartz veins potassic alteration and the most economically significant mineralization are related to 52 wt nacl equivalent brines that coexist with very low density vapor in the western part of the system peripheral to the hydrothermal core lower quartz vein densities accompanied by sodic potassic alteration and lower grade mineralization are associated with 38 wt nacl equivalent brines and low density vapor sulfide mineralization precipitated late in this early alteration event at temperatures between 375 and 330 c fluids related to sodic potassic alteration minerals have 18 o signatures from 6 0 to 10 5 vsmow and d values from 70 to 41 vsmow which are consistent with a magmatic fluid source fluids related to potassic alteration assemblages have 18 o of 1 7 to 2 3 vsmow and d of 68 to 59 vsmow which suggests that the magmatic fluids evolved to lighter oxygen isotope signatures due to quartz precipitation during alteration lower temperature 280 c sericite and illite alteration followed the high temperature magmatic stage and formed from the rising vapor plume as it mixed with varying amounts of meteoric fluid sericite in quartz sericite pyrite alteration on the periphery of the deposit and illite from areas of illite kaolinite alteration which overprints sodic potassic alteration and forms quartz illite pyrite alteration within the deposit are related to low salinity aqueous fluids that have a significant magmatic component 2 1 to 4 1 18 o and 76 to 67 d illite alteration which overprints both potassic alteration and quartz sericite pyrite alteration formed from fluids with a large meteoric component 9 1 to 4 8 18 o and 101 to 90 d the higher vein density and therefore higher permeability in the core of the deposit facilitated ingress of larger amounts of meteoric fluid compared with the more peripheral region advanced argillic alteration and associated high grade mineralization are related to a second pulse of magmatic fluid which did not intersect the two phase field during cooling and depressurization the fluid contracted to form a 3 wt nacl equivalent aqueous fluid that resulted in a sericite pyrite bornite digenite bearing assemblage with a magmatic signature 4 6 to 6 5 18 o and 108 to 102 d at 340 c cooling and mixing of this fluid with meteoric water resulted in a fluid that formed a pyrophyllite quartz sericite chalcopyrite bearing assemblage 8 9 to 0 6 18 o and 110 to 96 d at 300 c compared to older potassic and sodic potassic alteration the advanced argillic alteration has a highly depleted d signature which is attributed to degassing of a crystallizing intrusive fluid source

two step deglaciation at the oxygen isotope stage 6 5e transition the zeifen kattegat climate oscillation comparison of marine lacustrine and terrestrial records from twenty four sites suggests the existence of a younger dryas type climate oscillation just prior to the oxygen isotope stage 6 5e boundary these records include results from biostratigraphic pedostratigraphic and speleothem studies as well as analyses of stable isotope compositions of marine records and ice cores the climate oscillation is named after the warm zeifen interstadial and the cold kattegat stadial the zeifen interstadial may be related to a major meltwater pulse in the baffin bay labrador sea norwegian sea region the climate oscillation is presumably in part a result of a variation in ocean circulation especially in the strength of the north atlantic drift but changes in the atmospheric circulation also played an important role the geographically widespread distribution of the oscillation suggests that the two step deglaciation influenced both the northern and southern hemispheres c 1996 elsevier science ltd

a review of the geological characteristics and geodynamic setting of late paleozoic porphyry copper deposits in the junggar region xinjiang uygur autonomous region northwest china abstract in this review we describe the geological characteristics of porphyry copper deposits in junggar region xinjiang and place these into their metallogenic tectonic context these porphyry copper deposits are mainly found in four metallogenic belts 1 a late silurian to early devonian cu mo metallogenic belt in the qiongheba area 2 the late devonian kalaxiange er cu metallogenic belt 3 the early carboniferous xilekuduke suoerkuduke porphyry skarn cu mo metallogenic belt and 4 the late carboniferous baogutu porphyry cu metallogenic belt the ages of mineralization can be divided into three broad intervals

dating of fossil shells with electron spin resonance electron spin resonance esr dating of sea shells has been made using the paramagnetic defects produced by natural radiation the total dose of natural radiation of the materials termed the archaeological dose has been determined from esr signals of defects in sea shells from northern japan whose ages are known from the sediments or from the radioisotope dating an annual dose of about 0 03 0 04 rad yr explains the age of shells from a few thousand to a million years the new method of esr dating will be useful for sediment age determination and for other geological studies

formal stratigraphy of the neopleistocene middle and upper late pleistocene in the kola region nw russia abstract this paper presents available litho chrono biostratigraphy data on sediment sequences in the kola region derived from russian publications based on this compilation key sections have been suggested for primary stratigraphic subdivisions or horizons according to the general quaternary stratigraphic chart of russia the regional quaternary scheme is correlated with the international chart summarizing the available data 10 geological sections have been proposed as key sites sections for the middle and upper late neopleistocene horizons in different sections in the southern kola peninsula the most ancient deposits correspond to the chekalinsky early saalian mis 9 horizon which is identified by esr dating and multi proxy data and also to the moskovsky late saalian mis 6 horizon specified according to litostratigraphic data the last interglacial glacial cycle relates to the mikulinsky entire mis 5 podporozhsky mis 4 leningradsky mis 3 and ostashkovsky mis 2 horizons two marine events identified in key sections on the coastal kola peninsula correspond to the last interglacial mikulinsky mis 5 horizon they are referred to as the ponoi and strelna beds in the regional stratigraphic classification the third marine unit is correlated to the interstadial leningradsky mis 3 horizon key sections in the central and western kola region provide the interglacial and interstadial terrestrial sequences there is a high probability that litho biostratigraphy data and a single numerical ir osl dating testify to the glacial podporozhsky mis 4 horizon deposits in coastal natural outcrops and boreholes in the lovozero tundra mountains key sections of the ostashkovsky mis 2 horizon have not been referred to in the formal kola region stratigraphy yet

middle pleistocene marine deposits on the kola peninsula nw russia abstract a unique middle to late pleistocene site is situated in the southern part of the kola peninsula on the right bank of the lower varzuga river providing for the first time valuable evidence concerning middle pleistocene climate change and a marine transgression event during this period the corresponding strata are exposed in a 2 km long natural outcrop traceable along the abrupt slope of the river valley where the fluvial erosion and slumping have dissected a remnant elongated hill middle pleistocene marine deposits compose here the basal part of the sedimentary succession lithological sedimentological and structural field study accompanied by esr dating of mollusc shells taken from marine sediments and a detailed palynological investigation have been carried out the basal part of the varzuga section is represented by superposition of consolidated clay loam sandy loam with subfossil mollusc shells and small lenses of coarse grained sand and pebbles unit 1 marine shells were esr dated between 319 0 38 5 ka and 316 0 23 6 ka glacial diamicton and glacifluvial sands unit 2 probably also middle pleistocene in age overlay the marine sediment with sharp contact the uppermost part of the sequence consists of the late pleistocene marine sediments glacial diamicton glacifluvial sand and presumably late glacial and early holocene lacustrine deposits one hundred samples of marine unit 1 and lowermost part of glacial unit 2 deposits were palynologically reinvestigated on the basis of detailed palynostratigraphy 19 pollen assemblage zones were identified recurring vegetative assemblages characterized by increasing quantity of betula with occurrence of mesophilous and thermophilous components alnus quercus tilia ulmus carpinus corylus osmunda nuphar nymphaea indicate five middle pleistocene warm events mostly during marine isotope stage mis 9

long term palaeoenvironmental changes recorded in palynologically studied loess palaeosol and esr dated marine deposits of northern eurasia implications for sea land correlation abstract original materials of pollen analysis and esr chronostratigraphic studies provided a basis for reconstruction chronological subdivision and inter regional correlation of palaeoclimatic events and sediments of palaeo shelf glacial periglacial and extra glacial regions of northern eurasia within the scope of the brunhes epoch chronostratigraphic position of the identified palaeoenvironmental events and corresponding horizons in the composite chronostratigraphic column is established on the base of esr analyses of subfossil mollusc shells collected from marine freshwater and terrestrial deposits the palyno chronostratigraphic record displays a sequence of 8 intervals the holocene included of warm climate and high sea level stands when marine sedimentation occurred on palaeo shelves and 7 glacial epochs the alternating intervals are either fully recorded as complete glacial interglacial rhythms or represented by a large enough number of consecutive climatic phytocoenotic phases the rhythmic regularity in the sequence of glacial and interglacial events has been inferred from detailed palynological data on reference sections of loess palaeosol series in the centre of the east european plain arapovichi otkaznoe likhvin strelitsa sections a clear agreement between long pollen record directly dated warm climate related deposits and other records of palaeoenvironmental evolution known from literature has been established for the upper 15 oxygen isotope stages ois 15 to 1 finally we come to a conclusion that the integrated climate chronological sequence may be taken as a basis for inter regional correlations of palaeo shelf and terrestrial sediments within northern eurasia it may be used as an intermediate link in the continent ocean correlations

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

stable isotope geochemistry of the pierina high sulfidation au ag deposit peru influence of hydrodynamics on so42 h2s sulfur isotopic exchange in magmatic steam and steam heated environments abstract the pierina high sulfidation au ag deposit formed 14 5 my ago in rhyolite ash flow tuffs that overlie porphyritic andesite and dacite lavas and are adjacent to a crosscutting and interfingering dacite flow dome complex the distribution of alteration zones indicates that fluid flow in the lavas was largely confined to structures but was dispersed laterally in the tuffs because of a high primary and alteration induced permeability the lithologically controlled hydrodynamics created unusual fluid temperature and ph conditions that led to complete so 4 2 h 2 s isotopic equilibration during the formation of some magmatic steam and steam heated alunite a phenomenon not previously recognized in similar deposits isotopic data for early magmatic hydrothermal and main stage alunite 34 s 8 5 to 31 7 18 o so 4 4 9 to 16 5 18 o oh 2 2 to 14 4 d 97 to 39 sulfides 34 s 3 0 to 4 3 sulfur 34 s 1 0 to 1 1 and clay minerals 18 o 4 3 to 12 5 d 126 to 81 are typical of high sulfidation epithermal deposits the data imply the following genetic elements for pierina alteration mineralization 1 fluid and vapor exsolution from an i type magma 2 wallrock buffering and cooling of slowing rising vapors to generate a reduced h 2 s so 4 6 highly acidic condensate that mixed with meteoric water but retained a magmatic 34 s s signature of 1 3 so 2 disproportionation to hso 4 and h 2 s between 320 and 180 c and 4 progressive neutralization of laterally migrating acid fluids to form a vuggy quartz alunite quartz clay intermediate argillic propylitic alteration zoning magmatic steam alunite has higher 34 s 8 5 to 23 2 and generally lower 18 o so 4 1 0 to 11 5 18 o oh 3 4 to 5 9 and d 93 to 77 values than predicted on the basis of data from similar occurrences these data and supporting fluid inclusion gas chemistry imply that the rate of vapor ascent for this environment was unusually slow which provided sufficient time for the uptake of groundwater and partial to complete so 4 2 h 2 s isotopic exchange the slow steam velocities were likely related to the dispersal of the steam column as it entered the tuffs and possibly to intermediate exsolution rates from magmatic brine the low d values may also partly reflect continuous degassing of the mineralizing magma similarly data for steam heated alunite 34 s 12 3 to 27 2 18 o so 4 11 7 to 13 0 18 o oh 6 6 to 9 4 d 59 to 42 are unusual and indicate a strong magmatic influence relatively high temperatures 140 to 180 c based on 18 o so 4 oh fractionations and partial to complete sulfur isotopic exchange between steam heated sulfate and h 2 s restricted lithologically controlled fluid flow in the host tuffs allowed magmatic condensate to supplant meteoric groundwater at the water table and create the high temperature low ph conditions that permitted unusually rapid so 4 2 h 2 s isotopic equilibration 50 300 days and or long sulfate residence times for this environment late void filling barite 34 s 7 4 to 29 7 18 o so 4 0 4 to 15 1 and later void filling goethite 18 o 11 8 to 0 2 document a transition from magmatic condensate to dominantly meteoric water in steam heated fluids during cooling and collapse of the hydrothermal system these steam heated fluids oxidized the top 300 m of the deposit by leaching sulfides redistributing metals and precipitating barite acanthite gold and goethite hematite gold steam heated oxidation rather than weathering was critical to forming the orebody in that it not only released encapsulated gold but likely enriched the deposit to ore grade au concentrations

pleistocene collapse of the west antarctic ice sheet some glacial sediment samples recovered from beneath the west antarctic ice sheet at ice stream b contain quaternary diatoms and up to 108 atoms of beryllium 10 per gram other samples contain no quaternary diatoms and only background levels of beryllium 10 less than 10 6 atoms per gram the occurrence of young diatoms and high concentrations of beryllium 10 beneath grounded ice indicates that the ross embayment was an open marine environment after a late pleistocene collapse of the marine ice sheet

pleistocene climatic stratigraphy and environments of the terek kuma lowland nw caspian sea region inferred from palynological paleomagnetic and rodent records of the long otkaznoye sediment sequence abstract the paper presents the results of a high resolution palynological paleomagnetic and microtheriological study of the pleistocene sediment sequence at otkaznoye in the eastern ciscaucasian foreland a sequence which is unique in its stratigraphic completeness and thickness 160 m the sequence includes loess paleosol alluvial and alluvial proluvial beds the detailed climatostratigraphic subdivision of the otkaznoye sequence allows a correlation of the established paleoclimatic record with the global marine isotope stages the past climatically induced variability in the landscape of the terek kuma lowland is reconstructed for all neopleistocene i e middle and late pleistocene interglacial and glacial periods and for some intervals during the later early pleistocene stages

esr dating of quaternary shells recent advances abstract this paper deals with the key problems of the esr dating of subfossil mollusc shells the estimation of the stored palaeodose of natural radiation it is shown that the use of the analytical line or peak in the integrated spectrum at g 2 0012 0 0001 with the half width 0 6 mt seems most advisable for the estimation of the relative concentration of radiation defects equivalent to the stored palaeodose in the calcareous shell skeleton optimal esr spectrometer settings have been determined results of esr dating of subfossil mollusc shells from eemian deposits of boreal transgression are discussed

first wind shear observation in pmse with the tristatic eiscat vhf radar c american geophysical union reprinted with permission article also available at source https doi org 10 1002 2016ja023080

erratum to severnaya zemlya arctic russia a nucleation area for kara sea ice sheets during the middle to late quaternary quaternary science reviews 25 21 22 2006 2894 2936 abstract quaternary glacial stratigraphy and relative sea level changes reveal at least four expansions of the kara sea ice sheet over the severnaya zemlya archipelago at 79 n in the russian arctic as indicated from tills interbedded with marine sediments exposed in stratigraphic superposition and from raised beach sequences that occur at altitudes up to 140 m a s l chronologic control is provided by ams 14c electron spin resonance green stimulated luminescence and aspartic acid geochronology major glaciations followed by deglaciation and marine inundation occurred during mis 10 9 mis 8 7 mis 6 5e and mis 5d 3 the mis 6 5e event associated with the high marine limit implies ice sheet thickness of 2000 m only 200 km from the deep arctic ocean consistent with published evidence of ice grounding at 1000 m water depth in the central arctic ocean till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively suggesting wet based ice cap advance followed by cold based regional ice sheet expansion local ice caps over highland sites along the perimeter of the shallow kara sea including the byrranga mountains appear to have repeatedly fostered initiation of a large kara sea ice sheet with exception of the last glacial maximum mis 2 when kara sea ice did not impact severnaya zemlya and barely graced northernmost taymyr peninsula

the late pleistocene palaeoenvironmental evolution in northern eurasia through the prism of the mollusc shell based esr dating evidence abstract long term investigations devoted mostly to the eurasian arctic sedimentary deposits have provided dated climatic sequence within the late pleistocene period most of the dates ca 315 were obtained by electron spin resonance esr method on marine mollusc remains taken directly from transgressive marine sedimentary deposits here it is shown that the climatic signature revealed in the studied sedimentary sequences can be compared by proxy and chronologic correlation with the climatic signals recorded in different parts of the continent from deposits of marine freshwater and terrestrial origin the resulting climate chronostratigraphic record allow the last interglacial to be placed approximately between 145 140 ka and 70 ka with concentration of overwhelming majority of the warm climate related dates ca 82 in the second half of marine isotope stage mis 5 in the time range between 110 and 70 ka this evidence coincides with integrative multidisciplinary results derived from the south eastern coast of the gulf of finland they show unambiguously that the second half of the mis 5 sequence at least between ca 94 ka and 71 ka reflects the fully interglacial character of the studied deposits the climate chronostratigraphic record within mis 3 displays a sequence of three successive palaeoenvironmental events 59 0 52 0 ka 47 5 40 0 ka and 32 4 24 8 ka which are interpreted as the consequence of large scale climate amelioration during which marine sedimentation occurred on palaeo shelves what is now dry land the consistency of the parallel comparative dating results obtained in this study by different methods both the numerical and relative exemplify the potential of palaeodosimetric dating methods mainly used in this study mollusc shell based electron spin resonance esr and feldspar based infrared optically stimulated luminescence ir osl to chronologically organize the sequence of the late pleistocene palaeoenvironmental events and to improve understanding of the palaeoenvironmental evolution during this period

how long and how stable was the last interglacial abstract surface ocean indicators in the north atlantic during marine isotope stage mis 5 correlate closely with the vegetational succession in northeastern france the melisey i silty layer which marks the end of the last interglacial biozone in la grande pile pollen record appears coeval with the polar front advance c24 registered in the core v29 191 by a sharply increased presence of ice rafted detritus and the cold water foraminifer neogloboquadrina pachyderma sinistral since this event is younger than the peak of mis 5d the last interglacial as recognized in northern france correlates not only with the mis 5e but also with a substantial part of mis 5d the last interglacial in la grande pile was twice as long as the holocene and the climate in its first half was apparently not less stable than during the current interglacial if the future natural climates were to develop as analogs of the past then the onset of the next glacial environments on land would be still many millennia ahead

mineralogic and stable isotope zonation at the surface over the el salvador porphyry copper deposit chile we examined in detail the mineralogic and stable isotope characteristics of alteration minerals exposed at the surface of the el salvador porphyry copper deposit a total of 276 samples was collected from 203 localities over an area of 5 km 2 at elevations between 2 900 and 3 300 m the alteration assemblages can be separated into two groups broadly corresponding to the stages previously identified from underground studies although the early stage k silicate alteration identified underground is not evident at the surface a transitional to late stage is characterized at the surface by assemblages of 1 muscovite andalusite with trace diaspore including some areas rich in andalusite and 2 muscovite with trace diaspore there is a sharp contact outward with a marginal propylitic assemblage chlorite calcite epidote pyrophyllite occurs as a retrograde overprint of muscovite in both of the transitional to late stage assemblages these assemblages are concentrically zoned and centered on a core of least altered granodiorite porphyry a late intramineral intrusion the muscovite andalusite assemblage occurs up to 500 m away from the granodiorite porphyry and andalusite rich zones are located near the brecciated margin of the porphyry further outward is the muscovite zone from 500 to 1 500 m wide the pyrophyllite overprint overlaps the contact of the muscovite andalusite and muscovite zones and occurs mainly above 3 000 m elevation such that its present distribution is controlled largely by topography very late alteration minerals occur in radial pebble dikes of hydrothermal breccia and their extensions and they are dominated by an advanced argillic assemblage of alunite aluminum phosphate sulfate minerals diaspore zunyite pyrophyllite dickite with residual muscovite in one case a breccia extends upward and appears to be the root of a 300 500 m outcrop 80 m thick of massive quartz alunite replacement of rhyolite pure mineral separates were prepared from these samples for o h and s isotope analysis including 48 samples of silicate minerals muscovite pyrophyllite dickite and supergene kaolinite and 20 samples of alunite some supergene in origin information on mineral assemblage was used to estimate temperatures of formation which then allowed calculation of the isotopic composition of associated hydrothermal fluids the fluid responsible for forming the muscovite had a relatively narrow range of isotopic composition 6 5 1 5 per mil 18 o and 40 10 per mil d the heaviest 18 o and d values about 8 and 35 per mil respectively were obtained from the samples with andalusite muscovite diaspore assemblage this composition is close to that expected for a magmatic fluid with 10 to 20 percent meteoric water component responsible for forming the other muscovite samples the fluid compositions calculated for the very late stage alunite range from 5 and 30 per mil to 1 and 40 per mil 18 o and d respectively this range in composition agrees with the trend predicted for magmatic vapor absorbed by local groundwater the latter similar in composition to that responsible for forming the supergene kaolinite there is no systematic spatial zonation of the alunite samples in terms of isotopic composition or paleotemperature the temperature estimates from s isotope geothermometry are higher than those based on mineral assemblage possibly caused by partial supergene replacement of some hypogene alunites there is no strong isotopic zonation of hydrothermal minerals from surface alteration assemblages at el salvador that can be applied to generate clear exploration guidelines by contrast mapping of alteration mineralogy in the field backed up by laboratory checking of mineralogy and examination of relict minerals and replacement textures in thin section clearly indicates the center of the late intramineral intrusion

3 d radar imaging of e region field aligned plasma irregularities by using multireceiver and multifrequency techniques this paper reports the first use of a 3 d radar imaging for observing e region field aligned plasma irregularities fais in the midlatitude ionosphere five carrier frequencies equally spaced between 46 25 and 46 75 mhz were transmitted alternately with consecutive radar pulses and 20 receivers were employed for receiving the radar echoes the experiments were carried out using the middle and upper atmosphere radar 34 85 n 136 10 e with the radar beams steered to the geographic north and 6 6 north by east at the zenith angles of 51 0 and 51 5 respectively the 2 d imaging with the echoes collected by the 19 of the 20 receivers revealed that in zonal dimension the off beam direction of arrival doa of the echo region changed alternately between positive and negative values which can be attributed to the highly localized fais drifting zonally through the radar beam on the other hand the off beam doa in meridional dimension was negative and positive respectively at higher and lower range locations which were supposed to be due to the meridional drift component of fais a combination of 5 frequencies and 19 receivers achieved a 3 d imaging of the fai structures illustrating small scale fai striations and bubblelike plasma structures in the radar volume moreover declination of geomagnetic field line was examined from the imaged 3 d brightness distribution in the radar volume the estimated declination of geomagnetic field line was in agreement with that computed from the international geomagnetic reference field model in 2011 this paper has demonstrated some capabilities of radar imaging for ionospheric investigation

stratified interglacial lacustrine sediments from baffin island arctic canada chronology and paleoenvironmental implications abstract thirteen of 18 piston cores recovered from robinson lake in the mid arctic vegetation zone of baffin island arctic canada penetrated stratified lacustrine sediment beneath a thin over consolidated diamict till and postglacial lacustrine sediment the sub till lacustrine units are up to 120 cm thick of which the upper several decimeters frequently contain thick layered mats of aquatic moss pollen and diatoms are common throughout both lacustrine units a series of 23 ams 14c dates defines the chronology of the postglacial sequence which records a succession from a pioneer grass and oxyria dominated tundra between 10 4 and 8 ka bp to a sedge dominated tundra after 8 ka bp limiting 14c dates place the sub till lacustrine sediments more than 40 ka bp 10 luminescence dates centered on 85 ka indicate they were deposited late in oxygen isotope stage ois 5 the dominance of shrub and tree pollen especially shrub birch and alder in sub till lacustrine samples indicates low arctic tundra farther north than at any time during the holocene pollen concentrations are comparable to or higher than in the holocene units cooling late in the interglacial is indicated by declining birch and alder pollen percentages in the upper part of the section diatom floras in both the sub till and postglacial lacustrine sequences indicate similar development of lake water chemistry but input of silica and weathering products was greater in the older lake cycle suggesting more vigorous catchment processes macrofossils in the sub till units are characteristic of lakes ice free in summer based on pollen assemblages indicating local and regional vegetation diagnostic of summer temperatures higher than the holocene we interpret the sub till lacustrine units to be of interglacial character by analogy with holocene plant succession in central and eastern canada all of keewatin and labrador ungava must have been ice free throughout this interval suggesting essentially complete deglaciation of the laurentide ice sheet at the time

eustatic sea level and climate changes over the last 600 ka as derived from mollusc based esr chronostratigraphy and pollen evidence in northern eurasia we reconstruct and correlate palaeoclimatic events and deposits from shelf glacial periglacial and extraglacial zones of northern eurasia over the last 600 000 years the chronostratigraphical correlation of identified palaeoenvironmental and sealevel events and corresponding horizons is based on electron spin resonance esr analysis of subfossil mollusc skeletal remains from marine freshwater and acheulian bearing cave site deposits over 230 shell samples from more than 40 sites along the continental margin of eurasian north in the black and caspian sea basins and terrestrial shells from a lower palaeolithic cavesite in the northern caucasus were dated via esr to produce a late quaternary geochronology the pleistocene composite section of the loess palaeosoil formation includes two reference sections likhvin and arapovichi from the centre of the easteuropean plain the palyno chronostratigraphic record is interpreted as the product of six warm climate high sea level events including the current interglacial and six glacial events they are presented either as complete climatic rhythms of glacial and interglacial rank or by considerable portions of climatic phytocoenotic phases constituents of the rhythm the full interglacial conditions are centred at about 580 400 310 220 and between 145 70 calendar ka a broad correspondence between long palynological sequence directly esr dated warm climate related events and other palaeoenvironmental records described in the literature has been noted for 11 upper oxygen isotope stages 11 to 1 the results obtained in this study exemplify the potential of integrated chrono climatostratigraphic sequences in linking marine and terrestrial palaeoclimate records that may eventually span the whole brunhes chron d 2002 elsevier science b v all rights reserved

a multi proxy evidence for the transition from estuarine mangroves to deltaic freshwater marshes southeastern brazil due to climatic and sea level changes during the late holocene abstract the present study investigates a paleo estuary at the doce river delta southeastern brazil through a multi proxy approach that links palynology diatoms sedimentology and geochemistry analyses i e total c total n 13 c and 15 n these analyses temporally synchronized with five radiocarbon ages revealed environmental changes from marine to continental over the last 7550 years the studied sedimentary succession recorded the upward transition from estuarine channel until 7550 cal yr bp to estuarine central basin 7550 to 5250 cal yr bp deposits the latter containing increased mangrove vegetation marine and marine brackish water diatoms the range of geochemical values 13 c 30 10 15 n 2 8 and c n 4 40 also indicate marine estuarine organic matter and c 3 terrestrial plants to that time interval a following period recorded two phases lake ria 5250 to 400 cal yr bp and fluvial channel 400 cal yr bp until modern age during this stage mangroves were replaced by trees shrubs and herbs grasses due to the disconnection with the marine realm as a result the corresponding sediments contain only organic matter sourced from freshwater and c 3 terrestrial plants 13 c 29 26 15 n 0 8 and c n 10 45 the equilibrium between fluvial sediment supply and relative sea level changes during the holocene controlled the morphologic and vegetation changes in the studied littoral the estuary became established during the early holocene as a resulted of a eustatic sea level rise when the fluvial sediment supply to the coast was relatively lower due to a dry period however during the late holocene the climatic force was more significant to the development of coastal morphology due to a wet period that caused an increase in sandy sediment supply to coastal system then the increase of fluvial discharge associated to a relative sea level fall caused a marine regression and shrinkage of mangroves during the late holocene the evaluation of mangrove dynamics according to climatic and sea level changes mainly during the late holocene is essential for the understanding of their survival ability under future scenarios with a probable accelerated sea level rise and intensification of extreme climatic events in southeastern brazil for the next century

duration and structure of the past four interglaciations reanalysis and additional dating of the devils hole 18o paleotemperature record confirm that the last interglaciation in the great basin the continental analog of marine isotopic substage 5e lasted 22 000 yr consistent with the vostok paleotemperature record which suggests a duration of 19 000 yr for this event in antarctica the three preceding interglaciations in the devils hole record analogs of marine isotopic substages 7e 9c and 11c range from 20 000 to 26 000 yr in duration a 20 000 yr duration for the last interglaciation is consistent with tims uranium series dated sea level high stands thus the widely held view that interglaciations were of 11 000 to 13 000 yr duration and constituted only about 10 of mid to late pleistocene climatic cycles needs reexamination the warmest portion of each interglaciation in the devils hole time series is marked by a 18o plateau signifying apparent climatic stability for periods of 10 000 to 15 000 yr duration

geology and reconnaissance stable isotope study of the oyu tolgoi porphyry cu au system south gobi mongolia the oyu tolgoi porphyry cu au system in the south gobi desert mongolia comprises five deposits that extend over 6 km in a north northeast oriented zone they occur in a middle to late paleozoic arc terrane and are related to late devonian quartz monzodiorite intrusions the hugo dummett deposits are the northernmost and deepest with up to 1 000 m of premineral sedimentary and volcanic cover rock remaining they are the largest deposits discovered to date and characterized by high grade copper 2 5 cu and gold 0 5 2 g t mineralization associated with intense quartz veining and several phases of quartz monzodiorite intruded into basaltic volcanic host rocks sulfide minerals in these deposits are zoned outward from a bornite dominated core to chalcopyrite upward to pyrite enargite and covellite at shallower depth the latter high sulfidation state sulfides are hosted by advanced argillic alteration mineral associations this alteration is restricted mainly to dacitic ash flow tuff that overlies the basaltic volcanic rock and includes ubiquitous quartz and pyrophyllite kaolinite plus late dickite veins as well as k alunite al phosphate sulfate minerals zunyite diaspore topaz corundum and andalusite a reconnaissance oxygen hydrogen and sulfur isotope study was undertaken to investigate the origin of several characteristic alteration minerals in the oyu tolgoi system with particular emphasis on the hugo dummett deposits based on the isotopic composition of o h and s 18o so4 8 8 20 1 d 73 to 43 34s 9 8 17 9 the alunite formed from condensation of magmatic vapor that ascended to the upper parts of the porphyry hydrothermal system without involvement of significant amounts of meteoric water the isotopic data indicate that pyrophyllite 18o 6 5 10 9 d 90 to 106 formed from a magmatic fluid with a component of meteoric water muscovite associated with quartz monzodiorite intrusions occurs in the core of the hugo dummett deposits and isotopic data 18o 3 0 9 0 d 101 to 116 show it formed from a magmatic fluid with water similar in composition to that which formed the pyrophyllite mg chlorite 18o 5 5 d 126 is a widespread mineral retrograde after hydrothermal biotite and may have formed from fluids similar to those related to the muscovite during cooling of the porphyry system by contrast paragenetically later and postmineralization alteration fluid which produced dickite 18o 4 1 to 3 3 d 130 to 140 shows clear evidence for mixing with substantial amounts of meteoric water relatively low d values 140 for this meteoric water component may indicate that its source was at high elevations the geologic structure nature of alteration styles of mineralization and stable isotope data indicate that the oyu tolgoi deposits constitute a typical porphyry system formed in an island arc setting the outward zonation of sulfide minerals for the hugo dummett deposits from a bornite dominated core to chalcopyrite and pyriteenargite can be interpreted to be related to a cooling magmatic hydrothermal system which transgressed outward over enclosing advanced argillic alteration this resulted in some unusual alteration and sulfide parageneses such as topaz or pyrite enargite and tennantite entrained by high grade bornite

late quaternary multiple incised valley systems an unusually well preserved stratigraphic record of two interglacial valley fill successions from the arno plain northern tuscany italy

the esr age of portlandia arctica shells from glacial deposits of central latvia an answer to a controversy on the age and genesis of their enclosing sediments abstract the occurrence of portlandia arctica shells in glacigenic sediments of central latvia had created a controversy in many publications about 1 their age ranging from the holsteinian to the late weichselian and 2 the genesis of their enclosing sediments glacial glaciomarine or marine our reinvestigation of the main object of controversy the licupe site leads to a conclusion that the sedimentary package of diamictons clays and sands containing portlandia arctica shells and marine microfossils is a large glacial raft that had been transported and deposited by the riga lobe during the weichselian the electron spin resonance esr ages on five sets of portlandia arctica shells from the licupe and daugmales tom ni sites range from 86 0 6 8 to 105 0 9 2 ka bp these esr age determinations and the cool climate indicators of the associated microflora and microfauna suggest that their source sediments probably in the gulf of riga are marine clays of early weichselian age probably correlative to the brorup interstadial in central latvia portlandia arctica shells and their enclosing clay occur resedimented or translocated in glacial deposits during weichselian glacial advances

late pleistocene stratigraphy according to the sediment sequence from eastern kola peninsula ponoi river valley north western russia abstract the sedimentary sequence from the local stratotype section of the mikulinian mis 5 marine deposits at the ponoi river valley easternmost kola peninsula north western russia has been investigated to define the geological and numerical ages and chronostratigraphic position of a marine unit identified previously as a lithostratigraphic unit of the lower part of the mikulinian and named the ponoi beds in the regional kola stratigraphic scheme the new data indicate that the ponoi beds has two part sedimentary succession which was formed during two successive interglacial boreal and belomorian marine transgressions in the mikulinian mis 5 time the lower clay part of this succession accumulated in the interglacial marine basin until c 96 ka under favourable environmental and climatic conditions the upper sandy part of this lithostratigraphic formation also previously attributed to the ponoi beds accumulated in the late mikulinian marine basin about 70 ka ago under relatively cold and damp climate conditions in accordance with our new data obtained in this study it has to be attributed to another marine unit referred to as the strelna beds formed during the second belomorian interglacial marine transgression also during the mikulinian time formerly the strelna beds was correlated with the podporozhian mis 4 horizon in the current regional kola stratigraphic scheme both the ponoi and strelna beds marine sediments have to be related and linked with the marine basin during mis 5 these marine units have to be correlated with the mikulinian mis 5 horizon

imaging coherent scatter radar incoherent scatter radar and optical observations of quasiperiodic structures associated with sporadic e layers 1 during june and july 2002 a 30 mhz imaging coherent scatter radar was installed and operated on the island of st croix to view the e region ionosphere above arecibo puerto rico during the observing period 10 events with discernible quasiperiodic echo structure were observed with the coherent scatter radar in six of those events simultaneous measurements were made with the arecibo 430 mhz incoherent scatter radar the imaging coherent scatter radar allows us to locate and track the echo structures within the volume illuminated by the transmitter which shows structures that are generally aligned along wavefronts a slight preference for motion of the structures toward the southwest is evident throughout the period but the propagation directions and speeds vary greatly the incoherent scatter radar measurements show a close correspondence between the occurrence of the coherent echoes and the location of the enhanced electron density structures in particular the coherent echoes occur when the electron density layers show uplifts

new palaeontological assemblage sedimentological and chronological data from the pleistocene ma u oi cave northern vietnam abstract this paper describes recent material gathered during the second fieldwork at ma u oi in november 2002 by a vietnamese french japanese team the ma u oi cave located in the province of hoa binh 60 km sw from hanoi northern vietnam belongs to a karstic network developed in triassic dark grey limestones the cave is filled with coarse grained breccias containing numerous fossil remains partially preserved at several loci inside the cave wall vault and ground we describe new teeth which confirm the occurrence of mammal taxa already mentioned at ma u oi bacon et al 2004 bacon a m demeter f schuster m long v t thuy n k antoine p o sen s nga h h huong n t m 2004 the pleistocene ma u oi cave northern vietnam palaeontology sedimentology and palaeoenvironments geobios 37 305 314 while others mainly microvertebrates emphasize the occurrence of new species for the pleistocene of vietnam we report here for the first time the occurrence of these microvertebrates of different groups primates rodents insectivores small reptiles and amphibians in the faunal assemblage among mammal taxa the presence of one more hominid affiliated to archaic homo is also attested by our findings u th dating carried out on 2 samples extracted from breccia speleothems confirms the biochronological estimate with fossiliferous fillings ranging from late middle pleistocene to late pleistocene

differences between the last two glacial maxima and implications for ice sheet δ18o and sea level reconstructions studies of past glacial cycles yield critical information about climate and sea level ice volume variability including the sensitivity of climate to radiative change and impacts of crustal rebound on sea level reconstructions for past interglacials here we identify significant differences between the last and penultimate glacial maxima lgm and pgm in terms of global volume and distribution of land ice despite similar temperatures and radiative forcing our analysis challenges conventional views of relationships between global ice volume sea level seawater oxygen isotope values and deep sea temperature and supports the potential presence of large floating arctic ice shelves during the pgm the existence of different glacial modes calls for focussed research on the complex processes behind ice age development we present a glacioisostatic assessment to demonstrate how a different pgm ice sheet configuration might affect sea level estimates for the last interglacial results suggest that this may alter existing last interglacial sea level estimates which often use an lgm like ice configuration by several metres likely upward

incursion of meteoric water triggers molybdenite precipitation in porphyry mo deposits a case study of the chalukou giant mo deposit there has been a long term debate about the timing of the incursion of meteoric water into porphyry systems and whether it plays an important role in ore precipitation to evaluate the role of meteoric water in the mineralization in porphyry mo deposits typical hydrothermal veins of different stages from the chalukou giant porphyry mo deposit are selected for combined scanning electron microscope cathodoluminescence sem cl fluid inclusion microthermometry and high resolution secondary ion mass spectroscopy sims oxygen isotope analyses multiple generations of quartz are identified in almost all of the veins the barren quartz veins and quartz magnetite veins of the early mo mineralization stage are dominated by granular cl bright quartz emq1 which usually shows dissolution and re deposition textures and are overprinted by cl dark quartz emq2 filled healed fractures the molybdenite precipitation in the quartz molybdenite veins of the main mo mineralization stage is synchronous with small volumes 85 of cl bright quartz mmq1 similar to the quartz molybdenite veins the precipitation of pyrite in the quartz pyrite veins during the transitional stage and sphalerite in the quartz sphalerite pyrite veins during the zn pb mineralization stage are also directly associated with cl dark quartz tsq2 zpq2 the sims oxygen isotopic values of emq1 and mmq1 fall into the range of 5 42 9 79 o with calculated equilibrium fluid compositions of 2 07 6 45 0 indicating a magma dominated fluid composition whereas mmq2 tsq2 and zpq2 have very low oxygen isotopic values from 4 68 to 4 29 parts per thousand with corresponding fluid compositions of 13 64 to 5 94 parts per thousand implying that the fluid formed by the mixing of magmatic water and a large proportion of meteoric water the contrasting sem cl features and oxygen isotopic compositions of the two generations of quartz in the quartz molybdenite veins demonstrate that the incursion of meteoric water into the hydrothermal system occurred earlier than the molybdenite precipitation based on these results and the crosscutting relationships and spatial distribution of the veins we reconstructed the quartz evolutionary sequence during the vein development process after the early precipitation of barren quartz the reduction in fluid pressure from lithostatic to hydrostatic conditions allowed the incursion of convecting cool meteoric water into the relatively hot hydrothermal system and the temperature of the evolved mo rich fluid decreased rapidly from 500 degrees c to 400 degrees c leading to concentrated molybdenite precipitation with small volumes of quartz fluid cooling resulting from the incursion of meteoric water may have played a greater role in the metal precipitation in the chalukou mo deposit than wallrock interactions and fluid boiling moreover this process may have also occurred in other porphyry mo deposits

pueblo viejo high sulfidation epithermal gold silver deposit dominican republic a new model of formation beneath barren limestone cover a discussion sillitoe et al 2006 suggest that the pueblo viejo au ag deposit is younger than its early cretaceous los ranchos formation host rocks this interpretation contrasts with our earlier observations that the mineralization is coeval with the los ranchos formation although a younger age would allow pueblo viejo to be conveniently grouped with many other high sulfidation deposits in a subaerial calc alkaline setting evidence for it conflicts with geologic observations in and around the deposit the new interpretation of the age of mineralization depends largely on the contention that the hatillo limestone which overlies the los ranchos formation was replaced along its basal contact by silica and magnetite that are coeval with pueblo viejo mineralization in their figure 2 p 1429 sillitoe et al show two silicified and iron oxide bearing zones along the poorly exposed base of the hatillo limestone outliers one of these zones is along the southern edge of the pueblo viejo mine where mine workings and exploration drill holes immediately south of the contact provide good exposures in this area the contact which is tectonized locally ranges from a basal conglomerate with silicified cobbles to calcareous sandstone siltstone mudstone with abundant marine fossils silicified cobbles require that silicification preceded deposition of the hatillo limestone similarly carbonaceous sediments containing silicified boulders and cobbles and underlying fragmental rocks with clasts exhibiting different alteration assemblages are widespread in the mine area russell and kesler 1991 fig 3 sillitoe et al 2006 do cite one outcrop containing veinlets of iron oxide limonite with marginal silicification russell and kesler 1991 p 210 211 as evidence of silicification and iron oxides in the basal few meters of the hatillo limestone they acknowledge however that we interpreted these features as paleo supergene which they clearly are furthermore they are

sedimentary evolution of a late pleistocene temperate red algal reef coralligene on rhodes greece correlation with global sea level fluctuations autochthonous red algal structures known as coralligene de plateau occur in the modern warm temperate mediterranean sea at water depths from 20 to 120 m but fossil counterparts are not so well known this study describes from an uplifted coastal section at plimiri on the island of rhodes a 450 m long by 10 m thick late pleistocene red algal reef coralligene facies interpreted as being a coralligene de plateau and its associated deposits the coralligene facies constructed mainly by lithophyllum and titanoderma sits unconformably upon the plio pleistocene rhodes formation and is overlain by a maerl facies 2 m a mixed siliciclastic carbonate facies 0 2 m and an aeolian sand facies 2 5 m the three calcareous facies of heterozoan character are correlated with established members in the lindos acropolis formation in the north of the island while the aeolian facies is assigned to the new plimiri aeolianite formation the palaeoenvironmental and genetic stratigraphic interpretations of these mixed siliciclastic carbonate temperate water deposits involved consideration of certain characteristics associated with siliciclastic shelf and tropical carbonate shelf models such as vertical grain size trends and the stratigraphic position of zooxanthellate coral growths integration of these results with electron spin resonance dates of bivalve shells indicates that the coralligene facies was deposited during marine isotope stage 6 to 5e transgressive event ca 135 to 120 ka in water depths of 20 to 50 m and the overlying maerl facies was deposited during regression from marine isotope stage 5e to 5d ca 120 to 110 ka at water depths of 25 to 40 m the capping aeolian sand facies involving dual terrestrial subunits is interpreted as having formed during each of the glacial intervals marine isotope stages 4 71 to 59 ka and 2 24 to 12 ka with soil formation during the subsequent interglacial periods of marine isotope stages 3 and 1 respectively accumulation rates of about 0 7 mm year 1 are estimated for the coralligene facies and minimum accumulation rates of 0 2 mm year 1 are estimated for the maerl facies the existence of older red algal reefs in the plimiri region during at least marine isotope stages 7 245 to 186 ka and 9 339 to 303 ka is inferred from the occurrence of reworked coralligene type lithoclasts in the basal part of the section and from the electron spin resonance ages of transported bivalve shells

the red chris porphyry copper gold deposit northern british columbia canada igneous phases alteration and controls of mineralization red chris is a late triassic porphyry cu au mo deposit in the stikinia island arc terrane in northern b c late triassic sedimentary and volcanic rocks of the stuhini group host a series of late triassic to early jurassic 204 198 ma diorite to quartz monzonite stocks and dikes the red chris deposit is hosted in the 204 ma red stock the largest 6 5 1 5 km and most altered intrusion in the area volcanic rocks approximately time equivalent with the stock are exposed 2 km to the southwest and west postmineral early and middle jurassic sedimentary rocks unconformably overlie the stuhini group and red stock to the south and southeast the composite red stock consists of multiple phases of crowded porphyries 30 65 plagioclase hornblende biotite phenocrysts including abundant premineral p1 leucodiorite multiple subphases of synmineral p2 quartz monzonite porphyries and volumetrically minor late mineral monzonite p3 and monzodiorite p4 porphyries the stock evolved from subalkaline to silica saturated alkalic composition with the mineral related p2 porphyries being high k calcalkalic and high sr y common septa of stuhini biotitic hornfels are entrapped within the stock minor postmineral weakly altered mafic dikes cut the stock the zone of 0 25 cu equiv cu au is 2 km long wsw ene and up to 650 m wide early a type quartz veins with disseminated bornite accompanied biotitic and k feldspar magnetite alteration which was coeval with p2 porphyries higher cu and au grades correlate in a general way with zones of more abundant a veins chlorite carbonate epidote actinolite replaced hornblende peripheral to biotitic alteration and chlorite overprinted much of the secondary biotite late alteration affected all porphyry phases and is subdivided into earlier sericite clay pyrite and later low sulfide carbonate clay hematite late sericite clay pyrite alteration sulfidized much of the primary bornite to chalcopyrite with or without pyrite and carbonate clay hematite alteration converted most magnetite to hematite highest cu au grades 2 cu equiv occur in and around the early and intermediate stage p2 porphyries zoning of cu au au cu ratios sulfides and quartz veins is centered and mostly symmetrical around a core of high grade cu au within and surrounding apices of p2 porphyry contact relationships confirm the close association of p2 porphyry phases with cu au zones of 50 ppm mo surround the highest grade cu au zone at depth west northwest and east northeast strike slip to oblique slip faults offset sulfide cu au and mo patterns several lines of evidence indicate 15 to 20 of southward tilt since the system formed due to glaciation oxidation is very thin and supergene enrichment negligible red chris was previously considered by most workers as an alkalic or hybrid alkalic deposit new chemical data on synmineral porphyry phases instead suggest high k calc alkalic composition similar to the monzonitic cu mo au class of porphyry deposits which includes bingham and bajo de la alumbrera red chris is also classified as an a vein type deposit due to strong control of higher grade cu au by a vein stockworks with abundant disseminated cu sulfides

ore genesis and fluid evolution of the daheishan giant porphyry molybdenum deposit ne china abstract the daheishan giant porphyry mo deposit is located at the eastern segment of the caob ne china the ore bearing intrusion of daheishan deposit is a jurassic granitic complex that includes changgangling biotite granodiorite qiancuoluo seriate granodiorite and qiancuoluo granodioritic porphyry mineralization consists of disseminated breccia and veined types the hydrothermal fluids show significant magmatic signatures as evidenced by the hydrogen and oxygen isotopic compositions of quartz and sulfur isotopic characteristics of ores consistence of lead isotopic compositions of the sulfides and the daheishan intrusive complex further indicate a close relationship between the mineralization and magma the fluid inclusions in quartz comprise of predominant aqueous two phase as well as gas rich fluid inclusions and a small number of daughter mineral bearing inclusions the gas species in the fluid inclusions are h2o co2 n2 ch4 c2h6 ar and minor h2s the liquid compositions are so42 cl na k ca2 and mg2 raman spectroscopy on individual fluid inclusions reveals a main gaseous composition of h2o minor h2s and co2 the fluid system in daheishan mo deposit can be described as nacl kcl h2o type fluid inclusion microthermometry reveals subsolidus homogenization temperatures for fluid inclusions in the magmatic quartz phenocrysts th 400 450 c salinities 21 eq wt suggesting an obliteration of higher temperature history of the porphyry system by the superimposed processes most of the mineralization occurred at temperature range of 220 360 c or higher the temperature and salinity decreased to 100 170 c and 0 15 eq wt respectively when the hydrothermal fluid activities were gradually ending no distinct evolution pattern based on the homogenization temperature or stable isotopic analyses is observed among the different mineralization stages mineralization was supposed to be related to the multi phased boiling of fluids instead of the gradual cooling of fluids pressure may be more critical than temperature in controlling the precipitation of molybdenite

record of a mid pleistocene depositional anomaly in west antarctic continental margin sediments an indicator for ice sheet collapse abstract modern global warming is likely to cause future melting of earth s polar ice sheets that may result in dramatic sea level rise a possible collapse of the west antarctic ice sheet wais alone which is considered highly vulnerable as it is mainly based below sea level may raise global sea level by up to 5 6 m despite the importance of the wais for changes in global sea level its response to the glacial interglacial cycles of the quaternary is poorly constrained moreover the geological evidence for the disintegration of the wais at some time within the last ca 750 kyr possibly during marine isotope stage mis 11 424 374 ka is ambiguous here we present physical properties palaeomagnetic geochemical and clay mineralogical data from a glaciomarine sedimentary sequence that was recovered from the west antarctic continental margin in the amundsen sea and spans more than the last 1 myr within the sedimentary sequence proxies for biological productivity such as biogenic opal and the barium aluminum ratio and the supply of lithogenic detritus from the west antarctic hinterland such as ice rafted debris and clay minerals exhibit cyclic fluctuations in accordance with the glacial interglacial cycles of the quaternary a prominent depositional anomaly spans mis 15 mis 13 621 478 ka the proxies for biological productivity and lithogenic sediment supply indicate that this interval has the characteristics of a single prolonged interglacial period even though no proxy suggests environmental conditions much different from today we conclude that if the wais collapsed during the last 800 kyr then mis 15 mis 13 was the most likely time period apparently the duration rather than the strength of interglacial conditions was the crucial factor for the wais drawdown a comparison with various marine and terrestrial climate archives from around the world corroborates that unusual environmental conditions prevailed throughout mis 15 mis 13 some of these anomalies are observed in the pelagic southern ocean and the south atlantic and might originate in major ice sheet drawdown in antarctica but further research is required to test this hypothesis

petrology of philippine geothermal systems and the application of alteration mineralogy to their assessment abstract philippine geothermal systems occur in the vicinity of large holocene calc alkaline volcanic complexes wells drilled in these areas encountered multiple intrusions the latest dikes are the subsurface manifestations of the youngest heat source commonly at least two hydrothermal regimes are juxtaposed in a single area with the latest being in equilibrium with the present temperature and chemical regime alteration by neutral ph water is pervasive and abundant a contact metamorphic aureole also occurs near intrusives alteration due to acid sulfate fluids is generally confined to permeable structures neutral ph alteration is divided into four zones on the basis of key clay minerals and two subzones are defined by calc silicates these are the smectite ambient to 180 c transition 180 230 c illite 230 320 c and biotite 270 340 c zones subzones are defined by epidote 250 340 c and amphibole 280 340 c the four main zones of acid alteration are kaolinite ambient to 120 c dickite kaolinite 120 200 c dickite pyrophyllite 200 250 c and pyrophyllite illite 230 320 c where relict high temperature alteration reaches the surface the area being drilled is usually the outflow zone of the present system these hydrothermal mineral assemblages are used 1 as geothermometers 2 to assist in determining the depth at which the production casing will be set during drilling 3 to estimate fluid ph and other chemical parameters 4 to predict possible corrosion and scaling tendencies of the fluids 5 as a measure of permeability and possible cold water influx into wells 6 as a guide to field hydrology and 7 to estimate roughly the thickness of the eroded overburden

climatic oscillations 10 000 155 000 yr b p at owens lake california reflected in glacial rock flour abundance and lake salinity in core ol 92 earlier wetter cycles the lake overflowed to fill a series chemical analyses of the acid soluble and clay size fractions of of downstream basins including china lake basin searles sediment samples 1500 yr resolution reveal oscillations of lake valley panamint valley and ultimately death valley salinity and of glacial advances in core ol 92 back to 155 000 yr smith and street perrott 1983 in 1992 the u s geological b p relatively saline conditions are indicated by the abundance survey drilled a 323 m deep core ol 92 into owens lake of carbonate and smectite both pedogenic and authigenic re sediments near the depocenter of the basin to obtain a continflected by ca sr and mg in the acid soluble suite and by cs2o uous record of silty clay sediment spanning the last 800 000 excess mgo and loi loss on ignition in the clay size fraction yr a multiparameter reconnaissance study of the entire core rock flour produced during glacial advances is represented by ca 7000 yr resolution reported in a 13 chapter summary the abundance of detrital plagioclase and biotite in the clay size volume smith and bischoff 1997 revealed cycles characfraction the ratio of which remains essentially constant over the terized by closed and overflowing lake conditions entire time span these phases are quantitatively represented by na2o tio2 ba and mn in the clay fraction the rock flour record we report here the results of a second part of an intermediindicates two major ice advances during the penultimate glacial ate resolution study aimed at resolving shorter term events cycle corresponding to marine isotope stage mis 6 no major over just the past 155 000 yr using sediment samples of ca advances during the last interglaciation entire mis 5 and three 1500 yr resolution taken over the uppermost 90 m of olmajor advances during the last glacial cycle mis 2 3 and 4 92 the companion study menking et al 1997 reports on the ages of the latter three correspond rather well to 36 cl dates grain size tic total inorganic carbon content and stable reported for sierra nevada moraines the onset of the last intergla isotopic measurements proxies which tend to reflect variaciation is shown by abrupt increases in authigenic caco3 and an tions in water flow and which are most representative of abrupt decrease in rock flour at about 118 000 yr b p according variations during closed lake conditions the present study to our time scale in contrast the boundary appears to be gradual was concerned primarily with seeking a proxy for glacial in the d 18 o record in which the change from light to heavy values advances we found that the mineralogy and chemistry of begins at about 140 000 yrs b p the exact position of the termination therefore may be proxy dependent conditions of high car the clay fraction provide indices of glacial rock flour we bonate and low rock flour prevailed during the entire period from also report on the composition of the acid soluble carbonate 118 000 yr b p until the glacial advance at 53 000 yr b p signaled fraction which gives further detail on closed lake conditions

the late pleistocene duoi u oi cave in northern vietnam palaeontology sedimentology taphonomy and palaeoenvironments this paper describes new fossil materials recovered at the duoi u oi site in december 2003 by a vietnamese french japanese team the duoi u oi cave is located in man duc village 25 km of hoabinh city in northern vietnam it belongs to a karstic network developed in a dark grey micritic marine limestone dated from the lower to the middle triassic the sedimentary fill produced a rich mammalian fauna essentially composed of isolated teeth of middle to large sized mammals artiodactyla perissodactyla proboscidea carnivora rodentia primates and characteristic of late pleistocene the results of the duoi u oi fieldwork are of great interest for the following reasons 1 the biochronological age of the fauna is consistent with 230 th 234 u 238 u dating from the calcitic floors 6673 ka the duoi u oi fauna is thus the oldest well dated modern fauna known for the southeast asian mainland 2 in terms of sedimentology the analysis of the formation of the fossiliferous breccia and that of the processes of deposits shows a close relation between the karstic deposits inside the cave and the deposits in the alluvial terraces the observation of three levels of alluvial terraces associated with three caves situated at 62 10 and 3 m above the present alluvial plain suggests that exokarstic and endokarstic sediments evolved together 3 in terms of palaeobiogeography duoi u oi is the continental fauna showing the strongest resemblance with the late pleistocene faunas from indonesian islands punung gunung dawung lida ajer sibrambang and djambu caves this implies that at the time of duoi u oi ca 70 ka the sundaland was mainly characterised by faunas of modern aspect 4 the analysis of major taphonomic factors that led to the mammal assemblage reveals a combination of selective agents selective role of predators and porcupines selective destruction of age classes for some species selective preservation of fossils due to the deposition processes in the karstic network which contribute to the poor representation of the diversity of the fauna no arguments show that humans present at duoi u oi might have a possible role in the taphonomic process 5 the palaeoenvironmental reconstruction based on the composition of the faunal assemblage suggests a forested area and some open habitats under warm and humid conditions

sporadic e ionization layers observed with radar imaging and ionospheric modification sporadic e ionization layers have been observed in the daytime subauroral ionospheric e layer by a 30 mhz radar in alaska the radar detects coherent backscatter from meter scale field aligned plasma density irregularities the irregularities were generated by ionospheric modification by the emission of strong hf electromagnetic waves directly beneath the layers making the layers visible to the radar aperture synthesis methods are used to generate imagery of the layers from the radar data the layers are patchy with patches organized along fronts spaced by tens of kilometers and propagating slowly toward the southwest similar naturally occurring layers are commonly observed at middle latitudes at night in the absence of ionospheric modification that the patchy layers can be found at high magnetic latitudes during the day argues that they are most likely produced through the interaction of the ionospheric layer with neutral atmospheric waves and instabilities attenuation of the radar echoes when the hf emission frequency exceeded the third harmonic of the electron gyrofrequency was observed and is discussed

the role of the deep ocean in north atlantic climate change between 70 and 130 kyr ago the suggestion1 that changes in north atlantic deep water nadw production are linked through surface heat flux to the atmospheric temperature over greenland is supported by earlier indications2 3 that nadw production decreased during glacial times and by the subsequent finding4 6 that it declined during the younger dryas cool period at the end of the last glaciation changes in north atlantic surface temperatures have been found7 to mirror high frequency temperature changes recorded in greenland ice cores over the past 80 kyr but the connection to abyssal circulation has yet to be established except for one or two isolated oscillations8 9 here we present carbon and oxygen isotope analyses of benthic foraminifera in a high resolution north atlantic deep sea sediment core for the period 70 130 kyr ago these data allow us to reconstruct the history of nadw production which shows a close correlation with greenland climate variability for much of this time interval suggesting that the climate influence of nadw variability was widespread we see no evidence however for changes in nadw production during substage 5e the eemian interglacial period in contrast with recent ice core data10 which suggest severe climate instability in greenland during this time period our results may support suggestions based on data from a second ice core that this apparent instability is an artefact caused by ice flow11 alternatively the eemian climate instability may have had a different origin from the subsequent climate events

late pleistocene in the southeastern white sea and adjacent areas arkhangelsk region russia stratigraphy and palaeoenvironments abstract an overview of the late pleistocene and holocene stratigraphy of the southeastern white sea region is presented in the paper based upon the analysis of published data new results and correlation between marine and terrestrial archives the pleistocene stratigraphic record in the southeastern white sea region begins with mikulino horizon which comprises the whole mis 5 and is composed of marine sediments sands sandy clays and clays with boreal arctic boreal and lusitanean boreal microfauna and mollusc fauna dated back at 161 77 ka the podporozhie horizon in the southeastern white sea region comprises the mis 4 71 57 ka complex of marine mostly near shore sediments the glaciation during mis 4 was localized on one hand within the kola peninsula on the other hand the glacier probably overlapped the kanin peninsula and the mezen bay however the gorlo strait was not blocked and the northward river outflow was preserved the leningrad horizon had been formed also in the marine sedimentation pattern during the mis 3 57 29 ka however the lack of data in the region allows us to make only the comparative analysis the ostashkov horizon mis 2 29 11 7 ka is composed of the deposits of glacial paragenetic series tills glaciofluvial glaciomarine and glaciolacustrine deposits but also comprises the deglaciation late glacial sedimentary complex including marginal tills the holocene stratigraphic record is subdivided into three stages 11 7 9 5 9 5 3 5 and 3 5 0 ka bp and do not match with new formal stratigraphic subdivision of the holocene series

pleistocene marine deposits in the coastal areas of kola peninsula russia abstract on the basis of field data datings from both electron spin resonance and optically stimulated luminescence and micro and macrofauna in addition to presence of diatoms three late pleistocene marine units have been identified in the coastal areas of the kola peninsula the stratigraphically lowest sequence is correlated to the ponoi beds and the boreal transgression attributed to the marine isotope stages mis 5e to 5d in the white sea depression and to mis 5e to 5c in the barents sea thermophilic fauna and diatoms indicate normal water salinity and a water temperature above zero the second marine unit referred as the strel na beds can be correlated with the early weischselian transgression termed the belomorian transgression with low water salinity and a water temperature similar or colder than the present times belomorian transgressions are reliably detected in the white sea and are not clearly found in the barents sea the results obtained from the sediments of the ponoi and strel na beds indicate a continuously existing marine reservoir from 130 to 80 70 ka ago entire mis 5 in the white sea depression the early middle weichselian barents kara ice sheet invasion and its recession might have caused the glacioeustatic middle weichselian mis 3 transgression and the third late pleistocene marine sequence has been deposited in the regressing shallow cold sea with less saline waters the results help in the understanding of the history of late quaternary ice sheets in north eurasia and provide evidence for the debatable early and middle weichselian marine events

the mo deposits of northeast china a powerful indicator of tectonic settings and associated evolutionary trends abstract northeast ne china lies in the eastern sector of the central asian orogenic belt caob that connects with the circum pacific orogenic belt in the east and accommodates multistage magmatism crustal growth and mineralization in this region 69 mo only or mo dominated and 9 cu mo deposits have been discovered including 65 deposits ranking medium size 10 kt mo metal or larger in tonnage and containing a total resource of 10 5 mt mo metal six giant and seventeen large deposits have total reserves of 6 7 and 3 1 mt mo respectively these deposits occur in the areas surrounding the songliao basin including the northern margin of the north china craton the great hingan range and the ji hei fold belt and have been formed during paleozoic and mesozoic tectono magmatic events all the mo only or mo dominated deposits were formed in the mesozoic postdating the closure of the paleo asia ocean and in a series of pulses around 250 200 ma 200 160 ma 160 130 and

esr dating evidence for early man at a lower palaeolithic cave site in the northern caucasus as derived from terrestrial mollusc shells eight terrestrial shell samples from recent excavations at treugolnaya triangular cave northern caucasus were analysed by electron spin resonance esr to produce a chronology for the most ancient acheulian bearing layers of the cave site the lifetime of the 2 0012 centre used for dating is about 3 108 at 53c that allows to date the multi level sequence of the cave site at least in the range of the last one million years the dating results obtained suggest that the rst from the bottom archaeological layer 7a is likely to be about 583 000a old and the next 5b is some 393 000 a old these layers can be correlated with oxygen isotope stages 15 and 11 respectively the estimates obtained imply that man presumably reached the northern caucasus at least as early as the beginning of stage 15 i e much earlier than generally recognised the leaving of the cave by ancient man due to development of glacial environment during the subsequent stage s can probably be linked with the penetration of man to the southern areas of the east european plain 2000 elsevier science ltd all rights reserved

a 150 000 year climatic record from antarctic ice during much of the quaternary the earth s climate has undergone drastic changes most notably successive glacial and interglacial episodes the past 150 kyr includes such a climatic cycle the last interglacial the last glacial and the present holocene interglacial a new climatic time series for this period has been obtained using 18 o data from an antarctic ice core

zircon u pb geochronology geochemistry and sr nd hf isotopes of granitoids in the yulekenhalasu copper ore district northern junggar china petrogenesis and tectonic implications abstract the yulekenhalasu porphyry copper deposit is located in the kalaxiange er metallogenic belt in northern junggar china we present the results from zircon u pb geochronology and geochemical and sr nd hf isotope analyses of the granitoids associated with the ore deposits with a view to constrain their petrogenesis and tectonic setting the granitoids consist of quartz diorite diorite porphyry porphyritic monzonite and quartz porphyry emplaced at 382 379 375 374 and 348 ma respectively which span late devonian to early carboniferous ages the ore bearing intrusion is mainly diorite porphyry with subordinate porphyritic monzonite the late devonian intrusions are characterized by sio2 contents of 54 5 64 79 wt na2o contents of 3 82 8 24 wt enrichment in na light rare earth elements lrees and large ion lithophile elements they also display relative depletion in y ba p nb ta and ti and weak negative eu anomalies eu 0 6 0 87 the early carboniferous quartz porphyry is characterized by high sio2 content 72 26 73 35 wt enrichment in lrees k and sr and relative depletion in y 10 82 12 52 ppm and yb 1 06 1 15 ppm the late devonian and early carboniferous granitoids are characterized by positive end t values 5 2 10 1 one sample at 1 9 positive ehf t values 7 46 18 45 low 87sr 86sr i values 0 70363 0 70476 and young crustal residence ages these data indicate that the sources of the granitoids were mainly mantle derived juvenile rocks geochemical and nd sr hf isotopic data demonstrate that the late devonian granitoids formed in an oceanic island arc and they were formed from different sources among which the mineralized diorite porphyry might have originated from a mixed slab derived and mantle wedge melt source the early carboniferous quartz porphyry was likely emplaced in a mature island arc environment and was probably derived from juvenile crust

dating and characterization of polymorphic transformation of aragonite to calcite in pleistocene bivalves from rhodes greece by combined shell microstructure stable isotope and electron spin resonance study absolute dating of diagenesis is a challenging yet significant problem reconstructing the depositional and diagenetic history of a late pleistocene coralligene type red algal reef and overlying maerl red algal sand from the plimiri coastal cliff se island of rhodes greece is enabled using a combination of microstructure stable isotope analyses and electron spin resonance of large bivalve shells partially altered by diagenesis these shells consisting of both original shell aragonite and polymorphic transformed rims now consisting of neomorphic spar provide the opportunity to date the primary age when the shells were precipitated as well as the age of their polymorphic transformation the contamination of samples presented a significant problem for interpreting ages based on data from electron spin resonance esr alone however sample contamination was evaluated with quantitative xrd providing the opportunity to apply corrections which increased reliability of the ages the carbon and oxygen stable isotope values and the neomorphic spar microtexture suggested that the polymorphic transformation at plimiri took place in a meteoric environment with a high and increasing fluid rock ratio the electron spin resonance dates combined with the vertical sedimentary evolution allowed to assign the formation of the red algal reef to the marine isotope stages 6 to 5e transgressive event ca 135 to 120 ka and to identify meteoric diagenetic phases during possibly the marine isotope stage 5d and the upper marine isotope stage 5c to lower 3 the use of electron spin resonance dating of neomorphic spar and age correction for sample contamination is presented herein for the first time and the results suggest that it might provide a useful tool to date late pleistocene diagenesis

mid latitude e region field aligned irregularities observed with the mu radar fine structures e region field aligned irregularities were observed on june 24 25 1989 with the mu radar at shigaraki japan 34 9 n 136 1 e geomagnetic latitude 25 0 n the 3 2 m scale irregularities were observed with the mu radar in five main beam directions each of which was nearly perpendicular to the geomagnetic field at 100 km altitude doppler spectra were obtained every 20 s with a range resolution of 600 m field perpendicular echoes appeared from 2130 to 2330 lt and from 0400 to 1100 lt times that correspond to postsunset and postsunrise period in the e region a preliminary examination of the doppler spectra indicates spectral widths of 50 120 m s 1 and the mean doppler velocities are well below the ion acoustic speed these spectral characteristics are consistent with those obtained in the equatorial and auroral electrojets and have been attributed to the gradient drift instability the echoes observed during the postsunset and postsunrise periods showed quite different morphologies in the time height distribution for this reason they are classified into two types continuous and quasi periodic the appearance of the continuous echoes was mainly continuous in time and situated between 90 and 100 km altitude during the postsunrise period the appearance of the quasi periodic echoes was intermittent with periods of 5 10 min and situated above 100 km altitude during the postsunset period the quasi periodic echoes showed phase propagation toward the radar while the averaged mean doppler velocity was away from the radar by measuring the time delays in echo regions from five directions an apparent westward motion approximately 120 m s 1 of the irregularity regions was estimated

oyu tolgoi mongolia siluro devonian porphyry cu au mo and high sulfidation cu mineralization with a cretaceous chalcocite blanket the oyu tolgoi porphyry cu au mo deposit is located in the gobi desert of southern mongolia the deposit consists of three main mineralized zones north central and south oyu interpreted to constitute at least two separate porphyry copper centers oyu tolgoi is associated with a series of small structurally controlled stocks and dikes of monzonitic and dioritic composition which intrude a sequence of siluro devonian volcanic and sedimentary rocks country rocks consist of pillow basalt and basaltic andesite interbedded with fine grained clastic sedimentary horizons the sequence is interpreted to have formed in a subaqueous island arc volcanic environment which formed part of the extensive paleozoic tuva mongol arc these island arc rocks are covered by carboniferous terrigenous sequences and are intruded by carboniferous syenite and granite and permian alkaline granite much of the area is covered by poorly consolidated cretaceous sedimentary sequences central oyu consists of a multiple phase hydrothermal breccia crosscutting an altered fine grained feldspar porphyry containing porphyry type alteration and mineralization the breccia underwent texture destructive advanced argillic alteration characterized by several associations of quartz alunite dickite pyrophyllite sericite and zunyite plus lesser svanbergite and fluorite these associations overprint earlier formed k silicate and quartz sericite illite assemblages copper mineralization at central oyu is present in a supergene chalcocite blanket that formed at the expense of a pyrite rich hypogene chalcocite covellite tennantite arsenosul vanite sulvanite chalcopyrite bornite sulfide suite that accompanied the advanced argillic alteration event at south oyu a feldspar hornblende porphyry of monzonitic composition intrudes a sequence of fine grained andesite and basaltic andesite hypogene copper gold mineralization occurs as early magnetite rich pyrite poor quartz chalcopyrite bornite stockworks and sheeted veinlets hydrothermal alteration is composed of biotite and k feldspar with apatite and minor albite magnetite averages 7 to 10 vol percent and copper and gold grades vary sympathetically these early assemblages are overprinted by a sericite chlorite event with ore grade copper and erratic gold and molybdenum values and also by structurally controlled pyrite rich advanced argillic alteration k ar ages show that the hypogene copper gold mineralization at south oyu is latest silurian earliest devonian 411 3 ma and that the entire district was intruded by postmineralization syenite during the carboniferous 307 4 ma the supergene chalcocite blanket at central oyu formed in the early cretaceous earliest late cretaceous based on ages for supergene alunite of 117 1 and 93 1 ma which makes central oyu one of the oldest preserved chalcocite blankets in the world chalcocite blanket preservation was favored by climatic desiccation into the late cretaceous and the tertiary it is inferred that significant regional uplift took place at the silurian devonian boundary this synmineral ization uplift and erosion may have been in part responsible for the telescoping of the hydrothermal systems at oyu tolgoi including the superposition of epithermal style associations over higher temperature deeper seated assemblages typical of the porphyry environment

climate change dynamics in northern eurasia over the last 200 ka evidence from mollusc based esr chronostratigraphy and vegetation successions of the loess palaeosol records abstract the time span of the past 200 ka has been marked by many large scale global and regional climate changes between warmer and cooler conditions as is usually the case when studying the past palaeoenvironmental data become scarcer with increasing age therefore every detailed palaeoenvironmental record may be of special interest to quaternary geologists in terms of palaeoenvironmental reconstructions correlations and general stratigraphy of the quaternary in this paper we present a long palynological record of terrestrial flora and an esr dated marine record of global scale climatic variation obtained from a loess palaeosol sequence in the east european plain and continental margin of northern eurasia for the time span starting from the penultimate glacial period correlating with marine isotope stage mis 6 these records show that in combination they have a potential of assigning warm cold climate related deposits to the chronostratigraphically organised sequence of the late pleistocene palaeoenvironmental events

severnaya zemlya arctic russia a nucleation area for kara sea ice sheets during the middle to late quaternary quaternary glacial stratigraphy and relative sea level changes reveal at least four expansions of the kara sea ice sheet over the severnaya zemlya archipelago at 79 degrees n in the russian arctic as indicated from tills interbedded with marine sediments exposed in stratigraphic superposition and from raised beach sequences that occur at altitudes up to 140 m a s l chronologic control is provided by ams c 14 electron spin resonance green stimulated luminescence and aspartic acid geochronology major glaciations followed by deglaciation and marine inundation occurred during mis 10 9 mis 8 7 mis 6 5e and mis 5d 3 the mis 6 5e event associated with the high marine limit implies ice sheet thickness of 2000m only 200km from the deep arctic ocean consistent with published evidence of ice grounding at similar to 1000m water depth in the central arctic ocean till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively suggesting wet based ice cap advance followed by cold based regional ice sheet expansion local ice caps over highland sites along the perimeter of the shallow kara sea including the byrranga mountains appear to have repeatedly fostered initiation of a large kara sea ice sheet with exception of the last glacial maximum mis 2 when kara sea ice did not impact severnaya zemlya and barely graced northernmost taymyr peninsula