a sulfur carbon oxygen and strontium isotope study of the volcanic hosted el soldado manto type copper deposit chile the essential role of bacteria and petroleum strata bound manto type copper deposits of chile are a major source of copper and some deposits e g mantos blancos el soldado contain as much metal as do large porphyry copper deposits elsewhere el soldado 200 mt 1 35 cu the largest manto type copper deposit in the coastal cordillera of central chile is hosted by the rhyodacite basalt upper member of the marine lower cretaceous lo prado formation paragenetic studies indicate that the deposit formed in two stages the first was a low temperature stage stage 1 130 125 ma in which liquid petroleum migrated from underlying carbonaceous shales into the overlying host volcanic rocks and abundant framboidal pyrite developed in a paleopetroleum reservoir a later hydrothermal stage stage 2 ca 103 ma introduced copper and replaced earlier pyrite to form chalcopyrite bornite and chalcocite ores this study presents isotopic data that support bacterial sulfur reduction as the process that formed the essential precursor stage 1 pyrite and the participation of basinal fluids in the hydrothermal second stage a wide range of 34s values for early stage 1 pyrite 11 1 to 28 0 supports the hypothesis that low temperature incomplete sulfate reduction from connate seawater sulfate and fe enriched oil field brines took place in a compartmentalized petroleum reservoir by bacterial sulfate reduction with the exception of a small proportion of cu fe sulfides with 34s values between 2 0 and 2 0 per mil the bulk of stage 2 cu fe sulfides replaced earlier pyrite and mimic the broad range in 34svalues 12 7 and 19 0 of stage 1 pyrite sulfur from early pyrite was recycled with no significant homogenization fractionation or addition of new sulfur and indicates the essential role of hydrocarbons and bacteria in the formation of the deposit the 13c values of gangue calcite vary between 4 2 and 20 2 per mil and reflect a mixing of various proportions of oxidized pyrobitumen derived organic and inorganic carbon from the mineralizing fluid pyrobitumen in the ores has 13c values of 30 to 26 per mil consistent with it being a residue of the original liquid petroleum 18o values of k feldspar in both ore and barren samples are similar 12 0 12 7 and are compatible with the fluids being of metamorphic rather than magmatic origin the similar 18o ranges of calcite 2 7 and k feldspar 0 7 suggest that they formed from the same hydrothermal fluid and that the fluid was in equilibrium with the host rocks the 87sr 86sr ratios in calcite of 0 7041 to 0 7051 reflect isotopic ratios inherited from the subaerial andesitic rocks that overlay the deposit where the ore forming fluids are thought to have originated

in retrospect forty years of linking orbits to ice ages in 1976 it was demonstrated that tiny wobbles in earth s orbit led to the great ice age cycles of the past few million years this finding had wide implications for climate science and the details remain hotly debated today

determining the natural length of the current interglacial terglacials can be used to draw analogies with the present provided their duration is known here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar seesaw climate variability which requires ice sheets large enough to produce iceberg discharges that disrupt the ocean circulation we identify the bipolar seesaw in ice core and north atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice rafted debris the glacial inception during marine isotope sub stage 19c a close analogue for the present interglacial occurred near the summer insolation minimum suggesting that the interglacial was not prolonged by subdued radiative forcing 7 assuming that ice growth mainly responds to insolation and co2 forcing this analogy suggests that the end of the current interglacial would occur within the next 1500 years if atmospheric co2 concentrations did not exceed 240 5 ppmv

geochronology of the giant beiya gold polymetallic deposit in yunnan province southwest china and its relationship with the petrogenesis of alkaline porphyry abstract the beiya gold polymetallic deposit located at the junction of the sanjiang tethys himalaya orogenic belt and the yangtze craton in southwestern china is the largest gold deposit in the region mineralization mainly occurs in skarn which formed along the contacts between porphyry intrusions and limestone host rocks the ore formation process is suggested to be closely related to the himalayan age alkaline porphyries u pb dating of magmatic zircons from the beiya quartz syenite porphyry yields a weighted average 206 pb 238 u ages of 36 07 0 43 ma n 25 mswd 1 17 calculated isochron age of five molybdenite samples from beiya is 34 7 1 6 ma mswd 0 99 initial 187 os of 0 21 0 16 ppb which indicates that mineralization is coeval with the intrusion of the beiya alkaline porphyry this age is also in agreement with the results of apatite fission track analysis in the porphyry magmatic zircon e hf t values range from 7 4 to 0 1 which correspond to the two stage hf model with ages between 1112 ma and 1588 ma this finding suggests that the main source of porphyry was probably melting of thickened mesoproterozoic lower crust triggered by partial melting of the lithospheric mantle zircon ce iv ce iii ratios of ore related porphyry are high given that all eu n eu n ratios are above 0 4 which demonstrates that the magma source of the porphyry was highly oxidized which was favorable for cu au mineralization the medium re concentrations in molybdenite re 2 08 20 54 ppm suggest that the ore forming materials were characterized by mixed crustal mantle sources mineralization in the beiya deposit was one of the many metallogenic events related to the india eurasia collision that was responsible for the fertile deep sourced magmatism

modeling secondary oil migration with core scale data viking formation alberta basin the viking formation in the alberta basin contains approximately 88 7 x 106 m3 5 579 x 108 bbl of recoverable oil which migrated more than 200 km as indicated by oil source rock correlation simulating the mechanisms controlling secondary oil migration hydrodynamics buoyancy and permeability heterogeneity is beneficial for exploration but it remains extremely difficult to predict oil occurrences although core scale petrophysical data for the viking formation are abundant 69 000 core plugs the extent of fracture permeability and permeability alteration due to diagenesis are unknown moreover sampling bias may affect the permeability distribution in unpredictable ways numerical simulations of oil migration were conducted using the highest core plug measurement of permeability from each borehole to obtain an upper bound on oil migration velocities this permeability model is not appropriate for simulating stratigraphic entrapment of oil but it does reveal that core scale data are in the appropriate range of magnitude to have allowed significant oil migration regional groundwater flow was essential for charging several of the largest and most distant oil fields in the viking formation maximum core plug permeability data are useful for modeling the extent of secondary oil migration and may have applications to fluid flow and transport modeling in other foreland settings

the role of fission track dating in discrimination of provenance determination of single crystal ages by fission track dating analysis of zircons and subordinately apatites within a detrital heavy mineral assemblage together with frequency distribution and radial plot analysis of the measured ages permits identification of different age modes synopses are presented of published fission track provenance studies in north central victoria northeastern tasmania barbados the rockall trough the english wealden mexico utah and the central alps from authors

cretaceous to neogene cooling and exhumation history of the oetztal stubai basement complex eastern alps a structural and fission track study the central austroalpine oetztal stubai basement complex osk of the eastern alps together with its overlying sedimentary brenner mesozoic bmz and tectonic units upper austroalpine nappes underwent extension and exhumation during the cretaceous before its incorporation into the hanging wall of the neogene brenner normal fault during this late cretaceous to early tertiary deformation the brenner mesozoic and the immediately underlying uppermost part of the osk developed a strong stretching lineation within a near horizontal and often mylonitic foliation related to consistent top to ese directed transport quartz and calcite behaved ductilely throughout the area whereas dolomite shows a transition from brittle fracture in the north to plastic flow in the south consistent with the known cretaceous metamorphic temperature gradient the transition to crystal plastic flow of dolomite occurs at 480 c quartz textures indicate an increase in the contribution of prism glide together with a decrease in basal glide toward the south also consistent with the temperature gradient in the osk and bmz fission track analysis of both zircon and apatite along a n s profile in combination with existing data from the literature allows a continuous cooling path to be constructed for the osk cooling of the eastern osk started at 90 ma the thermal peak of metamorphism and ended some 30 myr later at near surface temperatures at 60 ma the northern region had already cooled below the upper limit of the apatite partial annealing zone whereas in the south cooling related to this exhumation phase stopped at temperatures between 100 and 200 c the ese directed shearing is interpreted as late cretaceous to early tertiary normal faulting that exhumed the osk and brought the upper austroalpine blaser and steinacher nappes into contact with the underlying brenner mesozoic the pattern of alpine metamorphic isograds established in the osk directly reflects the geometry and kinematics of this late cretaceous early tertiary exhumation due to low angle normal faulting

the middle permian hongshanliang manto type copper deposit in the east tianshan constraints from geology geochronology fluid inclusions and h o s isotopes abstract the hongshanliang copper deposit hosted in the tuff of the lower carboniferous yamansu formation is a typical copper deposit in the aqishan yamansu belt east tianshan based on crosscutting relationships of veins textural relationships and mineral assemblages five alteration mineralization stages at hongshanliang have been established chlorite sulfide stage stage i quartz pyrite stage stage ii quartz polymetallic sulfide stage stage iii late veins stage iv and supergene process stage v stage i has mineral assemblage of chlorite pyrite chalcopyrite quartz sericite and is commonly characterized by euhedral pyrite with silicates e g chlorite quartz and sericite and or chalcopyrite as its pressure shadow indicating an early mineralization event with apparent deformation stage ii is characterized by quartz pyrite chalcopyrite or locally quartz gypsum anhydrite pyrite veins cutting stage i chlorite pyrite the main mineralization stage stage iii at hongshanliang has typical mineral assemblages of quartz chalcopyrite chlorite calcite sericite quartz chalcopyrite sphalerite galena pyrite and quartz sphalerite galena chlorite with veins veinlets disseminations and local massive ore types similar to manto type copper deposits regarding mineralization and ore structures detailed fluid inclusion study shows temperature of fluids decreased from stage ii 307 484 c through stage iii peak at 160 180 c consistent with quartz chlorite oxygen isotope geothermometer of 190 c to stage iv 129 169 c with corresponding salinities of 2 7 26 2 wt nacl equiv peak at 8 wt 2 1 12 3 wt nacl equiv peak at 8 wt and 0 5 7 7 wt nacl equiv peaks at 4 6 wt respectively indicating an evolved hydrothermal ore forming system such fluid evolution can also be supported by h o isotopes during water rock reaction from stage ii 18ofluid 6 3 8 3 and dfluid 77 to 64 through stage iii 18ofluid 1 7 to 7 0 and dfluid 82 to 58 to stage iv 18ofluid 2 5 to 2 1 and dfluid 77 to 73 with a magmatic hydrothermal origin furthermore sulfur isotopes suggest that fluids of the two mineralization stages stage i and iii are predominantly magmatic hydrothermal with other influx contribution into the ore forming system i e minor early carboniferous seawater in stage i 34sfluid varying from 3 5 to 6 1 with peak at 0 and minor organic materials in stage iii 34sfluid varying from 6 5 to 4 1 with peak at 0 1 and detection of ch4 and c2h6 from fluid inclusions in combination of alteration paragenesis nature and source of ore forming fluids and comparison with other typical deposits we proposed that the hongshanliang copper deposit underwent two mineralization events with the main mineralization similar to manto type copper deposits 40ar 39ar dating of sericite from a massive chalcopyrite ore indicates the hongshanliang main mineralization formed at 269 0 0 4 ma generally coeval with regional k feldspar granite emplacement ca 272 ma integrating the regional tectonic setting magmatism and metallogenesis of the aqishan yamansu belt and the east tianshan we suggest that the aqishan yamansu belt has potential of mineral prospecting for the middle permian manto type copper deposits

a chlorine disinfectant for excess argon released from k felsspar during step heating abstract the release of excess 40 ar 40 ar e from virtually all alkali feldspars at low temperatures 40 ar 39 ar step heating experiments obscures potentially valuable age and thermal history information we report a method that takes advantage of the differential release of 40 ar e between contiguous isothermal heating steps due to the decrepitation of fluid inclusions and which permits derivation of a correction for the contaminating argon differences in age and cl k between successive temperature pairs commonly yield a single well correlated array on a 40 ar k versus cl k plot that identifies the cl correlated composition of 40 ar e 40 ar e cl affecting that sample eighteen of the twenty k feldspar samples we have measured yield a single 40 ar e cl component that varies from 1 1 10 3 to 4 2 10 6 making possible recovery of otherwise unobtainable thermochronological information the upper bound on the 40 ar e cl distribution of 10 3 may reflect ar saturation of pore fluids or the maximum duration between deuteric alteration and cooling below ar closure in k feldspar

thermal history of an early paleozoic epithermal deposit constraints from 40ar 39ar and u th he thermochronology at zhengguang eastern central asian orogenic belt abstract the zhengguang epithermal au zn deposit located in heilongjiang province ne china is an early paleozoic intermediate sulfidation epithermal deposit which is adjacent to the duobaoshan and tongshan porphyry cu deposits in the duobaoshan magmatic arc eastern central asian orogenic belt caob our new 40ar 39ar dating presents plateau ages of 276 9 1 2 ma mswd 1 5 for adularia and 265 7 1 2 ma mswd 3 5 for illite these ages are clearly younger than the mineralization age of zhengguang 480 ma and therefore represent a post ore event which reset the adularia and illite argon systems the resetting event could be related to post collision of xing an block and songliao xilinhot block the weighted mean of zircon u th he ages zhe and apatite u th he ages ahe from the same dacite porphyry with illite dating sample are 192 10 ma mswd 2 2 and 98 8 5 3 ma mswd 2 1 respectively the zhe age 190 ma indicates a tectonothermal resetting event possibly related to the development of tongshan fault whereas the ahe age 100 ma likely reflects 3 km deep burial at zhengguang the intra sample variations of u th he ages for zircon grains are mainly due to radiation damage while those for apatite are unknown we argue that the post ore volcanic eruption and slow uplift and exhumation rate caused by rollback of the paleo pacific plate could facilitate burial and preservation of the epithermal and by inference porphyry deposits in ne china considering the complex collisional and amalgamation history in this area we believe that there is exploration potential for ancient porphyry and epithermal deposits within the eastern section of the caob

the role of bitumen in strata bound copper deposit formation in the copiapo area northern chile in northern chile between 27 and 33 s there are numerous deposits where residual petroleum is associated with cu ag mineralisation the most famous being el soldado all of these deposits are hosted by lower cretaceous volcanic or volcanoclastic facies along the axis of a former backarc basin this close relationship suggests that the generation migration and emplacement of hydrocarbons in the cretaceous volcanic units is a regional process associated with the evolution of the cretaceous backarc basin and points to the importance of pyrobitumen as an exploration tool for similar cu ag deposits the present work analyses four small strata bound copper deposits located along a north south belt approximately 10 km east of copiapo in northern chile these deposits are typically hosted by pyrobitumen rich andesitic volcanic to volcanoclastic rocks intercalated with the marine carbonate pabellon formation the youngest formation within the chanarcillo group the strong genetic and spatial relationships between the pyrobitumen rich lavas and the mineral deposits allow us to define this volcanic belt as the ocoita pabellon metallotect two hydrothermal events can be distinguished based on the mineralogical textural fluid inclusion and isotope data of ore and gangue and on the optical properties of residual petroleum during the early event petroleum was mobilised from the source rocks into the primary and secondary porosity of the lavas by fe rich hydrothermal fluids which precipitated pyrite as an early sulphide phase the second event is characterised by cu rich hydrothermal fluids which induced three successive sub stages of cu sulphide precipitation the hydrothermal fluids chemically and thermally altered the first stage bitumen transforming it into pyrobitumen the present work documents similarities between the ocoita pabellon metallotect and the el soldado ore deposit and emphasises important differences in the el soldado host rocks a petroleum reservoir existed prior to the arrival of the mineralising hydrothermal fluids the framboidal pyrite was formed by assistance of bacteria the s of the cu sulphides was inherited from the pyrite and the fluid source was basin connate metamorphic brine in the ocoita pabellon metallotect the hydrocarbons were mobilised into the host rocks by hydrothermal fluids the pyrite is epigenetic the 34s values of pyrite and copper sulphides are very different with distinctive light 34s signature of cu sulphides 34s between 44 7 and 17 9 and the calculated 18o of hydrothermal fluids indicates the participation of meteoric water in the late phases of the hydrothermal system

argon loss by alkali feldspars abstract ar loss is generally thought to preclude the use of alkali feldspars for dating old rocks by the k ar method and has been thought to occur via structural features such as the boundaries of perthite lamellae or twins we have done a 40 ar 39 ar step heating study of a suite of alkali feldspars from the klokken syenite intrusion u pb age 1166 4 ma which have been fully characterized by transmission electron microscopy all are low albite low microcline intergrowths but some are non turbid strain controlled cryptoperthites while others are turbid coarse microperthites geological and textural evidence suggests that the turbidity developed by fluid rock interactions during the initial cooling of the pluton in the stability field of low microcline 5 a after crystallization the finest cryptoperthites have numerous fully coherent perthite lamellar boundaries lamellar periodicity 40 nm and twin composition planes the have retained radiogenic 40 ar and yield total degassing ages as high as 1125 16 ma and maximum ages on the age spectra of 1162 16 ma the coarse turbid microperthites with patchy intergrowths and twins on the mm scale gave total degassing ages as low as 650 ma maximum age 750 ma argon leakage occurs least in feldspars with the most lamellar interfaces but in proportion to the degree of turbidity which is thought to be caused by large numbers of micropores strain controlled intergrowths in perthites allow the recognition of volumes of alkali feldspar crystals which have not interacted with deuteric fluids these retain argon and can give reliable k ar ages in old rocks saddle shaped age spectra appear to result from the preferential degassing at 1000 c of part of the feldspar structure which has lost more of its argon in nature the laboratory degassing does not occur in a manner analogous to that which has occurred naturally

jurassic and early cretaceous island arc volcanism extension and subsidence in the coast range of central chile more than 2000 km 3 of acid and 9000 km 3 of basic volcanic rocks formed during the jurassic and early cretaceous in the coast range of central chile between 32 30 s and 34 s these rocks which constitute the major part of an 15 km thick pile of alternately marine and continental deposits issued from volcanic arcs situated between a land area with paleozoic basement in the west and a marginal sea in the east asthenospheric upwelling led to extension and bimodal volcanism the volcanic products were deposited in intra arc basins subsiding at high rates 100 300 m m y the source of the magmas became more depleted with time due to an increase in degree of partial melting and their compositions were modified by subduction related fluids and contamination with a progressively thinner and younger crust the basic lavas are of high k calc alkaline to shoshonitic affinity chemically resembling the lavas found in some mature island arcs in the western pacific the extension and subsidence resulted in a low relief topography close to sea level in contrast with the present day convergent type of andean volcanism at the same latitude where calc alkaline intermediate lavas erupt from volcanoes at great height above a thick crust

karst related outliers of the cretaceous chaswood formation of maritime canada the lower cretaceous chaswood formation is a terrestrial deposit preserved as scattered outcrops across maritime canada here we describe newly recognized outliers of the chaswood formation near windsor nova scotia a cretaceous age is confirmed only in bailey quarry where sediments are provisionally assigned a valanginian hauterivian 140 130 ma age based on palynology making them among the oldest known deposits of the chaswood formation at three nearby sites putative cretaceous sediments are recognized based on similar geological context facies and petrography however their age cannot be confirmed because sediments either lack palynomorphs or contain equivocal assemblages although the chaswood formation has been previously documented mainly in small tectonically generated basins these new found deposits are fluvial sands and gravels and lacustrine or floodplain clays associated with a karstified gypsum surface developed on the carboniferous windsor group deposits are preserved in karst val

age of mineralization by basinal fluids at the el soldado manto type copper deposit chile 40ar 39ar geochronology of k feldspar abstract manto type copper deposits of the southern central andes are strata bound epigenetic mineral concentrations hosted by bimodal volcanic and volcaniclastic rock suites they are economically important but since they are not obviously related to intrusions their genesis has been controversial to some extent because it has proven difficult to date the ore forming event and distinguish it from the age of low grade regional metamorphism el soldado the largest manto type copper deposit in central chile is hosted by marine volcanic and subvolcanic intrusive rocks of the lower cretaceous extensional arc to discriminate between regional metamorphism and mineralization we dated 11 samples of k feldspar by the stepwise heating 40 ar 39 ar method hydrothermally precipitated k feldspar associated with copper sulfides precipitated at temperatures of 300 c and range in age from 100 5 1 5 to 106 1 1 1 ma mean 103 1 6 ma n 8 syn mineralization k feldspar gave an age of 102 5 2 0 which is interpreted to be the age of mineralization k feldspar unrelated to ore yields older ages between 109 4 1 1 and 112 2 ma mean 110 3 1 4 ma n 3 is variably reset by the younger ca 103 ma mineralization episode the above ages are interpreted to represent the age of alkali redistribution and crystallization due to burial metamorphism of the host sequence fission track dating of apatite in the host rocks yields an age of ca 90 ma indicating fast cooling of the system to less than ca 100 c after mineralization time temperature modeling of fission track length data are compatible with initial fast exhumation followed by slow exhumation and cooling to surface temperatures high levels of atmospheric ar were detected in all k feldspar samples and are tentatively attributed to connate meteoric fluids incorporated into the basinal metamorphic mineralizing fluids

inverse modeling of annealing of fission tracks in apatite 2 application to the thermal history of the peace river arch region western canada sedimentary basin

the role of orbital forcing in the early middle pleistocene transition abstract the early middle pleistocene transition empt is the term used to describe the prolongation and intensification of glacial interglacial climate cycles that initiated after 900 000 years ago during the transition glacial interglacial cycles shift from lasting 41 000 years to an average of 100 000 years the structure of these glacial interglacial cycles shifts from smooth to more abrupt saw toothed like transitions despite eccentricity having by far the weakest influence on insolation received at the earth s surface of any of the orbital parameters it is often assumed to be the primary driver of the post empt 100 000 years climate cycles because of the similarity in duration the traditional solution to this is to call for a highly nonlinear response by the global climate system to eccentricity this eccentricity myth is due to an artefact of spectral analysis which means that the last 8 glacial interglacial average out at about 100 000 years in length despite ranging from 80 000 to 120 000 years with the realisation that eccentricity is not the major driving force a debate has emerged as to whether precession or obliquity controlled the timing of the most recent glacial interglacial cycles some argue that post empt deglaciations occurred every four or five precessional cycle while others argue it is every second or third obliquity cycle we review these current theories and suggest that though phase locking between orbital forcing and global ice volume may occur the chaotic nature of the climate system response means the relationship is not consistent through the last 900 000 years

the oldest pinus and its preservation by fire pinus pinaceae is a diverse conifer genus that dominates northern hemisphere forests today and is noteworthy for its fire adapted traits here we describe the oldest known fossils attributable to the genus from the lower cretaceous valanginian ca 133 140 ma part of the chaswood formation of nova scotia canada pinus mundayi sp nov comprises charred long shoots which show a constellation of derived characters including 1 axial resin ducts with thin walled epithelial cells in the secondary xylem and phloem 2 fenestriform or pinoid cross field pits and 3 helically arranged short shoots that pass through growth ring boundaries before distally diverging into two separate needle bases the fossils which are interpreted as remains of an evergreen two needle pine provide a new constraint on timetrees of pinaceae evolution their preservation as charcoal and the occurrence of resin ducts which produce flammable terpenes in modern pines show that pinus has co occurred with fire since its mesozoic origin

exploiting radiation damage control on apatite u th he dates in cratonic regions abstract apatites from four pairs of samples of precambrian basement from the western canadian shield were analyzed by u th he thermochronometry to test for the influence of radiation damage on apatite u th he dates in this cratonic region recent studies have demonstrated that the accumulation of radiation damage increases the apatite he retentivity so that apatites with a span of effective u concentrations eu that experienced the same thermal history may be characterized by a range of closure temperatures in this investigation each sample pair consisted of a mafic dike cross cutting felsic gneisses from a single outcrop or nearby outcrops that contained apatites with a span of eu the apatites yielded u th he dates from 846 to 123 ma and were positively correlated with eu within each sample pair these results can be explained using a model that tracks the evolution of he mobility in response to the accumulation of radiation damage when coupled with regional geological constraints the data appear to require partial to complete he loss due to burial and reheating in phanerozoic time new apatite fission track dates and length data were obtained for five of these samples the apatite fission track dates are proterozoic regardless of apatite eu thermal history simulations indicate that the apatite fission track data are compatible with the u th he results although the thermal histories are not identical in detail and the fission track results alone do not require phanerozoic heating together the data are consistent with burial of this region by 1 km of phanerozoic strata that were subsequently denuded thus pointing toward significant phanerozoic deposition in the north american cratonic interior hundreds of kilometers east of where previously documented the results suggest that exploiting radiation damage control on apatite u th he dates through investigation of surface sample apatites with a span of closure temperatures can impose tighter restrictions on thermal histories in low relief cratonic landscapes than was previously possible

is the spectral signature of the 100 kyr glacial cycle consistent with a milankovitch origin spectral analysis techniques traditionally applied to proxy climate records have involved the use of specialized windowing functions because of the finite length of the record available these have the effect of artificially broadening the spectral peaks such that closely spaced peaks may not be fully resolved alternatively use of a simple boxcar window following muller and macdonald 1997b will maximize the spectral frequency resolution this is achieved at the expense of potential truncation artifacts manifested as spurious peaks in the spectra although in the spectral analyses presented here such additional peaks are not significant in addition simple methods like this are not able to place any confidence intervals on the results global ice volume proxy records obtained

age and identity of the oldest pine fossils comment in their study of charred conifer twigs from the lower cretaceous chaswood formation of canada falcon lang et al 2016 established the species pinus mundayi that they interpreted as a two needled pine and the oldest stratigraphic evidence for the extant genus pinus this is based on their interpretation of what they thought was distinctive wood anatomy and paired needle bases of pinus evident in their fossils while the valanginian age ca 140 133 ma is based on revised palynostratigraphy if correctly interpreted this material predates the oldest known species pinus yorkshirensis from the hauterivian barremian transition at ca 131 129 ma ryberg et al 2012 and pushes back the earliest occurrence of the genus by 4 11 m y however we consider that a more thorough examination reveals that p mundayi is from the valanginian barremian ca 140 125 ma and that falcon lang et al have misinterpreted the anatomy of their fossils and erroneously assigned them to the genus pinus

organic petrology chemical composition and reflectance of pyrobitumen from the el soldado cu deposit chile solid pyrobitumen residual petroleum is found intimately associated with sulfides in several manto type strata bound cu deposits of central chile el soldado lat 32 38 8 s long 71 06 7 w is one of the largest deposits of this type 130 mt 1 5 cu and is hosted by volcanic and subvolcanic rocks of the cretaceous lo prado fm detailed organic petrology of authigenic sulfide inclusions degassing vesicles and anisotropic pyrobitumen and graphitic carbon allowed the elucidation of a complex diagenetic history of a biodegraded reservoir in faulted volcanic and subvolcanic rocks due to the overmaturity of the host sequence biomarker techniques aliphatic and aromatic were unsuitable to investigate the composition of the pyrobitumen however microprobe and laser ablation inductively coupled plasma mass spectrometry la icpms analyses rock eval pyrolysis and 13 c nmr techniques were used to ascertain the composition of the pyrobitumen spatial variations in the maturity of the pyrobitumen were assessed using both random reflectance r o and rotational reflectance r omax and r omin the data are consistent with the following evolution for el soldado as a result of burial in the cretaceous back arc basin petroleum was generated from organic rich shales in the underlying lower lo prado fm and migrated into primary and structural porosity in the host rocks the predominantly volcanic upper lo prado fm low temperature 90 c biodegradation of petroleum developed an early assemblage stage i assemblage of pyrite sphalerite chalcopyrite geopetal structures related to pressure degassing of semisolid petroleum suggest that migration occurred while the strata were horizontal at ca 130 ma continued basinal burial led to thermal degassing increased maturation and contraction of the petroleum into pyrobitumen around 20 ma later an influx of high temperature ca 250 350 c cu rich fluids induced by regional granitoid intrusion stage ii assemblage replaced preexisting pyrite and pyrobitumen the mineralizing fluids altered the pyrobitumen physically and chemically a increasing r o to greater than ca 5 in the core of the orebodies against a background level of ca 3 b developing anisotropy nongranular fine to coarse mosaic and coarse flow mosaic within the pyrobitumen and locally graphitized the pyrobitumen developing graphitic carbon and c incorporating cl cu fe into the pyrobitumen during the development of anisotropy

coupled fluid flow heat and mass transport and erosion in the alberta basin implications for the origin of the athabasca oil sands regional topography driven flow systems related to laramide tectonic rebound were simulated using two dimensional coupled fluid flow heat transport and solute transport numerical models to replicate present formation water salinity and temperature distributions and investigate the accumulation of the athabasca oil sands previous modelling of this system was replicated and it predicted repeated replacement of all basin formation water with freshwater during deposition of the oil sands due to high permeabilities to match present alberta basin temperature and salinity distributions model hydrostratigraphy permeabilities and heat fluxes were adjusted this revised model conducts fluids along the mannville aquifer rather than the upper devonian aquifer and replicates present salinity distributions assuming instantaneous uplift around 60 ma fluid fluxes in principal aquifers decrease by two orders of magnitude using new permeabilities resulting in primarily conductive heat transport thus genesis

the role of organic matter in the genesis of the el soldado volcanic hosted manto type cu deposit chile solid bitumen residual petroleum occurs intimately associated with sulfides in several manto type cu deposits of central chile el soldado 32 degrees 38 s 71 degrees 04 w is one of the largest manto type deposits 130 million metric tons1 5 cu and is hosted by rhyolites and andesites of the lower cretaceous lo prado formation as a result of basinal burial in the early cretaceous back arc basin petroleum was generated from organic rich shales in the underlying lower lo prado formation and migrated into primary and structural porosity in the upper lo prado formation migration was controlled by extensional basinal faults low temperature 90 degrees c biodegradation of petroleum developed an early stage i assemblage of mostly framboidal pyrite or sphalerite or chalcopyrite geopetal structures related to pressure degassing of semi solid petroleum suggest that migration occurred while the strata were horizontal at ca 130 ma continued basinal burial led to thermal degassing increased maturation and solidification of the petroleum low grade regional pumpellyite prehnite metamorphism of the sequence was followed at ca 110 to 103 ma by the influx of high temperature ca 300 degrees c cu rich fluids concurrently with emplacement of the cretaceous batholith into the basin basinal fluids were focused into a now tilted sequence by a brittle shear north south to north northwest fault system copper sulfides stage ii assemblage replaced preexisting pyrite and bitumen forming zoned orebodies with a central chalcocite hematite zone followed outward by bornite chalcocite chalcopyrite bornite and pyrite chalcopyrite zones the mineralizing fluids altered the bitumen thermally and chemically as follows 1 reflectance r o increased up to ca 5 percent in the core of the orebodies against a background of ca 3 percent 2 anisotropy nongranular microscale and domain developed and the bitumen was locally graphitized 3 chlorine or cu or fe was incorporated into the bitumen affecting its reflectance the source of cu was most likely the overlying oxidized volcanic pile the cu was transported as chloride cucl complexes precipitating where the cucl rich solutions reacted with bitumen adsorption reduction and pyrite from the stage i assemblage the study demonstrates that in the lower cretaceous basin of chile degraded petroleum reservoirs can be important controls for metallic mineralization derived from hydrothermal solutions of different sources particularly if biodegradation generated pyrite

combined obliquity and precession pacing of late pleistocene deglaciations a new statistical test shows that precession as well as obliquity contributes to the pacing of deglaciations in the late pleistocene the glacial cycles that characterize earth s climate history are paced by variations in earth s orbital orientation relative to the sun into the middle pleistocene about a million years ago glacial cycles were paced by 40 000 year cycles in earth s tilt or obliquity since then 100 000 year variations in orbital eccentricity seem to have dominated although it has been speculated that a combination of obliquity and precession orbital axis orientation might conspire to pace deglaciations firm quantitative evidence has not emerged peter huybers now uses advances in timing and statistics to show that indeed obliquity and precession simultaneously pace deglaciations milankovitch1 proposed that earth resides in an interglacial state when its spin axis both tilts to a high obliquity and precesses to align the northern hemisphere summer with earth s nearest approach to the sun this general concept has been elaborated into hypotheses that precession2 obliquity3 4 or combinations of both5 6 7 8 could pace deglaciations during the late pleistocene9 10 earlier tests have shown that obliquity paces the late pleistocene glacial cycles4 11 but have been inconclusive with regard to precession whose shorter period of about 20 000 years makes phasing more sensitive to timing errors4 11 12 no quantitative test has provided firm evidence for a dual effect here i show that both obliquity and precession pace late pleistocene glacial cycles deficiencies in time control that have long stymied efforts to establish orbital effects on deglaciation are overcome using a new statistical test that focuses on maxima in orbital forcing the results are fully consistent with milankovitch s proposal but also admit the possibility that long southern hemisphere summers contribute to deglaciation