uplift and submarine formation of some melanesian porphyry copper deposits stable isotope evidence hydrogen and oxygen isotope analyses of sericites and kaolinites from four young porphyry copper deposits ok tedi 1 2 ma and yandera 6 5 ma papua new guinea koloula 1 5 ma solomon islands and waisoi 5 ma fiji indicate that the fluids from which these minerals precipitated were of mixed magmatic and non magmatic sources the non magmatic component of the fluid from the island arc deposits koloula waisoi was ocean water for ok tedi the non magmatic component was a meteoric water with an isotopic composition different from that of the present meteoric water in the region the isotopic signature of the former meteoric water is consistent with a surface elevation of 200 m a s l or less at the time of mineralization the deposit was later exposed and supergene kaolinitization commenced at approximately 1200 m a s l uplift and erosion has continued to the present at which time the elevation of the exposed deposit is 1800 m a s l this rate of uplift is consistent with that known from other geological evidence if the rate of uplift were approximately constant during the last 1 2 ma the age of supergene enrichment can be dated at approximately 0 4 ma b p similarly influx of meteoric water at yandera occurred when the ground surface above the deposit was at an elevation of approximately 600 m a s l the deposit s present elevation is 1600 m a s l in this case a total uplift of approximately 2 2 km is indicated with removal of 1 2 km of overburden by erosion

impact of global sst gradients on the mediterranean runoff changes across the plio pleistocene transition this work explores the impact of the development of global meridional and zonal sea surface temperature sst gradients on the mediterranean runoff variability during the plio pleistocene transition about 3 ma results show that total annual mean pliocene mediterranean runoff is about 40 larger than during the preindustrial period due to more increased extratropical specific humidity as a consequence of a weakened and extended hadley cell the pliocene northwest africa hydrological network produces a discharge 30 times larger than today our results support the conclusion that during the pliocene the mediterranean water deficit was reduced relative to today due to a larger river discharge by means of a stand alone atmospheric general circulation model we simulate the separate impact of extratropical and equatorial sst cooling on the mediterranean runoff while cooling the equatorial sst does not imply significant changes to the pliocene mediterranean hydrological budget the extratropical sst cooling increases the water deficit due to a decrease in precipitation and runoff consequently river discharge from this area reduces to preindustrial levels the main teleconnections acting upon the mediterranean area today i e the north atlantic oscillation during winter and the monsoon desert mechanism during summer already have a large influence on the climate of our pliocene simulations finally our results also suggest that in a climate state significantly warmer than today changes of the hadley circulation could potentially lead to increased water resources in northwest africa

development of vegetation and continental aridity in northwestern africa during the late pliocene the pollen record of odp site 658 abstract a 200 m long marine pollen record from odp site 658 21 n 19 w reveals cyclic fluctuations in vegetation and continental climate in northwestern africa from 3 7 to 1 7 ma these cycles parallel oxygen isotope stages prior to 3 5 ma the distribution of tropical forests and mangrove swamps reached cape blanc 5 n of the present distribution between 3 5 and 2 6 ma forests occurred at this latitude during irregular intervals and nearly disappeared afterwards likewise a saharan paleoriver flowed continuously until isotope stage 134 3 35 ma when river discharge ceased wind transport of pollen grains prevailed over fluvial transport pollen indicators of trade winds gradually increased between 3 3 and 2 5 ma a strong aridification of the climate of northwestern africa occurred during isotope stage 130 3 26 ma afterwards humid conditions reestablished followed by another aridification around 2 7 ma repetitive latitudinal shifts of vegetation zones ranging from wooded savanna to desert flora dominated for the first time between between 2 6 and 2 4 ma as a response to the glacial stages 104 100 and 98 although climatic conditions recorded in the pliocene were not as dry as those of the middle and late pleistocene latitudinal vegetation shifts near the end of the pliocene resembled those of the interglacial glacial cycles of the brunhes chron

intensification of northern hemisphere glaciations in the circum atlantic region 3 5 2 4 ma ice rafted detritus evidence abstract records of ice rafted detritus ird from ocean drilling program sites 644 and 907 in the nordic seas and deep sea drilling program sites 610 and 607 in the north atlantic ocean are used to determine the growth and history of northern hemisphere glaciations spanning the interval from 3 6 to 2 4 ma the records document that the initiation of large scale glaciation in the circum atlantic region occurred stepwise between 3 5 and 2 4 ma with greenland leading the other areas the first major pulse of ird occurs at 3 3 ma suggesting a distinct expansion of the greenland ice sheet progressive increases in ird occur from 3 0 ma with a synchronous ice sheet development between the greenland scandinavian and north american regions starting around 2 72 2 75 ma the regional records of ird correspond to major trends in the oxygen isotope record suggesting a tight connection between the record of global ice volume and evidence for expanding glaciers in the northern hemisphere it appears as if widespread ird distribution occurs when the global ice volume surpasses certain thresholds similar to the late quaternary situation

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

influence of crude oil on the genesis of the lanjiagou porphyry molybdenum deposit western liaoning province china abstract the lanjiagou porphyry molybdenum deposit in western liaoning province china is hosted in fine grained jurassic granites la icp ms zircon u pb analyses indicate that the crystallization of the ore hosting granites took place 185 0 1 8 ma mswd 1 4 molybdenum mineralization in the deposit can be divided into three stages the stockwork quartz vein stage the planar quartz vein stage and the fissure filling quartz vein stage re os isotopic ages for the molybdenite from the stockwork quartz vein type ores yielded an isochron age of 188 8 9 9 ma mswd 3 0 while six samples from the planar quartz vein type ores yielded a similar isochron age of 185 6 1 2 ma mswd 0 5 re os isotopic ages for the molybdenite identical within error to zircon u pb isotopic ages indicate that the molybdenum mineralization is related to the host intrusions apart from primary inorganic fluid inclusions ifis a large number of primary organic fluid inclusions ofis are found in the latter two stages of vein quartz and minors found in the first stage the components and characteristics of ofis in the three stages of vein quartz differ from each other which is also true for the ifis ofis in stockwork vein quartz are characterized by halite bearing inclusions and organic liquids in the inclusions are brown and do not fluoresce under ultraviolet uv light homogenization temperatures t h for the primary ifis coeval with ofis of this stage ranges from 300 c to 450 c while the salinity varies from 10 to 53 wt nacl equiv in planar vein quartz ofis are predominately two phased liquid and gas and salt daughter minerals halite are absent organic liquids are light brown to colorless and show blue fluorescence under uv light the t h range for the ifis of this stage is 250 360 c and the salinity range is 3 17 wt nacl equiv finally ofis in fissure filling vein quartz are marked by liquid gas inclusions organic liquids are generally colorless and show yellow fluorescence under uv light the t h range for the primary ifis is 180 240 c and the salinity range is 4 11 wt nacl equiv organic geochemical analyses indicate that organic matter in the lanjiagou deposit was derived from mature crude oil we suggest that large volumes of crude oil bearing non magmatic fluids were flushed into the lanjiagou porphyry hydrothermal system during all phases of ore formation and likely played important roles in mineralization

rapid thermal rejuvenation of high crystallinity magma linked to porphyry copper deposit formation evidence from the koloula porphyry prospect solomon islands magmas containing the components needed to form porphyry copper deposits are relatively common within arcs yet mineralising events are uncommon within the long lived magmatic systems that host them understanding what causes the transition from barren to productive intrusions is critical to the development of conceptual deposit models we have constrained the tempo of pre and syn mineralisation magmatic events in relationship to the thermal evolution of the plutonic body that underlies one of the world s youngest exposed plutonic porphyry systems the inamumu zoned pluton koloula porphyry prospect solomon islands high precision id tims u pb dates of texturally and chemically characterised zircons indicate pluton emplacement over 50 crystals state past the point of rheological lock up we estimate that thermal rejuvenation of the deeper high crystallinity magma and generation of a mobile melt fraction may have occurred 10 kyr before its transport and emplacement within the porphyry environment the underlying pluton likely cooled and returned to high crystallinity states prior to subsequent remobilisation emplacement events titanium in zircon geothermometry and whole rock geochemistry suggest pre mineralisation intrusions were remobilised by mixing of a silicic magma with a high temperature less evolved melt in contrast syn mineralisation melts were most likely remobilised by the percolation of hot volatiles exsolved from contemporaneous less evolved intrusions cooling beneath the crystalline silicic magma the evidence for the rapid thermal rejuvenation and long term storage of highly crystalline silicic magmas is consistent with previous studies that indicate two components of exsolved volatiles contribute to ore forming fluids we conclude that the liberation of crystal rich porphyry copper deposit forming magmas and the addition of the chemical components required for ore formation are intrinsically linked to the volatiles released during the recharge of less evolved melt into a highly crystalline silicic magma

the progressive intensification of northern hemisphere glaciation as seen from the north pacific ocean drilling project odp site 882 50 22 n 167 36 e provides the first high resolution grape density magnetic susceptibility carbonate opal and foraminifera planktonic and benthic stable isotopes records between 3 2 and 2 4 ma in the northwest pacific we observed a dramatic increase in ice rafting debris at site 882 at 2 75 ma which is coeval with that found in the norwegian sea suggesting that the eurasian arctic and northeast asia were significantly glaciated from 2 75 ma onwards prior to 2 75 ma planktonic foraminifera 18o records indicate a warming or freshening trend of 4 c or 2 over 80 ka if this is interpreted as a warm pre glacial pliocene north pacific it may have provided the additional moisture required to initially build up the northern hemisphere continental ice sheet the dramatic drop in sea surface temperatures sst 7 5 c at 2 75 ma ended this suggested period of enhanced sst and thus the proposed moisture pump moreover at 2 79 and 2 73 ma opal mass accumulation rates mar decrease in two steps by five fold and is accompanied by a more gradual long term decrease in caco3 mars evidence from the southern ocean odp site 704 indicates that just prior to 2 6 ma there is a massive increase in opal mars the opposite to what is found in the north pacific this indicates that the intensification of northern hemisphere glaciation was accompanied by a major reorganisation of global oceanic chemical budget possibly caused by changes in deep ocean circulation the initiation of northern hemisphere glaciation occurred in the late miocene with a significant build up of ice on southern greenland however the progressive intensification did not occur until 3 5 3 ma when the greenland ice sheet expanded to include northern greenland following this stage we suggest that the eurasian arctic and northeast asia glaciated at 2 75 ma approximately 100 ka before the glaciation of alaska 2 65 ma and 200 ka before the glaciation of the north east american continent 2 54 ma

dansgaard oeschger and heinrich event imprints in alboran sea paleotemperatures past sea surface temperature sst evolution in the alboran sea western mediterranean during the last 50 000 years has been inferred from the study of c37 alkenones in international marine global change studies md952043 core this record has a time resolution of 200 years allowing the study of millennial scale and even shorter climatic changes the observed sst curve displays characteristic sequences of extremely rapid warming and cooling events along the glacial period comparison of this alboran record with 18o from greenland ice greenland ice sheet project 2 core shows a strong parallelism between these sst oscillations and the dansgaard oeschger events five prominent cooling episodes standing out in the sst profile are accompanied by an anomalous high abundance of neogloboquadrina pachyderma sinistral which is confined to the duration of these cold intervals these features and the isotopic record reflect drastic changes in the surface hydrography of the alboran sea in association with heinrich events hl 5

oxygen isotope constraints on the petrogenesis of volcanic arc magmas from martinique lesser antilles abstract volcanic rocks from the island of martinique in the lesser antilles island arc are highly diverse isotopically values of 18o smow in lavas erupted over the last 5 ma from five stratigraphically discrete and geochemically distinct volcanic centers are morne jacob 7 5to 7 9 pitons du carbet 8 0to 8 9 diamant 6 3to 7 4 piton mt conil 7 2to 7 3 andmt pelee 6 5to 7 4 13 of the 27 samples have been corrected for variable amounts of secondary alteration and low temperature hydration the least18o rich andesites on martinique have 18o values similar to those of the northern lesser antilles 18o 6 0 to 7 3 and other intra oceanic arcs like the marianas 18o 5 5 to 6 8 o isotope ratios are compositionally dependent correlations between 18o and radiogenic isotope ratios 87sr 86sr 143nd 144nd 206pb 204pb and indices of fractionation show that modification of isotopic compositions occurred during magmatic differentiation rather than at source a two stage model is proposed for the origin and differentiation of magmas on martinique primary basaltic melts which are broadly similar in composition to primitive island arc magmas elsewhere e g marianas aleutians south sandwich islands are generated from the subduction modified asthenospheric mantle wedge these magmas ascend into the arc crust and differentiate on martinique crystal fractionation is accompanied by contamination with isotopically distinct crust including a component of terrigenous sediments thus subduction zone processes at the lesser antilles and other island arcs are similar involving only a small albeit significant isotopically volumetric contribution from subducted sediment

greatly expanded tropical warm pool and weakened hadley circulation in the early pliocene the pliocene warm interval has been difficult to explain we reconstructed the latitudinal distribution of sea surface temperature around 4 million years ago during the early pliocene our reconstruction shows that the meridional temperature gradient between the equator and subtropics was greatly reduced implying a vast poleward expansion of the ocean tropical warm pool corroborating evidence indicates that the pacific temperature contrast between the equator and 32 n has evolved from 2 c 4 million years ago to 8 c today the meridional warm pool expansion evidently had enormous impacts on the pliocene climate including a slowdown of the atmospheric hadley circulation and el nino like conditions in the equatorial region ultimately sustaining a climate state with weak tropical sea surface temperature gradients may require additional mechanisms of ocean heat uptake such as enhanced ocean vertical mixing

formal ratification of the quaternary system period and the pleistocene series epoch with a base at 2 58 ma in june 2009 the executive committee of the international union of geological sciences iugs formally ratified a proposal by the international commission on stratigraphy to lower the base of the quaternary system period to the global stratotype section and point gssp of the gelasian stage age at monte san nicola sicily italy the gelasian until then had been the uppermost stage of the pliocene series epoch the base of the gelasian corresponds to marine isotope stage 103 and has an astronomically tuned age of 2 58 ma a proposal that the base of the pleistocene series epoch be lowered to coincide with that of the quaternary the gelasian gssp was also accepted by the iugs executive committee the gssp at vrica calabria italy which had hitherto defined the basal boundary of both the quaternary and the pleistocene remains available as the base of the calabrian stage age now the second stage of the revised pleistocene in ratifying these proposals the iugs has acknowledged the distinctive qualities of the quaternary by reaffirming it as a full system period correctly complied with the hierarchical requirements of the geological timescale by lowering the base of the pleistocene to that of the quaternary and fully respected the historical and widespread current usage of both the terms quaternary and pleistocene copyright 2009 john wiley sons ltd

origin and implications of orbital induced sedimentary cyclicity in pliocene well logs of the western mediterranean abstract the climatic origin of astronomically induced sedimentary cycles in the mediterranean and adjacent areas during the late neogene and quaternary remains puzzling as cycles have been linked to concomitant but seasonally opposite changes in african summer monsoon precipitation eastern mediterranean sapropels and atlantic regulated winter precipitation carbonate cycles on the atlantic side of the mediterranean particularly little is known about the cyclic sedimentation on orbital time scales in the western mediterranean with the prime exception of the messinian sapropels from the sorbas basin southern spain here we show that regular alternations in pliocene downhole logs from the industrial drill site muchamiel 1 located along the balearic promontory in the western mediterranean are related to eccentricity bundles and to obliquity and precession cycles basic meter scale alternations we establish an astronomically based age model for the interval between 5 33 and 2 8 ma by first correlating cycle bundles to eccentricity and then the basic dominantly precession related cycles to the 65 n summer insolation of la2004 the striking bed to bed similarities between the muchamiel 1 well logs and other records from both the atlantic margin and the central mediterranean suggest that the same climatic forcing was responsible for the formation of carbonate cycles across the western mediterranean and adjacent atlantic we conclude that formation of alternating carbonate rich carbonate poor beds was controlled by western mediterranean cyclogenetic mechanisms as well as by peri mediterranean precipitation associated with changes in the north atlantic system nas these findings highlight the importance of peri mediterranean precipitation on the sedimentary cyclicity by dictating terrigenous clay supply and potentially on the hydrology of the basin by providing additional freshwater required for sapropel formation consequently cyclic sedimentation in the mediterranean results from the combined effect of precipitation changes driven by i the north african monsoon ii the atlantic system and iii intrabasinal mediterranean atmospheric dynamics

the plio pleistocene glaciation of the barents sea svalbard region a new model based on revised chronostratigraphy based on a revised chronostratigraphy and compilation of borehole data from the barents sea continental margin a coherent glaciation model is proposed for the barents sea ice sheet over the past 3 5 million years ma three phases of ice growth are suggested 1 the initial build up phase covering mountainous regions and reaching the coastline shelf edge in the northern barents sea during short term glacial intensification is concomitant with the onset of the northern hemisphere glaciation 3 6 2 4 ma 2 a transitional growth phase 2 4 1 0 ma during which the ice sheet expanded towards the southern barents sea and reached the northwestern kara sea this is inferred from step wise decrease of siberian river supplied smectite rich sediments likely caused by ice sheet blockade and possibly reduced sea ice formation in the kara sea as well as glacigenic wedge growth along the northwestern barents sea margin hampering entrainment and transport of sea ice sediments to the arctic atlantic gateway 3 finally large scale glaciation in the barents sea occurred after 1 ma with repeated advances to the shelf edge the timing is inferred from ice grounding on the yermak plateau at about 0 95 ma and higher frequencies of gravity driven mass movements along the western barents sea margin associated with expansive glacial growth

petrogenesis of the proterozoic athabasca basin northern saskatchewan canada and its relation to diagenesis hydrothermal uranium mineralization and paleohydrogeology abstract in the athabasca basin proterozoic sandstones unconformably overlie archean and aphebian rocks multiple fluid events involving isotopically and chemically distinct fluids which have migrated laterally for considerable distances and along fault zones have produced a paragenetically identifiable assemblage of clay silicate and oxide minerals in the basin and basement rocks altered sandstones and the underlying metasedimentary rocks proximal to fault zones host high grade u ni co unconformity type uranium ore deposits and contain an alteration assemblage of highly crystalline 2m 3t illite 1m kaolinite clinochlore and sudoite hematite dravite and euhedral quartz in the sandstones 18o values of coeval quartz hematite quartz illite quartz dravite illite hematite and kaolinite hematite fluid inclusion temperatures in diagenetic quartz and d values of 1m kaolinite 2m 3t illite dravite and in fluid inclusions in the quartz indicate formation from a basinal fluid that had d values of 60 10 and which underwent salinity temperature and 18o increases from 5 to 34 wt nacl 120 to 240 c and 5 to 3 respectively as a result of increasing burial depth and sustained water rock interactions with the basinal sediments over substantial time periods 18 o 16 o and d h ratios of sudoite and clinochlore in meta sedimentary basement rocks within the alteration haloes indicate formation from a basement derived fluid with 18o and d values of 4 4 and 30 10 respectively that was isotopically distinct from the basinal fluids 18o and d values of late kaolinites in reactivated fault zones indicate formation mainly from low temperature 50 25 c fluids having 18o and d values of 16 and 130 respectively similar to relatively modern meteoric waters in the area some kaolinites have 18o and d values which suggest they formed from meteoric waters at mid latitudes and have experienced varying degrees of oxygen and hydrogen isotope exchange with relatively modern meteoric waters in the re activated faults illite sudoite and dravite have d values that vary by 100 without concurrent changes to their 18o values indicating preferential hydrogen isotope exchange with relatively modern meteoric waters at low temperatures and under conditions of high integrated water rock ratios rb sr isochron and model ages of 1477 57 and 952 ma respectively for the crystalline 2m 3t illites indicate the timing of the high temperature basinal fluid events associated with fluid mixing rb sr and k ar ages on illites with the lowest d values are as young as 300 ma and indicate late stage resetting of their radiogenic isotope systematics as a result of substantial interactions with relatively modern meteoric waters the evolution of sr isotopic compositions of fluids in the basin and basement rocks as reflected by the 87 sr 86 sr ratios of chlorite illite and dravite indicates that mixing of two isotopically distinct fluids in the vicinity of faults was the process by which uranium was precipitated similar to that suggested by oxygen and hydrogen isotope systematics in the clays and silicate minerals nd ratios in the high temperature diagenetic and hydrothermal clay and silicate minerals and the cogenetic uranium ores suggest they all have formed from similar fluids which have interacted substantially with the basin sediments in general the isotopic chemical microthermometric and petrologic data indicate that the athabasca basin has had a protracted fluid history comparable to that documented for more modern sedimentary basins the data clearly show that the major sandstone aquifers have been affected by widespread lateral flow of diagenetic fluids over distances of hundreds of kilometers and also that these fluid migration paths have been modified by cross formational fluid flow near active fault zones

late gauss to early matuyama invasions of neogloboquadrina atlantica in the mediterranean and associated record of climatic change a well dated high resolution record of climatic change is presented for the late pliocene mediterranean principal component analysis on abundances of 14 planktonic foraminiferal species reveals a series of late gauss to early matuyama surface water cooling events which can be correlated with north atlantic glacial isotope stages 108 to 94 the abundance record of the benthic foraminifer trifarina angulosa suggests lowered bottom water temperatures at times of surface water cooling the record of surface water oxygen and carbon isotopes shows an inverse pattern with 18o maxima and 13c minima at times of cool sea surface temperature conditions concomitant decrease in p b value and increased admixtures of clastic material suggest that late gauss to early matuyama surface water cooling events in the mediterranean are accompanied with glacioeustatic sea level low stands major surface water cooling events are associated with invasions of neogloboquadrina atlantica this north atlantic mid to high latitude species is at 2 55 ma close to the gibraltar portal whereafter it could invade the mediterranean repeatedly during periods of climatic cooling until it disappears from all over the north atlantic and mediterranean at the end of glacial stage 96

oxygen isotopic composition of the mediterranean sea since the last glacial maximum constraints from pore water analyses abstract interstitial waters recovered from ocean drilling program leg 161 site 976 in the western mediterranean sea are used in conjunction with a numerical model to constrain the 18o of seawater in the basin since the last glacial maximum including sapropel event 1 to resolve the oxygen isotopic composition of the deep mediterranean we use a model that couples fluid diffusion with advective transport thus producing a profile of seawater 18o variability that is unaffected by glacial interglacial variations in marine temperature comparing our reconstructed seawater 18o to recent determinations of 1 0 for the mean ocean change in glacial interglacial 18o due to the expansion of global ice volume we calculate an additional 0 2 increase in mediterranean 18o caused by local evaporative enrichment this estimate of 18o change due to salinity variability is smaller than previous studies have proposed and demonstrates that mediterranean records of foraminiferal calcite 18o from the last glacial period include a strong temperature component paleotemperatures determined in combination with a stacked record of foraminiferal calcite depict almost 9 c of regional cooling for the last glacial maximum model results suggest a decrease of 1 1 in seawater 18o relative to the modern value caused by increased freshwater input and reduced salinity accompanying the formation of the most recent sapropel the results additionally indicate the existence of isotopically light water circulating down to bottom water depths at least in the western mediterranean supporting the existence of an anti estuarine thermohaline circulation pattern during sapropel event 1

oxygen isotopes of phosphate and the origin of island apatite deposits abstract in an attempt to test the hypothesis that insular phosphorites on high islands e g nauru formed by chemical reactions between seabird guano and carbonate the oxygen isotope compositions of phosphate 18op in modern guano and in the apatite component of phosphorites of various ages and locations have been investigated guano from several species of seabird appears to have 18op values that are in equilibrium with the ambient seawater temperature at each site however recent apatites closely associated with modern guano can have 18op values that are as much as 2 higher than their inferred guano phosphate source this shift in 18op values could be the result of isotopic re equilibration with percolating meteoric waters which have been enriched by evaporative processes in the upper part of the soil profile bacterial degradation of the guano in the soil zone is a possible mechanism for resetting the 18op values in this environment ancient apatites on high islands such as nauru ocean island and makatea have 18op values that are significantly lower than the 18op values of recently formed apatites the results indicate that ancient apatite deposits could not have formed by processes similar to those forming recent apatites without unreasonably high palaeotemperatures and or equilibration with water with much lower 18o values such as meteoric water in a karstic terrain at the time of maximum infiltration if the 18op values in apatite are subject to modification during subaerial weathering and diagenesis perhaps aided by the metabolic activity of micro organisms the application of 18op signatures of insular phosphorites to palaeoenvironmental reconstructions is limited to post depositional history and provides few clues to original setting

late pliocene to early pleistocene astronomically forced sea surface productivity and temperature variations in the mediterranean abstract principal component analysis of late pliocene to early pleistocene planktonic foraminiferal abundances from the mediterranean yielded two significant components which represent first order approximations for sea surface productivity and temperature this interpretation is confirmed by the good fit between the score plots and sea surface productivity and sea surface temperature proxy records based on selected eutrophic and temperature sensitive species using present day habitat characteristics spectral analysis revealed significant peaks in the orbital frequency bands of the spectrum suggesting that variations in sea surface productivity and temperature are controlled by the quasi periodic variations in the earth s orbit precession forced variations are reflected primarily in sea surface productivity and to a lesser degree in sea surface temperature maxima in sea surface productivity and temperature in this frequency band occurred at times of sapropel formation the sea surface productivity maxima can be explained by an increased input of river borne nutrients and by the shoaling of the pycnocline and the associated intensification of the deep chlorophyll maximum dcm layer precession forced variations in sea surface temperature are not related to glacial cycles since this frequency component is almost completely absent in ice volume proxy records for this time interval sapropel bound sea surface temperature maxima presumably reflect periods of maximum insolation during the northern hemisphere summer the contrasting winter signal corresponds to minimum insolation values which may be reflected by peak abundances ofgloborotalia inflata obliquity forced variations are reflected primarily in sea surface temperature and not in sea surface productivity these temperature fluctuations correspond with ice volume changes registered in the oxygen isotope record at the north atlantic dsdp site 607 this shows that obliquity forced sea surface temperature variations in the mediterranean are primarily driven by glacial cycles

a major and long term pliocene intensification of the mediterranean outflow 3 5 3 3 ma ago largely continuous millennial scale records of benthic delta o 18 mg ca based temperature and salinity variations in bottom waters were obtained from deep sea drilling project dsdp site 548 east atlantic continental margin near ireland 1250 m water depth for the period 3 7 3 0 ma ago high epsilon nd values of 10 7 to 9 show that this site monitored changes in mediterranean outflow water mow throughout the mid pliocene bottom water variability at ocean drilling progam odp site 978 alboran sea 1930 m water depth provides a complementary record of mow composition near its west mediterranean source both sites show a singular and persistent rise in bottom water salinities by 0 7 1 4 psu and in densities by similar to 1 kg m 3 from 3 5 to 3 3 ma ago which is matched by an similar to 3 degrees c increase in bottom water temperature at site 548 this event suggests the onset of strongly enhanced deep water convection in the mediterranean sea and a related increase in mow flow as a result of major aridification in the mediterranean source region in harmony with model suggestions the enhanced mow flow has possibly intensified upper north atlantic deep water formation

episodic growth and homogenization of plutonic roots in arc volcanoes from combined u th and u th he zircon dating abstract tracing the fate of unerupted magma is challenging because plutonic roots of young volcanoes are largely inaccessible here we develop the use of zircon age spectra to determine crystal provenance and source rocks for volcanic products in analogy to detrital crystals in sediments u th zircon crystallization ages for the soufriere volcanic complex saint lucia lesser antilles frequently predate their eruption as determined from combined u th and u th he zircon dating the oldest dated eruptions are 273 15 ka and 264 8 ka 1 uncertainty for morne bonin dacite and bellevue pumice deposit respectively the most recent eruptions formed morphologically pristine domes in the center of the qualibou depression belfond 13 6 0 4 ka terre blanche 15 3 0 4 ka u th u pb zircon crystallization ages determined for crystal rims and interiors range between near eruption ages to 600 ka older xenocrysts are absent zircon crystallization age distributions are complex yet systematic crystal rim ages in the most recently erupted volcanic rocks match those of co erupted plutonic inclusions whereas crystal interiors are equivalent to the cumulative distribution of zircon ages from older eruptions this is evidence that silicic lava domes and pyroclastic flows share a common source that is located underneath the qualibou depression where the intrusive roots of this long lived arc volcanic system became homogenized through thermal and mechanical reprocessing of individual batches of unerupted magma from earlier volcanic episodes within timescales of

deep sea temperature and ice volume changes across the pliocene pleistocene climate transitions earth has undergone profound changes since the late pliocene which led to the development 2 7 million years ago ma and intensification 0 9 ma of large scale northern hemisphere ice sheets recorded as transitions in the benthic foraminiferal oxygen isotope 18ob record here we present an orbitally resolved record of deep ocean temperature derived from benthic foraminiferal magnesium calcium ratios from the north atlantic which shows that temperature variations are a substantial portion of the global 18ob signal the record shows two distinct cooling events associated with the late pliocene lpt 2 5 to 3 ma and mid pleistocene mpt 1 2 to 0 85 ma climate transitions whereas the lpt increase in ice volume is attributed directly to global cooling the shift to 100 000 year cycles at the mpt is more likely to be a response to an additional change in ice sheet dynamics

evolution of the grenada and tobago basins and implications for arc migration abstract the tectonic mechanisms controlling how volcanic arcs migrate through space and geologic time within dynamic subduction environments is a fundamental tectonic process that remains poorly understood this paper presents an integrated stratigraphic and tectonic evolution of late cretaceous to recent volcanic arcs and associated basins in the southeastern caribbean sea using seismic reflection data wide angle seismic refraction data well data and onland geologic data we propose a new tectonic model for the opening of the grenada and tobago basins and the 50 250 km eastward jump of arc volcanism from the late cretaceous aves ridge to the miocene to recent lesser antilles arc in the southeast caribbean based on the mapping of three seismic megasequences the striking similarity of the half graben structure of the grenada and tobago basins that flank the lesser antilles arc their similar smooth basement character their similar deep marine seismic facies and their similar paleogene sediment thickness mapped on a regional grid of seismic data suggest that the two basins formed as a single saucer shaped oceanic crust paleogene forearc basin adjacent to the now dormant aves ridge this single forearc basin continued to extend and widen through flexural subsidence during the early to middle eocene probably because of slow rollback of the subducting atlantic oceanic slab rollback may have been accelerated by oblique collision of the southern aves ridge and southern lesser antilles arc with the south american continent uplift and growth of the southern lesser antilles arc divided the grenada and tobago basins by early to middle miocene time inversion of normal faults and uplift effects along both edges of the lesser antilles arc are most pronounced in its southern zone of arc collision with the south american continent the late miocene to recent depositional histories of the grenada and tobago basins are distinct because of isolation of the grenada basin by growth and uplift of the neogene lesser antilles volcanic ridge

high temperature environments of human evolution in east africa based on bond ordering in paleosol carbonates many important hominid bearing fossil localities in east africa are in regions that are extremely hot and dry although humans are well adapted to such conditions it has been inferred that east african environments were cooler or more wooded during the pliocene and pleistocene when this region was a central stage of human evolution here we show that the turkana basin kenya today one of the hottest places on earth has been continually hot during the past 4 million years the distribution of 13c 18o bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 c and often in excess of 35 c similar soil temperatures are observed today in the turkana basin and reflect high air temperatures combined with solar heating of the soil surface these results are specific to periods of soil carbonate formation and we suggest that such periods composed a large fraction of integrated time in the turkana basin if correct this interpretation has implications for human thermophysiology and implies a long standing human association with marginal environments

a high resolution diatom record of the palaeoclimates of east siberia for the last 2 5 my from lake baikal abstract two parallel drilling cores bdp96 1 200 m and bdp96 2 100 m have been taken from top of the underwater akademichesky ridge in lake baikal and dated by paleomagnetic techniques these cores are part of the baikal drilling project kuzmin et al 1997a b diatom analysis of the first 100 m of these sediments reveals that they store a 2 5 myr high resolution continuous record of the palaeoclimates of east siberia sediments belonging to warmer climates have a high content of diatom algae frustules whereas those belonging to global glaciations are diatom barren the record of upper pleistocene 500 kyr bp strongly correlates with the oceanic specmap curve and contains distinct 100 41 23 and 19 kyr periods as revealed by fourier analysis diversity of diatom species was small in pliocene abrupt and frequent changes of the climate in pleistocene resulted in frequent dramatic changes in the diatom communities the extant dominating endemics cyclotella minuta and aulacoseira baicalensis became important in lake baikal 760 kyr and less than 120 kyr bp respectively

modelling pliocene warmth contribution of atmosphere oceans and cryosphere the relative role of the atmosphere oceans and cryosphere in contributing towards middle pliocene warmth ca 3 ma bp is investigated using the hadcm3 coupled ocean atmosphere general circulation model the model was initialised with boundary conditions from the usgs prism2 data set and a pliocene atmospheric co2 level of 400 ppmv and run for 300 simulated years the simulation resulted in a global surface temperature warming of 3degreesc compared to present day in contrast to earlier modelling experiments for the pliocene surface temperatures warmed in most areas including the tropics 1 5degreesc compared with present day the model predicts a general pattern of ocean warming 1 5degreesc in both hemispheres to a depth of 2000 m below which no significant differences are noted sea ice coverage is massively reduced up to 90 the flow of the gulf stream north atlantic drift is up to 100 mm s 1 greater in the pliocene case analysis of the model predicted meridional streamfunction suggests a global pattern of reduced outflow of antarctic bottom water aabw up to 5 sv a shallower depth for north atlantic deep water formation and weaker thermohaline circulation 3 sv the decrease in aabw occurs mainly in the pacific rather than atlantic ocean model diagnostics for heat transports indicate that neither the oceans nor the atmosphere are transporting significantly more heat in the pliocene scenario rather these results indicate that the major contributing mechanism to global pliocene warmth was the reduced extent of high latitude terrestrial ice sheets 50 reduction on greenland 33 reduction on antarctica and sea ice cover resulting in a strong ice albedo feedback these results highlight the need for further studies designed to improve our knowledge regarding pliocene terrestrial ice configurations

glacial variability over the last two million years an extended depth derived agemodel continuous obliquity pacing and the pleistocene progression abstract an agemodel not relying upon orbital assumptions is estimated over the last 2 ma using depth in marine sediment cores as a proxy for time agemodel uncertainty averages 10 ka in the early pleistocene 2 1 ma and 7 ka in the late pleistocene 1 ma to the present twelve benthic and five planktic 18 o records are pinned to the agemodel and averaged together to provide a record of glacial variability major deglaciation features are identified over the last 2 ma and a remarkable 33 out of 36 occur when earth s obliquity is anomalously large during the early pleistocene deglaciations occur nearly every obliquity cycle giving a 40 ka timescale while late pleistocene deglaciations more often skip one or two obliquity beats corresponding to 80 or 120 ka glacial cycles which on average give the 100 ka variability this continuous obliquity pacing indicates that the glacial theory can be simplified an explanation for the 100 ka glacial cycles only requires a change in the likelihood of skipping an obliquity cycle rather than new sources of long period variability furthermore changes in glacial variability are not marked by any single transition so much as they exhibit a steady progression over the entire pleistocene the mean variance skewness and timescale associated with the glacial cycles all exhibit an approximately linear trend over the last 2 ma a simple model having an obliquity modulated threshold and only three adjustable parameters is shown to reproduce the trends timing and spectral evolution associated with the pleistocene glacial variability

mineralogical and isotopic characteristics of sodic calcic alteration in the highland valley copper district british columbia canada implications for fluid sources in porphyry cu systems

evolution of mediterranean sea surface temperatures 3 5 1 5 ma regional and hemispheric influences abstract we present a composite time series of mediterranean sea surface temperature sst and marine biomarker accumulation for the time span from 3 5 to 1 525 ma based on alkenone unsaturation and concentration from hemipelagic sediments outcropping in southern italy and sicily paleotemperature data define three regimes a late pliocene climate on average 4 5 c warmer than modern a latest pliocene to early pleistocene onset of 41 kyr cycles and a major increase in the range of glacial interglacial temperature change at 1 84 ma that shortly precedes the former definition of the plio pleistocene boundary in the crotone sequence pliocene sea surface temperature sst cycles are dominated by precession with a 1 5 c range obliquity related rhythms influence sst significantly shortly after 2 8 ma equivalent to mis g10 and dominate after 2 51 ma equivalent to mis 100 however little if any long term cooling occurred on an interglacial basis until after 1 85 ma alkenone concentrations provide a good proxy for the accumulation of marine organic matter and primarily reflect regional hydrology organic sedimentation including the formation of layers highly enriched in organic matter sapropels was paced throughout by precessional variations despite changes in both average regional temperature and the shift in temperature variance to the 41 kyr obliquity cycle in the latest pliocene and early pleistocene our reconstruction therefore highlights the intermingling of both hemispheric wide changes in temperature and regional variations in the hydrological cycle that combined to force major evolutionary changes in the fauna and flora of northern africa and the southern mediterranean in late pliocene to mid pleistocene time

increased seasonality during the intensification of northern hemisphere glaciation at the pliocene pleistocene boundary 2 6 ma abstract near the pliocene pleistocene neogene quaternary boundary during marine isotope stage mis 104 at around 2 6 ma the intensification of northern hemisphere glaciation inhg was marked by a southward shift of the north atlantic current and arctic front and a concurrent drop in sea surface temperature sst in the mid latitudes of the north atlantic here we evaluate two mg ca based sea surface temperature reconstructions for the 2 78 2 52 ma interval using the planktonic foraminifera globigerina bulloides and globigerinoides ruber white sensu stricto as the biotic carriers sstbul and sstrub and a reconstruction based on the alkenone saturation index sstalk the mg ca based sst estimates begin to diverge from one another significantly during mis g3 2 66 ma culminating during mis 104 2 60 ma and remaining distinctly different for the remaining 80 kyr of the studied interval the magnitude of this divergence sstrub bul is caused mainly by a decrease in sstbul with sstrub remaining relatively constant we attribute this difference to a drop in sst during the early spring blooming season of g bulloides that was less pronounced during the late summer blooming season of g ruber using sstrub bul as a seasonality indicator we show that seasonality increased significantly owing to a drop in early spring temperatures from mis 104 onwards and peaked during glacial episodes maximum seasonality occurred during mis 104 in coincidence with a major expansion of the circum atlantic ice sheets particularly the north american ice sheet this expansion appears to have had a critical influence on global climate and especially seasonality

preservation of the alkenone paleotemperature proxy in uplifted marine sequences a test from the vrica outcrop crotone italy the alkenone organic paleotemperature proxy has been used with great success to generate sea surface temperature sst records from diverse areas of the world ocean to date however this methodology has been applied almost exclusively to unconsolidated marine sediments the fidelity of alkenone preservation in lithified uplifted marine sequences exposed on land has not been explicitly investigated such sedimentary sequences have been buried at depths of hundreds of meters to kilometers before uplift and in addition have been exposed to oxic pore fluids and subaerial weathering upon ascent to the surface any of which may cause alteration of biomarker compounds in this study we compare alkenone sst estimates from the vrica land section in crotone italy with alkenone sst estimates derived from coeval marine sediments retrieved at ocean drilling program site 964 which is 300 km offshore of the vrica location we find that sst records from the land and marine sections are well correlated showing similar mean values cyclicity and amplitudes although results from different sedimentary sequences might depend on the lithologies burial depths and weathering histories of individual outcrops this study suggests that it will be possible to reconstruct quantitative sst histories from marine strata exposed on land

extension of the astronomically calibrated polarity time scale to the miocene pliocene boundary the early pleistocene to late pliocene astronomically calibrated time scale of shackleton et al 1 and hilgen 2 is extended to the miocene pliocene boundary this is done by correlating the detailed record of caco3 cycles in the trubi and the lower part of the overlying narbone formation rossello composite section sicily to the astronomical record using 1 inferred phase relations between these caco3 cycles and the corresponding orbital cycles of precession and eccentricity and 2 calibration points provided by the previously established astronomical calibration of sapropelitic layers which occur in the topmost part of the caco3 record 2 this correlation allows all small scale caco3 cycles in the rossello composite section to be coded after the correlative precession peak and to be dated astronomically with an accuracy of 1 ky in combination with the available high resolution magnetostratigraphy it further allows the construction of an astronomically calibrated geomagnetic polarity time scale for the major part of the gilbert and gauss chrons this new time scale gives ages for the reversal boundaries of the kaena 3 04 3 11 ma and mammoth 3 22 3 33 ma the gilbert gauss chron boundary 3 58 ma and the reversal boundaries of the cochiti 4 18 4 29 ma nunivak 4 48 4 62 ma sidufjall 4 80 4 89 ma and thvera 4 98 5 23 ma these ages are significantly older than the ages given by conventional time scales age discrepancies gradually increase with increasing age the age of 5 32 ma for the miocene pliocene boundary as defined by the base of the trubi on sicily is almost 0 5 m y 9 5 older than the presently accepted age of 4 86 ma 3 these considerable discrepancies with the conventional time scale can either be explained by an consistent error in the decay constants used in k ar radiometric dating or more likely by diffusional loss of radiogenic argon

from crucible to graben in 2 3 ma a high resolution geochronological study of porphyry life cycles boyongan bayugo copper gold deposits philippines the boyongan and bayugo porphyry copper gold deposits are part of a belt of gold rich copper deposits in the surigao district of northeast mindanao philippines the detailed age relationships described in this study provide insight into the geologically short life cycles that characterize porphyry formation in dynamic arc environments since their late pliocene emplacement 2 3 2 1 ma shrimp sensitive highresolution ion microprobe u pb zircon dating at depths of 1 2 2 0 km these deposits were exhumed deeply weathered and buried weathering of these deposits led to the development of the world s deepest known porphyry oxidation profile 600 m thick at boyongan and a modest 30 70 m oxidation profile at adjacent bayugo this earlymiddle pleistocene supergene event followed a period of rapid uplift and exhumation in northeast mindanao 2 5 km ma u th he apatite age elevation spectrum subsequent rapid subsidence 0 34 km ma radiocarbon age elevation spectrum and burial of these deposits are attributed to a mid pleistocene shift from transpressional tectonics to the present day transtensional setting in northeast mindanao during this period debris flows volcanic material and fluviolacustrine sediments accumulating in the actively extending mainit graben covered the weathered deposits preserving the supergene profiles beneath 50 500 m of cover this detailed geochronological study documents the geologically short 2 3 ma time scales over which these major intrusion centered mineral deposits evolved from emplacement exhumation deep oxidation and burial highlighting the dynamism of tectonic processes in environments such as the philippine mobile belt 2012 geological society of america

obscuring of long eccentricity cyclicity in pleistocene oceanic carbon isotope records abstract long eccentricity 400 kyr cycles in carbon isotope records from the pacific and atlantic oceans and the mediterranean sea of the past 5 0 ma are compared all records show maximum 13c values 13cmax at eccentricity minima during the pliocene but this relationship obscured in the pleistocene after 1 6 ma in particular for the open ocean deep water 13c records since a clear anti phase relationship was set up between oceanic 18o and 13c in the 100 kyr band from this time we attribute the obscured 400 kyr signal to a major change in the oceanic carbon reservoir probably associated with restructure of the southern ocean a similar change occurred in the miocene at 13 9 ma when the 400 kyr cyclicity in 13c records flattened out together with a drastic cooling and antarctic ice sheet expansion a remarkable exception is the mediterranean surface water 13c record which remained paced by the long term eccentricity cycle throughout the pliocene and pleistocene suggesting a low latitude climatic origin of the 400 kyr signal that is independent of glacial interglacial forcing since the earth is currently passing through an eccentricity minimum it is crucial to understand the nature of the 13cmax events

seasonality intensification and long term winter cooling as a part of the late pliocene climate development abstract a mutual climatic range method is applied to the mediterranean marine pollen record of semaforo vrica section calabria italy covering the period from 2 46 ma to 2 11 ma the method yields detailed information on summer annual and winter temperatures and on precipitation during the nine obliquity and precession controlled glacial periods marine isotope stages 96 to 80 and eight interglacial periods marine isotope stages 95 to 81 characterising this time interval the reconstruction reveals higher temperatures of at least 2 8 c in mean annual and 2 2 c in winter temperatures and 500 mm in precipitation during the interglacials as compared to the present day climate in the study area during the glacials temperatures are generally lower as compared to the present day climate in the region but precipitation is equivalent along the consecutive interglacials a trend toward a reduction in annual and winter temperatures by more than 2 3 c and toward a higher seasonality is observed along the consecutive glacials a trend toward a strong reduction in all temperature parameters of at least 1 6 c is reconstructed climatic amplitudes of interglacial glacial transitions increase from the older to the younger cycles for summer and annual temperatures the cross spectral analyses suggest obliquity related warm humid cold dry interglacial glacial cycles which are superimposed by precession related warm dry cold humid cycles a time displacement in the development of temperatures and precipitation is indicated for the obliquity band by temperatures generally leading precipitation change at 4 kyr and on the precession band of 9 6 kyr in maximum

north pacific seasonality and the glaciation of north america 2 7 million years ago in the context of gradual cenozoic cooling the timing of the onset of significant northern hemisphere glaciation 2 7 million years ago is consistent with milankovitch s orbital theory which posited that ice sheets grow when polar summertime insolation and temperature are low however the role of moisture supply in the initiation of large northern hemisphere ice sheets has remained unclear the subarctic pacific ocean represents a significant source of water vapour to boreal north america but it has been largely overlooked in efforts to explain northern hemisphere glaciation here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic pacific ocean indicating that 2 7 million years ago late summer sea surface temperatures in this ocean region rose in response to an increase in stratification at the same time winter sea surface temperatures cooled winter floating ice became more abundant and global climate descended into glacial conditions we suggest that the observed summer warming extended into the autumn providing water vapour to northern north america where it precipitated and accumulated as snow and thus allowed the initiation of northern hemisphere glaciation

north atlantic climate evolution through the plio pleistocene climate transitions during the plio pleistocene the earth witnessed the growth of large northern hemisphere ice sheets and profound changes in both north atlantic and global climate here we present a 3 2 myr long orbitally resolved alkenone sea surface temperature sst record from deep sea drilling project dsdp site 607 41 n 33 w water depth 3427 m in the north atlantic ocean we employ a multi proxy approach comparing these new observations with existing bottom water temperature bwt and stable isotope time series from the same site and sst time series from other sites shedding new light on plio pleistocene climate change north atlantic temperature records show a long term cooling with two major steps occurring during the late pliocene 3 1 to 2 4 ma and the mid pleistocene 1 5 to 0 8 ma closely timed with intervals of major change in northern hemisphere ice sheets existing evidence suggests that the late pliocene cooling may have been caused by a thresholded response to secular changes in atmospheric carbon dioxide co2 while an explanation for the mid pleistocene cooling may involve glacial interglacial changes in atmospheric co2 it seems to also require a change in the behavior of the ice sheets themselves north atlantic climate responses were closely phased with benthic oxygen isotope 18o changes during the 41 kyr world indicating a strong common northern hemisphere high latitude imprint on north atlantic climate signals after the mid pleistocene transition mpt north atlantic sst records and the site 607 benthic carbon isotope 13c record are more closely phased with 18o whereas bwt significantly leads 18o in the 100 kyr band suggesting a shift from a northern to a southern hemisphere influence on north atlantic bwt we propose that the expansion of the west antarctic ice sheet wais across the mpt increased the production and export of antarctic bottom water from the southern ocean and subsequently controlled its incursion into the north atlantic especially during glacial intervals it follows that the early 100 kyr response of bwt implies an early response of the wais relative to the northern hemisphere deglaciation thus in the 100 kyr world both northern hemisphere and southern hemisphere processes affect climate conditions in the north atlantic ocean

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

assimilation of sediments embedded in the oceanic arc crust myth or reality abstract arc magmas are commonly assumed to form by melting of sub arc mantle that has been variably enriched by a component from the subducted slab although most magmas that reach the surface are not primitive the impact of assimilation of the arc crust is often ignored with the consequence that trace element and isotopic compositions are commonly attributed only to varying contributions from different components present in the mantle this jeopardises the integrity of mass balance recycling calculations here we use sr and o isotope data in minerals from a suite of volcanic rocks from st lucia lesser antilles arc to show that assimilation of oceanic arc basement can be significant analysis of 87sr 86sr in single plagioclase phenocrysts from four soufriere volcanic complex svc st lucia hand samples with similar composition 87sr 86sr 0 7089 0 7091 reveals crystal isotopic heterogeneity among hand samples ranging from 0 7083 to 0 7094 with up to 0 0008 difference within a single hand sample o 18 measurements in the svc crystals show extreme variation beyond the mantle range with 7 5 to 11 1 for plagioclase n 19 10 6 to 11 8 for quartz n 10 9 4 to 9 8 for amphibole n 2 and 9 to 9 5 for pyroxene n 3 while older lavas pre soufriere volcanic complex with less radiogenic whole rock sr composition 87sr 86sr 0 7041 0 7062 display values closer to mantle range 6 4 to 7 9 for plagioclase n 4 and 6 to 6 8 for pyroxene n 5 we argue that the 87sr 86sr isotope disequilibrium and extreme o 18 values provide compelling evidence for assimilation of material located within the arc crust positive correlations between mineral o 18 and whole rock 87sr 86sr 143nd 144nd and 206 207 208pb 204pb shows that assimilation seems to be responsible not only for the isotopic heterogeneity observed in st lucia but also in the whole lesser antilles since st lucia encompasses almost the whole arc range of isotopic compositions this highlights the need for detailed mineral scale investigation of oceanic arc suites to quantify assimilation that could otherwise lead to misinterpretation of source composition and subduction processes

regional synthesis of mediterranean atmospheric circulation during the last glacial maximum atmospheric circulation leaves few direct traces in the geological record making reconstructions of this crucial element of the climate system inherently difficult we produced a regional mediterranean synthesis of paleo proxy data from the sea surface to alpine altitudes this provides a detailed observational context for change in the three dimensional structure of atmospheric circulation between the last glacial maximum lgm 23 000 to 19 000 years ago and the present the synthesis reveals evidence for frequent cold polar air incursions topographically channeled into the northwestern mediterranean anomalously steep vertical temperature gradients in the central mediterranean imply local convective precipitation we find the lgm patterns to be analogous though amplified to previously reconstructed phases of enhanced meridional winter circulation during the maunder minimum the little ice age

biomarker records of late neogene changes in northeast african vegetation open savannah grasslands dominated by c4 plants became a significant component of northeast african vegetation during the late neogene we present molecule specific carbon isotopic mea surements of terrestrial plant biomarkers preserved in marine sed iments off northeast africa that allow reconstruction of orbital scale vegetation changes in short time windows over the past 9 4 m y the biomarker data show large amplitude vegetation vari ability as early as 3 8 ma with the greatest c4 expansion occurring after 3 4 ma we sampled orbital scale oscillations of up to 5 almost as large as the observed late neogene range of 7 sug gesting that large and repeated oscillations between more open and more closed landscapes were an important aspect of northeast af rican vegetation change during the past 4 m y

evolution of ocean temperature and ice volume through the mid pleistocene climate transition earth s climate underwent a fundamental change between 1250 and 700 thousand years ago the mid pleistocene transition mpt when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing over this time an increase occurred in the amplitude of change of deep ocean foraminiferal oxygen isotopic ratios traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep ocean temperature we have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios our results suggest that the mpt was initiated by an abrupt increase in antarctic ice volume 900 thousand years ago we see no evidence of a pattern of gradual cooling but near freezing temperatures occur at every glacial maximum

origin of the middle pleistocene transition by ice sheet erosion of regolith the transition in the middle pleistocene 0 9 ma seen in 18o deep sea core records from relatively low amplitude high frequency 41 kyr to high amplitude low frequency 100 kyr ice volume variations under essentially the same orbital forcing can be attributed to a change from an all soft bedded to a mixed hard soft bedded laurentide ice sheet through glacial erosion of a thick regolith and resulting exposure of unweathered crystalline bedrock a one dimensional ice sheet and bedrock model which includes transport of sediment and ice by subglacial sediment deformation demonstrates that a widespread deforming sediment layer maintains thin ice sheets before the transition which respond linearly to the dominant 23 and 41 kyr orbital forcing progressive removal of the sediment layer eventually causes a transition to thicker ice sheets whose dominant timescale of change 100 kyr reflects nonlinear deglaciation processes in model simulations over the last 3 ma initialized with no ice and a uniform 50 m sediment layer the time series of ice volume and extent agree in several important aspects with the observed records

plio pleistocene high low latitude climate interplay a mediterranean point of view abstract the high low latitude climate interplay during the plio pleistocene global cooling is not yet well understood insight on the mediterranean region can provide some clues about past significant climate changes since the basin reflects the climate dynamics of both high latitude and low latitude regions being connected to the north atlantic and subjected to monsoon influence here we shade light on this connection problem by performing a spectral analysis on an eastern mediterranean stack of planktonic records spanning the last 5 ma and by further comparing it to north atlantic and pacific deep and surface water records our main conclusion is that the mediterranean detected the main global climate transitions over the last 5 myr although sapropel depositions indicate that it remained influenced by the african summer monsoon during the whole interval our analysis reveals that until 2 2 ma the mediterranean planktonic record is driven by regional processes dominated by precession the progressive emergence of the 41 kyr frequency in the mediterranean records around 2 8 ma suggests that since this date the mediterranean was more and more affected by the high latitude climate dynamics forcing than by the low latitude one moreover during the ongoing plio pleistocene cooling the 41 kyr frequency signal in the mediterranean records anticipated high latitude deep water response to the intensification of the northern hemisphere glaciations nhg and lagged the signal in tropical latitudes finally toward 1 2 ma the results suggest that the progressive shift from the 41 kyr to the 100 kyr frequency was led by the northern high latitudes overall our results confirm that the mediterranean is an ideal site to study the interplay between high and low latitude climates

on a tectonic mechanism for regional sealevel variations abstract no satisfactory tectonic explanations have yet been offered for the apparent sealevel fluctuations of about 1 cm 1000 years and a magnitude of up to a few hundred meters that have been proposed by vail et al 1 we propose a mechanism that does appear to be able to explain these changes if horizontal stresses of the order of a few kilobars occur in the lithosphere and if changes in these stress fields occur on geological time scales the proposed model is one of an interaction between these stresses and the deflections of the lithosphere caused by sedimentary loading apparent sealevel changes of up to 100 m can be produced at the flanks of the sedimentary basins by this interaction the mechanism is most effective for young margins that are subject to rapid sediment loading by its nature the tectonic model can explain contemporaneous fluctuations in apparent sealevel in neighbouring depositional environments in principle it implies the possibility of regional correlations in different basinal settings

an isotopic study of a fluvial lacustrine sequence the plio pleistocene koobi fora sequence east africa stable isotopic analyses of plio pleistocene and modern sediments in the fluvial lacustrine system occupying the turkana basin east africa provide constraints on the paleoenvironmental and diagenetic histories of the pliocene through the recent sediments in the basin the 13c values for carbonates in lacustrine sediments range from 15 to 22 relative to pdb depending on the varying proportions of co2 from the atmospheric reservoir and from various metabolic sources the 18o values of carbonates in lacustrine sediments indicate that the isotopic composition of paleolake water varied by over 10 from the pliocene to the present the 13c values for pedogenic carbonates record paleoccologic variations and suggest that c4 plants did not become well established in the preserved depositional parts of the basin until about 1 8 myr ago the 18o values pedogenic carbonates suggest a range of over 10 for the isotopic composition of soil water during this interval they also suggest a period of major climatic instability from about 3 4 to 3 1 myr and at about 1 8 myr together the 13c and 18o values of pedogenic carbonates indicate that the present conditions are as arid and hot as any that had prevailed during deposition of these plio pleistocene sediments

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

subpolar link to the emergence of the modern equatorial pacific cold tongue the cold upwelling tongue of the eastern equatorial pacific is a central energetic feature of the ocean dominating both the mean state and temporal variability of climate in the tropics and beyond recent evidence for the development of the modern cold tongue during the pliocene pleistocene transition has been explained as the result of extratropical cooling that drove a shoaling of the thermocline we have found that the sub antarctic and sub arctic regions underwent substantial cooling nearly synchronous to the cold tongue development thereby providing support for this hypothesis in addition we show that sub antarctic climate changed in its response to earth s orbital variations from a subtropical to a subpolar pattern as expected if cooling shrank the warm water sphere of the ocean and thus contracted the subtropical gyres

astronomic forcing on the planktonic foraminifera assemblage in the piacenzian punta piccola section southern italy 1 a high resolution quantitative analysis of the calcareous planktonic assemblages planktonic foraminifers and calcareous nannofossils at the punta piccola section at the base of which the global standard stratotype section and point of the piacenzian stage is defined provided a more accurate biostratigraphy for the mediterranean middle pliocene 2 6 3 6 ma in particular an astronomically calibrated age of 2 87 ma was estimated for the pliocene first occurrence of neogloboquadrina atlantica instead of the younger previously proposed age of 2 72 ma spectral analysis performed on the globigerinoides species spp planktonic foraminifera assemblage along with cross spectral analysis between the same record and the astronomic target curve la 041 1 calculated for the summer season june july at 65 n provided solid evidence that the globigerinoides spp group of planktonic species is a reliable recorder of orbital forcing and can be appropriately used for astronomical tuning of marine sedimentary records the same procedures of spectral analysis were applied to the individual species that constitute the globigerinoides spp group g ruber g obliquus and g quadrilobatus thus resolving their different frequency structures and species specific response to the different astronomic periodicities whereas g obliquus and g quadrilobatus appear primarily controlled by precession g ruber is largely forced by obliquity small ecological differences mainly related to dissimilar food quality requirements were assumed to distinctively control the time distribution of the two groups of species precessionally forced oligotrophic conditions in the surface mediterranean waters induced by summer continental runoff led to a dominance of copepods based dietary typical of g quadrilobatus conversely obliquity cycles drove the abundance distribution of g ruber in the sea surface waters of the mediterranean influencing the sea surface temperature light intensity and or phytoplankton distribution sub milankovitch periodicities cycles 1500 2500 3000 and 4500 years long are reliably detected in the faunal records suggesting that millennial scale variability punctuated the mediterranean climate regime during the interval of the middle pliocene northern hemisphere glaciation

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

a stable isotope study of the palaeoproterozoic tallberg porphyry type deposit northern sweden the tallberg deposit is situated in the skellefte district in northern sweden it is a palaeoproterozoic equivalent of phanerozoic poryphyry type deposits the mineralization is situated within the jorn granitoid complex and is associated with intrusive quartz feldspar porphyries the granitoids are coeval with mainly felsic volcanic rocks hosting several massive sulphide deposits the alteration is generally of a mixed phyllic propylitic type but areas or zones associated with high gold grades exhibit phyllic alteration ore minerals are pyrite chalcopyrite sphalerite magnetite and trace amounts of molybdenite in this stable isotope study quartz sericite and chlorite from the alteration zones were sampled the magmatic quartz has a 18o composition of 6 2 to 6 7 whereas the quartz in the hydrothermal alteration zones have values ranging from 7 5 to 10 6 the calculated temperatures for this fractionation range from 430 to 520 c the sericites have 18o ranging from 4 6 to 8 2 average 6 6 and d 31 to 54 average 41 chlorites range from 18o 4 2 to 7 7 and d from 34 to 44 the range of 34s of 11 pyrite samples is 3 8 to 5 5 with an average of 4 6 0 5 suggesting a relatively homogeneous sulphur source probably of magmatic origin modelling waters in equilibrium with the minerals indicates early magmatic fluids with 18o of 6 5 this fluid mixed with a low 18o and high d fluid which is tentatively identified as seawater the 18o signature of sericite and chlorite also indicates significant water rock exchange explaining the positive 18o values for the waters in equilibrium with the hydrated minerals

geochemical evidence for magmatic fluids in porphyry copper mineralization the koloula igneous complex comprises 26 different intrusive phases that have been divided into two major magmatic episodes cycle 1 intrusions 4 5 ma and cycle 2 intrusions 2 4 to 1 5 ma the cycle 2 intrusions are further divided into the inamumu zoned pluton izp which is composed of 6 concentrically disposed quartz diorite and tonalite units and several satellite intrusions the izp is host to porphyry copper mineralization whereas the cycle 1 and cycle 2 satellite intrusions are barren presently exposed mineralization in the izp a system represents the deeply eroded core of a porphyry copper system where widely spaced veinlet alteration envelopes 1 mm thick are separated by large volumes of unaltered rock

formal subdivision of the quaternary system period present status and future directions abstract the quaternary system period and pleistocene series epoch were defined in 2009 by the global boundary stratotype section and point gssp for the gelasian stage age 2 58 ma which aligns with marine isotope stage mis 103 and approximates the gauss matuyama chron boundary contrary to earlier reports the vrica gssp 1 80 ma was repurposed in 2011 to define the calabrian stage effectively completing the lower pleistocene subseries subepoch the candidate for the middle pleistocene subseries and proposed chibanian stage gssp 774 ka is the chiba section japan it aligns with mis 19 and approximates the matuyama brunhes chron boundary 773 ka the upper pleistocene subseries with a base traditionally marked by the onset of the last interglacial is not yet defined by gssp the holocene series epoch was formally defined in 2008 by a gssp in the ngrip2 greenland ice core with an age of 11 700 yr b2k before 2000 ce and in 2018 was subdivided using climatic events at 8 2 and 4 2 ka into the greenlandian northgrippian and meghalayan stages ages and their corresponding lower early middle upper late subseries subepochs the northgrippian gssp 8236 yr b2k is defined in the ngrip1 greenland ice core and the meghalayan gssp 4250 yr b2k in a speleothem from meghalaya india this subdivision formally introduces the rank of subseries subepoch and incorporates by far the briefest of all stages into the geological time scale using ice cores and a speleothem for gssps is unique to the holocene the presently undefined term anthropocene is already used extensively and like holocene subdivisional terms its functionality will be enhanced by formal definition the anthropocene should not be confused with anthropogenic it reflects a tipping point in the earth system response to the marked intensification of human impacts not simply the fact of human impact the geological anthropocene as currently envisioned would start in the mid twentieth century holding the rank of series and terminating the holocene but not interfering with its subdivision other than to terminate the meghalayan stage

evolution and paragenetic context of low δd hydrothermal fluids from the panasqueira w sn deposit portugal new evidence from microthermometric stable isotope noble gas and halogen analyses of primary fluid inclusions abstract the evolution paragenetic context and origin of remarkably low d hydrothermal fluids from the hercynian panasqueira w sn cu ag deposit have been investigated through a combined microthermometric stable isotope halogen and noble gas fluid inclusion study large variations in d between 60 and 134 have been observed in primary fluid inclusions from growth zones in a quartz crystal pa66 paragenetically constrained to the main sulfide stage mss of ore formation the same fluids exhibited relatively constant fluid inclusion homogenisation temperatures 254 to 260 c salinities 7 4 to 8 7 wt nacl equivalent and calculated fluid 18o 3 8 to 4 4 all the fluids exhibited 40ar excesses mean molar br cl and i cl ratios varied from 2 3 10 3 4 2 10 3 and 8 10 4 10 10 4 respectively with the more br rich fluids being associated with the more deuterium depleted fluids the low palaeolatitude of panasqueira throughout the main stages of ore formation and the overwhelming predominance of meteoric fluids in the main late and post ore mineralising fluids with d of 40 to 65 lends little support for any models involving low d palaeometeoric water the limited range of 40ar cl ratios 1 1 10 5 1 6 10 5 also precludes boiling during the mss or mixing of meteoric water with highly fractionated deuterium depleted magmatic waters as viable mechanisms for producing the low d fluids the high br cl and i cl of the mss fluids indicate significant fluid interactions with organic rich sediments or metasediments in particular regionally abundant carboniferous coals or coaly sediments that are inferred to be depleted in deuterium by around 85 compared to palaeometeoric water the large range of d observed in the mss fluids may be explained by isotopic exchange of palaeometeoric water with these coals at varying water rock wt wt ratios between 0 02 and 0 002 with fluid oxygen isotopic compositions controlled by exchange with the beira schists such a model is consistent with the requirements that any satisfactory model must take into account viz i the relative constancy of temperature salinity 40ar and fluid 18o during excursions to low d ii the high i cl and br cl ratios observed and iii the coincidence of these low d fluids with the onset of precipitation of polymetallic sulfides and phosphates under reducing conditions the model indicates that meta sedimentary sources of ore forming components became increasingly important during the evolution of the panasqueira sn w deposit and accounts in part for the observed progression from oxide dominated to base metal sulfide dominated parageneses

global temperature calibration of the alkenone unsaturation index uk 37 in surface waters and comparison with surface sediments in this paper we compile the current surface seawater c37 alkenone unsaturation uk 37 measurements n 629 1 to 30 c temperature range to derive a global field based calibration of uk 37 with alkenone production temperature a single nonlinear global surface water calibration of uk 37 accurately predicts alkenone production temperatures over the diversity of modern day oceanic environments and alkenone synthesizing populations t 0 957 54 293 uk 37 52 894 uk 37 2 28 321 uk 37 3 r2 0 97 n 567 the mean standard error of estimation is 1 2 c with insignificant bias in estimated production temperature among the different ocean regions sampled an exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients e g the brazil malvinas confluence in contrast to the surface water data the calibration of uk 37 in surface sediments with overlying annual mean sea surface temperature anno is best fit by a linear model anno 29 876 uk 37 1 334 r2 0 97 n 592 the standard error of estimation 1 1 c is similar to that of the surface water production calibration but a higher degree of bias is observed among the regional data sets the sediment calibration differs significantly from the surface water calibration uk 37 in surface sediments is consistently higher than that predicted from anno and the surface water production temperature calibration and the magnitude of the offset increases as the surface water anno decreases we apply the global production temperature calibration to the coretop uk 37 data to estimate the coretop alkenone integrated production temperature coretop ipt and compare this with the overlying annual mean sea surface temperature anno we use simple models to explore the possible causes of the deviation observed between the coretop temperature signal as estimated by uk 37 and anno our results indicate that the deviation can best be explained if seasonality in production and or thermocline production as well as differential degradation of 37 3 and 37 2 alkenones both affect the sedimentary alkenone signal

multi proxy constraints on sapropel formation during the late pliocene of central mediterranean southwest sicily abstract the late pliocene piacenzian in the mediterranean region was punctuated by short lived episodes of widespread deposition of organic rich sedimentary layers known as sapropels the causes of their formation remain a long standing debate in the science community and require disentangling the roles of climatic oceanographic processes that triggered higher primary productivity or enhanced organic matter preservation the lack of data especially of sea temperatures at sufficient temporal resolution is one of the main challenges to solve this debate here we present new organic geochemistry and micropaleontological data from the late pliocene at punta grande punta piccola sections southwest sicily that allow untangling the mechanisms that favored the formation of two sapropel series noted s and a in the central mediterranean area during this period sea surface ssts and subsurface temperatures were estimated using three distinct organic geochemical proxies namely the alkenone unsaturation index u k 37 the long chain diol index ldi and the tetraether index tex86 reconstructed ssts are relatively stable throughout the late pliocene and 4 c higher than modern mediterranean ssts which is consistent with the climatic conditions inferred for this period from paleoclimate modeling an increase in sst is however recorded by u k 37 and ldi proxies across each sapropel horizon supporting that the two sapropel series s and a were formed during warmer climate conditions the comparison of sst data with variations in accumulation rates of total organic carbon and lipid biomarkers alkenones long chain alkyl diols archaeal and bacterial tetraethers and with changes in calcareous nannofossil assemblages indicates that the studied sapropels might have formed under different environmental conditions the first series of sapropels s deposited between 3 1 and 2 8 ma is likely due to a better preservation of organic matter induced by the development of a strong thermohaline stratification of the water column and to oxygen depleted bottom waters higher terrestrial input that occurred between 3 1 and 2 8 ma may interestingly explain the large discrepancies observed between tex86 and u k 37 ldi temperature values during this period the second series of sapropels a deposited between 2 7 and 2 6 ma is more likely due to enhanced primary productivity in a weakly stratified water column

high precision pb sr nd hf isotopic characterization of usgs bhvo 1 and bhvo 2 reference materials the recent development of multiple collector inductively coupled plasma mass spectrometry mc icp ms and increasing use of the technique have created the need for well characterized rock standards especially for isotopic systems where no internal fractionation correction can be applied this paper presents a careful leaching experiment on the u s geological survey usgs reference materials bhvo 1 and bhvo 2 hawaiian basalts and documents the evidence for contamination of the rock powders during processing this contamination accounts for the difference in pb isotopic ratios of bhvo 1 and bhvo 2 as well as for their lack of homogeneity both in pb isotopic compositions and in some trace element contents copyright 2005 by the american geophysical union

the first glacial maximum in north america despite marine evidence for at least 50 pliocene pleistocene ice sheet advances only the most recent one has been accurately reconstructed from terrestrial evidence because there are few techniques for dating older glacial deposits here we show that the cosmic ray produced nuclides beryllium 10 and aluminum 26 can be used to date tills that overlie paleosols

high frequency climate linkages between the north atlantic and the mediterranean during marine oxygen isotope stage 100 mis100 high resolution records of mediterranean and north atlantic deep sea sediments indicate that rapid changes in hydrology and climate occurred during marine oxygen isotope stage 100 mis100 at 2 52 ma which exhibits characteristics similar to late pleistocene dansgaard oeschger bond cycles and heinrich events as in the late pleistocene north atlantic oceanographic and atmospheric changes were probably transmitted into the mediterranean by some combination of surface water inflow and atlantic mediterranean atmospheric pressure gradients our data suggest that the mechanism s responsible for sub milankovitch and millennial scale climate oscillations were the same over at least the past 2 6 ma notwithstanding the transition from the 41 kyr dominated glacial cycles of the late pliocene to the 100 kyr cycles of the late pleistocene

an overview of the post messinian paleoenvironmental history of the western mediterranean a review of the pliocene pleistocene paleoenvironmental history of the western mediterranean is presented based on micropaleontological and geochemical studies of ocean drilling program odp leg 107 material and marine outcrops in southern italy the calcareous plankton biochronology proposed for the mediterranean by rio et al 1990 and 1991a provides the necessary age control for determining the timing of major climatic and oceanographic changes in the region the early pliocene period in the mediterranean was not a time of warm stable climate rather it was marked by relatively high amplitude climatic oscillations in marginal areas these climatic oscillations resulted in the rhythmic deposition of limestone marl couplets which have an average duration of approximately 19 000 years it is proposed that these sedimentary couplets are the result of precessionally induced changes in monsoon intensity which in turn cause variability in coastal divergence and upwelling the 18o and the calcareous plankton foraminifera and coccoliths records for tyrrhenian sea odp site 653 reveal a cooling of surface waters at 3 1 ma coincident with this cooling is an increase in the frequency of diatomite formation in southern italy bianco section the global cooling at 2 4 ma and the associated expansion of northern hemisphere glaciation resulted in a shift to more arid conditions in the mediterranean region this climate change may have altered the mediterranean water balance resulting in the establishment of antiestuarine water exchange with the atlantic at this time the 18o record for site 653 is also marked by a sharp cooling across the pliocene pleistocene boundary in the boundary stratotype section at vrica this cooling is manifested as an increase in the abundance of the planktonic foraminifer neogloboquadrina pachyderma

the rossello composite a mediterranean and global reference section for the early to early late pliocene a high resolution magnetostratigraphy planktonic foraminiferal biostratigraphy and cyclostratigraphy is presented for the pliocene trubi marls in the punta di maiata section on sicily the integrated stratigraphy of the rossello composite section of hilgen 1 newslett stratigr 17 1987 is thereby completed this composite section provides an unprecedented high quality reference section for the early to early late pliocene containing a continuous sequence ranging from below the thvera subchron into the matuyama chron 4 86 2 45 ma the punta di maiata section extends from the sidufjall subchron of the gilbert into the gauss chron 4 50 3 30 ma linear interpolation between paleomagnetic datum planes in this section yields first order age estimates of 3 72 0 01 and 3 59 0 01 ma for the last common occurrence lco and the actual last occurrence lo of globorotalia margaritae in addition this age of 3 59 ma provides an accurate age for the zanclean piacenzian z p boundary provided the lo of g margaritae is maintained as a criterion to define this boundary in the mediterranean irrespective however of the criterion used the punta di maiata and punta piccola subsections of the rossello composite are at present the most suitable sections to be designated as stratotypes for the z p boundary the global significance of the rossello composite is further strongly enhanced by the establishment of an astronomically calibrated geomagnetic polarity time scale based on the correlation of the trubi sedimentary cycles with the astronomical record

late miocene global cooling and the rise of modern ecosystems a period of continental aridification and ecosystem change occurred about seven million years ago a global sea surface temperature reconstruction identifies cooling temperatures and a strengthened meridional temperature gradient at this time

temperature and salinity variations of mediterranean sea surface waters over the last 16 000 years from records of planktonic stable oxygen isotopes and alkenone unsaturation ratios alkenone unsaturation ratios and planktonic d18o records from sediment cores of the alboran ionian and levantine basins in the mediterranean sea show pronounced variations in paleo temperatures and salinities of surface waters over the last 16 000 years average sea surface temperatures ssts are low during the last glacial averages prior to 13 000 years 11 15 c vary rapidly at the beginning of the holocene and increase to 17 18 ca t all sites during s1 formation dated between 9500 and 6600 calendar years the modern temperature gradient 2 3 c between the mediterranean sub basins is maintained during formation of sapropel s1 in the eastern mediterranean sea after s1 ssts have remained uniform in the alboran sea at 18 c and have fluctuated around 20 c in the ionian and levantine basin sites the d18o of planktonic foraminifer calcite decreases by 2 from the late glacial to s1 sediments in the ionian basin and by 2 8 in the levantine basin in the alboran sea the decrease is 1 7 of the 2 8 decrease in the levantine basin the evect of global ice volume accounts for a maximum of 1 05 and the temperature increase explains only a maximum of 1 3 the remainder is attributed to salinity changes we use the temperature and salinity estimates to calculate seawater density changes they indicate that a reversal of water mass circulation is not a likely explanation for increased carbon burial during s1 time instead it appears that intermediate and deep water formation may have shifted to the ionian sea approximately 2000 years before onset of s1 deposition because surface waters were as cold but saltier than surface water in the levantine basin during the younger dryas sapropel s1 began to form at the same time when a significant density decrease also occurred in the ionian sea 2000 elsevier science b v all rights reserved

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

late pliocene northern hemisphere glaciations the continental and marine responses in the central mediterranean abstract detailed pollen analyses and oxygen isotope records of three foraminiferal species globigerina bulloides uvigerina peregrina and cibicides pachyderma from the semaforo and vrica composite sections crotone southern italy have been compared to the global climatic changes depicted by late pliocene early pleistocene foraminiferal 18o records of site 607 in the north atlantic and hole 653a in the tyrrhenian basin west mediterranean major overturns in the mid altitude vegetation are shown near isotopic stages 82 60 58 and 50 at about 2 03 ma 1 6 ma and 1 37 ma according to the raymo et al 1989 and ruddiman et al 1989 timescales at the same dates glacial 18o maxima either became higher or display step increases in the western mediterranean or in the open ocean as well this suggests that size increases of northern hemisphere ice sheets were the driving factor for regional or local marine and continental environmental changes within the mediterranean basin near isotopic stages 62 60 close to the conventional plio pleistocene boundary the climatic conditions severed enough within the mediterranean basin to modify the continental environment as depicted by a sudden increase of artemisia percentages while the first significant southward migration of the north polar front may have been recorded by an influx of left coiling neogloboquadrina pachyderma in the central mediterranean it also appears that boreal guests entered the mediterranean during phases of 18o enrichment of foraminiferal calcite there does not seem to be any discrepancy between the climatic concept of the pliocene pleistocene boundary and its chronostratigraphic definition

revised tuning of ocean drilling program site 964 and kc01b mediterranean and implications for the δ18o tephra calcareous nannofossil and geomagnetic reversal chronologies of the past 1 1 myr 1 high resolution color reflectance records of kc01 and kc01b calabrian ridge ionian sea are presented and compared with a modified spliced high resolution color reflectance record of ocean drilling program odp site 964 this comparison revealed that kc01b is characterized by intensive deformation between 27 and 28 5 m piston depth and that some sapropels are tectonically reduced in thickness moreover the piston coring has caused considerable stretching in the top of kc01 and kc01b using a new splice of odp site 964 as guide previous astronomical tuned timescales of kc01b and odp site 964 were evaluated this evaluation resulted in a new sapropel based astronomical timescale for the last 1 1 myr the new timescale implies a much more uniform change in sedimentation rate for the ionian sea cores two prominent excursions to lighter values in the 18o record of the planktonic foraminiferal species globigerinoides ruber occur during marine isotopic stages 12 and 16 applying the new timescale these shifts correspond with maxima in obliquity and are punctuated by minima in the precession cycle they are absent in global ice volume records and are interpreted as reflecting a summer low salinity surface water lens that floats on top of extremely saline intermediate and deep waters at times of the very low sea levels during these glacial periods all biostratigraphic and magnetostratigraphic events found in kc01b and odp site 964 were re dated according to the new timescale and the ages of 33 tephra layers were reviewed the new ages for the calabrian ridge 2 and 3 magnetic events in the brunhes are concordant with minima in the global sint800 composite record derived from worldwide deep sea records of relative paleointensity and have been attributed to the big lost and la palma excursions respectively

tropical ocean temperatures over the past 3 5 million years determining the timing and amplitude of tropical sea surface temperature sst change is an important part of solving the puzzle of the plio pleistocene ice ages alkenone based tropical sst records from the major ocean basins show coherent glacial interglacial temperature changes of 1 to 3 c that align with but slightly lead global changes in ice volume and deep ocean temperature over the past 3 5 million years tropical temperatures became tightly coupled with benthic 18o and orbital forcing after 2 7 million years we interpret the similarity of tropical sst changes in dynamically dissimilar regions to reflect top down forcing through the atmosphere the inception of a strong carbon dioxide greenhouse gas feedback and amplification of orbital forcing at 2 7 million years ago connected the fate of northern hemisphere ice sheets with global ocean temperatures since that time

integrated stratigraphy and astronomical tuning of the serravallian and lower tortonian at monte dei corvi middle upper miocene northern italy an integrated stratigraphy calcareous plankton biostratigraphy magnetostratigraphy and cyclostratigraphy is presented for the serravallian and lower tortonian part middle upper miocene of the monte dei corvi section located in northern italy the detailed biostratigraphic analysis showed that both the discoaster kugleri acme and the first influx of neogloboquadrina acostaensis are recorded at monte dei corvi these events which passed unobserved in previous studies play an important role in delineating the serravallian tortonian boundary thermal and alternating field demagnetization revealed a characteristic low temperature component marked by dual polarities the resultant magnetostratigraphy for the upper part of the section can be unambiguously calibrated to the gpts ranging from c5n 2n up to c4r 2r unfortunately the lower part of the section including the serravallian tortonian boundary interval did not produce a reliable magnetostratigraphy despite the fact that some short reversed intervals and a single normal interval are recorded using sedimentary cycle patterns in combination with the calcareous plankton biostratigraphy the section can be correlated cyclostratigraphically in detail to the partially overlapping and previously tuned section of monte gibliscemi on sicily the monte dei corvi section is dated astronomically by calibrating the basic small scale sedimentary cycles to the precession and 65 n lat summer insolation time series of the la93 solution following an initial tuning of larger scale cycles to eccentricity an almost perfect fit is found between the cycle patterns and intricate details especially precession obliquity interference in the insolation target between 8 5 and 10 ma the tuning to precession remains robust for most intervals back to the base of the section dated at 13 4 ma and shows that the section is continuous apart from a possible short hiatus in the tortonian it provides accurate astronomical ages for all sedimentary cycles calcareous plankton events polarity reversals and ash layers and marks a significant improvement of the recently proposed astronomical calibrations of the monte dei corvi section and of parallel sections in the mediterranean astronomical ages for the ancona and respighi ashbeds are significantly older than previously reported 40 ar 39 ar biotite ages even if the revised older age for the fct san dating standard of 28 02 ma is applied the astronomical dating of the magnetic reversals in the monte dei corvi section results in the completion of the astronomical polarity time scale for the last 13 myr the monte dei corvi section has recently been proposed as the stratotype section for the serravallian tortonian boundary despite the moderate to

late pliocene and early pleistocene vegetation and climate change revealed by a pollen record from nihewan basin north china abstract the nihewan formation is an important early quaternary sedimentary formation in north china we conducted pollen analyses of 183 samples and 1611 modern surface samples to characterize the processes of vegetation succession and climate change during the pliocene pleistocene transition 2 89 2 34 ma in the nihewan basin the results show that pollen assemblages are dominated by arboreal pollen indicating that the vegetation in the study area was forest dominated and that the climate was more humid than today however the temperature varied substantially the most substantial vegetation and climate changes occurred at 2 8 ma when the pollen representation of warm and humid tolerant taxa such as evergreen quercus and carya disappeared and also broadleaved deciduous types such as ulmus deciduous quercus and betula decreased obviously on the contrary the pollen representation of cold and drought tolerant taxa increased substantially e g picea from generally less than 20 to more than 30 and chenopodiaceae from generally less than 10 to more than 20 the quantitative reconstructed results indicating that tann decreased by about 2 3 c and pann decreased by 150 mm compared to before 2 8 ma with a maximum decrease of 9 c for tann and 450 mm for pann another important vegetation and climate changes occurred at 2 6 ma which was the coldest and driest of the studied interval when the vegetation was substantially simplified with spruce generally above 80 as the dominated types

african climate change and faunal evolution during the pliocene pleistocene abstract environmental theories of african faunal evolution state that important evolutionary changes during the pliocene pleistocene interval the last ca 5 3 million years were mediated by changes in african climate or shifts in climate variability marine sediment sequences demonstrate that subtropical african climate periodically oscillated between markedly wetter and drier conditions paced by earth orbital variations with evidence for step like 0 2 ma increases in african climate variability and aridity near 2 8 ma 1 7 ma and 1 0 ma coincident with the onset and intensification of high latitude glacial cycles analysis of the best dated and most complete african mammal fossil databases indicates african faunal assemblage and perhaps speciation changes during the pliocene pleistocene suggesting more varied and open habitats at 2 9 2 4 ma and after 1 8 ma these intervals correspond to key junctures in early hominid evolution including the emergence of our genus homo pliocene pleistocene shifts in african climate vegetation and faunal assemblages thus appear to be roughly contemporary although detailed comparisons are hampered by sampling gaps dating uncertainties and preservational biases in the fossil record further study of possible relations between african faunal and climatic change will benefit from the accelerating pace of important new fossil discoveries emerging molecular biomarker methods for reconstructing african paleovegetation changes tephra correlations between terrestrial and marine sequences as well as continuing collaborations between the paleoclimatic and paleoanthropological communities

seasonality fluctuations recorded in fossil bivalves during the early pleistocene implications for climate change understanding the transformations of the climate system may help to predict and reduce the effects of global climate change the geological record provides a unique archive that documents the long term fluctuations of environmental variables such as seasonal change here we investigate how seasonal variation in seawater temperatures varied in the mediterranean sea during the early pleistocene approaching the early middle pleistocene transition empt and the beginning of precession driven quaternary style glacial interglacial cycles we performed whole shell and sclerochemical stable isotope analyses 18o 13c on bivalves collected from the lower pleistocene arda river marine succession northern italy after checking shell preservation our results indicate that seawater temperature seasonality was the main variable of climate change in the mediterranean area during the early pleistocene with the northern hemisphere glaciation nhg exerting a control on the mediterranean climate we show that strong seasonality 14 4 16 0 c range and low winter paleotemperatures 0 8 1 6 c were likely the triggers leading to the establishment of widespread populations of so called northern guests i e cold water taxa in the mediterranean sea around 1 80 ma the shells postdating the arrival of the northern guests record a return to lower seasonal variations and higher seawater paleotemperatures with seasonality increasing again approaching the empt the latter however is not associated with a corresponding cooling of mean seawater paleotemperatures showing that the observed seasonality variation represents a clear signal of progressive climate change in the mediterranean sea

vegetation response to upper pliocene glacial interglacial cyclicity in the central mediterranean abstract new detailed pollen analysis of the lower part of the upper pliocene semaforo section crotone italy documents cyclic behavior of vegetation at the beginning of the northern hemisphere glaciations the competition between four vegetation units subtropical humid forest deciduous temperate forest altitudinal coniferous forest and open xeric assemblage probably reflects modifications of vegetation belts at this montane site several increases in herbaceous open vegetation regularly alternate with subtropical humid forest which expresses rapid climatic oscillations the complete temporal succession deciduous forest rich in quercus followed by subtropical humid forest taxodiaceae and cathaya then altitudinal coniferous forest tsuga cedrus abies and picea and finally herbaceous open vegetation graminae compositae and artemisia displays the climatic evolution from warm and humid interglaciation to cold and dry glaciation it also suggests an independent variation of temperature and humidity the two main climatic parameters the vegetation history of southern calabria recorded in the semaforo section have been correlated with the 18o signal established in the atlantic ocean

geochemical evidence for magmatic fluids in porphyry copper mineralization part ii ion probe analysis of cu contents of mafic minerals koloula igneous complex