planktonic foraminiferal biostratigraphy and assemblages in the bering sea during the pliocene and pleistocene iodp sites u1340 and u1343 abstract iodp site u1340 and site u1343 in the bering sea have been investigated with regard to planktonic foraminifers and fragmentation the base of site u1340 dates back to the early pliocene and the base of site u1343 to the early pleistocene site u1340 is situated at bowers ridge the southern bering sea site u1343 is situated near the gateway to the arctic ocean in the northern bering sea at both sites there are none or very few planktonic foraminifers during the pliocene and early pleistocene after 1 3 1 4 ma the planktonic foraminifers are continuously present for most of the samples examined three stratigraphic events have been identified in this study the first occurrence fo of neogloboquadrina inglei is observed at 1 4 1 5 ma although this event may be affected by poor preservation of foraminifers in older sediments the observed age of the change in the coiling ratio of neogloboquadrina pachyderma from right to left at 1 2 ma agrees with the dating of the same event at the californian margin the age of the last occurrence lo of n inglei also seems to match the same event from the californian margin at 0 7 ma this implies that these events are robust regional events for the entire northern pacific multivariate analyses of the quantitative planktonic foraminifer data show three main faunal assemblages the oldest assemblage from 1 3 1 4 ma to 1 2 ma is dominated by n pachyderma s l dex together with globigerina bulloides other species in this fauna are n inglei n pachyderma s l sin globigerina umbilicata and turborotalita quinqueloba after 1 2 ma the faunal assemblage is dominated by n pachyderma s l sin but the remaining species are the same as before at 0 7 ma n inglei disappears whilst the remaining fauna assemblage stays the same with n pachyderma s l sin still dominating reflecting subpolar polar conditions prior to 1 4 1 3 ma there are very few or no planktonic foraminifers low shell fragmentation and lower toc suggest that the lack of planktonic foraminifers in these sediments cannot be explained either by a shoaling of the carbonate compensation depth or by enhanced supralysoclinal dissolution instead we argue that the appearance of abundant foraminifers in the sediment reflects the same evolutionary adaption of n pachyderma sin to cold conditions to have occurred after 1 1 1 0 ma as in the north atlantic

paleoenvironmental changes at the lower pleistocene montalbano jonico section southern italy global versus regional signals abstract integrated high resolution data from calcareous plankton assemblages foraminifera and nannofossils together with geochemical and mineralogical investigations have been collected at the on land montalbano jonico section southern italy in order to reconstruct the paleoenvironmental changes through marine isotope stages mis 23 37 time series analysis on globigerina bulloides and cassidulina carinata 18o records and on selected calcareous plankton proxies mainly revealed the occurrence of precession and obliquity forcing the deposition of sapropel layers which are interbedded in the montalbano jonico section was driven by water column stratification insolation cycle i 104 and enhanced sea surface water productivity insolation cycle i 112 i 102 and i 86 different paleoenvironmental conditions mark the sedimentary evolution of the section from 1240 to 1082 ka mis 37 mis 32 high percentage abundances of warm and oligotrophic planktonic foraminifera and calcareous nannofossil taxa indicate the establishment of oligotrophic and stratified surface water conditions a key paleoenvironmental change occurred during mis 31 from about 1080 to 1065 ka which was a very warm interglacial characterized by an increase of tropical subtropical globigerinoides ruber group and globigerinoides trilobus and low salinity braarudosphaera bigelowii sea surface water taxa during this interval more humid climate conditions coupled with changes in local paleomorphology may have triggered a higher and unusual freshwater input and the creation of a new entry point for sediment supply into the basin from a different drainage area from about 1065 to 1010 ka mis 30 mis 29 a cool and dry climate prevailed in the circum mediterranean area during a time of precession maxima this favored lowered sea surface temperatures and an increase of polar water neogloboquadrina pachyderma left coiling there are also indications of a reduction of the terrigenous input from the new source area from 1010 ka upward mis 28 mis 23 the higher abundances of globigerina bulloides turborotalita quinqueloba and calciosolenia spp indicate enhanced productivity conditions probably related to high turbidity of sea surface waters triggered by a more conspicuous sediment input from land analysis of the long term trends in the multiproxy patterns suggests that the major paleoenvironmental changes occurred as a consequence of the combined effect of orbitally controlled global climate and regional processes

thermal histories of co3 chondrites application of olivine diffusion modelling to parent body metamorphism abstract the petrologic sequence observed in the co3 chondrite group has been suggested to be the result of thermal metamorphism on a parent body we have developed a model to examine the possibility that chondrule and matrix olivines equilibrated in situ during parent body metamorphism the model considers fe mg interdiffusion between chondrule and matrix olivines zoning profiles comparable to those observed in chondrule olivines from partially equilibrated members of the series are reproduced successfully metamorphism of co3 chondrites on a parent body is therefore a viable model for the observed equilibration results indicate that peak metamorphic temperatures experienced by the co3 chondrites were around 500 c and that the range of peak temperatures between unequilibrated and equilibrated subtypes was relatively narrow around 100 c

latest quaternary north pacific surface water responses imply atmosphere driven climate instability a full sequence of brief interstadials dansgaard oeschger d o cycles are recorded from 60 to 25 ka in santa barbara basin california ocean drilling program hole 893a by planktonic foraminiferal isotopic and assemblage changes at unparalleled high resolution for the oceans synchronous climatic response between north pacific surface waters and the greenland ice sheet during d o cycling is strongly indicated by remarkable similarities in speed magnitude and character of rapid oceanic and atmospheric reorganizations inferred sea surface temperature warmings of as much as 5 c within a few decades and brief warming overshoots of as much as 3 c suggest involvement of an atmospheric amplification top down in situ atmospheric warming of the ocean is implied by differential responses partial decoupling in the changes recorded in surface and thermoclinal waters

surface and deep water variability in the western mediterranean odp site 975 during insolation cycle 74 high resolution calcareous plankton and molecular biomarker signals abstract we reconstructed changes in productivity and surface subsurface and deep water dynamics in the western mediterranean through a multi proxy study of ocean drilling program site 975 between late marine isotope stage mis 20 and early interglacial mis 19 our high resolution study down to 200 year resolution combines calcareous plankton assemblages coccolithophores and foraminifera biomarkers c37 alkenones n alkanes n alcohols and elemental proxies total organic carbon total nitrogen calcium carbonate surface water conditions are derived i from high resolution 18o and 13c records obtained from the planktonic foraminifer globigerina bulloides and ii from summer and winter foraminifera based sea surface temperature reconstructions sstjas foram sstjfm foram achieved through transfer function the integration of the whole dataset makes it possible to identify in the balearic sea and to accurately characterize for the first time an organic rich layer orl during latest mis 20 early mis 19 close to i cycle 74 its presence is marked firstly by higher values of total nitrogen tn and an increase of total c37 alkenone and total organic carbon toc preserved in the sediments the multi proxy approach reveals that the deglacial phase played a prominent role for orl formation that was characterized by centennial scale phases the alcohol preservation index api suggests that the shoaling of the circulation which boosted marine productivity started in the deglaciation and in combination with freshening by atlantic water inflow riverine input and surface water buoyancy during sea level rising culminated during the orl event at this time calcareous plankton proliferated on subsurface surface waters benefiting from ameliorating conditions which promoted maximum marine productivity and higher organic matter preservation on the seafloor

mid pleistocene environmental change in tropical africa began as early as 1 05 ma palynological records from the congo fan reveal environmental change in equatorial africa occurring 1 05 ma ago 100 k y before the mid pleistocene climatic shift at 0 9 ma prior to 1 05 ma a glacial interglacial rhythm is not obvious in the african vegetation variation afterwards podocarpus spread in the mountains of central africa mainly during glacials and congo river discharge decreased the sequence of vegetation variation associated with the mid pleistocene glacials and interglacials differed from that observed during the late pleistocene between 0 9 and 0 6 ma interglacials were characterized by warm dry conditions and glacials were characterized by cool humid conditions while during the past 0 2 ma glacials were cold and dry and interglacials warm and humid our data indicate that before the northern hemisphere ice caps dramatically increased in size 0 9 0 6 ma low latitude climate forcing and response in the tropics played an important role in the initiation of 100 k y ice age cycles during the mid to late pleistocene however the climate conditions in the tropics were increasingly influenced by the glacialinterglacial variations of continental ice sheets

marine and terrestrial climate variability in the western mediterranean sea during marine isotope stages 20 and 19 abstract the climate variability within late marine isotope stage mis 20 and mis 19 is examined with particular reference to the response of marine and terrestrial realms in the area surrounding the alboran sea western mediterranean sea sediment samples from the ocean drilling program site 976 were used to derive high temporal resolution average resolution of 450 years palynological pollen and spores and calcareous plankton coccolithophores and foraminifera records these data together with the new 18og bulloides make it possible to discuss the paleoenvironmental changes within a well constrained chronological frame cooler phases including late mis 20 and several cold spells during mis 19b a are marked on land by the expansion of open vegetation formations dominated by steppe and semi desert taxa at the same time the western mediterranean sea is marked by the incursion of north atlantic polar water planktonic taxa mis 19c and interstadials of mis 19b a are characterized by the spread of prevalent temperate forest taxa that parallel the expansion of warm water calcareous plankton taxa during periods of lighter 18o climate variations at both precessional and millennial to sub millennial time scales expressed by on land and marine signals highlight the sensitivity of the western mediterranean area to both orbital forcing and rapid internal oscillations of the climate systems involving remote connections with north hemisphere high latitudes the correlation within the central western mediterranean and north atlantic climate dynamics including the time spatial gradients related to regional and global climate processes contributes to the reconstruction of the earth climate dynamics and marine vs land responses in full early middle pleistocene transition these new evidences also provide an opportunity to improve knowledge of mis 19c now considered due to its orbital geometry the best orbital analogue to the holocene

biochronology and evolutionary implications of late neogene california margin planktonic foraminiferal events the biochronology of eight events first or last occurrences among species of the planktonic foraminifer neogloboquadrina plexus have been examined in six pliocene to quaternary deep sea sequences drilled during odp leg 167 off the coast of california the sites form a meridional transect along the california margin from 318 nt o 418n covering an area under the direct influence of the california current and associated upwelling system using age models based on combination of calcareous nannofossil and radiolarian data and magnetostratigraphic chron boundaries ages were assigned to the events thus allowing investigations of their spatial and temporal distribution three of the events have been identified as clearly diachronous two of these seem to represent examples of latitudinal immigrations the evolutionary activity in the neogloboquadrinid clade on the california margin appears centered around 2 1 ma with most of the events occurring between 2 5 and 1 ma this interval was a time of major climate change no events have occurred after 0 7 ma supporting the notion that the extreme climate variations of the late pleistocene inhibited speciation assignment of ages to events defining boundaries of the california margin cm zones of kennett and others has enabled us to compare this zonation with the standard planktonic foraminiferal zonal schemes seven of the neogloboquadrinid events occurred during the last 2 5 myr suggesting that the time resolution of the cm zones including the coiling dominance zones of lagoe and thompson during this interval is at least twice that of the standard planktonic foraminiferal zonation the remaining pliocene is divided only into two cm zones compared to six standard planktonic foraminiferal zones one of the pleistocene neogloboquadrinids is formally described as a new species q 2000 elsevier science ltd all rights reserved

orbital variations in planktonic foraminifera assemblages from the ionian sea during the middle pleistocene transition abstract the middle pleistocene transition 1 2 0 7 ma is the most recent re organization of the global climate system which includes variations in the frequency and amplitude of glacial interglacial cycles increased ice sheet volume sea surface temperature cooling and a significant drop in the co 2 atmospheric levels here we present high resolution planktonic foraminifera data mean sampling resolution of about 780 years from core lc10 recovered in the ionian sea eastern mediterranean between 1 2 and 0 9 ma selected taxa among them g ruber t quinqueloba and g bulloides show significant periodicities that can be associated to orbital cycles mainly precession and obliquity the planktonic foraminifera based paleoclimatic curve exhibits a cooling linear trend that can be associated to similar phenomena observed in the north atlantic on the other hand we refer to the influence of the north african monsoon the occurrence of two peaks of the low salinity tolerant species g quadrilobatus that fall in coincidence of sapropel layers finally we discuss the distribution pattern of n pachyderma sinistral coiling with peaks up to about 20 between mis 30 and 28 and compare it to middle late quaternary records of the sicily channel and western mediterranean

shallow bias in neogene palaeomagnetic directions from the guide basin ne tibet caused by inclination error summary too shallow inclinations have frequently been observed in cenozoic sedimentary strata in central asia and new palaeomagnetic results obtained by us from the guide basin in ne tibet are no exception we use a statistical analysis technique developed by tauxe and kent tk03 gad which is based on a geomagnetic field model that predicts distributions of palaeomagnetic directions and show that the too shallow neogene mean inclination 44 from 627 sites can be corrected to a value of 58 which closely matches the inclination predicted for the area we conclude that syn to post depositional flattening is the most likely cause for the widely observed inclination bias in central asia

final closure of panama and the onset of northern hemisphere glaciation abstract the greenland ice sheet is accepted as a key factor controlling the quaternary glacial scenario however the origin and mechanisms of major arctic glaciation starting at 3 15 ma and culminating at 2 74 ma are still controversial for this phase of intense cooling ravelo et al 1 a c ravelo d h andreasen m lyle a o lyle m w wara regional climate shifts caused by gradual global cooling in the pliocene epoch nature 429 2004 263 267 proposed a complex gradual forcing mechanism in contrast our new submillennial scale paleoceanographic records from the pliocene north atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation nhg since it was linked to a 2 3 c surface water warming during warm stages from 2 95 to 2 82 ma these records support previous models g h haug r tiedemann effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation nature 393 1998 673 676 2 claiming that the final closure of the panama isthmus 3 0 2 5 ma j groeneveld s steph r tiedemann d nurnberg d garbe schonberg the final closure of the central american seaway geology in prep 3 induced an increased poleward salt and heat transport associated strengthening of north atlantic thermohaline circulation and in turn an intensified moisture supply to northern high latitudes resulted in the build up of nhg finally culminating in the great irreversible climate crash at marine isotope stage g6 2 74 ma in summary there was a two step threshold mechanism that marked the onset of nhg with glacial to interglacial cycles quasi persistent until today

shell size variation of the planktonic foraminifer neogloboquadrina pachyderma sin in the norwegian greenland sea during the last 1 3 myrs implications for paleoceanographic reconstructions we present measurements of the maximum diameter of the planktonic foraminifer neogloboquadrina pachyderma sin from six sediment cores ocean drilling program sites 643 644 907 909 985 and 987 from the norwegian greenland sea our data show a distinct net increase in mean shell size of n pachyderma sin at all sites during the last 1 3 ma with largest shell sizes reached after 0 4 ma external factors such as glacial interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of n pachyderma sin we consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of n pachyderma sin to the cold water environment after 1 1 1 0 ma probably the mid pleistocene climate shift and the associated change of amplitude and frequency of glacial interglacial fluctuations have triggered the evolution of this planktonic foraminifer oxygen and carbon stable isotope analyses of diverent shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis for paleoceanographic reconstructions the evolutionary adaptation of neogloboquadrina pachyderma sin to the cold water habitat has significant implications carbonate sedimentation in highest latitudes is highly dependent on the presence of this species in the norwegian greenland sea carbonate poor intervals before 1 1 ma are therefore not necessarily related to severe glacial conditions they are probably attributed to the absence of this not yet polar adapted species further transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could therefore contain a large range of errors if they were applied to samples older than 1 1 1 0 myrs 2000 elsevier science b v all rights reserved

habitats abundance patterns and isotopic signals of morphotypes of the planktonic foraminifer globigerinoides ruber d orbigny in the eastern mediterranean sea since the marine isotopic stage 12 article i nfo the chemical composition of shells of the planktonic foraminifer globigerinoides ruber white is frequently used to determine past sea surface conditions recently it has been shown that arbitrarily defined morphotypes within this species exhibit different chemical and isotopic signatures here we investigate the occurrence through time and in space of morphological types of g ruber white in late quaternary and holocene sediments of the central and the eastern mediterranean sea in 115 samples representing two distinct time intervals mis 1 2 and mis 9 12 at odp site 964 and the piston core geotu sl96 we have defined three morphological types within this species and determined their relative abundances and stable isotopic composition a quantitative analysis of morphological variation within g ruber white in four samples revealed that the subjectively defined morphotypes occupy separate segments of a continuous and homogenous morphospace we further show that the abundance of the morphotypes changes significantly between glacials and interglacials and that the three morphotypes of g ruber show significant offsets in their stable isotopic composition these offsets are consistent within glacial and interglacial stages but their sign is systematically reversed between the two sites since the isotopic shifts among the three g ruber morphotypes are systematic and often exceed 1 their understanding is essential for the interpretation of all g ruber based proxy records for the paleoceanographic development of the mediterranean during the late

early onset and tropical forcing of 100 000 year pleistocene glacial cycles between 1 5 and 0 6 myr ago the period of the earth s glacial cycles changed from 41 kyr the period of the earth s obliquity cycles to 100 kyr the period of the earth s orbital eccentricity1 2 which has a much smaller effect on global insolation the timing of this transition and its causes pose one of the most perplexing problems in palaeoclimate research3 here we use complex demodulation to examine the phase evolution of precession and semiprecession cycles the latter of which are phase coupled to both precession and eccentricity in the tropical and extra tropical atlantic ocean we find that about 1 5 myr ago tropical semiprecession cycles with periods of about 11 5 kyr started to propagate to higher latitudes coincident with a growing amplitude envelope of the 100 kyr cycles evidence from numerical models suggests that cycles of about 10 kyr in length may be required to explain the high amplitude of the 100 kyr cycles4 combining our results with consideration of a modern analogue we conclude that increased heat flow across the equator or from the tropics to higher latitudes around 1 5 myr ago strengthened the semiprecession cycle in the northern hemisphere and triggered the transition to sustained 100 kyr glacial cycles

climate signatures through marine isotope stage 19 in the montalbano jonico section southern italy a land sea perspective abstract a multi proxy record based on calcareous plankton dinocysts pollen mineralogy and grain size has been acquired from the ideale section the portion of montalbano jonico succession southern italy that could host the gssp for the middle pleistocene the direct correlation between marine and terrestrial proxies provides a valuable indication of atmospheric and oceanic connections the record shows a distinct climate variability well expressed by the vegetational changes sediment input into the basin and sea surface water modifications biotic proxies indicate that during the study interval periods of prevailing subpolar transitional surface water conditions were concurrent with steppe and halophytic vegetation erosional processes on the hillslopes and terrigenous supply during these periods were likely favored due to reduced arboreal vegetation as attested to by sediment composition and pollen assemblages temperate subtropical surface water conditions were concomitant with prevalent expansions of thermophilous arboreal plants and moister conditions on land which likely promoted chemical weathering leading to an enhanced supply of kaolinite and smectite in the basin a relationship between mineral content and the nature of the outcropping units in the source area as well as sea level fluctuations has also been considered a well defined period of polar subpolar water incursion ranging from 793 2 ka to 788 1 ka matches the major expansion of steppic vegetation on land and the increase of terrigenous supply into the basin it likely represents the local response to north atlantic ice rafted debris deposition short lived warming cooling episodes punctuate the latest part of mis 20 and are tentatively correlated with analogue climate phases predating mis 1 inception full interglacial conditions of mis 19c lasting 10 6 kyr started at 784 3 ka and were characterized by warm oligotrophic and stratified surface waters coupled with forest expansion suggesting prevalent warm and humid conditions on land a potential sapropel like interval is identified within mis 19c and correlated to i cycle 74 the mis 19c 19b transition is marked at 773 2 ka by the reestablishment of millennial scale variability similarly to north atlantic marine and ice core records the results improve the paleoclimate framework of a middle pleistocene reference section and add further insight regarding climate development across mis 19 and on potential similarities with its closest holocene analogue

pliocene carbonate accumulation along the california margin recent modeling studies call on increased ocean heat transport to explain high latitude warming observed for intervals throughout the middle pliocene possible vehicles for ocean heat transport are the poleward arms of the subtropical gyres sites from the california margin ocean drilling program leg 167 provide monitors of wind field within the eastern arm of the gyre which may be an indication of basin wide subtropical gyral strength at most sites water depths from 1106 to 4212 m caco3 mass accumulation rate mar was highest in the middle pliocene 3 5 2 0 ma this high caco3 mar event is attributed primarily to higher caco3 production due to higher offshore upwelling associated with the zone of the greatest wind stress curl thus in the middle pliocene there was enhanced wind stress curl along the california margin and possibly enhanced north pacific sub tropical gyral circulation and meridional ocean heat advection

pleistocene sea surface temperature evolution early cooling delayed glacial intensification and implications for the mid pleistocene climate transition the mid pleistocene climate transition mpt is defined by the emergence of high amplitude quasi 100 ka glacial interglacial cycles from a prior regime of more subtle 41 ka cycles this change in periodicity and amplitude cannot be explained by a change in external astronomical forcing here we review and integrate published records of sea surface temperatures ssts to assess whether a common global expression of the mpt in the surface ocean can be recognized and examine our findings in light of mechanisms proposed to explain climate system reorganization across the mpt we show that glacial interglacial variability in ssts is superimposed upon a longer term cooling trend in oceanographic systems spanning the low to high latitudes regional variability exists in the timing of the onset and magnitude of cooling but in most cases a long term cooling trend begins or intensifies from 1 2 ma marine isotope stage mis 35 34 the sst cooling accompanies a long term trend towards higher global ice volume as recorded in benthic foraminifera 18o but predates a step like increase in 18o at 0 9 ma mis 24 22 that is argued to reflect expansion of continental ice sheets the strongest expression of pleistocene cooling is found during glacial stages whereas minor or negligible trends in interglacial temperatures are identified however pronounced cooling during both glacial and interglacial maxima is evident at 0 9 ma alongside the long term sst cooling trends quasi 100 ka cycles begin to emerge in both the sst and 18o records at 1 2 ma and become dominant with the expansion of the ice sheets at 0 9 ma we show that the intensified glacial stage cooling is accompanied by evolving pco2 abyssal ocean ventilation atmospheric circulation and or dust inputs to the southern ocean these changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the mpt in turn these modified boundary conditions may have altered climate sensitivity to orbital forcing by placing pre existing ice sheets closer to some threshold of climate ice sheet response

neogloboquadrina pachyderma sinistral coiling as paleoceanographic tracers in polar oceans evidence from northeast water polynya plankton tows sediment traps and surface sediments the abundance and chemistry of the planktonic foraminifera neogloboquadrina pachyderma sinistral coiling have long been used as tools for monitoring polar surface ocean changes and for correlating these changes to atmospheric and thermohaline circulation fluctuations however due to its remote habitat very little is known about how modern n pachyderma s respond to changing environmental conditions in the polar seas modern samples of n pachyderma s from the northeast water polynya provide a means for studying how environmental conditions affect the vertical distribution and chemistry of this species highest abundances of n pachyderma s were associated with the chlorophyll maximum in the surface 20 80 m where they are exploiting their primary food source evidence suggests that the addition of a calcite crust modifies the calcite tests of some n pachyderma s between 50 and 200 m increasing shell density and modifying shell chemistry the shell mass of encrusted forms is 3 4 times greater than the nonencrusted forms between 50 and 200 m the oxygen isotope composition of n pachyderma s shells increase by 1 5 in response to local water column gradients the 13c values of n pachyderma s are basically invariant with depth in this region are consistently 1 0 depleted in comparison with the 13c for equilibrium calcite and remain basically constant during the shell thickening process mass balance calculations suggest that encrustation occurs at all depths but abundance counts suggest that the process occurs mostly at the depth of the main pycnocline sediment fluxes of n pachyderma s occur during a 2 week bloom event and decrease to almost zero below complete ice cover the decoupling of the processes controlling abundances and shell chemistry explain the discrepancies between transfer function and isotopically derived paleotemperature estimates of surface conditions in some oceanic settings the ability of 18o to record surface ocean conditions will depend on vertical water column gradients as evidenced by the differences in core top calibrations between the north and south atlantic

causes and consequences of a middle pleistocene origin of the modern planktonic foraminifer neogloboquadrina pachyderma sinistral switches in coiling direction of shells of the planktonic foraminifer neogloboquadrina pachyderma have been extensively used as a paleotemperature proxy from the late miocene through the quaternary exploiting the specific modern polar affinity of the sinistrally coiled form here we have reexamined the origin of the modern sinistral form in pliocene and pleistocene sediments from ocean drilling program site 1014 in the eastern north pacific by using morphometric and stable isotope data we show that pliocene and pleistocene sinistral forms of n pachyderma are morphologically and ecologically different and that modern type sinistral form first appeared ca 1 ma these findings suggest that n pachyderma sinistral should not be used for calibrated paleoceanographic reconstructions prior to the middle pleistocene and reinforce the need to assess the origin of specific ecological affinities of other modern planktonic foraminifer species the first appearance of the modern form and the subsequent evolution of its mean shell size appear to have been synchronous in the north pacific and the north atlantic such hemispheric evolutionary synchronicity implies existence of trans arctic gene flow the modern type shell morphology and the specific cold water affinity of n pachyderma sinistral may have evolved in response to the onset of the 100 k y climate regime in the middle pleistocene

pacific ocean intermediate and deep water circulation during the pliocene abstract new benthic foraminiferal stable isotopic records of northeast pacific intermediate water odp site 1014 1177 m and mid depth water odp site 1018 2476 m were compared to isotopic records of deep water in the tropical pacific odp site 849 3851 m for the reconstruction of vertical profiles of nutrient and physical properties from the early pliocene to the early pleistocene approx 5 1 4 ma our data indicate that for the entire interval there was enhanced north pacific intermediate water ventilation relative to today and a similar to modern circulation pattern with northward flowing pacific bottom water pbw beneath its southward flowing return flow however the core of maximally aged return flow resided as deep as 2500 m as compared to 1500 m today probably due to the strengthened intermediate water flow less apparent aging of deep water along its path before 2 7 ma indicates that thermohaline overturning may have been more rapid in the warm period of the early pliocene in addition prior to 2 7 ma foraminiferal oxygen isotopic values at mid depth sites are higher than at deep sites a reversed vertical gradient relative to today in both the atlantic and pacific oceans we suggest that nadw was warmer and more saline than today and that it influenced mid depth waters throughout the atlantic and pacific oceans enhanced pliocene formation of warmer saltier intermediate water in the north pacific and deep water in the north atlantic may have been a result of higher than modern high mid latitude sea surface temperatures evaporation and salinity

major pleistocene stages in a carbon perspective the south china sea record and its global comparison 1 carbon isotope sequences at ocean drilling program site 1143 south china sea reveal a long term cyclicity of 500 kyr that is superimposed on the glacial cycles and is present in long 13c sequences from all oceans the quaternary 13c record is punctuated by four 13c maximum events 13cmax i which began in marine isotope stage mis 3 around 50 60 kyr ago 13cmax ii mis 13 0 47 0 53 ma 13cmax iii mis 27 29 0 97 1 04 ma and 13cmax vi mis 53 57 1 55 1 65 ma as the same cyclicity is also found in carbonate curves the 13cmax events must denote major reorganization in the carbon reservoir of the global ocean they also are associated with major changes in glacial cyclicity such as the mid brunhes event following 13cmax ii and the mid pleistocene revolution following 13cmax iii which in turn were associated with expansion of the ice sheets from a carbon perspective therefore the quaternary period has passed through three major stages and each appears to represent a further step in ice cap development

plus ca change a model for stasis and evolution in different environments abstract the plus ca change model proposes that morphological stasis is the usual response to widely fluctuating physical environments on geological timescales until thresholds are reached the lineages that survive in a more changing environment on geological timescales are those that are relatively inert to each environmental twist and turn in contrast to more sensitive lineages in less changing environments generalists in this long term sense are species with properties that enable them to survive throughout wide environmental fluctuations over geological timescales they are thus related to but distinct from ecological eurytopes the model predicts a tendency for continuous gradualistic evolution on land in the tropics and in the deep sea and for more stasis and occasional punctuations in shallow waters and temperate zones as the vast majority of the fossil record comes from dynamic shallow marine environments it is not surprising that many fossil lineages show approximate stasis and occasional punctuations punctuated equilibrium could be being mistakenly perceived as the overwhelming pattern in the history of life because the environments in which gradualism predominates are rarely preserved in the fossil record the evolutionary pattern in a lineage at a single locality is predicted to be stasis when there is greater environmental fluctuation and net directional change and or more widely fluctuating morphologies when environments are more narrowly fluctuating given the quaternary climate upheavals relatively little evolution may be occurring worldwide at present except for evolution induced by humans such a model is bound to have many exceptions it is only about tendency and relative frequency though few case histories are yet known many existing data sets probably contain clues that can be used in testing the model other relevant aspects of perception are also discussed including descriptive biases and evolutionary reversals