productivity collapses in the arabian sea during glacial cold phases 1 productivity in the arabian sea is one of the highest in the world it is controlled by seasonally reversing monsoonal wind driven upwelling of nutrient rich deeper waters which fuel phytoplankton growth the detailed history of upwelling induced productivity in the eastern arabian sea is unknown here we present paleoproductivity records from a composite sediment core at the millennial scale during the last 80 kyr b p these records are based on relative abundance counts of planktonic foraminifera and organic carbon contents which are shown to mainly vary in concert the eastern arabian sea upwelling induced productivity was higher in the glacial period than in the holocene but it fell repeatedly on millennial timescales these productivity declines occurred during cold events in the north atlantic region with the most pronounced changes prevailing during the heinrich events hence seasonal monsoon winds that drive upwelling induced productivity in the east were weak when the north atlantic was cold these weak winds resulted in stratification of the water column comparable to today s arabian sea stratification in the intermonsoonal period combining the new eastern with published western arabian sea results shows that the entire biological factory was severely diminished during the north atlantic heinrich events and the seasonal productivity change in the arabian sea monsoon system was reduced with year round low productivity

monsoonal dynamics and evolution of the primary productivity in the eastern arabian sea over the past 30 ka abstract this study presents a high resolution primary productivity record for the last 30 ka in the eastern arabian sea eas based on the coccolithophore assemblage at sk 17 core in the continental slope off goa india coccolithophores were proposed as indicators of primary productivity and nutricline position and the results were used to reconstruct the monsoonal dynamics which is a main factor controlling productivity changes in the eas both seasons in the indian monsoon winter and summer monsoon exert a strong control over the primary productivity in the arabian sea an increased productivity was recorded during the late glacial period in the eas contrasting with records obtained in the western and northern arabian sea this enhanced productivity was related to strengthened winter monsoon winds planktonic foraminifera data suggested a weakened winter mixing during the last deglaciation which would reduce productivity in the area however our coccolithophore data reveal a high primary productivity during the deglaciation provably maintained by the nutrient supply from the continental runoff due to the presence of enhanced summer monsoon regarding the holocene surface waters were highly stratified since 10 5 ka our data were compared with ice cores isotopic records from high latitudes of both hemispheres allowing us to observe a good correlation between the stratification of the eas and the climate variability over high latitude regions in the northern hemisphere however there has been some inconsistency between our coccolithophore data and planktonic foraminiferal records particularly during the short time intervals corresponding to the heinrich cold events described in the north atlanctic region

a new 27 ky high resolution east antarctic climate record the ice core recently drilled at the dome concordia site on the east antarctic plateau provides a new high resolution isotope record covering part of the last glacial the last transition and the holocene the two step shape of the deglaciation is remarkably similar for all the ice cores now available on the east antarctic plateau the first warming trend ends about 14000 years ago and is followed by the well marked antarctic cold reversal acr with a secondary peak common to all records during the deglaciation there are more similarities between the near coastal site of taylor dome and inland east antarctica than between taylor dome and central greenland however the results for epica do appear to confirm the taylor dome timescale after about 14 ka showing cooling into the acr roughly in phase between greenland and antarctica while the overall deglacial pattern is asynchronous this suggests that the now classical picture of a temperature seesaw between antarctica and greenland may be too simplistic

distribution of recent nannofossils beneath the benguela system southwest african continental margin abstract one hundred and forty eight surface samples recovered from the southwest african continental margin 35 17 s have been examined for their nannofossil content coccolith abundance is high in sediments from the deep water areas but declines toward the coast under the main areas of upwelling five distinct bathymetric oceanographic assemblages can be characterized by their nannofossil content coastal upwelling orange bank intermediate southern deep water and northern deep water angola current these distinctions are based on the distribution of eight ecologically significant taxa in order of decreasing abundance they are gephyrocapsa oceanica helicopontosphaera kamptneri cyclococcolithina leptopora coccolithus pelagicus syracosphaera div sp thoracosphaera div sp rhabdosphaera div sp and umbilicosphaera sibogae sea surface temperature and salinity variations which correlate with the extent and intensity of the main upwelling cells are thought to be the most important controls on coccolith distribution although nutrient availability and reduction of surface water transparency may be of local importance the exclusion of three stratigraphical index species for the quaternary emiliania huxleyi gephyrocapsa caribbeanica and g ericsonii from the quantitative analysis will permit the future application of these results to paleoceanographic reconstructions of the benguela system in pleistocene core sections

sea surface temperature and productivity records for the past 240 kyr in the arabian sea abstract deep sea sediments of two cores from the western ty93 929 p and the southeastern md900963 arabian sea were used to study the variations of the indian monsoon during previous climatic cycles core ty93 929 p was located between the sw monsoon driven upwelling centres off somalia and oman which are characterized by large seasonal sea surface temperature sst and particle flux changes by contrast core md900963 was situated near the maldives platform an equatorial ocean site with a rather small sst seasonality less than 2 c for both cores we have reconstructed sst variations by means of the unsaturation ratio of c37 alkenones which is compared with the 18o records established on planktonic foraminifera in general the sst records follow the 18o variations with an sst maximum during oxygen isotope stage 5 5 the last interglacial at about 120 130 kyr and a broad sst minimum during isotope stage 4 and 3 3 approximately 40 50 kyr the sst difference between the holocene and the last glacial maximum lgm is of the order of 2 c in both cores the ssts during isotope stage 6 are distinctly higher by 1 2 c than the cold sst minima during the last glacial cycle lgm and stage 3 to reconstruct qualitatively the past productivity variations for the two cores we used the concentrations and fluxes of alkenones and organic carbon together with a productivity index based on coccolith species florisphaera profunda relative abundance within each core there is a general agreement between the different palaeoproductivity proxies in the southeastern arabian sea core md900963 glacial stages correspond to relatively high productivity whereas warm interstadials coincide with low productivity all time series of productivity proxies are dominated by a cyclicity of about 21 23 kyr which corresponds to the insolation precessional cycle a hypothesis could be that the ne monsoon winds were stronger during the glacial stages which induced deepening of the surface mixed layer and injection of nutrients to the euphotic zone by contrast the records are more complicated in the upwelling region of the western arabian sea core ty93 929 p this is partly due to large changes in the sedimentation rates which were higher during specific periods isotope stages 6 5 4 5 2 3 and 2 unlike core md900963 no simple relationship emerges from the comparison between the 18o stratigraphy and productivity records the greater complexity observed for core ty93 929 p could be the result of the superimposition of different patterns of productivity fluctuations for the two monsoon seasons the sw monsoon being enhanced during interglacial periods whereas the ne monsoon was increased during glacial intervals a similar line of reasoning also could help explain the sst records by the superimposition of variations of three components global atmospheric temperature and sw and ne monsoon dynamics

quaternary carbonate record from the equatorial indian ocean and its relationship with productivity changes abstract the caco3 content in quaternary deep sea sediments from pacific and atlantic oceans have been suggested to respond differently to glacial interglacial cycles caco3 contents are highest during glacials in the pacific but highest during interglacials in the atlantic ocean it is not yet clear as to whether a pacific or an atlantic pattern of caco3 fluctuations dominates the indian ocean we have analyzed the ocean drilling program odp site 709a from the western equatorial indian ocean for the last 1370 ka to determine the relationships between percentages and fluxes of caco3 and quaternary paleoclimatic changes we also analyzed the coarse 25 m and fine 18 o of the planktonic foraminifera globigerinoides ruber this indicates that caco3 fluctuations at this site do not show either a pacific or an atlantic pattern of caco3 fluctuations fluxes of caco3 0 38 to 2 46 g cm 2 ka 1 in total sediment and ba al ratios 0 58 to 3 93 g cm 2 ka 1 show six fold variability through the last 1370 ka which points out that productivity changes are significant at this site fluxes of the fine caco3 component demonstrate a 26 fold change 0 02 to 0 52 g cm 2 ka 1 whereas the coarse caco3 component exhibit eight fold change 0 13 to 1 07 g cm 2 ka 1 this suggests that productivity variations of calcareous nannofossils are greater in comparison with the foraminifera on the other hand mean values of coarse caco3 fluxes are higher compared to those of fine caco3 which reveals that the foraminifera contribute more to the bulk caco3 flux than the calcareous nannofossils in the equatorial indian ocean

magnetic properties of sediments in the bay of bengal and the andaman sea impact of rapid north atlantic ocean climatic events on the strength of the indian monsoon abstract the results of a high resolution mineral magnetic study combined with major element geochemistry analysis oxygen isotopes and 14c ams stratigraphy are reported for deep sea gravity cores md77 169 and md77 180 located in the andaman sea and the bay of bengal respectively core md77 169 covers the last 280 kyr and core md77 180 covers the last 160 kyr in both cores rock magnetic parameters indicate that the magnetic assemblage is dominated by pseudo single domain titanomagnetite grains with grain size variations following a strong 23 kyr periodicity smaller magnetic grain sizes are observed during periods characterized by a strong summer monsoon in addition in core md77 180 we observe a correlation between magnetic grain size and a chemical index of alteration this suggests that these magnetic grain size changes are related to chemical weathering driven by summer monsoon rainfall a comparison of the gisp2 ice core isotopic record and the magnetic grain size record of the bay of bengal shows that rapid temperature variations documented in the ice core dansgaard oeschger cycles and heinrich events during the last glacial period are also present in the magnetic grain size record heinrich events and cold stadial events are characterized by relatively large magnetic grain sizes furthermore heinrich events are characterized by lower values of the chemical index of alteration implying a lower degree of chemical weathering related to significantly drier conditions on the continent we suggest that rapid cold events of the north atlantic heinrich events during the last glacial stages are characterized by a weaker summer monsoon rainfall over the himalaya via an atmospheric teleconnection

a middle pleistocene northeast atlantic coccolithophore record paleoclimatology and paleoproductivity aspects abstract changes in paleoclimate and paleoproductivity patterns have been identified by analysing in conjunction with other available proxy data the coccolithophore assemblages from core md03 2699 located in the portuguese margin in the time interval from the marine isotope stage mis 13 14 boundary to mis 9 535 to 300 ka during the mid brunhes event the assemblages associated with the eccentricity minima are characterised by higher nannoplankton accumulation rate nar values and by the blooming of the opportunistic genus gephyrocapsa changes in coccolithophore abundance are also related to glacial interglacial cycles higher nar and numbers of coccoliths g mainly occurred during the interglacial periods while these values decreased during the glacial periods superimposed on the glacial interglacial cycles climatic and paleoceanographic variability has been observed on precessional timescales the structure of the assemblages highlights the prevailing long term influence of the portugal pc and iberian poleward ipc currents following half and full precession harmonics related to the migration of the azores high ah pressure system small gephyrocapsa and coccolithus pelagicus braarudii are regarded as good indicators for periods of prevailing pc influence gephyrocapsa caribbeanica syracosphaera spp rhabdosphaera spp and umbilicosphaera sibogae denote periods of ipc influence our data also highlights the increased percentages of coccolithus pelagicus pelagicus during the occurrence of episodes of very cold and low salinity surface water probably related to abrupt climatic events and millennial scale oscillations of the ah icelandic low il system

late quaternary nannofossil indicators of climate change in two deep sea cores associated with the leeuwin current off western australia the stratigraphic variations in nannoflora observed in the two deep sea cores recovered from the offshore western australia revealed a sequence of paleoceanographic changes for the last 250 kyr the dominance of small placolith taxa in the upper photic flora indicates continuous mild upwelling for the isotope stages 7 5 in this region the most important controlling factor for the abundance variation of florisphaera profunda in this region is considered to be the lower photic temperature rather than the stability of water column or the water turbidity the significant reduction in the abundance of f profunda combined with the stable in the northern core rs96gc21 and reduced in the southern core rs9 150 abundance of the small taxa suggest an intensified upwelling for the penultimate glaciation the sharp increase in f profunda abundance indicates a weakening of upwelling at the last interglacial climax lic offshore western australia after isotope stage 5 the existence of upwelling is not clear except in stage 2 when it was not strong enough to produce blooms of emiliania huxleyi among the subordinate taxa calcidiscus leptoporus calciosolenia murrayi neosphaera coccolithomorpha and oolithotus fragilis provide meaningful paleoceanographic signals supporting the conclusions of previous studies a weakening or cessation of leeuwin current for the glacial periods the shift of dominance from small gephyrocapsa mostly g ericsonii to small reticulofenestra mostly r parvula can be an useful datum event offshore western australia the reduced diversity of nannoflora during the interglacial periods can be explained by a lessened competition within nannoplankton community caused by particularly favorable conditions for the opportunists such as e huxleyi f profunda and small placoliths the variations in nannofossil abundance suggests an increased aeolian flux at the stages 6 and 2 offshore north west cape as well as at stage 6 offshore southwestern australia

ore microscopic and geochemical characteristics of gold bearing sulfide minerals el sid gold mine eastern desert egypt gold deposits at el sid are confined to hydrothermal quartz veins which contain pyrite arsenopyrite sphalerite and galena these veins occur at the contact between granite and serpentinite and extend into the serpentinite through a thick zone of graphite schist gold occurs in the mineralized zone either as free gold in quartz gangue or dissolved in the sulfide minerals ore microscopic study revealed that au bearing sulfides were deposited in two successive stages with early pyrite and arsenopyrite followed by sphalerite and galena gold was deposited during both stages largely intergrown with sphalerite and filling microfractures in pyrite and arsenopyrite

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

coupled sea surface temperature seawater δ18o reconstructions in the arabian sea at the millennial scale for the last 35 ka two sediment cores from the western 905 10 46 9 n 51 56 4 e water depth 1586 m and eastern sk17 15 15 n 72 58 e water depth 840 m arabian sea were used to study past sea surface temperatures sst and seawater 18o 18ow variations for the past 35 ka we used coupled mg ca 18o calcite variability in two planktonic foraminiferal species globigerinoides ruber which thrives throughout the year and globigerina bulloides which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing ssts in both areas based on mg ca in g ruber were 3 to 4 c lower during the last glacial maximum lgm 21 ka than today and the holocene period the sst records based on g bulloides also indicate general cooling down to 18 c in both areas ssts in the western arabian sea based on g bulloides were always lower than those based on g ruber indicating the presence of strong seasonal temperature contrast during the holocene and lgm we interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling sw monsoon and winter convective mixing ne monsoon in the western arabian sea in the eastern arabian sea g bulloides based ssts were slightly lower about 1 c than g ruber based ssts during the holocene indicating the almost absence of a seasonal temperature gradient similar to today however a large seasonal temperature contrast occurred during the lgm which favors the assumption that strong ne monsoon winds forced winter upwelling or convective mixing offshore goa sst and 18ow reconstructions reveal evidence of millennial scale cycles particularly in the eastern arabian sea here the stadial periods northern hemisphere cold periods such as younger dryas and heinrich events are marked by increasing ssts and salty sea surface conditions relative to those during the interstadial periods indeed the 18ow record shows evidence of low saline surface waters during interstadial periods indicating increased freshwater runoff from the western ghats as a consequence of enhanced sw monsoon intensity

mid to late holocene indian ocean monsoon variability recorded in four speleothems from socotra island yemen four stalagmites covering the last 7 0 ka were sampled on socotra an island in the northern indian ocean to investigate the evolution of the northeast indian ocean monsoon iom since the mid holocene on socotra rain is delivered at the start of the southwest iom in may june and at the start of the northeast iom from september to december the haggeher mountains act as a barrier forcing precipitation brought by the northeast winds to fall preferentially on the eastern side of the island where the studied caves are located 18o and 13c and mg ca and sr ca signals in the stalagmites reflect precipitation amounts brought by the northeast winds for stalagmite stm6 this amount effect is amplified by kinetic effects during calcite deposition combined interpretation of the stalagmites signals suggest a weakening of the northeast precipitation between 6 0 and 3 8 ka after 3 8 ka precipitation intensities remain constant with two superimposed drier periods between 0 and 0 6 ka and from 2 2 to 3 8 ka no link can be established with greenland ice cores and with the summer iom variability in contrast to the stable northeast rainy season suggested by the records in this study speleothem records from western socotra indicate a wettening of the southwest rainy season on socotra after 4 4 ka the local wettening of western socotra could relate to a more southerly path more over the indian ocean taken by the southwest winds stalagmite stm5 sampled at the fringe between both rain areas displays intermediate 18o values after 6 2 ka similar precipitation changes are seen between eastern socotra and northern oman indicating that both regions are affected similarly by the monsoon different palaeoclimatologic records from the arabian peninsula currently located outside the itcz migration pathway display an abrupt drying around 6 ka due to their disconnection from the southwest rain influence records that are nowadays still receiving rain by the southwest winds suggest a more gradual drying reflecting the weakening of the southwest monsoon

coccolithophores in surface sediments of the arabian sea in relation to environmental gradients in surface waters abstract one hundred surface sediment samples of the arabian sea indian ocean were investigated and relative abundances of coccoliths were compared to mean annual gradients of temperature salinity chlorophyll po4 and mixed layer depth total coccolith concentrations ranged from 42 106 g sediment in coastal areas to more than 19 000 106 g sediment in oceanic regions the general distribution does not seem to be dependent on coccolithophore productivity in surface waters alone but also on the diluting input of terrigenous material a total of 27 taxa were identified the main species dominating the assemblages were gephyrocapsa oceanica emiliania huxleyi and florisphaera profunda with a combined average abundance of more than 70 several species and species groups reflect with their distribution the environmental parameters of the overlying water masses and may be successfully used to improve palaeoclimatic reconstructions e g a f profunda exhibits a high similarity or even positive correlation to the mean annual mixed layer depth b calciosolenids can be described as coastal or shelf species while temperature and salinity gradients do not seem to be crucial for coccolithophores in this region the mean mixed layer depth as well as the po4 concentration representative for total nutrient availability may control in part the coccolithophore assemblages according to the results of a cluster analysis and the distribution pattern of all species it was possible to differentiate three main coccolithophore assemblages a g oceanica dominated assemblage mainly occurs in the northern part of the study area and can be described as high nutrient assemblage the second assemblage dominated by f profunda may be typical for oligotrophic and stable conditions in open ocean waters a third assemblage with high amounts of coastal species characterises coastal conditions on the shelves

a tentative chronology for the epica dome concordia ice core a tentative age scale edc1 for the last 45 kyr is established for the new 788 m epica dome c ice core using a simple ice flow model the age of volcanic eruptions the end of the younger dryas event and the estimated depth and age of elevated 10be about 41 kyr ago were used to calibrate the model parameters the uncertainty of edc1 is estimated to 10 yr for 0 to 700 yr bp up to 200 yr back to 10 kyr bp and up to 2 kyr back to 41 kyr bp the age of the air in the bubbles is calculated with a firn densification model in the holocene the air is about 2000 yr younger than the ice and about 5500 yr during the last glacial maximum

high resolution holocene monsoon record from the eastern arabian sea through stable oxygen and carbon analyses of rapidly accumulating sediment cores from the eastern arabian sea we show that the excess of evaporation over precipitation e p steadily appears to have decreased during the last 10 000 to 2000 years most probably due to an increasing trend in the summer monsoon rainfall contrary to the land based paleoclimatic data from this region which indicate onset of aridity around 4000 years ago our results are consistent with the hypothesis that significant spatial variability in the monsoon rainfall observed today was persistent during most of the holocene alternatively the trend can be seen as an adjustment between two phases one between 10 000 and 6000 years ago of increasing precipitation and another between 3500 and 2000 years ago after the arid episode we also report a significant 700 year periodicity similar to that reported recently from the south china sea indicating that the centennial millennial scale response of the indian and chinese monsoons to high latitude forcing may be alike

a 225 kyr record of dust supply paleoproductivity and the oxygen minimum zone from the murray ridge northern arabian sea abstract analysis of a 15 m long sediment core recovered from the murray ridge northern arabian sea reveals a 225 000 year record of climate induced variations in surface water productivity mid water ventilation and dust input in the northern arabian sea productivity and dust input records closely resemble those from the owen ridge and oman margin also the phase lag of 10 kyr between maximum productivity and precession minimum is in phase with the summer monsoon upwelling record from the owen ridge and the oman margin this implies that the productivity variations in the northern arabian sea during the last 225 kyr are primarily controlled by changes in the indian ocean summer monsoon the winter monsoon obviously played a minor role in the productivity history of the northern arabian sea another result from this study is that the mg al record from the murray ridge nicely documents the post glacial flooding of the persian gulf which is the main glacial source for dolomite dust in this region finally it is concluded that the intensity of the omz co varies with surface water productivity being weak during periods of reduced summer monsoon especially during glacial periods

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

sea surface temperatures and the history of monsoon upwelling in the northwest arabian sea during the last 500 000 years abstract arabian sea sediments record changes in the upwelling system off arabia which is driven by the monsoon circulation system over the nw indian ocean in accordance with climate models and differing from other large upwelling areas of the tropical ocean a 500 000 yr record of productivity at odp site 723 shows consistently stronger upwelling during interglaciations than during glaciations sea surface temperatures ssts reconstructed from the alkenone unsaturation index uk 37 are high up to 27 c during interglaciations and low 22 24 c during glaciations indicating a glacial interglacial temperature change of 3 c in spite of the dampening effect of enhanced or weakened upwelling the increased productivity is attributed to stronger monsoon winds during interglacial times relative to glacial times whereas the difference in ssts must be unrelated to upwelling and to the summer monsoon intensity the winter ne monsoon was more effective in cooling the arabian sea during glaciations then it is now

distribution of coccoliths in surface sediments of the south eastern south atlantic ocean ecology preservation and carbonate contribution abstract recent coccoliths from 52 surface sediment samples recovered from the south eastern south atlantic were examined qualitatively and quantitatively in order to assess the controlling mechanisms for their distribution patterns such as ecological and preservational factors and their role as carbonate producers total coccolith abundances range from 0 2 to 39 9 coccoliths 109 g 1 sediment four assemblages can be delineated by their coccolith content characterising the northern benguela the middle to southern benguela the walvis ridge and the deeper water distinctions are based on multivariate ordination techniques applied on the relative abundances of the most abundant taxa emiliania huxleyi calcidiscus leptoporus gephyrocapsa spp coccolithus pelagicus and subtropical to tropical species the coccolith distribution seems to be temperature and nutrient controlled co varying with the seaward extension of the upwelling filament zone in the benguela a preservation index cex based on the differential dissolution behaviour of the delicate e huxleyi and gephyrocapsa ericsonii versus the robust c leptoporus is applied in order to detect the position of the coccolith lysocline although some samples were recognised as dissolution affected the distribution of the coccoliths in the surface sediments reflects the different oceanographic surface water conditions mass estimations of the coccolith carbonate reveal coccoliths to be only minor contributors to the carbonate preserved in the surface sediments the mean computed coccolith carbonate content is 17 wt equivalent to a mean contribution of 23 to the bulk carbonate

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

characteristics of seismicity in the coast and north of jalisco block mexico abstract several studies of local seismicity were carried out between 1996 and 1998 on the coast and north of the jalisco block jb using a portable seismic network consisting of five lennartz m88 seismographs with le 3d 1 hz seismometers the data from these studies complemented with data from resco colima seismic network is used to characterize three seismogenic zones in the region one seismicity zone located east of the middle america trench mat under the continental plate is associated with the interaction of the rivera and north america plates and can be characterized as a double seismic zone dsz with geometry suggesting a bending plate and probably oblique subduction this pattern is clearer south of the 20 n parallel a second zone of continental intraplate seismicity is located between ameca and amatlan de canas in the northeastern part of the study region where the source depths vary from very shallow to about 35 km the third zone is bahia de banderas where the stress pattern seems to be very complex here we observe different types of seismic events the first type consists of shallow events located in the southern part of the bay and a under continental area that seems to be associated with the interplate rivera north america activity a second event type with depths between 10 and 30 km seems to be related to features that cross the bay in an ew direction in this zone there is also a high shallow continental seismicity which agrees with continental topographic features